BACKGROUND OF THE INVENTION
[0001] The present invention relates to fluid engines and, more particularly, to pneumatic
engines adapted for use in toys such as aeroplanes and wheeled vehicles, including
toy cars, trucks and trains. The invention is, particularly, directed to a piston-operated
pneumatic engine. One prior art relative thereto is that of U. S. Patent No.
4,329,806 (1982) to Akiyama, entitled Fluid Engine, and the engine of an unpatented compressed air operated model
aeroplane sold in the United Kingdom in or about 1990 known as the Jonathan, utilizing
a so-called Z- model engine.
[0002] Addressing, firstly, the above reference to Akiyama, it differs, from that of the
present invention in a number of material respects, these including differences in
the respective input and exhaust mechanisms and in the relationship of the engine
piston to the air inlet means to the interior of the engine cylinder. More specifically,
Akiyama does not teach or indicate the possibility of a spring enhanced piston action,
much less one for providing pressurized air input control to the engine cylinder.
[0003] With respect to the Jonathan device known in the United Kingdom, the same constitutes
a direct predecessor of the instant invention which, however, differs therefrom in
a number of respects and as such provides a far less efficient pneumatic engine for
use with toy vehicles such as an aeroplane. More particularly, the Jonathan has two
distinct modes of operation, one a high pressure mode when the air tank or air pressure
canister thereof is at high pressure and a second mode when the air canister is at
low pressure. Such a distinction between high and low pressure operations does not
exist in the present invention.
[0004] Further, the Jonathan employs a piston diaphragm which constitutes the primary air
input control means of that system. In distinction, the present system employs a one-way
check valve which selectively co-acts with the piston to control air flow through
the system intake manifold. Further, the Jonathan possesses two different exhaust
channels, one in the lower cylinder housing and the other in the upper cylinder housing.
In distinction, the instant system employs a single plurality of air exhaust apertures,
all situated in the upper or proximal region of the cylinder housing.
[0005] More generally, the Jonathan does not afford efficient use of compressed air stored
within the inflatable air canister and, as such, cannot achieve a comparable period
of operation to that of the present invention. That is, to maintain operation of the
system when the canister air pressure falls below a certain level, requires a distinct
mode of engine operation during intervals of reduced pressure.
[0006] While the Jonathan, like the instant invention, makes use of a spring to enhance
performance of the engine piston, the length and radius of the spring differ materially
from that of the invention. Thereby, the Jonathan cannot optimally use the potential
energy resident in the compressed air as it passes through the intake manifold into
the engine cylinder housing. Also, the spring itself cannot contribute to system deficiency
in the manner of the present invention.
[0007] It is noted that the use of compressed air power as a motive force for model aeroplanes
and model vehicles has, in one form or another, existed in the art since approximately
1920. In such devices, so-called air motors which were constructed from brass and
employed a three-cylinder arrangement for purposes of balance. The limiting factor
in this technology was the air reservoir which, prior to the advent of contemporary
plastics, was of necessity metallic. Such metal reservoirs, while having significant
weight relative to the weight of the model aeroplane also did not possess properties
of elasticity and resilience resident in modem plastics as, for example, exists today
with two or three liter soda bottle. Accordingly, with the advent of a lightweight
plastic soda bottle, a practical air container or canister, for use in a compressed
air or pneumatic power plant for a so-called fluid expansion engine appeared. Thereby,
the above-referenced invention of Akiyama marketed by Tome Kogyo Company of Japan
and the Jonathan device with its Z-engine became possible.
[0008] The present invention may thereby be appreciated as a continuation of this process
of development of compressed air and expansion pneumatic engines usable with a variety
of toy vehicles including toy aeroplanes.
[0009] US-A-4 472 996 describes a fluid propulsion device for toys including a housing with a cylinder
located thereon. A pressurized fluid reservoir connects to the cylinder via a value.
[0010] In
EP-A-0 289 806 there is described a fluid-operated miniature engine operated by an expanding gaseous
fluid. The engine comprises a cylinder, a piston and an inlet value. An air canister
is compled with a chamber, which is in fluid communication with the cylinder, via
a fluid line.
