US2304638A - Circuit interrupter - Google Patents

Description

INVENTOR Q/mr/es/i Hady/rz'lzi J BY WARNEY 7 3 Sheets-Sheet l C. H. HODGKINS CIRCUIT INTERRUPTER Filed Dec.

Dec. 8, 1942.

Dec. 8, 1942. c HODGKlNs 2,304,638

CIRCUIT INTERRUPTER Filed Dec. 12, 1940 5 Sheets-Sheet 3 WITNESSES: INVENTOR Patented Dee. a, 1942.

2,304,638 cmcm'r ni'rannur'ma Charles H. Hodgkins, Fail-field, Conn. assignor to The Bryant Electric Company, Bridgeport, Coma, .a corporation of Connecticut Application December 12, 1940, Serial No. 369,820

15 Claim.

This invention relates in general to electric circuit interrupters, and more particularly to electric time-controlled switches.

One object of this invention is to provide a novel double-throw time-controlled switch which is adapted to close to one set of contacts for a pre-selectable period of time, at the endof which the switch is opened for a predetermined period of time, and thereafter the switch is closed to the other set of contacts.

Another object of this invention is to provide a novel arrangement in a time-controlled switch of timing and switching mechanism.

Another object of this invention is to provide in a switch comprising a plurality of sets of separable contacts, a novel arrangement with a single operating means for sequentially operating said contacts.

Another object of this invention is to provide a novel arrangement of a plurality of switches in a single casing for operation by a common actuating means.

A still further object of this invention is to provide a novel compact arrangement of a plurality of switches and operating means therefor which will occupy a relatively small space, but still be capable of interrupting load currents.

These and other objects of this invention will become more apparent upon consideration of the following detailed description of a preferred em- 9 bodimentthereof, taken in connection with the accompanying drawings, in which:

Figure l is a front view of a preferred embodiment of a time-controlled switchconstructed in accordance with this invention;

Fig. 2 is a front view of the switch shown in Fig. 1 with the operating handle, switch casing cover and timing mechanism removed;

Fig. 3 is a bottom view of the switch shown in Figs. 1 and 2;

Fig. 4 is a sectional view of the switch shown in Figs. 1 to 3 taken substantially on the line IV-IV of Fig. 2;

Fig. 5 is a central transverse sectional view of the switch taken substantially at right angles to the section of Fig. 4;

Fig. 6 is an enlarged plan view of the inner face of the switch control knob, with theindicator assembled therewith;

Fig. 7 is a transverse cross-sectional view through the switch control knob taken substantially on the line'VIIVII of Fig. 5;

Fig. 8 is a view like Fig. 7, but illustrating a different position of the parts; and

Fig. 9 is a view like Figs. 7 and 8 illustrating still a third position of the parts.

This invention is herein disclosed particularly with respect to a switching means comprising a plurality of switches adapted to be actuated in predetermined relation by a single switch actuating cam member, together with a timing mechanism which is manually adjustable to select any desired time interval during which the switches are adjusted to one position. At the end of the time interval selected, the timing mechanism is adapted to actuate the switches to another controlling position. The specific switch disclosed herein is particularly adapted for use in controlling heater circuits of the type wherein heating units are adapted for use in an electric range or the like. Such a circuit is shown, for example, in my copending application, Serial No. 369,819, filed Dec. 12, 1940, and assigned to the Westing house Electric & Manufacturing Company.

