US2794871A - Apparatus for operating high tension electric switches - Google Patents

Description

June 4, 1957 -r. F. JOHNSON 2,794,371

APPARATUS FOR OPERATING HIGH'TENSION mc-mxc swI'rcHEs Filed June 1s, 1956 4 Sheets-Sheet l 72 drew ATTJZVEY June 4, 1957 -r. F. JOHNSON 2,794,371

APPARATUS FOR OPERATING HIGH TENSION ELECTRIC SWITCHES Filed June 13, 1956 4 Sheets-Sneet 2 QQM M A7702 NE) June 4, 1957 'r. F. JOHNSON APPARATUS FOR OPERATING HIGH TENSION ELECTRIC SWITCHES Filed June 13, 1956 4 Sheets-Sheet 3 R, I E E1 R N m q Wk M I 1 .W.W\ NB Q 7 Q a m M E h mt Nm Qm m. 3

- INVENTOR.

- fulfil/4'50 f. Jam/50M June 4, 1951 T. F. JoHNsbN 2,794,871

APPARATUS FOR OPERATING HIGH TENSION ELECTRIC SWITCHES Q N Q 1.

N a; R g R Q 0 S n o i ml I; EH 'Q M Q INVENTOR.

7011/0/00 F. c/fl/V/VJfl/V 464M V W A Tree/v5 Y United States Patent APPARATUS FOR OPERATING HIGH TENSION ELECTRIC SWITCHES Tomlinson F. Johnson, Atlanta, Ga. Application June 13, 1956, Serial No. 591,068 20 Claims. (Cl. 200-48) This invention relates to high tension electric switches and has more particular reference to apparatus for controlling the opening and closing of gang operated high tension electric switches.

One object of the present invention is to provide novel and improved apparatus for controlling the opening and closing of a gang of high tension electric switches of the rotating insulator type.

Another object of the present invention is to provide novel and improved apparatus, as characterized above, including means for normally maintaining the switches in either a closed or open position, to which they have been moved manually, and means for automatically moving the switches to the opposite of the normally maintained position in response to actuation from an outside source.

A further and more specific object of the invention is to provide novel and improved apparatus for operating a group of high tension electric switches used in the take-ofi power line where the power line enters the customers transformer station to disconnect the power line when an abnormal current enters the customers transformers, including manually operable means forclosing the switches, latching means for normally holding the switches closed, and automatic means for opening the switches in response to actuation by a current sensitive device operable when an abnormal current enters the transformers.

Other objects and advantages of the invention will appear in the following specification when considered in connection with the accompanying drawings, wherein:

Fig. 1 is a plan view, with parts broken away, of a gang of high tension electric switches and showing them connected to one embodiment of apparatus for automatic opening and manual closing, constructed in accordance with the present invention;

Fig. 2 is a vertical sectional view, with parts broken away and taken on line 22 of Fig. 1;

Fig. 3 is a vertical sectional view taken on line 3-3 of Fig. 1, and showing the construction of a switch unit;

Fig. 4 is a vertical sectional view taken on line 4-4 of Fig. 3, and showing the details of the knock-out latch mechanism;

Fig. 5 is a horizontal sectional view taken on line 55 of Fig. 4, and showing the details of the pivoted lever forming part of the latching mechanism;

Fig. 6 is a vertical sectional view taken on line 6-6 of Fig. 4, and showing further details of the pivoted lever forming part of the latching mechanism;

Fig. 7 is a vertical sectional view taken on line 7-7 of Fig. 4;

Fig. 8 is a vertical sectional view taken on line 88 of Fig. 4, and showing the details of the mounting of the centrifugal knock-out disc;

Fig. 9 is a horizontal sectional view taken on line 9-9 of Fig. 4, and showing in plan view details of the knockout latch mechanism;

c Fig. 10 is a vertical sectional view taken on line 10-10 of Fig. 9, and showing the details of the knock-out disc; and

Fig. 11 is a perspective view showing the details of the latching mechanism.

The present invention provides novel and improved apparatus for operating high tension electric switches ineluding means for normally maintaining the switches in either a closed or an open position, to which they have been moved manually, and means for automatically moving the switches to the opposite of the normally maintained position in response to actuation by an outside source. The improved apparatus is particularly designed for controlling a group of high tension electric switches of the rotating insulator type used in take-off power lines, where the power line enters the customers transformer station, so that the switches are normally maintained closed, but are opened automatically when an abnormal current enters the customers transformers.

