Title: Press brake tool and tool holder
Abstract: A press brake tool and tool holder. The tool is provided having a body that terminates downwardly in a work piece engaging surface and that includes a tang extending upwardly from the body for reception in a tool holder. The tang has a first wall defining a vertical surface for engagement with a cooperating vertical surface of a tool holder, and a second wall on the reverse side of the tang that defines an arcuate, concave surface engagable with a clamp of the tool holder. The concave surface includes an upper contact surface tangent to a plane that is downwardly convergent with respect to the vertical surface such that a force delivered to the contact surface includes an upward component tending to lift the tang into the tool holder. The upper contact surface may be formed on a first radius about a horizontal axis and is tangent to a first plane that is downwardly convergent with respect to said vertical surface. The concave surface may include a lower contact surface formed on a second, larger radius about a horizontal axis and that is tangent to a second plane that is upwardly convergent with respect to said vertical surface, the angle between the vertical and said first plane being greater than the angle between the vertical and the second plane so that the clamp delivers a net upwardly force to the tool.
Patent Number: 6,848,291 Issued on 02/01/2005 to Johnson, et al.
| Inventors:
|
Johnson; Paul T. (Stillwater, MN);
Rogers; Bryan L. (Forest Lake, MN)
|
| Assignee:
|
Wilson Tool International, Inc. (White Bear Lake, MN)
|
| Appl. No.:
|
778296 |
| Filed:
|
February 13, 2004 |
| Current U.S. Class: |
72/482.2; 72/481.1; 72/482.1; 72/482.92 |
| Intern'l Class: |
B21D 037/04; B21D037/14 |
| Field of Search: |
72/481.1,481.2,481.3,481.6,481.9,482.1-482.8,482.91,482.92,482.93
|
References Cited [Referenced By]
U.S. Patent Documents
| 2755758 | Jul., 1956 | Johansen | 113/49.
|
| 4993255 | Feb., 1991 | Treillet | 72/462.
|
| 5460027 | Oct., 1995 | Takahashi | 72/481.
|
| 5619885 | Apr., 1997 | Kawano et al. | 72/481.
|
| 5642642 | Jul., 1997 | Kawano | 72/482.
|
| 5782308 | Jul., 1998 | Latten et al. | 72/481.
|
| 6138492 | Oct., 2000 | Vining et al. | 72/481.
|
| 6151951 | Nov., 2000 | Kawano | 72/481.
|
| 6494075 | Dec., 2002 | Pelech, Jr. | 72/481.
|
| 6564611 | May., 2003 | Harrington et al. | 72/481.
|
| Foreign Patent Documents |
| 237800 | Sep., 1987 | EP.
| |
| 2691652 | May., 1992 | FR.
| |
Primary Examiner: Jones; David B.
Attorney, Agent or Firm: Fredrikson & Byron, P.A.
Claims
What is claimed is:
1. A press brake tool having a body terminating downwardly in a
workpiece-engaging surface and a tang extending upwardly from the body and
adapted for reception in a tool holder, the tang having a first wall
defining a vertical surface and a second wall on the opposite side of the
tang defining an arcuate, concave surface, the concave surface including
an upper contact surface tangent to a plane that is downwardly convergent
with respect to said vertical surface.
2. The press brake tool of claim 1 wherein said concave surface includes a
lower contact surface that is beneath said upper contact surface and that
is tangent to a plane that is upwardly convergent with respect to said
vertical surface.
3. The press brake tool of claim 2 wherein said upper contact surface
includes a portion formed on a radius R.sub.1 about a first horizontal
axis, wherein said lower contact surface includes a portion formed on a
radius R.sub.2 about a second horizontal axis parallel to the first
horizontal axis, and wherein R.sub.1 <R.sub.2.
4. The press brake tool of claim 3 wherein said concave surface is formed
on a plurality of radii about a plurality of mutually parallel horizontal
axes, respectively.
