Gear cutting – milling – or planing – Planing – Means for cutting groove
Patent
1993-04-27
1994-03-08
Briggs, William
Gear cutting, milling, or planing
Planing
Means for cutting groove
409334, B23D 500
Patent
active
052922146
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an apparatus for manufacturing a plurality of parallel, longitudinally extending slots in the bore of a component. One example of such a component is the sleeve element of an automotive rotary power steering valve in which the slots are usually blind-ended and form a series of hydraulic ports circumferentially spaced within the sleeve bore, and which operate, in conjunction with similar circumferentially spaced ports in a co-acting cylindrical input-shaft element housed within the sleeve, upon slight relative rotation between these components. The present invention will be in particular reference to such sleeves even though it will be understood that it has wider application in the manufacture of parallel, longitudinally extending internal slots in the bore of components generally.
The prior art which is most closely related to that of the present invention is disclosed in Bishop U.S. Pat. No. 4,154,145 and Australian Provisional Patent Application PK3520 (Bishop). These so called "slotting machines" machine the slots in the bore of power steering valve sleeves. The design of these machines calls for each of the slots to be scooped out of the bore of a turned blank by a finger-like cutting tool mounted in a cutting spindle which angularly reciprocates about an axis in a series of progressively deeper cutting and return strokes so forming a closed chamber, or hydraulic port, which is arcuate in longitudinal section. The sleeve is held in a work holding collet, in turn mounted in a work holding spindle, having a rotational axis perpendicular to and offset with respect to the cutting spindle axis. By accurately indexing the work holding spindle upon completion of each slot, the required number of slots are precisely machined in the sleeve, usually 4, 6 or 8 slots for most automotive applications.
Slotting machines are designed such that the path of the cutting tool return stroke lies completely inside the circumference of the sleeve bore. This is highly desirable from a metal cutting viewpoint since it avoids "scuffing" the sides of the cutting tool tip, and hence promotes maximum tool life. This relieving action of the cutting tool during its return stroke, combined with the earlier referred to progressive infeed of the cutting tool during the cutting of each slot, is achieved by a "flying" bell crank mechanism combined with a spindle carrier arrangement.
The bell crank moves in space under the action of two cams. The first cam is arranged to rotate at high speed synchronously with the angular reciprocation of the cutting spindle and hence controls the relieving action of the cutting tool. This synchronisation is achieved by driving the cutting spindle via a connecting rod extending from a crank arranged on the shaft supporting this relieving cam. The second cam rotates at relatively low speed and controls the cutting tool infeed. The bell crank geometrically adds the inputs from these two cams and imparts its output via a lever integral with an oscillating spindle carrier. The cutting spindle is eccentrically housed within this spindle carrier, hence the output from the bell crank applied to the lever of the spindle carrier rotates the spindle carrier through a small angle and varies the aforementioned offset distance between the cutting spindle and work holding spindle axes. This mechanism provides progressive infeed of the cutting tool during the cutting of each sleeve slot together with a cyclic relieving of the cutting tool during each return stroke.
The two cam followers on the bell crank are held in contact with their respective cams by a spring which applies a turning moment to the spindle carrier so as to maintain contact between the cams and their respective followers at all times, otherwise the motion of the bell crank and the kinematics of the entire mechanism would be indeterminate.
Although elegant kinematically, use of a bell crank mechanism to combine cutting tool infeed and relieving actions has placed a major operational limitation on such slotting machines. In ord
REFERENCES:
patent: 2918849 (1959-12-01), Campbell et al.
patent: 4154145 (1979-05-01), Bishop
A. E. Bishop & Associates Pty Limited
Briggs William
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