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(11) | EP 0 261 702 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Switch provided with wire-shaped contact members |
| (57) A switch (1,29) provided with a first contact member (11) which is made of wire and
cooperates with a second contact member (13), this first contact member (11) upon
displacement from a first position to a second position being in engagement with a
wire guide (23) which is built as a form of a projection and is electrically insulated
from the second contact member (13) said first contact member performing a movement
associated with elastic bending in two orthogonal directions resulting in a uniformly
increasing or decreasing resistance force. |
[0001] The invention relates to a switch provided with a displaceable wire-shaped first metal contact member anchored at least at one end in a support and with a second metal contact member cooperating therewith, the first contact member being subjected, when displaced between a first and a second position, to an elastic deformation determined by an actuation force and a resistance force and the said resistance force exerted by a wire guide on the first contact member increasing uniformly in value during at least part of the displacement of the first contact member.
[0002] In a switch of the kind mentioned in the opening paragraph known from German Patent Specification 2925653, the first contact member consists of a wire, which is helically wound in a conical form and one end of which is anchored in the support, while the actuation force is exerted on the other end. In an embodiment having both a break contact and a make contact, the break contact to be considered as the second contact member is wire-shaped. A straight portion of the first contact member engaging the support serves as a so-called wire guide, which exert resistance force on a turn of the first contact member during the switching movement. This resistance force increases uniformly in value till the switching instant. The extent to which the resistance force increases during the switching movement entirely depends upon the wire diameter and upon the form of the first contact member.
[0003] A disadvantage of the known switch is that its manufacturing process has to be modified comparatively drastically if according to desires of users the same type of switch has to be delivered with a different force - displacement characteristic. For example, a characteristic is often required with which a resistance force initially increasing uniformly in value is followed by a resistance force uniformly decreasing in value.
[0004] The invention has for its object to provide a switch in which the said disadvantage is avoided.
[0005] A switch according to the invention is for this purpose characterized in that the wire guide is a projection which is dimensioned independently of the wire diameter of the first contact member and is electrically insulated from the second contact member, said form piece cooperating with a U-shaped part of the first contact member displaceable in two orthogonal directions.
[0006] A particular embodiment of the switch, in which the risk of contamination of the contact area is avoided as far as possible, is further characterized in that both the first and the second contact member are made of metal wire, the U-shaped second contact member being anchored in the support at both ends and being located in a plane which is at right angles to the plane in which the U-shaped part of the first contact member is located, which contact members engage each other in one of the said positions of the first contact member at two contact points, while the first contact member is in engagement with the wire guide, a ridge of the wire guide exerting during the displacement of the first contact member from the first position located on one side of the ridge to the second position located on the other side of the ridge an initially uniformly increasing and then uniformly decreasing and again uniformly increasing resistance force on the bracket-shaped part of the first contact member.
[0007] A further embodiment of the switch, in which the force - displacement characteristic is also determined to a considerable extent by torsion in the first contact member, is characterized in that the first contact member is symmetrical and comprises a first pair of parallel limbs which are anchored at their one ends in the support and adjoin at their other ends a second pair of aligned limbs, which are located together with a third pair of adjoining limbs in a plane at right angles to a plane including the first pair of limbs, the third pair of parallel limbs being interconnected by a bridge to form the bracket-shaped part of the first contact member.
[0008] A still further embodiment of the switch, in which, whilst maintaining the torsion in the first contact member, the desired distance between the wire guide and the contact points can be obtained, is characterized in that the bracket-shaped part of the first contact member has two limbs diverging in the direction of the second contact member.
[0009] The invention will be described more fully with reference to the drawing, in which:
Fig. 1 shows a cross-section of a first embodiment of the switch taken on the line I-I in Fig.2,
Fig. 2 is a plan view of the switch shown in Fig.1,
Fig.3 shows a cross-section of a second embodiment of the switch taken on the line III-III in Fig.4,
Fig. 4 is a plan view of the switch shown in Fig.3,
Fig. 5 shows diagrammatically an arrangement of the two contact members and the wire conductor.
