SIMPLIFIED ELECTRIC SWITCH CONSTRUCTION

Abstract: A simplified electric switch construction is disclosed. The switch construction comprises at least a pair of confronting first and second terminals each having a bridge portion, a conductive resilient plate having one end shaped as a polygonal pyramid disposed in confronting relation to the bridge portion of the first terminal and an opposite end con­ nected to the bridge portion of the second terminal, a presser for depressing an intermediate portion of the resilient plate to bring the tapered end into contact with the bridge portion of the first terminal, and a driver for depressing the presser. The switch construction may contain a printed-circuit board with an electric circuit thereon.

Description: The present invention relates to a simplified electric switch construction including movable conductive contact members having a high contact pressure for making electric connection between terminals, and more particularly to such a switch construction which is simple in structure, stable in ON-OFF operation, small in size, and contains an electronic circuit. Various mechanisms have been devised for electric connection between terminals in switches. The known mechanisms have suffered from the problem of poor contact between contacts of movable conductive contact members and contacts of terminals (hereinafter referred to as "bridge portions"). Fig. 1 of the accompanying drawings shows a conventional switch in which a terminal 1a has a bridge portion 2a to which a contact member 3 is fixed. A contact of the contact member 3 is brought into contact with a bridge portion 2b of a terminal lb by depressing one end 4 of the contact member 3. Since the contact 5 is pressed - merely by a push against the bridge portion 2b through an area of contact, any dust or flux therebetween cannot be effectively removed. Any oxidized coating formed on the contact surfaces with time cannot be coped with, and it is necessary to plate the contact surfaces with precious metal which is chemically stable. According to another prior switch illustrated in Fig. 2, a contact member 7 normally urged downwardly by a spring 8 is moved to the right (as shown) to bring a contact 8b of the contact member 7 into contact with a bridge portion 10b of a terminal 9b while keeping a contact 8a of the contact member 7 in contact with a bridge portion 10a of a terminal 9a. This arrangement is better than the depression-type switch construction since the contact 8b is held in frictional contact with the bridge portion 10b. However, there is a structural limitation against imposing a sufficient contact pressure to remove any unwanted deposit sufficiently from the contact surfaces. There is known a DIP (dual in-line package) switch construction having an electronic circuit responsive to operation of a switch drive unit for selecting desired terminals to achieve a certain electric fuction. The DIP switch construction is composed of ordinary DIP switch terminals connected to portions of an electronic circuit on a printed-circuit board and accommodated in a casing. Its fabrication requires separate preparation of a DIP switch and a printed-circuit hoard having an electronic circuit provided thereon and normally molded in a mass of resin. Therefore, the conventional DIP switch construction is likely to be increased in size. It would be possible to form the DIP switch and the printed-circuit board as an integral structure. However, prior individual switches used as DIP switches would have a structural limitation against miniaturization, and would suffer from less contact stability due to a small current to pass through the switch. No good contact would be obtained if the conventional switch contact members were pressed against contacts printed on the printed-circuit board. To avoid this shortcoming, the contacts on the printed-circuit board and contact members would have to be plated with gold, and would be provided with greater surfaces of contact. US-A-3 165 732 relates to an electric switch construction comprising at least a pair of confronting first and second terminals. A presser in the form of spherical balls is used for depressing a resilient element so as to provide contact between said resilient element and a screw contact. FR-A-2 168 162 relates to an electromagnetic relay. The relay comprises a coil, an armature and a plate which can be attracted by a pole piece and carries at a piece of insulation a flexible lever. At the distal end of the lever a contact 8 is located which is adapted for engagement with a stationary contact such that a cleaning effect is provided. US-A-3 297 851 relates to a commutator for measuring apparatus. Said measuring apparatus uses contacts which cooperates with points and contact plates. An arm carrying a pyramidal stud is rotated about an axis for contacting different bars which constitute an electrical contact. SUMMARY OF THE INVENTION The above-described drawbacks in the prior art apparatus have been successively eliminated by the present invention. It is an object of teh present invention to provide a simplified electric switch construction including movable conductive contact members having a high contact pressure for making electric connection between terminals. Another object of the present invention is to provide a switch construction which is simple in structure, stable in ON-OFF operation, small in size, and contains an electronic circuit. To achieve the above objects, a simplified electric switch construction according to the present invention comprises the features of claim 1. A preferred embodiment of the invention is disclosed in claim 2. These and other objects of the invention will become apparent from the