Note: Descriptions are shown in the official language in which they were submitted.
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0 8 1 0 61 -MPI!I
POWDERED METAL PINION GEAR
Description
Powder metallurgy is one of the lowest cost, mass
production methods of manufacturing high quality,
strong, complex parts with the substantial elimination
of subsequent machining or finishing steps. Also,
powder metallurgy reduces or eliminates material and
scrap losses. This type of manufacture is particular-
ly suited to the formation of gears, sprockets, hubs
and other semi- or non-structural parts where casting
or forging of these parts requires extensive machin-
ing after the forming operation.
A pinion or side gear for a screw jack or similar
device has been manufactured previously by cold
working or forming the head and gear teeth and back
extruding the shank. Such a process is disclosed in
U. S. Patent Nos. 3,862,577 and 3,895,422. The method
of making a pinion gear involves the steps of cold
forming preliminary tooth shapes on the end of a sized
blank, forming an enlarged collar and final tooth
shapes, back-extruding a cylindrical skirt to form a
shank for the gear, and crimping the end of the skirt
to form a non-circular opening. The present invention
provides a simplified manufacture of a si`de or pinion
gear from powdered metal.
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~ ccording to the present invention there i.s
provided a centered powdered metal side gear for use in a
screw jack or the like including a cyllndrical shank having
a flat surface at one end and terminating in an enlarged
generally cylindrical head at the opposite end. A planar
face is provided on the head and a plurality of gear teeth
radiate from a central hub projecting from the planar face.
Each tooth has convex flanks merging into an inclined edge
extending to and intersecting the upper edge of the tooth.
The shank has a passage extending axially from the flat end
to terminate at the enlarged head. The passage is defined
by a pair of parallel flat side walls joined by a pair oE
opposed arcuate surfaces. The gear is formed from a sub-
stantially iron powder briquetted to final shape in a single
stroke under a pressure of approximately 35 tons per square
inch and sintered.
It is an object of the present invention to
provide a powdered metal pinion gear for a screw jack or
similar device which is able to withstand the high stresses
encountered during operation of the screw jack to raise a
relatively heavy vehicle.
The powdered metal pinion of the invention may
have an accurate involute shape on the gear teeth for
cooperating with complementary teeth on the bottom gear
which provides lower jack handle stress to raise the jack
under load.
Further objects are to provide a construction of
maximum simplicity, efficiency, ecomony and ease of manu~
facture, and such further objects, advantages and capabi-
lities as will later more fully appear and are inherently
possessed thereby.
One way of carrying out the invention is described
in detail below with reference to drawings which illustrate
only one specific embodiment, in which:-
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081061-MPM - 3 -
Figure 1 is a side elevational view of the side
or pinion gear of the present invention.
Figure 2 is an end elevational view of the pinion
gear taken from the right hand end of Figure 1.
S Figure 3 is an end elevational view taken from
the left-hand end of Figure 1.
Figure 4 is a horizontal cross sectional view
taken on the line 4-4 of Figure 1.
Figure 5 is a side elevational view of the pinion
gear shown in its working relationship in a screw
jack.
Referring more particularly to the disclosure in
the drawings wherein is shown an illustrative embodi-
ment of the present invention, Figure 5 discloses a
fragmentary portion of a screw jack 10 for a truck or
other vehicle having a base 11 supporting a bottom
gear 12 for rotation thereon, and a housing 13 extend-
ing upwardly from the base and having a side pinion
housing or journal 14 extending outwardly and upwardly
at a slight angle to horizontal. The housing 14 has a
shoulder 15 and rotatably receives a side or pinion
gear 16 therein. An eiongated jack handle 17 acts to
rotate the side gear 16 which engages and rotates the
bottom gear 12 so as to rotate the screw member 18 to
raise or lower a load men~er 19.
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The pinion or side gear 16 includes a cylindrical
shank 21 terminating at one end in an enlarged circu-
lar head or collar 22 defining a rear shoulder 23 and
having a planar end face 24. A plurality of gear
teeth ~5 are formed on the face 24 radiating from a
central hub 26. Each tooth 25 has convex flanks 27
extending from the central hub 26 and merging into an
inclined outer edge 28, the gear teeth having an
accurate involute shape which cooperate with comple-
mentary teeth on the bottom gear 12 to lower jackhandle stress to raise the load member 19 under load.
The outer surface 29 of the hub and the upper edges 31
of the gear teeth ~orm a substantially flat planar
surface.
The cylindrical shank 21 extends rearwardly from
the head 22 to terminate in a flat end 32, and a
central axially e~tending passage 33 is formed in the
shank to terminate short of the head. The passage 33,
as seen in cross section, includes a pair of opposite-
ly disposed arcuate sur~aces 34 and a pair of parallel
flat surfaces 35 forming a non-circular openingO A
circular passage 36 perpendicular to the flat surfaces
35 extends diametrically through the shank. In use, a
jack handle of a non-circular cross section is adapted
to be inserted in the passage 33 in the shank and has
a bent end (not shown~ that extends into the opening
or passage 36, on one side of passage 33, such that
the handle can push or pull the screw jack 10 away
from or toward the operator and can rotate the side
gear to raise or lower the load member 19.
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The powdered metal gear is formed from an iron
powder mixed with 2~ by weight copper powder and
having 0.8% by weight carbon. The powders are blended
together and briquetted to final shape, including the
axial passage 33, in a suitable press at a pressure of
approximately 35 tons per square inch. The blended
powder is compacted in a single stroke to a density in
the range of 6.6 to 6.8 grams per cubic centimeter.
The formed side gear is then sintered in a furnace at
a temperature in the range of 202~ to 2060F. The
furnace contains a preheat zone, a heating zone and a
cooling zone, with the total time elapsed for the
part travelling through the furnace on a conveyor of
2-1/2 hours. After cooling, the transverse circular
passage 36 intersecting the axial passage 33 is
drilled through the shank 21.
The formation of the side or pinion gear from
powdered metal not only simplifies the manufacture of
the gear but also eliminates the necessity of a
powdered metal bearing that was required for the cold
worked gear previously used between the enlarged
collar or head and the side housing or journal.
