US3205790A

US3205790A - Impact forming apparatus

Info

Publication number: US3205790A
Application number: US328787A
Authority: US
Inventors: Leo C Bollar
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-12-02
Filing date: 1963-12-02
Publication date: 1965-09-14
Anticipated expiration: 1982-09-14

Description

Sept. 14, 1965 c. BOLLAR IMPACT FORMING APPARATUS Filed Dec. 2, 1963 I00 I 5 eq,

5 Sheets-Sheet 1 INVENTOR. LEO CBOLLQ/Q AT TORN EY Sept. 14, 1965 c, BOLLAR 3,205,790

IMPACT FORMING APPARATUS Filed Dec. 2, 1965 3 Sheets-Sheet 2 I63 i -lgl 3 [G7 PF M I r 124 I -4-'L' 4 v l I94 1'90 INVENTOR. LEO @BOLLAR ATTORN EY United States Patent 3,205,790 IMPACT FORMING APPARATUS Leo C. Bollar, 1886 Miramar St., Pomona, Calif. Filed Dec. 2, 1963, Ser. No. 328,787 16 Claims. (CI. 7220) This application is a continuation-in-part of my application of the same title, Serial No, 107,847, filed May 4, 1961, and now abandoned.

This invention relates to improvements in a high energy impact apparatus for processing workpieces, for example for forging metal parts or forming metal parts by extrusion.

The invention is directed to the elimination of a number of limitations that are inherent in the operation of a forming apparatus of the type wherein a workpiece together with forming dies is positioned on a platen on a frame or support structure and a highly pressurized con fined body of gaseous fluid drives the ram towards the platen to form the workpiece. The limitations may be understood when it is considered that in a conventional pneumatic forming apparatus, the ram itself applies the kinetic energy to the workpiece.

One limitation is that such an apparatus may be incapable of delivering a desirable magnitude of kinetic energy at a desirable velocity for optimum results on a given workpiece. In a typical well designed prior art apparatus of this type employing gaseous fluid at 2000 p.s.i. to drive the ram, the ram may develop as much as 150,000 ft.-lbs. of kinetic energy, whereas the optimum kinetic energy for many workpieces is on the order of 50,000 ft.-lbs. Unfortunately, however, lowering the pressure of the actuating fluid to reduce the applied kinetic energy to a desirable level has the effect of lowering the velocity of the ram to an unacceptable degree.

Another limitation is that the conventional apparatus does not provide a sufficient range of choice in the velocity of approach of the ram to the impact point, Too often, the initial closing movement of the dies is excessive for the forming operation. A workpiece of relatively soft material, such as aluminum, or a workpiece that is to be formed to a complex configuration, may require controlled reduction of the initial die velocity. Any solution to this problem must take into consideration the fact that the reaction of the support frame to the actuating force materially contributes to the velocity of the closing movement of the dies,

Still another limitation is that such an apparatus is inherently incapable of operating with a prolonged period of relatively moderate forming pressure in contrast to a short period of higher magnitude forming pressure. The excess energy is wasted but, more important, is the damaging effect on both the workpiece and the support frame. The abrupt high magnitude pressure rise has a fracturing effect on the workpiece and has a destructive effect on the apparatus in that it applies a high frequency vibration to the support frame and to all of the components on the support frame. The imparted vibration being audible, the apparatus is said to ring. It is highly desirable to reduce the maximum applied pressure and at the same time to spread the time base for more gradual as well as more complete utilization of the generated kinetic energy.

An additional limitation is in the damaging effect on the formed workpiece of rebound on the part of the ram. The ram tends to oscillate and to apply at least one objectionable additional impact to the already formed workpiece because high frequency impact energy is momentarily stored in the ram and is rapidly returned to overcome the downward force.

A further limitation is the excessive reaction displacement of the support structure. It is to be borne in mind "ice that the created kinetic energy is divided between the ram and the support frame in direct proportion to their respective displacements. In a typical well designed apparatus of this general type, the mass of the ram approximates the mass of the support structure and consequently the reaction displacement of the support structure may be, for example, on the order of 4 to 8 inches. It is usual 1y desirable to employ an upright apparatus delivering a downward work stroke with the result that the whole apparatus jumps 4 to 8 inches from the floor in reaction to the work stroke.

The violent high amplitude displacement of the support frame results in inertia stressing of the frame and its associated components including hose connections, etc., the inertia tressing varying directly with the forcing energy. High inertia energy per pound of the support frame has the further disadvantage of resulting in high inertia energy of the workpiece to reduce control of the dies over the workpiece and to reduce control over the relative movement between the dies and the workpiece. The high energy reaction of the support frame also makes it practically impossible to advance an elongated workpiece by stages through the forming dies for progressive forming of the workpiece by rapidly repeated operating cycles of the apparatus. The violent reaction of the support frame kicks the elongated workpiece away from the dies and thus necessitates a complicated workpiece support and also an appreciable pause between each step of the progressive forming operation.

