US2081623A - Fuse switch - Google Patents

Description

May 2s, 1937.

c, A. Fox

FUSE SWITCH Filed April 6, 1935 3 Sheets-Sheet 1 A TTORNE Y.

C. A. FOX

FUSE SWITCH May 25, 1937.

Filed April 6, 1935 3 Sheets-SheetZ INVENTOR 61A. Fox

ATTORNEY.

nv S

Aff/lll C. A. FOX

FUSE SWITCH May 25, 1937.

3 Sheets-Sheet 3 Filed April 6, 1935 flap INVENTOR. A6x1'. Fox

ATTORNEY.

Patented May 2.5,l 1937 iPATENT OFFICE russ swrrcn Charles Adin Fox, St. Louis, Mo.,V assigner to James R. Kearney Corporation, St. Louis, Mo., a corporation of Missouri Application April 6, 1935, Serial No. 14,999

Claims.

This inventionv relates generally to electrical fuse switches of the re-closing type adapted for use in protecting high voltage lines and equipment associated therewith, and more specifically to a structure of this type which includes a multiplicity of fuse cartridges adapted-for automatic movement sequentially into operative positions in an electrical circuit as previously operatively positioned fuse cartridgesof the group of fuse cartridges are rendered inoperative by short circuit or overload, the predominant object of the invention being to provide an apparatus of this type. which 'is extremely simple in construction and operation and iscapable of performing its intended function with a high degreey of elciency.

In protecting high voltage electrical lines and equipment associated therewith from the damaging effects of short circuits and overloads, it has become the practice of late to provide fusing apparatus which comprise each a plurality of fuse cartridges adapted for movement sequentially into operative fusing positions in the lines. These apparatus are usually capable of automatic actuation so that when the fuse element of the cartridge in the operative fusing position is blown because of av fault present in the line, such cartridge immediately drops out of theeffective fusing position and is automatically replaced by another fuse cartridge having an operative, unblown fuse element associated therewith. None of the previously known apparatus of this type with which I am familiar completely solved'the problem that made necessary the use of such apparatus, the deficiencies usually resulting from complexity of construction and operation, or, inthe l absence of this, an inability to perform the intended function in the required manner.

'I'he prime purpose of this invention is to provide a fusing structure o f .the type described, which is of extremely simple construction and is 40 operated inan equally simple manner. Because of the simple construction of the improved fusing structure disclosed herein, it is not necessary for the troublemen to familiarize themselves with a lot of mechanical details in order to service the apparatus. All a troubleman need know is'how to re-fuse a cartridge and to understand that to remove a blown cartridge a. certain lever must first be pulled to permit such removal. What need not know is that when he pulls the lever referred to so as to permit removal oi' the blown cartridge he sets the cartridge-operating mechanism for its next operation of moving the subsequently associated cartridge into its effective fusing position. An important 'feature ci the invenapertures through which a bolt 5 passes.

(Cl. 20o-126) suilicientto permit temporary fault clearances is 10 alkiwed.

Fig; .i is a side elevation of the improved apparatus showing same supported by a cross arm which is shown in section.

Fig. 2 is an enlarged view, partly in section and 15 partly in elevation, illustrating a cartridge-operating mechanism of the improved apparatus, and showing a fragment of a cartridge in the eiective fusing position.

Fig. 3 is a view similar to Fig. 1, but showing a 20 fragment of a cartridge in the reserve position.

Fig. 4 is a view partly in side elevation and partly in section, illustrating part of the mechanism shown in Figs. 2 and 3 but with a fragment of a cartridge in the ineffective or blown 25 position.

Fig. 5 is a sectional view taken on line 5 5 of Fig. l.

Fig. 6 is a sectional view taken on line 6 6 of Fig. 2. 30

Fig. 'l is a sectional view taken on line I 'l of 9 9 of Fig. 2, looking upwardly.

