US3218521A - Instrument type relay - Google Patents

Description

Nov. 16, 1965 N. P. ORTHS ETAL 3,218,521

INSTRUMENT TYPE RELAY Filed Jan. 12, 1962 2 Sheets-Sheet 1 FIG. 3

3 INVENTORS NORMAN P. ORTHS ERT J. CHERNANSKY BY 1% FIG. 2 V I ATTORNEY Nov. 16, 1965 N. P. ORTHS ETAL INSTRUMENT TYPE RELAY 2 Sheets-Sheet 2 Filed Jan. 12. 1962 FIG; 4

FIG.

INVENTORS NORMAN P. ORTHS OBERT J. CHERNANSKY ATTORNEY FIG. 6 I

United States Patent 3,218,521 INSTRUMENT TYPE RELAY Norman 1. Orths, Fanwood, and Robert J. Chernansky, Union, N .J., assignors, by mesne assignments, to Weston Instruments, Inc., a corporation of Texas Filed Jan. 12, 1962, Ser. No. 165,784 1 Claim. (Cl. 317-152) This invention relates to sensitive relays and particularly to instrument relays of the load current contact-aiding type.

Load current contact-aiding instrument relays are well known in the prior art and comprise broadly an intrument mechanism with a moving coil having two windings. One winding is connected to a source of small potential for advancing the moving coil and pointer to thus cause a moving contact element on the pointer to engage a stationary contact element at a predetermined point along the path of travel of the pointer. As a result of the initial closure of these contacts, a current is passed through the second winding in such a direction as to aid or increase the torque on the moving mechanism. This increases the mechanical pressure between the contact elements and thereby assures good electrical contact between them so that an external load circuit connected to these elements can be energized.

Relays of the above type are however subject to some unreliability. For instance, one aspect of this unreliability is due to the very low initial contact pressure between the contact elements and to the formation of high resistance films on these elements, either of which may prevent initial reliable closure and, of course, without satisfactory initial contact closure, improved closure by reason of the torque produced by the second winding is not assured.

Various designs have been evolved in an effort to eliminate the above disadvantages, and the problem of low initial contact pressure has been remedied to some extent by one known construction employing magnetic means for improving the contact pressure at the instant of closure. While there is some improvement on this aspect, other problems are then encountered, one of which is that the strength of the magnet is extremely critical. If the strength of the magnet is a small amount below the exact proper value, the desirable initial contact pressure is not obtained, and if the strength of the magnet is slightly too large, re-

setting of the mechanism cannot be reliably accomplished.

Moreover, the requirement of critical magnet strength substantially increases the cost of the magnet. Another disadvantage of the improved prior design referred to is that for instruments of different deflection sensitivities, different magnet strengths are required, and it is of course very advantageous to use only one magnet strength, if possible, for instruments of varying sensitivities. Among the advantages are that procurement of the magnet element and the storage and handling thereof are considerably simplified, which of course results in a cost reduction.

It is therefore an object of this invention to provide a load current contact aiding type instrument relay which is far more reliable than prior art relays of this type both with regard to the making of initial contact and with regard to resetting of the relay.

Another object is to provide a relay of the type referred to which has a higher initial contact pressure than similar type relays of the prior art.

Still another object is to provide an instrument type relay design having the improvements in the above stated objects which employs a magnetic contactclosure aiding means which does not require a critical magnet strength for satisfactory operation.

An important feature of the invention is that the identical magnetic contact closure aiding assembly can be employed with instruments of differing deflection sensitivities.

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These and other objects, features and advantages will become apparent from the following description and claim, taken with the accompanying drawings, in which:

FIGURE 1 is a plan view of the important parts of an instrument type relay constructed in accordance with the principles of our invention,

FIGURE 2 is a plan view of the instrument relay of FIGURE 1 showing various details of construction, and also showing the manner of connection of the relay contacts to an external circuit,

FIGURE 3 is a side view showing the relay as viewed from the left in FIGURE 2,

FIGURE 4 is an enlarged fragmentary view of the instrument relay of FIGURE 2 showing details of a magnetic system for aiding contact closure during operation of the relay, and

FIGURES 5 and 6 are perspective views of portions of the relay illustrating the position of the pointer under various conditions of operation.

Referring now to the drawings and particularly to FIG- URES 1, 2 and 3, the numeral 10 indicates generally the movable system of an instrument type relay which is supported by a pair of pivots, not shown, for rotation in a magnetic field between a pair of opposite magnetic poles 11 and 12. The instrument is of the load current contactaiding type having a moving coil assembly 13 comprising a signal coil terminating in a pair of wires 14a and 14b connected to a pair of terminals 15 and a contact-aiding coil terminating in a pair of wires 16a and 16b.

