GB2330016A - An electrical terminal housing - Google Patents

Abstract

An insulating housing (2) for an electrical terminal (36) comprises a hollow main body having a first aperture (12) in a first side and a second aperture in a first end, the second aperture being closeable by an insulating lid (11) including a third aperture (14), the main body also having a fourth aperture in a second end and first and second engaging means (17, 18) on the first side of the main body and a side opposite the first side respectively, the first and second engaging means being arranged for cooperation so that a plurality of insulating housings (2) can be secured together by their respective engaging means (17, 18), the size and shape of the first and third apertures (12, 14) being inaccessible to manual intrusion.

Description

An Electrical Terminal Housinq Technical Field and Background Art The present invention relates to an electrical terminal housing comprising an insulating body. Said housing may include a means within said body for connecting an electrical lead to a mounting. More particularly, the invention relates to a housing for an electrical terminal in which the terminal has an electrical connection portion to facilitate the connection of a wire. Such terminals may further include extending elements which serve to electrically connect the terminals to an apparatus which can supply or receive electrical loads. The housing prevents accidental touching of a live terminal and reduces the risk of electric shock.

Terminal blocks are extensively used in the electrical and electronics industry as a means of connecting wires to a piece of apparatus. For example, in electrical audio systems speaker wires can be connected to power amplifiers.

Conventional terminal blocks comprise a conductor located within an insulated body. Said blocks further comprise a means of clamping a wire to the conductor, usually by means of a screw, said screw acting directly on the wire or acting indirectly on the wire through a clamping plate.

While such terminal blocks are well known to facilitate the straightforward connection of wires they also present possible safety hazards because the live electrical parts of the block are accessible. The design and use of terminal blocks is dictated by safety regulations. These specify that terminal blocks cannot be used for high voltage connections if any of the conductive elements can be touched. As a result, conventional terminal blocks must be located within a housing if the voltage is in excess of 34 volts.

In addition, it should be noted that British International Safety Standards (those concerned with the checking of the inaccessibility of live parts of electrical components) require that all high voltage electrically live components be inaccessible to a standard "finger".

Therefore, the housings used in high voltage situations must generally only be accessible by means of the use of a tool of some kind and not simply by manual opening.

If it is desired to make a permanent electrical connection, it is conventional to use spade terminals as a means of making a connection of a wire to a terminal block.

The blocks conventionally comprise two metal conductive plates, with a means to clamp the two plates together. In order to make a connection a spade terminal is pushed between the two plates and is held there by the clamping means. Such means preferably comprises a screw or a spring loaded push button. Such conventional terminal blocks generally have fully exposed live metal parts and therefore must be located inside an insulating housing if high voltages are present.

One type of terminal block known in the art is made in discrete units containing a fixed number of conducting elements encased in a plastics material. It is usual to chop up the block to obtain the required number of elements when a smaller block is required. Similarly, a number of blocks can be mounted consecutively to make up larger groups of connections. However, such blocks cannot be adapted to carry different types of connectors, e.g. ones which fit into circuit boards.

There is a need in the art for terminal blocks which are capable of carrying high voltages safely, having conductive parts which cannot easily be touched and which can be adapted to different types of electrical connectors.

There is a further need for a terminal block which does not need to be cut from a larger strip and which can be easily connected to other terminal blocks if a plurality of connections are required.

These and other problems are solved by the present invention.

Statement of Invention and Advantages According to a first aspect of the present invention, there is provided an insulating housing for an electrical terminal comprising a box shaped main body having a first aperture in a first side and a second aperture in a first end, the second aperture being closeable by an insulating lid including a third aperture, the main body also having a fourth aperture in a second end and first and second engaging means on the first side of the main body and a side opposite the first side respectively, the first and second engaging means being arranged for cooperation so that a plurality of insulating housings can be secured together by their respective engaging means, the size and shape of the first and third apertures being inaccessible to manual intrusion.

According to a second aspect of the present invention there is provided an electrical terminal comprising a conductive tag, means for releasably securing a wire in electrical connection to the tag and an electrically insulating housing surrounding the securing means and having the tag projecting therefrom for connection to an external circuit, the housing having a first aperture allowing a wire held by the securing means to pass through the enclosure, a second aperture and a lid which can close the second aperture, the lid being releasably fixable in the closed position and incorporating a third aperture allowing access to the securing means, the size and shape of the first and third apertures being such that manual contact with the securing means is impossible when the lid is closed.

Detailed Description of the Invention The accompanying Figures serve to illustrate examples of the present invention.

Figure 1 shows a perspective view from one side of an insulated housing for a terminal unit embodying the invention; Figure 2 shows a perspective view from the other side of the insulating housing shown in Figure 1; Figure 3 shows a cross-section through a terminal unit including the housing of Figure 1 together with a first type of tag and an insulating bush; Figure 4 shows a cross-section through a housing according to Figure 1 containing means for fixing the housing to a surface; Figure 5 shows a number of housings joined to provide a multiple terminal block; Figure 6a shows a cross section through a terminal unit including the housing of Figure 1 together with a first type of tag without an insulating bush; and Figure 6b shows a cross section through a terminal unit including the housing of Figure 1 together with a second type of tag with an insulating bush, similar parts having the same reference numerals throughout.

