US2214609A - Torque amplifier for dancer field rheostats - Google Patents

Description

Sept. 10', 1940. C. w. DRAKE' 509 I 'ronqms AMPLIFIER FOR DANCER FIELD RHEOSTAI'S Filed April 25,,1939

1 5low Slay I I (fl INVENTOR Chester W Bra/re.

wnm-zssss: A/XM J BY W I M8 'ATTORNEY Patented. Sept. 10, 1940 roaoun mpirma roa mmcna rmm ansos'rsrs Chester W. Drake, Irwin, Pa., asslgnor to 'Westingliouse Electrio & Manufacturing Company,

East Pittsburgh, Pa, sylvania a corporation of Penn- Application April 25, 1939, Serial No. 270,037

12 Claim My invention relates to an operating mechanism for rheostats, and more specifically to a torque amplifier for a "dancer field rheostat.

In winding machines and the like wherein long thin sheets or material such as paper, or long strips of material suchas threads or rubber are wound or conveyed, it"is often desirable to control the speed of travel of such material in accordance with the size of a loop of the material.

For example, a weighted body may rest on the loop and its vertical movement as the result of changes in the loop size may be transmitted to a rheostat, which, in turn, controls the speed of a motor which is effective to restore the loop to its initial optimum 1| size. It has been found, however, in such applications that the amount of torque which can be developed by a weighted body resting on the loop and acting through a predetermined vertical distance is insufllcient to operate large rheostats.

It is, therefore, necessary that a force amplifying means or relay, or both, be interposed between the weighted body and the rheostat in order to develop suillcient torque to operate the large rheostat.

5 An object of my invention is to provide a novel torque amplifying means on a "dancer type rheostat.

Another object of my invention is to provide relay means to a torque amplified dancer rheostat which relay means includes a mercury switch which controls a motor which, in turn, drives a rheostat contact arm, thereby varying the speed olf a second or main motor in accordance with variations in the size of the loop of the material being wound.

' Other objects and advantages will become more apparent from a study of the following specification when considered in conjunction with the ac- L companying drawing, in which the single figure is a diagrammatic view embodying my invention andinwhich:

Numeral i denotes a strip of material, such as paper, rubber, or the like, which is being wound in a winding machine or which is otherwise being transferred from one part of a machinetc another. The material is driven by constant speed roll 2, then forming a loop 3, and finally is driven by a variable speed roll 4, which roll 4 is driven by a variable speed electric motor 5. Motor 5 is illustrated as being a shunt motor having a field winding 8 and a rheostat I.- In moving the contact arm 3 of the rheostat I, the speed of the motor 6 may be controlled; in other words, if

5 contact arm '3 is moved to the left, thereby putting in more resistance, the field. developed by winding 6 is weakened and the speed of motor 5 is increased; likewise when contact arm 3 is moved to the right the speed of motor-.5 is decreased. It "will be readily observed that in order to keep the size of loop 3 substantially constant, the speed of motor 5 should vary directly in accordance with the size of such loop.

The torque amplifying means for the rheostat, in accordance with my invention, comprises an arm 3 which is loosely pivoted on shaft [0, which shaft is journaled to a stationary bearing member (not shown). Pivoted at the opposite end of arm 3 is a link H which is secured to a weighted member l2 which rests on loop ,3. It will thus be obvious that as the size of loop 3 varies,.link II will move vertically in accordance with such variations and will, in turn, move arm 9 about shaft [0 as a'pivot in accordance with the size of the loop. Loosely pivoted on an intermediate portion of arm 9 is a gear l3 having a shaft portion It, Rigidly secured on gear 13 by a support I5 is a double pole mercury switch l6 having a pair of contact members H at the left end thereof and a similar pair of contact members l8 on the right end thereof. Integral with shaft 10 are contact arm 8, a smaller gear is and a sprocket 20. Sprocket 20 is driven by a reversible motor 2! having two reversing windings, 22 and 23. The motor drive is through shaft 24, sprocket 25, and chain26.

