US 3796937 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Loffler et a].
[451 Mar. 12, 1974 MOTOR-DRIVEN LINE TRANSFER CONTROL Inventors: Erich W. Loffler; Hans Kruger,
. both of 2466 Bay Rd., Redwood City, Calif. 90263 Filed: May 10, 1973 Appl. No.: 359,018
Related US. Application Data Continuation-impart of Ser. No. 238,280, March 27, 1972, Pat. No. 3,736,054.
US. Cl. 318/468, 200/153 T, 335/69 Int. Cl. HOlh 3/02 .Field of Search 318/468; 200/153 T;
Palmer et al 335/68 Engelhardt 335/69 Bottonari et a1 335/69 Primary Examiner-B. Dobeck Attorney, Agent, or Firm-Julian Caplan [5 7] ABSTRACT An oscillatory shaft line switch is driven by means of a motor which is responsive to load line voltage emergencies. A lever on the shaft of the line switch is connected by a link to a second lever on the shaft of a gear reduction box of the motor. The second lever is loose. Fixed to the shaft of the box is a crank having a bent'outer end which turns the second lever as the motor turns. The first mentioned shaft has a contactor which engages either of two micro-switches to deenergize the motor after the line switch has been thrown in either direction. The loose connection of the second lever enables the first lever to be thrown by hand when necessary.
3 Claims, 2 Drawing Figures Pmmmmz 1974 3796937 MOTOR-DRIVEN LINE TRANSFER CONTROL This application is a continuation-in-part of our copending application Ser. No. 238,280, filed Mar. 27, 1972 now US. Pat. No. 3,736,054.
This invention relates to a motor-driven line transfer control. The control is used with a commercially available, mechanically held line transfer control switch which is movable between two positions-one wherein the utility power lines are connected to the load, and the other wherein emergency power generator facilities are connected to the load in emergencies when the normal line supply is temporarily not available. The present invention provides means to actuate the switch between one position and the other. Equipment which is used in connection with the device, but which is not a part of the present invention, senses when any phase of the utility line voltage drops below a preselected point, such as 70 percent of normal. When this occurs, the sensing means starts a generator for the auxiliary source; when this source has brought the emergency line voltage up to 90 percent of needed voltage, then the present invention provides a means to throw the line transfer control switch from normal line position to emergency line position. In the event either that the emergency line voltage drops below a preselected point, or in the event that the normal line voltage is re-.
stored so that it builds up to a preselected percentage such as 90 percent of normal voltage, then the sensor also causes the control of the present invention to throw the line transfer control switch back to normal position.
It is, accordingly, a principal purpose of the present invention to provide a motor-driven means energized depending upon the sensing of the normal line and emergency line voltages to throw the aforementioned switch between one position and another.
One of the features of the invention is the fact that the line transfer control switch, which is commercially available, need not be altered in its interior in any manner, and hence there is no impairment of the function of such switch. The switch actuating lever, moreover, is exposed for manual actuation where, for one reason or another, an operator wishes to move the switch between its two positions and thus override the control switch of the present invention. This feature is important in emergencies when the sensing devices have failed.
Other objects of the present invention will become apparent upon reading the following specifications and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.
In the drawings:
FIG. 1 is a top plan view of the structure.
FIG. 2 is a side elevational view thereof.
The switch 11 is a commercially available switch, a suitable example of which is a Blue Line produced by Kraus & Naimer Gmbl-l of Austria. The details of such switch are not part of the present invention and are not herein illustrated. However, such switch 11 has a main shaft 12 which oscillates through a travel of approximately 60 and by mechanical means such as a cam held in each of its positions. The number of sets of switch contacts in switch 11 is subject to variation. For purpose of the present invention, it may be assumed to be a three-phase switch having three sets of contacts.
Each set consists of a main, or normal, line contact which is connected to the public utility power line, an emergency contact which is connected to an emergency generator, which may be diesel operated, and a load contact which is connected by buss bars to a load. Emergency power is required in many installations such as hospitals where any failure of the utility line power or the falling of the voltage thereof beyond a preselected percentage of normal may be very dangerous. Standby emergency equipment is available in such locations and means is provided to sense when the line voltage diminishes beyond percent of rated voltage in any phase, whereupon the emergency generator prime mover is started and the emergency line is brought up to a percentage of its rated capacity, such as percent. At this point, it is desirable to switch the load from the utility line to the emergency line. If for any reason the emergency line fails, it may be desirable to switch back to the utility line and the sensor senses when the emergency line voltage diminishes beyond a certain percentage of normal capacity. After the cause of the utility line voltage drop has been remedied, the main line voltage rises; when it reaches a preselected percentage of normal or rated value, then it is desirable to discontinue the emergency supply and to transfer to the public utility line. Oscillation of the shaft 12 accomplishes the switching.
