GB2181211A - Reciprocating long dwell mechanism - Google Patents

Abstract

A mechanism which can produce, with a constant speed rotary input, a reciprocating motion capable of producing long dwells at each end of the stroke, includes a reciprocating output device (102) at one end of which is journalled a connecting rod (126). An output shaft (38) is mounted for rotation in a frame. A crank member (122) is mounted on the output shaft (38) at its one end and journalled at its other end to the connecting rod (126). A rotary output member (36) is mounted on the output shaft (38). An eccentric drive member (34) engages a drive surface on the rotary output member (36) with a tangential driving relationship therebetween, the eccentric drive member (34) being mounted for rotational motion about its moving center and in driving engagement with the drive surface of the rotary output member (36). A rotative drive member (28) is mounted for movement in a path generally transverse of the drive surface of the rotary output member (36). The eccentric drive member (34) is mounted in non-rotational relation to the rotative drive member (28), with the axes (A3,A2) of the eccentric drive member (34) and the rotative drive member (28) parallel but spaced from each other, whereby rotation of the rotative drive member (28) causes it to rotate about the moving center of said eccentric drive member (34). Finally, there is provided a power drive for imparting a rotation to one of the drive members. <IMAGE>

Description

SPECIFICATION Reciprocating long dwell mechanism The present invention relates to reciprocating long dwell mechanisms which in combination can produce, with a constant speed rotary input, a long dwell output which can be utilized, for example, in gantrytype transfer systems with mechanical handsforwork parts.

In the field of mechanically generated motions, many applications arise in which it is desired to create a reciprocating motion from a rotary motion. These requirements are generally met with the well-known crank and slider mechanism or the related Scotch type yoke mechanism. However, these have a relatively short dwell which is inadequate for some applications.

It is an object of this invention to provide a mechanism which generates a reciprocating motion from a rotary motion and in which the output remains substantially stationary, that is, in dwell for an appreciable fraction of the overall cycle at each end of the reciprocating output stroke.

Motions of this type can also be generated by cam mechanisms, butthese are limited practically to strokes of a few feet or less before becoming very expensive.

In accordance with the present invention, there is provided a reciprocating mechanical drive system capable of providing a wide variety of kinematic objectives including long dwells atthe ends of a stroke, intermediate slowdowns, stops, or short reversals during a stroke, and non-symmetrical movement when moving in one direction as compared to the movement in the other direction, comprising:: a frame, a reciprocating output means mounted for reciprocation in said frame, connecting rod meansjournalled at one end to said reciprocating output means, an output shaft member mounted for rotation in said frame, a crank member mounted on said output shaft member at its one end and journalled at its other end to said connecting rod means, a rotaryoutput member mounted on said output shaft member, a drive surface on said rotary output member, an eccentric drive member adapted to engage said drive surface in a tangential driving relationship, means mounting said eccentric drive memberfor rotational motion about its moving centre and in driving engagement with said drive surface of said rotary output member, a rotative drive member, means mounting said rotative drive memberfor movement in a path generally transverse of said drive surface of said rotary output member, means mounting said eccentric drive member in non-rotational relation to said rotative drive member, with the axes of said eccentric drive member and said rotative drive member parallel but spaced from each other wherein rotation of said rotative drive member causes itto rotate about the moving centre of said eccentric drive member, and power drive means adapted to impart a rotation to one of said drive members.

One feature ofthe present invention is that it enables the provision of a mechanism which, by its nature, can be economically constructed to achieve strokes of 6 feet or more.

Anotherfeature of the present invention is that it enables the provision of a reversing mechanism having a dwell at each end of its stroke and having an additional dwell at a predetermined point along its stroke along one direction of travel and another such additional dwell at another predetermined point along the reverse direction of travel, where such dwells may be instantaneous stops or significant reductions of velocity.

The invention is described further hereinafter by way of example only, with reference to the accompanying drawings, in which: Figure lisa semi-schematic front view of a known mechanism disclosed in my U.S.Patent No. 3,789,676 dated February 5,1974; Figure2 is a plan view of the mechanism of Figure 1; Figure3 is a schematic representation of the mechanism of Figure 1, shown at the starting and stopping point of an index cycle; Figures 4, 5and 6are schematic representations of the mechanism of Figure 1 after rotation of the input shaft through angles of 90", 180" and 270 , respectively; Figure 7 is a front view of a known crank and connecting rod mechanism;; Figures a section taken on line 8-8 of Figure7; Figure 9 is a schematic diagram for determining the output motion ofthe crank and connecting rod mechanism of Figure 7; Figure 10 is an illustrative diagram used to define the terms "dwell amplitude" and "dwell length " ofany dwell producing mechanism, Figure 11 is a front view of an embodiment described in my U.S.Patent No. 4,490,091 dated December25, 1984, showing an application ofthis invention to rotate a mechanical hand during the lift,transfer, and rotate motion of a gantry type transfer mechanism; Figure 12 is a section taken on line 12-12 of Figure 11; Figure 13 is a graph showing the output characteristics of the mechanism of Figure 1 and the output char acteristics ofthe mechanism of Figure 11;; Figure 14is a plan view of another embodiment of this invention; Figure 15is a frontview ofthe mechanism of Figure 14; Figure 16is a graph showing the dwell characteristics of: the crank and connecting rod mechanism;the mechanism of Figure 1 with X = 1; the mechanism of Figures 14and 15with X = 1; and the mechanism of Figures 14 and 15 with A = 1 .1; Figure 17is a graph showing the angular dwell characteristics ofthe crankonlyofthe mechanism of Figures 14 and 15 forvarious values of A; Figure 18 is a graph showing the dwell characteristics of the mechanism of Figures 14 and 15 forvarious values ofX; Figure 19 is a graph showing the displacement characteristics of the mechanism of Figures 14 and 15 with a phase angle of 90 ; and a second graph showing the characteristics with a phase angle of 60";; Figure 20 is a graph showing the displacement characteristics ofthe mechanism of Figures 14 and 15, in which the output index angle ofthe mechanism 20 is 360 ; and Figure21 isa graph showing the displacement characteristics ofthe mechanism of Figures 14 and 15, in which the output index angle ofthe mechanism 20 is 90 .

