GB2407290A

GB2407290A - Apparatus for firing a product

Info

Publication number: GB2407290A
Application number: GB0324603A
Authority: GB
Inventors: Alan David Page
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-10-21
Filing date: 2003-10-21
Publication date: 2005-04-27
Anticipated expiration: 2023-10-21
Also published as: GB0324603D0; GB2407290B

Abstract

Apparatus 2 for firing a product 4, which apparatus comprises a body portion 8, a discharge chamber 10 in the body portion, and an elongate member 12 which is slidable in the body portion, and the apparatus being such that the elongate member is caused to slide in the body portion by a fluid. The apparatus may include first means, such as coil springs 14, for moving the elongate member to a non-firing position, and second means 16 for moving the elongate member to a firing position, such as gas introduced into a discharge chamber 10. The elongate member moves from the non-firing position to the firing position when pressure from the second means exceeds pressure from the first means. The apparatus may be a gun for firing a bullet, staple, rivet, harpoon or dart. It may also be used in the needleless injection of medical products into a human or animal body (Figure 3). A pressure regulating valve is also disclosed (Figure 2).

Description

APPARATUS FOR FIRING A PRODUCT

This invention relates to apparatus for firing a product.

There are many different types of apparatus for firing a product. Thus, for example, the apparatus may be a firearm for firing a product in the form of a bullet, a staple gun for firing a product in the form of a staple, or a rivet gun for firing a product in the form of a rivet.

The known different types of apparatus for firing a product operate in many different ways and come in many different designs.

It is an aim of the present invention to provide apparatus for firing a product, which apparatus operates in a novel, simple and highly effective manner.

Accordingly, in one non-limiting embodiment of the present invention there is provided apparatus for firing a product, which apparatus comprises a body portion, a discharge chamber in the body portion, and an elongate member which is slidable in the body portion, and the apparatus being such that the elongate member is caused to slide in the body portion by a fluid.

In a first embodiment of the invention, the apparatus includes first means for moving the elongate member to a non-firing position, and second means for moving the elongate member to a firing position, the apparatus being such that the elongate member moves from the non-firing position to the firing position when pressure from the second means exceeds pressure from the first means, and such that the elongate member moves from the firing position to the non-firing position when pressure from the first means exceeds pressure from the second means, and the second means being the fluid.

The second means may be a fluid in the form of a gas.

Any suitable and appropriate gas may be employed so that, for example, the gas may be air, oxygen, hydrogen, helium or carbon dioxide. When the second means is a fluid in the form of a gas, then the gas may be a single gas or a mixture of gases.

The second means may alternatively be a fluid in the form of a liquid. Any suitable and appropriate liquid may be employed including liquified gases, fuels and oxidising agents and mono-propellants Preferably, the first means is a spring. Devices other than springs may be employed if desired. Where a spring is employed as the first means, then the spring is preferably a coil spring. Springs other than coil springs may be employed.

The elongate member is preferably of a circular cross sectional shape.

Where the elongate member has a circular cross sectional shape, then the elongate member may comprise a downstream end, an upstream end, and a central portion positioned between the downstream end and the upstream end, the central portion being of a larger diameter than the downstream end and the upstream end. The downstream end may be of a larger diameter than the upstream end.

The apparatus of the invention may include pressure regulating means for regulating the pressure of the second means.

The pressure regulating means may be a pressure regulating device comprising a valve housing, a valve member in the valve housing, and biasing means for biasing the valve member to a predetermined position in the valve housing. The valve member may have a head and a shank, the shank being a hollow shank having a bore for permitting the passage of the second means through the valve member.

The pressure regulating device may include a resilient buffer seal which is adapted to be engaged by an end of the shank remote from the head when it is desired to seal the shank and prevent the passage of the fluid through the valve member.

The apparatus of the invention may include a trigger mechanism. The trigger mechanism may comprise a trigger and a sear.

