US2246890A - Transformer construction - Google Patents

Description

June 24, 1941. c. MILLER TRANSFORMER CONSTRUCTION Filed July 15, 1939 INVENTOR (Me/a 77AM N14 L 64 ATTORNEY Patented June 24, 1941 UETED STATES PATENT TRANSFORMER CON STRUGTION Christian Miller, Nor-walk, Conn, assignor to Edwards and Company, Inc., Norwalk, Conn, a

corporation of New York Application July 15, 1939, Serial No. 284,669

10 Claims. (or. 175-361) This invention relates to a transformer construction and installation, particularly of the low-voltage type such as is employed in obtaining lower voltages, as for bell ringing and the like, from the usual type of household power circuit which is usually of 110 volts.

One of the objects of this invention is to provide improved safety in a transformer of the above-mentioned character, and in general to improve the construction, housing and mounting of transformer and safety device, to achieve inexpensiveness of construction, facility of assembly, ease of installation, and reliability of operation. Another object is to provide a construction of the above-mentioned character with dependable, compact and emcient means for guarding the construction and related circuits and premises against the dangers of overloading or overheating. Another object is to provide for the simple, inexpensive and dependable interrelation between the transformer and a circuit controlling safety device such as a thermally-responsive switch. Another object is to provide for the construction of the various parts such as safety device, transformer core and windings, and casing or housing, in individually simple and inexpensive sub-units, for speed, efficiency and economy in assembly thereof. Another object is to provide a thermally-responsive circuit interrupting device that will be simple and inexpensive to manufacture and capable of ease of assembly with the transformer core and windings, and casing. Another object is to provide a construction for a transformer core and windings in the form of a sub-assembly and a circuit breaking device in the form also of a sub-assembly, for facilitating interrelation of the two sub-assemblies and to make for greater speed, efficiency and economy in manufacture and assembly. Another object is to provide constructions of the above-mentioned character in which the circuit connections as between the circuit breaking device and the transformer winding may be quickly and easily made and with minimum danger of breakage of terminal wires or minimum disruption of assemblies. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts as will be exemplified in the structure to be hereinafter described and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing in which is shown one of the various possible embodiments of my invention,

Figure l is an end elevation of a completed transformer ready for installation;

Figure 2 is a side elevation thereof as seen from the right in Figure 1;

Figure 3 is a horizontal sectional view, with certain parts omitted, as seen along the line 3--3 of Figure 1;

Figure 4 is a central vertical sectional View, with certain parts omitted, as seen along the line 4-4 of Figure 3;

shaped, thus to provide a middle core leg II that extends intermediate of-the outer core legs I2 and I3, all three being bridged at their ends by end core legs I4 and I5, and altogether forming two core windows I6 and IT.

The windings, comprising a high-voltage winding and a low-voltage winding are collectively and generally designated by the reference character I8 and are preferably pre-wound in any suitable way and preferably upon a suitably constructed bobbin of insulating material; thus the bobbin may comprise a hollow hub I9 (Figure 6) core leg I I.

which may be, as indicated in Figure 6, made up of several, illustratively four, strips or sheets of insulating material like fibre to form an internal cross-section adequate to receive therein the middle core leg II as the core is built up out of the sectionalized laminations as indicated above. It is upon this hub I9 that the windings I8 are Wound in any suitable Way, the hub I9 having secured to it in suitably spaced relation, end plates 20 and 2I also made of sheet insulation such as fibre. Suitable provision is made for bringing out of the resultant winding unit the four ends of the two windings, two for each winding.

One of the four sheets such as the sheet 22 (Figure 6) that make up the hub I9 projects at its two ends beyond the end plates 20 and 2I as is better shown in Figures 3 and 4, and centrally of its projecting ends it is slotted as at 22 and 22 (Figure 3) to permit the passage therethrough of the lugs 21-3 and 23 which are formed at the ends of a relatively heavy sheet metal strip 23 which underlies the insulating strip 22 (see Figures 4 and 6) and which thus lies snug against the endmost lamination of the middle Preferably the end plates 20 and ZI which abut respectively against the end core legs I4 and I5 respectively are shaped at their left-hand portions as viewed in Figures 3 and. 6 to provide end vice which is generally indicated by the reference stationary contact point 28, is warped or bent, upon the attainment of a certain temperature rise, in clockwise direction as viewed in Figure 3, thus to bring movable contact point 3| out of engagement with stationary contact point 28;

' and of course that condition is maintained until character 26 and which preferably takes the form of a thermally-responsive switch.

