US3037103A - Switch - Google Patents

Description

May 29, 1962 3,037,103

5. L. BINFORD ETAL SWITCH Filed March 18, 1959 g/g, VI'SNTORSJ AT T ORNE YS'.

3,037,103 Patented May 29, 1962 3,037,103 SWITCH Benjamin L. Binford, Chicago, and Arnold P. Darsch, Evanston, 111., assignors to Magnetrol, Inc., Chicago, Ill., a corporation of Illinois Filed Mar. 18, 1959, Ser. No. 800,245 8 Claims. (Cl. 200-112) This invention relates to switches and more particularly to magnetically operated switches having snap action characteristics.

It has heretofore been proposed to operate electric switches for controlling or indicating functions in response to movement of a magnetic element which is connected to a sensing device, such as a fioat, to be moved thereby. One problem encountered in such switches has been the provision of a snap action effect so that the switch will move positively to open or closed position and will remain in such position over a predetermined range of movement of the magnetic element to provide a high degree of stability. This problem is particularly acute in enclosed mercury type switches wherein the parts are relatively small and light and are easily moved in response to small magnetic or vibrational forces.

It is accordingly one of the objects of the present invention to provide a switch in which a movable contact element is moved to both its open and closed position with a positive snap action and is held in its existing position over a predetermined range of movement of the operating magnetic element.

Another object is to provide a switch of the enclosed mercury type in which the movable contact is operated with a positive snap action.

According to one feature of the invention, the movable contact is pivoted to swing toward and away from a fixed contact and carries an elongated magnetic element extending across the pivotal axis to provide a positive snap action.

A further object is to provide a switch in which the movable contact is pivotally carried by an elongated fixed contact, both of which project into a pool of conductive liquid so that no current is required to pass through the pivotal mounting of the pivoted contact.

According to one feature of the invention, one of the contacts is made of a material which is wettable by the conductive liquid and is formed with capillary passages to maintain it Wet so that its engagement with the other contact is always made through a film of the conductive liquid.

A still further object is to provide a switch in which the conductive liquid is confined to prevent loss of contact due to splashing.

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing, in which:

FIGURE 1 is a central section through a switch assembly embodying the invention;

FIGURE 2 is a section through the switch itself on the line 22 of FIGURE 1;

FIGURE 3 is a transverse section on the line 33 of FIGURE 2, and

FIGURES 4 and 5 are axial sections at right angles to each other of an alternative form of switch.

The switch, as shown, is adapted to be operated magnetically by movement of a magnetic piston member connected to an operating rod 11, which may in turn be connected to sensing means, such as a float or the like, to move the magnet in accordance with changes in a condition to be indicated or controlled. The piston of magnet 10 is shiftable in a tube 12 of non-magnetic mate rial such as brass which extends vertically through an enclosing housing 13 in which the switch mechanism is contained. The housing is closed at its bottom by a closure plate 14, to which the tube 12 is secured and a connection 15 is provided through which electrical wire can be led into the housing for connection to the switch.

The tube 12 carries a mounting clip structure 16 which may be formed of sheet metal with opposite spring arms, one of which is indicated at 17 fitting over the tube 12 and resiliently engaging a switch indicated generally at 18 to hold it in position closely adjacent and parallel to the tube. The spring clip may also carry a terminal block '19 connected through leads 21 to the switch and adapted to be connected to external leads entering the casing through the connector 15.

The switch 18 comprises an enclosing body 22, of glass or similar non-conductive material, receiving a pool of conductive liquid 23, such as mercury. Elongated terminals 24 and 25 extend vertically into the body in parallel spaced relation to each other with the terminal 24 projecting into the pool of mercury 23 and with the terminal 25 terminating above the pool of mercury and carrying a transverse contact bar 26. Preferably, the terminals 24 and 25 and the contact bar 26 are made of a material which will not be wetted by the conductive liquid. For example, when mercury is employed as the conductive liquid, the terminals and contact bar are made of a ferrous material, such as low carbon steel or iron.

The terminal 24 pivotally carries a movable contact structure for which purpose a U-shaped bracket 27 is secured thereto intermediate its ends with the arms of the bracket projecting horizontally from the terminal. A pivot bearing 28, which may be formed of carbon or the like, is rotatably mounted on one of the arms of the bracket 27 and carries an elongated magnetic element 29, such as an iron plate. The element 29 extends vertically across the axis of the pivot 28 and at its lower end carries a contact member 31 which extends into the conducting liquid 23, and which is movable into and out of contact with the contact "bar 26.

