US3036538A

US3036538A - Dynamic impacting machine

Info

Publication number: US3036538A
Application number: US763002A
Authority: US
Inventors: Jack B Ottestad; Samuel A Skeen; Edward W Baker
Original assignee: General Dynamics Corp
Current assignee: General Dynamics Corp
Priority date: 1958-09-24
Filing date: 1958-09-24
Publication date: 1962-05-29
Anticipated expiration: 1979-05-29

Description

May 29, 1952 J. B. oTTEsTAD ETAL 3,036,538

DYNAMIC IMPACTING MACHINE Filed Sept. 24, 1958 C5 Sheets-Sheet 1 Q w M M m N Q z l NPM A s* g i iii" `1 f k1 ||[1 wm: 15 |H| m SX $9 "i @n "QQ E 1 s l MI u' W i lll May 29, 1962 J. B. oTTEsTAD ETAL 3,036,538

DYNAMIC IMPACTING MACHINE 3 Sheets-Sheet 2 Filed Sept. 24. 1958 o. l sSHw EBM www. a4@ L@ ZW as@ mam),

fMRI/Ey May 29, 1962 J. B. oTTEsTAD ETAL 3,036,538

DYNAMIC IMPACTING MACHINE Filed Sept. 24, 1958 3 Sheets-5h98?l 3 rramdqy 3,036,538 DYNAMIC lMPACTIN G MACHINE Jack B. Otte-stad, Claremont, Samuel A. Sheen, West Covina, and Edward W. Baker, Pomona, Calif., assignors to General Dynamics Corporation, San Diego, Calif., a corporation of Delaware Filed Sept. 24, 1958, Ser. No. 763,002 8 Claims. (Cl. 113-45) This invention relates generally to a dynamic impact-V ing apparatus; more particularly, it relates to a dynamic impacting apparatus for providing high impact energy with relatively low foundation loading.

High energy rate devices of the prior art, for use in such applications as sheet metal forming, have generally been characterized by certain shortcomings and disadvantages, such as requiring relatively massive foundations. Among these devices are dead-weight machines, drop towers, devices utilizing explosive charges, and devices for transmitting high level energy to hydraulic systems. These devices have generally required large apparatus and/ or large foundations. The devices have generally not provided relatively accurate control of the rate of energy application. Some have not provided sufficiently high energy potentials. Further, use of certain of the devices has involved danger to personnel.

The present invention provides an apparatus wherein the accelerating action of an impacting member causes a movably mounted reaction assembly to be reactively accelerated in the opposite direction at relatively low acceleration. The impact member is accelerated by an actuator on the reaction assembly and impacts a workpiece on the reaction assembly. The present invention utilizes dynamic force systems within the apparatus itself for dynamically absorbing energy of acceleration and impact. The relatively large mass of the movably mounted reaction assembly is an important factor in preventing transmission of energy to the foundation, because the mass resists acceleration and movement of the reaction assembly. A large proportion of the impact energy is available for useful work. The preferred embodiment of the invention herein shown and described utilizes an actuator of the type described and claimed in the copending application of Jack B. Ottestad, Serial No. 617,0114, filed October 19, 1956, now Patent No. 2,979,938 and in the copending application of Jack B. Ottestad and Samuel Arthur Skeen, Serial No. 683,855, filed September 13, 1957, now Patent No. 2,949,096.

In the embodiment herein shown and described, shock absorber assemblies are provided to assist in restricting acceleration and movement of the reaction assembly in reaction to acceleration of the impact member and in response to the impact of that member on the reaction assembly. The shock absorbers thus reduce transmission of forces to the foundation. In the preferred embodiment, the reaction assembly and the impact member are moving in opposite directions at the time of impact, thus increasing the proportion of energy transmitted to the workpiece and decreasing the proportion of energy transmitted to the foundation. After impact, the impact lmember and reaction assembly are decelerated by dynamic force systems in the apparatus, including a decelerating force developed by a cushion plunger in the actuator.

The apparatus of the present invention produces high impact energy with relatively low foundation loading. It therefore obviates the necessity for massive foundations, because only a relatively small proportion of impact energy is transmitted to the foundation. It provides means for transmitting high impact energy at high rates with a relatively small apparatus. Utilization of the actuator shown and described in the copending applications hereite rates tent 3,036,538 Patented May 29, 1962 inabove mentioned provides means for accurately controlling the rate of energy application. Use of the present invention involves relatively little danger to operating personnel.

