US2363132A - Reversing rheostat - Google Patents

Description

N0V- 21, 1944 E. N. LlGHTFooT Erm. 2,353,132

REVERS ING RHEOSTAT Filed 001;. 7, 1943 Patented Nov. 2l, 1944 REVERSING RHEOSTAT Edwin N. Lightfoot, Wauwatosa, and Theodore F.

Rosing, Whitelsh Bay, Wis.,

assignors to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application October 7, 1943, Serial No. 505,266

14 Claims. (Cl. 201-62) This invention relates to improvements in rheostats of the reversing type.

A primary object of the invention is to improve and simplify the construction andoperation of rheostats of the aforementioned character.

Another object is to provide a simple form of rheostat which is operable to regulate and reverse the current through a load circuit from full positive to full negative through any desired number of steps, including complete interruption of said load' circuit at an intermediate point on the rheostat corresponding to substantially zero potential.

Another object is to provide a reversing rheostat which is adapted to be power operated, subject to selective manual control; or alternatively adapted for direct manual operation at will, as in the event of failure of the power operating means.

Another object is to provide an intermittent and reversing type of solenoid operating mechanism of novel form.

Another and more specific object is to provide for remote manual pushbutton control of said solenoid operating mechanism.

Another object is to provide a reversing rheostat embodying a common set of resistance sections electrically connected with a corresponding number of contact segments, the contact segments being so arranged as to be traversed by a pair of Contact brushes operable simultaneously in opposite directions.

Anotherobject is to provide such a rheostat affording a maximum number of steps of resistance variation with a minimum number of resistance sections.

Another object is to provide novel means for manually adjustingr or preselecting the speed of operation of the reversing rheostat.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates schematically and diagrammatically a preferred embodiment of our invention; it being'understood that the embodiment illustrated is susceptible of modification in respect of certain structural details thereof Without departing from the scope of the appended claims.

In the drawing, Figure 1 is a schematic and diagramma-tic illustration of a reversing rheostat embodying our invention.

Fig. 2 is, a diagrammatic illustration of the form and arrangement of certain of the parts .shown in Fig. l, and showing in detail certain additional elements of the timing mechanism, and

Fig. 3 is a fragmentary diagrammatic illustration, with the contact brushes in their neutral or off position, and showing one brush in stag' gered or offset relationship to the other, whereby the two'brushes are adapted to engage the several successive contact segments in alternate sequence instead of simultaneously, thus substantially doubling the number of resistance gradations afforded by the rheostat.

Referring to Fig. 1, the numeral 5 designates a winding in suitable load circuit through which it is desired to eiect a full positive or full negative flow of current, or any desired value of positive or negative current; the transition from positive to negative now of current, or vice versa, being effected in each case when the current is at a minimum or substantially zero value. In the device herein illustrated provision is made for completely interrupting the flow of current at the transition point of minimum value of the positive or negative current flow.

The winding 5 may be assumed to represent the eld coil of a generator employed in a degaussing system. Line Ll and L2 represent a suitable source of current supply for coil 5, and the numerals 6H, 6b designate resistances to which lines L1 and L2 are respectively connected at `the points 6c and 6d. The yterminals and 5b of coil 5 are respectively connected by flexible conduc tors 'l and B to contact brushes 9 and I0; the latter in the respective positions thereof shown in Fig. l providing for a full positive flow of current through said coil, said circuit extending from line L1 through point 6c and brush 9, conductor 1 through point 5a and coil 5, and through point 5b, conductor 8, brush I0 and point 6d to line L2.

As best illustrated in Fig. 3, resistances 6- and 6b are divided into any desired number of sections 6", the adjacent ends or terminals of each two sections 6 being electrically connected to one of the multiplicity of contact blocks or segments Il. In the diagrammatic illustration in Fig. 3 the resistance sections lie are shown interposed between the pairs of contact segments II, whereas actually said segments II are in practice located quite close to each other, so that each brush 9-or I0 will engage the next adjacent segment prior to disengagement thereof from the presently engaged segment in each direction of movement of said brushes. Ihe contact segments Il are spaced the desired distance from each other by interposing suitable insulating plates or blocks (not shown) therebetween, the

resistance sections being terminally connected to the spaced contact segments II in a manner to afford proper clearance for brushes 9 and I8.

The groups 6a and B1? (Fig. 1) of resistance sections 6e (Fig. 3) are preferably separated a substantial distance from each other, as by means of an insulating block or spacer I2, so thatl at approximately the mid-length of the complete range of travel of the brushes 9 and i0 both of the same will be disengaged from all of the contact segments il (see Fig. 3). As will be apparent from Figs. 1 and 3, when contact brushes 9 and il) are engaged'respectively with the contact segments Il, Il at opposite ends of block I2 all of the resistance sections Ie will be included in circuit in series with coil 5, whereby the current through the latter is reduced to its minimum value; and in practice the arrangement is preferably such as to provide substantially zero potential across the Vterminals of coil 5 under the condition just mentioned. Also it will be understood that the direction of current flow (positive or negative) through coil 5 will depend upon Whether brushes 9 and I il are respectively engaged with the contact segments Il at the right-hand and left-hand sides of block I2 (see Fig. 3) to provide a positive flow, or with those at the left-hand and right-hand sides of said block to provide a negative ow.

