Apparatus and method for incrementally rotating a shaft

An apparatus and method for incrementally advancing a shaft by a selected rotational amount. The apparatus includes a belt trained about a pair of space driven pulleys, the belt forming both first and second runs between the pulleys. Each pulley is associated with a shaft and is mounted for rotation in one direction only, with brake means designed to resist rotation of the pulley in the opposite direction. Means are provided for alternately deflecting the first and second runs of the belt to advance each shaft by an incremental amount in the one direction. In this manner, either or both shafts can be used for whatever purposes an incrementally advancing shaft is needed or desired.

BACKGROUND AND SUMMARY OF THE INVENTION 
This application relates to an apparatus and method for incrementally 
advancing a shaft by a selected rotational amount. There are numerous 
instances in both mechanical and electrical applications where it becomes 
either necessary or desirable to incrementally advance a shaft by a 
selected rotational amount. 
The present invention provides what is believed to be a simple and yet 
efficient apparatus and method to incrementally advance a shaft by a 
selected rotational amount. The invention provides for incremental 
advancing of a shaft by means of a drive mechanism which can be 
continuously operated and which coacts with the remaining elements to 
result in periodic incremental rotation of the shaft. The invention 
further provides for ready adjustability of the amount of incremental 
rotation. 
According to one aspect of the invention, a belt is trained about a pair of 
spaced driven pulleys, the belt forming both first and second runs between 
the pulleys. Each driven pulley is associated with a shaft and is mounted 
for rotation in one direction only, with brake means designed to resist 
rotation of the pulley in the opposite direction. Means are provided for 
alternately deflecting the first and second runs of the belt from their 
normal pulley-to-pulley paths to advance each shaft by an incremental 
amount in the one direction. The pulleys are rotatable in the same hand, 
i.e., clockwise or counterclockwise. Then, by deflecting the belt 
laterally of its initial track, e.g., by drawing the belt between the 
pulleys on either run, a length of belt must draw off of at least one 
pulley. However, since neither pulley can reverse, and since both have the 
same orientation, only one will rotate and allow the belt to move. Hence, 
that one pulley and shaft is rotated. The degree of rotation is determined 
by the extent of belt deflection. Then, by removing the deflecting force 
from the first run, while applying a deflecting force on opposite run, the 
other pulley and shaft are rotated a like amount. In this manner, either 
or both shafts can be used for whatever purposes an incrementally 
advancing shaft is needed or desired. 
According to the preferred embodiment the means for alternately deflecting 
the first and second runs of the belt includes a first means in engagement 
with the first run of the belt and adapted to continuously apply a first 
deflecting force against the first run of the belt having a component 
which is normal to the surface of the belt. There is also provided a 
second means for periodically applying a second deflecting force to the 
second run of the belt and in a direction having a component normal to the 
surface of the belt for alternately deflecting the first and second runs 
of the belt to advance each shaft by an incremental amount. The magnitude 
of the deflecting travel of the second deflecting means is adjustable so 
as to adjust the amount of incremental advancement which is effected. 
The present invention further provides a method of incrementally advancing 
a shaft. A pair of driven pulleys are each associated with a respective 
shaft and a belt is trained about the pulleys. The pulleys are mounted for 
rotation in one direction and are locked against rotation in an opposite 
direction. The degree of deflection of the first and second runs of the 
belt is alternately increased and decreased in order to advance each of 
the shafts by a selected incremental amount in the one direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As noted above, the present invention relates to an apparatus and method 
for incrementally advancing a shaft by a selected rotational amount. The 
following description sets forth the details of the preferred apparatus 
for effecting such incremental rotation of a shaft. It is believed that 
the many and varied uses to which such incremental shaft rotation can be 
put, as well as the various ways in which such shaft rotation can be 
achieved in accordance with the principles of the present invention will 
become readily apparent to those of ordinary skill in the art. 
