US2094713A - Automatic switch - Google Patents

Description

Oct. 5, 1937. MORRIS 2,094,713

AUTOMATIC SWITCH .Filed July 1, 1935 2 Sheets-Sheet 1 Oct. 5, 1937. N. MORRIS 2,094,713

AUTOMATIC SWITCH Filed July 1, 1935 2 Sheets-Sheet 2 Namam yarrzb' Patented Oct. 5, 1937 UNITED STATES PATENT OFFICE AUTOMATIC SWITCH Application July 1, 1935, Serial No. 29,394

4 Claims.

This invention relates to automatic electric switches of the type adapted to control circuits to current consuming devices of various kinds and, among other objects, aims to provide an improved relatively simple, rugged, noiseless, ex-

plosion proof, sensitive and reliable automatic switch adapted to be operated by a very small electric motor the circuit of which is controlled in accordance with the demand.

Other aims and advantages of the invention will appear in the specification, when considered in connection with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic illustration of an automatic switch embodying the invention;

Fig. 2 is a similar view but showing a modified form of the invention;

Fig. 3 is another similar view but showing a further modified form of the invention;

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 2; and

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 4.

Referring more particularly to the drawings,

the switch mechanism there shown is of the type wherein a main switch for controlling any circuit is operated indirectly by a small electric motor which is started and stopped according to the demands of the controlled circuit. Also, the motor circuit is controlled in such manner that the switching mechanism is reset automatically for a reverse operation when the main switch either opens or closes the circuit.

In Fig. 1, there is shown a simple design in as switch mechanism wherein the main control switch is operated by a motor, the circuit of which is controlled by an ordinary thermostat or double-throw switch. There is also provided a double-throw automatic switch operated by the mo- 40 tor to break the motor circuit when the main switch operation is completed and this switch is automatically reset for the reverse operation. The main switch and the motor controlling switch are operated by the same actuating member.

45 The mechanism is usually arranged in an ordinary metal box or casing (not shown) and is adapted to be connected between a supply line 10, II and a circuit I2, l3 which leads to the device to be controlled. In this instance, a main 50 switch in the form of a tilting mercury tube I! having contacts l5 and I6 is connected between the line and the load through a terminal block l'l. While other types of main switches may be employed, a mercury switch is preferred because 66 it is explosion proof and fire proof. When this switch is tilted to the position shown, the main circuit is broken. When it is tilted to its other position, themercury bridges the contacts l5 and I6 and closes the circuit.

The mercury tube It is shown as being removably mounted in a spring clip I! which is secured to a short shaft I8 journalled in a bifurcated bracket or support l9 and adapted to be tilted or oscillated by an arm 20 which is operated by a reciprocatable shaft 2i having an insulating 1 block 22 presenting a groove 23 engaging the free end of the arm 20. This shaft is adapted to be reciprocated in a frame 24 which is preferably made of sheet metal and is channelshaped. Herein, it is operated by a suitable mo- 5 tor 25 which is preferably of the self-starting synchronous type such as is shown in the Hanson Patent No. 1,952,498 through a reduction gearing 26 driving a crank pin 21 which cooperates with a slotted member or yoke 28 on the shaft 2|. The construction and arrangement is such that the motor is adapted to be operated to impart slow rotation of the crank pin 21 through 180 before it stops. Herein, the motor circuit, including conductors 29 and 30, is con- 25 trolled, first, by a bimetallic thermostat 3| which is representative of any type of automatic control equipment responding to the load demand. This thermostat is shown as being of the threepoint type coperating with two contacts32 and 30 33 connected to conductors 34 and 35, the blade being connected to a third conductor 36, all of said conductors leading to a common terminal block 31. When the thermostat closes the circuit through one or the other of the contacts, the mo- 35 tor is operated to tilt the switch and either open or close the circuit, depending upon which contact is engaged.

The motor is adapted to be cut ofl by an automatic switch shown in Fig. 1 as being of the double-throw flexible blade type, having two outer blades 38 and 39 and a movable inner blade 40, which is adapted to be flexed by the movement of the block 22, engaging in a relatively wide groove ll. The arrangement is such that all three blades make contact before the motor completes a cycle of operation and the motor circuit is not broken until the motor has completed its cycle. For this purpose, the blades are adjustable by bending them to their proper positions. The two outer blades 38 and 39 are connected to the conductors 34 and 35, respectively, leading to the thermostat contacts; while the middle blade is connected by a conductor 42 to the main line conductor I0. 66

The switch i4 is shown in its normal position with the circuit to the motor open. When the controlled device demands current, the thermostat 3| will make contact with the contact 33, thereby closing the motor circuit through main conductor H, conductor 29,.through the motor winding conductors 30, 36, thermostat 3|, contact 33, conductor 35, blades 39 and 40, conductor 42, back to line conductor ill. The motor will then start and rotate the crank pin 21 through 180 moving the grooved block 22 upwardly as viewed in Fig. 1. While the block is itself moving, it permits the flexible blade 40 of the double-throw switch to make contact with the blade 38. The width of the groove 4| is such that contact is maintained between blades 39 and 40 until the block has reached the upper end of its s roke. Then, the lower shoulder of the groove 4| flexes blade 40 against blade 38 and out of contact with blade 39, thereby breaking the motor circuit at the proper time to stop the motor and the crank pin in their uppermost positions. Thus, the main switch I4 is tilted to its circuit closing position and will remain in this position until the thermostat 3! again moves to the position shown in Fig. 1, when the motor circuit will again be closed and restore the parts to the position shown in Fig. 1.

