[0001] This invention relates to liquid propellant guns utilizing differential area pistons
to provide continued or regenerative injection of a liquid propellant into the combustion
chamber and, particularly, to such guns in which there are a plurality of coaxial
elements, including at least one differential area piston, arranged so as to provide
for relative action between elements as a means for controlling regenerative propellant
injection.
[0002] An extensive summary of the prior art appears in the "Description of the Prior Art"
of U.S. -A- 4,341,147 to R.E. Mayer. U.S.-A- 3,138,990, 4,023,463 and 4,050,349 cited
in that document and U.S.-A- 4,241,147 itself are exemplary of that prior art. In
general, the reference cited show differential pressure pistons for forcing liquid
propellant from a reservoir chamber into a combustion chamber responsive to combustion
pressures. Also pertinent to the present invention are the descriptions of our copending
European patent applications Nos. 84 112792.1 and 84112793.9 in which a moving differential
area piston cooperates with another member, i.e., the fixed bolt 5 in FIGURE 1 to
control the flow rate or dispersion pattern or both of the propellant as it is pumped
to the combustion chamber.
[0003] US-A4 099 445 describes a gun structure in which the various propellant componants
are forced from fixed volume reservoir into the combustion chamber by means of a differential
area piston to which an additional moving force is provided at the initial stage of
it working stroke movement.
[0004] US-A- 4 281 582 describes an injection piston of regenerative liquid propellant gun
which is attached to a second piston that has a programmed hydraulic resistance which
controls its motion.
[0005] US-A-4 341 147 describes a regenerative liquid propellant gun having a structure
which reacts to combustion pressure to dispense and regulate the flow of liquid propellant
from an included reservoir. Said structure includes a first differential area piston
and a second differential area piston in a bore in the first piston, said second piston
opening and closing injection ducts in the first piston and being hydraulically controlled.
[0006] This invention pertains to a novel breech, receiver and combustion chamber structure
for a liquid propellant gun of the regenerative injection monopropellant type and
pertains to improvements in structures in which a moveable differential area piston
cooperates with at least one other structural element to control propellant flow rate
or dispersion pattern or both as the propellant is pumped from a reservoir chamber
to a combustion chamber by a piston responsive to combustion pressures. The invention
contemplates an in-line annular piston (i.e. axially aligned with the gun bore, surrounding
a reservoir space and moving in direct reaction to the projectile) supported within
the breech mechanism section for reciprocal overruning motion axially of a fixed central
bolt member wherein the cylindro-annular space between the cylindrical differential
area piston wall and the bolt constitutes a reservoir chamber having a capacity between
the head of the piston and a moveable third member which is variable from zero to
a selected full charge capacity. The zero capacity capability provides a starting
position for an air free rapid fill to avoid ullage. An annular opening between the
bolt and the annular disk-like piston head constitutes an injector for transfer of
propellant from the reservoir to the combustion chamber as the piston is displaced
responsive to combustion pressure. In particular, the invention contemplates use of
a variable orifice hydraulic resistance to movement of the differential area piston
by itself or in addition to other means for controlling the flow rate of propellant
from a reservoir to a combustion chamber. The moveable third member provides shot-to-shot
variable charge capability. The variable orifice hydraulic system permits shot-to-shot
programmable mass flow rate of propellant into the combustion chamber. The invention
disclosure also contains structural refinements facilitating loading, sealing, ignition
and survival. The principal configuration has been tested to demonstrate the efficacy
of the structure for obtaining desired ballistic results from predetermined breech
pressure and time relationships as a result of controlled injection and burn rates.
[0007] More specifically, the present invention provides a direct injection regenerative
liquid propellant gun structure having a breech casing defining a breech bore having
a forward barrel end and an aft breech end characterized in that it comprises in combination
:
a fixed member within said breech bore extending from a supporting member near said
barrel end aftwardly toward said breech end, said fixed member being generally cylindrical
but having an enlarged portion near said supporting member;
a differential area piston having a head dividing the volume within said breech bore
between a combustion chamber at said barrel end on the forward side of said piston
head and a propellant reservoir on the aft side of said piston head, said differential
area piston having a cut out portion for overrunning said fixed member as said piston
moves along said fixed member from a gun charged position in which said cut out portion
is in register with and forms a seal with said enlarged portioin of said fixed member
to a gun discharged position in response to pressure of combustion gas generated in
said combustion chamber to inject propellant from said reservoir to said combustion
chamber;
said cut out portion and said enlarged portion being so sized and shaped to cooperate
as said differential area piston moves with respect to said fixed member to define
a variable area injection orifice between them for the flow of propellant from said
reservoir to said combustion chamber.
