US2073186A - Housed type of drop-out fuse - Google Patents

Description

March 9, 1937 A. G. STEINMAYER ET AL 2,973,186

HOUSED TYPE OF DROP OUT FUSE Filed April 9, 1934 5 Sheets-Sheet l March 3, 1937. A. e. STEINMAYER ET AL 2,@7318$ HQUSED TYPE OF DROP-OUT FUSE,

Filed April 9, 1934 3 Sheets-Sheet 2 ATTORNEY Marc 9, 19,37 A. s. sTEmMAYER ET AL 27973g136 HOUSED TYPE OF DROP-OUT FUSE Filed April 9, 193 3 Sheets-Sheet 3 WM Emu W 070 m m E g 4 Patented Mar. 9, 1937 PATENT OFFICE HOUSED TYPE OF DROP-OUT FUSE Alwin G. Steinmayer, Milwaukee, and William Schultz, South Milwaukee, Wis., assignors to Line Material Company,

South Milwaukee,

Wis., a corporation of Delaware Application April 9, 1934, Serial No. 719,624

26 Claims.

This invention relates to a housed type of dropout fuse.

This invention has for its major object the provision of a drop-out fuse structure which is enclosed or housed within a porcelain or other box, wherein all live parts are enclosed against accidental contact and are also protected from the weather.

In greater detail, objects of this invention are to provide an enclosed type of fuse which nevertheless is so constructed that the fuse assembly drops out of position, or, in other words, moves away from the live contacts when the fuse blows, the invention providing an expulsion type of fuse which is housed but which nevertheless actually disconnects both ends of the fuse assembly from the live contacts, so that the entire fuse assembly is dead, the invention providing means where by there are no live parts projecting outside of the housing when the fuse has blown.

Further objects are to provide a housed type of drop-out fuse in which a casing is provided with a door which is hingedly supported by supporting link mechanism directly from lower hinge means carried by the casing, an expulsion fuse being removably carried by the door and including a fuse link which restrains the supporting link mechanism against movement but which allows the supporting link mechanism to operate when the fuse link is ruptured, the door moving outwardly adjacent its lower end, at first, to release latch mechanism normally holding the upper portion of the fuse and door assembly, the fuse and door assembly thereafter rocking 5 bodily downward and away from the casing and the hinge means becoming electrically dead.

Further objects are to provide a construction of enclosed drop-out fuse in which the expulsion fuse may be readily detached from the door and the door closed to protect the contacts carried by the casing from the weather, in which the fuse may be refused and reattached to the door and the door and fuse assembly rocked upwardly back into operative position, in which means are provided whereby the door, together with the fuse, may be opened even though the fuse is not blown, and in which the opening and closing of the door may be accomplished by merely pulling the door open by means of a door ring or by merely pushing the door closed.

. Thisinvention has for its further objects the provision of means which insures the complete blowing of the fuse before the contacts are! opened so that there is no arcing at the con- 55 tacts, the interruption of the circuit always occurring inside the fuse tube by the blowing and expulsion action thereof, thereby avoiding burning or pitting of the contacts or other destruction of the permanent portions of the fuse.

Further objects are to provide a drop-out fuse construction which may be provided for high amperage service but which, due to the construction of the device, is not bulky, which hinges the door solidly to the casing by link mechanism, and in which an expulsion fuse is carried by the door and is provided with a hinged contact plate or contact lever held in place, under normal conditions, by the fuse link, the contact plate or contact lever itself holding the link mechanism against motion relatively to the door.

Further objects of this invention are to provide a housed type of drop-out fuse which may be as readily and freely handled as the usual housed type fuses, which may be easily refused, and which is of simple and reliable construction.

An embodiment of the invention is shown in the accompanying drawings, in which:-

Figure l is a vertical sectional view showing the fuse in closed position in full lines and showing in dotted lines successive positions occupied by the parts during the opening of the fuse.

Figure 2 is a sectional view on the line 2-2 of Figure l. 1

Figure 3 is a sectional view on the line 3-8 of Figure 1.

Figure 4 is a vertical sectional view showing 'a modified form of fuse in closed position in full lines and showing in dotted lines the position occupiedby the parts when the device is open.

Figure 5 is a sectional view on the line ll-ii of Figure 4.