Although this particular switching means is especially designed for use in the heating circuit disclosed in the above-mentioned copending application, wherein it has certain particular novel features of cooperation therewith, it is at the same time capable of use in other circuits for controlling other types of electrical apparatus. The switch disclosed is not only adapted to have two controlling positions by virtue of the fact that certain of the switches incorporated therein are of the double-throw type, but the switch has the further feature of providing a sequential operation of certain of the switches when the control means is initially moved to select a predetermined time interval for maintaining the switches in one active position, and this sequential operation obviously will also take place at the end of the time interval in a reverse sequence. The reason for providing sequential operation of certain of the switches preferably, is to obtain a time interval between the operation of the switches. Where the switches may also be manually operated, this purpose may be defeated if the operator quickly moves the switch control means so that the sequentially operated switches are actually operated substantially g simultaneously. In orderto provide against such an occurrence, the switch disclosed is arranged so that sequential operation of the contacts can take place at least upon movement of the switch control in one direction, only under the influence oi. the timing mechanism, to thereby preserve the time delay between succeeding switch operations.

The switch illustrated is preferably supported in an insulating casing 45 of any desired insulating material, preferably a molded insulating material. with the casing 45 having a bottom wall 2, side walls 4, 8, 8 and i8 and an open front face. Suitably secured on the bottom wall of the casing at one end thereof are terminals 44, 45 and 48. Mounted within casing 45 in adjacent corners thereof, respectively, are switch blade supports 58 and 52, conductively connected to terminals 44 and 48, respectively, for supporting switch blades 38 and 28. These switch blades are preferably of a resilient conducting material so as to be normally biased into engagement with fixed contacts 42 and 32, respectively, mounted on bottom wall 2 in opposite corners of casing 45. Switch blades 38 and 28 may be moved into engagement with fixed contacts 48 and 38, respectively, also mounted on bottom wall 2. Contacts 38, 32, 40 and 42 are mounted on supports extending through the bottom wall 2 of casing 45, to provide terminals I2, l4, l5 and 18, respectively, at the outer side thereof. Contacts 40-42 and 38-32 are located in restricted arcing chambers, formed by bailie members 54 in the casing integral with side wall 8 and bottom wall 2, and by an insulating cover plate 12 overlying the bailles and contacts to form arc chambers of insulating material having an opening merely to accommodate movement of the switch blades 28 and 38. Terminal 48 is conductively associated with contact 35 shown in Fig. 4 adapted to cooperate with switch blade 34 mounted in the casing on the bottom wall 2 thereof. Switch blade 34 (Fig. 4) is conductively associated, through bottom wall 2 of casing 45, with a terminal strap I34. It will be noted that the contact 38 is also positioned in a restricted arc chamber formed by a recess 58 in casing 45.

Switch blades 28, 38 and 34 are adapted to be actuated by a single cam member 58 in the form of a block of insulating material having a substantially central opening therethrough, so as to be rotatably mounted on a shaft 58 secured in the bottom wall of casing 45. Cam member 58 is ciroular in form, and is provided on its periphery with upper and lower cam surfaces 58-42 for actuating switch blades 28 and 38, respectively. By reference to Figs. 2 and 5, it will be noted that switch blades 38 and 28 are provided with relatively offset cam rollers I0 and 68, respectively, for cooperation with peripheral cam surfaces 52 and 68, respectively, on cam member 58. Cam member 58 is also provided with a recess 54 in its undersurface for cooperation with a struck-up portion 66 on switch blade 34, to actuate switch blade 34 in a predetermined sequence with respect to switch blades 38 and 28. Cam member 58 is provided in its upper surface with a pair of spaced sockets 14 adapted to receive a correspondingly spaced pair of driving prongs l8 fixed to the shaft 11 of a timing mechanism 80. The driving prongs 18 project through an opening in insulating plate 12 and are received in sockets 14 in the cam member for driving engagement therewith.