following description of embodiments thereof when taken together with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1 and 2 are cross-sectional views of conventional switches; Fig. 3 is an exploded perspective view of a rotary switch according to an embodiment of the present invention; Fig. 4 is a cross-sectional view of the rotary switch shown in Fig. 3; Figs. 5a, 5b, and 5c are cross-sectional views of switches according to other embodiments of the present invention; Fig. 6 is an exploded perspective view of a rotary switch according to a still other embodiment of the present invention; Fig. 7 is a cross-sectional view of the rotary switch shown in rig. 6; Figs. 8a and 8b are circuit diagrams of a potentiometer and a chip selector which constitute electronic circuits on a printed-circuit board; Figs. 9a, 9b, 9c are cross-sectional views of switches of other embodiments; Figs. 10 and 11 are fragmentary views illustrative of operation of the switch shown in Figs. 3 and 4; Fig. 12 is a fragmentary perspective view of the switch shown in Figs. 3 and 4; and Figs. 13(a) and 13(b) are perspective views showing a process of manufacturing a movable contact member in the switch shown in Figs. 3 and 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotary switch according to an embodiment of the present invention for binary settings for an electronic circuit will be described with reference to Figs. 3 and 4. The rotary switch comprises a casing 11 shown by the dotted lines in Fig. 3 supporting four output terminals 12a through 12d and a single common input terminal 3 which are attached in place by insert molding. The input terminal 13 has a bridge portion 14 to which there is affixed as by fusing a contact body 15 in the form of a conductive, resilient metal plate. The contact body 15 has four movable contact memberse 16a through 16d extending from the portion thereof fixed to the bridge portion 14. The contact members 16a through 16d are bent at their proximal ends and urged upwardly, and have distal ends 17a through 17d punched out thicknesswise to form an acute angle 17e (Fig. 13(a)) and bent in the direction of the arrow X to direct a vertex P (Fig. 13(b)) shaped as a triangular pyramid (polygonal pyramid) in confronting relation to bridge portions 18a through 18b, respectively, of the terminals 12a through 12d. When intermediate portions of the contact members 16a through 16d are depressed, the vertexes P shaped as triangular pyramids and acting as cutter blade edges of the contact ends 17a through 17d are brought into point-to-point contact with the bridge portions 18a through 18d to impose a high pressure contact on the order of 100 kg/mm² on the bridge portions 18a through 18b, respectively. At the same time, as shown in Fig. 11, each contact end formed as the cutter blade edge scratches the corresponding bridge portion from the solid-line position to the dotted-line position as the tapered contact end is depressed. Therefore, any flux, dust or dirt, and oxidized layer on the bridge portions 18a through 18d is removed or broken to thereby activate the contact surfaces. While in the illustrated embodiment the contact members 16a through 16d are connected to the common contact terminal 13 via the contact body 15, the contact body 15 may be dispensed with, and the contact members 16a through 16d may be fixed respectively to four independent input terminal bridge portions (not shown), so that four independent input-output circuits may be provided. The rotary switch also includes four pressers or steel balls 20a through 20d held respectively in holes 22a through 22d in a holder plate 21 disposed above the contact members 16a through 16d, the steel balls 20a through 20d serving to depress the vertexes P of the contact members 16a through 16d, respectively. The holder plate 21 is supported in the casing 11 by a pair of ledges 23 mounted on an inner wall surface of the casing 11 at dismetrically opposite corners thereof and also by a seat 24 (Fig. 4) disposed between the contact members 16b, 16c on the bottom of the casing 11. The holder plate 21 is fixed in place by being pressed down to resiliently hold down the contact members 16a through 16d which are urged upwardly for thereby positioning the contact ends 17a through 17d in upwardly spaced relation to the bridge portions 18a through 18d, respectively. The holes 22a through 22d in the holder plate 21 are positioned over intermediate portions of the contact members 16a through 16d, respectively, and have a diameter larger than that of the steel balls 20a through 20d. Therefore, the steel balls 20a through 20d can move verticlly in the holes 22a through 22d, respectively. The steel balls 20a through 20d are raised by the contact members 16a through 16d normally held against the lower surface of the holder plate 21 so that the steel balls 20a through 20d have portions exposed above the upper surface of the holder plate 21. When the steel balls 20a through 20d are depressed, they lower the contact members 16a through 16d, respectively, to cause the tapered contact ends 17a through 17d into abutting contact with the bridge portions 18a through 18d and then force the contact members 16a through 16d to flex downwardly to enable the tapered contact ends 17a through 17d to scratch the bridge portions 18a through 18d, as illustrated in Figs. 10 and 11. Since the tapered contact ends 17a through 17d not only contact the bridge portions 18a through 18d but also scratch theem under a high contact pressure, any unwanted foreign matter such as dirt, dust, flux, and oxidized coating can easily be removed from the bridge portions 18a through 18d which are then activated for reliable and stable electric contact with the contact