Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Locking means
Reexamination Certificate
1999-09-03
2001-12-04
Green, Mary Ann (Department: 3682)
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Locking means
C074S08400R
Reexamination Certificate
active
06324943
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an indexing drive having a mechanism for positioning a cam relative to roller followers mounted on a follower wheel.
2. Description of the Related Art
The indexing drives are a power transmitting device whose input shaft is driven to rotate at a given speed to thereby cause its output shaft to make intermittent rotational movements such that the output shaft stops rotating every predetermined rotational angle. One popular type of conventionally-known indexing drive is shown in
FIGS. 11 and 12
, where a continuous rotational movement of the input shaft is converted via a cam mechanism into intermittent rotational movements of the output shaft.
Specifically,
FIGS. 11 and 12
are side sectional and front sectional views, respectively, of the conventionally-known indexing drive A
1
, which show the interior construction of the indexing drive A
1
. Within a housing A
2
having a hollow box-like shape, there are contained a cam A
4
fixedly mounted on a cam shaft A
3
functioning as the input shaft, and a follower wheel A
6
fixedly mounted on the output shaft A
5
. A plurality of roller followers A
7
engageable with the cam A
4
are provided on the follower wheel A
6
at equal intervals along the outer peripheral surface of the wheel A
6
.
As shown in
FIG. 11
, holes H
1
and H
2
are formed in a pair of opposed side walls (i.e., front and rear walls) of the housing A
2
, and output-shaft-bearing holders A
8
and A
9
are fitted in these holes H
1
and H
2
, respectively. The bearing holders A
8
and A
9
have flanges F
1
and F
2
, respectively, which project outward of the bearing holder fitting holes H
1
and H
2
. The output-shaft-bearing holders A
8
and A
9
are secured at their respective flanges F
1
and F
2
to the walls of the housing A
2
via bolts A
10
.
The output shaft A
5
is rotatably supported in the housing A
2
via bearings A
11
and A
12
held in the bearing holders A
8
and A
9
. Further, two shims S are sandwiched between the housing A
2
and the flanges F
1
and F
2
of the bearing holders A
8
and A
9
, in order to adjust the axial position of the output shaft A
5
relative to the housing A
2
and set preloads on the bearings A
11
and A
12
.
As shown in
FIG. 12
, other bearing holder fitting holes H of a circular shape are formed in a pair of opposed side walls (left and right side walls) of the housing A
2
extending at right angles to the front and rear walls having the above-mentioned bearing holder fitting holes H
1
and H
2
. Eccentric bearing holders A
14
, each having a flange F
3
, are fitted in these bearing holder fitting holes H and secured to the housing A
2
by means of bolts A
15
. Bearings A
16
are held in the respective eccentric bearing holders A
14
, and the cam shaft A
3
is rotatably supported in the housing A
2
via the bearings A
16
and eccentric bearing holders A
14
.
As shown in
FIGS. 13 and 14
, each of the eccentric bearing holders A
14
has a surface C
2
for fitting engagement with the bearing holder fitting hole H, and this fitting surface C
2
and an outer peripheral surface C
1
of the flange F
3
lie concentrically about a central axis O of the holder A
14
. The flange F
3
has four arcuately-curved elongate recesses h formed at equal intervals along the outer periphery thereof, and each of the bolts A
15
extends through one of the recesses h.
Further, each of the eccentric bearing holders A
14
has a through-hole h
1
through which the cam shaft A
3
of
FIG. 12
extends and a bearing retaining hole h
2
in which the bearing A
16
is fitted, and these holes h
1
and h
2
are formed concentrically about and axis O′ displaced from the above-mentioned central axis O by a predetermined distance e. Sealing member G is inserted in the through-hole h
1
to seal between the bearing holder A
14
and the cam shaft A
3
. In generally the same manner as for the output shaft A
5
, a shim S′ is sandwiched between the housing A
2
and the flange F
3
of each of the eccentric bearing holders A
14
, in order to adjust the axial position of the cam shaft A
3
relative to the housing A
2
and set a preload on the bearing A
16
.
In the conventional indexing drive A
1
arranged as set forth above, as the cam A
4
is rotated via the cam shaft A
3
at a given constant speed, each rotation of the cam A
4
causes the roller followers A
7
, engaging with the cam A
4
, to be pushed by the cam A
4
, so that the follower wheel A
6
is allowed to rotate intermittently, a predetermined angle at a time, and such intermittent rotations of the follower wheel A
6
are transmitted to the output shaft A
5
.
The conventional indexing drive A
1
constructed in the above-described manner is normally assembled in the following sequence of steps a)-f):
a) The output shaft A
5
is inserted in place within the housing A
2
to set preloads on the bearings A
11
and A
12
via the shims S.
b) The output shaft A
5
is temporarily removed from within the housing A
2
, and then the cam shaft A
3
is inserted in place within the housing A
2
to set preloads on the bearings A
16
via the shims S′.
c) The output shaft A
5
is installed in the housing A
2
, and axial positioning of the center of the cam A
4
relative to the center of the output shaft A
5
is effected using the shims S′. More specifically, in this step, some special coating is applied to the cam A
4
, and the eccentric bearing holders A
14
, located on opposite sides of the cam A
4
, are turned in the same phase to thereby adjust the direction of displacement of the axis O′ from the central axis O so that the cam A
4
is brought into contact with the roller followers A
7
. Then, accuracy of the axial positioning of the cam A
4
is determined by ascertaining, via the eyes of the human operator, a degree or condition of adherence of the coating material from the cam A
4
onto the roller followers A
7
.
d) The output shaft A
5
is axially positioned using the shims S′ in such a way that the moving trajectory of the roller followers A
7
and the axial center of the cam A
4
substantially coincide with each other. In this step, the special coating is applied to the cam A
4
so that accuracy of the axial positioning of the cam A
4
is determined by ascertaining, via the eyes of the human operator, a degree or condition of the abutting engagement between the cam A
4
and the roller followers A
7
on the basis of adherence of the coating material from the cam A
4
onto the roller followers A
7
, similarly to step c) above.
e) The eccentric bearing holders A
14
, located on the opposite sides of the cam A
14
, are further rotated in the same phase to thereby produce preloads between the cam A
4
and the roller followers A
7
. After that, the special coating is again applied to the cam A
4
so that accuracy of the axial positioning of the cam A
4
is determined by ascertaining, via the eyes of the human operator, a degree or condition of the abutting engagement between the cam A
4
and the roller followers A
7
on the basis of adherence of the coating material from the cam A
4
onto the roller followers A
7
.
f) It is ascertained whether the moving trajectory of the roller followers
7
and the axial center of the cam A
4
coincide with each other. If the moving trajectory of the roller followers
7
and the axial center of the cam A
4
are determined as not substantially coinciding with each other, steps e) and f) are repeated.
However, according to the above-mentioned assembling and position-adjusting operations for the indexing drive, where the once-inserted output shaft has to be temporarily removed from within the housing and then built into the housing again and the relative positioning between the roller followers and the cam has to be performed, on a trial-and-error basis, by checking for uneven abutting engagement between the roller followers and the cam on the basis of adherence of the coating material, there would arise a need to repeat the positioning operations when the abutting
Dann Dorfman Herrell and Skillman, P.C.
Green Mary Ann
Skillman Henry H.
Tsubakimoto Chain Co.
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