US2166551A

US2166551A - Photoelectric control of variablespeed mechanism

Info

Publication number: US2166551A
Application number: US138344A
Authority: US
Inventors: William R Perry
Original assignee: Reeves Pulley Co
Current assignee: Reeves Pulley Co
Priority date: 1932-03-28
Filing date: 1937-04-22
Publication date: 1939-07-18
Anticipated expiration: 1956-07-18

Description

July 18, l939- w. R. PERRY 2,166,551

PHO'IOOELECTRIC CONTROL OF VARIABLE-SPEED MECHANISM Original Filed March 28, 1932 2 Sheets-Sheet l w @y @W @1' "/f/ J2 a! a@ I ze .35 v

INVENTOR. )fly/h ign/J, twv-o16 Y- calann ATTORNEYS MY 18, 1939- w. R. PERRY 2,166,551

PHOTOELECTRIC CONTROL OF VARIABLE-SPEED MECHANISM Original Filed March 28, 1932 2 Sheets-Sheet 2 ATTORNEYS.

Patented July 18, 1939 UNITED STATES PHOTOELECTRIC CONTROL OF SPEED MEUHANISM VARIABLE William Perry, Columbus, Ind., assignor to Reeves Pulley Company, Columbus, Ind., a corporation of Indiana original application Maren 2s, 1932, seriall No.

601,606. Divided an 22, 1937, Serial No.

y10 Claims.

The present application is a division of my col pending application Ser. No. 601,606, filed March 28, i932, and relates to speed control mechanism, and more particularly to mechanism for controlling the speed of a driven element, such mechanism including light-sensitive means adapted to be dominated by a member associated with the driven element.

My invention may be embodied in many different forms, and I have herein illustrated several of them, but it is tobe understood that I do not consider the specific form of any one of the mechanisms illustrated in the present application to be a limitation upon my invention. For instance, the specific control means of one illustrated embodiment of my invention might be applied to another illustrated embodiment without in any Way violating the scope of my invention. Y

Essentially, the objects of the present invention are to control strand-forwarding mechanism in such a manner as to maintain a substantially constant time-weight ratio of the material being forwarded; attention being called to the fact that, in the present application, I shall use the term strand in a broad enough sense to include either a string-like element or a web or strip or the like, the cross section of which may be of any form, so long as the material is flexible in a direction perpendicular to the direction of movement of the material.

To the accomplishment of the above and related objects, my invention may be embodied in the forms illustrated Vin the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that change may`be made in the specific constructions illustrated and described, so long as the scope of the appended claims is not violated.

Fig. 1 is a diagrammatic isometric view of an embodiment of my invention;

Fig. 2 is a view of structure closely similar to that of Fig. 1, but showing cycling means associated with the control; and

Fig. 3 is a view of a similar mechanism associated with a different type of machinery to be controlled.

The structure of Fig. 1 is intended primarily for forwarding plastic material of very low tensile strength, in such a manner that the material will leave the mechanism'under a substantially uniform weight-length ratio. The mechanism may be used, of course, for forwarding material of other characteristics, but its primary use is that above suggested.

d this application April 138,344

The material I is led from a storage reel or other source between a pair of forwarding rolls II and I2, which may be the discharge rolls of a machine for making or treating the material, and the material may be of varying thickness and of varying width, whereby its weight per unit length is a variable. In the illustrated embodiment of my invention, the roll II is mounted upon a shaft I3 which carries a pulley I4 adapted to be driven, through the medium of a belt I5, by any suitable prime mover (not shown). The shaft I3 carries aA second pulley I6 which, through the medium of a belt I1 drives a pulley I8 upon the in-put shaft I9 of a variable-speed transmission indicated generally at 20, and which is preferably but not necessarily of the well-known Reeves type. The transmission 20 is of wellknown construction and need not here be described in detail. As usual', said transmission includes a screw shaft 2I for varying the speed ratio between the in-put shaft I9 and the output shaft 22. The screw shaft 2I carries a gear 23 with which meshes a pinion 24 on the spindle of a reversible electric motor 25.

The shaft 22 carries a pulley 26 which, through the medium of a belt 21, drives a pulley 28 upon a shaft 29, said shaft 29 carrying a forwarding roll 3l) which cooperates with a roll 3| to forward the strand I0.

