Mechanical motion control apparatus

There is disclosed herein a mechanical motion control mechanism which in one form may comprise an input shaft drivingly connected to an output shaft in such a manner that continuous rotation of the input shaft produces varying rotational movement of the output shaft characterized by an initial dwell period, an acceleration period, a constant velocity period, a deceleration period and another dwell period. The input and output shafts may be drivingly connected by means of a gear secured to the input shaft which is in meshing engagement with a second gear supported at one end of a pivot arm, the other end of which is secured to the output shaft. Rotational and revolving movement of this second gear is controlled by the interaction of a plurality of cam followers engaging a cam surface so as to allow rotational, revolving, and various desired combinations of such movements in response to rotational movement of the first gear. Alternatively, the input and output shafts may be drivingly connected by sprockets in place of the first and second gears with an interconnecting drive chain, belt or other similar devices. Also, if desired, the first and second gears may be replaced with wheels having circumferential frictional surfaces in mutual driving engagement. In yet another embodiment the input and/or output may be in the form of linear motion in which case the first gear may be replaced with a rack engaging the second gear in such a manner as to produce the above movement period sequence.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates generally to motion control mechanisms and 
more particularly to such motion control mechanisms as are designed to 
provide respective periods of dwell, acceleration and constant velocity. 
The use of gears and shafts to transmit rotational forces which may 
thereafter be converted to linear motion is well known, the same being 
employed in various arrangements of work transfer machinery. In certain 
applications this linear motion is reciprocal in nature employing a 
reversible electric motor or transmission to effect movement in opposite 
directions. Accordingly, mechanisms must be provided to shut off or 
disconnect the driving means from the member being moved so as to properly 
position same within a machine preparatory to an operation being performed 
on a workpiece. As any such movement cannot be stopped instantaneously, it 
is necessary to provide a deceleration period as well as being desirable 
to also provide a dwell period during which rotation of an input shaft 
will produce no rotation of an output shaft so as to enable maximum 
transfer speed and insure accuracy of positioning. 
Accordingly, the present invention provides a mechanical motion control 
mechanism which provides a dwell period, acceleration period, constant 
velocity period, deceleration period and dwell period the relative lengths 
of which may be varied by alteration of the shape of the cam surface. In 
one form, the present invention employs a first gear, sprocket or wheel 
secured to a rotating input shaft which meshingly engages or is otherwise 
drivingly coupled to a second gear, sprocket or wheel supported on one end 
of a pivot arm the other end of which is connected to the output shaft. 
Cam followers are secured to the second gear and engage a stationary cam 
surface so as to control rotational and curvilinear movement of the second 
gear. In another embodiment a rack or the like is provided which is 
drivingly coupled to a gear, sprocket or wheel associated with output 
means upon which suitable cam followers are secured which cam followers 
engage a cam surface so as to control rotational and linear motion of the 
output means thereby providing controlled periods of dwell, acceleration, 
constant velocity, deceleration and dwell. Thus, the present invention 
provides a mechanical mechanism having a minimum number of moving parts 
which is capable of transmitting high torques thereby being operative to 
move massive articles which also provides a dwell period of sufficient 
duration to allow the drive means to be stopped without encountering 
overtravel. The present invention therefore greatly facilitates the 
transfer and positioning of articles such as workpieces within a machine. 
Additional advantages and features of the present invention will become 
apparent from the subsequent description and the appended claims taken in 
conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1 through 3, there is illustrated therein a 
mechanical motion control apparatus indicated generally at 10 in 
accordance with the present invention. The mechanical motion control 
apparatus 10 comprises an input shaft 12 which is rotatably journaled in a 
support member 14 secured to a lower base member 16. A gear 18 is secured 
to one end 20 of the input shaft and is adapted to be rotated thereby. A 
second gear 22 is disposed in meshing engagement therewith, the second 
gear being supported on a shaft 24 which is journaled in one end 26 of an 
output shaft pivot arm 28, the other end 30 of which is fixedly secured 
and adapted to rotate with an output shaft 32. Thus, shaft 24 is supported 
in radial spaced relationship to output shaft 32 which is substantially 
coaxial with the input shaft and is similarly rotatably journaled in 
another portion of shaft support member 14. Shaft support member 14 is 
fixedly secured to a base member 16 which may form a portion of the 
transfer apparatus or other machinery for which the mechanical motion 
control mechanism 10 is adapted to be utilized. 
Secured to the front face 34 of the second gear member is a cam follower 
support arm 36 which projects diametrically outward from opposite sides of 
the second gear member. First and second cam follower members 38 and 40 
are secured to the outer ends of cam follower support arm 36 and are in 
the form of rollers adapted to follow along selective portions of a cam 
surface. 
