Patent Description:
In livestock production plants, it is important to stun and disable an animal for processing. In livestock production farms, it is important to euthanize animals suffering from severe injury or irreversible disease so as to prevent the spread of illness. Although numerous methods have been used to stun and euthanize livestock, captive bolt mechanisms have proven to be the most efficient, inexpensive, and humane way to disable the animal. Particularly, pneumatic captive bolt devices have been used in this capacity.

Pneumatic stunners that provide for automatic retraction of the stunning rod typically have complex valve systems that are more difficult to manufacture and tend to add to the cost of the stunner. Such valve systems also tend to add to weight to the device, which may increase operator fatigue. Additional issues involve the requirement of supplying the pressurized fluid at relatively high pressures, typically in the range of <NUM> - <NUM> psi (<NUM> - <NUM> MPa). Portable stunners are generally lighter in weight, but after firing often require manual retraction of the stunning rod, also adding to operator fatigue.

In <CIT>, titled "STUNNER", an animal stunner used in livestock/slaughterhouse operations teaches a piston slideable within an inner chamber, and a fire pressure chamber within an annular configuration disposed adjacent a rearward or central end of the inner chamber. A valve system alternately controls flow of the pressurized fluid from the fire pressure chamber to the rearward end of the inner chamber to move the piston and drive the stunning rod. In contrast, the present invention utililzes reduced pressure of the pressurized fluid needed for operation, and has reduced complexity in valve and venting systems.

Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a pneumatic animal stunner and method of use that has reduced complexity in valve and venting systems and reduced cost to manufacture.

It is another object of the present invention to provide a pneumatic animal stunner that has reduced weight and reduced operator fatigue.

It is a further object of the present invention to provide a pneumatic animal stunner that may use reduced pressure of the pressurized fluid needed for operation, and has rugged construction to avoid accidental firing and damage.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The above and other objects, which will be apparent to those skilled in the art, are achieved in the present invention which is directed to a pneumatic animal stunner as set out in the appended set of claims <NUM>-<NUM>, which includes a housing having a catch piston chamber, a stunning rod chamber, a supply passageway disposed in the housing between a source of pressurized fluid and the catch piston chamber, a catch mounted within the housing for alternately holding and releasing the stunning rod, and a catch piston disposed adjacent the catch and in sliding contact within the catch piston chamber, the catch piston being adapted to move between a first position urging the catch to hold and prevent the stunning rod from being driven forward, and a second position permitting the catch to release and permit the stunning rod to be driven forward. A first passageway in the catch piston permits air to flow from the source of pressurized fluid through the first passageway to a rearward end of the stunning rod chamber. A second passageway in the catch piston permits air to flow from the source of pressurized fluid through the second passageway to a forward end of the stunning rod chamber.

The present invention is also directed to a method of stunning an animal. The method provides for a pneumatic animal stunner according to claims <NUM>-<NUM>. The method includes the steps according to claims <NUM>-<NUM>, including: moving the catch piston into the first position urging the catch to hold and prevent the stunning rod from being driven forward, moving the catch piston towards the second position to release the catch, causing pressurized fluid to flow from the source through the first passageway into the rearward end of the stunning rod chamber to drive the stunning rod forward upon release of the catch to stun the animal, and, upon movement of the catch piston into the second position, flowing pressurized fluid from the source through the second passageway into the forward end of the stunning rod chamber to drive the stunning rod rearward.

The invention also relates to a catch piston according to claim <NUM> for use in opening and closing catches in such a pneumatic animal stunner.

In an embodiment not part of the claimed invention, the method further provides a resilient annular cushion disposed at a front end of the stunning rod chamber, and an internal passageway. The method further includes the step of causing pressurized fluid to flow through the internal passageway into the forward end of the stunning rod chamber between the pair of resilient annular cushions to drive the stunning rod rearward.

The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. Some figures relate to embodiments that are not according to the invention, and are present for illustration purposes only. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:.

In describing the embodiment(s) of the present invention, reference will be made herein to <FIG> of the drawings in which like numerals refer to like features of the invention.