First dwell mechanism - background In my existing U.S.Patent No.3,789,676, a family of mechanisms are disclosed which are capable of generating an intermittent output motion, either linear or rotary, from an input motion rotating at a given constant angular velocity. Subsequently, in the present description, U.S.Patent 3,789,676 will be referred to as "the background patent". Reference is hereby directed to the latter United States patent. A review of this background patent will indicatethatthere are several embodiments, e.g., Figures 14,15,16; 22,23,24; 25,26,27; and 33,34,35, which all provide a rotary output.Specifically referring to Figures 14,15 and 16 of the background patent, and Figures 17 to 21, which illustrate the sequential position and motion characteristics ofthat system during an index cycle, it can be seen that the output gear330 rotates through an angle of 90" during a given index cycle. This is a result of the gear 328 having a pitch diameterwhich is 1/4the pitch diameterofthe output gear 330. In the present invention which is described hereinafter, that portion ofthe mechanism arising from the background patentwill utilize an indexangle of approximately 180 . Such a mechanism is described in connection with Figures 1 to 6 ofthe presentApplication.

These Figures 1 to 6 have also previously been shown as Figures 9to 14 in my U.S.Patent No.4,490,091 and a subsequent divisional patent application U.S.Ser.No. 670,224.

Referring to present Figures 1 and 2, a mechanism 20 includes an in put gear 22 mounted on an inputshaft 24 which isjournalled in a housingorframe25On axis A1 and driven by an appropriate external drive system.

The housing 25 is shown in phantom for application reference. Alsojournalled on the inputshaft24 isa tangential link26which oscillates thereon as will be described. A driving gear 28 is mounted on a shaft30, journalled in the outboard end ofthe link 26 on axis A2, and, an intermediate gear32, alsojournalled on the link 26, is formed to mesh with the input gear 22 and driving gear 28. An eccentric gear 34 is mounted on the shaft 30 through a cheekplate 35 with an eccentricity approximately equal to its pitch radius.This eccentric gear34, rotating on a moving axis A3, meshes with an outputgear36 mounted on an outputshaft38also journalled in the housing 25on axisA4.A radial link4O is alsojournalled on the output shaft 38 at its one end; at its other end, the radial link40 is journalled to a stub shaft 42 on axis A3 mounted concentricallyonthe eccentric gear 34. It is the purpose ofthis radial link 40 to keep the eccentric gear 34 in mesh with the output gear 36 as the eccentric gear 34 moves though its rotational and translational path.

When the mechanism is in the position shown in Figure 1, it is in a natural dwell position, i.e., a small rotation of the input gear22 causes a corresponding rotation of the driving gear 28 and the eccentric gear34, but this rotation of the eccentric gear 34 is accompanied by a corresponding movement of the shaft 42 about the output shaft 38, such that the gear 34 literally rolls about the output gear 36 which remains nearly statio naryorin dwell.

A qualitative schematic representation of the motion of the output gear 36 during a complete 360 rotation ofthe driving gear28 and eccentric gear34, at90" intervals, is shown in Figures 3to 6.An arbitrary radial marker line Z has been added to the output gear 36 to show its position change at these intervals. Figure 3 shows the position ofall gears atthe center of the dwell, which is the same configuration as shown in Figure 1.

After 90' of clockwise rotation of gears 34 and 28, the position shown in Figure 4 is reached. At this point,the acceleration of gear 36 in the counterclockwise direction has reached its approximate maximum, and the velocity ofthe gear 36 in the counterclockwise direction is approximately equal to its average velocity.

As the gears 28 and 34 continue their rotation clockwise, the output gear 36 continues to accelerate, at a decreasing rate, in the counterclockwise direction from the position shown in Figure 4. After an additional 90 of rotation of gears 34 and 28,the positions shown in Figure5 are reached. At this point, the acceleration ofthe gear 36 has substantially returned to zero, and its velocity in the counterclockwise direction has reached an approximate maximum which is approximately double the average velocity.

As the gears 28 and 34 continue to rotate clockwise, the output gear 36 continues to rotate counterclockwise from the position shown in Figure 5 but is decelerating. After an additional 90 of rotation of gears 28 and 34, or a total of 270" from the start of the cycle, the position shown in Figure 6 is reached. As this point, the deceleration ofthe output gear36 is at or near maximum, while thevelocity ofthe output gear36, still inthe counterclockwise direction, has slowed down to approximately its average velocity.

As the gears 28 and 34 continue to rotate clockwise, the output gear 36 continues to rotate counterclockwise from its position shown in Figure 6, but is still decelerating, though now at a decreasing rate. After an additional 90" of rotation of gears 28 and 34, or a total of 3600 from the start ofthe cycle, the position shown in Figure 3 is again reached, with the output gear 36 having completed 1800 of rotation and is now again in dwell. The position of the marker Z has now reached the position Z1.

It can be seen, therefore, that as the input gear 22 is driven by some external power means, at a substantially constant a ng u la r velocity, the gears 28 and 34 are driven bythe intermediate gear32. Gears 28 and 34 havean angularvelocity which is determined by the superposition of the effect of the oscillation of link 26 aboutshaft 24 on the velocity created by the input gear 22 so gears 28 and 34 do not rotate at a constant angularvelocity.

And the oscillation ofthe gear 34 along the arcuate path controlled by radial link40 and-created by itseccentric mounting on shaft 30 creates another superposition on the velocity of the output gear 36. With the prop ortions shown in Figures 2 to 6, the output gear 36 will come to a complete stop or dwell once every 180", since the pitch diameter of gear 34 is shown as being one-halfthe pitch diameter of gear36.

Whereas the rotaryoutputembodimentofthe background patent shown in Figures 14to 21 therein produced an output index angle of 90", due to the proportions of gears 328 and 330, the output index angle ofthe embodiment shown in Figures 1 to 6 herein produced an output index angle of 1800 as previously described.