It is therefore an object of the present invention to provide an apparatus for producing impact energy with relatively low foundation loading.

An object of this invention is the provision of an impacting apparatus wherein the inertia of a movable reaction assembly results in the transmission of only a relatively small proportion of impact energy to a foundation.

lt is an object of this invention to provide an impacting machine which provides high efficiency by utilizing a high proportion of energy for useful work While transmitting a low proportion of energy to a foundation.

An object of the present invention is the provision of an impacting apparatus wherein a large proportion of the energy developed is absorbed dynamically by force systems in the apparatus with relatively little transmission of energy to a foundation.

An object of this invention is the provision of a relatively small self-contained apparatus for the rapid transmission of high level impact energy.

An object of the present invention is to provide high impact energy through the impact of oppositely accelerated masses with relatively little transmission of energy to a foundation.

It is another object of this invention to provide an impacting machine wherein an impact member is accelerated to impinge on a movable reaction `assembly which has been accelerated in the opposite direction in reaction to the acceleration of the impact member.

Another object of the present invention is the provision of an impacting machine capable of high rate application of high level energy with a high degree of safety to personnel.

It is another object of this invention to provide an impacting machine capable of energy transmission to a workpiece at a high controlled rate.

Other objects and features of the present invention, as Well as many advantages thereof, will become apparent to those skilled in the art from a consideration of the following description, the appended claims and the accompanying drawings, wherein:

FIGURE 1 is an elevational view of an impacting machine according to the present invention;

FIGURE 2 is an enlarged elevational view, partially in section, of the impacting Vmachine of FIGURE 1;

FIGURE 3 is `an elevational View taken at line 3 3 of FIGURE 2;

FIGURE 4 is an elevational sectional View taken at line l-ri of FIGURE 2;

FIGURE 5 is an enlarged view, partially in section, showing details of the shock absorber assembly utilized with the present invention; and

FIGURES 6, 7, 8 and 9 are elevational views. partially in section, showing the impacting machine of FIGURES 1 and 2 at diiferent stages of its operation.

Referring to the drawings, and particularly to FIG- URES l and 2, a preferred embodiment of the dynamic reaction apparatus of the present invention is shown as including a frame structure 10 slidably mounted in a foundation formed by foot assemblies 12. The frame structure includes three

guide rods

14, 16 and 18 secured to an end member 26 by nuts 22. and by lock rings 24. Nuts 28 secure a bolster 26 on the guide rods, and lock sleeves 3i) provide for adjustment of the axial position of the bolster on the rods.

Guide rods 16 and 13 are slidable in bearings 32 in foot assemblies 12, as illustrated in FIGURES 1 and 5, to slidably mount the frame structure 10 on the foundation.

Disposed about each of guide rods 16 and 18 is a shock absorber assembly 34 which extends between the two foot assemblies supporting each respective guide bar as shown in FIGURE 5. Each of the assemblies includes two

cylindrical sections

36 and 38, which are secured in clamped relation with an orifice ring 4o by end caps 42 and 44. The end caps are provided with seal rings in appropriate grooves to provide pressure sealing between the cylindrical sections and the guide rod. The orifice ring has a plurality of small axially extending orifices, as shown, and is provided with appropriate seal rings for pressure sealing.

An annular piston 46 is secured to the guide rod between a pair of split lock rings 50 and piston 43 is similarly secured. The annular pistons are provided with seal rings in appropriate grooves for pressure sealing between the cylindrical housing and the guide rod.

From the foregoing and from FIGURE 5, it will be observed that a coaxial pressure chamber 52 is defined between the orifice ring and annular piston 46, and that a similar chamber 54 is defined between the orifice ring and annular piston 48. It will be observed that a coaxial pressure chamber 56 is defined between annular piston 46 and end cap 42, and that a chamber 5S is provided between the annular piston 48 and end cap 44. Chambers S2 and 54 are filled with oil through openings 60 and 62, respectively, in which appropriate filler plugs are threaded. A pneumatic valve 64 is provided for the provision and maintenance of air pressure .in chambers 56 and 58.

The frame structure and an actuator housing 66 together constitute a` reaction assembly. The actuator housing is slidably mounted on the guide rods by bearings 68 disposed in appropriate openings in

end walls

70 and 72 Of the housing. As illustrated in FIGURES 2 and 4, the actuator end walls are provided with circularly arranged openings for accommodating -tie bolts 74. Cylindrical sections 76 and 78, an orifice plate or wall 79 and end fitting plates Si) and 82 are secured in clamped relation with the end walls by the tie bolts. Pressure sealing for the actuator housing is provided by resilient seal rings in appropriate grooves in the fitting plates and in the orifice wall member. An orifice 84 is provided in the orifice plate for a purpose which is hereinafter explained.