The moving system also includes a pointer 17 which moves relative to a meter scale 18 provided on a suitable scale plate 19. This pointer carries a member 20 of magnetic material such as soft iron which may be cylindrical but may also be any other suitable shape, such as for example, rectangular. There is also atfixed to the pointer arm 17 a contact member 21 which may be of any suitable material such as, for example, platinum-iridium alloy and which is adapted to contact a relatively fixed contact as will later appear.

'There is also provided a set-point index arm 23 of nonmagnetic material, such as brass or aluminum, which is adjustable preferably about the axis of rotation of the pointer 17. AffiXed to this index arm is a mounting plate 24, also of non-magnetic material, which carries a pin 25 that is adapted to ride in a slot 26 in a member 27. This member is adapted tobe rotated by turning the screw 28 to thereby effect movement of the set-point index arm 23 to any desired position by means of the pin 25 and slot 26 driving arrangement.

A magnetized member such as a permanent magnet 31 is secured to the top of the mounting plate 24 and an elongated flux concentration or magnetic shielding member 32 in the form of one or more fiat stacked plates is secured to the bottom thereof. These plates 32 are of a high permeability magnetic material such as for example soft iron, to provide a predetermined magnetic flux pattern as seen in FIGURE 4 and which is described in detail hereinafter.

The set-point index arm 23 is further provided witha downwardly extending strip 34. This strip serves as a backing or support for a leaf-type spring contact 35 which is flexibly or resiliently mounted at one end to the strip and which may be of any suitable material such as platinum-iridium alloy similar to the movable contact 21. As can be seen from FIGURE 2, the contacts 21 and 35, when closed, complete a seriescircuit which includes a load 36, a suitable direct current source 37, a normally closed resetting switch 38 and the contact-aiding coil between the wires 16a and 16b. The load may be any device or circuit to be controlled, such as a relay or motor for example.

In order to fully appreciate the manner of operation of our improved instrument relay, reference is now made to FIGURE 4 which shows in detail the magnetic system employed to produce the particular flux pattern which makes superior performance over prior art devices possible. In this figure, the dashed lines 41 and the solid lines 41 represent the natural flux lines surrounding the magnet 31, and it will therefore be appreciated that depending upon the magnet strength, the magnetic field will influence a given magnetic object at different distances therefrom. This is obviously undesirable since only magnets falling within a certain range of magnetic strength could be employed in order to attract the magnetic member 20 of the pointer at a given position of the pointer. This disadvantage is obviated by directing sufficient flux on one side of the magnet through the high permeability magnetic shielding member 32 so that virtually no flux exists in the space to the left or downscale of this member in the path of travel of the magnetic member 20. Due to the flat shape of the member 32 however, considerable flux is allowed in the region directly beneath this member in the path of travel of the pointer 17 and the magnetic member 20. The resulting flux pattern is represented by the solid lines 42 in FIGURE 4. A controlled magnetic field is thus produced which eliminates the need for magnets of critical strength since the flux is now constrained to pass beneath and through the magnetic shielding member 32, so that there is negligible flux downscale of the magnetic shield 32 in the path of travel of the magnetic member 20.

The operation of our improved instrument will now be described. The point or particular value on the scale 18 at which it is desired to actuate the load circuit is initially preset by adjusting or setting the set-point index arm 23 such as, for example, to the value 80 as seen in FIGURES 5 and 6, by rotating the screw 23 shown in FIGURE 1. This will force the pin 25 to ride in the slot 26, thus moving the index arm 23 to the desired position. Once this is established no additional setting is necessary unless it is desired to change the particular pointer deflection at which it is desired to actuate the load circuit.

In the actual operation of the relay a suitable deflection potential is applied to the terminals to thus energize the signal coil connected to the wires 14a and 14b. When this signal coil is actuated a torque is produced which rotates the pointer 17 upscale in the direction of the index arm 23. As the pointer progresses toward the magnetic assembly on the index arm 23 (see FIGURE 4), there is no influence of the magentic field on the magnetic member 20 until the pointer tip reaches the exact point at which the index arm 23 is set. At that point the influence of the magnetic field 42 becomes effective to urge the magnetic member 20 and therefore the entire moving system further upscale to a position several degrees above that shown in FIGURE 5. The action of the magnetic field 42 on the soft iron member 20 is in the nature of a snapping action and is such as to accelerate the pointer so that the contact 21 on the pointer arm 17 engages the surface of the spring contact 35. When these contact elements engage, a wiping contact is made by reason of the raised position of the free end of the spring 35 and this fact, in combination with the contact pressure pro duced by the snapping action, assures a reliable electrical circuit between the contact elements 21 and 35. As can be seen from FIGURE 2, the load circuit is now completed and the load current will therefore pass through the current aiding coil connected between the wires 16a and 16b. This current produces an aiding torque to drive the moving coil assembly further upscale another several degrees. This torque flexes the spring 35 against the backing strip member 34 and the pointer is then in the position shown in FIGURE 6. It is to be observed that the soft iron member 20 does not come in physical contact with any part of the magnetic assembly along its path of travel.

