US2781424A

US2781424A - Electrical controlling apparatus

Info

Publication number: US2781424A
Application number: US390873A
Authority: US
Inventors: James W Woolf
Original assignee: Joy Manufacturing Co
Current assignee: Joy Manufacturing Co
Priority date: 1953-11-09
Filing date: 1953-11-09
Publication date: 1957-02-12
Anticipated expiration: 1974-02-12

Description

Feb. l2, 1957 J. w.'woo| F 2,781,424

I ELECTRICAL CONTROLLING APPARATUS I Filed Nov. 9, 1953 2 Sheets-Sheet 1 Feb. 12, 1957 J. w. wooLF ELECTRICAL CONTROLLING APPARATUS 2 Sheets-Sheet 2 Filed Nov. 9, 1955 .ggf/.fluff A fo 4? nited States Patent O ELECTRICAL CONTRLLING APPARATUS llames W. Woolf, Franklin, Pa., assignor to Joy Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Appiication November 9, 1953, lSerial No. 390,873 13 Claims. (Cl. 200 1) This invention relates to electrical controlling apparatus and more particularly to motor reversing apparatus having means forpreventing destructive arcing.

lt is an object of the invention to provide an improved motor reversing apparatus. Another object is to provide an improved motor reversing apparatus for preventing arcing. A further object is to provide an improved motor reversing apparatus for use with a motor having a main power circuit and a controlling pilot circuit and including means for interrupting the pilot circuit before the reverse switch elements can be moved. Still another object is to provide an improved motor controlling and reversing apparatus having separate control elements for separating and for moving to diierent relations for reverse operation the `contact elements of a reverse switch. Other objects and advantages of the invention will hereinatter more fully appear.

In the accompanying drawings, in which one embodiment of the invention is shown for purposes of illus tration:

Fig. l is a front end view of a reverse switch mechanism constructed in accordance with the invention.

Fig. 2 is a central longitudinal section on the plane of the line 2 2 of Fig. l.

Fig. 3 is a sectional view, similar to Fig. 2, showing a dierent position of the parts in which the pilot circuit is open.

Fig. 4 is a sectional View similar to Figs. 2 and 3 showing the reverse switch contacts also open.

Fig. 5 is a transverse section on the plane of the line 5 5 of Fig. 2.

Fig. 6 is a view corresponding to Fig. 5 and showing the main reverse controlling contacts in their other position.

Fig'. 7 is an end view of the switch mechanism of Fig. 1 showing the opposite end of the latter.

Fig. 8 is alongitudinal sectional view on the plane of the line 8 8 of Fig. 7 showing both the pilot and the main reverse contacts closed.

Fig. 9 is a transverse sectional view on the plane of the line 9 9 of Fig. 8 showing the stationary main reverse switch contacts etc. V

Fig. i0 is a transverse section looking in the opposite direction from Fig. 9, but taken on the same plane and showing the movable reverse switch contacts etc.

Fig. l1 is a wiring diagram showing the controlling apparatus of the invention in use in a simple circuit.

Referring to the drawings, it will be noted that in Fig. 11 a very much simplified wiring diagram has been provided to show the `control system for a direct current motor of such size that the progressive cutting out of resistance during motor starting is unnecessary, and from this view certain conventional protective devices such as overload protection means are omitted to make the drawing as simple as possible.

Power lines 1 and 2 may be connected with conductors 3 and 4 by

switch elements

5 and 6 which are connected for movement together by an appropriate connecting ele- 2 ment 7 of insulating material. An armature 8 is movable under force exerted thereon by a solenoid 9 to control the movements of the switch including the

parts

5, 6 and 7, which switch may be characterized as a main line switch. The conductor 3 leads to the series ield 11 of a motor 12, and also to the shunt lield 13 of the motor. The motor armature is designated 14 and has a c0mmutating winding 15 associated with it. A conductor 16 connects the shunt field to the conductor 4. At 18 there is diagrammaticaliy shown the reverse switch mechanism of this application. This reverse switch includes a Contact 29 connected to the conductor 4; another contact 21 connected by a conductor 22 to the end of the series iield which is not connected to the conductor 3; a third contact 23, connected to the commutating winding 15, and a contact 24 connected by a conductor 25, through appropriate brush means, with the armature 14. A pilot switch element 26, ringlike in shape as will later be explained, and constituting a conductor and contact element and forming a portion of the apparatus shortly to be more fully described in detail, is adapted to connect

