FIRE RATE CONTROL MECHANISM FOR A WEAPON

Abstract: A trigger mechanism for a gun capable of fully automatic firing comprising a timing device operable to determine the rate of fire of the gun, which device cyclically interrupts means (1) for discharging the ammunitiion to be discharged from the gun when a physically displaceable trigger (6) of the mechanism is moved to a firing position. Additionally, the ammunition discharge rate may be substantially constant and determined by the timing device independent of any other weapon characteristics. The timing device may comprise a pneumatic device (9) which is adjustable to enable variation of the ammunition discharge rate which remains substantially constant. A removable piston for a gun regulator.

Description: FIRE RATE CONTROL MECHANISM FOR A WEAPON The invention relates to a fire rate control system for a gun such as a submachine gun or light machine gun. The mechanism to be described, allows for the firing mechanism of an open-bolt or closed- bolt submachine gun (S.M.G.) or light machine gun (L.M.G.) to be upon firing, momentarily arrested in a cocked condition and then to be released to fire another round after a predetermined and preset lapse of time. Such a mechanism thereby allows the rate of fully automatic fire to be accurately controlled and preset. The importance of such a mechanism lies in the ability to choose a rate of fire which eliminates the negative effects of the phenomenon known as "climb" or "stitching" common to most S.M.G. 's in use today. Climb is caused by an excessive rate of fire. The weapon does not have sufficient time to return to its original point of aim before each successive round is fired on full auto. The general result is one round on target and thereafter a string of shots moving upwards and off target i.e. no control. Such lack of control over shot placement is obviously both dangerous and very undesirable. As the requirements of the military and law enforcement called for lighter and more concealable weapons, the laws of physics ensured increasing rates of fire and increasing rates of climb. The rate of fire of S.M.G. 's currently employed, varies from approximately 600 R.P.M. to over 2,000 R.P.M. Testing has shown however, that in S.M.G. 's weighing somewhere between 4.5 and 8 pounds, the phenomenon of climb does not disappear until the rate of fire is brought down below 450 R.P.M. (approximately) This can be demonstrated by the current model of the BUSHMAN I.D.W. - 9mm S.M.G which employs an electronic rate control system (see PCT/GB90/01969) set at 420 R.P.M. The weapon weighs 5.7 pounds and does not climb when fired on full auto, even when fired by untrained personnel The mechanism to be described is shown as an alternative to the electronic rate control system employed in the BUSHMAN I.D.W. 9mm S.M.G (see PCT/GB90/01969) and was developed in parallel so as to share as many components as possible between the two versions A comparison of the two versions would show that except for the rate control units themselves, the majority oi the remaining parts are interchangeable between the two models An advantage of the new system lies in its simplicity and the reduction of moving parts in the trigger mechanism It is an object of the present invention to provide a tire rate control mechanism which can eliminate weapon climb by limiting the firing rate to approximately 450 rpm or to whatever rate is determined, in practice, to eliminate climb tor any particular individual weapon model It is another object of the present invention to provide a fire rate control mechanism which allows a soldier in the field to alter a weapon's automatic rate of fire by removing and replacing a rate control piston, or to simply replace a defective unit, without the use of tools. It is another object of the present invention to provide a weapon which can function in either a semi-automatic mode or in an automatic mode with a predetermined rate of fire. It is another object of the present invention to provide a fire rate control mechanism which is simple in design, comprised of a minimum of parts, thus ensuring reliability of the mechanism. It is another object of the present invention to provide a fire rate control mechanism which provides a weapon which combines the simplicity and safety of an open-bolt system, with the first shot accuracy of a closed bolt system. It is another object of the present invention to provide a fire rate control mechanism which is both lightweight and compact enough to be positioned in the pistol grip of a weapon, thus not interfering with the position of the main spring or main spring guide rod or rear breech bolt buffer of the weapon. It is another object of the present invention to provide a fire rate control mechanism in which the fire rate control piston can be stored separate from the weapon and which