CN1186855C - Connecting means having flexible sleeve - Google Patents

Abstract

A terminal includes a sleeve obtained by cutting and folding a metal strip and includes a clamping screw received in a threaded hole provided on a top branch. The two terminal branches enclosing the elastic frame are separated in the untightened state by at least one first axial gap (J1) extending in the direction of movement of the screw. The stop device determines a first clamping threshold after the first play has been eliminated at the start of the tightening screw. The sleeve becomes stiffer as the screw is tightened further increasing the clamping force beyond a first threshold. The bushing returns to its original geometry when the terminal clamping screw is loosened.

Description

Terminals with flexible sleeves

technical field

The invention relates to a terminal.

Background technique

Sleeve terminals of this type involve the generation of high pulling forces when engaging in clamping the cables to be connected. These forces in the terminals can reach 300 daN (see curve A in Figure 5), while values ten times lower may be sufficient to ensure a suitable electrical contact pressure to enable current flow. A very high initial force value shows the advantage of causing the individual conductors of the cable to set, but this force decreases as the metal of the individual conductors creeps and deforms over time. This can lead to a loose effect on the terminals, creating a risk of overheating in the contact area.

Various terminals have been proposed with a certain elasticity to compensate for possible looseness of the screws. Documents FR-A-2696584 and DE-A-19513281 relate to ferrule terminals equipped with a compression spring for storing elastic energy to ensure that the conductor to be connected is properly tightened when the clamping screw loosens slightly .

Document EP336251 describes a screw terminal having a fastening frame and a vertically arranged fixing bracket and making it possible to form a double connection of a contact pad and a wire or cable. A gap is formed between the two ends of the open frame.

Contents of the invention

The object of the invention is to obtain a terminal with an elastic sleeve permanently ensuring good electrical contact with the cable without using some additional spring inside the sleeve, said terminal having:

Sleeve, obtained by cutting and folding a metal strip to form a frame defining an opening for inserting a quadrangular section of a cable to be connected.

a clamping screw for clamping the cable between a connection pad and the bottom of the bushing, said screw being housed in a threaded hole provided on a horizontal upper branch of said bushing,

And the elastic frame of the two terminal branches enclosing the sleeve is separated by at least one first axial gap extending in the screw moving direction in the untightened state.

The device according to the invention is characterized in that:

The stop device determines a first clamping threshold after the first gap at the start of the tightening screw has been eliminated,

The sleeve becomes stiffer as the screw is tightened further increasing the clamping force beyond said first threshold and then returns to its original geometry when the screw is loosened,

The metal sleeve has an elastic structure with a double slope so that the axial pulling force generated in the terminal when the tightening is performed increases faster in the second slope stage than in the first slope stage, from The transition from the first slope to the second slope occurs after the first clamping threshold has been exceeded.

Greater elasticity occurs at the beginning of the clamping until the stop surface is reached, and from this position the usual behavior of a strong sleeve is observed. In case the screw loosens slightly due to creep of the individual conductors of the cable, the bushing is elastically pushed towards a configuration corresponding to the first clamping threshold.

According to a first preferred embodiment, the bushing comprises a lateral branch protruding beyond the horizontal terminal branch of the support screw and comprising a rectangular eyelet, wherein an extension of said horizontal terminal branch-presses against the bottom of the rectangular eyelet The edge is separated from the top edge by a first axial gap when the terminal is in the untensioned condition. A second transverse gap is provided between the inner surface of the side branches and the two straight edges on each side of the base of the extension.

According to a second embodiment, the two terminal branches of the bushing are superimposed opposite the base and separated by a first axial gap. The outer branch is provided with a smooth circular eyelet with a larger diameter than the threaded hole provided on the inner branch. The second transverse gap is in this case provided on the side between the circular eye and the screw body on the side where the end of the outer branch is located, the lifting of the outer branch causing the latter to bear against the screw when a predetermined clamping threshold is reached body so that a torque limiter is obtained making it possible to generate a constant clamping force.

Description of drawings

Other advantages and characteristics of the invention will become more apparent from the following description of an embodiment of the invention, presented as a non-limiting example only, and shown in the accompanying drawings, in which

Figure 1 is an elevational view of a resilient sleeve terminal in accordance with the present invention in an untightened condition without a connection pad;

Figures 2 and 3 show perspective views of the terminals in Figure 1;

Figure 4 shows a view equivalent to Figure 1 when the terminal is in the tightened state;

Fig. 5 shows the clamping force and deformation graph of a conventional bushing terminal (single slope curve A) and a terminal according to the present invention (double slope curve B);

Figures 6 to 8 are views equivalent to Figures 1, 2 and 4 of another embodiment.

