[0001] The present invention relates to a constant volume valve for a combustion-powered
tool, such as a power framing tool. More specifically, it relates to a constant volume
valve assembly that measures a volume of a fluid before allowing it to flow into a
combustion chamber.
[0003] This invention also relates to a pneumatically powered, combustion-powered, or other
rapidly acting, fastener-driving tool of a type utilizing collated fasteners. Typically,
as exemplified in
Nikolich U.S. Pat. Re. 32,452, Nikolich
U.S. Pat. No. 4,522,162; Nikolich
U.S. Pat. No. 4,483,474; Nikolich
U.S. Pat No. 4,403,722 and Wagdy
U.S. Pat. No. 4,483,473, a combustion-powered, fastener-driving tool comprises a combustion chamber, which
is defined by a cylinder body and by a valve sleeve arranged for opening and closing
the combustion chamber. Generally, similar combustion-powered, nail- and staple- driving
tools are available commercially from ITW-Paslode (a unit of Illinois Tool Works Inc.)
of Vernon Hills, IL, under its IMPULSE trademark.
[0004] In such a tool, it is beneficial to apply a constant force during the driving stroke
to each fastener as it is driven into the workpiece. Measurement of the amount of
fuel to the combustion-powered tool, or the amount of compressed gas to a pneumatically
powered tool, helps provide a constant force. A combustion powered fastening tool
is described in
U. S. Patent No. 4,721,240 to Cotta that measures fuel by opening a valve for a length of time defined by movement of
a cam. Fuel passes through a fuel valve to a combustion chamber conduit, the amount
of which is equal to the volume that passes through a needle valve during the time
the fuel valve is open. Measurement of the flow of a fluid by time allows the amount
of fluid supplied to the tool to vary as flow rates of the fluid change. As a fuel
cylinder is emptied, the flow rate of the fluid changes as the cylinder pressure drops.
Similarly, pressure or flow variations in a common supply of pneumatic fluid will
also result in differences in the amount of power supplied on each charge of the cylinder.
[0005] Control of fuel into a combustion chamber by valve assemblies is shown in
U. S. Patent Nos. 655,996 and
1,293,858. Both references disclose a pressurized fluid inlet valve and fluid outlet valve
that bracket a machine-supply passage. High-pressure fluid is fed to a machine to
supply power via the inlet valve, and is discharged through the outlet valve when
it returns from the machine following expulsion of its power. Neither reference teaches
the use of such a system to supply a constant measurement of fluid. Further, following
combustion of a fuel or expansion of a high-pressure fluid, the fluid is no longer
useful to supply power to a tool and measurement at that point is ineffective.
[0006] U. S. Patent No. 4,913,331 to Utsumi describes an apparatus that drives a piston with an internal combustion engine that
utilizes a measuring chamber to dispense a constant volume of fuel. A fuel piston
containing the measuring chamber is reciprocally moveable within a fuel cylinder.
The fuel inlet channel and the fuel outlet channel are positioned such that the measuring
chamber is filled and emptied by movement of the piston between the inlet and outlet
channels. Seals are located on either side of the chamber between the fuel piston
and the cylinder, preventing leakage of fuel from the pressurized fuel supply to the
combustion chamber. Steady movement of the piston would cause rapid wear on these
seals, since they are constantly in contact with the cylinder surface.
[0007] One operational drawback of conventional combustion-powered tools, is that when operated
at relatively low temperatures, such as below 32 °F, the pressure of the pressurized
fuel falls, causing a greater pressure differential between the atmosphere and the
fuel. At this lower pressure, the fuel does not dissipate as rapidly through the appropriate
passageways and into the combustion chamber. This condition causes a delay in the
combustion, which interferes with the operational efficiency of the tool.
[0008] Another operational drawback of conventional combustion-powered tools, is that when
operated at relatively higher elevations or altitudes, there is less air for combustion.
As a result, when used at such higher elevations, conventional combustion-powered
tools with constant volume fuel metering valves can have overly rich fuel/air mixtures
in their combustion chambers, which can lead to fouling of the ignition system as
well as other operational difficulties. As such, there is a need for a combustion
-powered tool with a fuel metering valve which has the capability of adjusting the
amount of fuel in the combustible fuel/air mixture.
[0009] It is, therefore, an object of this invention to provide an improved constant volume
measurement of a fluid to an apparatus, such as a combustion-powered tool, to produce
a constant driving force.
[0010] It is yet another object of this invention to provide an improved constant volume
measurement of fluid in a compact space.
[0011] It is still another object of this invention to provide an improved constant volume
valve assembly, whose seals are not constantly wearing against a sealing surface.
[0012] It is a further object of the present invention to provide an improved constant volume
valve assembly that facilitates the movement of fuel even when fuel pressure drops,
such as when the tool is exposed to low temperatures.
[0013] It is a still further object of the present invention to provide an improved constant
volume valve assembly that provides the capability of adjusting the fuel mixture,
such as when the tool is operated at relatively high elevations.
SUMMARY OF THE INVENTION
[0014] These and other objects are met or exceeded by the present device for metering a
constant volume of fluid to provide constant energy to a tool. This apparatus is most
useful in a portable fastening tool powered either pneumatically or by an internal
combustion engine. In the preferred embodiment, configuration of the valves and control
mechanism also provides a delay between the closing of one valve and the opening of
another, ensuring that fluid is metered before moving downstream to the combustion
chamber.
[0015] More specifically, the present invention provides a variable volume metering chamber
and valve assembly for a combustion-powered tool includes a housing defining a metering
chamber having an internal volume and including an inlet and an outlet, and a plunger
configured for reciprocal movement relative to the chamber for adjusting the internal
volume of the metering chamber. The plunger is preferably adjustable by the user to
alter the volume of fuel retained in the metering chamber. In the housing, a first
valve controls control fluid flow through the inlet, a second valve controls fluid
flow through the outlet, and an actuator assembly, connected to the valves, is sequentially
operable from a first position, in which the first valve is open and the second valve
is closed, to a second position, in which the first and second valves are both closed,
and a third position, in which the first valve is closed and the second valve is open.
[0016] The present metering valve also produces a constant driving force by a fastener-driving
tool because it provides a consistent quantity and quality of fuel or hydraulic fluid
each time the tool is fired. The fluid supply to the power tool of this invention
is measured by volume, not by time, providing a more accurate and more consistent
supply of power to the tool. As pressure varies, the fluid density changes in either
system because the molecules become more or less densely packed. However, in a flow
system, flow rates will also change if the pressure drop across the metering valve
fluctuates. Change in flow rate will have no effect in a constant volume system as
long as the constant volume chamber is filled in the time the inlet valve to the metering
chamber is open.
