A switch, in particular a battery cutout switch for vehicles and the like

Abstract

 A switch, in particular a battery cutout switch for vehicles and the like, comprising:
- an insulating housing (12) carrying at least two fixed electrical contacts (22),
- a contact-holder body (28) movable relative to the housing (12) along a rectilinear direction (A) between a closed contacts position and an open contacts position,
- at least one movable electrical contact (32) carried by said contact-holder body (28) and having a first and a second contact zone (70, 72), cooperating with the head portions (23) of the respective fixed electrical contacts (22),

wherein said first contact zone (70) of said movable electrical contact (32) has two protuberances (76) with curved contact surfaces that establish two points of contact with the head portion (23) of the respective fixed electrical contact (22), and said second contact zone (72) has a single protuberance (78) with a curved contact surface that establishes a single point of contact with the head portion (23) of the respective fixed electrical contact (22), so that in the closed contacts position, said movable electrical contact (32) is in contact with said fixed electrical contacts (22) at three points.

Description

TEXT OF THE DESCRIPTION

Field of the invention

[0001] The present invention relates to a switch, in particular of the type intended for use as a battery cutout switch in electrical systems on board vehicles, boats, etc.

Description of the prior art

[0002] Battery cutout switches are usually used for selectively connecting a load, or rather the electrical system on board a vehicle, to a power source, or rather the vehicle battery. Switches of this type generally have a housing carrying two or more fixed electrical contacts and a contact-holder body carrying at least one movable electrical contact cooperating with the fixed contacts and movable between an open contacts position and a closed contacts position. A handle, rotatable between an open position and a closed position, cooperates with the contact-holder body to move it from the open contacts position towards the closed contacts position.

[0003] For example, the document EP-A-1296343 of the same Applicant describes a switch comprising a supporting body carrying at least one pair of fixed electrical contacts, a movable element carrying at least one electrical contact, movable in a rectilinear direction between an open contacts position and a closed contacts position, and vice versa. The movable electrical contact, in the closed contacts position, is elastically pushed against the fixed electrical contacts. The contact-holder body is subject to an elastic force that tends to push the contact-holder body towards the open electrical contacts position.

[0004] During operation, switches of this type are subject to vibrations due to the combustion engine of the vehicle and to the movement of the vehicle. The action of the vibrations, in combination with the elastic force, which tends to push the contact-holder body towards the open contacts position, can cause small oscillating movements of the movable electrical contact. These small oscillatory movements can cause the so-called fretting corrosion, which damages the contact surface. In addition, the oscillatory movements of the movable contact can produce micro-interruptions of the electrical contact and electrical discharges, which can cause damage to the contact surfaces and micro-fusions.

Object and summary of the invention

[0005] The present invention aims to provide a switch that can overcome the aforesaid drawbacks.

[0006] According to the present invention, this object is achieved by a switch having the characteristics forming the subject of Claim 1.

[0007] The claims form an integral part of the disclosure provided in relation to the invention.

Brief description of the drawings

[0008] The present invention will now be described in detail with reference to the attached drawings, given purely by way of non-limiting example, wherein:

• Figure 1 is an exploded perspective view of a switch according to the present invention,
• Figure 2 is a perspective view of the contact-holder body indicated by the arrow II in Figure 1,
• Figure 3 is a plan view of a movable contact,
• Figure 4 is a side view of the contact of Figure 3,
• Figures 5 and 6 are sections according to the lines V-V and VI-VI of Figure 3, respectively, and
• Figure 7 is a perspective view showing a movable electrical contact supported on two fixed electrical contacts.

Detailed description of the invention

[0009] With reference to Figure 1, numeral 10 indicates a switch according to the present invention, intended to be used, in particular, as a battery cutout switch for vehicles, boats, etc.

[0010] The switch 10 comprises a housing 12 of plastic material, including a base 14 and a cover 16. The cover 16 is attached to the base 14, for example, by means of screws 18. Between the cover 16 and the base 14, a gasket 20 may be placed.

[0011] Within the housing 12, at least one pair of fixed electrical contacts is housed. In the embodiment illustrated in the figures, the switch 10 comprises two pairs of fixed electrical contacts 22. Each fixed contact 22 has the shape of a pin with an enlarged head and a threaded shank. The shanks of the fixed contacts 22 extend through respective holes of the base 14 and are attached to the base 14 by means of respective nuts 24. On the shanks of the fixed contacts 22, respective O-rings 26 can be provided.

[0012] A contact-holder body 28 is mounted within the housing 12. The contact-holder body 28 is movable with respect to the housing 12 along a longitudinal axis A. Between the housing 12 and the contact-holder body 28, a rectilinear guide is provided, for guiding the contact-holder body 28 along the rectilinear direction of the axis A. The guide can be formed by ribs projecting from the inner walls of the base 14, between which the side edges of the contact-holder body 28 are engaged, in a drawer-like manner.

[0013] The contact-holder body 28 carries at least one movable electrical contact. In the illustrated example, the contact-holder body 28 has two through-openings 30 in which two movable electrical contacts 32 are housed, each of which cooperates with a pair of fixed contacts 22.