Referring to the drawings, it will be seen that the fuse housing or casing i, which is preferably of porcelain, is provided with a door 2 of in-- sulating material, such as a phenol condensate. The door is preferably formed with a door ring 3 by which the door may be pulled open either by a fuse pole or switch pole, or by the hand of the lineman.

The door is provided with a bracket 43 which carries an upper hinge pin A pair of links 6 are hinged at their upper ends to the hinge pin 5 and at their lower ends to the lower hinge pins 1. The lower hinge means includes brackets 8 carried by the lower portion of the porcelain housing and these brackets carry the pins l.

The upper portion of the door is provided with a bracket 9 which has projecting, spaced arms provided with outwardly bent cam portions to, for a purpose hereinafter to appear. (Qne of the cam portions is broken away in Figure 3 for the sake-of clearness.)

The casing is provided with an upper terminal i I and a lower terminal l2 provided, respectively, with yielding contacts l3 and Hi, which may be of the nature of laminated brush contacts as shown. The upper contact assembly carries an outwardly projecting stop is, which extends over the top of the expulsion fuse l6 and resists upward reaction, or upward motion of the fuse tube when the fuse blows.

The casing is preferably provided with a barrier ll, preferably integral, which is located between the upper and lower contacts.

A yielding retaining bracket is supported from the upper portion of the casing, and is provided with forwardly projecting arms I8 located on opposite sides of the upper contact of the expulsion fuse, see Figures 1 and 3. Preferably this bracket is clamped behind the upper terminal member and the arms are provided with inwardly turned portions 89 provided with downwardly and outwardly slanting cam faces 20. These faces engage the cam portions iii of the bracket 9 when the door is closed, as may be seen from Figure 3.

The expulsion fuse is provided with an upper contact 2| which normally engages the brush contact l3 and bends such brush contact backwardly when the device is in closed position. The upper fuse contact 24 is provided with outwardly projecting ears 22 which engage the slanting faces 2|] under normal conditions. The upper fuse contact 2! is also provided with. a forwardly projecting lip 23 which fits beneath the bracket 9 on the door.

The expulsion fuse is further provided with a hinge block 24 which is provided with hooklike portions 25 which hook over the pin 5. The door is provided with a leaf spring 28 whose free lower end bears against the fuse tube I6 and tends to rock the tube into the position shown in Figure 1. The fuse tube can be detached from the door by rocking the tube against the action of the spring to thus cause the lip 23 of the upper fuse contact to clear the bracket 9 of the door, and thereafter sliding the tube with ref-. erence to the door to unhook the hooks 25 from.

' clamps the lower end of the fuse link 29, such link electrically connecting the upper and lower contacts of the fuse in the usual manner. This contact lever is provided with laterally projecting ears 3B which are located behind and bear against the supporting links 6 and thus hold the supporting links 6 against releasing movement, though permitting the door and fuse assembly to be manually rocked to open position.

When the fuse and door assembly is manually opened, the following action takes placez-The door is pulled open by means of the ring 3 and a limited relative motion occurs between the door and the fuse, the fuse rockingabout the pin 5 against the action of the spring 26. The cam portions ll] of the door bracket 9, see Figure 3, spread the portions l9 and allow the projecting ears 22, see Figures 1 and 3, of the upper fuse contact to clear the faces l9 The lower contact or contact lever 21 of the,

fuse bears against and compresses the yielding brush contact M and, similarly to the upper fuse contact, thus makes excellent electrical contact with the stationary contact members.

When the fuse blows, the fuse link 29 releases the contact lever 21 and the supporting links 6, which directly support the door 2 from the easing, allow the lower portion of the door and fuse assembly to move first outwardly and then downwardly, disengaging the upper latch mechanism. The door and fuse assembly then bodily swing and rock downwardly into the lower dotted line position shown in Figure 1. I

It is to be noted that the door and fuse assembly is biased towards opening position both by the weight of the parts and by the yielding pressure of the stationary contacts. These yielding contacts follow the contacts of the fuse tube a material distance outwardly, after the fuse link has blown, thus giving ample time for the fuse to clear itself. and stop the current flow. Thus arcing at the contacts is prevented.

