CA1271055A - Reciprocating long dwell mechanism - Google Patents
Reciprocating long dwell mechanismInfo
- Publication number
- CA1271055A CA1271055A CA000515790A CA515790A CA1271055A CA 1271055 A CA1271055 A CA 1271055A CA 000515790 A CA000515790 A CA 000515790A CA 515790 A CA515790 A CA 515790A CA 1271055 A CA1271055 A CA 1271055A
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- Canada
- Prior art keywords
- drive
- gear
- output
- eccentric
- rotative
- Prior art date
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H37/00—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00
- F16H37/12—Gearings comprising primarily toothed or friction gearing, links or levers, and cams, or members of at least two of these types
- F16H37/124—Gearings comprising primarily toothed or friction gearing, links or levers, and cams, or members of at least two of these types for interconverting rotary motion and reciprocating motion
Abstract
ABSTRACT OF THE DISCLOSURE
Mechanisms which can produce, with a constant speed rotary input, a reciprocating motion capable of producing very long dwells at each end of the stroke, unequally long dwells at opposite ends of a stroke, and/or momentary stops intermediate the ends of a stroke. It can be utilized to coordinate a slave workpiece manipulation system in cooperation with a Gantry type transfer system or, with its own drive system, it can be utilized wherever the aforesaid characteristics are useful.
Mechanisms which can produce, with a constant speed rotary input, a reciprocating motion capable of producing very long dwells at each end of the stroke, unequally long dwells at opposite ends of a stroke, and/or momentary stops intermediate the ends of a stroke. It can be utilized to coordinate a slave workpiece manipulation system in cooperation with a Gantry type transfer system or, with its own drive system, it can be utilized wherever the aforesaid characteristics are useful.
Description
1~7~J~
Related Applications The subject matter of this application is related to that included in my United States Patent No. 4,490,091 which issued on December 25, 1984.
Title !
Reciprocating Long Dwell Mechanism Field of Invention Mechanism which in combination can produce, with a constant speed rotary input, a long dwell output which can be utilized, for example, in gantry type transfer systems with mechanical hands for work parts.
Backaround and Obiects of the Invention 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.
Itisan object of this inventiontoprovidea mechanism which generates a reciprocating motion from a rotary motion and in which the output remains substantially stationary, that is, - 1~71055 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, but these are limited practically to strokes of a few feet or less before becoming very expensive.
It is another object of this invention to provide a mechanism which, by its nature, can be economically constructed to achieve strokes of 6 feet or more.
Another object of this invention is to provide 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 anotherpredeterminedpoint alongthe reverse direction of travel, where such dwells may be instantaneous stops or significant reductions of velocity.
This invention is directed to 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 other direction.
The structure involves the use of a rotary output drive system ~27~05~
, .
which is comprised of a frame, an output shaft member mounted for rotation in said frame, a rotary output member mounted on said output shaft member, a drive surface on said rotary output member, an eccentric drive member rotatable about a moving center to engage said drive surface in a tangential driving relationship, means mounting said eccentric drive member for 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 to impart a rotation to one of said drive members, 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 drive member and said rotative 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. The invention also utilizes a reciprocating output .~
~271055 drive system which includes a crank member mounted at its one end to said output shaft member, connecting rod means journalled at its one end tothe other end of said crank member,reciprocating output means mounted for reciprocation in said frame, and pivotally connectedto the other end of saidconnecting rodmeans.
Other features of the invention will be apparent in the following description and claims in which the principle of the invention is disclosed together with details directed to persons skilled in the art to enable the invention to be utilized all in connection with the best modes presently contemplated for the invention.
Brief Description of the Drawinqs DRAWINGS accompany the disclosure and the various views thereof may be briefly described as:
-2b-A
`"-" 1~7105S
FIG. 1, a semi-schematic front view of a mechanism which is one embodiment of the mechanisms disclosed in my U.S.
Patent No. 3,789,676, dated February 5, 1974.
FIG. 2, a plan view of the mechanism of FIG. 1.
FIG. 3, a schematic representation of the mechanism of FIG. 1, shown at the starting and stopping point of an index cycle.
FIGS. 4, 5 and 6, schematic representations of the mechanism of FIG. 1 after rotation of the input shaft through angles of 90, 180 and 270, respectively.
FIG. 7, a front view of a crank and connecting rod mechanism.
FIG. 8, a section taken on line 8--8 of FIG. 7.
FIG. 9, a schematic diagram for determining the output motion of the crank and connecting rod mechanism of FIG. 7.
FIG. 10, an illustrative diagram used to define the terms dwell amplitude and dwell length of any dwell producing mechanism.
FIG. 11, a front view of an embodiment of my U.S.
Patent No.4,490,091, dated Dec. 25, 1984, showing an application of this invention to rotate a mechanical hand during the lift, transfer, and rotate motion of a gantry type transfer mechanism.
FIG. 12, a section taken on line 12--12 of FIG. 11.
FIG. 13, a graph showing the output characteristics of the mechanism of FIG. 1 and the output characteristics of the mechanism of FIG. 11.
FIG. 14, a plan view of another embodiment of this invention.
FIG. 15, a front view of the mechanism of FIG. 14.
FIG. 16, a graph showing the dwell characteristics of: the crank and connecting rod mechanism; the mechanism of ~27~0r,5 FIG. 1 with ~= 1; the mechanism of FIGS, 14 and 15 with ~ = 1; and the mechanism of FIGS. 14 and 15 with ~ = 1.1.
FIG. 17, a graph showing the angular dwell charac-teristics of the crank only of the mechanism of FIGS. 14 and 15 for various values of ~.
FIG. 18, a graph showing the dwell characteristics of the mechanism of FIGS. 14 and 15 for various values of ~.
FIG. 19, a graph showing the displacement characteristics of the mechanism of FIGS. 14 and 15 with a phase angle of 90; and a second graph showing the characteristics with a phase angle of 60.
FIG. 20, a graph showing the displacement charac-teristics of the mechanism of FIGS. 14 and 15, in which the output index angle of the mechanism 20 is 360.
FIG. 21, a graph showing the displacement charac-teristics of the mechanism of FIGS. 14 and 15, in which the output index angle of the mechanism 20 is 90.
First Dwell ~echanism - Backaround 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 this disclosure, the Patent 3,789,676 wiil be referred to as the background patent. A review of this background patent will indicate that there are several embodiments, e.g., FIGS. 14, 15, 16; 22, 23, 24; 25, 26, 27; and 33, 34, 35, which all provide a rotary output. Specifically referring to FIGS.
14, 15 and 16 of the background patent, and FIGS. 17 to 21, i~7~55 which illustrate the sequential position and motion characteristics of that system during an index cycle, it can be seen that the output gear 330 rotates through an angle of 90 during a given index cycle. This is a result of the gear 328 having a pitch diameter which is ~ the pitch diameter of the output gear 330. In this present invention which will subsequently be described, that portion of the mechanism arising from the background patent will utilize an index angle of approximately 180. Such a mechanism is described in FIGS. 1 to 6 of the present disclosure.
These FIGS. 1 to 6 have also previously been shown as Figs. 9 to 14 in my U. S. Patent No. 4,490,091.
Referring to FIGS. 1 and 2, a mechanism 20 includes an input gear 22 mounted on an input shaft 24 which is journalled in a housing or frame 25 on axis Al and driven by an appropriate external drive system. The housing 25 is shown in phantom for application reference. Also journalled on the input shaft 24 is a tangential link 26 which oscillates thereon as will be described. A driving gear 28 is mounted on a shaft 30 journalled in the outboard end of the link26 onaxisA2, and, anintermediate gear 32, also journalled in 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 gear 34, rotating on a moving axis A3, meshes with an output gear 36 mounted on an output shaft 38 also journalled in the housing 25 on axis A4. A radial link 40 is also journalled on the output shaft 38 at its one end; at its other end, the ~27~()55 .
radial link 40 is journalled to a stub shaft 42 on axis A3 mounted concentrically on the eccentric gear 34. It is the purpose of this radial link 40 to keep the eccentric ~ear 34 in mesh with the output gear 36 as the eccentric gear 34 moves through its rotational and translational path.
When the mechanism is in the position shown in FIG. 1, it is in a natural dwell position, i.e., a small rotation of the input gear 22 causes a corresponding rotation of the driving gear 28 and the eccentric gear 34, 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 stationary or in dwell.
A qualitative schematic representatiOn of the motion of the output gear 36 during a complete 360 rotation of the driving gear 28 and eccentric gear 34, at 90 intervals, is shown in FIGS. 3-6. An arbitrary radial marker line Z has been added to the output gear 36 to show its position change at these intervals. FIG. 3 shows the position of all gears at the center of the dwell, which is the same configuration as shown in FIG. 1.
