# Patent

## Title
Sliding contact switch

## Abstract

An electrical contact assembly includes an electrical terminal, a push button, and a contact member adapted to be in electrical contact with the electrical terminal when the push button is compressed. The contact member has a first contact portion forming a first angle with a surface of the electrical terminal, and a second contact portion forming a second angle with the surface of the electrical terminal. The second angle is smaller than the first angle, and the second contact portion is adapted to slide on the surface of the electrical terminal when the push button is compressed.

## Background
FIELD OF THE INVENTION
The present invention relates to an electrical system, and in particular to an electrical switch.
BACKGROUND OF THE INVENTION
Electrical switches are used to make electrical connections between electrical wires. Many electrical system failures result from bad contacts at electrical switches. The bad contacts may result from contaminations at contact surfaces or terminals, or may result from wearing of the contact surfaces and/or terminals.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a method and system for making a reliable and durable contact between electrical terminals.
In one aspect, an electrical contact assembly according to an embodiment of the present invention includes an electrical terminal, a push button, and a contact member. When the push button is compressed, the contact member comes in electrical contact with the terminal. The contact member has a first contact portion forming a first angle with a surface of the electrical terminal, and a second contact portion forming a second angle with the surface of the electrical terminal. The second angle is smaller than the first angle, and the second contact portion is adapted to slide on the surface of the electrical terminal when the push button is compressed.
The electrical contact assembly may include a spring member coupled to the contact member and to the push button. The assembly may have a housing and a cover together substantially enclosing the electrical terminal and the contact member. The electrical terminal may be adapted for retaining, and being in electrical contact with, an electrical wire.
The contact member of the assembly may be formed unitarily, for example, using beryllium copper. Alternatively, portions of the contact member may be formed separately and then coupled together.
The contact member is adapted to provide a resilient force between the contact member and the electrical terminal when in electrical contact with the electrical terminal. The resilient force at least partially results from a change in a relative angle between the first contact portion and the second contact portion.
These and other features, aspects and advantages of the present invention will become understood with reference to the following description, appended claims and accompanying figures.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is an exploded view of an electrical contact assembly according to an embodiment of the present invention.
FIG. 1B shows another exploded view of the electrical contact assembly of FIG. 1A from a different angle.
FIG. 2 is a perspective view of the assembled electrical contact assembly of FIGS. 1A and 1B.
FIG. 3 is a perspective view of a partial, internal structure of the electrical contact assembly showing a contact member, a spring and a pair of electrical terminals, according to an embodiment of the invention.
FIG. 4 is a cross-sectional view of the assembled contact assembly in its disconnected, or open, state, according to an embodiment of the invention.
FIG. 5 shows the contact member and the electrical terminals of the contact assembly in greater details, according to an embodiment of the invention.
FIG. 6A is a cross-sectional view of the assembled contact assembly in its connected, or closed, state, according to an embodiment of the invention.
FIG. 6B is a perspective view comparing the open and the closed states of the contact assembly.
FIG. 7A shows relative positions of the contact member and the electrical terminals, according to an embodiment of the invention.
FIG. 7B shows the contact member in essentially complete contact with the electrical terminals, according to an embodiment of the invention.
FIG. 7C shows the contact member in essentially complete contact with the electrical terminals without bending the top portion of the contact member, according to another embodiment of the invention.
FIG. 7D shows the contact member in essentially complete contact with the electrical terminals, according to another embodiment of the invention.
FIG. 8A shows a portion of an electrical system including a plurality of contact assemblies according to an embodiment of the invention.
FIG. 8B shows the electrical system with the contact assemblies removed, exposing the electrical terminals, according to an embodiment of the invention.
FIG. 8C shows further details of the electrical terminals, according to an embodiment of the invention.



DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a switch for connecting, for example, paired electrical wires. As shown in FIGS. 1A, 1B and 2, an electrical contact assembly or switch 10 in accordance with an embodiment of the invention includes one or more electrical terminals 11a, 11b, a spring member 12, a contact member 13, a push button 14, a housing 16, and a cover 18.
The terminals 11a and 11b have retaining portions 11a-2 and 11b-2 that are adapted to retain electrical wires 101a and 101b (e.g., FIG. 8B). The electrical wires may be extended through apertures 18-1 and 18-2 in the assembly 10 formed by the housing 16 and the cover 18, to connect to an electrical circuit 100 (FIGS. 8A-8C). When assembled, the housing 16 and the cover 18 together substantially enclose the contact member 13 and the terminals 11a and 11b, and partially enclose the push button 14.
The contact member 13 has a first contact portion 13a and a second contact portion 13b. The second contact portion 13b as shown is at an angle in relation to the first contact portion 13a, i.e., the portion 13b is “bent” in relation to the portion 13a. The second contact portion 13b is adapted to come in contact with a surface 11a-1 of the first terminal 11a. The contact member 13 may further include a third contact portion 13c and a fourth contact portion 13d. The fourth contact portion 13d is bent in relation to portion 13c, and is adapted to come in contact with a surface 11b-1 of the second terminal 11b. 
The contact member 13 is overall “U” shaped, with contact portions 13a and 13b forming a first “leg” 13-1, and contact portions 13c and 13d forming a second “leg” 13-2. The contact member 13 may also be of other shapes such as “V” shaped, etc. The contact member 13 may have more “legs” and contact portions, and may be unitarily formed using, for example, beryllium copper. Alternatively, different portions, such as the first contact portion 13a and the second contact portion 13b, may be formed separately and then coupled together.
The push button 14 has an internal extrusion 14a adapted to extend through an aperture 13f of the top portion 13e of the contact member 13, and extend through a first portion of the spring member 12 thus retaining the first portion of the spring member 12 to a substantially fixed location. For a contact member 13 having a width of about 3.15 mm at the top portion 13e, the aperture 13f has a diameter of about 1.52 mm.
The housing 16 has an aperture 16a adapted to have the push button 14 extend therethrough. As shown in FIG. 1B, the housing 16 has a guard 16b around the aperture 16a. The housing 16 has a plurality of extrusions 16c adapted to fit into corresponding indentions 18c in the cover 18 when the contact assembly 10 is assembled. The cover 18 also has an internal extrusion 18a adapted to extend through a second portion of the spring member 12 to fix the second portion of the spring member 12 into place.
FIG. 3 shows a perspective view of a partial, internal structure of the electrical contact assembly 10 showing only the terminals 11a and 11b, the spring member 12, the contact member 13, and the push button 14. In this state, the electrical contact assembly 10 is in a disconnected, or open, state since the electrically conductive contact member 13 is not in electrical contact with the terminals 11a and 11b to allow current to flow between the electrically conductive terminals 11a and 11b through the contact member 13.
FIG. 4 shows a cross sectional view of the contact assembly 10 after it is assembled. In accordance with an embodiment of the invention, the electrical terminals 11a and 11b are slanted relative to the bottom surface 18b of the cover 18. As further shown in FIG. 5, the terminals 11a and 11b are slanted slightly upwardly relative to the bottom surface 18b of the cover 18, and form an angle θ relative to the bottom surface 18b of the cover 18. The angle θ is smaller than β, i.e., 0°<θ<β, and is preferably about 10°.
As shown in FIG. 4, the contact member 13 and the terminals 11a and 11b are normally in a disconnected, or open, state (i.e., the contact assembly 10 is “normally open”). As illustrated in detail in FIG. 5, the first contact portion 13a forms a first angle α with a surface 11a-1 of the electrical terminal 11a. The first angle α may be between about 20° and 90°, and preferably about 75°.
The second contact portion 13b forms a second angle β with the surface 11a-1 of the terminal 11a. The second angle β is smaller than the first angle α, i.e., 0°<β<α, and preferably is about 25°. The first portion 13a and the second portion 13b form a relative angle γ=180°−α+β, which is preferably about 130°.
In one exemplary implementation, the second portion 13b is angled (bent) about γ=130° from the first contact portion 13a. In other words, the second portion 13b is angled (bent) about 50° vertically from the first contact portion 13a. 