The cylindrical actuator housing may be considered as divided into

pressure chambers

86 and 88 by the orifice plate. A passage 90 in the orifice plate interconnects chamber 86 with a source of pressure (not shown). The orifice plate has a passage 91 therein. A passage 92, extending through fitting plate 82 and end wall 72, is provided with an appropriate fluid coupling which interconnects chamber 88 with a source of pressure (not shown). A .coupling 93 in a similar passage is for the purpose of adding or removing oil.

An actuator piston 94 is positioned in chamber 88. A circular seal base 96 is secured by a bolt in an appropriate recess in the face of the piston and is provided with a groove in which a circular resilient pressure seal 9S is secured by bonding. As shown, circular seal 9S is adapted to encircle orifice 84 when the actuator piston is seated against the orifice plate. An annular sealing element 100 in a peripheral groove in the piston provides pressure sealing between the piston and cylindrical section 78. Bearing rings 102 are disposed on both sides of the sealing element in recesses in the piston periphery to reduce sliding friction and to maintain alignment between the piston and the cylindrical section. A reduced end portion of an impact member or thrust column 104 is secured in an opening in the piston. The thrust column extends through aligned openings in fitting plate 82 and end wall 72, and is slidably received in a bearing disposed opening 106 of the end wall. A seal ring in a groove within this opening provides pressure sealing.

A die element 107 at the end of the impact member M4 confronts a cooperating die member 108 on anvil lit), which is secured to bolster 26 in confronting relation with the thrust column. A workpiece 112 is positioned to be impacted between the thrust column and the die member, as shown in FIGURE 2.

A cushion plunger 114 is positioned in chamber 36 and carries a peripheral annular seal M6 and bearing rings in appropriate recesses. These are similar to the seal and bearing rings associated with the actuator piston. The plunger has an opening for securing a threaded portion of a connecting bar 118, which is slidably received in a bearing 12)` in an axial opening in end wall '70. A bolt 122 and a retaining disc assist in securing the plunger to the bar. The connecting bar is secured to end member 26' by bolts 124, which extend through circularly spaced openings in a flange portion of the bar. A helical spring T126 is retained between the head of each bolt and flange portion, so that the end member and the entire frame structure if) may move relative to the connecting bar and shock piston against the resilient urging of the springs, when the cushion plunger seats against end fitting plate 80.

From the foregoing description, it will be understood that the impacting machine includes three structures, each olf which is movable relative to the others land relative to a foundation. The frame structure 16 is slidably mounted in bearings on the foundation. As described above, the actuator housing is slidably mounted on the frame structure, these two structures forming the reaction assembly. The actuator piston and thrust column are movable relative to the actuator housing.

The actuator is adapted to impart high acceleration to the impact member or thrust ycolumn 104. The operation of the actuator is Idescribed in the copending applications hercinbefore identified. it is briefly described herein for convenience of reference to the present invention. A setting pressure is first introduced into chamber 8g through passage 92. This pressure acts upon the thrust column side of piston 94 and urges the piston against orifice plate 7 9. This compresses circular resilient seal against the surface of the orifice plate to effect a positive pressure seal which isolates chamber 8S from chamber S6. A second and higher pressure is established in chamber 66 through passage 90 in the `orifice plate. This actuating pressure acts upon the area of seal plate 96 within seal 98 and is predetermined to balance the `force exerted by the setting pressure upon the larger area on the opposite side of the piston.

To trigger the actuator, the pressure in chamber 86 is increased by a pressure differential sufficient to unbalance the forces upon the actuator piston and cause movement of the piston from the orifice plate. Circular seal 9S is thus disengaged and the high actuating pressure is released substantially instantaneously upon the area of piston 94 outside circular seedL 9S. A great net force is thus suddenly applied to the piston and impels it from the orifice plate with extremely high acceleration'. As explained in the copending applications hereinbefore mentioned, the force and acceleration of the piston and the thrust column 164 are functions of the pressures in

chambers

86 and 88, the piston and thrust column masses, and the ratio between the piston areas upon which the pressures act.