FIGURE 1 is a longitudinal sectional view of a fully charged breech section of a variable
charge regenerative liquid propellant gun in accordance with this invention.
FIGURE 2 is a longitudinal section view of the same gun structure having only half
a charge as compared to that of FIGURE 1.
[0008] The implementation of the breech or chamber section of a liquid propellant gun according
to the invention and as illustrated in FIGURES 1 and 2 of the drawings includes, as
common to most fire arms and cannon, a gun barrel 1 attached to an enlarged breech
mechanism section 2 which includes provisions for the introduction, ignition and burning
of a propellant material to create a gas to drive a projectile through the barrel.
The breech section 2 of this gun includes a casing 21 surrounding and defining a chamber
3, a breech plug structure 4 restraining two moveable pistons 6 and 7, and a fixed
bolt structure 5. The moveable pistons cooperate with the bolt to accept, retain and
dispense liquid propellant in a metered fashion in response to pressure created by
combustion acting on differential area pressure piston 6.
[0009] Chamber 3 as defined by the interior wall 30 of the casing is cylindrical with one
closed end wall 31 interrupted by the opening to the bore 11 of barrel 1 and two threaded
portions 32 and 34 representing a facility for positioning and securing a breech closure
mechanism, as for example, the breech plug structure 4, to provide reaction to propulsion
pressures and a facility for securing the fixed bolt structure 5 in place. Casing
21 is illustrated as merely abutting the enlarged barrel base 13 to constitute end
wall 31 of the chamber without defined restraining means. Any of the well known structures,
e.g. drop block, pivoted block, etc., which are outside of the scope of this invention
may be used to join this novel breech to the barrel while permitting loading of projectiles
12. Breech plug structure 4 is representative of a wide range of possible designs
and is illustrated as having plug portion 42, interconnection means 43 constituting
in this case a screw threads for securing the plug to the threaded portion 32 of breech
casing 21, spring buffer assembly 44 and internal bore 46 supporting a block or fill
piston block 7 by means of a cylindrical portion 72. There is no reason to preclude
the use of interrupted screw threads at 32 to provide for quick removal and adjustment.
[0010] Bolt structure 5 is fixed in a place in the breech structure axially of the gun by
a web structure 50 which has a threaded portion for attaching it to the threaded portion
34 of casing 21 and a reduced cylindrical portion 53 providing support for the annular
forward portion 70 of moveable block or fill piston 7 which slides between the reduced
cylindrical portion 53 and the casing wall 30. An essential aspect of this invention
is embodied in the shaped or contoured portion of the bolt which, as shown in FIGURE
1, has a cylindrical ledge portion 52 at the junction of the web structue 50, and
the reduced radius shaft portion 51 of the bolt which is within the propellant reservoir
35. The cylindrical surface at 52 may carry a seal 54 and interfaces with the annular
piston head 60 of the piston 6 in the position shown in FIGURE 1. The web portion
50 of bolt 5 also contains an axial cup-like combustion chamber 55 facing the opening
to barrel bore 11 and multiple passages 56 between the rear shoulder 57 of portion
53 and the combustion chamber. As illustrated, passages 56 are merely holes drilled
through the monolithic portion 53 of bolt 5.
[0011] The differential area annular piston 6 has a cylindrical skirt portion 63 which serves
as a piston rod and primarily defines cylindro-annular reservoir 35 about the shaft
portion 51 of bolt 5 which varies in capacity as pistons 6 and 7 are moved relative
to each other within the operating cylinder portion of chamber 3. Piston head 60,
which separates reservoir 35 from the entrances to passages 56 to combustion chamber
55 and acts as a valve to control flow of propellant from the reservoir, is disk-like
and annular in that it has a central hole defined by the cylindrical surface 62 dimensioned
to the diameter of bolt ledge 52 to permit seating on the ledge. The interior surface
64 of cylinder head 60 which may be shaped as illustrated to facilitate propellant
flow and to provide appropriate strength has, because of the thickness of skirt wall
63, a lesser area than the exterior head surface and causes annular piston 6 to be
a differential area piston acting between the combustion chamber and reservoir 35.
