US2987967A - Firearm with piston having springpressed inertia valve - Google Patents

Description

June 13, 1961 VALVE DISPLACEME NT- PRESSU RE R. H. WILD ETAL 2,987,967

FIREARM WITH PISTON HAVING SPRING-PRESSEID INERTIA VALVE Filed Feb. 27, 1959 CHARGE "A CHARGE "B" VALVE OPEN PRESSURE DROP DUE TO OPEN VALVE VALVE DISPLACEMENT FOR CHARGE "A" VALVE DISPLACEMENT FOR CHARGE "B" VALVE DISPLACEMENT TO OPEN INVENTORS. ROLF H. WILD By GEORGE DMITRIEFF nited States Patent P of:

2,987,967 FIREARM WITH PISTON HAVING SPRING- PRESSED INERTIA VALVE Rolf H. Wild, Hamden, and George Dmitrielf, Bethany,

'Conn., assignors to Olin Mathieson Chemical Corporation, a corporation of Virginia Filed Feb. 27, 1959, Ser. No. 796,087 2 Claims. (Cl. 89-193) The present invention relates to fluid pressure control devices and is particularly useful on powder actuated instrumentalities such as firearms and so-called powder actuated tools.

For purposes of disclosing and claiming the present invention, the term powder shall include propellants utilized to activate the firearm or tool involved either of solid or liquid form.

In powder actuated devices where hot gases generated upon firing a charge of propellant are utilized to perform work upon a piston or other power element, it is frequently desirable to control or limit the amount of energy imparted to the piston from charge to charge. For example, it is frequently desirable that velocity developed in the work piston be limited to a predetermined maximum value for each occurrence of firing.

Although equalization of effects of different pressure characteristics encountered from charge to charge or from shot to shot has been attempted by the use of bleed openings or bleed valves, responsive to given values of peak pressure, this approach has not been satisfactory because the time factor has been ignored.

To achieve the desired performance in the work piston, both pressure and time must be considered since the amount of energy imparted to the work piston is a function of the integral of pressure and time; not just pressure alone.

Thus, a bleed valve which is operative to open only upon being subjected to certain peak values of pressure would not control power in a work piston in the manner desired because, obviously, a given integral of pressure and time may be satisfied by various combinations of values of time and pressure.

Accordingly, a high pressure for an exceedingly short interval may open a conventional bleed valve to vent it to atmosphere while imparting little or no power to the piston; in contrast, a lower pressure applied for a sustained interval will not pop the valve but the power imparted to an adjacent work piston is appreciable and frequently above the desirable level.

Stated otherwise, a bleed valve is not satisfactory to control or limit power to a work piston, or the like, because such a valve responds to instantaneous pressures and is non-responsive to lower pressures applied for sustained intervals which actually may develop higher power than instantaneous pressures.

Accordingly, it is a particular feature of the present invention to provide a fluid power control device which is responsive to the integral of pressure and time.

It is a further feature of the invention to provide a control device of the class described which limits the velocity and thus the energy of the work piston.

A further feature of the invention is the provision of a fluid pressure control device operative to minimize the efiect of variations in energy encountered from charge to charge in powder actuated devices. 7

A still further feature of the invention is the provision of a self-integrating valve operable automatically to integrate pressure and time where the integrating feature is attained by tuning the valve or relating valve displacement necessary to open the valve to (I) valve inertia characteristics, (2) working area of the valve, and (3) restoring spring power. Proper construction and arrangement of the valve, considering the above attributes of dcsign, results in a valve capable to sensing and responding to a predetermined value of the integral of pressure and time.

A further feature of the invention is the provision of a novel arrangement of a work piston and a valve.

A further feature of the invention is the provision of a fluid pressure control device which is especially suited for use in powder actuated devices, such as firearms and stud driving tools wherein a charge of propellant is fired to accomplish a primary function such as driving a bullet or a fastener and in which a secondary function, such as feeding cartridges, metering propellant or ejecting spent cartridges, is accomplished by harnessing a portion of the fluid pressure developed during the primary function.

In devices of the type described above, the power generated for effecting the primary function may vary widely in that bullets of different weight and different power loads are frequently fired in the same firearm and in similar fashion. correspondingly, a wide variety of power loads are used in fastener driving tools depending upon the consistency or structure of the work piece.

In the performance of the secondary function, it is usually desirable to have available a fixed amount of energy and frequently, for consideration of structure and design, it is desirable that the secondary function is powered by energy that does not exceed a predetermined level.