Any suitable means (not shown) may be pro vided for manually interrupting the supply of current from lines L1, L2. Assuming completion of the circuit from the source of supply through lines L1, L2, and with the various elements of the system in the positions thereof shown in Fig. 1, it will be apparent that coil 5 is subjected to the full positive potential of lines L1, L2 as aforedescribed. As shown, the contact brush 9 is carried by a nut 9a which is adapted to travel upon a rotatable threaded shaft I3 having suitable fixed bearings I4 and I5; brush 9 being insulated from nut 9a in any suitable manner, as indicated at 3b. Also attached to n-ut 9a, but insulated therefrom as shown at 9, is an element Sid the end portion 9e of which acts in the position thereof illustrated to effect opening of a limit switch i6, the bridging contactor Iiia of which is normally biased to its closed position by a compression spring I1. With contactor I6a thus disengaged from the stationary contacts of limit switch i6 the contact brushes 9 and I0 cannot be driven by the power operated means beyond the extreme positions thereof illustrated. I

However, the power operated means may be utilized, under control of one of the manually operated push buttons hereinafter described, to eifect step by step movement of contact brushes 9 and I9 jointly toward or to their other respective extreme positions. Thus the contact brush I E! is carried by a nut Ilia, but insulated from the latter as shown atA Illb; the nut IIJa being adapted for cooperative engagement with a rotatable threaded shaft I8 having suitable xed bearings I9 and 29. Also attached to nut Illa, but

' insulated therefrom as shown at IIlc. is an element id the end portion llie of which acts, in the opposite extreme position of contact brush l0 from that illustrated, to eifect opening of a limit switch 2|, theV bridging contactor 2la of which is normally biased to the closed position thereof illustrated, as by means of compression spring 22.

The power operating means for contact brushes 2 and Ill comprises a pair of relatively small gears 23 and 24 keyed or otherwise rigidly connected to the reduced end portions of shafts I3 and I8, said gears being arranged to mesh continuously with a relatively larger gear 25 positioned therebetween. Gear 25 is rigidly attached to one end of a shaft 26 which is rotatably supported in suitable bearings (not shown). Shaft 26 projects outwardly from gear 25 and has rigidly attached thereto a pair of like toothed ratchet wheels 21, 21. Said wheels 21 are reversely arranged with respect to each other, so that the teeth, marked 21a, of one are arranged to be engaged by a pawl 28a, carried by the core of a solenoid 28, the coil of which is designated by numeral 281. Thus upon energization of coil 281 pawl 28a is moved upwardly from the normal position thereof shown in Fig. 3 into engagement with one of the teeth 212, thereby effecting a predetermined degree of clockwise rotation of shaft 26 and gear wheel 25, with consequent counterclockwise rotation of gears 23 and 24 and of the respective shafts I3 and I8 associated with the latter.

Inasmuch as shaft I3 is provided with a yrighthand thread and shaft I8 is provided with a lefthand thread such clockwise rotation thereof will result in downward movement of brush 9 (Fig, 1i and upward movement of brush I0 to increase in a step by step manner the number of sections of the resistances 6a and 6b included in the circuit of coil 5, pending attainment of the minimum value of the positive current at the transition point I2 of the rheostat, whereupon the minimum value of negative current is first applied to coil 5, such value being gradually increased until full negative current is applied when brush 9 is in its lower extreme position and brush I9 is in its upper extreme position.

When brush ID has reached the extreme position thereof last mentioned the end portion IIII,e of element IQd associatedwith nut Illa will have engaged and opened contactor 2 Ia of limit switch 2| to prevent overtravel of the brushes III and 9 to insure against interruption of the circuit of coil 5 under such conditions. n

With brush I in its upper extreme position and brush 9 in its lower extreme position (Fig. 1l. or with said brushes in any of their respective intermediate positions, simultaneous movement of brush 9 upwardly and of brush I9 downwardly may be effected by intermittent energization of coil 29b of solenoid 29, the core of which carries a pawl 2Sa adapted for engagement with the teeth, marked 21h, of the right-hand ratchet wheel 21 in Fig. 2. Upon each upward movement of pawl 292' gear 25 is rotated to a predetermined degree in a counterclockwise direction, with consequent clockwise rotation of shafts I3 and I8 for the purpose just mentioned.

The cores of solenoids 28 and 29 are respectively biased toward the disengaged positions thereof shown in Fig. 2, as by means of a pair of coiled tension springs 39 and 3I attached to downward extensions 28 and 29; said extensions being respectively pivotally connected at 32a and 32b to oppositely extending arms of a lever 32, which is pivotally supported at its mid-length, as by means of a pin 33. The intermediate or pivotal supporting portion of lever 32 is enlarged as shown at 32C, and said enlarged portion is provided with a downwardly facing double-inclined cam surface or 'notch 32d, which is adapted, in the intermediate or neutral position of lever 32, to accommodate the upper end of a stud or pin 34a attached to a switch contactor 34. Contactor 34 is pivoted at `31510, and is normally biased out of engagement with its associated stationary contact 34, as by means of a, coiled compression spring 34d. The

.bridged byv contactor 35",

asco-,rsa

arrangement is such that upon upward movement of either core 29 or 29 the double-inclined cam surface 32d`will act upon stud 34l to effect engagement of contactor 34 with stationary contact 34.