In FIGS. 1 and 2 a fixed support member 10 includes a first pair of 
vertically extending spaced apart standards 12, 14 having a shaft 16 
journaled therein for rotation in a manner to be set forth more fully 
hereinafter. A second pair of vertically extending standards includes 
vertically upstanding standard 18. This second pair of vertically 
upstanding standards supports a second shaft 20 in spaced relation to 
shaft 16. 
A pair of spaced apart pulleys are provided, each of which is mounted on a 
respective one of the shafts 16, 20. Referring to FIGS. 1 and 2, pulley 22 
includes an integral collar 24. The shaft 16 passes through a central bore 
in the pulley 22 and the collar 24, and a locking screw 26 serves to 
clampingly engage the collar 24 and pulley 22 with the shaft 16 so that 
they are rotatable together. The mounting of the second pulley 28 on the 
shaft 20 is effected in a similar manner. Of course, there are various 
other obvious ways that the pulleys 22, 28 could be connected with their 
respective shafts, as will be readily apparent to those of ordinary skill 
in the art. 
Each of the pulley shafts is mounted for rotation in one direction only, 
with rotation in the other direction being substantially blocked. 
Referring to FIG. 3, shaft 16 includes a collar 30 which is fixed thereon 
and which is journaled for rotation in standard 14. A fixed ring 32 is 
provided in fixed relation to the standard 14, and includes a series of 
locking cam surfaces 33 facing inwardly toward the collar 30 and each 
terminating in a locking tooth 34. Between the collar and the ring 32 
there are provided in plurality of locking members in the form of rollers 
36 disposed between the ring 32 and the collar 30. The diameter of the 
rollers 36 is large enough so that they cannot move in a clockwise 
direction beyond their respective locking teeth 34, and as the shaft 16 
attempts to rotate in a counter-clockwise direction the rollers become 
jammed between the collar 30 and their respective cam surfaces 33 on the 
ring 32. Thus, as shaft 16 rotates in a clockwise direction, as shown by 
the arrow in FIG. 3, collar 30 rotates therewith and rollers 36 remain 
lodged in substantially the position shown in FIG. 3 and in which position 
they do not interfere with rotation of shaft 16. If forces were applied 
tending to rotate the shaft 16 in the opposite, i.e., counter-clockwise, 
direction the rollers 36 would instantly become jammed between the cam 
surfaces 33 of ring 32 and collar 30, thus locking collar 30 and shaft 16 
against rotation in the counter-clockwise direction. Similar structure is 
associated with shaft 20, so that both shafts 16 and 20 are free to rotate 
in the clockwise direction but are blocked against rotation in the 
counter-clockwise direction. 
The mechanism above-described constitutes a one-way brake mechanism for 
each of the shafts, and various types of conventional one-way brake 
mechanisms can be substituted if desired, as will be readily understood. 
A belt 40 is trained about both pulleys 22, 28. Belt 40 is a continuous 
fixed length substantially nonstretchable belt and includes a first, or 
lower, run 42 and a second, or upper, run 44 between the pulleys 22, 28. 
In accordance with the invention the pulleys, and thereby the shafts 16, 20 
are rotated in a clockwise direction by an incremental amount by 
alternately increasing and decreasing the amount of deflection of the 
first and second runs of the belt 40. A standard 46 is fixed to support 10 
and pivotally mounts an L-shaped member 48. One end of the L-shaped member 
48 rotatably mounts a roller 50. The other end of the L-shaped member is 
biased by means of a spring 52 in a clockwise direction bringing roller 50 
into engagement with the first run 42 of belt 40 and with sufficient force 
to force the first run of the belt inwardly and thereby to apply a 
continuous force against the first run 42 of the belt sufficient to hold 
it consistently taut. 