In a second embodiment of the invention, the apparatus may include releaseable retainer means for retaining the elongate member in a prefiring position in which the elongate member is ready to be slid by the fluid.

The releaseable retainer means may comprise radially movable segments which are held in position by a retainer ring, the retainer ring being slidable to a position in which the radially movable segments are released, thereby to allow the sliding of the elongate member by the fluid.

The apparatus of the present invention may be produced in a wide variety of different designs for a wide variety of different uses. Thus, for example, the apparatus of the invention may be produced such that it is single firing apparatus, semi-automatic firing apparatus, or automatic firing apparatus, or single use, non-reloadable form. Also by way of example, the apparatus may be produced such that it fires using internal combustion or not using internal combustion.

The apparatus of the present invention may be produced as a firearm, in which case the product that is fired will usually be a bullet or shot. As indicated above, the firearm may be a single shot firearm, a semiautomatic firearm, an automatic firearm or a single use non- reloadable firearm. The firearm can be a low powered firearm, a medium powered firearm, a high powered firearm or a low/medium/high powered air or gas gun.

In alternative embodiments of the invention, the apparatus of the present invention may be a tool. For example, the apparatus of the invention may be a staple gun for firing a product in the form of a staple, a nail gun for firing a product in the form of a nail, or a rivet gun for firing a product in the form of a rivet.

The apparatus of the invention may be embodied in projectiles such as rockets, bombs, darts or bullets.

The apparatus of the present invention may alternatively be a harpoon gun for firing a product in the form of a harpoon or a fish spear.

Still further, the apparatus of the present invention may be medical or cosmetic apparatus for firing substances or objects through the skin into the blood stream of humans and animals. In this case, the product may be a pharmaceutical product or medicine and it may be in any suitable and appropriate form, for example in the form of a powder or a liquid. If desired, the product may be in the form of biological material such as hair folicles, cells, cellular, sub-cellular or genetic materials, bacteria, viruses and fungi or chemical substances or electronic devices or nano mechanisms.

In the above examples of apparatus of the present invention, it will be apparent that the product that is fired actually leaves the apparatus and does not return.

This is not always necessary and, for example, the apparatus of the present invention may be constructed for firing a product that does not actually leave the apparatus but that moves to and fro in a reciprocal manner. Thus, for example, the apparatus may be hammer apparatus for causing the repeated operation of a product in the form of a hammer, or chisel apparatus for causing the repeated operation of a product in the form of a chisel. Still further, the apparatus of the present invention may fire a needle or a matrix of needles into the skin of a human or animal for the purpose of subsequently passing a pharmaceutical product, medicine or pigment through or around the needle or needles and into the skin blood stream or other appropriate tissues of the humans or animals.

The apparatus of the present invention may further be embodied within a projectile, such as a dart or harpoon, arranged such that the trigger part or its functional equivalent is released upon impact or contact with a target.

The apparatus of the present invention may be made from any suitable and appropriate materials. These materials will vary depending upon the intended use of the apparatus of the invention. Thus, for example, the apparatus may be made of metals, plastics materials, ceramic materials, and combinations of these materials.

The apparatus may be constructed to operate with seals or without seals and relying on close fitting parts to achieve gas sealing.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 is a longitudinal cross sectional view through first apparatus of the present invention; Figure 2 is a longitudinal sectional view through a gas regulating device for connection to the apparatus shown in Figure 1; Figure 3 is a longitudinal cross sectional view through second apparatus of the present invention; and Figure 4 is a longitudinal cross sectional view through third apparatus of the present invention.

Referring to Figure 1, there is shown apparatus 2 in the form of a fully automatic machine gun mechanism for firing a product in the form of a plurality of bullets 4.

The bullets 4 are held in a revolving cylindrical magazine 6 which is mechanically fed by a mechanical linkage, the details of which are not shown because they are not central to the present invention. If desired, the mechanical linkage may be actuated by a link part 9.

