US1575010A - Limit switch - Google Patents

Description

Marh 2 1926.

' G. B. SCHEER LIMIT SWITCH Filed April 29, 1922 WITNESSYES: INVENTOR' pE Q. m Georye 5. 36/766,.

Patented Mar. 2, 1926.

"UNITED STATES PATENT OFFICE.

GEORGE B. SGHEER, OF BERKELEY, CALIFORNIA, ASSIGNOR T0 WESTINGHOUSEELEG- TRIO & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

' LIMIT SWITCH.

Application filed April 29, 1922. Serial No. 557,484.

To all whom it may concern:

Be it known that I, GEORGE B. SCHEER, a citizen of the United States, and a resident of Berkeley, in the countyofAlameda and State of California, have invented a new and useful Improvement in Limit Switches, of which the following is a speci-' fication. n My invention relates to electrical switching apparatus and it has particular relation to electric-motor control.

One object of my invention is to provide means for limiting the period of opera- Gil tion of a motor.

Another object of my'invention is to provide an adjustable limit-switch that shall be capable of-eifecting small movements of the apparatus to be controlled, such as the edging rolls in a reversing steel mill.

Other objects of my invention will become apparentv from the following specification and the appended claims.

.My invention comprises a switch having an operating shaft arranged to be controlled or rotated in accordance with certain movements of the operating motor or mechanismthat is actuated thereby.

One or more movable switch members are actuated preferably, by means of a cam which is operatively connected through an electromagnetic clutch to the operating shaft of the switch, The electromagnet is energized simultaneously with the. main motorcontrolling devices. The contact members are so arranged as to be capable of angular movement corresponding to the movement of the cam, thereby affording adjustable means for retarding or for advancing the operation of themovable switch member relative to therota-ry movement of the operating cam. A centering spring 1s pro-' vided for returning thecam to its inoperative or off position when the electromagnet becomes de-energized.

'Figure 1 of the drawing is a sectional view of apparatus embodying my invention; .Fig. 2- is a plan view of aportion of the apparatus illustrated in-Fig.v 1; and

Figs. 3 and 4 illustrate theessential details of the centering spring for the operating cam.

I Referring particularly to;Fi 1, a mov-' able switch member 1 is carrie by a lever 2 and is arranged to. be actuted by a cam 3. Boththe cam 3 and the lever 2 are supported by, and may be rotated about, a main 8 of an electromagnet 9 and is arranged to control theaxial movement of the clutch member 6 by means of a hub portion 10 that is semi-cylindrical in form for convenience inassembling the clutch member 6 therewith. -Any other convenient assembly may be employed; A compression spring 11 is designed to establish the necessary frictional engagement between clutch members 5 and 6 upon the energization of the electromagnet 9. A centering spring 12, also illus trated in Figs. 3. and 4, normally maintains the cam 3 in an operative position. A. torsional spring of this character is sufficiently familiar in design and function as not to require detailed description. The various elements of the limit switch are contained within a casing 13, which provides suitable support for these elements.

Referring to Fig. 2, it will be noted that movable contact member 1 is mounted upon and suitably insulated from the lever 2. Stationary contact member 14 is also carried by the lever .2. The switch contact members may be of any desired character but I prefer to employ members capable of establishing a rolling contact under heavy sprmg pressure, such as the familiar type that is illustrated in the drawing. Operation of the movable contact member 1 is effected by engagement of the roller switch member 15 with the inclined surface of the cam 3. The switch members are capable of any desired angular movement by means of the operating lever 2.

It may be assumed, for example, that the shaft 4 of the limit switch is to be geared to a motor for operating rolls, such as in a steel mill. The motor may be started by means of a master switch (not shown) which simultaneously effects the energization of the electromagnet 9,, by means of an operating coil 16, and any suitable motor con-. troller ofelectromagnetio type (not shown). It may also be assumed .that the lever 2 has been set in any desired position, such as that illustrated in Fig. 2.

The engagement of clutch members 5 and 6 is effected by the closing movement of the magnet armature 8. Rotary motion is transthe familiar no-voltage release coil of the main operating controller (not shown). or by any other well-known method, to effect interruption of the motor control circuit.

The limit switch may, if preferred, be arranged with normally closed contact members, the opening of which is effected by means of the cam 3.

A The interruption of the motor-control circuit results is de-energizing. the electromagnet 9, which returns the clutch member 6 to its normal or inoperative position, and also permits the centering spring 12 to restore the cam 3 to its normal position. It is presumed that the operator will return his master switch' or other controlling device to its inoperative ,position and reset the novoltage relay, after which a second operation of the motor may be effected, as previously described.

It should be noted that the length .of time during which the motor is permitted to operate depends upon the predetermined position or setting of the lever *2, which controls the angular movement of the cam 3 for advancing or delaying each operation of the movable switch member 1. The angular movement of the lever 2 is independent of the angular movement of rotation of the cam 3.

A reverse operation of the motor causes rotation of the cam 3 in the opposite direction and causes the-operation of the similarly disposed movable contact member 21, mounted upon a lever 22, which is provided as illustrated in Fig. 2 for interrupting the motor-control circuit in that direction.

For the purposes of illustrating my invention, I have shown two sets of switch members, one set for each direction .of rotation of the motors Other combinations may be arranged ahdother modifications may be made tosuit various operating requirements. I have described-a switch that may be 'used as a limit switch or that may be employed to accelerate or otherwise control a motor aswill be readily appreciated by those familiar with the art. The advantages of my invention will be apparent to those employing unskilled labor, since, for any predetermined setting of, the limit switch,

the'control of the motor is entirely indev pendent of the skill of the operator.

As there are many ways insiwhicha switch) of this character. may be employedin. systoms of control, I have not deemed it necessaryto illustrate any particular system. The application of my invention will be readily understood and various modifications therein may be made without departing from the spirit and scope thereof.

I claim as my invention:

1; A reversing limit switch comprising a rality of movable contact members and operating means therefor, comprising a single cam, an electromagnetic clutch for rendering said meanselfective, a device for controlling the relative movements of'said contact members and said operating means and means i for restoring said contact members totheir original positions independently of said operating means.

.3. A limit switch comprising a movable switch member, a cam for actuating the member, electromagnetic means for rendering the cam effective and means for predetermining the effective angular-movement of said cam and for actuating said switch member independently of said electromagnetic means.

4. A limit switch comprising a cam operated switch member, electromagnetic means .for rendering said member effective, and

means for predetermining the angular movement of the cam and for controlling the total angular movement required for actuating said switch member and for controlling said switch member independently of said electromagnetic means.

5. A limit switch comprising a movable switch member, a cam for actuating the member, electromagnetic means for rendering the cam effective and means for selectively controlling the effective angular movement-of said cam to actuate the switch member and for actuating said switch member independently of said electromagnetic means.

' In testimony whereof, I have hereunto subscribed my name this 15th day of April,

GEORGE B. SGHEER- Certificate of Correction.

1t hereby certified that in Letters Patent No. 1,575,010,- grented March 2, 1926,

upon the application of- George B. Sc-heer, of Berkeley, California, for an improvementin' Limit Switches, an errorappears in the printed specification requiring correction as follows: Page 2, line 87, claim 2, after-the word reversing insert the word limit; and-that-the said Letters Patent should be read withthis correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 13th day of April, A. D. 192 .6.

[m] M. J. MOORE,

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