US2766352A - Motor protector switch - Google Patents

Description

1956 E. ENDERLI 2,766,352

MOTOR PROTECTOR SWITCH Filed Nov. 9, 1953.

Fig.1 L9- United States PatentO MOTOR PROTECTOR SWITCH Ernst Enderli, Emmenbrncke, Lucerne, Switzerland, as-

signor to Weber A.-G., Emmenbrucke, Lucerne, Switzerland Application November 9, 1953, Serial No. 391,010

Claims. (CL 200-116) The invention relates to motor protector switches of the cam operated type, and has the primary object of providing a switch for the protection of electric motors, particularly for machine tools, against overloads and short circuits.

With this and other objects in view I provide a motor protector switch comprising in combination: for each pole of the switch an insulating carrier body, fixed contacts and movable contact and thermostatic bi-metal elements mounted on each of the said carrier bodies, connecting means holding the said carrier bodies together end-to-end in a single packet, a control shaft and a release shaft both journalled on the said packet of carrier bodies and extending the full thickness thereof, the said control shaft operatively controlling the position of the said movable contacts relative to the said fixed contacts, and the said release shaft having levers opposite of and controlled by the said bi-metal elements, a spring biased free release mechanism linked to the said control shaft and tending to turn the same into a position separating the said movable contacts from the said fixed contacts, and a spring biased pawl normally locking the said free release mechanism in its inoperative position and controlled by the said release shaft, the said pawl releasing the said mech-' anism when the said release shaft is turned by the said bi-metal elements bearing on the said levers.

These and other objects and features of the present invention will be clearly understood from the following description of a preferred embodiment of the invention and of a modification thereof given by way of example with reference to the accompanying drawings, in which:

Fig. 1 is an end elevation of the new motor protector switch, partly broken off so as to show a detail behind the front plate thereof, i

Fig.2 is a plan view of the said motor protector switch,

Fig. 3 is a section along the line 3--3 of Fig. 2,

Figs. 4, 5 and 6 are sections along the line 44 of Fig. 2 in various operational positions, and

Fig. 7 is a section corresponding to Fig. 3 of a modification of the embodiment according to Figs. 1 to 6.

Referring firstly to Figs. 1 to 6, the insulating carrier bodies I carry the fixed contacts 2 with their terminals 8, the movable contacts 3 with their holders 14 and pivots 15, the contact biasing springs 16, the fixing screws 17, as well as the thermostatic bi-metal elements 4 and their holders 18. The holders 14 of the movable contacts 3 are connected to the said bi-metal elements 4 by connecting pieces 19. The release shaft 5 passes through the insulating carrier bodies 1 and carries levers 20 with adjustment screws 21 cooperating with the respective bimetal elements 4. The switchor contact-shaft proper 7 carries cam discs 22 by means of which the movable contacts 3 are operated in cooperation with the rollers 23 thereof. Each of these cam discs 22 has a recess 34 on its circumference.

The front plate 9 forms a shield, indicating the positions 0 and 1 of the switch handle which is mounted on the axle 24. A free release mechanism comprising the linkage 25, 26, 27 and 28 and the release pawl 29 with biasing spring 30, and denoted as a whole 11 in Fig. 2, is arranged between the said switch shaft 7 controlling the contacts 3 and the said switch handle 10. The levers 31 and 32 are fixedly connected to the shafts 7 and 24, respectively. A biasing spring 33 is attached to a pin connecting the front plate 9 to the foremost insulating carrier body 1 at one end, and to the joint between the lever 31 and link 25 on the other end.

A cam 36 connected to the said release pawl 29 and to a dial 12 for the adjustment of the critical current intensity is pivoted at the front of the foremost insulating carrier body 1 and becomes visible and accessible upon removal of the switch lever 10 and front plate 9. The cam 36 cooperates with a leaf spring 37 attached to the release shaft 5. The individual'insulating carrier bodies 1 are held together in a packet by means of screws 13.

In the position illustrated in Fig. 3, the roller 23 of the movable contact 3 is in juxtaposition to the recess 34 in the cam disc 22 so that the biasing spring 16 can press the movable contact 3 resilient against the fixed contact 2 whereby the current is closed. The corresponding position of the switch lever 10 is indicated in Fig. 1, and that of the linkage 25-28, pawl 29 and lever 31 in Fig. 5.

When the switch lever 10 is turned from the position marked 1 on the front plate 9 into the position marked 0, the said linkage is moved into the position shown in Fig. 4, and the shaft 7 with the cam discs 22 (Fig. 3) is turned in the anti-clockwise direction, whereby the rollers 23 are raised out of the recesses 34 and their associated cam discs 22 and the movable contacts 3 are lifted off the fixed contacts 2. The switch is then in the open position, and the linkage in the position of Fig. 4.

When in the closed position of the switch the current intensity exceeds a predetermined limit (as adjusted by the dial 12) the bi-metal elements bend downwards, bear on the adjustment screws 21 of the levers 20 and turn the same and the release shaft 5 to which they are attached in the anti-clockwise direction, whereby the leaf spring 37 attached to the said shaft 5 turns the cam 36 from the position illustrated in Fig. 5 into the position of Fig. 6 against the action of the biasing spring 30 whereby the pawl 29 releases the lever 28. The toggle levers 26, 27 and link 25 accordingly allow the lever 31 to be turned anticlockwise by the action of the spring 33 whereby the switch shaft 7 is turned anticlockwise and the contacts 3 are lifted off the contact 2. Thus the circuit is opened, although the switch lever 10 is in the closed position. The current intensity at which this free release occurs depends on the initial position of the cam 36 which, as mentioned, can be adjusted by means of the dial 12.

