Cutting – Processes – Plural cutting steps
Reexamination Certificate
2000-11-06
2004-04-27
Shoap, Allan N. (Department: 3724)
Cutting
Processes
Plural cutting steps
C083S622000, C083S670000, C083S687000, C083S691000
Reexamination Certificate
active
06725751
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a rotary punch apparatus for punching or piercing openings in moving web sheet material, and in particular for punched openings having significant length along the longitudinal axis of the moving web.
BACKGROUND OF THE INVENTION
Making openings by punching into a moving web has been carried on for many years. Where the openings were relatively small, i.e., short along the longitudinal axis of the moving web, then simple rotary dies could be used satisfactorily, in many cases. However, where the openings were elongated or had significant length along the longitudinal axis of the moving web, a simple rotary die, or dies carried on a rotating drum or roll, could not be used. In this case the industry has used so-called flying dies. These were dies which were mounted on carriage moveable along linear rails. The carriages were movable in a straight line intermittently to and fro along the longitudinal axis of the moving web. The carriages would accelerate from a stationary position and reach the linear speed of the moving web. At this point the carriages would move towards one another, closing the dies on the web, and thereby punching or piercing the opening while the dies were moving longitudinally, with the web. The dies would then open, and the carriage would move back along the rails to the start position. This system required the use of relatively expensive equipment, and the control of the carriage required sophisticated computer controls. These were needed to ensure that the carriage reached a speed matching the speed of the moving web, and that the dies closed at exactly the right moment to make the opening at the precise point required. Another more serious problem was the fact that stopping the carriage and reversing it, and then restarting it once more to accelerate for the next opening, required a measurable length of time. During this time no openings could be made in the web. If the design of the web product called for openings at closely spaced intervals, then there were one of two solutions:
Either the web had to be slowed down so that its speed was slow enough to give the die carriage time to return to its start position, and then start its next acceleration, or
The line would be built with two or more such flying die carriages, mounted in tandem and operating in sequence.
Either solution was in practice expensive and unacceptable. Slowing down the web reduced the production volume per shift, and thereby increased product cost. Installing two or more flying die carriages was both expensive, and required even more sophisticated controls to ensure that the openings were in the right locations in the moving web.
The sheet metal industry, in particular, requires the production of web products having openings at relatively close spacings, and these openings have significant length along the longitudinal axis of the web. For example one sheet metal web product which is widely used is a so-called dry wall stud. This is a generally C-shaped channel, made of web sheet metal, which is used in erecting walls and partitions, usually interior partitions, in all kinds of office, commercial and industrial buildings. The market for this product, in particular, is highly competitive and manufacturers are constantly looking for ways to reduce their costs, and maintain market share. Such dry wall studs are made with relatively large or elongate openings at closely spaced intervals. These openings are required in construction to permit plumbing and electrical and other services to pass along the interior of the walls.
This is merely one example of a typical product which may be made from a continuously moving web. Numerous other products may be made from such a moving web. The web may be metallic or non metallic. The end product may be a web product with openings, or, in other cases the end product may be the portions of the web which are punched out from the web.
Clearly there is a need for a punching or piercing apparatus which can punch or pierce out relatively large or elongate openings from a moving web without the problems described above in connection with flying dies and moving carriages. Preferably, such an apparatus will be based on a rotary drum or roll, on which dies are mounted so that openings may be punched out or pierced, referred to herein as “punched”, at desired intervals and as close as may be required, without delaying production or causing extra expense. Relatively simple controls will be provided to ensure that the rotary dies, or rolls carrying the dies, are operated in timed relation to the movement of the web along the production line, and that when no openings are required the rolls are inactive and the web can pass between the rolls without openings being punched. Openings having “significant” length along the web axis are referred to herein as “elongate openings” whether round, rectangular or any other shape. “Elongate openings” also includes objects or pieces which are stamped out of a web.
BRIEF SUMMARY OF THE INVENTION
With a view to achieving the foregoing objectives the invention comprises a rotary punching apparatus for punching openings in a moving web workpiece the openings having a significant length along the longitudinal axis of the web and having a pair of rolls located on opposite sides of the path of the web workpiece, and power means for rotating the rolls and having at least a leading die mounted on one said roll of said pair, and movement means for moving said die generally outwardly relative to said roll so as to punch a leading die opening through said web, said leading die opening defining a leading edge and a trailing web portion, and there being a mating leading die recess in the other of said rolls, and further having a second die adjacent to said first die, said second die being located to engage and punch the web at a point adjacent the web portion trailing portion of the leading die opening whereby to punch a continuation of said leading die opening in said web, said first die opening thereby defining a continuous opening having significant length along said longitudinal axis of said web and defining a trailing edge remote from said leading edge.
The invention preferably provides that a median die is fastened relative to said roll between the leading and trailing dies so that it does not move outwardly, and in this way acts to continue and to extend the leading die opening.
In a particularly advantageous embodiment, the invention provides a trailing die being moveable whereby to punch said web and define a trailing edge of said opening.
The invention may also provide at least a hole punch die moveable outwardly relative to said roll operable to punch a further opening in the web spaced axially along the longitudinal axis of the web from the said elongate opening punched by the leading and trailing dies.
The invention preferably provides power operated means for rotating the rolls, the power operated means being operable intermittently so as to punch the openings at desired longitudinal spacings along the axis of the web, the rolls being held inactive where openings are not required so as to permit the web to pass between them without openings being punched. The power operated means may be an intermittently operable motor, or may include a clutch so that the motor can operate continuously, and the clutch being operable to deliver rotary power to the rolls when required.
The invention may be built as rolls which extend across the width of the web and being rotatably mounted on bearings on either side edge of the web.
In a preferred case the rolls are mounted on a single stand in a cantilever fashion located along one side edge only of the web path, the rolls being long enough to extend partly across the web to locate the dies along the desired axis of the web.
The invention provides die operating means such as of cam means. The leading dies are mounted on supports extending into the roll and terminating in followers located to be engaged by the cam means. The trailing and hole punch d
Formtek, Inc.
McCormick Paulding & Huber LLP
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