EP0704873A1

EP0704873A1 - Switch

Info

Publication number: EP0704873A1
Application number: EP94115473A
Authority: EP
Inventors: Ytzen c/o Johnson Contr.Ned.b.v. Tamminga
Original assignee: Johnson Service Co
Current assignee: Johnson Service Co
Priority date: 1994-09-30
Filing date: 1994-09-30
Publication date: 1996-04-03

Abstract

A switch comprising a housing (1), a trip mechanism (5) with a leaf spring (6) movable through a dead-centre position, the leaf spring comprising a contact tongue movable between two contact elements (2,3) and being connected to a contact pin (4), and with a plunger (7) abutting the leaf spring. The trip mechanism is adapted to be actuated by a setting movement of the plunger. The resetting mechanism (9) provided for the trip mechanism according to the invention is a setting lever pivotable between a position of rest and an actuation position and having a rotary member disposed in the space between the contact elements. The rotary member comprises bars aligned on either side of and parallel to the axis of rotation, the contact tongue engaging in the opening defined by the bars. When the setting lever is in the position of rest, the contact tongue is freely movable between the contact elements. In the actuation position of the setting lever the contact tongue is clamped between the bars and in this case, without contacting the contact elements, occupies an intermediate position between the contact elements in which the dead-centre of the leaf spring is overcome in the resetting direction.

Description

The invention relates to a switch comprising a housing, contact elements fixed on the housing, a trip mechanism with a leaf spring which is movable through a dead-centre position and which comprises a contact tongue movable between two contact elements and which is connected to a contact pin, and with a plunger abutting the leaf spring, the trip mechanism being actuatable by a setting movement of the plunger in a setting direction, a manually actuated resetting mechanism being provided to actuate the trip mechanism in the resetting direction. A transducer of known type can be connected to the plunger and converts a physical quantity, e.g. the temperature or the pressure, into a setting movement of the plunger.
Switches of the described construction can be used as protective switches, which break the current supply to operating equipment when the monitored physical quantity, e.g. an operating pressure or an operating temperature, reaches a predetermined critical value. If the switching operation has been triggered by the setting movement of the plunger, the switch can be manually reset if the operator ensures that the monitored physical quantity, e.g. the operating pressure or operating temperature, has again reached an admissible value. From the plant operator's viewpoint, switching operations on the part of the protective switch result in undesirable interruption to operation or production. To obviate this or reduce the duration thereof, switches of this kind are often subjected to inadmissible manipulation, the resetting mechanism being so locked that the trip mechanism cannot trigger the switching operation and the switch remains in the "ON" position. Of course operational safety suffers considerably as a result and there is a risk of equipment protected by the switch being damaged.
The object of this invention is so to develop a switch of the type described above as to make it impossible to carry out inadmissible manipulation with the object of preventing a switching operation triggered by the setting movement of the plunger.
To this end, according to the invention, the resetting mechanism consists of a setting lever which is mounted rotatably in the housing and which is pivotable between a position of rest and an actuation position and which comprises a rotary member disposed in the space between the contact elements associated with the contact tongue, the rotary member comprising bars aligned on both sides of and parallel to the axis of rotation, and the contact tongue engages in the opening defined by the bars, the contact tongue being freely movable between the contact elements in the position of rest of the setting lever, the contact tongue being clamped between the bars, in the actuation position of the setting lever, and in that case occupies, without contacting the contact elements, an intermediate position between the contact elements in which the dead-centre position of the leaf spring is overcome in the resetting direction. After a switching operation has been triggered, the contact tongue is returnable to the intermediate position by actuating the setting lever. In these conditions the contact tongue is clamped between the bars of the rotary member and fixed at a preset distance from the contact elements. If the setting lever is returned to the position of rest, the contact tongue is freely movable and can fully perform the resetting movement under the action of the leaf spring, provided the plunger position permits the complete resetting movement. If a resetting movement is not yet possible because of the plunger position, then a renewed switching operation takes place in the setting direction of the plunger. In the intermediate position occupied by the contact tongue, when the setting lever is actuated the electrical connection between the contact elements is broken. The switch occupies an operationally safe position. Thus it is not possible to manipulate the switch by holding the setting lever in the actuation position, with the object of locking the switch in the "ON" position. In every case operationally safe disconnection of the operational unit protected by the switch is guaranteed.
In another embodiment, according to the invention, the contact tongue is aligned parallel to the contact elements disposed at the top and bottom, and has contact studs associated with the contact elements. The rotational axis of the setting lever, which at the same time defines the intermediate position of the contact tongue, is advantageously disposed equidistant from the contact elements associated with the contact tongue. Adequate pivotability of the rotary member in the narrow installation space available between the contact elements is ensured particularly if, in accordance with a preferred embodiment of the invention, the rotary member is constructed as a substantially flat component. Preferably, the rotary member has end-face webs interconnected by the bars, one bar being disposed on the top of the webs and the other bar being disposed on the underside of the webs, a handle being formed on one web and a pivot being connected at the end face to at least one web. The webs have a substantially rectangular cross-section.
Finally, according to the invention, the resetting mechanism comprises a resetting spring returning the setting lever from the actuation position to the position of rest. Constructionally preferred is a leaf spring configuration such that the leaf spring comprises a trip arm and a separate arm providing contact with the contact pin.
The invention is explained in detail below with reference to a drawing illustrating just one exemplified embodiment and wherein:

