The present invention relates to improvements in apparatus for forming an insulator or other pressed article from glass or the like vitreous material while in a plastic or semiplastic state.

It is an object of the invention to provide novel means for producing an insulator which is adapted for ready removable attachment to a support.

Another object of the invention is to provide a novel apparatus for producing an insulator having an undercut cavity in one end thereof, said cavity having a shoulder adapted to receive and retain the head of a bolt or attaching screw.

A further object of the invention is the provision of a novel pressing plunger adapted to form an undercut cavity in an insulator of the type disclosed in my copending application for U. S. patent, Serial Number 402,197, filed July 12, 1941.

Other objects wm be in part apparent and in part pointed out hereinafter.

In the drawing:

Fig. 1 is a side elevational view of an insulator mold and plunger in mold charging position.

Fig. 2 is a vertical sectional view through the plunger and mold in pressing position.

Fig. 3 is a sectional elevational view through the mold after the pressing operation is completed and prior to removal of the auxiliary plunger.

Fig. 4 is a side elevational view of the pressing plunger.

Fig. 5 is a sectional plan view taken on line 5-5 of Fig. 2.

Fig. 6 is a horizontal sectional view through the insulator taken on line 6-6 of Fig. 2.

Fig. 7 is a sectional elevational view of an insulator produced by the present invention.

Generally, wire holders, or insulators, of relatively small type, are produced with the mounting pins, bolts or other attaching devices permanently molded therein. Owing to widely varying conditions of the use to which such insulators are placed, it has been found necessary to provide a great variety of shapes and types of units to meet the varying requirements of the installations. My invention provides for the manufacture of insulators having more or less universal application and permitting the use of bolts, lag screws and other such fastening devices without particular regard for the dimensions thereof.

The apparatus (Fig. 1) embodying my invention, comprises a partible mold 8, the complementary sections of which are pivoted to a common vertical hinge pin 9 and supported upon a base plate 10. A mold bottom plate 11, about which the mold sections close, completes the mold assembly which includes a cavity 12 designed to receive measured charges 13 of molten glass and impart the desired surface contour thereto during the forming operation.

A plunger assembly 13 which may be carried by a pressing head unit, is adapted to be moved downwardly into the mold by any conventional, or preferred means (not shown) for the purpose of pressing the mold charge of glass to the shape of a finished insulator A. The plunger assembly 15 comprises a tubular holder 17 which may have threaded connection at its upper end with the pressing head 16. This holder, near its lower end is formed with an annular external rib 18, the lower surface of which provides a downwardly facing seat for engagement with the upper end of a cylindrical cup-shaped mold closure plug 19 and to limit upward movement thereof relative to said holder. This plug is telescoped over the lower end of said holder and may be removably secured thereto by cap screws 20.

The closure plug 19 is formed with a flat or other shape of bottom surface 21, which imparts the desired contour to the bottom of the insulator and has depending therefrom and near one side thereof, a main plunger 22, which is of substantially rectangular block formation. A pair of opposed outwardly projecting vertical ribs 23 are formed on the main plunger 22 in the plane of the vertical surface thereof lying in proximity to the axis of the insulator. This plunger 22 produces a part of the cavity 27.

The other part, or undercut portion, of the cavity is formed by a secondary plunger 24 which is associated with the main plunger 22 and disposed substantially coaxially with the insulator. This secondary

plunger assumes the form of a rectangular head and embodies a  substantially semi-cylindrical upper portion 26 of somewhat smaller horizontal cross sectional area than the lower portion 25 or head. Thus a substantially L-shaped secondary plunger is provided. This head and upper portion are so relatively  positioned as to present a continuous vertical side surface, which, during the glass forming operation, snugly contacts the inner vertical surface of the main plunger 22, said main and secondary plungers together functioning to produce the substantially L-shape cavity indicated in Fig. 3.

A supporting rod 28 for the secondary plunger extends upwardly into the tube 17 through an axial opening 29 in the lower end of said closure plug 19. A detent 30 held in place on the tube 17 by a bolt 31 and coil spring 32 for adjusting the holding tension, projects through a side opening 25’ into the tube and bears against the

 rod 28. The pressure of the detent on the rod need only be sufficient for preventing dropping of the head by gravity and which at the same time effects a positive bearing of the head against the main plunger 22.

As the plunger is pressed into the glass (Fig. 2) the plastic material flows around the main and secondary plungers which temporarily become embedded therein. When the glass has cooled, or "set" sufficiently, the main plunger 22 is withdrawn (Fig. 3) leaving the secondary plunger 24 supported by and within the insulator. Removal of the secondary plunger is accomplished by sliding it laterally into the portion of the cavity 21 formed by the main plunger 22, to the successive positions indicated by broken lines in Fig. 3.

The secondary plunger 24, owing to its general L-shape, produces an undercut or inwardly facing shoulder 34 within the cavity 27 which is adapted to form a retaining, or bearing, surface for engaging the head of an attaching bolt 35 indicated by broken lines in Figs. 6 and 7.

Modifications may be resorted to within the spirit and scope of the appended claims.

I claim:

1. Glass forming apparatus comprising a holder, a plug on the holder for the charge receiving end of a mold, said plug having an axial opening in the bottom thereof, a main plunger formed integral with and depending from the plug at one side of the opening, said plunger being substantially rectangular in cross-section, a secondary plunger disposed axially of the plug and abutting the main plunger, said secondary plunger comprising a head of rectangular cross-section and an integral upper portion of reduced semi-cylindrical cross-section with respect to the head, a stem connected to the last named portion and extending upwardly through the opening, and means carried by the holder for readily releasably holding the stem in said opening.

2. Glass forming apparatus comprising a holder, a cuplike closure plug on the holder for the charge receiving end of a mold, said plug having an axial opening through its bottom, a main plunger depending from said plug at one side of the opening, a secondary plunger arranged alongside of and in sliding contact with the main plunger and including a head of rectangular cross-section and an integral upper portion of reduced semi-cylindrical cross-section with respect to the head, a stem connected to the secondary plunger and extending into the cup through said opening and means carried by the holder normally releasably holding the stem in said opening.

3. Glass forming apparatus comprising a tubular holder, a cup-like closure plug on the holder for the charge receiving end of a mold, said plug having an axial opening through its bottom, a main plunger depending from said plug at one side of the opening, a secondary substantially L-shaped plunger arranged alongside of and with its longest vertical surface in sliding contact with the main plunger, a stem connected to the secondary plunger and extending into the cup through said opening, and a spring device carried by the holder frictionally engaging the stem to releasably hold it in said opening.

   MINOT K. HOLMES.