Detailed ways

Referring to FIGS. 1 to 4 , a terminal 10 includes a sleeve 12 , a clamping screw 14 and a connection pad 16 . The bushing 12 appears as a one-piece member, obtained by cutting and folding a strip of conductive metal so as to form a frame of substantially quadrilateral cross-section. The inner side of the sleeve 12 forms an orifice 18 limited by a bottom 20 joined to two vertical side branches 22, 24 extending parallel to each other, the branch 24 extending at right angles from an upper branch 26, the clamping screw 14 across this stretch.

The vertical side branch 22 is provided at its top with a rectangular eyelet 28 into which an end extension 30 of the upper branch 26 in the form of a tenon is inserted. The screw 14 is housed in a screw hole 32 disposed in a collar flange 34 of the upper branch 26 .

The copper connection pad 16 is received in the aperture 18 of the bushing 12, extends in a direction parallel to the horizontal branch 26, and is designed to clamp the cable 36 against the base 20 when the screw 14 is tightened.

In the case of a fixed bushing 12, the connection pad 16 is pressed against the end of the screw 14 shank for vertical translation in both directions within the bore 18 as the screw 14 is turned. If the screw 14 is tightened, the connection pad 16 moves towards the fixed bushing 20, causing the cable 36 to be clamped against the latter.

In the case of a movable sleeve 12, the connection pad 16 is fixed and the tip of the screw 14 presses against the top surface of the pad 16 without mating it. If the screw 14 is tightened, the bushing 12 moves upward and the bottom 20 clamps the cable 36 against the bottom surface of the pad 16 .

According to the present invention, the end of the vertical side branch 22 protrudes above the horizontal branch 26, and the end extension 30 presses on the bottom of the rectangular hole 28 when the terminal 10 is in the unclamped state (Figs. 1 to 3). The edge is separated from the top edge by a first axial gap J1. A second transverse gap J2 is provided between the inner surface of the branch 22 and the two straight sides 38 on each side of the extension 30 to allow elastic deformation of the sleeve 12 when the screw 14 is tightened.

During the connection phase of a cable 36 shown in FIG. 4 , the tightening screw 14 causes an elastic deformation of the sleeve 12 at the beginning of clamping due to the lifting of the end extension 30 as indicated by arrow F1 . This lifting action is made possible by the presence of gaps J1 and J2 and stops as soon as the end extension 30 bears up against the stop surface formed by the top edge of the rectangular aperture 28 . The axial clamping force in the sleeve 12 during this elastic deformation is relatively moderate and lies in the vicinity of a first clamping threshold in the range from 10 to 40 daN. The variation of the axial clamping force during this elastic deformation is represented by the first slope of curve B in FIG. 5 . The first clamping threshold S1 is reached when the relative movement of the screw 14 relative to the thread of the eye 32 corresponds to the size of the first gap J1 which is approximately 0.5 mm. This first clamping threshold S1 is perfectly adapted to the current flowing between the pad 16 and the cable 36 .

When the screw 14 is further tightened after the extension 30 has pressed upward against the stop surface, the sleeve 12 becomes relatively rigid and the axial pulling force in the terminal 10 increases rapidly according to the second slope of the curve B , which is comparable to the performance of a normal bushing indicated by curve A. Depending on the torque applied to the screw 14 , a moderate clamping is then achieved, lying between the first threshold value S1 and a second maximum threshold value S2 of -300 daN. The deformation of the sleeve 12 during the second clamping phase is less than the elastic deformation that occurs when the first gap J1 is eliminated.

The deformation of the sleeve 12 when the screw 14 is tightened results in a spring function with a double slope. In the event of relaxation due to crushing and creeping of the wires of the cable 36 , the axial force in the bushing 12 decreases to a first threshold value S1 on the curve B . This spring energy is still sufficient to maintain proper contact between the pad 16 and the cable 36 .

