US2061132A - Process for making spindles for lamp standards and the like and products thereof - Google Patents

Description

Nov. 17, 1936. A. H. BELL 2,051,132

PROCESS FOR MAKING SPINDLES FOR LAMP STANDARDS AND THE LIKE AND PRODUCTS THEREOF F'iled Dec. 14, 1934 I. l...l.

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INVENTOR ALLANHBELL.

ATTOR Y Patented Nov. 17, 1936 UNITED STATES PATENT OFFICE PROCESS FOR MAKING SPINDLES FOR LAMP STANDARDS AND THE LIKE AND PRODUCTS THEREOF Application December 14, 1934, Serial No. 757,424

10 Claims.

' tend as integral and unitary structures, each substantially from the base of its standard to the head thereof, the spindle being adapted to be connected directly with the base and head portion of the standard, thereby making the usual internal tie tube unnecessary.

In casting parts for standards of the kind referred to, it is of the utmost importance that the moulds shall facilitate the accurate casting of desired ornamentation of said parts, that the moulds and cast metal shall produce smooth, finished surfaces on said parts, and that the mould for any particular part may be used repeatedly in making said part, to the end that a great many of said parts may be made in the same mould and be identical with each other, and that the cost may be less than if a new mould were required for each piece cast.

To meet the requirements mentioned, the moulds are made of metal or alloy, for example, brass or bronze, having a much higher melting point than that of the metal or alloy used in making the castings in said moulds, said moulds being referred to for convenience herein, as metal moulds. So-called White metal has been found to give satisfactory results in casting lamp standard parts in metal moulds, as it may readily be selected to have the requisite melting temperature and also to provide the strength and finished surfaces of castings required for such parts. Such white metal is preferably an alloy consisting, for example, largely of zinc, the percentage of which may in some cases be as high as 95%, and the other metals in said alloy may, for example, be aluminum and copper in desired proportions. As used herein, I mean by the term white metal, any metal or alloy having physical properties adapting it to be successfully cast in metal moulds, to produce castings having finished surfaces and the strength and hardness required of the castings.

In casting hollow parts of white metal in metal moulds, where it is not important that the inner surfaces of the parts shall have exact contours or a smooth finish, the slush method of casting is effectively used, as it materially lessens the cost of making the castings and at the same time produces castings having equally as good finish and strength, as though cores were used in making said hollow parts. For lamp structures having electric bulbs, it is desirable that the parts thereof shall be hollow to permit threading electric wires therethrough to supply the bulbs with current.

Heretofore, in using white metal in slush casting the spindles for the standards of floor lamps in metal moulds, serious limitations have developed as follows. The white metal adapted to the purpose has a high coefficient of contraction which may be as great, for example, as of an inch per foot; it is usually desired that said spindles shall have at their ends, laterally projecting ornamental parts; the metal moulds are rigid and do not yield under the pressures upon them produced by the cooling and contracting castings within them; as a result, for thicknesses of spindle wall that are practically permissible, the strains developed in the hollow spindle castings by their contraction in the moulds, where the spindles have exceeded 12 to 18 inches in length, have exceeded not only the limit of elasticity, but also the limit of rupture of the casting at its weakest section, and such attempts to cast spindles longer than from 12 to 18 inches have failed, due to the rupturing of the castings. In view of this, since spindles of floor lamp standards must have a length of from 30 to 40 inches, it has been the practice heretofore in casting hollow spindles for such standards, to cast them in sections longitudinally, each at least as short as the limiting length permitted by the wall thickness of the spindle, and to assemble them on and hold them together by tie rods or tubes which are secured at their ends to the bases and heads of the standards.

By my improved process, I provide a metal mould for the spindle, in which the mould proper has the same length as the complete spindle, and spaced longitudinally of the mould, I provide lateral extensions to form corresponding lateral and ornamental projections on the cast spindle, the spacing of said extensions being such with respect to the thickness of Wall and form of the spindle, as to distribute the strains of contraction in the cooling spindle in the mould, throughout the length of the spindle, maintaining the strains of contraction in the cooling metal of the spindle at all points in said spindle, below the respective limits of rupture at said points, although at the same time, the corresponding limits of elasticity of the spindle may be exceeded where the ends of the spindle are restrained by the mould, sufficiently stretching the cooling metal in such cases, as to produce complete unitary spindles of substantially the same length as the mould proper. In this manner, I find that I am able to successfully cast such hollow spindles in metal moulds, and to so produce each spindle as a complete and unitary structure and of a length of from 30 to 40 inches without rupture, or longer if desired, since the limiting length of tubes so cast is determined only by the length or distance that the casting metal will flow in the mould; the finish and strength of such spindles are unimpaired, and said spindles may be successfully so cast by the slush method, which, briefly, consists of filling the mould with the molten metal, and then, when the cast metal adjacent the surface of the metal mould has chilled and set to a desired thickness of cast wall, removing from the mould the metal within the chilled'and set walls, that is still molten.

