U.S. patent application number 12/549026 was filed with the patent office on 2010-09-02 for stripper unit for a punch retainer.
Invention is credited to David J. Moellering.
Application Number | 20100218656 12/549026 |
Document ID | / |
Family ID | 37727779 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100218656 |
Kind Code |
A1 |
Moellering; David J. |
September 2, 2010 |
STRIPPER UNIT FOR A PUNCH RETAINER
Abstract
A stripper unit incorporates a precision threaded plug that
preloads a mechanical die spring that, in turn, preloads the
movable or traveling stripper adjacent the punch tip. The precision
threaded plug simultaneously accurately locates the stripper unit
on a commercially available ball-lock punch retainer. The stripper
unit is entirely self-contained on the face of the ball-lock punch
retainer, thus minimizing the space required on the press
platen.
Inventors: |
Moellering; David J.;
(Orchard Lake, MI) |
Correspondence
Address: |
GIFFORD, KRASS, SPRINKLE,ANDERSON & CITKOWSKI, P.C
PO BOX 7021
TROY
MI
48007-7021
US
|
Family ID: |
37727779 |
Appl. No.: |
12/549026 |
Filed: |
August 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11485863 |
Jul 13, 2006 |
7581475 |
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12549026 |
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60706310 |
Aug 8, 2005 |
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Current U.S.
Class: |
83/143 |
Current CPC
Class: |
B21D 45/006 20130101;
Y10T 83/9476 20150401; Y10T 83/2166 20150401; Y10T 83/9428
20150401; Y10T 83/9437 20150401 |
Class at
Publication: |
83/143 |
International
Class: |
B21D 45/06 20060101
B21D045/06 |
Claims
1-4. (canceled)
5. A self-contained stripper unit for attachment to a punch
retainer having a punch retention hole with a punch received
therein, the punch extending from the punch retainer and having a
predetermined outside diameter where it extends from the punch
retainer, the stripper unit having an installed position wherein it
is received on the punch, the stripper unit comprising: a hollow
body having a hole in a flat bottom thereof and an upper bore in
the top of the hollow body; a stripper disposed at least partially
within the hollow body and movable in the upper bore; a die spring
engaging the stripper within the hollow body, the die spring
located within the hollow body; and a precision plug received into
the hole in the flat bottom of the hollow body so as to engage the
die spring, the precision plug having a central passage defined
therethrough, the passage having sides, the passage being sized
such that the sides contact the predetermined outside diameter of
the punch, whereby when the stripper unit is received on the punch,
the sides of the passage locate and align the stripper unit on the
punch; the precision plug, the stripper, the die spring and the
hollow body being attachable to the punch retainer as a single
unit.
6. The stripper unit of claim 5, wherein the upper bore and the
stripper have a D-shape to prevent rotation of the stripper
relative to the hollow body.
7. The stripper unit of claim 5, wherein the hole in the bottom of
the hollow body has a counterbored ledge, the precision plug being
seated on the counterbored ledge.
8. The stripper unit of claim 7, wherein the precision plug
preloads the die spring.
9. The stripper unit of claim 5, wherein the hole in the bottom of
the hollow body is a threaded hole, the precision plug being
threaded so as to engage the threaded hole.
10. The stripper unit of claim 5, wherein the stripper has a hole
shaped to match a shape of the punch.
11. The stripper unit of claim 5, wherein the precision plug and
the flat bottom of the hollow body cooperate to define a flush
surface that fits flush against the punch retainer when attached
thereto.
12. The stripper unit of claim 5, wherein the passage is a
multi-sided hole in the plug.
Description
REFERENCE TO RELATED APPLICATION
[0001] This patent application is a continuation of U.S. patent
application Ser. No. 11/485,863, filed Jul. 13, 2006, which claims
priority from U.S. provisional patent application Ser. No.
60/706,310, filed Aug. 8, 2005, both of which are incorporated
herein in their entirety.
BACKGROUND OF THE INVENTION
[0002] The field of the invention pertains to punches and dies for
forming holes and depressions in metals. In particular, the
invention pertains to devices and accessories for preventing work
pieces from adhering to punches during high-speed, high production
manufacturing.
[0003] Examples of modern punch retainers are shown in applicant's
previous U.S. Pat. Nos. 5,337,835, 5,410,932 and Des. 351,395.
Views of these punch retainers are also shown in FIGS. 1 and 2.
Modern punches for certain applications utilize either metal or
polyurethane strippers to prevent work piece drag on the punch. The
metal stripper units typically extend over the sides of the punch
retainers or otherwise interfere with the close placement of punch
retainers. Polyurethane strippers require separate metal retainers
to accurately position the strippers on the punch retainers. With a
view to eliminating some of the disadvantages attendant to previous
stripper units, the following more compact stripper unit has been
developed.