A front panel member 42 is also provided which has a curvilinear inwardly 
facing edge surface 44 machined thereon which provides the cam surface to 
be engaged by one or both of the cam follower members 38 and 40 provided 
on the cam support arm 36 secured to gear member 22. Cam surface 44 may be 
divided into five portions comprising a first dwell period 46, a first 
acceleration/deceleration period 48, a constant velocity period 50, a 
second acceleration/deceleration period 52, and a second dwell period 54. 
Secured to the opposite end of shaft 24 supported in the output shaft pivot 
arm 28 is a secondary cam follower support arm 56 which has disposed at 
its opposite end a cam follower 58 similar to cam followers 38 and 40 
provided on the cam follower support arm 36. Cam follower 58 is adapted to 
engage camming surfaces 60 and 62 provided on a rear surface member 64 
during dwell periods or possibly end portions of acceleration/deceleration 
movement so as to provide a stabilizing effect to insure proper 
positioning of a workpiece being transferred by the motion control 
apparatus thereby assuring precise locating of the member being moved. In 
order to support the front and back panel members 42 and 64 which provide 
the camming surfaces, a pair of side members 68 and 70 are provided 
extending therebetween and generally perpendicular to the parallel planes 
of the front and back pieces. 
Both dwell portions 46 and 54 as well as constant velocity portion 50 have 
constant radii of curvatures, the radius for the two dwell periods being 
equal. Also, the center of curvature of the constant velocity portion is 
necessarily coaxial with the axis of rotation of input shaft 12. 
Referring now to FIGS. 3 through 6, the operation of the mechanical motion 
control mechanism of the present invention will now be explained in 
detail. We will assume for the purposes of explanation that the mechanical 
motion control apparatus is in a dwell position such as is illustrated in 
FIG. 5 with cam follower 38 engaging dwell portion 54 of camming surface 
44. At time T.sub.1 a driving means which is drivingly connected to input 
shaft 12 is turned on so as to cause accelerating rotational movement of 
input shaft 12 thereby causing rotational movement of gear member 18. 
During the period of time T.sub.1 to time T.sub.2 the rotation of the gear 
member 18 will impart rotational movement to gear member 22 as the 
rotational axis 72 of gear member 22 is positioned at the center of 
curvature of dwell portion 54. Also, cam follower 40 does not engage any 
surface during this period. Thus, both cam followers 38 and 40 are allowed 
to move freely in rotational movement along with gear member 22 providing 
a dwell period 73 during which output shaft 32 remains stationary. At time 
T.sub.2 cam follower 38 enters acceleration/deceleration portion 52 of 
camming surface 44 at which time rotational movement of gear member 22 is 
caused to decrease and be gradually replaced by curvilinear or revolving 
motion of gear 22 with respect to output shaft 32. This acceleration 
period 74 will continue until time T.sub.3 at which time cam follower 40 
will have rotated into engagement with the constant velocity portion 50 of 
the camming surface 44. Thus, at time T.sub.3 both cam followers 38 and 40 
will be in engagement with spaced portions of the camming surface 44 
thereby totally preventing rotational movement of gear member 22 in 
response to the rotational movement of gear member 18 and thereby forcing 
curvilinear motion of gear 22 as the gear member 18 is continued to be 
rotated. This constant velocity period 76 will continue until time T.sub.4 
at which time the leading cam follower member 40 will enter the 
deceleration portion 48 of the camming surface 44. During the period 78 
from time T.sub.4 to time T.sub.5 the leading cam follower 40 will be 
moving into the deceleration portion 48 of the cam surface and the 
trailing cam follower 38 will be moving out of engagement with the camming 
surface 44 and beginning to rotate about the axis of rotation 72 of the 
gear member 22. As the input shaft continues to rotate gear member 18, the 
leading cam follower member 40 will move from the deceleration portion 48 
into the dwell portion 46 during which time the movement of gear member 22 
will become purely rotational in nature. This dwell period 80 will provide 
a sufficient time T.sub.5 to time T.sub.6 during which the driving force 
being applied to the input shaft 12 may be disengaged or turned off 
without concern as to overdriving or inaccurately positioning a workpiece 
being transferred by the mechanical motion control mechanism. 
As is apparent gear 22, being rotatably supported in a pivot arm and having 
an axis of rotation spaced from the axis of rotation of the output shaft, 
rotational movement of gear member 22 will impart no motion whatsoever to 
output shaft 32. Thus, during the periods of dwell 73 and 80 there will be 
no movement of the output shaft even though gear member 22 is rotating in 
response to rotation of gear member 18 secured to the input shaft 12. 
