US3418887A - High energy rate actuator - Google Patents

Description

Dec. 31, 1968 D. J. MATTESON 3,418,887

HIGH ENERGY RATE ACTUATOR Filed March 28, 1967 Sheet of 2 INVENTOR. DAVID J. MATTESON ATTORNEYS.

Dec. 31, 1968 D. J. MATTESON HIGH ENERGY RATE ACTUATOR Sheet Filed March 28, 1967 INVENTOR. DAVID J. MATTESON BY W ATTORNE United States Patent Ofice 3,418,887 Patented Dec. 31, 1968 3,418,887 HIGH ENERGY RATE ACTUATOR David J. Matteson, Upper Darby, Pa., assignor to E. W.

Bliss Company, Canton, Ohio, a corporation of Delaware Filed Mar. 28, 1967, Ser. No. 626,562 9 Claims. (Cl. 91392) ABSTRACT OF THE DISCLOSURE A high energy rate actuator including a housing forming a high pressure chamber and a piston member reciprocable in the chamber between a first and a second position. The piston member has an outer surface area exposed to the pressure in the chamber, and this outer surface area is such that the effective pressure area acted on by the pressure in the chamber acts to move the piston to the second position. Means are provided for moving the piston from the second to the first position. These means include a movable member for contacting the piston member and moving therewith while the piston member moves from the second to the first position. This movable member while contacting the piston member shields a portion of the outer surface from the pressure in the chamber. The portion shielded is such that the effective pressure area of the remaining exposed surface of the piston member 'acts to move the piston member toward the first position.

This invention relates to the art of high energy rate forming of metal and more particularly to an improved actuator for driving a high energy rate forming press.

The invention is particularly applicable for use in powering a high energy rate forming press and will be described with particular reference thereto; however, it is appreciated the invention is capable of broader application and could be used wherever it is desired to have a rapid release of a large amount of energy.

In general, high energy rate actuators comprise a piston mounted for reciprocation in a pressure cylinder. The pressure cylinder is connected with a second pressure chamber or cylinder through a large valved orifice. Means are provided to suddenly release the pressure in the second cylinder against the piston to drive it rapidly and with great force through its working stroke. Because of the necessity of suddenly releasing the relatively high pressure in the second chamber with as small fiow loss as possible, the valving arrangements become quite complicated. Usually they comprise a special valve seat and a floating valve piston moved between open and closed positions under the influence of fluid pressure. Consequently, flow nozzles, valve networks and related systems are required. Further, in order to move the actuator piston to its firing position, valves and bleed lines are needed to bleed the pressure from the piston and pressure chambers and then recharge the pressure after the piston has been moved to firing position. Alternately, it is necessary to apply an extremely large force to the piston to move it to the firing position against the pressure in the chamber. Consequently, because of the many associated systems required for these prior high energy rate actuators, their cost tends to be high and their reliability low.

The present invention overcomes these problems and provides a high energy rate actuator which is extremely simple in construction and reliable in operation. Further, because of the unique design of the present actuator, the problems involved in moving the actuator piston to its firing position are eliminated.

In accordance with the present invention, an improved high energy rate actuator is provided. This actuator has a housing forming a high pressure chamber and a piston member reciprocable in the chamber between a first and a second position. The piston member has an outer surface area exposed to the pressure in the chamber, and this outer surface area is such that the effective pressure area acted on by the pressure in the chamber acts to move the piston to the second position. Improved means for moving the piston from the second to the first position are provided. These means include a movable member for contacting the piston member and moving therewith while the piston member moves from the second to the first position. This movable member while contacting the piston member shields a portion of the outer surface from the pressure in the chamber. The portion shielded is such that the effective pressure area of the remaining exposed surface of the piston member acts to move the piston member toward the first position.

Because of the above arrangement, the pressure within the piston chamber is used to move the piston to its firing position. This eliminates the necessity of providing special bleed valve arrangements or of providing an extremely large power source to move the piston member to the firing position.

