Separating stock hydraulic crossbow

A crossbow apparatus includes a rearward stock portion including a bow string engaging structure; a forward stock portion including a bow fitted with a bow string; and a hydraulic drive mechanism interconnecting the rearward stock portion and the forward stock portion for separating the rearward stock portion and the forward stock portion while the bow string is engaged by the engaging structure to draw the bow. The forward stock portion preferably includes a longitudinal passageway and the rearward stock portion preferably includes a forwardly protruding guide rod slidably fitting into the longitudinal passageway for strengthening and stabilizing the apparatus when the forward stock portion and the rearward stock portion are separated. The rearward stock portion preferably includes the hydraulic drive mechanism base containing a fluid accumulation reservoir, a plunger slidably extensible from the base under pressure of hydraulic fluid within the reservoir, and a fluid pump for delivering fluid into the reservoir under pressure greater than atmospheric pressure. The rearward stock portion preferably contains a cavity and the base is retained within the cavity, and the plunger has a plunger forward end and the plunger forward end is preferably secured to the forward stock portion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to the field of archery equipment. 
More specifically the present invention relates to a crossbow including a 
forward stock portion fitted with a conventional bow and a separate 
rearward stock portion fitted with a conventional bow string engaging 
trigger mechanism. A projectile guide channel is recessed into the upper 
surfaces of the forward and rearward stock portions. These stock portions 
are interconnected by a hydraulic drive mechanism, similar in construction 
to a hydraulic jack. Stock portion guide rods longitudinally protrude from 
the rearward stock portion and slidably fit into longitudinal passageways 
within the forward stock portion. 
To use the crossbow, the bow string is first placed in a trigger mechanism 
catch. Then fluid within the hydraulic drive mechanism is pumped to 
advance a hydraulic plunger and thereby progressively separate the forward 
and rearward stock portions. This separation creates tension in the string 
and draws the bow. Once a desired draw position is reached, the user stops 
pumping the drive mechanism and loads a projectile such as a bolt into the 
projectile guide channel. The user applies pressure to a trigger mechanism 
lever and thereby mechanically releases the bow string from the catch. The 
string accelerates with the resilience of the bow and launches the 
projectile. 
2. Description of the Prior Art 
Archery bows are known to have been used in ancient Egypt at least 5000 
years ago. Funk & Wagnalls New Encyclopedia, 1979, Volume 2, page 211. 
Many centuries later, the crossbow evolved as a specialized variation of 
the longbow. During Hundred Years' War, mercenary crossbowmen from Genoa 
were instrumental in decimating half of French army at the 1346 Battle of 
Crecy. Yet the military value of the early crossbows was limited because 
they lacked the range of and were slower to cock and load than many of the 
long bows. Complete Book of the Bow and Arrow, G. Howard Gillelan, 
Stackpole Books (1977), pages 14-15. While crossbows have been effective 
in a variety of military situations and have also entertained sportsmen, 
even contemporary crossbows are notoriously slow and awkward to cock. 
"Cocking the crossbow has always been something of a problem. After a 
longbowman takes a shot, he merely reaches into his quiver for another 
arrow, puts it in position, and draws. The crossbowman must go through a 
more complicated procedure. At one time, a variety of devices were used, 
ranging from a stirrup to hold the front end to a ratchet-type crank, or 
handles which were turned in order to draw back the bowstring. Now, 
crossbowmen cock their weapons by hand, some of them hooking the front end 
to a stake in the ground. While using both hands, they haul back on the 
string far enough to position it. The string is drawn back and secured in 
a catch on the stock. When the trigger is pulled, the catch releases the 
bowstring and the bolt is discharged. . . . In 1970, one of the 
established archery manufacturers introduced a new crossbow. It has the 
foot stirrup up front for cocking, . . . " 
Complete Book of the Bow and Arrow, pages 36-37. 
