US2300822A - Electromagnetic switch - Google Patents

Description

' Nov 3,'1942. w. B. WELLS 2,300,822

ELECTROMAGNETIC SWITCH Filed June I2,- 1941 3 SheetsSheet 1 H15 A'r ToRNEY Patented Nov. 3, 1942 ELECTROMAGNETIC SWITCH Wesley B. Wells, Wilkinsburg, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application June 12, 1941, Serial No. 397,765

(Cl. Z104) 4 Claims.

My invention relates to electromagnetic switches, and particularly to electromagnetic switches which are subjected to severe vibration.

As is well known, in Searchlight signals of the type commonly used on railroads, such for example, as that disclosed in Letters Patent of the United States No. 2,224,417, granted to myself and another, on December 10, 1940, for Electromagnetic switches, a switch is included as a part of the signal operating unit. This switch is operated by a three position motor device which also actuates a spectacle arm carrying color filters for varying the signal indication, and includes two sets of contacts, each set of which comprises both front and back contacts. The control of the switch by the motor device is such that the front contacts of the one set or the other are closed according as the motor device is operated to one extreme position or the other, and that the back contacts of both sets are closed when the motor device is deenergized. In the deenergized position of the motor device, the only forces which have heretofore been relied upon to hold the back contacts closed are those due to the dead weight torque of the motor armature, and those due to certain counterweights which are provided especially for this purpose, and under most conditions of operation these forces are adequate. However, under certain adverse operating conditions such as occur when l the signals are mounted close to the track and the ground is frozen, or when they are used on elevated roads, it sometimes happens that sufficient vibration is transmitted to the operating unit to vibrate the back contacts open. Inasmuch as these contacts are frequently used to control similar signals, relays, or other signaling apparatus, it is desirable that these contacts should remain closed at all times except when they are opened by operation of the motor device, and one object of my invention is to provide novel means for accomplishing this desirable result.

According to my invention, a small auxiliary armature assembly is attached to each contact carrying rocker of theoperating unit, and the armatures of these assemblies both cooperate with a single permanent magnet in such manner that when the back contacts of either set of contacts is closed, the associated armature assembly will act to exert on the associated rocker a torque which assists that due to the motor armature and the associated counterweight in holding the contacts closed. The permanent magnet and the armature assemblies also improve the calibrationof the operating unit by causing the unit to release at a higher current without affecting the pick-up current, as will be pointed out more fully hereinafter.

Other objects and characteristic features of my invention will become apparent as the description proceeds.

I shall describe one form of electromagnetic switches embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a longitudinal vertical sectional view showing a Searchlight signal operating mechanism provided with an electromagnetic switch embodying my invention. Fig. 2 is a left-hand end view of the mechanism shown in Fig. 1. Fig. 3 is a top plan view of the switch forming part of the mechanism shown in Fig. l and embodying my invention.

Similar reference characters refer to similar parts in all three views.

Referring to the drawings; the mechanism here shown comprises a top plate A of suitable insulating material, which top plate serves as a support for the remaining parts of the mechanism; A transversely extending rectangular slot I is formed in thetop plate A adjacent its righthand end, as viewed in Fig. l, and secured to the top plate in vertical alignment with the slot l is a casing B provided in its front and rear walls with aligned windows 2 and 3. Extending upwardly into the casing B through the slot I is a spectacle arm 4, the upper end of which carries three differently colored filters 5, 6 and 1. The spectacle arm is secured at its lower end to a three position motor device M suspended from the top plate A, and is capable .of assuming a central or vertical position in which the filter 6 is located in axial alignment with the windows 2 and 3, a right-hand position as viewed in Fig. 2 in which the filter 5 is located in axial alignment with the windows 2 and 3, and a left-hand position, as viewed in Fig. 2, in which the filter 'l is located in axial alignment with the windows 2 and 3. In utilizing the signal, the light rays from a suitable optical assembly forming no part of my present invention are caused to pass through the windows 2 and 3, and to converge at a focal point at or near the center of the filter which is then in axial alignment with the windows 2 and 3, and it will be apparent, therefore, that the light rays passing through the focal point will pass through one or the other of the filters so that only light rays of the color which are not filtered out can emerge from the signal. Since the filters are differently colored, it follows that the signal is capable of displaying three different aspects depending upon which of the filters is located in axial alignment with the windows 2 and 3. The spectacle arm is biased to the vertical position by means which will appear hereinafter, and in actual practice the filters 5, 6 and l are colored green, red and yellow, respectively. It will be seen, therefore, that the beam projected by the signal will be green, red or yellow, according as the spectacle arm occupies its right-hand, its vertical, or its left-hand position, as viewed in Fig. 2.

