To all whom it may concern:

Be it known that I, ROBERT M. JOHNSTON, a citizen of the United States, residing at Detroit, in the county of Wayne and State of Michigan, have invented new and useful Improvements in Insulators, of which the following is a specification.

This invention is an improvement in high voltage insulators of the suspension type.

One of the objects of the invention is to provide an insulator for long distance power transmission and similar service, which shall have far greater dielectric strength than the insulators of this type now in general use.

A further object is to provide a high tension insulator constructed to prevent deterioration from excessive dielectric stress, and from differences in the coefficient of expansion of the metal parts and of the insulating material to which they are attached. A further object is to provide a high tension insulator which will resist direct puncture from all excess voltage on the line, and which will permanently withstand all electrical strains. A further object is to provide a high tension insulator in which the electrodes are constructed to furnish a uniform field of dielectric stress, whereby the maximum strength of the insulating material is brought out. A further object is to provide a high tension insulator of maximum tensile strength, having provision to minimize to the utmost, the strains due to temperature changes in metal and porcelain, and possessing flexibility to minimize the effect of shocks and vibrations. A further object is to provide a high tension insulator having means whereby the units may be quickly and securely coupled together, to permit slight relative play of the units, but to prevent relative rotation thereof.  A further object is to provide improved means for securing the metal parts to the insulating disks whereby a maximum tensile strength and increased toughness to resist shocks and vibrations is secured.  A further object is to provide means for so uniting the metal and porcelain parts that all air space between the two is eliminated thereby practically avoiding corona discharges.

The invention will be hereinafter fully set forth and particularly pointed out in the c1aims.

In the accompanying drawing:--

Figure 1 is a side elevation of a high tension insulator constructed in accordance with the invention. Fig. 2 is a longitudinal sectional view thereof. Fig. 3 is a transverse sectional view on the line 3-3, Fig. 2.  Fig. 4 is a detail sectional view illustrating one of the sockets in a porcelain unit. Fig. 5 is a perspective view of one of the metal supporting caps.  Fig. 6 is a sectional view on the line 6-6, Fig. 5. Figs. 7 and 8 are side views, partly in section, of modified forms of the invention.

Referring to the drawing, the invention is illustrated in the form of an insulator made up of two units, although it is not limited in this respect, as the number of units may be varied to conform to different conditions that may have to be met. Each unit comprises a porcelain disk 10, preferably circular in plan view, and provided with upper and lower hub like extensions or bosses 11, 12.  Each of said hub like portions or bosses is provided with a series of openings 13, parallel with the axis of the disk, each of said openings having an offset recess 14, at its inner end, said recesses being illustrated as extending in a clock-wise direction. The underside of the body of the disk 10, is provided with corrugations 15, as shown.

Attached to the hub-like portions or bosses 11, 12, are metal caps or supporting members 16, each of which is provided with an elongated slot 17 in its top, each of said caps being also provided with a plurality of equally spaced attenuated portions or legs 18; arranged in a circle, each leg being provided with a tangentially projecting foot extended in a clock-wise direction. In practice, the legs 18 are inserted in the openings 13, with which they correspond, and then the cap is given a turn so as to bring the feet 19 into engagement with the respective recesses 14. The cap is secured in this position by filling the openings 13 and recesses 14 with any material which will be plastic enough to apply and which will become sufficiently hard to prevent relative movement of the parts.  A metal alloy has been found to give good results.  Said alloy being applied in a molten condition and allowed to cool.

The porcelain being heated to prevent cracking by the hot metal or, if desired, a suitable cement may be employed in lieu of the metal.

