GB2066412A - Punch Press Assembly Including a Preloaded Encapsulated Spring and Method of Manufacture - Google Patents

Abstract

A preloaded spring assembly 10 is disclosed having a compression coil spring received interior of a housing. The housing is made of opposed cup- shaped housing members, one having a smaller diameter and having its open end projecting into the open end of the second housing member. The respective open ends are configured to provide a lock abutment preventing separation of the housing members beyond a certain dimension whereby the spring positioned interior of the housing members having its opposite ends in contact with the bottoms of the respective cup-shaped housing members is provided with a compressive pre-load. Also, disclosed is a method of manufacturing the pre- loaded spring assembly which configures the open ends to provide a mechanical interlock during assembly such that the spring is pre-loaded at the time of assembly. <IMAGE>

Description

SPECIFICATION Punch Press Assembly Including a Preloaded Encapsulated Spring and Method of Manufacture This invention relates to encapsulated spring assemblies and more particularly to a punch press assembly having a pre-loaded encapsulated spring element.

Springs are used extensively in punching set ups for applying a force to a punch guide, or for separating the work piece from the die.

Additionally, such springs are well-known in other machine environments where they may be used to bias two relatively movable members towards or away from one another. In certain instances it has been known to encase the spring in a protective housing either for safety purposes or to prevent the spring from being adversely affected by dirt and the like. Moreover, it is known in certain devices to provide a pre-load on a spring.

For example, where springs are used between a housing a part partially received in the housing and partially projectable from the housing, it is known to pre-load the spring at the time the part is assembled into the housing such that a desired initial bias is provided to the part.

Additionally, in the punching art, it has been known to provide punch assemblies wherein the punch is provided with a punch return spring or with a punch guide spring wherein the spring may be pre-loaded by the provision, for example, of an adjustable head on the punch.

Although each of the above designated features has been found individually in the art, the art has not thus far provided an inexpensive, multi-use, encapsulated pre-loaded spring assembly. In certain environments it is desired that the spring be received within a housing, for example, to confine spring pieces in the event of spring breakage. Further, it is frequently desired that the spring be provided with a predetermined pre-load so as to eliminate spring travel before attaining a usable spring pressure.

Additonally, it would be advantageous if encapsulated spring assemblies could be economically manufactured having a predetermined stack height at maximum permitted spring extension while also obtaining a preload at that point. It would also be advantageous to be able to provide an encapsulated spring assembly where the housing compresses along with the spring without opening any passageways to the interior of the spring housing.

It would further be advantageous to fixably mount such an encapsulated spring housing directly onto a stripper guide member in a punch press assembly to ensure proper alignment of the spring housing on the stripper lift surface.

It would further be an advance in the art to provide an inexpensive method of manufacturing pre-loaded encapsulated spring assemblies where the assemblies are manufacturable as multi-use stock devices.

It would additionally be of benefit to provide an inexpensive method of manufacturing encapsulated spring assemblies locked in place onto the stripper guide in a punch press assembly.

The present invention discloses an encapsulated pre-loaded spring assembly having each of the above desired features. In a first preferred form of the invention the housing encapsulating the spring consists of opposed cupshaped housing halves having open ends and bottom ends. One housing half has a smaller outer diameter than the other housing half whereby the housing halves are telescopable together at their open ends. A compression spring is received interior of the housing halves and the open ends of the housing halves are thereafter matingly deformed to provide a separation lock preventing the housing halves from being pulled apart beyond a certain predetermined dimension.

The dimension can be either with respect to a desired total maximum height of the assembly or with respect to a desired minimum pre-load.

According to the preferred method of manufacture disclosed herein, the housing halves are deformed to lock them together at the time of assembly of the housing with the spring positioned interior of the housing.

In a first preferred embodiment of the invention, telescoping inner and outer housing halves are provided with the inner housing half having an outer diameter with a first portion dimension which increases through an outwardly frusto-conical section adjacent its open end. The first dimension is less than the inner diameter of the second outer telescoping housing half. The second and outer telescoping housing half has a first portion inner diameter over a major axial length thereof, larger than the largest outer diameter of the telescoped portion of the inner housing half. The inner diameter of the outer housing half, at the time of assembly, is reduced through a frusto-conical section adjacent its open end after the housing halves have been overlapped.In this manner, the two housing halves will abut at their frusto-conical sections preventing separation of the two housing halves.

The open end of the inner housing half axially beyond the frusto-conical section will preferably have an outer diameter equal to the inner diameter of the first portion of the outer housing half and the inner diameter of the outer housing half at the open end axially of the frusto-conical section will preferably have a dimension equal to the outer diameter of the first portion of the inner housing half. In this manner, the housing halves will be substantially sealed such that no flow path will be open between the inner and outer housing halves even when they are relatively telescoped towards one another.

