Note: Descriptions are shown in the official language in which they were submitted.
6~
A hand holdable gauge is provided for measuring -the
pitch of gear teeth on a gear wheel or rack, and a method for
using the ~auge on a gear whee] wherein the outside diameter
of the gear is eccentric.
During the manufacture of gears and in servicing
gears in the Field it is often desirable to check Eor wear
or irregularity in the teeth~ as denoted by variations between
the pitch o* the teeth.
Prior hand held instrumentation has comprised a
highly precise scientific instrument of Swiss manu~acture
wherein the datum setting of the gear is provided by straddling
the instrument over a tooth to provide precise indexing on
both flanks of the tooth. Owing to variations in tooth
thickness which can readily occur, this can displace the
gauge radially, to produce a false reading, owing to non-
adherence to the reference circle initially selected. The
reference circle normally selected is the pitch circle of the
teeth.
In addition to undue complexity and impractical
sensitivity, the prior art instrument also is characteri~ed
by high cost and delicacy.
The presently disclosed gauge is a robust, simple
instrument costing about one order less than the known prior
instrument~ and providing acceptable accuracy and
repeatability.
In order to effectively operate the presently dis-
closed gauge in the case of large gears wherein the pitch
line or pitch circle may deviate from parallelism with the
tips of the teeth, there is provided a reference band having a
predetermined width such as one inch, the band being parallel
with the gear pitch line or pitch circle, in the case o~
racks and gear wheels respectively.
,
Thus there is provided a gear system having a
ga~tge for registry with the flanks of -the teeth, including
the steps of providing where necessary a re:Eerence surface
extending parallel with the pitch line o~ the gear teeth, the
gauge including gauge index means for locating the gauge in
pred~termined relation with the reference surface, first
flank index means to engage a predetermined portion of a
first too~h flank in gauge indexing relation, second flank
index means to contact a corresponding portion of a second
tooth flank, and displacement indicating means connected
with the second index means -to provide indication of
variations in the position of the second index means whereb~,
upon relocation of the gauge .in pitch gauging relation bet-
ween another set of teeth, a variation of the displacement
indicating means is representative of the di.~ference in
pitch distance between the two sets of teeth.
The presently disclosed system thereby provides a
method ~or gauging variations in pitch length between sets
of teeth on a gear. Comprising the steps of; providing a
fixed datum band parallel with the pitch line of teeth to be
gauged; mounting a pitch gauge in oriented relation relative
to the datum band, and in contracting relation with the flank
of a tooth proximate the pitch line; contacting a moveable
probe against the corresponding flank of another tooth;
positioning dleflection d~tection means in registering rela-
tion with the moveable probe; relocating the gauge in like
relation with another set of teeth, and recording the
variation of the deflection detection means between the first
and second sets of teeth. Certain embodiments of the gauge
and gauging system are described, reference being made to the
accompanying drawinqs, wherein,
Figure 1 is a general view showing a tooth pitch
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gauge as disclosed he~ein;
Figu.re 2 is a sicle view oE -che gauge mounted on a
gear ~orm;
Figure 3 is a general view of a portion of the rim
of a gear incorporating machined reference bands, and
Figure 4 is a side view of a rack gear, indicating
the presence or reference bands~
Turning to E'igs. l and 2, the pitch gauge 10 is
provided with a base plate 12 with orientation legs 14, 16,
each leg having a respective foot portion 18, 20 thereon.
In the illustrated embodiment, wherein the gauge 10
has a range o~ capability for teeth of difering si~e and
pitch, the legs 14, 16 are adjustable, both as to length and
as to spacing. Thus, the use of slotted base plate 12 and a
tightenable securing screw 22 holding lower plate 24 and
upper plate 26 in releasable sandwiching relation with the
base plate 12 permits the leg 28 to be repositioned in rela- -
tion to the length o the base plate 12 (i~e. along the slot).
The leg 28 has a cylindrical nose portion 30 providing a
radiused surface for contacting the tooth flank 32. The
legs 14, 16 are threaded along at least part of their length,
: having respective locking screws 34, 36 to secure the feet
portions 18, 20 a desired distance from the base plate 12 so
as to position and orient the base plate 12 such that the
base plate is generally parallel with the tooth pitch line,
while the probe nose portion 30 contacts the tooth flank 32
proximate the pitch line.
The gauge lO has a pivotally adjustable probe 38
with a cylindrical nose portion 40 for contacting the flank
portion of another tooth proximate the pitch line. The upper
end S0 of probe 38 makes contact wi-th a dial test indicator 52,
generally graduated in mils (0.001 inches)~
The arms of probe 38 are as a general rule of equal
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leng~h, so that displacement or probe nose portion 30 by a
certain amount produces an equal and opposite displacement oE
the remote probe nose portion 50.
Thus, by arranging the gauge on a ~irs-t pair or se-t
of g~ar teeth (not necessarily adjoining each other) such
that the probe noses 30, 40 respectively make contact on the
respective tooth flank closely adjacent to or on the pitch
line, whereby the gauge is stably supported b~ the feet
portions 18, 20, and in this condition setting to zero a
moveable bezel 54 of the dial -test indicator 52, the gauge
is read~ for use. By transferring the gauge to a second
pair or set of teeth any difference in pitch distance PD
between the first and the second set or teeth can then be
read directly off the dial test indicator, in thousandths oE
an inch.
Referring to Fig. 3 there is illustrated a reEerence
band 60 machined parallel with the pitch circle of the gear.
In Fig. 4 the gear is a rack or linear ~ear again having a
reference band 60 machined on one end of the teeth thereof
in a plane parallel with the pitch line.
Alternatively in Figs. 3 and 4, reference bands 65
may be provided on the body o~ the gear. In such instance,
the gauge lO required the provision of suitabl~ extended legs
14, 16, or extensions thereto; in order to position the gauge
10 above the teeth in the manner shown in Fig, 2.
While the gauge lO is illustrated as being
adju~table, it will be understood that a non-adjustable gauge
~a~ be utilized where large quantities of standard gearing
are to be checked.
It is general practice to check a gear against the
advancing tooth flank where driving contact normally occurs.
Furthermore, the pitch distance normall~ checked is a single
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pitch. Although in some instances a multiple pi-tch distance
could be used particularly where higher aCcUrac~l .iS required
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