US3858133A

US3858133A - Switch transfer mechanism

Info

Publication number: US3858133A
Application number: US00435230A
Authority: US
Inventors: R Rudy; H Swanson
Original assignee: G&W Electric Specialty Co
Current assignee: G&W Electric Specialty Co
Priority date: 1974-01-21
Filing date: 1974-01-21
Publication date: 1974-12-31
Anticipated expiration: 1991-12-31
Also published as: CA1007684A

Abstract

A switch transfer mechanism is disclosed having an actuating plate selectively movable through a snap-action movement to transfer connection of an electric load from a preferred feeder voltage to an emergency feeder voltage when the preferred feeder voltage drops below a predetermined value. The mechanism includes improved torque plates and latching means which prevents arming of energy storage means unless the latching means is disposed in latching relation with the actuating plate to prevent movement thereof during arming of the energy storage means.

Description

United States Patent 91 Swanson et al.

[ Dec. 31, 1974 SWITCH TRANSFER MECHANISM [75] Inventors: Howard E. Swanson, Chicago;

Richard S. Rudy, Chicago Heights, both of 111.

[73] Assignee: G & W Electric Specialty Company,

Blue Island, Ill.

[22] Filed: Jan. 21, 1974 [21] App]. No.: 435,230

[52] U.S. Cl 335/160, 74/97, 200/63, 335/164 [51] Int. Cl. H01h 9/22 [58] Field of Search 335/160, 161, 164, 120, 335/233; 317/136; 74/97, 112, 483; 200/63, 65

[56] References Cited UNITED STATES PATENTS 3,234,803 2/1966 Caswell et al 74/97 7/ 1968 Kowalski 335/ 164 10/1968 Kovats 200/63 R Primary Examinerl-larold Broome Attorney, Agent, or FirmFitch, Even, Tabin &

. Luedeka [57] ABSTRACT A switch transfer mechanism is disclosed having an actuating plate selectively movable through a snapaction movement to transfer connection of an electric load from a preferred feeder voltage to an emergency feeder voltage when the preferred feeder voltage drops below a predetermined value. The mechanism includes improved torque plates and latching means which prevents arming of energy storage means unless the latching means is disposed in latching relation with the actuating plate to prevent movement thereof during arming of the energy storage means.

12 Claims, 8 Drawing Figures mmmm v I 348523.133

' SHEET 20F PATENTEU 533.) 1974 3,858,133

SHEET u BF 5 I A), m

The present invention relates generally to switch transfer mechanism, and more particularly to automatic switch transfer mechanism employing novel constructional features which provide highly efficient and safe operational characteristics.

It is known to employ a switch transfer mechanism for transferring the connection of an electric load from a preferred feeder voltage to an auxiliary or emergency feeder voltage when the preferred feeder voltage drops below a predetermined value, such as 65 percent of its normal voltage supply. Transfer of the load to the emergency feeder voltage is preferably accomplished very rapidly so that harmful arcing does not occur in the transfer mechanism and so that the devices comprising the load are not subject to a temporary power failure. See, for example, US. Pat. No. 3,177,732, dated Apr. 13, 1965, and assigned to the assignee of the present invention. To accomplish rapid transfer, the known switch transfer mechanisms employ means, such as compression springs, which are armed and released in a manner to effect a rapid movement of an actuator plate which effects transfer of a switch arm from one set of contacts to another whereby the load is transferred from the preferred feeder voltage to the auxiliary or emergency feeder voltage. The switch transfer mechanism in accordance with the present invention provides improved operating and safety characteristics over the prior switch transfer mechanisms.

A primary object of the present invention is to provide an improved switch transfer mechanism which facilitates transfer of an electrical load from a preferred feeder voltage to an auxiliary or emergency feeder voltage when the preferred feeder voltage supply drops below a predetermined value.

Another object of the present invention is to provide a switch transfer mechanism wherein novel torque transfer plates are employed in cooperation with compression springs and an actuator plate to effect snapaction movement of the actuator plate when the preferred feeder supply voltage drops below a predetermined value, the torque transfer plates having enclosed slots therein which receive spring pivot members in a manner to prevent the pivot members from disengagement with the torque transfer plates as a result of rebound following release of the compression springs during a transfer cycle.

Another object of the present invention is to provide a switch transfer mechanism which finds particular application in automatic transfer and which has novel latch means and control circuit means operative to prevent arming or compression of the compression springs preparatory to a transfer cycle unless the latch means is in latching relation with the actuator plate to prevent unintentional movement thereof in a switch transfer direction.

Yet another object of the present invention is to provide a switch transfer mechanism which is highly efficient in operation and which provides optimum safety in preventing accidental and unintended switching.

Further objects and advantages of the present invention, together with the organization and manner of op eration thereof, will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings wherein like reference numerals designate like elements throughout the several views, and wherein:

FIG. 1 is a front elevational view of a switch transfer mechanism in accordance with the present invention with the outer casing removed and with the actuating plate being partially shown in phantom in a position prior to a switch transfer, and in solid lines in a position immediately following a transfer and prior to rearming of the compression springs;

FIG. 2 is an enlarged end view of the switch transfer mechanism of FIG. 1, taken substantially along the line 22 of FIG. 1;

FIG. 3 is a partial sectional view taken substantially along the line 3-3 of FIG. 1, looking in the direction of the arrows;

FIG. 4 is a partial front view showing the manner of interconnecting the actuator plate of FIG. 1 to the torque plates through energy storage compression springs, and with the latching lever being positioned in latching relation with the actuator plate;

FIG. 5 is a partial sectional view taken substantially along the line 55 of FIG. 1 to illustrate the latching lever mechanism;

FIG. 6 is a partial sectional view, taken substantially along the line 6-6 of FIG. 4, showing a spring pivot member interconnecting an end of one of the compression springs to the torque plates and the actuator plate;

FIG. 7 is a view similar to FIG. 4 but illustrating the torque plates moved to a position to arm the energy storage compression springs; and

FIG. 8 is a schematic circuit diagram showing a control circuit for use with the transfer mechanism of FIG. 1.