However, during periods of acceleration respective of cam followers 38 and 
40 will cause the rotational movement of gear member 22 to decrease and 
supplement such decreasing rotational movement with curvilinear movement 
thereby causing pivot arm 28 to impart a rotational movement to output 
shaft 32. Once the constant velocity portion 50 of the camming surface 44 
has been entered, there will be no rotational movement of gear member 22 
but rather all such rotational movement will be supplanted with pure 
curvilinear motion thereby causing pivot arm 28 to rotate through an arc 
of approximately 180.degree. as illustrated until such time as a leading 
cam follower 38 or 40, depending on the direction of movement enters the 
deceleration portion 48 or 52 of the camming surface 44. 
Referring specifically to FIG. 3, it will be seen that as cam followers 38 
or 40 enter their respective acceleration/deceleration portions 52 and 48, 
cam follower support arm 56 will be caused to begin rotation due to the 
increasing rotational movement of gear 22. As either cam follower 38 or 40 
moves into respective of dwell portions 54 and 46, cam follower 58 will 
move into engagement with either cam surface 60 or 62 respectively thereby 
acting as a stabilizer to insure proper positioning of a workpiece to be 
thus transported. During the constant velocity portion of movement, cam 
follower support arm 56 will be longitudinally aligned with pivot arm 28. 
It should be noted that while cam follower support arm 56, associated cam 
follower 58 and cam surfaces 60 and 62 provide a steadying function, they 
may be omitted should this be desired for particular applications. 
It should also be noted that the specific shape and contour of camming 
surface 44 may be varied to provide a wide variety of dwell periods, 
acceleration/deceleration, and/or constant velocity periods. For example, 
providing a longer acceleration/deceleration portion may be accomplished 
by lengthening portions 48 and 52 whereas greater or lesser dwell periods 
can be provided by increasing or decreasing the length of portions 46 
and/or 52. The relative size of gears 18 and 22 will also affect the 
duration of dwell and acceleration/deceleration periods as well; that is 
to say, the greater the ratio of the diameter of gear 18 to gear 22, the 
shorter the dwell and acceleration periods. 
Referring now to FIG. 7, there is illustrated another embodiment of the 
present invention indicated generally at 82 which is substantially 
identical to the embodiment of FIGS. 1 through 3, 5 and 6 described above 
with the exception of the driving connection between the input and output 
shaft. Accordingly, corresponding portions thereof are indicated by 
identical numbers primed. In this embodiment, gears 18 and 22 are replaced 
by sprockets 84 and 86 respectively, and a drive chain 88 is provided 
extending around portions of the circumference and between each of 
sprockets 84 and 86 so as to drivingly couple them together. The operation 
and motion produced will be substantially identical as that described 
above and therefore will not be described in detail. It should be noted, 
however, that while apparatus 82 employs a chain 88 and sprockets 84 and 
86, any other suitable drive arrangement may be easily substituted 
therefor such as for example a pair of V-belt sheaves and an 
interconnecting V-belt. 
Further, as illustrated in FIG. 8, another embodiment of the present 
invention is indicated generally at 90 which also is substantially 
identical to the embodiments described above and thus corresponding 
portions are indicated by like numerals double primed. However, in this 
embodiment, gears 18 and 22 are replaced by wheels 92 and 94 which are 
each provided with circumferential surfaces 96 and 98 respectively which 
provide a high coefficient of friction. For example, a circumferential 
surface coating or belt may be provided which has a high coefficient of 
friction and may be easily replaced when worn. In this embodiment 
circumferential surfaces 96 and 98 of wheels 92 and 94 respectively are in 
mutual frictional engagement so as to thereby transmit rotational forces 
between the input and output shafts. 
The present invention may also be easily adapted to provide sequential 
dwell periods, acceleration periods, constant velocity periods, 
deceleration periods, and dwell periods with both linear input and output 
motions. Such an embodiment is illustrated and will be described with 
reference to FIG. 9. 
Motion control apparatus 100 comprises a linear motion input drive means 
such as piston 102 having piston rod 104 extending outward therefrom and 
adapted to reciprocate longitudinally. The outer end 106 of piston rod 104 
is connected to an input carriage assembly indicated generally at 108 upon 
which a rack 110 of suitable length and having upwardly facing 
longitudinally extending teeth 112 is secured. An output gear 114 having 
teeth 116 is mounted in meshing engagement with teeth 112 of rack 110 and 
has a cam follower support arm 118 fixedly secured to a side surface 119 
thereof. Output gear 114 may be rotatably supported or mounted upon any 
desired output means (not shown) such as a carriage assembly or the like 
which is desired to be longitudinally reciprocated and which may be 
designed to carry a workpiece thereon. 
Cam follower support arm 118 is generally T-shaped having outwardly 
projecting legs 120, 122 and 124 each of which is provided with cam 
followers 126, 128, and 130 respectively secured to the outer ends 
thereof. 
