Improved terminal, particularly for automatic circuit breakers

Abstract

 An improved terminal for automatic circuit breakers, is formed by a metal strip which is blanked and bent so as to form a parallelepipedal body, with which an abutment screw is associated, the body is constituted by two side walls, an upper surface, and a lower surface; the lower surface is constituted by the ends of the plate which are mutually joined by two joining points.

Description

[0001] The present invention relates to an improved terminal particularly for automatic circuit breakers.

[0002] As is known, the main function that is required of terminals for electrical apparatuses, particularly for modular automatic circuit breakers, is generally to retain, by means of a screw, a rigid or flexible conductor against a connecting plate or block which is arranged within the terminal so as to provide a stable and strong electrical connection.

[0003] This type of connection must ensure a contact surface suitable to the current capacity, must not lose its mechanical retention over time, and, once clamping has been performed, the cable must not be damaged to the point of reducing its carrying cross-section below the limit set by the standard.

[0004] According to the prior art, box terminals are manufactured by bending a band or strip made of steel or equivalent material, transversely with respect to its length, in at least four points, so as to obtain a closed box shape which is capable of containing both the connection block and one or more rigid or flexible conductors, required in order to establish the connection.

[0005] The shape of the terminal may vary according to the various applications and to the types of conductor that one intends to use.

[0006] The clamping action is achieved by acting on the screw usually arranged on the upper side. The screw is inserted in a threaded hole and allows to move the terminal closer to the block and consequently achieve the clamping of the conductor between the lower inner side of the terminal and the lower side of the block or of the connecting plate.

[0007] A limitation observed in conventional box terminals is the low value of the clamping torque that can be applied without causing their deformation, ripping or, worse, breakage.

[0008] Over time, various more or less elaborate forms and systems for seaming or closing the box have been developed, achieving, in the case of simple systems, optimization of costs but low values of clamping torque or vice versa, in the case of complex systems, high torque values but with significantly high production costs.

[0009] The aim of the present invention is to provide an improved terminal, particularly for automatic circuit breakers, which overcomes the drawbacks of the prior art.

[0010] An object of the invention is to provide a terminal which allows to achieve a higher clamping torque.

[0011] A further object of the invention is to provide a terminal of the so-called box type, which can be manufactured by optimizing the use of raw material, allowing to reduce the waste of raw material to a minimum, during the step for blanking and bending and during closure.

[0012] A further object is to provide a terminal which allows durable clamping of rigid and flexible cables.

[0013] A further object is to provide a terminal which allows to fit a finger-safe protection.

[0014] A furher object of the present invention is to provide a terminal which, by virtue of its particular constructive characteristics, is capable of giving the greatest assurances of reliability and safety in use.

[0015] A further object of the present invention is to provide a terminal which can be manufactured by using commonly commercially available elements and materials.

[0016] This aim and these and other objects which will become better apparent hereinafter are achieved by an improved terminal, particularly for automatic circuit breakers, characterized in that it comprises a strip which is blanked and bent so as to form a parallelepipedal body, with which an abutment screw is associated; said body being constituted by at least two side walls, an upper surface, and a lower surface; said lower surface being constituted by the ends of said plate which are mutually joined by at least two joining points.

[0017] Further characteristics and advantages will become better apparent from the description of preferred but not exclusive embodiments of the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a partially exploded perspective view of the terminal;

Figure 2 is a perspective view of the terminal without the clamping screw;

Figure 3 is a partially exploded front view of the terminal;

Figure 4 is a side view of the terminal, in which the clamping screw is separated from the body of the terminal;

Figure 5 is a view, similar to the preceding one, but showing the clamping screw engaged in the body of the terminal;

Figure 6 is a bottom perspective view of the terminal body;

Figure 7 is a perspective view of the terminal body;

Figure 8 is a front view of the terminal body;

Figure 9 is a side view of the terminal body;

Figure 10 is a sectional side view, taken from the opposite side with respect to the preceding figure along the plane X-X of Figure 8;

Figure 11 is a side view, taken from the opposite side with respect to Figure 9;

Figure 12 is a sectional plan view, taken along the plane XII-XII of Figure 11;

Figure 13 is a bottom view of the terminal body.

[0018] With reference to the cited figures, the terminal according to the invention, generally designated by the reference numeral 1, comprises a parallelepipedal body 2 and an abutment screw 3. The abutment screw 3 is associated with the body 2 so that the end of a conducting cable, not shown in the figures, can be pressed, by acting on the screw, within the parallelepipedal body 2, between the base of the body 2 and the end of the block, which is not visible in the figures.

[0019] The parallelepipedal body 2 is constituted by a single piece of blanked and bent metal.

[0020] The body 2 is constituted by an upper surface 4 and two side walls blended thereto: a first side wall 5 and a second side wall 6.