The invention will now be described, by way of example only, with reference to the above Figures.

A terminal unit 1 includes an electrical terminal 31 having a bolt 32 to tighten a clamp formed by two opposed clamping members 33. The clamping members 33 serve to grip an electrically conductive wire or a spade terminal of a wire (not shown). The lower clamping member 33 includes a threaded hole which cooperates with the bolt 32.

Alternatively, the bolt 32 can cooperate with a nut to tighten the clamp. The head of the bolt 32 includes a crossed slot 35 so that the bolt 32 may be tightened by a tool such as a screwdriver. Alternatively, the bolt 32 could bear some other driving means such as a groove for cooperation with a screwdriver or a hexhead or socket for cooperation with a spanner or Allen key, or be adapted for manual operation.

The clamping members 33 are in electrical contact with a tag 36. The tag 36 can be inserted into and permanently electrically connected to a circuit board or electrical device. The lower clamping member 33 is preferably integrally formed with the tag 36. Once the bolt 32 is tightened, the wire or spade terminal thereof is enclosed between the clamping members 33 and current can pass from the wire to the circuit board or electrical device through the tag 36. In the embodiment of Fig. 3, the tag 36 and the lower clamping member 33 are integrally formed.

Alternatively the tag 36 could be integrally formed with the upper clamping member 33 or be formed separately from the clamping members 33 and connected to them later.

The electrically live parts of the terminal unit 1 are enclosed within a non-conductive enclosure 2. The enclosure 2 may be made from a thermo plastic material or a thermo setting material. The enclosure 2 is substantially box shaped and comprises four sides 10, a lid 11 and a base section. The enclosure 2 has a slot 12 with one side domed through which a wire or spade terminal can be inserted between the clamping members 33 when the bolt 32 is loosened. Thus, the wire or spade terminal can be electrically connected to the tag 36 as described above.

The slot 12 is sized to fit closely around a spade terminal or wire and to be too small to allow a standard IEC test finger (having the dimensions specified by BSEN60065/IEC65) to pass through the slot 12 to contact the clamping members 33. The slot 12 is surrounded by a protruding, substantially circular part 13 to ensure that all exposed conductive parts of a spade connector or wire are contained within the enclosure 2. However this may not be essential, depending upon the relative dimensions of the enclosure 2 and the exposed conductive parts of the spade connector or wire.

The lid 11 contains an aperture 14. The aperture 14 is of such a size that it does not allow access by a standard finger, but can allow access by the tip of a screw driver or some similar tool to the bolt 32 to allow the clamping members 33 to be tightened or loosened as described above. The enclosure 2 will hold the electrically live parts of the terminal unit 1 therein.

For example, the lower clamping members 33 may sit upon a support surface 22 formed by a small ledge or set of protuberances within the enclosure 2. Further, in order to prevent the electrical terminal 31 falling out of the enclosure 2 when the lid 11 is open, a number of barbs (not shown) are formed on the electrical terminal 31. These barbs lock the conductive parts into the enclosure 2 so that they cannot be removed. The use of such barbs is not essential and some other retaining means could be used if preferred.

Further, the shape of the inner surface of the enclosure 2 below the clamping member support surface 22 is preferably arranged to retain a nut against rotation, for example by having a hexagonal cross section. If the bolt 32 cooperates with a nut, this will prevent the nut rotating.

The lid 11 is securable in the closed position by a deformable tongue 15 which can be located within a corresponding aperture 16 on one of the sides 10 of the enclosure 2. The tongue 15 and aperture 16 cooperate so that when the lid 11 is closed the tongue 15 is retained within the aperture 16. As a result, the lid 11 can only be opened by pushing the tongue 15 out of the aperture 16.

The tongue 15 and aperture 16 are sized so that a standard finger cannot enter the aperture 16. Thus, the lid 11 can only be opened for access to the electrical terminal 31 by using a suitable tool, such as a screwdriver, to push the tongue 15 out of the aperture 16.

Preferably the end of the tongue 15 is formed as a cam surface to facilitate automatic engagement of the tongue 15 within the aperture 16 when the lid 11 is closed.

The enclosure 2 and lid 11 are preferably integrally formed by moulding.

The enclosure 2 is designed so that the enclosures are modular and a number of enclosures 2 can be fitted together to form terminal blocks comprising from two enclosures to an unlimited number. Each enclosure 2 has an engaging means 17 and a locating means 18 on respective opposite sides of the enclosure 2 together with associated securing means 19 and 20 respectively. In a preferred embodiment the engaging means 17 is substantially rectangular with outwardly angled edges so that it can be slidingly or snap fitted into cooperating locating means 18. This will require pressing together or a relative sliding movement of two enclosures 2. Securing means 19 comprises a spring finger 19 with a protrusion l9a while securing means 20 comprises a cooperating detent. The securing means 19 and 20 cooperate to ensure that once enclosures 2 are engaged together to form a module, the enclosures 2 cannot be slid apart from one another until the securing means 19 and 20 are released.

