GB2028591A

GB2028591A - Sliding electrical switch

Info

Publication number: GB2028591A
Application number: GB7929029A
Authority: GB
Original assignee: Bunker Ramo Corp
Current assignee: Bunker Ramo Corp
Priority date: 1978-08-24
Filing date: 1979-08-21
Publication date: 1980-03-05
Also published as: FR2434469A1; DE2933457A1; JPS5533405U; JPS5760510Y2; IN149864B

Abstract

A slide switch comprises a slide member 4, including a sliding contact 45, arranged to slide relative to the fixed contacts 1,2 between an OFF and an ON position, the contacting portion 30 of one of the contacts 1 including a pair of connected, spaced resilient arms 21, 24 extending parallel to the top surface of the base plate 3, each arm 21, 24 having a free end biased inwardly toward the other arm to capture the sliding contact 45 therebetween and electrically engage the sliding contact as the slide member 4 is moved from an OFF to an ON position. The contracting portion 29 of the other contact 1 has a shaped part 13, 16 in the path of the sliding contact 45 for electrically engaging the sliding contact 45 when the slide member 4 is moved to the ON position, the resilient arms 11, 14 of the one contact 1 being shaped to urge the sliding contact 45 against the shaped part of the other contact 2 when the slide member 4 is in the ON position. <IMAGE>

Description

SPECIFICATION Sliding electrical switch TECHNICAL FIELD This invention relates to the field of electrical switches, and in particular to sliding electrical switches which have an operating slide member movable in a rectilinear motion between OFF and ON positions.

BACKGROUND OF THE PRIOR ART Sliding electrical switches are commonly used in a variety of forms in electrical equipment. One particular application of such sliding switches concerns switching in circuits arranged on printed circuit boards. Sliding switches have been developed in extremely small packages, an example of which is the DIP switch that is configured in the form of a standard DIP package.

Such switches are constructed of a mounting base plate and at least a pair of spring contacts each having a terminal portion beiow the base plate and a contacting portion above the base plate. The contacting portions above the base plate are bent toward one another and define resilient fixed contacts for the switch. A sliding contact piece is mounted for slidably moving within the switch and contains a conductive member which makes and breaks connection between the fixed contacts mounted in the base plate.

However, in such a structure, the terminal portions of the contacts are generally adapted to bf soldered to the circuit board, and when the terminals are soldered, the high temperature of the contact resulting therefrom causes the mounting base plate to become soft and deformed, thereby rendering the fixing of the fixed contacts in the base plate insecure. Due to the softening of the base plate, the relative positions of the fixed contacts are altered to assume a lower position in the switch. Because of this, a reduced contact pressure results, and the switch can fail or become highly unreliable.

Thus, there is a need in the field of sliding electrical switches for a small size sliding switch that is highly reliable and does not produce a lessening of the contact pressure in spite of the application of high temperatures to the terminal portions of the contacts during the soldering operation. The present invention fulfils this BRIEF SUMMARY OF THE INVENTION According to the invention, there is provided a sliding electrical switch which avoids the shortcomings of prior art sliding switches and has, as a basic structure, a mounting plate, a pair of contacts, and a slide member, the contacts and slide member being arranged to produce reliable ON and OFF connections substantially independent of the security of the mounting of the fixed contacts in the mounting base plate.

Each contact has a terminal portion projecting out of the bottom surface of the base plate and a contacting portion projecting out of the top surface thereof. A slide member, including a sliding contact, is arranged to slide relative to the fixed contacts between an OFF and an ON position. The contacting portion of at least one of the contacts includes a pair of connected, spaced resilient arms extending parallel to the top surface of the base plate, each arm having a free end biased inwardly toward the other arm to capture the sliding contact therebetween and electrically engage the sliding contact as the slide member is moved from an OFF to an ON position.The contacting portion of the other contact has a shaped part in the path of the sliding contact for electrically engaging the sliding contact when the slide member is moved to the ON position, the resilient arms of the one contact being shaped to urge the sliding contact against the shaped part of the other contact when the slide member is in the ON position.

In a preferred embodiment, at least the one contact has a bridge portion connecting the arms together at one end with the free ends of the arms angled inwardly toward one another beginning adjacent the bridge portion in order to position the free ends in close spaced relationship. Preferably, but not necessarily, the other contact is constructed in a similar manner. The end of each contact arm has a bend near the free end thereof defining a tip portion which is angled outwardly to form a V-shaped nose for the contacts. In this manner, the slide member, as it moves to the ON position, carries the sliding contact to the region between the V-shaped noses of the contacts, and after passing the bends forming the tip portions of the one contact, the sliding contact is forced past the bends and is captured, under pressure, in the region between the noses.