The motor device taken by itself forms no part of my present invention, and is similar in all essential respects to that described in Letters Patent of the United States, No. 2,133,603, granted to me on October 18, 1938, for Light signals. Inasmuch as the motor device of itself forms no part of my present invention, and is similar to that described in the patent referred to, it is believed that for purposes of my present invention it is sufiicient to point out that this motor device comprises a rotor 8 which is pivotally supported at its ends for swinging movement between an intermediate position and two extreme positions, and to which the lower end of the spectacle arm 4 is secured. The rotor 8 is of suitable magnetizable material such as silicon steel, and is provided adjacent its ends with depending armatures 9 and I!) which cooperate with associated pairs of constantly magnetized pole pieces disposed in vertical planes on opposite sides of the pivotal axis of the rotor. Surrounding the rotor between the armatures 9 and I is an energizing winding II which is intended to be reversibly supplied with current. The rotor is biased to its intermediate vertical position by means which will be described hereinafter, and the parts are so proportioned that when the winding H is energized the rotor will be rotated to one or the other of its extreme positions depending upon the polarity of the current which is then supplied to the winding. The parts are further so proportioned that the spectacle arm 4 will occupy its vertical, its right-hand, or its left-hand extreme position, according as the rotor occupies its intermediate position or is rotated to one extreme position or the other.

Secured to the rotor 8 at the end opposite to the spectacle arm 4 is a triangular plate 14 pro vided with two rollers l and I6 disposed on opposite sides of the pivotal axis of the rotor. These rollers cooperate with operating arms I! and I8, respectively, pivoted on pivot pins I9 and mounted in a supporting bracket 2| secured to the front end of the motor device. Th arms I! and I 8 are provided with depending portions Fla and [Ba which cooperate at their lower ends with adjustable stop screws 22 and 23 mounted in the bracket 2|, and are biased by means of counterweights 24 and 25 adjustably mounted on the arms to positions in which the depending portions Ha and l8a engage the stop screws. The stop screws are so adjusted that when the rotor occupies its vertical position, the arms will just touch the rollers and their depending portions will just touch the associated stop screws. It will be seen, therefore, that if the rotor is rotated from its normal position in a clockwise direction, as viewed in Fig. 2, the operating arm I8 will be raised, but that, if the rotor is rotated from its normal position in a counter-clockwise direction, as viewed in Fig. 2, the operating arm I! will be raised. It follows, therefore, that the operating arms together with theassociated 75 counterweights act to bias the rotor to its intermediate or normal position.

The operating arms I! and 18, in addition to serving as a part of the means for biasing the rotor R to its normal position, are arranged to operate separate contact mechanisms. These contact mechanisms are similar, and their corresponding parts are designated by the same reierence characters with the distinguishing suilix a or b, as the case ma be, so that an understanding of both will be had from the description of only one. Referring particularly to the contact mechanism controlled by the operating arm l8, for example, thi contact mechanism can prises a plurality of flexible contact fingers 300., 3la, 32a and 33a secured at their lower ends to an insulating contact carrier 34a forming part of a rocker 35a. The rocker 35a is pivotally supported on horizontally aligned trunnion screws 36a mounted in the bracket 2|, and is provided with a laterally extending arm 31a which projects toward the operating arm 18. The free end of the arm 31a is bent at right angles to the main body of the arm and overlies a laterally projecting pin 38a secured to the arm l8. The rocker is biased by gravity to rotate in a clockwise direction as viewed in Fig. 2 to such a position that the arm 31a is constantly held in engagement with the pin 38a, and it will be seen, therefore, that the rocker 35a assists in biasing the rotor to its normal position. It will also be seen that when the rotor is rotated away from its normal position in a clockwise direction, as viewed in Fig. 2, the resultant rotation of the operating arm l8 will act through the pin 38a and arm 31a to rotate the rocker 35a in opposition to its bias from its normal position in which it is shown in the drawings to what I shall term its operated position. When th rocker occupies its normal position, the contact fingers 30a and 33a engage fixed contact members a and 39a secured to terminal posts mounted on the top plate A, to close back contact 30a-40a and 33a39a. When, however, the rocker is rotated to its operated position, the contact fingers 30a and 33a then move out of engagement with the fixed contact members 40a and 39a to open the contacts 30a-40a and 33a-39a, and the contact fingers 3Ia and 32a move into engagement with fixed contact members 41a and 42a secured to terminal posts mounted on the top plat A to form front contacts 3|a 4la and 32a42a.