It will be noted that operating cam 58 is provided with opposed substantially identical raised and depressed cam portions connected by intermediate cam portions 24 and 22. It will be obvious that when cam block 58 is rotated in a clockwise direction, as viewed in Fig. 2, the cam rollers and 68 on switch blades 38 and 28, respectively, will engage the intermediate cam portions 24 and 22 to be moved thereby to a position intermediate their associated contacts 48-42 and 88-82. It will also be noted that just prior to engagement of cam portions 14 and 12 with the switch blade rollers, that the struckup portion 55 on switch blade 84 will enter slot 84 in the lower face of cam block 58 to thereby permit switch blade 84, which is normally biased upwardly, to separate from its cooperating contact 36. Separation of switch blades 88 and 28 from their contacts 42 and 82, respectively, then occurs, after which the blade rollers 18 and 88 ride onto the outer raised portions of the cam block and move the switch blades into engagement with the outer contacts 48 and 88, respectively. An auxiliary switch contact 88 is positioned to be engaged by blade 38 at the same time. Rotation of cam block 58 in a counterclockwise direction will provide a reverse sequence of operation; that is, switch blades 88 and 28 will first be moved out of engagement with contacts 48 and 30, respectively, to a position intermediate their associated contacts and out of engagement therewith, after which the switch blades are permitted to close to inner contacts 42 and 32, and finally the end of slot 54 in cam block 58 is reached and blade 84 is' forced into engagement with contact 38.

The timing mechanism 88 is provided with a coil spring 18, one end of which is adapted to be connected to drive shaft 11, and the other end of which is connected to the timer frame as at 82. Drive shaft H has a gear 84 (Fig. 5), rotatably mounted thereon and frictionally secured for movement with the shaft by a resilient cup-shaped washer 88 keyed to the shaft and frictionally engaging gear 84. Gear 84 is adapted to mesh with a pinion gear 81, associated with escapement mechanism in a well-known manner, mounted in frame 88.

The structure described above, comprising the switch casing, switches, timing mechanism and all of the structure in the casing, is entirely my own invention. However, the structure now to be described, comprising the means located outside of the switch casing for the manual control of the timing mechanism and switches within the casing, is an improvement on the manual control means described and claimed in the copending application of E. K. Clark, Serial No. 370,049, filed December 13, 1940, and assigned to the Westinghouse Electric 8: Manufacturing Company.

Drive shaft 11 of the timer mechanism is provided with a squared portion 88 projecting outwardly from casing 45 for receiving an operating knob 80. Referring to Figs. 5 to 9, it will be apparent that operating knob 88 is hollow to receive the squared end 88 of the drive shaft, and is provided with a peripheral flange 8| having suitable indicia provided on the outer surface thereof, preferably calibrated to indicate minutes of time. A drive collet 82 is positioned within the hollow of operating knob 88, and includes a sleeve portion 83 terminating in a flange portion 85. Sleeve portion 83 has a squared opening therethrough to accommodate the squared end 88 of drive shaft ll. Drive collet flange 85 is provided with a slot 88 in the edge thereof for receiving a key projection 84 integral with knob 88. It will be noted that key projection 84 is of considerable less extent than notch 88, so as to provide for a limited lost motion between the knob and drive collet 82, and consequently between the knob and drive shaft 11. A coil spring 88 is provided about the sleeve portion 83 of the 'drive collet, and one end I84 of the coil spring is bent what to the right of that shown in Fig. 7. Now,

to extend into a slot I88 formed in the base portion of the drive collet. The other end III of the coil spring is bent to extend substantially radially outwardly into a notch I82 provided in the flange portion 9| of operating knob 98. Coil spring 98 may be,..a relatively light spring. since its function is merely'to' retain projection 84 on the knob in engagement with end wall 9'! of notch 98 in the drive collet, and the force exerted by this spring should be considerably less than that exerted by spring I8 of the timing mechanism, so that the drive collet may be moved relative'to the operating knob by spring I8 in opposition to spring 98. An indicator strip I88 is adapted to be assembled to operating knob 98, and, as shown, the indicator strip I88 is secured to a disk II2, for example, as by an eyelet H8, and the disk H2 is secured for rotation with the operating knob by having an integral key projection II4 thereof extended into slot I82 provided in operating knob flange 9|. Disk H2 is maintained in operative relation with knob 98 by a split ring 99.