It would be logical to multiply the mass of the work structure to meet some of these problems. This solution is obviously not practical, however, because the support structure is already large. Even if it were practical the result would be to increase the ram velocity which may undesirably increase the closing rate of the dies.

On the other hand, a promising direction of development to avoid these inherent limitations would be to use a free piston of only a small fraction of the mass of the support frame instead of a conventional heavy ram and to place a second floating impact body or plunger in the path of the piston to transmit the kinetic energy from the piston to the forming dies. By virtue of this arrangement, the mass of the support frame may be no greater than in a conventional apparatus but, nevertheless, may be many times the mass of the piston with consequent minimizing of the reaction displacement of the support frame. For example, the mass of the free piston may be approximately one-fortieth of the mass of the support frame. With the mass of the free piston one-fortieth of the mass of the support frame and with the free piston traveling 20 inches, the total kinetic energy developed by the piston is 97,560 ft.-lbs., whereas the kinetic energy of the support frame is only 2,440 ft.-lbs.

This inviting direction of development has been suggested heretofore in this art but has not been fruitful because of a basic difi'iculty that is explained by Newtons third law of motion. If the two impact bodies meet With metal-to-metal impact and both impact bodies have the same mass, all of the kinetic energy is transferred to the second impact body without change in velocity. If the mass of the piston is larger than the mass of the second impact body, the velocity imparted to the second impact body by metal-to-metal impact is unacceptably greater than the velocity of the piston. On the other hand, if the mass of the second impact body is a great deal larger than the mass of the piston, the piston simply rebounds at high velocity with relatively little transfer of kinetic energy to the second impact body.

This last fact, heretofore regarded as insurmountable, has been a serious obstacle because it would be highly advantageous to employ a second impact body that is a great deal larger than the free piston. One advantage is that the smaller the free piston the less the reaction of the support frame for a given amount of generated energy. Another and important advantage is that employing a relatively large second impact body steps down the velocity of approach to the workpiece. A third highly important advantage is that the use of a second impact body of relatively great mass affords a certain versatility in tooling because any desired proportion of the mass may be in the form of dies or tooling. In many instances tooling of large mass is optimum for performing a given operation on a given workpiece but the available impact forming apparatus cannot accommodate such a tool.

The broad object of the present invention is to circumvent this basic obstacle that is created by Newtons third law of motion and thus make it practical to use a free piston in combination with a second impact body of relatively large mass for a wide range of impact forming operations. A further object of the invention is to carry out this line of development in such manner as to avoid the previously mentioned limitations that are encountered in the operation of conventional single-ram impact forming machines. The attainment of these objects is based on certain interrelated concepts which will now be enumerated;

The first concept is to interpose a resiliently yieldable means between the piston and the second floating impact body. Conceivably such a resiliently yieldable means may be in the form of spring means. There is no loss of energy in the impact of two perfectly elastic bodies and the interposing of the yielding means has the same effect as increasing the elasticity of the two impact bodies. The elastic compression of the interposed resiliently yieldable means stores energy and makes acceleration of the second impact body more gradual.

The second concept is to use a body of fluid for the interposed resiliently yieldable means. The fluid may be a gaseous fluid but liquid such as oil is preferred because of its elastic behavior at the exceedingly high pressure that is created between the two bodies.

The third and most important concept is that of employing a confined body of fluid for the resiliently yieldable means between a free piston of relatively small mass and a much more massive second impact body with an energy-transferring interface of relatively small area between the free piston and the cushioning fluid and an energy-transferring interface of much larger area between the cushioning fluid and the second impact body. The cushioning body of fluid with its differential areas serves as a transformer to increase force at the expense of velocity, the arrangement being analogous to the employment of an electrical transformer to match the impedance of a load for the purpose of maximum transfer of energy to the load.

The fourth concept is to vary the position of the second floating impact body relative to the lower die of the tooling. In some instances, the floating impact body is substantially retracted to reach maximum velocity before acting on the workpiece. At the other extreme the floating impact body is positioned for immediate effect on the workpiece and is accelerated from zero velocity as it transmits energy to the workpiece. In other words, the dies for forming the workpiece are closed against the workpiece with the second impact body snug against the dies before the working stroke of the piston is initiated. The gradual deceleration of the free piston by the cushioning fluid and the delayed release of the energy of the compressed cushioning fluid provide a relatively long time base for the work of forming the workpiece. It is important to note that accelerating the second impact body from zero velocity while it is in energy-transmitting relation to the workpiece instead of accelerating the second impact body to high velocity before it is placed in energy-transmitting relation to the workpiece causes the initiation of the displacement of material in the workpiece to be relatively gradual instead of extremely abrupt and thus makes possible certain forming operations that would otherwise be destructive to the workpiece.

