CN206758293U - A kind of ultra-thin key switch with well balanced property - Google Patents

Abstract

The utility model discloses a kind of ultra-thin key switch with well balanced property, including pedestal, the pedestal upper surface offers an accommodating cavity, feed-through assembly is provided with the accommodating cavity, also include being arranged at leading core and being arranged on pedestal and enclose to be located on pedestal and lead the peripheral X-type balancing stand of core, wherein, described lead is connected between core lower end and pedestal by a spring；The X-type balancing stand generally all round closure type structure, and on the X-type balancing stand inwall inside projection it is some on guiding block, lead in core outer side edges described and be convexly equipped with guidance axis on some immediately below upper guiding block.The utility model key switch, during pressing, counterbalance effect is more preferable, and stationarity is stronger, and resistance to overturning improves.

Description

A kind of ultra-thin key switch with well balanced property

Technical field

It the utility model is related to a kind of key switch, more particularly to a kind of ultra-thin key switch with well balanced property.

Background technology

Many operations of existing equipment need to use key switch to determine defeated as input medium, key switch quality Enter the experience of equipment, it is necessary to ensure good feel and service life, while stability in use is also with very high Requirement, it is impossible to there is card horn shape condition, and these technical problems are all during continuously improving, but still not ideal enough.

Existing key switch is during pressing, and each internal structure cooperation is not close, and interaction is uncoordinated, and pressing is not Steadily, stability is low.

Utility model content

For above-mentioned deficiency, the purpose of this utility model is that providing a kind of ultra-thin key with well balanced property opens Close, during pressing, counterbalance effect is more preferable, and stationarity is stronger, and resistance to overturning improves.

The utility model is that technical scheme is used by reaching above-mentioned purpose：

A kind of ultra-thin key switch with well balanced property, including pedestal, the pedestal upper surface offer an accommodating cavity, Be provided with feed-through assembly in the accommodating cavity, it is characterised in that also include be arranged on pedestal lead core and be arranged on pedestal and Enclose located at the X-type balancing stand for leading core periphery, wherein, described lead is connected between core lower end and pedestal by a spring；The X-type is put down Weigh frame generally all round closure type structure, and on the X-type balancing stand inwall inside projection it is some on guiding block, lead core described Some upper guidance axis are convexly equipped with outer side edges and immediately below upper guiding block.

As further improvement of the utility model, one is provided with the pedestal and positioned at accommodating cavity inner bottom part is convex The axis of guide, a pilot hole is arranged with downwards on the axis of guide central axis direction；The core lower end of leading is provided with up and down insert Enter the guide pillar in pilot hole, the spring housing is located at the axis of guide and guide pillar periphery.

As further improvement of the utility model, the guide pillar is solid light-guiding pillar, the solid light-guiding pillar bottom tool There are interior concave arc light guiding surface or the square light guiding surface of indent, and it is integral type structure or split type knot that this, which leads core with solid light-guiding pillar, Structure.

As further improvement of the utility model, the accommodating cavity includes inserting for the feed-through assembly of feed-through assembly insertion Groove, the X-type balancing stand slot and torsion spring slot inserted around the axis of guide and for X-type balancing stand lower end, wherein, the X-type is put down Weighing apparatus frame slot is mainly made up of the small square groove positioned at the axial big square groove of guiding and positioned at big four edges of square groove, and this is big Square groove is including the first slot to make way between the axis of guide and feed-through assembly slot and between the axis of guide and torsion spring slot Second slot to make way；Meanwhile it is spaced from each other between the feed-through assembly slot, torsion spring slot and X-type balancing stand slot.

As further improvement of the utility model, the core side of leading is provided with a briquetting, has in the briquetting One presses convex point pressing；In the torsion spring slot and positioned at leading inserted with a torsion spring below the briquetting of core, the torsion spring, which has, to be located at By the push contact immediately below convex point pressing；Offer on the torsion spring slot inner side edge and one opened for briquetting is up and down Groove.

As further improvement of the utility model, in addition to it is respectively arranged on pedestal and positioned at X-type balancing stand with leading Big Shang Gai between core and small upper lid, wherein, the lid upper greatly is arranged at torsion spring slot upper end, and the big upper lid include one greatly on Cover plate and big upper cover plate both ends and the big inserted block extended downwardly are respectively arranged at, wherein, on the big inserted block end and to inner side It is provided with a snap fit；The small upper lid is arranged at feed-through assembly slot upper end, and the small upper lid includes a small upper cover plate and difference Small upper cover plate both ends and the small inserted block extended downwardly are arranged at, wherein, it is provided with the small inserted block end and to inner side in one Inserted block.

