FR2667989A1 - CONNECTING TERMINAL WITH IMPERSIBLE SCREW AND TERMINAL BOARD USING TERMINALS OF THIS KIND. - Google Patents

Abstract

The connection terminal according to the invention comprises a tightening screw (8) which is screwed into the threaded hole (6) of a connection part (3) integral with the body of an apparatus and a bracket (9) mounted captive under the head of the screw (8). The screw (8) has a second thread (16) formed on its head (10) which engages at the end of normal unscrewing in a threaded hole (12) made in a part integral with the body, so as to ensure the continuation of the axial retention and the backward movement of the screw (8) when the latter continues to undergo an unscrewing action during and after its extraction from the tapped hole (6). The terminal according to the invention can be used to connect to the device, both stripped wire ends and open or closed terminals.

Description

-1-

  CONNECTING TERMINAL WITH IMPERSIBLE SCREW AND TERMINAL USING

TERMINALS OF THIS KIND.

  The present invention relates to a captive screw connection terminal, which can be used in an electrical appliance to connect to the latter both bare wire ends, without any particular preparation, and

  open or closed lugs attached to these ends.

  In general, we know that to allow the

  connection of electrical wires, electrical appliances

  triques are fitted with screw terminals A type of terminal used

  Frequently read comprises a clamping screw whose threaded tail is capable of being screwed into a tapped hole of a fixed connection piece; a stirrup is mounted captive between the threaded part of the tail and the head of the screw. The screw-stirrup assembly is arranged inside a housing produced in a body made of insulating material and whose dimensions allow a displacement in translation. of the stirrup when screwing and

unscrewing the screw.

  To allow the passage of a screwdriver, the housing communicates with the outside of the device through an orifice located opposite the screw head and formed in the body or in a terminal cover fitted to the body The electric wire is inserted between the threaded tail of the screw and a wall of the housing; it is clamped between 2 - the stirrup and the connecting piece under the effect of the

  translation of the stirrup resulting from the screwing.

  In such terminals, the captivity of the screw is usually ensured by means of a stop integral with the body and against which the screw or the stirrup abuts

  and axially lock, at the end of unscrewing.

  It is clear that this solution does not allow the connection of a conducting wire provided with a closed terminal which requires, for the engagement of the terminal, that the screw is

  axially spaced from the connection piece.

  To remove this drawback, the Applicant also

  ment proposed (patent FR A 2 557 739 of December 30, 1983) a connection terminal, also involving,

  axially guided inside the housing, a plate

  stirrup with a threaded hole through which

just screw the screw.

  The disadvantage of this solution results from the additional cost imposed by the production of the stirrup plate and from the difficulty of then performing a mechanized mounting of

  the screw-caliper assembly in the caliper plate.

  There are, on the other hand, screw terminals using, to facilitate the introduction of closed lugs, an elastic means which spreads the screw as soon as its threaded tail has

  been cleared from the tapped hole But these known terminals exist

gent the presence of springs.

  The invention therefore more particularly aims to sup-

  override these disadvantages by simplifying to the extreme the

  design of the terminal while facilitating its use.

  To this end, it offers a connection terminal presented

  both the general structure previously mentioned, character-

  laughing in that the screw has beyond its thread, 3 - a portion having a conformation capable of cooperating, at the end of unscrewing, with a corresponding conformation of an element integral with the body, so as to ensure continued maintenance axial and of the recoil movement of the screw, when the latter continues to undergo an unscrewing action during and after its extraction from the tapped hole of the connection piece, -one of said conformations

  being, at least in part, helical.

  Thanks to this arrangement, after being released from the tapped hole, the screw on which a loosening action is still exercised, moves away from the connection piece until the gap is sufficient to engage or extract a (or more) closed terminal (s) Then, thanks to the fact that the screw always remains held coaxially with the tapped hole, it will be possible to re-tighten without

  worry about the positioning of the screw.

  Advantageously, the conformation of the screw may consist

  ter in a thread provided on the head of the screw, while the conformation of the element integral with the body may consist of an orifice coaxial with the threaded hole of

  the connecting piece and having a sensitive diameter-

  ment equal to that of the screw head This hole may itself have a thread corresponding to the

  screw head thread It will preferably be initiated

  at first smooth then self-tapping by the screw during the

first phase of unscrewing.