The fifth concept is to avoid rebound impacts on the workpiece, this end being accomplished by the use of a free piston in combination with a second impact body. When the second impact body tends to oscillate at high frequency as heretofore mentioned the tendency is effectively opposed and overcome by a much lower frequency force of the same high magnitude on the part of the free piston, the opposing force being-sustained by the deceleration of the free piston by the interposed cushioning fluid.

The sixth concept as will be fully explained hereafter is to employ an exceedingly simple arrangement for triggering the power stroke of the free piston wherein the piston is sustained at its upper retracted position by relatively light gaseous fluid pressure and the triggering is accomplished by merely bleeding off a portion of the sustaining gaseous fluid.

The various features and advantages of the invention, including features relating to the control system, may be understood from the following detailed description and the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative FIG. 1 is a vertical or longitudinal sectional view of the Structure of the apparatus Referring to FIG. 1, the principal parts of the apparatus include the following: an upright frame or support structure, generally designated 10; an inner upright cylinder 12 with lateral ports 14 near its upper end and lateral ports 15 near its lower end; an outer cylinder 16 which encloses an annular space around the inner cylinder; an annular wall member or ring 18 having inner and outer O-

rings

20 and 22 respectively which divide the annular space between the two cylinders into a relatively large annular reservoir 24 for high pressure gaseous fluid and a lower annular chamber 25, the annular reservoir being in communication with the upper ports 14 of the inner cylinder and the lower annular chamber being in communication with the lower ports 15 of the inner cylinder; a first impact member in the form of a free piston 26 having an upper O-ring 28' and a lower O-ring 30. positioned to nor mally straddle the upper ports 14; a triggering piston 32 in the inner cylinder 12 above the free piston 26-; a second impact member or body 34 in the form of a piston formed with an upper radial flange 35, that is equipped with an Caring 36; an annular cushioning chamber 38 surrounding the second impact member 34 below the radial flange 35, which chamber contains a gaseous fluid under pressure; a lower die 40 carried by the frame 10; and an upper die 42 which is actuated by the lower impact member 34 and which may be carried by the lower impact member.

The frame 10 includes a heavy base block 44 which rests on a pair of rubber pads 45 in a base pan 46. The platen for supporting the lower die 40 may comprise a stack of spacer plates 48 anchored by suitable screws 50, the number of spacer plates being varied in accord with the desired position of the lower die. An upper platen member may be provided but in the construction shown the lower face of the lower impact member 34 serves as a platen for the upper die 42.

An ejector plunger 52 for removing formed parts is slidable through an axial bore 54 through the spacer plates 48 and is actuated by a piston 55 in a cylinder 56 in the base block 44. The upper end of the cylinder 56 is sealed by a ring 58 equipped with inner and outer 0- rings and fluid communication with the cylinder is provided by upper and

lower passages

60 and 62 respectively.

The frame 10 further includes an upper support block 64 which is mounted in spaced relation to the base block 44 by frame members 65, the frame members being connected to the two blocks by suitable screws 66. This upper block 64 has a relatively large bore 68 forming the cushioning chamber 38 and has a smaller bore 70 which is a continuation of the inner cylinder 12.

A guide ring 72 for the lower impact member 34 is attached to the upper support block 64 by screws 74. The guide ring is equipped with an inner circumferential O-ring 75 to form a seal around the lower impact member 34 and is further provided with an outer circumferential O-ring 76 to seal off the cushioning chamber 38.

The upper support block 64 is bored to provide a fluid passage 78 that communicates with the cushioning chamber 38 and it is to be noted that the fluid passage connects with an expanded lower portion 80 of the cushioning chamber. The upper support block 64 is further bored to form an angular fluid passage 82 which communicates with the lower annular chamber 25 and which further communicates with the interior of the inner cylinder 12 through the lower lateral ports 15.

The annular wall member or ring 18 that separates the annular reservoir 24 from the lower annular chamber 25 is' supported and secured by an integral cylindrical skirt 84. The cylindrical skirt 84 is formed with a radial flange 85 on its lower end that interlocks with a corresponding inner circumferential groove of the outer cylinder 16. The outer cylinder 16 is formed, in turn, with a lower radial flange 85 that interlocks with a corresponding inner circumferential groove of a retaining ring 86, the retaining ring being anchored to the upper support block 64 by suitable screws 88. The lower edge of the outer cylinder 16 is provided with an O-ring that is compressed by tightening the screws 88.

