US3031993A - Metal-forming press - Google Patents

Description

y 1962 G. GERARD ETAL 3,031,993

METAL-FORMING PRESS Filed May 1, 1958 3 Sheets-Sheet 1 INVENTORS. GEORGE GERARD 8 JACOB BRAYMAN M, m 19m eir ATTORNEYS.

y 1962 G. GERARD ETAL 3,031,993

METAL-FORMING PRESS Filed May 1, 1958 FIG. 2. GEORGE GE QXR ID JACOB BRAYMAN y 1962 G. GERARD ETAL 3,031,993

METAL-FORMING PRESS Filed May 1, 1958 3 Sheets-Sheet 3 CONTROL UNIT A? INVENTORS. GEORGE GERARD 8| F IG 5 BY JACOB BRAYMAN flwl di fi their ATTORNEYS.

United States Patent 3,031,993 METAL-FORMING PRESS George Gerard, Yonkers, and Jacob Brayman, Staten Island, N.Y., assignors to Engineering-Supervision Company, N ew York, N .Y., a corporation of New York Filed May 1, 1958, Ser. No. 732,311 13 Claims. (Cl. 113-44) This invention relates to rubber pad deep draw metal presses and, more particularly, to a new and improved rubber pad press adapted to utilize the space available between the press platens to maximum advantage.

In metal-forming presses having two spaced platens which are adapted to move toward each other and exert a high compressive force on objects positioned between them, the platens usually have a limited maximum'separation, thus restricting the available space or daylight wherein the metal-forming equipment can be mounted. In order to adapt such presses for rubber pad operation, a male die is mounted on one platen and a rubber pad on the other so that a metal blank positioned between the die and the pad is forced against the die and formed by it when the two platens are moved together.

In order to prevent wrinkles, rough surfaces, and variations in the thickness of metal pieces formed in this manner, it is necessary to support the portion of the metal blank surrounding the die against the rubber pad in a controlled manner while the rubber pad is pressed against the die. A variety of back-up structures mountable in metal-forming presses have been devised to provide the necessary support, but all of the presently known devices are complex in design and occupy a substantial portion of the available space between the platens. For example, many conventional rubber pad units support the metal die on a crosspiece spaced from the lower pres platen and include a hydraulic cylinder arrangement between the crosspiece and the platen, adapted to exert a force against the portions of the metal blank surrounding the die. In this case, the crosspiece must be thick enough to Withstand the high pressures of the press while the space beneath must be large enough to permit motion of a piston within the cylinder arrangement from one extreme position to the other. I

Accordingly, it is an object of this invention to provide a new and improved rubber pad press arranged to occupy a minimum fraction of the distance between the platens.

Another object of the invention isto provide a press of the above character having a new and improved structure for applying back-up pressure to support the material around the die. I

A further object of the invention is to provide a new and improved system for controlling the back-up pressure in a rubber pad press.

These and other objects of the invention are accomplished by forming a die mount housing with 'a die support block extending directly from one platen to the die support position. Surrounding the support block,"a continuous channel in the housing receives a piston member of complementary shape operable by hydraulic pressure supplied to the bottom of the channel to support the portions of a material being formed around the die. In one embodiment of the invention, the piston member is keyed by shoes to the inner and outer surfaces of the channel and the material being formed is supported at thetop of the piston by rollable load transfer members, In addition, a second continuous piston member surrounding the first may be mounted in a second channel to support the outer portions of a material being formed by a die of larger base area which extends over. the first piston member.

Further objects and advantages of the invention will be:

apparent from a reading of the following description in conjunction 'with an examination of the accompanying drawings in which:

FIG. 1 is a side view showing a vertical section through V a typical deep draw rubber pad press arranged according to the invention with the press platens in the open position;

FIG. 2 is a side view showing the rubber pad press of FIG. 1 in the closed position;

' FIG. 3 is a view of the press in horizontal section, taken pad press according to the invention comprises an upper assembly 10 and a lower assembly 11 mounted on an upper platen 12 and a lower platen 13, respectively, of a conventional press machine. The usual drive apparatus (not shown) is arranged to drive the two platens together with a high compressive force, the upper platen 12 being vertically movable and the lower platen 13 being fixed, for example. Supported from the upper platen, as by clamps 14, the upper assembly 10 includes a rubber pad holder 15 containing a typical rubber pad 16 comprised of a series of layers of rubber, Mounted by clamps 17 on the lower platen 13 directly beneath the upper assembly, the lower assembly 11 includes a housing 18 having a recessed upper periphery 19 arranged to receive the pad holder 15 when lowered, as best seen in FIG. 2.

