US2543712A - High-voltage switch - Google Patents

Description

Patented F eb. 27, 1951 UNITED STATES PATENT OFFICE HIGH VOLTAGE SWITCH Charles L. Stroup, Oak Park, Ill.

Application January 19, 1946, Serial No. 642,215

8 Claims.

This invention relates to improvements in high voltage thermally operated switches which are particularly adapted for use in connection with transformers of the type which are installed out of doors and used in circuits distributing electricity in rural communities. This application is' for an improvement on the device disclosed in my application Serial No. 568,279, filed December 15, 1944, for High Voltage Switch now Patent No. 2,457,939, issued January 4, 1949,

Protective apparatus has been employed in connection with transformers of this type in the form of fuses located in the phase line to prevent overloads in the transformer. Fuse protection, however, is not entirely satisfactory because of its limitations. Fuses of a greater amperage are sometimes used in place of the proper size to overcome as much as possible blowouts of the fuse caused by lightning currents and to protect the service line against failure caused by mechanical stress in small delicately constructed fuses, the use of such fuses of greater amperage will not protect the transformer when it becomes overloaded, due to a short circuit in the secondary of the transformer or because of an increase in load. The fuse will only disconnect the transformer itself from the phase line in the eventthe transformer itself fails; thus avoiding grounding the phase line and cutting oil the current from other customers who are served from the primary circuitt It was to furnish complete protection at all times to the transformer itself and to avoid the heretofore setforth difficulties that I conceived the switch of my invention.

The main object of m invention is to provide a new and improved cut-out switch or circuit breaker located in. the line between the phase wire and the transformer. The switch is positivel actuated solely by thermo-responsive means submerged in the liquid medium contained in the transformer housing upon an abnormal rise in temperature of such liquid and/ or upon the overheating of the phase wire.

Other objects of my invention are to provide a simple mechanism for cutting out a transformer from the primary circuit of a high voltage distribution line upon abnormal rises in temperature in the transformer housing; to provide a simple mechanism for cutting out a trans' former from the primary circuit of a high voltage distribution line upon abnormal current in the phase wire; to. provide a simple inexpensive electrical cut-out mechanism of the character which can be added to a transformer of a character described and associated mechanism without changing the standard fixtures thereof; to provide acut-out switch mechanism of this. character which will automatically disconnect the transformer from the. primary supply circuit when the secondary or primary coils are shorted or overloaded and thereby overheated; to provide a releasing mechanism of the character which is. operable. either through a temperature rise of the liquid in the oil-filled transformer or because of an abnormal current in the. phaseline; to provide a releasing trigger mechanism in a device of this character which is actuated by a thermo-responsive device operable through a rise in temperature in the. transformer housing or by a normal current in the phase line; toprovide an improved oil-filled primary circuit breaker of the thermal-controlled type for cutting out a high voltage transformer when such transformer or phase line becomes overloaded, overheated, short-circuited Or any other condi tions arise whereby the transformer coils become abnormally overheated; to provide a releasing mechanism in a device of this character which is located outside of the transformer housing; to provide a heater element, electrically connected in the circuit between a high voltage switch and the primary coil of a transformer and associated with a thermally controlled remote bulb whereby to hasten generation of the gas in the bulb when abnormal conditions arise in the line; to provide an arc-quenching sleeve which is adapted to surround a movable contact in a mechanism of this kind; to provide in a device of this character a high voltage switching mechanism which will cause the switch to trip substantially immediately when a short-circuit current occurs in the line; to provide a device of this character which will cause the switch to trip when long-term overloads of an hour or more duration occur in the line, without unnecessary outages; to provide a switching mechanism which is so completely enclosed that it has no outside. openings through which insects or debris can enter; and to provide a circuit breaker of this character which is relatively inexpensive to manufacture and may be readily installed on standard transformers of the type described, and readil removed and replaced if desired.