The operation of the device is as follows: Assume that the start push button is depressed thereby closing contact members 21. A circuit will be completed which may be traced from supply conductor 28 through conductor 29, contact members 21, the bridged contact members 30 of the stop push button switch, relay coil 3|, then through a parallel path, one going through the armature of motor 5, the other going trough conductor 32, the resistors of rheostat I, contact arm 8, conductor 33, and field winding 6 then through a common conductor 34 to the other supply conductor 35. Energization of relay coil 3| will effect closing of contact members 36 which shunts contact members 21 of the start push button. Hence even though the start push button is released, thereby allowing its spring to open the contact members thereof, a parallel circuit will, 50 nevertheless, be established through contact members 33- and will be maintained as long as relay coil 3| remains energized. When the stop push button is depressed thereby opening contact members 30, relay coil II will become deenergized thereby opening contact members 36 and interrupting the motor circuit. 7

If the size of loop 3 diminishes an abnormal amount, weighted member i2 will be raised and through link II, will move arm 9. in a clockwise direction about shaft l0 as an axis. Gear I9 will tend to remain stationary because of the inertia and friction of the parts in driving engagement therewith including sprockets 20 and 25 and the reversible motor 21. Hence, gear I3 will rotate about stationary gear I9, at the same time tilting the mercury switch [6 to the right until finally the right-hand contact members i8 are closed by the mercury, thereby completing a circuit through one of the reversing windings 23 of reversible motor 2!. The above circuit may be traced from supply conductor 28 through conductors 31, 38, contact members i8, conductor 39, field winding 23, the armature or" motor 2!, conductor 40 to the other supply conductor 35.

Motor 2| will thus rotate in such direction so as to rotate gear i9 together with contact arm 8 in a clockwise direction. Clockwise rotation of contact arm 8 will cut out a portion of the resistance in the rheostat 1, hence will effect slowing of the speed of motor 5 which in turn will drive roll 4 at a lower speed thereby allowing loop 3 to increase in size. As hereinbefore explained, gear i9 is integral with contact arm 8. Hence as contact it rotates in a clockwise direction, gear it also rotates in such direction and by its geared relation to gear l3 it will rotate the gear it in a counter-clockwise direction. This rotation will continue until-switch i6 is tilted sufiiciently so as to open contact members it and interrupt the circuit through the reversible motor 2!. It will be observed that the amount of shortening of loop 3 controls the amount of tilting of mercury switch 16 which, in turn, determines the length of time that the reversible motor 2| must operate before mercury switch it is restored to its original or neutral position until both contact members I! and I8 are again open.

Likewise if loop 3 should for some reason become abnormally large, arm 9 will be moved in a counter-clockwise direction thereby rotating ear i3 in a counter-clockwise direction about the gear i 9 until contact members I! of the mercury switch are closed, thereby completing the circuit through the other field winding 22 which will effect a drive of gear I9 in a counter-clockwise direction thereby moving contact arm 8 to the left to put more resistance in series with field winding 6 so as to speed up motor 5 and roll 4, so as to again shorten the loop. Simultaneously, gear I3 will be rotated in a clockwise direction until mercury switch I6 is tilted sufficiently to open contact members IT, thereby deenergizing reversible motor 2! and stopping the above described movement.

In view of the fragile characteristics of the material i, which may be thin paper, rubber, or the like, only a very small force may be applied to link H by the changes in size of the loop; hence in order to apply sufficient torque to contact arm 3, a relay controlled reversible motor is used. By making the diameter of gear [3 larger than that of gear l9 so as to provide a larger number of teeth on gear l3 than on gear i9, say in the ratio of about 2 to 1 or even greater, it is possible .to achieve a greater angular movement of contact arm 8; hence a greater change in resistance in rheostat l for a given change in the size of the loop, thereby affording speed control through a wide range of speeds for the motor 5. This large movement of the rheostat contact arm in response to a small movement of arm 9 is the result of the change in loop and is quite important for the operation of most rheostats in order to obtain sufficient variation in resistance to secure the desired range of speed control. In accordance with my invention, it is possible to secure movement of the rheostat contact arm almost to the extent of 360 in response to a relatively small change in loop size. Of course, if such large movement of the rheostat arm is unnecessary, gears l3 and I8 may be of substantially the same diameter or gear is may even be larger than gear 13.

Speed adjustment may also be had with my system of control. For instance, instead of obtaining control by a loop such as 3, arm 9 could, as well, be manually settable at any position along the are (shown in dotted lines) so as to manually obtain preset speed control of motor 5. Instead of controlling the speed of motor 5 in order to restore loop 3 to a predetermined optimum size, speed of motor 5 may be controlled for any other reason whatsoever. Furthermore, while a winding machine has been described, it is obvious that sheets of rubber or the like which are moved by conveyors may likewise have regulatable travelling speed.