After 90 of clockwise rotation of gears 34 and 28, the position shown in FIG. 4 is reached. At this point, the acceleration of gear 36 in the counterclockwise direction has reached its approximate maximum, and the velocity of the gear 36 in the counterclockwise direction is approximately equal to its average velocity.
-~ ` 1271055 As the gears 28 and 34 continue their rotation clock-wise, the output gear 36 continues to accelerate, at a decreasing rate, in the counterclockwise direction from the position shown in FIG. 4. After an additional 90 of rotation of gears 34 and 28, the positions shown in FIG. 5 is reached. At this point, the acceleration of the 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 FIG. 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 FIG. 6 is reached. As this point, the deceleration of the output gear 36 is at or near maximum, while the velocity of the output gear 36, still in the 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 FIG. 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 360 from the start of the cycle, the position shown in FIG. 3 is again reached, with the output gear 36 having completed 180 of rotation and is now again in dwell. The position of the marker Z has now reached the position Zl ~7~(355 It can be seen, thereEore, that as the input ~ear 22 is driven by some external power means, at a substantially constant angular velocity, the gears 28 and 34 are driven by the intermediate gear 32. Gears 28 and 34 have an angular velocity which is determined by the superposition of the effect of the oscillation of link 26 about shaft 24 on the velocity created by the input gear 22 so gears 28 and 34 do not rotate at a constant angular velocity. And the oscillation of the gear 34 along the arcuate path controlled by radial link 40 and created by its eccentric mounting on shaft 30 creates another superposition on the velocity of the output gear 36. With the proportions shown in FIGS. 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-half the pitch diameter of gear 36.
Whereas the rotary output embodiment of thebackground patent shown in FIGS. 14 to 21 therein produced an output index angle of 90, due to the proportions of gears 328 and 330, the output index angle of the embodiment shown in FIGS. 1 to 6 herein produces an output index angle of 180 as previously described. Furthermore, in the background patent, the mechanism of FIGS. 14 to 16 shows a chain connection 320 from the member, sproc~et 322, on axis Al to the member, sprocket 318, on axis A2, whereas in the embodiment, FIGS. 1-6, shown herein, 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.
~ ~27~055 Second Dwell Mechanism - Back~round The second background mechanism utilized in the invention of the present disclosure i8 comprised of a crank and connecting rod mechanism described in many books on fundamental kinematics. It is illustrated here schematically in FIGS. 7, 8 and 9.
Referring to FIGS. 7 and 8, a shaft 50 rotates on axis As, and is journalled in a frame 52 through a bushing 54;
this shaft 56 can be driven by any suitable prime mover. ~ 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 on the crankpin 58; at its other end it is pivot connected to a slide block 62 through a pivot pin 64 on axis A7. The slide block 62 is supported by the frame 52 in which it is free to slide along an axis Ag, which, as shown in FIG. 8, intersects the axis A5.
In FIG. 9 is shown a schematic diagram useful to analyze the kinematic characteristics of the system. The distance on the crank 56 between axis As and A6 is defined as R
and 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 after the crank R
has rotated from its base position by some arbitrary angle ~ .
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 angle ~ from its base position is given by t _9_ 7~055 D = R - L - R cos~ + L cos a ( 1 ) where ~ = sin~l (~ sin~) (2) If it is assumed that L is large compared to R and therefore the angle N iS small, even when it is at a maximum, then cos a is very closely approximated by 1, whereupon:
D - R - R cos~ ~ R (1 - cos~) ~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 that the output of that mechanism is stationary while its input continues to move. In the theoretical sense, the output is zero;
cam generated output movements oftentimes 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 of the output is acceptable. Such a situation will be defined, for the purposes of this disclosure 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 of the mechanism. For example,a near dwell ~.OOl)would meanthat the outputoscillates during the defined near dwell through a total amplitude of .001 i271055 times the total stroke of the mechanism. This is shown schematically in FIG. 10 which further schematically de~ines the term "dwell length". If it is assumed that a mechanism is driven by an input shaft which rotates at a constant angular velocity, and that the time required for a given index cycle is divided into 360 units, then each of those units is defined as 1 degree of clock angle. A dwell length of 90 clock angle, for example, would represent a cycle in which the output would be in near dwell for 90/360 or for one quarter of the cycle.
Clearly, if the input shaft rotates through one revolution during an index cycle, then one degree of input shaft rotation equals one degree of clock angle; or, if, for example, the input shaft rotates through three revolutions during an index cycle, then every three degrees of input shaft rotation equals one degree of clock angle. Stated another way, the number of degrees of input shaft rotation equal to one degree of clock angle may be determined by dividing the total number of input shaft rotation degrees required for an index cycle by 360.
Description of the Invention The invention to be described herein is a combination or tandem 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 FIGS. 1 to 6 herein and having an output index angle of approximately 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.
)S~
A first embodiment of this invention is shown in my U. S.Patent No.4,490,091andis redescribedhereininconnection with FIGS. 11 and 12.
The embodiment of this invention as shown in FIGS. 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. The workpiece 100 is located and clamped by a cylinder actuated mechanical hand 102 mounted on a shaft 110 suitably journalled in a bracket 112; the shaft 110 is driven by an actuator arm 114 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 rotates 360 clockwise with respect to the transfer beam 116 during a typical transfer motion as is completely explained in my patent 4,490,091. The crank arm 118 supports the transfer beam 116 through a crankpin 120, which is ~ournalled in the transfer beam 116 and is used as the power and synchronizing source for the hand rotation mechanism to be described. The mechanism 20 in housing 25 is mounted to the transfer beam 116 and positioned such that the input shaft 24 is coaxial with the crankpin 120, to which it is directly coupled; or the input shaft 24 may be made integral with the crankpin 120. Within the housing 25, the gear system previously described in FIGS. 1 to 6 herein drives the output gear 36 and output shaft 38; the housing 25 is further oriented on the transfer beam such that the output 1271(~55 shaft 38 lies approximately in the plane of the actuator arm 114. A drive crank 122 is mounted on the output shaft 38 and on it is mounted a spherical headed crankpin 124 to which is journalled a connecting rod 126. The other end of thisconnecting rod 126 is pivotally connected to the actuator arm 114, again through a spherical headed pin 128 (FIG. 12).
In FIGS. 11 and 12, the drive crank 122, connecting rod 126, and actuator arm 114 are shown in their 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 Patent 4,490,091. This rotates the input shaft 24 360 clockwise causing the output shaft 38 to rotate 180 counterclockwise with anaccelerated-decelerated motionas shown by curve A of FIG. 13, and by arrow M in FIG. 11. It will be noted that curves A and B of FIG. 13 are also identical with the curves A and C respectively of FIG. 15, Patent 4,490,091.
This in turn drives the actuator arm 114, through the connecting rod 126, in the direction shown by arrow N in FIG. 12. At the completion of the forward stroke the drive crank 122, connecting rod 126 and actuator arm 114 reach the positions shown in dotted lines and respectively noted as 122A, 126A and 114A.
It can be seen that the crank arm 122 and actuator arm 114 rotate in different planes; hence, the requirement for the spherical 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 of the stroke (approximately harmonic motion), this ` ` ~"27~0~;~
effect is superimposed on the dwell of the mechanism of FIG. 1.
This increases the dwell in the movement of the actuator arm 114 relative to the rotation of the crank arm 118. This movement relationship is shown by curve B of FIG. 13 and approximates the characteristics of a cam mechanism.
The rotation angle of the actuator arm 114 is shown as 60 in FIG. 12. This is variable by changing the length of the drive crank 122 and/or changing the length of the actuator arm 114.
The description in connection with FIGS. 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 of the gantry mechanism. In this application, the very long dwell is of particular importance in delaying rotation of the workpiece during the lift portion of the transfer stroke.
However, this mechanism's usefulness is not limited to such auxiliary roles. A more generalized application is described below.
Referring to FIGS. 14 and 15, the mechanism 20, previously described in connection with FIGS. 1 to 6, is enclosed in the housing 25 and mounted on a base 140. Its input shaft 24 i8 driven through a coupling 142 by the output shaft 144 of a gear reducer 146 also mounted on the base 140. The input shaft 148 of this gear reducer is in turn driven by a motor 150 through a coupling 152. Depending on the application the motor may run continuously, or it may be stopped during the mechanism dwell ` 1271()55 with suitable conventional limit switches and electrical circuits. The crank 56 (FIGS. 7, 8 and 9) is directly mounted on the output shaft 38 of the mechanism 20, whereupon axes A4 and A5 become coincident. Clearly the shaft 50 and frame 52 (FIGS. 7 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 of the connecting rod 60 is connected to a reciprocating output member, which may be a slider block, such as shown in FIG. 8, from which the load is driven, or the connecting rod 60 may be directly connected to an input member of the 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 ~ is now the output angle of the mechanism 20.