Thepresent invention is particularly useful in insuring that the energy level in the secondary function does not exceed a predetermined maximum value.

Thus, it is a further feature of the present invention to provide a fluid power control device useful in powder actuated instrumenta-lities embracing a primary function and a secondary function where the control device is operative to minimize variations in power output developed in the primary function.

A still further feature of the invention is the provision of a control device including a valve stem in which the inertia, stroke, and efiective area of the stem are so selected with respect to the restoring force of the stem spring to provide a sudden pressure reduction as soon as a predetermined energy level has been reached.

A control device embracing certain features of the present invention may comprise a cylinder, a movable piston disposed in the cylinder operable to move in response to fluid introduced periodically into the cylinder, said cylinder having a port communicating with the atmosphere, valve means disposed in the cylinder and movable through a given stroke to an open position, said valve being maintained in the closed position by a restoring spring, the inertia of the valve, the length of said stroke and the force of said restoring spring being so selected that the valve opens only when a predetermined maximum value of the integral of time and pressure is sensed.

Other features and advantages of the present invention will become more apparent from an examination of the succeeding specification when read in conjunction with the appended drawings in which:

FIG. 1 is a vertical section of a portion of a powder actuated instrument with which the principles of the present invention may be associated.

FIG. 2 is a similar view to the showing of FIG. 1 disclosing an additional embodiment of the invention where in a work piston carries a pressure control valve.

FIG. 3 is a plot of pressure and valve displacement as a function of time.

Referring now to the drawings, there is shown a cylinder 10 fitted with a work piston 11 carrying piston rings 12. The work face 13 of the piston is exposed to fluid pressure directed to the interior of the cylinder 10 through passage 14.

It is well to note that the passage 14, although shown here communicating with a firearms barrel 15 (indicated in dotted lines), may be utilized as a propellant cavity eems or chamber in which a propellant charge in the form of a capsule or cartridge is'dis'posed. That is, the source of fluid pressure exerted on the work face of the piston 11 may or nate n e pa sage 14 it lf o the fluid ressure my fl w th ugh he pa m a p imary cyl nder such as the rifled barrel 15. In such a situation, thatis, where a primary cylinder is utilized, the cylinder housing the work piston may be referred to as the secondary c i n Fluid pressure admitted to the cylinder impinges uponthe working face 13 and is operative to drive the piston to the left as viewed in FIG. 1. At the same time, the fluid pressure is also operative to perform work upon the valve structure opposite the piston 11 referred to generally as a control device 16.

The right end of the cylinder 10 is enclosed by a cap 17 in threaded engagement with the cylinder as at 18. Disposed between the cap 17 and the working face of the piston 11 is a bored partition member 19 having an annular shoulder 21 which rests upon a corresponding shoulder 22 formed on the interior of the cylinder.

The partition is retained by a pressed fit into the cylinder or is otherwise keyed thereto as desired. The bore 23 of the partition carries a valve comprising a stem bore and inertia member 24 and a body portion 26 where the body is urged against the partition to a closed position by a coil spring 27. Note that the valve stem 24 must be fully withdrawn (to the right) from the bore 23 in order to vent the working face of the piston 13 to the atmosphere through ports 28 formed in the cylinder wall.

Stated otherwise, the valve stem '24 may reciprocate in the bore 23 through a variety of axial distances without venting to atmosphere.

In the embodiment of the invention disclosed in Fig. 2, a work piston 110 is shown carrying the pressure control device indicated generally by the reference numeral 116. The piston 110 is formed with a bore for receiving valve stem 124 and valve body member 126 is urged into contact with the rear face of the work piston by coil spring 127. Note again that the stem 124 is movable through an appreciable stroke before venting the working face 113 of the piston to the atmosphere through ports 120., formed in the piston and 128, formed in the cylinder side wall.

As described in connection with the disclosure of FIG. 1, the source of fiuid pressure may originate in the passage 114 upon the firing of an appropriate propellant charge disposed therein or fluid pressure may be transferred through the passage 114 from a primary cylinder such as the rifle barrel shown in dotted lines at 115.

The function of the control device will now be described while referring to the curves of FIG. 3.

FIG. 3 shows a graph of cylinder pressure (as applied to the work piston 11, for example) versus time, for two different propellant charges represented by the curves labelled A and B. It will be noted that the pressure curve A has a much higher peak and a shorter duration than the pressure curve B. Since the area under the pressure curve is proportional to the impulse of the gases generated which, in turn, is proportional to the product of mass and velocity of the piston, it is obvious that the area under curve A, or the impulse for the charge A, is much smaller than, that of the charge B. Consequently, the charge B would'impart a higher velocity to the work piston. To obtain the same velocity with the same piston mass, the two areas would have to be the same.