Furthermore, in the background patent, the mechanism of Figures 14to 16 shows a chain connection 320 from the member, sprocket 322, on axis A1 to the member, sprocket 318, on axis A2, whereas in the embodiment of present Figures 1 to 6, this equivalent drive connection is shown as being through gears 22,32 and 28.

This minor structural modification was made to achieve greater drive stiffness.

Second dwell mechanism - background The second background mechanism utilized in the present invention includes a crank and connecting rod mechanism described in many books on fundamental kinematics. It is illustrated here schematicaily in Fig ures7,8andS.

Referring to Figures 7 and 8, a shaft 50 rotates on axis A5, and isjournalled in a frame 52 through a bushing 54; this shaft 56 can be driven by any suitable prime mover. A crank 56 is fastened to the shaft 50, and at its outer end supports a crankpin 58 concentric about an axis A6. A connecting rod 60 is journalled at its one end onthecrankpin 58; at its other end it is pivot connected to a slide block 62 through a pivot pin 64 on axisA7.

The slide block 62 is supported bytheframe 52 in which it is free to slide along an axis A8, which, as shown in Figure 8, intersects the axis A5.

Figure 9 shows a schematic diagram useful to analysethe kinematic characteristics of the system of Figures 7 and 8. The distance on the crank 56 between axis A5 and As is defined as Rand the length of the connecting rod between pins 58 and 64 is defined as L. The mechanism is shown in two positions: a base position shown in solid lines (which is the top dead center position) and a position shown in dotted lines afterthe crank R has rotated from its base position by some arbitrary angle 4). From this diagram, it is easily seen that the amount the slider block 62 has moved from its base position as the crank R moves through the angleXfrom fro its base position is given by D = R- L- R cosX + Lcosa (1) where or

(2) If it is assumed that L is large compared to Rand therefore the angle a is small, even when it is ata maximum, the cos a is very closely approximated by 1,whereupon;; D=R-Rcos4)=R(1-cos4)) (3) (3) This approximate equation is for the kinematic displacement characteristics of the crank and slider block motion.

Dwell The term "dwell", in the generally accepted kinematic sense and as applied to any mechanism, is taken to mean thatthe output of that mechanism is stationary while its input continues to move. In thetheoretical sense, the output is zero; cam generated output movements often incorporate such a dwell as is well known.

However, many practical applications arise in which a true zero movement dwell is not required, but in which some very slight oscillatory motion ofthe output is acceptable. Such a situation will be defined, forthe purposes of this Application as a "near dwell"; and furthermore, it will be characterized by a numerical value which gives the maximum peak-to-peak amplitude of the output oscillation, expressed as a fraction of the total output stroke ofthe mechanism. For example, a near dwell (.001) would mean that the output oscillates during the defined near dwell through a total amplitude of .001 timesthetotal stroke ofthe mechanism.This is shown schematically in Figure 10 which further schematically defines the term "dwell length".If it is assumedthata mechanism is driven by an inputshaftwhich rotates ata constant angularvelocity, andthat the time requiredfora given index cycle is divided into 360 units, then each ofthose units is defined as 1 degree of clock angle. A dwell length of 90 clock angle, forexample, would represent a cycle inwhichthe outputwould be in near dwell for90/360 orforone quarter ofthe cycle.Clearly, ifthe inputshaftrotates through one revolution during an index cycle, then one degree ofinputshaft rotation equals one degree of clock angle; or, if, for example, the input shaft rotates through three revolutions during an indexcycle,then everythree degrees of input shaft rotation equals one degree of clock angle. Stated anotherway,the number of degrees of input shaft rotation equal to one degree of clock angle may be determined by dividingthetotal numberofinputshaft rotation degrees requiredforan index cycle by 360.

Description ofthepresentinvention The invention to be described herein is a combination ortandem mechanism employing two drive stages, the first stage of which is comprised of a rotary output indexing mechanism of the type disclosed in the background patent and in Figures 1 to 6 herein and having an output index angle ofapproximately 180'; and the second stage of which is comprised of the crank and connecting rod mechanism described above. This combination of mechanisms is both unique and useful and yields results which can be determined only by detailed analysis which must be made to ascertain the various system characteristics achievable.

The embodiment of this invention as shown in Figures 11 and 12 is used as an auxiliary mechanism to rotate a workpiece 100 during the lift, transfer and lower motion of a gantry type transfer system. Thework piece 100 is located and clamped bya cylinder actuated mechanical hand 102 mounted on a shaft 110suitably journalled in a bracket 112; the shaft 110 is driven by an actuatorarm 1 14 as will be described. The bracket 112 is mounted on one end of a transfer beam 116 which comprises the element of the gantry type transfer system which moves through the lift, transfer, and lower motion. This transfer beam 116 is supported by multiple crank arms from a horizontally moving overhead carriage.One such crank arm 118 is shown and rotates360" clockwise with respect to the transfer beam 116 during a typical transfer motion as is completely explained in my US patent4,490,091. The crank arm 1 I8supportsthetransferbeam 116 through a crankpin 120, which is journalled in thetransfer beam 1 16 and is used asthe power and synchronizing sourceforthe hand rotation mechanism to be described.The mechanism 20 in housing 25 is mounted to the transfer beam 116 and positioned such thatthe inputshaft24 is coaxial with the crankpin 120, to which it is directly coupled; orthe input shaft may be made integral with the crankpin 120, Within the housing 25, the gear system previously described in Figures 1 to 6 herein drivesthe outputgear36 and output shaft 38; the housing 25 isfurther oriented on the transfer beam such that the output shaft 38 lies approximately in the plane ofthe actuator arm 1 14. A drive crank 122 is mounted on the output shaft 38 and on itis mounted a spherical headed crankpin 124 to which isjournalled a connecting rod 126.The other end of this connecting rod 126 is pivotally connected to the actuator arm 114, again through a spherical headed pin 128 (Figure 12).