[0014] The contact-holder body 28 is movable along the longitudinal direction A between a closed contacts position and an open contacts position. Elastic means are provided to push the contact-holder body 28 towards the open contacts position. In the illustrated example, these elastic means are formed by a pair of compression coil springs 38 acting between the bottom wall of the base 14 and a pair of side protrusions 40 of the contact-holder body 28.

[0015] The contact-holder body 28 cooperates with a manually operated control device, which controls the movement of the contact-holder body 28 from the open contacts position to the closed contacts position. This control device comprises a handle 44, rotatable about the longitudinal axis A, which cooperates with a cam 64, fixed with respect to the contact-holder body 28. The control device is described in detail in a contemporary patent application by the same Applicant.

[0016] The cam 64 has a cylindrical side wall within which two inclined ramps are arranged, which cooperate with a pair of first control members 54 projecting from a shaft 46 of the handle 44. In the embodiment illustrated in the figures, the handle 44 also includes a second pair of control members 56, which cooperate with the inclined ramps of the cam 64, for controlling the movement of the contact-holder body 28 from the closed position to the open position in case of malfunctions that prevent the spontaneous movement of the contact-holder body 28 from the closed contacts position to the open contacts position under the action of the springs 38.

[0017] With reference to Figures 3 to 7, each movable electrical contact 32 is formed by a metal plate, having a first and a second contact zone 70, 72 located on opposite sides of a central portion 74. The first contact zone 70 has two protuberances 76 with curved contact surfaces. The second contact zone 72 has a single protuberance 78 with a curved contact surface.

[0018] The first and the second contact zones 70, 72 of each movable electrical contact 32 cooperate with the respective heads 23 of two fixed electrical contacts 22. The heads 23 of the fixed electrical contacts 22 have flat contact surfaces 80. The protuberances 76 of the first contact zone 70 establish two points of contact with the contact surface 80 of the head 23 of the respective fixed electrical contact 22, while the protuberance 78 of the second contact zone 72 establishes a single point of contact with the contact surface 80 of the head 23 of the respective fixed electrical contact 22. Therefore, in the closed electrical contacts position, each movable electrical contact 32 is in contact with the fixed electrical contacts 22 at three points.

[0019] With reference to Figures 1 and 2, each movable electrical contact 32 is positioned within a respective opening 30 of the contact-holder body 28. The central portion 74 of each movable electrical contact 32 is guided between the side walls of the opening 30 and the two contact zones 70, 72 protrude from opposite sides of the contact-holder body 28. Each movable electrical contact 32 is elastically pressed against the bottom wall of the respective opening 30 by at least one helical compression spring placed between the upper wall of the opening 30 and the central portion 74 of the movable electrical contact 32. In the illustrated example two helical compression springs 82, 84 are provided, arranged coaxially to each other, with the smaller diameter springs 84 arranged within the springs 82 with a larger diameter.

[0020] In the closed electrical contacts position, the contact-holder body 28 is positioned slightly lower than the position in which the movable electrical contacts 32 come into contact with the fixed electrical contacts 22. In this way, the movable electrical contacts 32 are pressed into contact with the heads 23 of the fixed electrical contacts 22 by the elastic force of the springs 82, 84. In this condition, each movable electrical contact 32 rests on two fixed electrical contacts 22 at three contact points, under the action of an elastic force that acts on the central zone 74, intermediate between the contact zones 70, 72. In this way, the position of the movable electrical contacts 32 is stable, and the contact pressure is univocally distributed between the two contact zones 70, 72. This arrangement greatly reduces the risk of micro-interruptions due to vibrations, prevents damage of the contact surfaces due to small oscillating movements, and effectively prevents the fretting corrosion of the contact surfaces.

[0021] Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to those described and illustrated, without departing from the scope of the invention as defined by the claims that follow.

Claims

1. A switch, in particular a battery cutout switch for vehicles and the like, comprising:

- an insulating housing (12) carrying at least two fixed electrical contacts (22),

- a contact-holder body (28) movable relative to the housing (12) along a rectilinear direction (A) between a closed contacts position and an open contacts position,

- at least one movable electrical contact (32) carried by said contact-holder body (28) and having a first and a second contact zone (70, 72), cooperating with the head portions (23) of the respective fixed electrical contacts (22),
characterized in that said first contact zone (70) of said movable electrical contact (32) has two protuberances (76) with curved contact surfaces that establish two points of contact with the head portion (23) of the respective fixed electrical contact (22), and that said second contact zone (72) has a single protuberance (78) with a curved contact surface that establishes a single point of contact with the head portion (23) of the respective fixed electrical contact (22), so that in the closed contacts position, said movable electrical contact (32) is in contact with said fixed electrical contacts (22) at three points.

2. A switch according to claim 1, characterized in that said contact-holder body (28) has at least one through opening (30) in which said movable electrical contact (32) is disposed, with said first and second contact zones (70, 72) located on opposite sides of the contact-holder body (28).

3. A switch according to claim 2, characterized in that said movable electrical contact (32) has a central portion (74) which is guided between the side walls of said through opening (30), with elastic means (82, 84) being arranged between said contact-holder body (28) and said central portion (74) of said movable electrical contact (32).

4. A switch according to any one of the preceding claims, characterized in that said protuberances (76, 78) of said first and second contact zones (70, 72) cooperate with flat contact surfaces (80) of said fixed electrical contacts (22).

Drawing