SUMMARY OF THE INVENTION
[0004] The new stripper unit incorporates a precision threaded plug
that preloads a mechanical die spring and simultaneously locates
the stripper unit on a commercially available ball-lock punch
retainer. The ball-lock punch retainers are commonly used in the
tool, die and metal stamping industry, and the new stripper unit is
an improvement on various punch stripping units commercially
available today. Use of the preloaded mechanical die spring
provides for time-tested long life.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a top plan view of a punch retainer;
[0006] FIG. 2 is a bottom plan view of a punch retainer;
[0007] FIG. 3 is a top plan view of the new stripper unit;
[0008] FIG. 4 is a side exploded view of the new stripper unit;
[0009] FIG. 5 is a side cross-section of the new stripper unit;
[0010] FIG. 6 is a bottom plan view of the new stripper unit;
and
[0011] FIG. 7 is a side view of the new stripper unit on a punch
retainer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0012] Illustrated in FIGS. 1 and 2 are the top and bottom views of
a typical commercially available ball-lock punch retainer 10. The
punch retainer 10 includes bolt holes 12 for attaching the punch
retainer to a press platen (not shown), threaded holes 14 with
dowel locating holes at bottom, and punch retention hole 16.
[0013] In FIG. 3, the top plan view of the new stripper unit 18
illustrates the very robust stripper body 20 and the movable
stripper 22. The movable stripper 22 is formed with a hole 24
shaped to match the shape of the punch (not shown).
[0014] In FIG. 4, the components of the stripper unit 18 are shown
in order of assembly. The stripper 22 is first inserted into the
stripper body 20 followed by the mechanical die spring 26 and the
precision threaded plug 28. The precision threaded plug 28 screws
into a precision threaded hole 30 in the bottom 32 of the stripper
body 20 and seats on an accurately machined counterbore ledge
34.
[0015] The upper bore 36 in the stripper body 20 includes a flat
38, such that the upper bore 36 has a "D" shape. The stripper 22 is
also "D" shaped to match the D-shape of the upper bore 36 and
thereby provide assembly only in its correct position. FIG. 5
illustrates in cross-section the completely assembled stripper unit
18. As shown, the precision threaded plug 28 is tightly seated on
the counterbored ledge 34. It is appreciated that FIGS. 4 and 5
teach bottom 32 is generally flat and that threaded plug 28 screws
into the precision threaded hole 30 leaving a flush surface across
the bottom 32.
[0016] In FIG. 6, the bottom view of the stripper unit 18 shows the
precision threaded plug 28 formed with a hexagonal hole 42
therethrough. The flats 44 of the hexagonal hole 42 are sized to
accurately contact the punch (not shown) and thereby accurately
align the stripper unit 18 over the punch retention hole 16.
Optionally, the hexagonal hole 42 may be made slightly smaller,
whereby each flat 44 is formed with a slight concavity matching the
curvature of the punch retention hole 16. A hex wrench can be used
to tighten the precision threaded plug 28 in place.
[0017] Thus, the stripper unit 18 can be perfectly aligned on the
punch retainer 10, as shown in FIG. 7 with a punch (not shown)
through the hexagonal hole 42, before a machine screw (not shown)
is inserted through hole 46 in the stripper unit 18 and threaded
into hole 14 of the punch retainer 10 to fasten the stripper unit
to the retainer.
[0018] The construction above provides a number of improved
features. The precision threaded plug 28 locates the stripper unit
18 while simultaneously pre-loading the die spring 26 for improved
die spring life. Because the plug 28 has a precision machined
hexagonal hole 42, the stripper unit 18 is accurately positioned
and retained on its mating retainer 10. The hexagonal hole 42
provides an alien wrench hex over the precision hole to provide for
easy assembly and disassembly. The new design provides that all die
spring 26 and stripping forces are completely isolated in the very
robust stripper body 20 with no force being transferred to any
outside component. Fully assembled, the stripper unit 18 is
completely "self-contained," eliminating the risk of components
being lost, or, even upon catastrophic failure, any of the units'
components being jettisoned into the stamping die. In addition, it
is appreciated that FIGS. 5 and 7 teach the stripper unit 18 can be
attached to the punch retainer 10 as a single unit and the bottom
32 can fit flush against the punch retainer 10.
[0019] The precision threaded plug 28 is designed to bottom out in
its mating pocket in the stripper body 20, which automatically sets
the die spring 26 pre-load and is fail safe, so the spring cannot
be overloaded.
[0020] Unlike some stripper units currently available, the new
stripper unit 18 universally fits all standard ball-lock punch
retainers, and most importantly requires no retainer
alterations.
[0021] The movable or traveling stripper 22 is preferably of a
hardened tool steel construction with a lubricating coating to
promote smooth stripping movement. The stripper 22 is guided not
only by the "D" body shape, but also by the stripper's head
diameter or hole size and shape 24. This provides a much improved
condition that will ensure the stripper 22 cannot twist or cock and
jam during production and will better facilitate side load to the
stripper when stripping non-flat surfaces.
[0022] The round portion of the stripper 22 and all the round
features of the stripper unit 18 are co-located along the
centerline of the punch and pierced hole, which simplifies design
and manufacture of the stripper unit. The unique "D" shape 40 of
the stripper 22 provides a failsafe assembly, allowing the stripper
22 to be assembled in the stripper body 20 only in the correct
position.
[0023] The pre-loading of the die spring 26 and stripper 22
provides instant stripping force upon contact with the work piece.
The instant stripping force on contact facilitates simplification
of the calculations and timing questions, which are issues,
especially with respect to cam activated die applications. The
pre-loading also makes the overall stripper unit 18 more compact.
The stripper body 20 is a one-piece construction designed with a
robust heel for the attachment hole 46, making the stripper unit 18
more stable and stronger than other stripper units.
* * * * *