Referring now to the drawings, and in particular to FIGS. 1 and 2, a switch transfer mechanism constructed in accordance with the present invention is indicated generally at 10. The switch transfer mechanism 10 finds particular application in the automatic transfer of electrical service to an electric load from a preferred or primary feeder voltage to an emergency feeder voltage when the preferred feeder voltage falls below a predetermined value, such as 65 percent of its normal voltage. When the preferred feeder voltage returns to a predetermined value, such as percent of its normal voltage, the transfer mechanism 10 will return the load to the preferred feeder voltage. The preferred feeder voltage and the emergency feeder voltage are illustrated schematically in the control circuit of FIG. 8, and will be described more particularly below in connection with the description of the circuit diagram of FIG. 8.

Briefly, the switch transfer mechanism 10 includes housing means, indicated generally at 12', actuator plate means, indicated generally at 14, operable between first and second positions to actuate an actuating shaft and multiple contact switch means, indicated generally at 16; torque plate means, indicated generally at 18; energy storage means, indicated generally at 20, interconnecting the torque plate means 18 to the actuating plate means 14 and adapted to effect snap-action movement of the actuator plate means 14 during a switch transfer function; and latch means, indicated generally at 22, selectively cooperable with the actuator plate means 14 to prevent movement thereof until a switch transfer is required, such as when the preferred feeder voltage drops to a predetermined lower limit or returns to a predetermined value after transfer of the load to the emergency feeder voltage.

A particular feature of the present invention lies in the cooperation of the latch means 22 and the control circuit to prevent loading or arming of the energy storing means 20 following a switch transfer unless the latch means 22 is in latching or locking relation with the actuator plate means 14.

The housing means 12 includes a rear support plate 24 which has mounted thereon a generally rectangularly shaped support panel 26 through four spacers 28 and associated mounting bolts 30. A cover housing or casing (not shown) may be secured to the support plate 24 to enclose and seal the internal elements of the switch transfer mechanism to be described in greater detail hereinbelow. The support panel 26 has a pair of parallel spaced side plates 32 mounted thereon through four mounting bolts 34 each of which supports a spacer sleeve 36 between the support panel 26 and the associated side plate 32 to maintain the side plates 32 in parallel outwardly spaced relation from the support panel '26. The spacer sleeves 36 also serve as abutment stops as will become apparent below. The upper ends of the side plates 32 support a horizontally disposed angle bracket 38 which in turn supports a pair of forwardly extending support brackets 40 to which may be secured a relay panel (not shown). The outermost ends of the mounting bolts 34 also serve to support a generally rectangular mounting plate 42 which is retained against, the outer surfaces of the side plates 32 by the heads of bolts 34.

Referring to FIGS. 3 and 4, taken in conjunction with FIGS. 1 and 2, the actuator plate means 14 includes an actuator plate 48 which is fixedly mounted on a horizontally disposed actuating shaft 50. The actuating shaft 50 is supported by and between the support panel 26 and the mounting plate 42 by a pair of sleeve bearings 52 which have annular end flanges 54 abutting a central hub 56 on the actuator plate 48. The actuating shaft50 includes a stepped end portion 58 which extends rearwardly through an appropriate opening in the support plate 24 and actuates a connecting linkage such as indicated by dash line 180 in FIG. 8. The connecting linkage 180 is operatively connectedto the movable contact arms of a conventional triple pole, double throw switch, indicated generally at 176, to complete a service circuit to an electric load L.

The end of the actuating shaft 50 opposite the end portion 58 extends outwardly from the mounting plate 42 and fixedly supports an actuating lever 60 thereon by means of a retainer washer 62 and screw 64. A con- I ventional counter mechanism 66 is secured to the left hand end of the mounting plate 42, as shown in FIG. 1, and has an actuating arm 68 connected to the actuating lever 60 through a connecting wire 70 in amanner to count the number of transfer movements of the actuator plate 48. The counter 66 thus affords an indication of the frequency of transfer of the load L from its preferred or primary feeder voltage to the emergency feeder voltage.

The outer end of the actuating lever 60 is pivotally connected to a linkage 72 which has its opposite end pivotally connected to the outer end of a radial actuating arm 74. The actuating arm 74 is secured on a shaft 76 (FIG. 2) which is fixed to and extends axially rearwardly from the multiple contact switch means 16, the rearward end of the shaft 76 being rotatably received through a suitable opening in the mounting plate 42. A pair of parallel support studs, one of which is shown at 77, is secured to the mounting plate 42 and support the multiple contact switch means 16 in a manner to allow rotational movement of the shaft 76 and thereby a plurality of switch contact elements 78 when the actuator plate 48 is rotated during a switch transfer operation.