While a shunt motor 5 has been described, any other variable speed motor control system such as a variable voltage system may be substituted and may be controllable by the movement of contact arm 8.

I am, of course, aware that others, particularly after having had the benefit of the teachings of my invention, may devise other devices and systems of control embodying my invention, and I, therefore, do not wish to be limited to the specific showings made in the drawing and the descriptive disclosure hereinbetore made, but wish to be limited only by the scope of the appended claims and such prior art that may be pertinent.

I claim as my invention:

1. Operating mechanism for an electrical switch comprising, in combination, an operating arm, a rotatable member pivoted on said operating arm, intermediate between the ends of the arm, an electrical switch which is actuable by partial rotation of said rotatable member about said pivot, a second rotatable member also plyoted on said operating arm and which is of smaller diameter than said first rotatable member and which is in driving engagement therewith, friction means normally restraining said second rotatable member against rotation thereby allowing rotation of said first rotatable member about said second rotatable member as the result of operation of said operating arm, thereby actuating said switch.

2. Operating mechanism for an electrical switch comprising, in combination, an operating arm, a gear pivoted on said operating arm intermediate the ends thereof, a mercury switch rigidly mounted on said gear, a second gear also pivoted on said operating arm and which is of smaller diameter than said first gear and which is geared thereto, friction means normally restraining said second gear against rotation so that upon predetermined movement of said operating arm, said first gear will rotate about said second gear to sufilciently tilt said mercury switch to effect actuation thereof.

3. Operating mechanism for an electrical switch comprising, in combination, an operating arm, a gear pivoted on said operating arm intermediate the ends thereof, a double pole mercury switch rigidly mounted on said gear, a second gear also pivoted on said operating arm and which is of smaller diameter than said first gear and which is geared thereto, friction means normally restraining said second gear against rotation so that upon predetermined movement of said operating arm in one direction, said first gear will rotate about said second gear sufilciently to tilt said mercury switch in one direction so as to close one of the poles ,of the mercury switch, and upon predetermined movement of said operating arm in an opposite direction, said gear will rotate about said second gear sunk ciently to tilt said mercury switch in an opposite direction so as to close the other of said poles, said second gear being rotatable to an intermediate position for restoring said mercury are ODBIL 4. Operating mechanism for an electrical switchcomprising, in combination, an operating arm, a gear pivoted on said operating arm intermediate the ends thereof, a mercury switch rigidly mounted on said gear, a second gear also pivoted on said operating arm and which is of smallerdiameter than said first gear and which is geared thereto, friction means normally restraining said second gear against rotation so that upon predetermined movement of said operating arm, said first gear will rotate about said second gear to sufiiciently tilt said mercury switch to effect actuation thereof, means for rotating said second gear in such direction so as to tilt said mercury switch in an opposite direction so as to restore said mercury switch to its original position.

5. Inc. device for conveying long, thin, strips of material, means which are -actuable by predetermined variations in the size of a loop of a strip of said material, operating mechanism 1 which is actuable by said means and which comprises, in combination, an operating arm, a rotatable member pivoted on said operating arm intermediate the ends of the arm, an electrical switch which is actuable by partial rotation of said rotatable member about said pivot, a second rotatable member also pivoted on said operating arm and which isof smaller diameter than said first rotatable member and which is in driving engagement therewith, friction means normally restraining said second rotatable member against rotation thereby allowing rotation of said first rotatable member about said second rotatable member as the result of operation of said operating arm, thereby actuating said switch.

6. In a device for conveying long, thin, strips of material, means which are actuable by predetermined variations in the size of a loop of a strip of said material, operating mechanism which is actnable by said means and which comprises, in combination, an operating arm, a gear pivoted on said operating arm intermediate the ends thereof, a mercury switch rigidly mounted,

on said gear, a second gear also pivoted on said operating arm and which isof smaller diameter than said first gear and which is geared thereto, friction means normally restrainingsaid second gear against rotation so that upon predetermined movement of said operating arm, said first gear will rotate about said second gear to sufliciently tilt said mercury switch to eiiect actuation there of.