members 16a through 16d. While the contact members 16a through 16d are shown as being depressed by the steel balls 20a through 20d, the contact members 16a through 16d may be pressed downwardly by any other suitable bodies such as cylindrical bodies or rods with rounded heads provided they can be smoothly engaged by a driver (described later on) and depress the contact members 16a through 16d until they flex downwardly. With such an alternative, the contact members 16a through 16d may have be of a substantially circular shape with a smooth projection. The steel balls 20a through 20d can selectively be depressed by a rotatable driver 25 (Fig. 3) having on its back cam lands 27 (Fig. 12) projecting from a surface 26 in positions of segments separated radially and circumferentially along four circular paths a through d according to numerical weighting of 2⁰ - 2³. Since any steel ball 20 positioned below the surface 26 is not depressed (Fig. 4), the corresponding contact member 16 disposed therebelow is not in contact with the output terminal bridge portion 18, and hence no electric output is produced from the output terminal 12. Any steel ball 20 positioned below one of the cam lands 27 is depressed, and hence the contact member 16 below the depressed steel ball 20 is caused to contact the corresponding bridge portion 18 which is then electrically connected to the input terminal 13 to issue an electric output. By rotating the driver 25 clockwise or counter-clockwise in the direction of the arrow 28 (Fig. 4), the signal from the input terminal 13 is delivered selectively to the terminals 12a through 12d according to the angular displacement of the driver 25 (angularly oriented to one of numbers "0" through "9" inscribed on a cover 32 (Fig. 3). A numerical value can then be produced in 4-bit parallel binary notation from the output terminals 12a through 12d dependent on the contact combination. An 0-ring 34 (Fig. 4) is mounted on a shoulder around a central shank of the driver 25. An indexing ring 30 has a pair of diametrically opposite ridges 31 placed in slots 29 in a corrugated surface of the driver 25. The cover 32 is placed over the casing 11 and fused thereto. The switch construction as thus assembled is shown in Fig. 4. While the rotary switch for binary settings have been shown and described, the present invention is in no way limited to such a switch construction. For example, the invention is applicable to a sliding switch having a slidable driver 35 as shown in Fig. 5a, a pushbutton switch having a pushbutton 36 with a pusher rod 37 as shown in Fig. 5b, or a pushbutton switch including a contact member 39 having a presser projection 38 as shown in Fig. 5c. With the switch of the foregoing embodiment, as described above, the movable contact members comprise conductive resilient plates having ends punched to form acute angles and bent into vertexes shaped as polygonal pyramids disposed in confronting relation to terminal bridge portions and opposite ends fixed to other terminal bridge portions. When intermediate portions of the contact members are depressed, the latter are moved down the cause the tapered contact ends thereof to contact the bridge portions under a high contact pressure and at the same time are caused to flex to enable the tapered contact ends to scratch the bridge portions, so that any flux, dirt, dust, and oxidized coating on the bridge portions can be removed or broken for activating the contact surfaces of the bridge portions. As a result, the switch construction of the invention is capable of stable and reliable switching operation, and can be used for passing or cutting off a small current. With this arrangement, there is no need for plating the contact surfaces with gold or silver, and the switch construction is simple in structure and hence quite inexpensive to manufacture. Figs. 6 and 7 show a switch construction according to another embodiment in which an electronic circuit is incorporated therein. Like or identical parts in Figs. 6 and 7 are denoted by like or identical reference characters in Figs. 3 through 5, and will not be described in detail. As illustrated in Figs. 6 and 7, output terminals 12a through 12d and a common input terminal 13 have vertically separated bridge portions 18a through 18d and 41a through 41d, and 14 and 42. These upper and lower bridge portions vertically sandwich a printed-circuit board 40 with an electronic circuit disposed on a lower surface thereof. The output terminals 12a through 12d and the common input terminal 13 are connected through the lower bridge portions 41a through 41d and 42 respectively to electronic-circuit portions of the printed-circuit board 40. The connected bridge portions and the printed-circuited board are molded integrally and housed in a casing 11. By thus integrally molding and placing the assembly in the casing 11, the switch construction can be greatly reduced in size. The upper bridge portions 18a through 18d and 14 are placed on an upper surface of the printed-circuit board 40. Although not shown, the printed-circuit board 40 itself has a number of terminals with joined lead wires extending outwardly of the casing 11. The electronic circuit on the printed-circuit board 40 may comprise a potentiometer as shown in Fig. 8a or a chip selector as shown in Fig. 8b. The potentiometer of Fig. 8a includes a common terminal COM which can be connected selectively to terminals a through d by brinding one of the contact members 16a through 16d into contact with a corresponding one of the bridge portions 18a through 18d of the output terminals 12a through 12d. When the common terminal COM is thus connected to one of the terminals a through d , an applied voltage Vcc as divided a