In Figures 11 and 12, the drive crank 122, connecting rod 126, and actuator arm 114 are shown intheir position corresponding to the position of the carriage in the starting position prior to a forward transfer stroke. As the carriage is moved forward through its stroke,the crank arm 118 is rotated 360' clockwise with respect to the transfer beam 116 as described in US Patent 4,490,091. This rotates the input shaft 24360" clockwise causing the output shaft 38 to rotate 180 counterclockwise with an accelerated-decelerated motion as shown by curve A of Figure 13, and by arrow M in Figure 11.It will be noted thatcurvesAand B of Figure 13 are also identical with the curves A and C respectively of Figure 15 of US Patent4,490,091. This in turn drives the actuator arm 1 14,throughthe connecting rod 126, in the direction shown by arrow N in Figure 12. Atthe completion oftheforward stroke the drive crank 122, connecting rod 126 and actuatorarm 114 reach the positions shown in dotted lines and respectively noted as 122A, 126Aand 1 14A.

It can be seen thatthe crank arm 122 and actuatorarm 114 rotate in different planes; hence, the requirement forthespherical pins at each end of the connecting rod 126. Since the crank arm and connecting rod in themselves comprise a second accelerating-decelerating mechanism, having its own dwell at each end ofthe stroke (approximately harmonic motion), this effect is superimposed on the dwell ofthe mechanism of Figure 1. This increases the dwell in the movement of the actuator arm 114 relative to the rotation of the crankarm 118. This movement relationship is shown by curve B of Figure 13 and approximates the characteristics of a cam mechanism.

The rotation angle ofthe actuator arm 114 is shown as 60 in Figure 12. This is variable by changing the length ofthe drive crank 122 and/orchanging the length ofthe actuator arm 114.

The description in connection with Figures 11, 12 and 13 presents a specific and very useful application of this invention in which it is used to provide a coordinated rotation of a workpiece synchronously with a primary lift, transfer and lower motion ofthe gantry mechanism. In this application, the very long dwell is of particular importance in delaying rotation ofthe workpiece during the lift portion ofthe transfer stroke.

However,this mechanism's usefulness is not limited to such auxiliary roles. A more generalized application is described below.

Referring to Figures 14 and 15, the mechanism 20, previously described in connection with Figures 1 to 6, is enclosed in the housing 25 and mounted on a base 140. Its input shaft 24 is driven through a coupling 142 by the output shaft 144ofa gear reducer 146 also mounted on the base 140. The input shaft 1 48 of this gear reducer is in turn driven bya motor 150 through a coupling 152. Depending on the application the motormay run continuously, or it may be stopped during the mechanism dwell with suitable conventional limit switches and electrical circuits. The crank 56 (Figures 7,8 and 9) is directly mounted on the output shaft 38 ofthe mechanism 20, whereupon axes A4 and A5 become coincident.Clearlythe shaft 50 and frame 52 (Figures7 and 8) could be retained and a coupling used to connect shafts 38 and 50 if this were more convenient. The crankpin 58 on crank 56 is used to drive the connecting rod 60 in a reciprocating motion. The other end ofthe connecting rod 60 is connected to a reciprocating output member, which may be a slider block, such as shown in Figure 8, from which the load is driven, orthe connecting rod 60 may be directly connected to an input member ofthe load to be driven. Such an input member may be a link, a bellcrank, or a sliding member.

In any case, the output movement will be as given by the approximate equation (3) derived above, where the angle 4 is nowthe output angle of the mechanism 20.

Referring to the background patent, the velocity was shown to be:

It will be noted that cur is the ratio of the distance from axis An to A2to the distance from the axis A2 toA2 (Figure 1) and is generally a large number. Therefore, as afirst orderapproximation,the denominator (a2- 1 + sin20)1/2 will be large, and the entire fraction negligibly small. Equation (4) will therefore reduce to: AcosO d6 This equation may be integrated to give the displacement: U=6-sin6+C1 (6) This is a general approximate equation for the displacement, properly dimensioned and scaled, for any of the embodiments of the background patent.

Unitized output For comparative purposes in comparing the dwells, and other characteristics, of the mechanism of Figures 1-6,thecrankmechanism of Figures 7-9, and the combination mechanism of Figures 14 and 15, it is convenientto scale the output of each system such that the index stroke is arbitrarily set to equal 1. Similarly,the input angle is defined in terms oftheclockanglewhich has a range of 360"to createthe output stroke ofi.

Underthese arbitrary scaling procedures, equation (3) becomes

where Du = "unitized" output 4)c= "clock" angle This rescaling is dependent on the following reasoning relative to equation (3). The minimum position occurs when 6 = 0, and D = 0 independentofthevalue ofR. The maximum position occurs when = 180 and D is equal to 2R. Therefore, by setting

the maximum reaches 1 when #c = 360 and it is by substituting these values for R and # into equation (3) that equation (7) is obtained.

The output displacement from equation (7), in the near dwell area, is tabulated in Table I and shown graph- ically by curve Ref Ain Figure 16.

TABLE I Unitized displacement ofa simple crank mechanism near dwell Clockangle Unitized displacement -20 .007596 -15 .004278 -10 .001903 - 5 .000476 0 0 5 .000476 10 .001903 15 .004278 20 .007596 By following a comparable process, the generalized displacement equation (6), which represents the mechanism 20, may be scaled to provide

The factor qr/180 is used as a multiplier of4)c to convertthe "clock angle" to radians, as required by the basic theory of the background patent; and the factor 1/2sir is a required scale factor on the bracketed quantity, since, when the clock angle reaches 360% the value of that bracketed quantity is 21T.The constant of integration C1 is in effect a phase angle and will besetto 0forthe initial comparative purposes.Equation (8) therefore reducesto:

By referring to equation (4), it can be shown thatforthevelocityto be zero when û = 0, A must be 1, i.e.,the distance from axis A2to axis A3 of the mechanism of Figures 1-6 must be equal to the pitch radius ofthe gear 34, whereupon equation (9) further reduces to:

The output displacement,from equation (10), in the near dwell area, istabulated in thefoliowing Table II and shown graphically by curve Ref B in Figure 16.

