Gear cutting – milling – or planing – Milling – Cutter spindle or spindle support
Reexamination Certificate
2002-08-22
2004-08-03
Cadugan, Erica (Department: 3722)
Gear cutting, milling, or planing
Milling
Cutter spindle or spindle support
C279S131000, C279S141000, C279S157000, C279S158000, C409S134000, C409S186000, C409S209000
Reexamination Certificate
active
06769846
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a coupling device for engaging an exchangeable tool support for corotation with the shaft of a motor, with the shaft comprising at its driven end a hollow shaft projection for receiving the tool support, or the tool support comprising a hollow shaft projection for receiving the driven end of the shaft, and with the shaft and/or the tool support comprising a locking device for securing the tool support.
A known coupling of rotatably driven tools with the shaft of a motor provides on a shank of the tool a cone that is inserted into an associated inner cone at the driven end of the motor shaft. By pressing the cone into the inner cone, a press fit is produced, which enables a transmission from the shaft to the tool. However, in the case of such couplings, it turns out to be very difficult to disengage the cone from the inner cone against the resistance of the press fit.
Further known are simple coupling devices, for example, for small, hand-held drills, which include in a conical hollow shaft, a chuck comprising a plurality of jaws and being likewise conical in its peripheral surface. This chuck is inserted into the hollow shaft. A coupling nut with an opening is adapted for being screwed onto the conical. hollow shaft. When being tightened, the nut causes the chuck to be pushed into the hollow shaft, and the jaws to be clamped against one another. In this manner, it is possible to connect a tool that is insertable into the chuck for corotation with the driven end of the drill.
However, it has shown that these coupling devices are on the one hand uncomfortable and time-consuming as regards the insertion of a tool or during a tool change, since they require many manipulations. Consequently, coupling devices of this type cannot be easily transferred to larger machines and heavy tools. On the other hand, however, these coupling devices provide no lasting connection between the tool and driven end, since the screw connection can disengage during the machining operation as a result of vibrations, and thus releases the tool. This constitutes a substantial safety risk primarily in the case of rapidly rotating tools.
It is therefore an object of the present invention to provide a coupling device, which enables a rapid insertion of even heavy tools, and simultaneously ensures a reliable locking engagement of the tool with the drive.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the present invention are achieved by the provision of a coupling device of the described type and which includes a locking device which is actuated by centrifugal force.
According to the invention, it has been recognized that, departing from previous construction principles which produce a locking engagement primarily as a result of separately applied forces, it is possible to use the naturally occurring centrifugal forces for locking the rotated bodies. With that, it becomes unnecessary to apply an additional force for purposes of locking, which saves the user of the device additional manipulations and time.
According to an advantageous development of the invention, the locking device comprises at least one locking member, which is adapted for engaging in a locking manner a connection element on the tool support and/or the shaft due to the centrifugal forces occurring during the rotation. To this end, the locking device comprises a locking member, whose mass center is arranged off center with respect to the axis of rotation of the drive shaft, and which thus tends to move outward as the rotation sets in. With that, the locking engagement is automatically produced between the connection element and the hollow shaft projection immediately upon the start of the rotation. This saves not only operating time and efforts for producing the locking engagement, but also excludes in addition a possible source of error due to a faulty operation.
In the case of machine tools with rapidly rotating tools, the highest priority should be given to work safety. In the construction of machine tools, which cannot be enclosed against an unwanted collision between other objects or of an operator with the tool, since they must be at least in part freely accessible as a necessity of machining the workpieces, it is therefore highly necessary to see to it that no hazards originate from the rapidly rotating tools, as would exist, for example, in the case of a premature or uncontrolled disengagement of the tool.
It is also desirable to provide a construction wherein with the tool inserted while the motor is still off and thus before the start of the locking engagement, an initial locking engagement occurs. This initial locking engagement could be realized in that the locking member is biased in the direction of the centrifugal force. It is therefore necessary to push the connection element into the hollow shaft projection against a biasing force. On the one hand, a noise occurring during the initial locking engagement gives the operator the certainty that the tool is secured. On the other hand, the initial locking engagement makes it possible that the connection element and hollow shaft projection reach that position, which is necessary for a functional locking engagement by the centrifugal force.
According to an advantageous development of the invention, it would be possible to bias the locking device hydraulically, pneumatically, or mechanically. Primarily, a bias by means of a spring provides a constructionally simple and cost-favorable biasing means.
The essential function of the coupling device is to transmit forces between the hollow shaft projection and the connection element. A transmission between these two parts may basically occur by a formfitting or by a frictional engagement. According to an advantageous development of the invention, it would therefore be possible to provide that the traverse cross sections of the hollow shaft projection and the connection element are made to correspond with each other, for example, in that they are realized as a standardized formfitting connection, and that they thus ensure a formfitting transmission. Such connections, for example, such with hexagonal cross sections can be produced in a simple and cost-favorable manner. Primarily, however, they are insensitive to axial displacements of the connection element relative to the hollow shaft projection.
In addition or as an alternative, the bore of the hollow shaft could include for a mutual contact an internal cone and the connection element a corresponding external cone. These rotationally symmetric cross sections offer the advantage that they can be produced with a high precision.
Contrary to a formfitting connection, it is also desirable to apply an axial force by frictional engagement to keep the force-transmitting surfaces in contacting relationship. This axial force can be manually applied when inserting the tool, and be maintained by a press fit of the conical parts. According to an advantageous development, an oblique surface on the locking member could deflect a portion of the centrifugal force that acts upon the locking member, and apply an axial force to the tool support. In this manner the press fit between the connection element and the hollow shaft projection can be produced. To this end, it would be possible to use as the oblique surface a sloping contact surface between the locking member and tool support. With that, it would be possible to eliminate a further operating step in the assembly of the tool support.
In an advantageous further development, the conical surfaces of the hollow shaft projection and/or the connection element could be made for a transmission by frictional engagement, in particular with a high surface quality. As a result of making the surfaces of the conical areas as smooth as possible, it is possible to avoid that they become wedged, and cannot be separated from each other, or that they can be separated only with great efforts after the use of the tool support.
Basically, any number of locking members is possible. Since the coupling
Campbell, Jr. Robert L.
Moran Kevin E.
Alston & Bird LLP
Cadugan Erica
Walter Persk{dot over (e)} GmbH
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