The upper ends of the inner and

outer cylinders

12 and 16 respectively are closed by a cylinder head 92 which interlocks with the outer cylinder 16 and which is provided with an O-ring 94 to seal the joint with the outer cylinder. The cylinder head 92 is reduced in diameter on its under side to nest into the inner cylinder 12 and is provided with a second O-ring 95 to seal the joint with the inner cylinder. The cylinder head 92 is provided with a vent passage 96 and is formed with a downwardly extending tubular projection 98 for downward extension of the vent passage, the upper end of the upper piston 26 being formed with an axial recess 100 to clear the tubular projection. The cylinder head 92 is further provided with a fluid passage 102 which leads to an annular recess 104 on the under face of the cylinder head. The triggering piston 32 is bored to clear the tubular projection 98 of the cylinder head 92 and is provided with an inner O-ring 105 for sealing contact with the tubular projection and an outer O-ring 106 for sealing contact with the inner cylinder 12.

Operating cycle FIG. 1 shows the state of the apparatus when it is set for carrying out an operating cycle. A body of oil 108 to serve as a fluid cushion occupies the lower portion of the inner cylinder 12 below the lower lateral ports 15. This body of oil may be omitted if a gaseous fluid cushion instead of a liquid fluid cushion is desired. The interior of the inner cylinder is filled with a gaseous fluid, for example air under suitable pressure to maintain the upper free piston 26 in its upper limit position as shown. The air used for this purpose may, for example, be under a pressure of 50 p.s.i. The annular reservoir 24 contains 5 a gaseous fluid under high pressure which, for example, may be in the range of 1500 to 2000 p.s.i. The highly compressed gaseous fluid in the annular reservoir 24 is cut off from the upper side of the free piston 26 by the upper O-ring 28 and is cut off from the lower side of the piston by the O-ring 30. The cushioning chamber 38 is filled with a gaseous fluid, the pressure of which may be on the order of 1500 p.s.i. This pressure acting on the under surface of the radial flange 35 of the lower impact member 34 holds the lower impact member at its upper limit position as shown.

To trigger the operating cycle a predetermined amount of fluid, preferably a liquid such as oil, is introduced through the fluid passage 102 in the cylinder head 92 to force the triggering piston 32 downward thereby to force the free piston 26 to the triggering position shown in FIG. 3. At this triggering position the upper O-ring 28 of the free piston 26 is in the region of the upper lateral ports 14 to permit the high pressure fluid in the annular reservoir 24 to communicate with the upper face of the free piston. Consequently the fluid pressure is applied to the upper face of the free piston 26 to force the free piston downward at exceedingly high acceleration.

As the free piston 26 approaches the body of oil 108 it displaces gaseous fluid from the interior of the inner cylinder 12 through the lower lateral ports 15 into the lower annular chamber 25 as indicated by the arrows in FIG. 5. The free piston 26 completes its work stroke by depressing the body of oil 108 as shown in FIG. 6 and in doing so compresses a thin interposed layer 110 of gaseous fluid. It is to be noted that the area of the free piston 26 that is effective on the body of oil 108 is less than the area of the second lower impact body 34 that is exposed to the body of oil. Thus, the force exerted by the free piston 26 is multiplied in its transmission to the lower impact body 34.

At the high pressures involved the body of oil 108 acts as a resilient cushion, the elastic contraction of the oil amounting to as much as /2 inch of displacement by the upper piston 26. It is apparent that the elastic contraction of the body of oil results in gradual transmission of kinetic energy from the free piston 26 to the lower impact body 34 and at the same time stores energy to prolong the application of force to the lower impact body.

To reset the apparatus for repeating the operating cycle, oil is pumped into the inner cylinder 12 under the free piston 26 through the angular fluid passage 82 and the lower lateral ports 15, the oil being pumped under sufficient pressure to lift the free piston in opposition to the pressure of the gaseous fluid in the annular reservoir 24. As the free piston 26 is elevated in this manner, oil is released from the upper side of the triggering piston 32 through the fluid passage 102 to permit the triggering piston to be returned to its starting position.

As the free piston 26 approaches its upper limit position it compresses a small amount of compressed gaseous fluid into the axial recess 100 of the piston. The vent 96 is normally closed but may be opened whenever it is desired to release gaseous fluid from the interior of the inner cylinder 12 in the region above the piston. With the piston lowered below the upper lateral ports 14, the vent passage 96 may also be utilized to introduce highly compressed gaseous fluid to replace losses and to recharge the annular reservoir 24. The annular reservoir may also be charged directly through a fluid passage 102 in the cylinder head 92.

When the free piston 26 has been lifted by the inflowing oil to its upper limit position, the oil is drained from the interior of the inner cylinder 12 through the angular fluid passage 82, the oil being drained down to the level of the lower edges of the lower lateral ports 15. During the draining of the oil, gaseous fluid pressure acts on the underside of the free piston to maintain the free piston in its upper limit position, this gaseous fluid pressure dropping to the initial 50 psi. as the oil is drained. The apparatus is then ready for initiation of a second operating cycle by the introduction of triggering fluid through the fluid pressure 162 in the cylinder head 92.