In the drawings, wherein is shown for the purpose of illustration, merely, one embodiment of the invention, A designates in Fig. 1 the improved apparatus generally. The improved apparatus in- .40 cludes a suitable insulator I about which a band 2 is arranged, said band being provided with spaced apart extensions 3 through apertures in which a clamping bolt 4 is extended for flxedly clamping the band aboutthe insulator i. 'I'he 45 outer end portions of the extensions 3 are turned inwardly in overlapped relation, and formed through these overlapped portions are alined The bolt 5 passes also through an aperture formed 50 through a clamp portion 6 which, in association with a companion clamp portion t, provides means for attaching the apparatus .A to a cross arm C or other support. The apparatus A may be shifted to various horizontal angular positions passage of an element therebetween.

by loosening the nut of the bolt I and movin! the apparatus to the desired positions, after which said nut may be again tightened to clamp the insulator I in the position to which it has been ldiuted.

Secured in any suitable manner to the insulator I at the upper end thereof as by means of a bolt is a cross member 1 which, as shown in Fig. 1, is of angular cross-sectional shape. The cross member 1 is provided with a lug 1- which is provided with a curved depression adapted to receive a portion of the insulator, and extended upwardly from said cross member is an extension 1h to which is attached by means of a suitable oonnector l a section P' of the power line of which the apparatus A forms a part.

Extended outwardly from the cross member 1 is a plurality of terminal elements B. Each terminal element comprises a section of material bent double so as to provide la pair of substantially parallel, spaced apart, terminal portions ioined together at one end of the terminal element by a connecting portion. These parallel portions oi each terminal element are provided with torsional loops Ill to increase the resiliency oi' said terminal elements, and said parallel terminal portions are ilared outwardly to facilitate Also, a clamp assembly Il is associated with the parallel portions of each terminal element so as to prevent undue spreading thereof relative to each other. The inner ends of the terminal elements are seated in depressions formed in the cross member 1, and bolts I2* are employed f or securing said terminal elements tol said cross member.

Suitably secured to the insulator I at the lower end thereof is a second cross member, which is designated by the referencecharacter I2. The.

cross member I2 in shape resembles the cross member 1 already referred to herein, said cross member I2 being of angular cross section and having a lug I2' formed thereon which is provided with a curved depression that receives a portion of the insulator I. The cross member I2 has attached to it through the instrumentality o! a suitable connector I3 a section P2 of the power line with which the apparatus A is associated.

Secured to the lower cross member I2 of the apparatus A is a plurality of housings Il, in the particular embodiment oi the invention illustrated in the drawings three of these housings being shown. The housings I4 are closed at their top sides and in part at their ends, and are open at the bottoms as shown most clearly in Fig. 5, and said housings are spaced longitudinally of the cross member I2, as shown in the view referred to. The forward ends of the housings I4 are connected by a channel element I5 which serves to provide the structure with the required rigidity, and said housings I4 are alined vertically with the terminal elements 9.'

Pivotally secured to each housing by a pivot element designated by the reference character Il is a carriage I1, each carriage comprising a rear wall II'l and parallel side walls Il, and formed in the opposite side walls of each carriage are alined,v angularly extended slots I1 which are open at the upper edges of said side walls. The opposed side walls oi eachoarriage are provided with alined depressions I2 which serve as trackways in a manner to`be hereinafter explained, the lower walls oi said depressions beingdenned by ribs Il" which have ribs Il associated therewith. The ribs I8 are provided with curved seats 20 which likewise serve a function to be hereinafter set forth.

Extended transversely of each housing I4 is a pivot element 2| which pivotally supports a cocking lever'22, said cooking lever having a portion extended forwardly of the pivot element 2l and a longer portion extended rearwardly thereof. At its rear end the cooking lever 22 is provided with a hook-like portion 22', and the rear wall oi' each housing is provided with a slot'which is Open at the bottom of said rear wall into which the rear end portion of said cocking lever is adapted to pass when it moves to an elevated position. The forward end of the cooking lever of each housing Il is connected to an ear 23 extended from the associated carriage I1 by a link 2l, and the top wall of each housing is provided with a screwthreaded opening that receives a screw 25 which extends into the interior of the housing and serves as an adjustable stop for limiting upward movement of the forward portion of the cooking lever. The screw 25 has a lock nut 2B associated therewith which is operable to lock the screw in positions to which it has been adjusted. Located Within each housing Il is a coil spring S which is attached at one end to the rear wall of the associated carriage I1 by being arranged in embracing relation relative to a portion of the link 2| which passes through Athe ear 23, the opposite end of said coil sprirm being attached to a hook-like element 21 formed on a portion 21 of the housing Il. Each housing I1 is also provided with a short section of ilexible electrical conductor 28 which is suitably connected to the rear wall of the carriage I1 and to the portion 21 of the housing and serves as a conductor of electricity between said parts.

