GB2282703A

GB2282703A - Mechanical key switch

Info

Publication number: GB2282703A
Application number: GB9320457A
Authority: GB
Inventors: Daw Shen Chen
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-10-05
Filing date: 1993-10-05
Publication date: 1995-04-12
Also published as: GB9320457D0

Abstract

A mechanical key switch includes a key body 40, a striking member 30 having a top projecting nipple 31 and two side wings 32, the side wings 32 being respectively inserted in a pair of sliding grooves 42 inside the key body 40 and stopped at horizontal stop walls 45, a key cap 10 having a projecting nipple (13, Fig 1) on its inner surface, and a compression spring 20 connected between the projecting nipple (13) of the key cap 10 and the projecting nipple 31 of the striking member 30, whereby pressing the key cap 10 causes the compression spring 20 to produce a click sound as the striking member 30 is oscillated to strike the membrane circuit board 50 below; the compression spring 20 returning to its former shape and simultaneously producing a click sound as the key cap 10 is released. The key cap 10 has hooked portions 12 slidable in guide grooves 43 in the key body 40 and ribs (14) for limiting the stroke of the key cap 10. <IMAGE>

Description

MECHANICAL KEY SWITCH FOR MEMBRANE KEYBOARDS The present invention relates to a mechanical key switch tor a membrane keyboard which is simple in structure, and which produces a click sound as it is depressed or released.

Various mechanical key switches are known and widely used in computer keyboards. These mechanical key switches are usually consisted of at least six parts. Therefore, these mechanical key switches are commonly expensive to manufacture, and complicated to assemble.

The present invention eliminates the aforesaid drawbacks. It is therefore an object of the present invention to provide a mechanical key switch which is consisted of less number of parts. It is another object of the present invention to provide a mechanical key switch is inexpensive to manutacture.

It is still another object of the present invention to provide a mechanical key switch which is easy to assemble and disassemble. It is still another object of the present invention to provide a mechanical key switch which is durable in use. It is still another object of the present invention to provide a mechanical key switch which produces a click sound as it is depressed or released. According to the preferred embodiment of the present invention, the mechanical key switch is simply comprised of four parts, namely, the key cap, the key body, the compression spring, and the striking member. The compression spring is retained inside the key body, having two opposite ends respectively connected to a bottom projecting nipple on the key cap and a top projecting nipple on the striking member. Pressing the key cap causes the compression spring to produce a click sound as the striking member is oscillated to strike the membrane circuit board below. The compression spring returns to its former shape and simultaneously produces a click sound as the key cap is released.

The present invention will now be described by way of example only with reference to the annexed drawings, in which: Fig. 1 is a sectional assembly view of a mechanical key switch according to the preferred embodiment of the present invention; Fig. 2 is a perspective exploded view of the key switch shown in Figure 1; Fig. 3-R is a longitudinal sectional view of the key switch showing the striking member forced by the deformed compression spring to oscillate in one direction as the key cap is depressed; Fig. 35 is another longitudinal sectional view ot the key switch showing the striking member forced by the compression spring to oscillate in the reversed direction as the key cap is released.

Referring to Figures 1, 2, 3-A, and 3-B, a mechanical key switch in accordance with the preferred embodiment of the present invention is generally comprised of a key cap 10, a compression spring 20, a striking member 30, and a key body 40. The striking member 30 comprises a first striking surface 33, a second striking surface 34 extended from the first striking surface 33, a projecting nipple 31 at the top, and two locating wings 32 vertically disposed on two opposite sides. The key cap 10 comprises two parallel rails 11 spaced at the bottom, two resilient hooks 12 spaced between the parallel rails 11, four ribs 14 arranged in crossing relationship inside the key cap 10, and a bottom projecting nipple 13 inside a narrow, rectangular bottom hole detined within the parallel rails II and the resilient hooks 12. The key body 40 comprises a rectangular center through hole 41, two vertical grooves 43 on two opposite shorter sides of the center through hole 41, two steps 44 respectively formed on the guide grooves 43, two adjacent pairs of opposite sliding grooves 42 disposed on two opposite sides by the center through hole 41 and respectively terminated to horizontal stop walls 45. The striking member 30 is received in the center through hole 41 inside the key body 40 by inserting the locating wings 32 into either pair of opposite sliding grooves 42 for permitting the locating wings 32 to be respectively stopped at the respective horizontal stop walls 45.

