US2275495A - Circuit and switch for reversing single-phase motors - Google Patents

Description

March 10, 1942. R. H. BENTLEY CIRCUIT AND SWITCH FOR REVERSING SINGLE-PHASE MOTORS 2 Sheets-Sheet 1 'Filed Feb. 11, 1938 N m m 1 a w W w m w v e a O O O a b.

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0 /h u w n d 3 ,7 6 u 2 j O O w r L 4 m INSULATION INSULATION' INVENTOR ROBERT H. BENTLEY BY HIS ATTORNEYS March 10, 1942. R. H. BENTLEY CIRCUIT AND SWITCH FOR REVERSING SINGLE-PHASE MOTORS Filed Feb. 11, 1938 2 Sheets-Sheet 2 Z REVERSE FORWARD INVENTOR ROBERT H. BENTLEY BY HIS ATTORNEYS Patented Mar. 10, 1942 CIRCUIT AND SWITCH FOR REVERSING SINGLE-PHASE MOTORS Robert H. Bentley, Hartford, Conn., assignor to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn., a corporation ofConnecticut Application February 11, 1938, Serial No. 190,074

2 Claims.

This invention relates to a circuit and switch for reversing the connections of single phase motors.

An object of the invention is to simplify the circuit arrangements and the apparatus employed therein for reversing single phase motors which have a starting-winding and a runningwinding.

Another object of the invention is to simplify the construction of a switch for reversing single phase motors.

Another object of the invention is to provide a switch for reversing single phase motors which will have fewer current carrying parts and contacts and in which the contacts will be posi tively insulated from each other by the interposition of solid insulating material when the contacts are not connected to the power supply. Another object of the invention is to provide a a circuit and switch which will, with the minimum number of switch contacts, accomplish reversing of single phased motors and will, when in open circuit position, provide for the complete isolation of the windings of the motor from the power lines.

Other objects and advantages of the invention will occur to those skilled in the art as the invention is described in connection with the accompanying drawings.

In the drawings- Fig. 1 is a plan view of the electric switch used in my invention, the operating mechanism of the switch being removed for clearness.

Fig. 2 is an exploded persmctive view of certain parts of the invention shown in Fig. l,

namely a movable contact and its carrier and one set of fixed contacts and wire terminals.

Fig. 3 is a diagrammatic view of my switch and circuit invention with the parts in position for causing the motor to run in reverse direction.

Fig. 4 is a diagrammatic view similar to Fig. 3, but with the parts in position to disconnect the motor from the power supply.

Fig. 5 is a diagrammatic view similar to Figures 3 and 4 with the parts in position for can..- ing the motor to run in forward direction.

In the drawings the mechanism for operating the switch which controls the connections between the power lines and the motor-windings have been omitted. Any suitable operating mechanism may be employed but the type of operating mechanism shown in the co-pending application of R. H. Bentley and W. A. Dietrich, now Patent No. 2,242,167, dated May 13, 1941, is preferred. In this prior co-pending ill application the operating mechanism is capable of moving the movable contacts of the switch into three positions of rest with a sna motion. In the present invention the movable contacts of the switch are required to occupy three positions in order that the motor may be caused to run forward or in reverse or may be stopped and completely disconnected from the power lines.

The running and starting-windings l0 and I2 of a single phase motor are diagrammatically shown in Figures 3, 4 and 5 with the direction of current flow therefrom being indicated by arrows. The running-winding I0 is connected to wire terminals l4 and 16 of the reversing switch, designated generally by the numeral 30. The starting-winding of the motor is connected to the wire terminals I8 and 20 of the switch and the power lines are connected to wire terminals 22 and 24 of the switch.

The switch 30 preferably comprises a rectangular casing of insulating material in one end of which are located wire terminal members I4 and 16 which may be stamped from relatively thick sheet metal of good conductivity. To the tops of these terminal members are secured. by riveting, or other suitable means, a pair of fixed contacts 32*, 32 which may be stamped into L-shape from thin strips of sheet metal with one portion of each contact member extending longitudinally of the casing, so that these portions of the contacts lie against the opposed faces (the inside surfaces) of rectilinearly slidable insulating plates 34*, 34 which extend lengthwise of the casing in parallel relation to each other and to the side walls of the casing.

