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(11) | EP 1 083 583 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Electrical switch |
| (57) An electrical switch (30) includes an insulative substrate (32) having a top surface
(36). Switch circuitry (34,34a) is disposed on the insulative substrate and includes
a first conductive contact (34) on the top surface of the substrate. A flexible, insulative
top layer (40) is disposed directly on top of the substrate (32). The top layer includes
an actuator portion (42) having a second conductive contact (44) on the bottom thereof
in registry with the first conductive contact (34). A step (46) in the top layer (40)
is formed about the actuator portion (42) to elevate the actuator portion and space
the second conductive contact (44) from the first conductive contact (34). Depression
of the actuator portion (42) toward the substrate (32) moves the spaced second conductive
contact into engagement with the first conductive contact. |
Field of the Invention
[0001] This invention generally relates to the art of electrical switches and, particularly, to a laminated or membrane-type electrical switch.
Background of the Invention
[0002] Laminated or membrane-type electrical switches are used in a wide variety of applications and sometimes are called "touch" switches. In particular, such a switch may include a bottom insulative substrate, such as of plastic material, which mounts or supports a lower contact, such as of stamped sheet metal, on a top surface thereof. A flexible top membrane is laminated to the substrate. The top membrane may be provided with an embossed dome having an upper contact adhered to the underside thereof in registry with the lower contact. In a normally open membrane switch, a spacer layer is sandwiched between the top membrane and the bottom substrate, with an aperture in the spacer layer aligned with the contacts. When the embossed dome is depressed in the area of the aperture in the spacer layer, the top membrane flexes such that the upper contact engages the lower contact to close the switch.
[0003] In laminated or membrane-type electrical switches as described above, most fabrication equipment costs center around the laminated nature of the structure. More fabrication equipment is needed for a greater number of layers having different configurations. The present invention is directed to reducing fabrication equipment costs by providing a unique top membrane or layer in a laminated switch, which completely eliminates the need for a spacer layer.
Summary of the Invention
[0004] An object, therefore, of the invention is to provide a new and improved electrical switch of the character described.
[0005] In the exemplary embodiment of the invention, the electrical switch includes an insulative substrate having a top surface. Switch circuitry is disposed on the insulative substrate and includes a first conductive contact on the top surface of the substrate. A flexible, insulative top layer is disposed directly on top of the substrate and includes an embossed dome having a second conductive contact on the bottom of the substrate in registry with the first conductive contact.
[0006] A step is formed in the top layer about the embossed dome to elevate the dome and space the second conductive contact from the first conductive contact. Therefore, depression of the embossed dome toward the substrate moves the spaced second conductive contact into engagement with the first conductive contact. The step includes an upwardly extending peripheral wall surrounding the embossed dome. A horizontal wall joins the peripheral wall with the dome.
[0007] Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.
Brief Description of the Drawings
[0008] The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with its objects and the advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the figures and in which:
FIGURE 1 is a fragmented vertical section through a membrane switch of the prior art;
FIGURE 2 is a fragmented vertical section through a membrane switch according to the invention; and
FIGURE 3 is a fragmented top plan view looking in the direction of line 3-3 of Figure 2.
Detailed Description of the Preferred Embodiment
[0009] Referring to the drawings in greater detail, and first to Figure 1, a laminated or membrane-type electrical switch, generally designated 10, is shown according to the prior art. The switch includes a bottom insulative substrate 12 having a pair of lower switch contacts 14 adhered to a top surface 16 of the substrate. The contacts are separated at a gap 18 to form a normally open switch. A flexible top membrane 20 includes an embossed dome 22 having an upper contact 24 adhered to the bottom of the dome in registry with lower contacts 14 and spanning gap 18. A spacer layer 26 is sandwiched between bottom substrate 12 and top membrane 20 and includes an aperture 28 aligned with lower contacts 14 and upper contact 24. When embossed dome 22 is depressed in the direction of arrow "A", the dome moves upper contact 24 through aperture 28 in spacer layer 26 and into engagement with lower contacts 14 spanning gap 18 to close the switch.