TABLE II Unitized displacement ofa mechanism ofpatent3,789,676 near dwell Clockangle Unitized displacement -20 .001121 -15 .000474 -10 .000141 - 5 .000018 0 0 5 .000018 10 .000141 15 .000474 20 .001121 Two observations may be made relevantto Tables land II andtheirgraphical representation in curves RefA and Ref B of Figure 16. The first concerns the relative shortness of their individual dwells. If,forexample,the dwell amplitude is arbitrarily defined as .001 (in unitized displacement), the dwell length ofthe connecting rod mechanism is approximately +8 foratotal length of approximately 16"; this is obtained from curve Ref A.For the mechanism 20, the intersection ofthe curve Ref Bwiththe the +.0005 and -.0005 lines (foratotal of .001) is found to be approximately + i60 for a total of approximately 32".

The second observation concerns the directional behavior of the displacement in the vicinity of the dwell.

Relative to the crank and connecting rod mechanism, it can be seen that the displacement on either side ofthe center of dwell, where the clock angle is0, is unidirectional as would be expected with an inherently reversing mechanism such as a crank and connecting rod. On the other hand, it can be seen that, relative to the mechanism 20, the displacement on either side of the center of dwell is bidirectional; this is again as would be expected for an indexing mechanism of this type; i.e.,for unidirectional input shaft rotation,the outputwill momentarily stop aftera given index, butthen reaccelerate in the same direction it had beforestopping.

Theforegoing data on the near dwell characteristics of each of the mechanisms operating independently are provided as reference data forthe new data to be shown.

In the present invention, as illustrated in the mechanism of Figures 11 and 12 and 14 and 15, it is necessary to rescale equation (6), representing the mechanism of Figures 1-6 and equation (3) representing the crank mechanism of Figures 7-9. By a process similarto the one described above, equation (6) is rescaledto:

which reduces to

where + is the true output angle, in degrees, ofthe shaft 38 (Figure 2).

Equation (3) is rescaledto: Du =5 [1 - cos(4))] (13) where + is again the true angle in degrees ofthe shaft 38 which is the input shaft ofthe crankmechanism.The displacementcharacterisics ofthe combined mechanism of Figures 14 and 15 is therefore obtained bycombining equations (12 and (13) as follows:

which simplifies to:

The arbitrary quantity C1 (which was the constant of integration) represents a phase angle between the two mechanisms. It it is set toO, it means physically that the mechanism 20 is at the center of its dwell when the crank is at its top dead center or bottom dead center position. For the first analysis, it is set toO; othervalues will be subsequently analyzed.

Similarly,thefactorX is initially set equal to 1 as was doneforthe analysis ofthe individual mechanism 20; subsequent analyses will be made with values ofX other than 1. The unitized displacementforthecombined mechanism, which comprises this invention, as calculated from equation (15) with C1 = 0 and A = 1 is given in Table III and shown as curve C in Figure 16.

TABLE III United displacement of one embodiment ofthis invention Clockangle Unitized displacement -60 .002050 -50 7.10x10-4 -40 1.91x104 -30 3.48x10-5 -20 3.10x10-6 -10 Lessthan 1 x 10-7 0 0 10 Less than 1x10-7 20 3.10x10-6 30 3.48 x 10-5 40 1.91x10-4 50 710x10-4 60 2.050 x 10-3 Two observations may also be made with respect to curve C, Figure 16 representing the dwell behavior of the combined mechanism.The first concerns the width ofthe dwell, again for the arbitrarily set value of dwell amplitude of .001.The magnitude of the dwell length is seen to be approximately 53" for a total dwell length of 106" which is more than double the sum ofthe dwells ofthe individual mechanisms.

Nextthe importance ofthe factorwill be shown. If, in equation (15) is arbitrarily set equal to 1 .1,whilethe phase angle C1 is still set equal toO, afurtherincrease in the dwell length is found as shown in Table IVand curve D in Figure 16.

TABLE IV Unitized displacement on an embodiment of this invention A = 1.1 Clockangle Unitized displacement -70 2.21 x 10-3 -60 5.59x10-4 -50 5.63 x 10-5 -40 4 99 x 10-6 -30 4.36x10-5 -20 4.61 x 10-5 -10 1.70x10-5 0 0 10 1.70x10-5 20 4.61 x 10-5 30 4.36x10-5 40 4.99 x 10-6 50 5.63x10-5 60 5.59x10-4 70 2.21 x 10-3 This highly desirable lengthening ofthe dwell may be explained as follows.The setting of at 1.1 means that the distance between axes A2 and A3 of the mechanism 20, Figures 1-6, is 1.1 times the pitch radius ofthe eccentric gear34. In turn,this condition causesthe output gear36to experience a slight "overshoot" before it reaches th'e center of the dwell, and then a reversal to the 0 point at the center of the dwell. This reversal continues through the 0 point, and "undershoots" with continued input shaft rotation, before the output gear continues its nextforward index. Since the crank 56, Figures 7,8, 14 and 15, and crank 122 of Figures 11 and 12, rotates in unison with the output shaft 38 and the output gear 36, this results in a slight oscillation ofthe crank 56 (Figures7 and 8).This is quantitatively shown by curve D' in in Figure 17 which shows the true crank angle, in degrees, plotted against clockangle, where 0 degrees on the crank angle scale represents atop dead center or bottom dead center position. For curve D', which represents the condition for A 1.1, it can be seen that the oscillation amplitude of the output gear 36 and crank 56 is + 0.82"; this in turn creates a significant increase in dwell length for the overall system as shown by curve D (X = 1.1) relative to curve C (A = 1.0) in Figure 16. lndeed,forthe arbitrary previously chosen dwell amplitude of.001,the dwell length forX = 1.1 is seen to be #64 for a total dwell length of 128 , which is some 20% more than for curve C (A = 1.0).