SUMMARY OF THE INVENTION
[0011] The within invention relates to a pneumatic compressed air engine for toy vehicles
according to claim 1. The engine includes a selectably inflatable air canister and
an intake manifold having an engine air inlet in fluid communication with said air
canister, the inlet including means for providing compressed air to said canister
through the manifold. The pneumatic engine also includes a cylinder housing which
is defined by distal and proximal regions thereof, an inlet in fluid communication
with said engine air inlet and, at said proximal region, a plurality of air exhaust
apertures. The engine further includes a one-way check valve including a proximal
element, reciprocally situated at least partially within said engine air inlet, of
the cylinder housing, the check valve residing in a normally closed position relative
to the inlet. The engine further includes a piston slidably mounted along a longitudinal
axis of said cylinder housing in a fluid-tight relationship to internal circumferential
region walls of the distal region of the cylindrical housing. The piston includes
an axial member projecting distally toward said cylinder housing inlet and proportioned
in diameter for insertion thereunto. Said piston exhibits a substantially concave
proximal surface. The pneumatic engine also includes a piston spring mounted about
said axial member of said piston and having a length greater than said axial member.
Thereby, at a distal end thereof, said piston spring exhibits a length sufficient
to effect selectable contact with the proximal element of said check valve during
intervals of high pressure between said piston and said distal cylinder housing. The
engine also includes a connecting rod having a distal end proportioned for complemental
non-rigid mechanical interface with said proximal surface of the piston. An eccentric
is rotationally mounted to an engine power delivery shaft, said eccentric rotatably
secured to a proximal end of said connecting rod, in which rotation of said eccentric
by said rod transmits angular momentum to said system power shaft. Resultingly, reciprocation
of said connecting rod by the eccentric will increase pressure between a distal side
of said piston and enclosed internal portions of said distal cylinder housing, compressing
said piston spring against said proximal element of said check valve. Thereby, potential
energy isimparted to both said spring and the compressed air within said cylinder.
As such, at a maximum of distal reciprocation, said proximal element of said check
valve will urge open relative to said inlet of said of said cylinder housing, thereby
effecting a brief high pressure input of compressed air from said canister, through
said intake manifold into said distal region of the cylindrical housing. Said high
pressure air input will thereby initiate an expansion of said piston spring and movement
of the piston toward said proximal region of said cylinder housing, this causing reiterative
cycles of reciprocation of said piston, connecting rod, cam and engine power shaft.
The piston is returned to its zero or distal-most position b angular inertia from
the cam and power shaft.
[0012] It is an object of the present invention to provide an improved compressed air expansion
engine having particular use as a power source for toy vehicles.
[0013] It is another object to provide an inflatable pneumatic engine for toy vehicles having
improved performance characteristics of stability, power, and flight duration over
compressed air engines heretofore known in the art.
[0014] It is a further object to provide a pneumatic engine of the above type that can be
manufactured through the use of lightweight non-molded plastic components.
[0015] It is a yet further object of the invention to provide a compressed air engine of
the above type which can be economically manufactured and which is far more durable
than such systems heretofore known in the art.
[0016] The above and yet other objects and advantages of the present invention will become
apparent from the hereinafter set forth Brief Description of the Drawings and Detailed
Description of the Invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017]
Fig. 1 is a cross-sectional view taken through the longitudinal centers of the main
engine shaft, connecting rod, and piston of the present pneumatic engine, in which
the cam thereof is at a zero degree position.
Fig. 2A thru 2C are sequential conceptual views showing he principles of co-action
of the cam connecting rod and piston, in which Fig. 2B is taken along Line 2B-2B of
Fig. 1.
Fig. 3 is a fragmentary view of Fig. 1 showing that portion of the present engine
including the piston, connecting rod, cylinder and intake manifold assemblies.
Fig. 4 is a view, sequential to the view of Fig. 1A showing the piston and connecting
rod location at a twenty degree position relative to the fixed engine bracket.
Fig. 5 is a view sequential to that of Fig. 3 and 4 showing the piston at its maximum
height and the cylinder at its lowest atmospheric pressure, this with said cam at
a 180 degree position relative to the engine bracket, the same representing the end
of the up stroke and beginning of the down stroke.
Fig. 6 is a schematic view sequential to the views of Figs. 3 to 5 showing the cam
at a rotational position of about 350 degrees.
Fig. 7 is view sequential to the view of Fig. 6 showing the rotational cam position
at about 355 degrees, that is, the first point of contact of the proximal element
of the check valve by the piston spring.
Figs. 8 is a view sequential to the view of Fig. 7 showing the completion of one engine
cycle. As such,
Fig. 8 indicates the piston and check valve position an instant before that of the
view of Fig. 3.