In the construction of the preferred embodiment, the inner housing is provided with the frusto-conical enlargement adjacent the open end prior to assembly. Thereafter, by use of a constricting die, the outer housing half is circumferentially constricted at the time of assembly while the entrapped internal spring is pre-loaded.

In a second preferred embodiment in the invention, rather than using frusto-conical sections, the inner and outer housing halves have their open ends respectively folded over outwardly and folded over inwardly into abutting relationship.

In a still further preferred form of the invention for use in a punch press assembly, one housing half of the inventive encapsulated spring assembly is formed at its bottom wall with an outwardly extending dovetail projection for interlocking with a corresponding dovetail recess located in the top wall lift surface of a stripper guide. A punch rod is threadably positioned adjacent the bottom wall of the other housing half and extends through the spring assembly, the dovetail interlock, and stripper for reciprocating movement during punching.

In assembly of the interlocking arrangement, the one spring housing is formed with an annular projecting wall of a diameter to be concentrically received in the female dovetail recess formed on the stripper. A wafer of a noncompressible, resilient material is then placed interiorly of the spring housing projecting wall and compressed to expand radially outward. The radial movement of the wafer serves to distend the projecting wall into a substantially mating, interlocked relationship with the dovetail recess sidewalls.

Thereafter, pressure on the wafer is released such that the resilient material resumes its original shape and the wafer is removed. A spring is positioned in the open end of the one spring housing and the other spring housing half is fitted thereon to entrap and pre-load the spring.

It is therefore an object of this invention to provide an improved pre-loaded spring assembly.

It is another, and more particular, object of this invention to provide an improved pre-loaded spring assembly having a compression coil spring received interiorly of telescoping cup-shaped housing halves having deformed open ends providing an interference relationship preventing separation of the housing halves, and providing a circumferential seal between the housing halves.

It is still a further object of this invention to provide an improved punch press assembly having an encapsulated spring housing fixably centered on a stripper guide for supporting a punch rod extending through the spring housing and stripper.

Although the teachings of my invention have herein been discussed with reference to specific theories and embodiments, it is to be understood that these are by way of illustration only and that others may wish to utilize my invention in different designs or applications.

Figure 1 is a fragmentary sectional vie';" of a punch and die assembly equipped witn the spring assembly of this invention.

Figure 2 is a fragmentary cross sectional view of a spring assembly of this invention used as a lifter.

Figure 3 is a fragmentary cross sectional view of a first forming die assembly shown forming an inner housing half of the spring assembly of this invention.

Figure 4 is a fragmentary sectional view of an assembly operation assembling the spring assembly of this invention and final forming tile outer housing half.

Figure 5 is a view similar to Figure 4 illustrating a further step in the assembly process. Figure 6 is a cross sectional view of a modified form of the spring assembly of this invention.

Figure 7 is a fragmentary sectional view of a punch assembly with the encapsulated spring assembly fixably mounted onto a stripper guide.

Figure 8 is a fragmentary cross sectional view of opposed interlocking male and female surfaces on one spring housing half and the stripper in a first stage of assembly.

Figure 9 is a fragmentary cross sectional view of the spring housing half and stripper concentrically fitted together with a wafer of resilient material positioned centrally thereof to be compressed in a further stage of assembly.

Figure 10 is a fragmentary cross sectional view of the resilient wafer being compressed radially outward to distend the spring housing male surface into mating, interlocking relation with the stripper female surface in a later stage of assembly.

Figure 11 is a fragmentary cross sectional view after compression of the resilient wafer has been removed and the spring housing and stripper mating surfaces are interlocked.

Figure 1 illustrates the pre-loaded spring assembly 10 of this invention used in connection with a punch. The punch 1 1 has a body 12 with an enlarged head end 13 and a working tip 14 on the body end opposite the head end. The punch 1 1 is received through a stripper 1 3A. The stripper 1 3A is in turn mounted in a punch assembly holder 1 4A which may, for example, be a punch turret of a turret punch press. A lifter spring 15 lifts the stripper 1 3A and punch 1 1. The spring assembly 10 is, in the illustrated embodiment, used as a stripper spring assembly and includes a compression coil spring 18 received within a housing 19. The housing consists of outer 20 and inner 21 cup-shaped housing halves each including a peripheral wall 23 and a bottom wall 24. In the embodiment illustrated, the bottom wall 24 may have apertures therethrough through which the punch body 12 projects. A washer member 25 received in the bottom of the outer housing half 20 has a central aperture 26 which engages the enlarged head 13 of the punch. A ram 27 is provided ko activate the punch to force it through a workpiece 30 and into a mating die 31 received in a die holder 32 which may, for example, be the die turret of a turret punch press.