can be issued and installed only when required, allowing the weapons automatic fire to be disabled, but still allowing personnel to train with the same weapon in a semi-automatic mode. This is also important with regard to security, since the rate control piston can be located separate from the weapon during storage or transport. The invention seeks to avoid or at least mitigate the specified problems and other problems of the prior art. One aspect of the present invention provides a fire rate control mechanism which allows an open bolt or closed bolt S.M.G. or L.M.G. to be, upon firing, momentarily arrested in a cocked condition and then to be released to fire another round after a predetermined and preset lapse of time. Another aspect of the invention provides a trigger mechanism for a gun capable of fully automatic firing comprising a timing device operable to determine the rate of fire of the gun. which device cyclically interrupts means for discharging the ammunition to be discharged from the gun when a physically displaceable trigger of the mechanism is moved to a firing position. Preferably the timing device comprises a hydraulic or pneumatic device operatively connected to a bolt of the gun. According to another aspect of the invention there is provided a gun having a bolt decelerator. Another aspect of the invention provides a bolt decelerator or a fire rate regulator for a gun which is readily attachable and detachable from the gun. An embodiment of a rate control mechanism according to the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 shows a sectional side elevation view of a trigger mechanism and rate control system according to the invention, in a cocked position; FIGURES 2 to 6 show successive steps in the operation of the mechanism and system shown in Figure 1 during firing. The trigger mechanism functions as follows. The main-sear 4, pivots about shaft 1 1 and engages bolt 1 at bent 2. The trigger 6 and secondary-sear 5 both pivot about shaft 12 and engage each other at face 19. The secondary-sear 5 engages the bolt 1 at bent 3. The cam hammer 7 pivots about shaft 13 and is connected to the rate control piston 9 at shaft 14. The cam hammer 7 engages the secondary-sear 5 at point 8. The rate control piston rod 10 is fixed to the frame 16 at shaft 15. For semi-automatic fire the cam-hammer 7 would be locked out of engagement with secondary-sear 5 by a selector unit (not shown) and would be in a position as seen in Figures 5 or 6. For semi-automatic fire disregard the cam-hammer 7 and piston 9 in those drawings. Figure 1 shows the weapon cocked and ready to fire. Main sear 4 is engaged with bolt 1 at bent 2. Trigger 6 has forced secondary sear 5 our of possible engagement with bolt 1 via contact at face 19. In Figure 2, when trigger 6 is pulled, main sear 4 is disengaged from bolt 1. Simultaneously, trigger 6 disengages contact with secondary-sear 5 at face 19. Secondary-sear 5 is now free to engage bolt 1 at bent 3 after a round has been fired. The bolt now is free to fly forward via a main spring force (now shown), strip a cartridge from the magazine, and chamber and fire said cartridge as seen in Figure 3. The force of the exploding cartridge sends the bolt 1 rearwards, where bolt 1 is engaged and arrested by secondary-sear 5 at bent 3. When the trigger 6 is released, it engages the secondary-sear 5 at face 19 and forces the secondary-sear 5 to disengage from bent 3. Simultaneously the main-sear 4 has been allowed to come up and is ready to engage the bolt 1 at bent 2 at the moment the secondary-sear 5 has disengaged from bent 3. The condition is as seen in Figure 1 . The weapon is now recocked and ready to be fired via another pull on trigger 6. For regulated full auto fire, the cam-hammer 7 and fluid filled piston unit 9 are brought into position as seen in Figures 1 , 2 and 3. This piston unit 9 is Figures 1 , 2 and 3 is shown at full expansion (via internal spring force) causing cam hammer 7 to exert a downward force on secondary-sear 5 at point 8. Secondary-sear 5 is forced out of possible engagement with bolt 1. Figure 1 shows the weapon cocked and ready to fire on regulated fully automatic fire. Figure 2 shows trigger 6 pulled and main-sear 4 just disengaged from bolt 1 at bent 2. The bolt 1 is now free to fly forward, strip a cartridge from the magazine and chamber and fire said cartridge. Conditions would be as in Drawing "C" at that moment. The explosive forces of the cartridge send the bolt 1 rearwards where bolt 1 then engages cam hammer 7 as seen in Figure 2 and the bolt 1 cams the cam hammer 7 completely down as seen in Figure 4 taking cam hammer 7 out of engagement with secondary-sear 5 at point 8. Secondary-sear 5 is now free to snap upwards, engage bolt 1 at bent 3 and arrest bolt l 's forward movement as seen in Figure 5. In Figure 5 cam hammer 7 has caused