5. The press brake tool of claim 2 including a downwardly open tool holder
for receiving and clamping said tool, said holder including a support
plate for receiving and supporting the vertical wall of the tool tang, and
a clamp movable between open and clamping positions, said clamp having a
portion engagable with said concave surface of the tool tang to urge the
vertical wall of the tool tang against the support plate.
6. The press brake tool of claim 5 wherein said tool and tool holder
include cooperating upwardly facing and downwardly facing
force-transmitting surfaces, respectively, and wherein said clamp portion
includes a first clamping surface engageable with the upper contact
surface of the tool tang to impart to the tang a force having an upwardly
directed force component to urge said force transmitting surfaces together
when the clamp in moved into its clamping position.
7. The press brake tool of claim 6 wherein said clamp portion includes a
second clamping surface engagable with the lower contact surface of the
tool tang to impart to the tang a force having a downwardly directed
vector component to force said vertical surface of the tang against the
support plate of the holder when the clamp is moved into its clamping
position, said upwardly directed vector component being greater than said
downwardly directed vector component.
8. The press brake tool of claim 7 wherein said first and second clamping
surfaces are joined by a substantially planar surface.
9. The press brake tool of claim 7 wherein said clamp includes a
horizontally extending rod rotatable about a horizontal axis within a
complementary groove formed in the clamp, said lip having a generally
cylindrical exterior surface and a planar surface segment intersecting
said generally cylindrical surface at said first and second clamping
surfaces, respectively.
10. A press brake tool having a body terminating downwardly in a
workpiece-engaging surface and a tang extending upwardly from the body
portion and adapted for reception in a tool holder, the tang having a
first wall defining a vertical surface and a second wall on the opposite
side of the tang defining an arcuate, concave surface, the concave surface
including an upper portion contact surface tangent to a first plane that
is downwardly convergent with respect to said vertical surface and a lower
portion contact surface tangent to a second plane that is upwardly
convergent with respect to said vertical surface, the angle between the
vertical and said first plane being greater than the angle between the
vertical and the second plane.
11. The press brake tool of claim 10 wherein said upper contact surface is
formed on a radius R.sub.1 about a first horizontal axis, wherein said
lower contact surface is formed on a radius R.sub.2 about a second
horizontal axis parallel to the first horizontal axis, and wherein R.sub.1
<R.sub.2.
12. The press brake tool of claim 10 including a tool holder for said tool,
the tool holder including a vertical surface engagable with the vertical
surface of the tang, and a clamp having a clamping portion engagable with
said upper contact portion of the tang to impart to the tang a force
having an upwardly directed force component to urge said tang upwardly
within the tool holder.
13. The press brake tool and tool holder of claim 12 wherein said clamp
includes a second clamping portion engagable with said lower contact
surface to impart to the tang a downwardly directed force component of
lesser magnitude than the upwardly directed force component.
14. The press brake tool and tool holder of claim 13 wherein said first and
second clamping portions are separated by a planar portion.
15. The press brake tool and tool holder of claim 13 wherein said clamp
includes a portion that is substantially congruent with the arcuate,
concave surface of the tang and that includes said upper and lower
clamping portions.
Description
FIELD OF THE INVENTION
This invention relates to press brake technology, and particularly to tools
and tool holders used in various press brakes.
BACKGROUND OF THE INVENTION
Press brakes are employed to bend metal sheets into desired configurations.
A press brake commonly is equipped with a lower table and an upper table,
one or both of which are moveable to close the tables upon a workpiece
positioned between the tables. Forming tools are mounted to the tables so
that when the tables are brought together, a work piece between the
forming tables is bent into an appropriate shape. The upper table commonly
includes a male forming tool having a lower work piece-deforming portion
of a desired shape, such as a right angled bend, and the lower table
commonly has an appropriately shaped and aligned die, which for example
may be V-shaped and open upwardly to receive the work piece-deforming
portion of the upper tool. A metal sheet positioned between the tool and
die thus is pressed into a desired shape. Forming tools and dies commonly
are horizontally elongated so that work pieces of various widths can be
accommodated.