Since the material of the strand I0 is of very low tensile strength, it must necessarily be supported at intervals upon rolls such as the

rolls

32 and 33. Two of said rolls, illustrated in Fig. 1, are spaced apart farther than others of the supporting series, whereby a portion 34 of the strand I3 is supported solely upon a floating idler roll 35 carried in a frame 36 depending from a rod 31. The upper end of said rod 31 is pivotally secured to one end 3l of a lever 33 suitably pivoted upon a base 40. The opposite end of said lever 33 carries an opaque counter-balancing block 4I, said block and lever being so proportioned that, so long as the portion 34 of the strand Il is of optimum weight-length ratio, the lever 39 will be maintained in a median position.

Adjacent the block 4I there is mounted a photo-electric cell 42, and a light source 43 is associated with said cell 42, but is positioned on the opposite side of the block 4I, with respect to the cell 42. Said light source 43 is adapted to direct a beam 44 toward said cell 42. Spaced slightly beneath the cell 42 is a second photoelectric cell 45 with which is associated a light source 43 positioned immediately beneath the said. cell 45. It will be obvious that, so long as the block 4| is maintained ata median position, the'two

cells

42 and 45 will be illuminated equally by the beams 44 and 4.1; but that any upward movement of the block 4| will decrease the intensity of the beam 44, and any downward movement thereof will decrease the intensity of the beam 41. It will also be obvious that a single light source capable of illuminating both of the cells 42 andv45 might be substituted for the two

sources

43 and 46.

A source of electricaienergy is indicated by the

line wires

48 and 49. A wire 50 leads from the line 49 to the common terminal of the motor 25. A wire leads from what may b'e termed Vthe forward terminal of the motor 25 to one terminal 52 of a carbon-pile rheostat 53, the

opposite terminal 54 of said rheostat V,being connected by the wire 55 to the line 48. What may be termed the reverse terminal of the motor 25 is connected -by a wire 56 to one terminal 51 of a second carbon-pile rheostat 58, the opposite terminal 59 of which is likewise connected by the wire 55 to the line 48. It will be seen that, when the plunger 60 of the rheostat 53 is depressed, current will flow through the circuit 49,

50, 25, 5|, 52, 53, 54,`55, 48 to cause forward rotation of the motor 25 which, in turn, will rotate the screw shaft 2| to increase the speed of the out-put shaft 22, and consequently to increase the speed of the roll 30. Conversely, when the plunger 6| of the rheostat 58 is depressed, current will flow in the

circuit

49, 56, 25, 56, 51,

' 58, 59, 55, 48 to cause operation of motor 25 in the opposite direction to rotate the screw shaft 2| to decrease the speed of the shaft 22 and roll 38.

The primary coil 62 of a transformer is connected across the

line wires

48 and 49 to excite the secondary coil 63 of said transformer. .A wire 64 connects one end of said coil 63 to a wire 65 which is connected to the cathode of the photo-electric cell 42. anode of said cell 42 with the grid 61 of the thermionic valve 68. The plate 69 of said valve is connected by a wire 18 with one end of a solenoid coil 1|, the midpoint of said coil being connected by al wire 12 with'the opposite end of the coil 63. The filament 13 of the valve 66 is energized through the medium of a wire 14 connected to an intermediate point on the coil 63 and to one side of the ,filament and a wire connected to the opposite side of said lament and to a wire 16 connected to the coil 63 at a point spaced somewhat from the, point at which the wire 14 is connected to said coil 63.

A wire 11 connects said wire 64 with the cathode ofthe photo-electric cell 45, and the anode 0f said cell is connected by a wire 18 with the grid 19 of a second thermionic valve 8|).v The plate 8| of said valve 8|! is connected by a wire l2'with the'opposite end of the solenoid coil 1|.

The filament. 83 of said valve 80 is connected to the wires 14 and 16in parallel with the lament 13. f

v A wire 84 leads from a point 85 on the negative side of the transformer secondary 63 to impress upon the

grids

61 and 19 of the thermionic.

valves

68 and 80, a negative potential, through resistors 86 and 81 shunted by

condensers

88 and 89, respectively. When the cells 42 andA 45 are fully illuminated, a further negative potential is impressed upon said

grids

61 and 19 through said cells, respectively; and the device is so calibrated that the algebraic sum of the negative A wire 66 connects thev amanti solenoid coil 1| will be energized, and the core 96 thereof will occupy a median position, as illustrated. If the intensity of the beam 44 is decreased, however, the Value of the negative potential impressed upon the grid 61 will be arithmetically reduced, whereby current flow through the valve 68 and the upper'portion of the solenoid coil 1| will be permitted and the core 98 will be moved upwardly to swing the arm 9|" in a counter-clockwise direction to depress the plunger 68 of the rheostat 53, whereby the motor will be energized to increase the speed of thev shaft 22 and the roll 38. Itv will also be obvious that the speed of rotation of the motor 25 will be dependent upon the degree of movement of the core 90 which, in turn, is a function of the rate of current ow through the valve 68, that rate being dependent upon the degree of reduction in the intensity of the beam 44 falling upon the cell 42. Similarly, if the intensity of the beam 41 falling upon the cell 45 is reduced, the core 90 will be moved downwardly to depress the plunger 6| of the rheostat 58 to cause rotation of the motor 25 inthe opposite direction at a speed dependent upon the degree of reduction of the intensity ofthe beam 41 falling upon the cell 45.