rate-control- piston 9 to fully compress against an internal spring force. During compression a check valve has opened, allowing the internal fluid to pass freely around the piston head. After the bolt 1 has been arrested by the secondary-sear 5 the rate-control-piston 9 is free to expand. The piston check valve closes and the resistance of the fluid trying to pass the piston head causes the piston to expand at a relatively slow and preset rate. The expanding piston forces the cam hammer 7 upward and into engagement with the secondary-sear 9 at point 8 as seen in Figure 5. When the rate-control-piston 9 has fully expanded, the cam hammer 7 will have forced secondary-sear 5 out of engagement with bolt 1 at bent 3 (as seen in Figure 2) and the bolt flies forward, repeating the sequence. The gun will continue to fire at the preset rate until all ammunition is expanded or until the trigger 6 is released, allowing the main sear 4 to engage the bolt 1. Rates of fire as low as 100 RPM can be achieved. An infinite control between 'o' RPM and the full natural unregulated rate of the weapon can be achieved by altering the internal functions of the piston and the fluid viscosity. For example the size of orifices in the piston could be altered. The rate-control-piston in the Bushman was designed to serve a dual function. The rate- control aspect has been explained. The second function is as a decelerator for the bolt. The camming action as the bolt 1 hits the cam hammer 7 and the internal expansion spring within the cylinder 9 were designed to absorb a maximum of energy from the returning bolt. This has allowed for the use of a light weight aluminium breech and a very light weight bolt. All other open bolt weapons rely on a relatively heavy bolt mass to absorb energy in an effort to reduce rate of fire and stress on the breech. This large moving mass is what makes traditional open bolt weapons less accurate than closed bolt version. The rate control devices of this system has taken away the need for a heavy bolt, thereby retaining the simplicity and safety of an open-bolt system, with first shot accuracy comparable to a closed bolt weapon. Of course, where required, this rate control system can be applied equally well to a closed bolt system. A very important and key aspect of the instant invention is the use of a release unit to accomplish a timed interruption of the weapons cycle of fire. A preferred form of release unit is embodied in the rate control piston assembly 50. Rate control piston assembly 9 contains hydraulic fluid, fluid chambers and machine orifices for regulating the passage of the fluid between the fluid chambers, in a known manner, thus defining the rate control pistons rate of expansion and therefore the period of interruption of the weapons cycle of fire. An exemplary form of rate control piston assembly is commercially available from Ace Controls, Inc. of Farmington, Michigan, Model ti 92-1201-06. Further, it is through the removable pins 13 and 15 that another important benefit of the invention is realised. These pins allow the removal of the rate control piston in the field, without tools. Depending on the desired firing rate, a particular firing rate control piston can be inserted into the weapon. Also, the removable pins allow the user to very easily replace a defective rate control piston. The pins 13 and 15 could for example be spring loaded and carry a locking finger such that they can be manually pressed and rotated into a locking arrangement with the finger engaged in a cooperating recess. Alternatively, the pins might be held in position by the pistol grip cover which in turn is secured by manually removable screws. Further, the piston device could be inserted into a cylinder formed in the pistal grip 16 such that a cover plate over the cylindrical hole secures the piston in place and causes the lower pin 15 to be retained by mechanical resistance at its ends. The top pin 13 might then also be retained by mechanical resistance for example from breech plates when the breech is closed such that the axis pins cannot move. Any configuration of these arrangements is possible. Also other pins such as pin 14 might be detachable to enable removal of piston 9. The rate control piston serves a dual function. The rate control aspect has been explained in the preceding paragraphs. In addition, the rate control piston serves as a decelerator for the bolt. The camming action which occurs as the bolt 1 hits the cam hammer 7, together with the force exerted by the internal expansion spring within the cylinder 9, serve to absorb a maximum of energy from the returning bolt. This allows the use of a light weight aluminium breech and a very light weight bolt, obviously contributing to the serviceability, reliability and maintainability of the weapon. Typically, open bolt weapons rely on a relatively