Operation of the system willy now be described with particular reference to the diagram of Fig. l. With the various elements in the respective positions illustrated, whereinA coil 5 is subjected to the full positive current from lines L1` and L2, step by step movement of brush 9 downwardly and of brush I9- upwardly, to decrease the value of the positive current, may be effected by manually depressing and holding the pushbutton 35, whereby its normally open stationary contacts 35a are i This completes an energizing circuit for the coil 29" of solenoid 29,

said circuit extending from line L1 by conductor 38 and a suitable fuse or similar protective device 3T, by conductor 38 through the normally closed contacts 39111 of a relay 39 (the operating coil of which is designated by numeral 39") by conductor 40 through the contacts 2|a of limit switch 2| (which is then in its normally closed position, as illustrated), by conductor 4I to and through said coil 29", by conductor 42 through said pushbutton contacts 35a and contactor 35", thence by conductor 43 through the normally closed contacts 44c and contactor 44" of a second pushbutton switch 44, and by conductors 45 and 46 through fuse 41 and conductor 48 to line L2.

Upon energization of coil 29" in the manner just described` the pawl 29a is moved upwardly to effect a predetermined degree of counterclockwise rotation of shaft 26 and the parts carried thereby, with consequent clockwise rotation of shafts I3 and I8 to effect downward movement of brush 9 and upward movement. of brush l0. It may be assumed that such step of movement of brushes: 9 and I0 simultaneously will only result in including oney of the sections i5e within the circuit of coil 5f, to decrease to a predetermined degree the value of positive current supplied to coil 5.

Upon such upward movement of pawl 29" the lever 32 (Fig. 2) is simultaneously rotated counterclockwise to such a degree that the left-hand inclined surface of notch 32d will act upon stud 34u t0 effect engagement of contactor 34 with stationaryy contact 34. As shown in Fig. 1, this will complete an energizing circuit for the operating r coil 39" of relay 39, which circuit extends from line L1 by conductor 36 through fuse` 31, conductors 49 and 50 through said coil 39", conductor 5I' through contact 3l!c and contactor 34, and by conductor 52 to line L2. The normally closed contacts 39i of relay 39 are thus opened to effect interruption o1. the aforedescribed circuit of coil 29" of solenoid 29, with consequent retraction of pawl 29a and lever 32 to the neutral positions thereof shown in Fig. 2, whereby contactor 34 is disengaged from contact 34c to interrupt` the energizing circuit of` coil 39".

In the absence of anyy additional elements such tially zero value.

loop containing it and coil 39" to maintain the relay contacts open for a predetermined period of time. By thus delaying the reclosure of contacts 39i of relay 39A the number of upward or operating strokes of pawl 29a per unit of time may be substantially reduced, to thereby correspondingly reduce the rate of change in the value of current supplied to coil 5.

We also prefer to provide a rheostat 54 connected in said loop in series with condenser 53; the contactor 55 of said rheostat being manually adjustable to provide for variation of the rate of charging of condenser 53, and to correspondingly vary the total charge of the latter during the normal period of energization of coil 39". In this manner the period during which contacts 39'il of relay 39 are held open after disengagement of contactor 34 from contact 34c may be varied throughout a relatively wide range, to thereby provide. a, correspondingly wide range of variation i'n the rate of change of the value of current 'supplied to coil 5-. Thus if rheostat contactor 55 1s moved toward the left to decrease the value of resistance 54 in circuit the rate of charging of condenser 53 will be increased to maintain coil 39" energized for a longer period; and the opposite effect results from movement of contactor 55 toward the right. 'I'he range of variation in the rate of change in value of current in coil 5 may of course be modified by substitution of a condenser and/or rheostat 54 of different value or caliber.

Although I have illustrated a slidable contactor type of rheostat 54 it will be apparent that I may employ any other suitable method of varying the value of the timing resistance, as, for example, a group of resistance sections with taps in combination with a exible connector associated with said taps to short circuit any desired number of the resistance sections.

If the pushbutton 35 is manually held in its depressed position the pawl 29a will be intermittently moved upwardly to effect simultaneous downward movement of brush 9 and upward movement of brush l0 at a rate determined by the adjustment of rheostat contactor 55, each such movement of brushes 9 and I0 jointlybeing adapted to effect inclusion in the positive current circuit of coil 5 an additional section 6 of the resistance, until just prior to the mid-length of the total range of travel of the two brushes when all of the resistance sections 6e will be included in such circuit, to thereby reduce the positive current through coil 5 to its minimum or substan- Thereafter one or both of the brushes 9 and I0 will move onto the insulating block f2 to insure complete interruption of the circuit of coil 5 (see Fig. 3).