To make cocking the bow faster and easier, and to increase the power and 
range of the crossbow, some hydraulic cocking mechanisms have been 
developed. These include Curcuzza, Sr., U.S. Pat. No. 3,561,419, issued on 
Feb. 9, 1971, which teaches a projectile launcher including an impeller 
within a barrel and an impeller retractor which draws the impelled back 
against elastic biasing, such as from a bow string, using fluid pressure. 
The impeller is connected to the impeller retractor by coupling means. 
Curcuzza, Sr. FIGS. 10-13 show the hydraulic cocking action. Problems with 
Curcuzza, Sr., are that the combined retracting and impelling mechanism is 
highly complex, and would be costly to produce and subject to mechanical 
failure. 
Choma, U.S. Pat. No. 5,220,906, issued on Jun. 22, 1993, discloses a 
crossbow after-market accessory for drawing the bow. Choma teaches an 
electric motor for rotating and advancing a threaded shaft to retract the 
bow string and bow. Choma states as an alternative, however, that "shaft 
22 may be moved by hydraulic pressure or the like." See column 3, line 55. 
A problem with Choma is that there is no explanation of exactly how 
hydraulics might be implemented for this purpose. Another problem with 
Choma is that it must be secured to an existing crossbow when the bow is 
to be drawn. 
Two patents issued to Van House disclose archery bows with substantially 
rigid bow arms which use compressed gas as the spring means for 
accelerating a projectile. U.S. Pat. No. 4,041,927, issued on Aug. 16, 
1977, recites "A gas spring 6 . . . made up of a piston 7 and cylinder 8" 
which can be adjusted to give different draw forces. See column 2, lines 
41-45 and 59-66 generally. U.S. Pat. No. 4,169,456, issued on Oct. 2, 
1979, states "As piston 50 moves rearwardly, air or other gas confined 
within the motor 48 is compressed. In full draw position . . . the air or 
other gas confined within the motor 48 represents stored energy urging the 
piston 50 forwardly . . . " See column 3, lines 43-65, generally. A 
problem with the Van House devices is that they do not teach a means for 
efficiently drawing conventional elastic bow arms. 
It is thus an object of the present invention to provide a hydraulic 
crossbow which provides a high power draw against high resistance elastic 
bow arms for enhanced shooting range and accuracy. 
It is another object of the present invention to provide such a crossbow 
which permits rapid cocking to varying degrees of bow arm draw for 
selected levels of firing power, and with minimal physical exertion by the 
user. 
It is still another object of the present invention to provide such a 
crossbow which separates the trigger mechanism from the drawing mechanism 
for greater simplicity, sturdiness and servicing convenience. 
It is a further object of the present invention to provide such a crossbow 
which retracts to a compact size for convenient storage and transport. 
It is finally an object of the present invention to provide such a crossbow 
which is reliable and relatively inexpensive to manufacture. 
SUMMARY OF THE INVENTION 
The present invention accomplishes the above-stated objectives, as well as 
others, as may be determined by a fair reading and interpretation of the 
entire specification. 
A crossbow apparatus is provided including a rearward stock portion 
including a bow string engaging structure; a forward stock portion 
including a bow fitted with a bow string; and an interconnection structure 
interconnecting the rearward stock portion and the forward stock portion 
including a hydraulic drive mechanism for driving apart the rearward stock 
portion and the forward stock portion while the bow string is engaged by 
the engaging structure to draw the bow. The forward stock portion 
preferably includes a longitudinal passageway and the rearward stock 
portion preferably includes a forwardly protruding guide rod slidably 
fitting into the longitudinal passageway for strengthening and preventing 
relative rotation between forward stock portion and the rearward stock 
portions when they are driven apart. The rearward stock portion preferably 
includes the hydraulic drive mechanism base containing a fluid 
accumulation reservoir, a plunger slidably extensible from the base under 
pressure of hydraulic fluid within the reservoir, and a fluid pump for 
delivering fluid into the reservoir under pressure greater than 
atmospheric pressure. The rearward stock portion preferably contains a 
cavity and the base is retained within the cavity, and the plunger forward 
end is preferably secured to the forward stock portion. 