While the improved apparatus, for automatic opening and manual closing of a gang of high tension electric switches, of the present invention, can be used with high tension electric switches of either the vertical break rotating type switch such as is disclosed in my prior Patent No. 2,248,876, or the side breaking rotating type, such as disclosed in my prior Patent No. 2,231,809, for the purpose of illustration, it will be shown and described as used with a high tension side break rotating switch of the type shown in Fig. 6 of my Patent No. 2,231,809.

Referring now to the drawings, there is illustrated in Figs. 1, 2 and 3, a gang or group of side break rotating insulator type switch units connected to one embodiment of apparatus constructed in accordance with the present invention for operating the switch units as a group to normally maintain them closed but to automatically open them when an overload of current flows through the power line. As there shown, the apparatus comprises a gang or group of switch units S, three such being shown, each having the operating arm A of its rotating insulator pivotally connected to an operating rod or lever 10; a spring operating assembly, indicated generally at 11, normally urging the rod 10 in a direction to rotate the rotating insulators to open the switches; a vertical rotatable rod or shaft 12 having its upper end fixedly connected to the rotating insulator of the outer switch unit for rotation therewith and its lower end portion journaled in a suitable bearing 13 carried by a suitable bracket 14 mounted on the frame, indicated generally at 15, which supports the switch units S and having a handle 16 pivotally connected to its bottom end for rotating the rod and thereby the rotating insulator to which it is connected; latching mechanism, indicated generally at 17, for normally holding the switches in closed position against the pressure of the spring mechanism 11; and a knock-out latch mech anism, indicated generally at 18, for automatically releasing the latch mechanism in response to outside actuation by overload, thereby permitting the spring mechanism 11 to open the switches.

The switch units S are generally similar to the switch unit shown in Fig. 6 of my prior Patent No. 2,231,809, and, as shown in Fig. 3, each comprises a stationary insulator 19, fixedly mounted on one end of an ordinary structural channel member forming the base member 20 of the switch units; and a rotating insulator 21 mounted on the other end of the base member. The stationary insulator 19 carries the usual switch jaws and terminal connections, indicated generally at 22, and the rotating insulator 21 carries the usual switch blade assembly and terminal connections, indicated generally at 23.

The operating rod 10 is pivotally connected to the usual operating arm A of each of the rotating insulators for rotating these arms simultaneously as a unit to simultaneously open or close all of the switches.

In the particular embodiment of the invention illustrated, the spring operating assembly 11 is biased to open the switches and is shown as comprising a pair of rods 24, one on each side of the outer end of the operating rod 10, and pivotally connected to a support member 25 fixedly mounted on the base member of the outer switch unit and with its inner end extending through an elongated slot formed in a lateral projection 26 formed on a collar 27 fixedly mounted on the rod in position to compress a coiled spring 28 loosely mounted on the rod 24, whenever the rod is moved to close the switches (to the left as viewed in Fig. l).

The vertical rotatable shaft 12 for manually closing the switches is shown as having 'its upper end fixedly connected to the rotating insulator of the outer or right hand switch unit, as viewed in Fig. 1, and has a holding member 29 in the form of a collar carrying a radially outwardly projecting semi-circular shaped flange or disc fixedly secured thereon intermediate its ends. The straight edge of the semi-circular disc maybe provided with laterally spaced upstanding lugs 30.

The latching mechanism, indicated generally at 17, is shown as comprising a horizontal rotatable rod or shaft 31 having one end suitably journaled in bearings 32 carried by support members 33 depending'from a housing base member 34 supported by the frame and its other end journaled in a bearing 35 carried by a sleeve 36 loosely mounted on the shaft 12 and supported thereon as by a collar 37 fixedly secured on the shaft 12. The

rod 31 has a collar 38 fixedly mounted thereon and carrying a holdingmember 39 in the form of a radially projecting pin. The horizontal shaft 31 is so positioned with respect to the shaft 12 and the semi-disc holding member 29 is so mounted on the shaft 12 that when the shaft 12 is rotated to close the switches the straight edge of the semi-disc shaped holding member 29 will extend in a direction substantially parallel to the horizontal shaft 31. Also, the collar 38 is so fixed on the horizontal shaft 31 that when the shaft is rotated to bring the holding pin 39 into an upwardly extending position, as shown in Fig. 11, it will engage the straight edge and an upstanding lug 30 of the semi-disc shaped holding member 29 and prevent the vertical shaft 12 from being rotated by the pressure of the spring means 11. A counterweight 40 is fixedly attached to the shaft 31 and extends therefrom in .a direction such that the counterweight tends to turn the shaft to bring the holding pin into a vertical position in holding engagement with the straight edge of the semi-disc shaped holding member 29 on the vertical shaft 12 after the switches have been closed.

