US2274838A - Circuit interrupter - Google Patents

Description

March 3, 1942. F. G. LOGAN 2,274,838

CIRCUIT INTERRUPTER Filed Oct. 14, 1939 2 Sheets-Sheet l March 3, 1942. F. G. LOGAN 2,274,838

CIRCUIT INTERRUPTER Filed Oct. 14, 1939 2 Sheets-Sheetl 2 @i 7 Z7@ .di

f ff v/l/l/I I. /NJauar/o/v Patented Mar. 3, 1942 CIRCUIT INTERRUPTER Frank G. Logan, Mount Vernon, N. Y., assignor to' Ward Leonard Electric Company, a corporation of `New York Application October 14, 1939,V Serial No. 299,426

(Cl. 20o-145) 11 Claims.

This invention relates to electric switches or contactors and is applicable to various forms of relays, circuit breakers of various kinds, manually operated switches and various forms of apparatus for closing and opening a circuit which may be manually or automatically controlled according to the particular requirements.

The particular feature of the invention is the provision of a form of construction and relationship of parts which will serve to minimize the duration and destructive effect of arcing at the contacts upon opening the circuit. This is accomplished by a number of different features which co-act in obtaining greatly improved results. A multiplicity of contact elements are provided which when separated form arcs between each element in series with each other and of such comparatively low voltage individually that ionization and oxidation of the metal of the contacts are so minimized as not to` produce objectionable deterioration over long continued use. Another feature is the limitation of the air spaces where the contacts separate which not only serve to smother and aid in extinguishing the arcs but result in forcing the turbulent gases into intimate contact with large surface areas of the contacts, the contacts being formed in such a manner as to present large cooling surfaces. A further feature is to provide an enclosure with walls surrounding the contacts i.

which not only aid in coniining and limiting the air spaces but also provide cooling walls as an aid in extinguishing the arcs. A further feature is the provision of contacts of a form which provides relatively large contact surfaces and the parts are so related that new portions of the sury of the invention are obtained such as compact- V ness of structure for comparatively large capacities, simplicity of manufacture and of assembly, durability and long life of the parts Without the necessity of inspection and renewal and dependability in operation. Another object is to avoid the provision of special blow-out devices, or special arc-chutes or.provision of other auxiliary devices for overcomingy objectionable arcing. Another object is the provision of a form of structure which permits flexibility and simplicity of design as` to size of the parts and number of contact elements over a wide range of capacityv as to amperages and voltages.

Another object is to 'provide an improved form ci control ofthe movable contacts which will insure their eiTective action in closing and opening the circuit and be especially applicable to the improved form of contact mechanism. Various other objects and advantages are attained which willbe understood by those skilled in the art from the following description and accompanying drawings.

Fig. l is a vertical central section of a preferred embodiment of the invention; Fig. 2 is another vertical central section taken at right-angles to that of Fig. 1; Fig. 3 is a horizontal section on the line 3 3 of Fig. l; Fig. 4 is a horizontal section on the line 4-4 of Fig. 2; Fig. 5 is a diagram of connections; and Figs, 6, 7 and 8 are sectional views of modified forms of contact elements and related parts.

In theparticular structure shown in Figs. l to 4, the contact elements are supported and enclosed by an .upper portion and a lower portion which are removably connected together. These portions are formed cf insulating material and may be molded from any suitable plastic material.` The upper portionfis shown as having an upwardly extending .back plate I and a forwardly extending part 2. The form shown is adapted to control a three-line or three-phase circuit and six sets of movable contact elements are provided. These elements are housed in the forwardly extending part 2 of the upper insulating portion and for this purpose six cylindrical chambers 3 arel provided in the underside of the part 2 as shown in Figs. l and 3. The lower ends of these cylindrical spaces are closed by the xed contacts 4, 4a in the form of circular plates fitted within rrecesses in the lower face of the part 2. The plates 4 are each provided with a forward extension or conducting strip 5 which passes outwardly through a slot in the part 2 and then upwardly in a slot in the face of the part 2. This upwardly extending portion 5 provides a terminal for the connection of the external lead 6. Each plate 4a is similarly provided With a rearwardly extending conducting strip 5a which passes upwardly through a slot in the part lof the upper portion toprovide means at the top for connection to an external lead 6a.

