Note: Descriptions are shown in the official language in which they were submitted.
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IN-LINE ANNULAR PISTON FIXED BOLT REGENERATIVE
VARIABLE CHARGE LIQUID PROPEL~ANT GUN
_ WITH VA~IABLE ~lYDRAULIC CONT~OL OF PISTON
Field of the I'nvention
This invention relates to liquid propellant
guns utilizing differential area pistons to provide
continued or regenerative particularly, to such guns
in which there are a plurality of coaxial elements,
including at least one di-fferential area pis-ton,
arranged so as to provide for relative action between
elements as a means for controlling regenerative pro-
pellant injection.
Descrip'tion'o'f the Prior Art
An extensive summary of the prior art appears
in the "Description of the Prior Art" of U.S. Pa-tent
No. 4,341,147, issued July 27, 1982 to R.E. Mayer. The
U.S. Patents Nos. 3,138,990, issued June 30, 1964 to
R.A. Jukes et al; 4,023,463, issued May 17, 1977 to
D.P. Tassie, and 4,050,349, issued September 27, 1977
to A.R. Graham; cited in that document and the above-
referenced U.S. Patent 4,341,147 itself are exemplary
of that prior art. In general, the references cited
show differential pressure pistons for forcing liquid
propellant from a reservoir chamber into a combustion
chamber responsive to combustion pressures. The
most pertinen-t of the prior art cited to this dlsclosure
are U.S. Patents Nos. 4,523,407, issued June 18, 1985
to Magoon and 4,523,408, issued June 18, 1985 to Mayer
et al, in which a moving differential area piston
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cooperates with another ~ber_ to control the flow rate
or dispersion pattern or both of the flow rate or
dispersion pattern or both of the propellant as it is
pumped to the combustion chamber, and Jaqua U.S.
Patent 4,281,582 issued August 4, 1981 which provides
a nonuniform resistance to movement of the
differential area piston. The aforementioned U.S. Patents
4,523,407 and 4,523,~08 are pertinent because, in a reverse
hollow piston arrangement, they also disclose a fill piston
and a hydraulic dashpot.
Summary of the Invention
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 improvèments in structures in which a moveable
differential area piston cooperates with at least one
other structural element to control propellant flow rate
or dispersion patt~rn or both as the propellant is pumped
from a reservoir c'1amber 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
overrrunning motion a~ially 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.
T~e zero capacity capability provides a starting position
for an air free rapid fill to avoid ullage. An annular
opening between khe bolt and the annular disk-like
piston head consitutes an injector transfer of propellant
from the reservoir to the combustor chamber as the piston
is displaced responsive to combustion pressure. In
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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 tes-ted to demonstrate the efficacy of the
structure for obtaining desired ballistic results from
predetermined breech pressure and time relationships as a
result of controlled injec-tion and burn rates.
_scripton of the Drawings
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 onlv half a charge as compared
to -that of FIGURE 1.
Descrip~ion of the Invention
_
General
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 ~ntrodu~tion, 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
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fixed bolt structure 5. The moveable pistons cooperate
wi-th the bolt to accept, retain and dispense llquid
propellant in a metered fashi.on in response to pressure
created by combustion acting on difEerential area
pressure piston 6.
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 illustr~ted as merely abutting the enlarged barrel
case 13 to constitute end wall 31 of the chamber without
defined restraining means. ~ny of the well known
structures, e.g. drop block, pivoted block, etc., which
are ou-tside 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
respresentative 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 block 7 by means of a
cylindrical portion 72. There is no reason to preclude
the use of interrupted screw th~eads at 32 to provide
for ~uick removal and adjustment.
_ incipal Components
Bolt 5 is fixed in 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 o moveable piston 7 which slides between the reduced
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bolt 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 ledye portion 52 at the
junction of the web structure 50, and the reduced
radius shaft portion 51 of the bolt which is within
the propellan-t 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 openiny 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
portions 53 of bolt 5.
The idfferential area annular piston 6 has
a cylindrical skirt portion 63 which serves as a piston
rod and primarily .lefines 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 6~ 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 skir-t 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
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to the interior surface 7] of the cylinclro-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 ancL the interior
surface of the forward portion of piston 7.