The operation of the impacting machine of the present invention is illustrated in FIGURES 6 through 9. The rapid rightward raccelerating action `of piston 94 causes a leftward reaction on the reaction assembly. From the geometric relations of the parts, as shown in

FlGURES

2 and 7, it will be observed and understood that the forces exerted within the housing by the actuating pressure become unbalanced upon rightward movement of the piston from the orifice plate. In effect, the forces on the orifice plate become balanced and an accelerating force is exerted leftward on the cushion plunger 114. This force is transmitted to the actuator housing `and to the frame structure, which are thereby accelerated leftward simultaneously, with the rapid rightward acceleration of the thrust column, as indicated in FIGURE 7.

The mass of the frame structure l and the housing being large relative to the mass of the actuator piston and thrust column, its high inertia restricts its movement and acceleration. Therefore, relatively low acceleration is imparted to the movable frame and housing in comparison with the high acceleration of the thrust column and actuator piston, and the heavy frame and housing absorb a considerable portion of the reaction energy in accelerating without transmitting the energy to the foundation.

Leftward movement of the reaction assembly is also resisted -by the shock absorbers 34, which decelerate the frame structure l@ by forcing oil through the restricted orifices in orifice ring 4b, in Aa manner well known in the art. Although these idecele-rating means assist in restricting movement `and acceleration of the reaction assembly, it is to be understood that the apparatus of the present invention may be designed to function without shock absorbers. rThe relation between the inertias of the reaction assembly mass and the mass of the piston and thrust column being 'a major factor in absorbing reaction energy, sufiiciently high inertia of the reaction assembly may be provided lto accomplish sufiicient deceleration `and restriction of movement without shock absorbers Because the reaction assembly and the impact member are accelerated in opposite directions, the workpiece 13.2 is impacted between the lanvil lili and thrust column while these members are moving in opposite directions, as shown in FGURE 7. The opposing momentums produce high impact energy. A large proportion of this energy is transmitted to the workpiece to do useful work in displacing the workpiece material. The impact energy is transmitted to the workpiece at a very igh rate to produce very rapid displacement.

Some energy is absorbed in decelerating leftward movement of the frame, some is absorbed in the shock absorbers, and a relatively small proportion of the energy is transmitted to the foot assemblies 12.

After impact, the remaining kinetic energy of the thrust column land piston carries the frame structure ri glitward, as indicated in FIGURE 8. Additional energy is absorbed in accelerating the frame structure rightward `after its leftward movement has been decelerated. Rightward acceleration is at a relatively low rate. The high inertia of the `frame restricts its acceleration and the shock absorbers 34 exert additional decelerating force. Rightward movement of the frame llt) is further resisted by the action of cushion plunger ill/l. Movement of the fratrie structure relative to the `actuator housing, as shown in FIGURE 8, `causes the cushion plunger to produce a partial vacuum between the piston and end wall itl of the housing. The cushion plunger produces compression in chamber 86, seal 116 on the piston providing pressure sealing. The pressure differential between the two sides of the plunger produces leftward decelerating force on frame structure i0. It is to be understood that the cushion plunger H4 is not essential to the operation of the apparatus of the present invention.

After rightward movement of the frame structure and the actuator piston is decelerated, the frame is urged leftward to its normal centered position. The setting pressure in chamber 855 urges the actuator piston leftward against orifice plate 79, as indicated in FIGURE 9. The pressures in the sealed pneumatic chambers 56 and 58 of shock absorbers 34 exert a centering force on the frame structure. A pressure differential between the two charnbers is produced by frame movement off center and exerts a centering force which Vassists in repositioning the frame relative to the foundation. The positions of annular pis- 6 tons 46 and 48, shown in FIGURE 5, correspond to the centered positions of the frame and actuator housing shown in FIGURE 2.

After the cushion plunger 114 contacts end wall 70 during leftward movement of the frame, frame structure 1t) may move a limited distance further leftward against the resilient urging of springs 126, as shown in FIGURE 9. This movement against the force of the springs serves to absorb some of the energy of rapid leftward movement of the frame and therefore reduces shock and stress on the frame structure and on the housing.

After the components of the apparatus have been repositioned to the configuration shown in FIGURES 2 and 9, the machine is ready for repeat operation.

In order to prepare the actuator for repeat operation, the actuator piston must be reseated against the orifice plate to re-establish pressure sealing by means of resilient seal 98. Reseating is preferably effected by reducing the ressure in chamber 86 to a value -below the pressure in chamber 83. The latter pressure then moves the piston to the orice plate.

