US2544761A - Electric switchgear - Google Patents

Description

March 13, 1951 G. KILMINSTER ELECTRIC SWITCH GEAR 2 Sheecs-Sheet 1 Filed July 29, 1948 any 1 March 13, 1951 G. KILMINSTER ELECTRIC SWITCH GEAR 2 Sheets-Sheet 2 Filed July 29, 1948 II/IIIIIMIIII/II/IIIII,

a e F PIC-3.4.

Patented Mar. 13, 1951 ICE ELECTRIC SWITCHGEAR George Kilminster, Birmingham, England, as-

signor of one-half to Ega Electric Limited, Wednesbury, England Application July 29, 1948, Serial No. 41,322 In Great Britain August 2, 1947 Claims.

Thi invention relates to electric switch gear and refers to switch gear which is of low-tension type and which includes contactors comprising fixed and movable contacts. Usually the movable contacts are solenoid operated to displace them into the on position.

The invention is primarily applicable to switch gear individually associated with a single appliance, which appliance is usually an electric motor, although it may sometimes comprise another form of appliance, such as for example an industrial furnace.

With such devices the arcing which occurs between the contacts of the contactor results in them becoming pitted and worn, so that after an extended period of use they require attention and are liable to fail during actual operation.

As hitherto constructed the contactors and solenoid have all been mounted upon an insulating base, the whole being enclosed within a suitable box-like casing, the base carrying the terminals for both the mains and the appliance, so that in the event of failure of the switch gear it is first necessary to find and then withdraw the fuses in the mains to isolate the switch gear before any repair can be eiiected, and in the result the appliance may be out of action for an appreciable period.

The primary object of this invention is to provide an improved construction in which this disadvantage is avoided, and in which the contactors and the solenoid are all carried upon a common supporting member removably mounted within the casin the supporting member carryin contact elements which have slidin engagement with fixed contact elements within the casing to which the mains and other 8X1- ternal leads are connected, so that in the event of -iailure of the contactor assembly the supporting member complete with its contactors and solenoid can be slidden out of the casing as a single unit and replaced immediately by a further similar unit without the necessity of efiecting isolation of the entire switch gear from the mains.

One embodiment of the present invention is illustrated in the drawings, wherein:

v Figure 1 is a view in side elevation and in section substantially on the line l-l of Figure 3 of a low-tension electric switch constructed in accordance with the present invention;

Figure 2 is a View in side elevation and in section along the line 22 of Figure 1 of the same switch with the supporting member and removable cover withdrawn from the casing;

Figure 3 is a plan view of the same switch partly in section, also with the supporting member and removable cover withdrawn from the casing; and

Figure 4 is a circuit diagram showing the electrical connections between the various contacts of the switch.

Referring first of all to Figure 4, which illustrates the circuit of the switch suitable for application to the control of a three phase motor, the circuit comprises isolator contacts seen at Ma, lob, Ha, Hb, i211, I2?) by means of which the switch is connected to the three phases of the incoming mains; from each of the contacts I 6b, lib and I217, each phase further includes the actuating winding seen respectively at I3, I4 and I5 for overload devices l5, l1 and I8 which are operative upon a single pair of overload release contacts l9a and I91).

From each of the overload actuating windings a connection in each phase is taken to one of the contacts of contactors comprising moving and. fixed contacts 26a and 20b, 21a andZib, 22a and 22b. In each phase a further connection is taken from the other contact of the contactors (as seen in Figure 4) from contacts 25a and 21b and 22b to one contact 23a, 24a and 25a of a further set of isolator contacts, the other contact of each 23b, 24b, 25b is connected to the motor which it is desired to control.

For actuating the contactorsZEJ, 2!, 22 a solenoid 26 is provided, the energisation of which is controlled by a normally open push-button switch known as the on button 2'! and a normally closed push-button switch known as the oil button 23. These two switches are connected in series with the winding of the solenoid and in series with the overload release contacts l9a and l9b across two of the phases. An auxiliary pair of contacts 29a and 291) on the contactor serve to short circuit the normally open on button 27 after this has been initially pressed and the solenoid has been energised to close all the contactors.