Referring to the slightly modified form of the invention shown in Fig. 2, the double-throw flexible blade switch shown in Fig. 1 is replaced by a mercury switch 43 to avoid any possibility of even the slightest arcing which might cause an explosion in chemical plants or in places where the fire hazard is great. In this example, the circuits are identical with that shown in Fig. 1, except for the connections to the second mercury switch 43. It is shown as being of the bent mercury tube type, being bent to insure contact at one end or the other of the tube. Herein, it is also mounted in a clip 44 on a bracket 45 which carries clip l'l' for the main switch l4. The bracket 45 and the clip H are in turn rigidly secured to the shaft or pin l8 and both tubes are supported in substantially parallel relation. However, they are separately adjustable as will be presently explained. The same type of block 22' is employed in this case as in Fig. 1, except that the grooved inner end for actuating the flexible bladed switch is omitted. It will be observed that the mercury tube has a pair of contacts 46 and 41 at one end and 48 and 49 at the other end. The contacts 46 and 48 are connected tothe conductors 34' and 35', respectively, leading to the thermostat contacts 32' and 33'. The contacts 41 and 49 are connected by branch conductors 50, to the conductor 42' leading to the main line conductor ID. The auxiliary switch 43 is so positioned on the bracket 45 that the gob of mercury in it will be caused to shift from one end to the other just as the motor completes its cycle in the same manner-as explained in connection with the flexible blade switch in Fig. 1. The mercury shifts almost instantaneously from one end to the other because of the shape of the tube.

To enable the two mercury switches to be ad Justed and the switch box to be supported in different positions, the bracket 45, which is rigidly secured to the pin or shaft I 3', may be adjusted to any angular position with respect to the arm 20. Referring to Figs. 4 and 5, the arm 20' is mounted on a sleeve or collar 5| conveniently secured to the shaft l8 by a set screw 52. This set screw is unscrewed to release the collar from the shaft when an adjustment of the tubes is made.

Thus, the arm '20 remains in engagement with its slot or groove 23' in the block 22', while the adjustment is made. Therefore, both of the mercury tubes may be turned through 360 if desired. Furthermore, the switch tube 43 may be independently adjusted angularly with respect to the bracket 45 by means of a nut 53 on a screw 54 secured to the clip 44. Incidentally, the main switch is shown in its circuit closing position, ready to be actuated by the motor to open the circuit when the thermostat 3| makes contact with the contact element 32'.

Referring to Fig. 3, the switching mechanism shown therein may be identical with that shown in either Fig. 1 or Fig. 2, except for the thermostatic control circuit. For convenience, it is shown as being like Fig. 1, no change being made in the circuits between the two terminal blocks l1 and 31. In this example, a two-point thermostat is shown as being employed in conjunction with a relay to make the device more sensitive. Herein, a bimetallic thermostat 55 is shown as having its blade connected to one side of a relay coil 56 by a conductor 51. It is adapted to make contact with a contact 58 connected to the other side of the relay coil by a conductor 59 through a battery 60. An armature 6| operated by the relay coil 56 is connected to the conductor 36 and is adapted to close the circuit through one or the other of conductors 34 and 35. When the thermostat circuit is closed, the relay coil moves the armature ill to the left against the tension of a spring 62 to close the motor circuit which tilts the main switch and closes the main circuit. When the thermostat contact is broken, the armature 6| swings to the position shown and again closes the motor circuit to open the main switch and restore the parts to the position shown in Fig. 3.

From the foregoing description, it will be noted that the embodiments of the automatic control switch are very simple in design and can be manufactured at a relatively low cost. All of the parts can be installed in a simple box and mounted in any convenient place to control various electrically operated or controlled devices, such as furnaces, electrical refrigerators, heaters, etc. It is entirely automatic in its operation and will last almost indefinitely. The time delay in the actuation of the main switch enables it to respond to a single controlling impulse or to the summation of a series of controlling impulses so that the current consuming device is not subjected to damage due to any chattering of the controlling instrumentalities. This is in accordance with the best engineering practices. Thus, switches of this type, even for controlling heavy duty equipment, can be made to respond to minute changes in demand without damage to the equipment.

Obviously, the present invention is not restricted to the particular embodiments thereof herein shown and described. Moreover, it is not indispensable that all the features of the invention be used conjointly, since they may be employed advantageously in various combinations and sub-combinations.

What is claimed is:

1. In an automatic switching mechanism of the character described, a main switch for controlling a circuit comprising a tiltable mercury tube having terminals therein; an adjustable, oscillatable supporting bracket for said mercury tube; and a motor operated longitudinally reciprocatable shaft carrying an insulating block member connected to impart oscillating movement to said bracket.

2. In automatic switching mechanism of the character described, a tiltable mercury switch in a circuit to be controlled; an adjustable oscillating support having a clip carrying said mercury switch; a motor operated longitudinally reciprocatable member having an-insulating block connected to impart oscillating movement to said support; and a second switch connected to be actuated by said insulating block to break the motor circuit as it completes the switch opening or closing movement.

3. In automatic switching mechanism of the character described, a main switch comprising a tiltable mercury tube in acircuit to be controlled; an osciilatable support for said main switch; a motor; a longitudinally reciprocable shaft connected to oscillate said support; a second mercury tube switch also mounted on said support to be tilted simultaneously with the main switch and arranged to break the motor circuit when the main switch is tilted in either direction and the motor has completed a switch operating movement; means to adjust the angular position of said support; and means to adjust the relative angular positions of said mercury tubes.

4. In automatic switching mechanism of the character described, a main switch for controlling a circuit comprising a tiltable mercury tube having terminals therein; an adjustable, oscillatable supporting bracket for said mercury tube; a motor operated longitudinally reciprocatable shaft; an insulating block secured to the shaft and having a groove connected to said bracket; 2. double-throw switch controlling the motor circuit; and a second groove in the block engaging said double-throw switch.

NATHAN MORRIS.

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