As further improvement of the utility model, on described on guiding block lower surface and directly over upper guidance axis Offer a guide channel.

As further improvement of the utility model, the X-type balancing stand is mainly intersected by balancing pole A with balancing pole B to be set Put and form, wherein, balancing pole A includes one first U-shaped frame and is horizontally placed at the first U type frame open rearward ends and is active in first The first cross bar in slot to make way, one is respectively arranged with the relative inwall of the first U-shaped frame and inserts axle；Balancing pole B includes one Second U-shaped frame and be horizontally placed on the second cross bar at the 2nd U type frame open rearward ends and being active in the second slot to make way, this second A jack is respectively arranged with the relative outer wall of U-shaped frame；The second U-shaped frame rear end is inserted in first U-shaped frame, and this is first U-shaped Slotting axle on frame inwall is inserted in the jack on the second U-shaped frame outer wall, and balancing pole A and balancing pole B is in enclosed type framework respectively Structure.

As further improvement of the utility model, the first U-shaped frame includes the first transverse axis and is arranged at the first transverse axis Both ends and the first support arm being extended to same direction, wherein, the first support arm is mainly by under horizontal part, first on one first Horizontal part and the one first rake composition being connected on first between horizontal part and first time horizontal part, this is inserted axle and is arranged at On first rake inner side edge, first cross bar is arranged on first time horizontal part；The second U-shaped frame include the second transverse axis, And the second transverse axis both ends and the second support arm being extended to same direction are arranged at, wherein, the second support arm is mainly by one the Horizontal part, second time horizontal part and one second rake being connected on second between horizontal part and second time horizontal part on two Composition, the jack are arranged in the second rake outer side edges, and second cross bar is arranged on second time horizontal part；It is described it is some on Guiding block is respectively arranged on first on horizontal part and second on the madial wall of horizontal part.

As further improvement of the utility model, on first time horizontal part end and second time horizontal part end The insertion locating piece being respectively arranged with the small square groove of insertion.

As further improvement of the utility model, the feed-through assembly includes still and moving plate, wherein, the still side A stationary contact is provided with, the moving plate side is provided with a movable contact, and the stationary contact is oppositely arranged with movable contact.

The beneficial effects of the utility model are：

(1) effect is engaged in the X-type balancing stand of all round closure type structure, with leading core and pedestal by using overall, filled Divide using space limited inside key switch, counteracting forces, equilibrium function are provided for the process of pressing up and down of key switch It is remarkably reinforced, counterbalance effect is more preferable, and stationarity is stronger, and resistance to overturning improves, meanwhile, realize key switch internal structure each Xiang Lineng；

(2) the single upper lid of tradition is divided into big Shang Gai and small upper lid, between making the axis of guide outer side edges of pedestal and above covering greatly, And slot to make way is formed respectively between the axis of guide outer side edges of pedestal and small upper lid, it is empty to provide activity resigning for X-type balancing stand lower end Between, beneficial to the pressing stability of equilibrium for improving key switch；

(3) using the solid light-guiding pillar of integral structure or split-type structural as guide pillar, solid light-guiding pillar bottom tool There are interior concave arc light guiding surface or the square light guiding surface of indent, beneficial to absorption and diffusion of the solid light-guiding pillar to light；Lead core and both played and lead To effect, luminous and guide-lighting effect is also functioned to, realization is led and lighted among core, and it is by small luminous to lead the solid light-guiding pillar in core Face imported into big light-emitting area, increases light-emitting area, and whole face is all luminous when realizing pressing；

(4) the feed-through assembly slot on pedestal, torsion spring slot and X-type balancing stand slot are spaced from each other, and form cavity Structure, it can separate handle independently of each other, the problem of Each part, significantly simplify workload；

(5) by covered on torsion spring slot one it is big on cover, covered on feed-through assembly slot one it is small on cover, play anti- The effect of dirt and protection torsion spring and feed-through assembly.

Above-mentioned is the general introduction of utility model technical scheme, below in conjunction with accompanying drawing and embodiment, to the utility model It is described further.