Structure and operation of the exemplary animal stunner <NUM> is shown in general in the cross-sections of <FIG> and the perspective and side views of <FIG>, and in the components shown in <FIG>. The stunner <NUM> includes an outer elongated hollow housing <NUM>, a head contact activator <NUM> moveable within an outer housing nose <NUM>, a front end <NUM>, a tail end <NUM>, a stunning rod <NUM> moveable forward and rearward about longitudinal axis <NUM> and catches <NUM> arrayed about longitudinal axis <NUM> for holding and releasing the stunning rod <NUM>. The stunner is grasped by a main handle <NUM> extending below body <NUM> and a rear handle <NUM> extending from tail end <NUM>. The forward and rearward directions described herein are with respect to the stunner front end <NUM>, and inward and outward directions described herein are with respect to axis <NUM>. Housing <NUM> includes within it a generally cylindrical inner pressure or stunning rod chamber <NUM> for the stunning rod and piston and a surrounding firing chamber <NUM> to receive and hold a pressurized fluid.

A circular stunning rod piston <NUM> surrounded by an O-ring seal <NUM> slides along the inner cylindrical surface of inner chamber <NUM> within housing <NUM>. Piston <NUM> moves forward and rearward along axis <NUM>, and carries stunning rod <NUM>. In the embodiment shown the stunning rod and piston are formed integrally of one piece, but they may be separate components secured together. An annular firing chamber <NUM> surrounds inner chamber <NUM> within housing <NUM> and is open at the rear, so that air can move freely and quickly from firing chamber <NUM> to the region of inner chamber <NUM> behind piston <NUM> upon firing of the stunner, as explained further below. Nose rear wall <NUM> at front of chamber <NUM> limits forward motion of piston <NUM> and stunning rod <NUM>, and carries a pair of resilient annular cushions 25a, 25b. The rearward end <NUM> of stunning rod <NUM> has an opening with an inward lip <NUM> extending about its periphery, which lip is alternately held and released by an outwardly extending flange <NUM> at the forward end of catch <NUM>. The body or shaft of stunning rod <NUM> may be circular or non-circular in shape as viewed in cross-section normal to the longitudinal axis. The forward or striking end <NUM> of the stunning rod extends in a sliding fit through a correspondingly configured opening <NUM> in head contact activator <NUM> at the front of housing <NUM> to be driven toward the animal's head when the catch releases the stunning rod lip <NUM>. The stunning rod forward end <NUM> is sized with a diameter and configuration either to penetrate, or prevent penetration of (i.e. concuss), the animal's head. The example shown in <FIG> is of a penetrating rod.

The catch system for holding and releasing the stunning rod as shown in the embodiment is disposed rearward of stunning rod chamber <NUM> in the rear of housing <NUM>. Catches <NUM> are further shown in <FIG> and in the embodiment shown are three (<NUM>) arcuate catches arrayed around axis <NUM>. Each catch may have a body curved in an arc segment about the longitudinal axis, with outwardly extending flanges <NUM> and <NUM> at the front and rear ends, respectively. Each catch <NUM> in the embodiment shown has an arc of more than <NUM>° and less than <NUM>° so that three catches may be arranged cylindrically about the longitudinal axis <NUM> with sufficient space between adjacent catches to pivot inwardly without interfering with one another. Fewer or more than three catches may be employed. A generally hollow cylindrical catch retainer <NUM> extends forward from the rear end of housing <NUM>. The front portion of catch retainer <NUM> extends over and around, and secures the rearward end portions of catches <NUM>. The catch retainer <NUM> has at its forward end an inwardly facing groove, which receives the catch rear end flanges <NUM> extending on a side away from axis <NUM>. Catch release piston <NUM> (see also <FIG>) slides within a central opening in catch cylinder <NUM> (see also <FIG>) disposed on stunner tail end <NUM> and a front portion is slidingly received within the central opening of retainer <NUM> and moves forward and rearward along axis <NUM>, as shown in cross-section in <FIG>. Catch piston <NUM> has circular release piston portion <NUM> sliding within a cylindrical catch piston chamber <NUM> behind the rear portion of catch retainer <NUM>. Catch release piston <NUM> has a central opening <NUM> extending along axis <NUM> to forward end <NUM>, and forward of release piston portion <NUM> catch release piston <NUM> has a generally cylindrical body portion within and contacting the rearward ends of catches <NUM> (see also <FIG> and <FIG>). The support provided to the catch rear end portions by the inner catch piston body and the outer catch retainer permits the catches <NUM> to rotate and their forward end flanges <NUM> to pivot inwardly and outwardly around rearward end flanges <NUM> in the retainer <NUM> groove.