7. In a device for conveying long, thin, strips of material, means which are actuable by predetermined variations in the size of a loop of a strip of said material, operating mechanism which is actuable by said means and which comprises, in combination, an operating arm, a gear pivoted on said operating arm intermediate the ends thereof, a mercury switch rigidly mounted on said gear, a second gear also pivoted on said operating arm and which is of smaller diameter than said first gear and which is geared thereto, friction means normally restraining said second gear against rotation so that upon predetermined movement of said operating arm, said first gear will rotate about said second gear to sufiiciently tilt said mercury switch to effect actuation thereof, means for rotating said second gear in such direction so as to tilt said mercury switch in an opposite direction so as to restore said mercury switch to its original position.

8. In a device for conveying long, thin strips of material, means supported by a loop of said material and which is movable by an amount which is proportional to the size of said loop, operating mechanism which is operable by said means and which comprises an operating arm which is connected to said means, a rotatable member-pivoted on said operating arm intermediate the ends of the arm, an electrical switch which is actuable by partial rotation of said rotatable member about said pivot, a second rotatable member also pivoted on said operating arm and which is of smaller diameter than said first rotatable member and which is in driving engagement therewith, friction means normally restraining said second rotatable member against rotation thereby allowing rotation of said first rotatable member about said second rotatable member as the result of operation ofsaid operating arm thereby actuating said switch.

9. In a device for conveying long, thin strips of material, means supported by a loop of said material and which is movable by an amount which is proportional to the size of said loop, operating mechanism which is operable by said means, and which comprises an operating arm which is connected to said means, a gear pivoted on said operating arm intermediate the ends thereof, a mercury switch rigidly mounted on said gear, a second gear also pivoted on said operating arm and which is of smaller diameter than said first gear and which is geared thereto, friction means normally restraining said second gear against rotation so that upon predeter mined movement of said operating arm, said first gearwill rotate about said second gear to sufil ciently tilt said mercury switch to effect actuation thereof.

10. In a device for conveying long, thin strips of material, means supported by a loop of said material and which is movable by an amount which is proportional to the size of said loop, operating mechanism which is operable by said means and which comprises an operating arm connected to said means, a gear pivoted on said operating arm intermediate the ends thereof, a double pole mercury switch rigidly mounted on said gear, a second gear also pivoted on said operating arm and which is of smaller diameter than said firstgear and which is geared thereto,

said first gear will rotate about said second gear 15 sufiiciently to tilt said mercury switch in one direction so as to close one of, the poles of the mercury switch, and upon predetermined movement of said operating arm in an opposite direction, said gear will rotate about said second gear sufficiently' to tilt said mercury switch in an opposite direction so as to close the other of said poles, said second gear being rotatable to an intermediate position wherein saidmercury is restored to a position in which both of its poles are open.

11. In a device for conveying long, thin strips of material, means supported by a loop of said material and which is movable by .an amount which is proportional to the size of said loop, operating mechanism which is operable by said means and which comprises an operating arm which is connected to said means, a gear pivoted on said operating arm intermediate the ends thereof, a mercury switch rigidly mounted on said gear, a second gear which is also pivoted on said operating arm and which is geared to said first gear, motor means coupled to said second gear and which, when inoperative, possesses suilicient inertia to restrain said second gear'against rotation thereby allowing a rotation of said first gear about said second gear as the result-oi operation of said operating arm due to an abnormal change in the size of said loop, thereby actuating said mercury switch to efie'ct operation of said motor. 12. In a device for conveying long, thin strips of material, means supported by a loop of said material and which is movable by an amount which is proportional to the size of said loop, operating mechanism which is operable by said means and which comprises an operating arm which is connected to said means, a gear pivoted on said operating arm intermediate the ends thereof, a double pole mercury switch rigidly mounted on said gear, a second gear which is also pivoted on said operating arm and which is geared to said first gear, a motor for efiecting travel of saidmaterial and a circuit therefor including a variable resistor having a contact arm'which is driven by said second gear, reversible motor means coupled to said second gear and which, when inoperative, possesses sufiicient inertia to restrain said second gear against rotation.thereby allowing rotation of said first gear about said second gear as the'result ofoperation of said operating arm due to an abnormal change in the size of said loop, thereby closing one of said poles of said mercury switch to eflect rotation of said reversible motor-in one direction if the loop is too large, or closing the other of said poles to effect rotation 01' said reversible motor in an opposite direction if the loop is too small, either of said rotations of said reversible motor restoring both poles of said mercury switch to the open position and at the same time moving said contact arm to sufiiciently vary the speed of said main motor so as to restore the size of said loop to its original

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