Within the housing 18, a base plate 20 lies on the lower platen 13 and a block 21 extends upwardly therefrom to support a male die 22 in spaced relation to the platen 13, the die being positioned on the block 21 by suitable locating pins and keys (not shown). Surrounding the support block 21, an endless inner channel 23 slideably receives-in fluid-tight relation a complementary-shaped piston member 24 which forms a closed loop about the block 21. Spaced outwardly from the inner channel 23 by a vertical septum 25, an endless outer channel 26 has a complementary piston member 27 slideably supported therein in the same manner, the spaces between each channel and its piston member being sealed by suitable chevron-type I packing rings 28 held in place by clamping members 29.

It will be observed that if the male die has a large base area, as does the die 22 shown in FIGS. 1 and 2, the outer portion of the die extends above the inner channel 23 to the top of the septum 25, and, in this case, the inner piston member 24 is kept inoperative. In order to pro-,

vide direct support for the periphery of large dies of this type, the septum 25 is a rigid member of suflicient thickness to [transmit the force of the press from the base plate 20 to thedie 22 without deformation, and preferably has the same height as the support block 21. It will be apparent that, in presses not intended to utilize small size nels and piston members of other shapes may be more suitable for use with dies having different base configurations. 1

In order'to guide the piston members'during vertical motion within the channels and prevent cocking under eccentric loads, the channel 26 is formed with shoes 30 projectingfrom its inner and outer surfaces which fit into permit vertical motion thereof but inhibit angular motion and the channel 23 has similar shoes 30 on its outer surface. Mounted at the top of the inner piston member- 24, a series of vertical pins 31 extends to a point just below the top of the block 21 and the septum 25 when the, piston is in its lower position, while a similar series of pins 32 is supported on the outer piston member 2 7, A h op. o ac of hese Pius t e en sur ace is suit; ablyfformed to receive 'a load transfer ball 33 and a bacle-up plate 34 having a recess 35' is supported by the plurality of balls, thus transmitting to the piston member; vertical components of force but not horizontal components which might cause angular deflection or cocking thereof. Inasmuch as the large size die 22, shown in FIGS. 1 and 2, extends over the inner channel23 no load transfer balls are illustrated therein on the pins 31, the inner piston 24 being inactive. In order to contain the rubber pad 16; within its holder 15 during compression, the back-up member 34 has an internal contour complementary to that of the base of the die 22 while its out- 7 side diameter fits within theyinside diameter of the pad holder 15.

Leading to the bottom of the outer channel 26 a duct 36 in the housing 18 conducts hydraulic fluid under pressure thereto from a line 46 to a raise the piston 27 to its top position as shown in FIG. 1. Similarly, a duct 37 connected to a pressure line 47 leads to the bottom of the inner channel 23. As illustrated in FIG. 1,, the piston 27-, in its raised position, extends only a short dis tance into, the channel 26 when the back-up plate 34 sup,v ports a sheet metal blank 38 level with the top surface of the die 22, while, in its lowered position as shown in FIG. 2, the upper portion of the formed blank is held adjacent the base of the die 22. Accordingly, in presses constructed according to the invention the height of the block 21 and the septum 25 need be only a little greater than the maximum height of the die 22.