Each of the housing halves 20 and 21 has an open end with the open end 32 of the inner housing projecting into the open end 33 of the outer housing half. The housing halves undergo a circumferential change adjacent the open end with the inner housing half 21 being circumferentially enlarged through a frustoconical section 35 extending outwardly from the main diameter portion 36 and then terminating in an axial section 37 which continues from the frusto-conical section 35 to the open end 32.

Conversely, the outer housing half has a diameter decreasing frusto-conical section 40 which extends inwardly and terminates in an axial extension 41 which in turn terminates in the open end 33.

Preferably, the diameters of the two housing halves are chosen such that their peripheral wall at the open ends engage respectively the inner diameter of the main or full diameter section of the outer housing and the outer diameter of the main or full diameter section of the inner housing.

In this manner, no leakage paths are open between the two housing halves and the housing halves are capable of telescoping movement to further compress the spring. However, due to the interference created by the frusto-conical section, the amount by which the housing halves can be separated from one another is limited. To the extent that the axial stack height of the telescoped inner and outer housing halves is limited by engagement of the frusto-conical sections to a total dimension less than the free dimension of the spring 18, the spring will be in a pre-loaded state.

Figure 2 illustrates the spring assembly 10 of this invention when used in connection with a stripper plate construction including a stripper plate 50, a die base 51 and a cutting die edge 52.

The spring asembly 10 is received in a space between the die base 51 and the stripper plate 50 and is used to urge the stripper plate outwardly to strip material cut or punched by the assembly. In such a construction it is desired to have a pre-load on the spring 18 while maintaining a fixed maximum stack height of the assembly. In this construction, a threaded washer 54 at the bottom of the outer housing half 20 can receive a taper headed bolt 55 for attachment to the stripper plate 50 whereas a threaded bolt 60 bottomed against a washer 61 received in the bottom of the housing half 21 can be used to attach the assembly to the base 51. By removal of the bolt 55, access with an allen wrench or the like can be had to the head of bolt 60 interior of the housing.

Once the bolts are in place, the housing is substantially leak proof, at least for viscous fluids, due to the engagement of the inner diameter of the outer housing half with the outer diameter of the inner housing half. It can be seen that by providing an axial constant diameter section beyond the frusto-conical sections extending to the open ends, that a relatively long seal face is maintained adjacent both open ends during compression of the spring assembly.

This feature allows the spring assembly to function as a lubricant storer if desired whereby, for example, in connection with the punch of Figure 1, lubricant can be stored within the interior to aid in lubricating the punch 12.

Additonally, in connection with Figure 2, lubricant can be relied upon to aid in helping to dissipate heat created by flexure of the spring 18.

Figure 3 illustrates one method of manufacture of the inner housing half. A male die member 70 having a desired outer configuration 71 with a frusto-conical section 72 cooperates with a female die 73 having a desired inner configuration 74 to form the circumferential expansion section 75 of the inner housing half 76.

Once the inner housing half has been formed, a die apparatus such as shown in Figures 4 and 5, can be used for forming the outer housing half which has previously been formed to a cupshaped configuration. The housing halves may be initially manufactured of tubular material such as tubular steel. Once the components such as the spring 18 and top 54 and bottom 61 washers as well as, in the embodiment of Figure 2, the bottom bolt 60 are inserted into the housing halves, the housing halves are telescoped onto one another. Thereafter a ram die 80 can be used to compress the spring 18 forcing the outer housing half against the deforming die 82 to deform the open end of the outer housing half substantially as shown in Figure 5. The pressure applied in the direction of the arrow 90 may be in one or more testing steps to achieve a desired set spring pre-load.However, where deformation of the outer housing is accomplished in a single step, it is preferred that the minimum deformation pressure of the housing wall should exceed the maximum obtainable pre-load at that point of spring compression. This insures against accidental separation of the housing halves.

Alternatively, the movement of the member 80 can be dimensionally controlled to provide a desired stack height. By use of dies or constricting members such as shown in Figures 4 and 5, the two housing halves may be moved towards one another as far as is necessary to achieve the desired spring preload and/or stacking height since the amount of telescoped overlap of the housing halves is not predetermined. The frustoconical engaging sections can be formed at any point along the length of the peripheral wall of the outer housing member since the circumferential constriction which forms the frusto-conical engaging section is axially continuous so long as the housing half 20 is being moved into the constricting die 82. The only effect of further movement is to increase the axial section 41.

