US2797372A - Electromagnetic switches - Google Patents

Description

' June 25, 1957 G. H. COLE 2,797,372

ELECTROMAGNETIC SWITCHES Filed May 15, 195:5

20' 1s 55 55 ss 55- l L. I15, 2 v IE. 3 y 33 INVENTOR. 1 66 GEORGE H.. couz BY 32 5 -/iw 4 I ATTORNEY 2,797,372 Patented June 25, 1957 See ELECTROMAGNETIC SWITCHES George H. Cole, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application May 15, 1953, Serial No. 355,364

Claims. (Cl. 317-182) This invention pertains to electromagnetic switches and more particularly to the type known as vibrators or synchronous choppers.

When electromagnetic Vibrators are used to interrupt electric circuits, a common arrangement is to have two sets of contacts, each set of contacts comprising a fixed and a movable contact. For each set of contacts, there is generally a first adjustment for positioning the fixed contact and a second adjustment for positioning the movable contact which also is a means for setting the contact pressure between the fixed and the movable contact. Each set of contacts may be adjusted so that they are closed or opened when the actuating reed or vibrating member is at its neutral or mechanical centered position, this being dependent upon the application of the vibrator. Normally, each set of contacts is adjusted with respect to its own movable and fixed contacts and to the reed when the vibrator is deenergized and the reed is in its mechanical neutral or center position. It is often found, however, that when the vibrator is energized, the center line of vibration of the reed is not the same as the mechanical centered position of the reed. In effect, this means that the preset contact arrangement has been upset and that one set of contacts will be open (or closed, depending upon the arrangement used) more than the other set of contacts. The reason for the electrical center (vibrator energized) being different from the me chanical center (vibrator deenergized) is that the driving mechanism for the vibrating reed has a greater effect on the reed When it is being displaced in one direction than when it is being displaced in the opposite direction. The uneven displacement of the reed results in the electrical. center being displaced from the mechanical center, and for precision applications, even a displacement of a small fraction of an inch will have an adverse effect on the performance of the vibrator.

The problem of the electrical center of vibration of the reed not coinciding with the mechanical center of the reed can be overcome by changing the relative positions of each set of contacts with respect to the reed. This is difficult and time consuming however, because four adjustments (the two fixed contact adjustments and the two movable contact or contact pressure adjustments) have to be made. There are actually three variables to consider. They are the position of each fixed contact with respect to its movable contact and the position of each set of contacts with respect to the reed. It follows that, at best, to satisfy three variables as a function of four adjustments is a costly calibration procedure from the standpoint of the time consumed.

It is with this problem in mind that I have devised a novel method of overcoming the characteristic of a vibrator which results in the electrical center being displaced from the mechanical center.

It is an object of my invention to provide a means in a vibrator whereby, using a single adjustment, the electrical center can be made to coincide with the mechanical center.

A further object of the invention is to provide a means 'of varying the center line of vibration of a vibrating reed in an electromagnetic vibrator without changing the amplitude of vibration.

Another object of the invention is to provide a means of varying the effects of a permanent magnet on the vibrating reed without performing any machining operations on the magnets.

Further objects, features and advantages will be apparent from a consideration of the following description taken in connection With the accompanying drawings in which:

Figure 1 is a plan view, partly in section, of an electromagnetic vibrator embodying my invention;

Figure 2 is a transverse cross-sectional view of the vibrator shown in Figure l and as viewed along section lines 2-2 of Figure 1;

Figure 3 is a right end view of the vibrator shown on Figure 1 with the cover in section; and

Figure 4 is a partial back side elevation of the vibrator shown on Figure 1.

The vibrator shown in Figure 1 comprises essentially a vibrating reed 11 which is pivoted at one of its ends and is adapted to be displaced at its other end under the combined effects of a pair of U-shaped permanent magnets 12 and 13 and a coil 14 wound on a bobbin 15 so as to circumscribe the free end of the reed.

The main base 20 for the vibrator is a rectangular nonmagnetic member of either metallic or non-metallic composition. It has been found desirable to make base 20 out of a metal such as aluminum or brass. The main support for the mechanical components of the vibrator is an essentially rectangular piece 21 hereafter referred to as the frame member which is secured to the main base 20 by a plurality of screws 22 and has at its right end a pair of bent up portions 23 which are disposed parallel to one another so as to form a U-shaped portion with the bight of the U being co-planar with the frame member 21. Frame member 21 may be of any suitable non-magnetic material, either metallic or non-metallic, but it has been found that aluminum or brass is especially suitable for this use. The material at the two left hand corners of the frame member 21 is removed so as to save weight and positioned at the left end of frame member 21 is a reed supporting member 24 secured to the frame member 21 by a pair of screws 25 which fasten into the reed support 24 from the bottom, passing through suitable holes in the main base 20 and the frame member 21. The reed support member 24 has a longitudinal slot 26 therein in which is disposed the reed 11 which, as is shown in Figure 2, has a rectangular cross section. A screw member 27 cooperates with the reed support 24 so as to clamp reed lLwith respect thereto.