A cam surface 132 is provided having a relatively straight longitudinally 
extending surface portion 134 which is adapted to be engaged by cam 
followers 126 and 128 so as to provide constant velocity motion. Arcuate 
shaped surface portions 136 and 138 are provided at opposite ends of 
straight surface portion 134 and merge smoothly therewith. Portions 136 
and 138 are each adapted to engage cam followers 126 and 128 respectively 
so as to provide accelerating or decelerating motion depending upon the 
direction of movement of carriage assembly 108. Additional arcuate 
portions 140 and 142 merge smoothly with and extend from respective 
arcuate portions 136 and 138 and are adapted to engage corresponding cam 
followers 126 or 128 so as to provide dwell periods. Arcuate portions 140 
and 142 are both of a constant radius of curvature the radius being 
substantially equal to the distance between the axis of rotation of gear 
114 and respective cam followers 126 and 128. 
As illustrated in FIG. 9, leg portion 124 of cam follower support arm 118 
may be slighty longer than legs 120 and 122 and is provided with cam 
follower 130 which operates in a similar manner to that described above 
with reference to cam follower 58 to provide a steadying function during 
the dwell period. Accordingly, constant radius of curvature camming 
surfaces 144 and 146 are provided spaced slightly outward from respective 
surfaces 136, 140 and 138, 142. 
The operation of motion control apparatus 100 is very similar to that 
described above with reference to apparatus 10. Let us assume that 
carriage assembly 108 is in the dwell position illustrated in phantom in 
FIG. 9 and about to begin movement to the left as seen therein. During the 
dwell period, that being the time during which cam follower 128 engages 
camming surface portion 142, gear 114 will be in pure rotational movement 
without any linear motion thereby allowing movement of piston rod 104 and 
rack 110 to the left. As cam follower 128 moves into arcuate camming 
surface portion 138, the pure rotational movement of gear 114 will 
decrease being supplanted by increasing or accelerating linear motion 
toward the left. When cam follower 126 moves into engagement with straight 
camming surface portion 134, all rotational movement of gear 114 will have 
ceased thereby preventing any further relative movement of rack 110 and 
gear 114 and thus producing a period of constant linear velocity toward 
the left due to the continued retracting of piston rod 104. As cam 
follower 126 moves into arcuate camming surface portion 136, the pure 
linear motion of gear 114 will be caused to decrease or decelerate being 
supplanted by rotational movement of gear 114 which in turn allows 
continued linear motion of rack 110. As cam follower 126 moves into 
camming surface portion 140, all linear motion of gear 114 will cease and 
be totally supplanted by rotational movement with cam follower 130 moving 
into camming surface portion 144 so as to insure precise accurate 
positioning of a workpiece being moved thereby. 
As previously mentioned, the relative lengths of the camming surface 
portions may be varied to provide any desired combination of period 
durations. Further, varying the diameter of gear 114 will also allow 
variances in the rate of acceleration/deceleration and length of dwell 
periods for a given rate of travel of rack 110. It should be noted, the 
length or rack 110 must be sufficient to insure continuous engagement with 
gear 114 throughout the periods of rotational movement of gear 114 which 
requires rack 100 to be equal to twice the length of the arc through which 
gear 114 rotates during a single deceleration/acceleration dwell period. 
While motion control apparatus 100 is illustrated employing a piston input 
drive arrangement, it should be noted that other linear drive arrangements 
may be easily substituted therefor. As illustrated in FIG. 10, a lead 
screw drive arrangement may be substituted therefor in which a rotating 
drive means 148 is drivingly connected to an elongated lead screw 150 
which extends through and threadedly engages a cylindrical member 152 
secured to input carriage assembly 108'. Thus rotation of lead screw 150 
will cause longitudinal motion of carriage assembly in substantially the 
same manner as with piston 102. 
Thus, as is apparent the present invention provides a relatively simple 
mechanical motion control mechanism which provides beginning and ending 
dwell periods during which a driving force connected to the input shaft 
may be either shut down or otherwise disconnected therefrom without loss 
of proper positioning of the workpiece being moved thereby. Further, the 
mechanism of the present invention requires relatively few moving parts 
thereby increasing a reliability thereof while maintaining extreme 
flexibility in that the arc periods defining dwell portions as well as the 
length of the acceleration periods and constant velocity periods may be 
easily varied to provide any desired combination of dwell 
acceleration/deceleration and constant velocity periods during the motion. 
Thus, the mechanical motion control mechanism of the present invention is 
uniquely adapted for transferring or otherwise moving articles into and 
out of machining apparatus or the like without subjecting the article 
being so moved to any jarring acceleration or deceleration forces as well 
as insuring that the articles are properly positioned in a desired 
location. 
While it will be apparent that the preferred embodiments of the invention 
disclosed are well calculated to provide the advantages and features above 
stated, it will be appreciated that the invention is susceptible to 
modification, variation and change without departing from the proper scope 
or fair meaning of the subjoined claims.