Referring to the background patent, the velocity was shown to be:
da = 1 - ~cosO [I + (a2 ~ 1 + sin2~
It will be noted that a is the ratio of the distance from axis Al to A2 to the distance from the axis A2 to A3 ~FIG. 1) and is generally a large number. Therefore, as a first order approximation, the denominator ~a2 - 1 + sin2~)~ will be large, and the entire fraction negligibly small. Equation (4) will therefore reduce to:
12710~5 d~ cos~ (5) This equation may be integrated to give the displacement:
u -- a - ~sin~ + Cl (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 FIGS. 1-6, the crank mechanism of FIGS. 7-9, and the combination mechanism of FIGS.
14 and 15, it i3 conver.ient to 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 of the clock angle which has a range of 360 to create the output stroke of 1. Under these arbitrary scaling procedures, equation ~3) becomes DU a .5 [1 - cos (~Pc)] (7) where DU = "unitized" output ~ C = "clock" angle This rescaling is dependent on the following reasoning relative to equation (3). The minimum position occurs when ~ =
lX7~
0, and D = O independent of the value of R. The maximum position occurs when ~= 180 and D is equal to 2R. Therefore, by setting R = ~and ~ C) the maximum reaches 1 when~c = 360 and it is by substituting these values for R and ~ into equation t3) that equation (7) is obtained.
The output displacement rom equation (7~, in the near dwell area, is tabulated in Table I and shown graphically by curve Ref A in FIG. 16.
TABLE I
Unitized Displacement of a Simple Crank Mechanism Near Dwell Clock Anqle Unitized Displacement -20 .007596 -15 .004278 -10 .001903 _ 5 .000476 O O
.000476 .001903 .004278 .007596 By following a comparable process, the generalized displacement equation (6), which represents the mechanism 20, may be scaled to provide ~2~0~5 Du 2~ [180 ~C ~ Asin~c)] 1 t8~
The factor ~/180 is used as a multiplier Of ~C
to convert the "clock angle" to radians, as required by the basic theory of the background patent; and the factor 1/2~ is a required scale factor on the bracketed quantity, since, when the clock angle reaches 360, the value of that bracketed quantity is 2~ . The constant of integration Cl is in effect a phase angle and will be set to 0 for the initial comparative purposes. Equation t8) therefore reduces to:
,, U ~C A sin (~C) 360 2~
By referring to equation (4), it can be shown that for the velocity to be zero when ~ = 0, A must be 1, i.e., the distance from axis A2 to axis A3 of the mechanism of FIGS. 1-6 must be equal to the pitch radius of the gear 34, whereupon equation (9) further reduces to:
DU = ~C ~ 12 sin (~C) (10) The output displacement, from equation (10), in the near dwell area, is tabulated in the following Table II and shown graphically by curve Ref B in FIG. 16.
1~ 71() '~
Table II
Unitized Displacement of a Mechanism of Patent 3,789,676 Near Dwell Clock Anqle Unitized Displacement -20 -.001121 -15 -.000474 -10 -.0001~1 - 5 -~000018 O O
.000018 .000141 .000474 ~001121 Two observations may be made relevant to Tables I and II and their graphical representation in curves Ref A and Ref B
of FIG. 16. The first concerns the relative shortness of their individual dwells. If, for example, the dwell amplitude is arbitrarily defined as .001 ~in unitized displacement), the dwell length of the connecting rod mechanism is approximately +8 for a total length of approximately 16; this is obtained from curve Ref A. For the mechanism 20, the intersection of the curve Ref B with the +.0005 and -.0005 lines (for a total of .001) is found to be approximately +16 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 of the center of dwell, where the clock angle is 0, is unidirectional as would 12710~:;5 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 output will momentarily stop after a given index, but then reaccelerate in the same direction it had before stopping.
The foregoing data on the near dwell characteristics of each of the mechanisms operating independently are provided as reference data for the new data to be shown.
In the present invention, as illustrated in the mechanism of FIGS. 11 and 12 and 14 and 15, it is necessary to rescale equation (6), representing the mechanism of FIGS. 1-6 and equation (3) representing the crank mechanism of FIGS. 7-9. By a process similar to the one described above, equation (6) is rescaled to:
~ = 180 12~ [180 ~C ~sin (~C~ + Cl (11) which reduces to ~ ~C 90~ sin (~C) + Cl (12) where ~ is the true output angle, in degrees, of the shaft 38 (FIG. 2).
~ " i271055 Equation (3) is rescaled to:
D = 5 [1 - cos(~)~ (13) where ~ is again the true angle in degrees of the shaft 38 which is the input shaft of the crank mechanism. The displacement characteristics of the combined mechanism of FIGS. 14 and 15 is therefore obtained by combining equations (12 and (13) as follows:
D = 5 { 1 - cos [ 2 ~ 90~ sin(~C) 1~ (14) which simplifies to:
[ 2 ~ ( ) ] (15) The arbitrary quantity Cl ~which was the constant of integration)representsa phase angle between the twomechanisms.
If it is set to 0, 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 to 0; other values will be subsequently analyzed.
Similarly, the factor ~ i3 initially set equal to 1 as was done for the analysis of the individual mechanism 20;
subsequent analyses will be made with values of ~ other than 1.
The unitized displacement for the combined mechanism, which comprises this invention, as calculated from equation ~15) with 127~(~55 Cl = 0 and ~= 1 is given in Table III and shown as curve C in FIG. 16.
Table III
United Displacement of One Embodiment of This Invention Clock Anqle Unitized Displacement -60 .002050 -50 7.10 x 10-4 -40 1.91 x 10-4 -30 3.48 x 10-5 -20 3.10 x 10-6 -10 Less than 1 x 10-7 O O
Less than 1 x 10-7 3.10 x 10-6 3.48 x 10-5 1.91 x 10-4 7.10 x 10-4
Related Applications The subject matter of this application is related to that included in my United States Patent No. 4,490,091 which issued on December 25, 1984.
Title !
Reciprocating Long Dwell Mechanism Field of Invention Mechanism which in combination can produce, with a constant speed rotary input, a long dwell output which can be utilized, for example, in gantry type transfer systems with mechanical hands for work parts.
Backaround and Obiects of the Invention 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.
Itisan object of this inventiontoprovidea mechanism which generates a reciprocating motion from a rotary motion and in which the output remains substantially stationary, that is, - 1~71055 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, but these are limited practically to strokes of a few feet or less before becoming very expensive.
It is another object of this invention to provide a mechanism which, by its nature, can be economically constructed to achieve strokes of 6 feet or more.
Another object of this invention is to provide 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 anotherpredeterminedpoint alongthe reverse direction of travel, where such dwells may be instantaneous stops or significant reductions of velocity.
This invention is directed to 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 other direction.
The structure involves the use of a rotary output drive system ~27~05~
, .
which is comprised of a frame, an output shaft member mounted for rotation in said frame, a rotary output member mounted on said output shaft member, a drive surface on said rotary output member, an eccentric drive member rotatable about a moving center to engage said drive surface in a tangential driving relationship, means mounting said eccentric drive member for 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 to impart a rotation to one of said drive members, 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 drive member and said rotative 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. The invention also utilizes a reciprocating output .~
~271055 drive system which includes a crank member mounted at its one end to said output shaft member, connecting rod means journalled at its one end tothe other end of said crank member,reciprocating output means mounted for reciprocation in said frame, and pivotally connectedto the other end of saidconnecting rodmeans.
Other features of the invention will be apparent in the following description and claims in which the principle of the invention is disclosed together with details directed to persons skilled in the art to enable the invention to be utilized all in connection with the best modes presently contemplated for the invention.
Brief Description of the Drawinqs DRAWINGS accompany the disclosure and the various views thereof may be briefly described as:
-2b-A
`"-" 1~7105S
FIG. 1, a semi-schematic front view of a mechanism which is one embodiment of the mechanisms disclosed in my U.S.
Patent No. 3,789,676, dated February 5, 1974.
FIG. 2, a plan view of the mechanism of FIG. 1.
FIG. 3, a schematic representation of the mechanism of FIG. 1, shown at the starting and stopping point of an index cycle.
FIGS. 4, 5 and 6, schematic representations of the mechanism of FIG. 1 after rotation of the input shaft through angles of 90, 180 and 270, respectively.
FIG. 7, a front view of a crank and connecting rod mechanism.
FIG. 8, a section taken on line 8--8 of FIG. 7.
FIG. 9, a schematic diagram for determining the output motion of the crank and connecting rod mechanism of FIG. 7.
FIG. 10, an illustrative diagram used to define the terms dwell amplitude and dwell length of any dwell producing mechanism.
FIG. 11, a front view of an embodiment of my U.S.