Fuses 3E, 31 and 32 are included in the leads between the incoming isolator contacts from the mains and the overload actuating windings l3, l4 and I5, respectively.

In an alternative arrangement where it is desired to provide for remote operation, a plurality of sets of remote control buttons may be provided in addition to the buttons 21 and 28, and each arranged as indicated by the dotted lines in Figure 4, wherein a single set of such buttons is indicated at 33 and 34, serving as on and ofi buttons respectively. l

Referring now to Figure 1 of the drawings, in the embodiment shown the switch comprises an outer case 35 conveniently formed of the usual metal casting provided with a removable cover 36 which is secured on to the case by means of nuts 38 screwing on to the threaded end portion, seen at 39, of rods 4!] secured at their other ends in tapped holes in the rear wall M of the casing, which wall is opposed to the removable cover.

The wall 14! carries an insulating mounting member 42 which has a plurality of guideways or passages, as seen at 43, communicating with cavities housing fixed contact elements 4 and 5.

One set of these fixed contacts, foraexample those seen at 44, are connected tothe incoming mains and the other set 45,.areconnectedto' the circuit of the motor which it is required to control.

Secured in tapped holes in the removable cover 36 are tubular guide members d5. 'Convenien'tly the case and the cover are of substantiallyrectangular form and onetubular guide member is A provided near. each of the corners ofthe cover.

Carriedvupon the tubularguide. members it is a supporting member' ll' preferably formedv of a .plate'or sheet of insulating material such as that knownbyothe name Bakelite,.in the peripheral .marginof which suitable openings are provided to receive'the'tubular'guide members 45 soth-at 'the, supporting member ill can executesliding movement towards and. away from the removable .cover along thellength of the: guide members.

{As seenin the drawings'the upper part of the supporting. member 47 carries aseries of further contact elements lfl shown .in Figure 3 at rlsaflltb, 48c and '48d respectively, a'corresponding number of contact elements l being provided but not .being visible in Figure 3 by reason of being po- 'sitioned beneath corresponding.contactsdii.

."Eachoof these further contact elements comprise, a prong extending rearwardly towards the .jfixe'jd, contact elements Maud Q5. Each prong is "formed of a plurality of; superposed substantially parallel resilient conducting metal strips Ell, l; 52 which areof L formation, one arm oi'the L form- 'ing'theactual vprongand the other arm being utilised to form an attachment portion by means of .which' thecontact is secured to the supporting member by. screws such as those seen at 53.

.Successively positioned strips have prong por- 'tionsof progressively" reduced length, that is to sayytheprong portion of the strip 5! is shorter than that of'the strip 5E3 andlikewise the strip 52 is shorter than that of the strip 5i so that the 'end'face of each prong lies inclined at an angle to the direction in which the prong extends which is also the'direction in which it is movedby movement of-the supporting member ll on the itubular'guides 46.

Theifixed contact elements M and d5 correspond in number to the prongsQB and do and are -each provided with a contact face seen at 56 and 55 which is substantiallyparallel'to the associated'end faces of the prongs.

Also carried on the supporting-member llpreferablypositioned centrally thereon on therearwardly directed face of the supporting member is a solenoid operated-contactor indicated generally at '56. Thecontactor includes a series-of fixed "contacts and in each pairof contacts in the series "there is a fixed "contactor member such as-that seen :atj51 and a moving'contactor member such 'asthat-seen at' 58.

The fixed-contactor member is of the same con- -structional form as thegfixed contact elements -48a,"48b,"48c"and MBd'ca-rried by the supporting member in that it;consists of a plurality ofsuperposed, substantially parallel resilient conducting metal strips having rearwardly extending'prong I portions and attachment portions 59 foriattach- :ment to the supporting member'by screws 6t.