Piston head 60 also has an exterior rim portion 61 journaled to the interior surface
71 of the cylindro-annular forward portion 70 of piston 7 which could be fitted with
a piston ring. The exterior of piston 6 has a slightly reduced portion 66 which creates
a narrow annular space 33 between the piston skirt 63 and the interior surface of
the forward portion of piston 7.
[0012] The face of piston head 60 is shaped to provide a stop surface 65 which abuts the
surface of shoulder 57 of bolt 5 when surface 62 is seated on bolt ledge 52. The central
aperture of the piston head adjoining cylindrical surface 62 is also shaped to provide
a conical surface 67 flaring away from cylindrical surface 62 so that the annular
gap between the piston head and ledge 52 which constitutes an injection annulus increases
gradually in size as piston 6 moves rearwardly during firing. The maximum size of
the injection annulus is the difference in radii of the cylindrical surface 62 and
the bolt shaft 51 which is reached as soon as the flared conical surface of the piston
head clears the ledge 52. Although both the ledge 52 and the piston head annulus surface
62 are defined here as cylindrical, it may be advantageous under certain conditions
to have those surfaces made slightly conical, but less conical than surface 67, to
facilitate seating and unseating.
[0013] The block or fill piston 7 of a liquid propellant gun according to this invention
performs the same functions as that of Co-pending European Patent Application 84 112792.1
but also includes structure which is specific to the present invention. The block
or fill piston 7 is fitted in chamber 3 for reciprocal motion and, as already noted,
has a cylindro-annular forward portion 70 projecting from its main body 73 which surrounds
the annular differential area pressure piston 6 and overruns the reduced cylindrical
portion 53 of the bolt structure. A rear cylindrical portion 72 is journaled in bore
46 in the breech plug 4, both supporting the piston and sealing the opening in the
breech plug. The main body 73 of piston 7 includes an annular nose portion 74 surrounding
and defining a partial axial bore 75 journaled on the stem portion 51 of bolt 5. The
nose portion is recessed with respect to the forward portion 70, is defined by an
annular recess 76 in the body 73 contoured to receive the annular skirt 63 of annular
piston 6 to constitute an annular dashport and is shaped to mate with the internal
surface 64 of the pressure piston 6 so that the capacity of reservoir 35 can be reduced
to zero on firing and prior to fill.
[0014] Piston 7 in the illustrated embodiment also has an internal accumulator cylinder
78 (which could be external if desired) interconnected with annular recess 76 by
multiple conduits 77 and is provided with feed line conduits 17 and 27 for charging
the cylinder 78. Free piston separator 79 with appropriate seals is located within
cylinder 78 and serves to separate, and balance pressures between, the fluids in cylinder
volumes 37 and 47 as they are charged through conduits 27 and 17 and respond to the
results of relative movement between pistons 6 and 7. It is contemplated that cylinder
portion 37, conduits 77 and annular recess 76 would be charged with water or a hydraulic
fluid and cylinder portion 47 charged with air or gas pressure. The accumulator structure
is an essential component of the invention and with the strategic locations of the
interconnections between the multiple conduits 77 and annular recess 76 and with the
optional valves 87 in conduits 77 constitutes a variable or programmed orifice hydraulic
damper provides a shot-to-shot programmable mass flow rate capability which includes
use of different charge quantities of propellant in reservoir 35.
[0015] The gun breech structure illustrated also contains features more fully disclosed
and explained in co-pending European Patent Application 84 112792.1 including, for
example, the annular space 33 closed off by aligned seals carried by piston 7 as shown
which also accommodate a variable capacity charge capability while retaining seal
integrity. When charged with an appropriate fluid through conduit 36, annulus 33 can
hydraulically support skirt 63 against firing pressures and can dispense lubricants,
preservatives or combustion enhancements or combinations thereof past the piston head
ring projection 61 into the combustion area. The breech structure 4 in this embodiment
of gun is principally an annular breech block 42 which is adjustably retained in the
casing by a threaded connection at 32 which as noted could be interrupted threads.