Fig. 1: is a diagrammatic longitudinal section through a switch constructed according to the invention.
Fig. 1: is a diagrammatic plan view of the subject of Figure 1 with the cover removed.
Fig. 3 to 5: are enlarged scale diagrams of a detail of Figure 1 in different operating positions.
Fig. 6: is a diagrammatic plan view of the components shown in Figures 3 to 5.

The basic construction of the switch shown in the drawings comprises a housing 1 with a bottom part 1a and a cover 1b, contact elements 2, 3, 4 fixed to the housing, a trip mechanism 5 with a leaf spring 6 movable through a dead centre position, and a plunger 7 abutting the leaf spring 7. A transducer of known type (not shown), which converts a physical quantity, e.g. the temperature or the pressure, into a setting movement of the plunger 7 in the direction indicated by the arrow, is connectable to the plunger 7. The leaf spring 6 comprises a contact tongue 8 which is movable between two contact elements 2, 3 and is connected to a contact pin 4. The leaf spring 6 comprises a trip arm 6aand a separate arm 10 which provides the contact with the contact pin 4. The contact tongue 8 is aligned parallel to the contact elements 2, 3 disposed at the top and bottom, and has contact studs 11 associated with the contact elements 2, 3. The trip mechanism 5 is adapted to be actuated by a setting movement of the plunger 7 in the direction indicated by the arrow. A manually actuated resetting means 9 is provided to actuate the trip mechanism 5 in the opposite direction to the setting movement, such opposite direction hereinafter being referred to as the resetting direction.
The construction and operation of the resetting mechanism 9 will be apparent more particularly from Figures 3 to 6. The resetting mechanism 9 consists of a setting lever 12 mounted rotatably in the housing 1 and pivotable between a position of rest shown in Figures 3 and 4 and an actuating position shown in Figure 5. Lever 12 has a rotary member 13 disposed in the space between the contact elements 2, 3 associated with the contact tongue 8. Member 13 comprises two bars 15, 16 disposed on either side of and parallel to the axis of rotation 14, such bars being connected to end-face webs 17. One bar 15 is disposed on the top of the webs 17 and the other bar 16 on the underside of the webs 17. It will also be apparent from Figure 6 that a handle 18 is formed on one web 17 and that a pivot 19 is connected at the end face to at least one web 17. The axis of rotation 14 is disposed equidistant from the contact elements 2, 3. It coincides with the axis of symmetry of the arrangement.
A comparison of Figures 3 to 6 will show that the contact tongue 8 of the leaf spring 6 engages in the opening defined by the bars 15, 16. The arrangement is such that when the setting lever 12 is in the position of rest the contact tongue 8 is freely movable between the contact elements 2, 3. In Figures 3 and 4 the setting lever occupies the position of rest. Figure 3 shows the "ON" position. The contact tongue 8 abuts the top contact element 2. The top contact element 2 and the contact pin are electrically interconnected by the leaf spring 6. Figure 4 shows the "OFF" position. Here the contact tongue 8 abuts the bottom contact element 3, the current path between the top contact element 2 and the contact 4 being interrupted.
Figure 5 shows the arrangement with the setting lever 12 pivoted, this position previously and hereinafter being referred to as the actuation position of the setting lever 12. In the actuation position of the setting lever 12, the contact tongue 8 is clamped between the bars 15, 16 and without touching the contact elements 2, 3 occupies an intermediate position between the contact elements 2, 3. In the intermediate position, the dead-centre position of the leaf spring 6 is overcome in the resetting direction. The current flow between the top contact element 2 and contact pin 4 is interrupted. If the setting lever is returned to the position of rest, then depending on the position of the plunger 7 the contact tongue trips either into the "ON" position shown in Figure 3 or into the "OFF" position shown in Figure 4.
In the actuation position of the setting lever 12 shown in Figure 5, the switch occupies an operationally safe position. It is therefore impossible to manipulate the switch in order to lock it in the "ON" position by holding the setting lever 12 in the actuation position.