With particular reference to FIGS. 4 and 7, the actuator plate 48 of the actuator plate means 14 has symmetrical generally arcuately shaped end portions 79 the outer peripheral edges of which lie on a common diam eter and terminate in radially inwardly directed edge surfaces 80. Each of the edge surfaces 80 on the actuator plate 48 lies on a common diameter with an edge surface 80 diametrically opposed therefrom. The edge surfaces 80 serve as abutment stops which are adapted to engage the spacer sleeves 36 and limit the extent of rotational movement of the actuator plate 48 about the axis of actuating shaft 50. Each end 79 of the actuating plate 48 has a pair of arcuately shaped recesses 82 formed thereon the purpose of which will become apparent hereinbelow. The actuating plate 48 has generally parallel straight edge surfaces 83 intermediate the recesses 82 to provide clearance for the energy storage means 20.

The actuator plate 48 is operable through an oscillatory snap-action rotational movement to effect a corresponding rotation of the actuating shaft 50 and cause a rapid transfer of the load L from a preferred feeder voltage supply to an emergency feeder voltage supply and subsequent return to the preferred feeder voltage. Such snap-action rotational movement of the actuator plate 48 is effected by the torque plate means 18 in cooperation with the energy storage means 20. The torque plate means 18 includes a pair of parallel spaced circular torque plates 86 which, as best seen in FIG. 3, are mounted on the actuating shaft 50 for rotational movement about the axis of shaft 50 in planes parallel to the plane of the actuator plate 48. The torque plates 86 are identical in configuration and have central openings 87 therein which slidingly receive the sleeve bearings 52 therethrough, each of the torque plates 86 being retained against the annular end flange 54 of the associated sleeve bearing 52 by a spacer sleeve 89 and an annular shim 91 disposed between each torque plate and the corresponding support panel 26 or mounting plate 42. In this manner, the torque plates 86 and the actuator plate 48 are maintained in spaced relation between the support panel 26 and the mounting plate 42.

The torque plates 86 are interconnected by a pair of connecting brackets 88 each of which is connected to one of the torque plates 86 through suitable means, such as bolts 90. The connecting brackets 88 are secured together intermediate their lengths by a cross bolt 92 having a spacer sleeve 94 supported on the shank thereof intermediate the brackets 88. The outermost ends of the connecting brackets 88 have aligned elongated slots 96 therethrough each of which receives the outer end of a trunion pin 98. The trunion pins 98 are fixed to a trunion support block 100 so as to extend outwardly from opposite sides thereof in axially aligned relation. The trunion support block 100 is mounted on a drive screw shaft 102 having an external right-hand thread thereon cooperable with a mating thread formed axially within the trunion support block 100.

The drive screw shaft 102 is operatively connected to an electric drive motor 104 in a manner to effect rotational movement of the drive screw shaft 102 upon energizing the drive motor 104. As will become more apparent hereinbelow, the control circuit used in conjunction with the switch transfer mechanism serves to energize the drive motor 104 and rotate the drive screw 102 to arm the energy storage means preparatory to each transfer operation. To this end, the drive motor 104 is controlled to rotate the drive screw 102 in alternate rotational directions after successive movements of the actuator plate 48 to effect successive switch transfers, the actuator plate 48 thereby undergoing oscillating movement about its rotational axis.

The drive motor 104 has an upstanding housing portion 106 which may enclose a gear reduction unit to which the drive screw 102 is directly connected. The upstanding housing portion 106 has a generally U- shaped support bracket 108 secured thereto, the parallel outwardly extending arms 110 of the bracket 108 being pivotally mounted between the rear support panel 26 and the vertical flange of the angle bracket 38 by a horizontal support shaft 112 such that the drive motor 104 is pivotable about the axis of the support shaft 112. Pivotal mounting of the drive motor 104 and its associated housing 106 is necessary to accommodate movement of the drive screw shaft 102 in a vertical plane during rotation of the torque plates 86 as the trunion block 100 is moved along the drive screw 102 during arming of the energy storage means 20.

Each of the torque plates 86 has a pair of generally arcuately shaped enclosed slots 114 formed therein which are symmetrical relative to a plane normal to the planes of the torque plates 86 and containing the axes of the actuating shaft 50 and the cross bolt 92. The arcuate slots 114 in each of the torque plates 86 are aligned with corresponding enclosed slots 114 in the opposing spaced torque plate 86. The torque plates 86 serve to support the energy storage means 20 for selective cooperation with the actuator plate 48 to effect snap-action rotational movement of the actuator plate 48 during a switch transfer operation.

The energy storage means 20 include a pair of coil compression springs 118 each of which is mounted between the spaced torque plates 86 through

pivot members

120 and 122 disposed on opposite ends of each compression spring. The compression springs 118 and their associated

pivot members

120 and 122 cooperate with the torque plates 86 in a manner similar to the coil compression springs (54, 55) and pivot members (56, 57, 58, 60) disclosed in US Pat. No. 3,403,565, dated Oct. 1, 1968, andassigned to the assignee of the present invention. Briefly, the pivot members 120 have outwardly extending cylindrical end portions 124 (FIG. 6) which are received within the opposing arcuate slots 114 in the torque plates 86 and are normally urged against arcuate end surfaces 126 in the associated slots 114 when the springs 118 are unarmed. Each of the pivot members 120 has a cylindrical recess 128 formed radially therein which serves to receive and seat an end portion of the associated compression spring 118. Each of the pivot members 120 also has secured thereto a guide rod 130 which is coaxial with the cylindrical recess 128 and extends axially through the associated compression spring 118.