Resetting of the movable system is accomplished by opening the normally closed resetting switch 38 thus breaking the load circuit and, therefore, interrupting the current through the current aiding coil. As a result, there is insuflicient torque to hold the spring element 35 in its compressed position against its backing strip 34, and the potential energy stored in the spring element produces a counter-torque on the movable assembly. This counter torque rotates the movable assembly downscale to the left of the magnetic flux field 42. The movable assembly will then assume a new position at some point on the scale 18 or will cause the contacts 21 and 35 to reengage in the manner described above, depending upon the value of the deflection potential applied to the terminals 15 when the resetting switch 38 is opened. Assuming this value to be zero, the pointer will of course assume the scale zero or reset position. Upon re-application to the terminals of a deflection potential suflicient to cause the pointer to reach the preset position of the index arm 23, the sequence of operation described above with regard to the engagement of the contacts 21 and 35 with consequent completion of the load circuit will occur.

Having now described our invention in accordance with the patent statutes, various changes will suggest themselves to those knowledgeable in this art. For example, it is apparent that instead of providing the flexible spring member 35 on the index arm 23, it could also be satisfactorily mounted to rotate with the moving coil assembly and the fixed contact could be carried by the index arm or its assembly. Also both contact elements could be flexibly or resiliently mounted, if desired. Further, the particular construction employed in FIGURE 4 to produce the controlled magnetic field 42 can also obviously be modified by the use of magnets and flux concentration or magnetic shielding members 32 of different configuration and position relative to each other to vary the influence of the magnetic field on the movement of the soft iron member 20.

By means of the invention described above a number of important advantages have been produced. One of the more important of these is that it is no longer necessary, as in prior devices of this type, to carefully se.ect only magnets of certain strength for use in the contact aiding magnetic assembly to assure reliable operation. This, of course, results from the improved construction which produces a controlled magnetic flux pattern that is substantially independent of the magnet strength, so that the point at which the pointer is drawn in by the magnetic field no longer depends critically upon the magnet strength. Furthermore, a magnet of a given strength can now be employed satisfactorily for instruments having substantially dilferent deflection sensitivities. Additionally, with this construction relatively strong magnets can be employed so that resetting can still be reliably achieved while permitting high contact closure pressures. Moreover, a much larger initial contact pressure is available while still allowing reliable resetting. Also, far more reliable contact closure is achieved in our design than with prior devices and contact life is considerably lengthened, since the greater initial contact pressures can more easily break through any oxide films or contaminants on the contacts to establish a good electrical path.

Since many changes could be made in the above construction and many apparently widely-different embodiments of this invention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

A load-current-contact-aiding type instrument relay comprising a movable system including a first coil adapted for connection to a source of deflection potential to produce a first torque for rotating said movable system from a rest position,

a first unmagnetized contact element mounted on said movable system,

a second unmagnetized contact element adapted to be engaged by said first contact element upon rotation magnetic flux source and a magnetic shield so disposed relative thereto that there is a region of negligible flux in the path of travel of said magnetic member between its rest position and said magnetic effect an accelerated rotation of said movable system and cause mutual engagement of said first and second contact elements, said magnetic member being out of physical contact with said magnetic flux sysof said movable system, at least one of said contact 5 tem along its entire path of travel, said magnetic elements being resiliently mounted, member being rotated by said first torque into said a second coil included in said movable system adapted magnetic field, said magnetic flux system and said to be energized upon the mutual engagement of said second unmagnetized contact element being seleccontact elements for producing a second torque to tively adjustable as a unit to predetermined positions further rotate said movable system to produce a wip- 10 adjacent the path of travel of said magnetic meming contact between said contact elements and to her to establish predetermined magnitudes of deflecflex said resiliently mounted contact element to build tion potential at which the mutual engagement of up potential energy of sufiicient magnitude in said resaid first and second contact elements is effected, siliently mounted contact element to cause said movand able system to return to its rest position when no switching means for de-energizing said second coil to potential is applied to said first coil, allow said movable system to return to its rest posimagnetic member rigidly secured to said movable tion when no deflection potential is applied to said system and adapted to be rotated thereby from a first coil, the magnitude of the potential energy built rest position along a curvilinear path of travel, up in said resiliently mounted contact element being magnetic flux system including a rigidly mounted sufficient to overcome the third torque produced by said magnetic field.

References Cited by the Examiner UNITED STATES PATENTS shield, said magnetic flux source establishing a mag- 593 47 1952 Snell 20 11 X netic field in the path of travel of said magnetic 2 331 942 4 195 Dreyer et 1 200G member between said region of negligible flux and 3 042 340 7 19 2 Eadie, 1 317 152 said magnetic flux source adapted to cooperate with said magnetic member to produce a third torque to SAMUEL BERNSTEIN, Primary Examine?-

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