According to one feature of the invention, the contact element 31 is made of a material which will be wetted by the conducting liquid so that it will at all times be coated by a film of conductive liquid and will engage the contact bar 26 through a film of conductive liquid to provide maximum contact area and minimum contact resistance. When mercury is used as the conducting liquid, the contact element 31 may be made of metal, such as copper, platinum, various alloys, or the like, which will be wetted easily by the mercury and will carry a film of mercury on its surface at all times. Preferably, the element 31 is cut out, as shown at 32, to provide an arcu-ate surface for maximum area of contact with the contact bar 26. Preferably, a capillary passage, such as groove 33, is provided in the element 31, opening into the cut out 32 to maintain mercury on the surface of the cut out at all times.

With the switch mounted, as shown in FIGURE 1, when the magnetic piston 10 is centered with respect to the pivotal axis 28, the magnetic force exerted on the element 29 on opposite sides of the pivot will be balanced and there is no tendency for the movable contact to move. If new the magnetic piston is moved upward, the magnetic attraction on the upper part of the element 29 will exceed the attraction on the lower part and the magnetic element will swing clockwise to move the contact element 31 into engagement with the contact bar 26 to complete a circuit through the switch. It will be noted that this circuit goes from the contact 24, to the conducting liquid, through the conducting liquid to the contact element 3 1, from the contact element 31 to the contact bar 26 and the contact '25, so that no current is required to be carried through the pivot 28 or the magnetic element 29. Thus, minimum contact resistance is assured for this reason and because of the engagement through a film of conducting liquid between the contact element 31 and the contact bar 26.

As the magnetic piston 10 moves downward and reaches a position where it is symmetrical with respect to the pivot 28, the switch will still be held in its closed position because the air gap between the upper part of the magnetic strip 29 and the magnet is smaller than the air gap between the lower part of the strip 29 and the magnet. As the piston continues to move downward, the magnetic attraction on the lower part of the strip 29 will eventually exceed the magnetic attraction on the upper part of the strip and the strip will swing counter-clockwise to move the contact element 31 away from the contact bar 26. It will be observed that this action will ocour rapidly with a snap acting effect since once the movement starts the air gap at the upper part of the magnetic element is increasing while that of the lower part thereof is decreasing. Thus, the movable contact will be moved positively and rapidly from its engaged position to its disengaged position.

Similarly, when the magnetic piston moves upward, the parts will remain in the disengaged position until the magnetic piston has moved above the pivotal axis 28 a predetermined amount, at which time the movable contact will be moved positively and quickly with a snap action operation into switch closing position. Due to this operation, fluttering of the contacts is avoided and the switch operation is highly stable even when it is subject to physical vibrations or is mounted on a moving device.

FIGURES 4 and 5 illustrate an alternative form of switch construction designed particularly for use in locations subject to severe vibrations or pitching, as on shipboard and the like. Parts in FIGURES 4 and 5 corresponding to like parts in FIGURES 1 to 3, are indicated by the same reference numerals, plus 0. In this construction, the tubular body 122 is pinched inwardly at opposite sides, as indicated at 135, to leave a relatively narrow, elongated throat extending across the body spaced above its bottom and slightly above the pool of conductive liquid 123. The fixed contact member 124 may extend through the top of the body and through the throat therein but, as shown, is inserted through the bottom of the body into the pool of conductive liquid.

The other fixed contact 125 terminates above the narrow throat in the body, and at its lower end is offset, as indicated at 125a, to extend toward the movable contact, as described hereinafter.

The movable contact comprises a trough-shaped element 131, formed of a material which will easily be wetted by the conductive liquid, and which is formed in the side facing the contact element 125a with a groove extending completely to the bottom of the element 131 and opening into the pool of conductive liquid. The element 131 may be moved by the armature 129 in the same way as the element 31 of FIGURES 1 to 3, or may, if desired, be spring biased in one direction and magnetically urged in the opposite direction.

In this construction, the grooves in the element 131 will be maintained substantially full of conductive liquid at all times due to the capillary action. When this element moves to the left, as seen in FIGURE 5, the tip portion 125a will enter the groove and contact the conductive liquid therein to complete a circuit between the contacts 124 and 125 through the pool of liquid and the contact element 131. It will be noted that in this case, as in FIGURES 1 to 3, no current passes through the pivotal mounting for the armature 129 and contact element 131. In all cases, engagement between the fixed contact 125a and the element 131 will be made through -a film or pool of conductive liquid so that good electrical contact is assured at all times. Furthermore, the making of contact through a film of liquid assists in the production of a quick make and break action, since the liquid will tend to remain in engagement with the fixed contact a, and will break away from it rapidly, as soon as the contact elements are sufliciently separated.