In the side walls of the casing, located at the midportions thereof, are wire terminals 22 and 24 which may be sheet metal stampings and may have fixed contacts 36 and 38 secured thereto by riveting or in other suitable manner. These contacts 36 and 38 may be stamped from thin sheet metal into the form as shown in Figures 1 and 2. As shown in Figure 2, the contact 36 (which is identical with contact 38) has a long narrow midportion 36 which extends transversely of the wire terminal 22. The end portions 36 and 36 of the contact 36 return upon the midportion but above the midportion and these end portions are slightly oifset from the midportion, as at 36 and 36, the ofiset being in a direction away from the side walls of the switch casing and being of such extent as to cause the ends of the contact 36 to lie adjacent the outside surface of the slidable plate 34 at points directly opposite the stationary contact 32 and the stationary contact 40- hereinafter described. In like manner the ends of the contact 38 are related to the plate 34".

Afi'ixed to the wire terminals [8 and by riveting or other suitable securing means, are a pair of fixed contacts 40 and 40 respectively, these contacts being of similar construction to the contacts 32 and 32 Like the contacts 32 and 32 the contacts 4m and 40 have portions extending longitudinally of the switch casing in position to lie adjacent the opposed faces (the inside surfaces of the slidable plates 34 and 34 By mechanism such as that shown in said copending application Serial No. 106,923, the insulating plates 34 and 34 may be caused to slide between the contact surfaces of the line connected contacts and 38 on one side (the outside) of the plates and the contacts 38 and 38 L.

and and 40 on the other sides (the inside) of the plates.

The plates 34 and 34 carry similar movable contact members 42 and 44 which may be stamped from sheet metal in the form shown best in Figure 2. These contacts are identical. As illustrated in Figure 2 the movable contact 42 is provided with an outer contact surface 42 and an inner contact surface 42 by bending the contact through slots provided in the top surface of the plate 34 These inner and outer surfaces 42 and 42 are directly opposite each other. The end 42 of the movable contact forms an extension of the contact surface 42 in the direction of the fixed contact 32 so that in all positions of the plate 34 the movable contact will be in engagement with the fixed contact 32 and in like manner the similarly formed movable contact 44 will, in all positions of the plate 34', be in engagement with the stationary contact 32 For the purpose of engaging another fixed contact 46 of a fourth pair of fixed contacts, to be hereinafter described, the movable contact 42 has a portion 42 projecting toward the lower edge of the plate 34 the end portion of this extension being bent through a slot in the bottom edge of the plate and reversely bent against the outside surface of the plate in order to hold the movable contact fixedly upon the plate 34. In like manner the contact 44 is provided with an extension which holds that contact on the plate 34 and engages a fixed contact 48.

In order to provide for reversing the connections of the starting-winding of the motor a fourth pair of fixed contacts 46 and 48 are provided in position to project upwardly from the fioor of the switch casing below the fixed contacts 32 and 32 and to lie adjacent the inside or opposed surfaces of the sliding plates 34 and 34 These contacts 46 and 4B are cross-connected to the wire terminals 20 and I8 respectively by means of connecting bars 46 48* which run along the floor of the switch casing. The midportions of these bus bars 46, 48 are offset in opposite directions and are insulated from each other by an insulating wafer 50. The bar 48 which may be formed integrally with contact 48, may be connected by riveting, or any other suitable manner, to the inturned foot l8 of the Wire terminal 18, and likewise the bar 4G may be connected to the foot of the terminal 20. From the foregoing the operation of the switch in controlling and reversing the connections of the windings of a single-phase motor may be understood.

Assuming that the parts are in position to open the circuit between the power lines and the windings, as in Figure 4, it will be noted that the movable contact in that position does not engage with the fixed contacts 22 and 24 and therefore the windings of the motor are completely isolated from the source of power. This is an advantage since, by such an arrangement there is no danger of shock to any person who may touch any part of the motor while it is at rest. Also repairs and adjustments can be made with safety.