An embodiment of this invention is shown in the accompanying drawing in which Figure 1 is a vertical sectional view of a switch embodying the present invention, showing the switch mechanism in closed or operating position.

An oil-filled tank I3 is secured to arm I by a headed stud l5 which extends through the bottom of the tank and has a threaded shank adapted for threaded engagement with the bronze coupler IS.

The oil-filled tank I3 is provided with an insulated cover plate |9, attached to the side walls in any suitable manner such as at 20, and has a medially located threaded aperture therein. A long-necked, porcelain bonnet or insulator 2| having an axially located aperture 22 is secured to the cover plate IS. A fiber tubing 23, having threads 24 is fitted into the bonnet. The lower end of the tube 23 is threaded into the cover plate |9; thereby firmly anchoring the tube 23 in an upright position to the tank.

The movable contact 27, preferably constructed of a copper rod threaded at one end and having an annular ring secured adjacent the opposite end, is of sumcient length to extend beyond the bonnet 2| and is adapted to be inserted through the tubing 23. The fiber tube 23 is bored axially from both ends to form chambers 29 and 29.|. The annular ring is positioned in the chamber 29.

The upper end of the contact arm 21 is provided with a pair of lock nuts 3fl-30. A heavy coiled spring 3| is also positioned on the upper end of contact arm 21, the lower end thereof seated in chamber 29' of the tube 23. A hollow cap 32, preferably constructed of metal is threaded over the top of contact 21 and positioned between the upper end of spring 3| and the nuts 3030. The coil spring normally urges the movable contact 21 away from the stationary contact |8.

Also threaded on the upper end of contact 21 and interposed between the nuts 3il30 and the top of the cap 32 are a flat spring 33 and a bracket 34. An inverted L-shaped arm 35, preferably constructed of insulating material, is pivotally attached to the bracket 34 as at 36 and is nor mally urged outwardl and upwardly by the action of the spring 33. A gripping member 31 is secured medially to the vertical side of arm in any suitable manner, such as by rivets 38.

and 39. The lower portion 40 of the vertical side of arm 35 is rounded and has a washer 4| secured.

The

thereto by means of a machine screw 42. purpose of this L-shaped arm will be hereinafter more fully described.

My temperature-responsive device, as shown in the drawing, comprises a thermal bulb 43 containing an expansible liquid, a length of capillary tubing 44 and an expansible bellows 45 secured in a vertical position by a pair of lock nuts 45.! positioned on both sides of shelf 45.2. The free end of bellows 45 is provided with an integrally formed rod 46 which moves in a vertical plane upon actuation of the bellows. The bulb 43 is wrapped with several turns of heater wire 41, and connected electrically between the primary of the transformer and the switch of my invention.

The bellows and the hereinafter described release mechanism are enclosed in a housing 48 which abuts against tank I3 and is secured to the lower side of arm H! by any suitable means such as by machine screws.

The automatic release mechanism comprises an L-shaped trigger 5| pivotally secured as at 52, the lower side of the horizontall extending leg being in contact with the upper end of rod 46 and the vertical leg arranged to move into and outof the notched recess 53 of the arm 54.

The arm 59 is integrally secured to the axle 54.2 to which the yoke 55 is also anchored by any suitable means, such as by machine screws. The axle 54.2 is pivotally secured to the housing 48. A stop member 54.| prevents the arm 59 from swinging beyond a horizontal plane as is apparent from the drawing. The outwardly diverging arms of the yoke form a seat for the lower end 40 of arm 35 to hold the arm 35 in the position shown in the drawing. When the vertical leg of the trigger is seated in the recess 53 and the arm 35 is held fast by arm 59, the spring 3| is compressed and the movable contact 21 and the stationary contact I8 are in electrical engagement with each other.

When the contacts are in electrical engagement, the coil spring 3| is compressed and the cap 32 is positioned over and covers the neck of bonnet 2|. The arm 35 is in a vertical position and is held fast by the arm 59. The trigger is in engagement with the notched recess 53 and holds the bar 54 in a horizontal position. The arm 35 keeps the coil spring in a compressed position and the contacts are thereby held in engagement until the release mechanism is tripped by the expansion of the bellows.

