CA1250247A - Transfer mechanism and drive with straight line lift and lower - Google Patents

Abstract

TRANSFER MECHANISM AND DRIVE
WITH STRAIGHT LINE LIFT AND LOWER

ABSTRACT OF THE DISCLOSURE
A power drive and lift-and-carry mechanism in which a rotary input drives a mechanical system to produce a relatively long dwell stage and, in combi-nation with a crank drive mechanism, produces a trans-fer motion with a substantially straight lift and lower motion coupled with a horizontal component in a smooth transfer motion for work parts.

Description

~0 ~ ~

Title Transfer Mechanism and Drive With Straight Line Lift and Lower.

Field of Invention Power combination utilizing a rotary power in-put and a mechanism to produce a rela-tively long dwell which in combina-tion can achieve a lift-and-carry motion for the transfer of parts from one station to another.

Background of Invention In the field of workpiece transfer there arise many applications in which it is required that a given workpiece or workpieces be lifted vertically upward out of a fixture, pallet, or other work holding device, then moved along an arcuate path through a given angle or distance and then lowered into an advanced fixture, palle~ or other work holding device. It is general prac-tice to use separate cylinders/ or independent mechanical - systems to generate the vertical motion and arcuate mo-tions respectively.

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It is one object of this invention to pro-vide a single simple mechanically interrelated system which is capable of generating the entire path com-prised of a lift motion, a rotate motion, and a lower motion.

Other applications arise in which it is re-quired that a workpiece be removed from a given fix--ture, pallet, or other work holding device, along a given arcuate or straight line and then transferred to a different location where it is reloaded into another given fixture, pallet, or work holding device, again along a given arcuate or straight line. It is again a general practice to use a separate cylinder, or independent mechanical system to generate the load-unload motion and another to generate the transfermotion.

It is another object of -this invention to provide a single simple mechanically interrelated sys-tem which is capable of generating the arcuate or straight line load and unload motions with a transfer motion therebetween in a smooth uninterrupted single path.

In a more general sense, it is another object oE
this invention to provide a mechanically interrelated system which is capable of generating a generalized path for a transfer mechanism in which a first portion of its motion is along a path created by movement along one of .its six degrees of freedom, a second portion of its movement is along a path created predominantly by movement along another of i-ts six degrees of freedom, and a third portion of its movement is along a path created by a movement along the same degree of freedom as the first portion of movement, but in the opposite direction.

More specifically, the invention includesa transEer mechanism which has two degrees of freedom for movement along or about any two axes, an interrelated mechanical system to drive said transfer mechanism along a predetermined path and the mechanism includes a frame, transfer means mounted in said frame for movement having said two degrees of freedom, crank drive means mounted in said frame, first coupling means connecting said crank drive means and said transfer means for movement along the first of said two degrees of freedom/
second coupling means connecting said transfer means for movement along the second of said degrees of freedom with long dwell drive means mounted in said frame, and a prime mover rotatable drive means for driving said crank drive means and said long dwell drive means in synchronism.

The long dwell drive means includes input means mounted for rotation in said frame, output means mounted for rotation in said framel variable gear ratio means inter-connecting said input means and said output means, whereby upon continuous rotation oE said input means, said output means rotates in a sequence of discrete unidirectional index steps separated by dwell intervals during which said output means is substantiall~ stationary.

Thus, when the prime mover is rotating in a forward direction, the transfer means is driven in a forward direction in a developed topologically U-shaped path comprising a first portion during which the crank drive means drivessaidtransfer means along said first degree oE freedom, and said long dwell drive means holds said transfer means substantially stationarv along said second degree of freedom; a second portion during which said long dwell drive means drives said transfer means along said second degree of freedom in a forward direction while said crank drive means moves said transfer means along said first degree of freedom and then reverses this movement along said first degree of freedom; and a third portion d~ring which said crank drive means drives said transfer means along said first degree of freedom in the opposite direction from said first portion and said long dwell drive means holds said transfer means substantially stationary along said second degree of freedom.

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Upon directional reversal of said prime mover drive means, the transfer means is driven in a reverse direction along the same topologically U-shaped path which had been traversed by said transfer means during its movement in the forward direction.

Also, alternatively, upon continued rotation of the prime mover drive means in a forward direction, the transfer means is driven forward along multiple, sequential, adjacent topologically U-shaped paths, which are geometrically identical but non-coincident.

Other objects and features of the invention will be apparent in the following description and claims in which the best modes of the invention are se-t forth together with the principles of operation and details to enable persons skilled in the art to practice the invention.

Brief Description of the Drawings DRAWINGS accompany the disclosure and the various views thereof may be briefly described as:
FIG. 1, a side view of one embodiment of the mechanisms disclosed in my U. S. Patent No. 4,075,911 for generating intermittent long dwell index cycles.

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FIG. 2, a plan view of the mechanism of FIG. 1.
FIG. 3, schematic drawings of principal ele-ments of the mechanism of FIGS. 1 and 2 shown in three positions during the dwell portion of the cycle.
FIGS. 4-6, schematic drawings of principal elements of the mechanism of FIGS. 1 and 2 shown at positions representing 1/4, 1/2 and 3/4 through an entire index cycle.
FIG. 7, a graph showing the true very slight oscillation of the output during the dwell for the mechanism of FIGS. 1 and 2.
FIG. 8, a graph showing the output movement or displacement in percent for a full index cycle for the mechanism of FIGS. 1 and 2.
FIG.9, a schematic drawing of a crank and slider block mechanism.
FIG. 10, a schematic drawing of a crank drive link mechanism.
FIG. 11, a plan view of a first embodiment of this invention.
FIG. 12, a side view of the mechanism of FIG. 11.
FIG. 13, a transverse section taken on line 13--13 of FIG. 11.
FIG. 14, a stepped section taken on line 14--14 of FIG.13.

FIG. 15, a partial section taken on line 15--15 of FIG. 13, FIG. 16, a vertical section taken on line 16--16 of FIG. 13.
FIG. 17, a graph showing the interrelation-ship between vertical and angular movement created by the first embodiment of this invention.
FIG. 18, an isometric representation of the path generated by the first embodiment of this inven-tion.
FIG. 19, an isometric representation of an alternate path which can be generated by the first embodiment oE this invention with changed gear ratio and eccentricity.
FIG. 20, an isometric representation of an al-ternate path which can be generated by the first embodiment of this mechanism when it is rotated in space to make the àxis of the ram horizontal.
FIG. 21, a longitudinal section of a mechanism useful for lengthening dwells and described as a differ-ential cam system.
FIG. 22, a transverse section of the mechanism of FIG. 21 taken on line 22-22.
FIG. 23, a transverse section of the mechanism of FIG. 21 taken on line 23--23.
FIG. 24/ a transverse section of the mechanism of FIG. 21 taken on line 24--24.

4~7 FIG. 25, a section taken on line 25--25 of FIG. 23.
FIG. 26, a schematic representation of the mechanism of FIG. 21 showing it in a base position and three additional displaced positions.
FIG. 27, a graph of the displacement charac-teristics of an illustrative differential cam mecha-nism, and of a combined mechanism comprlsed of a cycloidal output mechanism disclosed in my U. S.
10 . Patent No. 3,789,676 and a differential cam mechanism.
FIG. 28, a side view of one .embodiment of the mechanism disclosed in my U. S. Patent No. 3,789,676 for generating an approximate cycloidal output.
FIG. 29, a plan view of the mechanism of FIG. 28.
FIGS. 30-33, schematic drawings of principal elements of the mechanism of FIG. 28 shown in five positions during an index cycle.
FIG. 34, a plan view, analogous to FIG. 11, of an alternate embodiment utilizing a long dwell mechanism comprised of the mechanism of FIGS. 28 and 29 driving the differential cam mechanism of FIGS.
21-26~

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FIG. 35, a plan view, analogous to FIG. 11, of an alternate embodiment having an increased long dwell mechanism created by interposing the differen-tial cam mechanism of FIGS. 21-26 into the rotate drive system of FIG. 11.
FIG. 36, a longitudinal section of the mecha-nism disclosed in my U. S. Patent No. 4,018,090.
FIG. 37, a transverse section taken on line 37--37 of FIG. 36.
FIG. 38, a transverse section taken on line 38--38 of FIG. 36.
FIG. 39, a longitudinal section of one of the mechanisms disclosed in my U. S. Patent No. 3,730,014.
FIG. 40, a transverse section taken on line 40--40 of FIG. 39.
FIG. 41, a transverse section taken on line 41--41 of FIG. 39.
FIG. 42, a longitudinal section of a mecha-nism similar to the mechanism of FIGS. 31-33 but hav-ing no input eccentricity.
FIG. 43, a plan view, analogous to FIG.ll, showing three alternate tandem mechanisms utilized as long dwell mechanisms, each comprised of the common differential cam mechanism 278 with alternate predrive mechanisms of FIGS. 36-38 or FIGS. 39-41 or FIG. 42.

~i~5~ 7 Introductory Disclosure As will be disclosed, this invention incor-porates mechanisms disclosed in my U. S. Patent No.
g,075,911 and my copending Canadian application, Serial No. 440,311, filed November 2, 1983. Since -the dwell charac-teristics of one embodiment of my U. S.
Patent No. 4,075,911 are very pertinent -to the charac-teristics of this new invention, they will be briefly reviewed.