The hydraulic drive mechanism preferably additionally includes a fluid 
holding chamber and a fluid release device for releasing the fluid from 
the reservoir into the holding chamber to permit movement of the forward 
stock portion and the rearward stock portion toward each other, after the 
forward stock portion and the rearward stock portion have been driven 
apart by the hydraulic drive mechanism. The crossbow preferably 
additionally includes a return biasing structure for automatically moving 
the forward stock portion and the rearward stock portion toward each other 
upon activation of the release device. 
A crossbow apparatus is provided including a rearward stock portion 
including a bow string engaging structure; a forward stock portion 
including a bow with a bow string; and an interconnection structure 
interconnecting the rearward stock portion and the forward stock portion 
including a drive mechanism for driving apart the rearward stock portion 
and the forward stock portion while the bow string is engaged by the 
engaging structure, to draw the bow. The drive mechanism preferably 
includes a release device for releasing the drive mechanism to permit 
movement of the forward stock portion and the rearward stock portion 
toward each other, after the forward stock portion and the rearward stock 
portion have been driven apart by the drive device. The crossbow 
preferably additionally includes a return biasing structure for 
automatically moving the forward stock portion and the rearward stock 
portion toward each other upon activation of the release device. The 
forward stock portion preferably includes a longitudinal passageway and 
the rearward stock portion preferably includes a forwardly protruding 
guide rod slidably fitting into the longitudinal passageway for 
strengthening and preventing relative rotation between the forward stock 
portion and the rearward stock portion when they are driven apart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As required, detailed embodiments of the present invention are disclosed 
herein; however, it is to be understood that the disclosed embodiments are 
merely exemplary of the invention which may be embodied in various forms. 
Therefore, specific structural and functional details disclosed herein are 
not to be interpreted as limiting, but merely as a basis for the claims 
and as a representative basis for teaching one skilled in the art to 
variously employ the present invention in virtually any appropriately 
detailed structure. 
Reference is now made to the drawings, wherein like characteristics and 
features of the present invention shown in the various FIGURES are 
designated by the same reference numerals. 
Preferred Embodiments 
Referring to FIGS. 1-3, a crossbow 10 is disclosed including a forward 
stock portion 12 and a separate rearward stock portion 14. Forward and 
rearward stock portions 12 and 14, respectively, are separated with 
hydraulic means to draw the bow into a firing position. 
The forward stock portion 12 is fitted with a conventional resilient bow 22 
passing through and secured within a bow slot 26. The rearward stock 
portion 14 is fitted with a conventional trigger mechanism 30, having a 
bow string engaging catch 32 protruding upwardly from the upper surface of 
rearward stock portion 14. Trigger mechanism 30 extends downwardly through 
rearward stock portion 14 and a conventional trigger lever 36 within a 
trigger lever guard ring 38. 
A sight 42 is preferably provided just behind trigger mechanism 30 to help 
the user aim crossbow 10. A projectile guide channel 44 is provided in the 
upper surfaces of the rearward and forward stock portions 12 and 14, 
respectively, to retain and guide a bolt, arrow, pellet or other 
projectile or missile. 
Forward stock portion 12 and rearward stock portion 14 are interconnected 
by an extensible structure including a hydraulic drive mechanism 50 which 
drives stock portions 12 and 14 apart from each other. Drive mechanism 50 
is essentially a hydraulic jack. A hydraulic reservoir base 52 is snugly 
retained within a base mounting cavity 54 inside rearward stock portion 
14. The forward end of base 52 preferably protrudes forwardly out of 
rearward stock portion 12 and fits into a corresponding recess 62 in 
forward stock portion 14 for added stock strength when the crossbow 10 is 
retracted. 
