GB2246325A - Key assembly - Google Patents

Abstract

A key assembly includes a housing (2) in which a stem member (7) is slidably mounted. A coil spring (14) abuts a keytop member (11) and has a projecting portion (18), which may be in the form of an enlarged coil. The stem member (7) has a projection (10a). When the stem member (7) is forced downwardly by pressure applied to the keytop member (11), its projection (10a) engages the projecting portion (18) on the coil spring (10). Continued depression of the stern member (7) causes the spring (10) to deform, thereby providing a tactile feeling, and then the projecting portion (18) of the coil spring snaps over the projection (10) on the stem member (7) to produce a click sound. <IMAGE>

Description

KEY ASSEMBLY The present invention relates to a key assembly, and more particularly to a key assembly which preferably provides a tactile feeling and a click sound.

Basically, there are three types of key assembly on the market. These are the capacity type, the mechanical type and the membrane type. Since a typewriter needs feedback to ensure an effective input, a click sound and a tactile feeling or the like are preferable in the key assembly.

The first key assembly which came onto the market was the capacity type. However, it is not now widely used since the membrane type or mechanical type are preferred instead because they can provide the tactile feeling and click sound.

As the key assembly needs to be directly mounted on a printed circuit frame, this creates some difficulty if another part is to be installed within the housing, such as leaf spring or the like, in order to create a click sound.

In fact, no space is available for such an additional part.

Nevertheless, such a construction is simplest and cheapest compared with the others and it has higher reliability.

A typical mechanical type key assembly is manufactured by Alps Electronic Ltd. It has been widely used and accepted by users. In the latter key assembly, a leaf spring is used to create a tactile feeling, and a click sound is generated as the leaf spring slams back to an inside wall of a housing. Whilst this is a commendable invention, its mechanism cannot be applied to the membrane switch or to the capacity switch. Moreover, its manufacturing cost is high.

IBM has also provided a unique and simple key assembly for a membrane switch. It uses only a single coil spring together with a pad and both the tactile feeling and the click sound are provided by the spring and pad. However, this kind of assembly needs a larger space and a longer coil spring, compared with the above mentioned key assemblies.

Also, its mechanism cannot be applied on other forms of switches.

OAK has also provided a typical key assembly which is applied to the membrane switch. However, it cannot create the tactile feeling and click sound. It also has a complicated structure and parts.

Acer Inc. has provided a novel key assembly in its Taiwan Application No. 772-06294, which can be viewed as an improvement in a key assembly of the OAK type, see Figure 1.

It uses the leaf spring of Alps and the key assembly of OAK to create a click sound and tactile feeling.

The purpose of the present invention is to provide a novel key assembly which has few parts and is easy to manufacture. Consequently a low manufacturing cost can be achieved.

One advantage of the present invention is that the key assembly can be applied to different forms of switches, such as the membrane switch, the mechanical switch and the capacity switch.

Another advantage of the present invention is that the key assembly uses an improved coil spring which can be substituted for the leaf spring and coil spring used in the prior art. The improved coil spring, together with an improved stem member, can provide a good tactile feeling and a click sound.

In order to achieve the above mentioned purpose and advantages, the key assembly of the present invention comprises a housing in which a stem member is slidably located, said stem member having a projection thereon, and a coil spring having a projecting portion; the arrangement being such that when said stem member slides in said housing due to key pressure, the projecting portion of said coil spring initially abuts the projection on said stem member whereby further sliding movement of said stem member causes deformation of the projecting portion of said coil spring, and/or of said coil spring so as to provide a tactile feeling and further sliding movement of said stem member subsequently causes the projection on said coil spring to snap over the projection on said stem member thereby providing a click sound.

This invention can be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying Drawings as follows: Figure 1 is the section view of Acer's key assembly; Figures 2 and 3 are respectively a section through an embodiment of the present invention and a perspective, partly broken away view of parts of the same embodiment; Figures 4a and 4b are respectively a perspective view and a sectional view on line xx of a modified stem member for use in the embodiment of Figure 2, Figures 5-a - 5-c are step by step illustrative views of the same embodiment showing relative movement between a stem member and a coil spring; Figure 6 is a second embodiment of the present invention; Figure 7 is a third embodiment of the present invention; Figure 8 is a fourth embodiment of the present invention;; Figure 9 is a plan view of an insert for a coil spring; and Figure 10 is a force-distance chart for various coil spring.

