US3447795A

US3447795A - Self-contained die cushion with air saver

Info

Publication number: US3447795A
Application number: US653166A
Authority: US
Inventors: Robert V Vickers
Original assignee: EW Bliss Co Inc
Current assignee: EW Bliss Co Inc
Priority date: 1967-07-13
Filing date: 1967-07-13
Publication date: 1969-06-03
Anticipated expiration: 1986-06-03
Also published as: FR1572845A; GB1210454A; DE1752608A1

Description

June 3; 1969 R. v. VICKERS 3,

SELF-CONTAINED DIE CUSHION WITH AIR SAVER Filed July 15, 1967 Sheet of 5 5O 6O 58 6O 6O 52 v v v WV m I. c a x /VCI Vc Vb ama; ,38 42- z i 0 A 44 I /9O:/92||: 7O? 96' J N 36 |o2- X f a FIG. I

/J 56 I l l b 34 W FIG. 9

INVENTOR. ROBERT V. VICKERS BY Me MM, 8 M,

ATTORNEYS June 3, 1969 R. v. VICKERS SELF-CONTAINED DIE CUSHION WITH AIR SAVER Sheet Filed July 13, 1967 INVENTOR. ROBERT V. VICKERS ATTORNEYS June 3, 1969 R. v. VICKERS 3,447,795!

SELF-CONTAINED DIE CUSHION WITH AIR SAVER Filed July 13, 1967 Sheet 3 H AM k & 200 L E F|G.7

All INVENTOR. ROBERT V. VICKERS BY M mm, 3 M,

ATTORNEYS FIG.8

United States Patent 3,447,795 SELF-CONTAINED DIE CUSHION WITH AIR SAVER Robert V. Vickers, Warrensville Heights, Ohio, assignor to E. W. Bliss Company, Canton, Ohio, a corporation of Delaware Filed July 13, 1967, Ser. No. 653,166 Int. Cl. F161 1/22, 3/06 US. Cl. 267-1 Claims ABSTRACT OF THE DISCLOSURE A self-contained die cushion for use on a power press wherein the normal cushion chamber includes a separate reservoir sealed from the rest of the chamber and having a movable wall, such as a piston, to allow the fluid in the reservoir to assist in biasing the die cushion upwardly, but preventing exhaust of the reservoir fluid when the chamber is exhausted to drop the cushion for changing or repairing dies in the press.

The present invention relates to the art of self-contained die cushions, and more particularly to a self-contained die cushion having an air saver or reservoir incorporated therewith.

This invention is particularly applicable for use in a power press wherein depending rods are used to support a hold-down ring of a drawing die, and it will be described with particular reference thereto; however, it is appreciated that the invention has much broader applications and may be used in various other environments wherein a die cushion is required.

Many dies used within power presses incorporate holddown rings or other auxiliary elements which are controlled, to a certain extent, by a die cushion located below the bed of the power press. These die cushions take a variety of forms; however, the most common die cushion includes two telescoped sleeves with end walls defining an internal cushion chamber filled with a compressible fluid which biases the upper sleeve in an upwardly direction. A plurality of rods extending downwardly from the die within the press rests upon the upper sleeve. These rods coact with movable elements within the die so that the sleeve is forced downwardly -by the rods during the down ward stroke of the press. The downward movement of the upper sleeve compresses the fluid within the cushion chamber so that the rods are forced in an upward direction by the upper sleeve during the upward stroke of the power press. The volume of air, or other compressible fluid, within the chamber of the die cushion is quite large to provide the necessary biasing action for the downwardly extending rods. This presents a substantial difliculty.

