US2758173A - Electric circuit chopper - Google Patents

Description

Aug. 7, 1956 J. c. RILEY 2,758,173

ELECTRIC CIRCUIT CHOPPER Filed March 22, 1954 2 Sheets-Sheet 1 R 3? R 0 g A '8; INVENTOR.

' Jae/f C./?//gy BY 7, 1956 J. c. RILEY ELECTRIC CIRCUIT CHOPPER 2 Sheets-Sheet 2 Filed March 22, 1954 INVENTOR. Jack G/W/gy United States Patent ()fiFice 2,758,173 Patented Aug. 7, 1956 ELECTRIC cmcnrr CHOPPER Jack C. Riley, Portland, Oreg., assignor to Iron Fireman Manufacturing Company, Portland, Oreg.

Application March 22, 1954, Serial No. 417,851 3 Claims. (Cl. 200-93) This invention relates generally to electric relays and more particularly to that type of polarized high speed electric relays known in the art of electronics as choppers. A relay of this type may take the form of a single pole double throw switch inductively actuated from an en ergizing circuit the direction of current flow in which determines the throw of switch. For purposes of explanation such a construction is here illustrated and described.

it is to be understood that in the field to which this invention relates a relay such as that shown must be small, or miniaturized, and must be capable of continuous reversal or switching of its contacts at a rate of the order of 1000 times per second and yet must be capable of handling moderate electric current at the switch contacts with open circuit voltages as the contacts of the order of 100 volts or less. Again such a relay may be idle for extended periods of time and maybe subjected to wide extremes of temperature but the relay must operate precisely when called upon.

The critical point at which design and construction efforts must be pointed if such a relay is to operate successfully has been found to be the contact region of the switch. It has been customary in the past in this art to use noble metal contacts, to use a blade structure having a natural frequency reasonably close to the excitation current frequency and to rely on some method of blade damping such as a confined air space or a fretted blade for damping the blade action at contact. In this previous practice, so far as known, the required reliability of operation has not been achieved. At low voltages and low current loads the previously used noble metal contacts have been able to Work with reasonable success in spite of the contact bounce inherent in the previously used blade structure, but at higher voltages, sparking, build up of foreign deposits, and metal transfer at the contacts would occur. If tungsten contacts suitable for higher voltages were used the tungsten would oxidize and coat the contacts with an insulating surface which would not break down, thus preventing operation after extended periods of low or no voltage at the contacts.

In studying these relays I have found that it is highly desirable to provide a blade structure having a natural vibration frequency well out of the range of the electric excitation frequency, that the reed motion should be forced at all times rather than natural that the blade or reed motion should be positively damped at all times. in this I have had the advantage of my previous work on a high speed relay culminating in the frictionally damped reed disclosed in my previous U. S. patent application S. N. 354,525, filed May 12, 1953, of which the present blade structure is a further development.

In studying these relays I have also found that for the severe time and voltage conditions under which they must operate it is highly desirable to use tungsten for one of the contacts at each throw of the switch but that to do this the contact area must be small and closely controlled and the contact pressures must be relatively high and continuous once contact is made.

It is therefore a principal object of this invention to provide an electric circuit chopper which is reliable in operation over a considerable range of frequency of excitation and over a wide range of open circuit Contact voltage.

It is a second object to provide such a chopper with a blade structure in which substantially all motion of the blade or reed is forced.

It is a third object to provide such a relay with a blade structure having an inherent and substantially constant damping effect on the motion of the blade.

It is a fourth object to provide such a relay having contacts of material adapted to reduce deterioration at relatively high voltages.

it is a fifth object to provide such a relay having contacts formed to concentrate the contact pressure over a controlled small area.

It is a sixth object to provide such a relay with a blade structure and a Contact structure adapted to the use of high voltage contact materials over a range of open circuit contact voltage from near zero to one hundred volts.

It is a seventh object to provide such a relay with means for shielding the switch circuit from the electrostatic fields of the excitation circuit.