In the further embodiment of FIGS. 6 to 8 , the sleeve 112 of the terminal 100 comprises two superimposed end branches 123 , 125 opposite the bottom 120 separated from each other by a first axial gap J1 . The outer bent branch 125 joins the other right vertical side branch 124 and is provided with a smooth circular eye 127 allowing the screw 14 to pass through. The other inner branch 123 is folded over to form a bracket relative to the left vertical side branch 122 and is provided with a threaded hole 132 of smaller diameter for the screw 14 . The collar flange 134 is in this case arranged below the underside of the branch 123 . A second transverse gap J2 is provided between the circular eye 127 and the body of the screw 14 on the side where the ends of the branches 125 are located. The connection pad 16 is equivalent to that of the first embodiment.

The terminal 100 according to FIGS. 6 to 8 functions in the following manner:

In the untensioned state of FIG. 6 , the horizontal outer branches 125 are parallel to the inner branches 123 to be evenly spaced vertically corresponding to the first gap J1 .

When engaging in the connection of the cable 36, at the beginning of tightening the screw 14, when the end of the inner branch 123 has eliminated the first gap J1 and upwards against the stop surface formed by the bottom surface of the outer branch 125, the first is reached. Clamp threshold S1.

In FIG. 8 , when the screw 14 is tightened after the end of the branch 123 has pressed upward against the stop surface, the sleeve 112 becomes more rigid and the axial pulling force in the terminal 100 follows curve B The second slope increases rapidly. This results in a slight lifting of the outer branch 125 in the direction of the arrow F2, which branch then abuts against the body of the screw 14 when a predetermined threshold is reached. It then becomes impossible to tighten the screw 14 to obtain a torque limiter, making it possible to generate a constant clamping force.

In both embodiments of FIGS. 1 to 8 , the first axial gap J1 suitable for the elastic deformation of the sleeve 12 , 112 extends in the direction of movement of the screw 14 .

Claims (7)

1. terminals have:

One sleeve pipe (12,112) obtains to constitute a framework by a cutting and a folding metal strap, and this framework defines one and is used to embed an aperture (18) that the quadrangular section of cable to be connected (36) arranged,

One pinching screw (14) is used for cable (36) is clamped in the bottom (20 of a connection gasket (16) and sleeve pipe (12,112), 120) between, described screw is housed in a screwed hole (32 that is configured in the horizontal upper part branch (26,123) of described sleeve pipe, 132) among

And two end branches (22,26; 123,125), the elastic frame of the closed sleeve pipes of described two end branches (12,112) is not separated by at least one first end play (J1) that extends on screw (14) moving direction tightening under the state,

It is characterized in that,

Retaining device determines that at first gap (J1) one first clamps threshold value (S1) after the beginning that tightens screw (14) has been eliminated,

Sleeve pipe (12,112) further tightened and increased at screw (14) and become firmer when clamping force exceeds described first threshold value, then when screw is released, return its original geometric form again, described metal sleeve (12,112) has an elastic construction that has a diclinic rate, so that be created in terminals (10 when tightening when being engaged in, 100) the axial traction force among is more very fast than increasing in the first slope stage in the second slope stage, and the conversion from first slope to second slope occurs in first and clamps after threshold value (S1) has been exceeded.

2. according to the described terminals of claim 1, it is characterized in that, sleeve pipe (12) comprises a side branches (22), stretches out outside the horizontal end branch (26) of supporting screw (14) and has a rectangle eyelet (28), wherein engages an extension (30) of described horizontal branch (26).

3. according to the described terminals of claim 2, it is characterized in that extension, end (30) are pressed on the base of rectangle eyelet (28) when not tightening state when terminals (10) are in, and are spaced apart by first end play (J1) and top margin.

4. according to the described terminals of claim 3, it is characterized in that one second lateral clearance (J2) is arranged between the inner surface and two straight flanges (38) on the every side of extension (3) base portion of side branches (22).

5. according to the described terminals of claim 1, it is characterized in that, two terminals branches (123,125) in the bottom (120) opposite stacked, (J1) separates by first end play.

6. according to the described terminals of claim 5, it is characterized in that outer branches (125) is furnished with a smooth circular eyelet (127), diameter is greater than the diameter that is configured in the screwed hole (132) in the inner branch (123).

7. according to the described terminals of claim 6, it is characterized in that, second lateral clearance (J2) is arranged on a side at outer branches (125) place, end between circular eyelet (127) and screw (14) main body, the lifting of outer branches (125) can cause the latter to lean the main body of screw (14) when reaching a predetermined clamping threshold value, so that obtains a kind of torque limiter that may generate a constant clamping force that makes.

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