Astill furtherimprovementofthe dwell length can be made by increasing Still more. With setequalto 1.2, the dwell characteristics ofthe total system are shown by curve E of Figure 18which is plotted to the same scale as Figure 16. The corresponding curve showing the overshoot, reversal and undershoot of the crank 56, and output gear 36, as plotted in true crank angle, is shown by curve E' of Figure 17, from which it can be seen that the crank oscillates through an angle of +2.2". The magnitude of this oscillation is now sufficiently great to manifest itself in the overall system dwell curve E of Figure 18.Clearly the "lobes" ofthe curve E from -58" to 0"and from 0 to 58"are caused bythe crank oscillation shown by curve E', Figure 17. Itwill also be noted thatthe dwell length,foran amplitude of .001 and X 1.2, curve E, is now j74"foratotal dwell length of 148".

Itfollows, therefore, thatforthe dwell length to be maximized for some arbitrary but knowledgably set value ofthe dwell amplitude, a # can befound in which the heightofthe lobes on either side ofthe centerof dwell are equal in amplitude to the set dwell amplitude. With respect to the previously set dwell amplitude of .001, avalue of Awasfound which creates this condition.Fora X of 1.2829, the system displacement curve F, Figure 18 was calculated, in which it will be noted, the lobes on either side of the center of dwell just touch the .001 displacement line at i40". The corresponding crank angle oscillation is shown by curve F', Figure 17 and is # 3.624 , which values are reached at approximately +40"clock angle. The dwell length, as shown by curve F, Figure 18 is 79" fora total dwell length of 158". This issome49% longerthanthetotal dwell length of curve C, Figure 16 (A = 1) and over three times greater than the sum ofthe dwells ofthe individual mechanisms.

The value of A = 1.2829 used to calculate curve F and F' was found by a process of successive approximation. With a programmable calculator or computer, it is a relatively simple process to iterate the value of either by a manual or automatic loop process to achieve a maximum lobe amplitude equal to the set.001.

By a similar process of successive approximation, values of A were fond which give other dwell amplitu des, in which the lobes approximate the set values thereof. These, together with the resultant dwell lengths, are tabulated below: Set value Dwell Dwell amplitude h length .00001 1.058 74" .0001 1.13 114" .001 1.283 148" The selection of dwell amplitude is determined by the application intended. Oncethis is known, it is a simple process to find the Xthat gives the longest dwell, or conversely, if the dwell length required is known and the smallest dwell amplitudeforthatgiven dwell length is sought, A may be iterated again to the new objective.

The curves of Figures 17, 18 and 19, and the descriptions thereof addressed themselves to achieving the longest dwell length possible for a given dwell amplitude. This was accomplished by setting the phase angle equal to 0, where the phase angle mathematically is represented bythe value C1 in equation (15), and is mechanically represented by the angle ofthe crank 56 away from its top dead center or bottom dead center position when the mechanism 20 is at the center of its dwell. The maximum systems dwell is reached when the phase angle isO.

However, other useful objectives can be achieved when the phase angle is set to some value otherthan 0.

For example, if the phase angle is set equal to 90 , a dwell or near dwell ofthe crank rotation, and its output motion can be reached midway during its stroke, dependent on the value of A. Physicallythis meansthat when the mechanism 20 is atthecenter of its dwell,theangle+, Figure 9, is equal to 90". This is merelya matter of assembly positioning ofthe crank 56 on the shaft 38, for example, in Figure 15.

The unitized displacement curve G of Figure 19 represents the output ofthis invention for a given phase angle of 90with Xsetequal to 0.9. The clock angle is shown as moving through 720" which is two indexes of the mechanism 20 but only one revolution ofthe crank 56. The momentary stops atthe ends ofthe strokes are evident at clock angles of 1800and 540". Asignificantslowdown to a near stop at clock angles of 360 and 720" (720" is the same position as 0 ) is also evident.The slowdown, as differentiated from a complete stop, is a resultofthe arbitrarily illustrated X = 0.9; if were set equal to 1,the output would come to an instantaneous stop ate" and 360". Furthermore, if A were made slightly largerthan 1,therewould be a slight output reversal at these angles. This midstroke slowdown is useful in many applications such as lifting or lowering oftransfer bars which pick up ordepositworkpieces at our nearmidstroke.

Anotherillustrativeoutputdisplacementgraph is shown in curve H, Figure 19. Inthisexample,thephase angle was set to 60" and X set eq u al to 0.8. Again the momentary stops and reversals can be seen at215"and 575" clock angle. Asignificantslowdown is evident ate" and 360" clock angle. Here again, the slowdown can be greater if A is increased, and a momentary stop achieved at = = 1, or a slight reversal obtained by making X slightly more than 1.It is further evident that the slowdown occurs at different positions of the output on forward stroke than on the return stroke, iftheforward stroke is defined as 575" to 215"clockangle and the return stroke defined as 215" to 575". On the forward stroke,the slowdown occurs at a displacement of .25 and on the return stroke the slowdown occurs art a displacement of .75. A property such as this is useful,for example, in operating a lift system such as in my copending United States application Ser.No. 763,350, filed August 7,1985, where it is desired to slow down atone level moving up and at another level moving down.

The foregoing performance descriptions are illustrative only. Clearly there exist many combinations, which are mathematically represented by the factors and C1 in equation (15) which provide useful results; and as previously noted these factors and C1 are controlled inthetotal mechanical system by the design ofthe distance from axis A2 to axis and bythe assembly positioning ofthe crank 56 on the shaft 38 (Figures 14, 15).

All the performance curves shown in Figures 16-19 were derived on the basis of equation (15), which, itwill be recalled, was derived after making some approximating simplifications. However, in rigorously calculating the performance of these systems without approximations by numerical computer calculations (classical math non-approximating calculations become hopelessly complex), it has been found that a very high degree of correlation can be found between the characteristics described herein and the exact characteristics numerically calculated. This has involved adjusting, by successive approximations, such factors as the distance between axes A1 and A2 and between axes A4 and A1 of mechanism 20.

