US2421213A

US2421213A - Centrifugal operated switch

Info

Publication number: US2421213A
Application number: US529884A
Authority: US
Inventors: John L Moody
Original assignee: Friden Calculating Machine Co Inc
Current assignee: Friden Calculating Machine Co Inc
Priority date: 1944-04-05
Filing date: 1944-04-05
Publication date: 1947-05-27
Anticipated expiration: 1964-05-27

Description

' May 27, 1947. J. 1., MOODY I 2,421,213

CENTRIFUGAL OP'ERATED SWITCH Filed April 5, 1944 2' Sheets-Sheet 1 FlI3 il INVENTOR. JOHN 1,. Maooy ATIORNEY.

May 22 i942? g, MQODY 2,421,213

CENTRIFUGAL OPERATED SWITCH Filed April 5, 1944 2 Sheets-Sheet 2 I NV EN TOR. JOHN L. M000) ATTQRNEY.

Patented May 27, 1947 2,421,213 cnn'mrrucan orsaa'rnn swrron John L. Moody, Oakland, cant, assignor to Friden Calculating Machine 00., Inc., a corporation of California This invention relates to governors for maintaining the speed of electric motors constant.

One object of this invention is to provide a governor which can be adjusted for different speeds but which employs a constant spring pressure on the part responsive to centrifugal force.

Another object of the invention is to vary the speed control of the governor by adjusting a weight to change the effective centrifugal force acting on the means which opens and closes the circuit.

Other objects will become evident after the following description. In the drawings:

Fig. l is an end view of a motor having the governor installed thereon.

Fig. 2 is a side elevation with the governor parts in vertical section.

Fig. 3 is a side elevation with the governor rotated 90 from the position shown in Fig. 2.

Fig; 4 is a vertical transverse section taken on the line 4-4 in Fig. 2.

Fig. 5 is a detail view of the part responsive to centrifugal force.

Figs. 6 and '7 are diagrams to show how the eflective centrifugal force is changed by adjusting a weight in the governor.

The speed of the motor I0 is maintained constant by opening and closing a pair of contacts in the form of annular discs ll, I2 (Fig. 2). The disc II is secured to a strap l3 which is mounted on a piece of insulating material l4 supported byposts l5, l8 from the casing of the motor. One end of the strap I3 is connected to a binding post. I! to which a wire I8 is connected.

The other contact I2 is secured to a collar l9 formed integrally with a stud 20 riveted at one end in a piece of insulating material 2| and provided with a button head 22. A cylinder 23 is threaded into an aperture in the piece of insulating material l4. A follower 24 slidable in the cylinder 23 is maintained in contact with the head 22 by a spring 23. A wire 28 has a soldered connection 21 with the cylinder 23.

The wires l3 and 23 are connected in the circuit of the motor In in the usual manner. When the contacts II and I2 are touching as shown in Fig. 2, the motor circuit is closed as follows: current may flow from the wire l8 through the binding post H to the strap l3 and the contact II;

from the contact l2 the current flows through the stud 20 to the follower 24 and the cylinder 23 to the wire 20. I

The means for opening and closing the contacts will now be described. The piece of insulating Application April 5, 1944, Serial No. 529,884

4 Claims. (Cl. 200-40) material 21 in which the stud 20 is mounted is secured by rivets to a plate 28 which has a pair of ears 29 (Figs. 3 and 4) formed thereon by means of which it is pivotally mounted on a pintle rod 30 supported in ears 3| formed on a bracket 32.

The bracket 32 (Fig. 2) is secured to a collar 33 which is mounted on the armature shaft 34 and held in place by a set screw 35 so that upon rotation of the motor shaft the bracket 32 and the plate 28are caused to rotate in unison therewith.

The bracket 32 has a cup 36 mounted therein which contains a spring pressed ball 31. The spring 38 presses the ball 31 against the plate 28 tending to move the contact l2 into engagement with the fixed contact H. The spring 3% is not adjustable in accordance with this invention but exerts a constant pressure against the ball 37.

The adjustable weight is provided by means of a screw 39 having a head 40 which is threaded into the plate 23 and also into a slotted plate 4| which is riveted to the plate 28. The purpose of the plate 4| is to provide friction on the threads to hold the screw 39 in any adjusted position. Turning the screw 39 will move it bodily with respect to the plate 28 and along a line sub stantially perpendicular to a plane passing radially through the axis of the pivot 30 and at a point radially offset from the axis of the pivot 30, thereby changing the effective centrifugal force as will now be explained more in detail. The

bracket 32 has a counter balance portion 42 formed thereon.

