US3068333A

US3068333A - Control device

Info

Publication number: US3068333A
Application number: US54620A
Authority: US
Inventors: Jr John C Hewitt
Original assignee: Robertshaw Fulton Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1960-09-08
Filing date: 1960-09-08
Publication date: 1962-12-11
Anticipated expiration: 1979-12-11

Description

Dec. 11, 1962 J. c. HEwlTT, JR 3,068,333

CONTROL DEVICE Filed Sept. 8, 1960 2 Sheets-Sheet 1 Dec. 11, 1962 J. c. HEwlTT, .JR 3,068,333

coNTRo DEVICE Filed Sept. 8, 1960 v 2 sheets-sheet 2 United States Patent Otice 3,068,333 Patented Dec. l1, 1962 3,068,333 QNTRL DEVICE .lohn C. Hewitt, ltr., Long Beach, tlalif., assigner to Rohertshaw-Fuiton Controls Company, Richmond, Va., a corporation et Virginia Fiied Sept. 1959, Ser. No. 54,620 9 Claims. (Cl. 20d-S7) The invention presented herein relates to magnetically actuated switching devices and more particularly to magnetically actuated switching devices which are operated by varying the proximity of a source of magnetic flux and a magnetic responsive armature of a switching unit with respect to each other to control the relative position of the switch conta-cts in the switch unit.

Generally, the movable contact spring of a switch unit is provided with an armature of ferro-magnetic material which moves in response to the magnetic flux provided by a permanent magnet. The magnet is moved into proximity with the armature by an actuating means. Since the magnetic force of attraction increases more rapidly than the tension of the contact spring, the armature moves rapidly toward the magnet as the magnetic force of attraction increases, causing the contacts of the switch unit to move with a snap action. lf the Contact lspring is moved to close a circuit, the spring is then under tension and movement of the magnet away from the armature causes the contacts to open with a snap action. This snap action is desirable since it increases the life of the contacts by materially reducing any arcing that may be present.

The maintenance of contact pressure up to the point of snapover is also an important factor from the standpoint of switch life. However, it is apparent that in prior known magnetically actuated switches of this type, the build-up of the magnetic iorce of attraction up to the snap action point is gradual, causing a reduction in the contact pressure prior to the snap action movement between the source of magnetic ilux and the armature.

lt, therefore, is an object of the invention presented herein to provide an improved means for rapidly opening and/or closing switch contacts of magnetically actuated switch devices.

Another object of the invention is to provide an improved means or maintaining switch contact pressure u-p to the point of opening of the switch contacts.

An additional object of the invention is to provide a magnetically actuated `switching device which is easily adjusted.

A further object of the invention is to provide a magnetically actuated switching device requiring less force diiterential provided by the actuating means to change the proximity of the source of magnetic liux with respect to the armature to control movement of the contacts of the switch unit.

Still another object of the invention is to provide an improved magnetically actuated switching device which permits independent adjustment for two sets of contacts.

Yet another object of the invention is to provide an improved magnetically actuated switching device in which the force for varying the proximity of the source of magnetic flux with respect to the armature to close or o-pen switch contacts is stored and then suddenly released to provide the desired snap action between the source of magnetic iiux and the armature.

These and other objects of the invention presented herein are attained in a switching device comprising an auxiliary magnetic responsive member in combination with a magnetic responsive armature of a switch mechanism and a source of magnetic iiux. By using an auxiliary magnetic responsive member, the `speed with which the magnetic field builds up is increased to produce a more rapidly induced snap action movement. This is accomplished by positioning the auxiliary magnetic responsive member intermediate the source or" magnetic flux and the magnetic responsive member of the switch mechanism. An actuating force, suppiied by a thermally sensitive bimetal member, a pressure responsive diaphragm, or the like, is used to change the proximity of the source of magnetic iiux and the auxiliary magnetic responsive member to each other. As the distance between the source of magnetic iiux and the auxiliary magnetic responsive member is decreased, the magnetic force of attraction between them increases rapidly to cause a rapid decrease in the distance separating the source of magnetic ilux and the auxiliary magnetic responsive member.