Upon continuous downward movement of brush 9 and upward movement of brush ID the brush 9 will engage the first contact segment Il at the left-hand side of block I2 (Fig. 3) while brush I0 is still engaged with the first contact segment H at the right-hand side of said block, thus effecting completion of the negative current circuit of coil 5 with all of the resistance sections 6" included therein, whereby said negative current is initially of minimum or'substantially zero value. Thereafter the resistance sections E." will be exclude-d in sequence from the negative` current circuit,v until at the lowermost position of brush 9 and the uppermost position of brush l0 (as controlled by the operation of limit switch 2l as aforedescribed) all of the resistance sections 5e will be excluded from manually adjusted to either increase or decrease the rate of movement of the brushes, to thereby provide for decreasing or increasing the period of time required for change from one character and/ or Value to another of the current supplied to coil 5.

With brush 9 in its lowermost position and brush I9 in its uppermost position, or with said brushes jointly in any other than the respective extreme positions thereof shown in Fig. l, simultaneous movement of brush 9 upwardly and brush IU downwardly may be effected by manually depressing and holding pushbutton 44 so that its contactor 441 is engaged with stationary contacts 44a (the pushbutton 35, of course, having been released to permit return thereof to its normal position illustrated). Such depression of pushbutton 44 will complete an energizing circuit for the coil 26b of solenoid 28, which circuit may be traced from line L2 by conductor 48 through fuse 41, by conductors 46 and 56, stationary contacts 35c and contactor 35h of pushbutton switch 35, by conductor 51 through stationary contacts 44a and contacter 44h of pushbutton switch 44, by conductor 58 through the coil 28b of solenoid 28, by conductor 59 through the normally closed contacts of limit switch i6, by conductor 4U through contacts 39a of relay 39, by conductors 38 and 4S through fuse 31, and by conductor 36 to line L1.

In practice we prefer to provide a fixed resistance 69 and a condenser 6| connected in series with each other across the terminals of coils 28b and 29h. If the limit switches IB and 2l are both closed (as in any intermediate positions of brushes 9 and i9) upon release of the last active pushbutton switch 35 or 44 a discharge circuit through the resistance Ell, condenser 2l and the inactive coil 28h or 29", as the case may be, is provided for the last active coil 29b or 28h. This has the eiect of minimizing arcing at the contacts of pushbuttons 35 or 44 and at the contacts 39a of relay 39.

As shown in Figs. 1 and 2 We prefer to nonrotatably attach to the outer end of shaft 26 a manually rotatable knob 62, whereby manual adjustment or movement of brushes 9 and l0 may be eiiected at Will entirely independently of the power operating means of the rheostat. This feature is of importance in the event of failure or derangement of any part of the power operating means. Knob '62 is also useful for enabling manual presetting of the brushes 9 and i0 of the rheostat atk the desired positions thereof prior to completion of the rheostat circuit from the source of current supply which is here represented by lines L1, L 2.

' While we have herein illustrated a rheostat of the series type in which the circuit from the line through coil 5 is opened just prior to movement of brushes 9 and S) to their neutral or intermediate position, it will be apparent to those skilled in the art that what is commonly known as a potentiometer connection may be employed, where preferred for some specic installation, by substituting for insulating block I2 a conductive block which will maintain the circuit through the resistor 6e, 6b from one line to the other.

Furthermore, where a conductive block is used such block has the further function of short-circuiting coil 5 before the direction of current flow therein is reversed, thereby aording a discharge path for any energy in the magnetic field, if it is found desirable to provide some means for absorbing such energy; thus affording what is commonly known as a discharge circuit. Such operation will take place at a time when the current is reduced substantially to zero so that the magnetic energy is relatively small but nevertheless requires some means to guard against arcing or insulation failure consequent upon high discharge voltages.

We claim:

l. In a reversing rheostat, in combination, a single set of resistance sections, a single set of xed spaced contact segments respectively electrically connected with said resistance sections, the end contact segments of said set being respectively connected to opposite poles of a source of current supply, a pair of Contact brushes common to said contact segments and adapted to cooperate therewith, means for effecting movement of said contact brushes jointly in opposite directions respectively throughout the total length of said set of contact segments, a translating device including a coil the terminals of which are re spectively connected with said contact brushes, whereby in one eXtreme position of the respective brushes said coil is subjected to the full positive potential of said source of current supply and in the other eXtreme position of the respective brushes said coil is subjected to the full negative potential of said source of current supply, and wherebyat the midpoint of the total range of movement of said brushes jointly they are subjected to substantially zero potential wherefore no current iiows through said coil.

2. In a reversing rheostat, in combination, a single set of resistance sections, a single set of Xed spaced contact segments respectively electrically connected with said resistance sections, the end contact segments of said set being respectively connected to opposite poles of a source of current supply, a pair of contact brushes common to said contact segments and adapted to cooperate therewith, means for effecting movement of said contact brushes jointly in opposite directions respectively throughout the total length of said set of contact segments, a translating device including a coil the terminals of which are respectively connected with said contact brushes, whereby in one extreme position of the respective brushes said coil is subjected to the full positive potential of said source of current supply and in the other extreme position of the respective brushes said coil is subjected to the full negative potential of ,said source of current supply, whereby at the midpoint of the total range of movement of said brushes jointly they are subjected to substantially zero potential wherefore no current ows through said coil, and power operated means reversible at will for effecting movement of said brushes jointly toward and from either of their respective extreme positions.