Any number of the units 10 may be coupled together in series, by means of bolts, each of which, comprises a body 21, provided at its ends with elongated heads 22, of a size capable of being passed through the slots 17 of the caps. Each cap is provided in its inner face with recesses 23, disposed on opposite sides of the slot 17, and at right, angles thereto, to receive one of the heads 22, after the same has been passed through the slot 17, and given a quarter turn.  To couple two units together, one head of a bolt, 21 is passed through the slot 17 of the cap 16, attached to the upper boss 11 of one of the disks, said bolt then being given a quarter turn to seat the head in the recesses 23.  The other head of the bolt is then passed through the slot 17 of the cap 16, attached to the lower boss 12 of the next disk, said bolt being then rotated to bring the head in register with the seats 23 in the last mentioned cap.  Cotter pins 24, inserted through the respective caps, engage the heads of the respective couplings 21.  The suspension member 25 is provided with a head similar to the heads 22 of the bolts or couplings 21, and the supporting link 26 is similarly constructed.

In lieu of detachably connecting the units, as illustrated in Fig. 1, two porcelain disks may be joined together as illustrated in Fig 7. In this form of the invention, the insulators 10 are identical with those illustrated in Fig. 1, and provided with the openings 13 and recesses 14. The disks are permanently connected by means of legs, 27, each provided at its ends with a foot 28, corresponding to the feet 19, the ends of said legs being cemented within the openings 13.  Each leg 27, is slightly bent, as shown.

A second modification is illustrated in Fig. 8, in which form the, legs 29 of the cap 30, are joined by an annular ring, 31, said ring being cemented within an annular recess 32, the walls of which are provided with grooves 33, to receive the, cement, or other securing material.

In practice, the porcelain disks are of a thickness between one fourth and one sixth of the diameter, because, in order to keep the dielectric, stress low enough to prevent gradual failure of' the insulator, the dielectric thickness, or distance between the metal parts through the insulator, should be about one fourth the distance between the metal parts around the insulator, i.e. one fourth of the arcing distance.  This thickness varies with the dielectric properties of the insulating material and factors of safety considered necessary, but in any event, should be much greater than is necessary to resist puncture at the arcing over voltage of the insulator unit.

The metal legs attached to the porcelain units are, substantially rigid but possess a certain amount of flexibility, and the areas of contact between the said legs and the insulating material, above and below the disk, are substantially equal.  With rigid metal parts and connections, the tensile strength of the porcelain is apt to be far below its estimated strength, this being due to the very inelastic nature of the material. The flexibility provided for in the present invention is as great as possible for metal parts possessing the required strength, and one of the effects thereof is to distribute the strain on the porcelain and give a uniformly high tensile strength, rendering it possible for the insulator to successfully resist shocks or heavy tensile strains.  It also reduces to a minimum, any strain due to expansion or contraction of the metal parts due to heat, which is believed to be a common cause of failure of insulators in which solid caps and pins are employed.  By making the areas of contact between the metal parts and the porcelain above and below the disk, substantially equal, the dielectric field through the insulator is reduced to a very low intensity, and the insulator is given increased strength to resist high frequency and other electrical

effects common on transmission lines.  The density of lines of stress on the two opposite electrodes is the same instead of being much greater at the smaller electrode as is the case for instance with lead covered insulated wire where a very small wire is impossible to insulate successfully.

By coupling the units together, as illustrated in Fig. 1, relative rotation of the units is prevented by reason of the seating of the heads of the bolts or coupling members, in the recesses formed in the metal caps. At the same time, said coupling members are free to move longitudinally, to permit of any relative movement of the disks toward or from each other, due to the flexibility of the legs of the caps, or to the expansion and contraction thereof under changing temperature conditions.

By employing a metal alloy to secure the metal cap in position, the joint will possess great toughness capable of resisting shocks and vibration, and the alloy will have a much greater holding power in the porcelain than any non-metal.  The tensile strength of the unit, where the alloy is used, is very much greater than where cement is employed, there being an increase of more than sixty per cent in the tensile strength.  An important electrical advantage is attained in that the direct contact between the alloy and the porcelain, eliminates all air Space in which corona can form.  Several authorities consider this very important because of the increase of the life of the porcelain under electrical strain.  A further advantage lies in the fact that as soon as the alloy is poured in place and allowed to cool for a few minutes, the insulator is ready for testing and can be shipped at once, whereas if cement is employed considerable time is required for it to set before union is completed.