Referring to Figures 2 and 3, key assembly 1 comprises a housing 2 which can be easily mounted on a frame structure (not shown). The housing 2 has a rectangular base plate 3 with a hole 4 in its upper roof. A bridge portion 16, shown in section, is part of the housing 2 and it provides a firm location for a coil spring 14. Four vertical wall plates 5 extend downwardly from the base plate 3. A neck 6 extends upwardly from the base plate 3.

A hollow stem member 7 is slidably mounted within the neck 6 of the housing 2 so that it is capable of reciprocal movement in the hole 4. The stem member 7 has a bottom plate 8 on which a bumper 9 is mounted (not shown in Fig.

3). An annular rib 10a, 10b (seen in section) projects inwardly of the hollow stem member 7. A keytop member 11 having a conical recess 12 and an annular recess 13 is fitted to the upper end of the stem member 7.

A coil spring 14 is housed by the hollow stem member 7.

An upper end 14a of spring 14 is firmly located in the conical recess 12 of the keytop member 11 and a lower end 14b is located on a stem portion 15 of a bridge 16 so that the spring 14 is supported and thereby compressed when the keytop member 11 is depressed.

The coil spring 14 has a projecting portion in the form of one coil 18, adjacent its lower coils 14b, which coil 18 has a larger coil dimension than the other coils. This coil 18 projects radially outwardly on one side of the spring. Coil 18 is located adjacent a column of contiguous or closely spaced lower coils 14b so that coil 18 can be displaced and deformed relative to the body of spring 14 as explained below. The position and dimension of coil 18 is such that it engages the underside of a confronting portion 10a of the annular rib when the hollow stem member 7 is urged downwardly by finger pressure applied to the keytop member 11. This is shown in Figure 5-a where the stem member 7 has been depressed by such an extent that the annular rib portion 10a has engaged the coil 18. On further depressing the stem member 7, coil 18 is displaced and it starts to buckle or deform as shown in Figure 5-b.

Whilst the coil 18 buckles, it creates a tactile feeling for the user whose finger is depressing the keytop member 11.

The preferred tactile feeling largely depends on the torque between the enlarged coil 18 and the adjacent coils on the spring 14. However, where the lower coils are closely spaced, some compression can occur to assist with the rebound energy, although this may not provide as good a tactile feeling. Further finger pressure causes the stem member 7 to be depressed even more whereby the rib portion 10a slides past the coil 18. The coil 18 then rebounds upwardly and the coil 18 slams against the upper edge of the rib portion 10a creating a click sound. This is shown in Figure 5-c.

When the keytop member 11 is released, there is sufficient energy stored within the spring 14, since it is compressed in the position shown in Figure 5-c, to return the stem member 7 to its starting position. The coil 18 then slides back over the annular rib portion 10a and returns to its original position as shown in Figure 2.

In the embodiment of Figures 2 and 3, the stem member 7 needs to be inserted into the underside of the housing 2.

Figures 4a and 4b illustrate a modified stem member comprising a disc-shpaed top portion 7a which is integral with two half shell portions 7b. This modified stem member 7 can be fitted from the top of the housing 2, i.e. inserted into the neck 6. Each half shell portion 7b has a flexible hook portion 7c and deformation occurs as the stem member 7 is fitted to neck 6 so that the hooks snap over the shoulder between neck 6 and base plate 3 in order to retain the shell in the housing 2. A modified keytop member (not illustrated) would be used with the modified stem member, or the keytop member could be moulded integrally.

The coil spring 14 can easily be substituted for the coil spring and leaf spring of the prior art.

Referring to Figure 6, this shows a second embodiment of the present invention. Basically, this mechanism differs from the ACER type since the stem member and coil spring are removed and replaced by the improved stem member and coil spring of the invention. In Figure 6, the coil 18 is shown schematically although it may be a projection on the side of a uniform spring. Thus, the preferable tactile feeling and click sound can be created without a leaf spring. This kind of mechanism can also be applied to the membrane type.

Figure 7 is a third embodiment which differs from the ALPS type, mechanical type, by substituting the stem member and the spring with parts according to the invention. The coil 18 is again shown schematically. The invention can also be applied to the mechanical type switch.

