Abstract:
A stunning gun having a relatively massive cylindrical piston with annular recesses, such piston forming a slip fit with its containing cylinder and riding on an air bearing, is provided with a springless valving system which relies on differential air pressures to keep the valves closed and permits a massive air influx into the containing cylinder when one of the sources of air pressure acting on one of the valves is cut off by the manual opening of another valve in the system.

Description:
SPECIFICATION 
     RELATED CO-PENDING APPLICATION 
     This application is related to but constitutes an improvement over U.S. patent application Ser. No. 06/517,003, filed July 25, 1983, entitled Improved Stunning Gun and assigned to the same assignee as this application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to animal-stunning tools for use in slaughter houses. 
     2. Prior Art 
     Slaughter house techniques have varied over the ages from the crudeness of a sledge-hammer to the sophistication of electrical-shock equipment. The object of all of this equipment is to cause unconciousness in the animal during slaughter but not causing the cessation of the pumping action of the heart. The flow of blood through the animal is important to the quality of the meat obtained from the animal. 
     A search of the Patent Office records has revealed U.S. Pat. No. 4,219,905 (Thacker) which is related to but not anticipative of my invention. In the Thacker patent a piston of low mass and carrying a lowmass needle is moved forward by a blast of compressed air released through a complex combination of valves. Because of the low mass of the piston and needle, the penetrating power of the combination is limited. The combination of valves incorporated in Thacker is expensive, complex, and subject to malfunctioning. Further, the O-rings and seals in Thacker&#39;s device cause friction during operation of the piston and are also subject to wear and failure under the air pressure which must be used. 
     Therefore, it is the general object of this invention to provide an animal stunning gun which is free from the problems associated with prior art devices. 
     It is further object of this invention to provide a low-cost, highly effective stunning gun with a minimum number of parts and minimal operational problems. 
     SUMMARY OF THE INVENTION 
     By providing in a stunning gun having a relatively massive cylindrical piston with annular recesses in its outer surface, such piston having a diameter such that it forms a slip fit with its containing cylinder and rides on an air bearing, a springless valving system which relies on differential air pressures to keep the valves closed and permits a massive air flow when one of the sources of air pressure acting on one of the valves in the system is cut off by the manual opening of another one of the valves in the system, a compressed-air stunning gun with maximum simplicity and effectiveness is realized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Those and other features of my invention will be understood from the description which follows taken in connection with the accompanying drawings in which: 
     FIG. 1 is a partially cross-sectioned view of an animal stunning gun according to my invention; 
     FIG. 2 is a sectional view taken along the line 2--2 in FIG. 1; and, 
     FIG. 3 is an elevational view, partially in section, of a portion of the valving system of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1, stunning gun 10 includes cylindrical, hollow barrel 12 having an inside-diameter &#34;D&#34;. A cylindrical piston 18, of stainless steel, conventional steel or other material, having an outer-diameter &#34;O&#34; such that a slip-fit exists between piston 18 and the inner wall 19 of diameter &#34;D&#34; in barrel 12, is designed to move within barrel 12 without releasing air around its outer extremity. Piston 18 has annular recesses 20, 22, 24 and 25 which reduce surface friction between inner wall 19 and piston 18 without significantly reducing the mass of piston 18. A coaxial air passage 26 extends from end 28 of piston 18 to opposite end 30 thereof. The air passage 26 is enlarged at end 30 and internally threaded to permit insertion and retention of bolt or probe 32 therein. Probe 32 has an air passage 34 coaxially therethrough aligned with air passage 26 in piston 18. Annular stop 42 is provided on probe 32 to firmly seat probe 32 in piston 18. Piston 18 and probe 32 may be made of stainless steel to minimize corrosion and contamination. Probe 32, which must be very hard and cannot be made of stainless steel, terminates at its exposed end 36 in a concavity of conical shape. This concentrates penetrating forces in a sharp edge on end 36, enhancing the penetrating powers of probe 32. Air in front of piston 18 as it moves probe 32 into the animal&#39;s skull is exhausted through ports 31, 33. 
     Barrel 12 terminates at one end 43 in an enlarged portion 44 which may be part of barrel 12. A rubber or other shock-absorbing cushions 48, or a coil spring, is held in enlarged portion 44 by means of shoulder 47. A ring of magnetic material or a ceramic magnet, itself, 50 is secured in piston 18 near end 28. 
     The opposite end 52 of barrel 12 carries handle 54 by means of threads 56, for example. 