heavy bolt mass to absorb energy in an effort to reduce the rate of fire of the weapon and to reduce the stress on the breech. This large moving mass is what makes traditional open bolt weapons less accurate than closed bolt versions. The rate control device as described has alleviated the need for a heavy bolt, thereby retaining the simplicity and safety of an open-bolt system, with first shot accuracy comparable to a closed bolt weapon. Of course, where required, the inventive rate control system can be applied equally well to a closed bolt system. The use of a rate control piston assembly as described is distinctly different from the prior art methods of fire rate control. In particular, weapons incorporating such prior art inertial methods, including the use of springs or shock absorbers, for instance, are subject to a changing rate of fire depending on the particular cartridge load utilized. Weapons which incorporate the subject invention, on the other hand, do not experience a changing rate of fire depending on a particular cartridge loading. The fire rate control piston assembly of the present invention controls a weapons fire rate depending on the particulars chosed for each piston assembly, as has been discussed. The timed release of the breech-block of the weapon is a preset and predetermined quantity. In summary, the present invention is a fire rate control mechanism which allows an open bolt or closed bolt S.M.G. or L.M.G. to be, upon firing, momentarily arrested in a cocked condition and then to be released to fire another round after a predetermined and preset lapse of time and which provides a weapon which can function in either a semi-automatic mode or in an automatic mode. The present invention provides a fire rate control mechanism which allows a soldier in the field to alter a weapon's automatic rate of fire by removing and replacing a rate control piston, or to replace a defective unit, without the use of tools, in an approximately one minutes time, or less. In addition, the present invention provides a fire-rate control mechanism which is simple in design, comprised of a minimum of parts, thus ensuring reliability of the mechanism. Also, the present invention provides a fire-rate control mechanism which can eliminate weapon climb by limiting the firing rate to approximately 450 rpm or to whatever rate is determined, in practice, to eliminate climb for any particular individual weapon model. Further, the present invention provides a fire-rate control mechanism which is both lightweight and compact enough to be positioned in the pistol grip of a weapon, thus not interfering with the position of the main spring or main spring guide rod or rear breech bolt buffer of the weapon. Finally, the present invention provides a fire rate control mechanism in which the fire rate control piston can be stored separate from the weapon and which can be issued and installed only when required. While a preferred embodiment of a fire rate control system for a submachine gun or light machine gun utilizing a hydraulic cylinder release unit in accordance with the present invention has been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that a number of changes could be made, for example, in the type of release unit, i.e. the use of a gas cylinder or a mechanical release means, without departing from the true spirit and scope of the subject invention which is accordingly to be limited only by the following claims.

Claims: CLAIMS 1. The trigger mechanism for a gun capable of fully automatic firing comprising a timing device operable to determine the rate of fire of the gun, which device cyclically interrupts means for discharging the ammunition to be discharged from the gun when a physically displaceable trigger of the mechanism is moved to a firing position. 2. A trigger mechanism as claimed in claim 1 wherein the ammunition discharge rate is substantially constant. 3. A trigger mechanism as claimed in claims 1 or 2 wherein the ammunition discharge rate is determined by the timing device and is independent of any other weapon characteristics. 4. A trigger mechanism as claimed in any of the preceding claims wherein the ammunition discharge rate is determined by a hydraulic or pneumatic device. 5. A trigger mechanism as claimed in claim 4 which comprises a pneumatic timing device which is adjustable to enable variation of the ammunition discharge rate which remains substantially constant. 