US2265666A

US2265666A - Variable voltage transformer

Info

Publication number: US2265666A
Application number: US261456A
Authority: US
Inventors: Harold L Mekelburg; Stansbury Carroll
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1939-03-13
Filing date: 1939-03-13
Publication date: 1941-12-09
Anticipated expiration: 1958-12-09

Description

Dec. 9, 1941. H, L. MEKELBURG ETAL 2,265,666

VARIABLE VOLTAGE TRANSFORMER Filed March 13, 1939 2 Sheets-Sheet l 1941- H. L. MEKELBURG ETAL 2,255,666

VARIABLE VOLTAGE TRANSFORMER Filed uarch'ls, 1939 2 Sheets-Sheet 2 5% 5mm i; MA

Patented Dec. 9, 1941 VARIABLE VOLTAGE TRANSFORMER Harold L. Mekelburg, Milwaukee, and Carroll Stansbury, Wauwatosa, Wia, assignors to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application March 13, 1939, Serial No. 261,458

8 Claims.

This invention relates to variable voltage transformers and while not limited thereto is particularly applicable to variable voltage autotransformer dimmers for illumination control systems.

An object of the invention is to provide an improved transformer of the aforementioned type which is compact and has a large capacity for its size.

Another object is to provide a transformer which occupies a minimum of mounting space.

Another object is to provide a transformer which can be readily mounted in different positions to meet various space and operating conditions.

Another object is to provide a transformer which can be readily mounted in groups to be operated at will jointly or separately.

Another object is to provide a regulating transformer which has high heat radiating capacity.

Another object is to provide a transformer in which the heat radiating surfaces of the transformer itself are amplified by that of the other parts thereof.

Other objects and advantages will hereinafter appear.

The accompanying drawings are illustrative of an embodiment of the invention. In the drawings:

Figure 1 is a side view of a transformer.

Fig. 2 is a front view of the control part of the transformer shown in Fig. l with certain parts removed.

Fig. 3 is a top view of the contact mechanism.

Fig. 4 is a section of the device along the line 4-4 in Fig. 1.

Fig. 5 is a top view of certain details of the brush holders.

Fig. 6 is a rear view of the device.

Fig. 'l is a wiring diagram thereof.

The transformer comprises a ring shaped core I made of closely wound coil of strip steel. A magnetizing coil 2 of insulated wire is wound on said core in such a manner that the wires thereof are closely spaced to form a single layer on the outer perimeter of the core. The upper surface 3 of the wires on the outer cylindrical surface of the core is bared of insulation and the space between the wires is filled with a solid insulating material. After assembly with its support the entire outer cylindrical surface is finished to form a smooth commutator-like surface. The winding of the coil covers about 340 degrees of the entire circumference of the core, the ends of the winding being attached to terminals as will be ex plained hereinafter.

The core with the winding placed thereon as aforedescribed is fastened to a hub or support 4 by means of an electrical insulating cement I of good heat conductivity so as to form with the hub a solid self-contained structure. The cement employed may be a thermoplastic substance, a hydraulic cement or any other substance which is easily applied and which subsequently holds the parts rigidly together and assures good heat conductivity therebetween. This construction assures great rigidity and accurate centering of the cylindrical contact surface of the winding with respect to the hub center. It further assures rapid transmission'of heat from the winding to the hub thereby substantially increasing the effective heat radiating surface of the transformer.

The hub 4 is provided with a central huh I forming with rollers I a needle bearing for a shaft 8. One end of the shaft which protrudes outside of the bearing is provided with a section of reduced diameter 9 which is adapted to receive the hub ill of a contact lever II, the hub being fastened to the shaft by a press fit and the frictional engagement between the parts may be increased by roughening of the shaft.

An insulating plate I2 is fastened to the hub Ill by means of rivets or bolts l3 and to the plate in turn is riveted the diametrically extending arm l4 of the contact lever H which is thus rigidly connected to but insulated from the hub. The rivets or bolts l3 project axially through the hub, one on each side of the arm H, for a purpose to be explained hereinafter. A substantially radial lug I! cast integrally with the hub I0 is adapted to engage a stop to limit the rotation of the contact arm. The stop comprises a bolt l8 slidably mounted in the support 4 and biased outwardly by a spring H. The bolt near its outer end is conical and upon engagement with a suitably shaped surface of the lug Ills pushed inwardly, thereby compressing the spring I! and gradually increasing the resistance of the lever H to further rotation, until it comes to a stop by engagement of the lug with a reduced cylindrical extension of the conical portion of the bolt. The outward movement of the bolt II is limited by a pin through the rearward end of the bolt, which pin engages an abutment of the hub 4.

