Gear cutting – milling – or planing – Milling – With means to protect operative or machine
Patent
1983-05-20
1985-08-20
Briggs, William R.
Gear cutting, milling, or planing
Milling
With means to protect operative or machine
744248R, 82 27, 403 2, 403337, 411389, 411395, B23B 2100
Patent
active
045361126
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for protecting against overloads a machine tool having a lead screw for moving a carriage on a machine bed and at least one bolt having a flange and a nut connecting the screw to the carriage.
In machine tools it is known to provide an overload clutch between the lead screw for driving the carriage and the lead screw drive, for the purpose of uncoupling the motor if a collision occurs between the carriage and the chuck holding the workpiece. Such clutches are indeed capable of protecting the motor against damage, but they do not keep the lead screw from continuing to revolve in the event of a collision, so that the considerable forces produced thereby can result in damage to the carriage, the lead screw nut or the lead screw itself. It is also possible to provide shear pins at suitable locations, but these are unsuitable inasmuch as they also have to transmit the dynamic forces and the forces required for the machining operation.
Another disadvantage is that, in the event of a collision, the axial mounting of the lead screw is damaged. Also, the predetermined dimensional relationship between the lead screw nut and the tool rest is destroyed.
In the event of a collision, therefore, difficult and time-consuming repair work and replacement parts are required, which delay the restoration of the machine to service.
The object of the invention is to create an overload protection device which will make possible a very quick restoration of the machine to service after a collision between the carriage and any component that may be in its path, in which case the predetermined dimensional relationship will be restored without further readjustment.
This object is achieved in accordance with the invention by providing at least one connecting screw between the flange and the carriage, and at least one connecting screw between the flange and the nut, with each of said connecting screws having a break-away section.
Desirable further developments of the invention will become apparent from the remaining description.
In the event of a collision of the carriage with a stationary component, such as the chuck holding the workpiece, the lead screw of the carriage, which carries the tool slide rest, does not come immediately to a stop, so that considerable forces in the axial direction are exerted against the joining bolt by the lead screw nut. By the appropriate dimensioning of the break-away section of the joining bolt, which is under tension, it can be made to break at a specific stress.
Thus, if a collision occurs and breakage occurs at the break-away section, what takes place is the release of the connection between the nut and the carriage. At the same time, the second thread section, which is screwed into the carriage by means of the head of the joining bolt, remains in the carriage, while the first thread section, together with the remnant of the break-away section and the retaining nut, comes away from the lead screw nut. The first thread section can then easily be removed from the lead screw nut together with the retaining nut; this is also possible in the case of the second thread section of the joining bolt, since it can be unscrewed by means of the bolt head. Easy repair can thus be accomplished by the insertion of a new joining bolt.
The threaded bore for the accommodation of the second thread section of the joining bolt is best constructed such that the thread is not damaged even by a number of collisions. Its reuse is thus possible.
The use of a joining bolt of this kind also has the advantage that minor collisions can be detected by routine inspections, since such collisions in the plastic deformation range of the break-away section of the joining bolt produce a change in the length of the joining bolt and can thus be detected by measurement.
It is an important advantage of the overload protection device that it can be applied to existing machines, since the conventional joining bolts can be replaced by joining bolts provided with a break-away section.
The overload protection can
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Horsky Anton
Kuhn Siegfried
Voss Wolf-Dietrich
Briggs William R.
Oerlikon-Boehringer GmbH
Webb Glenn L.
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