US1231412A - Electromagnetic switch. - Google Patents

Description

E. J. MURPHY.

ELECTROMAGNETIC SWITCH.

APPLICATION FILED JULY 13. 1914."

1,231,1E12. Patented June 26, 1917.

Fig. l. v Fig. 2.

INT/ENTER EDI/WM J MURPHZ STATES PATENT ormon.

'nnwnr J. nunrnr, or SOHENECTADY, new roan, nssrcnon 'ro GENERAL ntncrnre comm, A CORPORATION or new YORK.

Specification of Letters Patent.

ELECTROMAGNETIC SWITCH.

Patented June 26, 1917.

Application filed July 13, 1914. Serial No. 850,596.

To all whom it may oonaem: Be it known that I, Enwm J. Munrmr, a citizen of the United' States, residing at Schenectad in the county of Schenectady, State of ew York, have invented certain new and useful Improvements in Electro-.

magnetic Switches, is a specification.

This invention relates to electromagnetic switches and has for its object the provision of a device of this character in which the contacts cannot stick or freeze together under the most trying conditions of service and at the same time are spring pressed apart at all times. I

In the operation of electromagnetic switches, especially as. used in the control of of which the following electric motors where the switches, are opery ated very frequently and the currents are heavy, .it sometimes happens that the are formed between the contacts fuses the metal and causes the contacts to stick together, due to the formation of a slight weld between them. This most fre uently happens when the magnetizing win ingl is not energlzed -long enough to cause t e contacts to be brought firmly into engagement with each other in their final position, but is only energized for an instant so that the contacts 80 just touch and then separate. This also happens sometimes because of the slow opening of the contacts due to slow decrease of magnetic pull and other causes. In the type of contact for electromagnetic switches now well known, in which the contacts slide or roll upon each other to produce a wiping action, any slight welding or sticking will be overcome by the wiping action if the contacts are closed or wiped home. If, however, the contacts merely engage or kiss without being wiped to the final position, a weld might form which would hold the contacts in the closed position against the tendency of gravity or the spring to open the switch. One of the objects of my invention is to overcome this difficulty and make it practically impossible for the. contacts ofv the switch to stick together in the manner above described.

Another object of my invention is to provide a switch which is spring pressed to the open position as distinguished from being biased to the open position by gravity. It is frequently desirable that the contactor should be capable of being tilted at an angle say of 45 or more without danger of the fO I'IIL 'TTTh B arrangement is such that closes.

the contacts so that contacts dropping closed. On shipboard for instance, a'cohtactor must be arrange so that the'eonta'cts cannot possibl drop closed under the worst conditions of rollmg-and co pitching. One of the inherent difliculties in making a switchof this kind with spring opened contacts is thatif the spring is strongenough to be of any advantage in causlnga-strong pressure betweenthe contacts in closed position, it will be so strong that the magnet cannot move it from the open position. As the contactor approaches closed position, the closing force Increases very rapidly, but in the open position the force-is relatively weak and it is therefore the open position.

carry ng out my invention, 1 provide a switch. WhICll is'spring pressed to the open necessary that the spring should be-weak in position, the contacts being forced apart near the'closed position with sufiicient force to break any weld which might possibly the effective pressure tending to hold the eontacts apart is less when the switch is in the open position than it is just before the switch This is accomplished by decreasing the leverage at which the magnet acts upon the spring just prior to the engagement of 8-5 the effective pressure tending to hold the contacts open will be considerably increased. From this point on until the contacts reach their final position, there is a strong spring pressure between the contacts so that any weld which might form between the contacts will be instantly broken, and while it might be possible that the contacts would be brought into engagement with each other in such a way as to form a weld, this weld would be immediately broken by the strong spring pressure which acts over a suflicient ran e to break any weld which could form. Other objects and purposes of my invention will appear in the course of the following specification in which I have shown my invention embodied in concrete form for purposes of illustration.

In the accompanying drawing, Figure 1 represents a side view of an electromagnetic c'arryihg member 17and' presses. the latter against the sto'pli19. ,This spring engages the member, 17 between the' pivot and the" stop,'and thepoint of engagement s 1mport'ant because it afiects. the leverage at pivot pin 18. on thearmature of course moves with thearmaturc, but the spring 20 forces the lower end of the member 17 againstv the stop 19. The effective action of the spring 20 tending to move the contacts apart is therefore due to ,acomp'ound lever age. Representing the distance between the pivot pin 18 and the stop19'by a, and the distance between the spring and the stop 19 by b, and the distance between the pivot pin ltand the pivot pin-18 by-c, then the efiective action of the spring tending to hold the contacts apart is dueto the force of the spring acting at the distance OX2- The.

nearer the spring is located to the stop 19 the less Wlll bethe efiectivejl'everage at which the spring-acts and hence the less eifective force there will be to hold the armature in the open position. When the armature moves inward, the member 17 slides and rolls on the stop 19 and a relatively large movement of the member 13' compresses the spring a relativelysmall amount. This will be seen by reference to Fig. 4. In this figure the switch has reached the position in which the effective pressure of the spring tending to open the contacts is increased.- This is brought about by the engagement of 'the lower end of the member 17 with the shoulder 21. From this point on in the movement of the switch arm it will be seen that the spring will act directly upon the armature member since the member 17 now moves as a unit with the member 13. Relatively small movement of the armature to closed position now compresses the spring a relatively large amount. When the contacts 15 and 16 engage, they wipe or roll on each other and the member 17 is 's'shown in the.