stationary contacts

27 and 28, of which 27 is connected by a conductor 29 to one end of the solenoid 9, while 28 is connected by a conductor 30 with the power line 1. The other end of the solenoid 9 is connected with a conductor 31, between which Vand a further conductor 32 connected with the power line, there are arranged a suitable starting switch 33 and a suitable stop switch 34. These switches are connected by a. conductor 35 which is in turn connected by a conductor 36 to a contact element 37, and the contact element 37 is connectable by a movable contact 33 with another contact element 39 connected as at 40 to the conductor 31. Contact element 37, movable contact 38 and contact element 39 constitute an interlock switch. The contact element 38 is connected by a suitable non-conducting element 41 with the armature 8. The way in which the structure so far de* scribed operates will be readily understood. On closing movement of the starting switch (shown as a push button) 33, a circuit will be established through conductor 32, normally closed'stop switch 34, conductor 35, start switch 33, conductor 31, solenoid 9, conductor

29thenclosed pilot switch

27, 26, 28 and conductor 30 to the power line 1. The solenoid 9 then moves the armature 8 to bring the

main line switch

5, 6, 7 to closed position, and thereupon the interlock switch V38 will be moved to establish connections between the ycontact elements 37 and 39, establishing a holding circuit through the solenoid by which the starting push button switch 33 and a portion of the conductor 31 will be shunted by the conductor 36,

interlock switch

37, 38, 39 and conductor 40. Thereafter, until the stop switch 34 is opened, the main line switch will be maintained closed, even though the start switch 33 is allowed to open. Upon closing of the main line switch, the motor 12 will operate in one direction or the other7 depending upon the position of the reverse switch mechanism 18, this reverse switch in different positions being effective respectively to connect

contacts

20 and 23, and

contacts

24 and 21 to eiect motor rotation in one direction, or to connect

contacts

20 and 24 and

contacts

23 and 21 to effect motor rotation in the other direction. Whenever the reverse switch is to be moved, the pilot switch 26 will first be opened, as will later be explained, resulting in the breaking of the circuit through the solenoid 9, and movement to open position of the

main line contacts

5 and 6 before movement of the reverse switch to elect a reversal of connections will be possible. n

Now, taking up in some detail the reverse switch structure shown in Figs. l to l0, it may. beobserved that the improved device therein disclosed includes a ,built-up supporting structure 45 comprising a cover plate 46, a spaced rear plate 47, spacer sleeves 48, elongated connecting studs 49 and nut and lock washer devices S0. The rear plate 47 is constructed of insulating material and carries a series of four contact elements, these being respectively designated C1, C2, C3 and C4, each of these contact elements being received in a socket 52 formed on the plate 47 and held in position by a threaded element 53 which has a rotation preventing head portion at the opposite side of the plate 47 from the contact element.

The threaded element 53 has an enlarged portion 55 with which a nut 56 cooperates to secure a conductor thereto. As shown in Fig. 9, the contact elements C1, C2, C3 and C4 are arranged at the four corners of a square, and they are so spaced apart rthat a pair of pilot contacts 61 and 62 generally similarly supported by the plate 47 may be arranged within the rectangle formed by thc disposition of the four contacts C1, C2, C3 and C4, and be connected by a ring contact 65 of such diameter that it contacts none of the contacts C1, C2, C3 and C4. The ring contact 65 is supported on a boss 67 carried or formed on a support element 68 whose relationship to other parts will be later explained.