FIGS. 1 and 2 are simplified schematic draw-ings of this embodiment which is proportioned to pro-vide a 360 output for one acceleration-decleration cycle of its output shaft. Referring to FIGS. 1 and 2, an input shaft 2 rotates on axis Ao in stationary bear-ings in a case which is not shown. An eccentric seg-ment 4, on the shaft 2, is concentric about an axis A
displaced a small amount from the axis Ao. An input gear 6, fastened on the eccentric segment 4, is also concentric about axis Al. Tangen-tial links 8 are journalled on the eccentric segment 4. A driving gear 10 is mounted on a shaft 12 journalled in the tangential links 8 and rotates on a moving axis A2; it is driven by the input gear 6 through an intermediate gear 1~ also journalled in the tangential links 8. In this ins-tance the ratio between the input gear 6 and the driving gear 10 is exactly 2:1, i.e., the input gear 6 rotates two times for every revolution of driving gear 10.

An eccentric plate 16 is mounted on the shaft 12 and in turn supports an eccentric gear 18 concentric about a moving axis A3. This eccentric gear 18 meshes with an output gear 20 mounted on an output shaft 22 rotating on a stationary axis A4 in bearings mounted in the case not shown. The eccentric gear 18 and the out-put gear 20 are equal in si~e to provide the 360 out-put cycle. The eccentric gear 18 is held in mesh with the output gear 20 by a radial link 24 which is journalled on the output shaft 22 and on a stub shaft 26 mounted on the eccentric gear 18 concentric about axis A3.

The distance from axis Ao to axis Al will be defined as eccentricity E2, while the eccentricity be-tween axis A2 and axis A3 is defined as eccentricity El.The addition of this second eccentricity E2, which ro-tates at an integral multiple number of times for each rotation of the eccentricity El, makes it possible to achieve a wide variety of kinematic effects on the ro-tation of the output shaft 22. This is disclosed inconsiderable mathematical detail in my existing U. S.
Patent No. 4,075,911.

The mechanism of FIGS. 1 and 2, designated mechanism 28, is configured to create a relatively long dwell in terms of input angle rotation, in which the

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dwell is not a true stationary condition of the out-put shaf-t, but rather, multiple small amplitude oscilla-tion of the output shaft about the center of these oscillations, which is defined as the zero point for output angle measurement.

The qualitative behavior of the system near dwell is shown in FIGURE 3~.~ At the starting point, or center of dwell, the primary elements are shown in solid lines in FIG. 3 and are labeled without sub-script. If, from this starting position, the inputshaft is rotated 120 clockwise, the relative posi-ti.on of the elements is shown by dotted lines and the suffix label "A". Similarly, if the input shaft is rotated 120 counterclockwise, the relative position of the elements is shown by dashed lines and the suffix leter "B". Throughout this movement range of the in-put shaft, the movement of the output gear is too small to be shown diagrammatically. In effect, the eccentric gear 18 rolls on a nearly stationary output gear 20.
A marker line, Z, has been placed on the output gear 20 to show its rotation during a given cycle. With the plus or minus 120 rotation of the input shaft 2, illustrated inFIG.. 3, the resultant rotation of the output gear 20 is too small to be shown graphically through the marker line Z.

However, through a quantitative analytical process, the output movement characteristics versus input movement, in the dwell area of the mechanism, are graphically portrayed in FIG. 7. The data for this graph were obtained by the methods and formulas disclosed in my U. S. Patent No. 4,075,911. The out-put movement is scaled to read in percent of total output movement per cycle which is most convenient for the applications intended, as will be shown. The input movement is scaled in "clock" degrees, which has a defined range of 360 per cycle. Since the input shaft 2 rotates through two revolutions or 720 per cycle, due to the 2:1 gear ratio between input gear 6 and drive gear 10, which corresponds to a 360 clock angle, it is clear that each degree of clock angle corresponds to 2 degrees of input shaft angle. From FIG. 7, it is clear that the output movement oscillates within a band of +0.1% for an input movement range from -74 to +70; this output movement is equivalent to +0.36 degrees rota-tion of the output shaft 22, while the input movement is equivalent to -148 to +140 of actual rota-tion of the input shaft 2. Therefore, while no actual true dwell or standstill of the output shaft 2 is achieved, the extremely small oscillation of the output shaft 2 for such a wide range of input movement is very useful in the practical application to be disclosed.
The input angle in FIG. 7 is also noted from 284 to 432 to indicate that the "dwell" characteristics are the same for each cycle of the mechanism.

2~

The qualitative behavior of the mechanism 28 at 90 clock angle intervals is shown in FIGS. 4-6.
In FXG. 4, the input shaft 2 has been rotated 180 (90 clock) clockwise fxom the base or starting posi-tion shown in FIGS. 1 and 2 and the solid lines posi-tion in FIG. 3. It will be noted that the eccentric gear 18 has rotated somewhat less than 90 in space, but has still rolled clockwise around -the periphery of the output gear 20. The resultant movement of the out-put gear 20, as shown by the marker line Z, is about 3coun-terclockwise.

In FIG. 5, the input shaft 2 has been rotated 360 (180 clock) from its base or starting position.
The eccentric gear 18 has rotated slightly more than 180 in space, and has rolled back up the side of the output gear 20, relative to FIG. 4. The total movement of the output gear 20, relative to its starting position, as shown by the marker line Z, is slightly more than 180, counterclockwise. Therefore, in the interval represented between FIG~ 4 and 5, most of this motion has taken place.

In E'IG. 6, the input shaft 2 has been rotated 540 clockwise (270 clock) from its base or starting position. The eccentric gear 18 has rotated slightly more than 270 in space and has rolled to the other side of the output gear 20 relative to FIG. 5. The total movement of the output gear 20, as shown by the marker line Z, relative to its starting position, is almost 360 counterclockwise. In the interval represented between FIGS. 4 and 5, almost 180 of additional rota-tion of the output gear 20 has taken place.

After an additional rotation of 180 (90 clock~ of the input shaft 2 has taken place, relative to FIG. 5, the total rotation of the input shaft 2 is 720 (360 clock) and the position reached by the mechanism is again represented by the solid lines of FIG. 3. Ihis completes a single cycle. In this final interval, represented between FIG. 5 and the solid line representation of FIG. 3, the output gear 20 has rotated approximately 2 to create the full 360 of output rota-tion for the cycle.

FIGS. 3, 4, 5 and 6 were presented to providea qualita-tive representation of the behavior of the mechanism 18 during a single index cycle. The input-output characteristics are quantitatively shown by curve A of FIG. 8. The data for this curve were again analytic-ally obtained using the methods and formulas disclosed in my U. S. Patent No. 4,075,911. The input movement is again scaled in "clock" degrees, while the output move-ment is again scaled in percent of movement relative to ~o~

the total cycle movement. Curve A of FIG. 8 and the curve of FIG. 7 represent the same movement but over a different range of input movement and with a different total output scale range. Clearly, the small oscilla-tions which comprise the output "dwell", as shown in FIG. 7, are imperceptible in FIG. 8.

A second mechanism assembly which comprises a portion of this invention is shown in FIG. 9. This is the well-known crank and slider block mechanism which has been known to the art, and its output displacement characeristics are briefly reviewed as a reference only.

A crank arm 30 of length L is journalled in a frame 32 through a journal 34 and is driven by a suitable source, not shown in the schematic diagram of FIG. 9. A connecting rod 36, of length C, is connected at its one end to the crank arm 30 through a crankpin 38;
at its other end, the connecting rod 36 is pivotally con-nected to a slider block 40 through a pin 42. The slider block 40 is guided for straight line motion by guides 44 attached to the frame 32.

In this instance, the "clock" angle of the mecha-nism is defined as the angle ~ between the crank arm 30 and the base line B, defined as the line which represents Z'~7 the position of the crank arm 30 when it is colinear with the connecting rod 36; this colinear position is also taken as the startinCJ position of this "crank drive" mechanism. In the starting position of the crank drive mechanism, the slider block 40 is shown by dotted lines in FIG. 9 and designated as 40A; this is also the position of the slider block where it is most distant from the crank journal 34.

If, from this starting position, the crank arm is displaced through an angle ~, (clock angle), the slider block will move through a distance, S, and the angle between the connecting rod and the base line is taken as ~. From these definitions, it can be seen that:
Lsin~ = Csin~
or, ~ = arc sin (C-sin~

It can also be seen that:
S = L + C - Lcosa - Ccos~ (2) Equations (1) and (2), with perhaps different symbols, have been long known and used. For any given values of L and C, it is possible to calculate the value or ~ and S for all values of ~, which is considered to be the inpu-t angle. The maximum value, Sm, of S is ;~S~ 7 reached when 3 = 180 and Sm = 2L, independent of the value of C. If C is arbitrarily chosen to be four times the value of L and the value of the output, S, expressed as percent of full stroke, Sm, then curve B
of FIG. 8 is obtained. As expected, a value of 100%
is reached at 9 (clock angle) = 180.

FIG. lO is a variant of the crank drive mecha-nism in that the slider block and its guides are re-placed by a link 46 pivoted to the frame 32 through a pivot pin 48. If the angle between the base liner as previously defined, and the link 46 at mid-stroke is approximately 90, and, if the distance between pins 48 and 42 on link 48 is large relative to the maximum stroke, the ouput, SL~ of this variant, again expressed as percent of full stroke, is almost identical to curve B
of FIG. 8; and the greater the distance between pins 42 and 48 on link 46, the better the approximation.