     Handle 54 contains therein retaining ring magnet 58 polarized to attract and cooperate with ring 50, assuming ring 50 is a magnet. Handle 54 further contains compressed air inlet aperture 60 which selectively communicates through actuating or control valve assembly 62 with intermediate chamber 64, and continuously communicates, through longitudinal and concentrically disposed channels 65, 66, 67 and 68 (FIG. 2) of insert 69 with annular surface 70 on main spool 72, urging spool 72 out of engagement with valving surface 74 of porting element 76. Insert 69 is supported coaxially in handle 54 by longitudinal, angularly spaced, ribs 71, 73, 75, 77 (FIGS. 1 and 2). 
     Porting element 76 has a coaxially disposed opening 78 and peripherally disposed, but spaced openings, 80, communicating through openings in magnetic ring 50, with end 28 of piston 18. Porting element 76 carries &#34;O&#34;-ring 82 to prevent air leakage thereby. 
     Activating-valve-assembly 62 includes plug 84 which is secured in insert 69 by means of threaded region 86. In addition, control spool 88 with its actuator rod 90 is guided but is free to move along its axis between the inner-upper conically-shaped surface 92 of plug 62 and the lower stepped-conical surface 94 of insert 69. The configuration of control spool 88 can be seen more clearly in FIG. 3. 
     Actuator rod 90 is engaged by trigger 96 which is pivotally supported on bracket 98, which, in turn, is secured to handle 54 by shoulder 100 on plug 62. 
     When a source of air or other compressible fluid under pressure is connected to inlet 60, the initial surge of air causes control spool 88 to move to its upper limit, at which point the upper conical surface 104 of control spool 88 engages inner-upper surface 92 of plug 62 and prevents any flow of air around spool 88 and actuator rod 90, to the atmosphere. However, the lower conical surface 106 of spool 88 then is no longer seated on inner-lower surface 94 of insert 69. As a result, air or other activating fluid may flow freely around spool 88 and thru opening 108 into intermediate chamber 64, thereby putting full source pressure on face 110 of main spool 7, urging it with considerable force towards valving surface 74 of porting element 76 and preventing the flow of air into outlet chamber 79. At the same time, however, there is a lesser but significant counter-force caused by pressure on annular surface 70 as a result of air flowing through longitudinal channels 65, 66, 67 and 68, and openings 112 caused by a fore-shortening of the body portion 114 of insert 69 between ribs 71, 73, 75, 77 (FIG. 2). This counter-force is small compared to the main force acting on surface 110 of spool 72, because of the significant difference in areas of surfaces 110 and 70. But that counterforce becomes significant, as will be explained hereinafter. 
     Upon depression of trigger 84, with piston 18 in a retracted position, air under pressure behind surface 110 of main spool 72 is vented, through depressions or serrations 89 in control spool 88, to the atmosphere and the entry of further air to intermediate chamber 64 is cut off by the engagement between surface 106 of spool 88 and lower-inner surface 94 of insert 69. Thus, all pressure urging main spool 72 into closing engagement with surface 74 of porting element 76 is removed. At the same moment, however, the reverse pressure on annular surface 70 urging spool 72 out of engagement with surface 74 remains and forces spool 72 into the &#34;valve-open&#34; position. The air, under pressure, from inlet 60 is applied, with full force, thru openings 78 and 80 and thru magnet 50 to end 28 of piston 18, propelling it forward with great speed and force. Probe 32 penetrates the skull of the animal and enters its brain. Compressed air is injected through openings 31, 33 into the brain cavity thus causing the animal to become comatose, although the heart pumping action continues in the animal. The rebound action produced by the cushions 48 assists the removal of the probe 32 from the skull. The gun is then re-cocked by holding it with probe 32 upright, causing probe 32 to retract into a position with magnetic material 50 in contact with ring magnet 58. 
     It should be noted that magnet 58 may be an electromagnet. The flux field of magnet 58 is made such that ring 50 and piston 18 are retained in the retracted position until the pressure on piston 18 becomes high so that piston 18 is released in impulse fashion and achieves its operating speed rapidly. Further, the length of barrel 12 is made longer than the combined lengths of piston 18 and the exposed portion of probe 32 so that the combination of piston and probe will achieve a significant forward momentum before probe or bolt 32 strikes the skull of the animal being stunned. 
     Piston 18 rides on an air bearing produced by the impulse of air applied to its surface 28. No O-rings are required to prevent pressure loss because the surge of air produced when control valve 88 is actuated is so great as to form an air barrier at the outer periphery of surface 28. 
     Thus, it can be seen that there has been provided a stunning gun which is simple in construction, is subject to little failure in operation and is effective in its performance. 
     While particular embodiments have been shown and described, it will be apparent to one skilled in the art that variations and modifications thereof may be made without departing from the spirit and scope of my invention. It is the purpose of the appended claims to cover all such variations and modifications.