After a free release, the switch lever 10 has to be turned first from the position 1 into the position 0 whereby the linkage is returned into the position shown in Fig. 4. When the bimetal elements 4 have cooled down and have retracted into the position shown in Fig. 3, the switch handle 10 can again be turned to the position 1 whereby the linkage returns into the position of Fig. 5 and the cam discs 22 and contacts 3 return into the position of Fig. 3, so that the switch is closed again.

There are as many insulating carrier bodies 1 as there are poles to be controlled, for example three of them as shown in Fig. 2 for a three phase alternating current system.

Referring now to Fig. 7, instead of a release shaft 5 passing through the insulating carrier bodies 1 as in the embodiment of Figs. 1 to 6, a release shaft 35 may be provided which passes outside the said insulating carrier bodies. Apart from this modification, the arrangement according to Fig. 7 corresponds substantially to that of Figs. 1 to 6.

While I have described and illustrated what may be considered typical and particularly useful embodiments of my said invention, I wish it to be understood that I do not limit myself to the particular details and dimensions described and illustrated, for obvious modifications will occur to a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent, is:

1. A motor protector switch comprising in combination: for each pole of the switch an insulating carrier body, fixed contacts and moveable contacts and thermostatic bi-metal elements mounted on each of the said carrier bodies, connecting means holding the said carrier bodies together end-to-end in a single packet, a control shaft and a release shaft journalled on the said packet of carrier bodies and extending both the full thickness thereof, the said control shaft operatively controlling the position of the said moveable contacts relative to the said fixed contacts, and the said release shaft having levers opposite of and controlled by the said bi-metal elements, a spring biased free release mechanism linked to the said control shaft and tending to turn the same into a position separating the said moveable contacts from the said fixed contacts, and a spring biased pawl normally biased for locking the said free release mechanism in its inoperative position and controlled by the said release shaft, the said release shaft being operable to move the said pawl against its bias for releasing the said mechanism when the said release shaft is turned by the said bi-metal elements bearing on the said levers.

2. A motor protector switch as claimed in claim 1, wherein the said release shaft passes through the said packet of insulating carrier bodies.

3. A motor protector switch comprising, in combination, for each pole of the switch an insulating carrier body, fixed contacts and movable contacts and thermostatic bi-metal elements mounted on each of the said carrier bodies, connecting means holding the said carrier bodies together end-to-end in a single packet, a control shaft and a release shaft journalled on the said packet of carrier bodies and extending both the full thickness thereof, the said control shaft operatively controlling the position of the said movable contacts relative to the said fixed contacts, and the said release shaft passing outside the said packet of insulating carrier bodies and having levers opposite of and controlled by the said bi-metal elements, a spring biased free release mechanism linked to the said control shaft and tending to turn the same into a position separating the said movable contacts from the said fixed contacts, and a spring biased pawl normally locking the said free release mechanism in its inoperative position and controlled by the said release shaft, the said pawl releasing the said mechanism when the said release shaft is turned by the said bi-metal elements bearing on the said levers.

4. A motor protector switch comprising, in combination, for each pole of the switch an insulating carrier body, fixed contacts and movable contacts and thermostatic bi-metal elements mounted on each of the said carrier bodies, connecting means holding the said carrier bodies together end-to-end in a single packet, a control shaft and a release shaft journalled on the said packet of carrier bodies and extending both the full thickness thereof, the said control shaft operatively controlling the position of the said movable contacts relative the said fixed contacts, and the said release shaft having levers opposite of and controlled by the said bi-metal elements, a spring biased free release mechanism linked to the said control shaft and tending to turn the same into a position separating the said movable contacts from the said fixed contacts, a spring biased pawl normally locking the said free release mechanism in its inoperative position and controlled by the said release shaft, the said pawl releasing the said mechanism when the said release shaft is turned by the said bi-metal elements bearing on the said levers, a front plate fixed removably to the said packet of insulating carrier bodies spaced from the foremost of the said bodies, a switch handle pivoted on the said front plate and linked to the said control shaft, the said front plate carrying marks indicating the position of the said switch handle, and the said free release mechanism being arranged in the space between the said front plate and the foremost of the said bodies.

5. A motor protector switch as claimed in claim 4, comprising in addition: a cam and a dial fixedly connected therewith, both rotatably mounted in the said space and accessible to view and adjustment after removal of the said switch lever and front plate, the said cam being fixedly connected to the said pawl, and a leaf spring mounted on the said release shaft resiliently bearing on the said cam in the sense of turning the said pawl into its release position.

References Cited in the file of this patent UNITED STATES PATENTS 2,302,551 Jackson Nov. 17, 1942 2,376,793 Link May 22, 1945 2,416,163 Dyer et a1. Feb. 18, 1947 2,418,359 Link Apr. 1, 1947 2,610,272 Platz Sept. 9, 1952 2,669,627 Gelheizer Feb. 16, 1954

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