[0017] Further, arrangement of the metering chamber and the spring-biased valves in the
present invention leads to compact use of space, as would be useful in a compact,
portable tool. Collinear placement of the valves and the oblique angle of the combustion
chamber passageway features a shorter distance from the pressurized fluid supply to
the combustion chamber, compared to other designs.
[0018] Using spring-biased valves to control fluid flow is also advantageous. The seat of
the valve that forms the seal with the inlet and outlet of the metering chamber is
in contact with the walls of the chamber only for a relatively short time. As the
valves open and close, there is no constantrubbing of the seals with adjacent walls.
This leads to longer life for the seals.
[0019] Another advantage of the present valve assembly is that a disk is preferably provided
to at least one of the spring-biased valves which facilitates the flow of fuel into
a combustion chamber passageway even in operational conditions when fuel flow is impaired,
as when outside operational temperatures fall below freezing.
[0020] Still another feature of the present valve assembly is that the actuator assembly
is configured to provide an inherent delay in the operation of the upper and lower
spring-biased valves to ensure that a designated volume of fuel will be retained in
the metering chamber before the lower valve releases the fuel to the combustion chamber.
In the preferred embodiment, this delay is achieved in part by a deliberately loose
mating engagement between a tongue of an actuator pivoting link arm and a notch in
an actuator control arm. This loose engagement ensures that, while the pivoting link
arm travels a continuous motion due to the engagement of the tool upon a workpiece,
the actuator control arm is not continuously moved, resulting in a slight "pause"
in the operation of the spring-biased valves. In this manner, the consistency of the
volume of fuel temporarily held in the metering chamber is maintained.
[0021] Yet another feature of the present valve assembly is that the valve features an adjustment
for changing the amount of fuel passed to the combustion chamber in each firing cycle.
This is accomplished by providing an adjustable shaft which can be threadably advanced
by the user into the fuel metering chamber to reduce the volume of the chamber, and
thus reduce the space available for incoming fuel. Thus, as more fuel or a richer
mixture is desired, the shaft is backed off away from the fuel metering chamber to
increase the chamber volume. A leaner fuel mixture is obtained by advancing the shaft
into the fuel metering chamber.
[0022] A still further feature of the present valve assembly is that the adjustable shaft
described above can be replaced by an electric heating element for use when the tool
is used in colder conditions of the type which induce lower fuel pressure. The heating
element heats either the fuel metering chamber itself or the surrounding portion of
the valve housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023]
FIG. 1 is a back view of the present constant volume valve assembly as attached to
a fuel canister;
FIG. 2 is a front vertical sectional view of the present constant volume valve assembly;
FIGS. 3A-3C are a series of fragmentary sectional views of the present constant volume
valve assembly depicting three valve positions as the actuator assembly moves through
an operational sequence;
FIG. 4 is a fragmentary sectional view of the present constant volume valve shown
equipped with a disk for facilitating the movement of fuel from the metering chamber
into the combustion chamber;
FIG. 5 is a fragmentary sectional view of an alternate embodiment of the present constant
volume valve showing the sealing connection between the valve and the interior nozzle
of a pressurized fuel cartridge;
FIG. 6 is a partial cross-section taken along the line 6-6 of FIG. 4 and in the direction
indicated generally, and depicts an alternate embodiment of the present valve assembly;
and
FIG. 7 is an alternate embodiment of the valve assembly depicted in FIG. 6, in which
the metering adjustment shaft is replaced with a heating element.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Referring to FIGs. 1 and 2, a constant volume valve assembly and metering chamber
is, generally designated 10. In the following description, the terms "upper" and "lower"
refer to the assembly in the orientation shown in the drawings. However, it is contemplated
that the present assembly may be used in a variety of positions as is well known in
the art. The present valve assembly 10 is particularly useful in a pneumatic or combustion
powered tool (not shown), having a valve housing 12 in which the fluid to be metered
is injected under pressure. The valve assembly 10 provides a fixed amount of fuel
to the combustion chamber (not shown) of the tool. Alternatively, it is contemplated
that the present valve assembly 10 may also meter pressurized air, which expands to
provide power, to the pneumatic tool. The present valve assembly 10 is usable in any
tool or device that would benefit from a steady, uniform supply of a pressurized fluid.
[0025] The housing 12 of the valve assembly 10 includes at least two spring-biased valves,
a first spring-biased valve 16 and a second spring-biased valve 18 that respectively
control the fluid flow to an inlet 20 and an outlet 22 of a metering chamber 24. The
metering chamber 24 is defined by the housing 12, and optionally has one or more ports
in addition to the inlet 20 and outlet 22, as will be discussed below. Neither the
shape of the metering chamber 24, nor the position of the inlet 20 or outlet 22 is
particularly important. However, it is preferable to place the inlet 20 and the outlet
22 at diametrically opposed ends of the metering chamber 24. In this configuration,
the spring-biased valves 16, 18 are preferably approximately axially collinear, conserving
space. In this preferred configuration, fluid flow through the metering chamber 24
will flow from the inlet 20 to the outlet 22, generally parallel to the axes of the
spring-biased valves 16, 18.
[0026] The metering chamber 24 may be any type of chamber capable of providing a constant
volume space for measurement of the fluid, meaning that the volume of fluid collected
in the metering chamber is equal to the volume of fluid released from the metering
chamber. While the fluid is sealed within the metering chamber 24, the pressure remains
constant. The metering chamber 24 may be a separate vessel or it may simply be a cavity
24 within the housing 12. The housing 12 will generally also be used to support other
components of the propulsion system, such as a pressurized fluid canister 28 (shown
in FIG. 1) and the spring-biased valves 16, 18. Preferably, the metering chamber 24
is stationary relative to the housing 12.
[0027] The volume of the metering chamber 24 while preferably fixed, is optionally adjustable
by, for example, placement of a movable wall or opening of valves to additional chambers
(not shown). However, its usefulness for metering purposes depends upon the ability
of the chamber 24 to remain at a constant volume until some setting, valve or adjustment
is purposely changed.
[0028] The spring-biased valves 16, 18 each include a preferably conical seat 30, 32, a
rod 34, 36, and a spring 38, 40, respectively. Although discussed in terms of the
first spring-biased valve 16, it is to be understood that the following description
also applies to the corresponding parts of the second spring-biased valve 18. The
seat 30 is sized and configured to sealingly engage with the inlet 20 of the metering
chamber 24 when the spring-biased valve 16 is in a closed position. Movement of the
seat 30 between an open position and the closed position, is controlled by the rod
34. Although the spring 38 is an economical method of biasing the valve, use of other
biasing devices is contemplated. The spring 38 is used to bias the valve 16 toward
the closed position. Each of the springs 38, 40 has an anchored end 42, 44 and a movable
end 46, 48, respectively. The movable end 46 exerts a force against the seat 30 tending
to move it in the direction of the metering chamber 24 by the force of the spring
40 pushing against the anchored end 42. Although the anchored end 42 may be anchored
directly to the housing 12, preferably, the anchored end is seated within a compartment
described in greater detail below.