The mechanism 28 of FIGS. l and 2 and the crank drive mechanism of FIG. lO are combined in this invention to produce very useful combinations.

~:5~ 7 Description of the Invention Referring to FIGS. 11-16, a base 50 supports a tubular column 52 reinforced with gusset plates 54.
The tubular column 52 guides a ram 56 through a bush-ing 58 for both axial and rotary motion. A mounting block 60 is fastened to the top of the ram 56; this block 60 in turn supports two transfer arms 62 and 64 positioned at 90~ to one another in this illustrative embodiment. Each transfer arm 62 and 64 in turn car-ries a mechanical hand 66 at its outboard end; these mechanical hands 66 are adapted to grasp or release workpieces 68. For purposes of identification, these workpieces are serially given suffix labels A, B, C, ` etc. A workpiece holding fixture 70 is mounted to the base 50 and acts as an idle station in the transfer system as will be disclosed. The mechanism 28 described in connection with FIGS. 1~6 is enclosed in a housing 72 attached to the base 50; its input shaft 2 is driven by a flange mount gear reducer 74 in turn driven by a motor 76. The axes labelling Ao and A4 noted in FIGS. 1~6 are also applicable to FIGS. 11~16.

,~ . . . .
The workpieces 68A, 68B and 68C are shown as being supported on an auxiliary conveyor 78, which is a schematic representation of a roll conveyor, belt con-veyor, or pallet type workpiece transfer system such as disclosed in my U. S. Patent No. 4~316,535. Further-more, for the purposes of this embodiment disclosure, it will be understood that the position taken by workpiece 68E represents a delivery point in a machine load sta-tion, second transfer conveyor, or other system from which the workpiece 68E is taken away, and into which a vertical downloading of the workpiece is requiredO

Referring to FIGS. 13 and 14, a ball spline shaft 80 is fastened to the bottom of the ram 56, and passes through a ball spline nut 82 through which it is driven in rotation. The ball spline nut 82 in turn is mounted into a sleeve 84 to which it is keyed through a key 86. Bearings 88 and 90, mounted in a boss 92 which is part of the base 50, and held in place by a retainer ring 94, support the sleeve 84 for rota-tion with respect to the base. A bevel gear 96 is mounted to the sleeve 84 for driving; this bevel gear 96 in turn is driven by a bevel gear pinion 98 (FIG. 14) mounted on and driven by the output shaft 22 of the mechanism 28 in housing 72. The ratio between the driv-ing pinion 98 and the driven gear 96 is illustratively shown as 4:1; i.e., for one revolution of the pinion 98 the gear 96 rotates 1/4 revolution or 90. As shown, the output shaft 22 is supported by an outboard support bearing 100 in the base 50.

At its lower endr the ball spline shaft 80 is supported by a bearing 102 housed in a split lift block 104; this bearing 102 is retained on the shaft S~ 7 through a retainer 106. The lift block 104 is pivot~
ally connected to a lift lever 108 through two stud type cam follower rollers 110, FIGURE 15, used as pivot bearings. At its other end the lift lever 108 is connected to the base 50 through two rollers 112, which are closely fitted into slots 114 formed by guide blocks 116 mounted on brackets 118 which are attached to the base 50 (FIG. 14). It can be seen that connec-tion of the lift lever 108 to the base 50 through roll-ers 112, guide blocks 116 and brackets 118, permits the right end of the lift lever (FIG. 13) to move freely in a horizontal direction, while it is still confined in a vertical direction.

Near its midpoint, the lift lever 108 is pivo-t-ally connected to one end of a connecting rod 120 through a pin 122. At its other end the connecting rod 120 is rotatably connected to a crankpin 124, which is eccen-trically mounted through a flange 126 into a crank drive gear 128. The crank drive gear 128 is mounted to a flanged shaft 130 journalled through bearings 132 and 134 into a tubular housing 136 which is part of the base 50.
A doubler plate 138, also part of the base 50, provides additional support for the housing 136. The crank drive gear 128 is driven by a pinion gear 140, which is splined onto the input shaft 2 of the mechanism 28. At its other end, as previously noted, this input shaft 2 is driven by the gear reducer 74; intermediately it drives the input gear 6 of the mechanism 28. Immediately inboard of the drive pinion 140, this input shaft 2 is journalled in bear-ings 142 and 144 mounted in a second tubular housing 146 which is also part of the base 53 and further supported by the doubler plate 138. The ratio of the pinion 140 to the crank drive gear 128 is shown as 2:1 although this ratio may be varied as will subsequently be discussed.

The starting position of the system is as shown in FIGS. 11-16, and a cycle requires two revolu-tions of the input shaft 2 as driven by gear reducer 74 and motor 76. These two revolutions of the input shaft 2 and the pinion 140 mounted thereon cause the crank drive gear 128 to rotate through one revolution.
This in turn causes the connecting rod 120 to lift and then lower the lift lever 108 through pin 122, with rollers 112 acting as the fulcrum point of the lift lever 108. The lift lever 108, acting through the lift block 104, bearing 102, and ball spline shaft 80, lifts and lowers the ram 56 through a vertical stroke deter-mined by the eccentricity of crankpin 124 relative to the centerline of crank drive gear 128, and the leverage ratio of lift lever 108. The transfer arms 64 and mech-anical hands 66 lift and lower through this same vertical stroke, the highest point of which is shown by the dotted outline of the transfer arm 62 designated as 62A in FIG.
12. Since this lift mechanism is driven by a crank drive ~LZ~ 7 system, the vertical position of the transfer arms 62 and 64 and the mechanical hands 66 mounted thereon, as a function of "clock" angle, as measured by the rotation of the crank drive gear 128, is substantially represented by curve B of FIG. 8. The vertical position of the trans-fer arms and mechanical hands is measured from their lower-most position, and the crank drive gear angle is measured from the position shown in FIGS. 13 and 16.

As the input shaft 2 rotates through two revolu-tions to create the lift-lower cycle described above, it also drives the mechanism 28, causing its output shaft 22 to make one revolution, while following the displace-ment characteristics shown by curve A of FIG. 8. The rotation of outpu-t shaft 22 is transmitted through bevel pinion gear 98 to crea-te a 90 rotation of the bevel gear 96. This bevel gear transmits its motion through the sleeve 84, ball spline nut 82, and ball spline shaft 80 to the ram 56 which also rotates 90, carrying the transfer arms 62 and 64 and mechanical hands 66 with it.
This rotary motion of the ram 56 occurs independently of the vertical position of the ram, due to the sliding connection of the ball spline nut and ball spline shaft.
The angular position of the ram, transfer arms and mech-anical hands is therefore also represented by curve A
of FIG. 8 due to the linearity or proportionality of the rotary motion transfer system.

In essencethen, the vertlcal movement of the mechanical hands as a function of the clock angle is shown by curve B of FIG. 8 and the angular movement of the mechanical hands, as measured about the centerline of the ram 56, and also as a function of the clock angle, is shown by curve A of FIG. 8.

When this vertical movement and angular move-ment are plotted against one another, with the clock angle as a parameter, the curve C of FIG. 17 is ob-tained. This is, in effect, the "developed path" oEthe mechanical hands generated by two revolutions of the input shaft 2. Referring again to FIGS. 11 and 12, and presuming an obvious control of the mechanical hands, the overall system will lift the workpiece 68D from its position in the idle station fixture 70; transfer arm 64 rotates 90 counterclockwise on ram 56, reaching the posi-tion 64A and then lowers to its original height beinging the workpiece to the position shown as 68E. Simultaneously, the transfer arm 62 and -the mechanical hand thereon will transfer a workpiece from position 68C to 68D through the same lift, rotate, and lower sequence. In this example, it is further designated that after the system has ad-vanced the two workpieces as described above, the mech-anicai hands release the workpieces, the drive motor reverses, and the empty hands return to their starting position retracing the path followed in their advancing movement while carrying the workpieces.

~s~

As noted above, the curve C of FIG. 17 repre-sents the developed path of the mechanical hands for this embodiment. The actual path is a line on the sur-face of a cylinder as shown isometrically by path Pl in FIG. 18.
Two other relevant points need to be made. The first is thak during the "vertical" portion of the path there occurs a very slight angular cscillation of the ram 56, which creates a very slight deviation of the path (near the ends of the stroke) from a true vertical straight line, -this is, of course, caused by the oscillation of the output shaft 22 during the "dwell" that is graphically portrayed by the curve of FIG. 7. Secondly, while it is convenient to describe the overall motion of the hands as being a lift, rotate, and lower motion, it is clear from the developed path of FIG. 17, and the isometric representa-tion of FIG. 18 that the vertical motion (with the very slight aforesaid oscillation) takes place only for about 40% of the total lift stroke. Nevertheless, this general path configuration is of great practical value in loading and unloading of fixtures, pallets, or o-ther workpiece holding devices which require that the workpiece enter or depart along a vertical or nearly vertical line.