The pivot members 122 are substantially identical to the pivot members 120 and have axially aligned cylindrical end portions which are received within the opposed arcuate slots 114 in the torque plates 86 and are normally urged against the ends 126 of the arcuate slots 114 opposite the pivot members when the compression springs 118 are unarmed. Each of the pivot members 122 has a radial recess 128 therein to receive the end of the associated compression spring 118 opposite the end thereof received within the pivot member 120. A guide sleeve 132 (FIG. 4) is secured to each of the pivot members 122 in a manner to be telescopically received over the guide rod disposed within the associated compression spring. In this manner, the

pivot members

120 and 122 on the opposite ends of each spring 118 may move toward each other during compression of the associated compression spring, with the associated guide rod 130 and guide sleeve 132 serving to maintain the axis of the compression spring generally straight during compression and release thereof.

Each of the

pivot members

120 and 122 has an annular groove 134 (FIG. 6) in its peripheral surface, a portion of which receives and selectively abuts an edge surface 82 on the actuating plate 48 during arming or compression of the associated compression springs 118. The

edge surface

82 and 126 on the actuator plate 48 and torque plates 86, respectively, are aligned when the compression springs are in their relaxed or unarmed positions, as illustrated in FIG. 4, such that the

pivot members

120 and 122 engage both the end surfaces 126 and the abutment surfaces 82. Energizing the drive motor 104, while the actuator plate 48 is prevented from rotating by the latch means 22 serves to rotate the torque plates 86 through the drive screw 102, such as from the position shown in FIG. 4 to the position shown in FIG. 7, and arm or compress the compression springs 118.

As noted, the latch means 22 serves to prevent movement of the actuator plate 48 during arming or compression of the compression springs 118. With reference to FIG. 1, taken in conjunction with FIGS. 4, 5, and 7, the latch means 22 includes a latch lever 138 supported for pivotal movement about a horizontal pivot shaft 140 secured to and between the support panel 26 and the right-hand side plate 32, as considered in FIG. 1. Spacer sleeves 142 (FIG. 5) maintain the latch lever 138 in spaced relation between the support panel 26 and the side plate 32 such that a latch roller 144 rotatably supported by the latch lever underlies the actuating plate 48.

The end of the latch lever 138 opposite the latch roller 144 has a cross rod 146 secured thereto for engagement with the lower end of a generally U-shaped solenoid actuating bracket 148. The bracket 148 is vertically movable with the piston portion 150 of a conventional electrically operated solenoid 152. The solenoid 152 is shownin FIG. 1 in a normal nonenergized position wherein the latching lever 138 is disposed in a substantially horizontal position. Energizing the electrical solenoid 152 serves to retract the piston 150 and effect pivotal movement of the latch lever 138 in a counterclockwise direction about the pivot axis 140 so as to lower the latching roller 144. The latching roller 144 is rotatably mounted on a support shaft 154 which is secured to the latch lever 138 and extends outwardly from the latch lever where it is engaged by a leg 156 of a biasing spring 158. The biasing spring 158 is coiled about a spring support pin 160 secured in normal relation to the support panel 26. A lower leg portion 162 of the biasing spring 158 abuts a stop pin 164 secured to the support panel 26. The leg 156 of the biasing spring 158 urges the latch roller 144 upwardly against the actuating-plate 48 when the actuating solenoid 152 is de-energized. The latch roller 144 is urged toward a position where it may be engaged by one of the stop edge surfaces 80 on the lower end of the latch lever 48, as considered in FIG. 1, to selectively prevent rotational movement of the actuating plate 48. The latch roller 144 is positioned such that when it is in a latching position, its axis of rotation lies in a vertical plane containing the longitudinal axis of the actuating shaft 50. ln this manner, the latch roller 144 is operative to be engaged by either of the lower stop edge surfaces 80 on the actuator plate 48 when the actuator plate is disposed in either of its angular positions whereby to prevent movement of the actuator plate 48 from one position to another without first energizing the actuating solenoid 152 to release the latch roller 144 from the actuator plate 48.

A conventional microswitch 166 is secured to the support panel 26 and has an actuating arm 168 which extends angularly upwardly for engagement with the outer end portion of the support shaft 154. Movement of the support shaft 154 through actuation of the solenoid 152 will effect a switching of the switch 156 for a purpose to be described hereinbelow.

Briefly reviewing the mechanical operation of the switch transfer mechanism 10, it may be assumed that the electric load L is connected to a preferred feeder voltage supply through a conventional oil switch contact arrangement under the control of the end portion 58 of the actuating shaft 50. lt may be further assumed that under such normal operating conditions, the torque plates86 have been moved or rotated about the actuating shaft 50 to a position to arm or compress the compression springs 118 of the energy storage means 20. Under such conditions, the actuating solenoid 152 is normally de-energized so as to allow the biasing spring 158 to urge the latch roller 144 to an up ward position wherein it abuts a lower stop edge surface 80 on the actuating plate 48 to prevent rotational movement of the actuating plate 48 in the direction toward which it would be urged by the armed compression springs 118.

When the feeder voltage drops below a predetermined value, such as 65% of its normal operating feeder line voltage, a signal is transmitted to the actuating solenoid 152, after a predetermined time delay, to energize the solenoid 152 to effect pivotal movement of the latch lever 138 in a direction to release the latch roller 144 from the actuating plate 48. Release of the actuating plate 48 causes it to undergo a rapid snapaction rotational movement as a result of the release of energy stored in the armed compression springs 118 to actuate the connecting linkage 180 (FIG. 8) associated with the actuating shaft 50 in a manner to actuate the switch 176 and transfer the electrical load L from the preferred feeder voltage to an emergency feeder voltage supply.

