Adjustable punch assembly

Details Adjustable punch assembly Adjustable punch assembly

1999-07-12

2002-01-01

Dexter, Clark F. (Department: 3724)

Cutting

Means to drive or to guide tool

Constantly urged tool or tool support

C083S640000, C083S686000, C083S698910

Reexamination Certificate

active

06334381

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to punch assemblies such as those usable with indexable multiple station turret punch machines.
BACKGROUND OF THE INVENTION
It is known to provide rotatable and indexable punching tools in a turret punch press where the upper and lower punching tools are rotated synchronously for different orientations of the punch tools. Further, it is known to provide multiple station turret punch machines which provide a large number of different punch stations for use in conjunction with a like number of opposing die surfaces. Each station may include an upper punch assembly and a lower die assembly. The typical configuration of the punch assembly includes a punch tip that is mounted onto the lower end of a punch driver which, in turn, is threadably connected to a punch head.
As illustrated in U.S. Pat. No. 4,375,774, which is incorporated herein by reference, the punch tip can become dull or worn during use. As a result, the tips are routinely sharpened using a grinding operation which shortens the overall length of the punch tip, and accordingly, the overall length of the punch assembly. Because the distance between the cutting edge of the punch tip and the workpiece is a critical dimension, control of the vertical position, and hence the overall length of the punch assembly, is important. U.S. Pat. No. 4,375,774 discloses an adjustable punch assembly whereby the punch driver is threadably attached to the punch head. By rotating the punch driver with respect to the punch head, the overall length of the punch assembly can be shortened or lengthened.
Further, punch presses having indexable tool stations enable the punch assembly, and hence the punch tip, to be rotated so that the punch tip can be applied to the workpiece in different orientations. Punch presses employing indexable punch stations are disclosed in U.S. Pat. Nos. 5,048,385 and 4,658,688, both of which are incorporated herein by reference and both of which are owned by the assignee of the present application.
Specifically, U.S. Pat. No. 4,658,688 discloses a turret punch press having an upper and lower turret tool holder which carries a number of punch and die sets in individual tool holding stations in the turrets. At least one of the corresponding tool holding stations in the upper and lower turrets is indexable to different angular orientations. Rotation of the indexable punch tools is accomplished by a slidably mounted motor for engagement with a timing pulley, which, through a timing belt and harmonic gear drive, acts to rotate the tool holder which carries the punch and die set. In this device, each of the turrets may be equipped with tool stations which receive tool support devices that are rotatable to selectively position the tools at chosen angular positions by rotating the tool sets about their longitudinal axes.
U.S. Pat. No. 5,048,385 discloses a punch assembly for an indexable punching station which includes a striker body having a solid portion and a punch carrier which carries a plurality of individual punches. A selectively actuable stop holds the striker body stationary, allowing the punch holder to be rotated so that one of the plurality of punches will underlie the solid portion of the striker body. The stop may then be deactivated so that the entire punch assembly may be rotated to a variety of angular orientations. Rotation of the assembly thus permits a single punch to be used to punch holes of the same shape but with differing angular orientations.
Thus, U.S. Pat. No. 4,375,774 discloses an adjustable punch assembly whereby the overall length of the punch assembly may be adjusted to accommodate for wear on the punch tip or the shortening of the punch tip due to sharpening or grinding operations. U.S. Pat. Nos. 4,658,688 discloses an indexable tool station which permits the angular rotation of the punching tool. U.S. Pat. No. 5,048,385 expands on this concept by enabling the angular rotation of the entire punch assembly and further angular rotation of a tool holder to thereby selectively dispose a selected punch tool under the solid portion of the striker body.
However, the punch tip disclosed in U.S. Pat. No. 4,658,688 and punch tips generally known in the art are attached to the punch driver by a threaded shaft that passes through axial passageways in both the punch head and the punch driver. The shaft needs to be tightened to a specific torque rating in order to properly retain the punch tip. Thus, changing the punch tip in favor of an alternative punch tip is time consuming and therefore costly. Accordingly, there is a need in the punch press art for punch tips that may be changed more quickly and therefore more economically than currently available punch tips.
Further, while U.S. Pat. No. 4,658,688 discloses a punch assembly having an overall length that may be adjusted by rotating the punch head with respect to the punch driver, the design disclosed in U.S. Pat. No. 4,658,688 requires that any length adjustment be made during the initial installation of the punch tip. There is no way to adjust the overall length of the punch assembly during operation of the punch press. Accordingly, there is a need for an improved punch assembly that may be length adjusted during operation to compensate for tip wear, changes in the workpiece material or other operational variables.
SUMMARY OF THE INVENTION
The present invention satisfies the aforenoted needs by providing an improved punch assembly and an improved punch press.
The punch assembly of the present invention includes a punch driver with an axial passageway extending therethrough. The axial passageway of the punch driver accommodates a locking shaft that is releasably coupled to the punch tip. More specifically, the locking shaft includes a downwardly directed tapered socket for receiving an upper end of a punch tip shaft that extends upward from the punch tip. The upper end of the punch tip shaft includes one or more detents that form one half of a ball/detent connection between the punch tip and the punch driver.
The axial passageway extending through the punch driver includes a lower end that accommodates a cylinder which receives the punch tip shaft. The cylinder includes a plurality of spaced holes, each hole being in alignment with a ball that is trapped between an inside surface of the socket and a cylinder.
To connect the punch tip to the locking shaft that extends through the punch driver, the locking shaft, and specifically the socket, is pushed downward onto the upper end of the punch tip shaft. As a result, an inside surface of the socket pushes the balls through the spaced holes of the cylinder so that the balls engage the detent disposed at the end of the punch tip shaft to provide a ball/detent connection between the punch tip shaft and the locking shaft.
In an embodiment, the locking shaft further comprises an upper end that is spring biased upwards and a middle section disposed between the upper end of the locking shaft and the socket, which is disposed at the lower end of the locking shaft. This middle section comprises a slot having a lower portion and an upper portion. The punch driver further comprises a cooperating key that is accommodated in the slot. As the locking shaft is pushed downward, and the key is disposed in the upper portion of the slot, the balls are pushed inward through the base openings of the cylinder by the inside surface of the socket so that the balls engage the detent of the punch tip shaft to make the ball/detent connection.
In an embodiment, an upper portion of the slot disposed in the middle section of the locking shaft extends horizontally and the lower portion of the slot extends vertically so that in order to lock the socket of the locking shaft onto the upper end of the punch tip shaft, the locking shaft is pushed downward so that the key of the punch driver extends through the vertical portion of the slot and then the locking shaft is twisted thereby causing the key to travel along the horizontal portion of the slot to lock the socket over th

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