In such form, the base member 25 is preferably made of a suitably heavy piece of sheet insulating material such as Bakelite, fibre or the like and in outline a preferred shape for member 25 is like that shown in Figure 5. Thus it preferably has a length greater than the length of the core Window l6 so that it may be bridged across the end core legs I4l5 being at its ends cut away as at 25 and 25 to provide end portions to rest respectively against these two core legs and to provide -an intermediate elongated or depending portion 25 that fits and projects into the core window It, as shown in Figure 5, thus to be held against displacement in the direction of its longitudinal axis.

And as is better shown in Figures 6 and 3, it fits snugly into the space between the inner vertical face of the core leg l2 and the parallel edges 20- and 20 of the end plates 20 and 2i, being thereby suitably held against tilting in clockwise or counterclockwise direction as viewed in Figure 6.

The insulating base 25 of the safety device 26, where it takes the form of a thermally-responsive circuit interrupter, has mounted preferably on its left-hand face as viewed in Figures 3 and 6 a contact point 28 of suitable alloy carried preferably in a sheet metal member 23 shaped and positioned so that the contact point 28 is positioned adjacent one end, illustratively the lower end as seen in Figure 5, of the supporting base 25, and so that the other end of the metal strip ,29 terminates along the central edge portion of member 25 where it is anchored to the latter preferably by an eyelet 30, member 29 having a suitable prong 29 (Figure which projects into a suitable recess or hole in the insulating plate 25 to hold metal strip 29 against rotation about the axis of the hollow rivet 39. The strip 29 is thus compactly and snugly held flat against the face of member 25.

Coa'cting with the contact point 28 is a contact point 3|, also preferably of suitable alloy, mounted and carried in one end of bi-metallic strip 32 whose other end (the upper end as viewed in Figures 3 and 5) is secured and anchored to the upper end of plate 25 preferably by a hollow rivet or eyelet 33, the latter being positioned preferably in that part of member 25 that overlies the end .core leg I4 as viewed in Figure 3 and as is well shown in Figure 5. Any suitable means may be employed to prevent bimetallic strip 32 from partaking of rotation and for thereby holding its contact point. 3| always alined with the stationary contact point 28; for

example some of the metal in the flat end por tion that rests flat against the member 25 adjacent the eyelet 33 may be distorted or pressed inwardly to form a prong-like projection that takes into a small recess or hole in the member 25 as indicated at 34 in Figure 5. I

The bi-metallic strip 32 is suitably bent or shaped as is better shown in Figure 3 and the two metals employed in making it up are so chosen with respect to their temperaturecoefiicientsof expansion that the strip 32, normally biased to press contact point 3| tightly against the temperature drops below the critical point.

The device 26, in above preferred form, is thus madeup as a separate unit and as such has assembled to it a relatively heavy lead wire 33 (Figure 3) suitably and usually heavily insulated, as for inclusion in a -volt circuit; the wire itself may be and usually is relatively heavy, on the order of a No. 16 gage. A suitable length of such insulated lead wire 36 has the insulation removed from one extreme end, thus to expose the bare wire as at 31 in Figure 3, and that bared wire 3] is inserted into the hollow rivet 33, the latter being preferably of brass or the like, from the right-hand side of the insulating plate 25 as viewed in Figure 3. The bare wire is suitably anchored thereto, as by sweating or soldering to the eyelet 33, and thus the resultant subassembly 25-36 is ready for assembly to the assembled transformer core and windings.