After the actuating plate 48 starts such snap-action movement to transfer the load L to the emergency feeder voltage, the actuating solenoid 152 is deenergized to release the latch lever 138 whereupon the biasing spring 158 urges the latch roller 144 upwardly for engagement with the stop edge surface 0f the actuator plate 48 when it has moved to a position generally overlying the latch roller 144. After the latch roller 144 has returned to such a latching position, as detected by the microswitch 166, the drive motor 104 is energized to effect rotation of the torque plates 86 about the actuating shaft 50 in a direction to again arm or compress the compression springs 118, such latter rotational direction being opposite to the rotational direction given the torque plates 86 during the previous arming of the compression springs.

When the preferred supply voltage returns to a predetermined value above the value at which a switch transfer to the emergency feeder voltage took place, such as 90 percent of its normal voltage supply, the transfer mechanism 10 will, after a predetermined time delay, return the load L to the preferred feeder voltage by energizing the actuating solenoid 152 to release the latching roller 144 and allow a rapid snap-action movement of the actuator plate 48 to effect return transfer of the load L to the preferred feeder voltage, after which the drive motor 104 is again energized in a direction to rearm the compression springs 118 preparatory to a subsequent switch transfer cycle.

To carry out automatic operation of the switch transfer mechanism 10, a control circuit, indicated generally at in FlG. 8, is provided which serves to automatically transfer the electric load L from a preferred or primary three-phase feeder voltage, indicated generally at 172, to a secondary or emergency three-phase feeder voltage, indicated generally at 174, when the primary feeder voltage drops below a predetermined value, and to return the electric load L to the preferred feeder voltage 172 when it again returns to a predetermined value which is generally greater than the value at which transfer to the emergency feeder voltage took place. With reference to FIG. 8, the three phases of the preferred feeder voltage supply 172 are indicated at 172A, 1723, and 172C. The three phases of the secondary feeder voltage supply 174 are indicated at 174A, 174B, and 174C. The three phases of the preferred and

emergency feeder voltages

172 and 174 are connected, respectively, to contacts 172a, 172b, l72c and 174a, 174b, 1740 of the triple-pole, double throw switch 176 which may comprise a conventional oil, gas or dielectric grade fluid insulated switch. The switch 176 includes three fixed contacts 178a, 178b and 178C to each of which is connected a movable switch contact arm 181a, b, or c. The switch contact arms 181a, b and c are operatively interconnected by the connecting linkage to the actuating shaft 50 of the switch transfer mechanism 10. The fixed contacts 178a, b and c are each connected to the load L which is normally connected to the preferred feeder voltage supply 172 through the switch ,176 but which is alternately connected to the emergency feeder voltage supply 174 when the primary voltage supply 172 drops below a predetermined value.

The control circuit 170 includes a first sensing relay coil 182 connected in series with a conventional fuse 184 which is connected to the secondary winding of a voltage step-down transformer 185 having its primary winding connected between

phases

172A and 1728 of the preferred voltage supply 172. The relay coil 182 controls normally open contacts 182a. A second sensing relay coil 186 is connected in series with a fuse and the relay contacts 182a to the secondary winding of a step-down transformer 187 which has its primary winding connected between

phases

1728 and 172C of the preferred voltage supply 172. The sensing relay coil 186 controls normally open relay contacts 1860, normally closed relay contacts 186b, normally open relay contacts 186C, and normally closed relay contacts 186d. The circuit through the sensing relay coils 182 and 186 is completed to ground through a conductor 191. A voltage potential step-down transformer 188 has its primary winding connected between phases 1748 and 174C of the emergency voltage supply 174, and has its secondary winding connected through a fuse 193 to the relay contacts 1860'. In this manner the three phases of the preferred feeder voltage 172 are sensed, and phases 174B and 174C of the secondary feeder voltage 174 are sensed. Thus, a voltage drop on any phase of the preferred feeder voltage 172 will be sensed as a feeder voltage failure.

The sensing relays 182 and 186 and their associated

relay contacts

182a, 186a and 186d, along with the normally closed contacts 166a of the microswitch 166, control the power supply from the

transformers

185, 187 and 188 to a timing circuit, indicated generally at 192. The timing circuit 192 includes a time delay relay coil 194 which controls normally open relay contacts 194a to in turn control energizing of a trip control relay coil 196. The trip control relay coil 196 controls normally open relay contacts 196a connected in series with the solenoid 152. The time delay relay coil 194 is of conventional design and is adjustable over a variable time period, such as from less than I to greater than 40 seconds, to selectively delay closing of the relay contacts 194a and thus control energizing of the solenoid 152. The time delay relay 194 serves to prevent transfer of the load L between the

feeder voltages

172 and 174 on merely momentary dips in the feeder voltage.

The timing circuit 192 is completed to ground through a circuit branch including the normally closed relay contacts 186b, a set of contacts 78a controlled by the multiple contact switch means 16, and through contacts 198a of a single pole, double throw limit switch 198 mounted on the lower horizontal flange portion of the angle bracket 38 (FIG. 1). The contacts 198a of the limit switch are closed when the torque plates 86 are in positions as shown in FIG. 1, and are open when the connecting brackets 88 are moved away from switch 198. The limit switch 198 also includes contacts 198b which are open when the torque plates 86 are in the positions shown in FIG. 1, and are closed when the torque plates undergo a clockwise rotational movement, as considered in FIG. 1. The contacts 78a are closed when the actuatorplate 48 is in the position shown in phantom in FIG. 1, and are open when the actuator plate 48 is in the position as shown in solid lines in FIG. 1.