The outer end of shaft 12, which is preferably noncircular, is provided with an exposed first lever 13 which may be manually used to move the shaft 12 through an approximately 60 travel. The present invention provides a motor-driven means for moving shaft 12, as hereinafter explained.
One end of elongated link 14 is connected by pivot bolt 16 to a point on lever 13 approximately one-third of the distance from shaft 12, leaving the remaining length of lever 13 to function as a handle for manual actuation. The opposite end of link 14 is connected by means of pivot bolt 18 to approximately the midpoint of loose (second) lever 17 with spacer bushing 19 interposed between link 14 and lever 17. Lever 17 is freely rotatable about the output shaft 21 of gear box 22. Gear box 22 is driven in one direction only by means of electric motor 23 which is supported by bracket 24 from the frame 25 attached to the body of switch 11.
Fixed to shaft 21 between lever 17 and gear box 21 is fixed (third) lever 26 which has an outward bent end 27. As lever 26 rotates on shaft 21, the end 27 engages lever 17 and causes it to turn and this in consequence causes lever 13 to oscillate. However, because there is no positive connection between levers 26 and 17, the handle portion of lever 13 may be grasped and the shaft 12 thrown independently of motor 23.
Mounted on subframe 31 fastened to switch 11 are two micro-switches 32a, 32b which function as limit switches and each of which has a switch contact 33 and a spring 34. Fixed to shaft 12 is a switch contactor 36 which projects to a position between the switches 32a, 32b. When lever 13 has been thrown to the limit of one of its positions by means of turning of motor 23, the contactor 36 engages one or the other of the two micro-switches and through a relay system the motor 23 is de-energized. The motor 23 is re-energized only by operation of the sensor of line voltages which has heretofore been mentioned. To simplify the electrical wiring of the device, preferably one of the switches 32a, 32b is normally open and the other normally closed.
In operation, when the sensor senses that the line voltage or any of the phases thereof has fallen below a preselected level, then through a relay system it energizes motor 23 which turns shaft 21 and causes the lever 26 to turn in a clockwise direction. As said lever 26 revolves, the end 27 thereof contacts lever 17 and begins to turn said lever. This in turn moves link 14, which causes the lever 13 to be shifted 60 in the opposite direction from that where it was originally. When this shifting movement has been completed, contactor 36 engages one of the micro-switches 32a, 32b and this causes de-energization of the motor 23. After the emergency has ceased to exist, the motor 23 is re-energized and the lever 13 is oscillated to the opposite position and motor 23 is stopped by micro-switch 32a or 32b. If, at any time, the operator needs to throw switch 11, he may grip the outer or handle portion of lever 13 and turn the shaft 12 the desired angular distance. This movement is possible because lever 17 is loose on shaft 21 and the connection of lever 26 to lever 17 is not positive but enables the lever 17 to be turned in a clockwise direction in advance of turning of lever 26.
What is claimed is:
1. A control for a line transfer switch comprising an oscillatory operating shaft having a limited angular movement and switch means turned by said operating shaft, a first lever fixed to and extending out from said operating shaft, a switch contactor fixed to said operating shaft, a first and a second micro-switch, means mounting said micro-switches relative to said line transfer switch so that said first micro-switch is contacted by said contactor when said operating shaft reaches the limit of its oscillatory angular movement in one direction and said second micro-switch is contacted by said contactor when said operating shaft reaches the limit of its movement in the other direction, a motor arranged to rotate in a single direction, a gear box driven by said motor having an output shaft, a second lever fixed for rotation with said output shaft through 360, 21 third lever freely rotatable about said output shaft, a link pivotally interconnecting said third and first levers, said second lever having means to turn said third lever only in one direction, said motor when energized turning said second lever in said one direction and said second lever thereby turning said third lever through a 360 travel, said link oscillating said first lever, said microswitches being connected to de-energize said motor when either of said micro-switches is contacted by said contactor.
2. A control according to claim 1 in which said second lever has an upturned extremity positioned to engage behind said third lever to cause rotation of said third lever as said second lever rotates, said third lever being freely rotatable in advance of said second lever.
3. A control according to claim 1 in which said link is connected to said first lever inward of its outer end to provide a handle for manually oscillating said first lever independently of said motor.