The assembly of co-operating parts associated with each housing includes a fuse cartridge 29, which is of so called expulsion type and comprises an open end tube 30 of insulating material. Although the precise construction of the tube is not important in so far as this invention isv concerned, it preferablyV is of composite construction, embodying an inner tubular portion of horn fiber and an outer jacketing portion of bakelite, or other insulating material having equivalent weather-resisting properties. Fixed to the upper end portion of the tube 3U of each fuse cartridge 29 is a cap 3|, which serves as a terminal member. The cap 3| is secured to the tube by suitable means, such as rivets or pins, and is provided with a bore which receives an upper portion of the tube structure. Extended outwardly beyond the end wall of the cap 3l is a flnger 32, which is adapted to move into the passageway between the parallel terminal portions of the associated terminal 9 during switchclosing movement of the cartridge. In the particular fuse cartridge illustrated in the drawings, the upper end thereof is closed by a head element in the form of an externally convex disk 33, and due to its convexity the disk will center itself relative to the resilient parallel portions of the terminal 9 so as to distribute the spring pressurev equally on opposite sides of the fuse cartridge. A fuse link 34, having a fusible section 34', is suitably connected to the disk 33 and passes downwardly through the tube 30, and the downward pressure exerted by the resilient terminal 5 against the upper end of the cartridge tends to move the cartridge axially downwardly, which, as will hereinafter appeal, results in tensioning of the fuse link.

at its lower end each fuse cartridge is proneath the right-hand housing Il. At the opposite end of the rod portion Bl an arm l is fixed thereto. and this arm is extended downwardly from the rod portion il and is provided at its` lower end with a transversely extended member Il, which is locatedl beneath the left-hand housing I For convenience in describing the operation of the improved apparatus, the three fusing units of the apparatus will be given separate reference characters; that is to say, reading from left to right in Fig. 5. these units will be designated respectively by the reference characters A1, A, and A. With this in mind it will be assumed that the unit Al is in the circuit-closing position shown in Fig. 2, and that the units Az and An are each in the reserve position illustrated in Fig. 3. The unit Al being in the closed circuit position, the

coil spring S thereof is contracted, whereby the carriage I1 is drawn inwardly at its upper end, the toggle produced by the forward end portion of the cocking lever 22 and the associated link 2l being broken downwardly, as shown in Fig. 2. Also, the units A2 and A3 being in the reserve position, the rear end portions of the cocking levers 22 thereof are drawn downwardly, as shown in Fig. 3, with the result that the toggles produced by the folward end portions of the cocking levers and the links 2l have moved the upper portions of the carriages outwardly and thereby placed the coil springs under tension. With respect to the toggles referred to, it is important to note that the points of connection between the forward end portions of the cocking levers and the links 2l are located slightly above dead center as defined by an imaginary line drawn from the center of the points of connection between the links 2l and the carriages, and the center of the pivot elements 2l. It' is also to be noted that the screws 25 form stops which limit upward movement of the forward end portions of the cocking levers. This relation of the parts referred to locks the carriages in the position shown in Fig. 3.

Assume, now, with the units A1, A, and A3 arranged as described, the fuse link of the unit A1 blows, due to a fault in the line. The ruptured fuse link will permit the hinge member at the lower end of the fuse cartridge of said unit Al to swing about its pivot Il, whichwiil result in downward movement of the fuse cartridge longitudinally of its major axis, whereby the finger 32 will be freed from the terminal 9 and the end of the lower extension Il will be freed from the seats 2l. The cartridge will then rotate outwardly and downwardly about the conn'ectionbetween the cartridge and its carriage defined by the trunnions 3B and the slots I1", and the lower end of the hinge member 35 will strike the lower end portion 53' of the releasing element ll (Fig. 5). This will result in the member Il' of said releasing element striking the cocking lever 22 of the unit A. whereby the toggle produced by said cocking lever and the associated link 2l will be broken downwardly to permit the coil spring S of the unit Az to forcibly snap the fuse cartridge of the unit Az from the reserve position to the circuit-closing position. In like manner, when the unit A2 is inthe circuitclosing position a the fuse link blows, the cocking lever 22 of th unit A3 in reserve position is struck by the/member 51 of the releasing element to cause the fuse cartridge of said unit A to be thrown into the circuit-closing position.