Having thus explained the nature of my invention and described an operative manner of constructing and using the same, although without attempting to set forth all of the forms in which it may be made, or all of the forms of its use, what I claim is:--

1. A high tension insulator comprising a plurality of units, metal caps attached to said units and possessing flexibility, and means for coupling a cap of one unit with a cap of an adjacent unit.

2. A high tension insulator comprising a plurality of insulating units, metal caps attached to said units and possessing flexibility, and coupling members for uniting caps of different units, said caps and coupling members having complemental means for preventing relative rotation of said units.

3. A high tension insulator comprising a plurality of insulating units, metal caps having legs attached to said units, said legs possessing flexibility, and means for coupling a cap of one unit with a cap of an adjacent unit.

4. A high tension insulator comprising a plurality of insulating units having openings therein, each opening being provided with an offset recess, caps provided with legs extending into said openings, said legs having feet engaging said recesses, and means for coupling a plurality of units together.

5. A high tension insulator comprising a plurality of insulating units each provided with metal caps having legs embedded within said units, said legs being provided with offset feet, and means for coupling a plurality of units together.

6. A high tension insulator comprising a plurality of units, metal caps each having legs embedded within the insulating material of a unit, said legs possessing flexibility, and coupling members for uniting caps of different units, said caps and coupling members having complemental means for preventing relative rotation of said units.

7. A high tension insulator comprising a plurality of units each comprising a disk of insulating material, and metal caps possessing flexibility and having portions embedded in the respective disks, each cap being provided with an elongated slot, the inner face of the cap being provided with recesses arranged transversely of the slot, and coupling members having elongated heads passed through the slots of adjacent caps and seated in the respective recesses of said caps.

8. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material, and metal supporting members having each a plurality of portions embedded in a face of said disk, there being one member for each face, each supporting member being a duplicate of the other, whereby the areas of contact between the said metal parts and the insulating material being substantially the same.

9. An improvement in high tension insulators comprising a disk of insulating material, and metal members having a plurality of portions embedded in the opposite faces of said disk, the dielectric thickness of the disk being between one-fourth and one-sixth of the arcing over distance.

10. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material, and a plurality of sets of metal lingers located on opposite sides of said disk, each finger having an end attached to the disk, the areas of contact between the respective sets of fingers and the insulating material being substantially the same.

11. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material, and caps located on opposite sides of said disk, each cap having curved fingers attached to the disk, the areas of contact between the fingers of the respective caps and the insulating material being substantially the same.

12. As an improvement in high tension insulators, an insulating unit comprising a disk of insulating material, and a plurality of sets of metal members having portions embedded in the opposite faces of said disk, the areas of contact between the said metal parts and the insulating material being substantially the same, the dielectric thickness of the disk being between one-fourth and one-sixth of the arcing over distance.

13. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material, and caps located on opposite sides of said disk, each cap having curved fingers attached to the disk, the areas of contact between the fingers of the respective caps and the insulating material being substantially the same, the dielectric thickness of the disk being between one-fourth and one-sixth of the arcing over distance.

14. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material, and metal parts having substantially rigid attenuated portions possessing slight inherent flexibility embedded within said disk and attached thereto by means of metal capable of being applied in molten condition.

15. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material and metal caps having portions extending into the body of the disk and embedded in a separate metal within said disk.

16. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material provided with spaced apart recesses, and metal parts having attenuated portions extending into said recesses and embedded in a metal filling in said recesses, which filling is of a nature capable of being applied in a molten condition, said recesses and said attenuated metal parts having complemental offset portions.

17. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material, provided with recesses, and metal caps having legs extended into said recesses and embedded within a metal filling in said recesses and capable of being applied in a molten condition.

18. As an improvement in high tension insulators, an insulator unit comprising a disk of insulating material, provided with recesses having offset portions, and metal caps provided with legs extending into said recesses and provided with feet extending into said offset portions, said legs and feet being embedded in metal filling said recesses and capable of being applied in molten condition.

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

ROBERT M. JOHNSTON.

Witnesses:

W. B. HELFRE,

A. L MCLEOD.