US2992307A - Magnetic switches - Google Patents

Description

H. REIFEL MAGNETIC SWITCHES July 11, 1961 Filed May 4, 1959 Ill United States Patent 2,992,307 MAGNETIC SWITCHES Harry Reifel, Waltham, Mass, assignor to Stevens- Amold Inc, a corporation of Massachusetts Filed May 4, 1959, Ser. No. 810,776 4 Claims. (Cl. 200-90) This invention relates to magnetic switches having cantilever supported, vibratory reeds.

Magnetic switches having cantilever supported reeds of spring metal are widely used as choppers and relays. Such reeds are deflected by magnetic fields set up by flow of current through associated coils, and usually bear contacts which touch other stationary contacts. Since the contacts on such reeds move in circular arcs having centers at the fixed ends of the reeds, there is rubbing wear between the movable and fixed contacts. Such contacts may be of precious metal such as gold or platinum, and the rubbing wear to which they have been subjected has required frequent servicing of the contacts.

For reducing the wear of the contacts, I remove them form the reeds and place them on contact lifters of spring metal which are moved by the reeds, and which are so shaped and arranged that there is no rubbing wear between the contacts they bear and the fixed contacts. This still leaves rubbing wear where the contact lifters touch the reeds, but I reduce the friction between such rubbing surfaces by coating the surfaces of the reeds where they are in rubbing contact with the contact lifters with a dry lubricant such as tetrofluorethylene. Such a lubricant does not adhere to the contact lifters as all previously tried lubricants have done, and has no adverse eifect upon the operation of the switches.

Using these two features, the life of a magnetic switch of this type has been greatly prolonged, and its maintenance greatly reduced.

An object of this invention is to reduce the rubbing wear in a magnetic switch having a cantilever supported reed.

Another object of this invention is to reduce the friction between the rubbing components of a magnetic switch having a cantilever supported, contact actuating reed.

This invention will now be described with reference to the annexed drawings, of which:

FIG. 1 is a top plan view of a magnetic switch embodying this invention;

FIG. 2 is a side view of the switch;

FIG. 3 is an enlarged fragmentary view of the switch showing the coatings of dry lubricant on the reed surfaces opposite the contact lifters, and

FIG. 4 is a fragmentary bottom plan view of the switch.

A metal base has one end portion with reduced width to which are clamped by a bolt 11, a pair of metal blocks 12 which extend above and below the base on opposite sides of said end portion. Above the base 10, there are clamped between the tops of the blocks 12, insulating spacers 13 next to th blocks 12, metal spacers 14 next to the spacers 13, the outer ends of metal plates 15 next to the spacers 14, the outer ends of metal contact strips 16 next to the plates 15, metal spacers 17 next to the strips 16, insulating spacers 18 next to the spacers 17, metal spacers 19 next to the spacers 18, the outer ends of metal contact lifters 20 next to the spacers 19, and the outer end of a reed 21 of non-magnetic, spring metal between the outer ends of the contact lifters 20, the reed being cantilever supported at its outer end.

Below the base 10 and between the lower ends of the blocks 12 is a spacer block 23, the previously referred to, reduced width base portion being above the block 23.

The contact lifters 20 have inner portions 24 which curve from and towards the reed 21, and which have at their inner ends, contacts 25 which are U-shaped in section, and between the legs of which extend the inner ends of the contact strips 16. Contact spacing bolts 26 are threaded into the plates 15 with their inner ends in contact with the contact lifters 20, and are used for adjusting the spacing between the legs of the contacts 25 and the inner ends of the strips 16.

The reed 21 has attached to its free outer end portion by staples 26, laminar reeds 27 of non-magnetic spring metal which extend in contact with opposite sides of the reed to adjacent its fixed end, and straps 28 of magnetic metal in contact with outer end portions of the reeds 27 on outer sides thereof. The straps 28 have flanges 29 extending approximately parallel to and spaced from the top of the base 10. The base 10 has a slot extending along the longitudinal center of its other end in which is fitted a permanent magnet bar 30 under the magnetic to magnetic field changes at the pole pieces 35. Attached to said other end of the base 10 by machine screw 32 and clamp plates 33 is an electromagnet 34 which has pole pieces 35 which are bent inwardly towards the free end of the reed, with their inner ends spaced apart opposite the free end of the free end of the reed. One of the blocks 12 has a terminal lug 37 attached thereto.