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 led~e 52 which constitues 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.
The block or fill piston 7 of a liquid
propellant gun according to this invention performs the
same functions as that of United States Patent
Number 4,523,508 issued June 18, 1985 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.
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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
79, is defined by an annular recess 76 :in the body 73
contoured to receive the annular skirt S3 of annular
piston 6 to constitute an annular dashpot and is
shaped to mate with the internal surface 64 of the
pressure piston 6 so that the capaicty of recervoir
35 can be reduced to zero on firing and prior to fill.
Piston 7 in the illustrated embodiment also
has an internal accumulator cylinder 78 (which could
be external if desired) interconnected with dash pot 76
by multiple conduits 77 and is provided with feed line
conduits 17 and 27 for charging the cylinder 78. Free
piston separator 73 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
25 portion 37, conduits 77 and dashpot 76 would be charged
with water or a hydraluic fluid and cylinder portion ~7
charged with air or gas pressure. The accumulator
structure is an essential component of the invention and
with the strate~ic 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 o~ different charge
quantities of propellant in reservoir 35.
The gun breech structure illustrated also
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contains features more fully disclosed and explained in
United States Patent Number 4,523,508 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 charyed with an appropriate
fluid through conduit 36, annulus 33 can hydraulically
support skirt 63 against firing pressures and can
dispense luhricants, preservatives or combus~on
enhancements or combinations thereof pas-t 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 aspringbuffer assembly 44 made up of Belleville
washers 14, pressure ring 15 and pins 16 for positioning
piston 7 and for allowing a set back movemen-t of the
combined structure of pistons 6 and 7 and the included
reservoir 35 to unseat ~iston head 60 from ledge 52
to inititate feed of propellant from reservoir 35
to the combustion chamber. Other structure,
e.g. a liquid spring, liquid damper, coil springs, etc.,
could be 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
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an igniter 26 communicating with combustion chamber 55
which can be of any con~enient 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
5 from ledge 52 to open the annular injector.
FIGURE 2
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 with
respect -to one another to accommodate a half charge.
Most notieable 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 ~all 31,
and the exposure of a length of screw threads 32 at 22
indicating that the adjustment of the mechansim to
determine load charge is made by turning breech plug 4
farther into the c'lamber 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 hydrualic 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 ancl 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 reeess 76 to accumulator 78 to produce
the desired hydraulic resistance. The amount of
hydraulic resistance to be applied is determined by
taking into account all factors including the
design of piston head 60, the size of the injection
annulus, the burning charaeteristics of the partieular
propellant etc., to produee the desired pressure/time
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curve on firing. The location of conduits 77 to cause
some to be blocked off by piston s]~irt 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 apertures
through a range of partially coincident positions.
OPERATION
Firing
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 acti~ation 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
in~ection of liquid propellant from reservoir 35 into
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combustion chamber 55 and ignite the lnjected liquid
propellant. Ignition oE 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.
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 i.ncrease duriny early movement of the piston 6 to
produce an ever increasing thic~ness 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 diEference 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 dampin~ lntroduced 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 hydrualically b~ the
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closing down of conduits 77 by piston skirt 63. The
variable orifice hydraulic damper also provides
tailored combustion cha~ber pressure rises to accommodate
acceleration sensitive projectiles and projectiles of
different weights.
Chargin~
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 pro~ectile 12 by whatever breech
actions 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
of reservoir 35 for the next firing. The valve in
conduit 45 is then opened to admit li~uid propellant
under pressure into the collapsed reservoir at 35.
As liquid proellant is inserted into and
expands reservoir 35 by forcing fill piston 7 away
from pistion 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 effec-ted as a result
of the rearward movement of piston 7 wh~ch automatically
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expands space 13.
SUMMARY
l'he foregoin~ 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 pis-ton
head overrxuns 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 to the combustion chamber. An
additional moveable piston member cooperates with the
annular piston and with positioning means to limit travel
of the additional rnoveahle 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 reser~oir to be increased from zero to
a desire content as the liquid propellant is introduced
to provide for aid free rapdi proellant fill. Structural
integrity is enhanced by use of a hydraulic pressure
support of the annular piston road which also facilitates
lubrication and cooling of the structure.
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