`unit is out of service.

A150, when the una A is in the circuit-closing position and the unit A1 is in the reserve position, rupture of the fuse link of said unit A3 will resultin the member Il of the releasing element 5I striking the cocking lever of the unit A1, to permit the coil spring S of said unit A1 to draw the cartridge thereof to the circuit-closing position.

'Because a blown fuse cartridge assumes a horizontal position, as illustrated in Fig. 4, which is different from the circuit-closing and reserve positions, troublemen may immediately recognize blown cartridges during their tours of inspection. In order to remove a blown fuse cartridge it is necessary rst to re-cock the cocking lever 22 of the unit of ,which the blown cartridge forms part by drawing the rear end portion thereof downwardly. This is so because the forward upper portion of the housing Il overhangs the slots I1c of an uncocked unit so as to prevent upward movement of the trunnions 36 out of said slots. After the cocking lever of a unit which has been blown is re-cocked, the slots I1c of the carriage I1 are positioned as shown in Fig. 3. The hookshaped portion l5 of the hinge member may then be engaged with the aid of a suitable switch hook and the cartridge moved upwardly and outwardly. During such removal of a blown cartridge the outwardly extended portions 4B at the end of the lower extension 48 of the bracket member 31 at the lower end of the cartridge tube pass longitudinally through the guideways 41 of the housing I4 and into and through the related guideways I8 of the associated carriage I 1. When a fuse cartridge is removed for inspection when itis in the reserve position, it is necessary merely to free the end of the lower extension 46 from the seat 20 and raise the trunnion out of the slots I'I'=.

When the troubleman has removed a blown fuse `cartridge from the apparatus he re-fuses same and replaces it in the reserve position, the carriage I1 and the parts associated therewith having been moved to the reserve position when the cartridge was removed. 'I'he re-fused cartridge is then again ready for movement into the circuit-closing position in the manner already explained.

It is obvious in the operation of the improved apparatus disclosed herein that no set cycles of operations are followed. In other words, the present invention does not include a primary fusing unit and a secondary fusing unit which is placed in service only while the primary fusing In the operation of the improved structure no particular fusing unit need be placed in operation at any certain time. as the apparatus follows its .normal sequence of operations regardless of what fusing unit is in service. Also, as already stated herein, an inherent time delay is allowed between blowing of one fuse cartridge and automatic introduction of the succeeding fuse cartridge in the line to permit temporary fault clearances.

Another feature of the invention is that if it is desired to inspect any one of the fuse cartridges, the other two cartridgesV may be placed in fusing service while the inspection is being made. This reduces the possibility of the switch operating while the inspection is being made. A fuse cartridge may be moved by hand to an open position by drawing the rear end portion of the associated cocking lever 22 downwardly, and may bel closed by tripping said cocking lever. When. so operated by hand quick break and recloser action is produced, winch tends to eliminate arcing. Cooking of-the levers 22 is accomplished by engaging the hook-shaped rear end portions thereof with the aid of a suitable switch hook.

The adjusting screws 25 constitute important elements of the improved structure, inasmuch v as they serve to regulate the amount of travel of the levers' 22 in the oif center direction, and they must be adjusted very carefully with respect to the weight of various cartridges employed with' the apparatus. In other words, switches of lower voltage rating using shorter cartridges require that the adjustments of the screws be made finer, while, in cases where higher voltage cartridges are used, the adjustments ofthe screws 25 must be such as to compensate for the additional weight of the longer cartridges.

l claim: e

l. A fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supported thereby, energy means connected to the carriage of each fusing unit and adapted to move said carriage, cooking means associated with each fusing unit for moving and locking the carriage thereof in a manner to render saidenergy means effective, and releasing means operable by movement of a -fusing unit out of the fusing position and adapted to release the energy means of another fusing unit so as to permit said energy means to move the associated carriage to a position Where the fuse cartridge carried thereby assumes the fusing position.