Themovingcontactor members 58 are-of V shape when viewedin'side elevation; onearmof each" V shaped moving contactor extending at-an inclination to the lengthof the prong portion of the fixed contactors and lying in'a plane substantially parallel to the inclined end face of the fixed contactors so as to make contact with the send face thereof.

In making such contact the moving contactor ;.has a Wiping action across the end face of the 'fixed contactor and at the same time displaces "the component metal strips of the latter apart relatively whereby there is provided an air space between the strips to facilitate the cooling there- "shaped arm both being constructed of magnetic material in laminated form.

Above the contactor assembly and positioned intermediate theconta'ctor-elements d8 are two push-button switches fi l and 65 which are indicated in the circuit diagram shown in Figure 4 by the referencenumerals 2i and 28.

The push-button switch 65 seen inside elevation inFigurei 2 comprises a pair of spaced fixed contacts SG-andfii secured by screws to" the supportingmember' il and a spring loaded bridging piece @Gwhich is operable by means of the pushbutton which is:.mounted' on .aystem 69 projecting through the supporting member ll and the removable :coverfifi and; is thus accessible from the outside of thecasing. ,The pushebuttonswitch 6 5; is of similar construction but the fixed spaced contacts corresponding to thoseiifi andfi'l of the switch -65 are suitably modified, for example,

their ends are bent over inwardly towards each other-so thatthese end portions are of U shape, contact between the bridging piece and these ends being between the rearward face of the bridging piece instead of the forward face as seen in the case of switch 55 and the bent over end face of the strips. In this way the loading sprin in the case of theswitch 6 results in the switch being normally open instead of normally closed as in the case of switch 65.

:Alsocarried upon the supporting member 41 and to one side of the contactor assembly is an overload device housed in an associated outer casing'lii and on the other side of the contactor assembly sandalso carried upon the supporting member a? are a set of fuses housed in an associated casing ii. Preferably the overload device is of thetype described in my co-pendingo application of even date.

. As seen in Figure l the supporting member 41,

the removable cover Stand the tubular guide .members 46 by means of which the supporting contact is established between the end faces of the contact elements 68 and 39 and the respectively associated contact faces55 and 54 ofthe-fixed contact elements 44 and 45.

As shown in the drawings this means takes the form of a knob 12 mounted on the outer portion of a stem 13 secured to the supporting member 41 by means of spaced washers 14 retained by associated cross pins 15, the stem projecting through an opening in the removable cover 36.

For retaining the supporting member 41 in the rearmost position with the contact elements 48 and 49 in contact with their respective fixed contact elements 44 and 45 suitable locking means are provided associated with the operatin knob 12 comprising a cross pin 16 which in one position of rotation of the knob and stem can pass through a suitably shaped portion of the opening in the removable cover and upon turning the knob 12 to another position of rotation engage the inner face of the removable cover to retain the stem and the supporting member against outward movement.

For the sake of clarity in Figures 1, 2 and 3 the connecting leads corresponding to the connections shown in the circuit diagram in Figure 4 have been omitted but with the following explanation the functions of the various parts shown in Figures 1, 2 and 3 will readily be understood. The contact elements 48 carried on the supporting member correspond to contacts lBb, Ill) and 12b on the circuit diagram and the fixed contacts '44 in Figure 1 are represented in the circuit diagram by contacts a, Ha and [2a, these being connected to the mains supply in the particular application described.

The contact elements 49 seen in Figure 2 are shown in the circuit diagram as contacts 23a, 24a and 25a and fixed contacts 45 as contacts 23b, 24b and 25b, these latter being connected to the motor which it is desired to control. As seen in Figure 3 there are four contacts in series 48a, 48b, 48c and 48d and four in the corresponding series 49a, 49b, 49c and 49d which is not seen in the drawings. The fourth contact in each of these series for example 48d and 49d corresponds with contacts 71a and 18a on the circuit diagram used when control by remote push-buttons is required and there are corresponding fixed contacts as for example that seen at (1 which are shown in the circuit diagram at 11b and 18b.