As illustrated in FIG. 4, a rubber pad press arranged according to the invention may be adapted to utilize a small size male die 39 having a base no larger than the,

top of the block 21 by supporting a smaller back-up plate 4 0 with a coupling member. 41 mounted on both the inner and'outer piston members 24. and 2 7. This smaller diameter back-up plate 40' has an internal aperture con: formingto the .contour of the .base of the die 39, the coupling member 41 being supported by load transfer balls 33 on both the series of pins 31 and 32. With both piston members raised, the top surface of the back-up plate 40 is level with the top of the die 39 andsupports the outer portion of a metal blank 42, while in the lowered position the top of the back-up plate is level With the base of the die, which is supported on t e block 21 by a spacing member 43. Inasmuch as the area of the metal blank 42 to be drawn by. the smaller die 39. is considerably less than that of the pad holder 15, an annular reducing ring 44 is mounted within the padholder 15 and a smaller rubber pad 45 is inserted in the holder. In order to maintain ahi'gh pad pressure, the back-up plate 40 is shaped to receive the inside diamter of the reducing ring 44 when lowered, thereby restricting the rubber pad 45 within the confines of the holder- 15.

Inthe process of forming a metal blank with a male die in a rubber pad press, it is essential that the Proper amount of metal from the blank be fed to-the die at each moment during the drawing operation to prevent wrinkling of the finished surface and variations ofmetal thickness. in the formed piece.v One method of obtaining this result is by controlling the speedof the movable platen at each position in its downward motion according to a.

. precise program wherein the speed is a .function of the shape of the die. In addition, the metalsupply may also be regulated by appropriately controlling the pressure oi he ac up a e su p tin the s in P ti n of the metal blank against the rubber pad at each position during the. compression When drawing relatively imple shapes, utilization of either of these methods may be suffi cient to prevent wrinkling and thickness variations. However, for complex die shapes both these controls are necessary to assure feeding of the correct amount of metal to the die at the proper rate at each position during the downward stroke of the upper platen.

Accordingly, apparatus arranged according to the invention includes aspeed and pressure control system of the type illustrated schematically in FIG. 5. As indicated therein, the speed of the upper platen 12 and the upper pr ss mbly 10 during its motion toward the lower assembly 11 is controlled in a predetermined manner at each platen position by a controlunit 48 linked to the power press (not shown) driving the platens together. This unit may be, for example, of the type described in the copending US. application Serial No. 714,639, filed February 11, 1958 now abandoned, which regulates'the speed of the platen 12 in a predetermined manner as a function of its position'according to the contour of a particular die.

In order to control the beck-up pressure, the pressure line 46 to the outer channel 26, which may have a pressure gauge 49 connected thereto leads through a throttle valveStl and a stop valve 51 to a low pressure hydraulic line 52. Bypassing the throttle valve 5%), a unidirectional valve 53 permits hydraulic fluid to flow toward the lower assembly 11; to. raise the outer piston member 27 but blocks fluid flow in the other direction. From the inner channel, the hydraulic line 47, which also has a pres-. sure gauge 49, is linked to the line 46 through a stop valve 54 and fluid may be emptied from the system by opening a drain valve 55 in the line 47, Each of thevalves 51 54 and 55 may, for example, be a solenoid valve actuable by electrical signals received through each oi three conductors 56, 57 and 58, respectively, While the throttle valve is operated byan electric motor 59 in response to the voltage between a pair of conductors 60 and 60:; leading from a pressure vs stroke controller 61.

As shown in 131G. 5, a typical pressure vs. stroke controller 61 mayinclude a rotary cam 62 turned by motion of therplaten 12 through a mechanical linkage 63 1 and formed with a'varying radius which is proportional to. the back-up pressure required at the corresponding position of the platen in its downward stroke as determined by the shape of the die taking into account the fluid velocity generated by the speed of the platen during that portion of its stroke. In response to variation in the radius ofthe cam 62, a spring-biased cam follower 64v drives the movable tap 65 of a potentiometer 66 connected between positive and negative voltage sources, the tap 65 being electrically joined to the motor control condoctor 60. Another potentiometer 67, is also connected between positive and negative voltage sources and has a movable tap 68; linked to the conductor 666;, the tap 68 being driven by a spring-biased plunger 69 responsive to changes in the fluid pressure in a line- 70 connected to the line;46 Thus, the motor 59, which may be any conventional type, adapted to close the throttle 50 when the conductor 60 is negative with respect to the conductor 60a and open the th'rottle when the conductor 64 is posi- 70 is the same as that represented by the cam radius (and this will be indicated by equality of the potentials on the lines 60 and 6.0a), the throttle 58 will remain in the same position. It, because of an increase in fluid velocity, for example, the pressure in the line 70 rises above the deired value, this will be de e ed y the Pl ng d,

" the potentiometer 67 will apply voltage to drive the motor 59. in the proper direc on to open the throttle 50 and reduce thepressure to the desired value.

