US 2707774 A
Description (OCR text may contain errors)
United States Patent TERMINAL BLOCKS Bernhard Keller, Winterthur, Switzerland Application February 3, 1951, Serial No. 209,255 7 Claims priority, application Switzerland March 5, 1950 1 Claim. (Cl. 339-198) The present invention relates to terminal blocks adapted for electrically connecting two or more electrical conductors.
Many kinds of terminal blocks are known, some of which are made of ceramic materials such as porcelain L or steatite, whilst others are made of thermosetting resins such as phenolic resins of the kind sold under the registered trade-mark Bakelite. Ceramic terminal blocks have the disadvantage of being rather heavy because they must be manufactured with relatively thick walls,
whereas terminal blocks of synthetic resin are inclined to be brittle. In both cases, unless proper care is used tightening the screws of the terminal blocks will cause cracks in the screw holes, thus impairing insulation. Moreover the terminal blocks are easily broken by vibrations occurring in transport or the screws may be shaken out so that screwed parts are lost.
According to the present invention there is provided a terminal block adapted for electrically connecting two or more electrical conductors, comprising a body of Hence, the screws will be frictionally held throughout their entire length of travel in said holes; in other words, they are held between their positions fully screwed into the sleeves and their positions fully screwed out of the sleeves.
The invention also provides a terminal block for connecting two or more electrical conductors, comprising a body of insulating material, one or more electrically conductive sleeves housed in said body, said sleeves having screws engaging therewith and adapted to secure conductors therein, and guide holes in said body through which screws are inserted in said sleeves, the relative dimensions of said holes being such that said screws are frictionally held against falling out or being shaken out of said holes by engagement with the sides thereof whilst the material of which said body is composed is sutiiciently elastic to permit desired movement of said screws in their sleeves.
The invention further provides a terminal block for connecting two electrical conductors, comprising an insulating body of synthetic resin thermoplastic material of predetermined hardness and elasticity, screws for holding the conductors in said block, and guides for embracing the heads of the screws, even when not screwed in, to prevent the screws from dropping out, said hardness and elasticity being such that the screws can be readily screwed in whilst so embraced.
Several embodiments of the present invention will now be described, by way of example only, as shown in the accompanying drawings, in which:
Figure 1 shows an underneath view of a terminal block in strip form,
Figure 2 shows a side elevation of the terminal block of Figure 1, and
Figure 3 shows a plan view of the terminal block of Figure 1.
Figure 4 shows, on an enlarged scale a section along line IV-IV in Figure 3, and
Figure 5 shows, on an enlarged scale, a section along line V--V in Figure 3.
Figure 6 shows a sectional side elevation through an alternative form of terminal block for use as a plug socket, whilst,
Figure 7 shows an alternative way of connecting the conductors to the terminal block of Figure 6, and
Figure 8 shows a plan view of the terminal block of Figure 6.
Referring firstly to Figures 1 to 5, the body 1 of the terminal block is made of polyvinyl-chloride, a material which can be made to combine relatively high elasticity and breaking strength with good insulating properties.
The body 1 has a plurality of holes 3 each adapted to house a metal junction sleeve 7. Each sleeve 7 has a hole s'therethrough in opposite ends of which are inserted the conductors 9 and 11 which are to be joined, screws 10, having a screw threaded shank and an enlarged head, pressing the conductors 9 and 11 against the inner wall of the sleeve 7 and holding them therein.
On the top of the body 1 screw guides 2 are formed having holes 6 of substantially uniform diameter through out their lengths through which the screws can be inserted into screw-threaded holes 7a in the sleeves 7. The diameter of the holes 6 is greater than the diameter of the screw-threaded holes 7a and is such that the holes 6 grip firmly the enlarged head of the screws 10, but because of the resilience of the material of which the body is composed the screws can readily be screwed in and out. In other words, the diameter of the holes is slightly less than the diameter of the screw heads. The depth of the holes 6 is greater than the length of the screw threaded shanks of the screws 10 so that even when a screw 10 is fully screwed out of its hole 7a the head is still held by the walls of the screw guide 2 so that the screw cannot fall out or be shaken out by vibrations. Holes 4 are provided in the body 1 to facilitate the severing of a required number of sections from the block. The terminal blocks can, of course, be made originally in a predetermined number of one or more sections, instead of being made in long strips which are subsequently cut-up. Holes for fixing screws may be provided if required.