Prior to this snap action movement, the magnetic responsive member of the switch mechanism has not moved. Since the auxiliary magnetic responsive member is located intermediate the magnetic responsive member of the switch mechanism and the source of magnetic tlux, the lines of magnetic ilux at the source of the magnetic flux are -rapidly transferred to a point closer to the magnetic responsive member of the switch mechanism when the source of magnetic iiux and the auxiliary magnetic responsive member are brought together with a snap action movement. The increase in density of the lines of magnetic iiux adjacent the magnetic responsive member of the switch mechanism is thus very rapid, causing a rapid movement of the magnetic responsive member of the switch mechanism toward the auxiliary magnetic responsive member.

in another embodiment, the auxiliary magnetic responsive member is positioned adjacent the source of magnetic flux. An actuating force which increases in magnitude is applied to the source of magnetic iiux tending to move the source toward the magnetic responsive member of the switch mechanism. The actuating force builds up until it is suflicient to overcome the magnetic force of attraction between the auxiliary magnetic responsive member and the source of magnetic flux. The separation of a source of magnetic liux and the auxiliary magnetic responsive member is sudden, causing the force acting on the source of magnetic tlux to move the source of magnetic flux rapidly to the point adjacent the magnetic -responsive member of the switch mechanism. The magnetic torce of attraction between the magnetic responsive member of the switch mechanism and the source of magnetic flux is therefore built up very rapidly, causing the magnetic responsive member of the switch mechanism to move toward the source of magnetic linx very rapidly.

The invention wiil best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FiG. 1 is a side elevation of a magnetically actuated switch embodying the invention, with some parts shown in section and the switch in one operating position;

FIG. 2 is like FIG. 1, showing the switch in its othe operating position;

FiG. 3 is an end elevation of the device shown in FlG. 2 looking in the direction of arrow 3 of FlG. 2;

FlG. 4 is a fragmentary side elevation of another ernbodiment of the invention with some parts shown in section;

FIG. 5 is a fragmentary side elevation of another embodiment of the invention;

FIG. 6 is a fragmentary side elevation of Athe device illustrating a modification of the embodiment shown in FGS. 1-3; and

FIG. 7 is an end elevation of the device as shown in FIG. 6, looking in the direction of arrow '7 of FIG. 6.

In FIG. l, there is illustrated Ia simple thermal responsive switching device embodying the invention. The switching device comprises a switch mechanism 1 having a magnetic responsive member 2 and switch contact 3 carried lat one end of a flexible leaf spring d; a permanent magnet 5 carried by yieldable member 6 and an auxiliary magnetic responsive member 7 adjustably positioned intermediate magnetic responsive member 2 by means of a screw 8.

The switch mechanism 1 is mounted in a glass or quartz ltube 9 which is either lair-filled at par-tial vacuum or filled with any suitable gas, such as hydrogen, nitrogen, or neon. Hydrogen is especially suitable as it has good thermal conductivity and maintains the contacts clean. The tube 9 is carried by a lC-shaped bracket 10 secured to a support or base member 11, as by screws. This mounting permits the ltube 9 to be moved along i-ts longitudinal axis and to be rotated about its longitudinal axis for proper positioning of the switch mechanism 1 with respect to the other parts of the device. After the tube 9 is positioned, it is secured in place by any suitable means, such as by application of an adhesive resin 'applied adjacent the bracket 1t) and the tube 9.

The yieldable member 6 is in the form of a leaf-type bimetallic element which is secured at one end to the support or base member 11 by suitable means, such as a screw 12. Any suitable arrangement can be used to move the bimetal element 6 toward or away from the auxiliary magnetic responsive member 7 to provide temperature calibration. Thus, for example, the yieldable member 6 can be a flat spring member which can be actuated by a bellows or Bourdon tube.