- In operation, withthe platen 12 raised and the lower assembly in position beneath the upper assembly 10, the drain valve 55 is closed and the stop valve 51 is opened to supply fluid to the line 46 under low pressure through the bypass valve 53. If a large size die 22 is used the valve 54 is kept closed to prevent fluid from reaching the inner channel 28, and the large diameter back-up plate 34 is supported on the pins 32 of the outer piston 27. Fluid entering the outer channel through the line 46 raises the outer piston to its top position, as shown in FIG. 1, and a metal blank 38 is placed over the die and the backup plate. As the upper assembly is brought down over the die, its speed is regulated in accordance with the contour of the die by a predetermined program set into the control unit 48 as described above. At the same time, the outer piston 27 is pressed downwardly into the outer channel 26, forcing the hydraulic fluid therein out through the line 46 and the throttle 50 into the low pressure line 52. Inasmuch as the bypass valve 55 blocks fluid flow in this direction the rate of flow, and therefore the force exerted by the back-up plate 34- pressing the metal blank 38 against the rubber pad 16, is determined by the setting of the throttle 50.

As previously mentioned, the pressure vs. stroke controller 61 regulates the back-up pressure inaccordance with a program determined by the shape of the cam 62 which is based on the shape of the die 22 so that the proper amount of metal is fed to the die at each position. It will be apparent from an examination of FIG. 5 that decreased pressure in the line 70 lowers the plunger 69 so that the tap 65 of the potentiometer 67 becomes more positive. Similarly, depression of the cam follower 64 by an increase in cam radius moves the tap 65 to a more negative portion of the potentiometer 66. In each case, the motor 59 is actuated by the potential difference between the conductors to close the throttle 50, thus raising the pressure in the line 76 until the conductors 6t and 60a are again at the same potential. On the other hand, increased pressure on the plunger 69 or decreased radius of the cam 62 moves the element 64 or 69 in the opposite direction to prodtie a potential diiference in the opposite direction, opening the throttle 50. It will be readily apparent that, for optimum operation of the system, the cam 62 should be advanced with respect to the position of the platen 12 by an amount equal to the reaction time of the system in order to assure the proper back-up pressure in the channel 26 as the platen reaches each position lower assembly may be withdrawn from beneath the upper assembly to extract the formed metal. Actuation of the valve 51 to supply fluid pressure to the outer cylinder 26 will assist in removing the work piece from the die by jogging the outer piston member and the back-up plate. When the piece has been removed the valve 51 may be closed and the lower assembly 10 is replaced beneath the upper assembly 11. If desired, the outer piston member 27 can be lowered when the stop valve 51 is closed by opening the connecting valve 54 and the drain valve 55.

The forming of metal blanks with a small size die 39 is carried out in a similar manner with the coupling plate 41 supporting the back-up plate 40 on both pistons 24 and 27, the reducing ring 44 and the smaller rubber pad 45 being inserted in the pad holder 15. In this case, the connecting valve 54 is opened along with the stop valve 51, permitting hydraulic fluid to pass through both the lines 46 and 47 to raise vboth piston members to" their top positions, as shown in FIG. 4. During the downstroke the connecting valve 54 is held open so that the throttle 50 regulates the pressure in both the channels 23 and 26 in the manner described above.