Figures 6 and 8 show a terminal block which is adapted for use as a plug socket, the body 31 being of polyvinyl chloride. Metal junction sleeves 14 and 15 are housed in holes and 19 respectively, and further holes 21 are provided through which screws 22 and 23 are inserted in screw-threaded holes 14a and 15a in the sleeves 14 and 15 respectively. The holes 19, 20 and 21 are of similar dimensions and as in the previous construction the diameter and depth of the holes relative to the screws 22 and 23 is such that the screws are held firmly therein and cannot shake out. When driven home the screws 22 and 23 press the conductors 16 and 17 against the wall of the sleeves 14 and 15 and hold them firmly therein. Sleeves 14 and 15 also serve as sockets into which the prongs 12 and 13 of a plug 32 are inserted. An opening serves as a guide and retainer for a fixing screw 18 by which the terminal block can be secured to a supporting member.
Figure 7 shows the same body 31 as in Figure 6 but with a single sleeve 24 extending almost right through the hole 21. The screws 28 and 29 are inserted through the holes 3 19 and 20, to hold the conductors 26 and 27 in contact with the wall of the sleeve 24. In this way the same body can be adapted for various purposes.
Although polyvinyl-chloride is preferred as the material for the body of terminal blocks according to the invention, other synthetic resinous plastic materials, particularly thermoplastic materials, having the desired properties of elasticity, breaking strength and insulation may also be used. The properties of the basic resins may be modified, for example, with plasticisers, to give appropriate properties.
The metal parts used in the terminal blocks may be coated prior to assembly with insulating varnish to enable the insulating walls of the terminal blocks to be made thinner.
What I claim is:
A terminal block for electrically connecting electrical conductors comprising, a deformable and resilient electrical insulating body having an open first hole and an open second hole of substantially uniform diameter throughout its length disposed at substantially a right angle to the first hole and issuing into the same, a metal sleeve fitted in said open first hole in the body and removably receiving a conductor lengthwise therein and having a screw threaded bore therein in alignment with said open second hole in the body and of smaller diameter than that of said open second hole, a clamping screw having a screw threaded shank screw threadedly received in said screw threaded bore in the sleeve and clamping the conductor in the sleeve and having an enlarged head received in said I open second hole in the body, the diameter of said enlarged head of the clamping screw being slightly larger than the diameter of said open second hole for effecting a frictional grip therebetween by deformation of the deformable and resilient inner wall of said open second hole by said enlarged head to prevent free movement of the clamping screw with respect to the body but to permit forced movement thereof, and the length of said screw threaded shank of the clamping screw being appreciably less than the length of the open second hole in the body so that the enlarged head of the clamping screw will not be forced completely out of said open second hole in the body even though the screw threaded shank of the clamping screw should be completely unscrewed from the screw threaded bore in the sleeve, whereby the clamping screw is at all times frictionally gripped in the open second hole of the body.
References Cited in the file of this patent UNITED STATES PATENTS 1,825,867 Hopland Oct. 6, 1931 1,970,078 Dillon Aug. 14, 1934 2,178,092 Werner Oct. 31, 1939 2,399,402 Spengler Apr. 30, 1946 2,424,986 Hubbell et al Aug. 5, 1947 FOREIGN PATENTS 59,918 Denmark June 29, 1942 535,532 Great Britain April 11, 1941 587,574 France a- Jan. 20, 1925 872,768 France June 18, 1942 OTHER REFERENCES Vinylite Resins, copyright 1942, page 20, Cat. Plastics.