When a die is to be repaired or replaced, the die cushion must be dropped into an inoperative position. One common way of accomplishing this is to exhaust most of the fluid from the chamber of the die cushion. This requires a substantial amount of time to exhaust and then replace the large volume of fluid within the die cushion. In an eifort to reduce the time for exhausting and filling the chamber of the die cushion, relatively large supply hoses have been used. These are expensive, and they do not substantially reduce the total time required to drop the die cushion into its inoperative position and then raise the die cushion into its operative position. To overcome the disadvantages of this particular arrangement, it has been suggested that a fluid reservoir should be mounted adjacent the die cushion with a valve between the reservoir and the cushion. When the die cushion is to be dropped, the valve is opened to store fluid within the reservoir. The valve was then closed so that the fluid would remain in the reservoir. To raise the die cushion, the valve was again opened which allowed flow of fluid back to the die cushion. This again involved complex and expensive mechanical arrangements to accomplish the operation of the die cushion.

The structure explained above has been modified to provide the reservoir and valve within the die cushion itself. When this is done, the piping between the reservoir and the die cushion chamber is eliminated; however, certain inherent disadvantages are built in. The valve between the reservoir and die cushion must be operated, mechanically, from a position outside of the die cushion. Thus, a rod or other valve operating means must be provided internally of the die cushion. Also, when the valve becomes defective, the die cushion must be taken apart and repaired. By providing internal valving within the die cushion, it is diflicult to provide hydraulic snubbers or hydraulic hold-downs which are generally used in the operation of a die cushion. A hydraulic snubber is used to control the upward movement of the die cushion so that it is somewhat out of phase with the upward stroke of the power press. The hydaulic hold-down is utilized to lock the die cushion in a downward position when the die cushion is not to be used.

The disadvantages of the prior die cushions are completely overcome by the present invention which is a completely new concept to the art of die cushions and includes a simplified structure which will allow movement of the die cushion between its upward operative position and its lower inoperative position.

In accordance with the present invention, there is provided an improvement in a self-contained die cushion, comprising a movable, operative member and fluid means for, biasing the member in a given direction for movement between points a and b. The improvement comprises providing the fluid means with means defining a cushion chamber filled with a compressible fluid and having a volume V when the member is at point a and a volume V when the member is at point 11, V being greater than V Also provided is a means defining a sealed fluid filled reservoir within the chamber with at least one movable exterior wall, this reservoir having variable volume V which forms part of the volume of the chamber and is, at all times, substantially less than volume V Also provided are means for exhausting fluid from the chamber while the reservoir remains filled with fluid. In this manner, the die cushion may be dropped by exhausting only a portion of the cushion chamber. During normal operation of the die cushion, the filled reservoir within the chamber coacts through the movable external Wall to provide a continuous, relatively large volume of air against which the die cushion operates.

The primary object of the present invention is the provision of a self-contained die cushion which is inexpensive to produce, usable in existing presses without modification and easily and rapidly dropped into the inoperative position and raised into the operative position with a minimum of fluid.

Another object of the present invention is the provision of a self-contained die cushion which requires a lesser amount of air, or fluid, to shift from the inoperative position to the operative position.

Yet another object of the present invention is the provision of a self-contained die cushion which incorporates two separate, isolated fluid compartments in the cushion chamber, both of which coact to provide the biasing action of the cushion and one of which is exhausted to drop the cushion into its inoperative position.

These and other objects and advantages will become apparent from the following description used to illustrate preferred embodiments of the invention as read in con- 3 nection with the accompanying drawings in which:

FIGURE 1 is a partial, cross-sectional view illustrating, somewhat schematically, the preferred embodiment of the present invention;

FIGURE 2 is a partial, cross-sectional view illustrating a modification of the preferred embodiment of the present invention as shown in FIGURE 1;

FIGURES 35 are partial, cross-sectional views illustrating certain modifications of the invention shown in FIGURES 1 and 2;

FIGURE 6 is a cross-sectional view illustrating still a further modification of the present invention;

FIGURE 7 is a partial, cross-sectional view illustrating the operational characteristics of the embodiment of the invention illustrated in FIGURE 6;

FIGURE 8 is an enlarged, cross-sectional view illustrating still a further modification of the present invention; and

FIGURE 9 is a partial cross-sectional view showing the operating characteristics of the embodiment of the invention illustrated in FIGURE 8.