The slide member is of generally T-shaped cross-section and has a downwardly depending bearing plate and a horizontally extending support plate upon which is positioned an operating button. The bearing plate has a lower edge which slidably bears against the top surface of the mounting base, and the sliding contact extends out of the plane of the side surfaces of the bearing plate. The spacing between the flat sides of the bearing plate is less than the spacing between the extremities of the sliding contact projecting from the sides of the bearing plate. This is to permit the bearing plate to slide without obstruction or high frictional drag between the contact arms, and yet permits a strong pressure force against the sliding contact as it reaches the free ends of the contact arms.

A flat positioning projection can be provided on the upper surface of the base plate to act as a bearing surface for the bearing plate and to vertically position the sliding contact relative to the vertical position of the tips of the contact arms.

Retaining tabs are provided on the terminal portion of the contacts such that the space between the bridge portion of the contact and the retaining tab will accommodate the thickness of the-mounting base plate in an interference fit. For added rention, security of the contacts on the mounting base plate, edge notches can be -provided in the base plate to accommodate the neck portion of the contact between the bridge and the retaining tab.

Preferably, the bearing plate of the slide member has an opening therethrough to accommodate a spherical metal ball in either a fixed or freely rotating condition.

An insulative housing is provided to cover the contacts and slide member and is adapted to be firmly fastened to the base plate. The inside construction of the housing can be such as to provide a guide for the slide member, and an elongated opening can be provided in the upper surface of the housing to allow unrestricted movement of the operating button as the slide member is moved between OFF and ON positions.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in detail with reference to the accompanying drawings representing preferred embodiments of sliding electrical contacts according to the present invention. In the drawings: FIGURE 1 is a cross-sectional view of a prior art sliding electrical switch; FIGURE 2 is a cut-away, partial perspective view of a sliding electrical switch made in accordance with the present invention; FIGURE 3 is an exploded view of the parts making up the sliding electrical switch accordingto the present invention; FIGURE 4 is a schematic representation of the positioning of the contact arms of the switch with the sliding member in an OFF position; FIGURE 5 is a view similar to that of FIGURE 4 with the sliding member in an ON position;; FIGURE 6 is an alternate embodiment of the contact arrangement shown in FIGURE 4, the FIGURE 6 embodiment illustrating that the two contacts need not be of identical configuration.

DETAILED DESCRIPTION OF THE INVENTION FIGURE 1 illustrates, in cross-section, a typical prior art sliding electrical switch with a base plate 9 holding fixed contacts 6 and 7, having contacting portions 6a and 7a and terminal portions 6b and 7b. A sliding contact piece 8 is shown to be electrically, engaging-both fixed contacts 6 and 7 to complete an electrical path therebetween. As explained above, when the terminal portions 6b and 7b are soldered to a circuit board, the heat of the soldering operation can cause the contacting portions 6a and 7a to be lowered due to the deformation of the mounting base 9 at the point where the contacts pass through. As will be evident from the following, the present invention is not susceptible to this substantial disadvantage of the prior art.

The perspective view of an electrical sliding switch made in accordance with the present invention can be seen in FIGURE 2 wherein a nonconductive mounting base plate 3 mounts fixed contacts 1 and 2 and a housing 5 covering the entire assembly. A sliding member 4 is shown confined between the arms of fixed contact 1, and an operating button 41 of an adjacent sliding member is shown protruding through opening 60 in the upper surface of housing 5.

The invention can be best understood by reference to the exploded view of the parts making up the sliding electrical switch, as shown in FIGURE 3. In this figure, the preferred configuration of the contacts are shown. By way of example, contact 1 includes a terminal 18, a connecting bridge 17, a neck 71 lying between bridge 17 and terminal 18, and a pair of contact arms 14 connected at the bridge 17. The bridge 17 and arms 11 and 14 make up the contacting portion of the contact, while terminal 1 8 with its neck 71 and retaining tabs 19 make up the terminal portion of the contact.The connected spaced resilient contact arms 11 and 14 extend substantially parallel to the top surface of mounting base plate 3, each arm 11 and 1 4 having a free end biased inwardly toward the other arm by angling the arms toward one another in the direction of the free ends. Bends 1 3 and 1 6 define tip portions 12 and 1 5 angled outwardly to form a V-shaped nose 29 for contact 1.

Contact 2 has a similar construction as that of contact 1 and includes bridge 26, terminal 27, neck 72, retaining tabs 28, contact arms 20 and 23, bends 22 and 25, and tips 21 and 24 defining a V-shaped nose 30. In this respect, while contact 2 is shown to have an identical configuration to that of contact 1, it is not necessary to have such correspondence, and contact 2 could be shorter or even of totally distinctive form, so long as the nose region 30 is shaped to open outwardly. This will be discussed in more detail below.