As shown in FIG. 6A, when the push button 14 is pressed, the contact member 13 is in turn pressed, compressing the spring member 12. The second contact portion 13b comes in contact with the surface 11a-1 of the first terminal 11a, and the fourth contact portion 13d comes in contact with the surface 11b-1 of the second terminal 11b. Electrical connection may thus be established between the terminals 11a and 11b through the contact member 13. In this state, the contact assembly 10 is connected, or closed. When wires 101a and 101b are connected to the terminals 11a and 11b as shown in FIG. 8B, the contact assembly 10 provides electrical connection between wires 101a and 101b. 
The contact assembly 10 remains closed (providing electrical connection between the terminals 11a, 11b) so long as the spring member 12 remains compressed, allowing the contact member 13 to maintain electrical contact with both the terminals 11a and 11b. 
FIG. 6B further illustrates the contact member 13 in its open state and in its closed state 13′. In the closed state, the spring member 12 is compressed, and contact portions such as the portion 13d′ are in electrical connections with terminals such as terminal 11b. 
As illustrated in FIG. 7A, and described above, when the contact member 13 is pushed down from its first position (normally open) 22 to a second position 23, the second contact portion 13b comes in initial contact with the surface 11a-1. When the push button 14 is pressed further, the contact member 13 is pushed to a third position 33 (FIG. 7B). The second contact portion 13b may be bent outwardly further, decreasing the relative angle γ and the second angle β. Such a bending provides a resilient force on the contact member 13. This causes contact member leg 13-1 formed by the portions 13a, 13b to be pushed away from the contact member leg 13-2 formed by the portions 13c, 13d. 
FIG. 7B shows the contact member 13 being pressed such that the contact portion 13b has its almost entire bottom surface in contact with the surface 11a-1 of the terminal 11a, after a tip of the contact portion 13b has slid on the surface 11a-1 for a distance d. The distance d may be comparable with the length of the second contact portion 13b, e.g., 0<d<1.5 mm. As discussed further below, such a sliding range increases the reliability of the electrical connection.
The relative angle between the contact portions 13a and 13b decreases until the angle γ′=180−α′ as shown, where the angle α′ between the contact portion 13a and the surface 11a-1 may also have decreased, depending on the flexibility between the portion 13a and the top portion 13e of the contact member 13.
As shown earlier in FIG. 1, the width of the contact member 13 may be designed to taper down from the top portion 13e toward the contact portions 13b and 13d. For a switch assembly 10 having a width of about 12 mm and a thickness of about 9 mm, for example, the contact member 13 may be tapered down from the top portion 13e at a width of about 3.15 mm to a width of about 1.6 mm at the tip of the second contact portion 13b. 
The tapered width of the contact member 13 provides a softer resilient force between the contact portions 13a and 13b as compared with the resilient force between the top portion 13e and the contact portion 13a when the contact member 13 is compressed. Thus, it is easier to bend the second contact portion 13b from the first contact portion 13a as compared with bending the first contact portion 13a from the top contact portion 13e. As illustrated in FIG. 7B, the first contact portion 13a may be bent from the top portion 13e for an angle δ, e.g., about 0°<δ<30°. Preferably δ is limited to be less than about 26.2° to avoid damages to the contact member 13. This can be achieved, for example, by stop ribs 11a-3 and 11b-3 on the terminals 11a and 11b, respectively, or by the range of the top portion 13e can travel. The change in the angle γ, i.e., γ−γ′, is larger than δ because of the less resilient force between the portions 13a and 13b as compared with that between the first portion 13a and the top portion 13e. 
As shown in FIG. 7C, according to another embodiment of the invention, the connection 13e-1 between the top portion 13e and the first portion 13a is so rigid that δ=0 even after the tip of the second contact portion 13b has slid for a distance d on the terminal 11a when the contact member 13 is pressed to a position 35. Those of ordinary skill in the art will recognize that other variations of the contact member 13 are possible. For example, the contact portions 13a and 13c may not be parallel even in an “open” state. Rather, an angle may exist between the portions 13a and 13c. Further, the top portion 13e may be smaller than shown, or may be so small that the contact member 13 is essentially “V” shaped instead of “U” shaped. In this case, a resilient force may be provided directly between the portions 13a and 13c. Moreover, contact portions 13b and 13d may not be necessary, and the tips of portions 13a and 13c may directly slide on the terminals 11a and 11b. 