3. In a reversing rheostat, in combination, a single set of resistance sections, a single set of xed spaced contact segments respectively electrically connected with `said resistance sections, the end contact segments of said set being respectively connected to opposite poles of a source of current supply, a pair of contact brushes common to said contact segments and adapted to cooperate therewith, means for effecting movement of said contact brushes jointlyin opposite directions respectively, a translating device including a coil the terminals of which are respectively connected with said contact brushes, whereby in one extreme position of the respective brushes said coil is subjected to the full positive potential of said source of current supply and in the other extreme position of the respective brushes said coil is subjected to the full negative potential of said source of current supply, whereby at the midpoint of the total range of movement of said brushes jointly they are subjected to Vsubstantially zero potential wherefore no current flows through said coil, power operated means reversible at will for effecting movement of said `brushes jointly toward and from either of their respective extreme positions, said last mentioned means including a pair of oppositely threaded parallel rotatable shafts, traveling nuts on said shafts in a predetermined relationship to each other, said brushes being attached to the respective nuts for movement with the latter, a third shaft geared to said shafts first mentioned, a pair of oppositely toothed ratchet wheels non-rotatably attached to said third shaft, a solenoid including a coil, a core and a pawl associated with each ratchet wheel, and a pair of pushbutton switches selectively operable to control intermittent energization of the respective solenoid coils.

4. In a reversing rheostat, in combination, a single set of resistance sections, a single set of xed spaced contact segments respectively electrically connected with said resistance sections, the end contact segments of said set being respectively connected to Opposite poles of a source of current supply, a pair of contact brushes common to said contact segments and adapted to cooperate therewith, means for effecting movement; of said Contact brushes jointly in opposite directions respectively, a translating device including a coil the terminals of which are respectively connected with said contact brushes, whereby in one extreme position of the respective brushes said coil is subjected to the full posiktive potential of said source of current supply and in the other extreme position of the respective brushes said coil is subjected to the full negative potential of said source of current supply, whereby at the midpoint of the total range of movement of said brushes jointly they are subjected to substantially zero potential wherefore no current flows through said coil, power operated means reversible at will for effecting move- 4ment of said brushes jointly Ytoward and from either of their respective extreme positions, said last mentioned means including a pair of oppositely threaded parallel rotatable shafts, traveling nuts on said shafts in a predetermined relationship to each other, said brushes being attached to the respective nuts for movement with the latter, a third shaft geared to said shafts rst mentioned, a pair of oppositely toothed ratchet wheels non-rotatably attached to said third shaft, a solenoid including a coil, a core and a pawl associated with each ratchet wheel, a pair of pushbutton switches selectively operable manually to provide for operating energization of one or the other of the solenoid coils, means comprising a cam-operated normally open switch adapted to be closed automatically upon operating movement of either of the solenoid cores, a normally closed electromagnetically operable relay adapted to be energized upon each closure of said last mentioned switch, said relay when opened being adapted to eifect deenergization of either of said solenoid coils to provide for resetting of its re- A spective pawl and reopening of said normally open switch whereby 'the energizing circuit of said relay is interrupted, and said relay when deenergized effecting reenergization of the active solenoid coil to provide a repeated operation of the pawl associated therewith.

y5. In a reversing rheostat, in combination, a single set of resistance sections, a single set of xed Vspaced contact segments respectively electrically connected with said resistance sections, the end Icontact segments of said set being respectively connected to opposite poles of a source of current supply, a pair of contact brushes common to said contact segments and adapted to cooperate therewith, means for effecting movement of said contact brushes jointly in opposite directions respectively, a translating device including a coil the terminals of which are respectively connected with sa'id contact brushes, whereby in one extreme position of the respective brushes said coil vis subjected to the full positive potential of said source of current supply and in the other extreme position of the respective brushes said coil is subjected to thev full negative potential of said source of current supply, whereby at the midpoint of the total range'of movement of said brushes jointly they are subjected to substantially zeropotential wherefore no current flows through said coil, vpower operated means reversible at will for effecting movement of said brushes jointly toward and from either of their respective extreme positions, said last mentioned means including a pair of oppositely threaded parallel rotatable shafts, traveling nuts on said shafts in a predetermined relationship to each other, said brushes being attached to the respective nuts for movement with the latter, .a third shaft geared to said shafts first mentioned, a pair of oppositely toothed ratchet'wheels non-rotatably attached to said third shaft, a solenoid including a coil, a core and a pawl associated with each ratchet wheel, a pair of 'pushbutton switches selectively operable manually to provide for operating energization of one or the other of the solenoid coils, means -comprising a cam-operated normally open switch adapted to be closed automatically upon operating movement of either of the solenoid cores, a 'normally closed electromagnetically opy erable relay adapted to be energized upon each closure of said 'last mentioned switch, said relay when opened being adapted to effect deenergization of either of said solenoid coils to provide for resetting of its respective pawl and reopening of said normally open switch whereby the energizing circuit of said relay is interrupted, said relay when deenergized effecting reenergization of the active solenoid coil to provide a repeated operation of Athe pawl associated therewith, and adjustable means associated Awith said relay to delay reclosure thereof upon interruption of its energizing circuit, whereby the `rate of movement of said vbrushes jointly by said power operated means may be preselected.