The timing circuit 192 is also completed to ground through a second circuit branch which includes the normally open relay contacts 186e, a set of contacts 78b which are controlled by the multiple contact switch means 16 and are open when the actuator plate 48 is in the position as shown in phantom in FIG. 1, and a set of normally open contacts 200a of a double pole, single throw limit switch 200 supported on the horizontal flange portion of the angle bracket 38 so as to be actuated by the connecting brackets 88 when the torque plates 86 are rotated to positions as shown in FIG. 7.

The relay coil 186 and its contacts 186a and 186d also control the power supply to the electric drive motor 104 for the drive screw shaft 102. The control circuit for the motor 104 is completed to ground through a first branch including switch contacts 780 of the multiple contact switch means 16, which are open when the actuator plate 48 is in the position as shown in phantom in FIG. 1, and a set of contacts 20011 which are controlled by the limit switch 200 and are normally closed when the torque plates 86 are positioned as in FIG. 1. The circuit for the motor 104 is also completed to ground through a second circuit branch which includes contacts 78d of the multiple contact switch means 16 and contacts 198b of the limit switch 198. The contacts 78d are closed when the actuator plate 48 is in the position as shown in phantom in FIG. 1. The contacts 198b are open when the torque plates 86 are in positions as shown in FIG. 1.

A pair of indicating

lights

202 and 204 are controlled by the relay contacts 186a and 186d, the switch contacts 166a, and switch

contacts

78e and 78f of the switch means 16 to provide a visual indication of the position of the switch transfer mechanism 10 during operation. The switch contacts 78e are open and the switch contacts 78f are closed when the actuator plate 48 is positioned as shown in phantom in FIG. 1.

Assuming the load L to be connected to the preferred feeder voltage supply 172 through the switch 176 when the actuator plate 48 is disposed in a position as partially snown in phantom in FIG. 1, with the latching means 22 preventing rotational movement thereof, and further assuming that the torque plates 86 have been rotated through the connecting brackets 88 by means of the feed screw 102 to a position as in FIG. 1 wherein the compression springs 118 are compressed or armed, the load L will be supplied by the primary feeder voltage supply 172. In this mode of operation, the sensing relay coils 182 and 186 will be energized to close their relay contacts 182a and 186a but the circuit through the timing circuit 192 to ground will be open due to the open relay contacts l86b and the open contacts 781) and 200a.

When the primary feeder voltage 172 drops below the predetermined value, such as 65 percent of its normal supply voltage, the sensing relays 182 and 186 will be de-energized sufficiently to open the relay contacts 182a, 186a and 186C, and close the relay contacts 18612 and 186d. The arrangement of contacts 186a and 186d ensures that the control circuit means 170 receives power for operation from the feeder source to which the load L will be transferred. Further, if the emergency voltage 174 is not sufficient percent) to energize the time delay relay 196 and thereby close contacts 196a, the control circuit will not transfer the load L to the emergency voltage source 174. Closing the relay contacts 186b and 186d completes the circuit through the timing circuit 192 and allows the time delay relay 194 to be energized by the secondary feeder voltage 174 through the switch contacts 186d, the normally closed microswitch contacts 1660, the relay contacts 186b, the switch contacts 78a, and the limit switch contacts 198a. After a predetermined time delay period, as determined by selection of the time delay of relay 194, the time delay relay contacts 1940 close to energize the trip relay 196 which, in turn, closes the trip relay contacts 1960. This serves to energize the solenoid 152 which, as noted above, effects pivotal movement of the latch lever 138 about its pivot axis 140 in a manner to release the latch roller 144 from its engagement with a stop surface 80 on the actuator plate 48 when positioned as shown in phantom in FIG. 1, whereupon the actuating plate 48 undergoes a rapid snap-action movement in a counterclockwise direction to the position shown in solid lines in FIG. 1 as a result of the release of energy from the armed compression springs 118. The actuating rod 50 is thereby rotated in a corresponding counterclockwise direction which results in transfer of the contact arm 180 of the oil switch 176 to a position contacting the emergency feeder voltage contact l74a with a resulting connection of the load L to the emergency feeder voltage 174. Rotation V of the actuator plate 48 during its snap-action transfer movement is limited by engagement of two of the leading stop surfaces 80 thereon with the stop sleeves 36 disposed in the path of travel of the leading stop surfaces.

Rotation of the actuating shaft 50 upon transfer of the actuating plate 48 to the position shown in solid lines in FIG. 1 causes the

switch contacts

78b, 78c and 78e to close, with a simultaneous opening of the mechanically operated

switch contacts

78a, 78d, and 78f. When the solenoid 152 is energized to pivot the latch lever 138 to a releasing position, the microswitch 168 is actuated in a manner to open the switch contacts l66a=thereof so that the drive motor 104 cannot be energized until the latch lever has returned to a latching position under the force of the biasing spring 158. Opening the switch contacts 78a during transfer of the actuating plate 48 opens the circuit through the timing circuit 192 to deenergize the solenoid 150 and allow such return movement of the latch lever 138 to a latching position.

After the actuating plate 48 has completed its transfer movement, the latch lever 138 is returned to its latching position with the actuator plate whereupon the switch contacts 166a of the microswitch 166 are returned to their normally closed positions to effect energizing of the drive motor 104 through the switch contacts 780 and 200b. Energizing the drive motor 104 rotates the feed screw 102 in a direction to rotate the torque plates 86 to a position as shown in FIG. 7, with a correspondingcompressing or arming of the compression springs 118. The motor 104 rearms the springs 118 until the switch contacts 200b of the limit switch 200 are opened by engagement of the connecting brackets 88 with the switch 200 which simultaneously closes the switch contacts 200a. When the compression springs 118 are fully compressed and the rotation of torque plates 86 is complete, the contacts 198a of the limit switch 198 open and the switch contacts l98b close. The transfer switch mechanism is now latched in a position connecting the load L to the emergency feeder voltage 174 and the compression springs 118 are armed preparatory to a subsequent transfer function.