It is important to prevent the trapping of pressure, as circular seal 98 contacts the surface of the orifice plate on reseating, in the space defined by annular seal it), circular seal 98, the piston, the orifice plate, and cylindrical section 78. Such trapping is prevented, in the manner described in the copending application of Jack Benton Ottestad and Samuel Arthur Skeen, hereinbefore mentioned, by the provision of exterior fluid connections and a unidirectional check valve (not shown) between orifice plate passages 9) `and 91. Pressure is automatically relieved through the passages, connections, and unidirectional check valve into chamber 86. If it were not relieved, trapped prsure would act upon the actuator piston area outside seal 9S and would tend to balance the force exerted on the opposite side of the piston by the setting pressure. Obviously, the pressure in chamber 86 could not be increased to the actuating pressure required for sudden release over the piston to effect rapid piston acceleration. instead, upon increasing the pressure in chamber 86, the piston would be moved and seal 98 would be disengaged by a lower pressure in chamber 86 `acting upon the area within circular seal 98%, because of the force exerted by the trapped pressure.

Although a specific embodiment of the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only; it is to be understood that the invention is not limited thereto, as many variations will be readily apparent to those versed in the art and the invention is to be given its broadest possi-ble interpretation within the terms of the appended claims.

The inventors claim:

1. An impacting apparatus comprising a reaction assembly slidably mounted relative to a foundation, said reaction assembly including actuator housing means, an actuator piston in the housing means, a thrust column connected with the piston, said piston and thrust column having relatively small mass, a plate in the housing confronting the `actuator piston and defining an orifice, sealing means between the actuator piston and the plate for effecting pressure sealing therebetween about the orifice, means for exerting a setting force to urge said actuator piston toward the plate to cover the orifice and effect said pressure sealing, and means for establishing an actuating pressure to act upon a portion of the actuator piston within the sealing means to overbalance the setting force and expose an increased area of the actuator piston to said actuating pressure to accelerate said actuator piston and said thrust column, and means on the reaction assembly confronting the thnust column for receiving the impact thereof, the reaction assembly having relatively high inertia to resist acceleration in reaction to the acceleration of the thrust column and to resist deceleration and acceleration in response to said impact, whereby a relatively 7 small proportion yof impact energy is transmitted to said foundation.

2. An impacting apparatus comprising a reaction assembly of relatively large mass, foundation means slidably supporting the reaction assembly, decelerating means for opposing movement of the reaction assembly, said decelerating means including an hydraulic shock absorber connected between said foundation means and said reaction assembly, said shock absorber having pistons and means defining at least one orifice between said pistons, said pistons 'being carried by said reaction assembly when said reaction assembly slides relative to said foundation to produce hydraulic resistance to such sliding movement of said reaction assembly, an impact member of relatively small mass slidably positioned in the reaction assembly, means for rapidly accelerating the impact member to high velocity relative to the reaction assembly, and means on the reaction assembly for receiving the impact of the impact member, the reaction assembly having relatively large lmass to resist acceleration in reaction to the acceleration of the thrust column and to resist acceleration and deceleration in response to said impact, whereby a relatively small propo-rtion of impact energy is transmitted to the foundation.

3. An impacting apparatus comprising, a frame structure slidably supported by a foundation, a housing having opposite ends being slidably carried by said frame structure, an impact member of relatively low inertia being movably positioned in said housing, actuator means in said housing for accelerating said impact member relative to said housing, means for admitting a pressurized medium into said housing to actuate said actuator means, means on said frame structure for receiving the impact of said impact member, said frame structure and said housing constituting a reaction assembly having relatively high inertia to resist acceleration in reaction to the acceleration of said impact member and to resist acceleration and deceleration in response to said impact, and a cushion plunger positioned within said housing at one end thereof and attached directly to said frame structure through said one end of said housing for resisting movement of said frame structure af-ter said impact by producing a pressure differential on opposite sides of said plunger in said housing, said pressure differential being lthe differential between the pressure within the space between one side of said plunger and said one end of said housing and the pressure of said pressurized medium in said housing on the opposite side of said plunger.

4. A dynamic impacting machine comprising a frame structure having at least two guide rods, actuator means slidably mounted on at least one of the guide rods, foundation means adapted to slidably receive at least one of the guide rods to support the frame structure, a thrust column of relatively low inertia carried by the foundation means and adapted to be rapidly accelerated in a first direction by the actuator means, and means on the frame structure for receiving the impact of the thrust column, the frame structure and the actuator means constituting a reaction assembly of relatively high inertia to resist acceleration in a second direction in reaction to acceleration of the thrust column and to resist acceleration in said first direction in response to said impact of the thrust column, and an hydraulic shock absorber connected with said foundation means and disposed about the guide rod slidably received by the foundation means, said shock absorber having piston and means defining at least one orifice Ibetween said pistons said pistons being carried by said guide rod to cooperate therewith to produce hydraulic resistance to movement of said frame structure, whereby impact energy is provided with only limited transmission of forces to the foundation.