In the embodiment of FIGS. 11-16, the angle of rotation of the ram and the transfer arms was shown as being 90, as a result of the ratio 4:1 between pinion gear 98 and bevel gear 96. Clearly this angle of rotation of the ram can be changed by changing the aforesaid gear 5~3~

ratio. Similarly, the total lift stroke of the ram is determined by the eccentricity of crankpin124 and leverage of lift lever 108 as previously noted. Fig. l9 is an isometric representation of a path P2 of the mech-anical hands if the lift stroke is halved and the angleof rotation increased to 120. Nevertheless, the de-veloped path representation of FIG. 17 still applies since the coordinates are scaled in the general terms of percentage movement.

The embodiment of FIGS. 11-16 operates with two transfer arms, 62 and 64, and two mechanical hands;
for other applications, only one transfer arm may be required or for still others, a larger number of arms may be required. It is clear that the basic interrelated mechanical system will function with as many transfer arms as a practical application may require.

In the illustrative sequence described above, it was necessary for the system to reverse (with the mechanical hands open) as part of the overall applica-tion requirements. Again applications arise in whichonly a unidirectional operation is required. The basic path generation capabilities of the interrelated mechanical system also make this possible.

While the path representa-tions of FIGS. 18 and 19 show the ends of the path as being vertical and the rotation component as being around a vertical axis of rotation, it is also clear that the mechanism assembly can operate in any required spatial orientation. As an illustrative example of this situation, FIG. 20 shows one of the many path configurations, P3, obtainable if the mechanism is rotated in space such that the axis of the ram 56 is made horizontal.

In a broad generalization, the path generating characteristics of this total mechanism derive from the differences in the dwell and displacement characteris-tics of two independent but simultaneously driven mecha-nisms; the first is the crank drive mechanism briefly reviewed through FIGS. 9 and 10 and (as shown in FIGS.
13 to 16) comprised of the gear 128, crankpin 124, con-necting rod 120, pin 122, and lift lever 108; and the second is the mechanism 28, briefly reviewed through FIGS. 1-6, and illustrative of a class of mechanisms which will be defined as "long dwell" mechanisms.

The displacement characteristics of a crank drive mechanism are generally shown by curve B of FIG.
8, while the displacement characteristics of a long dwell mechanism are generally shown by curve A of FIG.
8. Additionally, for a given cycle, comprised of 360 :~Z~Z~7 of clock angle, a crank drive mechanism makes a com-plete inherent reversing motion, returning to its starting position at the end of a cycle; while the long dwell mechanism makes a unidirectional movement during a cycle, and in which the actual movement takes place predominantly during the center two-thirds, approximately, of the cycle, and there is little or no output movement during the approximately one-sixth of the cycle at each end.

As previously noted, when these two move-ments occur simultaneously, with one driving a body, such as a mechanical band, along one axis oE movement -while the o-ther moves that body along another axis of movement, a composite path such as shown by curve C
of FIG. 17 results.

The term "long dwell" is qualitative; for some practical applications, a dwell or near dwell at each end of a cycle which represents one-twelfth of the total input movement per cycle is adequate; other applications require a. longer dwell proportion. From the parametric interrelationship between the outputs of the crank drive mechanism and the long dwell mechanism, it can be seen that the longer the dwell of the long dwell mechanism, the longer is the straight or near straight portion of the resultant path illustrated by curve C of FIG. 17.

~o~

Other "Long Dwell" Mechanisms The long dwell mechanism 28, of FIGS. 1-6, may be replaced by other long dwell mechanisms having the same general output characteristics. A11 of the embodiments of my copending Canadian patent application, Serial No. 440,311, filed November 2, 1983, may be con-sidered as long dwell mechanisms and each is especially well suited as an alternative to the mechanism 28.
Because of the particular suitability of these mecha-nisms, they are briefly reviewed as follows.

A differential cam system usable as a longdwell mechanism, either singly or in combination with other long dwell mechanisms, is shown in FIGS. 21 to 26.
Referring to these figures, an input shaft 230 is mounted in bearings 232 and 234 supported in a housing 236, and held in place by a nut 238. A crank arm 240 is made in-tegral with the input shaft 230 or rigidly fastened thereon; at its outer end the crank arm 240 carries a c-ankpin 242 on an axis substantially parallel to the axis of the input shaft 230.

A cover plate 244 is bolted to the housing 236 to complete the mechanism enclosure; a cam groove 246 is cut into -the plate 244 and forms a closed curve around the input shaft axis. An output shaft 248 is mounted in a bearing250 mounted in the cover plate 244 and in a bearing 252 in the input sha.ft 230. The bear-ing 250 is retained in the cover plate 244 by a retainer 4~

ring 254 which also carries a seal 256 operating on the output shaft 248. An output arm 258 is splined to the output shaft 248 and axially positioned there-on through a spacer 260 and nut 262. The output arm 258 has formed in it a slot 264 (FIG. 23~ into which is closely fitted a slider block 266 which can slide therein along a substantially radial line.

A bellcrank link 268, triangular in outline, and U-shaped in section to straddle the output arm 258 and slider block 266, is used to connect the in-put crank arm 240 to the output arm 258 as follows.
~~ At its apex, the bellcrank link 268 is pivoted on the crankpin 242 through a bushing 270. At the end of one leg, the bellcrank link 268 is connected to the slider block 266 through pivot pin 272 and bush-ing 274; and at the end of the other leg, the bell-crank link 268 carries a cam follower roller 276 and this roller operates in the cam groove 246 in the cover plate 244. The entire mechanism enclosed in the housing 236 and cover plate 244 will be referred to as the differential cam mechanism 278.

It can be seen that if it is presumed that the bellcrank link 268 is stationary with respect to the crank arm 240 that there is no relative motion between the crank arm 240 and the output arm 258, and if it is further pre-sumed that the input shaft 230 is rotated at some given angular velocity, that the output shaft 248 will ro-tate in exact synchronism with the input shaft, and that under these presumptions, the path traced by the cam follower roller 276 will be a true circle concen-tric about the axis of the input shaft. Conversely,it can also be seen that if the cam groove 246 is a true circle about the axis of the input shaft, there is no relative motion of the bellcrank link 268 with re-spect to the crank arm 240, and therefore no relative motion is generated between the input and output shafts, and the output shaft rotates in exact synchronism wi-th the input shaft. If, under these hypothetical condi-tions, torque and work is required by an external load on the output shaft, this torque and work must be sup-plied by the input shaft, but the work will be trans-mitted directly from the input shaft to the output shaft without passing through the cam and cam follower.
This must be so since it was shown that the bellcrank link does not move relative to the input arm and hence can contribute no work.

The conditions of movement and work transfer with an illutrative contoured cam groove can be visual-ized through FIG. 26 which shows the essential system elements schematically at several representative angles in a one-revolut:ion cycle. Only the centerline of the cam groove 246 is shown, together with a circular "base"

circle 280 from which the actual cam follower posi-tion can be judged. The cam groove centerline 246 in FIG. 26 corresponds to the cam groove 246 illustrated in FIG. 24, and the position of the essential elements, shown in solid lines and without suffix, correspond to their positions in FIGS. 21-25; this is the arbitrary starting position of the mechanism.

The position reached by the mechanism after the input shaft and crank arm 240 have rotated approxi-mately 12 counterclockwise from the starting positionis shown by the elements in dotted schematic having the suffix letter A. The crank arm has reached the position 240A and the bellcrank link has reached the position 268A as driven by the cam follower 276A in cam groove 246. It will be noted that the output arm 258 has not moved, since the positions 258 and 258A are coincident. This situation is created by the fact that the illustrative cam groove 246 was designed to achieve exactly this result; i.e., that a portion of the movement of the crank arm 240 on either side of its starting position would result in no output movement of the output arm 258.

As the crank arm 240 rotates further counter-clockwise, with the cam roller 276 confined to follow the cam groove 246, the relative rotation of the bell-crank link with respect -to the crank arm slows down causing the output arm 258 to accelerate counterclock-wise. At the maximum radius of the cam groove 246, this relative rotation ceases and the output arm ro-tates at the same angular velocity as the crnak arm, though it is still lagging in displacement.

After the crank arm has rotated approximately 80 from the starting position, a position is reached as shown by the elements having the suffix letter B.
Since the cam groove 246 when engaged by the cam follow-er roller 276B has a greater radius than the base cir-cle 280, the output arm 258B still lags the crank arm 240B, but, since the radius of the cam groove 246 is decreasing, the output arm 258B is now moving at a greater angular velocity than the crank arm 240B.

It should also be noted that where the cam groove 246 recrosses the base circle 280, the bell-crank link has the same relative position with respect to the crnak arm as it had at the starting position and hence the output arm has "caught up" wi-th the crank arm.

After the crank arm has rotated approximately 280 from the starting position, a position is reached as shown by the elements having the suffix letter C.
Here the cam groove 246, where engaged by the cam follower roller 276C, has a smaller radius than the base circle 280, and it can be seen that the bellcrank link has forced the output arm 258C ahead of the crank arm 240C. Futhermore, since the cam groove 246 is still becoming smaller in radius, the output arm 258C
is still moving ahead of the crank arm 240C. This continues until -the minimum radius of the cam groove is reached by -the cam follower roller 276C at which point the output arm and the crank arm rotate at the same angular velocity.

In essence, and as more fully explained in the aforesaid copending application, the contour of the cam groove 246 can superimpose a predetermined variation on the output relative to the input. For the specific cam groove configuration shown in FIG.
24, the output will dwell for a relatively short period as shown by curve D of FIG. 27, which is ana-logous to curve A of FIG. 8. If the differential cam mechanism 278, shown in FIGS. 21-25 is substituted for mechanism 28 in the transfer mechanism, FIGS. 11-16, the resultant U-shaped path of the mechanical hands will have correspondingly shorter true straight portions than are shown in FIGS. 17-20.