The switch mechanism 1 is shown as a double-pole switch capable of operating two separate circuits and has three

terminals

13, 14, and 15, which extend through one end of tube 9. The middle terminal 14 is common to both circuits to be controlled. r[he terminal 13 is connected to one circuit and terminal 15 is for connection to another circuit. The switch mechanism 1 has two subasseinblies, each having an elongated frame with a U-shaped cross section. These brackets or frames are made of materials having a low magnetic permeability. The bottom or connecting legs of the frames are spaced apart by the outer legs of the lower frame 16 which lie within the outer legs of the upper frame 17 and abut the connecting leg of the upper frame 17.

A frame insulator 18 is positioned adjacent the outer surface of the connecting leg of frame 17 and a similar frame insulator 19 is positioned adjacent the inner surface of the connecting leg. The frame insulators 18 and 19 consist of thin strips of suitable electrical insulating material, such as mica. A contact leaf 20 of thin resilient material is positioned adjacent the frame insulator 1S and is electrically connected to terminal 13. A contact leaf 21 is positioned parallel to the frame insulator 19 and is spaced from the insulator 19 by metal spacer 22. The contact leaf 21 is made from a material having a low magnetic permeability. A rivet 23, positioned intermediate the ends of the frame 17 and staked in place, is used to hold the frame 17, frame insulator 18, 19, contact leaf Zt?, spacer 22, `and contact leaf 21 together as a unit. A hole having a diameter in excess of the diameter of the rivet 23 is provided in frame 17 to prevent electrical con-tact between the rivet 23 and frame 17. The contact leaf 21 is secured at one end portion. The frame 16 has similar components secured tot it.

Frame insulators

24, 25, contact leaf 26, spacer 28, and contact leaf 27 are secured to frame 16 by rivet 29, and correspond respectively to frame insulators 18, 19, contact leaf 20, spacer 22, contact leaf 21, and rivet 23 of frame 17. Contact leaf 26 is electrically connected to terminal 15.

The ex-ible leaf `spring 4 is bent at one end and is Secured to the inside of the leg of frame 16 adjacent the terminals 13-15 in any suitable manner, such as by soldering or spot welding. In addition, it is electrically connected to terminal 14. The spring 4 is bent so that the switch contact 3 carried by it at its free end is biased against the contact leaf 21. The magnetic responsive armature 2 is secured in Vany suitable manner, such as by spot welding, to the side of spring 4 away from contact leaf 21. Spring 4 and armature 2 are made from materials having -a high magnetic permeability. The switch contact 3 is a rive-t that is pressed into a matching hole in the armature 2 and the spring 4 is staked in place to provide a low resistance contact on both sides of the arma-ture 2.

The switch mechanism 1 is maintained in position within the tube 9 by frame 16, the edges of which contact the inner surface cf tube 9 and contact leaf 20 which has one or both end portions bent away from frame 17 to engage the inner surface of tube 9.

Electrical continuity exists between terminal 13 and terminal 14 via contact leaf 20, rivet 23, contact leaf 21, switch contact 3, and leaf spring 4. When the magnetic responsive armature 2 is drawn toward the permanent magnet 5, the switch contact 3 engages contact leaf 27 to establish electrical continuity between

terminals

14 and 15 via leaf spring 4, switch contact 3, contact leaf 27, rivet 29, and contact leaf 26.

The tube 9 is positioned within bracket 10 so that the contact leaf 21 is away from the auxiliary magnetic responsive member 2. The tube 9 can be rotated about its axis prior to being secured in one position and the auxiliary magnetic responsive member 7 may be adjusted by means of screw 8 to secure the desired lock-up force and adjustment of the temperature or mechanical differential. An `adhesive resin, or other `suitable means, such as a mechanical locking device, is used to secure the position of the screw 8.

With the high expansion side of the bimetal element 6 toward the switch mechanism 1, the permanent magnet 5 is moved from its position shown in FIG. l toward the switch mechanism 1 and the auxiliary armature 7 as the temperature drops. The magnetic force of attraction between the permanent magnet 5 and the auxiliary armature 7 increases to the point where the permanent magnet 5 is moved with a snap action into position against the auxiliary armature 7 as shown in FIG. 2. The gap between the permanent magnet 5 `and the armature 2 is reduced by the presence of the auxiliary armature 7 between the permanent magnet 5 and armature 2, causing a rapid increase in the magnetic force of attraction between the permanent magnet 5 4and the armature 2 to cause the spring biasing force of leaf spring 4 to be overcome very rapidly to bring the switch contact 3 carried by leaf spring 4 into contact with contact leaf 27 very rapidly.