A feature of the invention is that the operating cycle may be triggered without using triggering oil and with the triggering piston 32 omitted. The required triggering action is carried out simply by bleeding ofl gaseous fluid from the region below the elevated free piston 26 thereby to cause the fluid pressure under the free piston to drop to a level that is insuficient to support the free piston. The free piston then gravitates to the triggering position shown in FIG. 3 for initiation of the operating cycle.

The effect of employing a cushioning fluid body 108 acting on different areas of the free piston 26 and the lower impact member 34 may be appreciated by first considering what the relationship of the two masses must be for complete transfer of the kinetic energy with equal areas of the masses acted upon by the elastic fluid. The two masses must be acted upon by an identical impulse i; f Fdt that is both masses will experience the same force F for the same period of time.

Let m be the mass of the free piston 26 and V be the velocity of the free piston before impact. Let m be the mass of the lower impact member 34 with a velocity V which is zero. For complete transfer of the kinetic energy the velocity V of m is zero and mi has some velocity V m V =m V equal momentum and /2m V /2m V since kinetic energy must be conserved.

Substituting:

Tflfi So both masses must be equal for complete transfer of the kinetic energy when the two masses have equal areas acting on the cushioning fluid.

Consider now the relationship of the two masses necessary for complete transfer of the kinetic enregy when the area A of the mass m that is acted upon by the interposed fluid is less than the area A of mass m As m collides with the interposed fluid, a pressure develops which acts on both m and m;;,. If the fluid is relatively massless, the pressure P will be uniform over the pressurized areas. It is apparent, then, that the two impulses acting on m and m will not be equal. The period of time will be the same, but F A P and F =A P. The impulse momentum relationship will be:

But

F2=%iF1 so that t F J; mzvg For example, if the area of the low impact body 34 that is acted upon by the interposed fluid is twice the area of the free piston 26 -2 and 4 In that case complete transfer of the kinetic energy of the free piston 26 to the lower impact body 34 will occur if the lower impact body weighs four times as much as the free piston.

The control system of the presently preferred embodiment of the invention includes hydraulic, pneumatic and electrical components. The hydraulic and pneumatic components are shown in FIG. 3 and the cooperating electrical components are shown in the circuit diagram in FIG. 4.

In FIG. 3 a pump operated by a motor 122 draws oil from a reservoir 124 through the usual strainer 125. The output of the pump is connected to a high pressure line 126 wherein the pressure is controlled by a maximum pressure valve 128 which has a return line 130 to the reservoir 124.

A normally closed valve 132 operated by a solenoid 134 controls flow of oil from the high pressure line 126 through a line 135 to the fluid passage 102 in the cylinder head 92 of the apparatus. The line 135 has a branch 136 back to the reservoir 124, this branch being equipped with a normally open valve 133 controlled by a solenoid 140. The high pressure line 126 is connected to a second line 142 by a normally closed valve 144 that is operated by a solenoid 145. This second line 142 leads to the angular passage 32 of the apparatus. The second line 142 has a branch 146 back to the reservoir 124, the branch being equipped with a normally open valve 148 that is operated by a solenoid 150. A pressure switch 152 is connected to the line 135 to respond to pressure changes therein and two

pressure switches

154 and 155 are connected to the line 142 to respond to changes of pressure therein.

The pneumatic components of the control system include a source 156 of highly compressed gaseous fluid that is connected to the previously mentioned line 142 through a line 158 under the control of a valve 160. The source 156 is connected by a line 162 to the previously mentioned fluid passage 78 of the apparatus. This line 162 is controlled by a valve 164 and may be equipped with a pressure gauge 165. The line 162 may be open to the atmosphere when desired through a valve 166. The vent passage 96 through the cylinder head 92 is controlled by a normally open valve 163 that is operated by a solenoid 167.

Referring now to the wiring diagram in FIG. 4;, the circuit is shown as a direct current circuit for simplicity with one side of the circuit energized by a line 168 and the other side of the circuit grounded.

A timer 170 controlled by a normally open switch 172 has two normally

open contactors

174 and 175. The contactor 174 energizes the solenoid 134 that controls the normally closed valve 132 and the contactor 175 energizes a normally open relay 176 having two normally

open contacts

178 and 180. The contactor 178 closes a holding circuit for the relay 176, which holding circuit includes the previously mentioned pressure switch 154. The second contactor 180 energizes the solenoid 140 that controls the normally open valve 138 and also energizes the solenoid 167 that controls the normally open vent valve 163.

previously mentioned normally open valve 148. A shunt 192 around the contactor 190 is controlled by a normally open contactor 194 of a fourth relay 195. The fourth relay 195 is controlled by the previously mentioned pressure switch 155.