A low speed adjustment of the screw 39 is shown in Figs. 2, 3 and '7 while a high speed adjustment is shown in Figs. 5 and 6. Referring to i '7, the forces acting on the movable part 28 with reference to its pivot 30 comprise a force Fae acting through the center of gravity of the body 39 of the screw at a lever arm a and a force F40 acting through the center of gravity of the head 40 of the screw at a lever arm b. These forces tend to cause counterclockwise rotation which is opposed by the force of the spring For tending to cause clockwise rotation. It is to be noted in this adjustment that all of the screw is on one side of a plane 43 containing the pivotal axis 33 and the direction of centrifugal force.

The high speed adjustment shown in Figs. 5 and 6 results in a reduction in the effective centrlfugal force for a given speed as compared to the adjustment shown in Fig. 7 as will now be explained. The force Fm still acts on the head 40 of the screw but at a shorter lever arm c so that the moment is reduced. The body 39 of the screw, to facilitate this explanation, is shown as divided by the plane 43 so that the force F30 is represented as two arrows /zFao as acting at lever arms d but on opposite sides of the plane 43 so that the resultant moment is "0. Thus the only centrifugal force moment is FMJXC which is opposed by the constant spring force Faa. It will be evident that the moment F40Xc is less than the moment (FaaXa) (F40X b).

Although it is believed that the mode of operation of the governor will be apparent from the foregoing description taken in connection with the accompanying drawings, a brief description of the operation may be of some help. When the parts are adjusted, for example as shown in Fig ure '7, and are at rest, no centrifugal force will be acting and the spring 38 will press the ball 31 against the plate 28 with sufilcient force to urge the contact [2 into engagement with the contact ll. When the motor circuit is completed by closing of a control switch (not shown) the motor will begin to run, causing the bracket 32 and the parts it carries to rotate. When a predetermined speed is attained the centrifugal force exerted by the weight 3940 will cause the plate 28 to swing counterclockwise against the urge of the spring 38 so as to move the contact l2 out of engagement with the contact ll, thus opening the motor circuit and permitting the motor to slow down. The slowing down of the motor will diminish the centrifugal force exerted by the weight 39-40, again enabling the spring 38 to move the plate 28 clockwise and so close the contacts I i and i2, again completing the motor circuit. The repeated making and breaking of the circuit by closing and opening of the contacts II and i2 maintains the actual operating speed substantially constant.

I claim:

- l. A governor for an electric motor comprising contacts in the motor circuit, said contacts being relatively movable to open and close the motor circuit, means movable in response to centrifugal force for causing relative movement of said contacts, a member rotated by the motor, means for pivoting said movable means on said member, a weight mounted on said movable means and adiustable as a unit with respect to the pivotal axis of said movable means to position selected parts of the unitary weight respectively on opposite sides of said pivotal axis, centrifugal force acting on one part of said weight in one direction around said pivotal axis and centrifugal force acting on another part of said weight in the opposite direction around said pivotal axis.

2. A governor for an electric motor comprising contacts in the motor circuit, said contacts being relatively movable to open and close the motor circuit, means movable in response to centrifugal force for causing relative movement of said contacts, a member rotated by the motor, means for pivoting said movable means on said member, a weight mounted on said movable means and ad- Justable as a unit with respect to a plane containing the pivotal axis of said movable means and the direction of centrifugal force to selectively position all of said weight on one side of said plane or parts of said weight on opposite sides of said plane.

3. A governor for an electric motor comprising contacts in the motor circuit, said contacts being relatively movable to open and close the motor circuit, means movable in response to centrifugal force for causing relative movement of said contacts, a member rotated by the motor, means for pivoting said movable means on said member, a screw adjustable as a unit in said movable means, the axis of said screw being disposed at a distance from said pivotal axis and intersecting a plane containing said pivotal axis and the direction of centrifugal force, said screw being adjustable as a unit to selectively position the entire screw on one side of said plane or to position parts of said screw on opposite sides of said plane.

4. An electric motor governor comprising a bracket rotatable by the motor, a plate, pintle means offset radially from the axis of rotation of said bracket pivotally mounting said plate on said bracket to normally lie in a plane substantially perpendicular to said axis of rotation of said bracket, a fixed contact, a relatively movable contact carried by said plate and being engageabie with and disengageable from said fixed contact by pivotal movement of said plate, a cup on said bracket offset radially from said axis of rotation, a spring pressed ball in said cup bearing against said plate for urging it to effect engagement of said contacts, and a screw threaded into said plate to be adjustable along a line substantially perpendicular to a plane passing radially through the axis of said pintle means and at a point radially oflset from said pintle means axis whereby said screw can be adjusted as a unit to position it entirely on one side of said pintle means axis or to position selected parts of the screw on opposite sides of said pintle means axis.

JOHN L. MOODY.

REFERENCES CITED The following references are of record in the file of this patent:

, UNTI'ED sTXTEs PATENTS Number Name Date 1,057,436 Leeds Apr. 1, 1913 1,476,824 Leeds Dec. 11, 1923