Brief description of the drawings

Fig. 1 is explosive view of the present utility model；

Fig. 2 is the overall structure diagram of the utility model in the raw；

Fig. 3 is the sectional view of the utility model in the raw；

Fig. 4 is a part of structural representation of the present utility model；

Fig. 5 is another part structural representation of the present utility model；

Fig. 6 is the utility model balancing pole A structural representation；

Fig. 7 is the utility model balancing pole B structural representation；

Fig. 8 is the structural representation of the utility model lid upper greatly；

Fig. 9 is the structural representation of the small upper lid of the utility model；

Figure 10 is the structural representation that the utility model is in pressed status.

Embodiment

Further to illustrate that the utility model is to reach the technological means and effect that predetermined purpose taken, below in conjunction with Accompanying drawing and preferred embodiment, specific embodiment of the present utility model is described in detail.

Fig. 1 to Figure 10 is refer to, the utility model embodiment provides a kind of ultra-thin key switch with well balanced property, Including pedestal 1, the upper surface of pedestal 1 offers an accommodating cavity, feed-through assembly 2 is provided with the accommodating cavity, in the present embodiment, The feed-through assembly 2 includes still 21 and moving plate 22, and the side of still 21 is provided with a stationary contact, and the side of moving plate 22 is provided with One movable contact, and the stationary contact is oppositely arranged with movable contact.The present embodiment ultra-thin key switchs, in addition to is arranged on pedestal 1 Lead core 3 and be arranged on pedestal 1 and enclose located at the X-type balancing stand 4 for leading the periphery of core 3, wherein, it is described to lead the lower end of core 3 and base Connected between seat 1 by a spring 5；The X-type balancing stand 4 generally all round closure type structure, and in the X-type balancing stand 4 Inside some upper guiding blocks 41 of projection on wall, if leading in the outer side edges of core 3 and being convexly equipped with immediately below upper guiding block 41 described Dry upper guidance axis 31.Meanwhile in the present embodiment, on described on the lower surface of guiding block 41 and directly over upper guidance axis 31 Offer a guide channel 411.

In the present embodiment, as shown in figure 1, being provided with one on the pedestal 1 and positioned at accommodating cavity inner bottom part is convex and leading To axle 12, a pilot hole 121 is arranged with downwards on the central axis direction of the axis of guide 12；The lower end of core 3 of leading is provided with up and down Activity is inserted in the guide pillar 32 in pilot hole 121, and the spring 5 is sheathed on the axis of guide 12 and the periphery of guide pillar 32.

Meanwhile the accommodating cavity includes the feed-through assembly slot 111 for the insertion of feed-through assembly 2, around the axis of guide 12 And for the X-type balancing stand slot 112 and torsion spring slot 113 of the lower end insertion of X-type balancing stand 4, wherein, the X-type balancing stand slot 112 mainly by the big square groove 1121 around the axis of guide 12 and the small square groove 1122 positioned at big 1,121 4 edges of square groove Composition, the big square groove 1121 include the first slot to make way 11211 and position between the axis of guide 12 and feed-through assembly slot 111 The second slot to make way 11212 between the axis of guide 12 and torsion spring slot 113；Meanwhile the feed-through assembly slot 111, torsion spring slot It is spaced from each other between 113 and X-type balancing stand slot 112.

As shown in Figure 8, Figure 9, the present embodiment ultra-thin key switchs, in addition to is respectively arranged on pedestal 1 and is located at X-type Balancing stand 4 and the lid 7 upper greatly between core 3 and small upper lid 8 are led, wherein, the lid 7 upper greatly is arranged at the upper end of torsion spring slot 113, and The lid 7 upper greatly includes a big upper cover plate 71 and is respectively arranged at the big both ends of upper cover plate 71 and the big inserted block 72 extended downwardly, its In, it is provided with a snap fit 721 on the big end of inserted block 72 and to inner side；The small upper lid 8 is arranged at feed-through assembly slot 111 Upper end, and the small upper lid 8 includes a small upper cover plate 81 and is respectively arranged at the small both ends of upper cover plate 81 and the small inserted block extended downwardly 82, wherein, it is provided with inserted block 821 in one on the small end of inserted block 82 and to inner side.