However, by combining the differential cam mechanism 278 wi-th other "predrive" mechanisms having an intrinsic or natural dwell once for each revolution, a significant lengthening of the dwell can be achieved. A
first such predrive mechanism is shown in the simplified schematic drawings, FIGS. 28 and 29, which represent one embodiment of an approximate cycloidal motion generating mechanism 300 from my U. S. Patent No.

3,789,676.

Referring to FIGS. 28 and 29, an input gear 302 is mounted on an input shaft 304 which is journalled in a suitable housing or frame on axis A
and driven by an appropriate external drive system.
Also journalled on the input shaft 304 is a tangen-tial link 306 which oscillates thereon as will be described. A driving gear 308 is mounted on a shaft 310 journalled in the outboard end of the link 306 on axis A2, and, an intermediate gear 312, also journalled in the link 306, is formed to mesh with ]5 the input gear 302 and driving gear 308. An eccen-tric gear 314 is mounted on the shaft 310 with an eccentricity approximately equal to its pitch radius.
This eccentric gear 314, rotating on a moving axis A3, meshes with an output gear 316 mounted on a shaft 318 also journalled in the housing or frame on axis A4.
A radial link 320 is also journalled on the output shaft 318 at its one end; at its other end, the radial link 320 is journalled to a stub shaft 322 on axis A3 mounted concentrically on the eccentric gear 314. It is the pur-pose of this radial link 320 to keep the eccentric gear 314 in mesh with the output gear 316 as the eccentric gear 314 moves through its rotational and translational path.

2 L~7 When the mechanism is in the position shown in FIG. 28, it is in a natural dwell position, i.e., a small rotation of the input gear 302 causes a corres-ponding rotation of the driving gear 308 and the eccen-tric gear 314, but this rotation of the eccentric gear 314 is accompanied by a corresponding movement of the shaft 322 about the output shaft 318, such that the gear 314 literally rolls about the output gear 316 which remains stationary or in dwell.

A qualitative schematic representation of the motion of the output gear 316 during a complete 360 ro-tation of the driving gear 308 and eccentric gear 314, at 90 intervals, is shown in FIGS. 30-33. An arbi-trary radial marker line Z has been added to the out-put gear 316 to show its position change at these in-tervals. FIG. 30 shows the position of all gears at the center of the dwell, which is the same configura-tion as shown in FIG. 28. Additionally, a second posi-tion is shown in which the driving gear 308 and eccen-tric gear 314 have been rotated 10 counterclockwise (as driven by intermediate gear 312 and input gear 302). The rolling action of the gear 314 on the out-put gear 316 which remains substantially stationary during this 10 interval can therefore be visualized.
In this second position, the components are redesig-nated by the callout siffix letter a.

æ~

As the gears 308 and 314 continue to rotate counterclockwise, the output gear 316 is accelerated and moves in tne clockwise direction. After 90 of this rotation of gears 314 and 308, the position shown in FIG. 31 is reached. At this point, the acceleration of gear 316 in the clockwise direction has reached its approximate maximum, and the velocity of the gear 316 in the clockwise direction is approximately equal to its average velocity.

As the gears 308 and 314 continue their ro-tation counterclockwise from their position shown in FIG. 31, the output gear 316 continues to accelerate, at a decreasing rate, in the clockwise direction.
After an additional 90 of rotation of gears 314 and 318, the positions shown in FIG. 32 is reached. At this point, the acceleration of the gear 316 has substantially returned to zero, and its velocity in theclo¢kwisedirection has reached an approximate maximum which is approximately double the average velocity.

As the gears 308 and 314 continue to ro-ta-te counterclockwise from the position shown in FIG. 32, the output gear 316 continues to rotate clockwise but is decelerating. After an additional 90 of rotation of gears 308 and 314, or a total of 270 from the start of the cycle, the position shown in FIG. 33 is reached.
At this point, the deceleration of the output gear 316 is at or near maximum, while the velocity of the out-put gear 316, still in the clockwise direction, has slowed down to approximately its average velocity.

As the gears 308 and 314 continue to rotate counterclockwise from the position shown in FIG. 33, the output gear 316 continues to rotate clockwise, but is still decelerating, though now at a decreas-ing rate. After an additional 90 of rotation ofgears 308 and 314, or a total of 360 from the start of the cycle, the position shown in FIG. 30 is again reached, with the output gear 116 having completed one revolution and is now again in dwell.

It can be seen, therefore, that as the input gear 302 is driven by some external power means at a substantially constant angular velocity, the gears 308 and 314 are driven by the intermediate gear 312. Gears 308 and 314 have an angular velocity which is deter-mined by the superposition of the effect of the oscilla-tion of link 306 about shaft 304 on the velocity created by the input gear 302 so gears 308 and 314 do not rotate at a constant angular velocity. And the oscillation of the gear 314 along the arcuate path controlled by radial link 320 and created by its eccentric mounting on shaft 310 creates another superposition on the velocity of the output gear 316. With the proportions shown in FIGS. 28-33, the output gear 316 will come to a com-plete stop or dwell once in each revolution, since the pitch diameters of gears 314 and 316 are shown as being equal.

With the mechanism shown in FIG. 28, the out-put motion of gear 316 has the hroad characterlstics of cycloidal motion, but slight distortions exist which are caused by the short length of link 306 and the arcuate rather than linear path of shaft 322. To some degree, these distortions can be compensated for by the proper choice of gear ratio between input gear 302 and driving gear 308 and the ratio of the length of link 306 to the center distance between input shaft 304 and output shaft 318.

In order to determine the exact quantitative kinematic characteristics of the mechanism shown in FIG. 28, it is necessary to,use,numerical methods for which a programmable calcula-tor or computer is a great convenience, but not a necessity. Setting up classical equations of motion and then differentiating to find velocity and acceleration is excessively laborious and time consuming. But numerical calculation for the exact determination of the output shaft position for a series of discrete positions of the input shaft can be accomplished using straightforward goemetry and ~L~5~ 7 trigonometry. By making these calculations at suffi-ciently small intervals, it becomes possible, by numerical differentiation, to obtain the velocity, and then by numerically differentiating a second time, to obtain the accelerations. These calculations can be repeated as required for different values of the geo-metrical parameters to very closely approximate the conditions to be described below.

Pure cycloidal motion displacement in unitized coordinates and using radian angular notation is given by:

S = l (2~t - sin2~t) 2~

where t is the input variable having a range of 0 to 1 for one cycle of cycloidal motion, and S is the output displacement, a]so having a range of 0 to l.

If degree notation is used and for an input angle and output angle range through one revolution of 360~, equation (3) may be rewritten:

o i ~ 2~ sinO

where ~O = output angle in degrees (shaft 318) i = input angle in degrees shaft3 304 The relationship of equation l4) is plotted as curve E of FIG. 27; and represents the functional output of the mechanism 300 of FIGS. 28 and 29. It will be noted that there is a very slow initial rise of the output from the starting point of both input and output, which can be more easily discerned from the following table:

Input AngleOutput Angle o o . O
10 10 .05O
20 .40 30O 1.35 40 3.17 50o 6.11 15 60 10.38 70 16.16 It can be seen from FIG. 27 that the output characteristics of the mechanism 300 of FIGS. 28 and 29, as represented by curve E, has a longer dwell than -the basic differential cam mechanism 278, as représented by curve D. However, by coupling the output shaft 318 of the mechanism 300 to the input shaft 230 of the differ-ential cam mechanism 278, the characteristies of the output shaft 248 of the differential cam mechanism 278, relative to the input shaft 304 of the mechanism 300, are shown by eurve F of FIG. 27; a significant inerease in dwell is achieved with this "tandem" meehanism, and curve F compares favorably with curve A of FIG. 8.

FIG. 34 is a plan view of an arrangement in which this tandem mechanism is used as the long dwell mechanism in place of the mechanism 28 in providing the drive to the gear 98 which drives the rotary motion of the transfer mechanism of FIGS. 11-16. Referring to FIG. 34, which is analogous to FIG. ll, the shaft 22 (see also FIG. 14) is directly coupled to and driven by the output shaft 248 of the differential cam mechanism 278 through a coupling 350. The input shaft 230 of the diferentialcammechanism 278 in turn is coupled to and driven by the output shaft 318 of the mechanism 300 through a coupling 352. Both the differentlal cam mechanism 278 and the mechanism 300 are mounted on a base extension 50A. The input shaft 304 of the mecha-nism 300 in turn is driven by the gear reducer 74 and motor 76 as in FIG. ll. Additionally, and as shown in FIG. 34, the input shaft 304 is directly coupled to the shaft 2 (FIG. 14) through a coupling 354 which drives the lift and lower crank drive mechanism of -the transfer system. However, since mechanism 300 is shown in FIGS.
28 and 29 as requiring three revolutions of its input shaft 304 for one 360 cycle of the output shaft 318, it is clear that the gear ratio between gears 140 and 128 (FIG. 14) must be changed to 3:1 from the 2:1 pre-sently shown in FIGS. 13, 14 and 16.