The apparatus 2 comprises a body portion 8, a discharge chamber 10 in the body portion 8, and an elongate member 12 which is slidable in the body portion 8. The apparatus 2 further comprises first means 14 for moving the elongate member 12 to a non-firing position as shown in Figure 1. The apparatus 2 further comprises second means 16 for moving the elongate member 12 to a firing position.

The apparatus 2 is such that the elongate member 12 moves from the nonfiring position shown in Figure 1 to the firing position when the pressure from the second means 16 exceeds pressure from the first means 14. In order to move from the non-firing position shown in Figure 1 to the firing position, the elongate member 12 moves to the right from the position shown in Figure 1. The apparatus 2 is also such that the elongate member 12 moves from the firing position to the non-firing position when pressure from the first means 14 exceeds pressure from the second means 16.

As can be seen from Figure 1, the first means 14 is in the form of a coil spring. As can also be seen from Figure 1, the second means 16 is a fluid means which is in the form of a gas. The gas shown is a combustible gas. Any single gas or gas mixture may be employed, as may be combustible liquids or liquid/gas combinations, such for example as those employed in liquid fuel rocket engines.

The elongate member 12 is of a circular cross sectional shape. The elongate member 12 comprises a downstream end 18, an upstream end 20, and a central portion 22 positioned between the downstream end 18 and the upstream end 20. The central portion 22 is of a larger diameter than the downstream end 18 and the upstream end 20. The downstream end 18 is of a larger diameter than the upstream end 20.

The first means 16 in the form of gases is able to be introduced into the discharge chamber 10 by means of two inlet tubes 24, including if desired non-return valves.

The direction of flow is indicated by arrows as shown.

The apparatus 2 includes a trigger 26 which pivots about a pivot 28. The trigger 26 has notch 30 which cooperates with an end 32 of a sear 34. The sear 34 pivots about a pivot 36. The sear 34 has an end 38 which cooperates with an end 40 of the upstream end 20 of the elongate member 12. The trigger 26 is biased to the position shown in Figure 1 by a coil spring 42. The coil spring 42 acts on a pip 44 of the trigger 26, the pip 44 being such that it acts to locate the lower end of the coil spring 42.

The apparatus 2 further comprises a piezo-electric crystal 46 which is connected by a conductor 48 to a switch 50. A conductor 52 passes from the switch 50 to a spark plug 54. The conductors 48, 52 and the switch 50 are located in a tubular part 56 of the firearm 2. The spark plug 54 screws into the body portion 8 as shown such that the electrodes 58 of the spark plug 54 are located in the discharge chamber 10.

When the bullets 4 are fired from the apparatus 2, they pass along a barrel 60 which extends from the body portion 8 as shown. The barrel 60 has a bore 62.

The downstream end 18 of the elongate member 12 slides in a gas discharge port 64 formed in an inwardly projecting part 66 of the body portion 8 as shown. The upstream end slides in a bore 68 of an inwardly projecting part 70.

The central portion 22 slides in a bore 72 as shown.

The apparatus 2 shown in Figure 1 operates such that the discharge chamber 10 is pressurized with the second means 16 in the form of combustible gas or gases. The combustible gas or gases is/are introduced to the discharge chamber 10 via the inlet tubes 24.

When the trigger 26 is pulled back (to the right as shown in Figure 1), the trigger 26 pivots about the pivot 28 and the notch 30 disengages from the end 32 of the sear 34. The pressure of the second means 16 in the form of the combustible gas in the discharge chamber 10 is greater than the pressure of the first means 14 in the form of a coil spring. Thus, when the trigger 26 is pulled back, the force of the end 40 of the elongate member 12 on the end 38 of the sear 34 causes the sear 34 to pivot anti-clockwise about its pivot 36 and out of the way of the elongate member 12. The elongate member 12 then travels to the right as shown in Figure 1 and engages the piezo-electric crystal 46. This causes an electric current to pass along the conductor 48, through the switch 50 when the switch 50 is closed, along the conductor 52, and to the spark plug 54. The current causes a spark to appear at the electrodes 58 of the spark plug 54, which then ignites the combustible gas in the discharge chamber 10.