My invention also includes the improved tubular structures cast as described.

My invention will best be understo'od'by reference to the accompanying drawing showing a preferred exemplification thereof, in which Fig. 1 illustrates in side elevation, a floor lamp assembly having a standard construction as above described,

Fig. 2 shows in side elevation, the spindle of the standard construction shown in Fig. I, removed from the rest of the lamp construction,

Fig. 3 is a horizontal, sectional view to an enlarged scale, of the spindle shown in Fig. 2, taken along the line 3-3,

Fig. 4 shows in vertical, sectional view to an enlarged scale, the upper part of the standard construction illustrated in Fig. 1,

Fig. 5 illustrates in longitudinal sectional view, and to an enlarged scale, a part of the metal mould employed in casting the spindle illustrated in Figs. 1 and 2, and

Fig. 6 shows in central vertical, sectional view, a lamp standard embodying my invention, in which the parts thereof are secured together by a tie rod or tube, the central portion of the spindle and tie rod or tube being broken away and omitted, to more clearly show the remaining parts.

Similar numerals refer to throughout the several views.

As shown in Fig. 1, the floor lamp standard illustrated, consists of a base II], a spindle I I, a head I2, and lamps and mountings therefor not specifically described, as they do not constitute a part of the present invention.

As shown in Fig. 2, the spindle I I has threaded ends Ma, and II b for engaging similar threads carried respectively by the base In and the head I2. As shown in Fig. 3, the spindle II is hollow to form a continuous tube to permit wiring consimilar parts nected with the lamps to extend through said spindle. It will be noted that no tie rod or tube is necessary to hold the parts together, since the spindle, which may, for example, be from 30 to 40 inches long, is a single, unitary structure ex tending from the base I 0 to the head I2, to which parts it is securely connected to constitute a rigid standard. However, if desired, a tie rod or tube may be used with the spindle I I, as below described. I

The parts described are preferably cast of white metal in metal moulds by the slush method, the long spindles being successfully so cast as unitary and integral structures, as below described.

As shown in Figs. 1 and 2, the spindle I I is provided at spaced intervals throughout its length, with laterally extending ornamental projections M0, M11, the spaces between said projections longitudinally of the spindle, being preferably proportional to the cross-sectional areas of said spindle between said projections, to limit the strains of contraction between any adjacent sets of projections to less than the limit of rupture of the weakest cross section between said projections.

In Fig. 4, the head I2 is shown as extended downwardly at I2a and internally threaded to engage the threads I lb by which the head is supported. In this view is also shown threaded into the head I2, a vertically extending support I3 carrying the central and vertically disposed lamp socket Id of the floor lamp. With this construction, no tie rod or tube is necessary to hold the parts of the lamp standard tigether.

In Fig. 5 I illustrate a part of a metal mould I5 with the corresponding part of a cast spindle, for example, the spindle II, therein. As shown, the ornamental projections He and IId interlock with the corresponding mould depressions to effect the operation of my improved process as follows. The distance from center to center of the projections H0 and IId is designated a, and the center to center distance of the corresponding mould depressions is designated A. Assuming that the coefiicient of contraction of the casting metal employed is K, if the casting were permitted to contract without restraint, we would have the following result:

that is, a would necessarily be less than A by an amount equal to KA. By my process, however, the casting is not permitted to so contract. The mould I5 experiences substantially no changes in its dimensions during the casting of successive spindles, since there is little change in its tem perature. As a result, the distance A remains substantially constant, and the interlocking of the spindle projections He and Hal with the mould, maintains the distance a substantially equal to A. The strains of contraction so set up in the chilled and set wall of the casting, are effective in stretching the length a of the casting by an amount substantially equal to KA, thus exceeding the limit of elasticity of the cast metal as it is chilled and sets, but at the same time not reaching the limit of rupture of said cast metal. This result is secured by so selecting the length A for each portion of the spindle, with respect to the cross section of the cast metal for that portion, that the limit of rupture of the weakest cross-section of that portion, is not reached. In this manner I am able to cast in rigid moulds, long tubular structures from metal having a large coefficient of contraction, meaning by the term long in this connection, a length approximately equal to 20 times the external diameter of the tubular structure, or of greater length, the greater limit of said length being determined only by the distance the molten metal can be caused to flow in the mould.

In Fig. 6, I show an assembly of parts similar to that shown in Figs. 1 and 4, excepting that the parts, including a spindle I I made as above described, are secured together by a tie tube I'I extending through said parts, having threaded ends provided with nuts I 8 and 2I engaging washers I 9 and 20 which respectively press against the head I2 and the base It]. In this case, the socket I4 is shown as mounted on the upper end of the tube I1, and the head I2 includes as a supporting means, an intermediate short tubular member I6 of cast metal, resting upon the spindle II.

