Tools – Wrench – screwdriver – or driver therefor – Machine
Reexamination Certificate
1999-04-07
2002-01-29
Meislin, D. S. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Machine
C081S433000
Reexamination Certificate
active
06341542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an automatic screwing device with automatic screw supply, in particular a hand screwdriver of this kind, comprising a screw driving tool and a collet for holding a secured, protruding screw, in which the screw driving tool is coupled to an actuating device for the generation of a rotary movement and a feed of the screw driving tool, which takes place relative to the collet, wherein the actuating device has a rotationally drivable, first threaded element, which is connected to the screw driving tool and has a first thread, and also at least one second threaded element, which stands in working engagement with the first threaded element via the first thread.
2. Description of the Prior Art
In such known automatic screwing devices, the actuating device is, for example, driven by means of an air motor to produce the rotary movement and by a pneumatic piston-in-cylinder unit to produce the feed.
Disadvantageous in the use of air motors and pneumatic piston-in-cylinder units is the fact that two different actuating devices are required to produce the rotary movement and the feed, namely an air motor and a pneumatic piston-in-cylinder unit, which is naturally associated with additional manufacturing costs.
Furthermore, it is of disadvantage that the operation of the two actuating units is, on the one hand, associated with a relatively loud noise, and, on the other hand, that the air which acts on the motor and the piston must be oiled, which often leads to undesired contamination as a result of the not completely avoidable oil spray.
An automatic screwing device is known from EP-A-0 284 755, in which the rotary drive and the feed are driven from a single drive shaft. A first threaded element in the form of a splined shaft is rotationally fixed, but axially displaceable within the drive shaft. The splined shaft is connected via a thread to a second threaded element in the form of a spindle such that, on rotation of the splined shaft via the drive shaft, the splined shaft executes an axial movement together with the screw driving tool secured thereon. Disadvantageous with this automatic screwing device is the fact that, with a constant rotation of the drive shaft, the return travel of the screw driving tool for the purpose of a renewed automatic screw supply involves a comparatively long dead time.
SUMMARY OF THE INVENTION
An object of the invention is to further develop an automatic screwing device of the initially named kind, so that it can be manufactured less expensively, in particular with both the rotary movement and also the feed being produceable by a unitary actuating device. At the same time, a high working speed of the automatic screwing device should be made possible.
In accordance with the invention this object is satisfied in that the second threaded element is connected to the collet, and in that two different feed speeds can be produced for a constant speed of rotation of the first threaded element by the provision of two different thread pitches at the first thread and at a second thread, which is provided on the first threaded element or on the second threaded element.
Thus, in accordance with the invention, in distinction to the prior art, the feed movement is ultimately also derived from a rotary movement, and both the rotary movement and also the feed movement can be produced by means of two cooperating threaded elements. In this arrangement, different speeds of advance can be produced through the provision of two different thread pitches. These different speeds of advance are of substantial importance for an operation of the automatic screwing device taking place with a higher cycle rate, since, in automatic screwing devices with an automatic screw supply, measures must be taken to ensure that the screw driving tool can be retracted very rapidly out of the region of the collet after a screwing procedure has been completed in order to avoid a newly supplied screw colliding with the screw driving tool during the supply procedure. After the new screw has been supplied, measures must again be taken quickly to ensure that the screw driving tool is moved into the region of the collet, since the newly supplied screw must be held there by the screw driving tool in the normal manner by elements of the collet which are resiliently biased.
When, therefore—as in the invention—a rapid movement of the screw driving tool is made possible away from the collet and subsequently back to the collet again, it can be ensured that a new screw can be supplied in the shortest possible time after a screwing procedure has been completed and can be held as a secured, protruding screw between the collet and the screw driving tool. A screw held in this manner is then ready for a new screw driving process.
If now, in accordance with the invention, two different speeds of advance can be provided despite constant speed of rotation of the first threaded element, then, on the one hand, a rapid relative movement between the screw driving tool and the collet is made possible and, on the other hand, it is ensured that the pressing of the screw out of the collet, which is required during the screwing process, takes place with a lower speed of advance and thus adequately slowly, so that a problem-free screwing procedure is ensured.
In accordance with the invention both the rotary movement of the screw driving tool required for the screw driving process and also the feed required for the operation of the automatic screwing device are achieved by a rotation of the first driveable threaded element. The rotating drive of the threaded element can in this respect be effected, for example, by means of an electric motor fed from a power supply or from an accumulator. Thus, in accordance with the invention, it is no longer necessary to use a pneumatic piston-in-cylinder unit or an air motor. The disadvantages which are known from the prior art are thus removed by the invention.
At the same time it is, however, ensured that no penalties have to be tolerated with respect to the operating speed or cycle rate of the automatic screwing device, since, as a result of the two different speeds of advance, an adequately rapid manner of operation of the automatic screwing device can be ensured.
It is preferred when the first threaded element is formed as a threaded spindle (first thread) and the second threaded element is formed as a nut. The nut can, in this case, have an internal thread (first thread) which cooperates with the threaded spindle and an external thread (second thread) which cooperates with a sleeve element, with the sleeve element then having a corresponding internal thread (second thread) and preferably being connected to the collet.
Through a rotation of the threaded spindle, a situation can then be achieved in which the nut, on the one hand, is moved along the axis of the threaded spindle. On the other hand, through a rotation of the nut which takes place jointly with the threaded spindle, for example after the nut running along the spindle has reached its abutment position, a situation can be achieved in which the sleeve element moves along the axis of the nut, which coincides with the axis of the threaded spindle.
If now the thread active between the sleeve element and the nut has a different pitch than the thread active between the threaded spindle and the nut, then different relative speeds can be achieved between the threaded spindle and the sleeve element by a rotary movement of the threaded spindle with a constant speed of rotation. Since the threaded spindle is connected to the screw driving tool and the sleeve element is connected to the collet, different relative speeds are accordingly also achieved between the screw driving tool and the collet.
Since the threaded spindle is, as a rule, fixedly coupled to an electric motor which is arranged in a fixed position in the housing of the automatic screwing device, it is of advantage, in accordance with the invention, when the screw driving tool executes no feed movement re
Ade Reiner
Listmeier Wolfgang
Wolf Bolger
Meislin D. S.
Townsend and Townsend / and Crew LLP
Weber Schraubautomaten GmbH
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