As the combustible gas burns in the discharge chamber 10, it heats and therefore increases the pressure of the propelling charge needed to propel the bullet 4 from the magazine 6 and along the bore 62 of the barrel 60. After the bullet 4 has been fired, the gas pressure in the discharge chamber 10 drops below the pressure of the first means 14. The first means 14 in the form of the coil spring is then able to slide the elongate member 12 back to the position shown in Figure 1 and, if desired, provide the energy required to operate the projectile feed mechanism.

The trigger 26 and the sear 34 then become re-positioned as shown in Figure 1. The magazine 6 revolves so that the next bullet 4 for firing is placed in line with the bore 62 of the barrel 60 and the apparatus 2 is then ready for firing again.

When a combustible gas, gases, liquid or liquids or a suitable mixture is constantly fed to the discharge chamber 10, and the trigger 26 is held in the pulled-back firing position, then the apparatus 2 operates in a fully automatic manner with the above described firing cycle repeating in an automatic manner. The cycle repeats at a rate determined by factors such for example as the pressure in the discharge chamber 10, and the pressure of the first means 14.

If during automatic operation of the apparatus 2, the trigger 26 is released, then the sear 34 interrupts the to and fro movement of the elongate member 12. This causes the firing to stop and the apparatus 2 assumes the ready- to-fire position shown in Figure 1.

The combustible gas required for the discharge chamber may be introduced along one or more of the inlet tubes 24 utilising pressure regulating means in the form of a pressure regulating device 74 as shown in Figure 2. The pressure regulating device 74 comprises a valve housing 76, a valve member 78 in the valve housing 76, and biasing means in the form of a coil spring 80 for biasing the valve member 78 to a predetermined position in the valve housing 76 as shown in Figure 2.

The valve member 78 has a head 82 and a shank 84. The shank 84 is a hollow shank 84 having a bore 86 for permitting the passage of the second means 16 in the form of the combustible fluid through the valve member 78. The head 82 has an O-ring seal 88 which locates against an internal wall 90 of the valve housing 76. Other dynamic sealing means, such as a flexible diaphragm, may be used in place of O-ring seal 88.

The valve housing 76 has an inwardly directed portion 92 which may support dynamic sealing means 94 as shown, or a flexible diaphragm sealing the shank 84 to the portion 92. A gas sealing buffer 96 is provided in a chamber 98 of the valve housing 76 as shown. The valve housing 76 is provided with an inlet 100, a vent 102, and an exit port 104. The exit port 104 connects to a chosen one of the inlet tubes 24 in the apparatus 2. If desired only one of the inlet tubes 24 may be employed.

The pressure regulating device 74 operates such that the valve member 78 is able to slide to and fro in a chamber 106 in the valve housing 76. When the valve member 78 slides downwardly as shown in Figure 2, it does so against pressure from the coil spring 80. The coil spring thus acts as a biasing means which biases the valve member 78 upwardly towards the position shown in Figure 2.

The required fluid is aspirated through the inlet 100, from where it flows to the exit port 104. The fluid is unable to flow into the chamber 106 due to the dynamic sealing means 94. Providing the end 108 of the shank 84 of the valve member 78 is not in sealing contact with the gas sealing buffer 96, then the fluid in the chamber 96 can pass up the bore 86. The fluid can then pass through the exit port 104 and along the inlet tube 24 to the discharge chamber 10 of the apparatus 2 shown in Figure 1. Vent 102 may communicate with ambient pressure, or pneumatic or hydraulic pressure, to assist or replace the coil spring 80. The flow of the fluid is able to continue until there is sufficient gas pressure in the discharge chamber 10 to act as a back pressure at the exit port 104, and thereby to overcome the pressure from the coil spring 80 and move the valve member 78 downwardly as shown in Figure 2 such that the end 108 of the shank 84 makes sealing contact with the gas sealing buffer 96 and thus stops further transfer of the gas from the chamber 98 into the exit port 104. Thus the bias pressure from the coil spring 80 is able to govern the maximum fluid delivery pressure at the exit port 104 and therefore in the discharge chamber 10.