`5. A dynamic impacting machine comprising a frame structure having at least two guide rods, foundation means adapted to slidably receive at least one of the guide rods to support the frame structure, an actuator housing slidably mounted on at least one of the guide rods, a plate defining an orifice within the housing, an actuator piston positioned in the housing, a thrust column connected with the piston and extending from the housing, sealing means between the actuator piston and the plate for effecting pressure sealing therebetween about the orifice, means for exerting a setting force urging said actuator piston toward the plate to cover said orifice and effect said pressure sealing, means for establishing an actuating pressure within said housing means, means for releasing the actuating pressure over an area of the actuator piston to rapidly accelerate the piston and thrust column in a first direction, and means on the frame structure for receiving the impact of the thrust column, the frame structure and the actuator housing having high inertia to resist acceleration in a second direction in reaction to the thrust column acceleration and to resist deceleration and acceleration in response to said impact of the thrust column, whereby high impact energy is provided with transmission of only a relatively small porportion thereof to said foundation.

6. A dynamic impacting apparatus comprising a frame structure slidably -supported by a foundation, actuator housing means slidably mounted on the frame structure, an actuator piston in the housing means, a thrust column connected with the piston, a plate in the housing confrontting the actuator piston and defining an orifice, sealing means between the actuator piston and the plate for effecting pressure sealing therebetween about the orifice, means for exerting a setting force to urge said actuator piston toward the plate to cover the orifice and effect said pressure sealing, and means for establishing au actuating pressure to act upon a portion of the actuator piston within the sealing means to overbalance the setting force, thereby exposing an increased area of the actuator piston to said actuating pressure to accelerate said actuator piston and said thrust column in a first direction, means on the frame structure for receiving the impact of the thrust column, said frame structure and said actuator housing having high inertia to resist acceleration in a second direction in reaction to the acceleration of the thrust column and to oppose deceleration and acceleration in response to said impact, and a cushion plunger connected with the frame structure and slidable in the actuator housing, said cushion plunger opposing movement of the frame structure in said first direction after said impact by moving relative to said housing to produce compression on one side of the plunger and a partial vacuum on the opposite side thereof, whereby high impact energy is provided and only a relatively small proportion thereof is transmitted to said foundation.

7. A dynamic impacting apparatus according to claim 6, `and further including decelerating means connected with said foundation for opposing movement of the frame structure relative to the foundation, whereby high impact energy is provided with transmission to the foundation of only those forces developed by the decelerating means.

8. A dynamic impacting machine comprising a frame structure having at least two guide rods, foundation means adapted to slidably receive at least one of the guide rods to support the frame structure, an actuator housing slidably mounted on at least one of the guide rods, a plate defining an orifice within the housing, an actuator piston positioned in the housing, a thrust column connected with the piston and extending from the housing, sealing means between the actuator piston yand the plate for effecting pressure sealing therebetween about the orifice, means for exerting a setting force urging said actuator piston toward the plate to cover said orifice and effect said pressure sealing, means for establishing an actuating pressure within said housing means, means for releasing the actuating pressure over an area of the actuator piston to rapidly accelerate the piston .and thrust column in a first direction, means on the frame structure for receiving the impact of the thrust column, the frame structure and the actuator housing having high inertia to resist acceleration in a second direction in reaction to the thrust column acceleration and to resist deceleration and acceleration in response to said impact of the thrust column, and an hydraulic shock absorber connected with said foundation means and disposed about the guide rod slidably received by the foundation means, said shock absorber having means defining at least one orifice between pistons carried -by said guide rod to cooperate therewith to produce hydraulic resistance to movement of said frame structure, whereby impact energy is provided with only the forces developed in the shock absorber being transmitted to the foundation.

References Cited in the file of this patent UNITED STATES PATENTS Nickerson Jan. 15, 1889 Reilly Jan. 10, 1893 Saives May 17, 1938 Johnson Oct. 11, 1938 Fletcher Jan. 1, 1952 FOREIGN PATENTS Great Britain Feb. 19, 1937 Great Britain Dec. 12. 1956