r6. In a reversing rheostat, kin combination, a single set of 'resistance sections, a single set of fixed spaced contact segments respectively electrically connected with said resistance sections, the end contact segments of said set being respectively connected to opposite poles of a source of current supply, a pair of contact brushes common to said contact segments and adapted to cooperate therewith, meanssfor effecting movement'l of said contact brushes jointly in opposite directions respectively, a translating device including a coil the terminals of which are respectively connected with said contact brushes, whereby in one extreme position of the respective brushes said coil is subjected to the full positive potential of said source of current supply and in the other extreme position of the respective brushes said coil is subjected to the full negative potential of said source of current supply, whereby at the midpoint of the total range of movement of said brushes jointly they are subjected to substantially Zero potential wherefore no current ows through said coil, power operated means reversible at will for eiecting movement of said brushes jointly toward and from either of their respective extreme positions, said last mentioned means including a pair of oppositely threaded parallel rotatable shafts, traveling nuts on said shafts in a predetermined relationship to each other, said brushes being attached to the respective nuts for movement with the latter, a third shaft geared to said shafts first mentioned, a pair of oppositely toothed ratchet wheels non-rotatably attached to said third shaft, a solenoid including a coil, a core and a pawl associated with each ratchet wheel, a pair of pushbutton switches selectively operable manually to provide for operating energization of one or the other of the solenoid coils, means comprising a .cam-operated normally open switch adapted to be closed automatically upon operating movement of either of the solenoid cores,l a normally closed electromagnetically operable relay adapted to be energized upon each closure of said last mentioned switch, said relay when opened being adapted to effect deenergization of either of said solenoid coils to provide for resetting of its respective pawl and reopening of said normally open switch whereby the energizing circuit of said relay is interrupted, said relay when deenergized eifecting reenergization of the active solenoid coil to provide a repeated operation of the pawl associated therewith, adjustable means associated with said relay to delay reclosure thereof upon interruption of its energizing circuit, whereby the rate of movement of said brushes jointly by said power operated means may be preselected, and said adjustable means comprising a condenser and an adjustable resistance connected in a closed loop in series with each other and with the coil of said relay to provide for maintaining the operating energization of the latter for a predetermined period f time after interruption of the normal energizing circuit of said relay coil.

7. In a reversing rheostat, in combination, a

single set of resistance sections, a single set ofspaced contact segments electrically connected in series relationship to each other through the medium of the respective resistance sections, said contact segments being arranged in a line, the contact segments at opposite ends of said line being respectively connected to opposite poles of a suitable source of current supply, a pair of contact brushes common to and jointly cooperable with said contact segments throughout the length of said line, a translating device including a coil whose terminals are respectively connected with said brushes to provide for passage of current to said coil from said source of supply, the arrangement being such that when said brushes are respectively engaged in one relation with opposite end contact segments of said line said coil will be subjected to the full positive potential of said source, and when said brushes are respectively reversed in position with respect to said end contact segments said coil will be subjected to the full negative potential of said source, of means for effecting movement of said brushes simultaneously from' each of their respective extreme positions to their other extreme positions, and vice versa, across the intermediate contact segments of the line, whereby the variation in character and value of said change from full positive to full negative value, and vice versa, of the current supplied to said coil may be effected in increments corresponding to the resistance value or values of said multiplicity of resistance sections.

8. In a reversing rheostat, in combination, a multiplicity of resistance sections, contact segments electrically connected in series relationship through the medium of the respective resistance sections, said contact segments being arranged in a straight line in fixed spaced relationship to each other, the Contact segments at opposite ends of said line being respectively connected to opposite poles of a suitable source of current supply, a pair of contact brushes movable simultaneously in opposite directions in slidable engagement with different portions of the respective contact segments throughout the total length of said line, a translating device including a coil whose terminals are respectively connected with said brushes to provide for passage of current through said coil from said source of supply, the arrangement being such that when said brushes are respectively in one of their extreme positions full positive current is supplied to said coil and when the same are respectively in the other of their extreme positions full negative current is supplied to said coil, said brushes cooperating with said segments and said resistance sections to effect transition from full positive to full negative current in a step by step manner, including reduction of said current to substantially zero value at the midpoint of the total range of travel of said brushes jointly, power operated means for effecting the aforementioned simultaneous opposite movement of said brushes in either direction throughout their total range, and associated means for automatically controlling said power operated means to prevent overtravel of said brushes at each of their extreme positions.

