US482872A - Insulator - Google Patents

Description

(NoModeL) G. T. LEE. INSULATOR.

No. 482,872. Patented Sept. 20, 18-92.

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UNITED STATES PATENT OFFICE.

CHARLES TENNANT LEE, OF BOSTON, MASSAOHUSE'I S, ASSIGNOR TO TH E J OHNSJRATT COMPANY, OF HARTFORD, (ONNE )TICU'I.

INSULATOR.

SPECIFICATION forming part of Letters Patent No. 482,872, dated September 20, 1892.

' Applicationfiledli'cvemher 14,1891. Serial No. t1l,925.- iNoinudel.)

' To all whom, it may concern.-

Be it known that 1, CHARLES TENNANT LEE, a citizen of the United States, residing at 13oston, in the county of Suffolk and State of Mas- 5 sachusetts, haveinvented certainnew and useful Improvements in Insulators, of which the following is a specification, reference being therein had to the accompanying drawings.

My invention has for its object to produce a durable and efficient insulatorfor electrical purposes; and it consists of an insulator comprising an insnlation-blockeornposed of sheets of mica pressed and compacted together, said block having a parallel-sided seat formed r thereon, and an outer case or shell, which incloses or partially incloses said block, the said case or shell having a clasping portion, which tightly compresses the seat formed on the edges of the sheet of mica and which is held on the said sheet by frictional contact, all as hereinafter set forth, and the novel features of which are pointed out in the claims which are appended hereto.

It is not new, broadly, to construct an insulator having a stem or rod upon which are strung sheets of mica, and also having an outer casing, which 'isinsulated from the stem or rod by said sheets of mica; but such insulators, so far as known to me, have been difli- 3o cu1t,and consequently expensive, to construct, and unless constructed with great care have been objectionable.

It is necessary to secure the parts of the insulator very firmly together, and to do this it p 5 has hitherto been usual to provide the central bolt or core with a head at its inner end, larger in size than the opening in the outer case,thus necessitating the making of the outer casein two parts and screwing them 0 or otherwise joining them together. The

making of thecase in two parts necessitates a joint, which is objectionable for obvious reasons. An insulator made in accordance with my invention is free from these objections.

In the accompanying drawingsI have shown two forms of my insulator.

Figure 1 represents a lengthwise central section of a handle which may be used for any purpose for which an insulated handle is required. Fig. 2 represents a lengthwise central section of one form of electrical insulator which is known as strain-insulator and is used in the overhead construction of electrical railways.

My invention will be readily understood from the following description, in which reference is made to the accompanying drawings. The central core or metallic portion is shown at a, and consists of a rod of metal which is headed at one end to retain the mica in place and screw-threaded at the other end, so that a retaining-nut 7L may be secured onto the rod to retain the mica in place at that end. The mica 1) consists of sheets, which are pro vided with a central aperture, through which the rod passes, and which are of a shape in the portion of the insulation-block which is inclosed and clasped by the case or shell (Z corresponding to the cross-sectional shape of the interior of the case (Z. The sheets of mica. forming the said portion of the insulationbloek should be cut as large or vt y little larger than the cross-section of the elasping portion of the shell or case and so that they cannot be slid into the case (Z when the case is cold. The exterior of the said portion of the insulation-block forms a parallel-sided seat' of any desired outline in cross-section corresponding with that of the interior of the clasping portion of the shell or case. The case d is of metal and may be of any convenient or desired exterior shape; but that portion of its interior which is designed to come in contact with the mica should be parallel-sided in the direct-ion of the length of the case or shell. In applying the case or shell to the insulation-block the metallic case is heated, and when expanded by the heat the body or block of insulating material is forced to place within it. The case is then allowed to cool and shrink to its seat 011 the insulation. \Vhen shrunk to its place, it very tightly compresses its seat on the insulation-block and is very firmly secured on said seat by its frictional contact therewith, and the insulator may be 5 subjected to a great strain without breaking or separating the outer case from the insulated core. As will be obvious, the mica sheets may be strung on rod a, then compressed together, and then turned down to the size and zoo shape desired. It will also be clear that the seat for the outer case on the insulating ma- .ticity which is the quality of horn. In practeria1--that is, the part of the insulating ma terial which comes in contact with the outer case d-1naybe turned down or otherwise reduced, as shown'in the drawings, so that the finished insulator will have a smooth exterior, with no break or diiferenoe in the exterior diameter between the metal and the mica portions. the drawings.

In the strain-insulator, which is shown in Fig. 2, the construction which 1 have de scribed is only varied-by the duplication of the metallic case d and by the formation of an annular flange f-i'n'the mica at a point about midway-between the metallic casings.

This annularfiange is for the purpose'o'f' allowing moisture to drop freely from the insulator when it. is used out of doors. The

outer casing may be'varied in form, as de tice in fitting, together the parts it is necessary to apply-considerable pressurejin order to put the seat portion of the insulation-block within the receivingportion ofthe shell or casing, even when the latter'is expanded by heat, the parts being-so proportioned as to secure such a iitas this implies. It is found that, whereas beforethe insnlatinghloclr is 'lhis'is the construction shown in inserted into the shell or case the central core or rodon which the mica sheets are strung admits of being withdrawn by the exertion of a moderate degree of force, after the metal shell or case-has been shrunk to its seat the sheets of mica have become compressed and shortened radially-that is, the radii of the disks are of less 1engthand they are so.

forced in toward or on to the metal core or rod subjecting it to great strain, while, also, rod is found to be scored and out by the mica.

What I claim is 1. Ah insulator comprising an insulationblock composed of a series. of sheets of mica compressed and compacted together, the said block having a parallel-sided seat formed thereon, and a metallic shell .or casing inclosing or partially inclosing the said block,

lightly compressing the seat thereon, and

held on the seat by frictional contact, for the purposes and substantially as set forth.

2. An insulator comprising a core, a series of sheets of mica strung on said core and closely compressed and compacted together thereon, the said block having a parallel-sided seat formed thercon,and a metallic shell or casinginclosing or partially inclosin g the mica on said core, tightly compressing the seat thereon, and held on the seat by frictional contact, for the purposes and substantiall y as set forth.

In testimony whereof I aflix my signatu re in. presence of two witnesses.

CHARLES TENNAN'I" LEE.

' \Vitnesses:

WM. A. Mltcnnon, Unas- F. RANDALL.

- that the latter cannot be Withdrawn unless by

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