[0010] The switch 1 shown in Figures 1 and 2 has a housing 3, made by injection-moulding from a synthetic material, such as, for example, polycarbonate with a teflon filling and a glass filling, and in which a push-button 5 is displaceable in a direction parallel to an arrow 7. The push-button 5 is provided with a ram 9 which engages a first wire-shaped contact member 11, which is made of metal (for example a nickel-manganese alloy) and is indicated diagrammatically in Fig.5. As can be seen from Figures 1, 2 and 5, the contact member 11 has a pair of parallel vertical limbs L₁ and L₂, a pair of aligned horizontal limbs L₃ and L₄, a pair of parallel horizontal limbs L₅ and L₆ and a horizontal limb L₇ which is parallel to the limbs L₃ and L₄. The limbs L₁-L₇ are formed from one piece of round wire by bending and cutting on a known processing machine. The said vertical or horizontal location of the limbs L₁-L₇ corresponds in the aforementioned case to the switched-off state of the switch. In Fig.1, the position of the first contact member 11 corresponding to the switched-on state of the switch 1 is indicated by dotted lines. The switch 1 further has a second wire-shaped contact member 13 made of metal (for example a nickel-manganese alloy). The U-shaped contact member 13 is manufactured from one piece of round wire by bending and cutting on a similar or the same processing machine on which the first contact member 1 is formed. The second contact member 13 has two vertical limbs L₈,L₉ and a horizontal limb L₁₀. The limbs L₁ and L₂ of the first contact member 11 and the limbs L₈ and L₉ of the second contact member 13 are located by injection-moulding or are clamped (anchored) in holes 15,17 and 19,21, respectively, of the housing 3 serving as a support.
[0011] The housing 3 of the switch 1 injection-moulded from synthetic material is provided with a so-called wire guide 23, which consists of a form piece of electrically insulating material, which is manufactured (moulded) integrally with the housing and whose dimensions are independent of the wire diameter of the first contact member 11. The housing 3 further has a stop 25 for the limbs L₅ and L₆ of the first contact member 11 formed integrally with the housing. The limb L₁₀ of the second contact member 13 is supported in a horizontal gutter 27 of the housing 3. The switch 1 is symmetrical with respect to a plane at right angles to the plane of the drawing in Fig. 3 and including the line I-I.
[0012] When a force is exerted on the push-button 5 in the direction of the arrow 7 (Fig.1), the ram 9 engaging the limbs L₅ and L₆ of the first contact member 11 causes a downward movement parallel to the Z direction of the limb L₇, which is simultaneously subjected to a displacement parallel to the direction by means of the wire guide 23. After the limb L₇ has passed the ridge-shaped wire guide 23, which limb engages at two contact points C₁ and C₂ (cf. Fig.2) the limb L₁₀ of the second contact member 13. The stop 25 for the limbs L₅ and L₆ prevents too large a deformation of the first contact member 11 and also determines the maximum contact force at the contact points C₁ and C₂. Since the wire guide 23 is ridge-shaped, the operator meets during the switching movement an initially uniformly increasing resistance force, which is followed by a uniformly decreasing resistance force and then by a resistance force again increasing uniformly to a maximum value. The form of the force - displacement diagram corresponding thereto is often prescribed by the user of the switch because in this manner a remote indication is obtained of the fact that the switch has operated. In the switched-on state of the switch 1 shown in Fig.1, the first contact member 11 is subjected to a resetting force which is sufficiently large to set the switch to its neutral switched-off state after the push-button 5 has been released. The displacement of the limb L₇ parallel to the X direction during the switching movement results in an elastic deformation of the first contact member 11 which is a combination of bending and torsion of the limbs L₁ and L₂ and of bending of the limbs L₃ and L₄. The displacement of the limb L₇ parallel to the Z-direction results in an elastic deformation of the contact member 11 which is built up of torsion of the limbs L₃ and L₄ and of bending of the limbs L₁ and L₂ and the limbs L₅ and L₆. It has been shown both from calculations and from measurements that in the switch 1 shown in Figures 1 and 2 the torsion of the limbs L₃ and L₄ provides a comparatively larger contribution to the displacement of the limb L₇ parallel to the Z direction than the bending of the limbs L₁ and L₂ and the limbs L₅ and L₆. In general a combination of torsion and bending is to be preferred if comparatively small dimensions for the switch are desired. Because of the symmetry of the contact member 11 there is no displacement of the