6. A trigger mechanism comprising a bolt having a first and second bent, and two sears each engageable with one of the bolt bents, the first sear being operative to engage a first bent and * thereby prevent movement of the bolt, a second sear being operatively connected to a timing device when the trigger mechanism is set to a fully automatic mode. 7. A trigger mechanism as claimed in claim 6 wherein the timing device cyclically enables the second sear to engage the second bent and thereby interrupt movement of the bolt whilst the first sear is in operative position. A gun comprising a trigger mechanism according to any of the preceding claims and having an aluminium breech and light weight bolt. 8. A gun according to claim 7 comprising an energy absorbing device which acts to decelerate the bolt. 9. A gun according to claim 8 wherein the energy absorbing device comprises a pneumatic or hydraulic piston. 10. A firing rate control apparatus for an automatic weapon having a breech-block which moves during the weapons cycle of fire comprising: means for stopping the motion of the weapons breech-block during the weapons cycle of fire for a preset and predetermined period of time. 1 1 . The apparatus of claim 10, wherein said means includes a sear for releasably engaging the breech-block and, means for controlling the release time of the sear. 12. The apparatus of claim 1 1 , wherein said means for controlling the release time of the sear is a hydraulic piston cylinder assembly which is compressed by rearward travel of said breech-block to the same degree regardless of travel speed. 13. The apparatus of claim 1 1 wherein said means for controlling the release time of the sear is removably attached to the weapon allowing replacement without the use of tools, and wherein the weapon is operational upon removal of said means. 14. The apparatus of any preceding claim wherein the breech-block is a bolt. 15. A method of controlling the firing rate of an automatic weapon having a breech-block which moves during the weapons cycle of fire, comprising the steps of: interrupting the motion of the breech-block of the automatic weapon during the weapons cycle of fire for a preset and predetermined period of time. 16. The method of claim 15 wherein interrupting the motion of the breech-block of the automatic weapon includes the steps of: stopping the motion of the breech-block; and releasing the weapons breech-block after a preset and predetermined period of time. 17. Apparatus for controlling the firing rate of an automatic weapon comprising: a sear; a breech-block with a bent for releasable engagement by said sear; and means for controlling the amount of time that said sear stops the motion of said breech-block during the cycle of fire of the weapon. 18. The apparatus of claim 17, wherein said means is a hydraulic piston cylinder assembly which is compressed by rearward travel of said breech-block to the same device regardless of rearward travel speed, and which causes said sear to release said breech-block after a preset and predetermined period of time. 19. The apparatus of any of claims 17 or 18 wherein, said breech block is a bolt. 20. The apparatus of claim 17, 18 or 19 wherein said means is removably attached to the weapon, allowing replacement without the use of tools, and wherein the weapon is operational upon removal of said means. 21. Apparatus for controlling the firing rate of an automatic weapon comprising: a sear; a breech-block with a bent for engagement by said sear; and a release unit for controlling the amount of time in which said sear is in stopping engagement with said breech-block, in a predetermined and preset manner. 22. The apparatus of claim 21 , wherein, said release unit is a hydraulic piston cylinder assembly which is compressed by rearward travel of said breech-block to the same device regardless of rearward travel speed. 23. The apparatus of claim 22 wherein, said breech-block is a bolt. 24. The apparatus of claim 21 , 22 or 23 wherein said release unit is removably attached to the weapon allowing replacement without the use of tools, and wherein the weapon is operational upon removal of said release unit. 25. A firing rate control apparatus for an automatic weapon having a breech-block which moves in a forward and rearward motion during the weapons cycle of fire comprising: sear means for stopping the motion of the breech-block by releasably engaging a bent on the breech-block; and a hydraulic piston cylinder means for controlling the release of the sear to breech-block engagement in a preset and predetermined time, said cylinder means compressed a constant amount for each rearward movement of the breech-block. 26. The apparatus of claim 25 wherein said hydraulic piston cylinder means is removably attached to the weapon, allowing replacement without the use of tools, and wherein the weapon remains operational in a semi-automatic mode upon removal of said means. 27. A piston for a gun regulator.

Inventors: EALOVEGA GEORGE D, WEST RICHARD PETER, EALOVEGA, GEORGE, D., WEST, RICHARD, PETER
Applicants: BUSHMAN LTD, EALOVEGA GEORGE D, WEST RICHARD PETER, BUSHMAN LIMITED, EALOVEGA, GEORGE, D., WEST, RICHARD, PETER
Application year: 1993
Main classification: F41A19
IPC codes: F41A3, F41A9, F41A19