:~,5~

Since curve F, representing -the output charac-teristics of the tandem long dwell mechanism, comprised of the mechanism 300 driving the differential cam mechanism 278 (FIG. 34) is very similar to curve A of FIG. 8, it followc that the path followed by the mecha-nical hands on the transfer arms will be very similar to the paths represented by FIGS. 17-20.

It is also possible to interpose the differ-ential cam mechanism 278, FIGS. 21-25 between the natural long dwell mechanism 28, FIGS. 1-6, and the rotate drive pinion 98, thereby further lengthening the dwell of the rotate drive system. This arrangement is shown in FIG.
35, which is again analogous to FIG. 11. The rotate drive pinion 98 is mounted on and driven by the output shaft 248 of the differential cam mechanism 278; in place of its being mounted on the output shaft 22 of the long dwell mechanism 28, as shown in FIG. 14. The input shaft 230 of the differential cam mechanism 278 in turn is directly coupled to the output shaft 22 of the long dwell mecha-nism 28 through a coupling 356. The input shaft 2 of the long dwell mechanism 28 is still driven by the gear reducer 74 and motor 76 as in the original embodiment, FIG. 11. Furthermore, this input shaft 2 also still drives the pinion gear 140, as before (FIG. 14) although it must be physically lengthened to accommodate the axial space required by the differential cam mechanism 278 as can be seen from FIG. 35; because of this lengthening, the input shaft is designated 2A in FIG. 35.

This interposition of the differential cam mechanism 278 between the original long dwell mecha-nism 28, and the rotate drive portion of the original transfer mechanism, as depicted by FIG. 35, and when properly phased such that the dwells of both mecha-nisms are superimposed, will increase the dwell por-tion of the overall output cycle. The actual perform-ance of this tandem arrangement is shown by curve G of FIG. 8. It is clear thatthe increase in dwell brought about by the interposition of the differential cam mechanism is shown by the difference between curve A
and curve G in FIG. 8. The overall transfer path is effected by having the verticalportions of the path curve C of FIG. 17 be proportionally longer.

Not only does the interposition of the diff-erential cam mechanism 278 described above increase the dwell portion of the overall output cycle for the rotary drive, but the oscillations described in con-nection with FIG. 7 are eliminated. In reviewing the operation of the differential cam mechanism as de-scribed in connection with FIG. 26, it can be seen than any small oscillations of the crank (input) arm 240 will result in no movement of the output arm 258 for the configuration of the cam groove 246 shown.

g~3'~ ~7 Other mechanisms which can also be used as the predrive mechanism for the differential cam mecha-nism 278 to create tandem mechanisms which achieve a long dwell, and asalready shown in the aforesaid co-pending application will be briefly reviewed.

The mechanism 400 (FIGS. 36-38) which also has a natural dwell, has been disclosed in my U. S. Patent No. 4,018,090 and will be briefly described as follows.
A case 402 supports a stationary shaft 404 on which in turn is mounted a stationary sun gear 406. A planetary carrier assembly is made up of a plate 408 and a housing 410 bolted thereto. The planetary carrier 408, 410 is mounted to -the stationary shaft 404 through bearings 412 and 414 and rotates about the axis Ao. I'he periphery of the plate 408 is formed into a gear sui-table for meshing with an input gear 416 mounted on a shaft 418 which ro--tates in bearings 420 and 422 mounted in the case 402.

A planetary gear 426 suitably formed to mesh with sun gear 406 is mounted on a planetary shaft 428 which in turn is carried in the planetary carrier 408, 410 through bearings 430 and 432. The planetary gear 426 rotates on the moving axis Al as the planetary carrier 408, 410 rotates about axis Ao as ariven by the input gear 416.

~f~2~7 An eceentrie support plate 434 is mounted to the planetary shaft 428 and has projeeting therefrom an eeeentrie shaft 436 on an axis A2 displaced from the axis Al. A slide block 438 is rotatably mounted on the eecentrie shaft 436; this slide bloek 438 in turn is slideably movable in a slot 440 of an output spider 442 (FIG. 38). This output spider 442 is mounted on an output shaft 444 which rotates in bear-ings 446 and 448 mounted in a case eover 450 fastened by bolts (not shown) to the case 402. The shaft 444 and output spider 442 rotate about an axis A3 dis-placed from the primary axis Ao.

It can be seen that as the planetary carrier 408, 410 rotates about the axis Ao, and the planetary shaft 428 is driven about the moving axis Al, the eceentrie shaft 436 and its axis A2 move in an epi-troehoidal or epieycloidal motion, depending on the amount of displaeement of the axis A2 from the axis Al. Provided only that the axis A3 lies within the path of the axis A2, the eeeentric shaft 436 and the slide block 438 cause the output spider 442 and output shaft 444 to rotate about the axis A3. The mathematical development of the kinematics of this system is covered in my U. S. Patent No. 4,018,090, with specific refer-~5 ence to the effeets created thxough the displacement of the axis A3 from axis Al.

~:~5~ 7 In the specific configuration shown in FIGS.
36-38, and applicable to a combination mechanism, the pitch diameter of the planetary gear 426 is equal to the pitch diameter of the sun gear (R=l~, and an out-put cycle repeats for every 360 rotation of the out-put shaft 444 and planetary carrier 408, 410. Further, if the eccentricity of axis A2 to Al (K~ approximates the pitch radius of the planetary gear 426 (K=l), the output spider 442 and output shaft 444 will come to a stop or near stop once every 360.

The specific configuration of FIG. 36 arbi--trarily shows the eccen-tricity of axis A2 to Al equal to the pitch radius of the planetary gear 426 (K=l~, and arbitrarily shows the eccentricity of the axis A3 to axis Ao to be equal to one-half of the pitch radius of the planetary gear 426, along the master center line (El = .5, E2 = ) Under these condi-tions, the displacement characteristic of the output shaft 444 relative to the displacement of the input, planetary carrier 408, 410, are such that there exists a momentary stop or dwell of the output once for each revolution. Here again, this dwell can be significantly enhanced by combining the mechanism 400 with the differential cam mechanism 278 by directly coupling the output shaft 444 to the input shaft 230 as is illustrated -through FIG. 43.

Referring to FIG. 43, the rotate drive pinion 98 is again mounted on the shaft 22, which is driven through coupling 350 from the output shaft 248 of the differential cam mechanism 278. The input shaft 230 of the difEerential cam mechanism 278 in -turn is driven through coupling 352 by the output shaft 444 of the natural dwell mechanism 400. The input shaft 418 of the natural dwell mechanism 400 is driven through coupling 451 from the output shaft of a worm gear reducer 452; the input shaft of this reducer 452 is connected -through a coupling 453 to the input shaft of a second worm gear reducer 454. The input shaft of the reducer 454 extends through the reducer and at its other end is driven through a coupling 455 by an electric motor 456. The output shaft 457 of the worm gear reducer 454 is connected through a coupling 458 to an extended shaft 2A, which drives the crank mecha-nism for the lifting and lowering of the transfer arms.

The differential cam mechanism 278 is phased with respect to the natural dwell mechanism 400 such that their dwells are additive as previously described, and the ratios of the gear reducers 452 and 454 are selected such that the shafts 444, 230, 248 and 22 make one revolution, from dwell to dwell, while the shafts 457 and 2A make two revolutions, with the ratio between pinion 140 and gear 128 again 2:1 as shown in FIG. 13.

~5~

Stated another way, the various gear ratios are se-lected such that the crank drive mechanism, whieh operates the lift and lower portion of the transfer mechanism, completes one 360 cycle, while the rotate drive mechanism makes one revolution moving from dwell to dwell.

The dwell eharacteristics of the tandem mechanism comprised of predrive mechanism 400, and the differential cam mechanism 278, which together constitute a long dwell mechanism, are described more fully in the aforesaid copending patent application.
They are roughly approximated by curve F, FIG. 27, while having a slightly shorter true dwell. The de-veloped path of the transfer path, accordingly, has slightly shorter straight line vertieal lift and lower seetions as compared to the path shown by curve C of FIG. 17. This arrangement is still very useful for many transfer applications.

The mechanism 460 shown in FIGS. 39, 40 and 41 is one embodiment of the mechanismsdisclosed in my U. S. Patent No. 3,730,014 and may also be used to advantage as a predrive for the differential cam mechanism 278. This mechanism 460 is configured to provide a 360 output cyele as is appropriate for this combination. A case 462 supports a stationary shaft 464 on which is mounted an input assembly, comprised of ~2~ 7 gear 466 and input spider 468 journalled on the shaft 464 through bearings 470 and 472. The gear 466 is dri~en by an input gear 474 mounted on an input shaft 476 journalled in the case 462 through bearings 478 and 480.

The stationary sun gear 482 is directly mounted to the shaft 464 which also supports a planetary earrier assembly, made up of plates 484 and 486 connected by spacers 488, through bearings 490 and 492. The planet-ary carrier assembly 484-488 carries one or more planet-ary gears 494, each of which is mounted on a plane~ary shaft 496, journalled in the planetary earrier assembly 484-488 through bearings 498 and 500. Three such planetary gears are utili~ed although only one is shown in FIGS. 39-41 and each gear meshes wi-th the stationary sun gear. At one end of each of the planetary shafts 496 is mounted an input eccentric 502 on an axis dis-placed from the axis of the assoeiated planetary shaft.
Eaeh input eecentrie 502 can rotate in a slide block 504 (FIG 41~ elosely fitted in a corresponding slot 506 of the input spider 468.