The control system cycle With the mechanism set for an operating cycle, all the parts being positioned as shown in FIG. 1, an operating cycle is triggered by closing switch 172, which may be a push button switch, to cause the timer to operate for closing the

contactors

174 and 175 for a predetermined time period. This predetermined time periodis precisely-the time required for flow of the correct amount of the triggering oil through the cylinder head passage 102 to move the triggering piston 32 to its triggering position shown in FIG. 3. The timer 170 opens the normally closed valve 132 to supply triggering fluid and closes the normally open valve 138 to keep the triggering fluid from being returned to the reservoir 124. The closing of the normally open valve 138 and the normally open vent valve 163 is accomplished by the energizing of the relay 176 by the contactor 175. When the relay 176 is energized,

it is locked by the holding circuit through the pressure I switch 154 sothat the normally open valve 138 will remain closed until the pressure switch 154 breaks the holding circuit. v

After the working stroke of the apparatus has been.

completed the switch 182, which may be a push button switch, is closed to reset the apparatus for anew cycle of operation. Since the operating cycle through the work stroke is carried out in an instantaneous manner and since an appreciable period of time is required for the resetting operation to be initiated by the closing of the second switch 182, it has been found to be practical to close both switches at once. Thus a single pushbutton may be employed to close switches 172 and 182 simultaneously for automatically carrying out the whole cycle of operation including the resetting of the apparatus.

The closing of the switch 182 energizes the relay 184 to close the two

contactors

185 and 186 and the closing of the contactor 186 energizes the third relay 188 to close the contactor 190. The relay 184 is locked by a holding I circuit through the pressure switch 152 with the result that the normally closed valve 144 is held open and the normally open valve 148 is held closed until the holding circuit is broken by the pressure switch 152.

As oil flows into the inner cylinder 12 of the apparatus from the line 142 through the angular fluid passage 82,

the pressure in the inner cylinder progressively rises from a pressure of, say, 450 p.s.i. As the upwardly moving free piston 26 approaches the triggering piston 32, the pressure in the oil under the free piston climbs to a predetermined pressure in the range of 1500-2000 p.s.i. The pressure in the oil line 142 rises correspondingly and at the predetermined pressure the pressure switch 154 responds by opening the holding circuit of the relay 176. The de-energization of the relay 176 causes the normally open valve 138 to open for flow of the triggering fluid to the reservoir 124 and also opens the vent valve 163. The triggering piston 32 then yields to the pressure against its underside and returns to its normal retracted position thereby displacing the triggering oil into the oil line 135.

Up to this time in the operating cycle the pressure in the r 10 oil line for triggering fluid has been substntial but when the oil has been returned to the reservoir through the normally open valve 138 the pressure in the line 135 drops to zero. The pressure switch 152 responds to this pressure drop by opening the holding circuit of the relay 184. Deenergization of the relay 184 closes the valve .144 tocut off the supply of high pressure oil to the line 142. The deenergization of the relay 184 also results in deenergization of the relay 188 to open the valve 148 to permit the oil filled inner cylinder 12 to be drained to the reservoir 124, the draining of the oil down to the level of the lower lateral ports 15 being promoted by expansion of highly compressed gaseous fluid from the lower annular chamber 25. As the oil, empties from the inner cylinder 12 of the apparatus the pressure in the oil line 142 progressively drops. When' the pressure drops to 50 p.s.i., the pressure switch responds by energizing the relay to close the valve 148 thereby to hold the pressure as required to sustain the free piston 26 at its upper limit position in preparation for a new operating cycle.

If'it is desired to initiate the operating cycle by'reducing the gaseous pressure under the piston 26, a normally closed switch 200 may be provided in series with the contactors'190 and194. With the pressure switch 155 energizing the relay 195 to maintain suflicient gaseous pressure in the cylinder 12 to support the piston 26, the switch 200, which may be a pushbutton switch, may be :opened to cause the valve 148 to open to reduce the preschamber 38 or by interposing spacer rings between the upper side of the impact body and the shoulder at the upper end of the cushioning chamber 38. If the lower impact body 34 starts at the position shown in FIG. 1, it will be fully accelerated by the time that the closing movement of the dies begins the actual forming operation. On the other hand, if the starting position of the impact body 34 is lowered until the upper die is in contact with the workpiece, the impact body will be stationary at the beginningof the forming operation and will be accelerated in the course of the forming operation. Obviously any adjustment may be made between these two extremes.

My description in specific detail of the presently preferred embodiment of the invention will suggest various changes, substitutions and other departures from my inh vention within the spirit and scope of the appended claims.