In effecting such assembly, the supporting plate 25 is simply interfitted with the core and winding parts as already above described and as shown in Figures 3, 5 and 6, that being a simple and quick manual operation. But in completing that operation, the heavily insulated and relatively heavy Wire 36 becomes laid down against the projecting portion 22 of the fibre strip 22 (see Figures 3 and 4), and between the thus far upstanding lug 23 and the end plate 20. By means of any suitable tool the lug 23 is now bent over into the relationship shown in Figures 3 and 4, thereby securely clamping the lead wire 7 36 in position. and at the same time substantially holding the device 26 in assembled relation to the assembled transformer core and windings.

One end 38. (Figure 3) of the high-voltage winding, that being of relatively fine wire, may

, now be brought into engagement with or through the eyelet 30 of the stationary contact plate 29, preferably from the right-hand side of the insulating plate 25 as seen in Figure 3, whence it is soldered or'otherwise mechanically anchored and thus electrically connected to the contact plate 29.

The other end 39 (Figure 3) of the high voltage winding may now also be connected, but to a heavily insulatedlead wire 4'0, like the lead wire 36, the lead wire 40 being clamped and mechanically anchored by the lug 23 as shown in Figures 3 and 4, and to its one bared end, the comparatively fine and fragile terminal wire 39 may now be secured as by soldering.

With heavy lead wire 43 thus dependably anchored, and with the device 26 held in assembled relation by the lug 23 subsequent handling of the resultant assemblage may be proceeded with without danger of breaking either of the fine wires 3839, since the parts to which they are electrically connected are held against such movement as would endanger the fine wire or its soldered or other connection to the respective relatively much heavier parts.

With the assemblage thus far completed, it is now ready to have interrelated with it suitable mounting means which preferably comprise also suitable enclosing or casing means. This preferably takes the form of a sheet metal casing structure preferably made up of two pairs of preferably identical parts, preferably and illustratively opposed upper and lower casing sections 4| and 42 (Figures 1 and 2) and opposed end casing sections 43 and 44.

Casing sections 4| and 42 are preferably of identical construction and hence may be made up by the same die or tool, preferably in the form of a sheet metal stamping. Each is shaped preferably to provide a peripheral flange-like portion to rest against the peripheral edge face of the transformer core Ill, and with a suitable conformation to cover over the bulging or projecting portions of the windings, and related parts, and at least one of them and the insulating support 25 of the safety device 26 are conformed to coact to hold the device 23 in the position of assembly earlier above described.

Since preferably the two casing sections 4| and 42 are identical, and where the core I is, as is usually the case, rectangular as seen in Figure 3, each casing section has a flange-like rectangular peripheral portion A which in outline matches the outline of the core It), so that when the two casing sections are positioned as shown in Figure 6, one to each side of the core ID, the flange portions A rest flatwise against the respective faces of the core I3 but preferably close to the extreme periphery of the latter. Preferably on only two opposed sides, the peripheral flange portions A have flange extensions B (see Figure 6) that overlap the two opposed side edges of the core Ill, thus achieving an interfitting of the three parts, namely casing parts 42 and 4| and core |3, so that relative lateral displacement between them cannot take place. The remaining opposed portions of the peripheral flanges A are provided with pairs of cars C (Figures 1 and 2) for a purpose later described.

From the plane of the peripheral flange portions A, the sheet metal of the casing sections 4 |-42 is drawn or formed preferably in the form of a frustrum of a pyramid, each having therefore top or end wall portions D with four sloping side wall portions E.

As is better shown in Figure 6 casing section 42 is related to that side of the core Ill from which the insulating support 25 of the safety device 26 projects, and the parts are preferably so proportioned, as better appears from Figures 4, and 6, that the exposed edges of the member 25 snugly interfit with the inside faces of the wall portions E, D, and E of the section 42. When section 42 therefore is secured in place, member 25 is additionally and also securely held in assembled relation and becomes moreover also encased along with the winding and core.

of the sloping wall portions E of the two casing sections 4|42, two of them, one for each casing section and illustratively those two facing the observer viewing Figure l, are suitably apertured or cut away and over the apertures are secured in any suitable manner, as by bendable ears or legs F insulating plates 41, for casing section 4|, and 43 for casing section 42.