The portion of the operating unit thus far described is all well known, and its operation will be understood from the foregoing without further detailed description.

With the operating unit constructed in the manner just described, when the unit is ubjected to abnormally severe vibration, the back contacts tend to vibrate open. According to my present invention I provide the operating unit with magnetic hold-down means which not only effectively prevents the back contacts from opening due to vibration under the most adverse operating conditions, but which means also improves the calibration of the operating unit by causing the unit to release at a higher current value without affecting the pick-up current.

In the form illustrated, these magnetic holddown means comprise a permanent magnet 45 and two similar armature assemblies, one of which is secured to each of the rockers 35a and 35b. The permanent magnet 45 is U-shaped and is formed with two upstandin poles 45a and 4511 which form a channel 450. Fitting snugly within the channel 450 is a longitudinally extending non-magnetic spacer 4,6, and disposed above this spacer is a longitudinally extending shunt bar 41, the opposite sides of which are separated from the adjacent magnet poles by air gaps d and 45s, respectively. The shunt bar and nonmagnetic spacers are so proportioned that the upper surface of the shunt bar lies in the same horizontal planeas the upper surfaces of the magnet poles 45a and 45b, and formed in the shunt bar and spacer on opposite side of the magnet 45 are vertically aligned holes through which hold-down screws 48 and 49 pass. The heads of these screws are countersunk within the shunt bar and their lower ends are screwed into screw threaded holes provided in the bracket 2 I, whereby when the screws are tightened the permanent magnet and associated parts are firmly secured to the bracket 2 I.

Each armature assembly consists of a rigid arm 50a or 50b provided at one end with an upstanding bent portion 51a or 5112 which is bolted to the associated rocker 35a or 35?) by means of suitable bolts 52a or 52b. Each arm 50a or 501) supports a flexible member 53a. or 53b, the free end of which carries a small armature 54w or 5413 partially surrounded by a non-magnetic shield 55a or 552). Each shield and armature is riveted to the associated flexible member 530, or 5% by a non-magnetic rivet 5611 or 56b the lower end of which is machined off to form a core pin. The permanent magnet 45 is a relatively strong magnet preferably of the Alnico type, and the nonmagnetic spacers act when the strips 44a and 44b are held down by the associated armature to prevent the armature from actually touching the magnets or the shunt bar and thus exerting a force on the rocker in excess of the desired force. The free ends of the arms 50a and 5011 are provided with depending portions 51a, and 57b, and the flexible members 53a and 531) are so adjusted that when the armatures are moved away from the permanent magnet, the armatures will be held, by the resiliency of the flexible members,

in engagement with the depending portions 56a and 56b; whereby vibration of the armatures under these conditions is reduced to a minimum.

With the hold-down means constructed in the manner described it will be seen that when either rocker occupies its normal position in which it is shown in the drawings, the associated armature will bridge the air gap between the associated pole of the permanent magnet and the shunt bar, thereby causing the armature to be attracted toward the magnet. The attraction of the armature toward the magnet will act through the associated arm to exert on the associated rocker a force which assists that due to the biasing mean outlined hereinbefore in holding the back contact closed. If the armature were mounted rigidly on the contact rocker, a sudden jar would tend to release the armature from the magnet and overcome its usefulness in holding the back contacts closed. However, inasmuch as the armature is mounted on a flexible member some small motion of the contacts is permitted before the armature will lift away from the permanent magnet. This permissible motion, however, is not suflicient to open the back contacts. It will be seen, therefore, that when an operating unit equipped with magnetic holddown means embodying my invention is subjected to vibration, some motion of the contact carrying rockers will occur, but that the pull of the permanent magnet and the flexible mounting of, the auxiliary armatures will prevent the back contacts from opening.