The catch forward ends are moved outwardly to a hold position, away from axis <NUM>, so that forward end flanges <NUM> contact the rod <NUM> rear end portion and prevent the stunning rod from being driven forward. To accomplish such movement, catch piston <NUM> has a forward end portion <NUM> within the catches which has a diameter sufficient to contact and urge catch forward end portion flanges <NUM> outward into engagement with the stunning rod opening lip <NUM>. When catch piston <NUM> is moved rearward into the hold position, the catch forward end portion <NUM> is aligned with and in contact with both the stunning rod opening lip <NUM> and the catch piston forward end portion <NUM>.

Rearward of the forward end portion <NUM> the catch piston has a relief portion <NUM> with a diameter smaller than the forward end portion diameter. This relief portion diameter is sufficiently small to permit catch forward end portion <NUM> to move freely inward to the release position, with flanges <NUM> out of engagement with the stunning rod opening lip <NUM>. When catch piston <NUM> is moved forward from the first, hold position to the second, release position, catch front ends <NUM> are no longer in a position to prevent catch front end <NUM> from moving inward. The rearward sides of front flanges <NUM> are beveled <NUM> at an angle greater than <NUM>° with the catch body <NUM> (see also <FIG> and <FIG>), so that as piston <NUM> and stunning rod <NUM> move forward pressure from stunning rod lip <NUM> will cause flanges <NUM> to spring inward into relief portion <NUM> as the stunning rod lip moves along the beveled flange surfaces <NUM>. When the catch forward end flanges <NUM> are disengaged from rod lip <NUM>, the stunning rod <NUM> is fully released and driven forward.

Stunner <NUM> is operable by pressurized fluid, such as compressed air or any other suitable fluid. For the example shown, compressed air is the fluid and is supplied from a hose or line connected to an air compressor. Air pressure and flow may be controlled by a regulator (not shown) and the compressed air flows through into inlet <NUM> in housing <NUM>, rearward of main handle <NUM>.

Flow of the pressurized air is then split after inlet <NUM>, between internal passageway <NUM> and trigger supply passageway <NUM>. Internal passageway <NUM> communicates with catch release piston <NUM>, and the terminus of the passageway may encircle the piston, and trigger supply passageway <NUM> communicates with main valve <NUM> operated by trigger <NUM> in handle <NUM>. A spring (not shown) in valve <NUM> urges the valve into a first, downward position, and urges the trigger to the undepressed position. When trigger <NUM> is in the undepressed position, a first passage 112a in main valve <NUM> permits air to flow from trigger supply passageway <NUM> to supply passageway <NUM>, in communication with catch piston cylinder chamber <NUM>.

When the pressurized fluid source is connected via inlet <NUM>, catch release piston <NUM> is locked in the first, rearward hold position, supply trigger <NUM> is undepressed, and stunner <NUM> is in a neutral state, as shown in <FIG>. Air flows up through passageway <NUM>, the terminus of which encircles chamber <NUM> adjacent a rear portion of catch piston <NUM>. One or more first radial passageways <NUM> extend through the body of catch piston <NUM> from the periphery to catch piston central opening <NUM>, and passageways <NUM> and <NUM> are aligned when catch piston <NUM> is rearward in the hold position. Because there are spaces between the individual catches <NUM>, pressurized air may flow freely from passageway <NUM> through passageway <NUM>, through central opening <NUM> and forward within stunning rod lip <NUM> to inner chamber <NUM>, behind stunning rod piston <NUM>, and through the open rear end into firing chamber <NUM> around the inner chamber. To maintain catch release piston <NUM> in the hold position, alignment of the first slot 112a in main valve <NUM> in the trigger <NUM> undepressed position allows pressurized air to flow through supply passageway <NUM> to catch piston cylinder chamber <NUM> forward of the catch release piston portion <NUM> and rearward of catch retainer <NUM>, urging catch piston <NUM> rearward. This constant pressure holding catch piston <NUM> is maintained so long as trigger <NUM> remains undepressed, which ensures the stunning rod <NUM> does not fire accidentally in the event the stunner is dropped or otherwise mishandled.

