Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Utility Patent
1999-04-09
2001-01-02
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
C074S424830
Utility Patent
active
06167769
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a screw mechanism in which reciprocating movement of a shaft is converted into rotary movement at the output of the screw mechanism and particularly relates to the connection between the reciprocating shaft and a rotatable rod for producing rotary movement.
It is already known to provide a shaft with at least one helix on its outer surface and to insert the shaft into a sleeve having at least one corresponding driver. The shaft is mounted securely against rotation by means of a groove or a square and the shaft can be moved only axially. By contrast, the sleeve is secured against axial displacement and rotates about its central axis upon axial movement of the shaft. In this case, the transmissible torque depends essentially on the diameter of the shaft or sleeve. If it is a large diameter, the available torque is generally sufficient. However, matters become critical when the diameter becomes small and a relatively large torque nevertheless has to be made available. In many cases, the available torque is insufficient. Since the influence of friction also increases for relatively small shaft diameters, this can cause stoppage of the rotary movement of the sleeve and can thus cause operational failures.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a screw mechanism which produces sufficient torque even with the screw mechanism at small dimensions.
A screw mechanism of the invention includes a reciprocating rod, which does not rotate on its axis, coupled to a round slide which rotates but does not reciprocate, and which meet at the adjacent ends of each element through a helical connection. The screw mechanism is distinguished in that, at the round slide at the output of the screw mechanism, it is possible to tap a torque which is substantially greater than is obtainable with a known screw mechanism, even with a large stroke of the reciprocating rod because the transmission of force is performed from a reciprocating rod onto the round slide over elongate, axially extending, engaging guide surfaces, which are formed over relatively large overlapping contact surfaces of the engaging guide surfaces. It is particularly advantageous that the guide surfaces can be of relatively large or elongate construction even with a small shaft diameter, and thus it becomes possible to transmit a relatively large torque with a small shaft diameter.
In a preferred embodiment, the reciprocating rod has means with which the reciprocating rod is guided predominantly in the axial direction. This means can, for example, be a groove which runs in the axial direction and into the circumference of the reciprocating rod. As an alternative, it is also possible to provide a profiled edge along the rod. In this case, the reciprocating rod can be constructed as a four cornered shaft with a rectangular cross section, or the like. In order to increase the angle of rotation of the round slide, it has also proven favorable for the groove or profiled edge of the reciprocating rod to be constructed in the form of a helix running around and axially along the circumference of the reciprocating rod. If the helix is arranged in the sense of rotation of the round slide, the result is a substantially larger angle of rotation due to a stroke of the reciprocating rod than if the groove or profiled edge is axially parallel, since the reciprocating rod is simultaneously rotated in the direction of rotation during a stroke and the rotary movement of the round slide is supported and increased by the process.
It is also advantageous that the guiding groove is arranged on the reciprocating rod in the axial region of its guide surface. Consequently, the design for the reciprocating rod can be relatively short, with the result that the screw mechanism overall has a compact design.
In a further embodiment of the screw mechanism, an axial bore is provided in the reciprocating rod and the round slide. This axial bore has relatively little influence on the transmission of force. On the other hand, it is possible to insert a sliding rod in the bore, for example to stabilize the arrangement. A sleeve serving to guide the reciprocating rod and the round slide is then no longer required for the screw mechanism.
Alternatively, it is beneficial to arrange a spring, for example a return spring, in the bore, so that the rotary movement of the round slide is supported upon an oscillating stroke of the reciprocating rod.
Since the screw mechanism can be designed very compactly, for example as a cartridge, it is also possible to arrange a plurality of such screw mechanisms tightly next to one another in a tool. It is advantageous to construct screw mechanisms in an oppositely rotating fashion. An appropriate pin, preferably on the rotating disks of two round slides arranged next to one another, can limit the angle of rotation in a simple way.
Since the screw mechanism is finished in a very compact way owing to the short design, it is advantageously possible to use any drive sources. For example, the reciprocating rod is driven via a piston rod or is constructed directly as a piston which is driven by a pressure cylinder.
It is also regarded as favorable that the drive for the rotary movement can be freely selected. The screw mechanism can thereby be used universally.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 5601121 (1997-02-01), Bonacina
patent: 5937699 (1999-08-01), Garrec
Fenstermacher David
Mapal Fabrik f{umlaut over (u)}r Pr{umlaut over (a)}zisionswerkz
Ostrolenk Faber Gerb & Soffen, LLP
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