A conventional bleed valve, which is sensitive to pres sure only, would be operated by the short lived pressure peak of charge A, but may not respond to the charge 8.

In contrast, the control device, in accordance with the present invention, however, is sensitive to pressure and time and will respond in the following fashion: When a charge similar to that represented by curve A is fired, the piston will be accelerated to the left in Fig. 1 and simultaneous lythe control valve stem will be pushed to the right. The force pushing the control valve stem will be a function of the pressure and the displacement of the control valve relative to time is shown by the dotted curved labelled A in the graph. It is noted that while the valve moves towardsits opening position, it does not reach the full open position and, consequently, the pressure is retained inthe cylinder.

On the other hand, if a fluid pressure having a characteristic represented by the curve B is introduced into the cylinder, the valve stem will move toward the open position and at the point noted will uncover the passage lead ing from the cylinder into the atmosphere, thus causing an immediate pressure drop. Since the valve responds to pressure and time, it will tend to modify the pressure curve B in the manner shown by the dotted line, that is, as soon as the desired impulse has been imparted to the piston the valve will uncover the venting passage causing an immediate pressure drop and preventing the accumula tion ofexcess energy in the working piston. The travel or displacement of the valve with respect to time when subjected to pressure curve B is shown by the dotted curve labelled B in FIG. 3.

After the fluid pressure falls off, the restoring spring will close the valve device and restore it to its initial position.

It is readily seen that this control device, which responds to pressure and time, that is, which is self-integrating, will tend to level the momentum imparted to the working piston and thus limit the energy that is taken from the propellant gases.

FIG. 2 showing another embodiment of the invention operates on the same principle. In this case, there is again a cylinder into which pressurized fluid is introduced through an opening. The piston has a central cylindrical hole in which is inserted a control valve. The control valve extends through the piston and is supported by the return spring which tends to hold the piston and valve in their initial position. On introduction of gas pressure into the cylinder, the piston will be driven to the left, while at the same time, the valve will also be subjected to pressure. If the mass of the valve is properly chosen, there will be a differential movement between piston and valve which will result in the opening of the lateral passage in the piston when the impulse of the fluid exceeds a certain value. This will permit fluid to escape into the atmosphere and thus limit the amount of momentum that can be imparted to the piston. After the pressure drops sufficiently the spring will move the control device back into its original condition in the piston.

Obviously, the embodiments shown are exemplary only and a wide variety of embodiments of the invention may be devised without departing from the spirit and scope thereof.

What is claimed is:

l. A fluid pressure control device for powder actuated instrumentalities comprising a movable piston disposed in a cylinder, said piston being operative to move upon the application of fluid pressure thereto, said cylinder having a port communicating with the atmosphere and said piston being subjected periodically to random values of fluid pressure, and valve means disposed in the cylinder and movable through a predetermined stroke to an open position wherein the interior of the cylinder is vented to atmosphere, said valve means being received within and movable relative to the piston, spring means for urging said valve means towards a closed position, said length of stroke, the inertia of the valve, the effective area of the valve, and said spring means being so selected that the valve is operative to vent only when a predetermined integral of pressure and time has been exceeded.

2. A fluid pressure control device for a powder actuated instrumentality comprising a primary cylinder and a secondary cylinder communicating with the primary cylinder, a piston disposed in the secondary cylinder operative to move upon the introduction of fluid pressure into the a Mi e;

secondary cylinder from the primary cylinder, said piston being subjected to a range of values of fluid pressure, means for reducing the energy effect of said fluid pressures upon the piston comprising a resiliently mounted inertia member, said inertia member characterizing a valve stem disposed in said secondary cylinder and movable upon the application of" fluid pressure through a predetermined stroke to vent the secondary cylinder, said inertia member being received within and movable relative to the piston, a restoring spring for urging the stem to a closed position, the inertia of said valve stem, the working area thereof, and the restoring spring being so 1,738,501 Moore Dec. 3, 1929 2,482,880 Sefried Sept. 27, 1949 2,750,849 Harvey June 19, 1956 2,783,685 Green Mar. 5, 1957 2,814,972 Simmons Dec. 3, 1957 2,918,847 Barr Dec. 29, 1959

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