Figure 6 illustrates a modified form of the invention where the spring assembly 95 has the open ends 96 and 97 respectively of the housing halves 20A and 21 A folded back.

In the embodiment of Figure 6 the inner housing member 21 A has its open end 96 folded through a reversed end outwardly to provide a ledge face 98 circumferentially around the exterior of the housing half 21 A and facing away from the open end 96. The open end 97 of the outer housing half ZOA is folded back upon itself inwardly to provide a ledge face 99 circumferentially around the inner diameter of the housing half 20A facing away from the open end 97. In this manner, the ledge faces 98 and 99 will abut one another preventing separation of the housing halves. The reverse bends of the open ends 96 and 97 can be formed by standard die techniques. Again the outer housing may have a reverse bend formed at the time of assembly in substantially the same manner as shown in Figure 4 but with a reverse bend forming die in place of the die 82.

It can therefore be seen from the above that my invention provides a pre-loaded spring assembly wherein a compression coil spring is received interior of two telescoping housing halves which are locked together by mechanical interference fit adjacent their open ends caused by circumferential deformation of the open ends providing opposed engagable circumferential faces, the housing halves being telescopable into one another and the opposed engagable faces limiting the separation of the housing halves.

In connection with a punch press assembly such as shown in Figure 1 , the present invention further provides for an interlocked assembly 100, as illustrated in Figure 7, of a encapsulated spring housing 101 and stripper guide 102. This relation enhances proper alignment of the spring housing on the stripper lift surface. The spring housing is formed with outer 105 and inner 106 cup-shaped halves having respective outer 107 and inner 108 frusto-conical free ends telescoping together in the manner described above and respective bottom walls 109 and 110. Inside the spring housing, a coil spring 111 is in a pre-loaded state.

The lower end of the spring 111 rests against bottom wall 110; while the upper end of the spring abuts against a spacer ring 112 which is pressed against a fitting ring 113. The fitting ring is positioned in a central aperture 114 of the outer housing half bottom wall 109 and supports a mounting head 11 5 for support of the punch rod 104.

The punch rod body 103 has a threaded upper end for engagement in a central threaded channel 11 6 formed in the head 11 5. This thread connection permits selective vertically adjustable positioning of the rod in the assembly 100, such positioning being controlled by a detent element 117.

The punch rod body extends coaxially downwardly through the spring housing and through a central opening 118 in the bottom wall 110. The opening 118 is annularly bounded by a male dovetail shaped projecting wall 11 9 which interlocks in mating fashion with a dovetail recess 120 formed on the top wall lift surface 121 of the stripper body 122. The recess is defined by an annular upwardly convergent sidewall 123 and a planar bottom surface shelf 124 through which extends a central passage 125. The passage 125 passes axially through the stripper body to slidably contain the puncher rod body. A lifer spring 126 extends concentrically about the stripper in upper engagement with an overhanging lip portion 127. The assembly 100 operates in a fashion as described above in connection with Figure 1 as those skilled in the art will readily appreciate.

Figures 8-11 illustrate a method of manufacturing the interlocked assembly 100.

With reference to Figure 8, the inner housing half 106 is initially empty and open-ended. The projecting wall 11 9 formed on the housing half begins as a vertically extending annular wall having a diameter less than that of the smallest diameter along the stripper recess sidewall 123.

Accordingly, the projecting wall 11 9 can be concentrically received in the stripper's lift surface dovetail recess 120, as illustrated in Figure 9, such that the bottom wall surface 110 of the inner spring housing rests or abuts upon the top wall surface 121 of the stripper.

In order to form the dovetail interlock a waverlike piece 130 of a noncompressible but resilient material such as urethane is placed across the shelf 124 so as to be centered concentrically of the wall surfaces 119 and 123. The original wafer diameter may be substantially less than that of the male projecting wall 119 but must be larger than the passage 125 diameter. A compression element, such as a ram 131 , flattens the wafer to create a radially outward movement of the resilient material as shown in Figure 10. The radial pressure of the wafer material serves to distend the projecting wall 119 into a substantially contiguous or mating relation with the sidewall 123, thereby making a dovetail interlock.

When the interlock is complete, as illustrated in Figure 11, the ram pressure is released. The wafer reverts back to its original shape for easy removal from the recess 120. Thereafer, the spring 111 is positioned in the inner housing half 106 and the outer housing half 105 is fitted thereon to form the encapsulated spring housing in the manner heretofore described.