The movable contacts are formed of a series of comparatively heavy plates or disks I positioned one above the other and above each of the fixed contact plates 4 and 4a. Fig. l shows the parts in their open position. It has been found that the spacing between these plates or disks for securing the best results in the particular structure shown is approximately onesixteenth of an inch and the number of such plates or disks used would depend upon the voltage of the circuit to be interrupted. It has been found for best results that the voltage per space between plates or disks is made in the neighborhood of 40 to 60 volts. If the number of spaces between the separable contacts is made to impose ess than 40 volts per space, no material advantage in the suppression of the arcing is obtained by such lesser voltage; and if the number of plates used is such that the voltage per space is made more than say 60 volts, the suppression of the arcing is less effective and the durability of the parts is decreased. The number of the plates being determined by the voltage of the circuit to be interrupted for securing best results, the size of the plates or disks and their thickness is determined by the amperage of the circuit to be interrupted; and the device may be subjected to heavy overloads without objectionable effects. The contact plates or disks may be made of any suitable conducting material, such as copper or bronze and may have their surfaces coated or formed with other material which is adapted to preserve a low contact drop at the contact surfaces, such as silver or other metals or compositions.

The upper contact element of each set is provided with an upwardly extending central circular stem 8 which passes freely through a hole in the horizontal part 2 of the upper insulating portion. The top surface of the upper plate engages the underside of the insulating housing and thereby limits its upper movement. A coneshaped element 9 of suitable insulating material is secured at its upper end to the center of the lower face of the upper disk I as by means of a screw-threaded projection 9a extending downwardly from the upper plate. The lower portion of the element 9 is cylindrical and adapted to pass freely through each of the xed contacts 4 and 4a respectively. The lower insulating portion IIJ is provided with circular upwardly extending portions II which extend under and support the fixed contacts 4 and 4a respectively and clamp them against the lower part of the upper insulating portion. A cylindrical opening is formed at the center of each projecting portion II and extends downwardly in the lower portion of the base for housing a spring I2. These springs engage the lower ends of the insulating elements 9 respectively and tend to maintain the upper contacts I in their uppermost positions. In this open position of the parts, the intervening plates or disks I are properly spaced and supported by the conical portions of the elements 9. That is, the lowest intermediate plate I of each set is perforated with a conical opening so as to be supported by the lower portion of the conical element, while the next upper plate is perforated with a smaller conical opening so as to rest upon an intermediate part of the cone; and similarly any additional number of intervening contact plates would be provided with an opening of such size that when the conical element is raised the intervening plates will be spaced from each other and from the upper and lower contact plates by approximately the same distance. It is apparent that when the upper contact plate 'I is depressed by its stem 8 being forced downwardly, it will force the cone 9 against the pressure of the spring I2 and first permit the lowest intervening plate to Contact with the fixed plate, then the next intervening plate to contact with the one below it and so on until the top plate 'I forces all the plates together against the lower fixed plate. In this position, the circuit is closed by the ample surface contacts of the plates. Referring to Fig. 1 the circuit may be traced from the lead Ea through the strip 5a to the lowest iixed contact 4a, then through the plates 'I to the left-hand stem 8 and then by a flexible conductor I3 to the upper end of the right-hand stem 8 through the plates 'I to the fixed contact 4 and thence to the lead 6. A similar circuit is completed through each of the three lines when the upper contact plates are forced downwardly.

When the circuit is opened, the release of the stems 8 permits the springs I2 to rapidly raise the cones 9 and again bring the parts to the position shown in Fig. l. In this opening movement the upper plate I of each contact set is first raised from its adjoining intermediate plate l, then that plate is raised from its next lower plate and so on until the lowest intermediate plate is raised from the xed contact. This sequential separation of the plates is accomplished so rapidly as to be almost a simultaneous separation of the plates. The arcing which occurs between the plates occurs only between opposite points in the intervening spaces over slight portions of the faces of the plates. The effective suppression of the arcing, as already explained, is due to providing a number of arcs in series with each other from line to line, the presence of a limited amount of air in the small confined spaces, the provision of large surface areas of the contacts of cooling metal for rapidly extinguishing the arcing, the provision of surrounding walls of the confined space for providing additional cooling surfaces, the turbulence of the gases in the confined spaces which forces the gases into intimate contact with the various cooling surfaces and a rapid separation of the plates. The upper plate has the largest surface area of any of them and the surface area of each plate below it successively decreases somewhat with the result that during the sequential opening of the plates, the quenching of the arcs is substantially equalized, as the arc drawn between the plates is successively less as the plates open in sequence.