[0021] The first side wall 5 ends with an inner lower side 7 and the second side wall 6 ends with an outer lower side 8.

[0022] The lower sides 7 and 8 are mutually joined in two joining points. A first joining point is constituted by a lateral seam 9, which is constituted by a tab 10 which protrudes from the outer lower side 8 and is engaged within a seat formed in the first side wall 5.

[0023] The second joining point is constituted by a stud 11, which is provided on the outer lower side 8 and engages a hole 12 provided in the inner lower side 7.

[0024] A lateral seat 13 is provided in the lower part of the second side wall 6, at the outer lower side 8 blended therewith, which is partially engaged by a lateral tooth 14 formed on the free end of the inner lower side 7.

[0025] A lower tooth 15 is also provided on a lateral edge of the outer lower side 8.

[0026] The lateral tooth 14 and the lower tooth 15 constitute an engagement means for a protection device 16.

[0027] The protection device 16 is constituted by a plate 17 provided with a lateral hook 18 and a rear hook 19.

[0028] The lateral hook 18 enters the lateral seat 13 and engages the lateral tooth 14.

[0029] The rear hook 19 engages the lower tooth 15, which partially enters an opening 20 formed in the rear hook 19.

[0030] Accordingly, the safety device 16 is simply engaged with a snap action on the terminal body 2, and in the active condition becomes an integral part thereof.

[0031] The safety device 16 constitutes a so-called finger-safe protection, because it obstructs the opening formed by lifting the body of the terminal, when the screw 3 is tightened to lock the conductor, in a per se known manner.

[0032] The exposed surface of the inner lower side 7 has a knurling 77, which facilitates the adhesion of the end of the conductor to the surface when the terminal is clamped.

[0033] The conductor is therefore locked between the exposed surface of the upper inner side 7 and the lower side of the block or an optional abutment member.

[0034] In practice it has been found that the invention achieves the intended aim and objects, an improved terminal particularly for automatic circuit breakers having been provided which has substantial advantages with respect to terminals of the prior art.

[0035] The shape of the terminal is optimized in order to minimize the waste of raw material during the blanking and bending step, and its closure is provided in multiple points.

[0036] In particular, the lateral seam 9 prevents the axial deformation of the terminal in the direction of the action of the screw 3, while the stud 11, arranged on the outer lower side and engaged in the hole 12 formed in the second lower side, prevents its transverse deformation.

[0037] This double seam system allows a clamping of both flexible and rigid cables which is durable over time.

[0038] The maximum clamping torque that can be obtained with this system is a function of the type of material used, of the cross-section and of any thermal treatments for hardening.

[0039] Laboratory tests have confirmed that, for an equal cross-section, for an equal material and an equal thermal treatment, the clamping torque that can be applied reaches higher values than obtainable with prior systems without deformations of the terminal.

[0040] Suitable engagement members allow the snap fitting of the finger-safe protection 16.

[0041] This application claims the priority of Italian Patent Application No. GE2007A000130, filed on December 28, 2007, the subject matter of which is incorporated herein by reference.

Claims

1. An improved terminal, particularly for automatic circuit breakers, characterized in that it comprises a strip which is blanked and bent so as to form a parallelepipedal body, with which an abutment screw is associated; said body being constituted by at least two side walls, an upper surface, and a lower surface; said lower surface being constituted by the ends of said plate which are mutually joined by at least two joining points.

2. The terminal according to claim 1, characterized in that said two side walls comprise a first side wall and the second side wall; said first side wall ends with an inner lower side and said second side wall ends with an outer lower side.

3. The terminal according to claim 2, characterized in that said lower sides are mutually joined in said two joining points: a first joining point is constituted by a lateral seam, which is constituted by a tab which protrudes from the outer lower side and is engaged in a seat formed in the first side wall; a second joining point is constituted by a stud provided on the outer lower side, which engages a hole formed in the inner lower side.

4. The terminal according to one or more of the preceding claims, characterized in that it comprises a lateral seat which is formed in the lower part of said second side wall, at the outer lower side blended therewith, said lateral seat being partially engaged by a lateral tooth which is formed on the free end of said inner lower side; said terminal comprising a lower tooth, which is formed on a lateral edge of said outer lower side; said lateral tooth and said lower tooth constituting an engagement means for a protection device.

5. The terminal according to one or more of the preceding claims, characterized in that said protection device is constituted by a plate which is provided with a lateral hook and a rear hook; said lateral hook being inserted in said lateral seat and engaging said lateral tooth; said rear hook engaging said lower tooth, which partially enters an opening formed in said rear hook.

6. The terminal according to one or more of the preceding claims, characterized in that the exposed surface of said inner lower side has a knurling which facilitates the adhesion of the end of the conductor to said surface when the terminal is clamped.

Drawing