In the present embodiment, as shown in Figures 6 and 7, the X-type balancing stand 4 is mainly by balancing pole A 42 and balancing pole B 43 it is arranged in a crossed manner form, wherein, balancing pole A42 includes one first U-shaped frame 421 and is horizontally placed on the first U-shaped rear end of frame 421 and opens At mouthful and the first cross bar 422 for being active in the first slot to make way 11211, set respectively on the relative inwall of the first U-shaped frame 421 It is equipped with one and inserts axle 4211；Balancing pole B 43 includes one second U-shaped frame 431 and is horizontally placed at the second U-shaped open rearward end of frame 431 And the second cross bar 432 in the second slot to make way 11212 is active in, it is respectively arranged with the relative outer wall of the second U-shaped frame 431 One jack 4311；The second U-shaped rear end of frame 431 is inserted in the first U-shaped frame 421, and the slotting axle on the first U-shaped inwall of frame 421 In jack 4311 on 4211 the second U-shaped outer walls of frame 431 of insertion, balancing pole A42 and balancing pole B 43 is in enclosed type frame respectively Frame structure.

Meanwhile the first U-shaped frame 421 includes the first transverse axis 4212 and is arranged at the both ends of the first transverse axis 4212 and to same The extended first support arm 4213 in one direction, wherein, the first support arm 4213 is mainly by horizontal part 42131 on one first, the Once horizontal part 42132 and one first inclination being connected on first between horizontal part 42131 and first time horizontal part 42132 Portion 42133 forms, and this is inserted axle 4211 and is arranged on the inner side edge of the first rake 42133, and first cross bar 422 is arranged under first On horizontal part 42132；The second U-shaped frame 431 includes the second transverse axis 4312 and is arranged at the both ends of the second transverse axis 4312 and to same The extended second support arm 4313 in one direction, wherein, the second support arm 4313 is mainly by horizontal part 43131 on one second, the Two times horizontal parts 43132 and one second inclination being connected on second between horizontal part 43131 and second time horizontal part 43132 Portion 43133 is formed, and the jack 4311 is arranged in the outer side edges of the second rake 43133, and second cross bar 432 is arranged under second On horizontal part 43132；Some upper guiding blocks 41 are respectively arranged on first horizontal part on horizontal part 42131 and second On 43131 madial wall.

It is meanwhile slotting with being respectively arranged with second time end of horizontal part 43132 in the end of first time horizontal part 42132 Enter the insertion locating piece (42134,43134) in small square groove 1122, for balancing pole A42 and balancing pole B 43 lower ends is spacing In in X-type balancing stand slot 112.

As further improvement of this embodiment, the guide pillar 32 is solid light-guiding pillar, the solid light-guiding pillar bottom tool There are interior concave arc light guiding surface or the square light guiding surface of indent, and it is integral type structure or split type knot that this, which leads core 3 with solid light-guiding pillar, Structure, integral structure can reduce cost.When the square light guiding surface of the interior concave arc light guiding surface or indent of illumination to solid light-guiding pillar, Solid light-guiding pillar goes light inspiration, and square guide-lighting towards surrounding diffusion, solid leaded light by interior concave arc light guiding surface or indent The setting of the interior concave arc light guiding surface or the square light guiding surface of indent of post bottom, beneficial to absorption and expansion of the solid light-guiding pillar to light Dissipate.In the present embodiment, the core 3 of leading both plays guide effect, also functions to luminous and guide-lighting effect, and hair among core 3 is led in realization Light, and it is to imported into big light-emitting area by small light-emitting area to lead the solid light-guiding pillar in core 3, increases light-emitting area, when realizing pressing Whole face is all luminous.

As further improvement of the utility model, the side of core 3 of leading is provided with a briquetting 33, in the briquetting 33 Convex point pressing 331 is pressed with one；In the torsion spring slot 113 and positioned at leading below the briquetting 33 of core 3 inserted with a torsion spring 6, The torsion spring 6 has the push contact 61 being located at by immediately below convex point pressing 331；Opened up on the inner side edge of torsion spring slot 113 Have for the up and down fluting 1131 of briquetting 33.It is engaged by using torsion spring 6 with leading the briquetting 33 of core 3, by pressing through Cheng Zhong, the push contact 61 that torsion spring 6 is beaten by convex point pressing 331 of briquetting 33, realizes sounding effect, and works well, Meanwhile greatly improved using torsion spring as generating device, life-span.