  The invention also relates to a terminal block comprising at least one terminal described, attached by the thread of its

  screw head to a terminal cover.

  Embodiments of the invention will be described

  below, by way of nonlimiting examples, with reference to

  Reference to the accompanying drawings in which: 4 - Figures 1 to 5 are schematic views of a connection terminal according to the invention, during its various phases of use; Figure 6 is a perspective view of a terminal block according to the invention; Figure 7 is a schematic section of a

  connection terminal of the type shown

  Figures 1 to 5, but using a special screw

cial with asymmetrical end;

  Figures 8 to 10 are axial cross-sections

  trant several modes of execution

asymmetrical ends.

  The terminal shown in these drawings equips an electrical appliance box which has simply been shown

  parts 1, 2 necessary for understanding the invention

tion.

  This terminal involves, according to a conventional arrangement

  a connection piece 3 fixedly mounted in the housing 1, 2 and on an internal region 4 of which is located a contact pad 5 o is connected a

  other conductive part of the electrical circuit

device.

  This connection piece 3 is provided with a tapped hole 6 located opposite a cavity 7 provided in the material

insulating case.

  In this tapped hole is screwed a clamping screw 8 provided with a clamping bracket 9 mounted captive under the head 10 of the screw 8 The bracket 9 is flat in order to clamp a closed terminal or a conductive end of a cable between itself and the part 3 The bracket can, if necessary, be V-shaped. - The terminal's protection against touch is ensured

  by a part attached to the housing, here a cover

  terminals 11 removably mounted on a return portion 2 of the housing, said part (here the cover 11) comprising, in the axis of the screw 8, an orifice 12 allowing the passage of a screwdriver intended to tighten and loosen the screw 8 The engagement of elements to be connected such as conductive wires or lugs 13 is effected by a lateral passage 14 left free between the housing and the

terminal cover 11.

  According to this embodiment of the invention, the head 10 of the screw 8 comprises a coaxial cylindrical portion of which

  the cylindrical surface 16 is threaded, while the surface

  cylindrical face of the orifice 12 has a thread in which the head 10 of the screw 8 can come to screw,

  as will be described later.

  The axial distance between the tapped hole 6 and the tapped hole 12 is less than the total length of the screw 8, so that before the end of the unscrewing of the screw outside the tapped hole 6, the head 10 of screw 8 comes to engage and begins to screw into the tapped hole

12 of cover 11.

  Given the fact that the cover 11 is made of an easily machinable plastic, the tapping of the orifice 12 can be advantageously obtained by a self-tapping effect produced by the thread of the screw

  8, during the first complete unscrewing of the latter.

  Figure 1 illustrates the phase preceding this autotarau-

  dage, phase during which the screw 8 is largely screwed, the head of the screw 8 as well as the stirrup 9 being in the free volume comprised between the part

  3 and the terminal cover 11.

  6 - Before the end of the unscrewing of the screw 8, the head 10 engages in the orifice 12 of the cover 11 and begins the self-tapping phase (FIG. 2) This phase continues until the end free of the screw 8 is sufficiently spaced from the tapped hole 6, for example to allow the engagement of two closed lugs 13 (Figures

3 and 4).

  It is important to note that the complete unscrewing of the screw 8 is made impossible due to the fact that the stirrup 9 abuts against the cover 11, thus preventing any

  possibility of extracting the screw 8 (FIG. 4).

  Once the lugs 13 have been introduced, we proceed to

  of screw 8 until the pods are

  fairly tight against the connection piece 3 (figure) In this position, the head 10 of the screw 8 is not

  no longer engaged in the tapped hole 12.

  To extract the pods 13, the screw 8 is again unscrewed, the thread of the head 10 then being screwed into

  the tapped hole previously made.

  The pitch of the thread of the tail of the screw 8 can be equal to the pitch of the thread of the head 10, in particular so as not to cause tearing of the plastic material of the cover. It can also be less than that of the head for allow rapid maneuvering in case of insertion and extraction of a closed terminal It can also be greater than that of the head when, for reasons of space or feasibility, the cover is produced

  in a flexible and thin plastic.

  When the steps are different, the overlapping of the two screwing operations is accompanied by a slight

bending of the hood.

  In addition, one can provide a shoulder 17 preferably chamfers between the end of the head 10 carrying the slot - and the threaded portion 16, this shoulder serving to facilitate the engagement of the head 10 in the orifice 12 of the

cover 11 (self-centering effect).