When the primary feeder voltage supply 172 again rises to a predetermined value, such as 90 percent of its normal voltage supply, the sensing relays 182 and 186 will again be energized to close the relay contacts 182a, 186a and 1860, and open the relay contacts 186b and 186d. The time delay relay 194 is then again energized and times out through the closed relay contacts 186a, 166a, 1860, 78b and 200a. After the pre-established time delay, established to prevent transfer upon a mere momentary rise of the primary voltage 172 to 90 percent of its normal voltage, the time delay relay contacts 194a close to energize the trip relay 196 which closes the relay contacts 196a. The solenoid 152 is then energized to release the latching lever 138 and allow rapid snap-action rotational movement of the actuating plate 48 to transfer the contact arm 180 from the secondary feeder voltage supply contact 174a back to the preferred feeder voltage supply contact 172a. Such transfer of the actuating plate 48 actuates the multiple contact switch means 16 to open the

switch contacts

78b, 78c, and 78e, and close the

switch contacts

78a, 78d, and 78f. The contacts 166a of the microswitch 166 will again be momentarily opened when the latch lever 138 is pivoted to a release position so as to prevent energizing of the drive motor 104 in a direction to rearm the compression springs 118 until the latch lever 138 is again returned to a safety latching position with the actuator plate 48.

With the relay contacts l86b and switch contacts 78b now open, the power supply to the solenoid 152 is terminated allowing return of the latch lever to a latching position to close switch contacts 166a. The drive motor 104 is then energized to rearm or compress the compression springs 118 through the'drive screw 102 by effecting rotational movement of the torque plates 86 until the connecting brackets 88 engage the limit switch 198 to close the contacts 198a and open the contacts 198b, while allowing the contacts of the switch 200 to revert to positions wherein the contacts 200a are open and the contacts 20% are closed. Opening the switch contacts 198b deenergized the drive motor 104. The switch transfer mechanism 10 is now again latched onto the preferred feeder voltage 172 and the compression springs 118 are rearmed preparatory to a subsequent transfer function.

Having thus described a preferred embodiment of the switch transfer mechanism 10 in accordance with the present invention, itcan be seen that the transfer mechanism provides for the automatic transfer of a load from a preferred feeder voltage to an emergency feeder voltage in a rapid and efficient manner. The employment of totally enclosed arcuate slots 114 in the torque plates 86 prevent the associated pivot members and 122 from dislodgement from the slots 114 during release and rebound of the compression springs 118. The control circuit 170 in association with the latching means 22 and torque plate arming motor 104 provide improved safety for the transfer mechanism and associated devices by preventing arming of the compression springs 118 unless the latching means 22 is in latching or locking relation with the actuator plate 48 to prevent movement thereof. The manner of rotating the torque plates 86 to arm the compression springs 118, as through the drive motor 104 and drive screw 102, provides a positive arming means effective to apply a mechanical advantage and thereby a substantial rotational torque to the torque plates 86 while employing a relatively low torque drive motor 104.

While a preferred embodiment of the switch transfer mechanism in accordance with the present invention has been illustrated and described, it will be obvious to those skilled in the art that changes and modifications will be made therein without departing from the invention in its broader aspects. Various features of the invention are defined in the appended claims.

What is claimed is:

1. A switch transfer mechanism for selectively transferring an electric load between a preferred and an emergency feeder voltage, comprising, in combination, housing means, first actuating means supported by said housing means and movable between a first position connecting the load to the preferred feeder voltage and a second position connecting the load to the emergency feeder voltage, torque plate means supported by said housing means for movement between first and second positions, second actuating means connected to said torque plate means and operative to move said torque plate means between said first and second positions, energy storing means operatively interconnecting said first actuating means and said torque plate means, said energy storing means being adapted to be placed in a potential energy storing condition when said torque plate means is moved between its said first and said second positions with said first actuating means retained in generally fixed position, latch means operative between a first position retaining said first actuating means in a generally fixed position and a second position allowing movement of said first actuating means between its first and second positions, and control circuit means operative to prevent operation of said second actuating means unless said latch means is in its said first position retaining said first actuating means in a fixed position, release of said latch means from its said first position serving to effect a snap-action movement of said actuator means through release of the potential energy storedin said energy storing means.

2. A switch transfer mechanism as defined in claim 1 wherein said control circuit means is operative to automatically release said latch means from its said first retaining position when said preferred feeder voltage drops below a first predetermined value to allow transfer of the load to said emergency feeder voltage.

3. A switch transfer mechanism as defined in claim 2 wherein said control circuit means includes time delay means operative to prevent release of said latch means from its said first position until after a predetermined time period following dropping of said preferred feeder voltage below said predetermined value, whereby to prevent transfer upon a momentary drop in the feeder voltage.

4. A switch transfer mechanism as defined in claim 2 wherein said latch means includes a latch lever means operative to selectively engage said first actuating means and prevent movement thereof in a switch transfer direction, andsolenoid means under the control of said control circuit means to effect disengagement of said latch lever means from said first actuating means when said preferred feeder voltage falls below a predetermined value.

5. A switch transfer mechanism as defined in claim 2 wherein said latch means includes a latch lever biased to a position engaging said first actuating means to retain said first actuating means in said generally fixed position immediately after each movement thereof between its said first and second positions, and wherein said control circuit means is operative to release said latch lever from engagement with said first actuating means when said preferred feeder voltage rises to a second predetermined value after dropping below said first predetermined value.