Figure 8 illustrates another embodiment wherein the improved coil spring 14 is sleeved on the stem member 7 and the keytop 11 is recessed to engage a projecting rib 19 on the stem member 7. The lower end of spring 14 rests on the periphery of the hole 4 in the housing 2. When the keytop 11 moves downwards by a fixed distance, a tactile feeling together with a click sound is created.

From the above description, it can be understood that the structure of the stem member, leaf spring and coil spring on the mechanical switch assembly can easily be replaced by the stem member and coil spring of the present invention. The tactile feeling and click sound will still be present even without the leaf spring. Consequently, the manufacturing cost is reduced. This concept can be applied to an OAK switch or to other switches without any difficulty.

Figure 9 is a plan view of an insert for use in an alternative coil spring assembly. In this alternative, a coil spring can be used having a uniform coil cross-section.

This is not illustrated in Figure 9 but the drawing shows, in plan view, an insert in the form of a disc 20 to which a ring 21 is attached (.e.g by a weld 22). The ring 21 forms an "auxiliary" coil, which has a larger coil size than the size of the coils of the uniform spring. Thus, when the disc 20 is inserted in the stack of coils of the spring, the ring 21 projects circumferentially so as to provide the same effect as the enlarged coil 18 of spring 14. The disc 20 can have a recess, or a protuberance 23 which assists in locating the disc in the coil stack so that the disc is not displaced laterally when the coil is compressed by key pressure. This coil spring assembly, which can be considered as a coil spring having a projection (21), can be used in any of the previously described embodiments.

Figure 10 is a force versus distance diagram of embodiments of the present invention and other types of switch.

Various modifications will be apparent to those skilled in the art without departing from the scope of the invention.

Claims (15)

CLAIMS:

1. A key assembly comprising a housing in which a stem member is slidably located, said stem member having a projection thereon, and a coil spring having a projecting portion; the arrangement being such that when said stem member slides in said housing due to key pressure, the projecting portion of said coil spring initially abuts the projection on said stem member whereby further sliding movement of said stem member causes deformation of the projecting portion of said coil spring and/or said coil spring so as to provide a tactile feeling and further sliding movement of said stem member subsequently causes the projecting portion on said coil spring to snap over the projection on said stem member thereby providing a click sound.

2. A key assembly according to Claim 1 wherein the projecting portion of said coil spring is an enlarged coil which is part of said spring.

3. A key assembly according to Claim 2 wherein said enlarged coil is located in said coil spring adjacent a column of contiguous coils whereby said enlarged coil can be displaced relative to said column of contiguous coils.

4. A key assembly according to Claim 1 wherein the projecting portion of said coil spring is a projection attached to one of its coils.

5. A key assembly according to Claim 1 wherein the projecting portion of said coil spring is a coil attached to a member which is inserted into the coils of said coil spring, said coil having a larger size than the size of the coils in said coil spring.

6. A key assembly according to any of the preceding Claims wherein said coil spring is located within said stem member and abuts the housing so that the stem member can move relative to said coil spring, the projection on said stem member being on a path of movement for engaging with the projecting portion of said coil spring.

7. A key assembly according to any preceding Claim wherein said stem member includes a base portion and upstanding portions which are spaced apart to define channels, and wherein said housing has an opening therein with a bridge member extending thereacross, said upstanding portions being slidably received in said opening so that said channels accommodate said bridge member when said stem member slides in said housing.

8. A key assembly according to Claim 4 wherein said stem member comprises shell portions for surrounding said coil spring and-wherein said housing has an opening therein with a bridge member extending thereacross, said shell portions being slidably received in said opening so that gaps between said shell portions accommodate said bridge member when said stem member slides in said housing.

9. A key assembly according to any preceding Claim in which a keytop member is attached to the stem member.

10. A key assembly according to any one of Claims 4 to 7 wherein the projection on said stem member is an annular rib.

11. A key assembly according to any of Claims 1 to 3 wherein said stem member is in the form of a post on which said coil spring is mounted, an upper end of said post terminating in a keytop member which abuts an upper end of said coil spring and a lower end of said coil spring abutting a peripheral portion of said housing surrounding a hole in which the post is slidable.

12. A key assembly substantially as herein described with reference to Figures 2 and 3 of the accompanying Drawings.

13. A key assembly substantially as herein described with reference to Figure 4 of the accompanying Drawings.

14. A key assembly substantially as herein described with reference to Figure 5 of the accompanying Drawings.

15. A key assembly substantially as herein described with reference to Figure 6 of the accompanying Drawings.