How these and other objects are attained are explained in the following description referring to the attached drawings in which Fig. 1 is a longitudinal section through the preferred form of my chopper to be described as typical of the forms it may take. Fig. 2 is a cross section along the line 2-2 of Fig. 1, Fig. 3 is a cross section along the line 33 of Fig. 1, Fig. 4 is a fragmentary view in side elevation of the contact structure of the switch of my chopper. Fig. 5 is a fragmentary view taken along the line 55 of Fig. 4.

Like numerals of reference refer to like parts in the several figures of the drawings.

Referring now to the drawings a pair of similar laminated insulating outer frame members 11 and 12 are shown respectively to carry relay steel magnet support angles 13 and 14 secured thereto by relay steel pole piece rivets 15 and 16.

Insulating sleeve 17 has stacked thereon bronze adjusting plate 18, bronze adjusting screw backing plate 19, steel blade backing spring 20, bronze spacer 21, bronze blade or reed 22, tipped with platinum iridium contact 23, bronze spacer 24, steel blade backing spring 25, bronze adjusting screw backing plate 26 and bronze adjusting plate 27. The stack is secured in place by nut 28 threaded onto bolt 29, and inserted as shown through outer frame members 11 and 12 and through sleeve 17. Adjusting screws 30 and 31 inserted respectively through holes 32 and 33 formed in frame members 11 and 12 and threaded through adjusting plates 18 and 27 to rest against backing plates 13 and 26 are adapted to position blade 22 and adjust the friction load thereon of backing springs 20 and 25.

At the other end of the switch structure insulating sleeve 34 has stacked thereon bronze terminal plate 35, bronze contact arm 36 to which is welded longitudinally thereof tungsten contact rod 37, steel backing plate 38, insulating spacer 39, steel backing plate 40, bronze contact arm 41, to which is welded longitudinally thereon tungsten contact rod 52, and bronze terminal plate 43. This stack is secured in place by nut 44 threaded onto bolt 45 inserted as shown through outer frame members 11 and 12 and through sleever 34. Adjusting screws 46 and 47 inserted respectively through holes 4-8 and 49 formed in frame members 11 and 12 threaded through 38 and 40 are adapted to positions and tion of contact rods 37 and 42.

adjust the separa- Switch polarizing C-shaped permanent magnet 50 cut away at 51 and 52, see Fig. 3, to receive bolts 53 and 54 is fitted closely to magnet support angles 13 and 14 and pole pieces and 16.

Brass electrostatic shield 55 formed with a cylindrical section 56 an end closing section 57 and another end flange section 58. Sections 56 and 58 are slotted in an axial plane at 59 to prevent the absorption of energy which might otherwise be received inductively from excitation electromagnetic coil 60 wound on insulating spool 61 magnetically coaxial with the switch structure. Pen manent magnet 50 and shield 55 are secured in place on angle supports 13, 14 by bolts 53, 54 and nuts 62, 63.

The entire relay structure is sealed in a metal can 64 Sealed to cylindrically flanged base 66 carrying terminal pins 66, 67, 65 69 and 70 insulatedly sealed therein.

insulated wires, 71., 72, connect the ends of magnet coil 60 to terminal pins 66, 67 and are shielded electrostatically from the switch structure by woven lead sleeve 73 electrically connected to shield 55 at one end and at the other to brass shield 74 secured on base 65 and adapted to isolate the space 75 within can 64.

Insulated wires 76, 77 respectively connect switch stationary contact terminal plates 35 and 43 to base pins )3 and 69. Insulated wire 78, as shown connects switch blade or reed 22 through spacers 21, 24, springs 20, 25 and plates 19, 26, to base pin 70.

In use my switch is adapted to complete an electric circuit between pins 70 and 68 by closing blade contact 23 on stationary contact 37 or to complete an electric circuit between pins 70 and 69 by closing blade contact 23 on stationary contact 42 depending on the direction of the magnetic flux Within or the polarization of the magnetic steel blade backing springs and determined by the direction of current flow in coil 60. The free ends of springs 20, 25, both biased into contact with blade 22 and positioned in the strong magnetic field between pole pieces 15, 16 of permanent magnet 50 will together move towards pole piece 15 or pol'e piece 16 carrying with them blade 22 and thus causing contact 23 to close on one of the stationary contacts 37 or 42. On a reversal of current flow in coil 60 the movement of springs 20, 25 will be in the opposite direction to force blade 22 to carry contact 23 to the other stationary contact.