In all ofthe combination mechanisms shown above, independent ofthe values ofX and the phase angle C1, the mechanism 20 was scaled to generate a 180" output rotation during a given index cycle, as previously explained. However, this invention has still further applications when the output index angle of mechanism 20 is otherthan 1800. As noted earlier, and as shown in the reference patent, the output angle index angle is determined by the ratio ofthe pitch diameter ofthe output gear 36 to the pitch diameter of the electric gear34.

If thins ratio is defined as M, the output index angle is 360/M. Stated another way, there are M indexes per revolution. If equation (6) which, it will be recalled, is the equation for calculating the output angle of mech anism 20, is rescaled in the general form, it becomes:

which simplifies to:

When Mis 2, the index angle is 180" and equation (17) reduces to the already stated equation (12). If equation (17) is substituted into equation (13) and simplified, the total combination mechanism output, in unitized displacement, is found to be:

Again, it can be seen that when M = 2, equation (18) reduces to the form, previously derived forthe 180" index angle, of equation (15).Using equation (18), the unitized displacement characteristics ofotherembodi- ments ofthis invention have been calculated.

The first of the illustrative examples is shown in Figure 20. In this instance, M was set equal to 1 represent ing a 3600 output index angle ofthe mechanism 20, h Awas set equal to 1.1 and C1 set equal toO. The curve of Figure 20 shows a reciprocating output having a very long dwell atone end ofthe stroke, and a relatively short dwell at the other end ofthe stroke; this is useful in applications in which the sevice is such that the prime movere.g., motor 150, Figure 14, is stopped after each reciprocation, and it is requiredthata very accurate output position be maintained over a wide range of stopping positions of the prime mover.

Another illustrative example is shown in Figure 21. In this instance M was set equal to 4, representing a 90" output index angle ofthe mechanism 20, h Awas set equal to 1 and C1 set equal toO. The curve of Figure21 again shows a reciprocating output having a relatively long dwell at each end of the stroke, together with a significant dwell atthe midpoint of each stroke. This duplicates the performance, in principle, ofthe con- ditions ofcurve G of Figure 19, except that by using the conditions of Figure 21, both the dwells at the ends of the strokes are longer, providing more stopping leeway for motor stoppage when that mode is being used in the application.

From the descriptions of the above illustrative combinations, it is clearthat a wide variety of kinematic characteristics can be achieved through a proper selection of the various parameters involved, which may be summarized asfollows: A. The Afactor controls the cyclic behavior of the mechanism 20; with A = 1,this output shaft will cometo a momentary stop onceforeach revolution ofthe eccentric gear; with X slightly less than 1,the outputshaftwill cometo a near stop after each revolution of the eccentric gear; and, with A slightly more than 1 ,the output shaft will slightly reverse after each revolution of the eccentric gear.

B. The M factor controls the number of stops, near stops, or reversals ofthe output shaft made during one total revolution ofthe output shaft.

C. The phase angle + controls the angular relationship ofthe output crank angular position from itstop dead center position when the driving mechanism 20 is at the center of its dwell or neardwell.

The description made above relates to the rotary output indexing system typified by Figures 14, 15 and 16 of the background patent, US No. 3,789,676, as earlier noted, exceptthatthe chain 320 was replaced by an equivalentgeartrain in the mechanism of Figures 1-6 herein. It should be noted, however,thatthe chain drive system of Figures 14,15 and 16 ofthe background patent is usable for many applications in which extreme accuracy or rigidity are not required. lndeed,the double chain system illustrated in Figures 33, 34 and 35 ofthe background patent is also usable subject to chain load and rigidity limitations. Furthermore, the rotary output systems illustrated in Figures 22, 23 and 24 and by Figures 25, 26 and 27 in the background patent are also usable subjecttothe limitationthatthese embodiments are limited to maximum output index angles of 120".

Claims (15)

1. A reciprocating mechanical drive system capable of providing a wide variety of kinematic objectives including long dwells at the ends of stroke, intermediate slowdowns, stops, orshort reversals during a stroke, and non-symmetrical movement when moving in one direction as compared to the movement in the other direction, comprising:: a frame, a reciprocating output means mounted for reciprocation in said frame, connecting rod means journalled at one end to said reciprocating output means, an output shaft member mounted for rotation in said frame, a crank member mounted on said output shaft member at its one end and journalled at its other end to said connecting rod means, a rotary output member mounted on said output shaft member, a drive surface on said rotary output member, an eccentric drive member adapted to engage said drive surface in a tangential driving relationship, means mounting said eccentric drive memberfor rotational motion about its moving center and in driving engagement with said drive surface of said rotary output member, a rotative drive member, means mounting said rotative drive member for movement in a path generally transverse of said drive surface of said rotary output member, means mounting said eccentric drive member in non-rotational relation to said rotative drive member, with the axes of said eccentric drive member and said rotative drive member parallel but spaced from each other wherein rotation of said rotative drive member causes it to rotate about the moving center of said eccentric drive member, and power drive means adapted to impart a rotation to one of said drive members.

2. A reciprocating mechanical drive system capable of providing a wide variety of kinematic objectives including long dwells at the ends of a stroke, intermediate slowdowns, stops, orshort reversals during a stroke, and non-symmetrical movement when moving in one direction as compared to the movement in the other direction, comprising: (a) a rotary output drive system comprising:: (1) a frame, (2) an output shaft member mounted for rotation in said frame, (3) a rotary output member mounted on said output shaft member, (4) a drive surface on said rotary output member, (5) an eccentric drive member adapted to engage said drive surface in a tangential driving relationship, (6) means mounting said eccentric drive memberfor rotational motion about is moving center and in driving engagement with said drive surface of said rotary output member, (7) a rotative drive member, (8) means mounting said rotative drive memberfor movement in a path generally transverse of said drive surface of said rotary output member, (9) means mounting said eccentric drive member in non-rotational relation to said rotative drive member with the axes of said eccentric drive member and said rotative drive member parallel but spaced from each other wherein rotation of said rotative drive member causes itto rotate about the moving center of said eccentric drive member, (10) power drive means adapted to impart a rotation to one said drive members, whereby upon such a rotation of one of said drive members said output shaft member rotates ata cyclically varying velocityincluding cyclically slowing down, stopping, and undergoing a slight reversal, dependent upon the distance between the axes of said eccentric drive member and said rotative drive member, and the number of such cyclic variations per revolution of said output shaft is the ratio ofthe pitch radius of said output member to the pitch radius of said eccentric member, and (b) a reciprocating output drive system comprising:: (1) a crank member mounted at its one end to said outputshaftmember, (2) connecting rod means journalled at its one end to the other end of said crank member, and (3) reciprocating output means mounted for reciprocation in said frame, and pivotal ly connected to the other end of said connecting rod means.