Indicator strip I88 is not fixedly secured to disk II2 by eyelet H8, but this connection is preferably formed under just sufllcient pressure to enable relative rotation of the indicator strip and disk I I2, while maintaining these parts in frictional engagement. Indicator strip I88, as shown in Fig. 6, is provided in the portion thereof underlying flange 9| of the operating knob, with an arcuate shaped slot II8 adapted to coincide with a portion of arcuate slot 1I8 provided on the underside of flange 9| of the operating knob. A pin I28 fixed to the cover I88 for switch casing 45, is adapted to project through the opening H8 in indicating strip I88, into slot I I8 in the operating knob.

Referring now to Fig. 7 of the drawings, the operating knob and indicator are shown in the position of the switch corresponding to the positions of the contacts shown in Figs. 1 to 5; that is, the position of the switch wherein switch blades 38 and 28 are in engagement with their inner contacts 42 and 32, respectively, and switch blade 34 is in engagement with contact 38. In this position, it will be noted that pin I28 on the casing cover is in engagement with one end of the slot H8 in the knob and with one end of opening H8 in indicating strip I88. As viewed in this figure, spring I8 of the timing mechanism tends to rotate operating shaft I1 in a "counterclockwise direction. It will also be noted that spring I8 of the timing mechanism has rotated the drive collet until key projection 94 on the operating knob is positioned at the end of slot 96 in the collet which is opposite from end '91, thereby stressing coil spring 98 connected between the drive collet and knob. Now, if it is desired to adjust the timing mechanism to move switch blades 38 and 28 into engagement with their outer contacts 48 and 38, respectively, and to move switch blade 34 out of engagement with contact 36, the operating knob '98 is grasped and manually rotated in a clockwise direction, for example, to the position shown in Fig. 8 where the knob has been rotated to adjust the switches, in the manner previously described, for a fifteen-minute period. It will be noted that when the knob is rotated from the position shown in Fig. 7 to the position shown in Fig. 8, the position of key projection 94 in slot 96 of the drive collet remains unchanged, but indicator" strip I88, due to its friction mounting with respect to the operating knob, moves with the knob a distance determined by the length of the opening I I8, to a position somewhen the operating knob is released after having been manually moved to the position shown in Flg. 8,-coil spring 98 will cause the knob and indicating strip I88 to move backwards a distance determined by the length of opening H9 in indicating strip I88 and the length of slot 96 in the drive collet, to the position shown in Fig. 9. With the parts in this position, it will be observed that the timing mechanism spring I8 has been wound an amount sufficient to cause it to require eighteen minutes to attain the position shown in'Fig. '7. The operating knob and indicating means, however, have moved backwardly from this position so that a fifteen minute period is indicated and when the knob driven by drive collet 92 indicates that the switch has attained its original position, the timing mechanism will not as yet have driven shaft 11 to the position shown in Fig. 7 because of the lost motion between the timing shaft and operating knob. However, at this time cam portions 22 and 24 between the high and low portions of each cam surface of cam 58 are positioned to move switch blades 38 and 28 to an off position intermediate their respective contacts, where they are not in engagement with any of the contacts, so that even though the drive shaft "has not reachedthe end of its movement when operating knob 98 indicates the switch as being off, the transfer switches, nevertheless, will be in an off position since they will be in engagement with cam portions 22 and 24 at this time. In the remainder of its movement, which will require three minutes in the embodiment shown, drive shaft 11 will permit switch blades 38 and 28 of the transfer switch to move to the position shown in Fig. 2, and will thereafter move switch blade 34 into engagement with contact 38. During this latter movement, drive collet 92 will move relative to operating knob 98 to move end wall 91 of slot 98 in the drive collet away from key projection 94 until the opposite end wall of slot 96 engages key pro- 'Jection 94, and thereby stops rotation of drive shaft II in a counter-clockwise direction.