A disc or plate element 71B of insulating material carries a pair of tie bars or .connector elements later more fully described and these in turn support movable contacts K1, K2, K3 and K4 which are provided for cooperation with the stationary contacts C1, C2, C3 and C4. rl`l1e movable contacts are rotatable (through approximately 90) about an axis perpendicular to the insulating plate '70, and also movable bodily towards and into contact with and away from and out of contact with the stationary contacts. Screw or stud elements 72 having heads 73 and lock washers 74 secure the movable contacts to the connector elements, two movable contacts to each connector element, and are also adapted to secure conductors to the movable contacts. The contacts K1, K2, K3 and K4 are, like the contacts C1, C2, C3 and C4, arranged at the corners of a square, such square of the same side length as the square at whose corners the contacts C1, C2, C3 and C4 are arranged, and the disc or plate element 70 is so disposed that its center is opposite the central point of the square at whose corners the contact elements C1, C2, C3 and C4 are arranged. The insulating plate o1' disc element 74B is resiliently supported upon a support element 76. The element 76 has at its opposite ends projecting ear portions 77 through which there extend and on which there are mounted support elements 80 surrounded by springs 81 and secured as at 82 to the plate element 70. The support elements 8i) extend through openings 83 in the ears 77 and, accordingly, the plate 70 and the contacts K1, K2, K3 and K4 are yieldably supported by the element 76, but also, when the element 76 is rotated, as will shortly be explained, the elements 8th, and so the plate element 70, and so the contacts K1, K2, K3 and K4 are rotatable on an axis perpendicular to the plate element 71B. The ears 7'7 of the element 76 are mounted on arm portions 84, which are supported by a central transverse portion 85 of the element 76, and vwhich extend at right angles tothe length of the portion 85. The portion S has a projecting boss 86 which is pinned at 87 to an enlarged socketed hub portion 88 of the support element l68 which carries the boss 67, and a spring 90 presses the ring contact element 65 toward the stationary pilot contacts, but is yieldable to provide a certain amount of play of the ring contact along the boss. .Any suitable means, such as la cotter pin 91 prevents escape of the ring contact 65 from the boss.

The pin 87 also connects the element 76 to the reduced end portion 92 of a collared shaft A93 whose collar 94 has the transverse portion 85 of the element 76 against it. The shaft 93 is rotatably supported by the end plate 46 and extends through a boss or sleeve portion 97 which itself extends from the inner side of the plate 46 towards rthe plate 47. Suitable means for effecting longitudinal movement of the shaft 93 relative to the plate 46 and contactbetween thecontacts of the series K1, K2, K3 and K4 and the contacts of the series C1, C2, C3 and C4, is provided in the form of a hand wheel 1119, between which (as shown) and an outwardly extending externally threaded boss 101, there is a 4threaded connection at 162. The shaft 93 has a reduced outer end portion 104, and to this outer reduced portion there is pinned at 1115 a handle element 106 by means of which the shaft 93 may at times be rotated. Between the handle element 166 and a shoulder 103 on the shaft 93, there is received with a small degree of longitudinal play an inturned flange 109 carried by the hand wheel 100.

Returning to the support element 76, it may be noted that the arm portions S4 thereof have at their outermost ends further short, inturned, arm portions 1111, these being disposed diametrically cppositely from each other, and each being adapted to engage with

stationary stop portions

113, 113, diametrically projecting from the sleeve portion 97 and with

other stop portions

113, 113 formed on the boss or sleeve portion 97. The

stop portions

113, 113 extend for the full length of the boss 97, the

stop portions

113, 113 are at the inner end of the boss. Between the

stop portions

113 and 113 are slots 114 of a width to receive the arm portions 111 when the support element 76 is in extreme lett position, as in Fig. 2, and in their extreme right position, as in Pig. 4, lthe arm portions 111 are moved out of the slots 110i, and the support element 76 can be turned some 90. The stop portions 113', 115 are so spaced and the arcuate extent of the inturned arm portions 111 are of such width that the element 76 may be selectively disposed in two positions in each of which the transverse portion 35 of the clement 76 is Vat right angles to its other rotated position.

The rotatably supported contacts K1, K2, K3 and K4 have been noted to be carried and connected together in pairs by tie bars or connector elements 115, which are made of good conducting material. The tie bars or connector elements 115 are received in recesses 116 formed by upstanding flanges 117 on the plate element '7n and are held in the recesses as by pins 118. The 'tie bars are held away from the bottoms of the recesses 116 by narrow rib portions 119 formed on the plate element 7@ and extending transversely of the recesses and midway between the ends of the latter.

It will be appreciated that the handle element 106 can position the support element "I6 in either of its rightangularly related positions by rotation of the shaft 93, and it may be noted that the amount of play between the collar 94 on this shaft yand the inner end of the boss 97 is equal to the play of the inturned flange 169 lengthwise of the reduced portion 104 of the shaft 93 adjacent the other endof such shaft. The distance the hand wheel 10i) can be moved along the threaded boss 101 is suicient to separate the ring contact rather widely from the stationary pilot kcontacts, 61, 62, and thereafter to permit movement of the contacts K1, K2, K3 and K4 out of spring-pressed engagement with the stationary contacts C1, C2, C3 and C4, and finally movement of the arm portions 111 out of the slots or grooves 114.