[0029] Fluid is supplied to the housing 12 under pressure. It is generally desirable that
the tool is portable, and in such a case, the fluid is delivered from the pressurized
canister 28 that fits within or attaches to the tool. In the case where the tool is
to be used in a shop or other location where a large supply of pressurized fluid is
available, the fluid is preferably available to the tool through a hose or similar
device (not shown). The valve assembly 10 of the present invention is useful in either
of these situations, and use in either setting is contemplated. Since temperature
and pressure affects the density of any fluid, these factors should be kept as constant
as possible to minimize variation in the amount of fluid supplied.
[0030] Before entering the valve assembly 10, the fluid preferably flows through a filter
50 (FIG. 2) to minimize unwanted contaminants. The filter 50 is preferably disposed
at one end of a nipple 51, which matingly and sealingly engages the canister 28. After
passing the filter 50, the fuel travels into an upper passageway 52. The upper passageway
52 leads from the source of the pressurized fluid, such as the pressurized canister
28, to the inlet 20 of the metering chamber 24. To achieve the most consistent amount
of fluid, the upper passageway 52 is preferably sufficiently wide to consistently
achieve supply pressure before closure of the first spring-biased valve 16.
[0031] In some cases, it is desirable to provide an upper chamber 54 for accumulation of
pressurized fluid. Where, for example, the flow rate of the fluid is low, fluid accumulates
in the upper chamber 54, providing a burst of fluid to enter the metering chamber
24 when the inlet 20 is opened. Fluid released from the metering chamber 24 flows
into a lower chamber 56. Metering is accomplished through opening and closing of the
first and second spring-biased valves 16, 18 by an actuator assembly 60. The actuator
assembly 60 is any mechanism capable of causing the opening and closing of the first
and second spring-biased valves 16, 18 in a particular sequence to allow measurement
of the fluid in the metering chamber 24. While a mechanical linkage is the preferred
form of the actuator assembly 60, a computer controlling one or more cams is an example
of an acceptable alternative configuration.
[0032] In the preferred embodiment, the actuator assembly 60 includes a C-shaped actuator
arm with an upper arm 62, which is connected to the rod 34 of the first spring-biased
valve 16, and a lower arm 64, which is connected to the rod 36 of the second spring-biased
valve 18. The upper arm 62 and the lower arm 64 are connected to each other by a control
arm 66 (FIG. 1). A notch 67 in the control arm 66 is engaged by a pivoting link arm
68 which is pivotally engaged to the housing 12 at a point 68a. The specific engagement
between the link arm 68 and the notch 67 is via a tongue 69. The control link arm
68 is operated through movement of the nosepiece valve linkage (not shown), the construction
and operation of which is disclosed in the Nikolich patents incorporated by reference
here.
[0033] An important feature of the present actuator assembly 60 is that a delay is created
in the movement of the control arms 62, 64, 66 and their actuation of the upper and
lower spring-biased valves 16, 18 so that a constant volume of pressurized fluid is
momentarily retained in the metering chamber 24. This delay is created in part by
a loose mating engagement between the tongue 69 and the notch 67. In the preferred
embodiment, the tongue 69 is provided with a reduced area compared to the notch 67,
so that the control link arm 68 can move slightly along its arcuate travel path without
causing movement of the control arms 62, 64, and 66. The looseness or "sloppiness"
of the engagement between the tongue 69 and the notch 67 can vary with the application,
as can the specific configuration of the mating engagement, including having the notch
on the arm and the tongue on the control arm 66.
[0034] The actuator assembly 60 moves the first and second spring-biased valves 16, 18 in
either a first valve sequence or a second valve sequence, depending on which valve
is to be opened and which valve is to be closed. The valve sequence is determined
according to the combustion cycle, in the case of a combustion tool, or the impact
cycle of a pneumatic tool.
[0035] Turning now to FIGs. 3A-3C, the valve sequences are described. The beginning of the
first valve sequence is defined when the tool is in between uses. In this position,
the tool is powered up and ready to be used, but is not yet in contact with the workpiece
into which a fastener is to be driven. At this time, the actuator assembly 60 is in
the first position as depicted in FIG. 3A, the arm 62 is spaced a maximum distance
from an opposing wall of the housing 12. The first spring-biased valve 16 is in an
open position and the second spring-biased valve 18 is closed. The metering chamber
24 is thus filled with fuel or fluid due to communication with the cartridge 28 through
the passageway 52.
[0036] During the first valve sequence, the first spring-biased valve 16 moves from an open
position to a closed position and the second spring-biased valve 18 opens, but the
second valve does not begin to open until first valve is completely closed. This first
valve sequence will generally be triggered by some stimulus in preparation for firing
of the tool. To have power to drive a fastener, the metered fluid is moved into position
to deliver that power, i.e., fuel is moved into the combustion chamber or air into
an expanding cylinder. The sequence is preferably initiated by any preparatory mechanism,
such as contact of the tool with a workpiece, beginning to squeeze the trigger mechanism
and the like. If a combustion powered framing tool is used, priming of the combustion
chamber preferably takes place when a workpiece contact element comes in contact with
the workpiece, allowing the fuel to flow from the metering chamber 24, through the
lower chamber 56, into a combustion chamber passageway 70 and ultimately to the combustion
chamber (not shown). In the depicted and preferred embodiment, the sequence is initiated
by contacting the tool with a workpiece, which causes the pivoting link arm 68 to
begin its arcuate path of travel represented by the arrow A (FIG. 1).
[0037] It is important to note that the metering chamber 24 is used solely for measurement
of the fluid, and that there are no physical or chemical changes to the fluid while
it is sealed in the chamber. To provide constant power, the fluid is preferably delivered
at the same volume, temperature and pressure for each cycle. Fluids cannot be accurately
measured while chemical or physical reactions are taking place, thus it is preferred
that the fluid have the same chemical composition when it is released from the metering
chamber 24 as when it entered the metering chamber.
[0038] Referring now to FIG. 3A, which corresponds to the first position in the preferred
embodiment shown, in this position, fluid freely enters the metering chamber 24. As
the pivoting link arm 68 moves in an arc defined by the arrow A (FIG. 1), the tongue
67 moves in a reverse arcuate direction. As such, the former upward pressure exerted
upon the first rod 34 by the upper arm 62 is released, allowing the spring 38 to bias
the first seat 30 of the first valve 16 into engagement with the inlet 20 of the metering
chamber 24.
[0039] At this point, both spring-biased valves 16, 18 are closed, preventing flow of the
fluid from the fluid supply canister 28 into and out of the metering chamber 24. This
position is depicted in FIG. 3B, and corresponds to the second position of the actuator
assembly 60. The metering chamber 24 is closed at both the inlet 20 and the outlet
22, sealing the fluid within it and providing a measured volume of fluid within the
chamber.