Claims

A switch comprising
a housing (1),
contact elements (2. 3. 4) fixed on the housing
a trip mechanism (5) with a leaf spring (6) which is movable through a dead-centre position and which comprises a contact tongue (8) movable between two contact elements (2, 3) and which is connected to a contact pin (4), and
a plunger (7) abutting the leaf spring (6),
the trip mechanism (5) being actuatable by a setting movement of the plunger (7) in a setting direction, and a manually actuated resetting mechanism (9) being provided to actuate the trip mechanism (5) in the resetting direction, characterised in that the resetting mechanism (9) consists of a setting lever (12) which is mounted rotatably in the housing (1) and which is pivotable between a position of rest and an actuation position and which comprises a rotary member (13) disposed in the space between the contact elements (2, 3) associated with the contact tongue (8), the rotary member (13) comprising bars (15, 16) aligned on both sides of and parallel to the axis of rotation (14), and in that the contact tongue (8) engages in the opening defined by the bars (15, 16), the contact tongue (8) being freely movable between the contact elements (2, 3) in the position of rest of the setting lever (12), the contact tongue (8) being clamped between the bars (15, 16), in the actuation position of the setting lever (12), and in that case occupies, without contacting the contact elements (2, 3), an intermediate position between the contact elements (2, 3) in which the dead-centre position of the leaf spring (6) is overcome in the resetting direction.
A switch according to Claim 1, characterised in that the contact tongue (8) is aligned parallel to the contact elements (2, 3) disposed at the top and bottom, and has contact studs (11) associated with the contact elements (2, 3).
A switch according to Claim 1 or 2, characterised in that the axis of rotation (14) of the setting lever (12) is disposed equidistant from the contact elements (2, 3) associated with the contact tongue (8).
A switch according to any one of Claims 1 to 3, characterised in that the rotary member (13) has end-face webs (17) interconnected by the bars (15, 16), one bar (15) being disposed on the top of the webs (17) and the other bar (16) being disposed on the underside of the webs (17), in that a handle (18) is formed on one web (17) and in that a pivot (19) is connected at the end face to at least one web (17).
A switch according to any one of Claims 1 to 4, characterised in that the resetting mechanism (9) comprises a resetting spring returning the setting lever (12) from the actuation position to the position of rest.
A switch according to any one of Claims 1 to 5, characterised in that the leaf spring (6) comprises a trip arm (6a) and a separate arm (10) providing contact with the contact pin (4).