It is seen that with the construction shown movement of blade 22 by springs 20, 25 is accompanied by a relatively longitudinal movement of the blade and springs and the engagement of blade 22 with springs 20, 25 is frictional and adapted to absorb the energy of either undesired natural vibration or bounce of the parts. It is also seen that the extension or overhand of blade 22 beyond springs 20, 25 is so short that the natural frequency of vibration of the blade end is too high to be of interest. All movement of blade 22 is forced and continuously damped and all spurious or parasitic action is minimized.

With this construction it is seen that the contact of contact 23 with either contact 37 or 42 will be with a predetermined controlled pressure determined by the current through coil 60 and that this pressurev will not be varied excessively by any free or natural action of the moving parts. Also it is seen that the contact area will be along a very narrow line of tangency of the relatively fiat surface of contact 23 with the small radius cylindrical surface of either contact 37 or 42. This controlled and minimal area of contact assures high unit contact pressure from the continuous and controlled pressure of springs 20, 25 on blade 22. With this construction contacts 37, 42 are successfully made of tungsten thus making use of its characteristics of minimum sparking and minimum metal transfer while at the same time its surface oxidation insulating eifect is minimized by the contact form and action.

Having thus recited some of the objects of my inven- 4 tion, illustrated and described a preferred form in which my invention is practiced, and explained its operation, I claim:

1. An electric circuit chopper comprising a resilient switch blade having a fixed end and a free end movable between a first contact position and a second contact position, a pair of resilient magnetizable spring blades, each of said spring blades having a fixed end and a free end, said spring blades being positioned on opposite sides of said switch blade with their fixed ends spaced from the fixed end of said switch blade, said free ends of said spring blades being biased into contact with the opposite sides of said switch blade near the free end thereof, means adapted to set up a first magnetic field through the free ends of said spring blades normal to said switch blade, means adapted to set up a second magnetic field longitudinally of said spring blades, one of said magnetic fields being of constant direction and substantially constant strength and the other of said magnetic fields being reversible thereby to select the one of the said contact positions toward which said free end of said switch blade will be moved by the combined action of said magnetic fields on said spring blades.

2. An electric switch comprising a resilient switch blade having a fixed end and a free end said free end having a neutral position and a pair of contact positions positioned respectively on opposite sides of said neutral position, magnetic means adapted to set up a first magnetic field normal to said switch blade near its free end and a second magnetic field along said switch blade, resilient frictional means biased into contact with said switch blade near its free end, said magnetic means including means adapted to move said free end of said switch blade to a selected one of its said positions, said frictional means being adapted yieldingly to resist the movement of said switch blade by said magnetic means, and said means adapted to move said free end of said switch blade including a pair of magnetizable spring blades positioned respectively on opposite sides of said switch blade, each of said spring blades having a free end and a fixed end spaced from the fixed end of said switch blade, the free ends of each of said spring blades being biased into contact with said switch blade in said first magnetic field and said spring blades being entirely in said second magnetic field.

3. An electric switch comprising a resilient switch blade having a fixed and a free end, said free end having a neutral position and a pair of contact positions posi tioned respectively on opposite sides of said neutral position, magnetic means adapted to set up a first magnetic field normal to said switch blade near its free end and a second magnetic field along said switch blade, resilient frictional means biased into contact with said switch blade near its free end, said magnetic means including means adapted to move said free end of said switch blade to a selected one of its said positions, said frictional means being adapted yieldingly to resist the movement of said switch blade by said magnetic means and said switch blade with said spring blades comprising said resilient frictional means.

References Cited in the file of this patent UNITED STATES PATENTS 1,159,189 Dempster Nov. 2, 1915 1,676,979 Cheeseman July 10, 1928 2,013,513 Dressel Sept. 3, 1935 2,207,292 Hensel et al. July 9, 1940 2,409,054 McBerty Oct. 8, 1946 2,423,524 Side July 8, 1947 2,433,740 Collins et al. Dec. 30, 1947 2,499,420 Sakatos Mar. 7, 1950 2,675,440 Reifel Apr. 13, 1954 2,678,360 Bellis May 11, 1954

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