Due to the friction clutch between gear 84 and drive shaft II, it is possible to manually move indicating knob 98 backwardly from an adjusted position to its off position. However, it is often desirable to prevent manual movement of the switches at least during the portion of their movement where a sequential operation of the switches occurs, as previously stated. It will be observed, accordingly, that by means of the lost-motion connection described above between the operating knob 98 and drive shaft II of the timer mechanism, it will be impossible to move the shaft 11 by means of operating knob 98 to throw switch blades 28 and 38 from engagement with contacts 38 and 48, respectively, into engagement with contacts 32 and 42. Thus, for example, if the operating knob 98 is moved in a counter-clockwise direction from the position shown in Fig. 9 as far as possible, it will be observed that this only moves drive shaft I1 to the point where cam portions 24 and 22 engage the cam rollers on blades 38 and 28, respectively, to move them to an open position; and transfer to the other contacts and engagement of contacts 34 and 36 can be accomplished only by movement of drive shaft 11 by timer spring I8, at a rate predetermined by the escapementmechanism, the distance required to move end wall 81 of the slot 98 in the drive collet from engagement with key projection 94 on the knob until the other end wall of slot it. engages key pro- .lection N.

- It is believed apparent from the foregoing that.

the switching device described herein provides a particularly noveland compact arrangement of ranged for sequential operation when driven by a timing mechanism, and constructed so that it is impossible to manually operate the switches through the sequence in which they are operated by the timing mechanism. The entire switching means and timing mechanism described above are adapted to be arranged in a novel manner in a single casing with manually operable means at the outside of the casing for adjusting the switches to one operating position for a selected period of time, with provisions whereby the switches, after having been set to said one position cannot be returned to their original position manually. After the switches have been set manually to one active position for a-selected period of time, they may thereafter be moved manually only to an off position, movement to the original position being solely under the control of the timing mechanism.

Having described preferred embodiments of the invention in accordance with the patent,

statutes, it is desired that the invention be not limited to the particular embodiment disclosed, inasmuch as it will be obvious, particularly to those skilled in the art, that many changes and modifications may be made in this particular embodiment without departing from the spirit and scope of this invention. It is desired, therefore, that this invention be interpreted as broad as possible and that it be limited only by the prior art and by the following claims.

I claim as my invention:

1. In circuit interrupting means, a switch casing having bottom, side and end walls, a set of switch contacts mounted in each of a pair of opposite corners of said casing, one contact of each set being carried on one end of a movable contact arm, said movable contact arms extending along opposite walls of said casing to be supported at their opposite ends in the opposite corners of said casing, a third movable contact arm extending along the bottom wall of said casing intermediate said first-mentioned contact arms, said third arm being supported at one end adjacent one wall of said casing and carrying at its other end one contact of another set of contacts, a rotatable cam block in said casing above said third contact arm and including an end cam surface for controlling movement of said third arm, and peripheral cam surfaces for controlling movement of said firstmentioned contact arms.

2. In circuit interrupting means, a switch casing having bottom, side and end walls, a pair of double throw switches in said casing, said switches including sets of switch contacts mounted in each of a pair of opposite corners of said casing, each set of contacts including spaced contacts secured to said casing and a contact mounted on one end of a movable contact arm for movement into engagement with either of said spaced contacts, said movable contact arms extending along asoasss oppositewallsofsaidcasingtobesupportedat theiroppositeendsinthe opposite cornersofsaid casing. a third movable contact arm extending along the bottom wall of said casing intermediate said first-mentioned contact arms, said third arm being supported at one end adjacent onewallofsaidcasingandcarryingatits other end one contact of another set of contacts, s rotatable cam block in said casing above said third contact arm and including an end cam surface for controlling movement of said third arm, and peripheral cam surfaces for controlling movement of said first-mentioned contact arms.