Further, according to the invention, there is provided a means for 
alternately deflecting the second run 44 of the belt to incrementally 
advance the shafts 16, 20 by a selected rotational amount. This means 
applies sufficient force to the belt to overcome the bias of the spring 
52, thereby allowing the run 44 to deflect by an amount determined by the 
travel of its deflecting means. Referring to FIG. 1, the means for 
alternately deflecting the second run of the belt includes a drive member 
54 formed by a shaft 56 having a roller 58 at its lower end. A fixed 
support 60 allows the shaft 56 to move vertically as shown in FIG. 1 but 
constrains the shaft 56 against movement in any other direction. Moving 
the shaft 56 in a downward direction causes the roller 58 to apply a 
downward force on the upper run 44 of the belt. This force on the upper 
run 44 tends to draw run 44 toward the space between the pulleys but, 
since pulley 28 cannot rotate counter-clockwise, the belt will rotate only 
the pulley 22. The force on the upper run 44 overcomes the deflection 
provided through spring 52 and causes belt movement around pulley 22 and 
serves to rotate pulley 22 and shaft 16 in a clockwise direction. Since 
the belt runs are at substantially equal tension at all times, there is, 
of course, no unbalanced force tending to rotate pulley 28 in a clockwise 
direction, and it remains stationary. As shaft 56 is moved in an upward 
direction, the deflection provided by spring 52 and roller 50 against the 
lower run 42 causes a drive for pulley 28 similar to the drive action 
described for pulley 22. The return drive of roller 50 serves to keep the 
belt taut by deflecting the bottom run 42 and thereby rotating only the 
pulley 28 and shaft 20 in a clockwise direction. Thus, the combination of 
the constant bias on lower run 42, and the alternate deflecting and 
withdrawal motion applied to the upper belt run 44 serves to rotate shafts 
16, 20 alternately in a clockwise direction and by a selected incremental 
amount. Because the shafts are mounted in the manner set forth above they 
are blocked against rotation in a counter-clockwise direction. 
One arrangement for axially shifting the shaft 56 is shown in FIG. 1, and 
includes a lever 62 which is oscillated through a predetermined angle in 
any well-known manner. The pin and slot connection between shaft 56 and 
lever 62, along with the mounting of shaft 56 in the fixed support 60, 
translates the oscillation of lever 62 into linear oscillating movement of 
shaft 56 in an up and down direction. 
The preferred embodiment of this invention further provides for adjusting 
the amount of rotation of the pulleys 22, 28 during each increment of 
movement. In FIG. 1, shaft 56 includes a pair of sections 64, 66 which are 
interconnected by a turnbuckle 68. This allows adjustment of the length of 
shaft 56 in a well-known manner, and thereby provides a means for 
determining what portion of the shaft stroke will be in interfering 
relationship with the belt, and hence determining the maximum degree of 
deflection attained at maximum throw of the lever 62. Put another way, 
this adjustment may be said to control the effective stroke of the belt 
deflecting means. Thus the amount of belt deflection, and the resulting 
amount of incremental rotation of the shafts 16, 20 and of the pulleys, 
can be readily adjusted. 
The present invention further contemplates many other forms of apparatus 
for deflecting the upper belt run 44. One such alternate arrangement is 
shown in FIG. 4 wherein is provided a roller 70 which is eccentrically 
mounted with respect to shaft 72 on an arm 74. As shown in FIG. 4, the arm 
74 is rotated in a constant (e.g., clockwise) direction and this constant 
rotation periodically brings the roller 70 along a path in which it 
engages upper belt run 44 and serves to deflect it. In other positions of 
rotation the roller 70 is out of contact with upper belt run 44 thus 
serving to allow restoration as a result of the bias of spring 50 (FIG. 
1). 
It will be understood, of course, that the length of arm 74 can also be 
made adjustable so as to control the amount by which the pulleys 22, 28 
are incrementally rotated, as discussed above in connection with the 
adjusting means 68 of FIG. 1. 
As will be readily appreciated from the foregoing description, the present 
invention further provides a method for intermittently advancing the 
shafts 16, 20 by predetermined increments. The application and withdrawal 
of a deflecting force to the upper belt run, along with the continuously 
applied deflecting bias in the lower belt run serves to alternately 
deflect the first run and the second run of the belt 40, and thereby serve 
to intermittently rotate the shafts 16, 20 and their pulley in the same 
direction by predetermined increments. 
In view of the foregoing description, it is believed that many and varied 
obvious modifications of the principles of the present invention will 
become readily apparent to those of ordinary skill in the art.