In the use of the mechanism disclosed in Fig. l, the strand I0 is threaded in the manner illustrated. Normally, the parts will be in the positions illustratedyandfthe roll 30 will be rotated,

ata speed synchronous with the speed of thev roll If, as the strand I0 `is forwarded, a portion of undue thickness reaches a position between the illustrated rolls 32 and 33, to be supported upon the roll 35, said roll 35 will be depressed with the result that the block 4| will be elevated to reduce the intensity with which the beam 44 illuminates the cell 42, whereby, in the manner above described, the arm 9| will be operated to depress the plunger 60. The motor 25 will thus be operated to increase the speed of the shaft 22 and roll 30. Since the roll 80 will then be operating at a speed greater than the speed of the roll the material between said rolls and 30 will be elongated, whereby the unduly thick portion will be reduced in thickness. Obviously, if the speed ratio between the rolls and is continued, the aboved scribed attenuation will be carried beyond the desired point, whereupon the weight-length ratio of the portion 34 of web |0 will eventually be reduced below the optimum. When this occurs. the roll will move upwardly beyond its median position, whereby the beam 41 willbe intercepted and the motor 25 will be operated in the opposite direction to reduce the speedr of the roll 30 to a value dependent upon the weight-length ratio of that portion of the strand currently supported upon the roll 35.

As above-described, this is, of course, a hunting control; and in Fig. 2 I have illustrated a modified embodiment of my invention whereby the hunting tendency of the control may be overcome.

The structure disclosed in Fig. 2 is identical with that disclosed in Fig. l, except that the wire 92 has been substituted, in Fig. 2, for the'wire of Fig. l, and acycling mechanism has been ,cated at ||2.

added to control the hunting tendency of the control.

The wire 92 leads from the line wire 49 to a contacter 93 carrying a contact button 94. Cooperatively associated with the contacter 93 is a second contactor 95 carrying a. contact button 96 adapted to contact the button 94. Preferably, the contacter 95 is a spring finger, but it may be any one of a number of other suitable types. Said contactor 95 is connected by a wire 91 to the common terminal of the motor 25.

The parts of the organization are so proportioned and correlated that the cam |04 makes one complete revolution in the time which is required for a point on the web I0 to travel from al position between the rolls and l2 to the supporting roll 33. The contact buttons 94 and 96 are normally separated, and are brought into contact only when the high portion of the cam |04 comes into engagement with the contacter 95, the shape of the cam being such that said buttons are in contact substantially'during the time required for a point on the web to move from between the rolls and l2 to a point on the roll 32; and beinlfseparated during the time required for said point to move thence to a point on the roll 33. It will thus be seen that operation of the motor 25 is possible only at intervals.

If, at a time when the contact buttons 94 and 96 are in contact, the portion 34 of the web I0 is unduly heavy, the motor 25 will be energized to increase the speed of the shaft 22, and consequenty of the rolls 30 and 3|. After a short period of operation, the motor circuit will be broken at 94-96, and the rolls 30 and 3| will continue to operate at increased speed during the time required for a point on the web I0 to move from the roll 32 to the support roll 33. At that time, the contacts 94 and 96 will again be closed,

and the mechanism will take another weight of the material supported between

rolls

32 and 33 to determine whether or not another adjustment of the variable speed transmission is required. If the portion 34 of the web I0 supported upon the roll 35 is now too light, the motor 25 will be operated in the reverse direction to reduce the speed of the rolls 30 and 3|.

This arrangement cures the hunting defect of the organization of Fig. 1. ,f

In Fig. 3 there is illustrated an embodiment of the present invention which is similar in some respects to that illustrated in Fig. 1, in that it comprises mechanism operable to deliver a given weight of material to a discharge station within a given period of time.