Patent No.4,490,091, dated Dec. 25, 1984, showing an application of this invention to rotate a mechanical hand during the lift, transfer, and rotate motion of a gantry type transfer mechanism.
FIG. 12, a section taken on line 12--12 of FIG. 11.
FIG. 13, a graph showing the output characteristics of the mechanism of FIG. 1 and the output characteristics of the mechanism of FIG. 11.
FIG. 14, a plan view of another embodiment of this invention.
FIG. 15, a front view of the mechanism of FIG. 14.
FIG. 16, a graph showing the dwell characteristics of: the crank and connecting rod mechanism; the mechanism of ~27~0r,5 FIG. 1 with ~= 1; the mechanism of FIGS, 14 and 15 with ~ = 1; and the mechanism of FIGS. 14 and 15 with ~ = 1.1.
FIG. 17, a graph showing the angular dwell charac-teristics of the crank only of the mechanism of FIGS. 14 and 15 for various values of ~.
FIG. 18, a graph showing the dwell characteristics of the mechanism of FIGS. 14 and 15 for various values of ~.
FIG. 19, a graph showing the displacement characteristics of the mechanism of FIGS. 14 and 15 with a phase angle of 90; and a second graph showing the characteristics with a phase angle of 60.
FIG. 20, a graph showing the displacement charac-teristics of the mechanism of FIGS. 14 and 15, in which the output index angle of the mechanism 20 is 360.
FIG. 21, a graph showing the displacement charac-teristics of the mechanism of FIGS. 14 and 15, in which the output index angle of the mechanism 20 is 90.
First Dwell ~echanism - Backaround 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 this disclosure, the Patent 3,789,676 wiil be referred to as the background patent. A review of this background patent will indicate that there are several embodiments, e.g., FIGS. 14, 15, 16; 22, 23, 24; 25, 26, 27; and 33, 34, 35, which all provide a rotary output. Specifically referring to FIGS.
14, 15 and 16 of the background patent, and FIGS. 17 to 21, i~7~55 which illustrate the sequential position and motion characteristics of that system during an index cycle, it can be seen that the output gear 330 rotates through an angle of 90 during a given index cycle. This is a result of the gear 328 having a pitch diameter which is ~ the pitch diameter of the output gear 330. In this present invention which will subsequently be described, that portion of the mechanism arising from the background patent will utilize an index angle of approximately 180. Such a mechanism is described in FIGS. 1 to 6 of the present disclosure.
These FIGS. 1 to 6 have also previously been shown as Figs. 9 to 14 in my U. S. Patent No. 4,490,091.
Referring to FIGS. 1 and 2, a mechanism 20 includes an input gear 22 mounted on an input shaft 24 which is journalled in a housing or frame 25 on axis Al and driven by an appropriate external drive system. The housing 25 is shown in phantom for application reference. Also journalled on the input shaft 24 is a tangential link 26 which oscillates thereon as will be described. A driving gear 28 is mounted on a shaft 30 journalled in the outboard end of the link26 onaxisA2, and, anintermediate gear 32, also journalled in 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 gear 34, rotating on a moving axis A3, meshes with an output gear 36 mounted on an output shaft 38 also journalled in the housing 25 on axis A4. A radial link 40 is also journalled on the output shaft 38 at its one end; at its other end, the ~27~()55 .
radial link 40 is journalled to a stub shaft 42 on axis A3 mounted concentrically on the eccentric gear 34. It is the purpose of this radial link 40 to keep the eccentric ~ear 34 in mesh with the output gear 36 as the eccentric gear 34 moves through its rotational and translational path.
When the mechanism is in the position shown in FIG. 1, it is in a natural dwell position, i.e., a small rotation of the input gear 22 causes a corresponding rotation of the driving gear 28 and the eccentric gear 34, 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 stationary or in dwell.
A qualitative schematic representatiOn of the motion of the output gear 36 during a complete 360 rotation of the driving gear 28 and eccentric gear 34, at 90 intervals, is shown in FIGS. 3-6. An arbitrary radial marker line Z has been added to the output gear 36 to show its position change at these intervals. FIG. 3 shows the position of all gears at the center of the dwell, which is the same configuration as shown in FIG. 1.
After 90 of clockwise rotation of gears 34 and 28, the position shown in FIG. 4 is reached. At this point, the acceleration of gear 36 in the counterclockwise direction has reached its approximate maximum, and the velocity of the gear 36 in the counterclockwise direction is approximately equal to its average velocity.
-~ ` 1271055 As the gears 28 and 34 continue their rotation clock-wise, the output gear 36 continues to accelerate, at a decreasing rate, in the counterclockwise direction from the position shown in FIG. 4. After an additional 90 of rotation of gears 34 and 28, the positions shown in FIG. 5 is reached. At this point, the acceleration of the 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 FIG. 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 FIG. 6 is reached. As this point, the deceleration of the output gear 36 is at or near maximum, while the velocity of the output gear 36, still in the 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 FIG. 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 360 from the start of the cycle, the position shown in FIG. 3 is again reached, with the output gear 36 having completed 180 of rotation and is now again in dwell. The position of the marker Z has now reached the position Zl ~7~(355 It can be seen, thereEore, that as the input ~ear 22 is driven by some external power means, at a substantially constant angular velocity, the gears 28 and 34 are driven by the intermediate gear 32. Gears 28 and 34 have an angular velocity which is determined by the superposition of the effect of the oscillation of link 26 about shaft 24 on the velocity created by the input gear 22 so gears 28 and 34 do not rotate at a constant angular velocity. And the oscillation of the gear 34 along the arcuate path controlled by radial link 40 and created by its eccentric mounting on shaft 30 creates another superposition on the velocity of the output gear 36. With the proportions shown in FIGS. 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-half the pitch diameter of gear 36.
Whereas the rotary output embodiment of thebackground patent shown in FIGS. 14 to 21 therein produced an output index angle of 90, due to the proportions of gears 328 and 330, the output index angle of the embodiment shown in FIGS. 1 to 6 herein produces an output index angle of 180 as previously described. Furthermore, in the background patent, the mechanism of FIGS. 14 to 16 shows a chain connection 320 from the member, sproc~et 322, on axis Al to the member, sprocket 318, on axis A2, whereas in the embodiment, FIGS. 1-6, shown herein, 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.
~ ~27~055 Second Dwell Mechanism - Back~round The second background mechanism utilized in the invention of the present disclosure i8 comprised of a crank and connecting rod mechanism described in many books on fundamental kinematics. It is illustrated here schematically in FIGS. 7, 8 and 9.
Referring to FIGS. 7 and 8, a shaft 50 rotates on axis As, and is journalled in a frame 52 through a bushing 54;
this shaft 56 can be driven by any suitable prime mover. ~ 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 on the crankpin 58; at its other end it is pivot connected to a slide block 62 through a pivot pin 64 on axis A7. The slide block 62 is supported by the frame 52 in which it is free to slide along an axis Ag, which, as shown in FIG. 8, intersects the axis A5.
In FIG. 9 is shown a schematic diagram useful to analyze the kinematic characteristics of the system. The distance on the crank 56 between axis As and A6 is defined as R
and 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 after the crank R
has rotated from its base position by some arbitrary angle ~ .
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 angle ~ from its base position is given by t _9_ 7~055 D = R - L - R cos~ + L cos a ( 1 ) where ~ = sin~l (~ sin~) (2) If it is assumed that L is large compared to R and therefore the angle N iS small, even when it is at a maximum, then cos a is very closely approximated by 1, whereupon:
D - R - R cos~ ~ R (1 - cos~) ~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 that the output of that mechanism is stationary while its input continues to move. In the theoretical sense, the output is zero;
cam generated output movements oftentimes 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 of the output is acceptable. Such a situation will be defined, for the purposes of this disclosure 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 of the mechanism. For example,a near dwell ~.OOl)would meanthat the outputoscillates during the defined near dwell through a total amplitude of .001 i271055 times the total stroke of the mechanism. This is shown schematically in FIG. 10 which further schematically de~ines the term "dwell length". If it is assumed that a mechanism is driven by an input shaft which rotates at a constant angular velocity, and that the time required for a given index cycle is divided into 360 units, then each of those units is defined as 1 degree of clock angle. A dwell length of 90 clock angle, for example, would represent a cycle in which the output would be in near dwell for 90/360 or for one quarter of the cycle.
Clearly, if the input shaft rotates through one revolution during an index cycle, then one degree of input shaft rotation equals one degree of clock angle; or, if, for example, the input shaft rotates through three revolutions during an index cycle, then every three degrees of input shaft rotation equals one degree of clock angle. Stated another way, the number of degrees of input shaft rotation equal to one degree of clock angle may be determined by dividing the total number of input shaft rotation degrees required for an index cycle by 360.