FIG. 7D shows yet another embodiment of the contact member 13. As shown, the first contact portion 13a comprises two portions 13a-1 and 13a-2, and the deflection or bending of the contact member 13 may occur between these two portions 13a-1 and 13a-2 in addition to between the second contact portion 13b and the first contact portion 13a. The second contact portion 13b as shown is in essentially complete contact with the terminal 11a. When the contact member 13 is pressed further, a further deflection may occur between these two portions 13a-1 and 13a-2 in addition to, or alternative to, the deflection between the first contact portion 13a and the top contact portion 13e. As shown δ increases from about 0° to about 13.1°, while the angle γ′ reaches about 118.1°. The tip of the second contact portion 13b slides for a distance d of about 0.40 mm before being stopped by the rib 11a-3.
The resilient force causes an outwardly sliding tendency of the second portion 13b on the surface 11a-1. When the sliding tendency overcomes the friction between the second portion 13b and the surface 11a-1, at least a tip of the second contact portion 13b slides outwardly on the surface 11a-1, in the direction shown as a block arrow 71 in FIG. 7A. The sliding tip of the second contact portion 13b cleans a portion of the surface 11a-1 to remove, for example, oxidation layers, dust, and other contaminations that may cause a bad electrical contact. This is a self-cleaning action that allows proper electrical contact between the terminal surfaces 11a-1, 11b-1 and the contact portions 13a, 13d, respectively.
Even after repetitive open and close state cycles of the contact 20 assembly (switch 10) such that wearing on the contact portions 13b, 13d and the surfaces 11a-1 and 11b-1 may occur, proper electrical contact may still be ensured as a result of the range of relative positions (between position 23 and position 33) the contact member 13 can move while trying to make electrical contact with terminals 11a and 11b. Thus, the contact assembly 10 of the invention provides a reliable electrical connection through the “self cleaning” function and the range of contact positions.
As noted, when the push button 14 is pressed, the spring member 12 is compressed. When the push button 14 is partially released, the second portion 13b slides back on the surface 11a-1 of the terminal 11a as a result of the resilient force between the contact member 13 and the surface 11a-1. When the push button 14 is further released, the contact member is moved by the spring member 12 passing the second position 23, and the second portion 13b breaks electrical contact with the surface 11a-1.
In another embodiment of the present invention, the push button 14 may be locked into one or more lock positions using mechanisms known in the art.
FIG. 8A shows a portion of an electrical system 100 including a plurality of contact assemblies 10a, 10b, and 10c according to an embodiment of the present invention. Each of the contact assemblies 10a, 10b, and 10c is similar to the contact assembly 10 (e.g., FIGS. 1A-2) described above.
As shown in FIG. 8A, contact assembly 10a acts as a single termination for electrical wires 101a and 101b, while contact assembly 10b acts as a double termination for wires 101a, 101b, 101c and 101d. A conventional switch 80 may also be included in the circuitry. FIG. 8B shows the electrical system 100 with the contact assemblies partially removed, exposing the electrical terminals such as 11a and 11b. FIG. 8C shows further details of an electrical terminal 81. The retaining portion 81-1 of the terminal 81 retains two wires 83 and 85. Thus terminal 81 can be used to as a splitting point for wires 83 and 85.
Advantageously, the invention provides a reliable and durable electrical switch. The switch has a “self-cleaning” function that helps maintain a reliable electrical connection.
The present invention has been described in considerable detail with reference to certain preferred versions thereof; however, other versions are possible.
For example, those of ordinary skill in the art will recognize that many design variations of the contact member 13 may exist without departing the scope of the invention. The contact member 13 may have more “legs,” and each leg may include more than two portions having different relative angles with respect to the corresponding electrical terminal. The dimensions and the materials of the portions may vary.
In addition, the different portions may be made separately and then coupled together. Moreover, although the contact member 13 as shown has two, symmetrical legs each having two portions, the legs may be configured asymmetrically. Moreover, although the contact member as shown in the drawings is “bent” outwardly, it is possible that it can be designed to be bent inwardly; so long the terminals are slanted inwardly accordingly.
Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