[0040] The loose mating engagement between the tongue 69 and the notch 67 described above
results in a temporary delay in the opening of the second valve 18 while the pivoting
link arm 68 continues its arcuate path defined by the arrow A (FIG. 1). Due to the
loose engagement, as the pivoting link arm 68 moves, there is a delay while the upward
bias opening the first valve 16 is released, and the control arm 66 has not been moved
sufficiently to open the second valve 18. This delay ensures that the volume of fuel
in the metering chamber 24 will remain constant, and that unwanted additional amounts
cannot enter the chamber, or that premature leakage from the outlet 22 into the lower
chamber 56 cannot occur.
[0041] The third position of the actuator assembly 60 is shown in FIG. 3C, which is attained
after the first valve 16 has completely closed and the second spring-biased valve
18 is opened. In this position, the fluid is released from the metering chamber 24.
In the preferred embodiment, the entire first valve sequence takes place as the actuator
arm 60 moves continuously from the first position through the second position to the
third position.
[0042] Following firing of the tool 12, the second valve sequence is initiated, in which
the lifting of the tool from the workpiece causes the pivoting linking arm 68 to move
the actuator assembly 60 from the third position, through the second position, to
the first position. This sequence closes off the outlet 22 of the metering chamber
24 from flow downstream, and reopens the inlet 20 to again allow flow of fluid into
the metering chamber 24. Any stimulus that follows firing of the tool 12 but precedes
the first valve sequence may be used to start this sequence.
[0043] The second valve sequence moves the first and second spring-biased valves through
the same steps as the first valve sequence, but in the reverse order. Starting with
the third actuator assembly 60 position shown in FIG. 3C, the second spring-biased
valve 18 is disengaged from the outlet 22, preventing flow of the fluid from the metering
chamber 24. After the second valve 18 is completely closed, the second actuator assembly
60 position is obtained, as shown in FIG. 3B. Here both valves 16, 18 are closed to
prevent backflow of the fluid, and the metering chamber 24 contains only a residual
amount of fluid. Finally, the first spring-biased valve 16 is disengaged from the
inlet 20, allowing free flow of the fluid from the fluid supply 28 into the metering
chamber 24, but that fluid is prevented from flowing freely from the pressurized fluid
supply 28 through the inlet 20 and the outlet 22 of the metering chamber 24 to the
combustion chamber passageway 70.
[0044] In the preferred embodiment, this operation or valve sequence is controlled by the
pivoting action of the link arm 68 which moves the actuator assembly 60 from a position
where the upper arm 62 has a maximum spacing from the housing 12 (FIG 3A), to a position
where the lower arm 64 has a maximum spacing from the housing 12 (FIG 3C). In the
preferred embodiment, in addition to the loose mating engagement between the notch
67 and the tongue 69, the actuator assembly 60 also includes a delay mechanism also
operating between the closing of one of the valves 16, 18 and the closing of the other
valve 18, 16. Any type of delay mechanism is suitable, such as an electrical delay,
electronic means of a mechanical delay mechanism. In the most preferred mechanical
delay mechanism, the actuator assembly 60 is slidably connected to each of the rods
34, 36. The first rod 34 has a first opener 71 such as a 'C'-clip secured to the rod
34 and the second rod 36 has a second opener 72. Spacing of the openers 71, 72 on
the rods 34, 36 are preferably used to create a delay in the closing of one valve
16, 18 before the opening of the other valve 18, 16.
[0045] In the preferred delaying mechanism, the control arm 66 of the actuator assembly
60 is longer than the housing 26 in which the valve assembly resides. The excess length
is sufficient to allow the upper arm 62 and the lower arm 64 to sandwich the housing
12 between them with excess space between the housing, and the actuator arms 62, 64.
In response to the stimulus that triggers the valve sequences, the control arm 66
moves up and down (directions relate to the tool, as oriented in FIG. 3).
[0046] Referring now to FIG. 3A, as the actuator assembly 60 moves through the first valve
sequence, the upper arm 62 begins in contact with the first opener 71. As the control
arm 66 moves downward, release or expansion of the first spring 38 holds the first
opener 71 against the upper arm 62 until the first seat 30 comes into contact with
the inlet 20 of the metering chamber, closing the first spring-biased valve. Once
the control arm 66 moves sufficiently so that the upper arm 62 is disengaged from
the first opener 71 (as shown in FIG. 3B), the first spring 3 8 biases the valve 16
into the closed position. During this movement from the first position (FIG. 3A) to
the second position (FIG. 3B) of the control arm 66, the lower arm 64 has slid along
the second rod 36, partially, but not totally decompressing the second spring 40.
Next, in moving from the second position (FIG. 3B) to the third position (FIG. 3 C)
of the control arm 66, the lower arm 64 slides along the second rod 36 and finally
contacts the second opener 72, compressing the second spring 40, and opening the second
spring-biased valve 18. The second valve sequence similarly reverses the above steps,
introducing a delay between the closing of the second spring-biased valve 18 and the
opening of the first spring-biased valve 16.
[0047] Seals are used where suitable to prevent flow of the fluid into the area outside
the valve assembly 10, the metering chamber 24, and the housing 12. The exact number,
shape and placement of such seals depend on the exact configuration of the valve assembly
10 for a specific application. In the preferred embodiment shown, a removable insert
74 is optionally used to surround the rod 34, 36 of each of the spring-biased valves
16, 18 as the rod passes through the housing 26 and contacts actuator assembly 60.
O-rings 76, gaskets or similar devices, are preferably used to prevent leakage between
the removable insert 74 and the housing 12 or the rods 34, 36. In some applications,
it will be preferable for the length of the spring 38, 40 to exceed the dimensions
of the upper chamber 54 or the lower chamber 56. When this is desirable, the removable
insert 74 includes a hollow compartment 78 that is sized and configured to receive
a portion of the length of the spring 38, 40, and to receive the anchored end 42.
The removable insert 74 also provides easy access to the spring-biased valves 16,
18 and their component parts when replacements are installed.
[0048] Referring now to FIG. 4, it is preferred that the present valve assembly 10 be provided
with a mechanism for facilitating the movement or evacuation of fuel from the metering
chamber 24 through the outlet 22 and ultimately into the passageway 70 leading to
the combustion chamber. As described above, it has been found that when combustion-powered
tools of this type are operated at cold temperatures, such as below 32° F, the fuel
pressure drops and it becomes more difficult to move the fuel into the combustion
chamber. To address this problem, the present valve assembly 10 is preferably provided
with a disk 80 secured to the valve 18, specifically at the end of the rod 36 disposed
in the metering chamber 24. The disk 80 is preferably located closer to the inlet
20 when the valve 18 is closed. To that end, the disk 80 is secured to a pedestal
82 which in turn is secured to the conical seat 32. In the preferred embodiment, the
disk 80 is made of brass or equivalent rigid, heat resistant material, and the pedestal
82 is made of rubber or similar resilient polymeric or plastic material. However,
other materials are contemplated. Preferably, the disk 80 is friction fit to the pedestal
82 through a frictional mating engagement between a lug 84 on the pedestal and an
axial bore 86 in the disk. However, other ways of fastening the disk 80 to the pedestal
82 are contemplated, including butnot limited to ultrasonic welding, insert molding,
adhesives or other mechanical fasteners. The disk 80 is dimensioned to have a diameter
which approximates, but is less than the diameter of the metering chamber 24.