In a preferred embodiment, two grooves 21 are cut through the wall of the enclosure 2, one on each side of the spring finger 19 and the protrusion l9a of the spring finger 19 bears a cam surface 19b and an opposite surface 19c parallel to an opposing wall of the detent. Once the lid 11 is closed, the edge of the lid 11 bears against the inner surface of the spring finger 19 behind the protrusion 19a so that the spring finger 19 cannot be moved to withdraw the protrusion 19a from the detent and the two engaged enclosures 2 cannot be separated. Once the lid 11 has been opened, the spring finger 19 can be pushed back within the enclosure 2, thus releasing the protrusion 19a from the corresponding detent of the securing means 20.

The engaged modules can then be separated by sliding engaging means 17 out of locating means 18. The cam surface l9b of the spring finger 19 allows two enclosures 2 to be engaged by sliding together even when their lids 11 are closed. The caming action of the cam surface 19b allows the spring finger 19 and corresponding securing means 20 to deform to allow the protrusion 19a to reach and enter the detent. However, if it is attempted to slide the two enclosures apart without opening their lids 11, surface 19c of the spring finger 19 comes into face to face contact with the parallel wall of the detent, preventing separation of the two enclosures.

Figure 5 shows a number of enclosures stacked together to form a single terminal block. Enclosures 50, 51 and 52 are engaged by respective interconnecting means 17 and 18.

Enclosures 53 and 54 have been slid away from the main stack of enclosures, their lids 11 having been opened to allow their respective spring fingers 19 to be moved such that the modules 53 and 54 can be slid apart.

The conductive parts of the terminal unit 31 may be in various forms. Figure 3 shows a terminal unit with a first type of tag 36 which is surrounded by an non-conductive insulating bush 37. The insulating bush 37 may be of the same material as the enclosure 2 and may be integral therewith. Alternatively, the insulating bush 37 can be made separately and securely fitted onto the enclosure 2.

The insulating bush 37 allows the terminal unit 1 to be insulatively mounted on a conductive surface without coming into electrical contact with the mounting surface, eg it can be mounted on a metal enclosure and all electrical contacts will be isolated from the enclosure. However, if it is desired to mount the assembly directly onto an insulated system, for example a printed circuit board, the insulated bush 37 can be omitted and the tag 36 shortened.

Such a device is shown in Figure 6a. Figure 6b shows a second type of tag 61 often used in the electronics industry. The conductive tag 61 shown in Figure 6b is provided with an insulated bush 37.

The inventive terminal unit may incorporate any type of tag, with or without an insulating bush.

A further advantage of the present invention is that the individual terminal units or multiple terminal units assembled into terminal blocks can easily be removably fixed to a surface.

The enclosure 2 can be used to retain a means to fix the enclosure to a surface. One example of this is shown in Figures 4a and 4b. In Figure 4a a hexagonal nut 71 is located within the enclosure 2. As explained above, the inner surface of the lower part of the enclosure 2 may include a hexagonal cross section to secure a nut against rotation. As a result, the nut 71 cannot rotate. A bolt 72 is passed up through a hole in a surface and locates in the nut 71. The bolt 72 is then tightened to clamp the mounting surface and the enclosure base between the nut 71 and bolt 72, thus fixing the enclosure 2 onto the surface.

In an alternative arrangement shown in Figure 4b, a bolt 73 is passed down through an enclosure 2 and into the surface on which the enclosure 2 is to be mounted.

The base of the enclosure 2 includes an internal bearing surface 23 against which the nut 71 or head of the bolt 73 bears to secure the house 2 in place.

The fixing units formed by enclosures containing fixing means instead of electrical connectors may be located anywhere within or at the ends of a strip of joined terminal units as shown in Figure 5 where the enclosures 50 contain fixing means.

The individual terminal units may be made of any coloured material. The enclosure 2 can be made in different colours in order to ease identification of the function of the contents within the enclosure. For example, identification of the polarity of individual connectors can be given, ie positive can be identified by a red enclosure, negative by a black enclosure and earth with a green or yellow enclosure. Alternatively, or additionally, the enclosures containing fixing means can be a different colour to those containing electrical connectors.

The above description is intended as an example only and it will be clear to the person skilled in the art that many variations can be made within the scope of the present invention.

Claims (2)

1. CLAIMS 1. An insulating housing for an electrical terminal comprising a box shaped main body having a first aperture in a first side and a second aperture in a first end, the second aperture being closeable by an insulating lid including a third aperture, the main body also having a fourth aperture in a second end and first and second engaging means on the first side of the main body and a side opposite the first side respectively, the first and second engaging means being arranged for cooperation so that a plurality of insulating housings can be secured together by their respective engaging means, the size and shape of the first and third apertures being inaccessible to manual intrusion.
2. 2. A housing as claimed in claim 1 further including a conductive tag together with a means for releasably securing a wire in electrical connection to the tag, the tag projecting from said housing for connection to an external circuit, the housing having a first aperture allowing a wire held by the securing means to pass through the enclosure.