ELASTOMERIC KEYPAD

Abstract

The present invention relates to an elastomeric keypad (1) having at least one key (3) comprising an elastomeric dome (41) defining a chamber (42) and provided inside with an activating means (43), an activation means (44) cooperating with said activation means (44), and at least one compensating channel (48) opening at said chamber (42) to enable for a flow of fluid from said chamber (42), while said elastomeric dome (41) collapses, and to said chamber (42), while said elastomeric dome (41) releases. In order to suppress the sound intensity of the pushup event, at least one of said compensating channels (48) comprises at least one valve arrangement (5) generating fluid restrictions while the fluid returns to said chamber (42). Preferably said valve arrangement (5) has a form of a Tesla Valve.

Claims

1. An elastomeric keypad (1) having at least one key (3) comprising an elastomeric dome (41) defining a chamber (42) and provided inside with an activating means (43), an activation means (44) cooperating with said activating means (43) to transmit a signal indicating said key (3) activation to an external control system, and at least one compensating channel (48) opening at said chamber (42) to enable for flow of fluid from said chamber (42), while said elastomeric dome (41) collapses, and to said chamber (42), while said elastomeric dome (41) releases, characterised in that at least one of said compensating channels (48) comprises at least one valve arrangement (5) acting as a passive check valve generating fluid restrictions while the fluid returns to said chamber (42), while providing substantially laminar flow of fluid while said elastomeric dome (41) collapses.

2. The keypad according to claim 1, characterized in that, said passive check valve (5) has a form of a Tesla Valve.

3. The keypad according to claim 1, characterized in that, said passive check valve (5) extends along the entire length of said compensating channel (48).

4. The keypad according to claim 1, characterized in that, said compensating channel (48) is terminated with a compensating chamber (47).

5. The keypad according to claim 1, characterized in that, it comprises a plurality of said domes (41), formed integrally in an elastomeric sheet (4)

6. The keypad according to claim 5, characterized in that, said compensating channels (48) and said passive check valves (5) are formed within said elastomeric sheet (4).

7. The keypad according to claim 5, characterized in that, said elastomeric sheet (4) adjoins a support plate (6).

8. The keypad according to claim 1, characterized in that, said at least one key (3) comprises a key cap (32) disposed slidably within a housing (2) and said elastomeric dome (41) cooperates with said key cap (32).

9. The keypad according to claim 1, characterized in that, said activating means (43) and/or said activation means (44) has/have a form of a conductive layer(s).

10. The keypad according to claim 1, characterized in that, said at least one key (3) comprises a spring disposed inside said elastomeric dome (41).

Description

BRIEF DESCRIPTION OF DRAWINGS

[0020] The invention shall be described and explained below in connection with the attached drawings on which:

[0021] FIG. 1 is a schematic cross-sectional view of a part of an embodiment of a keypad according to the present invention;

[0022] FIG. 2 is a perspective view of an elastomeric sheet of the keypad shown in FIG. 1;

[0023] FIG. 3a illustrates a top view of the elastomeric sheet shown in FIG. 2;

[0024] FIG. 3b illustrates a bottom view of the elastomeric sheet shown in FIG. 2;

[0025] FIG. 3c illustrates a side view of the elastomeric sheet shown in FIG. 2;

[0026] FIG. 4a illustrates the operation of an embodiment of the keypad while the key is pressed in a cross-sectional view;

[0027] FIG. 4b illustrates the operation of the embodiment of the keypad of FIG. 4a while the key is pressed in a bottom view;

[0028] FIG. 5a illustrates the operation of the embodiment of the keypad of FIG. 4a while the key returns to its normal position in a cross-sectional view; and

[0029] FIG. 5b illustrates the operation of the embodiment of the keypad of FIG. 5a while the key returns to its normal position in a bottom view.