Referring now to Figure 3, there is shown second apparatus 108 for firing a product. The product that is fired may be in the form of a powder or other micro projectile.

The apparatus 108 comprises a divergent nozzle 110 with provision for holding a particle containment cartridge 112 and pneumatic sealing means 114. In Figure 3, a particle charge from the particle containment cartridge 112 is shown as particle charge 116.

The parts 110, 112, 114 form an assembly which is attached to a body portion 118. The assembly may be Remountable from the body portion 118.

An elongate member 120 achieves a dynamic pneumatic seal at points 122 and 124. The elongate member 120 is retained in a pre-firing position as shown in Figure 3 by spheres 126 acting in a waisted region of the elongate member 120. The spheres 126 may alternatively be plungers (not shown). A retaining bias is applied to the spheres 126 by compression springs 128. This retaining bias is adjustable by means of adjustment screws 130. Further retaining bias is applied by first means in the form of a compression spring 132.

A carbon dioxide bulb 134 forms part of the apparatus 108. The bulb 134 is housed such that upon fully closing its part 136, pressure is applied by the bulb 134 to a piercer 138. This pierces the bulb 134 or opens its valve.

A pneumatic seal is achieved under the circumstances between the neck of the bulb 134 and sealing means 140, 142. The bulb 14 is thus sealed and carbon dioxide gas cannot enter a transfer port 144.

The apparatus 108 is activated by slightly unscrewing the part 136, whereupon the carbon dioxide (or other gas employed) is permitted to pass the sealing means 140 and enter the transfer port 144. Via the transfer port 144, a discharge chamber 146 is pressurized. The pressure of the gas in the discharge chamber 146 acts as a second means for acting on the elongate member 120. When the gas pressure acting on the elongate member 120 exceeds the combined retaining bias of the springs 128 and 132, then the retaining spheres 126 are displaced. This permits a rapid movement of the elongate member 120 from its illustrated non-firing position to the right as shown in Figure 3 and to a firing position. When this happens, the sealing means 122 is disengaged from the body portion 118, thereby permitting a very rapid discharge of gas from the chamber 146 through the nozzle 110.

The apparatus 108 shown in Figure 3 operates as a simply constructed valve mechanism which is able to operate with either liquifiable or nonliquifiable gases. The apparatus 108 provides for the extremely rapid evacuation of a fixed volume of gas at constant pressure, regardless of temperature. The apparatus 108 is also able to provide for adjustment of the pressure of the volume of gas upon release. Multiple discharge at variable pressure may be achieved. The apparatus 108 is equally applicable to injection devices for the needleless injection of liquids, powders or suspended materials.

Referring now to Figure 4, there is shown third apparatus 148 of the present invention. The apparatus 148 is for firing a product wherein the product fired is a ballistic bobbin 150. The ballistic bobbin 150 is retained within the apparatus 148 both during and after actuation.

The apparatus 148 comprises a needleless syringe barrel 152, a plunger part 154, a body portion 156, a sleeve part 158 and a compression spring 160. The compression spring 160 may, if desired, be moulded integrally with the sleeve part 158. The ballistic bobbin operates in a space including a discharge chamber 162.

The discharge chamber 162 is contained between unidirectional seals 164 and 166. The discharge chamber 162 contains a compressed gas.

The material to be injected using the apparatus 148 may be in dissolved, suspended or gel form. The material is provided in a discharge chamber 168. An injection port is sealed by sealing means (not shown) prior to use.

The sealing means for the port 170 may, if desired, be provided by a snapoff portion (not shown).

The plunger part 154 is provided with hydraulic sealing means 172. The plunger part 154 provides a closure for the material within the discharge chamber 168. The needleless syringe barrel 152 and the plunger part 154 together with the sealing means for the port 170 and the material in the discharge chamber 168 may be in the form of an independent unit.