The moving contacts of the contactor indicated at 58 in Figure 2 are shown in the circuit diagram at 29a, 28a, Zia, and 22a, these being connected to the overload actuating windings by means of flexible conductors and the fixed contacts 51 of the contactor are shown at 2%, b, 2th and 22b in the circuit diagram.

The overload release contacts Illa and |9b seen in the circuit diagram are not shown in Figures 1, 2 and 3 since they are enclosed within the casing 10 but it will be apparent from the circuit diagram that an overload carried in any one of the three phases serves to open these contacts and de-energise the operating solenoid of the contactor.

In the event of failure of the switch occurring during use the knob 72 is first rotated to a suitable position and pulled out so as to withdraw the slidable isolating contacts 48 and 49 from their respectively associated fixed contacts 44 and 45, after which the nuts 38 are removed and the cover 35 complete with the supporting member and associated parts of the switch is withdrawn as a single unit and can be replaced immediately by a further similar unit whilst the original Withdrawn assembly is being repaired.

Since as soon as the contacts of the switch are withdrawn as above described they are necessarily completely isolated from the electrical supply there is no necessity to remove any isolating fuse external to the switch before repair can be efiected, all that is required being to operate the isolator of the switch by moving the knob 12 and remove the cover 36 as described.

Thus in event of failure of the switch, assuming that a spare unit is available, the motor or other appliance is out of use for the minimum period of time.

What I claim then is:

1. In a low tension electric switch having an outer case with fixed contact elements carried by an insulating mounting member therein, a removable and replaceable assembly comprising a cover for the outer case, a supporting member mounted slidably within said outer case, said supporting member carrying fixed and moving contactor members and further contact elements connected electrically with said contactor members, said further contact element being adapted to engage with said fixed contact elements, and means accessible externally of said cover for sliding said supporting member towards and away from the cover, respectively to effect isolation and establish contact between said fixed contact elements and said further contact elements.

2. In a low tension electric switch having an outer case with fixed contact elements carried by an insulating mounting member therein, a removable and replaceable assembly comprising a cover for the outer case, guide means on said cover projecting inwardly in relation to said outer case, a supporting member mounted slidably on said guide means, said supporting member carrying fixed and moving contactor members and further contact elements connected electrically with said contactor members, said further contact elements being adapted to engage with said fixed contact elements and means accessible externally of said cover for sliding, said supporting member towards and away from the cover respectively to effect isolation and establish contact between said fixed contact elements and said further contact elements.

3.'In a low tension electric switch having an outer case with fixed contact elements carried by an insulating mounting member therein, 'a removable and replaceable assembly comprising a cover for the outer case, guide means in the form of a plurality of tubes projecting inwardly in relation to said outer case from the edge portions of said cover and in register with outwardly projecting support rods in said outer case, a supporting member mounted slidably on said tubes, said supporting member carrying fixed and moving contactor members and further contact elements connected electrically with said contactor members, said further contact elements being adapted to engage with said fixed contact elements and means accessible externally of said cover for sliding said supporting member towards and away from the cover, respectively to efiect isolation and establish contact between said fixed contact elements and said further contact ele ments.

4. In a low tension electric switch having an outer case with fixed contact elements carried by an insulating mounting member therein, a removable and replaceable assembly comprising a cover for the outer case, a supporting member mounted slidably within said outer case, and manually operable means accessible externally of said cover movable between a visible isolating switch.

T5. In a low tension electric switch having an .outer case with fixed contact elements carriedlby an insulating mounting member therein, a removable and replaceable assembly comprising a cover .for the outer case, guide means in the form of a plurality of tubes projecting inwardly in relation ;to;said.outer case from the edge portions of said cover and in register'withoutwardly projecting :support rods in said outer case, a supporting :member mounted slidably on said tubes, said supporting member carrying fixed and moving contactor members and further contact elements connected electrically with said contactor members, said further contact elements being adapted to engage with said fixed contact elements and a stem fixed to said supporting rnem :er substantially centrally in relation to said tubes and project-- ing outwardly through an opening in said cover manual handling means on said stem portionpositiened externally of said cover whereby endwise movement can be imparted to said stem for sliding said supporting'member towards and away from the cover, respectively to effect isolation and establish contact between said fixed contact elementsand said further contact elements.