Catch piston <NUM> includes in its body a second passageway <NUM>, rearward of the first passageway <NUM>, which in the embodiment shown comprises an open-top slot in the outer wall of catch piston <NUM> extending around all or a portion of the circumference of the catch piston. In the hold position of <FIG>, second passageway <NUM> is aligned with passageways 90a and 90b, whose ends encircle the catch release piston and are connected, and vent to atmosphere. Second passageway <NUM> is also aligned with passageway <NUM>, and encircles the chamber, and which extends forward from catch release piston chamber <NUM> to the forward end of inner chamber <NUM> and in communication with one or more openings <NUM> alongside and between cushions 25a, 25b. Rearward of second passageways <NUM>, third radial passageways <NUM> extend from central opening <NUM> to the periphery of the catch piston <NUM> body.

Pressurized fluid from the rear of firing chamber <NUM> exerts a force against stunning rod piston <NUM>, which is held from forward movement only by the position of catch flanges <NUM> retaining stunning rod rear lip <NUM>.

To actuate the firing of stunning rod <NUM>, an embodiment of the present invention employs main trigger <NUM>, controlling main handle valve <NUM>, in combination with head contact activator <NUM>. In the embodiment shown, a head activator chamber passageway <NUM> extends through the handle and housing from main valve <NUM> forward to head contact activator <NUM>. A passageway <NUM> extends rearward from head contact activator <NUM> to the back end of catch piston cylinder chamber <NUM>. Passageway <NUM> does not intersect with passageway <NUM>.

The head contact <NUM> slides fore and aft within nose <NUM> forward of chamber <NUM> (see also <FIG>) and is extended by spring (not shown) pressure toward a forward (rightward) position. In the forward, deactivated position, the rear portion or cylindrical projection <NUM> of the head activator <NUM> extends partially through the opening in the nose rear wall <NUM> at the rear of the activator chamber <NUM>, and within the opening of forward cushion 25a. A head contact passageway <NUM> comprises a slot extending around the periphery of the cylindrical body <NUM> of head contact <NUM>. When trigger <NUM> is undepressed, head contact slot <NUM> is not aligned with passageway <NUM>, and a second passage 112b in valve <NUM> aligns to vent any air in head activator passage <NUM> to atmosphere through an opening in the handle <NUM>. When head contact <NUM> is in the forward position, head contact passageway <NUM> is aligned with both passageway <NUM> and head contact vent <NUM>, and when the catch release piston <NUM> is in the rearward position, catch piston slot <NUM> is aligned with both passageway <NUM> and vent passageway 90b, so that the rearward end of catch piston cylinder chamber <NUM> vents through the front of housing <NUM>, via vent <NUM>, and the forward end of inner chamber <NUM> vents through the rear of housing <NUM>, via vent 90b, as shown in <FIG>. The stunner will not fire in this position, wherein main trigger <NUM> and head contact <NUM> are not depressed. Optionally, a second or auxiliary trigger <NUM> may be provided to open and close flow though passageway <NUM>, which also must be depressed to open passageway <NUM> and actuate the stunning rod, as discussed further below. Installation of this optional auxiliary trigger <NUM> may require passageway <NUM> to be accessed at a point closer to the tail end <NUM> of the housing to allow for this added safety feature, with no additional change to the flowpath of passageway <NUM> as shown in <FIG> being required.