In the modified form of construction shown in Figures 4 and 5, it will be seen that the casing is indicated by the reference character 33! and the door by the reference character 32. The door is provided with a bracket 34 having a pair of inwardly directed arms terminating in hooklike portions 35. Further, a-plate 36 is carried by the door and pivotally supports a latch indicated generally at 37. A spring 38 is attached to the latch and urges it in a clockwise direction.

This latch comprises ahooklike portion 39 and an operating finger 50, which is displaced and consequently rocks the latch whenever the fuse tube 4| is in position, as shown in Figures 4 and 5. The upper portion of the fuse tube is constructed as previously described and is provided with an upper contact 42 cooperating with the brush contact or stationary contact 43, as previously described, and provided with outwardly projecting latching lugs M corresponding to the lugs 22 of Figure 1.

These lugs fit behind the slanting faces 55 of the inwardly turned spring arms 66 in the same manner as that described in connection with Figure 1. Similarly, a stop 41 may be provided and carried by the casing which when the device is closed, is positioned above the upper contact and resists the upward reactive thrust when the fuse blows.

The lower portion of the casing carries a pair of ears 8 which pivotally support a pair of links 59. upper ends to the arms of the bracket 36- and thus support the door from the lower pivot point. These links are provided with inwardly directed lugs 50 which are engaged by the latch 39 when the fuse tube is removed from the door and thus the latch locks the door to the links 49 and causes the door and links to operate as a unitary structure, whereby the door may be closed and will be held in closed position, the bottom being prevented from rocking out by the latching action described. The top portion of the door is prevented from moving out by the cam portions or spring arms 5i which are identically similar to the arms 9 as shown and described in connection with Figure 3 of the drawings.

The fuse is provided with a hinge block 52 to which a hinge plate or contact plate 53 is pivotally attached. This hinge block or plate 53 is provided with clamping means 54 by means of which the end of the fuse link 55 is locked to the plate 53, as previously described in connection with the first form of the invention.

These links are in turn pivoted at their It is preferable to provide a spacing member 56 which may be carried by the plate 53 as a unitary part thereof and which contacts with the fuse tube and holds the plate properly spaced therefrom.

It is to be noted from Figures 4 and 5 that the lower ends of the levers 49 are joined by an integral web or transverse portion 51.

The hinge contact plate 53 also presses against the stationary brush contact 58 in the same manner as that previously described. It may be provided with a widened lower portion which fits behind the inwardly propecting studs 59 which are continuations of the pivot pins for the links 49, as most clearly shown in Figure 5.

When the device is closed, as shown in full lines, and the fuse blows, the plate 53 is no longer held in the position shown in the drawings but allows relative rocking motion to occur between such plate and the fuse tube. Consequently the door and fuse tube rock outwardly pivoting on the levers t9 and thereafter drop downwardly and swing to the open dotted line position.

Limit means may be provided if desired by equipping the links 39 with outwardly turned feet 50 which engage beneath the supports 58, as indicated in dotted line position Figure 4.

It sometimes happens that it is desirable to wholly remove the fuse from the door, and this is easily done by pressing the fuse tube towards the door against the action of the spring 38 whose force is transmitted through the lip ll? and thereby disconnecting the pivot pin 6i which also pivots the plate 53 from the hooklike members 35 of the brackets 3d. The tube may then be slid upwardly a slight distance to clear the hooklike members 35 and thereafter may be removed from the door.

It is to be noted in this connection that the inwardly projecting tongue 52 formed integrally with the upper contact 32 of the fuse tube is located above the spring fingers 5i as distinguished from the construction shown in Figure 1. This spacing tongue, therefore, is free to slide upwardly with reference to the door and permits the detaching of the fuse tube in the manner described.

When the fuse tube is removed from the door, it is desirable to close the door and to have the door remain closed. This is readily accomplished as the latch 39 now swings inwardly and engages the inwardly projecting portions 50 of the levers 49 and thus locks the door to the levers, thus holding the lower portion of the door and the levers together as a unit. The door may then be rocked into closed position about the lower pivot pins 59. The spring fingers 5i will engage between the spring fingers 46 and hold the upper portion of the door closed.

It'will be seen that this invention provides a fuse which has the advantages of both a housed type and a drop-out type. It is also to be noted that when the door and fuse assembly areJn open position, that the fuse contacts and the hinge supporting means are electrically dead.

Although this construction is well adapted for high amperage fuses, though not limited thereto, it is not bulky. It is also of simple and reliable construction.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted a laimed.

