Note: Descriptions are shown in the official language in which they were submitted.
115106Z
SPECIFICATION
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 sepa-
rating 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 and a part partially
received in a 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, cf an adjustable head on
the punch.
~;
1151062
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.
Additionally, it would be advantageous if encap-
sulated spring assemblies could be economically manu-
factured having a predetermined stack height at maximum
permitted spring extension while also obtaining a pre-
load 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 stocX devices.
It would additionally be of benefit to provide an
inexpensive method of manufacturing encapsulated spring
.
llSlO~;Z
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 de-
sired features. In a first preferred form of the inven-
tion the housing encapsulating the spring consists of
opposed cup-shaped 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 there-
after 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
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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 pre-
ferably 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 por-
tion 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 inven-
tion for use in a punch press assembly, one housing halfof the inventive encapsulated spring assembly is formed
at its bottom wall with an outwardly extending dovetail
il5106Z
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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 relation-
ship 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.
1~51062
-6-
It is still a further object of this invention to
provide an improved punch press assembly having an en-
capsulated 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 view of a
punch and die assembly equipped with 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 the outer housing half.
Figure 5 is a view similar to Figure 4 illustra-
ting 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 andfemale surfaces on one
spring housing half and the stripper in a first stage
of assembly.
115106Z
Figure 9 is a fragmentary cross sectional view
of the spring housing half and stripper concentrically
fitted together with a wafer of resilient material posi-
tioned 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 assem-
bly 10 of this invention used in connection with a punch.
The punch 11 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 11 is received through a stripper 13A.
The stripper 13A is in turn mounted in a punch assembly
holder 14A which may, for example, be a punch turret of
a turret punch press. A lifter spring 15 lifts the
stripper 13A and punch 11. 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
1151062
which engages the enlarged head 13 of the punch. A
ram 27 is provided to 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 circum-
ferentially enlarged through a frusto-conical section 35
extending outwardly from the main diameter portion 36
and then terminating in an axial section 37 which con-
tinues from the frusto-coni~al section 35 to the open
end 32. Conversely, the outer housing half has a diameter
decreasing frusto-conical section 40 which extends in-
wardly 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 leak-
age paths are open between the two housing halves and thehousing halves are capable of telescoping movement to
further compress the spring. However, due to the inter-
ference 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
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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 assembly
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. Additionally, in connection
llS106Z
--10--
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 pre-
viously been formed to a cup-shaped 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 substan-
tially 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
1151~6Z
--11--
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 pre-
load and~or stacking height since the amount of tele-
scoped overlap of the housing halves is not predetermined.
The frusto-conical 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 in-
vention where the spring assembly 9~ has the open ends
96 and 97 respectively of the housing halves 20A and
21A folded back.
In the embodiment of Figure 6 the inner housing
member 21A 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 21A and facing
away from the open end 96. The open end 97 of the outer
housing half 20A 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
115106Z
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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 ~resent invention further pro-
vides for an interlocked assembly 100, as illustratedin 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 sprin~ housing,
a coil sprir,g 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
3~ mounting head 115 for support of the punch rod 104.
The punch rod body 103 has a threaded upper end
for engagement in a central threaded channel 116 formed
in the head 115. This thread connection permits selective
1151062
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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 119
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 lifter 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 119 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 pro-
jecting wall 119 can be concentrically received in the
stripper's lift surface dovetail recess 120, as illustra-
ted 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.
1151062
In order to form the dovetail interlock a ~afer-
like 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
S 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 resil-
ient material as shown in Figure 10. The radial pressureof the wafer material serves to distend the projecting
wall 119 into a substantially contiguous or mating re-
lation 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. Thereafter, 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 themanner heretofore described.
Although various minor modifications may be
suggested by those versed in the art, it should be under-
stood 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.