If it is desired to start the motor to have it run in a forward direction the slidable plates 34 and 34 will be moved to the right in the position shown in Figure 5. In this position the outside surfaces 42 44 of the movable contacts 42 and 44 will engage with the right ends 36, 38 of the power line contacts 36 and 38 and the inside surfaces of the movable contacts 42 and 44 will engage with the fixed starting- winding contacts 40 and 40 and also with the fixed running- winding contacts 32 and 32 The current will flow from the wire terminal and contact 24, 38 through movable contacts 44 to the fixed starting-winding contact 40 and then through the starting-winding in the direction of the arrow shown in Figure 5 to the fixed contact 40 movable contact 42, fixed power line contact 36 and wire terminal 22 to the opposite power line. At the same time current will flow from the movable contact 44 through the fixed running-winding contact 32 and the running-winding in the direction of the arrow in Figure 5 to the fixed contact 32*, movable contact 42 and fixed contact 35 and to the power line as previously described.

In case it is desired to reverse the direction of the motor the slidable plates 34 34 will be moved into the position shown in Figure 3. In that position the current will flow from the power line contact surface 38' to the movable contact 44 and through the fixed running-winding contact 32 and through the running-winding in the same direction as in the forward running of the motor; and then to the fixed Contact 32 and movable contact 42 and fixed line contact 36 to the line. At the same time the current will flow from the movable contact 44 through the downward extension 44 (corresponding to the downward extension 42 of the movable contact 42) to the cross-connected stationary contact 48, through the bar 48 to the terminal [8 to the starting-winding and through it in the direction of the arrow in Figure 3 to the terminal 20 and bar 45* to the cross-connected stationary contact 46 and downward extension 42 of the movable contact 42 to the fixed line contact 35.

From the foregoing it will be seen that I have provided a circuit and switch which is capable of reversing the direction of a single-phase motor and of completely isolating the windings of that motor from the power lines. I have accomplished this with the use of a lesser number of fixed and movable contacts than has heretofore been possible and at the same time I have provided a positive insulation between the line-connected contacts of the switch and every switch contact which is not at a given time positively connected to the power lines. My invention has the additional advantage of utilizing the well known principle of quenching arcs by the interposing of solid insulation and extensive cool insulating surfaces at the moment of circuit interruption.

Many modifications within the scope of my invention will occur to those skilled in the art and therefore I do not limit the invention to the specific embodiment of the invention as herein described.

I claim: 7

1. In an electric switch, a pair of slidable insulating plates, movable contacts carried by said plates, a pair of fixed switch contacts at one end of said plates, each contact of said pair lying adjacent the opposed surfaces of said plates, a second pair of fixed contacts at the other end of said plates, each contact of said second pair lying adjacent the opposed surfaces of said plates, a third pair of fixed contacts, each contact of said third pair lying adjacent the opposed surfaces of said plates, a fourth pair of fixed contacts lying adjacent the opposite sides of said plates to which the contacts of said first, second and third pairs lie, said plates being movable into three positions in one of which each movable contact engages with one contact of each of said first and third pairs, and with one contact of said fourth pair, and in a second position each movable contact engages with one contact of each of said first and second pairs and with one contact of said fourth pair, and in a third position each movable contact being disengaged from all said contacts except said first pair.

21. In an electric switch, a pair of slidable insulating plates, movable contacts carried by said plates, a pair of fixed switch contacts at one end of said plates, each contact of said pair lying adjacent the opposed surfaces of said plates, a second pair of fixed contacts at the other end of said plates, each contact of said second pair lying adjacent the opposed surfaces of said plates, a third pair of fixed contacts, each contact of said third pair lying adjacent the opposed surfaces of said plates, a fourth pair of fixed contacts lying adjacent the opposite sides of said plates to which the contacts of said first, second and third pairs lie, said plates being movable into three positions in one of which each movable contact engages with one contact of each of said first and third pairs, and with one contact of said fourth pair, and in a second position each movable contact engages with one contact of each of first and second pairs and with one contact of said fourth pair, and in a third position each movable contact being disengaged from all said contacts except said first pair, said plates in each switch position insulating said fourth pair of contacts from all pairs of contacts which are not connected to said fourth pair in any given position.

ROBERT H. BENTLEY.

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