The present embodiment provide ultra-thin key switch, small volume, be it is a can apply to it is smaller using in space Key switch, it can be used with keycap is closed.

Operation principle of the present utility model is：As shown in Fig. 2 key switch is in the raw, after keycap is closed, only Keycap is pressed down on, core 3 is led and is moved down with X-type balancing stand 4 by downward active force, with moving down for core 3 is led, lead core 3 Compression spring 5, and the movable contact of moving plate 22 contacts with the stationary contact on still 21, then key switch is in the conduction state, such as schemes Shown in 10, meanwhile, the push contact 61 that torsion spring 6 is beaten by convex point pressing 331 of briquetting 33, send sound；When release is to leading core 3 with the downward active force of X-type balancing stand 4 when, under the elastic restoring force effect of spring 5, lead core 3 and move up returning to nature shape State, and the upper guiding block 41 acted on by leading the upper guidance axis 31 on the side of core 3 on X-type balancing stand 4, so as to drive X-type to put down Moved on weighing apparatus frame 4, recover nature, then key switch is off.

Emphasis of the present utility model essentially consists in：

(1) effect is engaged in the X-type balancing stand of all round closure type structure, with leading core and pedestal by using overall, filled Divide using space limited inside key switch, counteracting forces, equilibrium function are provided for the process of pressing up and down of key switch It is remarkably reinforced, counterbalance effect is more preferable, and stationarity is stronger, and resistance to overturning improves, meanwhile, realize key switch internal structure each Xiang Lineng；

(2) the single upper lid of tradition is divided into big Shang Gai and small upper lid, between making the axis of guide outer side edges of pedestal and above covering greatly, And slot to make way is formed respectively between the axis of guide outer side edges of pedestal and small upper lid, it is empty to provide activity resigning for X-type balancing stand lower end Between, beneficial to the pressing stability of equilibrium for improving key switch；

(3) using the solid light-guiding pillar of integral structure or split-type structural as guide pillar, solid light-guiding pillar bottom tool There are interior concave arc light guiding surface or the square light guiding surface of indent, beneficial to absorption and diffusion of the solid light-guiding pillar to light；Lead core and both played and lead To effect, luminous and guide-lighting effect is also functioned to, realization is led and lighted among core, and it is by small luminous to lead the solid light-guiding pillar in core Face imported into big light-emitting area, increases light-emitting area, and whole face is all luminous when realizing pressing；

(4) the feed-through assembly slot on pedestal, torsion spring slot and X-type balancing stand slot are spaced from each other, and form cavity Structure, it can separate handle independently of each other, the problem of Each part, significantly simplify workload；

(5) by covered on torsion spring slot one it is big on cover, covered on feed-through assembly slot one it is small on cover, play anti- The effect of dirt and protection torsion spring and feed-through assembly.

It is described above, only it is preferred embodiment of the present utility model, not technical scope of the present utility model is made Any restrictions, therefore identical with the utility model above-described embodiment or approximate technical characteristic is used, and obtained other structures, Within the scope of protection of the utility model.

Claims (10)

1. a kind of ultra-thin key switch with well balanced property, including pedestal, the pedestal upper surface offer an accommodating cavity, should Feed-through assembly is provided with accommodating cavity, it is characterised in that also include being arranged at leading core and be arranged on pedestal and enclose on pedestal Located at the X-type balancing stand for leading core periphery, wherein, described lead is connected between core lower end and pedestal by a spring；The X-type balance Frame generally all round closure type structure, and on the X-type balancing stand inwall inside projection it is some on guiding block, led described outside core Some upper guidance axis are convexly equipped with side and immediately below upper guiding block.

2. the ultra-thin key switch according to claim 1 with well balanced property, it is characterised in that on the pedestal And an axis of guide is provided with positioned at accommodating cavity inner bottom part is convex, a guiding is arranged with downwards on the axis of guide central axis direction Hole；The core lower end of leading is provided with the up and down guide pillar being inserted in pilot hole, and the spring housing is located at the axis of guide and guide pillar Periphery.

3. the ultra-thin key switch according to claim 2 with well balanced property, it is characterised in that the guide pillar is real Heart light-guiding pillar, the solid light-guiding pillar bottom have interior concave arc light guiding surface or a square light guiding surface of indent, and this lead core with it is solid Light-guiding pillar is integral type structure or split-type structural.