Description of the Invention The invention to be described herein is a combination or tandem 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 FIGS. 1 to 6 herein and having an output index angle of approximately 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.
)S~
A first embodiment of this invention is shown in my U. S.Patent No.4,490,091andis redescribedhereininconnection with FIGS. 11 and 12.
The embodiment of this invention as shown in FIGS. 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. The workpiece 100 is located and clamped by a cylinder actuated mechanical hand 102 mounted on a shaft 110 suitably journalled in a bracket 112; the shaft 110 is driven by an actuator arm 114 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 rotates 360 clockwise with respect to the transfer beam 116 during a typical transfer motion as is completely explained in my patent 4,490,091. The crank arm 118 supports the transfer beam 116 through a crankpin 120, which is ~ournalled in the transfer beam 116 and is used as the power and synchronizing source for the hand rotation mechanism to be described. The mechanism 20 in housing 25 is mounted to the transfer beam 116 and positioned such that the input shaft 24 is coaxial with the crankpin 120, to which it is directly coupled; or the input shaft 24 may be made integral with the crankpin 120. Within the housing 25, the gear system previously described in FIGS. 1 to 6 herein drives the output gear 36 and output shaft 38; the housing 25 is further oriented on the transfer beam such that the output 1271(~55 shaft 38 lies approximately in the plane of the actuator arm 114. A drive crank 122 is mounted on the output shaft 38 and on it is mounted a spherical headed crankpin 124 to which is journalled a connecting rod 126. The other end of thisconnecting rod 126 is pivotally connected to the actuator arm 114, again through a spherical headed pin 128 (FIG. 12).
In FIGS. 11 and 12, the drive crank 122, connecting rod 126, and actuator arm 114 are shown in their 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 Patent 4,490,091. This rotates the input shaft 24 360 clockwise causing the output shaft 38 to rotate 180 counterclockwise with anaccelerated-decelerated motionas shown by curve A of FIG. 13, and by arrow M in FIG. 11. It will be noted that curves A and B of FIG. 13 are also identical with the curves A and C respectively of FIG. 15, Patent 4,490,091.
This in turn drives the actuator arm 114, through the connecting rod 126, in the direction shown by arrow N in FIG. 12. At the completion of the forward stroke the drive crank 122, connecting rod 126 and actuator arm 114 reach the positions shown in dotted lines and respectively noted as 122A, 126A and 114A.
It can be seen that the crank arm 122 and actuator arm 114 rotate in different planes; hence, the requirement for the spherical 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 of the stroke (approximately harmonic motion), this ` ` ~"27~0~;~
effect is superimposed on the dwell of the mechanism of FIG. 1.
This increases the dwell in the movement of the actuator arm 114 relative to the rotation of the crank arm 118. This movement relationship is shown by curve B of FIG. 13 and approximates the characteristics of a cam mechanism.
The rotation angle of the actuator arm 114 is shown as 60 in FIG. 12. This is variable by changing the length of the drive crank 122 and/or changing the length of the actuator arm 114.
The description in connection with FIGS. 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 of the gantry mechanism. In this application, the very long dwell is of particular importance in delaying rotation of the workpiece during the lift portion of the transfer stroke.
However, this mechanism's usefulness is not limited to such auxiliary roles. A more generalized application is described below.
Referring to FIGS. 14 and 15, the mechanism 20, previously described in connection with FIGS. 1 to 6, is enclosed in the housing 25 and mounted on a base 140. Its input shaft 24 i8 driven through a coupling 142 by the output shaft 144 of a gear reducer 146 also mounted on the base 140. The input shaft 148 of this gear reducer is in turn driven by a motor 150 through a coupling 152. Depending on the application the motor may run continuously, or it may be stopped during the mechanism dwell ` 1271()55 with suitable conventional limit switches and electrical circuits. The crank 56 (FIGS. 7, 8 and 9) is directly mounted on the output shaft 38 of the mechanism 20, whereupon axes A4 and A5 become coincident. Clearly the shaft 50 and frame 52 (FIGS. 7 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 of the connecting rod 60 is connected to a reciprocating output member, which may be a slider block, such as shown in FIG. 8, from which the load is driven, or the connecting rod 60 may be directly connected to an input member of the 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 ~ is now the output angle of the mechanism 20.
Referring to the background patent, the velocity was shown to be:
da = 1 - ~cosO [I + (a2 ~ 1 + sin2~
It will be noted that a is the ratio of the distance from axis Al to A2 to the distance from the axis A2 to A3 ~FIG. 1) and is generally a large number. Therefore, as a first order approximation, the denominator ~a2 - 1 + sin2~)~ will be large, and the entire fraction negligibly small. Equation (4) will therefore reduce to:
12710~5 d~ cos~ (5) This equation may be integrated to give the displacement:
u -- a - ~sin~ + Cl (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 FIGS. 1-6, the crank mechanism of FIGS. 7-9, and the combination mechanism of FIGS.
14 and 15, it i3 conver.ient to 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 of the clock angle which has a range of 360 to create the output stroke of 1. Under these arbitrary scaling procedures, equation ~3) becomes DU a .5 [1 - cos (~Pc)] (7) where DU = "unitized" output ~ C = "clock" angle This rescaling is dependent on the following reasoning relative to equation (3). The minimum position occurs when ~ =
lX7~
0, and D = O independent of the value of R. The maximum position occurs when ~= 180 and D is equal to 2R. Therefore, by setting R = ~and ~ C) the maximum reaches 1 when~c = 360 and it is by substituting these values for R and ~ into equation t3) that equation (7) is obtained.
The output displacement rom equation (7~, in the near dwell area, is tabulated in Table I and shown graphically by curve Ref A in FIG. 16.
TABLE I
Unitized Displacement of a Simple Crank Mechanism Near Dwell Clock Anqle Unitized Displacement -20 .007596 -15 .004278 -10 .001903 _ 5 .000476 O O
.000476 .001903 .004278 .007596 By following a comparable process, the generalized displacement equation (6), which represents the mechanism 20, may be scaled to provide ~2~0~5 Du 2~ [180 ~C ~ Asin~c)] 1 t8~
The factor ~/180 is used as a multiplier Of ~C
to convert the "clock angle" to radians, as required by the basic theory of the background patent; and the factor 1/2~ is a required scale factor on the bracketed quantity, since, when the clock angle reaches 360, the value of that bracketed quantity is 2~ . The constant of integration Cl is in effect a phase angle and will be set to 0 for the initial comparative purposes. Equation t8) therefore reduces to:
,, U ~C A sin (~C) 360 2~
By referring to equation (4), it can be shown that for the velocity to be zero when ~ = 0, A must be 1, i.e., the distance from axis A2 to axis A3 of the mechanism of FIGS. 1-6 must be equal to the pitch radius of the gear 34, whereupon equation (9) further reduces to:
DU = ~C ~ 12 sin (~C) (10) The output displacement, from equation (10), in the near dwell area, is tabulated in the following Table II and shown graphically by curve Ref B in FIG. 16.
1~ 71() '~
Table II
Unitized Displacement of a Mechanism of Patent 3,789,676 Near Dwell Clock Anqle Unitized Displacement -20 -.001121 -15 -.000474 -10 -.0001~1 - 5 -~000018 O O
.000018 .000141 .000474 ~001121 Two observations may be made relevant to Tables I and II and their graphical representation in curves Ref A and Ref B
of FIG. 16. The first concerns the relative shortness of their individual dwells. If, for example, the dwell amplitude is arbitrarily defined as .001 ~in unitized displacement), the dwell length of the connecting rod mechanism is approximately +8 for a total length of approximately 16; this is obtained from curve Ref A. For the mechanism 20, the intersection of the curve Ref B with the +.0005 and -.0005 lines (for a total of .001) is found to be approximately +16 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 of the center of dwell, where the clock angle is 0, is unidirectional as would 12710~:;5 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 output will momentarily stop after a given index, but then reaccelerate in the same direction it had before stopping.
The foregoing data on the near dwell characteristics of each of the mechanisms operating independently are provided as reference data for the new data to be shown.
In the present invention, as illustrated in the mechanism of FIGS. 11 and 12 and 14 and 15, it is necessary to rescale equation (6), representing the mechanism of FIGS. 1-6 and equation (3) representing the crank mechanism of FIGS. 7-9. By a process similar to the one described above, equation (6) is rescaled to:
~ = 180 12~ [180 ~C ~sin (~C~ + Cl (11) which reduces to ~ ~C 90~ sin (~C) + Cl (12) where ~ is the true output angle, in degrees, of the shaft 38 (FIG. 2).