Referring now to the drawings, wherein the showings are for the purpose of illustrating preferred embodiments of the invention only and not for the purpose of limiting the same, FIGURE 1 shows a self-contained die cushion A which is mounted on a support plate B attached to the under frame of a press (not shown) by a plurality of

rods

10, 12. The general operation of the die cushion is well known in the power press art; therefore, further discussion of the press itself, except with regard to the general operation of the die cushion, is not required.

Self-contained die cushion A includes a fixed sleeve having a lower flange 22 secured onto a lower end wall 24 by a plurality of circumferentially spaced bolts 26. In

like manner, bolts 28 secure the wall 24 onto the support plate B. An appropriate seal, such as O-ring seal 30, is provided between flange 22 and wall 24. Sleeve 20 also includes an outer bearing surface 32 which terminates at a recess 34 to form an abutment 36. Adjacent the upper portion of sleeve 20 there is provided appropriate seal 38, for a purpose which will be apparent from the further description of this embodiment. Also at the upper end of sleeve 20 is a relatively large opening defined by a flange 42 having a lower abutment 44.

Reciprocally and telescopically received on sleeve 20 is a movable sleeve which forms the operative member of the die cushion, in a manner to be described later. Sleeve 50 has an upper end wall 52, an inner mounting surface 54 slidably received on surface 32, and a lower stop 56 adapted to coact with abutment 36 to prevent withdrawal of sleeve 50 from sleeve 20. End wall 52 is provided with an upwardly facing, top surface 58 which is adapted to contact the lower end of operating rods 60. These rods are connected to various elements within the die mounted upon the bolster of a power press, in a manner well known in power press art.

Sleeves

20, 50 combine to form an internal cushion chamber 70 which is filled with pressurized fluid from an input line 72. Line 72 includes a branch 74 communicated with the lower portion of chamber 70 and a branch 76 communicated with the upper portion of chamber 70. This last-mentioned communication is through a passage 80, line 82, check valve 84, and control valve 86. The valve 86 is positioned as indicated in FIGURE 1. The upper portion of chamber 70 is communicated with pressurized fluid from input line 72. Check valve 84 prevents fluid flow from the upper portion of chamber 70 to the supply line. In a like manner, a check valve can be provided in branch 74. To exhaust the upper portion of chamber 70, valve 86 could be manually actuated to connect line 82 with exhaust line 88. As so far described, the self-contained die cushion does not differ substantially from normal die cushions, except for flange 44 and certain aspects of the fluid inlet system.

In operation, rods 60 are connected onto certain elements within the die, such as knock-out pins or a drawing ring. As the power press moves downwardly to close the die, rods 60 push sleeve 50 downwardly from an upper point a to a lower point b. This is done against the fluid bias of cushion chamber 70. As the power press moves upwardly, the fluid pressure within chamber forces sleeve 50 back to its initial upper point a. The rods 60 are raised and perform the necessary function within the die, in accordance with the particular element being controlled by the rods. This procedure is repeated in each cycle of the power press. The volume of fluid within chamber 70 is approximately V when the sleeve 50 is at point a. In like manner, the volume of chamber 70 is V when the sleeve 50 is at point b. Consequently, the difference in volume during the normal operation of die cushion A is V minus V In accordance with the present invention, sleeve 20 is provided with a vertically movable wall 90, in the form of a piston having a top 92, a skirt 94, and a peripheral seal 96. Spring 98 biases the piston 90 in an upward direction. The movable wall 90 divides chamber 70 into an upper portion 100 and a lower portion 102. The lower portion has a variable volume V which is dependent upon the position of the wall 90 with respect to sleeve 20. The volume V is always substantially less than volume V and, in accordance with the embodiment of the invention illustrated in FIGURE 1, volume V is also substantially less than volume V Piston or wall 90 forms two isolated, separate portions in chamber 70. This has an extremely beneficial result which will be described later In operation, during normal function of the die cushion A, sleeve 50 moves between points a and b. This causes the fluid within

chamber portion

100, 102 to be alternately compressed and expanded. During this operation, piston or wall 90 oscillates within sleeve 20, and it does not substantially affect the operation of the die cushion. There is no inter-fluid flow between

portions

100, 102 of the embodiment shown in FIGURE 1. The interrelationship between these portions can be described as being mutual fluid pressure relationshi or inter-force transmitting relationship. In other words, the air or other fluid within

portions

100, 102 functions in a manner generally simulating a situation Where no wall or piston 90 is used.