In order to maintain the holding pin 39 in its holding position so that the switches will normally remain closed after having been manually closed by the rotation of the vertical rod 12, a stop member in the form of a latch cam 41 is fixedly mounted on the horizontal shaft 31. The latch cam 41 is longitudinally spaced from the holding pin 39 and has a spiral outer surface or face 42 terminating in a radial shoulder or face 43 which is substantially in longitudinal alignment with the holding pin 39 so that the shoulder or face 43 of the cam extends vertically from'the shaft when the holding pin 39 is in holding engagement with the semi-disc shaped holding member 29. The shoulder or face 43 of the latch cam, when the holding pin 39 is in holding position, is adapted to be engaged by a stop member 'in the form of .an idle roller 44 journaled between the spaced apart parallel legs 45, 46 of an elongated U- shaped pivoted lever or member 47. The outer ends of the legs 45, 46 are pivotally mounted on a pin 48 extending through a spaced apart pair of dependinglugs 49, 50, carried by a roller51 journaled between a spaced "apart pair of bracket supporting members 52, 53 secured to the underside of the base member 34. The roller 51 is provided with lateral arms 54, 55 projecting outwardly from opposite sides thereof. Threaded bolts 56, 57, threaded in a threaded opening in the arms 54, 55, respectively, with their upper ends engaging the under surface of the base member 34, provide means for tilting the depending lugs 49, 50, thereby adjusting the roller 44 toward and away from the face of the latch cam 41. The inner end of the U-shaped member 47 has an elongated U-shaped extension 58 secured thereto as by welding, and the outer free end of the extension 58 extends through a depending U-shaped support member 59 secured to the underside of the base member 34. The U-shaped support member 59 is vertically adjustably mounted on the base member 34 by means of adjusting nuts so that the member may be raised or lowered to vary the depth of engagement between the roller 44 and the latch cam 41.

The knock-out latch mechanism, indicated generally at 18, for automatically releasing the latch mechanism 17, is shown as comprising a motor 60 mounted on the base member 34; a disc 61 fixedly mounted on a projecting end portion 62 of the armature shaft of the motor for rotation therewith; a centrifugal knock-out disc 63 pivotally mounted on the disc 61 and provided with a slot 64 through which the armature shaft of the motor project-s; a pivotally mounted mercury switch 65; a hotshot battery66 mounted on the support base 34; a control switch 67; an electrical circuit, indicated generally at 68, connecting the motor 60, mercury switch 65, battery 66, and control switch 67 in series; an upstanding arm 69 having its lower end secured, as by Welding, to the inner end of the pivoted lever 47 and projecting upwardly through an opening 70 in the base member 34 and having a lateral extension 71 on its upper'end carrying a plate 72 positioned to be engaged by the centrifugal knock-out disc 63 when the disc rotates about the armature shaft of the motor; and a shell-like cover member 73 enclosing the motor and battery and detachably connected to the base member 34.

The motor 60 may be of any suitable type, preferably and as shown, it is a 7 volt, 10 amp. full load, D. C. motor.

The disc 61 is fixedly mounted on a projecting end of the armature shaft 62 of the motor for rotation therewith and carries a laterally projecting pin 74. The centrifugal disc 63 is pivotally mounted on the pin 74 and the slot therein through which the armature shaft 62 projects, is in the shape of an arc having the pin 74 as a center. This construction permits the centrifugal disc 63 to swing outwardly about the pin 74 to the limit imposed by the end of the slot 64 so that, as the disc 63 rotates, it will engage the plate 72 and, through the arm 69, swing the lever 47 upwardly about its pivot, thereby raising the roller 44 out of engagement with the shoulder of the latch cam 41.

The mercury switch 65 may be of any usual suitable type and is shown as mounted on a carriage member 75 which is pivotally mounted on a stub shaft 76 projecting inwardly from the side wall of the cover member 73 so that the switch normally is closed. The carriage 75 is provided with an integral downwardly extending arm 77, by which it is tilted about its pivotal axis by means of a link 78 pivotally connected to the arm 77 and an extension 79 project-ing laterally from the plate 72. The construction being such that, when the plate 72 is lifted by the rotation of the centrifugal disc 63, the link 77 will tilt the mercury switch from its normally closed position to a position in which the switch will be opened.