limb L₇ parallel to the Y direction when the switch is switched on or off. The limbs L₅, L₆ and L₇ of the first contact member 11 form a bracket-shaped or U-shaped part of the contact member which cooperates with or is in engagement with the wire guide 23 and is then subjected to a displacement both parallel to the X direction and parallel to the Z direction. This combined movement in two orthogonal directions of a wire-shaped limb (L₇) along a four piece (wire guide 23) offers the possibility of many variations in the desired force- displacement characteristic and many variations of the switch itself. The form of the two contact members, the length and thickness of the limbs and the form of the wire guide are the parameters which are available for variations of the switch whilst maintaining the principle of the invention. The manner in which the contact members and the wire guide can be constructed will be explained below. As an introduction thereto, a second embodiment of the switch is now described with reference to Figures 3, 4 and 5, in which use is made of reference numerals corresponding as far as possible to those used in Figures 1, 2 and 5.
[0013] The second embodiment shown in Figures 3 and 4 of a switch 29 according to the invention is distinguished from the switch 1 of Figures 1 and 2 by a first contact member 11 whose limbs L₅ and L₆ diverge in a direction towards the second contact member 13, while the contact member 13 is no longer located in a single plane and has five limbs. For the sake of simplicity, the push-button 5 is omitted in Figures 3 and 4. Due to the divergence of the limbs L₅ and L₆, in general the contact points C₁ and C₂ can be arranged in lateral direction comparatively remotely from the area at which the limb L₇ is in engagement with the wire guide 23, while nevertheless the effective torsional length of the limbs L₃ and L₄ can be comparatively great. Since at the area of the contact between the limb L₇ and the wire guide 23 wear particles are formed, the contact points C₁ and C₂ should not be arranged too closely in order to prevent contamination. In the first embodiment of the switch 1 shown in Figures 1 and 2, in principle there is a greater risk of contamination of the contact points C₁ and C₂ than in the switch 29 shown in Figures 3 and 4. By a suitable choice of the synthetic material used for the wire guide 23 (for example polycarbonate with a teflon filling and a glass filling), the amount of wear and hence also the permissible variation in the force - displacement characteristic can be kept within acceptable limits. The second contact member 13 of the switch 29 has besides the limbs L₈ further limbs L₁₁ and L₁₂. This offers the possibility of arranging the contact points C₁ and C₂ comparatively remotely in the X direction from the wire guide 23 without the overall dimension of the switch being enlarged. Furthermore, the actuation force is absorbed by the limb L₁₀ and the stop 25 via the gutter 27, as a result of which the anchoring of the limbs L₈ and L₉ in the housing 3 is no longer loaded.
[0014] As can be seen from Fig.5, an actuation force K a(2 × ½ K a) exerted by the ram 9 of the push- button 5 on the lines L₅ and L₆ is absorbed during the switching movement entirely in the anchorages of the limbs L₁ and L₂ in the housing 3. At the contact points C₁ and C₂, a reaction force is not yet exerted on the limbs L₅ and L₆ by the limb L₁₀. The wire guide 23 exerts a horizontal reaction force K h on the limb L₇ and a vertical reaction force K v is also exerted thereon. The force K h causes torsion of the limbs L₁ and L₂, while the force K v and the actuation force K a determine the torsion in the limbs L₃ and L₄. Further, the pairs of limbs L₁-L₂, L₃-L₄ and L₅-L₆ are subjected to bending. It will be appreciated that a modification of the switches 1 and 29 described is obtained if the pair of limbs L₁-L₂ or both pairs of limbs L₁-L₂ and L₃-L₄ of the first contact member 11 are omitted. In fact, the aforementioned elementary bracket-shaped part constituted by the three limbs L₅,L₆ and L₇ is then only left, of which the limb L₇ cooperates with the wire guide 23. In such an embodiment entirely lying within the scope of the invention, the limbs L₅ and L₆ are anchored in the housing 3. In order to obtain a sufficient displacement from the centre of the limb L₇ in the X and Z directions, the limbs L₅, L₆ and L₇ must have a comparatively small resistance to bending and the limbs L₃ and L₆ must preferably further have a comparatively small resistance to torsion. In the case in which only the pair of limbs L₁-L₂ is omitted, the limbs L₃ and L₄ are anchored in the housing 3. Since now the limbs L₃ and L₄ can contribute by means of torsion to the displacement in the Z direction of the limb L₇, in principle a comparatively smaller switch can be composed than when the two pairs of limbs L₁-L₂ and L₃-L₄ are omitted.