It is often necessary to exchange forming tools and dies to accommodate
different bending operations. The dies, commonly resting on the lower
table of a press brake, are readily removed and exchanged for others. The
forming tools that are mounted to the upper table of a press brake often
are not so easily replaced, however. Tool holders that are carried by the
upper table commonly make use of a clamp that clamps upon an upwardly
extending tang of a forming tool to hold the tool in the holder.
Tool holders and tools may have respective interlocking safety keys and
key-receiving grooves to restrain accidental dropping of tools once the
clamp of the holder has been loosened. Forming tools can in some instances
be removed downwardly from the holder once the clamp is loosened, and in
other instances the forming tool must be removed by horizontally sliding
it from the holder. If a forming tool of some length (and hence of some
substantial weight) is to be replaced, it sometimes is difficult to slide
the forming tool horizontally from its holder because of the proximity of
neighboring forming tools which may themselves have to be removed in order
to complete the tool exchange process. Because long forming tools can be
quite heavy, when a clamp is loosened to the point that the tool can be
removed by moving it downwardly, care must be taken to prevent the tool
from slipping from the tool holder and falling.
Various press brake tool holders have been devised in an effort to
facilitate the exchange of one forming tool for another. Examples of the
tool holders of this type are shown in U.S. Pat. Nos. 5,513,514, 5,511,407
and 5,572,902. More recent tool holders are described in U.S. Pat. Nos.
6,003,360, 5,245,854, and 6,467,327.
U.S. Pat. No. 5,619,885, the disclosures of which are incorporated herein
by reference, shows a press brake tool and tool holder in which the tang
of the tool is provided with a vertical sliding surface that slides
against a vertical surface of a plate of the holder. The reverse side of
the tang is provided with a slanted planar surface that diverges
downwardly from the vertical surface. The holder and tool also have
engagable, generally horizontal, force-transmitting surfaces for
transmitting vertical forces between the upper table and the tool. The
slanted surface of the tang is designed to come into surface-to-surface
contact with a clamp element of the tool holder when the tool is pushed
upwardly into the holder. Because of this slanted configuration of the
tang, the clamp of the tool holder is forced open when the tool is forced
upwardly between the plate and clamp. As the tool is pushed upwardly, a
lip on the clamp engages a safety-groove formed in the tool. The force
exerted by the clamp upon the tang has a horizontal component to clamp the
tang against the vertical surface of the holder plate, but this force also
has a downwardly directed component. Clamps and tools of this type
generally are known as "Amada style", and are commonly sold under the
trademark "One Touch".
Other Press brake tools and tool holders are shown in U.S. Pat. Nos.
6,138,492 and 6,557,390, both of which are assigned to the assignee of the
present invention. See also U.S. Pat. No. 6,564,611. A summary of certain
types of press brake tools and tool holders is provided in U.S. Pat. No.
6,467,327, the contents of which are incorporated herein by reference
also. U.S. Pat. No. 6,003,360, assigned to the assignee of the present
application, shows a tool holder manufactured by Wilson Tool
International, Inc. and sold under the registered trademark
"Express.RTM.". Note should be made that the tangs of the press brake
tools described in this patent are exemplified as being generally
rectangular in cross-section, as compared to the generally wedge-shaped or
slanted tangs of the Amada-type tools shown in U.S. Pat. No. 5,619,885.
It would be beneficial to provide a press brake tool that on the one hand
would be configured to be forced upwardly by the tool holder clamp as the
clamp is forced against the tang, and which on the other hand would be
appropriate for use in both Amada-style and Wilson-style tool holders.
SUMMARY OF THE INVENTION
A press brake tool is provided having a body that terminates downwardly in
a work piece engaging surface and that includes a tang extending upwardly
from the body for reception in a tool holder. The tang has a first wall
defining a vertical surface for engagement with a cooperating vertical
surface of a tool holder, and the tang has a second wall on the reverse
side of the tang that defines an arcuate, concave surface. The concave
surface includes an upper contact surface that is tangent to a plane that
is downwardly convergent with respect to the vertical surface such that a
force delivered to that contact surface includes an upward component
tending to lift the tang into the tool holder.