At the other end of each planetary shaft 496 is mounted an eccentric support plate 508, a portion of which is formed into an output eccentrie 510. A slide block 512 (FIG. 40) is rotatably mounted on each output ~;~5~

eccentric 510 and is closely fitted into a correspond-ing slot 514 in an output spider 516. This output spider 516 is mounted on an output shaft 518 which rotates in bearings 520 and 522 mounted in a case cover 524 fastened by bolts (not shown) to the case 562. The output shaft 518 and output spider 516 ro-tate about the same axis as the axis of the sun gear 582 and on which the input spider 468 and planetary carrier assembly 484-488 also rotate, as must be when multiple plentary gears 494 are employed.

It can be seen that as the input spider 468 is driven by the gear 466 from input gear 474, the input spider drives the planetary gears 494 through the slide blocks 504 and input eccentrics 502. If it is assumed that the input spider rotates at constant angular velocity, the planets and planetary carrier assembly will rotate at a variable angular velocity due to the eccentricity of the drive point, i.e., the input eccentric. This is covered in mathematical detail in my U.S. Patent No. 3,730,014. The planet gears 494 in turn drive the output spider through the output eccen-trics 510.

In the specific configuration shown, the planet gears 494 are equal in size to the sun gear 482, and the axis of the output eccentric lies on the pitch diameter of the planet gears 494 (Rl = 1). Therefore, the output spider and output shaft will come to a mo-mentary stop or dwell once for each revolution of the output shaft and planetary carrier assembly. Further-more, in the specific configuration shown, the input eccentric is on a radial line diametrically opposite from the radial line on which the output eccentric is located, and the input eccentric axis is displaced from the axis of the planetary gear a distance equal to 0.3 times the pitch radius of the planetary gear (R2 = 3) Under these conditions, the planetary carrier assembly is rotating more slowly than the input spider, at the time in the cycle that the output eccentric axis lies on or near the pitch line of the sun gear. This has the effect of lengtheningj in terms of time-or input ..
angle, the portion of the cycle that the output spider is stopped and in dwell, or on either side of this point near dwell.

The mechanism 460 may be utilized as an alter-nate predrive mechanism for the mechanism 400, as is also shown by FIG. 43, utilizing the alternate callout numbers 476 and 518 (in lieu of 418 and 444 respectively).

In this instance, -the tandem mechanism, constituting the long dwell mechanism, is comprised of mechanism 460 and the differential cam mechanism 278. The dwell characteristics of this combination are again more fully described in the aforesaid copending ap-plication, but may again be considered as being roughly comparable to curve F of FIG. 27 though having a slight-ly shorter true dwell, and therefore generating a de-veloped path having shorter straight end segments as compared to curve C, FIG. 17.

If the input eccentricity of mechanism 460 is reduced to zero by moving the input eccen-tric 502 to the axis of the planet gear 494, there will exist no relative movement of the input spider relative to the planetary carrier assembly 484-488. In the de-sign of this type the input spider may be eliminated and the mechanism simplified as shown in mechanism 530, FIG. 42.

Referring to FIG. 42, a case 532 supports a stationary shaft 534 on which is mounted the sun gear 482 and the plane-tary carrier assembly is again made up of plates 484 and 486 and spacers 488~ In this case a gear 536 is directly bolted to the plane-tary carrier assembly for driving; the gear 536 is driven by the input gear 474 mounted on the input shaft 476 journalled in the case as before.

'2~

The remainder of mechanism 530, FIG. 42, is identical with the mechanism 460, FIG. 39, except that the input eccentric 502 is deleted on the planetary shaft 496, since the planetary carrier assembly is now driven directly by the gear 536. In the configura-tion shown, the planet gear is again equal in size to the sun gear, and -the axis of the output eccentric lies on the pitch diameter of the sun gear. Therefore, the output spider and output shaft will come to a momentary stop or dwell once for each revolution of the output shaft and planetary carrier assembly.

Because of the deletion of the input eccentric in mechanism 530 relative to the mechanism 460, the natural dwell characteristics o~ mechanism 530 are slightly shorter. It is still useful as a predrive mechanism in a tandem mechanism with the differential cam mechanism 278, as is again shown as an alternate in FIG. 43. The detailed dwell characteristics of mechanism 530 and the dwell characteristics of its tandem combination with the differential cam mechanism 278 are again shown more fully in the aforesaid copend-ing application.

~:5~2'~

The alternate configurations of long dwell mechanism shown by the embodiments of FIGS. 34, 35 and 43 are presented as viable alternatives to the embodiment of FIG. 11 and any selection will be de-pendent on a variety of other engineering considera-tions.

In the embodiment of FIGS. 11-16, the crank drive mechanism generated the up and down movement of . the mechanical hands while the long dwell mechanism generated their rotary motion about the center of the column and ram. In a more general situation, it is equally possible to have the crank drive mechanism drive the mechanical hands about or along a firs-t axis of motion, while the long dwell mechanism drives the mechanical hands about or along a second axis of mo-tion. In all cases, the resultant developed path will be a "U" shaped path as shown by curve C of FIG. 17.

Claims

THE EMBODIMENTS OF THE INVENTION TO WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1.

In a transfer mechanism which has two degrees of freedom for movement along or about any two axes, an interrelated mechanical system to drive said transfer mechanism along a predetermined path comprising:
(a) a frame, (b) transfer means mounted in said frame for movement having said two degrees of freedom, (c) crank drive means mounted in said frame, (d) first coupling means connecting said crank drive means and said transfer means for movement along the first of said two degrees of freedom, (e) second coupling means connecting said transfer means for movement along the second of said degrees of freedom with:
(f) long dwell drive means mounted in said frame, (g) prime mover rotatable drive means for driving said crank drive means and said long dwell drive means in synchronism (h) said long dwell drive means comprising:
(1) input means mounted for rotation in said frame, (2) output means mounted for rotation in said frame, (3) variable gear ratio means interconnecting said input means and said output means, whereby upon continuous rotation of said input means, said output means rotates in a sequence of discrete unidirectional index steps separated by dwell intervals during which said output means is substantially stationary, whereby when said prime mover is rotating in a forward direction, said transfer means is driven in a forward direction in a developed topologically U-shaped path comprising a first portion during which said crank drive means drives said transfer means along said first degree of freedom, and said long dwell drive means holds said transfer means substantially stationary along said second degree of freedom; a second portion during which said long dwell drive means drives said transfer means along said second degree of freedom in a forward direction while said crank drive means moves said transfer means along said first degree of freedom and then reverses this movement along said first degree of freedom; and a third portion during which said crank drive means drives said transfer means along said first degree of freedom in the opposite direction from said first portion, and said long dwell drive means holds said transfer means substantially stationary along said second degree of freedom;
and whereby, upon directional reversal of said prime mover drive means, said transfer means is driven in a reverse direction along the same topologically U-shaped path which had been traversed by said transfer means during its movement in the forward direction;
and alternatively whereby, upon continued rotation of said prime mover drive means in a forward direction, said transfer means is driven forward along multiple, sequential, adjacent topologically U-shaped paths, which are geometrically identical but non-coincident.

2.
In a transfer mechanism which has two degrees of freedom for movement along or about any two axes, an interrelated mechanical system to drive said transfer mechanism along a predetermined path comprising:
(a) a frame, (b) transfer means mounted in said frame for movement having said two degrees of freedom, (c) crank drive means mounted in said frame, (d) first coupling means connecting said crank drive means and said transfer means for movement along the first of said two degrees of freedom, (e) second coupling means connecting said transfer means for movement along the second of said degrees of freedom with:
(f) long dwell drive means mounted in said frame, (g) prime mover rotatable drive means for driving said crank drive means and said long dwell drive means in synchronism (h) said long dwell drive means comprising:
(1) an output member adapted for tangential drive and supported by said frame for rotation and connected in an operating relationship with said second coupling means, (2) a first rotating pair supported by said frame comprising:
(i) a first rotating member mounted for rotation in said frame, (ii) a first eccentric member mounted eccentrically, in non-rotational relation to, and on said first rotating member, (3) a second rotating pair mounted in fixed spatial relationship with said first rotating pair comprising:
(i) a second rotating member, (ii) a second eccentric member mounted eccentrically in non-rotational relation to, and on said second rotating member;
(4) means connecting for rotation said first rotating pair and said second rotating pair for substantially an integral angular velocity ratio, (5) means connecting said output member and said second eccentric member in a driving relationship, and (6) means connecting said first rotating member and said prime mover drive means in a driving relationship, whereby when said prime mover is rotating in a forward direction, said transfer means is driven in a forward direction in a developed topologically U-shaped path comprising a first portion during which said crank drive means drives said transfer means along said first degree of freedom, and said long dwell drive means holds said transfer means substantially stationary along said second degree of freedom; a second portion during which said long dwell drive means drives said transfer means along said second degree of freedom in a forward direction while said crank drive means moves said transfer means along said first degree of freedom and then reverses this movement along said first degree of freedom; and a third portion during which said crank drive means drives said transfer means along said first degree of freedom in the opposite direction from said first portion, and said long dwell drive means holds said transfer means substantially stationary along said second degree of freedom;

and whereby, upon directional reversal of said prime mover drive means, said transfer means is driven in a reverse direction along the same topologically U-shaped path which had been traversed by said transfer means during its movement in the forward direction;

and alternatively whereby, upon continued rotation of said prime mover drive means in a forward direction, said transfer means is driven forward along multiple, sequential, adjacent topologically U-shaped paths, which are geometrically identical but non-coincident.
3.
A transfer mechanism as in claim 1 in which said crank drive means comprises:
(a) an input member rotatable in said frame and driven by said primer mover drive means, (b) a crankpin member mounted on said input member and eccentric from the axis of rotation of said input member, (c) a connecting rod member rotatably connected at its one end to said crankpin member and pivotally connected at its other end to (d) lever means operating between said frame, said connecting rod and said first coupling means.