Another advantage in greatly lessening the deterioration of the surfaces of the plates and prolonging their life without attention is due to the fact that in the opening movement, the intervening plates change their relative positions so as to keep bringing a new relationship of contact surfaces of the parts. This is due, aside from any movement which might occur on account of unbalancing or imperfections of manufacture, to the induction of eddy currents in the plates. During the opening action the intervening plates 'I are loose and free to move around the cone 9. This permits them to be rotated slightly during the opening action by the eddy current reaction; and by reason of the fact that the intervening plates are of slightly different mass and by reason of the irregularities of the arcs formed, it results that the intervening plates are moved in amounts differing from each other. This diierence in movement of the plates results Ain the contact surfaces in relation to each other being changed more or less during each openmg movement. The presence of this differential movement of the intervening plates is established by the fact that Iafter long continued use, an examination of the surfaces of al1 the plates discloses a substantially uniform condition of all of the contact faces as regards the effects of arcing.

The closing of the six sets of contacts in the particular form shown is accomplished by the downward movement of a cross bar I4 of insulating material. This bar is provided with three downwardly projecting pins I5 which pass freely through central openings in three metal cross-pieces I6. These pieces are perforated at their ends and pass freely over pins 8a which extend upwardly from the stems 8 of the upper movable contacts. The pieces I6 therefore respectively bridge each pair of movable contacts. Between these bridges I6 and the underside of the cross bar I4 and surrounding each of the pins I5 are springs I1. When the cross-bar I4 is moved downwardly, the springs I1 force the cross-pieces I6 downwardly and they in turn push the upper plates 1 of the movable contacts downwardly with equalized pressure to close the circuit. Fixed to the cross bar I4 is a pair of rods I8 which extend downwardly through openings in the insulating portions of the device and are threaded at their lower ends into a movable iron piece I9. The cross bar I4 is provided with conical extensions on its lower face which surround the rods I8 and serve as additional supports therefor. The cones 20 extend within recesses in the upper part of the insulating portion 2 which recesses are formed by upwardly extending cylinders 2I which `are connected to upwardly extending ribs 2Ia for strengthening the insulating part 2.

A cover 22 encloses the front and sides and top of the apparatus being secured in place by screws which enter bosses 23 formed on the upper insulation portion of the device. The base portion I0 is removably secured to the upper portion of the device by the provision of threaded metal inserts 24 in the lower face of part 2 at the two rear corners `and at two spaced locations at the front of part 2, as shown in Fig. 3. Screws 25 are passed through counter-sunk openings in the base II) to engage the threaded inserts 24 of the upper part.

The actuation of the rods I8 and cross bar I4 for closing the contacts is accomplished in the particular form shown by a closing magnet which is secured to the bottom of the base IIl in any suitable manner. The main fixed portion of the magnet is formed of an iron casting having a back plate 26 provided with bosses 26a at its four corners for fastening the device on a panel. This magnet frame is provided with a vertically extending cylindrical portion 26h having a closed base 26C and an upwardly extending central core 26d which projects about half way towards the top of the cylinder. Within the length of the cylinder 25o and around the core 26d is located the closing magnet 21. From the center of the base portion 26e of the magnet frame is a downwardly extending central core 26e; and at its lower end is secured an iron cross-piece 28. The holding magnet 29surrounds,;the core 26e and is located between the cross-piece 28 and the base 2caof the frame. The movable portion of the magnet comprises the circular ironplate I9 from the underside of which extends a centrally positioned core 3 I. This core extends part way within the closing coil 21. A pair of bosses or lugs 30 are formed on the upper surface of the plate I9 and receive the threaded lower ends of the rods I8. At the outer end of each of the bosses 3D extends a pair of spaced projections 30a which pivotally support the upper ends of a pair of arms 32 of iron. The upper ends of these arms are notched and T-shaped so that the projecting arms 32ay of the T project over the projections 33a and are supported thereby. A pin 30h in the outer ends of the projections 30a retain the upperk ends ofthe arms 32 in position. A spring 33 is secured to each of the arms 32 on their inner faces for the purpose of forcing themupwardly in the position shown in Fig. 2 when the magnet is deenergized. The lower ends of the arms 32 are provided with inwardly extending portions 32h which are opposite the outside ends of the cross-piece 28 when the magnet is deenergized, as shown in Fig. 2.

When current is supplied to the closing coil 21, the core 3|, plate I9 and rods I8 are drawn downwardly, thereby closing the contactors of the switch in the manner already described. In the downward movement of the movable portion of the magnet, the arms 32 are forced downwardly so that the projections 32h are below the bottom face of the cross-piece 28. The magnetic attraction of the arms 32 then draws them inwardly so that the projections 32h pass under the ends of the cross-piece 28. This attraction of the arms 32 is accomplished by the closure of the circuit of the holding coil 29 by the downward movement of the parts. As long as the holding coil is excited, the arms 32 will be. retained in their inner position by a magnet circuit through the central core 26e, cross-piece 28 to the arms 32 and then through the portion 26C of the frame to the core 26e. The closing coil may now be deenergized and the parts will remain locked in the closed switch position by the holding coil retaining the arms 32 in their inner positions. Upon deenergization of the holding coil 29 the springs 33 will force the arms 32 outwardly and permit the movable portion of the magnet to be raised with a rapid separation of the contact plates by the action of the springs I2.

