Worm wheel and method of hobbing same
AssigneeDK-Gleason, Inc.
InventorGene A. Stritzel
Life of this patent
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Abstract
An hourglass worm wheel and method of hobbing same wherein the finished worm wheel (70) includes a mid zone (B) where the root surface and outside helix are cylindrical for a predetermined distance along the axis of the worm wheel. The method forming the mid zone includes a combination radial and axial feeding of a hobbing tool (58) rotating in synchronization with the rotating worm wheel blank (50).
Claims33
An hourglass worm wheel having a longitudinal axis, a generally hourglass-shaped root surface and at least one gear tooth formed thereon, said root surface increasing in diameter from opposite ends of a mid zone which is substantially cylindrical and which cylindrical mid zone extends over a predetermined axial distance.
A gear set comprising:
- (a) an hourglass worm wheel having an axial center lying on a longitudinal axis, and
- (b) a mating helical gear,
- wherein,
- the hourglass worm wheel is formed with a root surface which increases in diameter from opposite ends of a cylindrical portion formed by an axial cut zone of predetermined dimensions spanning the axial center thereof.
In a combination gear comprising an elongated axially extending body formed with a centrally located elongated hourglass worm wheel portion, and spur gear portions integrally formed at either end thereof, and wherein said elongated worm wheel portion is adapted for meshing engagement with a mating helical gear, the improvement comprising:
- a cylindrical root surface and outside helix in an axial cut zone located along the length of the hourglass worm wheel portion, said root surface increasing in diameter from opposite ends of said axial cut zone toward the spur gear portion.
In a vehicle differential assembly of the type which includes a differential case having means for receiving a pair of axle ends together with a pair of side gears coupled to said pair of axle ends for rotation therewith, at least two pairs of combination gears associated with said side gears and rotatably carried by said differential case and arranged such that for each pair, one combination gear of a pair associated with one of said side gears meshes with a second combination gear of the pair associated with the other of said side gears, said first pair of combination gears meshing together via spur gears, each of said combination gears including an hourglass worm wheel portion having an axial center, and provided at either end thereof with spur gear portions, the worm wheel portion being formed with an outside helix and root surface which are of substantially hourglass shape, the improvement comprising:
- a cylindrical root surface and outside helix in an axial cut zone of predetermined dimensions located along the length of the worm wheel portion, and spanning said axial center.
A method of providing lengthwise mismatch between an hourglass worm wheel and a mating cylindrical worm gear without substantial loss of backlash comprising the steps of:
- (a) radially inwardly feeding a finish hobbing tool having a gear tooth form substantially the same as that of the mating cylindrical worm gear toward the radial center of a rough formed hourglass worm wheel;
- (b) while in the radially inward position, axially feeding the finish hobbing tool a predetermined distance in a direction parallel to the longitudinal axis of the hourglass worm wheel to form an axial cut zone spanning an axial center of said worm wheel;
- and
- (c) withdrawing the finish hobbing tool radially outwardly away from the hourglass worm wheel.
A method of hobbing an hourglass worm wheel comprising the steps of:
- (a) mounting an elongated worm wheel blank for rotation about its longitudinal axis, said worm wheel blank having radial and axial centers;
- (b) providing a cylindrical hobbing tool rotatable about an axis perpendicular to the axis of rotation of the blank;
- (c) rotating the worm wheel blank and the hobbing tool in synchronized relationship;
- (d) plunge cutting the blank by radially inwardly feeding the hobbing tool toward the radial center of the blank;
- (e) while in its radially innermost position axially feeding the hobbing tool in a direction parallel to the longitudinal axis of the blank to form an axial cut zone spanning the axial center of said worm wheel;
- and
- (f) withdrawing the hobbing tool radially outwardly away from the blank.
Dependencies are inferred from the claim text.