.6. In alow tensionelectric switch having an outercase withfixed contact elements carried by ,an insulating mounting member therein, a removable and replaceable assembly comprising a cover for the outer case, guide means in the form of a plurality of tubes projecting inwardly in relation to said outer case from the edge portions of said cover and in register with outwardly projecting support rodsin said .outervcase, a supporting member mounted slidably on said tubes, saidsupporting member carrying fixed and moving contactor members and further contact elements connected electrically with said contactor members, means on said cover for locating it. in relation to said outer case independently of said guide tubes and means accessible externally of said cover for sliding said supporting member towards and away from the cover, respectively to effect isolation and establish contact between said fixed contact elements and saidfurthercontact elements.

7. In a low tension electric switch having an outer case with fixed contact elements carried by an insulating mounting member therein, a removable and replaceable assembly comprising a cover for the outer case, a supporting member mounted slidably within said outer case and having relatively to the depth thereof a relatively short travel, said supporting member carrying fixed and moving contactor members and further contact elements connected electrically with said contactor members, said further contact elements being adapted to engage with said fixed contact elements and means accessible externallyvof said cover for sliding said supporting member towards and away from the cover, respectively to effect isolation and establish contact-between said fixed contact elements and said further contact elements.

,8. In alow tension electric switch having a removable and replaceable assembly carrying ,fixed and moving contactor elements andfurther contact elementsin the form of prongs, means ,for establishing connection between said prongs and conductors of an external circuit in which the switch is required to operate, comprising fixed contact elements in said switch supported by insulatingsupporting means, having cavities for housing said fixed contact elements and guideways communicating with said cavities and adapted to receive said prongs, whereby on removal of said assembly live fixed contact elements are not exposed to accidental handling.

9.111 a low tension electric switch having an outer case withv fixed contact elements carried by -an-insulatingimounting member therein, anda removable and replaceable assembly carrying fixedland moving contactor members and further contact. elements connected electrically with said contactor members, said further contact elements are in the form of prongs formed each of a plurality of superposed parallel resilient conducting metal strips, successively positioned strips having aprong portion of progressively reduced length to provide an end face for each prong which lies inclined at an angleto the direction in which the prong extends, for co-operation with said fixed contact elements in said outer case which 'have contact faces which are substantially parallel to respectively associated end faces of said contact elements.

10. In a low tension electric switch having an outer case with fixed contact elements carried cyan insulating mounting member therein, a removable and replaceable assembly comprising a cover for the outer case, guide means on said cover projecting inwardly in relation to said outer case, a supporting member mounted slidably on said guide means, said supporting member carry- .ing fixed and moving contactor members and further contact elements connected electrically with said contactor members, said further contact elements, being adapted to engage with said fixed contact elements a stem fixed to said supporting member and projecting outwardly through an opening in said cover, manual handling means onsaid stem positioned externally or" said cover whereby endwise movement can be imparted to said .stem for sliding said supporting member towards and away from the cover respectively to effect isolation and establish contact between said fixed contact elements and said further contact elements, and, a retaining member on said stern co-acting with said cover to latch the supporting member in the position in whichthe fixed and further contact elements are respectively engaged with each other.

GEORGE ,KILMINSTER.

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

UNITED STATES PATENTS Number Name Date 1,052,920 Hinckley Feb. 11, 1913 1,211,752 Pieper Jan. 9, 1917 1,954,583 Caswell Apr. 10, 193 i 2,077,160 Wilson Apr. 13, 1937 2,086,424 Koehler July 6, 1937 2,151,756 Fletcher Mar. 28, 1939 2,438,454 Riebe Mar. 23, 1947 2,439,326 Wilson Apr. 6, 1948

Images