The mode of operation of the structure which has been described may now be noted. ln the position of the parts shown in Fig. 2, the ring contact 65 is pressed very firmly into engagement with the pilot contacts 61 and 62, and thesprings 81 are pressing the insulating plate towards the end plate 47 so that irm contact is establish-d between the mutually opposite contacts of the K and C series. Now, if it is desired to effect a reversal of the motor, the hand wheel 10i? will be run out along the threaded boss 161 and this will cause substantial separation of the ring Contact 65 from the stationary pilot contacts 61 and 62 to take lplace (as shown in Fig. 3), while the main switch contacts of the K and C series are still pressed together and have not opened any circuit.

The opening ofthe pilot circuit will cause the main line switch to drop open and therefore no current will be average owing between the contacts of the C and K series and through the connector elements 115 in the position of the parts shown in Fig. 3. Note that in Fig. 3, as compared with Fig. 2, the connector elements 80 have had the support element 76 moved to the right along them, and the distance between the ears 77 and the insulating plate 70 has substantially increased. A slight further outward movement of the hand wheel 100 lalong the threaded boss 101 from the position shown in Fig. 3 to that shown in Fig. 4 will cause the arm portion 111 to move out from slots or grooves 114 in which they have been held in a locked position, and then the shaft 93 may be rotated by the handle 106 to rotate the support element 76 and with it the contacts of the K series, to reposition the contacts of the K series `at 90 from the position they occupied in Fig. 2. It should here again be noted that the stop portions 113', 113 limit the angle through which the element 76 can be turned in such a manner that the contacts of the K series in opposite extreme limits of rotation of the shaft 93 always come opposite contacts of the C series.

After the new position of the contacts of the K series has been effected by rotation of the shaft 93 by the handle element 106, the hand wheel 100 may be caused, by reverse rotation thereof, to move the element 76 to the left in Fig. 4, and thereupon both the contacts of the K series and the ring contact will be moved to the left in Fig. 4. The K series contacts will engage the C series contacts rather promptly and thereby connections for causing reverse operation of the motor 12 will be established, so that lafter further rotation of the hand wheel 100 and engagement of the ring contact 65 with the pilot contacts 61 and 62, with resultant energization of the solenoid 9 and closure of the

main switch

5, 6, 7 the motor 12 will be caused to operate in the reverse direction.

With the mention of one further item, a complete understanding of the invention will have been made possible. The threaded connection 102 is made with such comparatively fine threads that the time requisite for moving the moving contact system between a point at which the pilot circuit is opened and a return to such position after shifting of the reverse contacts has been effected, is so great that if the motor armature has not indeed ceased to rotate, its rate of rotation will b e so very slow that no harm can come from the reapplication of current to the motor windings.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration, and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What is claimed is:

1. In a reverse switch, ya shaft, means for supporting said shaft for rotation on its axis and for bodily longitudinal movement, reverse switch contacts carried by said shaft and yieldingly supported thereby for movement 1ongitudinally of the latter, relatively station-ary reverse switch contacts, a handle for turning said shaft on its axis to change the relation of said first contacts to the second contacts to effect connections for reverse operation, means for preventing rotation of said shaft upon its axis when it is in a predetermined longitudinal relation to its supporting means, a second handle having a connection with said means for supporting said shaft for causing said second handle to undergo movement, upon rotation, in a direction lengthwise of sai-d shaft and also having a connection with sai-d shaft for moving the latter longitudinally with it, and a pilot switch arranged for opening and closing by said shaft, said means for preventing rotation of said shaft including an interlock controlled by longitudinal movement of said Vshaft and requiring said reverse switch contacts carried by said shaft to be 6 moved -in a direction longitudinal of said shaft to open circuit position'before said shaft can be rotated.

2. In a reverse switch, a shaft, means for supporting said shaft for rotation on its axis and for bodily longitudinal movement, reverse switch contacts carried by said shaft and yieldingly supported thereby for movement longitudina'lly of the latter, relatively stationary reverse switch contacts, a handle for turning said shaft on its axis to change the relation of said first contacts to the second contacts to effect connections for reverse operation, means for preventing rotation of said shaft upon its laxis when it is in a predetermined longitudinal relation to its supporting means, a second handle movable 4in a direction lengthwise of said shaft and also having a connection with said shaft for moving the latter longitudinally with it, and a pilot switch arranged for opening and closing by said shaft, said means for preventing rotation of said shaft including an interlock controlled by longitudinal movement of said shaft and requiring saidreverse switch contacts carried by said shaft to be moved in a direction longitudinal of said shaft to open circuit position before said shaft can be rotated and said second handle having means for maintaining it in positions in one of which said reverse switch contacts are in open position and in another of which said pilot switch is closed.