It includes a spring buffer assembly 44 made up of Belleville washers 14, pressure
ring 15 and pins 16 for positioning piston 7 and for allowing a set back movement
of the combined structure of pistons 6 and 7 and the included reservoir 35 to unseat
piston head 60 from ledge 52 to initiate feed of propellant from reservoir 35 to the
combustion chamber. Other structure, e.g. a liquid spring, liquid damper, coil springs,
etc., could by substituted for some of these elements. The structure also includes
a drive cylinder 10 with conduit 28 for the insertion of fluid under pressure to drive
piston 7 toward the barrel to reseat piston 6 onto the ledge 52 of bolt 5 in preparation
for filling the reservoir. The structure also includes fill conduit 45 for the insertion
of the liquid propellant and vent conduit 49 communicating with the enclosed cylindrical
volume 78. In the embodiment illustrated, the flexible connections required to connect
conduits 36, 45, 49, 17 and 27 to their proper supplies, valves, etc., are not shown
because they are elements readily selected from available technology. The FIGURES
include an igniter 26 communicating with combustion chamber 55 which can be of any
convenient design but must have, or be accompanied by, a means for providing a sufficient
charge to move pistons 6 and 7 to unseat piston head 60 from ledge 52 to open the
annular injector.
[0016] The gun mechanism illustrated in FIGURE 2 is the same mechanism as that in FIGURE
1 but charged with only half of the amount of liquid propellant present in FIGURE
1. This shows the adaptability of the structure, a prime feature of the design, and
the slightly changed positions of the components wih respect to one another to accommodate
a half charge. Most noticeable are the smaller capacity of reservoir 35, the smaller
volume of empty chamber at 3 between the forward end of piston 7 and chamber end wall
31, and the exposure of a length of screw threads 32 at 22 indicating that the adjustment
of the mechanism to determine load charge is made by turning breech plug 4 farther
into the chamber to reduce the distance between the nose portion 74 of piston 7 and
piston head 60 in the loaded position. Less obvious is the volume reduction of annular
recess 76 and a corresponding volume increase of the accumulator hydraulic cylinder
37. In addition in FIGURE 2, some of the conduits 77 are obstructed by the bottom
of skirt 63 of the annular piston 6. The number and location of conduits 77, as already
noted, must be determined to produce the desired throttling of flow of hydraulic fluid
as it is forced from recess 76 to accumulator 78 to produce the desired hydraulic
resistance. The amount of hydraulic resistance to be applied is detemined by taking
into account all factors including the design of piston head 60, the size of the injection
annulus, the burning characteristics of the particular propellant etc., to produce
the desired pressure/time curve on firing. The location of conduits 77 to cause some
to be blocked off by piston skirt 63 prior to firing a partial charge is a part of
this determination. Other mechanical means could be used as a substitute for valves
87 to change the flow capacity of conduits 77 as, for example, a rotating sleeve structure
to move identically shaped and aligned apertures into and out of registry or to move
skewed elongated aperture through a range of partially coincident positions.
OPERATION
Firing
[0017] The gun structure as illustrated in FIGURE 1 is fully charged and ready for firing
with reservoir 35 filled with the liquid propellant to the maximum capacity and with
annular ring 62 of the annular piston 6 seated on ledge surface 52 of the bolt so
as to preclude leaking of the liquid propellant into the passages 56 leading to the
combustion chamber 55. Space 33 is charged with an inert liquid to provide a hydraulic
support for annular piston wall 63 during firing. The liquid in 33 as already noted
may be very viscous, may have lubricant properties, or may contain materials chemically
similar to those added to powders in conventional ammunitions for the treatment or
preservation of barrels. The valve in conduit 45 is closed against backflow of the
liquid propellant. Any existing pressure in space 10 and conduit 28 is relieved. Firing
is initiated by means of activation of ignitor 26 which is provided with a charge
or other means sufficient to create enough pressure in the combustion chamber 55 and
communicating passages 56 to unseat piston head 60 from its mating position with the
ledge on bolt 5 by driving the reservoir and fill piston 7 rearwardly against pins
16 partially collapsing belleville washers 14. The action of the igniter will both
cause an initial injection of liquid propellant from reservoir 35 into combustion
chamber 55 and ignite the injected liquid propellant. Ignition of the liquid propellant
flowing from reservoir 35 will increase the pressure in the combustion chamber and
passages 56 and produce a regenerative feeding of liquid propellant from reservoir
35 into the combustion chamber because of the differential area piston head 60 of
the annular piston. As the pressure in combustion chamber 55 increases, it reaches
the point of causing the obturation band portion of the projectile 12 to become deformed
and permit the projectile to move.