Fig. 9 is a schematic view showing the location of the engine assembly and compressed
air canister relative to a vertical axial cross-section of a model aeroplane.
DETAILED DESCRIPTION OF THE INVENTION
[0018] With reference to the schematic view of Fig. 1, there is shown a selectably inflatable
compressed air canister 10 which is in the nature of a resilient polymeric plastic
bottle such as the type of a two or three liter soda bottle. In one embodiment of
the invention, the canister 10 will have a capacity of about 2.5 liters with the range
thereof preferably between 2 and 3 liters. The canister 10, the geometry of which
follows the aerodynamics of the toy vehicle that it is to power, is filled through
a one-way check valve 12, which includes a proximal ball 14 situated within channel
16 of intake manifold 18. The check valve will optionally include a distal ball 20
which communicates with a proximal ball 14 through valve spring 22. The air canister
10 is filled with pressurized air by pumping through check valve 12 which in turn
causes distal ball 20 of the check valve 12 to compress along the axis of spring 22
in the direction of the proximal ball 14. Spring 22 will compress sufficiently to
permit passage of air through air aperture 26 of a distal part of channel 16 and therefrom
into a channel 24 from which the air enters the air canister 10 for eventual usage
with the pneumatic engine in the manner set forth below. Except during pumping, distal
ball 20 will seal against the aperture 26 of the intake manifold 18 thereby providing
a tight fluid seal of the compressed air in canister 10. The intake manifold 18 also
extends to the right to form a portion of the a canister cap 18a, which potion is
secured to a canister neck 29 of canister 10 by means of a retaining cap bracket 28.
Provided between the canister neck 29 and the cap 18a of intake manifold 18 is a circumferential
elastomeric gasket 30. It is noted that retaining cap bracket 28 and neck 29 of the
canister 10 are both secured within an engine bracket 32 which is also secured to
a proximal cylinder housing 34 through the use of a mounting screw 36. Further, the
engine assembly is attached to air canister 10 by means of the intake manifold 18
and retaining cap 28. It is very important that the alignment of shaft 38 stay stationary,
especially in that large forces impacting into, and perpendicular to, the centering
of the shaft axis are common during normal usage. To eliminate any movement or excessive
forces on intake manifold 18 the bracket 32 is attached to upper cylinder 34 with
screw 36 and on an opposite end of bracket radial ring 32a, that is, to part of engine
bracket 32. Radial ring 32 is held between vertical wall 10a or air canister 10 and
retaining cap 28. The attachment of this engine bracket 32 is crucial in eliminating
vibration and impact forces during normal usage of the vehicle.
[0019] A main engine shaft 38 is, through bearings 40 and 42, secured to a cam 44. (See
also Figs. 2A to 2C). Further, through said bearings 40 and 42, the main shaft 38
is rotationally secured to the proximal cylinder housing 34. Accordingly, shaft 38
rotates within the left hand part of proximal cylinder housing 34 and cam 44 rotates
thereupon. The cam 44 is provided with a cam shaft 46, the operation of which is more
fully described below.
[0020] To the left of bearing 40 is shown a propeller adapter 48 which is journalled upon
main shaft 38. Thereon is mounted a nose cone adapter 50 over which the propeller
of a model aircraft may be secured.
[0021] The position of cam shaft 46 relative to the proximal cylinder housing 34 which is
shown in Fig. 1 is herein referred to as the zero degree position of the cam. At this
rotational position of the cam 44 and cam shaft 46, connecting rod 52 and piston 54
are at their lowest, that is, distal-most position relative to the main shaft 38 of
the system. The operation of cam 44 and connecting rod 52 relative to piston 54 may
be more fully appreciated with reference to the sequential views of Figs. 2A, 2B and
2C. These figures comprise radial cross-sectional views taken in the direction of
Line 2B-2B of Fig. 1. The position of the engine of Fig. 1 shown in Fig. 2B, is the
point of greatest extension of connecting rod 52 and piston 54 relative to the main
engine shaft 38 upon which cam 44 rotates.
[0022] In Fig. 2A is shown a position of the connecting rod 52 relative to the zero position
of Fig. 2B which is 15 degrees before the zero position. As such, the same would comprise
the so-called 345 degree position, that is, a downstroke position of the engine, while
the position of the connecting rod 52 and cam 44 shown in Fig. 2C would constitute
the 15 degree, that is, an upstroke position of the engine. The significance of these
rotational cam positions is further set forth below.