4.
A transfer system as in claim 1 in which said first degree of freedom of said transfer means is linear along a first axis and said second degree of freedom of said transfer means is rotational about said first axis.

5.
A transfer system as in claim 1 in which said first coupling means comprises first bearing means operating between said crank drive means and said transfer means and transmitting axial movement but not transmitting rotary relative movement.
6.
A transfer system as in claim 1 in which said second coupling means comprises second bearing means operating between said long dwell drive means and said transfer means and transmitting rotary movement but not transmitting axial relative movement.
7.
A transfer system as in claim 1 in which said first degree of freedom of said transfer means is linear and said second degree of freedom of said transfer means is rotational.
8.
A transfer system as in claim 1 in which said long dwell drive means comprises a tandem mechanism in which a first mechanism is directly coupled to and driven by a second mechanism and said first mechanism comprises:
(a) a frame, (b) an input shaft member journalled in said frame and rotating on a first axis, (c) offset driving means mounted on said input shaft member, (d) an output shaft member journalled in said frame and rotating on a second axis substantially parallel to said first axis, (e) offset driven means mounted on said output shaft member, (f) stationary annular plate cam means mounted on said frame in a plane substantially perpendicular to said first axis and said second axis and encompassing said first axis and said second axis, and (g) cam follower means operatively associated with said plate cam means and interconnecting said offset driving means and said offset driven means, whereby a movement generated by said plate cam means in said cam follower means creates a substantially proportional movement of said driven means relative to said driving means, and said second mechanism comprises:
(h) an output member connected in an operating relationship with said input shaft member of said first mechanism, (i) a drive surface on said output member, (j) a rotary member to engage said drive surface in a tangential drive relationship, (k) means mounting said output member to guide said drive surface in a predetermined path, (1) means mounting said rotary member for rotational motion about its moving center and in driving engagement with said drive surface of said output member, (m) a rotative drive member, (n) means mounting said rotative drive member for movement in a path generally transverse of said path of said drive surface of said output member, (o) means mounting said rotary member in non-rotational relation to said drive member with the axes of said rotary member and said drive member parallel but spaced from each other wherein power rotation of said drive member causes it to rotate about the moving center of said rotary member, and (p) means to drive one of said members to impart a rotation to said rotary member while in driving relationship with said drive surface.
9.
A transfer system as in claim 1 in which said long dwell drive means comprises a tandem mechanism in which a first mechanism is directly coupled to and driven by a second mechanism and said first mechanism comprises:
(a) a frame, (b) an input shaft member journalled in said frame and rotating on a first axis, (c) offset driving means mounted on said input shaft member, (d) an output shaft member journalled in said frame and rotating on a second axis substantially parallel to said first axis, (e) offset driven means mounted on said output shaft member, (f) stationary annular plate cam means mounted on said frame in a plane substantially perpendicular to said first axis and said second axis and encompassing said first axis and said second axis, and (g) cam follower means operatively associated with said plate cam means and interconnecting said offset driving means and said offset driven means, whereby a movement generated by said plate cam means in said cam follower means creates a substantially proportional movement of said driven means relative to said driving means, and said second mechanism comprises:
(h) a frame, (i) an output member adapted for tangential drive and supported by said frame for rotation, and connected in an operating relationship with said input shaft member of said first mechanism, (j) a first rotating pair supported by said frame comprising:
(1) a first rotating member mounted for rotation in said frame, (2) a first eccentric member mounted eccentrically, in non-rotational relation to, and on said first rotating member, (k) a second rotating pair mounted infixed spatial relationship with said first rotating pair comprising:
(1) a second rotating member, (2) a second eccentric member mounted eccentrically in non-rotational relation to, and on said second rotating member, (l) means connecting for rotation said first rotating pair and said second rotating pair for substantially an integral angular velocity ratio, (m) means connecting said main output member with said first eccentric member and with said second eccentric member comprising:

(1) a first output member in tangential driving engagement with the periphery of one of said eccentric members, (2) a second output member rotatably mounted to the other of said eccentric members, and (n) power means connected to one of said rotating pairs to impart a rotary motion to that of said rotating pair.

10.
A transfer system as in claim 1 in which said long dwell drive means comprises a tandem mechanism in which a first mechanism is directly coupled to and driven by a second mechanism and said first mechanism comprises:
(a) a frame, (b) an input shaft member journalled in said frame and rotating on a first axis, (c) offset driving means mounted on said input shaft member, (d) an output shaft member journalled in said frame and rotating on a second axis substantially parallel to said first axis, (e) offset driven means mounted on said output shaft member, (f) stationary annular plate cam means mounted on said frame in a plane substantially perpendicular to said first axis and said second axis and encompassing said first axis and said second axis, and (g) cam follower means operatively associated with said plate cam means and interconnecting said offset driving means and said offset driven means, whereby a movement generated by said plate cam means in said cam follower means creates a substantially proportional movement of said driven means relative to said driving means, and said second mechanism comprises:
(h) a frame, (i) a circular reaction member mounted in said frame and concentric about a first axis, (j) a first rotating member mounted for rotation in said frame and rotating about said first axis, (k) a second rotating member of the same diameter as said circular reaction member mounted for rotation on said first rotating member and rotating about a second axis displaced from said first axis and adapted for tangential driving engagement with said circular reaction member, (1) an eccentric member mounted on said second rotating member concentric about a third axis displaced from said second axis, (m) an output member mounted for rotation in said frame and rotating about a fourth axis displaced from said first axis and in driven engagement with said eccentric member, and connected in an operating relationship with said input shaft member of said first mechanism, and (n) input power means driving one of said rotating members.

11.
A transfer system as in claim 1 in which said long dwell drive means comprises a tandem mechanism in which a first mechanism is directly coupled to and driven by a second mechanism and said first mechanism comprises:
(a) a frame, (b) an input shaft member journalled in said frame and rotating on a first axis, (c) offset driving means mounted on said input shaft member, (d) an output shaft member journalled in said frame and rotating on a second axis substantially parallel to said first axis, (e) offset driven means mounted on said output shaft member, (f) stationary annular plate cam means mounted on said frame in a plane substantially perpendicular to said first axis and said second axis and encompassing said first axis and said second axis, and (g) cam follower means operatively associated with said plate cam means and interconnecting said offset driving means and said offset driven means, whereby a movement generated by said plate cam means in said cam follower means creates a substantially proportional movement of said driven means relative to said driving means, and said second mechanism comprises:
(h) a first support member, (i) an input member rotatably mounted in said support member, (j) an output member rotatably mounted in said support member and on the same axis as said input member, and connected in an operating relationship with said input shaft member of said first mechanism, and (k) an intermediate means connecting said input member to said output member comprising:
(1) a stationary circular reaction member on the same axis as said input member and said output member, (2) a planetary carrier frame rotatably mounted in said support member, (3) one or more planetary members mounted in said planetary carrier frame positioned to roll without slipping on said circular reaction member in a planetary configuration, (4) an input shaft extending from each said planetary members, the axis of each said shaft being parallel to, but displaced from, the axis of each said planetary member, (5) means connecting said input member to each said input shaft, (6) an output shaft extending from each said planetary member, the axis of each said output shaft being parallel to the axis of each said planetary member, and (7) means connecting said output member to said output shaft.

12.
A transfer system as in claim 1 in which said long dwell drive means comprises a tandem mechanism in which a first mechanism is directly coupled to and driven by a second mechanism and said first mechanism comprises:
(a) a frame, (b) an input shaft member journalled in said frame and rotating on a first axis, (c) offset driving means mounted on said input shaft member, (d) an output shaft member journalled in said frame and rotating on a second axis substantially parallel to said first axis, (e) offset driven means mounted on said output shaft member, (f) stationary annular plate cam means mounted on said frame in a plane substantially perpendicular to said first axis and said second axis and encompassing said first axis and said second axis, and (g) cam follower means operatively associated with said plate cam means and interconnecting said offset driving means and said offset driven means, whereby a movement generated by said plate cam means in said cam follower means creates a substantially proportional movement of said driven means relative to said driving means, and said second mechanism comprises:
(h) a first support member, (i) an output member rotatably mounted in said support member, and connected in an operating relationship with said input shaft member of said first mechanism, and (j) input means rotatably mounted in said support member and on the same axis as said output member comprising:
(1) a stationary circular reaction member on the same axis as said output member, (2) a planetary carrier frame rotatably mounted in said support member, (3) one or more planetary members mounted in said planetary carrier frame positioned to roll without slipping on said circular reaction member in a planetary configuration, (4) an output shaft extending from each said planetary members, the axis of each said output shaft being parallel to the axis of each said planetary member,and (5) means connecting said output member to each said output shaft.