9. In a reversing rheostat, in combination, a multiplicity of stationary contact segments arranged in a straight line in fixed spaced relationship to each other, a multiplicityof resistance sections the terminals of which are connected to said contact segments in series relationship to each other, a pair of current supply lines respectively connected to the opposite end contact seg-- ments, a pair of -contact brushes slidably engageable with said contact segments at opposite side edges thereof, a translating device including a coil the terminals of which are connected to the respective brushes, each of said contact brushes being movable into and out of engagement with all of said contact segments selectively, means for effecting movement of said contact brushes simultaneously in opposite directions from each end contact segment to the other, said means comprising a pair of oppositely threaded shafts, traveling nuts on said shafts, each nut having one of said brushes attached thereto for movement therewith, means for effecting intermittent rotation of said shafts jointly in 'one direction or the other, said means comprising a third shaft and gearing between the same and said shafts first mentioned, a pair of oppositely toothed ratchet wheels non-rotatably attached to said third shaft, a solenoid including a coil, a core and a pawl associated with one 'of said ratchet Wheels, said pawls being normally biased to positions alfording clearance for the respective ratchupon intermittent energization of its coil to efy fect step by step movement of said brushes jointly toward the respective extreme positions thereof providing full positive energization of said first mentioned coil, the other solenoid when intermittently energized being adapted to effect step by step movement of said brushes jointly toward their opposite extreme positions providing full negative energization of said first mentioned coil, said brushes at the mid-point of their complete range of travel being subjected to substantially zero potential so that no current will be supplied to said rst mentioned coil, and means including a pair of pushbutton switches selectively operable manually to provide for intermittent operating energization of one or the other of said solenoids.

10. In a reversing rh'eostat, in combination, a multiplicity of stationary contact segments arranged in a straight line in xed spaced relationship to each other, a multiplicity of resistance sections the terminals of which are connected to said contact segments in series relationship to each other, a pair of current supply lines respectively connected to the opposite end contact segments, a pair of contact brushes slidably engageable with said contact segments at opposite side edges thereof, a translating device including a coil the terminals of which are connected to the respective brushes, each of said contact brushes being movable into and out of engagement with all of'said contact segments selectively, means for effecting movement of said contact brushes simultaneously in opposite directions from each end contact segment to the other, said means comprising a pair of oppositely threaded shafts, traveling nuts on said shafts, each nut having one of said brushes attached thereto for movement therewith, means for elfecting intermittent rotation of said shafts jointlyin one direction or the other, said means comprising a third shaft and gearing between the same and saidshafts first mentioned, a pair of oppositely toothed ratchet wheels non-rotatably attached to said third shaft, a solenoid including a coil, a core and a pawl associated with each of said ratchet wheels, said pawls being normally biased to positions affording clearance for the respective ratchet wheels, one of said solenoids being adapted upon intermittent energization of its coil to effect step by step movement of said,brushes jointly toward the respective extreme positions thereof providing full positive energization of said rst mentioned coil, the other solenoid when intermittentiy energized being adapted to effect step by step movement of said brushes jointly toward their opposite extreme positions providing full negative energization of said rst mentioned coil, said brushes at the mid-point of their complete range of travel being subjected to substantially zero potential so that no current will be supplied to said first mentioned coil, means comprising a pair of pushbutton switches selectively operable manually to provide for operating energization of one or the other of said solenoids, means comprising a normally open switch adapted to be closed automatically upon operating movement of either of said solenoid cores, a normally closed electromagnetically operable relay adapted to be energized upon each closure of said last mentioned switch, said relay when opened being adapted to effect deenergization of either of said solenoid coils to provide for resetting of its respective pawl and reopening of said normally open switch, said switch when reopened effecting interruption of the energizing circuit of said relay, and said relay when deenergized and closed providing for reenergization of the active solenoid coil, whereby a repeated operation of its associated pawl is effected.

11. In a reversing rheostat, in combination, a multiplicityof stationary contact segments arranged in a straight line in fixed spaced relationship to each other, a multiplicity of resistance sections the terminals of which are connected to said contact segments in series relationship to each other, a pair of current supply lines respectively connected to the opposite end contact segments, a pair of contact brushes slidably engageable with said contact segments at opposite side edges thereof, a translating device including a coil the terminals of which are connected to the respective brushes, each of said contact brushes being movable into and out of engagement with all of said1 contact segments selectively, means for effecting movement of said contact brushes simultaneously in opposite directions from each end contact segment to the other, said means comprising a pair of oppositely threaded shafts, traveling nuts on said shafts, each nut having one of said brushes attached thereto for movement therewith, means for effecting intermittent rotation of said shafts jointly in one direction or the other, said means comprising a third shaft and gearing between the same and said shafts first mentioned, a pair of oppositely toothed ratchet wheels non-rotatably attached to said third shaft, a solenoid including a coil, a core and a pawl associated with each of said ratchet wheels, said pawls being normally biased to positions affording clearance for the respective ratchet wheels, one of said solenoids being adapted upon intermittent energization of its coil to elfect step by step movement of said brushes jointly toward the respective extreme positions thereof Aproviding full positive energization of said nrst mentioned coil, the other solenoid when intermittently energized being adapted to effect step by step movement of said brushes jointly toward their opposite extreme positions providing full negative energization of said first mentioned coil, said brushes at the mid-point of their complete range of travel being subjected to substantially zero potential so that no current will be supplied to said first mentioned coil, means comprising a pair of pushbutton switches selectively operable manually to provide for operating energization of one 'or the other of said solenoids, means comprising a normally open switch adapted to be closed automatically upon operating movement of either of said solenoid cores, a normally closed electromagnetically operable relay adapted to be energized upon each closure of said last mentioned switch, said relay when opened being adapted to effect deenergization of either of said solenoid coils to provide for resetting of its respective pawl and reopening of said normally open switch, said switch when reopened effecting interruption of the energizing circuit of said relay, said relay when deenergized and closed providing for reenergization of the active solenoid coil, whereby a repeated operation of its associated pawl is effected, and adjustable means associated with said relay to delay reclosure thereof upon interruption of its energizing circuit, whereby the rate of movement of said brushes jointly by said power operated means may be preselected.