It should be noted that since contact leaf 21 is biased by the spring leaf 4 to cause it to move with spring leaf 4 as spring leaf 4 is drawn toward the contact 27, the break between switch contact 3 and contact leaf 21 occurs when both the switch contact 3 and the contact leaf 21 are in motion to create a wiping action during the break. Further, since spring contact 27 is flexed by spring contact 3 as it moves toward the permanent magnet 5, a wiping action occurs as the contact is made and there is a minimum of rebound which reduces the possibility of arcing as this contact is established.

Upon an increase in temperature, the bimetal member 6 creates a force to pull permanent magnet 5 away from auxiliary armature 7. The separation of the permanent magnet 5 from the auxiliary armature 7 occurs suddenly, causing the contact pressure between the switch contact 3 and contact leaf 27 to be maintained up to the time the snap action movement of the permanent magnet 5 away from the auxiliary armature 7 occurs. The switch contact 3 is drawn away from contact leaf 27 due to the biasing force stored in the spring leaf 4 when moved into contact with leaf 27 by the permanent magnet 5. This biasing force causes the contact leaf 27 and switch contact 3 to move together a short distance prior to separating to provide a wiping action when permanent magnet 5 is moved rapidly away from the auxiliary armature 7.

FIG. 4 shows a modification of the embodiment shown in FIGS. 1-3. In the switching device shown in FIG. 4, two

auxiliary armatures

7a, 7b are used with a switching mechanism 1a and a switching mechanism 1b, respectively. Switch mechanism 1a and switch mechanism 1b are similar in structure to switch mechanism 1 shown in FIG. l but are single-pole switches. Switch mechanism' 1a has a spring leaf 4a to which a magnetic responsive armature 2a is secured. Similarly, switch mechanism 1b has a spring leaf 4b to which a magnetic responsive armature 2b is secured.

A yieldable member 6, in the form of a leaf spring, carries two

permanent magnets

5a, 5b at one end, one mounted on each side to provide a source of magnetic flux. The yieldable member 6 is connected at the other end to the moving end of a thermally responsive member 30 which can be a spiral type bimetal, as shown. The yieldable member 6 is positioned so that it is movable between the

auxiliary armatures

7a and 7b. Of course, as is the case for the embodiment shown in FIGS. 1 3, the force producing actuator for the source of magnetic llux provided by

magnets

5a, 5b is not limited to thermally responsive elements, such as illustrated in FIGS. 1-3 and 4, but can be a pressure responsive diaphragm or the like.

The thermal responsive element 30 provides the force necessary to move the

permanent magnets

5a and 5b between the

auxiliary armatures

7a and 7b. The action of permanent magnet 5a in cooperation with auxiliary armature 7a and armature 2a carried by leaf spring 4a and permanent magnet 5b in cooperation with auxiliary armature 5b and armature 2b carried by leaf spring 4b is the same as described for the action of permanent magnet 5 with auxiliary armature 7 and armature 2 carried by leaf spring 4 shown in FIG. 1. Switch mechanism 1a can be connected to control one circuit and switch mechanism 1b can be connected to control a second circuit as could be done with the switching device shown in FIGS. l-3. However, the switching device of HG. 4 has an advantage over the switching device shown in FIGS. 1-3 in that a separate temperature differential can be Set for each circuit by proper adjustment of the position of the auxiliary armature 7a with respect to switch mechanism ia and adjustment of the position of the auxiliary armature 7b and the switch mechanism 1b.

FIG. 6 illustrates another way of providing an adjustable auxiliary armature. In this case, the auxiliary armature is in the form of a C-shaped band 3l of ferro-magnetic material which is friction-litted over the tube 9. Variations in spacing from the permanent magnet 5 and its position with relation to the armature within tube 9 can be varied by rotation of the band 31 about the tube 9 and moving the band 31 along the length of the tube 9. The band 31 can be secured after positioning with an adhesive resin or other suitable means.

Another embodiment of the invention is shown in FIG. 5. The details of the magnetic responsive switch mechanism contained within tube 9 are not shown, but it should be understood that the permanent magnet 5 secured to the end of yieldable member 6 cooperates with a switch mechanism positioned within tube 9 that is of the type shown in FIGS. 1 and 4. Permanent magnet 5 has an actuating force applied to it via the yieldable member 6 which is secured to the movable end of a spiraltype bimetal element 30, and in this respect is similar to the device shown in FG. 4. Permanent magnet 5, however, is positioned intermediate the tube 9 and the auxiliary armature 7 and is in contact with the auxiliary armature' 7. The auxiliary armature 7 is carried by a screw 8 so that the position of armature 7 may be adjusted.

As in the previous embodiment, the auxiliary armature 7 causes the magnetic lux provided by permanent magnet 5 to be positioned very rapidly adjacent the tube 9. When a force is exerted on permanent magnet 5 by the bimetal element 30 tending to move permanent magnet 5 away from auxiliary armature 7, it is necessary that the force build up until the magnetizing force of attraction between the permanent magnet S and the auxiliary armature 7 is overcome. When the point of separation is reached, the movement of permanent magnet 5 away from auxiliary armature 7 .will be a snap action type movement, causing the permanent magnet 5 to be moved very rapidly adjacent the tube 9 to in turn cause rapid action of a switch mechanism contained within tube 9. It is apparent that the actuation of a switch mechanism contained in tube 9 will be more rapid than is possible with such a device which does not employ an auxiliary armature 7 as described.

The invention described herein is not limited to the details shown but may assume numerous forms and the scope of the invention is to be dened solely by the following claims.

I claim:

l. A magnetically actuated switching device comprising a source of magnetic ux; a switch structure including switch contacts and a first magnetic responsive member for altering the relative position of said contacts; means for moving said source of magnetic flux relative to said rst magnetic responsive member at a particular rate; and a second magnetic responsive member fixedly positioned with respect to said switch structure and cooperating with said Source of magnetic flux to alter the rate of change of magnetic flux density at said rst magnetic responsive member by varying the rate of movement of said source of magnetic ux relative to said iirst magnetic responsive member.

2. A magnetically actuated switching device comprising a source of magnetic ux; a switch unit including switch contacts and a rst magnetic responsive member carried by a flexible member for altering the relative position of said contacts; means for moving said source of magnetic iiux relative to said first magnetic responsive member at a particular rate; and a second magnetic responsive member lixedly positioned with respect to said switch unit and cooperating with said source of magnetic tlux to alter the rate of change of magnetic flux density at said rst magnetic responsive member by varying the rate of movement of said source of magnetic ux relative to said rst magnetic responsive member.

3. A magnetically actuated switching device comprising a source of magnetic flux; a switch unit including switch contacts and a rst magnetic ally responsive member for altering the relative position of said contacts; means for moving said source of magnetic flux relative to said first magnetic responsive member at a particular rate; and a second magnetically responsive member ixedly positioned with respect to said switch unit in the path of movement of said source of magnetic flux with respect to said first magnetically responsive member to alter the rate of change of magnetic ilux density at said rst magnetically responsive member by varying the rate of movement of said source of magnetic flux relative to said first magnetic responsive member. l

4. A magnetically actuated switching device comprising a housing; a switch unit including switch contacts enclosed in said housing and a first magnetic responsive member for altering the relative position of said contacts; a source of magnetic tlux outside of said housing; means for moving said source of magnetic flux relative to said housing at a particular rate; and a second magnetically responsive member fixedly positioned with respect to said switch unit in the path of movement of said source of magnetic flux with respect to said rst magnetic responsive member to alter the rate of change of magnetic flux density at said first magnetic responsive member by varyepesses 27 ing the rate of movement ot' said source of magnetic flux relative to said housing.

5. A magnetically actuated switching device comprising a source of magnetic flux; a switch unit including switch contacts and a first magnetic responsive member altering the relative position of said contacts; means for movinn said source of magnetic fiux relative to said first magnetic responsive member at a particular rate; and a second magnetic responsive member fixedly positioned With respect to said first magnetic responsive member and disposed intermediate said rst magnetic responsive member and said source of magnetic flux to alter the rate of change of magnetic fiux density at said first magnetic responsive member by varying the rate of movement of said source of magnetic fiux relative to said first magnetic responsive member.

6. A magnetically actuated switching device comprising a source of magnetic fiux; a first switch unit having a first set of contacts and a first magnetic responsive member for altering the relative position or" the contacts ot said first set of contacts; a second switch unit having a second set of contacts and a second magnetic responsive member for altering the relative position of the comfcts of said second set of contacts; means for moving "ci CS d source of magnetic flux relative to said rst and second magnetic responsive members at a particular rate; a third magnetic responsive member xedly positioned with rcspect to said first switch unit and cooperating with said source of magnetic fiux to alter the rate of change of magnetic fiux density at said first magnetic responsive member by varying the rate of movement of said source of magnetic uX relative to said first magnetic responsive member; `and a fourth magnetic responsive member fixedly positioned with respect to said second switch unit and cooperating with saidsource of magnetic flux to alter the rate of change of said magnetic flux density at said second magnetic responsive member by varying the rate of movement of said source of magnetic fiux relative to said second magnetic responsive member.

7. A magnetically actuated switching device comprising a source of magnetic fiux; a first switch unit hai-ing first set of contacts and a rst magnetic responsive member for altering the relative position of the contacts of said first set of contacts; a second switch unit having a second set of contacts and a second magnetic responsive member for altering the relative position of the contacts of said second set ot contacts; means for moving said source of magnetic fiux relative to said first and second magnetic responsive members at a particular rate; a third magnetic responsive member fixedly positioned with respect to said first switch unit in the path of movement of the path of source of magnetic flux with respect to said first magnetic responsive member to alter the rate of change of fiux density at said first magnetic responsive member by varying the rate of movement of said source of magnetic flux relative to said first magnetic responsive member; and a fourth magnetic responsive member fixedly positioned with respect to said second switch unit in the path of movement of said source of magnetic flux with respect to said second magnetic responsive member to alter the rate of change oflmagnetic fiux density at said second magnetic responsive member by varying the rate of movement of said source of magnetic flux relative to said second magnetic responsive member.

8. A magnetically actuated switching device comprising a source of magnetic flux; a first switch unit having a first set of contacts and a first magnetic responsive member for altering the relative position of the contacts of said first set of contacts; a second switch unit having a second set of contacts and a second magnetic responsive member for altering the relative position of the contacts of said second set of contacts; means moving said source of magnetic flux relative to said first and second magnetic responsive members at a particular rate; a third magnetic responsive member fixedly positioned with respect to said first magnetic responsive member and disposed intermediate said first magnetic responsive member and said source of magnetic fiux to alter the rate of change of the magnetic fiuX density at said first magnetic responsive member by varying the rate of movement of said source of magnetic flux relative to said first magnetic responsive member; and a fourth magnetic responsive member fixedly positioned with respect to said second magnetic responsive member and disposed intermediate said second magnetic responsive member and said source of magnetic flux to alter the rate of change of the magnetic fiux density at said second magnetic responsive member by varying the rate of movement of said source of magnetic flux relative to said second magnetic responsive member.

9. A magnetically actuated switching device comprising a source of magnetic flux; a switch unit including switch contacts and a first magnetic responsive member for altering the position of said contacts; and elongated housing enclosing said switch unit, said housing having a portion of circular cross section adjacent said first magnetic responsive member; means for moving said source of magnetic fiux relative to said housing at a particular rate; and a second magnetic responsive member consisting or a C-shaped ring fixedly positioned outside said housing along said portion of circular cross section and cooperating with said source of magnetic flux to alter the rate of change of magnetic flux density at said first magnetic responsive member by varying the rate of movement of said source of magnetic flux relative to said first magnetic responsive member.

References Cited in the ie of this patent