Use of Ep-shaped joints in farm-machine and compressor building

Abstract

To date, use of moment-transmitting joints with an EP-profile in lieu of splined and keyed joints has been suppressed by lack of specialized highly productive domestic equipment with an acceptable price tag. In this connection, means of implementing conversion of a different kind of moment-transmitting joints to a noncircular profile on the basis of procedures and equipment that exist at establishments involved with the building of farm machinery are under development at the Tashkent State Technical University. The procedure of fabricating splined joints was adopted as a base. The typical procedure for the machining of slotted openings in farm-machine and compressor building consists in pull broaching in a single or several passes and heat treatment with subsequent calibration; in that case, a degree of accuracy corresponding to a quality grade of approximately 9 is attained. After grinding the external surface, splined shafts with a setting along the external diameter are machined on a slot-milling machine with subsequent heat treatment. In the majority of cases, the shafts are not machinod after heat treatment, although more precise splined shafts, which can be subjected to slot grinding, have recently come into increasingly broader use. This operation, however, is not very productive.For the pull broaching of noncircular openings and subsequent machining, it is necessary to work out the design and fabrication procedure for the pull broaches, arbors and gage calibers, the noncircular profiles of which should correspond with an accuracy to quality grades of 6-7. When there are no special grinding machines, various models of back-off lathes and thread grinders are suitable for this purpose. The following scheme is used to form an EP-profile [1]: a rotating shaR is machined by a harmonically oscillating "cutting plane," the oscillation frequency of which exceeds the rotational speed of the shaR by a factor of a whole number equal to the number of faces on the EP-profile. In that case, harmonic oscillations are impart~ to the tool by a cam-eccentric, which is kinematically linked with the rotating mechanism of the shaft being machined. The "cutting plane" is simulated by the face of the grinding wheel on the backing-off lathe, or the periphery of the wheel on the thread grinder. In the latter case, no EP-profile is formed, but rather the equidistance of a sinoid similar to the EP-profile with an accuracy to 0.01-0.02 nan. To generate a profile that approaches as closely as possible the EP-proffle, we can, in this ease, turn the grinding wheel about the axis normal to the shaft being machined by an angle defmed by the dimension of the EPprofile and the width of the grinding wheel. In that case, deviations from the correct profile do not exceed limits corresponding to a quality grade of 6-7, and depend primarily on the machine's precision.The machining of noncircular openings consists mostly in single-pass pull broaching after drilling and fmishing by boring or countersinking. Occasionally, we are restricted only to ...