Gear cutting – milling – or planing – Planing – Means for cutting groove
Reexamination Certificate
2000-09-29
2001-06-12
Briggs, William (Department: 3722)
Gear cutting, milling, or planing
Planing
Means for cutting groove
C409S334000
Reexamination Certificate
active
06244799
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method and apparatus for manufacturing a plurality of longitudinally extending slots in the bore of a component. One example of such a component is the sleeve element of an automotive power steering rotary valve. More particularly the invention is directed towards sleeve elements having varied slot configurations and the manufacture thereof.
BACKGROUND ART
The prior art most closely related to that of the present invention is that covered by U.S. Pat. No. 5,328,309 (Bishop et al), U.S. Pat. No. 5,292,214 (Bishop et al) and U.S. Pat. No. 5,390,408 (Bishop et al). These prior art references relate to “slotting machines” which 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 on a cutting spindle which angularly reciprocates about an axis in a series of progressively deeper cutting and return strokes so forming a (usually) 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.
Such prior art slotting machines have always been arranged to form each slot longitudinally in the bore surface, which is at the time of cutting furthest from the cutting spindle axis. In view of this and having regard to the arcuate path of the cutting tool during each cutting stroke, the slot has necessarily had a concave floor. This has limited the nature and configuration of the slots that have been able to be formed. The concave slots typically used have been blind-ended, but in some designs the concave slots exit from either or both axial extremities of the sleeve bore surface to provide for oil return from the sleeve.
It has been found that the aforesaid limitations on slot configuration have imposed limitations on design of steering gear valves and an object of the invention is to alleviate that situation.
SUMMARY OF INVENTION
In a first aspect the present invention is a machine for machining slots longitudinally disposed within the bore of a sleeve, comprising a work holding device for holding said sleeve, at least one cutting tool mounted on a cutting spindle, the axis of said cutting spindle being offset from and substantially at right angles to the axis of said sleeve, means of supporting said cutting spindle for angular reciprocation to effect cutting strokes of said tool relative to the surface of said bore, infeed means to permit said cutting tool to execute a succession of progressively deeper cuts in relation to said bore of the sleeve, characterised in that when said cutting tool is cutting at least one of said slots, the cutting tool engages the surface of the bore at a location substantially closest to said axis of the cutting spindle.
Preferably the cutting operation takes place in a substantially diametral plane and the location closest to said axis of the cutting spindle therefore lies in this substantially diametral plane. Preferably the cutting tool is adapted to effect a convex path with respect to the surface of the bore which it is engaging.
In a second aspect the present invention is a machine for machining slots longitudinally disposed within the bore of a sleeve, comprising a work holding device for holding said sleeve, at least one tool head carrying cutting means, said tool head mounted on or integral with a cutting spindle, the axis of said cutting spindle being offset from and substantially at right angles to the axis of said sleeve, means of supporting said cutting spindle for angular reciprocation to effect cutting strokes of said cutting means relative to the surface of said bore, infeed means to permit said cutting means to execute a succession of progressively deeper cuts in relation to said bore of the sleeve, characterised in that said cutting means comprises of two or more independent cutting tools.
Preferably in a first embodiment at least one of the cutting tools is adapted to effect a convex path with respect to the surface of the bore which it is engaging.
Preferably in a second embodiment at least one of the cutting tools is adapted to effect a concave path with respect to the surface of the bore which it is engaging.
In a third aspect the present invention is a one piece sleeve for a rotary valve, the sleeve comprising an array of communication slots formed in the bore of the sleeve, characterised in that at least a portion of the floor of one of said slots is convex.
Preferably in one embodiment the slot having a convex floor portion is a return slot which extends longitudinally to at least one axial extremity of said bore surface.
REFERENCES:
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Arent Fox Kintner & Plotkin & Kahn, PLLC
Bishop Steering Pty Limited
Briggs William
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