To all whom it may concern:

Be it known that I, HOMER BROOKE, of the city, county, and State of New York, have invented a new and useful Improvement in the Manufacture of Insulators and other articles of glass, of like form and character, of which the following is a full, clear, and exact description, reference being had to the accompanying drawing, forming part of this specification; and in which--

Figures 1 and 2 represent sectional elevations of a first and secondary press used in the manufacture of insulators, in accordance with my improvement, the same being shown as in the act of producing or forming an insulator.

Figure 3, a plan of the mould, with insulator therein.

Figure 4, a view, in perspective, of the insulator, to the manufacture of which my improvement relates.

Similar letters of reference indicate corresponding parts.

My improvement more especially relates to the manufacture of glass insulators, formed with a countersink and hole or recess at the base of the countersink, with a screw-thread cut in it.

Great difficulty has been experienced in the manufacture of such articles by the process which has heretofore obtained, of forming the insulator, countersinking, and making the hole and cutting the screw-thread therein, by one and the same operation, through the agency of a screw-press. This is both a slow and imperfect process, causing an objectionable amount of heat (which necessitates stoppage and cooling) to be communicated to the plunger, on account of the long retention of the latter within the glass, as necessary to cut the screw-thread, over or above and in addition to merely forming the insulator, and pressing the countersink and hole therein; and is, furthermore, objectionable on account of the liability of the glass to be rotated in the mould, which makes the insulator "stringy" or "cordy.”

By my improved process, I first "form" the insulator, and make the hole, or countersink and hole therein, by the action of a lever or quick-press, and before the glass has set in the mould, transfer the latter, with the hot insulator in it, under a slow or screw-press, to cut or form the thread in the hole of insulator. This latter press has a retainer on its plunger, to preserve the shape of the insulator, while the screw-thread is being cut or formed in its hole, said retainer preferably being detachable to meet wear and renewal.

In this way the manufacture of screw-insulators is expedited and improved, excessive heating of the plunger or plungers being avoided, and a most perfect insulator produced.

In the accompanying drawing-

A represents the insulator.

b, its countersink;

c, its hole; and

d, the screw-thread formed therein.

B is the mould in which the hot glass is put, and that is first placed under the plunger and "former" of a quick or lever-press, C, to shape the insulator, and form the countersink b and hole c therein.

This is a quick operation, and does not give time for the heating of the plunger or “former," nor allow of the glass setting in the mould, which, with the hot insulator in it, is then transferred under a screw-press, D, the plunger of which requires to rotate, as well as to descend, when performing its work; but such action, though comparatively slow, is much quicker than if it had the whole work to perform of forming, recessing, and threading, instead of having only the screw-thread d to produce, in the already formed hole c, as is here the case, and whereby excessive heating of the plunger or its tap attachment is avoided. The division of the work between the presses likewise gives pause or rest to them.

To prevent injury to the moulded insulator, while the screw d is being formed In it, the plunger of the press D is made with, or has fitted on it a form-retainer, E, which fits the countersink b, previously produced by the first press c, and which carries or is made with a screw-extension or tap, e, to produce the screw-thread d in the insulator. This retainer E it is advisable to make detachable, as represented in the drawing, by giving it a socketed connection with the plunger, and securing it by a locking-pin, to allow of its being Interchanged or renewed, as wear or other circumstances may require.

What is here claimed, and desired to be secured by Letters Patent, is--

1. The process of manufacturing glass insulators, having screw-threads in their interior, by first forming them, and making the cavity or hole therein by one press c, and then transferring them, before setting and while in the mould, to or under a second press, D, that produces the Screw-thread in their interior, substantially as specified.

2. The screw-press D, having Its plunger fitted or provided with a form-retainer, E. and Screw-tap e, for operation on the heated glass in the mould, after the same has been shaped or formed, externally and internally, by previous pressure, essentially as herein set forth.

   HOMER BROOKE.

Witnesses:

FRED HAYNES,

JAMES J. CAMPBELL.