[0049] In operation, as the valve 18 opens, as described above in relation to FIG. 3C, the
disk 80 moves with the seat 32 from its rest position near the inlet 20 of the metering
chamber 24, (best seen in FIG. 4) to a location closer to the outlet 22. This movement
will push any residual fuel from the metering chamber 24 through the outlet 22 and
ultimately into the passageway 70 leading to the combustion chamber. In this manner,
the fuel is mechanically moved from the metering chamber 24. However, since the problem
of low fuel pressure is temperature-related, an alternate solution would be to provide
a supplemental exhaust passageway 88 through which hot exhaust from the combustion
chamber heats up the metering chamber during operation of the tool. An equivalent
arrangement is the provision of an electric heating element powered by a resistor
or other known arrangement which maintains a satisfactory temperature in the metering
chamber 24 to maintain fuel pressure.
[0050] Referring now to FIG. 5, the connection between the valve 10 and the fuel canister
28 is shown in greater detail. It is important that a sealing relationship be established
between the valve 10 and the fuel canister 28 to prevent loss of fuel, as well as
avoid unwanted combustion. The fuel canister 28 is provided with an internal stem
90 which defines an outlet for the fuel contained in the canister under pressure,
as is known in the art. As is well known in the art, and exemplified by
U.S. Patent No. 5,115,944 which is incorporated by reference, the stem 90 is secured to, and is circumscribed
by an endcap 92 which encloses the end of the canister 28 and forms a rolled seam
94 thereover.
[0051] An adapter 96 frictionally engages the endcap 92 and circumscribes and protects the
projecting stem 90. An axial passageway 98 is defined by the adapter 96 and accommodates
the stem 90. In the preferred embodiment, the adapter also includes a frangible end
membrane 100 which blocks the passageway 98, and provides a visible indication of
whether or not the canister 28 has been used. The membrane 100 is configured to be
pierced upon mating engagement with the nipple 51. Accordingly, the passageway 98
is dimensioned for accommodating the nipple 51.
[0052] By the same token, the nipple 51 is preferably generally cylindrical in shape, and
has a diameter or cross-sectional parameter dimensioned to slidably and matingly engage
the passageway 98, and a length dimensioned to engage an end 102 of the stem 90 to
effect fluid communication between the canister 28 and the valve 10. In the preferred
embodiment, the nipple 51 is cylindrical, however, other non-circular cross-sectional
shapes are contemplated depending on the application, and including oval, square,
rectangular and polygonal shapes.
[0053] In the preferred embodiment, the nipple 51 and the stem 90 are configured so that,
upon operational engagement as depicted in FIG. 5, a sealing relationship is achieved.
This relationship, designed to prevent unwanted loss of fuel, may be achieved through
frictional contact between the end 102 of the stem 90 and an end 104 of the nipple
51. However, it is preferred that some sort of sealing formation be provided to at
least one of the nipple 51 and the stem 90. In the preferred embodiment, the sealing
formation is a resilient O-ring 106 provided to the nipple 51. However, other known
types of sealing formations are contemplated, including but not limited to ring seals,
molded seals and flat washers.
[0054] Also, the present nipple end 104 defines a chamber 108 for receiving or capturing
a resilient sealing member such as the O-ring 106. More specifically, the end 104
is tapered or chamfered for both retaining the O-ring 106 and also for facilitating
insertion of the nipple 51 into the adapter passageway 98. The tapered end 104 more
easily pierces the membrane 100, especially when the nipple 51 is fabricated of metal
such as brass, which is preferred, however other suitably rigid and durable materials
are contemplated.
[0055] To further enhance the sealed relationship of the engaged nipple 51 and the stem
90, the end 102 of the stem is configured for matingly engaging or accommodating the
O-ring 106. As such, the end 102 is preferably provided with an annular groove 110.
Naturally, it is contemplated that the O-ring 106 or other resilient sealing member
may be alternately mounted to the stem 90, or that it may be attached to the nipple
end 104 by adhesive, in a groove (not shown) or other known type of O-ring attachment
technology.
[0056] It is also contemplated that, depending on the application, if fluid communication
with the canister 28 is required for any reason, a connector may be provided in the
form of the nipple 51 which, at the end opposite to the end 104, is in fluid communication
with a fluid container or reservoir as desired.
[0057] In use, the canister 28 is inserted into the combustion tool so that the nipple 51
matingly engages the adapter 96. The canister 28 is pressed upon the nipple 51 so
that the membrane 100 is pierced and the nipple end 104 enters the passageway 98 until
contact is made with the stem end 102. As described above, as sealing relationship
is preferably obtained, and it is contemplated that other locking apparatus may be
employed to secure the canister 28 in this position.
[0058] Thus, it will be seen by those skilled in the art that the present valve assembly
and metering changer provide a simple method of providing a constant volume of fluid
to a power fastening tool. The two spring-biased valves 16, 18 control the inlet and
the outlet to the constant volume metering chamber 24, measuring a constant amount
of fluid, independent of in fluctuations in the fluid flow rate. The actuator assembly
60 manipulates opening and closing of the valves 16, 18, receiving the fluid from
the pressurized source 28 and metering it before it flows downstream to a combustion
or expansion chamber. This arrangement of the valves 16, 18 minimizes wear on the
seals, reducing maintenance.
[0059] Referring now to FIG. 6, an alternate embodiment of the present valve assembly is
generally designated 120. Shared components ofthe assemblies 10 and 120 are identified
with identical reference numbers. The main difference between the assemblies 10 and
120 is that the valve assembly 120 includes a mechanism for varying the volume of
the fuel metering chamber 24, so that the user can selectively adjust the volume of
fuel sent by the valve assembly to the combustion chamber of the tool. This adjustability
is especially useful when the tool is used at higher altitudes or elevations, where
the air is thinner and less fuel is needed for efficient combustion.
[0060] In the preferred embodiment, the mechanism for varying the volume of the fuel metering
chamber is a dosage plunger 122, referred to here as a plunger, which is an elongate
member oriented to linearly reciprocate relative to the metering chamber 24. It is
preferred that the plunger reciprocates along a longitudinal axis which is generally
normal to an axis of operation defined by the valves 16, 18.