We claim:

1. A housed type of drop-out fuse comprising a casing, a door for said casing, said door being supported from said casing by hinged supporting means, a fuse assembly carried by said door, said fuse assembly having a fuse link, and means releasably holding said door closed and restrained against releasing movement by said fuse link, said hinged supporting means joining said door and said casing independently of said fuse assembly.

2. A housed type of drop-out fuse comprising a casing, a door for said casing, said door being hingedly supported from said casing, a fuse assembly removably carried by said door, said fuse assembly having a fuse link, and means releasably holding said door closed and restrained against releasing movement by said fuse link, said fuse assembly being removable from said door without interrupting the hinged support of said door.

3. A housed type of drop-out fuse comprising a casing, a door for said casing, said door being hingedly supported from said casing, a fuse as sembly removably carried by said door, said fuse assembly having a fuse link, and means releasably holding said door closed and restrained against releasing movement by said fuse link, said fuse assembly being removable from said door and said door being closable when said fuse assembly has been removed.

4. A housed type of drop-out fuse comprising a casing having spaced contacts, a door for said casing, a fuse assembly carried by said door and having spaced contacts, a fuse link forming a portion of said fuse assembly, and means releasably holding said door closed and holding the contacts of said fuse assembly in engagement with the contacts of said casing, said fuse link holding said means against releasing, said door being movably supported directly from said casing.

5. A housed type of drop-out fuse comprising a casing, contacts carried by said casing, an expulsion fuse and door assembly for said casing, said assembly including an expulsion fuse having contacts normally engaging the contacts carried by said casing and having a fuse link normally joining the spaced contacts, lever mechanism for supporting said assembly from said casing and restrained against motion by said fuse link, and latching means for said assembly for normally holding said assembly in closed position, said lever mechanism when released by the expulsion of said fuse link moving said assembly to open position, said expulsion fuse being removable fromsaid door without interrupting the support of said door from said casing.

6. A housed type of drop-out fuse comprising a casing, contacts carried by said casing, an expulsion fuse and door assembly for said casing, said assembly including an expulsion fuse having spaced contacts normally engaging the contacts of said casing and having a link normally joining said spaced contacts, hinge means distinct and separate from the contacts of said casing for pivotally supporting said 'door directly from said casing, and latch means for said assembly biased towards open position and restrained by said fuse link and releasable when said fuse link blows, whereby said assembly will move to open position when said fuse blows, said hinge means being electrically dead after said door has moved to open position.

7. A housed type of drop-out fuse comprising a casing having contacts, a unitary assembly of contacts of said casing, hinge means carried by said casing mechanically distinct from the contacts of said casing, link mechanism pivotally supported from said hinge means and directly supporting said door, said link assembly being held in its normal position by a fuse link forming a portion of said expulsion fuse and being adapted to rock said assembly to open position with reference to said casing when said fuse link is ruptured, and latching means for the upper portion of said assembly, said latching means being releasable when the lower portion of said assembly moves toward open position, said assembly subsequently moving bodily downwardly to open position, said hinge means being electrically dead after said assembly has moved to open position.

8. A housed type of drop-out fuse comprising a casing, contacts carried by said casing, an expulsion fuse and door assembly for said casing, said assembly including an expulsion fuse having spaced contacts engaging the contacts car,- ried by said casing and having a fuse link normally joining said spaced contacts, latch mechanism including lever mechanism for normally holding said assembly in closed position, said fuse link normally directly engaging a portion of said latch mechanism and holdingsaid lever mechanism from moving to releasing position, and hinge means for supporting said door from said casing independently of said expulsion fuse, said hinge means being electrically dead after said assembly has moved to open position.

9. A housed type of drop-out fuse comprising a casing, stationary contacts carried by said casing, a door for said casing, a fuse carried by said door and-having spaced contacts engaging the stationary contacts when said door is closed, said fuse including a fuse link normally electrically joining the contacts of said fuse, said door being biased for motion away from said casing, and mechanism directly joining .said door and casing, said mechanism releasably holding said door closed and being held against opening movement by said fuse link.

10. A housed type of drop-out fuse comprising a casing, stationary contacts carried by said casing, a door for said casing, an expulsion fuse carried by said door and having spaced contacts is closed, said fuse including a fuse link normally electrically joining the contacts of said fuse, said door being biased for motion away from said casing, and mechanism directly joining said door and easing, said mechanism releasably holding said door closed and being held against opening movement by said fuse link.

