Cutting – With product handling means – By fluid current
Reexamination Certificate
2000-09-25
2004-12-21
Peterson, Kenneth E. (Department: 3724)
Cutting
With product handling means
By fluid current
C083S099000, C083S268000, C083S653000
Reexamination Certificate
active
06832535
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to rod cutting machines.
More particularly, the invention relates to apparatus for automatic discharge of cut rods in closed-knife rod cutting machines, and which is particularly useful in connection with discharge of rods cut to a relatively short length and in high-speed machines.
2. Description of Prior Art
A number of rod cutting machines are known and available for cutting either wire stock or rod stock into shorter rods of a desired length, the cut rods being typically intended for further processing such as (but not limited to) in the production of roller bearings and other generally cylindrical parts.
One such type of machine is a so-called “straighten and cut” machine. In this instance, wire is fed into the machine from a coil of wire, the wire is then straightened and drawn into a length of rod stock material, and then cut into rods of the desired length.
Other machines are adapted for receiving and cutting elongated rod stock into shorter rods of a desired length.
Accordingly, it will be understood that reference to rod stock herein will include and alternately mean both pre-shaped, pre-cut rod stock and/or a supply of wire provided to an appropriate rod cutting machine.
Most conventional prior rod cutting machines are equipped with an open knife for cutting rod stock into shorter rods. The rod stock is fed by, for example, a pair of friction engaging rollers through a stationary cut-off support die and through a downwardly opening slot in the open knife until the stock extends through the knife a desired distance that will result in cut rods of the desired length. The rod stock is positioned in the knife with a gage pin or other suitable structure having a gage surface located downstream of the knife, the free end of the rod stock engaging the free end or gage surface of the gage pin to stop the rod stock from advancing further in the knife, the gage pin typically being adjustable for establishing different lengths of cut rods. With the rod stock in its desired position in the knife, an actuating mechanism actuates the knife downwardly to shear the rod stock at the junction between the knife and the cut-off die, producing a shorter rod cut to the desired length. The downwardly opening slot in the open knife allows the cut rod to then simply fall away from the knife and into, for example, a collection bin. The knife actuating mechanism then actuates the knife upwardly, returning the knife to the rod loading position, whereupon the rod stock automatically advances through and is positioned in the knife in preparation for another cutting cycle.
As is well known, cut rods are deformed during the shearing process, resulting in a material condition known as “roll-over” at the cut ends. In order to reduce this material deformation during shearing of the rods, the clearance between the knife and the adjacent end of the cut-off die is often reduced to within a few thousandths of an inch. Nevertheless, the lack of support under the rod extending past the cut-off die and through the open knife results in unavoidable distortion of the ends of the cut rods during the shearing process.
In certain instances, such as when cutting relatively long rods of several inches in length, this roll-over may not be of substantial concern, and is addressed or compensated for in subsequent processing.
However, the shorter the length of the cut rods, the more pronounced this distortion becomes since it accounts for an increasing percentage of the rod length, and the more difficult it becomes to remove or compensate for during subsequent processing. In certain instances and for certain subsequent processes, this distortion is simply not acceptable.
As a result, the open knife arrangement of conventional prior rod cutting machines is not suitable for use where precision cut rods with reduced end distortion are desired, and in particular, in connection with relatively short rods.
In order to reduce the distortion of cut rods, certain prior conventional rod cutting machines are equipped with a closed knife for shearing rods to the desired length. In this instance, the rod stock is again fed through the stationary cut-off die and the closed knife until the free end of the rod stock engages the free end of the gage pin. The closed knife is characterized by a bore for receiving the rod stock, the bore at least substantially encircling and preferably complete encircling the rod stock, and having the same cross-sectional profile as the rod stock. In order to provide for maximum support of the free end of the rod stock during the shearing operation, the bore is sized for a relatively close radial sliding clearance with the rod stock such as within a few thousandths or ten-thousandths of an inch radial clearance. As with the open knife, an actuating mechanism actuates the closed knife to shear the rod stock at the junction between the knife and the cut-off die.
The support provided by the bore of the closed knife, and the relatively close clearance fit between the bore and the rod stock results is substantially less end deformation and/or roll-over as compared with cutting the rod with a conventional open knife.
However, unlike the open knife machine, the cut rod can not simply fall away from the closed knife after the shearing operation. As a result, conventional prior closed-knife machines include a mechanical ejection arrangement including a second actuating mechanism for ejection of the cut rod from the closed knife. This second actuating mechanism is adapted for actuating an ejecting member at least partially into and out of the knife bore for ejection of the cut rod from the knife. After ejection of the cut rod and retraction of the ejection mechanism from the knife, the knife returns to the rod loading position whereupon the rod stock advances through the cut-off die and knife in preparation for another shearing cycle.
Although such conventional closed-knife rod cutting machines offer advantages over open knife machines with respect to reducing end deformation, operation of the closed knife and associated ejection apparatus suffer from several other drawbacks and disadvantages:
The need for the mechanical ejection apparatus including the second actuating mechanism raises the cost and reduces the reliability of a closed-knife machine as compared with an open-knife machine.
The need for contact between the ejection mechanism and the cut rod results in the need for a longer knife stroke, as compared with the stroke of an open-knife machine, in order for the cut rod to clear the cut-off die. Other things being equal, this longer stroke results in a slowdown of production in the conventional prior closed-knife machine.
In order for the rod ejection mechanism to operate, it must be precisely timed and synchronized with the timing of the knife actuating mechanism. Error in this synchronization can result in work stoppage and/or damage to the machine.
The need for the ejection mechanism to actuate at least partially into and out of the bore in the closed knife can result in the need for an additional pause or slowing down of the knife actuation cycle, resulting in further reduction of the production rate of the closed-knife machine.
In such closed-knife machines, additional expensive apparatus is typically provided to compensate for the reliability, increased stroke and timing requirements of the mechanical ejection actuating mechanism, and to raise the production rates back up to approaching the rates of a typical open-knife machine.
The relatively close clearance between the knife bore and the rod, which is desirable to reduce distortion of the rod during the shearing operation, can result in jamming of the cut rod in the knife. This jamming results from the distortion at the cut end of the rod, and/or fine debris or shavings from the shearing operation that remain in the bore after the cut rod has been ejected. Consequently, as the clearance is reduced to reduce the distortion, the greater the likelihood of the cu
Flores Sánchez Omar
Leydig , Voit & Mayer, Ltd.
Peterson Kenneth E.
Rockford Manufacturing Group
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