The invention relates to insulators used for the support of high tension transmission lines and has special reference to insulators of peculiar and special construction rendering them particularly appropriate for use in localities where there are fog and dust conditions which render the ordinary types inefficient.

It is well known that it is necessary to provide in an insulator a relatively long leakage distance over which current must flow in passing from whatever metallic support is provided to or from the conductor ordinarily it is the practice to provide an insulator with a plurality of depending annular petticoats or ridges located at the underside for the purpose of providing a relatively long leakage path. An objection to such a construction, especially where the insulator is to be used in a locality subject to fogs or in the vicinity of cement mills and other manufacturing plants giving off dust or chemicals which may deposit upon the insulators, is the fact that such moisture or such dust or chemicals accumulates upon the depending petticoats or ridges, thereby reducing the efficiency of the insulator owing to the fact that such deposits are fairly good conductors and have the effect of materially shortening the leakage distance with the attendant risk of flash-over and ether objections. Another disadvantage in the ordinary construction is the fact that even in severe rain storms the depending petticoats or ridges, being on the underside of the insulator, are not washed off and in fact are not always even wetted. It is a matter of common knowledge that in the event of only partial wetting of the exposed surfaces electrical stresses are set up which have a very detrimental effect.

It is with all of the above facts in view that I have devised the present invention which has for its general object the provision of an insulator having a large leakage distance and of such construction that the surfaces providing the long leakage path will be effectually washed off when rain storms occur, any accumulations or deposits of chemicals, dust or the like being consequently removed, the surfaces providing the leakage path being moreover so located that in the event of rain all the surfaces will become wet, thereby avoiding the development of any undue electrical stresses.

Another object of the invention is to provide an insulator having the above mentioned characteristics and which may be of the one-piece or multi-part pin type, these and other variations being permissible within the purview of the invention.

Another object of the invention is to provide an insulator in which the underside of the disk-like body may be made flat, the body being furthermore preferably of more or less wedge or tapered shape in cross section so as to obtain certain advantages during the firing operation in the manufacture and so as to obtain a high degree of mechanical strength which will reduce likelihood of breakage of the insulator in case it is struck by missiles thrown or shot by destructive persons.

Another object is to provide an insulator having the above pointed out features of advantage and which will yet at the same time be free from any undue difficulties in manufacture and which will not be subject to the development of any unusual thermal strains.

An additional object is to provide an insulator of this or an analogous character which will be simple and inexpensive to make and also to assemble in case it be of the multi-part type, and yet which will at the some time be highly efficient and durable in service and a general improvement in the art.

To the attainment of the foregoing and other objects and advantages, the invention preferably consists in the details of construction and the arrangement and combination of parts to be hereinafter more fully described and claimed, and illustrated in the accompanying drawing in which:

Figure 1 is a view partly in side elevation and partly in vertical cross section showing one embodiment of the invention,

Figure 2 is a similar view showing an increased leakage distance and constructed with a flat underside,

Figure 3 is a similar view through a pin type insulator formed of a plurality of parts.

Referring more particularly to the drawing, it will at once be apparent that while I have illustrated different modifications or embodiments, yet at the same time each variation involves the same general principle of electrical construction. Figure 1 discloses an insulator Indicated as a whole by the numeral 10 and comprising a dielectric, preferably porcelain, body having an outstanding disk or skirt portion 11 from which rises a stem 12 formed with a recess 13 within which may be secured, as by cement 14, a metallic thimble 15 threaded for engagement therein of a metallic supporting pin 16 of conventional type. Usually the walls of recesses such as the one at 13 are sanded or otherwise roughened to afford an adequate grip for the cement. However, this is a detail which need not enter into the device though it is mentioned for the sake of explanation. In insulators of this general variety there is provided a transverse groove 17 in the top of the stem and also a peripheral groove 18, the former being for the reception of a straight line conductor and the latter being intended for the accommodation of a suitable tie wire or else receiving the conductor itself in the event that the line makes a turn or other change in direction.

Up to this point there is nothing unusual about the construction. The novel feature involved reside in the formation or shape of the surface of the upstanding stem which is represented as provided with a plurality of outstanding ridges or corrugations 19 which provide the necessary long leakage path and

which are located at this position in lieu of being constructed as annular ribs on the underside of the skirt or disk 11 as is usual practice. Of course the number of such corrugations may be varied depending upon the contemplated safe carrying capacity of the insulator.