Insulating plate 48 is provided with two spaced apertures through which are brought the heavy lead wires 36 and 48 as the casing section 42 is related to the core safety device as above described, and as better appears from Figures 1, 2 and 4, it being noted that, because of the abovedescribed anchorages of these lead wires they may be freely bent or curved and fitted into appropriate spaces to bring them out through the insulating plate 48 but without danger of dislodging safety device 28 or of rupturing or harming sloping manner.

the connection of the fine lead wires 38 and 39 extending from the high-voltage winding.

In the insulating plate 4'! of the" other casing section 4| there are preferably mounted two binding posts 43-50 of any suitable construction and, prior to assembling the casing section 4| to the core and winding, the two terminal or lead Wires (not shown) from the low-voltage winding are first connected, as by soldering, to suitable parts of these binding posts exposed internally of the casing section 4|.

The assemblage is now ready to receive the remaining two casing sections 43 and 44 they too are preferably identical in construction and are preferably in the form of a flat sheet metal plate G having end flanges H to take over or to receive therebetween the core with parts of the flange portions A of the two casing sections 4|42, as appears better in Figure 2; but these plate portions G are also apertured to receive therethrough the bendable ears or legs C which are in effect extensions of the flanged portions A which the flanges G overlap; these ears C may now be bent over into clamping position as shown in Figures 1 and 2, thus not only holding the casing parts 4| and 42 with the interposed core and safety device 25 against parting movements but also holding the two casing sections 4|-42 and the core against relative lateral displacement as viewed in Figure 2.

Each casing section 43--44 has an extension 5| downwardly as viewed in Figures 1 and 2 provided with spaced flanges 52 terminating at 53 to form stops for a purpose about to be described; at their lower ends the extensions 5| are bent transversely as at 54, the latter parts being adapted to rest against a suitable supporting surface, such as a panel board or the like, and being suitably apertured so that they may be secured as by screws, thus to mount the transformer structure where it is permissible or desired to mount it in such an exposed position.

But there are installations where it is desired or necessary to mount the transformer with relation to a wall box or an outlet box and for such purpose a plate indicated at 55 in Figure 2 and which may take the form of a barrier or cover plate may be employed; the plate 55 is provided with a generally rectangular aperture large enough to permit the core It! as viewed in Figure 3 together with the peripheral overlapping casing sections to pass freely therethrough, first entering that end of the construction corresponding to the casing section 4| through the hole in the plate 55 to an extent permitted by the stop flanges 53 which thus engage one edge face of the plate 55 adjacent to opposed sides of the hole. With the wide spacing of the stops 53 (see Figure 1) at each of these two sides, absence of tilting of the transformer structure relative to the plate 55 may be adequately insured.

The transformer structure is held assembled to the plate 55 preferably by means of two relatively large tongues J preferably formed integrally with the two casing sections 43-44 respectively, as by cutting the sheet metal thereof and bending it outwardly as is better shown in Figure 2, the lower free ends of the tongues J being suitably curved or bent inwardly, preferably in a Accordingly as the transformer structure is passed into the hole in the plate 55, the long downwardly and outwardly sloping portions of the tongues J (see Figure 2) act as cams to flex the tongues J-J inwardly until the highest points thereof by-pass the opposed edges of tongues JJ is such that they act as cams or wedges, under the spring action of the metal, to draw the transformer structure in an upward direction as viewed in Figure 2 and thus effect a continuous gripping of the plate 55 between themselves and the spaced and distributed stops 53. Thus the structure may be quickly mounted in relation to a cover plate or barrier plate or like plate structure, as for example part of a wall box, outlet box or the like.

If desired the extensions 5|, forming supporting legs as described above may be scored or weakened as along the line 56 of Figure 1 so that, where the structure is mounted on to a plate 55, the extensions 5| may be severed or broken ofi.