The hub 4 is bolted to a bracket I! which is a substantially flat metal plate arranged at right angles to the central axis of the transformer and at one side of the latter. By being in intimate heat transmitting contact over its entire peripheral edge with the plate the radiating surface of the hub is further amplified. The plate |9 has its opposite ends and 2| and one side 22 upturned to provide feet for mounting the same inside of a frame 23 which surrounds the transformer at its perimeter and at some distance therefrom. V

A pinion 24 is rigidly mounted on the shaft 8 at the end opposite to that on which the hub. I0 is mounted. The pinion is provided at one side thereof with two axial clutch jaws 25, the purpose of which will be explained in detail -hereinafter. A gear sector 26 which engages the pinion 24 is rotatably mounted on a stud 21 which in turn is mounted on the bracket IS. The sector 26 is provided with a clevis 28 to whichmay be attached a reciprocable operating rod 23 by means of which the transformer lever is rotated. I

The arm I4 carries at one end a pin 30 on which are pivotally mounted the ends of a number of substantially semi-circular brackets 3|, each comprising two parallel spaced fiat strips fastened together at intervals by means of rivets with spacers 32 interposed between the strips to maintain their spacing. The opposite ends of said brackets "form closed forks in which are slidingly fitted headed bolts 33. A spring 34 is interposed between the head at the inner end of the-boltand the fork so as to urge said bolt inwardly of the fork, The outer ends of the bolts passthrough properly spaced holes in the end- 35 of the arm l4 opposite 'the end which carries the ,pi'n30. For this purpose the arm is bent at substantially right angles to its main portion, so asto be parallelito the in :0. Individual cotter pins 36 inside of the lever end 35 and a single pin 31 common to all bolts outside of the lever end 35' retain said bolts in engagement with the arm. A contact brush 38, preferably of carbon is mounted in'a brush holder 39 on each bracket 3| intermediate of its ends in such a manner as to make contact with the bared wires 3 of the transformer as the contact lever is rotated. Bythis means each individual brush make contact with. the wires of the transformer winding. A fiat retainer 4| has a recess which fits over the brush. The brush and the retainer are assembled between the two strips which form' the brackets 3| and pressure is applied to thebrush by screws 42 on either side of the brush, which screws also serve to confine the retainer. If one of the-brush extensions has been worn down due to extensive use the brush may be reversed so as to use the other extension thereof. The arms", being in good heat conducting contact with the brushes, serve to in crease the effective heat radiating surface of the latter to keep them cool and prevent overheating of the winding at the points of contact.

To conduct the current from the lever H to the outside circuit,,the former is provided with a circular slip ring 43, conductively fastened to the lever. A spring-pressed brush 44 is mounted on an insulating block 45 so as to engage the slip ring 43 asthe latter rotates. The block 45 fedly attached tothe core I and serving to anchor the ends of the winding 2 and to conduct the current to the latter.

A limit switch is interposed between the terminal 5| and the terminal 52 for opening one side of the power supply circuit after the voltage of the lamp circuit has been reduced to the minimum value. The line wires 1.. and L are confiected to the terminals and 52, respectively,

while the lamp circuit is connected between the

terminals

48 and 50. The limit switch comprises a lever 51 which normally bridges

contacts

53 and 59, respectively, connected to the terminals 5| and 52. The lever is biased to circuit closing position bya spring cooperating with a bolt 6| which is fastened to the insulating block 43.

The lever 51 is provided with an extension 62 which is adapted to abut an insulating block 63 attached to one end of the lever II when the latter is in the position corresponding to minimum lamp voltage. In this Position the block 63 lifts the lever 51 out of contact with one or both of the

contacts

58 and 59, thereby opening the circuit as aforedescribed;

If it is desired to couple two transformers together and operate them by a single operating rod they are mounted as shown in Fig. 4 at a suitable lateral distance'from each other on a supporting frame 84 and an insulating disc or coupling 65 having recesses to receive the pins l3 and the jaws 25, respectively, is interposed so as to engage said pins and laws, thereby providing a driving connection between the shafts 3 of adjacent transformers and permitting power transmission from one to the other.

What we claim as new and desire to secure by Letters Patent is:

1. An alternating current transformer comprising, a circular iron core, an inducing winding on said core having its turns arranged to form a commutator on a surface of said winding, a brush adapted to complete a circuit including a variable section of said winding through said commutator, and means to dissipate heat to the ambient air, including a hub to support said core and said brush, and further including a filling of electrical insulating cement or good heat conductivity interposed between said winding and said hub for attaching the former to the latter and to facilitate the conduction of .heat from said core to said hub to thereby increase the heat dissipating capacity of said transformer, said cement forming the sole supporting connection between said hub and the core with'its inducing winding.