A first conveyor is indicated by the showing of a conveyor roll |05 about which passes one end of the conveyor belt |06. Said roll |05 is mounted upon a shaft |01 which carries a pulley |09 driven by a belt |09 from a pulley ||0 on the output shaft of a variable speed transmission indi-` Said transmission includes a shifter shaft H3 carrying a gear ||4 with which meshes the pinion 24 carried upon the spindle of the electric motor 25 identical with that disclosed in Fig. 1. i

The input shaft ||5 of the transmission ||2 carries a pulley ||6 driven by a belt |1 from a pulley ||8 on a shaft 9, said shaft 9 carrying a pulley |20 driven by'a belt |2| from a prime mover (not shown) said shaft ||9 likewise carries a roll |22 about which one end of a conveyor belt |23 is passed.

'I'he elements 32 to 83, inclusive, 90, and 9|, of Fig. 3 are identical with the similarly indicated elements of Fig. 1, except that the wires 5| and 56 disclosed in Fig. 1 are reversed in Fig. 3, so that the wire 56 is connected to the forward terminal of the motor 25, while thev wire 5| is connected to the reverse terminal of said motor. Thus, it will be apparent that, in the organization disclosed in Fig. 3, if the roll 35 is depressed, the motor 25 will be operated to decrease the speed of the shafts and |01.

A hopper |24 is associated with the conveyor belt |06 in a well known manner, so that material will be delivered from said hopper to said belt at a more or less constant rate which will be somewhat dependent upon the rateof movement of said belt |06. It will be assumed that containers are successively brought into registration with the discharge end of the conveyor belt |23. The object of the organization is, of course, to discharge a uniform weight of material into each of such containers.

Assuming that the belts |06 and |23 are moving at the same linear speed, and that material is being discharged from the hopper |24 onto the belt |06 at the desired rate, the roll 35 will occupy the median position illustrated in which neither the beam 44 nor the beam 41 will be obstructed by the block 4|. If, for some reason, an unduly large mass of material is deposited suddenly upon the belt 06 from the hopper |24,

that mass will shortly be deposited upon the belt |23, and will be carried onto that portion |25 of said belt |23 between the supporting rolls 32 and 33, and will there affect the roll 35. The roll 35 will vthus be depressed, whereby the block 4| will be elevated, to intercept or decrease the intensity of the beam 44. Thereby, the motor 25 will be caused to rotate, shifting the transmission elements to reduce the speed of the shaft |01, A

thereby reducing the linear speed of the belt |06. As a result of this reduction, material will be less rapidly deposited upon the belt |23, whereby the time-weight ratio of the material carried across the roll 35 will be reduced and, after a suitable interval, said roll 35 will be` lifted, whereby the motor 25 will be operated in the opposite direction to bring 'the shafts and |01 back to normal speed.

I claim as my invention:

1. Means for forwarding ductile material of low tensile strength at constant weight per unit length, comprising forwarding means, means for driving said forwarding means, a forwarding roll spa-ced from said forwarding means, variablespeed means for driving said forwarding roll, a vertically reciprocable idler roll positioned between said forwarding means and said forwarding roll, a portion of said material being constantly supported upon said idler roll, two vertically spaced photo-electric cells, a light source directing beams of light toward said cells, an opaque element shiftable in response to reciprocation of said idler roll, and normally disposed out of shielding relation with both of said cells and adapted, when shifted in either direction from its normal position, to obstruct one or the other of said beams, and connections between said cells and said variable-speed means whereby, when said opaque element is shifted in response to downward movement of said idler roll, said variable-speed means will be operated to increase the speedof said forwarding roll,'and when said opaque element is shifted in response to upward movement of said idler roll, said variable-speed means will be operated to decrease the speed of said forwarding roll.

2. Means for forwarding ductile material of low tensile strength at constant weight per unit length, comprising a forwarding roll, means for driving said roll, a second forwarding roll spaced from said first roll, variable-speed means for driving said second forwarding roll, a vertically reciprocable idler roll positioned between said forwarding rolls, an opaque element urging upward movementof said idler roll, said material being supported at all times upon said forwarding rolls and upon said idler roll and the weight 4of. such material supported upon said idler roll at ment is shifted in response to downward movement offsaid idler roll, said variable-speed means f will be operated to increase the speed of said second forwarding roll, and when said opaque element is shifted inresponse to upward movement of said idler roll, said variable-speed means will be operated to decrease the speed of said second forwarding roll.'