Where the inner ends of the contact lifters 20 would otherwise rub against the opposite sides of the laminar reeds 27 when the reed 21 is vibrated, there is applied to such opposite sides, coatings 40 of the dry lubricant tetrofluorethylene which greatly reduces the rubbing friction between such reed sides and the contact lifters.

In operation, assuming the device is operating as a chopper, alternating current applied to the electromagnet 34 would change the magnetic field at the magnetic straps 28 on the free end of the reed 21, causing the reed to vibrate. The inner ends of the contact lifters 20 are in contact with the coatings 40 on the laminar reeds 27, and are deflected outwardly by the vibration of the reed, moving during a first halfcycle, one contact 25 outwardly, and moving during the second halfcycle, the other contact 25 outwardly. The outward movements of the contacts 25 cause them to break contact with the outer ends of the contact strips 16, opening previously closed circuits connected to the contact lifters 20 and the contact strips 16.

The contact making surfaces of the contacts 25 and of the contact strips 16 would be gold or platinum, and by using the lifters 20 instead of the reed directly, to make and break contacts, rubbing wear of the contact surfaces is greatly reduced.

By using the lubricating coatings the reed laminations 27 where the contact lifters contact such surfaces, the rubbing friction betweoen the reed surfaces and the rubbing lifter surfaces is greatly reduced, resulting in increased life and decreased maintenance.

Electrical terminals which are not shown, would be provided for the electromagnet 34 and for the contact lifters 20 and the contact strips 16.

The base 10 is designed to take one reed assembly, one contact assembly and one electromagnet as shown by the drawings, or to take another reed assembly, another contact assembly and another electromagnet which would be placed, looking at FIG. 2, above the base 10.

The coatings 40 are insulators so that electrostatic voltages are generated by their rubbing contact with the contact lifters. These voltages, however, are shorted out by the reed 21 being directly connected to the contact lifters 20 where they are supported.

40 on the surfaces of What is claimed is:

l. A magnetic switch having a cantilever supported reed of spring metal, means including an electromagnet for vibrating said reed, said reed having a contact lifter deflecting surface, a cantilever supported contact lifter of spring metalhaving a surface opposite said surface, a layer of tetrofluorethylene lubricant on one of said surfaces in contact with the other of said surfaces, a contact surface on said lifter, and means providing a fixed contact surface opposite said contact surface.

2. A magnetic switch having a cantilever-supported reed of spring metal, means including an electromagnet for Vibrating said reed, said reed having a contact lifter deflecting surface, a layer of tetrofluorethylene lubricant on said surface, a gantilever supported contact lifter of spring metal having a surface in contact with said layer, a contact surface on said lifter, and means providing a fixed contact surface opposite said contact surface.

3. A magnetic switch having a cantilever supported reed of spring metal, means including an electromagnet for vibrating said reed, said reed having a contact lifter deflecting surface, a cantilever supported contact lifter of spring metal having a surface opposite said surface, a

4 layer of tetrofiuorethylene lubricant on one of said surfaces in contact with the other of said surfaces, means directly connecting said reed and lifter electrically together, a contact surface on said lifter, and means providing a fixed contact surface opposite said contact surface.

4. A magnetic switch having a cantilever supported reed of spring metal, means including an electromagnet for vibrating said reed, said reed having a contact lifter deflecting surface, a layer of tetrofluorethylene lubricant on said surface, a cantilever supported contact lifter of spring metal having a surface in contact with said layer, means directly connecting said reed and lifter electrically together, a contact surface on said lifter, and means providing a fixed contact surface opposite said contact surface.

References Cited in the file of this patent UNITED STATES PATENTS Vazquez Sept. 18, 1956 2,790,129 Barnes Apr. 23, 1957 2,859,299 Howell Nov. 4, 1958

Images