' Although the invention has been described herein with reference to a specific embodiment, many modifications and variations therein will readily occur to those skilled in the art. Accordingly, the invention is not to be limited to the exact details of construction shown and described. I We claim:

' 1. Metal-forming apparatus for use in a press having two spaced platens arranged to be driven toward each other by a high compressive force, one of the platens having a rubber pad mounted thereon, said metal-forming apparatus comprising a housing adapted to be mounted on the other platen including die support means extending directly between a die position and the other platen, channel means surrounding the die support means and'within the housing, piston means slideably supported in the channel means in fluid-tight relation therewith, back-up means supported on the piston means and movable therewith between a position adjacent the top of a die mounted on the support means and a position adjacent the base of the die, and rollable load transfer means interposed between the piston means and. the back-up means and sup orting the back-up means on the piston means to transmit components of force parallel to the motion of the piston means and prevent transmission of components perpendicular thereto.

2. Metal-forming apparatus for use in a press having two spaced platens arranged tobe driven toward each other by a high compressive force, one of the platens having a rubber pad mountedthereon, said metal-forming apparatus comprising a housing adapted to be mounted on the other platen includingdie support means extending directly between a die position and the other platen, first channel means in the housing surrounding the die support means, piston means slideably supported in the first channel means in fluid-tight relation therewith, second channel means surrounding the first channel means and separated therefrom by a septum extending from the base of the housing to the die support position, piston means slideably supported in the second channel means in fluid-tight relation therewith, and back-up means supported on-the first and second piston means and movable therewith between a position adjacent the top of a die supported on thedie support means and'the septum and a position adjacent the base of the die.

.3. Apparatus according tolclaim 2 wherein each of the channel means and piston means is annular in shape.

4. Metal-forming apparatus for use ina press having two spaced platens arranged to be driven toward each other by a high compressive force, one of the platens having a rubber pad mounted thereon, said metal-forming apparatus comprising a housing adapted to be mounted on the other platen including die support means extending directly between a die position and the other platen and first channel means surrounding the die support means and within the housing, piston means slideably supported in the first channel means in fluid-tight relation therewith, second channel means surrounding the first channel means and separated therefrom by a septum extending from the base of the housing to the die support position, piston means slideably supported in the second channel means in fluid-tight relation therewith, a back-up plate supported on the second piston means and movable therewith between a position adjacent the top of a die supported on the die support means and the septum and a position adjacent the base of the die, and rollable load transfer means interposed between the ,second piston means and the back-up plate and supporting the back-up plate on the second piston means to transmit components of force parallel to the motion of the piston means and prevent transmission of components perpendicular thereto. a

5. Metal-forming apparatus for use in a press having two spaced platens arranged to be driven toward each other by a high compressive force, one of the platens having a rubber pad mounted thereon, said metal-forming apparatus comprising a housing adapted to be mounted on the other platen including die support means extending directly between a die position and the other platen and first channel means surrounding the die support means and within the housing, piston means slideably supported in the. first channel means in fluid-tight relation therewith, second channel means surrounding the first channel means and separated therefrom by a septum extending from the base of the housing to the die sup: port position, piston means slideably supported in the second channel means in fluid-tight relation therewith, and a back-up plate supported on the first and second piston means and movable therewith between a position adjacent the top of a die supported on the die support means and a position adjacent the base of the die.

6. MetaLforming apparatus for use in a press having two spaced platens arranged to be driven toward each other with a high compressive force, one of the platens having a rubber pad mounted thereon, said metal-forming apparatus comprising a housing adapted to be mounted on the otherplaten including die support means extends ing directly between a die position and the other platen, channel means surrounding the die support means and within the housing, piston means slideably supported in the channel means in fluid-tight relation therewith, a back-up plate supported on the piston means and movable therewith between a position adjacent the top of a die mounted on the support means and aposition adjacent the base of the die, a fluid conduit leading from the chain nel means, adjustable throttle means in the conduit, throttle control means for varying the setting of the throttle means in a predetermined manner in response to relative motion of the platens, and pressure-sensitive means adapted to regulate the control means in accordance with the fluid pressure in the channel means.

7. Apparatus according to claim 6 wherein the fluid conduit leads from the throttle means to a low pressure fluid source and including a unidirectional valve in parallel with the throttle means permitting fluid to flow from thesource toward the channel means.