In operation, as the thermal bulb 43 is immersed in the oil in the tank I3 and is wrapped with several turns 41 of the resistance wire, any circumstance happening in the transformer which causes the oil to overheat or any circumstance causing the heater coil to heat, will va porize the liquid in the thermal bulb 43 which causes the bellows 45 to expand lengthwise. The trigger 5| will be tripped by the upward movement of the rod 46 of the bellows 35. The arm 59, being free to pivot about axle 54.2, will shift upwardly because the spring 3| will shift the housing 32 upwardly and permit the rounded end 43 of the arm 35 to move upwardly and outwardly from the clip arms 58 and 59. The flat spring 33 causes the arm 35 to move away from and upward from the arm 59. The coil spring 3| being freed by the release of the arm 35 will urge the movable contact 21 away from the stationary contact |8. It will, therefore, be seen that the transformer is cut out of the primary circuit by the opening of the contacts.

When the circumstance which caused the overheating and the tripping of the release mechanism has been eliminated, the repair man pulls the arm 35 down and thus causes the rounded portion 4|! of the arm to be engaged by arm 59 thereby shifting the movable contact and the stationary contact into electrical engagement once again.

When the cause for overheating has been remedied, and the oil in the transformer has returned to normal temperature, the bellows 45 will contract and position the trigger of the releasing mechanism into the position shown in the drawing.

A lever 62 extending from the housing 48 is connected to the trigger in any suitable manner to provide means for manually breaking the circuit when desired.

' If an arc is formed between the contacts I8 and 21 when the contact is broken, the arc will follow the upward movement of the movable contact and be confined within chamber 29 of tube 23. The heat of the arc will cause the fiber tube to emit a gas which will smother the are almost at once. The oil surrounding the contacts will also aid in minimizing the arc as is well known.

In my invention, as only aminimum of working parts are exposed, the danger of foreign bodies fouling the mechanism is practically ellminated.

. It is to be especially noted that; the remote bulb 43 is secured within the contact housing or oil tank I3.

In this embodiment of the invention, the stationary contacts H; are spaced from the bottom-of the tank l3 by securing them to an insulating washer which is itself. secured at its marginal edges to a fiber liner 1| It is also to be noted that one of the stationary contacts 12 is shaped, whereby the lower end of movable contact 21 is adapted to seat thereon, while the lower edge portion 13 thereof contacts a brass sleeve 14 located on the lower end of the elongated hollow insulator plug 15. The plug 15 is provided with threads 16 on its upper end for threaded engagement to the insulator cover. plate I3 as will be apparent. One end of the heater coil 41 is secured to the brass sleeve 14 and the other end to the brass fitting H which makes electric. contact with the tank I 3 as at 78 to complete the electri-- cal circuit. It will be apparent that the circuit will be identical with that shown in Fig. 2.

A thin walled brass. sleeve. or tube 1 9 is seated in an aperture formed in the bottom wall of tank l3 and extends upwardly into. the interior of plug 15 whereby to house the remote bulb 43. The tube 19 is press-fitted or welded to the bottom wall of tank I 3 to make atight fit.

In operation. when a normal full load current passes through the heater coil 41 it will remain substantially cool and hence not heat the oil in the tank I3. However, when a short circuit occurs the heater coil will quickly heat up and cause the oil to become abnormally hot which in turn vaporizes the liquid in the bulb 43 to cause the bellows 45 to expand and trip the lever 5| to release the latch arm 54. The spring 3| will then cause the arm to shift upwardly and the spring 33 to move outwardly, hence disengaging the lower end from yoke arms 58 and 59. When the spring 3| is released it also draws the movable contact arm 21 upwardly and away from the stationary contacts I3 and- 12 to break the circuit, thereby completely disconnecting. the transformer from the circuit as is apparent;

In a short circuit of approximately 25 times normal rated current, the switch will open the circuit in about 4 seconds, thereby preventing injury of any character to the transformer itself. This is because the heater coils 4! become extremely hot quickly and such heat is transmitted to the liquid in the bulb 43, thereby making it react quickly and cause the switch to trip and open the circuit.