2. A fuse switch comprising a plurality of fusing units including each a pivotally supported carriage and a fuse cartridge supported thereby,

Y an expansihle and contractile coil spring connected to the carriage of each fusing unit and adapted to move said carriage, cooking means associated with each fusing unit for moving and locking the carriage thereof in a manner to tension the associated coil spring, and releasing means operable by movementof a fusing unit out of the fusing positionrand adapted to release the tensioned coil spring of another fusing unit so as to permit said coil spring to move the`associated carriage to a position where the fuse cartridge carried therebyassumes the fusing position.

3. A. fuse switch comprising a plurality of fusing units including each a pivotally supported carriage and a fuse cartridge pivotally supported thereby, an expansible and contractile coil spring connected to the carriage of each fusing unit and adapted to move said carriage, cooking means amociated with each fusing unit for moving and looking the carriage thereof in a manner to ten'- sion the associated coil spring, and releasing means operable by movement of a'fusing unit out of the fusing position and adapted to release the tensioned coil spring of another fusing unit so as to permit said coil spring to move the associated carriage to a position where the fuse cartridge carried thereby assumes the fusing position.

d. t fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supported thereby, an enpansible and contractile coil spring confnected to the carriage of each fusing unit' and adapted to move said carriage, cooking means associated with each fusing unit formoving and locking the carriage thereof in a manner to tension the associated coil spring, and releasing means operable by being struck by a fusing inuit moving outjof the fusing position and adapted to release the tensioned coil spring of another fusing unit so as to permit said coil spring to move the` associated carriage to a position where the fuse cartridge carried thereby assumes the fusing position.

5. A fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supportedthereby, an expansible and contractile coil spring connected to the carriage of each fusing 'unit and adapted to move said carriage, cooking means, including n pivotally supported lever, associated with each fusing unit for moving and locking the carriage thereof in a manner to tension the associated coil spring, and releasing means operable by movement of a fusing unit out of the fusing position and adapted to release the tensioned coil spring of another fusing unit so as to permit said coil spring to move the associated carriage to a position Where the fuse cartridge carried thereby assumes the fusing position.

6. A fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supported thereby, an expansible andv contractile coil spring connected to the carriage of each fusing unit and movement of a fusing unit out of the fusing position and. adapted to release the tensioned coil spring of another fusing unit so as to permit said coil spring to move the associated carriage to a position where the fuse cartridge carried thereby assumes the fusing position.

7. A fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supported thereby, an expansible and contractile coil spring connected to the carriagevof each fusing unit and adapted to move said carriage, cooking means associated with each fusing unit for moving and locking the carriage thereof in a manner to tension the associated coil spring, said cooking means comprising a pivotally supported lever and a link connected to said lever and to the associated carriage in a manner to provide a toggle connection for said carriage, and releasing means operable by movement of a fusing unit out of the fusing position and adapted to release the tensinned coil spring of another fusing unit so as to permit said coil spring to move the associated carriage to a position where the fuse cartridge carried thereby assumes the fusing position.

d. A fuse switch comprising a plurality of fus ing units including each a movably supported carriage and a fuse cartridge supported thereby, an expansible and contractile coil spring connected to the carriage of each fusing unit and adapted in move said carriage, cooking means associated with each fusing unit for moving and locking the carriage thereof in a manner to tension the associated coil spring, said cooking means comprising a pivotally supported lever and a link connected to said lever and to the associated carriage in a manner to provide a toggle connection for said carriage, and releasing means operable by movement of a fusing unit out of the fusing position and adapted to release the tensioned coil spring of another fusing unit by actuating the y cooking means thereof so as to permit said coil tion where the fuse cartridge carried thereby assumes the fusing position.