The apparatus 148 includes firing means in the form of releaseable retainer means including radially movable segments 174 which may be formed integrally with the body portion 156. The segments 174 are held in the retaining position shown in Figure 4 by means of the sleeve part 158.

Thus the releaseable retainer means formed by the segments 174 and the sleeve 158 retains the ballistic bobbin 150 in a pre-firing position as shown in Figure 4.

In order to discharge the apparatus 148, a tear-off band 176 is removed. The band 176 may, if desired, be formed integrally with the sleeve 158. The port 170 is placed against the intended injection site, and pressure is then applied to the sleeve part 158, thereby compressing the compression spring 160. Pressure is applied to the injection site by application of pressure to the sleeve part 158. The segments 174 are radially supported by the sleeve part 158. Thus, when the sleeve part 158 passes a point 178, the segments 174 are no longer radially supported. The segments 174 are such that, when they are deprived of the radial support from the sleeve part 158, the segments 174 are unable to retain the ballistic bobbin in its pre-firing position. The ballistic bobbin 150 is then propelled from right to left as shown in Figure 4.

The propulsion is initially due to a differential bias provided for by different diameters on the sealing means 164, 166. as the sealing means 166 passes a point 180, pneumatic pressure contained within the discharge chamber 162 is applied across the entire area of the sealing 164.

The ballistic bobbin 150 accelerates from right to left as shown in Figure 4 until the ballistic bobbin 150 strikes the plunger 154. The kinetic energy thus acquired by the ballistic bobbin 150 is instantly transferred via the plunger 154 to the injectable material contained in the discharge chamber 168.

The hydraulic pressure resulting from the dynamic impact between the ballistic bobbin 150 and the plunger 154 is sufficient to produce a hydraulic pressure momentarily in the injectable material contained in the discharge chamber 168, which hydraulic pressure is sufficient to puncture skin, membranes, or other tissues or materials.

The injectable material in the discharge chamber 168, for example in dissolved or suspended form is thereby injected through the puncture. The injection is sufficiently slow to permit tissues perfusion, without bruising being caused by residual pneumatic pressure. More specifically, at the end of the injection stroke, the seal 164 is arranged to clear a point 182 whereupon residual gas pressure is released to the atmosphere.

The apparatus 148 shown in Figure 4 operates as a simple constructed valve mechanism which may be produced at low cost with relatively few components. High consistent release pressure with reference to pressure exerted on the skin of patients is achieved. Consistent delivery pressure characteristics are achieved. The apparatus 148 has the potential for simple bulk gas filling. Tensile forces resulting from gas filling pressure are highly localized.

Gas filling vents to atmosphere after discharge make for safe disposal of the gas. The apparatus 148 may be constructed from plastics material so that it may be easily produced by moulding.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example, other ignition means than the piezo-electric crystal 46 and the spark plug 54 may be employed. Other timing means may similarly be employed. The switch 50 may be omitted. In modified apparatus 2, the gas in the discharge chamber 10 need not be combustible.

The apparatus of the present invention may be constructed for a wide variety of applications. Thus, for example, the apparatus of the invention may be in the form of a staple gun for firing staples, a nail gun for firing nails, or a rivet gun for firing rivets. The apparatus of the invention may also be formed as a reciprocating tool for operating chisels or hammers. In these various applications of the apparatus, the apparatus may be operated by a non-combustible gas such as air or one or more other gases as may be suitable and appropriate.

As indicated by Figures 3 and 4, the apparatus of the present invention may be produced in the form of medical apparatus, for example for administering substances directly through the surface of the skin into the tissue of animals or humans or into or on to inert matter. Such medical apparatus may be may be operated by any suitable and appropriate gas, mixture of gases, fluids or fluid gas mixtures. Any suitable and appropriate medical and pharmaceutical products may be employed and they may be in any suitable and appropriate form, including powders, liquids and pellets.