When the circuit has an overload of long duration, the heater coils 41 will slowly heat up causing the oil to become warm, which warm oil reacts on the liquid in bulb 43 and causes the switch to trip and open the circuit.

Although but one specific embodiment of this plate. for said tank, a hollow insulator secured to the upper end of said tank, the lower end of said insulator adapted to house said cover plate and seat thereon, a fiber tube disposed within said insulator and securedv axially to said cover plate and extending into said tank, a stationary contact positioned in said tank adjacent the bottom thereof, an elongated movable contact positioned in and movable within said fiber tube and arranged to make electrical contact with said stationary contact, a cylindrical cap secured to the upper end ofv said movable contact and substantially housing said insulator, latching means operably connected to said movable contact, a coiled spring threaded on the upper end of said movable contact to urge said movable contact away from said stationary contact upon release of said. latching means, a remote thermo-responsive bulb immersedin the oil in said oilfilled tank, a heater for said thermo-responsive bulb, an. expansible liquid-filled bellows operatively connectedto said latching means for actuating the same, and a capillary tube for connecting said bulb and bellows.

2. In a device of the class described a high voltage switch: arranged to be placed in circuit between the phase line and the primary winding of an oil-filled distribution transformer comprising an oil-filled tank, an insulated cover plate for said tank, a hollow insulator having an elongated neck' portion, said insulator being secured to the upper end of said tank and adapted to seat on said cover plate, a fiber tube disposed within said insulator and secured adjacent its lower end to said cover plate and the lower end extending into said tank, a stationary contact secured adjacent the bottom of said tank comprising spring clips, an elongated movable contact positioned in and vertically movable within said tube and. arranged to make electrical contact with said stationary contact, a cylindrical cap adapted to fit over and substantially house said insulator, saidcap being secured to the upper end of said movable contact whereby said cap shifts upon movement of said contact, latching means secured to said tank, an arm connecting said latching means and movable contact, a coiled spring threaded on the upper end of said movable contact and interposed between said fiber tube and said cap to urge said movable contact away from said stationary contact upon release of said latching means, a remote thermo-resp'onsive bulb containing an expansible substance under pressure immersed in the oil in said oilfilled tank, a heater for said thermo-responsive bulb, an expansible liquid-filled bellows operatively connected to said latching means for actuating the same when expanded, and a capillary tube for connecting said bulb and bellows.

3. In a device of the class described a high voltage switch arranged to be placed in the circuit between the phase line and the primary winding of an oil-filled rural distribution transformer, comprising an internally insulated oilfilled tank, an insulator-cover plate for said tank, a long-necked hollow insulator secured to the upper end of said tank and seated on said cover plate, a tube axially positioned within said insulator, secured adjacent its lower end to said cover plate, the lower end of said tube extending substantially to the bottom of said tank, an insulated washer secured adjacent the bottom of said tank, a stationary contact secured to said washer, an elongated movable contact positioned in and vertically movable within said tube, the

lower end thereof adapted to make electrical contact with said stationary contact, latching means secured. to the outer walls of said tank and operatively connected to said movable contact, a coiled spring threaded on the upper end of said movable contact whereby to normally urge said movable contact away from said stationary contact upon release of said latching means, a thermo-responsive bulb positioned in said tank, a heater for said thermo-responsive bulb, an ,expansible liquid-filled bellows operatively connected to said latching means and adapted to actuate the same, a capillary tube for connecting said bulb and bellows, and a housing secured to the side of said tank and encasing said bellows and latching means.