3. In a reverse switch, a shaft, means for supporting said shaft for rotation on its axis and for bodily longitudinal movement, reverse switch contacts carried by said shaft and yieldingly supported thereby for movement longitu-dinally of the latter, relatively stationary reverse switch contacts, a handle for turning said shaft on its axis to change the relation of said first contacts to the second contacts to effect connections for reverse operation, means for preventing rotation of said shaft upon its axis when it is in a predetermined longitudinal relation to its supporting means, a second handle having a connection with said means for supporting said shaft for causing said Second handle to undergo movement, upon rotation, in a direction lengthwise of said shaft and also having a connection with said shaft for moving the latter longitudinally with it, and a pilot switch arranged for opening and `closing by said shaft, said means for preventing rotation of said shaft including an interlock controlled by longitudinal movement of said shaft and requiring said reverse switch contacts carried by said shaft to be moved in a direction longitudinal of said shaft to open circuit position before said shaft can be rotated and said connection between said second handle and said means for supporting said shaft providing for relatively slow movement of said second handle as the latter is manually rotated.-

4. In a reverse switch, a shaft, means for supporting mined longitudinal relation to its supporting means, a

second handle coaxial with said shaft and having a connection with said means for supporting said shaft for causing said second handle to undergo movement, upon rotation, in a direction lengthwise of said shaft and yalso having a connection with said shaft for moving the latter' longitudinally with it, and a pilot switch arranged for opening and closing by said shaft, said means for preventing rotation of said shaft including an interlock controlled by longitudinal movement of said shaft and requiring said reverse switch contacts carried by said support means to be moved in a direction longitudinal of said avergli-24,

shaft to open circuit position before said shaft can be rotated.

5. In an apparatus of the character described, in combination, a frame, a shaft supported by said frame for rotation and for longitudinal movement, means for rotating said shaft, a support element carried by said shaft, means for moving said shaft longitudinally, means for preventing rotation of said shaft except when it occupies a predetermined longitudinal relation with respect to said frame, a pilot switch movable between open and closed positions by said shaft .and in open position when said shaft is in such predetermined longitudinal relation with respect to said frame, reverse contacts carried o-n said support element and rotatable by rotation of said shaft, said support element moving said reverse contacts `axially of said frame to open circuit position during movement of said shaft to said predetermined longitudinal relation with respect to sai-d frame.

6. In an apparatus of the character described, in combination, a frame, a shaft supported by said frame for rotation and for longitudinal movement, means for rotating said shaft, a support element carried by said shaft, means for moving said shaft longitudinally, means for preventing rotation of said shaft except when it occupies a predetermined longitudinal relation with respect to said frame, a pilot switch movable between open and closed positions by said shaft and in open position when said shaft is in such predetermined longitudinal relation with respect to said frame, reverse contacts carried on said support element and rotatable by rotation of sai-d shaft, said support element moving said reverse contacts axially of said frame to open circuit position during movement of said shaft to said predetermined longitudinal relation with respect to said frame and prior to its attainment thereto.

7. In an apparatus of the character described, in combination, a frame, a shaft supported by said frame for rotation and for longitudinal movement, means for rotating said shaft, a support element carried by said shaft and fixed against rotation relative thereto, means for moving said shaft longitudinally, means including arm portions carried by said support element for preventing rotation of said shaft except when it occupies a predetermined longitudinal relation with respect to said frame, a pilot switch movable between vopen and closed positions by said shaft and in open position when said shaft is in such predetermined longitudinal relation with respect to said frame, reverse contacts carried on said support element and rotatable by rotation of said shaft, said support element moving sai-d reverse contacts axially of said frame to open circuit position during movement of said shaft to said predetermined longitudinal relation with respect to said frame.

8. in an apparatus of the character described, in cornbination, a frame, a shaft supported by said frame for rotation and for longitudinal movement, means for rotating said shaft, a support element carried by said shaft and fixed against rotation relative thereto, means for moving said shaft longitudinally, means including arm portions carried by said support element and coacting portions on said frame for preventing rotation of said shaft except when it occupies a predetermined. longi' tudinal relation with respect to said frame, a pilot switch movable between open and closed positions by said shaft and in open position when said shaft is in such predetermined longitudinal relation with respect to said frame, reverse contacts carried on said support element and rotatable by rotation of said shaft, said support element mov'mg said reverse contacts axially of said frame to open circuit position during movement of said shaft to said predetermined longitudinal relation with respect to said frame.