~ " i271055 Equation (3) is rescaled to:
D = 5 [1 - cos(~)~ (13) where ~ is again the true angle in degrees of the shaft 38 which is the input shaft of the crank mechanism. The displacement characteristics of the combined mechanism of FIGS. 14 and 15 is therefore obtained by combining equations (12 and (13) as follows:
D = 5 { 1 - cos [ 2 ~ 90~ sin(~C) 1~ (14) which simplifies to:
[ 2 ~ ( ) ] (15) The arbitrary quantity Cl ~which was the constant of integration)representsa phase angle between the twomechanisms.
If it is set to 0, 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 to 0; other values will be subsequently analyzed.
Similarly, the factor ~ i3 initially set equal to 1 as was done for the analysis of the individual mechanism 20;
subsequent analyses will be made with values of ~ other than 1.
The unitized displacement for the combined mechanism, which comprises this invention, as calculated from equation ~15) with 127~(~55 Cl = 0 and ~= 1 is given in Table III and shown as curve C in FIG. 16.
Table III
United Displacement of One Embodiment of This Invention Clock Anqle Unitized Displacement -60 .002050 -50 7.10 x 10-4 -40 1.91 x 10-4 -30 3.48 x 10-5 -20 3.10 x 10-6 -10 Less than 1 x 10-7 O O
Less than 1 x 10-7 3.10 x 10-6 3.48 x 10-5 1.91 x 10-4 7.10 x 10-4
2.050 x 10-3 Two observations may also be made with respect to curve C, FIG. 16 representing the dwell behavior of the combined mechanism. The first concerns the width of the 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 of the dwells of the individual mechanisms.
Next the importance of the ~ factor will be shown.
If ~ , in equation (15) is arbitrarily set equal to 1.1, while 1271~55 the phase angle Cl is still set equal to 0, a further increase in the dwell length is found as shown in Table IV and curve D
in FIG. 16.
Table_IV
Unitized Displacement On An Embodiment of this Invention ~ = 1.1 Clock Anqle Unitized Displacement -70 2.21 x 10-3 -60 5.59 x 10-4 -50 -5.63 x 10-5 -40 4.99 x 10-6 -30 4.36 x 10-5 -20 4.61 x 10-5 -10 1.70 x 10-5 ~ o O
1.70 x 10-5 4.61 x 10-5 4.36 x 10-5 4.99 x 10-6 5.63 x 10-5 5.59 x 10-4 2.21 x 10-3 This highly desirable lengthening of the dwell may be explained as follows. The setting of ~ to 1.1 means that the distance between axes A2 and A3 of the mechanism 20, FIGS. 1-6, is 1.1 times the pitch radius of the eccentric gear 34. In turn, this condition causes the output gear 36 to experience a slight "overshoot" before it reaches the center of the dwell, 127~055 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 next forward index. Since the crank 56, FIGS. 7, 8, 14 and 15, and crank 122 of FIGS. 11 and 12, rotates in unison with the output shaft 38 and the output gear 36, this results in a slight oscillation of the crank 56 (FIGS. 7 and 8). This is quantitatively shown by curve D' in FIG. 17 which shows the true crank angle, in degrees, plotted against clock angle, where 0 degrees on the crank angle scale represents a top dead center or bottom dead center position. For curve D', which represents the condition for ~ 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 (~ = 1.1) relative to curve C (~ =1.0) in FIG. 16. Indeed, for the arbitrary previously chosen dwell amplitude of .001, the dwell length for ~ = 1.1 is seen to be +64 for a total dwell length of 128, which is some 20% more than for curve C ( ~= 1.0).
A still further improvement of the dwell length can be made by increasing ~ still more. With ~ set equal to 1.2, the dwell characteristics of the total system are shown by curve E of FIG. 18 which is plotted to the same scale as FIG. 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 FIG. 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 ~ystem dwell curve E of FIG. 18.
Clearly the "lobes" of the curve E from -58 to 0 and from 0 1;~71V55 to 58 are caused by the crank oscillation shown by curve E', FIG. 17. It will also be noted that the dwell length, for an amplitude of .001 and ~ 1.2, curve E, is now + 74 for a total dwell length of 148.
It follows, therefore, that for the dwell length to be maximized for some arbitrary but knowledgably set value of the dwell amplitude, a A can be found in which the height of the lobes on either side of the center of dwell are equal in amplitude to the set dwell amplitude. With respect to the previously set dwell amplitude of .001, a value of ~was found which creates this condition. For a ~ of 1.2829, the system displacement curve F, FIG. 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 + 40. The corresponding crank angle oscillation is shown by curve F', FIG. 17 and is
Next the importance of the ~ factor will be shown.
If ~ , in equation (15) is arbitrarily set equal to 1.1, while 1271~55 the phase angle Cl is still set equal to 0, a further increase in the dwell length is found as shown in Table IV and curve D
in FIG. 16.
Table_IV
Unitized Displacement On An Embodiment of this Invention ~ = 1.1 Clock Anqle Unitized Displacement -70 2.21 x 10-3 -60 5.59 x 10-4 -50 -5.63 x 10-5 -40 4.99 x 10-6 -30 4.36 x 10-5 -20 4.61 x 10-5 -10 1.70 x 10-5 ~ o O
1.70 x 10-5 4.61 x 10-5 4.36 x 10-5 4.99 x 10-6 5.63 x 10-5 5.59 x 10-4 2.21 x 10-3 This highly desirable lengthening of the dwell may be explained as follows. The setting of ~ to 1.1 means that the distance between axes A2 and A3 of the mechanism 20, FIGS. 1-6, is 1.1 times the pitch radius of the eccentric gear 34. In turn, this condition causes the output gear 36 to experience a slight "overshoot" before it reaches the center of the dwell, 127~055 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 next forward index. Since the crank 56, FIGS. 7, 8, 14 and 15, and crank 122 of FIGS. 11 and 12, rotates in unison with the output shaft 38 and the output gear 36, this results in a slight oscillation of the crank 56 (FIGS. 7 and 8). This is quantitatively shown by curve D' in FIG. 17 which shows the true crank angle, in degrees, plotted against clock angle, where 0 degrees on the crank angle scale represents a top dead center or bottom dead center position. For curve D', which represents the condition for ~ 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 (~ = 1.1) relative to curve C (~ =1.0) in FIG. 16. Indeed, for the arbitrary previously chosen dwell amplitude of .001, the dwell length for ~ = 1.1 is seen to be +64 for a total dwell length of 128, which is some 20% more than for curve C ( ~= 1.0).
A still further improvement of the dwell length can be made by increasing ~ still more. With ~ set equal to 1.2, the dwell characteristics of the total system are shown by curve E of FIG. 18 which is plotted to the same scale as FIG. 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 FIG. 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 ~ystem dwell curve E of FIG. 18.
Clearly the "lobes" of the curve E from -58 to 0 and from 0 1;~71V55 to 58 are caused by the crank oscillation shown by curve E', FIG. 17. It will also be noted that the dwell length, for an amplitude of .001 and ~ 1.2, curve E, is now + 74 for a total dwell length of 148.
It follows, therefore, that for the dwell length to be maximized for some arbitrary but knowledgably set value of the dwell amplitude, a A can be found in which the height of the lobes on either side of the center of dwell are equal in amplitude to the set dwell amplitude. With respect to the previously set dwell amplitude of .001, a value of ~was found which creates this condition. For a ~ of 1.2829, the system displacement curve F, FIG. 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 + 40. The corresponding crank angle oscillation is shown by curve F', FIG. 17 and is
3.624, which values are reached at approximately + 40 clock angle. The dwell length, as shown by curve F, FIG. 18 is +79 for a total dwell length of 158. This is some 49~ longer than the total dwell length of curve C, FIG. 16 (~- 1) and over three times greater than the sum of the dwells of the 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 A either by a manual or automatic loop process to achieve a maximum lobe amplitude equal to the set .001.
~L~7~5 By a similar process of successive approximation, values of were found which give other dwell amplitudes, in which the lobes approximate the set values thereof. These, together with the resultant dwell lengths, are tabulated below:
Set Value Dwell Dwell Amplitude ~Lenqth .00001 1.058 74 .0001 1.13 114 .001 1.283 148 The selection of dwell amplitude is determined by the application intended. Once this is known, it is a simple process to find the ~ that gives the longest dwell, or conversely, if the dwell length required is known and the smallest dwell amplitude for that given dwell length is sought, ~ may be iterated again to the new objective.
The curves of FIGS. 16, 17 and 18, 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 by the value Cl in equation (15), and is mechanically represented by the angle of the 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 is 0.
However, other useful objectives can be achieved when the phase angle is set to some value other than 0. For example, if the phase angle is set equal to 90, a dwell or near dwell of the crank rotation, and its output motion can be reached midway ~27~0~
during its stroke, dependent on the value of ~. Physicallythis means that when the mechanism 20 is at the center of its dwell, the angle ~ , FIG. 9, is equal to 90. This is merely a matter of assembly positioning of the crank 56 on the shaft 38, for example, in FIG. 15.