FIGURE 3 also shows a slide member 4 having a flat-sided bearing plate 42 connected to the bottom surface of a horizontal support plate 40, the latter two elements defining the body of the slide member having a T-shaped cross-section. An operating button 41 is located on the top surface of support plate 40 for easy access by an operator of the switch In a preferred embodiment, a bearing hole 43 is provided in bearing plate 42 to accommodate a sliding contact in the form of a metal ball 45 which is an inexpensive and readily available part. The relative sizes of the bearing hole 43 and metal ball 45 are chosen to either fix the ball 45 rigidly in the hole 43 or to allow ball 45 to rotate freely within hole 43.

The mounting base plate 3 can be provided with a flat-topped projection 52 having a top surface acting as a bearing surface for the lower edge 46 of bearing plate 42. This will ensure that sliding contact 45 is positioned a predetermined distance vertically relative to the top surface of the mounting plate 3. Notches 50 and 51 are provided in the lateral edges of base plate 3 to accommodate pressure fitting the contact neck portions 71 and 72 lying between the respective bridge portions and retaining tabs of each contact 1 and 2. As predetermined, the spacing between the top surface of base plate 3 and the nose regions 29 and 30 of contacts 1 and 2 is made equal to the aforementioned predetermined distance between the sliding contact 45 and the top surface of base plate 3.

Insulating housing 5 is open at its bottom and is adapted to be fastened, as by bonding, to mounting base plate 3 and covers the internal elements comprised of sliding member 4, sliding contact 45, and contacts 1 and 2. It is desirable that the internal construction (not shown) of housing 5 form a guide for permitting smooth rectilinear sliding motion of slide member 4. The guiding of slide member 4 is further enhanced by the provision of elongated slots 60 in a top surface of housing 5 to accommodate and guide the projecting operating buttons 41. In the assembled condition, housing 5 also serves to keep the contact neck portions 71 and 72 confined in notches 50 and 51, respectively.

FIGURES 4 and 5 aid in illustrating the operation of the sliding switch made in accordance with the invention. In FIGURE 4, the contact arms are in a normal relaxed position, the metal ball 45 is confined between arms 11 and 14 and, due to the resiliency of the arms, is urged to the left as shown in FIGURE 4. The distance between arms 11 and 14 at the bridge 17 may be selected to be slightly larger than the diameter of sliding contact 45.

As slide member 4 is moved to the right (see FIGURE 5), it forces arms 11 and 14 apart while making sliding electrical engagement therewith.

As the metal ball 45 passes bends 13 and 16, the angled tips 12 and 15 serve to cam ball 45 further to the right. However, the distance between noses 29 and 30 are such that, before arms 11 and 14 can fully relax, ball 45 is forced against tips 21 and 24 of contact 2 resulting in the urging of arms 20 and 23 apart. Again, however, the angles of each tip portion of each contact, the resiliency of the arms, and other design factors including the spacing between arm and nose regions, are chosen to prevent ball 45 from passing by bends 22 and 25 of contact 2. Accordingly, as FIGURE 5 indicates, the ball 45 is captured between the nose regions 29 and 30 with all four tips 12, 1 5, 2l,.and 24 engaging and exerting pressure against ball 45.

When the slide member is subsequently moved to the OFF position, the sliding contact again forces arms 11 and 1 7 apart at bends 13 and 16, and further movement to the left is aided by the tapered positioning of arms 11 and 1 7 to create a snap-action feel to the switch operation. This snap-action occurs, of course, in moving the slide member to either the ON or OFF position.

It can be appreciated that regardless of any moderate deformation of the base plate when soldering to the contact terminals 18 and 28,the biasing force against the ball 45 does not change because such deformation will be only in the vertical direction, and reliable electrical engagement is effected between all four tips of the two contacts and the ball 45. Projections 52 additionally aid in maintaining the contacts at a predetermined distance from the base 3, even if a heated terminal 1 8 would otherwise allow the contacts to droop.

FIGURE 6 shows an alternative embodiment of the contact configuration, wherein contact 2 is shown to be of smaller dimension than that of contact 1. In this manner, optimum design characteristics for each contact can be obtained.

Contact 2, for example, can be made more rigid and less resilient, since there is no need for spreading the two arms so widely apart to allow the ball 45 to pass between the bends 22,25 therein.

Because of the configuration of the contacts 1, 2 and use of a slide member as described, assembly of the switch is not complicated by the need of dies and precision assembly jigs.

Production costs are thus low, and yet, because of the ball shape, the switch has excellent wearability.