The battery 66 may be of any suitable usual type. It is shown as a hot-shot 9 volt, 6 cell battery having one of its terminals connected to one terminal of the mercury switch and the other of its terminals connected to one terminal of the control switch 67.

The motor 60 is connected to the other terminal of the mercury switch 65 and to the. other terminal of the control switch 67. This arrangement permits the battery to operate the motor when both the control switch 67 and the mercury switch 65 are closed.

:The control switch 67 may be of any suit-able usual type and is adapted to be operated by any type of cur rent sensitive protective device, such as an overload relay, diagrammatically shown at '80, which acts to close the normally open control switch 67 in response to abnormal current flowing through the power take-off lines to the transformers or to other difliculties which adversely affect the transformers and thereby actuate the current sensitive protective device.

From the foregoing description, the manner in which the apparatus of the invention is employed to manually close and automatically open a group of high tension electrical switches S used in a power take-off line to a customers transformers is believed apparent.

The switches S are normally maintained in a closed position against the pressure of the spring means 11 which tends to turn the vertical shaft 12 in a direction to open them, by the roller 44 engaging the latch cam 41, thereby preventing rotation of the horizontal shaft 31 and maintaining the holding pin 39 in holding engagement with the semi-disc shaped holding member 29, thereby preventing the rotation of the vertical shaft 12 to open the switches S.

When the high tension switches S are closed, the electric circuit 68 connecting the battery 66 to the motor 60 through the mercury switch 65 and control switch 67, is open circuited as the control switch 67 is normally maintained in open position while the mercury switch is normally maintained in closed position. Whenever an abnormal flow of current flows through the power takeoff line in which the switches S are mounted or whenever, for any predetermined reason, the current sensitive protective device 80 with which the control switch 67 is associated, acts to close the switch 67, the circuit 68 will be closed circuited and the battery 66 will cause the motor to operate. As the motor starts rotating, the centrifugal knock-out disc 63 will be swung outwardly pivoting about the pin 74 by centrifugal force until it has reached a limit imposed by the slot 64 through which the motor armature shaft extends. When in this position, the knock-out disc 63 will engage the plate 72 and, through upright arm 69, swing the pivoted lever 47 upwardly about its pivotal axis, thereby raising the roller 44 out of engagement with the latch cam '41. As a result, the shafts 31 and 12 are free to be rotated by the spring means 11 and the switches S are automatically opened. When the plate 72 is raised by the knock-out disc 63, the mercury switch 65 is tilted by means of the link 78 to cause the switch to open, thereby opening the circuit 68 and causing the motor to stop. When the motor stops, the knock-out disc 63 will generally return by gravity to the position shown in Figs. 4 and 8 of the drawings, due to the fact that it can rotate freely about the pin 74 to the limits of the slot 64. Regardless of the position of the knock-out disc 63 when the motor stops, it will never extend above the disc 61 when at rest.

When the roller 44 is lifted and the latch cam 41 turns, the roller 44 rests on top of the latch cam after the motor has stopped. When the switches S are again closed against the pressure of the spring means 11, the counterweight 40 will cause the horizontal shaft to rotate so that the roller 44 will drop back to the latched position in engagement with the face 43 of the latch cam 41.

From the foregoing description, it readily will be seen that there has been provided novel and improved apparatus for operating as a unit a gang of high tension electric switches including manually operable means for closing the switches, latching means for normally holding the switches closed, and automatic means for opening the switches in response to actuation by a current sensitive device; apparatus particularly adapted for opcrating a group of high tension electric switches forming a multipole switch used in the take-off power line where the power line enters the customers transformer station to disconnect the power line whenever a predetermined abnormal current enters the customers transformers.

While the apparatus of the invention has been described as operating the gang of high tension electric switches to manually close them and automatically open them, obviously, the apparatus can be employed just as readily to manually open the switches and automatically close them. While the apparatus of the invention has been illustrated and described as operating a triple pole switch made up of three high tension switch units of the rotating insulator type, obviously, it could just as readily be employed to operate double pole or single pole switches made up of high tension switch units of the rotating insulator type. And while the motor employed as an unlatching device has been shown and described as operated by a battery supplied current, obviously, the current can come from any suitable source and may be D. C. or A. C. and of any voltage suitable for the particular motor employed.

Obviously, too, the invention is not restricted to the particular embodiment thereof herein shown and described.