[0023] With further reference to Figs. 2A through 2C, it is noted that the bottom of connecting
rod 52 is provided with a substantially spherical bottom surface 58 which fits against
a female spherical radius 60 of piston 54. Therein, connecting rod 52 is not attached
to the piston 54 but rather simply mates against it through a low friction engagement
which exists between spherical surface 58 of connecting rod 52 and female spherical
radius 60 of piston 54.
[0024] It is noted that each rotation of cam 44, caused by rotation of main shaft 38, will
cause connecting rod 52, mounted upon said cam shaft 46, to effect a net vertical
linear, that is, up-and-down motion of piston 52 relative to main shaft 38 of 0.32
inches, i. e., approximately 8.5 millimeters. Accordingly, the power stroke of the
instant engine, effected by the low frictionless action between the cam 44 and cam
shaft 46, on the one hand, and male spherical surface 58 of connecting rod 52 and
female spherical surface 60 of piston 54, on the other hand, is that of about 8.5
millimeters.
[0025] In further regard the schematic view of Fig.1, it is noted that the engine cylinder
housing includes said proximal housing 34 and a lower or distal housing 56. It is
the distal housing 56 of the cylinder housing and a cylinder inlet 62 (see Fig. 3)
which is in fluid communication with the inlet 16 of the intake manifold 18. The distal
cylinder housing 56 is seated upon asealing O-ring 64 which thereby sits upon the
intake manifold 18.
[0026] By virtue of a piston seal 66 and a circumferential integral skirt 67 thereof, piston
54 is slidably mounted along a longitudinal axis of the distal cylinder housing 56
and assures a fluid tight relationship between the piston and the internal circumferential
walls of said distal housing 56. See Fig. 3.
[0027] The piston 54 includes an axial member 68 which projects distally toward said cylinder
housing inlet 62 and is proportioned in diameter for insertion thereunto. Mounted
about said axial member 68 is a piston spring 70 having an outside diameter which
is barely sufficient to clear the cylinder housing inlet 62 and having a length sufficient
to effect selectable contact with the proximal ball 14 of the one-way check valve
within the intake manifold 18. Spring 70 plays a special role in the function of the
present pneumatic engine by which there is provided to the engine much of its power.
More particularly, as piston 54 moves downward within distal cylinder housing 56,
the spring 70 will, as is shown in Fig. 3, contact proximal ball 14 which, prior to
such contact, is held against a generally conical surface 72 at the entrance of the
cylinder housing inlet 62. Prior to such spring contact, proximal ball 14 is held
against conical surface 72 by reason of the air pressure against the distal side 56a
of the ball 14 from the air canister 10 passing through channels 24 and 16 of the
intake manifold 18. This is the condition which is shown in the views of Figs. 4 through
7, more fully described below. Accordingly, only in the condition shown in Figs.1,2B,
3 and 8, that is, in which the cam is at a zero degree position, that is, a maximum
piston rod stroke extension, will the spring force of piston spring 68, less the spring
force of check valve spring 22, be sufficient to overcome the air pressure against
distal side 56a of ball 14. This force is calculated by multiplying the air pressure
from the air canister 10, that is, approximately 100 pounds per square inch, times
the area of the housing inlet 62, which has a diameter of about 1.7 millimeters. Thereby,
the force necessary to accomplish closure of ball 14 against conical surface 72 and
inlet 62 is 0.332 pounds. That is about 151 grams of force. Such opening of ball 14
can only be accomplished at the lowest point of the cam stroke, that is, the zero
degree position shown in Figs. 1,2B, 3 and 8.
[0028] Further, since spring 70 is only about one millimeter longer than the minimum distance
required to open ball 14, only the downward-most position of piston 54 and, with it,
of axial member 68 will effect an opening of the ball 14 relative to conical surface
72 of only one millimeter (in vertical linear terms), thereby allowing air to pass
about the sides of ball 14 and into the distal cylinder housing 56. This process will
enable air to pass about the spring 70 through inlet 62 as is indicated by arrows
76 in Fig. 3. As this occurs, air pressure will quickly equalize around ball 14 creating
high pressure within the lowermost part of the cylinder housing 56, thus initiating
the upward stroke of the piston 54 and connecting rod 52, causing skirt 67 of piston
seal to expand radially against walls of said housing 56.