[0018] The conical surface of the portion of the annular piston head 60 indicated at 67
causes the annular space between that surface and the edge of ledge 52 to increase
during early movement of the piston 6 to produce an ever increasing thickness of the
annular sheet of liquid propellant injected into the combustion chamber until all
of the surface 67 clears ledge 52 after which the thickness of the annular sheet is
a function of the difference in diameters of bolt shaft 51 and annular surface 62.
The initial flow rate of liquid propellant produces an increased burn rate with an
attendant pressure increase which is adequate to overcome the increased volume of
the combustion chamber caused both by displacement of the annular piston and by the
accompanying displacement of the projectile 12. The continued flow and burn rate after
the injection annulus reaches full size, as already noted, is a function of the design
of piston 6, the relative sizes and volumes of components and the characteristics
of damping introduced by the variable orifice hydraulic damper which includes the
dashpot recess 76, restrictive conduits 77, valves 87 and the accumulator structure
37, 47, 79. As piston head 60 approaches the nose portion 74 of fill piston 7, the
injection piston 6 is brought to a halt hydraulically by the closing down of conduits
77 by piston skirt 63. The variable orifice hydraulic damper also provides tailored
combustion chamber pressure rises to accommodate acceleration sensitive projectiles
and projectiles of different weights.
Charging
[0019] At the completion of the firing, annular piston 6 is seated onto fill piston 7 with
piston 7 being located against or near the stops 16, depending on the relationship
of the reaction of the buffer assembly and dissipation of the chamber pressures. After
the insertion of a new projectile 12 by whatever breech action means has been incorporated
into the specific gun using this invention, hydraulic or pneumatic pressure, whichever
is used, may be inserted through conduit 28 to expand annular space 10 to drive both
pistons, in register, toward the gun barrel until piston 6 seats onto the bolt ledge
portion surface 52. The pressure on conduit 28 is then relieved and, if appropriate,
breech plug 4 rotated, or reset if an interrupted screw is used, to obtain the proper
position of stops 16 to provide for the proper capacity of reservoir 35 for the next
firing. The valve in conduit 45 is then opened to admit liquid propellant under pressure
into the collapsed reservoir at 35.
[0020] As liquid propellant is inserted into and expands reservoir 35 by forcing fill piston
7 away from piston 6, if necessary, against a residual pressure in cylinder 10, to
prevent, or at least reduce, the amount of ullage in the liquid propellant in the
reservoir. The fill process is continued until the fill piston seats onto pins 16.
The gun mechanism is then charged for a subsequent firing and the annular space 33
can be filled if the charging system does not cause that to be effected as a result
of the rearward movement of piston 7 which automatically expands space 33.
[0021] The foregoing describes the structure and operation of a regenerative monopropellant
liquid propellant gun structure according to this invention employing the cooperation
of a fixed axial bolt and an annular piston wherein the cylindro-annular piston rod
cooperates with other members to define a reservoir for liquid propellant, wherein
the annular planar piston head overruns part of bolt as it moves in response to combustion
pressure, cooperates with a shaped portion of bolt and with variable orifice hydraulic
means for applying a variable resistance back pressure to the piston to deliver a
predetermined pattern and flow rate of propellant the combustion chamber. An additional
moveable piston member cooperates with the annular piston and with positioning means
to limit travel of the additional moveable piston member to cause the propellant reservoir
to have a variable capacity to provide a variable charge capability and shot-to-shot
programmable mass flow rate of propellant and to facilitate charging of the gun by
permitting the capacity of the reservoir to be increased from zero to a desire content
as the liquid propellant is introduced to provide for aid free rapid propellant fill.
Structural integrity is enhanced by use of a hydraulic pressure support of the annular
piston rod which also facilitates lubrication and cooling of the structure.