## Claims

1. An electrical contact assembly, comprising:
a slanted electrical terminal;
a push button; and
a contact member disposed between the electrical terminal and the push button,
the contact member comprising:
a first portion forming a first angle in relation to a surface of the electrical terminal; and
a second portion, connected to the first portion, and forming a second angle in relation to the surface of the electrical terminal,
wherein the second angle is unequal to the first angle,
such that the second portion is adapted to make contact with, and slide on the surface of the electrical terminal as the push button is pushed against the contact member,
wherein the second portion is substantially parallel to the electrical terminal when in contact.

2. The electrical contact assembly of claim 1, further comprising a spring member coupled with a portion of the push button and a bottom portion of a cover to normally maintain the contact member away from the electrical terminal.

3. The electrical contact assembly of claim 1, further comprising a housing and a cover together substantially enclosing the electrical terminal and the contact member.

4. The electrical contact assembly of claim 1, further comprising a retainer adapted for retaining an electrical wire, wherein the retainer is in electrical contact with the electrical terminal.

5. The electrical contact assembly of claim 1, wherein:
the electrical terminal has an essentially planar surface, the first portion of the contact member is transverse in relation to said surface of the electrical terminal and the second portion is transverse in relation to said surface of the electrical terminal, such that the second angle is less than the first angle.

6. The electrical contact assembly of claim 1, wherein the contact member comprises beryllium copper.

7. The electrical contact assembly of claim 1, wherein the second portion is adapted to wipe a portion of the surface of the electrical terminal when sliding on said surface.

8. The electrical contact assembly of claim 1, wherein the contact member further comprises:
a third portion and a fourth portion symmetrical in configuration to the first portion and the second portion, respectively; and
a top portion connecting the first and the third portions, forming an essentially U-shaped contact member.

9. The electrical contact assembly of claim 1, further comprising a spring member coupled to the contact member and to the push button, wherein an opening is defined in the top portion of the contact member to axially receive an extrusion of the push button therethrough extending through a portion of the spring member as the push button is urged against the contact member.

10. The electrical contact assembly of claim 1, wherein the contact member is adapted to provide a resistive mechanical force between the push button and the electrical terminal when in electrical contact with the electrical terminal, the resistive force at least partially resulting from a change in a relative angle between the first portion and the second portion as the push button is urged against the contact member.

11. The electrical contact assembly of claim 10, wherein the relative angle between the first portion and the second portion is about 130° when the contact member is not in electrical contact with the electrical terminal.