The advantage of URE 1 is best illustrated by describing how the die cushion is dropped into its inoperative position. When a die within the power press is to be repaired or replaced, the die cushion must be dropped. This is accomplished by exhausting portion 100 through valve 86. As the pressure within portion 100 is reduced, the pressure within portion 102 drives wall or piston 90 upwardly against abutment 44. In this manner, all of the fluid within portion 102 is retained within the die cushion, and it need not be replaced when the die cushion is again activated. To activate the die cushion, valve 86 is moved to the position illustrated in FIGURE 1, and fluid pressure from input line 72 is forced through passage into portion 100. This immediately pumps up the die cushion into its operative position.

It can be appreciated that only the volume of air necessary to fill chambers 100 is required to activate the die cushion, although the die cushion operates against the complete volume of fluid within both

portions

100, 102. Since only a small volume of air is needed to activate the die cushion, the time required to activate and deactivate the die cushion is substantially reduced. Wall provides a positive seal between the fluid in portion and portion 102 when the die cushion is in its inactive position. There is no possibility of an inrush of air to portion 100 which would cause the die cushion to inadvertently move to its outward position while the die is being changed or repaired. The embodiment of the invention illustrated in FIGURE 1 does not require complicated valving within the invention as illustrated in FIG- the die cushion itself or other complicated mechanisms to provide an internal reservoir of fluid which is not periodically exhausted and replaced when the die cushion is to be dropped and again actuated. The relatively small volume of air needed to activate the die cushion coacts with the air remaining Within portion 102 to provide normal operation of the die cushion.

Referring now to FIGURE 2, a modification of the preferred embodiment illustrated in FIGURE 1 is shown wherein sleeve is secured onto a mounting plate having a relatively large opening 112. A somewhat standard hydraulic locking device is secured to the lower end of plate 110. The control rod 122 for the hydraulic locking device extends from end wall 52 of sleeve 50, through an opening 124 in piston 90 having a bearing seal 126, and through opening of the device 120. The usual operating piston 134 is provided within the hydraulic locking device 120 and hydraulic fluid 136 is provided within the lower portion of sleeve 20 and is communicated by line 138 to the interior of the locking device 120. By utilizing the piston 90, the self-contained die cushion may be provided with this standard hydraulic locking device without substantial modification of the die cushion. This is a substantial advantage because certain installations require the hydraulic locking device to hold the die cushion in an inoperative position during portions of a cycle or during various operations of the press itself.

Referring now to FIGURE 3, a modification of the piston 90 is illustrated. Piston 90a is provided with an outer peripheral seal 140 and spaced vane seals 142, 144 for passage of rod 122. A spring 146 surrounds the rod 122 and biases the piston 90a in an upward direction.

Referring now to FIGURE 4, a hydraulic snubber 150 is provided below the end wall 24 of sleeve 20. The control rod 122 having a lower piston 134 is connected to the end wall 52, as shown in FIGURE 2.. The hydraulic snubber 150 includes a control valving assembl 152 so that the movement of sleeve 50 in an upward direction after being first moved downwardly is controlled. This prevents abrupt upward movement of rods 60 during the operation of the die cushion shown in FIGURES 1 and 2. This embodiment of the invention illustrates the ease by which a standard hydraulic snubber may be incorporated within a die cushion constructed in accordance with the present invention.