9. A fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supported thereby, an expansible and contractile coil spring connected to the carriage of each fusing unit and adapted to move said carriage, cocking means associated with each fusing unit for moving and'locking the carriage thereof in a manner to tension the associated coil spring, said cooking means comprlsing a pivotally supported lever and a link connected to said lever and to the associated carriage in a manner to provide a toggle connection for said carriage, and releasingmeans operable by movement of a fusing unit out of the fusing position and adapted to release the tensioned coil spring of another fusing unit by striking the pivotally supported lever of the cooking means thereof so as to permit said coil spring to move the associated carriage to a position where the fuse cartridge carried thereby assumes the fusing position. i

10. A fuse switch comprising a plurality oi fusing units including each a pivotally supported carriage movable to different positions and a fuse,

cartridge detachably supported thereby and havlng a fuse link associated therewith, said fuse cartridge being removable from said carriage by being moved relative thereto, means associated with each of said fusing units whereby rupture of the fuse link thereof' causes said fusing unit tofmove out of the fusing position, means associated with each fusing unit adapted to move the fusing unit into the fusing position, releasing means operable bymovement of a fusing unit out of the fusing position for releasing another fusing unit for movement into the fusing position. and a housing associated with each fusing unit and having a portion which is so related to the carriage thereof when said carriage is in a certain position that the fuse cartridge associated with said carriage may not be detached therefrom.

11. A fuse switch comprising a plurality of fusing units `including each a pivotally supported carriage movable to different positions and a fuse cartridge detachably supported thereby and hav-- ing a fuse link associatqzi therewith, said fuse cartridge being removable from said carriage by Vbeing moved 'relative thereto. means associatedA with each of said fusing units whereby rupturel of the fuse link thereof causes said fusing unit to move. out of the fusing position, means associated with each fusing unit adapted to move the fusing unit into theA fusing position, releasing means operable by movement of a fusing unit out of the fusing position for releasing another fusing unit for movement into the fusing position, and a housing associated with each fusing unit and having an overhanging portion which is so related to, the carriage thereof when said Y carriage is in a certain position that the fuse cartridge associated with said carriage may not be detached therefrom. i

12. A fuse switch comprising a plurality of fusing units includingeach a pivotally supported carriage movable to different positions and a fuse cartridge detachably supported thereby and having a fuse Ilink associated therewith, said fuse cartridge being removable from said carriage by being moved' relative thereto, means associated with each or said fusing units whereby rupture of the fuse link thereof causes said fusing unit to move out of the fusing position, means associated with each fusing unit adapted to move the fusing unit into the fusing position, releasing means operable by movement of a fusing unit out of the fusing position for releasing another fusing unit for movement into the fusing position. and a housing associated with each fusing unit and having a portion which is so related to the carriage thereof when said carriage is in a certain position that the fuse cartridge associated with said carriage may not be detached therefrom, the housing and the carriage of each fusing unit being provided with guideways which `are in co-operative relation when the carriage is positioned properly for removal of the associated fuse cartridge through which guideways parts of said fuse cartridge pass during detachment thereof.

13. A fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supported thereby, an expansible and contractile coil spring connected to the carriage of each fusing unit and adapted to move said carriage, cooking means associated with each fusing unit for moving and locking the carriage thereof in a manner to tension the associated coil spring,and pivotally supported releasing means operable by movement cf a fusing unit out of the fusing position and adapted to release the tensioned coil spring of another fusing unit so as to permit said coil spring to move the associated carriage to a position where the fuse cartridge carried thereby assumes the fusing position.

14. A fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supported thereby, an expansible and contractile coil springconnected to the carriage of each fusing unit and adapted to move said carriage, co( king means comprising a toggle assembly associated with each fusing unit for moving and locking the carriage thereof in a manner to tension the associated coil spring, a stop for limiting movement of said toggle assembly when the carriage is moved to the cocked position by the cooking means, and releasing means operable by movement of a fusing unit out of the fusing position and adapted to release the tensioned coil spring of another fusing unit so as to permit said coil spring to move the associatedcarriageto a position where the fuse cartridge carried thereby assumes the fusing position. 15. A fuse switch comprising a plurality of fusing units including each a movably supported carriage and a fuse cartridge supported thereby, an expansible and contractile coil spring connected to the carriage of each fusing unit and adapted to move said carriage, cocking means comprising a toggle assembly associated with each fusing unit for moving and locking the carriage thereof in a manner to tension the associated coil spring, an adjustable stop for limiting movement of said toggle assembly when the carriage is moved to the cocked position by the cooking means, and releasing means operable by movement of a fusing unit out of the fusing position and adapted to release the tensioned coil spring of another fusing unit so as to permit said coil spring to move the associated carriage to a position where the fuse cartridge carried thereby assumes the fusing position.

CHARLES ADIN FOX.

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