Figure 1 also shows the skirt portion 11 as being of slightly tapered or wedge shape in cross section with the undersides slightly dished and formed with a drain lip or ridge 20. However, this is not really the preferred construction in this respect as I have discovered that it may be preferable to form the underside of the disk as entirely flat. Figure 2 discloses such an alternative arrangement, the insulator 21 therein being of identically the same construction as the insulator 10 with the exception that the upstanding stem 22 has its periphery formed with a larger number of corrugations 23, represented by the broken lines as of indeterminate number, and with the additional exception that the outstanding skirt 24 has its bottom surface 25 flat. The 15 and pin 16 may be standard as in Figure 1, though the cavity 13a is deeper, as shown. The space between the end of the thimble and the bottom of the cavity is preferably filled with sand indicated at 13b.

There is no limitation as to the construction of the insulator as a single piece and in Figure 3 I have illustrated a multi-part construction embodying nested shells 26 and 27, the former having a cavity 28 therein within which is secured by cement 29 the upstanding stem 30 of the shell 27. In this form the upper shell 26 is represented as having a transverse conductor receiving groove 31 and a peripheral tie wire groove 32, the stem portion also having its surface formed with a series of corrugations 33, there being any desired number within reasonable limits depending upon the voltage to be carried. In this form the undersurface of the disk or skirt 34 of the upper shell is likewise represented as flat as indicated at 35 though obviously it could, if desired, be dished as in Figure 1 but it is repeated that the flat or plane construction is preferable as it gives greater thickness and therefore increased mechanical strength and as it facilitates the firing step in the customary saggers.

It will he noted that in each instance the uppermost groove defined by the outwardly extending ridges, ribs or corrugations constitutes the tie wire groove. It will also be observed that there is no overhanging hood at or near the top of the insulator, the general diameter above the outstanding disk being substantially uniform.

In all forms of the invention disclosed and in others which can be readily conceived of it is clear that the corrugations 19, 23 or 33 will provide a long leakage path so that even if the surfaces are wet or if any foreign matter of a conducting nature accumulates upon them there will be no likelihood of failure. Moreover as all of these corrugated surfaces are exposed they will be washed off whenever a rain occurs so that foreign matter deposited upon them cannot remain for any great length of time.  Another point of superiority is that in the event of rain, or fog for that matter, it is practically certain that all of the exposed surfaces will be wetted, thereby making the conditions uniform throughout and avoiding the bringing of any electrical stresses which would otherwise be concentrated at localized points.

The wedge shape of the skirt portion as disclosed in Figures 2 and 3 is of great advantage as it gives the skirt sufficient mechanical strength to withstand the effects of rocks and other missiles with which mischievous and destructive persons frequently bombard insulators. It has also been discovered that with this shape of the disk there is no great likelihood of warping or other distortion of the insulator during drying or firing, contrary to the opinions of numerous engineers adhering to the old established concaved shape.

From the foregoing description and a study of the drawing it will be apparent that I have thus provided a very simply constructed insulator possessing the numerous advantageous characteristics ascribed to it. It is believed that the construction, operation and advantages will be readily apparent to one skilled in the art without further explanation.

While I have shown and described the preferred embodiments of the invention it should be understood that the disclosure is merely an exemplification of the principles involved as the right is reserved to make all such changes in the details of construction as will widen the field of utility and increase the adaptability of the device provided such changes constitute no departure from the spirit of the invention or the scope of the claim hereunto appended.

Having thus described the invention, I claim:

A high tension insulator comprising a dielectric body including a disk having a substantially plane undersurface, and an upstanding stem rising from the disk and of substantially uniform general diameter throughout, the general diameter of the stem being relatively small as compared with that of the disk, said body being formed with a cavity extending into the stem and closed at the top and opening out at the bottom and adapted to receive a supporting element, said stem being formed with a series of circumferential alternating ribs and grooves, the upper end of the stem having a transverse line wire receiving groove, and the uppermost circumferential groove in the body constituting a tie wire receiving groove.

BENTLEY A. PLIMPTON.