I 'claim: p 1. In a high velocity impact apparatus, the combination of:

a support structure;

fa platen carried by the support structure to support a workpiece; i

an impact body positioned to cooperate with the platen "'for' forming the workpiece;

a free piston for impact action against the impact body,

the mass of the support structure being several times the mass of the -free piston with freedom for the free piston to travel a substantial distance before transmitting energy to the impact body;

means to apply abrupt high fluid pressure between the free piston and the support structure to drive the free piston over said distance with consequent rapid acceleration of the free piston to high velocity and corresponding development of high kinetic energy in the free piston with relatively little reaction displacement of the support structure;

and resilient yielding means between the free piston and the impact body to prolong the acceleration of the impact body by the free piston and to act in compression to momentarily store a portion of the kinetic energy from the free piston, the position of said impact body relative to the workpiece being variable whereby the impact body may be accelerated abruptly by spacing the impact body away from the point of initial energy transfer to the workpiece to permit substantial acceleration of the impact body before it affects the workpiece or the impact body may be accelerated more gradually by placing the impact body closer to said point or imparting energy to the workpiece before the impact body is substantially accelerated.

2. A combination as set forth in claim 1 in which said yielding means is a confined body of fluid.

3. In a high velocity impact apparatus, the combination of:

a support structure forming a guideway;

means to support a workpiece in the region of one end of the guideway;

a free piston movable along said guideway;

an impact body movable in said guideway and adapted to operate on a workpiece on said support means, said free piston being movable along the guideway from a starting position spaced from the impact body;

means to apply abrupt high fluid pressure to the free piston at said starting position to drive the free piston along said guideway with rapid acceleration to transfer energy to the impact body by impact action for operation on the workpiece;

and a body of fluid trapped between the free piston and the impact body for elastic compression and to transmit energy from the free piston to the impact body, the effective area of the impact body that receives the pressure of the body of fluid being greater than the effective area of the free piston that acts on the body of fluid for consequent increase in the force applied to the impact body.

4. A combination as set forth in claim 3 which includes reislient yielding means to oppose the advance of the impact body relative to the workpiece.

5. A combination as set forth in claim 4 in which said yielding means is a confined body of gaseous fluid.

6. In a high velocity impact apparatus, the combination of:

a support structure forming a guideway;

means to support a workpiece in the region of one end of the guideway;

a free piston movable along said guideway;

means to apply abrupt high fluid pressure to said free piston at said starting position to drive the free piston along said guideway with rapid acceleration to transfer energy to the impact body by impact action for operation on the workpiece;

and resilient yielding means to oppose the movement of the impact body towards the workpiece.

7. In an impact forming apparatus wherein an op erating cycle starts with a free piston at a limit position and is triggered by shifting the free piston slightly for access thereto of high pressure gaseous actuating fluid, the combination therewith of:

a triggering piston adjacent the rear side of the free piston in abutment therewith; means to apply fluid pressure to the triggering piston to shift the free piston to its triggering position;

means to apply progressively increasing fluid pressure to the free piston to restore it to its limit position after a work stroke;

and means to release the triggering fluid in response to rise of the progressively increasing pressure to a predetermined pressure.

8. In a high velocity impact apparatus wherein an operating cycle starts with a free piston supported at an upper limit position by a body of low pressure gaseous fluid below the piston and the operating cycle is initiated by lowering the free piston slightly to a triggering position where high pressure gaseous fluid drives the piston downward for a work stroke, the combination therewith of a control system comprising:

a first fluid passage means for introducing fluid above the free piston to lower the free piston to its triggering position;

a second fluid passage means in communication with the space below the free piston;

means to introduce fluid into said second fluid passage means to lift the free piston to its upper limit position after a work stroke;

means responsive to rise in pressure in said second passage means to open said first passage means to release the triggering fluid;

means responsive to drop in pressure in the first passage means to open the second passage means for release of the piston-lifting fluid;

and means to close the second passage means in response to drop in pressure therein thereby to hold suflicient gaseous pressure under the free piston to support the free piston at said upper limit position.

9. In a high velocity impact apparatus, the combination of:

a support structure adapted to support a workpiece;

a free piston movable along a predetermined path from a retracted starting position to anadvanced position, the mass of the support structure being several times the mass of the free piston;

means to apply abrupt high fluid pressure between the free piston and the support structure to drive the free piston along said path with high acceleration;

an impact body to receive the impact force of the free piston at said advanced position, said impact body being adapted to transmit the impact force to the workpiece,

the mass of the impact body being substantially greater than the mass of the free piston;

and a body of fluid trapped between the free piston and the impact body, the effective area of the impact body that is exposed to the body of fluid being greater than the effective area of the free piston that is exposed to the body of fluid to compensate at least in part for the greater mass of the impact body thereby to increase the'transfer of energy from the free piston to the impact body.

10. A combination as set forth in claim 9 in which the mass of the impact body is on the order of magnitude of A m AI in which m is the mass of the free piston, A is the effective area of the free piston that is exposed to the body of fluid, and A is the effective area of the impact body that is exposed to the body of fluid.

11. A combination as set forth in claim 10 which includes a second body of gaseous fluid positioned to be compressed by the Working stroke of the impact body.