During operation of the transformer, the thermally-responsive switch element 32 becomes subjected to the operating temperature of the transformer itself, receiving heat directly by conduction and also otherwise, being substantially encased with the windings and core so that heat losses generated therein affect the temperature of the bi-metallic element 32. So long as these heat losses are normal, corresponding to normal condition and also operation of the transformer within its intended capacity, the bi-metallic element, though raised above room temperature, maintains the contact points 3! and 23 in engagement and thus maintains the high-voltage transformer circuit closed. But should overloading of the transformer or some other condition arise to bring the temperature of the parts above any desired value, usually above the normal rating of the transformer, the bi-metallic element 32 promptly responds and opens the transformer circuit; the cause of the abnormal temperature rise may now be remedied but if not remedied a subsequent closure of the circuit which follows a cooling off of the structure, is but of short duration, for the bi-metallic element 32 again opens the circuit. An abnormal condition usually causes the temperature to rise more rapidly than the temperature falls after open circuiting, for decrease in temperature depends upon the rate of dissipation of the stored heat and that usually takes place at a relatively low rate.

Thus it will be seen that there has been provided in this invention a transformer construction-in which the various objects hereinbefore noted together with many thoroughly practical advantages are successfully achieved. Assembly is greatly facilitated not only in course of fabrication and manufacture but also in course of installation with respect to a suitable supporting structure. Also it will be seen that safety of operation or installation has been achieved in a thoroughly practical and reliable yet inexpensive manner.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is forth or shown in the accompanying drawing is to be'interpreted as illustrative and not in a limiting sense. i r

to be. understood that all matter hereinbeforeset Iclaim: v .1. A transformer construction comprising a core and windings, a circuit-controlling device connected in circuit with at least one of said windings and having a plate-like supporting part, I said core and said supporting part having respective portions shaped so that one portion is enterable into the other upon movement in one direction and is removable therefrom upon movement in reverse direction, said portions having one entered into the other for holding said supporting part in interfitting relationship to said core, thereby to form a sub-assembly, and a casing structure for substantially enclosing said core and windings and device, said supporting part being engaged by said casing structure when the latter is assembled to said core and windings and on that side of said part to form a stop against movement in said reverse direction, said support- .ing part thereby being secured against displacement relative to said core.

2. A transformer construction comprising a core and winding thereon, said core having a core window through which said winding passesfand said winding having spaced end plates at least ment in all directions excepting in a direction outwardly of said space, and means for holding said supporting means against movement, outwardly from its inserted position, thereby to hold said device assembled to said core and winding.

3. A transformer construction, as claimed in claim 2, in which said device has electrically connected and mechanically anchored thereto a relatively heavy conductor, and in which the means for holding said supporting means against movement out of inserted position comprises a sheetmetal member having a part fixedly held between the core and said winding and a part exposed externally of said core and on that side of the latter. from which said supporting means is insertable into said space, said last-mentioned part of said sheet metal member being bendable and being bent over said heavy conductor to clamp the latter and thereby hold said supporting means against movement in a direction outwardly from said space.

4; A transformer construction, as claimed in claim 2, in which said holding means comprises a casing structure for substantially enveloping said core and winding and having a portion overlying said supporting means at a portion of the latter remote from that portion that is inserted into said space, thereby blocking said supporting means from moving out of inserted position.

5. A transformer construction comprising a core having a substantially plane'face with a core window therein and a winding extending through said window and related to the core with a portion of the winding projecting beyond said face, a circuit-controlling device in circuit with said winding and having supporting means that has an intermediate portion dimensioned for entry into or removal from said core window from the plane-faced side of said core and end portions resting against said core face at the ends of said core window upon completion of movement of said supporting means to enter and project said intermediate portion into said core window, whereby said device may be assembled to said core and winding by inserting said intermediate portion into said window from the side of said core face, and means separate from said supporting means and having connection with said core and said supporting means for holding the latter against movement in a direction opposite the direction of inserting movement.