A primary object of the present invention is the provision of a high energy rate actuator which is simplified in operation and construction.

Another object of the present invention is the provision of a high energy rate actuator that is capable of rapidly releasing a large amount of stored energy Without the use of complicated control systems.

A further object of the present invention is the provision of a high energy rate actuator which eliminates the need for special valves and valve seats.

An additional object of the present invention is the provision of a high energy rate actuator which is inexpensive to manufacture and highly reliable in its operation.

These and other objects and advantages of the present invention will become apparent from the following description used to illustrate the preferred embodiment of the invention as read in connection with the accompanying drawings in which:

FIGURE 1 is a cross-sectional view through the actuator showing the internal parts in detail;

FIGURE 2 is a cross-sectional view showing the actuator immediately after the ram has been fired;

FIGURE 3 is a cross-sectional view showing the recock piston being moved to engage the ram piston;

FIGURE 4 is a diagrammatic cross-sectional view showing the actuator piston being moved to its firing position;

FIGURE 5 is an enlarged cross-sectional view of the torpedo valve shown in FIGURE 1.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIGURE 1 shows, in cross-section, the overall arrangement of the actuator.

In general, the actuator comprises a sealed housing 10 formed by a cylindrical side wall 11 and end walls 19 and 23. A center wall 16, having an opening 18 formed therein, divides the housing into a high pressure chamber 12 and a low pressure chamber 14. In the preferred embodiment, high pressure chamber 12 is charged with an inert gas to an operating pressure of approximately 2000 p.s.i., while low pressure chamber 14 is charged to approximately 300 p.s.i. However, as will become evident, the exact pressures used are not critical but depend, for example, on the sizes of the various parts and the power out-put desired.

Reciprocably mounted in end wall 23 is ram member 24. This member comprises a piston portion 25 positioned within high pressure chamber 12 and connected to a driven member, such as press anvil 26, by a shaft 28. Shaft 28 is sealed where it passes through end wall 23 by a sealing arrangement comprising a circular seal plate 34 carrying an annular seal 38. Seal 38 is maintained tightly in engagement with shaft 28 by a seal retaining ring 40 connected to the seal plate by screws 42.

Piston portion of ram 12 is comprised of two circumferentially extending collars 3t) and 31. Collar 31 functions to limit the movement of ram 24 between end Wall 23 and the inwardly extending stops 20 formed on the interior of high pressure chamber 12. As best shown in FIGURE 5, collar has a recess 52 formed in its left hand end. An annular seal surface 51 extends circumferentially around the recess and functions in a manner to be subsequently described.

As best seen in FIGURE 2, the high pressure gas in high pressure chamber 12 will normally act to force ram 24 to the right. This is because the only pressure area of the piston portion 25 which is not counterbalanced by an equivalent pressure area acting in the opposite direction is the area indicated by El. Note that area E1 is counterbalanced only by atmospheric pressure acting on an equivalent area of the anvil. Thus, the effective pressure area E1 against which the pressure within the high pressure chamber acts to move the piston, is effectively equal to the cross-sectional area of shaft 28. However, if the left hand end of the piston portion 25 is shielded from the high pressure gas (such as shown in FIGURES 1 and 4), the only pressure area not counterbalanced by an equivalent pressure area acting in the opposite direction will be the annular area designated E2. Thus, with the left end surface of the piston portion shielded, the high pressure gas tends to move the ram to the left end or firing position of the high pressure chamber.

In view of the above, it is apparent that merely by shielding and unshielding the left hand end surface of the piston portion 25 it is possible to have the high pressure gas within high pressure chamber 12 move ram 24 to the left or right.

The particular means for selectively shielding and unshielding the left end of piston portion 25 could take a variety of forms; however, according to the preferred embodiment, these means comprise the recock piston assembly 46. This assembly comprises a cylindrical portion or piston 48 carried on the end of shaft 68 and mounted for reciprocation through opening 18 of center wall 16. Piston 48 is sealed where it passes through center Wall 16 by an annular seal 49 held firmly against it by a seal retainer 47. Shaft 16 is likewise sealed where it passes through end wall 19 by a seal 21 and seal retainer 22.