An auxiliary frame member 30, shown clearly in Figure 2 as being U-shaped, is positioned with its open side facing the frame member 21 and is secured thereto by a plurality of machine screws 31. The auxiliary frame member 30 is made out of a non-magnetic material, either metallic or non-metallic, but it has been found that aluminum or brass is especially suitable for this purpose. The auxiliary frame member 30 is attached to the vibrator frame member 21 intermediate the latters two ends and defines a space therebetween. Each of the sides of the auxiliary frame member 30 have a pair of rectangular apertures therein, through which extend the two legs of the U-shaped permanent magnets 12 and 13. The legs of the permanent magnets 12 and 13 are inserted through the apertures until the yoke portion of the permanent magnets abuts against the auxiliary frame member 30. The permanent magnets are held in place with respect to the auxiliary frame member 30 by non magnetic bracket members 32 which overhang the yoke portions of the permanent magnets and are attached to the auxiliary frame member 30 by a plurality of machine screws 33. The bobbin member around which is wound coil 14 is adapted to rest on the frame member 21 and to be disposed between the legs of the permanent magnets 12 and 13 and is adapted to circumscribe the vibrating reed 11 with sufiicient clearance allowed to permit displacement of the reed in a direction transverse to the longitudinal axis thereof. Coil 14 is adapted to be energized by an alternating current voltage and suit able connections, not shown, are so provided.

It is to be noted that permanent magnets 12 and 13 are positioned in the auxiliary frame member so that their opposite polarity extremities are in near abutting relationship so as to define a pair of air gaps therebetween. Reed member 11. extends within the pair of air gaps defined by the magnets 12 and 13 and has attached thereto a pair of magnetic plates 34. It will be understood that when coil 14 is energized by alternating current, the magnetic plates 34 attached to reed 11 will assume alternating polarities and will react with the permanent magnets 12 and 13 in such a way so as to cause reed member 11 to vibrate transverse to the longitudinal axis of the reed.

Abutting each end of the auxiliary frame member 30 and secured to the same by machine screws 31 are a pair of high permeability steel shield members 35 and 36 which have a rectangular aperture 37 therethrough to permit displacement of the reed 11. The purpose of shields 35 and 36 is to provide a low impedance path for any stray flux that otherwise might have a tendency to get into the contact structure, to be described below and thereby induce voltages which would be adverse to the operation of the device.

A cover member 70 is adapted to enclose the vibrator and is secured to base 20 by a plurality of screws 71. An annular gasket member 72 is disposed between cover member 70 and base 20 so as to provide a dust tight seal. A second gasket member '73 is secured to the underside of base member 29 so as to provide a cushioned junction of the vibrator with a chassis or similar member, not shown.

Secured to the free end of the reed 11 as by riveting, not shown, is a bracket 40 made out of insulative material having a pair of extended portions 41, which are adapted to engage the free ends of a pair of movable contact members 42 which have button type contacts 43. The other ends of the movable contact members 42 are secured to but insulated. from a pair of spring brackets 44 which are secured to the vibrator frame 21 by any suitable means such as by riveting shown at 45. The free ends of the spring brackets 44 are adapted to cooperate with the ends of adjustment screws 46, the purpose of which will be explained below. The heads of the adjustment screws 46 are accessible from the underside of the main frame member 20 and are preferably of the Allen-head type. The adjustment screws 46 pass up through suitable apertures in frame members 20, 21, and are held in place by Elastic Stake Nuts 47.

A pair of insulaL ve support members 50 are secured to the upstanding legs 23 of the vibrator frame member 21 as by riveting shown at 51. A pair of metallic contact supports 52 are secured to the insulative support members 50 by any suitable means such as riveting, not shown. Suitable apertures are provided in the upstanding legs 23 of frame member 21 and insulative support members 50 so as to permit the passage therethrough of fixed contact members 53 each having at their inner end a contact button 54 which cooperates with the contact buttons 43 of the movable contact members 42 and have at their other end a head member preferably of the Allen-head type. It is seen that with this arrangement, the stationary contacts 53 are secured to but insulated from the upstanding legs 23 of the frame member 21.

The metallic contact blocks 52 and the movable contacts 42 are electrically connected to a plurality of terminal pins 55 which extend through but are insulated from the main base member 20, the electrical connection being a plurality of connecting wires 56. The lower ends of members 55 serve as connecting terminals when the vibrator is connected to an external circuit, not shown.