1. A direct injection regenerative liquid propellant gun structure having a breech
casing (21) defining a breech bore (30) having a forward barrel end (31) and an aft
breech end (32) characterized in that it comprises in combination :
a fixed member (5) within said breech bore (30) extending from a supporting member
(34) near said barrel end (31) aftwardly toward said breech end (32), said fixed member
(5) being generally cylindrical but having an enlarged portion (52) near said supporting
member (34);
a differential area piston (6) having a head (60) dividing the volume within said
breech bore (30) between a combustion chamber (55) at said barrel end (31) on the
forward side of said piston head (6) and a propellant reservoir (35) on the aft side
of said piston head (60), said differential area piston (6) having a cut out portion
(64) for overrunning said fixed member (5) as said piston (6) moves along said fixed
member (5) from a gun charged position in which said cut out portion (64) is in register
with and forms a seal with said enlarged portion (52) of said fixed member (5) to
a gun discharged position in response to pressure of combustion gas generated in said
combustion chamber (55) to inject propellant from said reservoir (35) to said combustion
chamber (55) ;
said cut out portion (64) and said enlarged portion (52) being so sized and shaped
to cooperate as said differential area piston (6) moves with respect to said fixed
member (5) to define a variable area injection orifice (52, 60) between them for the
flow of propellant from said reservoir (35) to said combustion chamber (55).
2. The gun structure of Claim 1 characterized in that :
said fixed member (5) is a bolt spaced from the wall (30) of said casing (21).
said differential area piston (6) has a substantially planar piston head (60);
said cut out portion (64) is an opening in said planar head (60);
said enlarged portion (52) is a band (52) protruding radially a discrete distance
from said bolt;
the surface of said cut out portion (64) and said band (52) being configured both
to mate to form a seal (64, 52) when said elements are in registry and to create a
ringlike opening which expands at a predetermined rate with respect to movement of
said piston (6) relative to said bolt (5) to a maximum opening measured by said discrete
distance when the distance of said planar head (60) from said band (52) exceeds said
discrete distance,
whereby the rate of expansion of the ringlike opening and the maximum opening through
which propellant flows from the reservoir (35) to combustion chamber (55) may be determined,
at least in part, by the configurations of said cutout portion and said band.
3. The gun structure of Claim 2 characterized in that :
said bolt (5) is fixed axially of said breech (2) by a web structure (5) removably
secured in the barrel end (31) of said breech (2);
said differential area piston (6) is an annular holow piston (6) having a cylindrical
wall (62) extending from the periphery of said planar head (60) toward said breech
end (32) of said casing, said periphery and said cylindrical wall being spaced from
the interior wall (30) of said casing, and said cut out (64) being centered in said
planar head (60);
there is a second piston (7) having a body portion (73) journaled in said breech casing
for reciprocal movement and two concentric cylindrical wall projections (70, 74) extending
from said body portion (73) toward the barrel and defining an annular slot (76) between
them, the outer (70) of said two cylindrical walls fitting between said differential
area piston (60) and said casing (21), and the inner (74) of said two cylindrical
walls fitting between said bolt (5) and the cylindrical wall of said differential
piston (6) to constitute a fill piston (7), and
said reservoir (35) is an annular volume of variable capacity defined by said bolt
(5), the differential area piston (60) and the fill piston (7);
whereby the open end of the said cylindrical wall of said differential area piston
constitute said secondary piston portion (63) of said piston (6) and whereby the annular
slot (76) between said concentric cylindrical wall projections (70, 74) of said second
piston (7) constitutes an additinal cylinder in which said secondary piston portion
(63) operates.
4. The gun structure of Claim 3 characterized in that :
there is an accumulator structure in said body portion (73) of said fill piston (7)
comprising an accumulator cylinder (78), means (17) for charging said accumulator
cylinder (78) with fluid pressure and fluid conduit means (77) interconnecting said
accumulator cylinder and said additional cylinder ;
whereby, when said accumulator structure (78) is charged with a fluid, said additional
cylinder (76) and said secondary piston portion (63) constitute a dashpot providing
resistance to movement of said differential area piston (60) during firing.
5. The gun structure of Claim 4 characterized in that:
said fluid conduit means (77) interconnecting said accumulator cylinder (78) and said
additional cylinder include a plurality of ports into said additional cylinder which
are located so as to be sequentially closed as said differential area piston (6) moves
from its gun charged position to its gun discharged position during firing;
whereby said dashpot provides a variable hydraulic resistance to movement of said
differential area piston (6).
6. The gun structure of Claim 5 characterized in that it further comprises:
adjustable valve means (87) in said fluid conduit means (77), interconnecting said
accumulator cylinder (78) and said additional cylinder for regulating the flow capacity
of said fluid conduit means (77);
whereby the movement of said differential area piston (6) can also be influenced by
the adjustment of said valve (87) means to control hydraulic resistance behind the
differential area piston (6).