4. In a device of the class described a high voltage switch arranged to be placed in the circuit between the phase line and the primary winding of an oil-filled rural distribution transformer comprising an internally insulated oilfilled tank, an insulator cover plate for said tank, a hollow long-necked insulator the lower end of which is secured to the upper end of said tank and seated upon said cover plate, a fiber tube disposed within said insulator and secured to said cover plate and extending substantially to the bottom of said tank, an insulated washer secured within said tank adjacent the bottom thereof and spaced away therefrom, a stationary contact located immediately below the lower end of said tube, comprising a pair of substantially vertically extending spring arms and a single spring arm of hemispherical-like shape, all secured to said washer, an elongated movable contact positioned in and movable within said fiber tube and arranged to seat within and make contact with said stationary contacts, latching means operatively connected to said movable contact, a coiled sprin threaded on the upper end of said movable contact to normally urge said movable contact away from said stationary contacts, an elongated hollow insulator plug removably secured at its upper end to said cover plate and positioned adjacent the fiber tube within said tank, a pair of brass fittings on said plug, one adjacent the upper end thereof in electrical con tact with the side wall of said tank, the other fitting located adjacent the lower end thereof and in electrical contact with said hemispherical contact spring, a heater coil on said plug connected to and between said fittings, a brass tube positioned within said plug and extending through both said washer and bottom of said tank, a thermo-responsive bulb secured within said brass tube, an expansible liquid-filled bellows operatively connected to said latching means for actuating the same, and a capillary tube for connecting said bulb and bellows.

5. The device according to claim 3, wherein said tube is formed of fiber and is provided with an axial bore in its upper end of greater diameter than the diameter of the movable contact to form a chamber to receive said coil spring.

6. The device according to claim 3, wherein said tube is formed of fiber and is provided with an axial bore in its upper end of greater diameter than the diameter of the movable contact to form a chamber to receive said coil spring, said fiber tube having an axial bore in its lower end of a diameter greater than the diameter of said movable contact to form a chamber wherein any arc created between said contacts upon disengagement thereof will be directed and extinguished therein.

7. The device according to claim 4, wherein said latching means comprises a trigger, a notched arm arranged to engage one leg of said trigger, a yoke having diverging arms connected to said notched arm, a pivoted arm operably connected at one end to said yoke and at the other end to said movable contact, and a flat spring secured to the upper end of said movable contact and interposed between said pivoted arm and said cylindrical cap to normally urge said pivoted arm upwardly and outwardly.

8. In a device of the class described a high voltage switch arranged to be placed in the circuit between the phase line and the primary winding of an oil-filled rural distribution transformer comprising an oil-filled tank, an insulator cover plate for said tank, a hollow insulator secured to the upper end of said tank, a fiber tube disposed within said insulator and secured to said cover plate and extending into said tank, a stationary contact adjacent the bottom of said tank, an elongated movable contact positioned in said fiber tube and arranged to make electrical contact with said stationary contact, latching means operatively connected to said movable contact, and thermo-responsive means for actuating said latching means when a short circuit or long term overload occurs in the circuit, said thermo-responsive means comprising a remote bulb located in said tank and immersed in said oil, a heater for said thermo-responsive bulb, an expansible liquid-filled bellows operatively connected to said latching means for actuating the same, and a capillary tube for connecting said bulb and bellows.

CHARLES L. STROUP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,473,960 Johnson Nov. 13, 1923 1,488,952 Stoekle Apr. 1, 1924 2,053,944 Cooney Sept. 8, 1936 2,053,952 Hill Sept. 8, 1936 2,142,188 Gaston Jan. 3, 1939 2,145,375 Schultz Jan. 31, 1939 2,250,165 Mitschrich July 22, 1941 2,349,609 Brown et a1 May 23, 1944 2,457,939 Stroup Jan. 4, 1949 FOREIGN PATENTS Number Country Date 309,895 Germany Nov. 17, 1917 599,119 Germany June 25, 1934

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