11. A housed type of drop-out fuse comprising a casing, contacts carried by said casing, a door normally closing said casing, releasable latching means normally holding said door closed, pivotal supporting means fordirectly supporting said door from the lower portion of said casing, an expulsion fuse carried by said door and having spaced'contacts normally engaging the contacts of said casing, a fuse link forming a portion of said expulsion fuse and normally holding said pivotal supporting means against movement, whereby when said fuse link is expelled, said door is released and swings outwardly away from said 12. A housed type of drop-out fuse comprising a casing, stationary contacts carried by said casing, a door for said casing, an expulsion fuse carried by said door and having spaced contacts normally engaging said stationary contacts and having a fuse link normally joining said spaced contacts, link mechanism for supporting said door from said casing independently of said expulsion fuse, said link mechanism being restrained against movement by said fuse link, and latching mechanism adjacent the upper portion of said casing for holding the upper portion of said door closed, said link mechanism when released by the expulsion of said fuse link first rocking the lower portion of said door outwardly, said door and expulsion fuse thereafter moving downwardly from said casing.

13. A housed type of drop-out fuse comprising a casing, stationary contacts carried by said casing, a door for said casing, an expulsion fuse carried by said door and having spaced contacts normally engaging said stationary contacts and having a fuse link normally joining said spaced contacts, link mechanism for supporting said door from said casing independently of said expulsion fuse, said link mechanism being restrained against movement by said fuse link, and latching mechanism adjacent .the upper portion of said casing for holding the upper portion of said door closed, said link mechanism when released by the expulsion of said fuse link first rocking the lower portion of said door outwardly, said door and expulsion fuse thereafter moving downwardly from said casing, said expulsion fuse being freely removable from said door when said door is open without interrupting the connection of said door to said casing through said link mechanism.

14. A housed type of drop-out fuse comprising a casing, stationary contacts carried by said casing, a door for said casing, an expulsion fuse carried by said door and having spaced contacts normally engaging said stationary contacts and having a fuse link normally joining said spaced contacts, link mechanism 'for supporting said door from said casing independently .of said expulsion fuse, said link mechanism being restrained against movement by said fuse link, and latching mechanism adjacent the upper portion of said casing for holding the upper portion of said door closed, said link mechanism when released by the expulsion of said fuse link first rocking the lower portion of said door outwardly, said door and expulsion fuse thereafter moving downwardly from said casing, the electrical connection between said spaced contacts and said stationary contacts being maintained throughout a material portion of the travel of said door and expulsion fuse.

15. A housed type of drop-out fuse comprising a casing, stationary contacts carried by said casing, a door for said casing, an expulsion fuse carried by said door and having spaced contacts normally engaging said stationary contacts and having a fuse link normally joining said spaced contacts, link mechanism for supporting said door from said casing independently of said expulsion fuse, said link mechanism being restrained against movement by said fuse link, and latching mechanism adjacent the upper portion of said casing for holding the upper portion of said door closed, said link mechanism when released by the expulsion of said fuse link first rocking the lower portion of said door outwardly, said door and expulsion fuse thereafter moving downwardly from said casing,-

said stationary contacts being yielding and maintaining engagement with the contacts of said ex-' pulsion fuse for a material portion of the movement of said door and expulsion fuse after said fuse link blows, whereby arcing at the contacts is prevented.

l6. Ahoused type of drop-out fuse comprising a casing, a pivotal door for said casing, an expulsion fuse carried by said door and having a lower contact and an upper contact, said upper contact having projecting means, a fuse link electrically joining said contacts, latch means carried by said casing and normally engaging said projecting means, and mechanism directly engaging said door and pivotally supporting said door from said casing, said mechanism normally holding said projecting means in engagement with said latch means and movable to disengaging position, said mechanism being restrained against motion by said fuse link, and releasing means carried by said door for releasing said latch mechanism when said door is forcibly pulled outwardly adjacent its upper end.