would tend to cause the contacts to stick ,together'will be overcome by the spring ten- "screw 23 which slides in the slot 23'. The

contact carrying member is made in the acts against each leg of the yoke. A bar 25 secured to the armature member corresponds with the shoulder 21,-Figs. 3 to 5:

form of a yoke 24 so that oneof the springs andkprojects beyond, the armature member at each end so asto be engaged by the legs of the contact carrying member. A plate 26 is secured in a stationary position by means of a rod 27 which is secured in the frame of the magnet and passes through a Nuts 28 on this rod secure the plate in place.

Screws 19 ,form stops corresponding to the stop 19 in Fig. 3. The'operation and general arrangement of parts is identical with that alreadydescribed in connection clearance hole in the armature member.

with Figs. 3and 5 and no further 'description is therefore. deemed necessary.

It will be seen that the electromagnetic switch above described is spring pressed to the open position but the force necessary to move the switch from, the open position to the intermediate position shown in Fig. 4 is relatively small as compared with the force necessary to move it the remainder of the distance. This makes a very strong pressure between the contacts for a short distance, enough to break any weld which might form, and produce a good spring pressure on the movable contact in the closed position. On the other hand, in the open position, the spring is weak enough so that it can be readily moved over the wide air gap which then exists. While I have desince various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. An electromagnetic switch comprising a magnetizing winding, a fixed contact, a pivoted armature member having a contact mounted thereon and spring pressed away from the-fixed contact so as to have a resilient movement with reference to the armature member, and means whereby the leverage at which the spring acts upon the armature member tending to keep the contacts apart is decreased before the movable contact reaches its closed position.

2. An electromagnetic switch comprising a magnetizing winding, a fixed contact, an armature member, a contact having a resilient mounting thereon to permit a yielding movement with reference to the armature member and press the armature member toward open position, and means whereby the effective pressure tending to hold the contacts apart is increased when the armature member reaches a predetermined position in the closing. movement. I

3. An electromagnetic switch comprising a magnetizing winding, a fixed contact, an armature member having a contact movably mounted thereon, and spring pressed away from the fixed contact, and means whereby the spring pressure tending to hold the con tacts open is substantially uniform during the closing movement until the armature member reaches a predetermined position and is then increased.

4. An electromagnetic switch comprising a magnetizing winding, a fixed contact, an armature member having a contact pivoted thereon to cooperate with the fixed contact,

a spring interposed between the pivoted contact and a stationary part of the switch so that the contacts will be held apart thereby and engage with a yielding pressure, and means whereby the effective pressure tending to hold the contacts apart is increased when the armature member reaches a predetermined position in the closing movement.

5. An electromagnetic switch comprising a magnetizing winding, a fixed contact, an armature member, a contact pivoted on said armature niember to cooperate with said fixed contact, a spring interposed between a stationary portion of the switch and said pivoted contact tending to turnthe latter on its pivot toward the xed contact, a fixed stop against which the contact ispressed by the spring, and a stop on the armature member which engages the pivoted contact at'a predetermined position 1n the closing movement so that further movement of the armature member moves the pivoted contact away from the fixed stop.

6. An electromagnetic switch comprising a magnetizing winding, a fixed contact, an armature, a contact carrying member pivoted thereto, a fixed stop in the path of said contact member to prevent it from rotating in a direction to cause engagement of the contacts, a spring mounted to press the member against the stop and bias the armature to open position, and a stop on the armature which engages the pivoted contact member at a predetermined position in the closing movement so that further movement of the armature moves the contact member away from the fixed stop.

7. An electromagnetic switch comprising a magnetizing winding, a fixed contact, an armature, a contact carrying member pivoted thereto, a stop on the armature which limits the rotation of the contact member on its pivot in a'direction to engage the fixed contact, a spring engaging said member between the pivot and the stop and tending to force it against the latter, and a fixed stop between the spring and the stop on the armature which acts as a fulcrum for the contact carrying member in compressing the spring during the closing movement until the contact carrying member engages the stop on the armature and is moved away from the fixed stop.

8. An electromagnetic switch comprising a magnetizing winding, a fixed contact, an armature member having a contact pivotally mounted thereon, and spring pressed away from the fixed contact so that there will be a yielding pressure between the contacts when they engage, and means whereby the spring pressure tending to hold the contacts open is substantially uniform during the ,closing movement until the armature member reaches a predetermined position and is then increased. 7

9. An electromagnetic switch comprising a magnetizing winding, a fixed contact, an armature member, a contact having a resilient mounting which permits yielding move ment with reference to the armature member and forces the contact away from the fixed contact, and means whereby the pressure tending to hold the contacts apart is substantially uniform during the closing movement until the armature member reaches a predetermined position and is then increased.

In witness whereof, I have hereunto set my hand this 11th day of July, 1914.

EDWIN J. MURPHY. Witnesses:

HELE ORFORD, MARGARET E. WOOLLEY.

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