,9. In an apparatus of the character described, in combination, ,a frame, a shaft supported by said frame for rotation and for longitudinal movement, means for rotating said shaft, a support element carried by said shaft and fixed against rotation relative thereto7 means for moving said shaft longitudinally, means including cooperating locking portions carried by said frame and support element for preventing rotation of said shaft except when it occupies a predetermined longitudinal relation with respect to said frame, a pilot switch movable between open and closed positions by said shaft and in open position when said shaft is in such predetermined longitudinal vrelation with respect to said frame, reverse contacts carried on said support element and rotatable by rotation of said shaft, said support element moving said reverse contacts axially of said frame to open circuit position during movement of said shaft to said predetermined longitudinal relation with respect to said frame.

l0. in an apparatus of the character described, in combination, a frame, a shaft supported by said frame for rotation and for longitudinal movement, means for rotating said shaft, a support element carried by said shaft, means for moving said shaft longitudinally, a pilot switch movable between open and closed positions by long-itudinal movement of said shaft, means for preventing rotation o-f said shaft except when it occupies a predetermined longitudinal relation With respect to said frame, said pilot switch in open position whenever said shaft is in such predetermined longitudinal relation with respect to said frame, reverse contacts carried on said support element and rotatable by rotation of said shaft, said shaft moving said pilot switch to open position and said support element thereafter moving said reverse contacts axially of said frame to open circuit position during movement of said shaft rto said predetermined longitudinal relation with respect to said frame.

ll. in an apparatus of the character described, in combination, `a frame, a shaft supported by said frame for rotation and for longitudinal movement, means for rotating said shaft, a support element connected with said shaft for bodily movement as the latter moves longitudinally, means for moving said shaft longitudinally, a pilot switch movable between open and closed positions by longitudinal movement of said shaft, means for preventing rotation of said shaft except when it occupies a predetermined longitudinal relation with respect to said frame, said pilot switch in open position when said shaft is in such predetermined longitudinal relation with respect to said frame, reverse contacts carried on said support element and rotatable by rotation of said shaft, said shaft moving said pilot switch to open position and said support element thereafter moving said reverse contacts toopen circuit position during movement of said shaft to said predetermined longitudinal relation with respect to said frame.

l2. in an apparatus of the character described, in combination, a frame, a `shaft supported by said frame for rotation and for longitudinal movement, means for rotating said shaft, a support element connected with said shaft for bodily movement as the latter moves longi tudinally, means for moving said shaft longitudinally, a pilot switch movable between open and closed positions by longitudinal movement of said shaft, means releasable upon predetermined longitudinal movement of said shaft for preventing rotation of said shaft except when it occupies a predetermined louvitudinal relation with respect to said frame, said pilot switch in open position when said shaft is in such predetermined longitudinal relation with respect to said frame, reverse contacts carried on said support element and rotatable by rotation of said shaft, said shaft moving said pilot switch to open position and said support element thereafter moving said lreverse contacts to opencircuit position during movement of said shaft to said predetermined longitudinal relation with respect to said frame.

13. In a reverse switch, a shaft, means for supporting said `shaft for rotation on `its axis and for bodily longitudinal movement, support means supported by said shaft for yielding movement longitudinally of the latter, reverse switch contacts carried by said support means, rela-tively stationary reverse switch contacts, a handle for mining said shaft on its axis to change the relation of said rst contacts to the second contacts to effect connections for reverse operation, means for preventing rotation of said shaft upon its axis when it -is in a predetermined longitudinal relation to its supporting means, a second handle surrounding said shaft at one end thereof and having a connection With said means for supporting said shaft for causing said second handle to undergo movement, upon rotation, in a direction lengthwise of said shaft and also having a connection with said shaft `for moving the latter longitudinally with it, and a pilot switch arranged for opening and closing by said shaft,

5 tudinal of said shaft to open circuit position before said shaft can be rotated.

References Cited in the le of this patent UNITED STATES PATENTS 2,231,598 Shroyer Feb. 11, 1941 2,426,306 Houck et al. Aug. 26, 1947 2,512,880 Russell June 27, 1950 2,565,114 Basnett Aug. 21, 1951