[0061] The plunger 122 is contemplated as having any configuration which can withstand the
operational environment of the combustion tool, and take up space in the metering
chamber 24 which would otherwise be taken up by fuel. In the preferred embodiment,
the plunger 122 is an elongate metal shaft or rod, having a valve end 124 and an adjustment
end 126. As stated previously, the valve end 124 is configured for reducing the volume
of the metering chamber 24 by taking up a certain amount of space otherwise occupied
by fuel prior to each firing cycle of the tool. As depicted here, the valve end 124
is generally cylindrical in shape with a truncated end, however the end is alternately
contemplated as having a complementary shape to a wall 128 of the metering chamber
24.
[0062] Opposite the valve end 124, the adjustment end 126 is configured for selective manipulation,
here axial rotation, which is accomplished in the preferred embodiment by a screwdriver
slot 130. Any conventional shape of driver slot is considered suitable, including
but not limited to slotted, Phillips, Tor-x, etc., as well as hex-shaped for an Allen
wrench or a conventional socket. Custom-made adjustment configurations are also contemplated
for use in applications where only certain qualified service personnel are permitted
to adjust the tool.
[0063] Between the valve end 124 and the adjustment end 126, the plunger 122 is preferably
provided with threads so that the axial reciprocation of the valve end 124 into and
out of the metering chamber 24 may be positively controlled. Any equivalent structure
for achieving this goal is also contemplated. Also, the plunger 122 is provided with
a sufficient length so that adjustment can be made externally of the valve housing
12.
[0064] A sleeve 132 is configured for mounting in operational relationship to the valve
housing 12 and reciprocally accommodates the plunger 122. More specifically, the sleeve
132 circumscribes and thus supports the plunger 122, and is fixed to the housing 12,
preferably by being press-fit into a bore 134. The bore 134 is in communication with
the metering chamber 24. Other ways to fix the sleeve 132 to the housing 12 are contemplated,
including welding, chemical adhesives and the like. The sleeve 132 is provided with
a central, axial throughbore 136 which is in communication with the metering chamber
24 and which is dimensioned to accommodate the plunger 122. To adequately support
the plunger 122, the sleeve 132 has a sufficient length, which extends generally normally
to the valve housing 12. However, the plunger 122 is preferably longer than the sleeve
132. An outer end 138 of the sleeve 132 is preferably threaded to engage threads 140
of the plunger 122. The specific location of the corresponding threaded portions of
the plunger 122 and the sleeve 132 may vary to suit the application.
[0065] Since the bore 134, as well as the throughbore 136, are in fluid communication with
the metering chamber 24, it is important that they be sealed to prevent the unwanted
leakage of fuel. Accordingly, the sleeve 132 is preferably provided with a seal 142
in the form of an O-ring located in a suitably-dimensioned O-ring groove 144. Depending
on the application, the groove 144 may be positioned either on the sleeve 132 or in
the bore 134. In addition, a plunger seal 146, also preferably an O-ring, seals the
throughbore 136 and is disposed in a groove 148, either in the throughbore 136 or
the plunger 122.
[0066] So that the operation of the valves 16, 18 is not impaired, it is preferred that
the plunger 122 be disposed in the metering chamber in an offset position. In other
words, the longitudinal axis of the plunger 122 is offset from a vertical plane bisecting
the metering chamber 24 in the direction of reciprocal movement of the plunger. Practically
speaking, and referring now to FIG. 6, the plunger 122 is located behind the axis
of movement of the valves 16, 18.
[0067] Referring now to FIG. 7, another feature of the present system 120 is that the plunger
122 or the sleeve 132 is heated so that the tool can be used in relatively low temperatures
(below 32°F) when the fuel pressure decreases as described above. The heat can be
provided electrically by connecting live leads 150 powered by the battery (not shown)
of the tool.
[0068] Alternately, replacing the plunger 122 with a stationary heating element 152 can
provide heat. The heating element 152 may be reciprocated within the sleeve 132 through
a friction fit, and is also contemplated as being connectable to the battery as is
well known in the art. As described above in relation to the supplemental exhaust
passageway 88 (FIG. 4), additional heat can be provided from the combustion chamber.
[0069] While a particular embodiment of the constant volume valve assembly and metering
chamber has been shown and described, it will be appreciated by those skilled in the
art that changes and modifications may be made thereto without departing from the
invention in its broader aspects and as set forth in the following claims.
1. A constant volume metering chamber and valve assembly (10) for use with a pressurized
fluid supply containing a fluid in a combustion-powered tool, said assembly comprising:
a housing (12) defining a metering chamber (24) having a plurality of ports including
an inlet (20) and an outlet (22);
a first spring-biased valve (16) disposed in said housing to control fluid flow through
said inlet (20);
a second spring-biased valve (18) disposed in said housing to control fluid flow through
said outler (22);
an actuator assembly (60), connected to said first and second spring-biased valves
(16, 18) and sequentially operable from a first position, in which said first spring-biased
valve (16) is open and said second spring-biased valve (18) is closed, to a second
position, in which said first and second spring-biased valves (16, 18) are both closed,
and a third position, in which said first spring-biased valve (16) is closed and said
second spring-biased valve (18) is open; and
said valve assembly being configured and arranged so that a volume of fluid entering
said chamber (24) from said inlet (20) in said first position is collected in said
metering chamber (24), sealed within said metering chamber (24) in said second position,
and released from said metering chamber (24) in said third position to provide a constant
volume of fluid for each sequential movement of said actuator (60) from said first
position to said third position, characterized in that the valve assembly is further comprising a delay mechanism (67, 69) configured for
causing a delay between the closing of one of said first or second spring-biased valves
and the opening of the other of said first or second spring-biased valves.
2. The valve assembly of claim 1, wherein said actuator assembly (60) is operable from
said third position, in which said first spring-biased valve (16) is closed and said
second spring-biased valve (18) is open to said second position, in which said first
and second spring-biased valves (16, 18) are both closed, to said first position,
in which said first spring-biased valve (16) is open and said second spring-biased
valve (18) is closed, such that, after a volume of fluid is released from said metering
chamber in said third position to provide a constant volume of fluid, said metering
chamber (24) is sealed to prevent backflow of said fluid in said second position,
and said metering chamber (24) is refilled with a volume of fluid in said first position
for each sequential movement of said actuator from said third position to said first
position.
3. The valve assembly of claim 1, wherein said metering chamber (24) is configured and
arranged so that volume of fluid collected equals the volume of fluid released from
said metering chamber.
4. The valve assembly of claim 1, wherein said metering chamber (24) is provided with
a device (80) for facilitating the evacuation of fuel from said chamber.
5. The valve assembly of claim 1, wherein each of said first and second spring-biased
valves (16, 18) include a biased tod (34, 36), and said actuator assembly is slidably
connected to each of said rods between said housing and an opener (71, 72), said opener
being positioned on said rod such that the delay is caused due to slideable movement
of said actuator assembly between said opener of one of said spring-biased valves
and said opener of the other one of said spring-biased valves.