[0015] The wire guide 23 can be constructed as a form piece having solely an ascending edge or as a form piece having an ascending edge and a descending edge and thus being ridge-shaped. In the first case, a force - displacement characteristic is obtained, in which K a solely rises uniformly, whereas in the second case a characteristic is obtained having a K a successively increasing uniformly, decreasing uniformly and increasing uniformly. Within the scope of the invention, the possibility is offered in a simple manner to obtain all kinds of force - displacement characteristics by changing the wire guide 23. This may be effected, for example, by using differently shaped inserts in an injection mould. The invention has additionally the advantage that without modifications of the nature of the manufacturing process a series of switches of different dimensions can be obtained. By the comparatively free choice of force - displacement characteristics and dimensions, a mass production of switches is possible which can be adapted in a flexible manner.
[0016] The switch according to the invention may have make and/or break contacts and may be of multiple construction. The second contact member may be strip- or plate-shaped. At the area of the anchoring, the contact members may have a rectangular cross-section. It should be noted that the wire guide, which is electrically insulated from the second contact member may be made either of an insulating synthetic material or of a metal. In the latter case, the wire guide must be separated by a separate arrangement or by an insulating envelope from the second contact member. The wire guide may also be in the form of a non-integral insert. The wire guide may be either narrower or wider than the distance between the limbs L₅ and L₆.
1. A switch provided with a displaceable wire-shaped first metal contact member anchored
at at least one end in a support and with a second metal contact member cooperating
therewith, the first contact member being subjected, when displaced between a first
and a second position, to an elastic deformation determined by an actuation force
and a resistance force and the said resistance force exerted by a wire guide on the
first contact member increasing uniformly in value during at least part of the displacement
of the first contact member, characterized in that the wire guide is a projection
which is dimensioned independently of the wire diameter of the first contact member
and is electrically insulated from the second contact member, said form piece cooperating
with a U-shaped part of the first contact member displaceable in two orthogonal directions.
2. A switch as claimed in Claim 1, characterized in that both the first and the second
contact member are made of metal wire, the U-shaped second contact member being anchored
in a support at its two ends and being located in a plane at right angles to the plane
in which the bracket-shaped part of the first contact member is located, which contact
members engage each other in one of the said positions of the first contact member
at two contact points, while the first contact member is in engagement with the wire
guide, a ridge of the wire guide exerting during the displacement of the first contact
member from one position located on the one side of the ridge to the second position
located on the other side of the ridge an initially uniformly increasing, then uniformly
decreasing and again uniformly increasing resistance force on the bracket-shaped part
of the first contact member.
3. A switch as claimed in Claim 1 or 2, characterized in that the first contact member
is symmetrical and comprises a first pair of parallel limbs which are anchored at
their one end in the support and adjoin at their other end a second pair of aligned
limbs, which are located together with a third pair of adjoining limbs in a plane
at right angles to the plane including the first pair of limbs, the third pair of
parallel limbs being interconnected by a bridge and constititung with it the bracket-shaped
part of the first contact member.
4. A switch as claimed in Claim 1, characterized in that the bracket-shaped part of
the first contact member has two limbs diverging in the direction of the s
econd contact member.