What is claimed is:

1. Apparatus for operating a group of high tension electric switches of the rotating insulator type comprising a horizontal rod pivotally connected to the rotating insulator of each of said switches for turning the rotating insulators as a unit to simultaneously open and close all of said switches; .a vertical rotatable shaft having its upper end connected to turn the rotating insulator of one of said switches and having a radially projecting holding member fixedly mounted thereon intermediate its ends; spring means normally biasing said vertical shaft to cause it to turn in one direction; manual means for turning said shaft in the other direction; latching means including a horizontal rotatable shaft carrying a holding member adapted to engage said holding member mounted on said vertical shaft for normally holding said vertical shaft in the position to which it has been manually turned against the pressure of said spring means; and electrically operated unlatching means including a motor connected in an electrical circuit for knocking out said latching means whenever a current is caused to flow in said circuit, thereby permitting said spring means to operate said switches.

2. Apparatus as set forth in claim 1, wherein the holding member fixedly mounted on said vertical shaft is in the form of a semi-disc shaped member mounted on the vertical shaft so that its straight edge will extend in a direction substantially parallel to the axis of said horizontal shaft when said vertical shaft has been manually turned to a position to operate said switches against the pressure of said spring means; and wherein the holding member carried by said horizontal shaft is in the form of a pin projecting radially from said horizontal shaft and mounted on said shaft so as to project therefrom in a vertical direction and in engagement with said straight edge of said semi-disc shaped holding member on said vertical shaft when said switches are in the posiion to which they have been manually turned.

3. Apparatus as set forth in claim 1, including a stop member fixedly mounted on said horizontal shaft and longitudinally spaced from said holding member mounted thereon; and wherein said latching means includes a pivoted lever extending transversely above said horizontal shaft and carrying a stop member positioned to engage said stop member fixedly mounted on said horizontal shaft to hold said horizontal shaft in a position so that the holding members carried by said vertical shaft and said horizontal shaft will be in engaged position to hold said vertical shaft against rotation by said spring means;

and means limiting the downward swing of said pivoted leverso that said stop member carried thereby will normally be held by gravity in engagement with said stop member fixed on said horizontal shaft.

4. Apparatus as set forth in claim 3, wherein the means for limiting the downward swing of said pivoted lever comprises a depending vertically adjustable U-s'haped member in which the outer free end of said 'pivoted lever is received and supported.

5. Apparatus 'as set forth in claim 3, wherein said stop member carried by said pivoted lever is in the form of an idle roller and wherein said stop member fixedly mounted on said horizontal shaftis in the form of a cam member having a radially extending face adapted to be engagedb'y said roller when in latching position and an outer face extending outwardly in a spiral direction from said shaft.

6.-Apparatus as set forth in'claim 5, wherein means are-provided for adjusting theposition of the pivotal axis of said pivoted lever so that said roller may be moved toward and away from the radial face of said cam, including a pivotally mounted member having at least one integral depending arm carrying an axis pin-and a pair of integral oppositely positioned laterally extending arms, each having a threaded adjusting bolt extending therethrough whereby said depending arm can be'angularly adjusted, and wherein the pivoted end of said lever is pivotally mounted on said axis pin.

7. Apparatus as set forth in claim 5, wherein said pivoted lever has an upstanding arm fixedlysecured thereto intermediate its ends, said arm having a lateral extension on its upper end positioned to be engaged by said unlatch'ing'means to swing said pivoted lever upwardly about its pivotal axis so that said roller will be lifted out of engagement with said latch cam member.

8. Apparatus as set forth in claim 7, wherein the electrically operated unlatching means includes a battery connected in said circuit to supply the-current for operating said motor, and wherein said circuit includes a normally open switch adapted to be closed in response to actuation by a current sensitive device.

9. Apparatus as setforth in claim 8, wherein the electrically operated unlatching means includes a centrifugal knock-out disc mounted on the armature shaft of said motor so that as the armature shaft rotates said knockout disc will be swung outwardly by centrifugal force and follow a path which will bring it into engagement with said lateral extension on said arm connected to said pivoted lever and thereby cause said pivoted lever to be swung upwardly a sufiicient distance to raise said idle roller out of engagement with the radial face of said latch cam.

10. Apparatus as set forth in claim 9, wherein a disc is fixedly mounted on the armature shaft of said motor and carries a laterally projecting pin; and wherein said knock-out disc is pivotally mounted on said laterally projecting pin and is provided with a slot in the shape of an arc with said laterally projecting pin as its center and through which slot the armature shaft of said motor loosely projects.