To commence the firing sequence, the main handle valve <NUM> is activated by the operator depressing main trigger <NUM> with one hand against the force of the spring in the valve, and head contact <NUM> is activated by the operator pressing against the animal's head to move and depress the contact <NUM> rearward (leftward) in the direction shown by the arrows against the force of the head contact spring, as shown in <FIG>, so the rear portion of the head activator <NUM> moves further into the opening in the rear of the activator chamber <NUM>. As the main handle valve <NUM> moves into the second, upward position, valve <NUM> first passageway 112a connects passageway <NUM> with the handle vent opening and pressurized air from the forward end of catch piston cylinder chamber <NUM> is exhausted to the atmosphere, and valve <NUM> second passageway 112b connects passageway <NUM> to passageway <NUM> to provide pressurized air from inlet <NUM> to head contact activator <NUM>. Since head contact <NUM> is in the rearward position, head contact slot <NUM> aligns with head activator passageway <NUM> and permits communication between passageways <NUM> and <NUM>. Compressed air then flows via passageway <NUM> to the rearward end of catch piston cylinder chamber <NUM>. If the optional auxiliary trigger <NUM> is used, it must be depressed to open the valve to permit pressurized air flow through passageway <NUM>. As a result of main trigger <NUM> and head contact <NUM> being depressed, and optionally auxiliary trigger <NUM>, catch release piston <NUM> is moved by the compressed air in the rear of chamber <NUM> and begins to extend forward (rightward) to its limit, against catch retainer <NUM>. This forward movement of end <NUM> releases catches <NUM> and permits inward retraction of forward catch latches <NUM> to relief portion <NUM>. A result of the pressurized air behind stunning rod piston <NUM>, stunning rod lip <NUM> is urged forward and moves against the catch beveled flange surfaces <NUM>, moving catch forward end flanges inward and releasing stunning rod <NUM>.

The pressure of air from inlet <NUM> that had flowed through catch piston central opening <NUM> (<FIG>) is assisted by pressurized charge air flowing from firing chamber <NUM> against the rear of piston <NUM>. As a result, as stunning rod <NUM> is released from the catches it moves forward (rightward) at a high rate of speed, with the stunning rod forward or striking end <NUM> moving through the head contact opening <NUM> in the direction of the arrow as shown in <FIG>. The remaining air in inner chamber <NUM> forward of the stunning rod piston <NUM>, which previously had been vented (<FIG>) begins to be compressed.

<FIG> shows the catch piston in an intermediate position as it is moved forward from the first, hold position toward the second, release position. Passageway <NUM> has moved out of alignment from passageway <NUM>, and passageway <NUM> is consequently closed to prevent the pressurized fluid from flowing from inlet <NUM>. When the catch piston is moved forward toward the release position, operation of valve <NUM> by depressing the supply trigger does not permit further pressurized fluid to flow from the source into either the inner stunning rod chamber <NUM> or firing chamber <NUM> because of the misalignment of supply passageway <NUM> and catch piston first passageway <NUM>. Because the catch piston <NUM> has begun to be moved forward toward its second release position, the second passageway slot <NUM> is not yet aligned with supply passageway <NUM>.

<FIG> shows the animal stunner <NUM> with the stunning rod <NUM> in the full forward, end-of-stroke position. At the end of the forward stroke of stunning rod <NUM>, piston <NUM> contacts cushion 25b, and both cushions 25b and 25a at the forward end of stunning rod chamber <NUM> compress to cause forward motion of piston <NUM> and rod <NUM> to decelerate and stop within the stunning rod chamber. The stunning rod striking end <NUM> is now fully extended through head contact opening <NUM>.