12. In an apparatus of the character described wherein a first free body is accelerated to generate high kinetic energy and is free at peak velocity for transmission by impact action to a second body, the improvement comprising:

a body of liquid being confined between the first body and the second body for resilient compression by the impact force.

13. In an apparatus of the character described wherein a first body is accelerated to generate high kinetic energy for transmission by impact action to a second body of greater mass than the first body, the improvement comprising:

- a body of fluid being confined between the first body and the second body for compression by the impact force, the effective area of the second body that is exposed to the body of fluid being larger than the 13 effective area of the first body that is exposed to the body of fluid thereby to compensate at least in part for the greater mass of the second body to increase the transfer of energy from the first body to the second body.

14. The improvement as set forth in claim 13 in which the eifective area of the second body that is exposed to the body of fluid is at least approximately equal to in which m is the mass of the first body, m is the mass of the second body, and A is the effective area of the first body that is exposed to the body of fluid.

15. In an apparatus of the character described, wherein a movable structure including die means acts on a workpiece on a support structure and a ram means accelerated by fluid pressure acting between the ram means and the support structure is accelerated to transmit energy to the movable structure by impact action, the improvement comprising:

said ram means being of substantially smaller mass than the mass of the movable structure to minimize the displacement of the support structure in reaction to the acceleration of the ram means;

and a body of fluid being confined between the ram means and the movable structure to receive the impact force of the ram means for transmission to the movable structure,

14 the effective area of the movable structure that is exposed to the body of fluid being greater than the effective area of the ram means that is exposed to the body of fluid whereby the impact force is amplified for increase in the energy transmitted to the movable structure.

16. The improvement set forth in claim 15 in which the effective area of the movable structure that is exposed to the body of fluid is at least approximately equal to in which m is the mass of the ram means, m is the mass of the movable structure, and A is the effective area of the ram means that is exposed to the body of fluid.

References Cited by the Examiner UNITED STATES PATENTS 1,346,166 7/20 Bernhard 78-42.3 1,440,807 1/23 Wineman 7842.31 1,885,235 11/32 Davis 91-424 2,101,159 12/37 Stevens 722-4231 2,862,475 12/58 Kinsman 9139 FOREIGN PATENTS 741,556 1/45 Germany.

WILLIAM J. STEPHENSON, Primary Examiner.

Claims

1. IN A HIGH VELOCITU IMPACT APPARATUS, THE COMBINATION OF: A SUPPORT STRUCTURE; A PLATEN CARRIED BY THE SUPPORT STRUCTURE TO SUPPORT A WORKPIECE; AN IMPACT BODY POSITIONED TO COOPERATE WITH THE PLATEN FOR FORMING THE WORKPIECE; A FREE PISTON FOR IMPACT ACTION AGAINST THE IMPACT BODY, THE MASS OF THE SUPPORT STRUCTURE BEING SEVERAL TIMES THE MASS OF THE FREE PISTON WITH FREEDOM FOR THE FREE PISTON TO TRAVEL A SUBSTANTIAL DISTACNE BEFORE TRANSMITTING ENERGY TO THE IMPACT BODY; MEANS TO APPLY ABRUPT HIGH FLUID PRESSURE BETWEEN THE FREE PISTON AND THE SUPPORTING STRUCTURE TO DRIVE THE FREE PISTON OVER SAID DISTANCE WITH CONSEQUENT RAPID ACCELERATION OF THE FREE PISTON TO HIGH VELOCITY AND CORRESPONDING DEVELOPMENT OF HIGH KINETIC ENERGY IN THE FREE PISTON WITH RELATIVELY LITTLE REACTION DISPLACEMENT OF THE SUPPORT STRUCTURE; AND RESILIENT YIELDING MEANS BETWEEN THE FREE PISTON AND THE IMPACT BODY TO PROLONG THE ACCELERATION OF THE IMPACT BODY BY THE FREE PISTON AND TO ACT IN COMPRESSION TO MOMENTARILY STORE A PORTION OF THE KINETIC ENERGY FROM THE FREE PISTIN, THE POSITION OF SAID IMPACT BODY RELATIVE TO THE WORKPIECE BEING VARIABLE WHEREBY THE IMPACT BODY MAY BE ACCELERATED ABRUPTLY BY SPACING THE IMPACT BODY AWAY FROM THE POINT OF INITIAL ENERGY TRANSFER TO THE WORKPIECE TO PERMIT SUBSTANTIAL ACCELERATION OF THE IMPACT BODY BEFORE IT EFFECTS THE WORKPIECE OR THE IMPACT BODY MAY BE ACCELERATED MORE GRADUALLY BY PLACING THE IMPACT BODY CLOSER TO SAID POINT OR IMPARTING ENERGY TO THE WORKPIECE BEFORE THE IMPACT BODY IS SUBSTANTIALLY ACCELERATED.