The key cap 10 is slidably fastened to the key body 40 by inserting the parallel rails 11 and the resilient hooks 12 into the center through hole 41 and the guide grooves 43 respectively tor permitting the resilient hooks 12 to be respectively hooked up with the steps 44. The compression spring 20 is received inside the center through hole 41 with its two opposite ends respectively fastened to the projecting nipple 13 of the key cap 10 and the projecting nipple 31 of the striking member 30. The membrane circuit board 50 comprises an upper circuit board 51, a lower circuit board 52, and an isolating board 53 between upper and lower boards.

Referring to Figures 3-A and 3-B again, pressing the key cap 10 to compress the compression spring 20 causes the striking member 30 to be oscillated, and therefore the second striking surface 34 is forced to strike against the membrane circuit board 50 below, then the upper circuit board 51 is pressed down to contact the lower circuit board 52 in producing a correspondent electrical signal, the stroke of key cap can be limited by its 4 ribs while pressed down. As the compression spring 20 is compressed to deform and the striking surface 34 striked against the membrane circuit board, a click sound is simultaneously produced.

As the hand is released from the key cap 10, the key cap 10 is moved back to its former position by the compression spring 20 with its resilient hooks 12 respectively hooked on the steps 44, and the striking member 30 is forced by the compression spring 20 to oscillate in the reversed direction, and the second striking surface 34 is lifted from the membrane circuit board 50 that the upper circuit board 51 returns to its former position and cuts off the the circuit. As the striking member 30 is returned to over ride its former position by the inertia of spring expansion force, and the first striking surface 33 is forced to strike against the membrane circuit board 50 in producing a click sound. As the compression spring 20 returns to its former shape, a click sound will also be produced.

As indicated, the present invention provides a mechanical key switch which is consisted of only four parts, and which produces sound upon each strike. As the striking of the striking member against the membrane circuit board is made through an oscillating motion, less force is needed to press the key cap.

While only one embodiment of the present invention has been shown and described, it will be understood that various modifications and changes could be made without departing from the spirit and scope of the invention

Claims

What is claimed is:

1. A mechanical key switch comprising: a key body, said key body comprising a rectangular center through hole, two vertical grooves on two opposite shorter sides of said center through hole, two steps respectively formed on said guide grooves, two adjacent pairs of opposite sliding grooves disposed on two opposite sides by said center through hole and respectively terminated to horizontal stop walls; a striking member received inside said center through hole of said key body, said striking member comprising a projecting nipple at the top, and two opposite locating wings respectively inserted in either pair of sliding grooves and stopped at said horizontal stop walls; a key cap vertically slidably fastened to said key body at the top, said key cap comprising two parallel rails spaced at the bottom and respectively inserted into said center through hole, two resilient hooks spaced between said parallel rails and inserted into said guide grooves and releasably hooked on said steps, four ribs arranged in crossing relationship inside the said key cap can limit the stroke of the key cap while pressed down, and a bottom projecting rod inside a narrow, rectangular bottom hole defined within said parallel rails and said resilient hooks; and a compression spring received inside said center through hole of said key body and having two opposite ends respectively fastened to the projecting nipple on said key cap and the projecting nipple on said striking member; whereby pressing said key cap to compress said compression spring causes said compression spring to produce a click sound, and simultaneously causes said striking member to strike a membrane circuit board below through an oscillating motion in producing a corresponding electric signal; said striking member is forced by said compression spring to oscillate in the reversed direction and return to its former position as said compression spring returns to its former shape in producing a click sound upon releasing of said key cap.

2. Mechanical key switches as claimed in claim 1 and as herein described.

3. Mechanical key switches as herein described with reference to the accompanying drawings.