In addition to preventing opening of the back contacts due to vibration, the magnetic holddown means embodying my invention also improves the calibration of the operating unit, inasmuch as it causes the unit to release at a higher release current without increasing the pick-up current. The current at which the operating unit releases is increased due to the fact that before either contact operating rocker reaches its full released position, the associated armature is attracted by the permanent magnet and creates a torque tending to assist the release, thus causing the operating unit to reach the full released position at a higher value of energization than would otherwise occur. When the rotor is moving to one extreme position or the other, the magnetic hold-down due to one or the other of the auxiliary armatures increases the initial pickup, that is, a higher value of energization is required in order to start motion in the picked up direction, but the operating unit has sufficient torque below the complete pick-up torque to pull the permanent magnet armature away from the magnet, and as soon as the auxiliary armature starts to move away from the magnet, the pull on the armature is materially reduced. Consequently, the operating unit completes its pickup stroke with very little or no effect from the permanent magnet.

It should be pointed out that while in describing my invention I have shown a permanent magnet as a part of the hold-down means, any permanently magnetized means that will constantly supply flux may be used in place of the permanent magnet.

One advantage of magnetic hold-down means embodying my invention i that while it is relatively simple, it not only minimizes the chance of the back contacts opening due to vibration but also improves the calibration of the operating unit by causing it to release at a higher current value without affecting the pick-up current.

Although I have herein shown and described only one form of electromagnetic switch embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In an electromagnetic switch the combination with a pivoted contact carrying member provided with a back contact which is biased by gravity to a closed position when the switch is deenergized and is moved to an open position when the switch is energized, of means for preventing said back contact from opening due to vibration comprising a rigid arm secured to said contact carrying member, an armature secured to said arm by a resilient member which cooperates at its free end with a stop portion formed on said arm to at times position said armature with respect to said contact carrying member, and a permanent magnet cooperating with said armature to exert on said member a force which assists that due to gravity in holding said back contact closed when said device is deenergized.

2. In an electromagnetic switch, the combination with a pivoted contact carrying member provided with back contacts which are biased by gravity to their closed positions when the switch is deenergized and are moved to their open positions when the switch is energized, of means for preventing the back contacts from opening due to vibration comprising a rigid arm attached to said contact carrying member, an armature attached to said contact carrying member by a flexible arm, a shield secured to said armature by a core pin, and a permanent magnet provided between its poles with a flux path including an air gap, said magnet being so disposed that when said back contacts are closed said armature will bridge said air gap and will thus cause a force to be exerted on said contacts which force is effective to hold said contacts closed.

3. In an electromagnetic switch, the combination with two rockers each pivotally mounted in a supporting frame for movement between a first and a second position and each biased by gravity to its first position and each arranged to be at times moved to its second position by a three position motor means, of a rigid arm secured to each rocker, an armature secured by flexible means to each arm, and a U-shaped permanent magnet secured to said frame and provided with two upstanding poles and with a shunt bar disposed between said poles and separated from each pole by an air gap, said magnet being so disposed that when said rockers occupy their first positions each said armature will bridge a different one of said air gaps, whereby a force is exerted on each said rocker by the flux from said magnet traversing said armatures when the rocker occupies its first position which force is effective to prevent the contacts carried by the associated rocker from vibrating open.

4. In an electromagnetic switch of the type in which two rockers are each biased to one position and are each arranged to be moved to another position according as a polarized three position motor means is supplied with current of one relative polarity or the other and in which each rocker is provided with back contacts which are closed except when the rocker is moved to its other position, the combination of a rigid arm secured to each rocker, an armature secured to each arm by a flexible member which urges the armature to a position in which the member engages a stop portion formed on the arm, and a permanent magnet provided with two air gaps between its poles each arranged to be bridged by a different armature when said rockers occupy their one position, whereby when said rockers occupy their one position said armatures will act through said flexible members and said arms to exert a torque on said rockers which torques assist in preventing the back contacts from opening due to vibration, the parts being so proportioned that each armature will be moved out of the effective field of said magnet when the asso ciated rocker is moved to its other position.

WESLEY B. WELLS.

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