12. The electrical contact assembly of claim 1, wherein the first angle is between about 20° and 90°.

13. The electrical contact assembly of claim 12, wherein the first angle is about 75°.

14. The electrical contact assembly of claim 12, wherein the second angle is about 25°.

15. An apparatus, comprising:
a plurality of slanted electrical terminals;
a switch for making an electrical connection between at least two of the plurality of electrical terminals, wherein the switch comprises:
a push button; and
an essentially U-shaped contact member disposed between the electrical terminals and the push button, and adapted to provide an electrical connection between a first terminal and a second terminal when the push button is urged against the contact member to bring the contact member in electrical contact with the first and second electrical terminals to electrically close the switch, the contact member comprising:
a first element forming a first transverse angle in relation to a surface of the first electrical terminal; and
a second element forming a second transverse angle in relation to a surface of the second electrical terminal;
such that at least a portion of the first element is adapted to make contact with and slide on the surface of the first electrical terminal as the push button is urged against the contact member, and at least a portion of the second element is adapted to make contact with and slide on the surface of the second electrical terminal as the push button is urged against the contact member,


whereby the contact member provides an electrical connection between the first and second electrical terminals,
wherein all of a flat surface of the first element is coupled with the first electrical terminal when the push button is depressed.

16. The apparatus of claim 15, wherein the contact member is adapted to reversibly deform as the push button is urged against the contact member, to allow a change in the first angle that enables a tip portion of the first element to slide on the surface of the first electrical terminal, and to allow a change in the second angle that enables a tip portion of the second element to slide on the surface of the second electrical terminal.

17. The apparatus of claim 16, wherein:
the contact member further comprises a top element connecting the first and second elements;
the first element includes a mid portion connecting the tip portion of the first element to the top element, the mid portion of the first element forming a third transverse angle in relation to the tip portion of the first element, the second element includes a mid portion connecting the tip portion of the second element to the top element, the mid portion of the second element forming a fourth transverse angle in relation to the tip portion of the second element.

18. The apparatus of claim 17, further comprising a spring member disposed between at least a portion of the contact member and the terminals to normally maintain the contact member away from the electrical terminals to electrically open the switch.

19. The apparatus of claim 18, wherein the spring member provides a counter force to disconnect the contact member from the first and second electrical terminals when the push button is not urged against the contact member, thereby transitioning the switch from electrically closed to electrically open.

20. The apparatus of claim 19 further comprising a housing and a cover together substantially enclosing the electrical terminals and the contact member, the housing forming an opening that slidably retains at least a portion of the push button, such that a top portion of the push button is exposed outside the housing to allow urging the push button against the contact member to electrically close the switch.

21. An electrical system, comprising:
a plurality of electrical terminals; and
a switch for making an electrical connection between at least two of the plurality of electrical terminals, wherein the switch comprises:
a push button; and
a contact member disposed between the electrical terminals and the push button, and adapted to provide an electrical connection between a first terminal and a second terminal when the push button is urged against the contact member to bring the contact member in electrical contact with the first and second electrical terminals,
the contact member comprising:
a first element forming a first transverse angle in relation to a surface of the first electrical terminal;
a second element, connected to the first element, and forming a second transverse angle in relation to the surface of the first electrical terminal; and
a third element connected to the first element;
such that the second element is adapted to make contact with, and slide on the surface of the first electrical terminal as the push button is urged against the contact member, and
the third element is adapted to make contact with the second electrical terminal as the push button is urged against the contact member, whereby the contact member provides an electrical connection between the first and second electrical terminals,
wherein all of a flat surface of the second element is coupled with the first electrical terminal when the push button is depressed.

22. The electrical system of claim 21, wherein the second element is adapted to wipe a portion of the surface of the first electrical terminal when sliding on the surface.

23. The electrical system of claim 21, wherein the contact member is adapted to provide a resistive mechanical force against the push button when in electrical contact with the first electrical terminal and the second electrical terminal, the resistive force resulting from a change in a relative angle between the first element and the second element.

24. The electrical system of claim 21, wherein the switch further comprises a spring member disposed between a portion of the contact member and terminals, for providing a counter spring force to disconnect the contact member from the first electrical terminal and the second electrical terminal when the push button is not urged against the contact member.

25. The electrical system of claim 21, further comprising a spring member to normally maintain the contact member away from the electrical terminals.