3. In circuit interrupting means, a switch casing having bottom, side and end walls, a set of switch contacts mounted in each of a pair of opposite corners of said casing, one contact of each set being carried on one end of a movable contact arm, said movable contact arms extending along opposite walls of said casing to be supported at their opposite ends in the opposite corners of said casing, a third movable contact arm extending along the bottom wall of said casing intermediate said first-mentioned contact arms, said third arm being supported at one end adjacent one wall of said casing and carrying at its other end one contact of another est of contacts, said contact arms being resilient and biased to one position thereof, a rotatable cam block in said casing between said first two arms and above said third contact arm intermediate the ends of said arms and including an end cam surface for controlling movement of said third arm, and peripheral cam surfaces for controlling movement of said first-mentioned contact arms 4. In circuit interrupting means, a switch casing of insulating material having bottom, side and end walls, a set of switch contacts mounted in each of a pair of opposite corners of said casing, one contact of each set being carried on one end of a movable contact arm, said movable contact arms extending along opposite walls 0! said casing to be supported at their opposite ends in the opposite comers of said casing, a third movable contact arm extending along the bottom wall of said casing intermediate said first-mentioned contact arms, said third arm being supported at on end adjacent one wall of said casing and carrying at its other end one contact of another set of contacts, each of said sets of contacts being substantially entirely closely confined in arc chambers of insulating material formed at least in part by the material of said casing, and common operating means for said contact arms.

5. In circuit interrupting means, a switch casing of insulating material including side and bottom walls, a plurality oi switch means in the lower portion of said casing, a single cam means for actuating said switch means, timing mechan sm in the upper portion of said casing and including a timing shaft rotatable at a predetermined rate directly coupled to said cam means, and said shaft projecting from the top of said casing 50 as to be manually controllable.

6. In circuit interrupting means, a switch casing of insulating material including side and bottom walls, a plurality of switch means in the lower portion of said casing, a single cam means of insulating material for actuating said switch means, timing mechanism in the upper portion of said casing, insulating partition means between the upper and lower portions of said casing, said timing mechanism including a shaft rotatable thereby at a predetermined rate and extending through an aperture in said partition means to be directly coupled to said cam means, and a cover plate for said casing.

7; In circuit interrupting means, a switch casing of insulating material having bottom, side and end walls, a set of switch contacts mounted in each of a pair of opposite corners of said casing. one contact of each set being carried on one end of a movable contact arm, said movable contact arms extending along opposite walls of said casing to be supported at their opposite ends in the opposite corners of said casing, a third movable contact arm extending along the bottom wall of said casing intermediate said first-mentioned contact arms, said third arm being supported at one end adjacent one wall of said casing and carrying at its other end one contact of another set of contacts, each of said sets of contacts being substantially enclosed in arc chambers of insulating material formed at least in part by the material of said casing, and common operating means for said contact arms, including timing mechanism also mounted in said casing.

8. In circuit interrupting means, a switch casing of insulating material including side and bottom walls, a plurality of switch means in the lower portion of said casing, a single cam means of insulating material for actuating said switch means; timing mechanism in the upper portion of said casing, insulating partition means between the upper and lower portions of said casing, said timing mechanism including a shaft rotatable thereby at a predetermined rate and extending through an aperture in said partition means to be directly coupled to said cam means, and a cover plate for said casing having an aperture through which said shaft projects for manual control thereof.

9. In switching apparatus, timing mechanism having a rotatable shaf't adapted to be rotated thereby in one direction for a time predetermined by the amount said shaft is moved in an opposite direction, switch means actuated by said shaft to perform a plurality of successive switching operations as said shaft approaches the end of its predetermined movement, a hollow handle mounted on said shaft for manual manipulation thereof, and means in said handle connecting said handle and shaft whereby said handle is operative to move said shaft in said opposite direction any selected amount, but is operative to move said shaft in said one direction only a lesser amount to a position at which said successive switching operations are initiated, whereby to insure the carrying out of said successive operations at a rate predetermined by said timing mechanism.