In a preferred embodiment, the arcuate surface is formed on a plurality of
radii formed on spaced horizontal axes and including an upper radius and a
lower radius, the upper radius being smaller than the lower radius.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic end-view of a prior art Amada-style press-brake tool
and tool holder;
FIG. 2 is a schematic end-view of a press-brake tool of the invention
together with an Amada-style tool holder;
FIG. 3 is a schematic end-view of another embodiment of a press-brake tool
of the invention as received within a Wilson-style tool holder;
FIG. 4 is an enlarged view of the circled portion of FIG. 2; and
FIG. 5 is a broken away cross-section of a portion of a press-brake tool of
the invention.
DETAILED DESCRIPTION
As background, FIG. 1 shows an Amada-style tool and tool holder, the tool
holder having a vertical mounting plate 2 and a clamp 3. The tang 4 of a
press brake tool 5 has a slanted surface 6 so configured that when the
tool is forced upwardly between the plate and the clamp, the clamp is
cammed open by the slanted surface 6. The holder is generally of the type
shown in U.S. Pat. No. 5,619,885, assigned on its face to Amada Metrecs
Company, Ltd.
Referring now to FIG. 2, a similar press brake tool holder is shown having
a body 12, a downwardly extending plate 14 and a clamp 16. It will be
understood that in certain of these schematic views of well known press
brake tool holders, the structure holding the clamp 16 to the remainder of
the holder has been omitted. It should be understood that the omitted
structure is such that the clamp 16 generally pivots about its connection
to the holder 12 such that the lower portion of the clamp is moved
generally horizontally toward and away from the support plate 14. In the
current commercial embodiment of the tool holder shown in FIG. 2, the tool
holder includes a lever which is movable by the operator to pivot the
clamp toward and away from the plate 14.
In FIG. 3, the holder, which is of the Wilson type, includes a body 12'
that includes a support plate 14' and a clamp 16', the clamp being
pivotally attached to the body 12. A lever 13, movable parallel to the
plane of the paper, can be operated by the operator to move the lower end
of the clamp toward and away from the plate 14.
FIGS. 2 and 3 depict press brake tools that are substantially different
from the slanted tool shown in FIG. 1. Each tool has a body portion 18, an
upwardly extending tang 20 adapted to be received between the support
plate and the clamp of a press brake tool holder, and a lower, work
engaging surface 22. The tools themselves include generally horizontal,
upwardly facing shoulders 24 that engage complementary downwardly facing
surfaces 26 of the tool holder's support plate 14, 14', the surfaces
serving to transmit force downwardly from the upper table (not shown) to
the press brake tools 10, 10' of FIGS. 2 and 3. Moreover, the tool holder
support plates 14, 14', respectively of the embodiments of FIGS. 2 and 3
each have vertical surfaces 28, 28' that engage vertical surfaces 30 of
the tangs 20. As shown in FIGS. 2 and 3, as the tools 10, 10' are moved
upwardly, the surfaces 28, 30 (FIG. 2) and 28', 30 (FIG. 3) come into
surface to surface contact. As teach tool moves upwardly, its shoulder 24
comes into contact with and is locked against the bottom surface 26, 26'
of the support plate.
The reverse surface 32 of the tang has an arcuate, concave shape, and is
described best with reference to FIGS. 4 and 5, to which we now turn.
Referring to FIG. 5, the tang portion 20 of a tool of the invention is
shown in cross section. Its arcuate surface 32, the reverse of the surface
30, is formed desirably on a plurality of radii about spaced horizontal
axes. In FIG. 5, the upper portion of the arcuate surface--that indicated
at point P.sub.1 --is formed on a radius R.sub.1, whereas the lower
portion of the arcuate surface indicated at P.sub.2 is formed about a
larger radius R.sub.2. That is, the radius upon which different portions
of the arcuate surface 32 is formed is smallest near the top of that
surface and largest at the bottom of that surface, in a desired
embodiment.