8. Metal-forming apparatus for use in a press-having two spaced platens arranged to be driven toward each other by a high compressive force, one of the platens having a rubber pad mounted thereon, said metal-forming apparatus comprising a housing adapted to be mounted on the other platen including die support means extending directly between a die position and the other platen, channel means surround-ing the die support means and within the housing, piston means slideably supported in the channel means in fluid tight relation therewith, a back-up plate supported on the piston means and movable therewith between a position adjacent the top of a die mounted on the support means and a position adjacent the base of the die, a fluid conduit leading from the channel means, adjustable throttle means in the conduit responsive to an electrical control signal, potentiometer means having a movable tap linked to the throttle means and generating a control signal, cam means for driving the movable tap in response to relative motion of the platens having a surface which is a function of the shape ofthe die, and pressure-sensitive electrical means responsive to the fluid pressure in the channel means generating a second control signal in accordance with changes in the fluid pressure in the channel means,

9. Apparatus according to claim 8 wherein the PICS? sure-sensitive means includes a potentiometer adapted to generate a second control signal balancing the first when the 'fluid pressure has a predetermined relation to the cam means.

10. Metal-forming apparatus for use in a press having two spaced platens arranged to-be driven toward each other by a high compressive force, one of the platens having a rubber pad mounted thereon, said metal-forming apparatus comprising a housing adapted to be mounted on the other platen including die support means extending directly between a die position and the other platen and first channel means surrouding the die support means and within the housing, piston means slideably supported in the first channel means in fluid-tight relation therewith, second channel means surrounding the first channel means and separated therefrom by a septum extending from the base of the housing to the die support position, piston means slideably supported in the second channel means in fluid-tight relation therewith, a first fluid conduit leading from the second channel means, a second fluid conduit leading from the first channel means joined to the first fluid conduit through a stop valve, adjustable throttle means connecting the first fluid conduit to a low pressure source, throttle control means for varying the setting of the throttle means in a predetermined manner in response to relative motion of the platens, and pressure-sensitive means adapted to regulate the throttle control means in accordance with the fluid pressure in the first conduit.

11. In apparatus for controlling fluid back-up pressure in a press in a predetermined manner in response to relative motion of the press platens, conduit means leading from the press to a low pressure fluid source, back-up piston means connected to drive fluid through the conduit means at a pressure higher than that of the source in response to relative motion of the press platens toward each other, adjustable throttle means in the conduit means, throttle control means for varying the setting of the throttle in a predetermined manner in response to relative motion of the platens, and pressure-sensitive means adapted to regulate the control means in accordance with the back-up pressure in the press.

12. In apparatus for controlling fluid back-up pressure in a press in a predetermined manner in response to relative motion of the, press platens, conduit means leading from the press to a low pressure fluid source, adjustable throttle means in the conduit means responsive to an electrical control signal, poteniometerg means having a movable tap linked to the throttle means and generating a control signal, cam means for driving the movable tap in response to relative motion of the platens having a surface which is a function of the required back-up pressure, and pressure-sensitive electrical means responsive to the back-up pressure in the press adapted to vary the throttle means in accordance with changes in the back-up pressure.

13. Apparatus according to claim 12 wherein the pressure-sensitive means includes a potentiometer generating a second control signal adapted to balance the control signal from the cam-driven potentiometer means when the fluid pressure has a predetermined relation to the cam means.

References Cited in the file of this patent UNITED STATES PATENTS 495,591 Knight et al Apr. 18, 1893 1,080,482 Roberts Dec. 2, 1913 1,240,791, Czajka Sept. 18, 1917 1,893,951 Kuhner Jan. 10, 1933 2,075,847 Hothersall Apr. 16, 1937 2,192,778 Stacy Mar. 5, 1940 2,375,599 Walton May 8, 1945 2,390,359 Ernst Dec. 4, 1945 2,403,339 Byerlein July 2, 1946 2,605,731 Schulze et a1. Aug. 5, 1952 2,783,728. Hoffman Mar. 5, 1957 2,917,066 Bergson Dec. 15, 1959

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