6. The valve assembly of claim 1, wherein said actuator assembly (60) includes a control
arm (66) configured for actuating said first and second spring-biased valves, and
a pivoting link arm (68) configured to engage said control arm (66) to cause said
actuation, said arms being configured to have a loose mating engagement (67, 69) for
causing said delay.
7. The valve assembly of claim 1, further including means (122) for adjusting the internal
volume of said metering chamber (24).
8. The valve assembly of claim 7, wherein said means for adjusting includes a plunger
(122) configured for adjustable reciprocation relative to said metering chamber (24).
9. The valve assembly of claim 1, further including a heater provided in operational
relationship to said housing (12) for heating said metering chamber (24).
10. A variable volume metering chamber and valve assembly for use with a combustion-powered
tool, said assembly comprising:
a housing (12) defining a metering chamber (24) having an internal volume and including
an inlet (20) and an outlet (22), and
means (122) for adjusting the internal volume of said metering chamber (24), characterised in that said means is comprising an adjustable shaft configured to be threadably advanced
by an user into said metering chamber to reduce said internal volume.
1. Konstantvolumendosierkammer- und -ventileinheit (10) zur Verwendung mit einer unter
Druck stehenden Fluidzufuhr, die ein Fluid in einem verbrennungskraftbetriebenen Werkzeug
enthält, wobei die Einheit Folgendes umfasst:
ein Gehäuse (12), das eine Dosierkammer (24) mit mehreren Öffnungen und mit einem
Einlass (20) und einem Auslass (22) definiert;
ein erstes federvorgespanntes Ventil (16), das sich im Gehäuse befindet, um den Fluidstrom
durch den Einlass (20) zu kontrollieren;
ein zweites federvorgespanntes Ventil (18), das sich im Gehäuse befindet, um den Fluidstrom
durch den Auslass (22) zu kontrollieren;
eine Betätigereinheit (60), die mit dem ersten und dem zweiten federvorgespannten
Ventil (16, 18) verbunden ist und sequentiell von einer ersten Position, in der das
erste federvorgespannte Ventil (16) offen und das zweite federvorgespannte Ventil
(18) geschlossen ist, zu einer zweiten Position, in der sowohl das erste als auch
das zweite federvorgespannte Ventil (16, 18) geschlossen ist, und hin zu einer dritten
Position betätigt werden kann, in der das erste federvorgespannte Ventil (16) geschlossen
und das zweite federvorgespannte Ventil (18) offen ist; und
wobei die Ventileinheit so konfiguriert und angeordnet ist, dass ein Volumen des Fluids,
das vom Einlass (20) in der ersten Position in die Kammer (24) eintritt, in der Dosierkammer
(24) gesammelt, in der zweiten Position innerhalb der Dosierkammer (24) abgeschlossen
gehalten und in der dritten Position aus der Dosierkammer (24) freigegeben wird, um
für jede sequentielle Bewegung des Betätigers (60) aus der ersten Position hin zur
dritten Position ein konstantes Fluidvolumen bereitzustellen, dadurch gekennzeichnet, dass die Ventileinheit weiterhin einen Verzögerungsmechanismus (67, 69) umfasst, der so
konfiguriert ist, dass er eine Verzögerung zwischen dem Schließen des einen der ersten
oder der zweiten federvorgespannten Ventile und dem Öffnen des anderen der ersten
oder der zweiten federvorgespannten Ventile bewirkt.
2. Ventileinheit nach Anspruch 1, bei der die Betätigereinheit (60) von der dritten Position,
in der das erste federvorgespannte Ventil (16) geschlossen und das zweite federvorgespannte
Ventil (18) offen ist, zur zweiten Position, in der sowohl das erste als auch das
zweite federvorgespannte Ventil (16, 18) geschlossen ist, hin zur ersten Position,
in der das erste federvorgespannte Ventil (16) offen und das zweite federvorgespannte
Ventil (18) geschlossen ist, so betätigt werden kann, dass, nachdem ein Fluidvolumen
in der dritten Position aus der Dosierkammer freigegeben wurde, um ein konstantes
Fluidvolumen bereitzustellen, die Dosierkammer (24) abgeschlossen bleibt, um einen
Rückfluss des Fluids in der zweiten Position zu verhindern, und dass die Dosierkammer
(24) in der ersten Position für jede sequentielle Bewegung des Betätigers von der
dritten Position zur ersten Position mit einem Fluidvolumen aufgefüllt wird.
3. Ventileinheit nach Anspruch 1, bei der die Dosierkammer (24) so konfiguriert und angeordnet
ist, dass das Volumen des gesammelten Fluids dem Volumen des aus der Dosierkammer
freigegebenen Fluids entspricht.
4. Ventileinheit nach Anspruch 1, bei der die Dosierkammer (24) mit einer Vorrichtung
(80) ausgestattet ist, um ein Ablassen von Kraftstoff aus der Kammer zu ermöglichen.
5. Ventileinheit nach Anspruch 1, bei der jedes der ersten und der zweiten federvorgespannten
Ventile (16, 18) eine vorgespannte Stange (34, 36) beinhaltet, und wobei die Betätigereinheit
in gleitender Ausführung mit jeder der Stangen zwischen dem Gehäuse und einem Öffner
(71, 72) verbunden ist, wobei der Öffner so an der Stange positioniert ist, dass die
Verzögerung aufgrund einer Gleitbewegung der Betätigereinheit zwischen dem Öffner
des einen der federvorgespannten Ventile und dem Öffner des anderen der federvorgespannten
Ventile bewirkt wird.
6. Ventileinheit nach Anspruch 1, bei der die Betätigereinheit (60) einen Steuerarm (66),
der so konfiguriert ist, dass er die ersten und die zweiten federvorgespannten Ventile
betätigt, sowie einen Schwenkverbindungsarm (68) beinhaltet, der so konfiguriert ist,
dass er in den Steuerarm (66) eingreift, um die Betätigung zu bewirken, wobei die
Arme für einen losen Gegeneingriff (67, 69) konfiguriert sind, um die Verzögerung
zu bewirken.
7. Ventileinheit nach Anspruch 1, die weiterhin ein Mittel (122) beinhaltet, um das interne
Volumen der Dosierkammer (24) einzustellen.
8. Ventileinheit nach Anspruch 7, bei der das Mittel zum Einstellen einen Kolben (122)
beinhaltet, der für eine einstellbare Hinundherbewegung im Verhältnis zur Dosierkammer
(24) konfiguriert ist.
9. Ventileinheit nach Anspruch 1, die weiterhin einen Erwärmer beinhaltet, der in einem
Funktionsverhältnis zum Gehäuse (12) vorgesehen ist, um die Dosierkammer (24) zu erwärmen.