From the foregoing, it can be readily realized that this invention can assume various embodiments. Thus, it is to be understood that the invention is not limited to the specific embodiments described herein, but is to be limited only by the appended claims.

Claims

1 A sliding electrical switch comprising: a mounting base plate; a pair of contacts fixed in said base plate, each contact having a terminal portion projecting out of the bottom surface of said base plate and a contacting portion projecting out of the top surface thereof; and a slide member, including a sliding contact, arranged to slide relative to said fixed contacts between an OFF position and an ON position;-the contacting portion of at least one of said contacts including a pair of connected, spaced resilient arms extending parallel to said top surface, each arm having a free end biased inwardly toward the other arm to capture said sliding contact therebetween and to electrically engage said sliding contact as said slide member is moved toward said free ends from said OFF to said ON position; said contacting portion of the other of said contacts having a shaped part in the path of said sliding contact for receiving and making electrical contact with said sliding contact when said slide member is moved to said ON position, said resilient arms being configured to urge said sliding contact against said shaped part of said other contact when said slide member is in said ON position.

2. The sliding switch as claimed in Claim 1, wherein: said one contact has a contact bridge portion connecting said arms opposite said free ends; said arms are angled inwardly toward one another beginning adjacent said bridge portion in order to position said free ends in close spaced relationship; and each arm of said one contact has a bend near said free end defining a tip portion angled outwardly to form a V-shaped nose for said one contact.

3. The sliding switch as claimed in Claim 2, wherein said other contact comprises: a pair of connected, spaced resilient arms extending parallel to said top surface, each arm having a free end biased inwardly toward the other arm; and a contact bridge portion connecting said arms of said other contact opposite the free ends thereof, said arms of said other contact being angled inwardly toward one another beginning adjacent said bridge portion in order to position said free ends of said other contact in close spaced relationship, each arm of said other contact having a tip portion angled outwardly to form a V-shaped nose defining said shaped part of said other contact.

4.The sliding switch as claimed in Claim 2, wherein: said slide member includes a flat bearing plate having spaced flat sides and a lower edge slidably bearing against said top surface; and said sliding contact projects out of the plane of said flat sides on both sides of said bearing plate, the spacing between said flat sides of said bearing plate being less than the spacing between the extremities of said sliding contact projecting from said sides of said bearing plate.

5. The sliding switch as claimed in Claim 4, wherein said base plate comprises a raised flattopped projection positioned on its top surface to provide a bearing surface for said bearing plate and to space said sliding contact a predetermined distance from said base plate top surface.

6. The sliding switch as claimed in Claim 5, wherein said V-shaped nose and said shaped part are spaced from said base plate top surface by said predetermined distance.

7. The sliding switch as claimed in Claim 3, wherein: said contacting portions of said contacts are formed to extend at right angled to said terminal portions; and said terminal portions include at least one retaining tab spaced from said bridge portion and protruding laterally outwardly, said contacts being rigidly mounted to said mounting base plate by pressure-fitting said base plate between said bridge portion and said at least one tab.

8. The sliding switch as claimed in Claim 7, wherein said mounting base plate has edge notches therein for receiving the portion of said contacts between said bridge portion and said at least one tab.

9. The sliding switch as claimed in Claim 4, wherein: said flat bearing plate has a circular opening therethrough; said sliding contact is a spherical metal ball confined in said opening; and said arms of said one contact are spaced sufficiently close so as to prevent said ball from falling out of said opening as said slide member is moved between said OFF and ON positions.

1 0. The sliding switch as claimed in Claim 1, including: an insulative housing covering said contacts and said slide member; and means for fastening said housing to said base plate.

11. The sliding switch as claimed in Claim 10, wherein said slide member comprises: a flat support plate fixed to the top of said bearing plate and having an upper planar surface parallel to said base plate; and an operating button protruding out of the plane of said support plate upper surface.

12. The sliding switch as claimed in Claim 11, wherein said housing has an elongated slot therein for loosely receiving said operating button, said slot having a length sufficient to permit unrestricted rectilinear movement of said button as said slide member is moved between said OFF and ON positions.

13. The sliding switch as claimed in Claim 11, wherein said housing has an internal structure cooperating with said support plate upper surface for guiding said slide member in a rectilinear path between said OFF and ON positions.

14. The sliding switch as claimed in Claim 3, wherein said noses of said contacts are spaced to define a region of confinement for said sliding contact, said tip of each arm of each contact electrically engaging and applying pressure to said sliding contact confined in said region.

1 5. The sliding switch as claimed in Claim 9, wherein said ball is fixed in said opening against rotation.

1 6. The sliding switch as claimed in Claim 9, wherein said ball is dimensioned relative to said opening to be freely rotatable therein.