6. A transformer construction comprising a core having at least two core legs with a core window therebetween and a winding about one of said legs and extending through said core window, a sheet-metal member interposed between said winding and its core leg and having bendable end portions, relatively heavy insulated conductors having portions clamped, respectively, by said bendable end portions and thereby anchored in position, a circuit-controlling device comprising a block of, insulatingmaterial having portions removably interfitted and resting in detachable engagement with said core and winding and carrying switch means in circuit with said winding by connections which include at least one of said heavy conductors, said device having means for electrically connecting and anchoring thereto that one of said heavy conductors by which it is connected in circuit with said winding for thereby holding said device in position with said portions interfitted with said core and winding.

'7. A transformer construction comprising a core-and-winding structure with the winding projecting from two opposed faces of said core, said winding having insulating end members at its ends, two casing sections, one for each side of said structure, having respectively portions engaging said core faces and bulges respectively enveloping the projecting portions of said winding, a thermally-responsive circuit-controlling device in engagement with and held in alinement with said structure by said insulating end members of said winding and interposed between said structure on one side thereof and the corresponding casing section and engaged and covered over by the bulging portion of the latter and one of said core faces, and thereby held in engagement with said insulating end members and in position tobecome responsive to heat produced in said structure, and means for holding said two casing sections in assembled relation to said structure.

8. A transformer construction comprising a core-and-winding structure with the winding projecting from two opposed faces of said core, casing means for said structure comprising four casing parts of which two are in the form of two casing sections, each related to one of said core faces for enveloping the projecting portions of said winding, two other of said four casing parts comprising two end casing sections related, respectively, to opposite ends of said core and each having flange means at its ends to overlap opposedend portions of said first-mentioned two casing sections, the latter having flange means only at their remaining opposed end portions and overlapping the remaining opposite ends of said core, and each of said second-mentioned two casing sections being connected to said first-mentioned two casing sections to hold the latter assembled to said structure, said end casing sections having stop means to engage against one face of a supporting plate having an aperture large enough to receive the aforesaid assembled parts therein and at least one of said end casing sections having a yieldable tongue projecting outwardly therefrom and adapted to yield as said assemblage is entered into said plate aperture, said tongue having means for engaging with the other side of said plate to hold the assemblage against movement out of said aperture.

9. A transformer construction comprising a core-and-winding structure with the winding projecting from two opposed faces of said core, casing means for said structure comprising four casing parts of which two are in the form of two casing sections, each related to one of said core faces for enveloping the projecting portions of said winding, said two casing sections having marginal portions resting, respectively, against marginal portions of said two opposed core faces, two opposed marginal portions of each of said two casing sections having flange means overlapping respectively two opposite ends of said core and the remaining two opposed marginal portions of each of said two casing sections terminating substantially at the respective planes of the remaining two opposed end faces of said core, two other of said four-part casing means comprising two sheet metal plate-like members, each having two portions one of each of which extend along and cover over said two remaining opposed end faces respectively of said core, means connecting said second-mentioned opposed marginal portions of said first-mentioned two casing sections to said two sheet metal plate members, the other portions of said two sheet metal plate members forming two spaced supporting legs for supporting said transi ormer construction from a suitable supporting surface, at least one portion of each of said two sheet metal plate members having a yieldable tongue projecting outwardly therefrom and adapted to yield as said transformer construction, where it is to be supported in the aperture of a supporting plate, is entered into said plate aperture, there being means coacting with said yieldable tongue and engaging one face of said supporting plate to hold the transformer construction assembled to and alined with said plate.

10. A transformer construction comprising a core and winding thereon, said core having a core window through which said winding passes and said winding having spaced end plates at least portions of which extend through said window, said portions presenting parallel edges spaced from and parallel to the adjacent core wall in said window, a thermally responsive circuit-controlling device in circuit with said winding and comprising a block of insulating material bridged across said core window and having end portions resting against one face of said core with a depending portion intermediate of said end portions, said depending portion upon insertion entering the space between said core wall and said parallel edges and being of a thickness to substantially snugly interfit between said core wall on the one hand and said parallel edges on the other, whereby said block of insulating material is held against tilting relative to said core face though otherwise movable in a direction opposed to the direction of insertion, and means engaging said block of insulating material for holding it against movement in a direction to remove said inserted portion from said space.

CHRISTIAN MILLER.

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