Referring now to FIGURE 5, a further modification of a preferred embodiment of the invention is illustrated. In accordance with this embodiment, fixed sleeve includes an inwardly extending flange 162 having a peripheral, lower seal 164. Reciprocal piston includes a downwardly extending rod 172 which is received within a bore 174 having a spring 176 held in place by a plate 178. The piston 170 is provided with a plurality of peripheral grooves 180 which allow communication between the upper fluid portion 182 and the lower fluid portion 184 within sleeve 160. The peripheral grooves 180 are sealed when piston 170 is in its uppermost position against seal 164. Consequently, when a die cushion including this structure is to be dropped, fluid portion 182 and the iriterior of the upper sleeve 50, not shown, is exhausted. This causes a rapid increase in the pressure differential across piston 170. This differential forces the piston in an upward direction to seal against seal 164. The pressure within fluid portion 184 maintains the piston in its sealed condition until fluid pressure is again introduced into the portion 182. This embodiment of the invention functions somewhat differently from the previously mentioned embodiments in that actual fluid communication is provided between the upper and lower fluid portions defined by the movable piston 170.

Attention is now directed to FIGURES 6 and 7. These figures illustrate a further embodiment of the present invention wherein a fixed sleeve has an upper opening 192 which is covered by a flexible diaphragm 194. Above the diaphragm there is secured, onto the sleeve 190, a

rigid perforated plate 196. The diaphragm divides the fixed sleeve into two separate, sealed, isolated

fluid portions

200, 202. In FIGURE 6, portion 202 is substantially zero. The diaphragm 194 flexes downwardly as sleeve 50 is forced downwardly by rods 60 and flexes upwardly as the rods 60 are allowed to move upwardly.

When portion 202 in the interior of sleeve 50 is exhausted, fluid within portion 200 is retained as diaphragm 194 moves upwardly into contact with plate 196, as shown in FIGURE 6. A similar device is illustrated in FIG- URES 8 and 9. In this embodiment, a fixed sleeve 210 is provided with a support spider 212 onto which .is mounted a rod guide 214. Rod 122, for a hydraulic snubber, or locking device, is received within the guide by bearing

seals

216, 218. Since the central guide is used, an annular opening 220 is provided at the upper portion of the fixed sleeve, and this opening is sealed by an annular diaphragm 222. Above the diaphragm there is secured an annular perforated plate 224 which limits the upward extent or deflection of diaphragm 222. The diaphragm divides the interior of the fixed sleeve into separate, isolated, sealed

portions

230, 232 with portion 232 being substantially zero when the diaphragm is in its upwardmost position, as shown in FIGURE 8.

The present invention has been described in connection with certain structural embodiments; however, many modifications of these embodiments can be made.

Having thus defined my invention, I claim:

1. In a self-contained die cushion comprising a first sleeve, a second sleeve telescopically and reciprocally received on said first sleeve, said sleeves having end walls and combining to define a cushion chamber for a compressible fluid between said end walls, said second sleeve being biased upwardly by the fluid in said cushion chamber during operation of said die cushion and being dropped to an inoperative position when said die cushion is to be inoperative, the improvement comprising: means for dividing said chamber into separate, isolated first and second fluid chamber portion-s, means for limiting the expanded volume of said first portion to an extent incapable of preventing said second sleeve from dropping to an inoperative position upon exhausting of said second portion, and means for exhausting said second portion to drop said second sleeve to the inoperative position.

2. The improvement as defined in claim 1 wherein dividing means is a rigid wall reciprocally mounted within said first sleeve.

3. The improvement as defined in claim 2 wherein said limiting means is an abutment afiixed to said first sleeve and above said movable wall.

4. The improvement as defined in claim 2 wherein said movable wall includes a skirt portion reciprocally supported in said first sleeve.

5. In a self-contained die cushion comprising a first sleeve, a second sleeve telescopically and reciprocally received on said first sleeve, said sleeves having generally closed ends and combining to define a cushion chamber for a compressible fluid between said ends, the improvement comprising: a vertically movable wall means in sa d first sleeve for dividing said cushion chamber into a first portion above said movable wall means and a second portion below said wall means, said portions being substantially sealed from each other, means for limiting the up wardmost vertical position of said wall means, and means for exhausting said first portion whereby said second sleeve is dropped to an inoperative position.