It will be appreciated that the fixed contacts 53 are adjustable transverse to the longitudinal axis of the vibrating reed 11 and that the adjusting screws 46 provide a means of varying the contact pressure between the movable contacts and the stationary contacts.

It will be seen that there are two sets of contacts in the described vibrator, each set of contacts comprising a fixed and a movable contact. Depending upon the appli tion of the vibrator in an external circuit, not shown, each set of contacts may be adjusted so that they are opened or closed when the vibrating reed 11 is at its neutral or mechanically centered position. In other words, when coil 14 is deenergized, the reed 11 assumes an intermediate position determined by reed supporting block 24. At this point, the contacts of the vibrator may be adjusted so that each set of contacts is a prescribed distance away from the center of reed 11 and also so that the movable and fixed contacts making up each contact set are correctly positioned with respect to each other. The contact adjustments are made by adjusting the fixed contact screws 53 and the movable contact adjustment screws 46. It is generally found, however, that when coil 14 is energized, the center line of vibration of the reed is not the same as the mechanical centered position. One of the main reasons for the electrical center (vibrator energized) being different from the mechanical center (vibrator deenergized) is that one of the permanent magnets 12 and 13 has a greater effect upon the magnetic plates 34 than the other permanent magnet and consequently there is a greater displacement toward the one than the other.

To overcome the discrepancy in the effects of each of the permanent magnets upon the magnetic plates 34, a magnetic member 69, of a high permeability steel, is positioned so as to bridge one of the air gaps formed by the permanent magnets and is adapted to be in metallic contact therewith. The shunt member has a threaded aperture extending therethrough transverse to the longitudinal axis of the reed 11 and threaded therethrough is a shunt adjustment screw 63.

Screw 63 has a head portion 64 with a tool receiving slot therein and is journallcd at its ends in the auxiliary frame member 36. As shown in Figure 4, the unheaded end of screw 63 is reduced in diameter as at 65 and is journallcd in a vertically elongated aperture 66 in one side of auxiliary frame member 30. A horizontal slot 66a of slightly greater width than end 65 of screw 63 connects aperture 66 to the edge of auxiliary frame member 30. The headed end 64 of screw 63 is journallcd in an aperture in the other side of auxiliary frame member 36, said last named aperture being similar to aperture 66. A shoulder portion 67 on screw 63 is integral therewith and is of a greater diameter than the aperture in which the headed end 64 of the screw is journallcd. A washer 63, also of greater diameter than said last named aperture, is positioned around screw 63 near head 64 and on the outer side of auxiliary frame member 30. A snap ring 69 cooperates with a groove, not shown, on screw 63 and abuts against washer 68. Shoulder 67 and washer 63 abutted by snap ring 69 serve to position screw 63 with respect to auxiliary frame member 30 and allow screw 63 to be rotated in member 3%) but prevent any relative transverse motion. A spring member 61, fastened to the underside of the auxiliary frame member 30 as by rivets 62 is adapted to bear against the top of magnetic shunt member 60 and thus insure a good metallic contact of the shunt member 60 with the leg portions of the permanent magnets 12 and 13. The purposes of the elongations in the apertures in which screw 63 is journalled (see aperture 66 in Figure 4) is to allow for vertical displacement of screw 63 and shunt member 60 under the influence of spring 61. The purpose of slot 66a is to allow the insertion of screw 63 into member 30.

It will be appreciated that rotation of screw member 63 will result in the magnetic shunt member 68 being moved along the legs of the permanent magnets 12 and 13 and transverse to the longitudinal axis of reed member 11. It follows that as the magnetic shunt member 60 is moved or displaced in one direction or the other, the amount of metallic contact with it and one of the permanent magnets is increased while at the same time the amount of metallic contact with it and the other permanent magnet is decreased. As the amount of metallic contact of the magnetic shunt member 60 is increased with one of the permanent magnets, the eifect of that magnet upon the magnetic plates 34 attached to the reed 11 will be decreased. At the same time, as the amount of metallic contact of the magnetic shunt member 60 is decreased with the other of the permanent magnets, the eifect of that magnetupon the magnetic plates 34 attached to the reed 11 will be increased.

Thus, if it is determined that the electrical center of vibration of the reed 11 is not the same as the mechanical center, simply by adjusting screw member 62 and consequently transversely moving shunt member 60 with respect to the permanent magnets 12 and 13, the eifects of the magnets upon the plates 34 are varied in opposite sense and the vibrator is quickly and easily brought into adjustment without any time consuming adjustments of the fixed contacts 53 and movable contact adjustments 46.