  Figure 6 illustrates a terminal block according to the invention

  comprising several sets of screws 8-caliper 9 pre-assembly

  blés with the cover terminal cover 11 by the engagement of the threads of the heads 10 of the screws in the holes 12 of the cover The terminal block thus produced forms a sub-assembly which can be fixed to the body of the electrical appliance, either during the manufacture of the latter, either during its assembly and its connection to the place of use. The cover, provided with at least one or more screw-caliper sub-assemblies, can constitute a removable element which can, at will, be added to an appliance body at the time

  during production or only during assembly and connection

dement final.

  This cover 11 can also be designed as a sub-

  assembly which can be a housing or a device cover comprising the functions mentioned above as well as

  others, such as, for example, the protective function

  tion against touch, etc. Advantageously, the tail of the screw 8 may have, at

  its end, an asymmetrical shape 22 forming a forward

  axial rib offset from the longitudinal axis of

screw 8.

  This shape can be constituted by a bevel 23 (Figure 8) or even by two bevels 24, 25 forming a dihedral whose edge 26 is offset relative to the longitudinal axis of the screw 8 (Figure 9) It can also be constituted a

  eccentric axial advance 27 (Figure 10).

8 2667989

  In all cases, this form 22 to 27 is designed so as to avoid the tightening of a wire 21 between the tail of the screw 8 and the connection piece 3 opposite the tapped hole 6 of this piece 3 It also has intended to allow self-centering of a terminal during its wiring. 9 -

Claims (9)

Claims   1 Connection terminal for electrical appliance with insulating body (1, 2), of the type comprising a clamping screw (8) whose threaded tail can be screwed into a tapped hole (6) of a fixed connection piece (3) and a stirrup (9) mounted captive under the head of the screw (8), the stirrup being displaceable in translation following the screwing and unscrewing of the screw (8) to tighten and   loosen an element between itself and the connection piece   ment to be connected, characterized in that the screw (8) has, beyond its   threaded tail, a portion (16) having a conforma-   tion able to cooperate, at the end of unscrewing, with a corresponding conformation of an element (11) integral with the body (1, 2), so as to ensure the continuation of the axial maintenance and the recoil movement of the screw (8) , when the latter continues to undergo an unscrewing action during and after its extraction from the tapped hole (6) of the connection piece (3), one of said conformations   being, at least in part, helical.   2 connection terminal according to claim 1, characterized in that the conformation of the screw consists of a thread (16) provided on the head (10) of said screw (8). 3 connection terminal according to claim 2,   characterized in that the conformation of the solid element   body body consists of an orifice (12) coaxial with   threaded hole (6) of the connecting piece (3) and present   both a diameter substantially equal to that of the head (10) of the screw (8).   4 connection terminal according to claim 3,   characterized in that the orifice (12) has a thread   dage corresponding to the thread of the head (10) of the screw (8). 2667989   Connection terminal according to claim 4, characterized in that the thread pitch of the tail   the screw (8) is equal to that of the head (10).   6 connection terminal according to claim 4, characterized in that the pitch of the thread of the tail   the screw (8) is different from that of the head (10).   7 connection terminal according to claim 3, characterized in that the orifice (12) of the element (11) integral with the body (1, 2) is initially smooth and is self-tapping by the screw (8) during the first unscrewing phase.   8 Connection terminal according to one of the claims   previous cations, characterized in that the element (11) integral with the body   (1, 2) is a removable terminal cover.   9 Connection terminal according to one of the claims previous cations,   characterized in that the tail of the aforementioned screw   feels, at its end, an asymmetrical shape (22) for-   mant an axial offset offset from the long axis gitudinal of the screw (8).   Connection terminal according to claim 9, characterized in that the said form consists   by a bevel (23) or includes two bevels (24, 25) for-   mant a dihedral whose edge (26) is offset relative   to the longitudinal axis of the screw (8).   11 Terminal block comprising at least one terminal   connection according to claim 8, attached by the file-   of the head (10) of screws (8) to the terminal cover   (11), the terminal (s) and the cover constituting a sub-   il 2667989 assembly capable of being fixed to the body (1, 2) of the electrical appliance.   12 Terminal block according to claim 11, characterized in that the cover (11), provided with at least one or more screw-caliper subassemblies (8, 9), constitutes a removable assembly which can be added at will to a device body.