6. In a self-contained die cushion comprising a generally fixed sleeve with a lower closed end and an upper opened end, a cup-shaped element having an upper closed end and a lower open end, said element being telescopically and reciprocally received on said fixed sleeve whereby said sleeve and element define a cushion chamber to be filled with a compressible fluid, the improvement comprising: a vertically movable partition dividing said chamber into an upper portion and a lower portion, means limiting the vertical movement of said partition, and means for exhausting said upper portion of said chamber to drop said element into an inoperative position whereby fluid is retained in said lower portion.

7. The improvement as defined in claim 6 wherein said partition is a rigid piston reciprocally mounted in said fixed sleeve and said limiting means is an abutment on said sleeve to prevent excessive expansion of said lower portion of said chamber.

8. The improvement means for filling said upper compressible fluid.

9. In a self-contained die cushion comprising a container having an internal fluid reservoir and an opening, a cover reciprocally mounted on said container and having an internal fluid chamber communicated with said opening, said chamber and reservoir combining to form a cushion compartment which contains fluid to bias said cover upwardly, the improvement comprising: means for sealing a portion of said reservoir from said chamber, said sealing means being vertically movable upon changes in pressures within said chamber and reservoir; and means for exhausting fluid from said chamber.

10. In a self-contained die cushion comprising a movable operative member and a fluid means for biasing said member in a given direction, the improvement comprising: said fluid means including means defining first and second separate, fluid chambers; said chambers being contractible and expandable upon increases and decreases of externally applied forces; said chambers being in interforce transmitting relationship; said first chamber having a limited expanded volume; and means for exhausting said second chamber.

11. The improvement as defined in claim 10 wherein chamber defining means includes a cylinder and a pressure, movable piston in said cylinder.

12. In a self-contained die cushion comprising a movable, operative member and a fluid means for biasing said member in a given direction, the improvement comprising: said fluid means including first and second fluid chambers; a pressure movable, impervious element isolating said chambers from interfluid flow and connecting said chambers in mutual fluid pressure relationship whereby both of said chambers contribute to the biasing action of said fluid means; and means for exhausting fluid from said first chamber to change the operative position of said member by changing the total volume of said cham bers.

as defined in claim 6 including portion with pressurized 13. In a self-contained die cushion comprising at movable, operative member and fluid means for biasing said member in a given direction for movement between points a and b, the improvement comprising: said fluid means including means defining a cushion chamber filled with a compressible fluid and having HI volume V when said member is at point a and V- when said member is at point b, V being greater than V means defining a sealed fluid filled reservoir in said chamber with at least one movable exterior wall, said reservoir having a variable volume V which forms part of the volume of said chamber and is, at all times, substantially less than V,; and means for exhausting fluid from said chamber while said reservoir remains filled with fluid.

14. The improvement as defined in claim 13 wherein V is, at all times, greater than V 15. In a self-contained die cushion comprising a movable member and a generally fixed member, said movable member being reciprocally mounted on said fixed member and said members being hollow to define a cushion chamber, and means for filling said chamber with a compressible fluid to bias said movable member away from said fixed member, the improvement comprising: a movable piston in said hollow fixed member dividing the interior of said fixed member into first and second portions, the position of said piston being determined by the relative fluid pressures within said portions; an abutment in said fixed member to stop movement of said piston at a given point in a direction increasing said second portion; means on said piston for sealing said portions, at least, when said piston is at said given point; and means for exhausting fluid from said first portion and the interior of said movable member when said die cushion is to be dropped whereby said piston is forced to said point by fluid pressure in said second portion.

References Cited UNITED STATES PATENTS 3,013,791 12/1961 Gold 2671 3,379,430 4/1968 Hennells 267-1 ARTHUR L. LA POINT, Primary Examiner.

US. Cl. X.R. 267-64