In the manufacturing process, When the vibrator has been assembled and is being calibrated, each of the sets of contacts is adjusted with respect to the mechanical center of the reed 11 and the pressure between the individual stationary and moving parts thereof. The Vibrator is then energized and suitable means such as connecting an oscilloscope to the output terminals 55 are used to determine Whether or not the action of the contacts is symmetrical. Assuming that the action is not symmetrical, screw 62 is rotated until the magnetic shunt member 60 brings the electrical center of vibration to coincide with the mechanical center, this being indicated visually on the oscilloscope.

It will be appreciated by those skilled in the art that I have developed a positive and quick method of making the electrical center of vibration of the reed 11 coincide with its mechanical or neutral position. It will be further appreciated by those skilled in the art that the tot-a1 amplitude of vibration of the reed remains constant for variations in the position of shunt member 60 due to the fact that as the efiect of one magnet is increased, the effect of the other is decreased.

While I have shown and described the specific embodiment of this invention, further modifications and improvements will occur to those skilled in the art. I desire it to be understood, therefore, that this invention is not limited to the particular form shown and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of this invention.

What I claim is:

1. In a vibrator, a base frame member, an auxiliary non-magnetic rframe comprising apertured sides attached to said base member forming an open rectangular space therewith, a plurality of magnets attached to said auxiliary frame member, said magnets having pole portions extending through said apertures into said space defining a pair of air gaps, a non-magnetic reed attached at one of its ends to one end of said base. and extending through said space and Within said air gaps, a pair of magnetic plates attached to said reed adjacent to said magnets, a coil adapted to be energized by alternating current positioned around said plates, and a magnetic shunt member associated with said magnets and bridging one of said air gaps, said shunt member being adjustable trans verse to the longitudinal axis of said reed so as to vary the effects of said magnets on said pair of plates.

2. In a vibrator, a base member, a non-magnetic member having sides with apertures therein and being attached to said base member so as to define a space therebetween, a plurality of magnets attached to said nonmagnetic member, said magnets having leg portions extended through said apertures into said space so as to define a pair of air gaps, a non-magnetic reed attached at one of its ends to one end of said base and extending through said space and within said air gaps, magnetic means attached to said reed adjacent to said magnets, a coil adapted to be energized by alternating current positioned around said magnetic means, and a magnetic shunt member in direct contact with said magnets and bridging one of said air gaps, said shunt member being adjustable transverse to the longitudinal axis of said reed so as to vary the etfects of said magnets on said magnetic means.

3. In a vibrator, a base member, a non-magnetic member having sides with apertures therein attached to said base member so as to define a space therebetween, permanent magnetic means attached to said non-magnetic member, said permanent magnetic means having portions extended through said apertures into said space so as to define a plurality of air gaps, a reed attached to said base and extending within said air gaps, magnetic means attached to said reed adjacent to said permanent magnetic means, a coil adapted to be energized by alternating current positioned within said space and around said reed, and a magnetic member associated with said permanent magnetic means and bridging one of said air gaps, said magnetic member being adjustable parallel with said portions of said permanent magnetic means so as to vary the effects of said permanent magnetic means on said magnetic means.

4. In a polarized vibrator, a non-magnetic frame member, a plurality of magnets attached to said frame member and positioned with opposite polarity extremities in near abutting relationship so as to define a pair of air gaps therebetween, a non-magnetic vibrating reed member mounted at one extremity at one end of said frame member and disposed to extend Within said air gaps, a pair of plates of magnetic material mounted on said reed and disposed adjacent the extremities of said magnets, a coil encircling said reed and said pair of plates and adapted to be energized by alternating current, and a transversely adjustable magnetic member bridging one of said air gaps so as to vary the elfect of each magnet on said pair of plates.

5. In a polarized vibrator, a non-magnetic frame member, a plurality ofmagnets attached to said frame member and positioned with opposite polarity extremities in near abutting relationship so as to define a pair of air gaps therebetween, a vibrating reed member mounted at one extremity at one end of said frame member, and comprising a magnetic portion disposed within said air gaps, a coil encircling said magnetic portion and adapted to be energized by alternating current, a magnetic member bridging one of said air gaps, and means for moving said magnetic member in a direction transverse to the longitudinal axis of said reed so as to simultaneously vary the effect of at least a pair of said magnets on said reed.

References Cited in the file of this patent UNITED STATES PATENTS 840,987 Athearn Jan. 8, 1907 1,816,558 Zupa July 28, 1931 2,423,524 Side July 8, 1947 2,433,740 Collins et al. Dec. 30, 1947 2,443,784 Bullen et al. June 22, 1948 2,473,353 Aust June 14, 1949 2,593,508 Washburn Apr. 22, 1952 2,642,508 Wilson June 16, 1953

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