The unitizeddisplacement curve Gof FIG.19represents the output of this invention for a given phase angle of 90 with ~ set equal to 0.9. The clock angle is shown as moving through 720 which is two indexes of the mechanism 20 but only one revolution of the crank 56. The momentary stops at the ends of the strokes are evident at clock angles of 180 and 540.
A significant slowdown to a near stop at clock angles of 0, 360 and 720 (720 is the same position as 0) is also evident.
The slowdown, as differentiated from a complete stop, is a result of the arbitrarily illustrated ~ = 0.9; if ~ were set equal to 1, the output would come to an instantaneous stop at 0 and 360. Furthermore, if ~ were made slightly larger than 1, there would be a slight output reversal at these angles.
This midstroke slowdown is useful in many applications such as lifting or lowering of transfer bars which pick up or deposit workpieces at or near midstroke.
Another illustrative output displacement graph is shown in curve H, FIG. 19. In this example, the phase angle was set to 60 and ~ set equal to 0.8. Again the momentary stops and reversals can be seen at 215 and 575 clock angle. A
significant slowdown is evident at 0 and 360 clock angle.
Here again, the slowdown can be greater if ~ is increased, and a momentary stop achieved at ~ = 1, or a slight reversal obtained by making ~ 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, if the forward stroke is defined as 575 to 215 clock angle 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 at a displacement of .75. A property such as this is useful, for example, in operating a lift system such as in my U. S. Patent No. 4,750,605, where it is desired to slow down at one 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 Cl in equation (15) which provide useful results and as previously noted these factors ~ and Cl are controlled in the total mechanical system by the design of the distance from axis A2 to axis A3 and by the assembly positioning of the crank 56 on the shaft 38 (FIGS. 14, 15).
All the performance curves shown in FIGS. 16-19 were derived onthe basis of equation (15), which, it will 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 A
approximations, such factors as the distance between axes A
and A2 and between axes A4 and Al of mechanism 20.
In all of the combination mechanisms shown above, independent of the values of ~ and the phase angle Cl, 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 other than 180. As noted earlier, and as shown in the reference patent, the output angle index angle is determined by the ratio of the pitch diameter of the output gear 36 to the pitch diameter of the eccentric gear 34. If this ratio is.defined as M, the output index angle is 360/M. Stated anotheE way, there are M indexes per revolution.
If equation (6) which, it will be recalled, is the equation for calculating the output angle of mechanism 20, is rescaled in the general form, it becomes:
~ M 2~ [180 C (~C)~ + Cl (16) which simplifies to:
5 MC - 180~ sin (~C) + Cl (17) When M is 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 combinationmechanism output, in unitlzed displacement, is found to be:
`- 12710S5 D ~ 5 - .5 cos[~c ~ 18M ( C) ] (18) Again, it can be seen that when M = 2, equation t18) reduces to the form, previously derived for the 180 index angle, of equation (15). Using equation (18), the unitized displacement characteristics of other embodiments of this invention have been calculated.
The first of the illustrative examples is shown in FIG. 20. In this instance, M was set equal to 1 representing a 360 output index angle of the mechanism 20, ~ was set equal to 1.1 and Cl set equal to 0. The curve of FIG. 20 shows a reciprocating output having a very long dwell at one end of the stroke, and a relatively short dwell at the other end of the stroke; this is useful in applications in which the service is such that the prime mover, e.g., motor 150, FIG. 14, is stopped after each reciprocation, and it is required that a very accurate output position be maintained over a wide range of stopping positions of the prime mover.
Another illustrative example is shown in FIG. 21. In this instance M was set equal to 4, representing a 90 output index angle of the mechanism 20, A was set equal to 1 and Cl set equal to 0. The curve of FIG. 21 again shows a reciprocating output having a relatively long dwell at each end of the stroke, together with a significant dwell at the midpoint of each stroke.
This duplicates the performance, in principle, of the conditions of curve G of FIG. 19, except that by using the conditions of FIG. 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.
i.~710~;5 From the descriptions of the above illustrative combinations, it is clear that a wide variety of kinemati~
characteristics can be achieved through a proper selection of the various parameters involved, which may be summarized as follows:
A. The ~ factor controls the cyclic behavior of the mechanism 20; with ~ = 1, this output shaft will come to a momentary stop once for each revolution of the eccentric gear;
with ~ slightly less than 1, the output shaft will come to a near stop after each revolution of the eccentric gear; and, with ~ 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 of the output shaft made during one total revolution of the output shaft.
C. The phaseangle~ controls the angular relationship of the output crank angular position from its top dead center position when the driving mechanism 20 is at the center of its dwell or near dwell.
The disclosure made above related to the rotary output indexing system typified by FIGS. 14, 15 and 16 of the background patent, No. 3,789,676, as earlier noted, except that the chain 320 was replaced by an equivalent gear train in the mechanism of FIGS. 1-6 herein. It should be noted, however, that the chain drive system of FIGS. 14, 15 and 16 of the background patent is usable for many applicationq in which extreme accuracy or rigidity are not required. Indeed, the double chain system illustrated in FIGS. 33, 34 and 35 of the background patent is 1.;~7~055 . .
also usable subject to chain load and rigidity limitations.
Furthermore, the rotary output systems illustrated in FIGS. 22, 23 and 24 and by FIGS. 25, 26 and 27 in the backgraund patent are also usable subject to the limitation that these embodiments are limited to maximum output index angles of 120.
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 A either by a manual or automatic loop process to achieve a maximum lobe amplitude equal to the set .001.
~L~7~5 By a similar process of successive approximation, values of were found which give other dwell amplitudes, in which the lobes approximate the set values thereof. These, together with the resultant dwell lengths, are tabulated below:
Set Value Dwell Dwell Amplitude ~Lenqth .00001 1.058 74 .0001 1.13 114 .001 1.283 148 The selection of dwell amplitude is determined by the application intended. Once this is known, it is a simple process to find the ~ that gives the longest dwell, or conversely, if the dwell length required is known and the smallest dwell amplitude for that given dwell length is sought, ~ may be iterated again to the new objective.
The curves of FIGS. 16, 17 and 18, 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 by the value Cl in equation (15), and is mechanically represented by the angle of the 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 is 0.
However, other useful objectives can be achieved when the phase angle is set to some value other than 0. For example, if the phase angle is set equal to 90, a dwell or near dwell of the crank rotation, and its output motion can be reached midway ~27~0~
during its stroke, dependent on the value of ~. Physicallythis means that when the mechanism 20 is at the center of its dwell, the angle ~ , FIG. 9, is equal to 90. This is merely a matter of assembly positioning of the crank 56 on the shaft 38, for example, in FIG. 15.
The unitizeddisplacement curve Gof FIG.19represents the output of this invention for a given phase angle of 90 with ~ set equal to 0.9. The clock angle is shown as moving through 720 which is two indexes of the mechanism 20 but only one revolution of the crank 56. The momentary stops at the ends of the strokes are evident at clock angles of 180 and 540.
A significant slowdown to a near stop at clock angles of 0, 360 and 720 (720 is the same position as 0) is also evident.
The slowdown, as differentiated from a complete stop, is a result of the arbitrarily illustrated ~ = 0.9; if ~ were set equal to 1, the output would come to an instantaneous stop at 0 and 360. Furthermore, if ~ were made slightly larger than 1, there would be a slight output reversal at these angles.
This midstroke slowdown is useful in many applications such as lifting or lowering of transfer bars which pick up or deposit workpieces at or near midstroke.
Another illustrative output displacement graph is shown in curve H, FIG. 19. In this example, the phase angle was set to 60 and ~ set equal to 0.8. Again the momentary stops and reversals can be seen at 215 and 575 clock angle. A
significant slowdown is evident at 0 and 360 clock angle.
Here again, the slowdown can be greater if ~ is increased, and a momentary stop achieved at ~ = 1, or a slight reversal obtained by making ~ 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, if the forward stroke is defined as 575 to 215 clock angle 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 at a displacement of .75. A property such as this is useful, for example, in operating a lift system such as in my U. S. Patent No. 4,750,605, where it is desired to slow down at one 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 Cl in equation (15) which provide useful results and as previously noted these factors ~ and Cl are controlled in the total mechanical system by the design of the distance from axis A2 to axis A3 and by the assembly positioning of the crank 56 on the shaft 38 (FIGS. 14, 15).
All the performance curves shown in FIGS. 16-19 were derived onthe basis of equation (15), which, it will 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 A
approximations, such factors as the distance between axes A
and A2 and between axes A4 and Al of mechanism 20.
In all of the combination mechanisms shown above, independent of the values of ~ and the phase angle Cl, 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 other than 180. As noted earlier, and as shown in the reference patent, the output angle index angle is determined by the ratio of the pitch diameter of the output gear 36 to the pitch diameter of the eccentric gear 34. If this ratio is.defined as M, the output index angle is 360/M. Stated anotheE way, there are M indexes per revolution.