3. Means for forwarding ductile material of low tensile strength at constant weight per unit length, comprising forwarding means, means for driving said forwarding means, a forwarding roll spaced from said forwarding means, a variablespeed transmission connected to drive said for.- warding roll at variable'speeds, a reversible, vari- .able speed electric motor dominating said transmission, av vertically reciprocable idler roll positloned .between said forwarding means and said forwarding roll, a portion of said material being supported at all times upon said idler roll, two vertically spaced photo-electric cells, ay light source directing Abeams of light toward said cells, an opaque element shiftable in response to reciprocation of said idler roll,4and normally disposed out of shielding relation with both of said cells and adapted, when shifted in either direction from its normal position, to decrease the intensity of illumination of one or the other of said cells, and electrical connections including a pair of rheostats between said cells and said motor, whereby said motor will be energized to operate said transmission, upon movement of said opaque element from its median position, in a direction and at a speed dependent upon the direction and degree of movement of said opaque element from its median position.

4. Means for forwarding material in accordance with a predetermined time-weight ratio, comprising a weighing station, means for continuously delivering material to supported relation at said weighing station, means for continuously withdrawing material from said weighing station, mechanism for driving said Vdelivering and withdrawing means, said mechanism being adjustable to vary the speed of operation of one of said means with-respect tothe speed of operation of the other of said means, light-sensitive means connected to control said mechanism',-

movable means at said weighing station movable i to a weighing station,l means forv continuouslywithdrawing material from said weighing station, mechanism for driving one-,of said means, variable-speed mechanism for driving the other of said means at speeds variable withrespect to the speed of said one means,l means for varying the output speed of said variable-speed mechanism including a light-sensitive cell, a light source directing a light beam toward said cell and means for varying the intensity of said beam falling upon said cell, and movable means atsaid weighing station movable in response to the weight of material delivered thereto, saidV movable means dominating said light-intensity-varying means.

6. Means for ,forwarding material in accordance with a predetermined time-weight ratio, comprising means for continuously delivering material to a weighing station, means for continuously withdrawing material from said station, a prime mover connected to drive one of said means directly and to drive th'e input shaft of a variable-speed transmission, means connecting the output shaft of said transmission to drive the other of said means, anelectric motor for varying the speed ratio between said input and output shafts, means including a light-sensitive cell, a light source directing a light beam toward said cell, and beam-obstructing means, for con-- means.

7. Means for forwarding material in accordance with a predetermined time-weight ratio, comprising means for continuously delivering material to a .weighing station, means for continuouslywithdrawing material from said station, constant-speed mechanism for driving said delivering means, variable-speed mechanism for driving said withdrawing means, electrically operatd means for controlling the output speed of said variable-speed mechanism, means including a light-sensitive cell, a light source.v directing a light beam toward said cell, and beam-obstructing means, for controlling said motor, and movable vmeans atsaid weighing station movable in response to thev weight of material delivered thereto, said' movable means dominatingv said beam-obstructing means.

8. Means for forwarding material in accordance with a predetermined time-weight ratio,

comprising means for continuously deliveringl material to a weighing station, means for continuously withdrawing material from said station, variable-speed mechanism for driving said delivering means, constant-speed mechanism for driving said withdrawing means, electrically operated means for controlling' the output speed of said variable-speed mechanism, means including a light-sensitive cell, a light source directing a. light beam towardsaid cell, and beamobstructing means, I' for controlling said motor, and movable means at said Weighing station movable in response to the weight of material delivered thereto, said movable lmeans dominating said beam-obstructing means.

9. In combination, means for advancing a strand, a pair of spaced stationary elements providing supports for portions oi' said strand, la movable element intermediate said stationary elements, supporting at all times the portion of said strand between said stationary elements and movable in response taweight changes impressed thereon, variable-speed mechanism for driving said advancing means, means associated with said movable element and with said variablespeed mechanism for controlling the output speed of said' variable-speed means in accordance with the position of said movable element, and cycling means normally rendering said last-mentioned means ineifective and operable to render said last-mentioned means effective only at intervals corresponding substantially to the time required for a given point on said strand to move from one of said stationary elements to the other of said stationary elements.

10. The combination with a variable-speed driving mechanism, of means for controlling the driving speed thereof comprising means for advancing a strand, a pair of spaced stationary elementsproviding supports for portions of said strand, a movableelement intermediate said stationary elements, supporting at all times the portion of said strand between said stationary elements and movable in response to weight changes impressed thereon, means associated with said movable element and with said variable-speed mechanism forcontrolling the speed of said variable-speed means in accordance with the posiltion of said movable element, and cycling means normally rendering .said last-mentioned means ineffective and operable to render said last-mentioned means effective only at intervals corre- Sponding substantially to the time required for