10. In switching apparatus, timing mechanism having a rotatable shaft adapted to be rotated thereby in one direction for a time predetermined by the amount said shaft is moved in an opposite direction, switch means actuated by said shaft to perform a plurality of successive switching operations as said shaft approaches the end of its predetermined movement, a hollow handle mounted on said shaft for manual manipulation thereof, and means in said handle connecting said handle and shaft whereby said handle is operative to move said shaft in said opposite direction any selected amount, but is operative to move said shaft in said one direction only a lesser amount to a position at which said successive switching operations are initiated, whereby to insure the carrying out of said successive operations at a rate predetermined by said timing mechanism, indicating means frictionally associated with said handle so as to be movable therewith, and means limiting movement of said indicating means with said handle to an amount corresponding to the movement of said shaft necessary to complete said successive switching operations.

11. In switching apparatus,.timing mechanism having a rotatable shaft adapted to be rotated thereby in one direction for a time predetermined by the amount said shaft is moved in an opposite direction, switch means actuated by said shaft to perform a plurality of successive switching operations as said shaft approaches the end of its predetermined movement, a hollow handle mounted on said shaft for manual manipulation thereof, a lost-motion connection between said handle and shaft, resilient means in said handle for biasing said handle in said one direction with respect to said shaft, stop means for said handle positioned to stop movement of said handle when moved in said one direction, whereby said shaft may be moved a further distance in said one direction by said mechanism while stressing said resilient means to complete said switching operations.

12. In switching apparatus, timing mechanism having a rotatable shaft adapted to be rotated thereby in one direction for a time predetermined by the amount said shaft is moved in an opposite direction, switch means actuated by said shaft to perform a plurality of successive switching operations as said shaft approaches the end of its predetermined movement, a hollow handle mounted on said shaft for manual manipulation thereof, a lost-motion connection between said handle and shaft, resilient means in said handle for biasing said handle in said one direction with respect to said shaft, stop means for said handle positioned to stop movement of said handle when moved in said one direction, whereby said shaft may be moved a further distance in said one direction by said mechanism while stressing said resilient means to complete said switching operaperform a plurality of successive switching operations as said shaft approaches the end of its predetermined movement, a hollow handle mounted on said shaft for manual manipulation thereof, and means mounted at least in part in said handle connecting said handle and shaft and permitting movement of said shaft by manual manipulation of said handle in said opposite direction any selected amount, but permitting unrestrained movement of said shaft in said one direction only up to the position at which said successive switching operations are initiated, whereby to prevent the carrying out of said switching operations too rapidly.

14. In a switching apparatus, timing mechanism having a rotatable shaft adapted to be rotated thereby in one direction for a time predetermined by the amount said shaft is moved in an opposite direction, switch means actuated by said shaft to perform a plurality of successive switching operations as said shaft approaches the end of its predetermined movement, a casing member for said timing mechanism and switch means with said shalt extending through one wall of said casing member, a handle member mounted on said shaft for manual manipulation thereof, one of said members having an opening facing the other of said members, and means mounted at least in part in said opening connecting said handle and shaft and permitting movement of said shaft by manual manipulation of said handle in said opposite direction any seiected amount, but permitting unrestrained movement of said shaft in said one direction only up to the position at which said successive switching operations are initiated, whereby to prevent the carrying out of said switching operations too 15 rapidly.

15. In circuit interrupting means, a switch casing of insulating material including side and bottom walls, a plurality oi switch means in tbs lower portion of said casing, a single cam means for actuating said switch means. timing mechanism in the upper portion 0! said casing and including a timing shaft rotatable at a predetermined rate; said shaft having a slidably removable but non-rotatable coupling with said can means to permit ready removal oi said timing mechanism from the top of said casing to gain access to said switch means, and a removable cover for said casing having an aperture through which said shaft projects.

CHARLES H. HODGKINS.

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