As best shown in FIGURE 5, the right end of piston 48, which functions to contact and shield the end of piston portion 25 of the ram, has a resilient seal 50 affixed to it. Thus, when the piston 48 is moved into contact with the piston portion 25, the resilient seal 50 contacts the annular seal surface 51 and effectively shields the end of the piston portion 25 from the pressure within high pressure chamber 12. However, as can be seen, when piston 48 is moved into engagement with seal surface 51, a small amount of high pressure gas is trapped within the relieved portion 52.

A variety of means could be employed to exhaust this gas; however, according to the preferred embodiment, these means comprise a torpedo valve assembly 54. As best shown in FIGURE 5, this assembly comprises a conically shaped valve element 60 mounted in a correspondingly shaped opening 56 formed in the right end wall of piston 48. A circumferentially extending O-ring 58, positioned within a suitable recess in opening 56, serves as the valve seat. Valve element 60 is biased firmly against the seat by a spring 54. Spring 54 is of sufiicient strength to maintain valve element 60 sealed against the pressure of high pressure chamber 12 acting against its right end. Extending from the right end of valve element 60 is a Cit cylindrical actuating member 62. This member is of a length sufficient to permit it to just contact the bottom of relieved portion 52 when seal contacts seal surface 51. However, further movement of the recock piston assembly 46 against piston portion 25 will cause seal 50 to be compressed and actuating member 26 to force valve element away from its seat against the bias of spring 51. In this manner, the pressure trapped within the relieved portion 52 is exhausted through chamber-64 and orifice 66 into the low pressure chamber 14.

The means for moving the recock piston assembly into shielding position on the piston portion 25 of ram 24 could take a variety of forms; however, as shown in FIGURE 1, the particular means utilized in the preferred embodiment comprise a reversible electric motor 82. This motor is connected through a worm and wormgear (not shown) to a conventional ball screw actuator which engages the threads of shaft 68. Depending on its direction of rotation, ball screw actuator 80 will cause shaft 68, and consequently piston 48, to be moved to the left or right.

A conventional torque limiting device is provided on motor 82 so that rightward travel of the recock piston assembly is stopped after a predetermined set force has been effected between the recock piston assembly and piston portion 25 of the ram. Any convenient controls, manual or automatic, could be used to control the direction of rotation of motor 80.

No mention has been made concerning the function of the low pressure chamber 14. In reality, the device could function without such a low pressure chamber. In that case, the torpedo valve assembly 54 would be arranged to exhaust the gas trapped within the relieved portion 52 to the atmosphere. However, it should be noted that since the diameter of piston 48 is relatively large, the pressure forces acting on its end in the high pressure chamber would be substantial. Thus, a larger motor would be required to drive the piston downwardly into engagement with piston 25. By using the low pressure chamber, the pressure forces acting against the right end of piston 48 are, to some extent, balanced by pressure forces against the left end in the low pressure chamber. In this manner, less force is required to move the piston downwardly into sealing engagement with the head end of the ram and, consequently, a smaller drive motor can be used. Further, during the fire stroke, the low pressure chamber acts as a thrust absorbing device to absorb some of the forces applied to the recock piston assembly by the high pressure gas in high pressure chamber when the device is fired.

OPERATION With the device constructed as described above, it functions in the following manner. Assume the ram is in its extreme right, or end of fire stroke position, as shown in FIGURE 3. At this time motor 82 is energized and the recock piston assembly 46 driven to the right into contact with the piston portion 25 of the ram. As previously discussed, seal 50 contacts seal surface 51 and thus shields the end of the piston portion 25 from the pressures within high pressure chamber 12. During the final portion of the rightward movement, seal 50 is compressed and valve element 60 moved open by actuating portion 62, thus permitting the high pressure gas trapped within relieved portion 52 to escape to low pressure chamber 14. When the proper set force has been achieved between seal 50 and seal surface 51, the torque limiting device on motor 82 stops further movement to the right.