[0010] Figures 2 and 3 show a laminated or membrane-type electrical switch, generally designated 30, according to the invention. Like the prior art switch, a bottom insulative substrate 32 includes a pair of lower contacts 34 disposed on a top surface 36 of the substrate. The contacts are separated at a gap 38 to create a normally open switch. As seen in Figure 3, the contacts include leads 34a for electrically coupling the switch contacts to appropriate electrical apparatus with which the switch is operatively associated.
[0011] Electrical switch 30 according to the invention also includes a flexible, insulative top membrane or layer 40 disposed directly on top of substrate 32 and lower contacts 34. The top membrane includes an embossed dome 42 having an upper contact 44 adhered to the underside thereof in registry with lower contacts 34 spanning gap 38 between the contacts. The top membrane includes a unique step, generally designated 46, which functions to elevate dome 42 and particularly upper contact 44 spaced above lower contacts 34.
[0012] More particularly, the flexible, insulative top membrane or layer 40 is fabricated of plastic material such as polyester and embossed dome 42 and step 46 are formed integrally therewith. The step is formed by an upwardly extending peripheral wall 48 which surrounds embossed dome 42. A horizontal wall 50 integrally joins the peripheral wall with embossed dome 42.
[0013] In operation of switch 30, embossed dome 42 is depressed in the direction of arrow "B" (Fig. 2) toward bottom substrate 32. By depressing the dome, upper contact 44 is moved through the space formed by step 46 into engagement with lower contacts 34, spanning gap 38 between the lower contacts and closing the switch.
[0014] It can be seen in Figure 2 that step 46 can be formed sufficiently high that embossed dome 42 can be completely eliminated while still spacing upper contact 44 above lower contacts 34. However, the embossed dome gives a "snapping" type tactile indication of closing the switch. In addition, it should be understood that the use of such terms as "top", "bottom", "upper", "lower", "vertical", "horizontal" and the like herein and in the claims hereof are not intended in any way to be limiting in nature. Switch 30 is omni-directional in use, and such terms have been used herein and in the claims hereof to better provide a clear and concise understanding of the invention.
[0015] It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.
an insulative substrate (32) having a top surface (36);
switch circuitry (34,34a) on the insulative substrate and including a first conductive contact (34) on the top surface of the substrate; and
a flexible, insulative top layer (40) disposed directly on top of the substrate (32) and including an embossed dome (42) having a second conductive contact (44) on the bottom thereof in registry with said first conductive contact (34), and a step (46) in the top layer (40) about the embossed dome (42) to elevate the embossed dome and space the second conductive contact (44) from the first conductive contact (34), whereby depression of the embossed dome (42) toward the substrate (32) moves the spaced second conductive contact into engagement with the first conductive contact.
an insulative substrate (32) having a top surface (36);
switch circuitry (34,34a) on the insulative substrate and including a first conductive contact (34) on the top surface of the substrate; and
a flexible, insulative top layer (40) disposed directly on top of the substrate (32) and including an actuator portion (42) having a second conductive contact (44) on the bottom thereof in registry with said first conductive contact (34), and a step (46) in the top layer (40) about the actuator portion (42) to elevate the actuator portion and space the second conductive contact (44) from the first conductive contact (34), whereby depression of the actuator portion (42) toward the substrate (32) moves the spaced second conductive contact into engagement with the first conductive contact.
a pair of switch contacts (34) opposed to each other at a gap (38);
an insulative substrate (32) having a top surface (36) supporting the switch contacts (34); and
a flexible, insulative top layer (40) disposed directly on top of the substrate and including an actuator portion (42) having a conductive contact (44) on the bottom thereof in registry with said switch contacts (34) at said gap (38), and a step (46) in the top layer (40) about the actuator portion (42) to elevate the actuator portion and space the conductive contact (44) from the switch contacts (34), whereby depression ofthe actuator portion (42) toward the substrate (32) moves the spaced conductive contact into engagement with the switch contacts.