Although various minor modifications may be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

Claims (9)

Claims

1. A pre-loaded spring assembly comprising first and second housing members, each housing member including a substantially tubular peripheral wall with a bottom wall portion at a first axial end of the peripheral wall and an open end at a second axial end of the peripheral wall, the first housing member having a maximumouter diameter less than a maximum inner diameter of the second housing member, the open end of the first housing member inserted into the open end of the second housing member, the first and second housing members being telescopically axially movable, an outer diameter increasing section of the first housing member intermediate the axial ends thereof, an inner diameter decreasing section of the second housing member intermediate the axial ends thereof, the sections abuttable with one another and the abutment preventing removal of the first housing member from the second housing member, a spring received interior of said housing members, the spring having a free spring height greater than a maximum axial internal length of the housing members when the surfaces are abutted whereby the spring is pre-loaded.

2. A device according to claim 1 wherein the peripheral wall of the first housing member is radially enlarged adjacent the open end through a frusto-conical section, the frusto-conical section terminating in an axial substantially constant diameter section, the constant diameter section terminating at the open end, the peripheral wall of the second housing member having the diameter reduction portion adjacent the open end, the diameter reduction portion including a frustoconical section terminating in an axial section of substantially constant diameter, the axial section terminating in the open end, the diameter of the axial section of the first housing member being substantially equal to the inner diameter of a portion of the peripheral wall of the second housing section axially beyond the frusto-conical section in a direction away from the open end, the inner diameter of the axial section of the second housing half being substantially equal to the outer diameter of the peripheral wall of the first housing half axially beyond the frusto-conical section in a direction away from the open end of the first housing section, whereby the axial sections of each of the housing halves engaged the surface of the peripheral wall of the other housing half providing a circumferential seal.

3. The device of claim 1 wherein the open ends of the housing halves are defined by portions of the peripheral wall bent back upon themselves, the first housing half being bent back radially outwardly and the second housing half being bent back radially inwardly, the bent back portion of the first housing half having an outer diameter substantially equal to the inner diameter or portions of the second housing half axially beyond the bent back portion of the second housing half away from the open end, the bent back portion of the outer housing half having an inner diameter substantially equal to the outer diameter of the first housing half axially beyond the bent back portion of the first housing half whereby axial ends of the bent back portions oppose one another preventing separation of the housing halves and surfaces of the bent back portions contact surfaces of the peripheral wall of the opposing housing half providing a circumferential seal.

4. The device of claim 1 wherein the bottom wall portion of the second housing member is secured to a stripper guide member with interlock means.

5. The device of claim 4 wherein the interlock means comprises a dovetail shaped peripheral wall projecting downward from the second housing member bottom wall portion and fitted in a substantially corresponding dovetail-shaped recess formed in an upper surface of the stripper guide member.

6. The device of claim 5 further comprising a punch rod for a punch rod assembly extending through the stripper guide member and the first and second housing members of the spring assembly and supported for reciprocable movement, said punch rod having an upper end secured to the bottom wall portion of the first housing member.

7. A method of manufacturing an interlocked encapsulated pre-loaded spring assembly and stripper guide for use in a punch press assembly which comprises the steps of forming first and second substantially cup-shaped housing halves each having a circumferential peripheral wall, a bottom wall portion, and an open end such that the open end of the first housing half is insertable into the open end of the second housing half, circumferentially deforming the first housing half adjacent its open end to provide a localized increased diameter section, forming a peripheral connector wall projecting substantially axially outward from the bottom wall of the first housing half, forming a central peripheral recess shaped with a sidewall of axially inwardly diverging diameter in an upper surface of a stripper guide, positioning the connector wall within the central recess so as to be substantially concentric with the central recess sidewall, distending the connector wall radially outward into substantially contiguous mating relation with the central recess sidewall to interlock the first housing half bottom wall with the stripper guide, inserting a spring into the first housing half such that one end of the spring is operatively bottomed against the bottom wall of the first housing half and the opposite end of the spring projects from the first housing half.

open end, assembling the second housing half over the first housing half and spring with the first housing half positioned substantially concentric of a deforming die, urging the second housing half towards the deforming die to compress the spring and deform the peripheral wall of second housing half at its open end to form a localized reduced diameter section, and reducing the diameter of the reduced diameter section to a diameter less than a maximum diameter of the increased diameter section of the first housing half whereby the first and second housing halves are locked together.

8. A pre-loaded spring assembly substantially as herein described with reference to the accompanying drawings.

9. A method of manufacturing a spring assembly and stripper guide subtantially as herein described with reference to the accompanying drawings.