US2693024A - Method of making insulated pull chains - Google Patents

Description

NOV. 2, 1954 WQLD METHOD OF MAKING INSULATED PULL CHAINS Filed Mapch 24, 1952 United StatesPatent ()fiice METHOD @F MAKIN G MSULATED PULL CHAINS Trygve Wold, Georgetown, Ontario, Canada, assignor to & Stone Lindted, Toronto, Ontario, Canada, a corporation of Canada Application March 24, 1952, Serial No. 278,224

Claims priority, application Canada January 17, 1952 1 Claim. (Cl. 29155.52)

This invention has to do with the manufacture of insulators and more particularly of insulators of the type used along the length of pull chains for electric switches. These insulators are commonly known as secondary insulators.

insulators of this particular type are used to break the electrical conductivity of pull chains used on electric switches when such switches are located in a damp room such as a bathroom or basement. The present practice concerning the installation of the insulators is such that considerable loss of time and expense is experienced when it is necessary to use these insulators. Normally, the pull chains are made in the continuous length and attached to the switch. If an installation is made in a damp location the chain must be broken and an insulator inserted between the two broken ends.

This practice has many drawbacks. In the first place, the insulator in common use is made up of three pieces; an insulating shank, two members attached to the end of the shank and adapted to engage the ends of the chain. This particular construction necessitates the installation of the insulator by hand with the consequent loss of time. If the installation is done at home by the householder, the possibility of an insecure installation is very great and an insulator so installed may be of little or no use when it is needed.

The primary purpose of this invention is to provide a method of incorporating an insulator in the chain as a unit thereof in such a manner that its insulating properties may be realized to the best advantage. Another important object of this invention is to provide for installing an insulator in a pull chain economically and quickly using assembly line production methods.

The insulator to be inserted in a pull chain which is the embodiment of this invention is moulded of a plastic material of high tensile strength and of good insulating qualities. This insulator may be installed singly in one length of chain to serve as a single pull chain or may be moulded about a long length of chain at spaced intervals so as to provide any number of pull chains which may be cut from a single length of chain. One feature of the method of the present invention is that the pull chains may be produced from a continuous chain length. It will be appreciated, however, that two separate chain lengths may be joined together with the plastic insulator unit without departing from the spirit and scope of the invention. This method of construction enables a manufacturer to produce a better quality insulator for pull chains more economically than was possible with the previous type of chain insulators.

Other features and advantages of the invention will be apparent from the following description when read in conjunction with the appended drawings in which:

Figure 1 is a perspective view of the insulated chain.

Figure 2 is a sectional view of the insulator and chain.

Figure 3 is a plan view of the insulator and chain.

Figure 4 is a perspective view of the chain with the plastic gripping knobs and the ornamental mouldings attached.

Referring now to the drawings it will be seen that the insulator comprises a piece of plastic moulded about the chain 11 and extends in a longitudinal direction over a plurality of links of the chain. In practice it has been found satisfactory to have the insulator extending so as to enclose five links. In the centre of the insulator 10 there is a hole 12 which passes completely through the insulator and breaks the chain. The

purpose of this hole is to provide the required discontinuity in the conductivity of the chain. Various means can be applied to effect the removal of the link inside the insulator among which are punching a hole through the insulator or drilling a hole through the insulator or removing the link prior to moulding the insulator about the broken ends of the chain. if the link is to be removed during the moulding operation an instrument is mounted within the mould which will engage a link of the chain and remove it as the mould is being closed and the plastic being introduced therein. If the link is to be removed after the insulator has been moulded about the chain a hole is either drilled or punched through the insulator to effect the removal of the link. in practice the removal of the link before the moulding of the insulator occurs is not practical as mass production methods are desirable and can only be effected if a continuous length of chain is used upon which the insulators are moulded at spaced intervals. After the moulding process is complete the chain may be cut into the appropriate lengths each length containing one insulator and these chains installed upon the switches with which they are to be used.

The moulding operation comprises the placement of a length of chain across the mould and securing it in that position. The moulds are then closed about the chain and the plastic is injected into the mould to completely surround the chain and form the insulator. At some time during this process a link has been removed from the chain in a position such that the vacant spot left by the removal of the link will be in the centre of the plastic insulator. The removal of this link can be accomplished either during, before or after the moulding operation. if it is accomplished during the moulding operation, then it is removed by a projection on onehalf of the mould which as the mould closes, engages a length of the chain and forces it against a cutting edge on the other halt of the mould thereby breaking the chain and removing a link. if it is accomplished after the moulding operation then it is done by either boring or punching a hole through the insulator which removes a link of the chain in the process. If it is done before the moulding operation the chain is broken before it is placed across the mould and the two broken ends project into the mould from either side leaving a space therebetween to provide the required discontinuity in the conductivity of the chain.

In addition to moulding an insulator into the chain as has been described above, it is contemplated by this invention to mould at random or at predetermined intervals configurations of plastic on the chain for ornamental purposes.

It is further contemplated to mould a pull knob at the end of the chain to facilitate the grasping of the chain. This pull knob may be made of luminously coated or impregnated material to facilitate its location in the dark. These embodiments of the invention may be seen in Figure 4 in which 20 is the pull knob and 21 the ornamental moulding.

It will be obvious from the foregoing description that the invention allows an insulator to be mass produced with an efficiency and economy far superior to that possible with insulators made by previous methods. The insulator produced according to the invention cannot be removed from the chain as it is moulded as an integral part thereof and is actually stronger than the chain itself. Its insulating properties are superior to those of insulators previously used. Various colours can be used in the manufacture of these insulators in order to provide an insulator which will blend or contrast with the lampholder or other interior decoration.

In the preferred embodiment of the invention a phenolic formaldihyde of the thermosetting type has been found to be most suitable. This composition possesses high tensile strength together with good insulating properties.

I claim:

A method for providing an insulator to electrically insulate one portion of a chain from another portion thereof comprising the steps of molding a body of insulating plastic about the chain to engage therewith and after the molding operation removing plastic and chain material so as to form a hole through said plastic body, said hole passing through the path of the chain and severixlilg it to provide discontinuity in the conductivity of the c am.

References Cited in the file of this patent Number 5 1,104,009 1,419,644 1,769,245 2,298,591 2,401,451

UNITED STATES PATENTS Name Date Seguin July 21, 1914 Recker June 13, 1922 Tregoning July 1, 1930 Ross Oct. 13, 1942 Arey June 4, 1946

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