6. A switch transfer mechanism as defined in claim I wherein said energy storing means includes at least one compression spring, and a pivot member disposed at each end of said spring, said torque plate means having at least one slot therein to receive said pivot members in guiding relation therewith, said pivot members being engageable with said first actuating means so that said compression spring is compressed when said first actuating means and said torque plate means undergo selective relative movement therebetween, release of said first actuating means from its said fixed position serving to release the potential energy in the compressed spring and effect relative movement of said first actuating means between its said first and second positions, said slot in said torque plate means being totally enclosed to prevent release of said pivot members from said slot during rebound of said compression spring after release of the potential energy therein.

7. A switch transfer mechanism as defined in claim 1 wherein said first actuating means comprises a generally planar actuator plate supported by said housing means for movement about an axis normal to the plane of said actuator plate, said actuator plate having abutment stops on its peripheral surface, and wherein said latch means includes a latch lever having a stop element thereon selectively movable to engage one of said abutment stops on said actuator plate, said control circuit means including means operative to move said latch lever to a position wherein said stop element engages an abutment stop on said actuator plate and prevents movement thereof about its axis of rotation, said control circuit means effecting selective automatic release of said latch lever means to allow movement of said actuator plate in a first rotational switch transfer direction whereafter said latch lever is returned to a position wherein said stop element engages a different abutment stop on said actuator plate to prevent movement of said actuator plate in a rotational direction opposite said first rotational direction of movement.

8. A switch transfer device as defined in claim 7 wherein said latch means includes means biasing said latch lever to a position wherein said stop element engages one of said abutment stops on said actuating plate to prevent movement of said actuating plate.

9. A switch transfer mechanism as defined in claim 1 wherein said energy storing means comprises a pair of compression springs each having its ends operatively associated, respectively, with said first actuating means and said torque plate means, said compression springs being disposed such that selective movement of said torque plate means serves to compress both of said compression springs when said first actuating means is retained in a generally fixed position such that release of said latch means from said first actuating means allows the release of stored energy from both of said compression springs to effect a snap-action movement of said first actuating means from its said first to its said second positions.

10. A switch transfer mechanism as defined in claim 9 wherein said energy storing means includes a pivot member mounted at each end of said compression springs, said torque plate means having enclosed generally arcuate shaped slots to receive said pivot members in guiding relation therein, said arcuate slots being adapted to retain said pivot members therein and prevent release thereof during rebound as may result from release of stored energy from the compression springs upon release of said latch means from said first actuating means and movement thereof between its said first and second positions.

11. A switch transfer mechanism as defined in claim 1 wherein said first actuating means includes a generally planar actuator plate supported by said housing means for rotation about an axis normal to the plane of said actuator plate, said torque plate means including at least one generally planar torque plate supported by said housing means in parallel relation to said actuating plate for rotation about the rotational axis of said actuating plate, and wherein said second actuating means includes a drive motor and drive screw connected to said torque plate and operative to effect rotation of said torque plate, said control circuit means including means for energizing said drive motor in a manner to rotate said torque plate about its rotational axis in a direction to place said energy storing means in a potential energy storing condition after each transfer of the load between the preferred and emergency feeder voltages.

movement between its said first and second positions. a:

Claims

1. A switch transfer mechanism for selectively transferring an electric load between a preferred and an emergency feeder voltage, comprising, in combination, housing means, first actuating means supported by said housing means and movable between a first position connecting the load to the preferred feeder voltage and a second position connecting the load to the emergency feeder voltage, torque plate means supported by said housing means for movement between first and second positions, second actuating means connected to said torque plate means and operative to move said torque plate means between said First and second positions, energy storing means operatively interconnecting said first actuating means and said torque plate means, said energy storing means being adapted to be placed in a potential energy storing condition when said torque plate means is moved between its said first and said second positions with said first actuating means retained in generally fixed position, latch means operative between a first position retaining said first actuating means in a generally fixed position and a second position allowing movement of said first actuating means between its first and second positions, and control circuit means operative to prevent operation of said second actuating means unless said latch means is in its said first position retaining said first actuating means in a fixed position, release of said latch means from its said first position serving to effect a snap-action movement of said actuator means through release of the potential energy stored in said energy storing means.

4. A switch transfer mechanism as defined in claim 2 wherein said latch means includes a latch lever means operative to selectively engage said first actuating means and prevent movement thereof in a switch transfer direction, and solenoid means under the control of said control circuit means to effect disengagement of said latch lever means from said first actuating means when said preferred feeder voltage falls below a predetermined value.

6. A switch transfer mechanism as defined in claim 1 wherein said energy storing means includes at least one compression spring, and a pivot member disposed at each end of said spring, said torque plate means having at least one slot therein to receive said pivot members in guiding relation therewith, said pivot members being engageable with said first actuating means so that said compression spring is compressed when said first actuating means and said torque plate means undergo selective relative movement therebetween, release of said first actuating means from its said fixed position serving to release the potential energy in the compressed spring and effect relative movement of said first actuating means between its said first and second positions, said slot in said torque plate means being totally enclosed to prevent release of said pivot members from said slot during rebound of said compression spring after release of the potential energy therein.

12. A switch transfer mechanism as defined in claim 11 wherein said circuit means further includes switch means connected in circuit with said drive motor in a manner to prevent energizing of said drive motor unless said latching means is disposed in a position preventing movement of said first actuating means after each movement between its said first and second positions.