While two embodiments of the invention have been shown and described herein, it will be understood these are illustrative only and are not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. A switch comprising a pair of elongated fixed spaced contact members, a movable contact pivotally mounted on one of the contact members on an axis transverse to the length thereof and swingable about said axis into and out of engagement with the other contact member, an elongated magnetic element rigidly secured to the movable contact and extending on opposite sides of said axis transversely thereto, and a complementary magnetic element movable parallel to the contact members across said axis to move the movable contact with a snap action.

2. A switch comprising a non-conducting enclosure, a pair of elongated vertical contact members in the enclosure in fixed spaced relation to each other, a movable contact pivotally mounted on one of the contact members on a horizontal axis and extending downward from the axis to swing toward and away from the other contact member, a vertically elongated magnetic element secured to the movable contact and extending across the pivotal axis thereof and a complementary magnet movable parallel to the contact members across said axis to move the movable contact with a snap action.

3. A switch comprising a non-conducting enclosure, a pair of elongated vertical contact members in the enclosure in fixed spaced relation to each other, a movable contact pivotally mounted on one of the contact members on a horizontal axis and extending downward from the axis to swing toward and away from the other contact member, a pool of conducting liquid in the enclosure, the movable contact and said one of the contact members extending into the pool of conducting liquid and the other contact member terminating above the surface of the pool of liquid, and a vertically elongated magnetic element secured to the movable contact and extending across the pivotal axis thereof to move the movable contact toward and into conductive engagement with said other contact member.

4. A switch comprising a vertical tube of non-magnetic material, a magnetic element movable longitudinally in the tube, an elongated enclosure of non-conducting material secured to the tube in parallel relation thereto, a pair of vertical spaced contact members fixedly mounted in the enclosure, a movable contact pivotally mounted on a horizontal axis on one of the contact members to move toward and away from the other contact member, and a vertically elongated magnetic element secured to the movable contact and crossing its pivotal axis, the magnetic elements being complementary whereby as the first named element moves in the tube the second element and the movable contact will be moved with a snap action.

5. A switch comprising a Vertical tube of non-magnetic material, a magnetic element movable longitudinally in the tube, an elongated enclosure of non-conducting material secured to the tube in parallel relation thereto, a pair of vertical spaced contact members fixedly mounted in the enclosure, a movablecontact pivotally mounted on a horizontal axis on one of the contact members to move toward and away from the other contact member, a pool of conducting liquid in the lower part of the enclosure, the movable contact and said one of the contact members extending into the conducting liquid and the other contact member terminating above the pool of liquid, and a vertically elongated magnetic element secured to the movable contact and crossing its pivotal axis, the magnetic elements being complementary whereby as the first named element moves in the tube the second element and the movable contact will be moved with a snap action.

6. A switch comprising an enclosure of non-conducting material, a pool of conducting liquid in the lower part of the enclosure, a fixed contact in the enclosure extending into the pool of liquid, at second fixed contact in the enclosure terminating in a contact tip above the pool of liquid, at contact member mounted for pivotal movement toward and away from the contact tip and projecting into the pool of liquid, the contact member being formed of a material which is wetted by the liquid and having a portion of concave section complementary in section to the contact tip to fit against the contact tip whereby con tact between the contact member and contact tip will be through a film of the liquid,

7. A switch comprising an enclosure of non-conducting material, a pool of conducting liquid in the lower part of the enclosure, a fixed contact in the enclosure extending into the pool of liquid, a second fixed contact in the enclosure terminating in a contact tip above the pool of liquid, 3. contact member mounted for pivotal movement toward and away from the contact tip and projecting into the pool of liquid, the contact member being formed of a material which is wetted by the liquid and having a portion of concave section complementary in section to the contact tip to fit against the contact tip, and means defining a capillary passage in the contact member ex tending from below the level of the pool to the portion of concave section.

8. The switch of claim 6 in which the enclosure is formed with a portion of reduced section above the pool and below the contact tip to limit splashing of liquid in the enclosure.

References Cited in the file of this patent UNITED STATES PATENTS 1,950,178 Hunciker Mar. 6, 1934 2,085,316 Hunciker June 29, 1937 2,524,261 Kaminky Oct, 3, 1950 2,921,161 Scata et a1. Jan. 12, 1960

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