Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Patent
1986-04-23
1987-11-03
Kannan, Philip C.
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
744248R, 74661, 74841, 464 79, F16H 2902
Patent
active
047036664
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF INVENTION
The invention relates to a linear drive device with two motors firmly arranged relative to each other, one driving a nut, the other driving a screw spindle. Such drive devices with two firmly arranged motors are known from Swiss Pat. No. 647,305. In these known drive devices the screw spindle is always arranged rotatably, but axially fixed, whereas the axial displacement movement of the nut is led to the exterior of the device. This type of construction has been chosen in order to obtain a favorable relationship between the maximum stroke and overall length.
If such a linear drive device is designed to perform fast movements with a small stroke, which can be achieved by electronic control of the motors, the mass to be moved is important. According to the invention the moving mass can be reduced by holding the motor-driven nut axially firmly, whereas the other motor drives the screw spindle by means of a non-rotatable but axially movable coupling element.
It is advantageous to use in a drive device with a small stroke a coupling element having a rigid driving part and a membrane serving as power take-off part connected therewith. By means of such a coupling element, which allows but only a small stroke, the axially moving mass is further reduced because only the membrane is deformed.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing a few embodiments of the invention are represented simplistically:
FIG. 1 shows an axial section of a drive device with axially aligned motors;
FIG. 2 shows an axial section of a drive device with juxtaposed motors; and
FIGS. 3 and 4 show axial sections of drive devices with axially aligned motors of which one has a hollow shaft.
DETAILED DESCRIPTION OF THE DRAWING
The linear drive device according to FIG. 1 functions with two motors arranged in a housing G. Motor M1 drives a nut 10, whereas motor M2 drives a screw spindle 20. The nut 10 is axially firmly, but rotatably mounted. To this purpose it is connected firmly with the shaft of motor M1 and additionally supported axially by means of the axial bearing 11.
Motor M2 drives the spindle 20 by means of an axially movable coupling element which is designated with the numerals 21 as a whole.
In the represented embodiment this coupling element consists of a platelike driving part 22 connected with the shaft of motor M2 and an annular, undulated membrane 23 attached at the edge of part 22. The membrane serves as driving part and is provided with a centrally disposed hub which establishes the connection to the screw spindle 20. To the extent of the stroke permitted by the elastic deformation of membrane 23, the spindle 20 is therefore axially movable.
The axial displacement or stroke of the spindle occurs with simultaneous rotation thereof. This movement is led to the exterior of the housing with the aid of an axial bearing 24 in a sled 25 which is axially guided by means of bars connected exteriorly with a traverse 27.
As results from the previously described construction of the drive device the membrane allows only a relatively small stroke of the traverse 27. Of course the stroke could be increased by use of a coupling element with a coupling sleeve and an axially movable core piece therein. However, this would increase the mass of the parts to be moved, which is a disadvantage for rapid reciprocating motions.
The drive device is used namely in a machine tool for movement of a working tool with variable stroke and variable frequence. According to the invention the number of revolutions per time unit is controlled electronically relatively to each other, according to the working pattern.
An important field of use is the superfinish of internal combustion engine pistons which are superfinished according to a certain working pattern. Its originally exclusively cylindrical form is transformed into a slightly embossed and at the same time not circular form. If this superfinish is performed on a lathe, the lathe tool has to be moved to-and-fro at each revolution of the work piece by a small amou
REFERENCES:
patent: 2481477 (1949-09-01), Peery
patent: 2630022 (1953-03-01), Terdina
patent: 2882503 (1959-04-01), Huff et al.
patent: 3202009 (1965-08-01), Geyer
patent: 4373404 (1983-02-01), Heinz
Farley Walter C.
Kannan Philip C.
Lars International S.A.
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