12. In a reversing rheostat, in combination, a multiplicity of stationary contact segments arranged in a straight line in fixed spaced relationship to each other, a multiplicity of resistance sections the terminals of which are connected to said contact segments in series relationship to each other, a pair of current supply lines respectively connected to the opposite end contact segments, a pair of contact brushes slidably engageable with said contact segments at opposite side edges thereof, a translatingdevice including a coil the terminals of which are connected to the respective brushes, each of said contact brushes being movable into and out of engagement with all of said Contact segments selectively, means for effecting movement of said contact brushes simultaneously in opposite directions from each end contact segment to the other, said means comprising a pair of oppositely threaded shafts, traveling nuts on said shafts, each nut having one of said brushes attached -thereto for movement therewith, means for eecting intermittent rotation of said shafts jointly in one direction or the other, said means comprising a third shaft and gearing between the same and said shafts first mentioned, a pair of .oppositely toothed ratchet wheels non-rotatably attached to said third shaft, a solenoid including a coil, a core and a pawl associated with each of said ratchet wheels, said pawls being normally biased to positions affording clearance for the respective ratchet wheels, one of said solenoids being adapted upon intermittent energization of its coil to eifect step by Step movement of said brushes jointly toward the respective extreme positions thereof providing full positive energization of said rst mentioned coil, the other solenoid when intermittently energized being adapted to effect step by step movement of said brushes `jointly toward their opposite extreme positions providing full negative energization of said rst mentioned coil, said brushes at the mid-point of their complete range of travel being subjected to substantially zero potential so that, no current will be supplied to said rst mentioned coil, means comprising a pair of pushbutton switches selectively operable manually to provide for operating energization oi one or the other of said solenoids, means comprising a normally open switch adapted to be closed automatically upon operating movement of either of said solenoid cores, a normally closed electromagnetically operable relay adapted to be energized upon each closure of said last mentioned switch, said relay when opened being adapted to eiect deenergization of either of said solenoid coils to provide for resetting of its respective pawl and reopening of said normally open switch, said switch when reopened effecting interrupton of the energizing circuit of said relay, said relay when deenergized and closed providing for reenergization of the active solenoid coil, whereby a repeated operation of its associated pawl is effected, adjustable means associated with said relay to delay reclosure thereof upon interruption of its energizing circuit, whereby the rate of movement of said brushes jointly by said 'power operated means may be preselected., and said adjustable means comprising a condenser and a variable resistance connected in a closed loopwith the coil of said relay to insure operating energization of the latter for a predetermined periodv of time after interruption of the normal energizing circuit thereof in the manner aforementioned.

13. In a reversing rheostat, in combination, a multiplicity of fixed contact segments arranged in a straight.line in spaced relationship to each other, a pair of contact brushes on opposite sides of said contact segments and movable simultaneously in opposite directions respectively from each extreme contact segment toward the other, a multiplicity of resistance sections associated with said contact segments, said extreme contact segments being respectively connected with opposite poles of a source of current supply, a translating device including a winding the terminals of which are connected with the respective brushes, a pair of traveling nuts to which said brushes are respectively attached, a pair of oppositely threaded shafts with which said nuts are respectively associated, power operated electrical means common to said shafts nfor effecting rotation thereof jointly in one direction or the other, means including a pair of pushbutton switches operable selectively to eiTect operation of said power operated means in one direction or thel other, and means including a cam operated'switch and an electromagnetically operable relay associated with said power operated means to insure operation thereof intermittently in each direction respectively to thereby insure movement of said brushes jointly in a step by step manner.

1li.` In a reversing rheostat, in combination, a multiplicity of fixed contact segments arranged in a straight line in spaced relationship to. each other, a pair of contact brushes on opposite sides of said Contact Segments and movable simultaneously in opposite directions respectively from each extreme contact segment toward the other, a multiplicity of resistance sections associated with said contact segments, said eXtreme contact segments being respectively connected with opposite poles of a source of current supply, a translating device including a winding the terminals of which are connected with the respective brushes, a pair of traveling nuts to which said brushes are respectively attached, a pair of oppositely threaded shafts with which said nuts are respectively associated, power operated electrical means common to said shafts lfor effecting rotation thereof jointly in one direction or the other, means including ya pair of pushbutton switches' operable selectively to effect operation of said power operated means in one direction or the other, means including a cam operated 'switch and an electromagnetically operable relay associated with said power operated means to insure operation thereof intermittently in each direction respectively to thereby insure movement of said brushes jointly in a step by step manner, said relay having a set of normally closed contacts, a condenser and a rheostat connected in series with each other in a closed loop including the operating winding of said relay, said condenser1 and said rheostat coacting with the operating winding of said relay to delay reclosure of the latter after interruption of the normal energizing circuit of said winding by said cam operated switch, and said rheostat being adjustable to vary at will 4within a given range the time delay afforded by said relay.

EDWIN N. LIGHTFOOT.

THEODORE F. ROSING.

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