DETAILED DESCRIPTION OF EMBODIMENTS

[0030] FIG. 1 presents an embodiment of a keypad 1 according to the present invention comprising a housing 2 having seven keys 3. Each key 3 comprises a key cap 32 having a plunger 31 disposed slidably within an opening 21 of the housing 2. An elastomeric sheet 4 is disposed inside the housing 2 and comprises seven domes 41 disposed beneath the plungers 31 of the keys 3. Each dome 41 defines a chamber 42 and is provided inside with an activating means 43, in a form of a conductive layer, cooperating with an activation means 44, also in a form of a conductive layer, disposed beneath the elastomeric sheet 4 at a rigid support plate 6 of the keypad. Each dome 41 normally maintains an inactive position of the key 3 acting on a plunger 31 and keeping the key cap 32 in its upward position with respect to the drawing. To this end a limiter 33 in a form of a circumferential recess is snap-locked over the edge of the opening 21 preventing the key cap 32 from sliding out.

[0031] As it is known from the state of art, when user presses the key cap 32 with a finger, the plunger 31 moves downward acting on the dome 41, the dome 41 collapses and eventually the activating conductive layer 43 inside the dome 41 touches the activation conductive layer 44 having two or more separate electrical paths (not shown) creating a conducting path between them and transmitting the signal indicating a given key activation to an external control system (not shown), the keypad 1 is coupled with. Moving and interacting elements of the key 3, as well as the deforming dome 41 generate a sound during such a push down event. When user releases the key cap 32, strain energy stored in the dome 41 during its deformation is also rapidly released forcing the dome 41 to rapidly return to its neutral position along with the key cap 32. Another sound is generated during such a push up event which is usually louder than the sound of the push down event, as the dome 41 collides with the plunger 31 of the key cap 32, which in turn collides with the keypad housing 2.

[0032] To enable for a flow of air from the chamber 42, while the elastomeric dome 41 is pushed down, and back to the chamber 42, while the elastomeric dome 41 is pushed up, the chamber 42 is fluidly connected with a compensating channel 48. The compensating channels 48 are terminated with compensating chambers 47 or led outside via openings 47a.

[0033] As shown in FIG. 2 and FIG. 3b each compensating channel 48 comprises a valve arrangement 5 in a form of a Tesla Valve extending almost along the entire length of the channel 48.

[0034] The interior of each Tesla Valve 5 is provided with meanders 51 and baffles 52 which, while offering virtually no resistance to the flow of air from the chamber 42 to the compensating chamber 47 (cf. FIGS. 4a and 4b), other than surface friction, constitute an almost impassable barrier to its flow in the opposite direction (cf. FIGS. 5a and 5b).

[0035] In other words, as shown with dashed arrows in FIG. 4b and FIG. 5b, the valve arrangement 5 act as a passive check valve providing substantially laminar flow of air during a push down event, and substantially turbulent flow during a push up event. This in turn requires more time for the dome chamber 42 to be filed by returning air and therefore supresses strain energy release of the dome 41. Therefore the dome 41 releases or returns slowly to its neutral position not hitting the plunger 31. Consequently the sound intensity of the push up event is suppressed.

[0036] Though in the presented embodiment the valve arrangement 5 extends along the entire length of the compensating channel 48 it is obviously not necessary. The dome 41 may also be connected with more than one compensating channel 48.

[0037] The above embodiments of the present invention are merely exemplary. The figures are not necessarily to scale, and some features may be exaggerated or minimized. These and other factors however should not be considered as limiting the spirit of the invention, the intended scope of protection of which is indicated in appended claims.

LIST OF REFERENCE NUMERALS

[0038] 1. keypad [0039] 2. housing [0040] 21. opening [0041] 3. key [0042] 31. plunger [0043] 32. key cap [0044] 33. limiter [0045] 4. elastomeric sheet [0046] 41. dome [0047] 42. chamber [0048] 43. activating means (conductive layer) [0049] 44. activation means (conductive layer) [0050] 45. plunger [0051] 46. fixing hole [0052] 47. compensating chamber (opening) [0053] 48. compensating channel [0054] 5. valve [0055] 51. meander [0056] 52. baffle [0057] 6. support plate