If equation (6) which, it will be recalled, is the equation for calculating the output angle of mechanism 20, is rescaled in the general form, it becomes:
~ M 2~ [180 C (~C)~ + Cl (16) which simplifies to:
5 MC - 180~ sin (~C) + Cl (17) When M is 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 combinationmechanism output, in unitlzed displacement, is found to be:
`- 12710S5 D ~ 5 - .5 cos[~c ~ 18M ( C) ] (18) Again, it can be seen that when M = 2, equation t18) reduces to the form, previously derived for the 180 index angle, of equation (15). Using equation (18), the unitized displacement characteristics of other embodiments of this invention have been calculated.
The first of the illustrative examples is shown in FIG. 20. In this instance, M was set equal to 1 representing a 360 output index angle of the mechanism 20, ~ was set equal to 1.1 and Cl set equal to 0. The curve of FIG. 20 shows a reciprocating output having a very long dwell at one end of the stroke, and a relatively short dwell at the other end of the stroke; this is useful in applications in which the service is such that the prime mover, e.g., motor 150, FIG. 14, is stopped after each reciprocation, and it is required that a very accurate output position be maintained over a wide range of stopping positions of the prime mover.
Another illustrative example is shown in FIG. 21. In this instance M was set equal to 4, representing a 90 output index angle of the mechanism 20, A was set equal to 1 and Cl set equal to 0. The curve of FIG. 21 again shows a reciprocating output having a relatively long dwell at each end of the stroke, together with a significant dwell at the midpoint of each stroke.
This duplicates the performance, in principle, of the conditions of curve G of FIG. 19, except that by using the conditions of FIG. 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.
i.~710~;5 From the descriptions of the above illustrative combinations, it is clear that a wide variety of kinemati~
characteristics can be achieved through a proper selection of the various parameters involved, which may be summarized as follows:
A. The ~ factor controls the cyclic behavior of the mechanism 20; with ~ = 1, this output shaft will come to a momentary stop once for each revolution of the eccentric gear;
with ~ slightly less than 1, the output shaft will come to a near stop after each revolution of the eccentric gear; and, with ~ 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 of the output shaft made during one total revolution of the output shaft.
C. The phaseangle~ controls the angular relationship of the output crank angular position from its top dead center position when the driving mechanism 20 is at the center of its dwell or near dwell.
The disclosure made above related to the rotary output indexing system typified by FIGS. 14, 15 and 16 of the background patent, No. 3,789,676, as earlier noted, except that the chain 320 was replaced by an equivalent gear train in the mechanism of FIGS. 1-6 herein. It should be noted, however, that the chain drive system of FIGS. 14, 15 and 16 of the background patent is usable for many applicationq in which extreme accuracy or rigidity are not required. Indeed, the double chain system illustrated in FIGS. 33, 34 and 35 of the background patent is 1.;~7~055 . .
also usable subject to chain load and rigidity limitations.
Furthermore, the rotary output systems illustrated in FIGS. 22, 23 and 24 and by FIGS. 25, 26 and 27 in the backgraund patent are also usable subject to the limitation that these embodiments are limited to maximum output index angles of 120.
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1.
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 other direction, comprising:
a. frame, b. reciprocating output means mounted for reciprocation in said frame, c. connecting rod means journalled at one 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 other end to said connecting rod means, f. a rotary output member mounted on said output shaft member, g. a drive surface on said rotary output member, h. an eccentric drive member rotatable about a moving center to engage said drive surface in a tangential driving relationship, i. means mounting said eccentric drive member for rotational motion about its moving center and in driving engagement with said drive surface of said rotary output member, j. a rotative drive member, k. means mounting said rotative drive member for movement in a path generally transverse of said drive surface of said rotary output member, l. 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 m. power drive means 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, 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 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 rotatable about a moving center to engage said drive surface in a tangential driving relationship, 6. means mounting said eccentric drive member for rotational motion about its 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 member for 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 it to rotate about the moving center of said eccentric drive member, 10. power drive means to impart a rotation to one of said drive members, 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 drive member and said rotative 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, b. a reciprocating output drive system comprising:
1. a crank member mounted at its one end to said output shaft member, 2. connecting rod means journalled at its one end to the other end of said crank member, 3. reciprocating output means mounted for reciprocation in said frame, and pivotally connected to the other end of said connecting rod means.
3.
A reciprocating mechanical drive system as 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 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 member are substantially colinear.
5.
A reciprocating mechanical drive system as 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 in claim 2 in which said rotary output member has a pitch radius which is four times the pitch radius of said eccentric drive member.
7.
A reciprocating mechanical drive system as 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 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 other direction, comprising:
a. frame, b. reciprocating output means mounted for reciprocation in said frame, c. connecting rod means journalled at one 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 other end to 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 rotatable about a moving center to engage said gear teeth in a tangential driving relationship, i. means mounting said eccentric gear drive member for 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 member for movement in a path generally transverse of said gear teeth of said rotary output gear member, l. means mounting said eccentric gear drive 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 it to rotate about the moving center of said eccentric gear drive member, and m. power drive means 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 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 gear member mounted on said output shaft member, 4. gear teeth on said rotary output gear member, 5. an eccentric gear drive member rotatable about a moving center to engage said gear teeth in a tangential driving relationship, 6. means mounting said eccentric gear drive member for rotational motion about its moving center and in driving engagement with said gear teeth of said rotary output gear member, 7. a rotative gear drive member, 8. means mounting said rotative gear drive member for movement in a path generally transverse of said gear teeth of said rotary output gear member, 9. means mounting said eccentric gear drive 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 it to rotate about the moving center of said eccentric gear drive member, 10. power drive means to impart a rotation to one of said drive members, 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, b. a reciprocating output drive system comprising:
1. a crank member mounted at its one end to said output shaft member,
2. connecting rod means journalled at its one end to the other end of said crank member,
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 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 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 member are substantially colinear.
12.
A reciprocating mechanical drive system as in claim 9 in which the pitch radii of said rotary output gear member and said eccentric gear drive member are equal.
13.
A reciprocating mechanical drive system as in claim 9 in which said rotary output gear member has a pitch radius which is four times the pitch radius of said eccentric gear drive member.
14.
A reciprocating mechanical drive system as 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 member are substantially colinear.
10.
A reciprocating mechanical drive system as 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 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 member are substantially colinear.
12.
A reciprocating mechanical drive system as in claim 9 in which the pitch radii of said rotary output gear member and said eccentric gear drive member are equal.
13.
A reciprocating mechanical drive system as in claim 9 in which said rotary output gear member has a pitch radius which is four times the pitch radius of said eccentric gear drive member.
14.
A reciprocating mechanical drive system as 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 member are substantially colinear.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US78188285A | 1985-09-30 | 1985-09-30 | |
| US781,882 | 1985-09-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1271055A true CA1271055A (en) | 1990-07-03 |
Family
ID=25124262
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000515790A Expired CA1271055A (en) | 1985-09-30 | 1986-08-12 | Reciprocating long dwell mechanism |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS6280351A (en) |
| CA (1) | CA1271055A (en) |
| DE (1) | DE3633034A1 (en) |
| FR (1) | FR2592123A1 (en) |
| GB (1) | GB2181211A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102072299B (en) * | 2011-01-22 | 2012-10-24 | 青岛理工大学 | Space crank rocker device |
| CN103144927A (en) * | 2013-03-29 | 2013-06-12 | 苏州市职业大学 | Automatic workpiece conveying mechanism |
| CN109533928B (en) * | 2018-11-20 | 2020-09-25 | 常国明 | Intermittent feeding mechanism |
| CN112747097B (en) * | 2020-12-30 | 2022-05-24 | 苏州绿科智能机器人研究院有限公司 | Alternative operation type RV reducer integrated device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4490091A (en) * | 1983-03-29 | 1984-12-25 | Brems John Henry | Slave rotate mechanism for mechanical hands of gantry type transfer system |
-
1986
- 1986-07-24 GB GB08618143A patent/GB2181211A/en not_active Withdrawn
- 1986-08-12 CA CA000515790A patent/CA1271055A/en not_active Expired
- 1986-09-04 FR FR8612443A patent/FR2592123A1/en not_active Withdrawn
- 1986-09-05 JP JP20808886A patent/JPS6280351A/en active Pending
- 1986-09-29 DE DE19863633034 patent/DE3633034A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB2181211A (en) | 1987-04-15 |
| FR2592123A1 (en) | 1987-06-26 |
| JPS6280351A (en) | 1987-04-13 |
| DE3633034A1 (en) | 1987-04-02 |
| GB8618143D0 (en) | 1986-09-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |