US2612572A

US2612572A - Magnetic control mechanism

Info

Publication number: US2612572A
Application number: US701017A
Authority: US
Inventors: Benjamin L Binford
Original assignee: Magnetrol Inc
Current assignee: Magnetrol Inc
Priority date: 1946-10-03
Filing date: 1946-10-03
Publication date: 1952-09-30
Anticipated expiration: 1969-09-30

Description

p 2 B. L. BINFORD MAGNETIC CONTROL MECHANISM Filed Oct. 3, 1946 Patented Sept. 30, 1952 MAGNETIC .ooNrRoLfMEcHAmsM Benjamin L. Binford, Chic ago, Ill., assignor to Magnetrol, Inc., Chicago, 111., a corporation of Illinois Application October 3, 1946 Serial No. 701,017

' 2 Claims. (Cl. 20087') This invention relates to magnetic control mechanism and more particularly to a mechanism employing electrical switches which are op erated magnetically in'accordance with changes in a condition to be indicated or controlled.

One of the objects of the invention is to provide a magnetic control mechanism whichis extremely flexible in use in performing a desired number and sequence of control operations. According to one feature of the invention the mechanism may be built up by assembling a plurality of interfitting control units in a desired combination.

Another object is to provide a magnetic con: trol mechanism including a self-contained switch assembly which can be easily and quickly installed in various types of control installations. Still another object is to provide a magnetic control mechanism in which a tiltable Switch is connected to flexible lead wires in such a way as to minimize flexing of the wires and to maintain a substantial balance of the switch in all positions thereof.

Still another object is to provide a magnetic control mechanism in which a tiltable switch is controlled by a spring which is so arranged as to maintain a substantially constant tilting force on the switch in all positions thereof.

The above and other objects and advantages of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing, in which- Figure l is a vertical section with parts in elevation of a control installation embodying the invention; and

Figures 2, 3, and 4 are top, plan, side, and end elevations, respectively, of a switch unit embodying the invention.

As shown in Figure l, the installation is adapted to indicate or control the level of liquid in a, boiler, tank or the like and comprises a level chamber having top and bottom connections through which it may be connected to the tank or boiler so that the level in the chamber will be the same as that in the tank or boiler. The chamber I0 is closed at its top by a cover ll formed with a central threaded opening for mounting of the control unit. A float I2 is mounted in the chamber and is connected to an elongated magnetic armature l3 to move the armature in accordance with level changes.

The magnetic control mechanism comprises a'base having a central hub portion 14 which is adapted to be fixedly threaded into the opening in the cover H. The

adjustedposition on the hub by a set. screw 16. The base plate I5 is formed with a threaded opening I! at one side for connection with an electrical conduit and. can be rotated to bring the conduit and the wires therein into the base plate at any convenient, position.

The hub I4 fixedly carries a nonmagnetic tube 18 which may be formed of brass or the like. As shown, the tube extends up through the base to terminatein a closed upper end and opens at its lower end intothe chamber Hi. When the base is assembled on the chamber, the armature i3 fits loosely into the tube for vertical sliding movement therein as the float rises and falls.

'The tube [8 is adapted to carry one or more switch units, as more particularly shown in Figures 2 to 4. Each of the units comprises a gener ally rectangular non-magnetic frame having an end portion 2] which is integral with a side wall 22. At its lower edge the wall 22 is formed with a downwardly extending skirtv portion 23 which is offset outward from the upper part of the wall and whichhas an open bottomed notch 24 therein. At its upper edge the wall 22 is notched or offset as indicated at. 2,5 for a purpose to ap.- pear later. The opposite site of the frame, as shown at 26, is connected by riveting or the, i e to the end wall 21 and is relatively narrow. At the opposite end of the frame the wall 25 is bent over to form a stop finger or arm 21.

Within the central part of the frame there is provided a split mounting block 28 adapted to be drawn together by a screw 29 and of a size to receive the tube I 8. In mounting the unit on the tube, the block 28 can be slipped over the tube and moved to the desired level, and the screw 29 can then be tightened to hold the unit in position on the tube. Preferably the lowermost unit is, closed at its bottom by a non-magnetic plate 3| fitting over the tube and held at the desired elevation by a spacer 32. y

At one end the switch unit carries an insulating contact block 33 provided with a plurality of terminals for connection to the cable and to the switches as described hereinafter. The contact block may be separated by an insulating plate 34 which extends beyond the rectangular outline of the frame and is formed with notches, as best seen in Figure 4, for the flexible leads. At the Opposite end the frame rotatab'ly supports an axle 35 which carries a downwardlyextending arm 36. At its lower end the arm 36. carries a permanent magnet 31 which is adapted hub portion [4 rotatablyf supports a base plate I5 which may be held in to move toward the tube 18 when attracted by the armature and which normally occupies a position spaced from the tube, as illustrated. Movement of the magnet away from the tube may be limited by engagement of the arm 35 with the stop finger 21.

The arm is formed with a bracket extension 38 which projects beyond the side 22 of the frame to carry a switch. According to one feature of the invention the switch is carried by a supporting plate 39 pivoted on the bracket 38 and adjustable relative thereto through an adjusting screw 4 i. In this way the position of the switch can initially be set for any given installation to compensate for slight angularity of the tube l8 with respect to the vertical and to insure proper opening and closing of the switch.

As shown the mechanism embodies tiltable mercury type switches 42 which may be either, single or double throw switches, as desired. The

switches are supported by supporting clamps 43 carried by the plate 39 and preferably lying above the pivotal axis of the arm, the bracket and the plate. With this construction the entire arm, bracket and plate assembly may .be balanced about the pivotal axis to provide for easy and constant operation at all times. I

To turn the arm, bracket and plate assembly to the position shown in which the magnet is spaced from the tube, a spring 44 is provided. According to the present invention a relatively lon tension spring is employed connected at one end to a finger on the side 22 of the frame and at its opposite end to the plate 39. The connections are so located that asthe magnet moves away from the tube toward the position shown, the spring approaches a line through the finger and the pivotal axis of the arm, bracket and plate assembly. As this assembly is turned clockwise to move the magnet toward thetube, as seen in Figure 3, the spring acts through an increasing moment arm to become increasingly effective. Therefore, the tilting forces exerted on the assembly by the spring varies. for each position of the magnet in such a manner that the total tilting force on the assembly is substantially constant throughout the full range of movement. Thus when the magnetis remote from the tube and its attraction for the armattue is at a minimum, assuming the armature to be in the field of the magnet, the moment produced by the spring on the arm 36 and bracket 39 is at a minimum. Similarly when the magnet is adjacent the tube and its magnetic attraction is maximum the spring moment is maximum. With this construction, a substantially constant and uniform tilting force is produced in one direction or the other depending upon whether or not the armature I3, is in the field of the magnet to provide a uniform and reliable operation substantially insensitive to minor unbalance or vibration.

The switch 42, when installed in the brackets 43, is adaptedto be connected to the terminal block 33 by flexible leads 45, as shown in Figure 1. As illustrated in this figure, the switch is a double throw switch requiring three leads. As shown, the leads connect to the switch at points lying on a line crossing the pivotal axis of the assembly and symmetrically spaced about the pivotal axis. With this construction, each of the leads is of a slightly different length so that the connections cannot be confused. Furthermore, the leads extend from the switch generally parallel to the line on which their points of connection to the switch lie. This arrangement involves spect to each other.

minimum flexing of the leads during tilting of the switch and maintains the weight and resistanceto fiexure of the leads balanced about the pivotal axis. Operation of the mechanism is, therefore, not interfered with by the leads.

In installing a switch mechanism embodying the invention, one or more switch units may be mounted on a single tube l8 at points spaced along the length thereof to perform different indicating or control operations at different points in the travel of the float. According to one feature of the invention, the frames of the switch units are so formed that they will interfit and can be mounted on the same tube relatively close together in making up an assembly. As shown in Figure 1, when the units are so stacked, the positions of alternate units are reversed with re- In this position the lower edge'of the side wall 26 of the upper unit fits into the notched or cut away portion 25 of the unit beneath it while the offset skirt 23 of the upper unit fits over the wall 26 of the unit beneath it. The notch 24 is provided to receive the pivot support carried by the wall-26 of the lower unit so that the units can bestacked relatively close together and will interfit without interference with desired movement'of the parts. When the switch units are assembled on the tube, they may be connected with cable wires brought in through the opening I! in the base plate and which extend up around the sides of the units. The cable wires may be brought up along side the terminal blocks 33 and may be held in the desired location by flanges 46 formed on the end walls 2| of the frames which engage the cable Wires to hold them in positions where they. will not interfere with proper operation of the switch mechanisms. The entire assembly may be covered by a cup-shaped cover 41 fitting against the base plate l5 and secured by a screw 48 threaded into the upper end of the tube l8. When the cover-4'! is installed, it preferably fits relatively closely against the flanges 46 positively to confine thecable wires against tangling.

While one embodiment of the invention has been shown and described in detail herein, it will be understood that it'is illustrative only and is not intended as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. Magnetic control mechanism comprising a non-magnetic frame having a terminal block at one end and having one side formed with an offset skirt to fit over the other side of an underlying mechanism when the frames are stacked in reverse position, means in the central part of to the switch.

2. Magnetic control mechanism comprising a non-magnetic frame, means on the frame to receive a tube to secure the frame to the tube, an arm pivoted on the frame about an axis transverse to the tube length, a magnet carried by the free end of the arm for movement toward and away from the tube, a bracket connected to the arm to move therewith,'a switch carried by the bracket, and a tension spring connected at one end to the frame and at its other end to the bracket, the latter connection being made at a point between the pivotal axis and. the point of connection of the spring to the frame, said point of connection to the bracket being displaced a slight amount to one side of a straight line passing through said axis and the point of connection of the spring to the frame so that the spring will approach said straight line as the magnet moves away from the tube.

BENJAMIN L. BINFORD.

REFERENCES CITED The following references are of record in the file of this patent:

Number 6 UNITED STATES PATENTS Name Date Rutledge June 21, 1927 Davis Sept. 6, 1932 Morris et a1 Dec. 20, 1932 Van Vulpen et a1. June 15, 1937 Shrode Jan. 3, 1939 Gross et a1. June 10, 1941 Moore Aug. 11, 1942 Beam Mar. 16, 1943 Thompson May 4, 1948