Since the catch piston <NUM> is still in the second, forward position, pressurized fluid continues to flow from the source through the supply passageway <NUM>, through the slot <NUM> extending around the catch piston <NUM> and into internal passageway <NUM> and through openings <NUM> into the forward end of the stunning rod chamber <NUM> at cushions 25a, 25b ahead of stunning rod piston <NUM>. A portion of the pressurized air flows from the front of stunning rod chamber <NUM> through a passageway comprising one or more small slots <NUM> between the rear portion or projection <NUM> of the head contact activator <NUM> and the opening in nose rear wall <NUM> at the rear of the activator chamber <NUM>, which pressurized air along with the spring assist moves the head contact <NUM> fully forward to its deactivated position. While one or more of these slots <NUM> may be formed in or around the opening in nose rear wall <NUM> (<FIG>), the embodiment shown in <FIG> for the head contact <NUM> shows slots <NUM> comprising four (<NUM>) slots or grooves arrayed around and formed in the periphery of the rear portion or projection <NUM> of the head contact activator. With the head contact <NUM> in the forward, deactivated position, further flow of pressurized air from main valve <NUM> through passageway <NUM> is blocked, and head contact passageway <NUM> connects passageway <NUM> to the head contact vent <NUM> to exhaust air pressure from catch piston cylinder chamber <NUM> to the atmosphere, so that catch piston <NUM> is no longer urged forward. This air flow through passageway <NUM> to push head contact <NUM> forward acts as a safety feature, so that the stunner can not be repeatedly fired by continuing to press the trigger.

With the catch release piston <NUM> remaining in the second, forward position, third radial passageways <NUM> are in alignment with vent passageways 90a, 90b, and permit air behind piston <NUM> to flow through catch piston central opening <NUM> and vent to atmosphere out of housing rear portion <NUM>. Pressurized air being supplied from passageway <NUM> to the forward end of stunning rod chamber <NUM> acts against stunning rod piston <NUM> to begin to drive it rearward.

As shown in <FIG>, the pressurized air in chamber <NUM> forward end retracts the stunning rod <NUM> rearward (leftward; as shown by the arrow) until lip <NUM> of stunning rod <NUM> passes behind the front flanges <NUM> of catches <NUM>, and stunning rod rear end <NUM> contacts the forward end <NUM> of catch piston <NUM>. Because catch piston cylinder chamber <NUM> is fully vented fore and aft of catch release piston portion <NUM>, as stunning rod piston strikes forward end <NUM>, catch release piston <NUM> is free to begin to move back from the second, forward position toward the first, hold position. In an intermediate position between the second and first positions, the catch piston second passageway <NUM> moves out of alignment with air supply passageway <NUM>, third passageway <NUM> moves out of alignment with vent passageways 90a, 90b, and catch piston first passageway <NUM> is not yet in alignment with the air supply passageway <NUM>. As a result, in this intermediate position no additional pressurized air is supplied into stunning rod chamber <NUM> forward of the stunning rod piston <NUM>, and the stunning rod piston <NUM> is driven back by the remaining air pressure.

However, as a result of momentum of piston <NUM> striking it, catch piston <NUM> is retracted rearward (leftward) into the catch cylinder <NUM> fully into its first, hold position. This rearward movement closes the catches <NUM> by the force of catch piston forward end <NUM> sliding within the catch forward end portions and urging them outward to cause catch forward end flanges <NUM> to engage and capture stunning rod lip <NUM>, so that the stunning rod <NUM> is retained by the catches, as shown in <FIG>. and the stunner is automatically reset. Trigger <NUM> may be released by the operator, and in its undepressed position as shown in <FIG>, with catch piston <NUM> is the first, neutral, hold position, the stunner is again pressurized via air through supply inlet <NUM> and the initial, downward position of valve <NUM> as described above, so that pressurized air flows via passageway <NUM> to urge catch piston portion <NUM> rearward and prevent catch piston <NUM> and stunning rod <NUM> from forward motion, so that the stunner is ready for operation again.

An alternate embodiment of a nose <NUM>' and a head contact activator <NUM>' disposed on a front end <NUM>' of an animal stunner <NUM>' and sized to receive a larger stunning rod <NUM>' having a larger striking end <NUM>' is presented in <FIG>. This particular nose and head contact configuration is for use in the animal stunner <NUM>' embodiment constructed to prevent penetration of (i.e. concuss) an animal's head, as previously described.

The head contact <NUM>' slides fore and aft within nose <NUM>' forward of chamber <NUM>' and is biased by a spring <NUM> pressure toward a forward (rightward) position. A nose valve <NUM> is disposed within the nose <NUM>' and is interactive via the sliding motion of the head contact <NUM>'. In the forward, deactivated position, a cylindrical projection <NUM>' of the head contact activator <NUM>' extends partially through the opening in the front end of the nose <NUM>', and is disengaged with the nose valve <NUM>. The stunner will not fire in this position, wherein main trigger <NUM> and head contact <NUM>' are not depressed.