A drive plunger 56 slidably protrudes forwardly out of base 52 and includes 
an anchoring lip 58 extending radially outward from the plunger 56 forward 
end. Anchoring lip 58 is securely embedded in forward stock portion 14, to 
such a depth that forward and rearward stock portions 12 and 14, 
respectively, abut each other when drive plunger 56 is retracted into base 
52. When plunger 56 is advanced out of base 52 a certain distance, stock 
portions 12 and 14 are therefore separated from each other by an 
equivalent distance. 
Plunger 56 is advanced from base portion 52 by operating a drive pump lever 
64 pivotally extending from a linkage 66, which is in turn, pivotally 
connected to base 52, and bearing against a drive pump piston 72. Pivoting 
lever 64 axially reciprocates drive pump piston 72 to pump hydraulic fluid 
into a reservoir of conventional hydraulic jack design within base 52. 
Fluid entering the reservoir drives plunger 56 outwardly and forwardly, to 
separate stock portions 12 and 14. Plunger 56 may be retracted to permit 
forward and rearward stock portions 12 and 14 to move toward each other, 
and preferably to abut, each other, by opening a fluid valve with a valve 
handle 76 on the side of rearward stock portion 14. This fluid valve opens 
a port between the reservoir and a fluid holding chamber within base 52 
through which the hydraulic fluid can escape from the reservoir into the 
chamber. A return spring 74 is preferably provided to bias forward and 
rearward stock portions 12 and 14 toward each other, so that opening the 
fluid valve causes stock portions 12 and 14 to retract together 
automatically. Hydraulic drive means 50 might equivalently be mechanically 
connected to an extensible stock portion interconnecting member. 
Mechanical drive devices other than hydraulic mechanisms, such as rack and 
ratchet structures similar to those used in automobile jacks, are 
contemplated. 
Stock portion guide rods 80 preferably protrude forwardly from rearward 
portion 14, where they are anchored with spring pins 84, and slidably fit 
into guide passageways 82 bored longitudinally into forward stock portion 
12. Passageways 82 are preferably lined with metal or plastic tubes (not 
shown) which each receive a guide rod 80, to better retain guide rod 
lubrication material. Guide rods 80 strengthen crossbow 10 and prevent 
relative rotation between the forward stock portion 12 and the rearward 
stock portion 14 when these stock portions 12 and 14, respectively, are 
spaced apart from each other by drive mechanism 50. An accordion sleeve 
(not shown) optionally encloses and conceals the gap between the stock 
portions when they are separated. 
Method 
In practicing the invention, the following method may be used. To operate 
crossbow 10, the bow string 16 is hooked onto catch 32, the fluid valve is 
closed with valve handle 76, drive pump lever 64 is pivoted to drive the 
forward and rearward stock portions 12 and 14, respectively, apart from 
each other to create tension in string 16 and thereby draw bow 22 back 
into a desired firing position. Then a bolt, arrow, pellet or other 
projectile (not shown) is placed in guide channel 44 adjacent to string 16 
in a conventional way. Crossbow 10 is aimed and trigger lever 36 is pulled 
in an ordinary way to release string 16 from catch 32 and release the 
energy stored in resilient bow 22 to act upon and launch the projectile 
longitudinally out of crossbow 10. The fluid valve is then opened to 
permit the stock portions to retract together. 
The degree of draw and thus the degree of firing power can be infinitely 
varied by selecting the extent of stock portion separation, which is 
accomplished by ceasing operation of lever 64 at the proper moment. A 
light draw could be appropriate where the crossbow 10 is operated at a 
site other than a range, to prevent possible injury to bystanders and to 
make fired projectiles easier to find and retrieve. 
While the invention has been described, disclosed, illustrated and shown in 
various terms or certain embodiments or modifications which it has assumed 
in practice, the scope of the invention is not intended to be, nor should 
it be deemed to be, limited thereby and such other modifications or 
embodiments as may be suggested by the teachings herein are particularly 
reserved especially as they fall within the breadth and scope of the 
claims here appended.