A diagram of connections for accomplishing the magnetic closing of the switch and for holding the parts closed and for permitting the opening of the switch is shown in Fig. 5. A portion of the magnetic structure and the closing coil and holding coil are indicated in Fig. 5 by reference numerals corresponding to those already applied. 'I'he upper plate I9 is indicated as carrying anr insulated contact 34 on a projection from its lower face and when the movable portion of the magnet is attracted, the contact 34 will engage a xed contact 35 connected to one terminal of the holding vcoil 29. The other terminal of this coil is connected through a resistance 36 to one side of supply lines 31. Tle contact 34 is connected through a normally closed push button switch 38 to the other side of the line 31. One terminal of the closing coil 21 is connected through a normally open push button 39 to the push button 38 and thence to one side of the line 31 while the other `terminal of the closing coil is connectedto. the other side offthe line. When it is desired to close the sets of switch contacts, the push button 39 is closed which completes a circuit through the closing coil 21 and moves the parts to their closed position. This causes contact 34 to engage contact 35 and close the circuit of the holding coil from one side of the line through switch 38, contacts 34 and 35vand thence through the holding coil and resistance 3B to the other side of the line. The push button 39 may now be released and the parts will be retained in their closed position in the manner already described. When it is desired to open the switch, the push button 33 is operated to open the circuit of the holding coil which releases the parts and permits them to assume their open position.

Although a preferred embodiment of a magnetic closing and holding mechanism has been described, various other means for closing and releasing the contacts may be utilized, either manually or automatically Operated according to particular requirements. Likewise the contact structure may be embodied in various forms and types of switch mechanisms for Various uses, such as circuit breakers of Various forms, relays and various other forms of manually operated and automatically controlled switches. Likewise the form of the contacting parts and the manner of actuating them may be varied, a few of such modifications being shown in Figs. 6, 'l and 8.

The form of contact sets shown in the previously described gures is adapted for operation in a vertical, or nearly vertical, position. In the form shown in Fig. G the contact sets may be operated in any desired position, such as vertical, horizontal or any intermediate position. Here an enclosing insulating iixed housing for the contacts is formed of an insulating cylinder 40 having a conical central chamber. The lower xed plate 4I extends across the bottom of the chamber while the upper movable plate 42 closes the top of the chamber. These two outer plates are shown as forming the terminals of the switch contacts. An insulating cone 43 is secured to the center of the upper plate and passes through the lower plate and supports the intermediate plates in properly spaced positions when the cone 43 is in its uppermost position. The parts are shown held in open position by the spring 44 which forces the cone 43 upwardly. When it '1s desired to close the switch a force is applied to the upper plate 42 which thereby forces the cone 43 against the action of the spring 44 and brings the sets of plates together in close contact. Upon release of the plate 4'?. for opening the switch, the cone 43 will move the plates to their spaced positions and as the size of these plates are graduated not only to the cone 43 at their central openings but to the conical chamber walls at their peripheries, the plates will be forced to assume an equally spaced position as shown in Fig. 6 upon the opening of the circuit. Obviously this structure permits the parts to be operated in any desired position.

Fig. '7 shows another form which permits the use of unperforated contact plates. Here a movable cylinder 45 having an inverted, central, conical chamber is provided. At the bottom of the chamber is a fixed plate 46 from which connection is made to one side of the circuit. Above the plate 56 is a series of plates 4l graduated in their diameters so as to be equally spaced by their engagement with the wall of the chamber when the cone 45 is in its raised position shown. Contact with the upper plate is made to the out;- side circuit by a lead 48 which maintains connection with the upper plate and tends to force the same toward the lower plate. A spring 49 tends to maintain the cylinder 45 in its upper position as shown. When force is applied to the cylinder 45 to move it downwardly, to close the circuit, the plates 4l are forced together and in engagement with the fixed plate 46. The release or removal of the closing force from the cylinder 45 permits the same to be moved upwardly by the spring 49 and accomplishes the opening of the circuit in the manner already described and attains a substantially equal spacing of the contacting plates.

Fig. 8 is similar to the form described in Figs. l to 4 except a stepped element is provided for the actuation of the plates to their open position. Here the enclosing cylinder 50 has a cylindrical interior and the lower plate 5I forms one terminal while the upper plate forms the other. The insulating cone 53 is in the form of a series of stepped portions of increasing diameters from top to bottom for receiving and positioning the intervening plates 54 in their open positions. The spring 55 tends to hold the plates in their open position properly spaced from each other and the closing of the circuit is accomplished by applying a force to the upper plate and stepped cone 53 to permit the plates to be brought together in close contact.