17. A housed type of drop-out fuse comprising a casing, a pivotal door for said casing, an expulsion fuse carried by said door and having a lower contact and an upper contact, said upper contact having projecting means, a fuse link electrically joining said contacts, latch means carried by said casing and normally engaging said projecting means, and mechanism directly engaging said door and pivotally supporting said door from said casing, said mechanism normally holding said projecting means in engagement with said latch means and movable to disengaging position, said mechanism being restrained against motion by said fuse link, and releasing means carried by said door for releasing said latch mechanism when said door is forcibly pulled outwardly adjacent its upper end, said releasing means having motion with respect to the upper end of said expulsion fuse during releasing action.

18. A housed type of drop-out fuse comprising a casing, a pivotal door for said casing, an expulsion fuse carried by said door and having a lower contact and an upper contact, said upper contact having projecting means, a fuse link electrically joining said contacts, latch means carried by said casing and normally engaging said projecting means, and mechanism directly engaging said door and pivotally supporting said door from-said casing, said mechanism normally holding said projecting means in engagement with said latch means and movable to disengaging position, said mechanism being restrained against motion by said fuse link, releasing means carried by said door for releasing said latch mechanism when said door is forcibly pulled outwardly adjacent its upper end, said releasing means having motion with respect to the upper end ofs aid expulsion fuse during releasing action,

and spring means tending to hold said expulsion .fuse in a predetermined position with respect to said door.

19. A housed type of drop-out fuse comprising a casing, a door for said casing, said door being supported from said casing by hinged supporting means, an expulsion fuse carried by said door and having a fuse link, a stop carried by said casing and positioned above said expulsion fuse for resisting the reaction of said expulsion fuse, and means releasably holding said door closed and biased towards open position and restrained against releasing movement by said fuse link,

said hinged supporting means joining said door and said casing.

20. A housed type of drop-out fuse comprising a casing having spaced contacts, a door for said casing, a'fuse carried by said door and having spaced upper and lower contacts normally engaging the contacts of said casing, the lower of said spaced contacts including a pivotally mounted contact lever, a fuse link electrically joining said spaced contacts and normally holding said contact lever against motion relatively to said fuse, and means including link mechanism for supporting said door from said casing, said contact lever normally holding said link mechanism against motion.

21. A drop-out fuse comprising an insulating support having a pair of relatively spaced terminal contacts, an expulsion fuse tube closed at one end and open at the other end, a lever hingedlyconnected with the tube adjacent the open end and pivotally mounted on said support, means engageable with said lever, and a fuse link in said tube controlling said means for holding said tube in closed circuit position until said fuse link is severed.

22. A drop-out fuse comprising an insulating support having stationary contacts, an expulsion fuse tube having spaced contacts normally engaging said stationary contacts and having a fuse link normally joining said spaced contacts, lever mechanism pivotally connected with said tube and pivotally supported by said insulating support, latch mechanism at the upper end of said tube holding said tube against swinging movement, and mechanism at the lower end of said tube controlled by said fuse link and holding said lever mechanism against pivotal movement until said fuse link is severed.

23. A drop-out fuse including an insulating support having a pair of terminal contacts, a fuse tube closed at one end and open at the other end and having spaced contacts normally electrically connected to said terminal contacts, supporting means pivotally supporting said fuse tube adjacent the open end of said fuse tube and pivotally supported from said insulating support, a lever pivotally supported from said fuse tube and normally interlocking with said supporting means and preventing pivotal action of said supporting means, and a fuse link in said tube closing the circuit between said spaced contacts and restraining said lever against rocking motion until said fuse link is severed.

24. A housed type of circuit interrupting switch comprising a casing, contacts carried by said casing, an expulsion tube and door assembly for said casing, said assembly including an expulsion tube having contacts normally engaging the contacts carried by said casing and having a flexible conductor normally joining said spaced contacts, lever mechanism for supporting said assembly from said casing and restrained against motion normally, restraining means for said assembly for normally holding the assembly in closed position, said lever mechanism when normally engaging said stationary contacts and 26. A housed type of drop-out circuit interrupting switch comprising a casing, stationary contacts carried by said casing, a door for said. casing, an insulating tube carried by said door and having spaced contacts normally engaging said stationary contacts, a flexible conductor within said tube connecting said spaced contacts, movable latch means at eachend of said door cooperating to hold the tube in circuit closed position under normal circuit conditions, and current responsive means for releasing the tube and door under overload conditions in the circuit.

ALWIN G. STYER'.

n I O. SCHULTZ.

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