[0029] It is noted that an important function of spring 70, accomplished by careful selection
of the spring rate thereof, is that the expansion of spring 70 against ball 14, prior
to air pressure equalization about the ball permits a longer interval of compressed
air from the air canister to enter the lowest part of the cylinder, than that existent
in prior art compressed air engines. This results in a more powerful engine stroke.
Further, by selection of a suitable spring constant, spring 70 will expand powerfully
against ball 14 upon the initiation of the pressure stroke.
[0030] The same is represented by the transition in piston positions shown between the zero
degree cam position of Fig. 3 and the 20 degree cam position of Fig. 4, in which skirt
67 remains flush with the walls of housing 56, thereby assuring high pressure within
said housing during the Fig. 4 phase of the engine stroke. It is, accordingly, to
be appreciated that the view of Fig. 3 represents both completion of a downward stroke
and the initiation of an upward stroke in which the downward stroke is completed when
the spring force against ball 14 exceeds 151 grams.
[0031] The beginning of the upward motion of piston 54 is shown in Fig. 4, this corresponding
to the twenty-degree position of the cam. Therein, high pressure within distal cylinder
housing 56 piston moves the cylinder 54 upward and, with it, connecting rod 52, thus
furthering the rotation of cam 44 and, with it, main shaft 38. During this entire
period, ball 14 is closed while check valve spring 22, which connects balls 14 and
20, remains in an expanded state. Therein, piston spring 70 completes its push off
from proximal ball 14 of the check valve 16.
[0032] Shown in Fig. 5 is the point of maximum height, that is, the top of the 8.5 millimeter
stroke of the engine which corresponds to the point of lowest air pressure within
distal cylinder housing 56. At that point, piston seal 66 will pass exhaust apertures
78 permitting escape of air from cylinder housing 56 thereby creating a relative vacuum
therewith. This escaping air is shown by arrows 80.
[0033] After the maximum stroke height of Fig. 5 is accomplished, the angular inertia from
the aircraft propeller, is transmitted, through shaft 38, to cam 44, to connecting
rod 52 and to piston 54. This will, as is shown in the transition from Fig. 5 to Fig.
6, cause downward motion of the rod and piston. As this occurs, air pressure within
distal cylinder housing 56 will increase as will potential energy within spring 70.
This process continues causing spring 70 to contact ball 14 at about 350 degrees.
At this point, skirt 67 of seal 66 is not sealed against the wall of housing 56, thereby
allowing air to leak between said skirt and walls of housing 56. In the view of Fig.
7 which corresponds to a cam position of 355 degrees, a point of near maximum pressure
within distal housing 56 is accomplished. The 360 degrees or zero degrees position
is shown in the view of Fig. 8. At that point, as above described with reference to
Fig. 3, the spring force of spring 70 will overcome the 151 grams of force applied
by the compressed air input from canister 10 against the distal surface 56a of ball
14.
[0034] Summarizing this action, the power of the downstroke of the piston derives from the
angular inertia of the propeller which, during a period of low cylinder pressure,
is transmitted through the power shaft to the piston 54 and to the piston spring 70
during which potential energy is imparted to both said spring and to compressed air
within distal cylinder housing 56. Conversely, power for the upward stroke of the
piston derives from a combination of the mass and energy of the compressed air input
and the release of potential energy within piston spring 70 as it pushes off of ball
14 at the beginning of the expansion process which is shown in Fig. 4. Therein, the
one way check valve, as actuated by piston spring 70, keeps the supply of air from
the air canister 10 closed for all but a brief interval during which the spring force
of piston spring 70, less the spring force of one way check valve spring 22, overcomes
the air pressure against surface 56a of ball 14 of the check valve. The spring force
and spring rate of piston spring 70, as well as the narrow clearance of less than
a millimeter between the outside diameter of the spring and the cylinder inlet 20,
taken with the conical geometry 72 of housing inlet 62, all co-act to provide a reiterating
high pressure air inlet of suitable duration, thereby initiating a process of engine
expansion and compression respectively using the potential energy stored within the
air canister 10 and spring 70.
[0035] Fig. 9 is a schematic view showing the location of the entire engine assembly, as
above described, and air canister 10, relative to fuselage 76, main wing 78 and propeller
80 of a model airplane equipped with the present inventive pneumatic engine.
[0036] While there has been shown and described the preferred embodiment of the instant
invention it is to be appreciated that the invention may be embodied otherwise than
is herein specifically shown and described and that, within said embodiment, certain
changes may be made in the form and arrangement of the parts without departing from
the underlying ideas or principles of this invention, as claimed herein.