Instead of using parts having conical or stepped surfaces for controlling the intermediate contacts, they may be of pyramid form in some cases or of various other forms.

It is apparent that this invention secures a segregation of the arcing upon opening the circuit in a number of portions in series with each other and obtains a rapid quenching and extinguishing of the arcs without material deterioration of the contacts over long continued use in the manner already described. Furthermore the method of suppressing the arcing by the separation of a series of plates a comparatively short distance from each other results in the overall movement of the parts for securing the opening of the circuit being comparatively small. r)This short stroke of movement permits the size of the actuating parts to be correspondingly reduced and results in a compact structure not only of the contacts and housing thereof but also in the actuating or controlling mechanism.

Although a preferred embodiment of the invention has been described and a few modifications of the contact structure explained, it will be understood that the invention is capable of wide application to various uses and may be embodied in various structural forms without departing from the scope of the invention.

I claim:

l. A circuit interrupter comprising a series of contact plates, an insulating element of conical form passing centrally through said plates for separating them from each other in their open circuit positions, and means for forcing the surfaces of the plates together in series with each other in their closed circuit position.

2. A circuit interrupter comprising a series oi' Contact plates, an insulating element having portions of successively different diameters engaging the edges of said plates for supporting and spacing the plates from each other in their open circuit positions, and means for forcing the surfaces of the plates together in series with each other in their closed circuit position.

3. A circuit interrupter comprising a series of contact plates, insulating means for moving said plates to positions spaced from each other in their open circuit positions, said plates being individually and relatively movable on said means for changing the relationship of the contact surfaces, and means for forcing the surfaces of the plates together in series with each other in their closed circuit position.

4. A circuit interrupter comprising a series of contact plates, a housing of insulating material having a chamber surrounding said plates, an element of insulating material at the end of said plates removably connected to said housing for closing said chamber, insulating means for moving said plates to positions spaced from each other in their open circuit position, a spring housed in said element of insulating material for actuating said insulating means for moving the plates to their open circuit position, and means for forcing the surfaces of the plates together in series With each other in their closed circuit position against the action of said spring.

5. A circuit interrupter comprising a fixed end plate, a movable end plate and intermediate plates, a housing of insulating material surrounding said plates and for limiting the movement of the movable end plate in one direction, an element of insulating material engaging the fixed plate and removable from said housing, insulating means secured to the movable end plate and engaging the intermediate plates for spacing them from each other in their open circuit position, a spring for actuating said insulating means to move the plates to open circuit position, and means for forcing the surfaces of the plates together in series with each other in their closed circuit position.

6. A- circuit breaker comprising a plurality of sets of contact plates, an insulating housing for separately surrounding the said sets of plates, actuating means for moving the plates of each set to positions spaced from each other in their open circuit positions and for loosely supporting the intermediate plates of the different sets during the movement to open circuit positions for permitting their relative movement for changing the relationship of the contact surfaces, and means for forcing the surfaces of the plates of the different sets together in series With each other in their closed circuit positions.

7. A circuit interrupter comprising a series of contact plates, insulating means having portions of successively different diameters for supporting and spacing the plates from each other in their open circuit positions, and means for forcing the plates and their surfaces together in series with each other in their closed circuit position.

8. A circuit interrupter comprising a series of contact plates, insulating means having portions of successively different diameters for supporting and spacing the plates from each other in their open circuit positions, said plates having a common axis and being individually and relatively rotatable on said axis as a center for changing the relationship of the contact surfaces, and means for forcing the plates and their surfaces together in series With each other in their closed circuit positions.

9. A circuit interrupter comprising a series of contact plates, insulating means passing through said plates and having portions of successively different diameters for supporting and spacing the plates from each other in their open circuit positions, and means for forcing the plates and their surfaces together in series with each other in their closed circuit position.

10. A circuit interrupter comprising a series of contact plates, insulating means surrounding said plates and having portions of successively different diameters for supporting and spacing the plates from each other in their open circuit positions, and means for forcing the plates and their surfaces together in series with each other in their closed circuit position.

11. A circuit interrupter comprising a series of contact plates, insulating means for moving said plates to positions spaced from each other and for supporting said plates in their open circuit positions, said means having a central axis and said plates being individually and relatively movable about said axis as a center for changing the relationship of the contact surfaces, and means for forcing the surfaces of the plates together in series with each other in their closed circuit positions.

FRANK G. LOGAN.

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