11. Apparatus as set forth in claim 9, including a mercury switch connected in said electrical circuit connecting said battery and said motor, said mercury switch being pivotally mounted in a position to normally maintain the switch closed; and means connecting said mercury switch to said lateral extension on said arm connected to said pivoted lever so that when said centrifugal knockout disc raises said arm said mercury switch will be tilted to open position, thereby shutting off the current to said'motor.

12. Apparatus for operating a high tension electric switch of the rotating insulator type comprising a vertical rotatable shaft having its upper end connected to turn the rotating insulator of said switch and having a holding member fixedly mounted thereon intermediate its ends;

spring means normally biasing said shaft to cause it to turn in one direction to operate s'aid switch; manual means for turning said shaft in the other direction to operate said switchflatc'hing means including a horizontal ro tatable shaft carrying aholding member adapted to engage said holding'member mounted lon'said vertical shaft for normally holding saidivert-ical shaft in the position to which it-has beenmanually'turned against the pressure of said spring means; and unlatching means including an electrically operated device connected in an electrical circuit for knocking out said latching means whenever a current is caused to flowin said circuit, thereby permitting said spring means to operate said switch.

13. Apparatus as s'efforthdn claim 12, wherein the holding member fixedly mounted on said vertical shaft is in the form of a semi-disc shaped member mounted on the vertical shaft so that its straight edge will extend in a direction substantially parallel to the axis of said horizontal shaft when said vertical'shaft has been manually turned to a position to operate said switches against the pressure of said spring means; and wherein the holding member carriedby said horizontal shaft is in the form of a pinp-rojecting radially from said horizontal shaft and mounted on said shaft so as'to'project therefrom in a vertical direction and in engagement with said straight edge of said semi-disc shaped holding member on said vertical shaft when said switch is in the position to which it has been manually turned.

14. Apparatus as set forth in claim 12, including a stop member fixedly mounted on said horizontal shaft and longitudinally spaced from said holding member mounted thereon; and wherein said latching means includes a pivoted lever extending transversely above said horizontal shaft and carrying a stop member positioned to engage said stop member fixedly mounted on said horizontal shaft to hold said horizontal shaft in a position so that the holding members carried by said vertical shaft and said horizontal shaft will be in engaged position to hold said vertical shaft against rotation by said spring means; and means limiting the downward swing of said pivoted lever so that said stop member carried thereby will normally be held by gravity in engagement with said stop member fixed on said horizontal shaft.

15. Apparatus as set forth in claim 14, wherein said stop member carried by said pivoted lever is in the form of an idle roller and wherein said stop member fixedly mounted on said horizontal shaft is in the form of a cam member having a radially extending face adapted to be engaged by said roller when in latching position and an outer face extending outwardly in a spiral direction from said shaft.

16. Apparatus as set forth in claim 14, wherein said pivoted lever has an upstanding arm fixedly secured thereto intermediate its ends, said arm having a lateral extension on its upper end positioned to be engaged by said unlatching means to swing saidpivoted lever upwardly about its pivotal axis so that said roller will be lifted out of engagement with said latch cam member.

17. Apparatus as set forth in claim 14, wherein said electrically operated device comprises a motor connected in said circuit and having a centrifugal knock-out disc mounted on its armature shaft so that as the armature shaft rotates said knock-out disc will be swung outwardly by centrifugal force and follow a path which will bring it into engagement with said lateral extension on said arm connected to said pivoted lever and thereby cause said pivoted lever to'be swung upwardly a suflicient distance to raise said'idle roller out of engagement with said latch cam.

18. Apparatus as set forth in claim 17, wherein a disc is fixedly mounted on the armature shaft of said motor and carries a laterally projecting pin; and wherein said knock-out disc is pivotally mounted on said laterally pro jecting pin and is provided with a slot in the shape of an arc with said laterally projecting pin as its center and through which slot the armature shaft of said motor loosely projects.

19. Apparatus as set forth in claim 17, including a mercury switch connected in said electrical circuit to said motor, said mercury switch being pivotally mounted in a position to normally maintain the switch closed; and means connecting said mercury switch to said lateral extension on said arm connected to said pivoted lever so that when said centrifugal knock-out disc raises said arm said mercury switch will be tilted to open position, thereby shutting ofi? the current to said motor.

20. Apparatus as set forth in claim 17, including a battery connected in said circuit to supply the current for operating said motor and wherein said circuit includes a normally open switch adapted to be closed in response to actuation by a current sensitive device.

No references cited.

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