3. A reciprocating mechanical drive system as claimed in claim 2 in which said rotary output member has a pitch radius which is two times the pitch radius of said eccentric drive member.

4. A reciprocating mechanical drive system as claimed in claim 2 in which said crank member is positioned on said output shaft member such that when said rotary output drive system is positioned equally between any two adjacent indexing cycles, said crank member and said connecting rod memberaresubstan- tially colinear.

5. A reciprocating mechanical drive system as claimed in claim 2 in which the pitch radii of said rotary output member and said eccentric drive member are equal.

6. A reciprocating mechanical drive system as claimed in claim 2 in which said rotary output member has a pitch radius which is fourtimes the pitch radius of said eccentric drive member.

7. A reciprocating mechanical drive system as claimed in claim 2 in which said crank member is positioned on said output shaft member such that when said rotary output drive system is positioned equally between any two adjacent indexing cycles, said crank member is positioned by some predetermined phase angle from a reference position, in which said crank member and said connecting rod member are substantially colinear.

8. A reciprocating mechanical drive system capable of providing a wide variety of kinematic objectives including long dwells atthe ends of a stroke, intermediate slowdowns, stops, or short reversals during a stroke, and non-symmetrical movement when moving in one direction as compared to the movement in the other direction, comprising:: (a) a frame, (b) reciprocating output means mounted for reciprocation in said frame, (c) connecting rod meansjournalled atone end to said reciprocating output means, (d) an output shaft member mounted for rotation in said frame, (e) a crank member mounted on said output shaft member at its one end and journalled at its otherendto said connecting rod means, (f) a rotary output gear member mounted on said output shaft member, (g) gear teeth on said rotary output gear member, (h) an eccentric gear drive member adapted to engage said gearteeth in a tangential driving relationship, (i) means mounting said eccentricgeardrive memberfor rotational motion about its moving center and in driving engagement with said gear teeth of said rotary gear output member, (j) a rotative gear drive member, (k) means mounting said rotative gear drive memberformovement in a path generally transverse of said gear teeth of said rotary output gear member, (I) means mounting said eccentric gear member in non-rotational relation to said rotative gear drive member with the axes of said eccentric gear drive member and said rotative gear drive member parallel but spaced from each other wherein rotation of said rotative gear drive member causes itto rotate aboutthe moving center of said eccentric gear drive member, and (m) powerdrive means adapted to impart a rotation to one of said drive members.

9. A reciprocating mechanical drive system capable of providing a wide variety of kinematic objectives including long dwells at the ends of a stroke, intermediate slowdowns, stops, or short reversals during a stroke, and non-symmetrical movement when moving in one direction as compared to the movement in the otherdirection,comprising: (a) a rotary output drive system comprising:: (1) a frame, (2) an outputshaft member mounted for rotation in said frame, (3) a rotary output gear member mounted on said output shaft member, (4) gearteeth on said rotary output gear member, (5) an eccentric gear drive member adapted to engage said gearteeth in a tangential driving relationship, (6) means mounting said eccentricgeardrive memberfor rotational motion about is moving center and in driving engagementwith said gearteeth of said rotary output gear member, (7) a rotative gear drive member, (8) means mounting said rotative gear drive memberfor movement in a path generallytransverse of said gearteeth of said rotary output gear member, (9) means mounting said eccentric gear drive member in non-rotational relation to said rotative gear drive memberwith the axes of said eccentric gear drive member and said rotative gear drive member parallel but spaced from each other wherein rotation of said rotative gear drive member causes itto rotate aboutthe moving center of said eccentric gear drive member, (10) powerdrive means adaptedto impart a rotation to one of said drive member, whereby upon such a rotation of one of said drive members said output shaft member rotates at a cyclically varying velocity including cyclically slowing down, stopping, and undergoing a slight reversal, dependent upon the distance between the axes of said eccentric gear drive member and said rotative gear drive member, and the number of such cyclic variations per revolution of said output shaft is the ratio of the pitch radius of said output member to the pitch radius of said eccentric member, and (b) a reciprocating output drive system comprising:: (1) a crank member mounted at its one end to said output shaft member, (2) connecting rod meansjournalled at its one endtothe other end of said crank member, and (3) reciprocating output means mounted for reciprocation in said frame, and pivotally connected to the other end of said connecting rod means.

10. A reciprocating mechanical drive system as claimed in claim 9 in which said rotary output gear member has a pitch radius which is two times the pitch radius of said eccentric gear drive member.

11. A reciprocating mechanical drive system as claimed in claim 9 in which said crank member is positioned on said output shaft member such that when said rotary output drive system is positioned equally between any two adjacent indexing cycles, said crank member and said connecting rod memberaresubstan- tiallycolinear.

12. A reciprocating mechanical drive system as claimed in claim 9 in which the pitch radii of said rotary output gear member and said eccentric gear drive member are equal.

13. Areciprocating mechanical drive system as claimed in claim 9 in which said rotaryoutputgear member has a pitch radius which isfourtimes the pitch radius of said eccentric gear drive member.

14. A reciprocating mechanical drive system as claimed in claim 9 in which said crank member is positioned on said output shaft member such that when said rotary output drive system is positioned equally between any two adjacent indexing cycles, said crank member is positioned by some predetermined phase angle from a reference position, in which said crank member and said connecting rod memberaresubstanti ally colinear.

15. A reciprocating mechanical drive system, substantially as hereinbefore described with reference to and as illustrated in Figures 11 to 21 ofthe accompanying drawings.