Metal deforming – By use of closed-die and coacting work-forcer – With stripping or ejecting from tool
Reexamination Certificate
2002-12-16
2004-09-28
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of closed-die and coacting work-forcer
With stripping or ejecting from tool
Reexamination Certificate
active
06796158
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to press systems and, more particularly, to a knockout assembly for parts formed on a press system.
2. Background Art
Knockout assemblies are commonly used in parts forming presses to separate the parts from die surfaces against which the parts are formed. In an exemplary press system, a translatable die element is advanced in a predetermined path to cause a workpiece blank to be formed against a surface on the die element. The forming surface may have sufficient complexity that the part will not consistently release from against the forming surface without the application of a separation force. The separation force is typically imparted through a bar on a knockout assembly.
In one known knockout assembly construction, the knockout bar has an associated element which can be selectively a) advanced through the die element and past the forming surface with the knockout bar in an extended position and b) withdrawn therefrom with the knockout bar in a retracted position. The knockout bar follows movement of a slide, which is guided in translation from a starting/first position into a second position, as an incident of which a workpiece blank is forced conformingly against the forming surface on the die element on the slide. Upon completion of the slide stroke, the slide is returned to its first position. As the slide moves back towards its first position, spaced locations on the knockout bar encounter cantilevered knockout pins which arrest further movement of the knockout bar. Continued movement of the slide towards the first position with the knockout bar blocked causes the knockout bar to translate relative to the slide, as an incident of which the knockout bar is changed from its retracted position into its extended position and, in so doing, effects separation of the formed part from against the die element surface.
Conventionally, the knockout pins have been in the form of cantilevered elements with free ends which directly contact the knockout bar. Proper operation of a knockout assembly requires a specific spatial relationship between the knockout pins and the knockout bar. If the required relationship between the knockout bar and knockout pins is not maintained, a number of different conditions could result, which could either impair performance of, or cause damage to, the press.
One such condition occurs in the event that the knockout pins do not engage the knockout bar so as to maintain its intended orientation with respect to the slide. If the knockout pins skew the knockout bar, a misalignment of the knockout bar with the slide may result which could cause uneven wear on guidingly cooperating parts, jamming, or destruction of one or more parts on the slide and/or knockout assembly.
Another more serious condition may occur in the event that the movement of the slide fully into its first position does not coincide with the movement of the knockout bar to its extended position. That is, if the knockout bar achieves its fully extended position as the slide continues to move towards its first position, the slide may be forced against the knockout pins and frame, upon which the knockout pins are mounted, so as to cause damage to be inflicted thereto and/or to the knockout assembly.
To avoid the above conditions, it is known to allow for adjustment of the knockout pins. This adjustment is desirable not only from the standpoint of avoiding the above conditions, but also to permit the press system to be set up for the performance of different operations and/or to accommodate different workpiece dimensions requiring a different slide stroke.
Heretofore, knockout pins in this type of press system have been made adjustable through manual operations performed by a technician directly at the location of the knockout pins. In one such press system, the knockout pins are elongate elements with a separate piece at the ends thereof, each of which has a surface to directly engage a knockout bar. Each end piece is threadably connected to the remainder of its associated knockout pin. By rotating the end piece, the effective length of the knockout pin can be changed. This operation needs to be performed on each of the knockout pins on the system in such a manner that their length adjustment corresponds. The effective length of the knockout pins is determined by separately taking a measurement for each adjusted knockout pin.
This manual adjustment has a number of inherent drawbacks. First of all, the technician must walk directly upon the press system components to access the knockout pins. Oft times the knockout pins are located so as not to be conveniently accessible. There is always a danger that the technician may be injured during this process. Additionally, the adjustment process is time consuming. The technician is required to climb over the equipment to each of the separate knockout pins and, through a wrench or otherwise, make the necessary adjustments. Significant down time may result. Further, the on site measuring of the altered effective length of the knockout pins through a tape measure may be awkward and imprecise. This could ultimately result in one of the conditions that is described above.
With the manually adjusted system, the operator may have to periodically visually inspect the knockout pins to make certain that they are situated and operating properly. Fine adjustments may have to be made which necessitates shutting down of the press system and proceeding again with manual adjustment. This adjustment will normally be required at each die change. Die changes may be required frequently in press operations. A die change may take 45 minutes for a 15 minute run. Thus minimizing down time may become extremely important to press efficiency.
A further problem with the manual adjustment is that it may require a considerable amount of trial and error to make certain that the operative relationship between the slide, frame, knockout pins, and knockout bar is as desired. This process is inconvenient and time consuming as it may require several test adjustments and test runs before full operation is undertaken.
SUMMARY OF THE INVENTION
In one form, the invention is directed to a press system having a frame, a slide, a first die element on the slide, and a knockout assembly. The slide is movable guidingly relative to the frame in a predetermined path between a first position and a second position. The first die element has a forming surface against which a workpiece can be borne to conform the workpiece to the forming surface as the slide is moved from the first position towards the second position. The knockout assembly has an ejecting element that is movable selectively relative to the first die element between extended and retracted positions. The ejecting element causes a workpiece conformed to the forming surface to be separated from the forming surface as an incident of the ejecting element moving from its retracted position into its extended position. The knockout assembly further includes a knockout bar and at least a first knockout pin. The knockout bar is movable relative to the slide between a retracted position and an extended position and causes the ejecting element to move from its retracted position into its extended position as an incident of the knockout bar moving from its retracted position and into its extended position. The at least first knockout pin causes the knockout bar to be moved from its retracted position into its extended position as an incident of the slide moving from the second position into the first position. The first knockout pin and the knockout bar have an operative relationship that is variable from a location remote from the first knockout pin.
In one form, the knockout bar is movable guidingly relative to the slide between its extended and retracted position.
In one form, the at least first knockout pin has a first surface. With the knockout bar in its retracted position and the slide in the second position, the first surface is spaced from the knockout bar a fir
Brzezniak Edward J.
Washington James
Aida Engineering Ltd.
Larson Lowell A.
Wood Phillips Katz Clark & Mortimer
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