Metal deforming – With means to drive tool – With means to selectably control movement of tool
Reexamination Certificate
1999-11-23
2001-10-09
Jones, David (Department: 3725)
Metal deforming
With means to drive tool
With means to selectably control movement of tool
C072S446000, C072S472000, C470S138000, C470S140000, C083S561000
Reexamination Certificate
active
06298708
ABSTRACT:
FIELD OF THE INVENTION
My present invention relates to a tool-holder assembly for a machine tool, especially a press, wherein the tool holder is equipped with a plurality of tools, especially press rams, plungers or stampers and whereby the tool holder is movable in a working motion toward a workpiece which is held in a parts holder or die so that the too land die together shape the workpiece. The invention is especially directed to production machine tools of this type wherein, after a certain run, the wear of the stamping tool necessitates its replacement, usually by an identical tool performing the same operation.
BACKGROUND OF THE INVENTION
Especially in the case of machine tools used for mass production, for example, the mass production of screws or bolts, productivity is determined by the weakest link in the production train. In the manufacture of screws, for example, this weak link has been in the past the stamper, plunger or ram of the press which had to be replaced after a relatively limited run. The press run, depending upon the particular product and the material from which the product was made, could amount to 30,000 to 250,000 pieces.
In a high-capacity press, capable of producing 800 pieces per minute, it was not uncommon to have to replace the ram or plunger tool every two hours. The replacement process was relatively time consuming and required that the apparatus be brought to a costly standstill, thereby limiting productivity.
To reduce the drop in productivity and to allow tool replacement with little investment in labor, it has been proposed to provide an automatic tool-replacement system. For this purpose, a number of identical tools, for example, stamping tools, were stored in a magazine and fed from the magazine to the tool holder. A mechanism was provided for removing a stamping tool from the tool holder, inserting it into the tool holder, removing the worn tool from the tool holder and placing it in the magazine and advancing the tool in the magazine to the replacement position. The tools could then be removed from the magazine for machining or refinishing.
The tool holder had to be arrested in a certain position for the tool change and, especially when the tool did not have a regular shape, there was always the danger that the tools in the magazine would jam against one another, delaying the withdrawal of a tool or the reinsertion of a worn tool into the magazine. As a consequence, in spite of the automatic tool replacement mechanism and the availability of a magazine with a store of replacement stamping tools, there was always the danger of delay in the tool chain and of a productivity drop.
OBJECTS OF THE INVENTION
It is the principal object of the present invention, therefore, to provide an alternative tool replacement system for a tool magazine whereby the drawbacks of the former approach can be avoided and productivity drops which were so associated therewith can be eliminated.
Another object of the invention is to provide an improved tool replacement system for a machine tool, especially a production press, whereby productivity drops caused by defective tools in a magazine or tool jamming and the like can be avoided.
Still another object of the invention is to provide a tool replacement system which minimizes the amount of manual labor required and the down time to which a press may be subject in undergoing tool replacement.
SUMMARY OF THE INVENTION
These objects and others are attained, in accordance with the invention by mounting a plurality of identical tools, capable of being substituted for one another upon wear of the one in use, rigidly on a tool holder and moving them with the tool holder into the operative or working position. More particularly, a tool-holder assembly for a machine tool can comprise:
a support movable toward and away from a workpiece holder in a working motion;
a tool holder having a plurality of tools fixed thereon for performing a certain machining operation and alternatively positionable at a workpiece-shaping position for performing the operating upon wearing of the tools, the tool holder being movable on the support in a tool-replacement motion; and
positioning means operatively connected with the tool holder for shifting same with the tool-replacement motion to substitute one of the tools for another at the workpiece-shaping position.
The system is particularly desirable when the machine tool is a production press, the tools are stamping tools of the press, e.g. for stamping and shaping the heads of screws or the like and the workpiece holder is the anvil of such a press shaping the workpiece in conjunction with the stamping die.
By fastening the tools fixedly in the tool holder, it is unnecessary to display individual tools relative to the tool holder so that jamming in a magazine or the like can be avoided. The number of tools which can be mounted on the tool holder is practically unlimited and will be chosen so that each tool can produce a fraction of the tool run and the total number of tools can produce an entire production run as the tools are substituted for one another and without a significant downtime since the tools can be substituted for one another in the time it takes for the press to open and close normally. The personnel utilization is minimal and down time need occur only when the production line is brought to standstill for another operation.
The tool holder is so constructed that it is moved as a unit, i.e. with all of the tools mounted thereon, toward the parts holder or fixed die member for the working motion. In this working motion, however, only one of the tools on the tool holder is aligned with the workpiece and thus can participate in the shaping operation. While the invention is described here primarily in conjunction with a production press, it will be understood that it also applicable to other production machine tools, although it is particularly important for such a press.
When the workpiece in use has worn sufficiently that the workpieces which it produces can be considered rejects, a new tool is shifted into the working position and production continued with the new tool until that tool begins to produce rejects and a further tool change is carried out.
For the movement of the tool holder to bring a tool into the working position, it is advantageous to mount the tool holder so that it is slidable in a rail. The use of a rail system to slidably support the tool holder enables the entire tool holder to be removed from the rail and replaced by another tool holder which is identical to the first one which has previously been equipped with a corresponding set of tools so that the worn tools on the replaced tool holder can be removed or machined to restore their effectiveness.
After replacement of the individual tools on the removed tool holder, the latter can again be substituted on the rail for the tool holder then in use. To position the tool holder on the rail, for example, so that the first of its tools is in line with the workpiece and is in position for a stamping operation, a stop can be provided on the rail for the tool holder.
It has been found to be advantageous to provide the positioning means for the tool holder with a pinion whose teeth mesh with a rack on the tool holder. The pinion itself can be driven in a variety of ways. Advantageously, the pinion is advanced through a given angular displacement corresponding to the linear displacement of the tool holder by a distance D between the tools mounted on the tool holder. This displacement, therefore suffices to remove a worn tool from the shaping position and replace it by a fresh tool and corresponds to the pitch of the tools in their linear array along the tool holder. This discrete motion can be effected by a pneumatic cylinder which can angularly displace a lever. The angular displacement of the pinion and thus the linear movement of the tool holder can correspond to a maximum stroke of the piston rod of the cylinder.
To allow return of the piston rod to its starting position without rotation of the pinion, the pinion ca
Ausländer Wolfgang
Gaul Kurt
Dubno Herbert
Gebr. Hilgeland GmbH & Co.
Jones David
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