From the above it will appear that I provide a process for successfully casting long tubular structures in rigid moulds, that is particularly applicable where the cast metal has a large coefiicient of contraction, and that is particularly adapted to the casting of such structures having external projecting parts constituting ornamentation in relief, and that my invention includes the cast metal structures so made, as well as the process of making said structures.

In my cop-ending application filed of even date herewith, I disclose an improved process for making spindles for lamp standards and the like, and products thereof, by permitting the spindles to contract in the moulds in which they are made, which I do not claim specifically in the present application.

While I have described my invention in the particular manner exemplified, I do not limit myself specifically thereto in carrying out my invention, as I may employ equivalents of the steps of treatment described, and produce structures which are the equivalents of those described, without departing from the scope of the appended claims.

What I claim is: v

1. The process of making long unitary and tubular cast metal spindles for floor lamp standards and similar purposes in metal moulds, consisting of introducing molten white metal having a large coefficient of contraction into and filling the mould, removing from the mould the still molten metal when the white metal in contact with the mould has chilled and set to a desired thickness of tubular Wall, and restraining the chilled metal from relative movement longitudinally of the mould at spaced locations throughout the length of the casting, whereby distortional strains are produced in the casting exceeding the limit of elasticity of the chilled white metal, the spacing of said locations of restraint distributing said distortional strains throughout the length of the casting and maintaining said strains below the limit of rupture of the chilled white metal, thereby producing a. unitary spindle having substantially the same length as the mould.

2. The process of making long unitary and tubular cast metal spindles for floor lamp standards and similar purposes in metal moulds, consisting of producing a chilled tubular wall of cast white metal along the surface of the mould by the slush method of casting, said white metal having a large coefficient of contraction, and restraining the chilled metal from relative movement longitudinally of the mould at spaced locations throughout the length of the casting, whereby distributed distortional strains are produced in the casting exceeding the limit of elasticity and less than the limit of rupture of the chilled white metal, thereby producing a cast metal spindle of substantially the same length as the mould.

3. The process of making long tubular cast metal structures in rigid moulds, consisting of chilling casting metal having a large coefiicient of contraction in tubular form along the surface of the mould by the slush method of casting, and restraining the chilled cast metal at longitudinally spaced locations against longitudinal contraction, thereby producing in the cast metal strains in excess of the limit of elasticity and within the limit of rupture of the chilled cast metal, and distributing said strains throughout the length of the tubular structure.

4. The process of making long tubular cast metal structures in rigid moulds, consisting of chilling casting metal having a large coefiicient of contraction in tubular form along the surface of the mould by the slush method of casting, and restraining the chilled cast metal against longitudinal contraction at locations longitudinally spaced proportionally to the cross-sectional areas of said structure between said locations, thereby producing in the cast metal strains in excess of the limit of elasticity and Within the limit of rupture of the chilled cast metal, and distributing said strains substantially uniformly throughout the length of the tubular structure.

5. The process of making long tubular cast metal structures in rigid moulds, consisting of chilling casting metal having a large coefiicient of contraction in tubular form along the surface of the mould by the slush method of casting, and restraining the casting at spaced locations against contraction, thereby maintaining the strains of contraction in the casting below the limit of rupture thereof.

6. The process of making long tubular cast metal structures in rigid moulds, consisting of chilling casting metal having a large coefficient of contraction in tubular form along the surface of the mould by the slush method of casting, and restraining the casting against contraction at locations longitudinally spaced proportionally to the cross-sectional areas of said structure between said locations, thereby distributing the strains of contraction substantially uniformly throughout the structure and maintaining said strains below the limit of rupture of said structure.

7. A slender tubular metal structure suitable for lamp spindles and the like, consisting of a slush casting of white metal having a large coemcient of contraction, the length of said structure from end to end being at least twenty inches.

8. A long slender tubular metal structure suitable for lamp spindles and the like, consisting of a slush casting of white metal having a large coefficient of contraction, said casting being in stretched condition by substantially uniformly distributed internal strains exceeding its limit of elasticity and less than its limit of rupture, whereby said cast tubular structure is of substantially the same length as the cavity in the mould producing it.

9. A long tubular metal structure according to claim 7 wherein the casting is substantially of the same length as the cavity in the mould producing it.

10. A long slender tubular metal structure suitable for lamp spindles and the like, consisting of a slush casting of white metal having a large coefficient of contraction, said casting being in stretched condition by internal strains exceeding its limit of elasticity and less than its limit of rupture, whereby said cast tubular structure is of substantially the same length as the cavity in the mould producing it.

ALLAN H. BELL.

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