resistor R1, R2, or R3 is obtained from an output terminal OUT. The chip selector illustrated in Fig. 8b has a common terminal COM which can be connected selectively to terminals a through d in the same manner as that of the potentiometer of Fig. 8a. When the common terminal COM is coupled to one of the terminals a through d , one of output terminals a ' through d ' which corresponds to the one of the terminals a through d that has been connected to the common terminal COM is changed from the potential of a divided voltage Vcc applied to the ground potential. The chip selector can however meet a requirement to provide an output in a binary code. More specifically, the terminals a through d may be numerically weighted with 2⁰ - 2³, and a plurality of terminals may be switched in synchronism to obtain parallel binary codes from the output terminals a' through d ' Although in the arrangements of Figs. 8a and 8b the components employed in the potentiometer and the chip selector are all resistors, capacitors, diodes, or logic elements may be used in place of the resistors. The casing 11 and the cover 32 may be molded of a thermosetting resin. However, the manufacturing control is awkward since the temperature at which the resin is set is high (280°c for example) and it takes a long time for the resin to set. Where the parts are molded of a thermoplastic resin, the manufacturing control is easy and the cost is low because the molding temperature is relatively low (170 through 260°C for example) and the molding Process takes a short period of time. While the casing 11 and the cover 32 of thermoplastic resin are thermally deformable and softenable, they are reinforced by the printed-circuit board 40 which is made of ceramics, glass, or epoxy resin for increased mechanism or physical dimensional stability and strength. Where the casing 11 and the cover 32 shown in Figs. 3 through 5 are made of a thermoplastic resin, a reinforcing board (with no electronic circuit) may be placed in the position of the printed-circuit board shown in Figs. 6 and 7 to strengthen the components for increased mechanical or physical dimensional stability and strength against thermal deformation. While the rotary switch for binary settings have been shown and described with respect to Figs. 6 and 7, the present invention is in no way limited to such a switch construction. For example, the invention is applicable to a sliding switch having a slidable driver 35 as shown in Fig. 9a, a pushbutton switch having a pushbutton 36 with a pusher rod 37 as shown in Fig. 9b, or a pushbutton switch including a contact member 39 having a presser projection 38 as shown in Fig. 9c. In each of these alternatives, the printed-circuit board 40 is disposed in the switch casing. With the switch construction having an electronic circuit contained therein, as described above, a printed-circuit board with an electronic circuit thereon and a separate DIP switch are not employed, but a DIP switch and a printed-circuit board with an electronic circuit thereon are intergrally put together with the printed-circuit board sandwiched between upper and lower terminal bridge portions and disposed in the casing. Therefore, the switch construction is quite small in size. In addition, the movable contact members comprise conductive resilient plates having ends punched to form acute angles and bent into vertexes shaped as triangular pyramids disposed in confronting relation to terminal bridge portions and opposite ends fixed to other terminal bridge portions. When intermediate portions of the contact members are depressed, the latter are moved down the cause the tapered contact ends thereof to contact the bridge portions under a high contact pressure and at the same time are caused to flex to enable the tapered contact ends to scratch the bridge portions, so that any flux, dirt, dust, and oxidized coating on the bridge portions can be removed or broken for activating the contact surfaces of the bridge portions. As a result, the switch construction of the invention is capable of stable and reliable switching operation, and can be used for passing or cutting off a small current. With this arrangement, there is no need for plating the contact surfaces with gold or silver, and the switch construction is simple in structure and hence quite inexpensive to manufacture.

Claims: An electric switch construction comprising: at least a pair of confronting first and second terminals (12,13) each having a bridge portion (14,18); a conductive resilient plate (15) having one end forming a contact means, and an opposite end connected to the bridge portion (14) of said second terminal (13); a presser (20) for depressing an intermediate portion of said resilient plate (15) to bring said contact means into contact with the bridge portion (18) of said first terminal (12); and a driver for depressing said presser, characterized in that said contact means at one end of the resilient plate (15) has an acute angle (17e) and the same thickness as the resilient plate (15) and is bent to direct a vertex (P) shaped as a triangular pyramid into confronting relation to the bridge portion (18) of said first terminal (12). An electric switch construction according to claim 1, wherein said presser (20) comprises a steel ball, further including a holder plate (21) holding down said resilient plate (15) and having a hole (22) positioned over said intermediate portion of the resilient plate (15), said steel ball (20) being placed in said hole (22) and being pushed by said resilient plate (15) so as to be partly exposed out of said hole (22).

Inventors: SENOO, YASUTAKA
Applicants: OTAX CO., LTD.
Application year: 1984
Main classification: H01H1
IPC codes: H01H19, H01H1