With the high pressure gas exhausted from relieved portion 52, the gas in high pressure chamber 12 is acting, as previously explained, to move the recock piston assembly and the ram to the left. At this time, the motor 82 is reversed and the recock piston assembly and the ram moved together as a joined pair, to the left, as shown in FIGURE 4. The recock piston assembly and ram continue to move to the left as a joined pair until, as shown in FIGURE 1, stop collar 31 of piston portion 25 contacts the inwardly extending stops 20. Further leftward movement of recock piston assembly 46 causes seal 50 to be separated from seal surface 51, and permits the high pressure gas in high pressure chamber 12 to act against the left end of piston portion 25. With the gas pressure acting against the left end of the piston portion, the ram is driven rightwardly with great force and velocity, and the anvil 26 thus driven into engagement with the material to be formed or pressed.

The above cycle of operation can be repeated a substantial number of times with a single charge of gas in the pressure chambers. However, as can be seen, because torpedo valve assembly 54 bleeds a small amount of gas from the high pressure chamber 12 to the low pressure chamber 14 during the cocking portion of each cycle, the gas pressures within the chambers must be restored to their desired valves after a substantial number of cycles. For this reason, valved lines 90 are provided to permit the pressure within each of the chambers to be adjusted to its desired value whenever necessary.

As can be seen from the above description, the operation and construction of the actuator of the present invention is extremely simple. As a result, the cost of building and operating the actuator is substantially less than for prior actuators.

The invention has been described in great detail sufficient to enable one skilled in the art of high energy rate actuators to duplicate the invention. Obviously, modifications and alterations of the preferred embodiment described will occur to others upon a reading and understanding of this specification, and it is my intention to include all such modifications and alterations as part of my invention insofar as they come within the scope of the appended claims.

Having thus described my invention, I claim:

1. In a high energy rate actuator having a housing forming a high pressure chamber, a piston member reciprocable in said chamber between a first and a second position, said piston member having an outer surface area exposed to the pressure in said chamber, said outer surface being such that the effective pressure area acted on by the pressure in said chamber acts to move said piston to said second position; the improvement comprising: means for moving said piston from said second to said first position, said means including a movable member for contacting said piston member and moving therewith while said piston member moves from said second to said first position, said movable member, while contacting said piston member, shielding a portion of said outer surface from the pressure in said chamber, said shielded portion being such that the elfective pressure area of the remaining exposed surface of said piston member acts to move said piston member toward said first position, said actuator further including stop means defining said first position for preventing movement of said piston member beyond said first position but permitting said movable member to move beyond said first position.

2. The improvement as defined in claim 1 wherein said movable member is mounted for reciprocal motion in said chamber.

3. The improvement as defined in claim 1 wherein said movable member comprises a cylindrical piston.

4. The improvement as defined in claim 1 including power means operable to move said movable member into engagement with said piston member.

5. The improvement as defined in claim 1 further comprising means forming a low pressure chamber adjacent said high pressure chamber, said movable member being mounted for simultaneous reciprocation in both said high pressure chamber and said low pressure chamber.

6. The improvement as defined in claim 1 wherein said stop means is positioned in said high pressure chamber.

7. The improvement as defined in claim 1 wherein said piston member has an annular sealing surface positioned to be engaged by said movable member.

8. The improvement as defined in claim 7 including a relieved portion formed centrally of said annular sealing surface and means for exhausting pressure from said relieved portion.

9. The improvement as defined in claim 8 wherein said exhaust means include a valve operable to open position in response to contact with said piston member by said movable member.

References Cited UNITED STATES PATENTS 3,105,414 10/1963 Cuyetkovic et a1 91-392 3,267,677 8/1966 Bollar 91166 PAUL E. MASLOUSKY, Primary Examiner.

US. Cl. X.R. 91-404, 416, 417

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