Referring to FIG. 4, which is an enlargement of the circled portion 4 in
FIG. 2, the tool holder clamp 16 includes a horizontally extending rod 34
that is received within a generally circular groove 36 of the clamp and
hence can rotate within the clamp about an axis 38. A portion of the
surface of the rod is planar, as shown at 40, that planar surface
intersecting the generally cylindrical outer surface of the rod at edges
42, 44. As the clamp is forced against the surface 32 of the tang, its
edges 42, 44 come into contact with the arcuate surface of the tang at
P.sub.1, P.sub.2, respectively. Slight rotation of the rod 34 distributes
the load between the edges 42, 44. A horizontally extending helical spring
46 supports the rod 34 and bears upwardly against a second flat surface 48
of the rod.
Referring again to FIG. 5, P.sub.1 represents the upper contact surface of
the arcuate surface 32 that is contacted by the point 42 of the rod 34 as
the clamp engages the arcuate surface of the tang. Similarly, P.sub.2
represents the lower contact surface that is engaged by the point 44 of
the rod. It will be understood that the edges 42, 44 of the rod are shown
as points in the side view of FIG. 4, these points actually represent
lines that are the intersection of the planar surface 40 and the generally
cylindrical surface of the rod, and that P.sub.1 and P.sub.2 represent
lines on the arcuate surface of the tang that are contacted by the
respective intersections 42, 44.
Referring to FIG. 5, one may draw a plane 50 that is tangent to the arcuate
surface of the tang at P.sub.1, and another plane 52 that is tangent to
the arcuate surface at point P.sub.2. Whereas plane 50 is convergent
downwardly with respect to the vertical surface 30 of the tang, the plane
52 is convergent upwardly with that surface. From the standpoint of force
vectors, a force delivered by the edge 42 of the rod 34 at point P.sub.1
will act normal to the tangent 50, and the force thus will have a
horizontal component and a vertical component. The vertical component
urges the tang upwardly when the tang is clamped in the tool holder.
Similarly, the force exerted by the clamp at point P.sub.2 will act normal
to the plane 52, and that force will have horizontal and vertically
downward components. Inasmuch as the angle between the vertical surface 30
and plane 50 is greater in absolute value than the angle between the
vertical surface 30 and the plane 52, the upward component of force acting
at P.sub.1 will be greater than the downward component of force acting at
point P.sub.2, with the net vertical force then being upward. This assumes
that the force delivered at P.sub.1 and P.sub.2 will be essentially equal,
and the latter condition is a result of the slight rotation of the rod 34
as it comes into contact with the arcuate surface of the tang.
FIG. 3 shows another embodiment of a tool and tool holder of the invention.
Here, the arcuate surface 32 of the tool holder is formed generally as
shown in FIG. 5, but the portion of the clamp 16' that engaged the arcuate
surface of the tang is shaped to be at least partially congruent with that
arcuate surface, as shown in FIG. 3. As thus illustrated, the curved
surface of the clamp that fits congruently against the, upper arcuate
surface of the tang exerts a net upward force against the upper surface of
the tang.
The use of an arcuate surface 32 of the tang against which the clamp
presses, as opposed to a flat surface, for example, assures that the force
exerted by the clamp will act in a direction normal to the tangent of a
plane drawn to that portion of the arcuate surface contacted by the clamp.
The distribution of force components against the arcuate tang can be
readily varied as desired by changing the degree of curvature of the tang
to thus change the angle that the planes 50, 52 make with the vertical.
Radius R.sub.2 may be several times greater than R.sub.1, and will act
about a horizontal axis spaced (in FIG. 5) far to the right of that figure
and accordingly not shown in FIG. 5. For example, the radius R.sub.1 may
be on the order of one inch, whereas the radius R.sub.2 may be on the
order of four inches. The surfaces that are generated by these radii about
their axes desirably merge smoothly into one another, and of course other
radii may appropriately be employed to sweep out other areas of the
arcuate surface, it being desired that the curve of the arcuate surface of
the tang be smooth and without abrupt surface changes.
While a preferred embodiment of the present invention has been described,
it should be understood that various changes, adaptations and
modifications may be made therein without departing from the spirit of the
invention and the scope of the appended claims.
*