4. the ultra-thin key switch according to claim 2 with well balanced property, it is characterised in that the accommodating cavity bag Include the feed-through assembly slot for feed-through assembly insertion, around the axis of guide and for the X-type balancing stand of X-type balancing stand lower end insertion Slot and torsion spring slot, wherein, the X-type balancing stand slot is mainly by positioned at the axial big square groove of guiding and positioned at big square groove The small square groove composition of four edges, the big square groove include the first slot to make way between the axis of guide and feed-through assembly slot, And the second slot to make way between the axis of guide and torsion spring slot；Meanwhile the feed-through assembly slot, torsion spring slot and X-type balance It is spaced from each other between frame slot.

5. the ultra-thin key switch according to claim 4 with well balanced property, it is characterised in that described to lead core side A briquetting is provided with, has one to press convex point pressing in the briquetting；In the torsion spring slot and positioned at leading under the briquetting of core Side has the push contact being located at by immediately below convex point pressing inserted with a torsion spring, the torsion spring；In the torsion spring slot inner side edge On offer for the up and down fluting of briquetting.

6. the ultra-thin key switch according to claim 4 with well balanced property, it is characterised in that also include setting respectively It is placed on pedestal and is located at X-type balancing stand and leads the big Shang Gai between core and small upper lid, wherein, the lid upper greatly is arranged at torsion spring Slot upper end, and the big upper lid includes a big upper cover plate and is respectively arranged at big upper cover plate both ends and the big inserted block extended downwardly, Wherein, it is provided with a snap fit on the big inserted block end and to inner side；The small upper lid is arranged at feed-through assembly slot upper end, and The small inserted block that the small upper lid includes a small upper cover plate and is respectively arranged at small upper cover plate both ends and extends downwardly, wherein, it is small at this Inserted block in one is provided with inserted block end and to inner side.

7. the ultra-thin key switch according to claim 1 with well balanced property, it is characterised in that guided on described A guide channel is offered on block lower surface and directly over upper guidance axis.

8. the ultra-thin key switch according to claim 4 with well balanced property, it is characterised in that the X-type balance Frame mainly by balancing pole A with balancing pole B is arranged in a crossed manner forms, wherein, balancing pole A includes one first U-shaped frame and is horizontally placed on the At one U-shaped frame open rearward end and the first cross bar for being active in the first slot to make way, on the relative inwall of the first U-shaped frame respectively It is provided with one and inserts axle；Balancing pole B includes one second U-shaped frame and is horizontally placed at the second U-shaped frame open rearward end and is active in second The second cross bar in slot to make way, a jack is respectively arranged with the relative outer wall of the second U-shaped frame；The second U-shaped frame rear end Insert in the first U-shaped frame, and the slotting axle on the first U-shaped frame inwall is inserted in the jack on the second U-shaped frame outer wall, the balancing pole A and balancing pole B is in enclosed type frame structure respectively.

9. the ultra-thin key switch according to claim 8 with well balanced property, it is characterised in that described first is U-shaped Frame includes the first transverse axis and is arranged at the first transverse axis both ends and the first support arm being extended to same direction, wherein, this first Support arm mainly by horizontal part, first time horizontal part on one first and is connected on first between horizontal part and first time horizontal part One first rake composition, this insert axle be arranged on the first rake inner side edge, first cross bar be arranged at first time level In portion；The second U-shaped frame includes the second transverse axis and is arranged at the second transverse axis both ends and be extended to same direction second Support arm, wherein, the second support arm mainly by horizontal part, second time horizontal part on one second and be connected on second horizontal part with One second rake composition between second time horizontal part, the jack are arranged in the second rake outer side edges, second cross bar It is arranged on second time horizontal part；Some upper guiding blocks be respectively arranged at horizontal part on first with second horizontal part it is interior In side wall；Inserted in first time horizontal part end with being respectively arranged with insert in small square groove one on second time horizontal part end Enter locating piece.

10. the ultra-thin key switch according to claim 1 with well balanced property, it is characterised in that the conducting group Part includes still and moving plate, wherein, the still side is provided with a stationary contact, and the moving plate side is provided with a movable contact, and should Stationary contact is oppositely arranged with movable contact.