To commence the firing sequence, the main handle valve <NUM> is activated by the operator depressing the main trigger <NUM> with one hand (and optionally auxiliary trigger <NUM> with the other hand) against the force of the spring in the valve <NUM>, and nose valve <NUM> is activated by the operator pressing the head contact <NUM>' against the animal's head to move and depress the head contact <NUM>' rearward (leftward) against the force of the springs <NUM>, as shown in <FIG>, such that a head contact tab 18a' extending from the rear portion of the head contact <NUM>' engages with the nose valve <NUM> to activate it and allow for the passage of fluid.

The larger striking end <NUM>' of the stunning rod <NUM>' used in the stunner <NUM>' has a larger diameter than that of its penetrating counterpart <NUM> as previously described. This striking end <NUM>' is affixed to the end of the rod <NUM>' by a bolt, screw, nail, or other acceptable fastening means. The inner diameter of head contact <NUM>' conforms to this striking end <NUM>' diameter to allow for a sliding fit, such that the rod does not rattle or otherwise displace itself during the firing sequence.

The remainder of the firing sequence and construction of the stunner <NUM>' is similar to that as described above for the penetrating stunner <NUM>, and other salient features of the concussion stunner <NUM>' may alternately be constructed as described in <CIT> titled "CONCUSSION STUNNER ROD AND NOSE".

The stunner and its components may be made of steel, aluminum, composite or other suitable materials. For example, the stunning rod may be constructed as described in <CIT> titled "LIGHTWEIGHT STUNNING ROD". The construction of the stunner shown is sufficiently robust so that it will avoid accidental firing if dropped by the operator.

The present invention therefore provides a pneumatic animal stunner and method of use that has one or more of the following advantages: <NUM>) reduction in the complexity of valve and venting systems; <NUM>) reduced cost to manufacture the stunner; <NUM>) reduction in weight of an automatically retracting stunner; <NUM>) reduced operator fatigue in using the stunner; <NUM>) reduced pressure of the pressurized fluid needed to operate the stunner, which may be below <NUM> psi (<NUM> MPa) and as low as about <NUM> psi (<NUM> MPa) and rugged construction to avoid accidental firing and damage.

Claim 1:
A pneumatic animal stunner (<NUM>) comprising:
a housing (<NUM>) having a catch piston chamber (<NUM>), a stunning rod chamber (<NUM>) and a front end (<NUM>) forward of the stunning rod chamber,
a supply passageway (<NUM>) in the housing (<NUM>) between a source of pressurized fluid and the catch piston chamber;
a stunning rod (<NUM>) slideable within the stunning rod chamber (<NUM>) capable of being driven forward along a longitudinal axis (<NUM>) towards and out of the front end (<NUM>) of the housing;
a catch (<NUM>) mounted within the housing for alternately holding and releasing the stunning rod;
a catch piston (<NUM>) disposed adjacent the catch and in sliding contact within the catch piston chamber, the catch piston being adapted to move between a first position urging the catch to hold and prevent the stunning rod from being driven forward, and a second position permitting the catch to release and permit the stunning rod to be driven forward;
a first passageway (<NUM>) in the catch piston in alignment with the housing supply passageway when the catch piston is in the first position permitting air to flow from the source of pressurized fluid through the first passageway to a rearward end of the stunning rod chamber; and
a second passageway (<NUM>) in the catch piston in alignment with the supply passageway when the catch piston is in the second position permitting air to flow from the source of pressurized fluid through the second passageway to a forward end of the stunning rod chamber;
wherein when the catch piston is in the first position, pressurized fluid may flow from the source through the supply passageway and the first passageway into the rearward end of the stunning rod chamber to drive the stunning rod forward upon release of the catch, and when the catch piston is in the second position after releasing the catch, pressurized fluid may flow from the source through the supply passageway and the second passageway into the forward end of the stunning rod chamber to drive the stunning rod rearward.