2. An alternating current transformer comprising, a circular iron core, an inducing winding'on said core having its tums arranged to form a commutator on a surface of said winding, a contact brush for said commutator including means to oscillate said brush about the center of said core, and means to dissipate heat to the ambient air, including a hub to support said core and said oscillating means. and including a filling of electrical insulating cement of good heat conductivity interposed between said winding and aacaeee said hub for attaching the former to the latter and to facilitate the conduction of heat from said core to said hub to thereby increase the heat dissipating capacity of'said transformer, said cement forming the sole supporting connection between said hub and the core with its inducing winding.

3. An alternating current transformer comprising,.a circular iron core, an inducing winding on said core having its turns arranged to form a commutator on a surface of said winding, and a heat dissipating support for said core and its winding including a metal hub concentric with and projecting inside of said core and its winding and attached thereto solely by an interposed filling of electrical insulating cement of good heat conducting capacity, said cement completely filling the space between said hub and the inside perimeter of said core and its winding, to thereby amplify the heat radiating capacity of said core.

4. An alternating current transformer comprising, a circular iron core,'an inducing winding on said core havingits turns arranged to form a commutator on a surface of said winding, a contact brush cooperating with said commutator and oscillatable around the central axis of said core, a heat dissipating support for said core and its winding including a metal hub concentric with and projecting inside of said core and its winding and having a pivot for said brush, and a solidifled electrical insulating cement of good heat conductivity filling the space between said hub and the inside perimeter of said core and its winding and forming the sole means to assemble them into a unitary structure and to amplify the heat radiating capacity of said core.

5. A contact for cooperating with and movable relative to and concentric with a cylindrical commutator comprising, a rotating shaft, a double ended lever attached intermediate its ends to said shaft, a substantially semi-circular arm of high heat conductivity having its one end pivoted at one end of said lever for rotation in a plane perpendicular to said shaft and having its other end resiliently attached to the other end of said lever to bias it toward said shaft, and a contact brush attached to said arm in heat conducting relation thereto, whereby said arm amplifies the heat radiating capacity of said brush.

6. A contact brush for cooperating with a cylindrical commutator and a rotatable concentric with the latter comprising, a rotating shaft supported concentric with a cylindrical commutator, means to rotate said shaft, a double ended lever attached intermediate its ends to said shaft, a substantially semi-circular arm of high heat conductivity having its one end pivoted at one end of said lever for rotation in a plane perpendicular to said shaft and having its other end resiliently attached to the other end of said lever to bias it toward said shaft, and a contact brush attached to said arm in heat conducting relation, whereby said am amplifies the heat radiating capacity of said brush,

7. A contact mechanism for completing a circuit between varying points of a stationary cylindrical commutator and a stationary terminal comprising, a support arranged for mounting in fixed relation to a cylindrical commutator, a rotatable shaft journaled on said support for rotation concentric with said commutator, a double ended lever insulatedly attached intermediate its ends to said shaft, a substantially semi-circular arm having its one end pivoted at one end of said lever for rotation in a plane perpendicular to said shaft and having its other end resiliently attached to the other end of said lever to bias it toward said shaft, a contact brush at-' tached to said arm, a slip ring attached to said arm concentric with said shaft, a second contact brush insulatedly mounted on said support and arranged to contact said ring and provided with a terminal.

8. An alternating current transformer comprising a circular iron core, an inducing winding on said core having its turns arranged to form a commuator on a surface of said winding, a support for said core including a hub concentric with and projecting inside of said core and having 'therein an opening providing a pivot bearing, a

solidified heat conducting cement interposed between said core and said hub to assembly them into a unitary structure and to amplify the heat radiating capacity of said core, a contact brush cooperativelyengaging said commutator and rotatably movable with respect thereto, mounting means for said contact brush comprising a rotatable shaft adapted for support within said pivot bearing, a double-ended lever attached in-- termediate its ends to said shaft, and a substantially semicircular arm of high heat conductivity having one end thereof pivotally connected to one end of said lever for rotation in a plane perpendicular to said shaft and having its other end yieldably attached to the other end of said lever to bias said arm toward said shaft, said contact brush being attached to said arm in heat conducting relation thereto, whereby said arm amplifies the heat radiating capacity ofsaid contact brush.

, HAROLD L. MEKELBURG. CARROLL STANSBURY.