10. Dosierkammer- und -ventileinheit mit verstellbarem Volumen zur Verwendung mit einem
verbrennungskraftbetriebenen Werkzeug, wobei die Einheit Folgendes umfasst:
ein Gehäuse (12), das eine Dosierkammer (24) definiert, die ein internes Volumen hat
sowie einen Einlass (20) und einen Auslass (22) beinhaltet, und
ein Mittel (122) zum Einstellen des internen Volumens der Dosierkammer (24), dadurch gekennzeichnet, dass das Mittel eine einstellbare Welle umfasst, die so konfiguriert ist, dass sie von
einem Benutzer über ein Gewinde hinein in die Dosierkammer geschraubt werden kann,
um das interne Volumen zu verringern.
1. Ensemble (10) de soupape et de chambre de dosage à volume constant destiné à l'utilisation
avec une alimentation en fluide sous pression contenant un fluide dans un outil entraîné
par combustion, ledit ensemble comprenant :
un boîtier (12) définissant une chambre de dosage (24) ayant une pluralité d'orifices
comportant une entrée (20) et une sortie (22) ;
une première soupape précontrainte par ressort (16) disposée dans ledit boîtier de
manière à réguler l'écoulement de fluide à travers ladite entrée (20) ;
une deuxième soupape précontrainte par ressort (18) disposée dans ledit boîtier de
manière à réguler l'écoulement de fluide à travers ladite sortie (22) ;
un ensemble d'actionneur (60), connecté auxdites première et deuxième soupapes précontraintes
par ressort (16, 18) et pouvant fonctionner séquentiellement depuis une première position
dans laquelle ladite première soupape précontrainte par ressort (16) est ouverte et
ladite deuxième soupape précontrainte par ressort (18) est fermée, dans une deuxième
position dans laquelle lesdites première et deuxième soupapes précontraintes par ressort
(16, 18) sont toutes les deux fermées, et une troisième position, dans laquelle ladite
première soupape précontrainte par ressort (16) est fermée et ladite deuxième soupape
précontrainte par ressort (18) est ouverte ; et
ledit ensemble de soupape étant configuré et prévu de telle sorte qu'un volume de
fluide entrant dans ladite chambre (24) depuis ladite entrée (20) dans ladite première
position soit recueilli dans ladite chambre de dosage (24), scellé à l'intérieur de
ladite chambre de dosage (24) dans ladite deuxième position, et libéré de ladite chambre
de dosage (24) dans ladite troisième position pour fournir un volume constant de fluide
pour chaque mouvement séquentiel dudit actionneur (60) de ladite première position
jusqu'à ladite troisième position, caractérisé en ce que l'ensemble de soupape comprend en outre un mécanisme de retardement (67, 69) configuré
pour créer un retard entre la fermeture de l'une desdites première ou deuxième soupapes
précontraintes par ressort et l'ouverture de l'autre desdites première ou deuxième
soupapes précontraintes à ressort.
2. Ensemble de soupape selon la revendication 1, dans lequel ledit ensemble d'actionneur
(60) peut fonctionner depuis ladite troisième position, dans laquelle ladite première
soupape précontrainte par ressort (16) est fermée et ladite deuxième soupape précontrainte
par ressort (18) est ouverte, dans ladite deuxième position, dans laquelle lesdites
première et deuxième soupapes précontraintes par ressort (16, 18) sont toutes les
deux fermées, jusqu'à ladite première position dans laquelle ladite première soupape
précontrainte par ressort (16) est ouverte et ladite deuxième soupape précontrainte
par ressort (18) est fermée, de telle sorte qu'après la libération d'un volume de
fluide depuis ladite chambre de dosage dans ladite troisième position pour fournir
un volume constant de fluide, ladite chambre de dosage (24) soit scellée de manière
à empêcher un retour de l'écoulement dudit fluide dans ladite deuxième position, et
ladite chambre de dosage (24) soit remplie à nouveau avec un volume de fluide dans
ladite première position pour chaque mouvement séquentiel dudit actionneur depuis
ladite troisième position dans ladite première position.
3. Ensemble de soupape selon la revendication 1, dans lequel ladite chambre de dosage
(24) est configurée et disposée de telle sorte que le volume de fluide recueilli soit
égal au volume de fluide libéré depuis ladite chambre de dosage.
4. Ensemble de soupape selon la revendication 1, dans lequel ladite chambre de dosage
(24) est pourvue d'un dispositif (80) destiné à faciliter l'évacuation de combustible
depuis ladite chambre.
5. Ensemble de soupape selon la revendication 1, dans lequel chacune desdites première
et deuxième soupapes précontraintes par ressort (16, 18) comporte une tige précontrainte
(34, 36) et ledit ensemble d'actionneur est connecté de manière coulissante à chacune
desdites tiges entre ledit boîtier et un dispositif d'ouverture (71, 72), ledit dispositif
d'ouverture étant positionné sur ladite tige de telle sorte que le retard soit dû
au mouvement de coulissement dudit ensemble d'actionneur entre ledit dispositif d'ouverture
de l'une desdites soupapes précontraintes par ressort et ledit dispositif d'ouverture
de l'autre desdites soupapes précontraintes par ressort.
6. Ensemble de soupape selon la revendication 1, dans lequel ledit ensemble d'actionneur
(60) comporte un bras de commande (66) configuré de manière à actionner lesdites première
et deuxième soupapes précontraintes par ressort, et un bras de liaison pivotant (68)
configuré pour s'engager avec ledit bras de commande (66) afin de causer ledit actionnement,
lesdits bras étant configurés de manière à avoir un engagement d'accouplement lâche
(67, 69) pour provoquer ledit retard.
7. Ensemble de soupape selon la revendication 1, comportant en outre un moyen (122) pour
ajuster le volume interne de ladite chambre de dosage (24).
8. Ensemble de soupape selon la revendication 7, dans lequel ledit moyen d'ajustement
comporte un plongeur (122) configuré de manière à effectuer un mouvement alternatif
ajustable par rapport à ladite chambre de dosage (24).
9. Ensemble de soupape selon la revendication 1, comportant en outre un dispositif de
chauffage prévu en relation fonctionnelle avec ledit boîtier (12) pour chauffer ladite
chambre de dosage (24).
10. Ensemble de soupape et de chambre de dosage à volume variable destiné à l'utilisation
avec un outil entraîné par combustion, ledit ensemble comprenant :
un boîtier (12) définissant une chambre de dosage (24) ayant un volume interne et
comportant une entrée (20) et une sortie (22), et
un moyen (122) pour ajuster le volume interne de ladite chambre de dosage (24), caractérisé en ce que ledit moyen comprend une tige ajustable configurée de manière à être avancée par
filetage par un utilisateur dans ladite chambre de dosage pour réduire ledit volume
interne.