If the apparatus 2 is to be medical apparatus, then the magazine 6 and the barrel 60 of Figure 1 may be replaced by administering means such for example as a spray bar (not shown) or an injector port such as a divergent nozzle (not shown). Appropriate connection can be made in the vicinity of the gas discharge port 64. The appropriate product for administration may be introduced into the discharge chamber 10.

The ignition means shown in Figure 1 and including the piezo-electric crystal 46 and the spark plug 54 will normally not be employed. Also, only one inlet tube 24 may be employed. The gas required for discharge may be helium, air, carbon dioxide or any other suitable gas or mixture of gases.

Where the medical apparatus is to give repeat doses, then any suitable andappropriate feeding mechanism giving accurate required dosage amounts may be employed.

The apparatus of the invention may be constructed for further applications if desired so that, for example, the apparatus may be constructed as a harpoon or spear gun for firing a product in the form of a harpoon, spear or dart.

The apparatus may also be arranged for firing a needle or a matrix of needles into the skin of a human or an animal so that substances can be passed from the needle or needles, or through the needle or needles into the human or animal tissues.

Claims

1. Apparatus for firing a product, which apparatus comprises a body portion, a discharge chamber in the body portion, and an elongate member which is slidable in the body portion, and the apparatus being such that the elongate member is caused to slide in the body portion by a fluid.

2. Apparatus according to claim 1 and including first means for moving the elongate member to a non-firing position, and second means for moving the elongate member to a firing position, the apparatus being such that the elongate member moves from the non-firing position to the firing position when pressure from the second means exceeds pressure from the first means, and such that the elongate member moves from the firing position to the non-firing position when pressure from the first means exceeds pressure from the second means, and the second means being the fluid.

3. Apparatus according to claim 1 or claim 2 in which the second means is a fluid in the form of a gas.

4. Apparatus according to claim 3 in which the gas is air, oxygen, or carbon dioxide.

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5. Apparatus according to claim 2 in which the second means is a fluid in the form of a liquid.

6. Apparatus according to claim 2 and in which the first means is a spring.

7. Apparatus according to claim 5 in which the spring is a coil spring.

8. Apparatus according to any one of the preceding claims in which the elongate member is of a circular cross sectional shape.

9. Apparatus according to claim 8 in which the elongate member comprises a downstream end, an upstream end, and a central portion positioned between the downstream end and the upstream end, the central portion being of a larger diameter than the downstream end and the upstream end.

10. Apparatus according to claim 9 in which the downstream end is of a larger diameter than the upstream end.

11. Apparatus according to claim 2 and including pressure regulating means for regulating the pressure of the second means.

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12. Apparatus according to claim 11 in which the pressure regulating means is a pressure regulating device comprising a valve housing, a valve member in the valve housing, and biasing means for biasing the valve member to a predetermined position in the valve housing.

13. Apparatus according to claim 12 in which the valve member has a head and a shank, the shank being a hollow shank having a bore for permitting the passage of the second means through the valve member.

14. Apparatus according to claim 13 and including a resilient buffer seal which is adapted to be engaged by an end of the shank remote from the head when it is desired to seal the shank and prevent the passage of the fluid through the valve member.

15. Apparatus according to any one of the preceding claims and including a trigger mechanism.

16. Apparatus according to claim 15 in which the trigger mechanism comprises a trigger and a sear.

17. Apparatus according to claim 1 and including releaseable retainer means for retaining the elongate member in a pre-firing portion in which the elongate member is ready to be slid by the fluid.

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18. Apparatus according to claim 17 in which the releaseable retainer means comprises radially movable segments which are held in position by a retainer ring, the retainer ring being slidable to a position in which the radially movable segments are released, thereby to allow the sliding of the elongate member by the fluid.

19. Apparatus according to any one of the preceding claims and which is single firing apparatus, semi-automatic firing apparatus, or automatic firing apparatus.

20. Apparatus for firing a product substantially as herein described with reference to the accompanying drawings.

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