ELECTRICAL SWITCHES AND METHODS

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Patent Application No. 13/035,769, filed February 25, 2011.

BACKGROUND

Electrical measurement instruments, such as digital multimeters (DMMs), can often be configured to measure a variety of electrical parameters, such as voltage, current, and resistance. Many DMMs are able to switch between various sets of inputs, with each set of inputs or channels supporting most measurement functions of the DMM. Electrical measurement instruments, therefore, typically include an electrical switch for selecting between the various channels.

In some electrical measurement instruments, an external switch may be installed onto a printed circuit board (PCB) for selecting between channels. In other instruments a PCB of the electrical measurement instrument may be configured to form a switch. In general, such a PCB switch comprises a plurality of contacts on a surface of the PCB and one or more conductive springs configured to make electrical contact with one of the respective plurality of contacts when pressed there against. In order to place the electrical measurement instrument in a first state, at least one of the conductive springs is compressed against a first contact formed on the PCB. In order to place the electrical measurement instrument in a second state, the conductive spring is translated to a second position, which for example, presses the conductive spring in contact with a second contact. As the conductive spring moves across the PCB from the first contact to the second contact, the free end of the conductive spring scrapes along the surface of the first and second contacts as well as the PCB. Thus, in such switches, switching from one state to another state may cause wear to the conductive springs therein due to frictional forces applied to the conductive springs. The wear caused to the end of the conductive spring may also potentially damage the contacts and the PCB.

US 4737602 discloses a simple slidable switch structure of click operation type for changing over conductive patterns on a printed circuit board fixed in a card housing of a card module. The switch comprises three fixed through hole contacts formed in the board, and a movable contact formed with two convex contact portions. The movable contact is preferably coated with an insulating material except for the two convex portions and is directly disposed within the housing. When the movable contact is moved to and fro, the movable contact member deformably assembled within the insulation member is selectively and slidably brought into contact with two of the three fixed through hole contacts for changing-over operation.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In accordance with the invention, a switch assembly is provided according to claim 1. In accordance with the invention, a method according to claim 6 is provided.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

• FIGURE 1 is a top isometric view of a switch assembly in accordance with aspects of the disclosure;
• FIGURE 2 is a bottom isometric view of the switch assembly of FIGURE 1;
• FIGURE 3A is a cross-sectional view of the switch assembly of FIGURE 2 shown in a first position in accordance with aspects of the disclosure;
• FIGURE 3B is a cross-sectional view of the switch assembly of FIGURE 3A shown in an intermediate position in accordance with aspects of the disclosure;
• FIGURE 3C is a cross-sectional view of the switch assembly of FIGURE 3A shown in a second position in accordance with aspects of the disclosure; and
• FIGURE 4 is a cross-sectional view of another switch assembly in accordance with the invention.

DETAILED DESCRIPTION

The following discussion provides examples of one or more switch assemblies and methods of using the same. Generally described, one or more embodiments of the present disclosure are directed to switch assemblies and methods for switching a switch assembly from one state to another, such as switching from a closed state to an open state and/or vice versa. In some examples, a switch assembly may be configured to switch from one state to another by moving a conductive component, such as such as a spring, bar, member, etc., from a first conductive contact located on a substrate, such as a printed circuit board (PCB), to a second conductive contact located on the substrate. As will be described in more detail below, embodiments of the present disclosure may be configured to reduce wear on the switch assemblies' conductive components, including the conductive component and conductive contacts, as well as associated components of the switch, when moving the conductive component (i.e., switching) from the first conductive contact to the second conductive contact. For instance, in one embodiment, the conductive component, such as a spring, member, rod, bar, etc., moves within a slot in the PCB, thereby eliminating contact between the conductive component and the surface of the PCB. In another embodiment, friction forces and/or other forces applied to the conductive component and/or the PCB are reduced as the conductive component moves across the PCB surface from a first conductive contact to a second conductive contact.

Although the switch assemblies may be shown and described in reference to electrical measurement instruments, it should be appreciated that the methods and assemblies described herein may be used in any electrical device or the like requiring the use of an electrical switch. Furthermore, although the examples illustrated herein are directed to double throw switches, it is to be appreciated that the switch assemblies may apply to any number of throws, including a single throw switch. In examples of single throw switches, the switch assembly may be in a closed state when a conductive spring is in contact with the single conductive contact allowing current to flow therethrough, or in an open state when the conductive spring is separate from the single conductive contact preventing current from flowing therethrough. It will be further appreciated that the electrical switches described herein apply to any number of poles.

Turning now to FIGURES 1 and 2, there are shown top and bottom isometric views of a switch assembly 100 in accordance with aspects of the present disclosure. The switch assembly 100 includes a substrate, such as a PCB 102, a slide plate 104, and an insulative body, such as switch body 106, that is movably retained on the PCB 102, for example, via retaining arms 108. As will be explained in more detail below, the switch body 106 is positioned on the PCB 102 and is configured to move relative to the PCB 102 between a first position, which places the switch assembly 100 in a first state, and a second position, which places the switch assembly 100 in a second state. In that regard, the switch assembly 100 may be configured to switch an associated electrical device between a first electrical state and a second electrical state, such as between a first channel and a second channel.

As best shown in FIGURE 2, the PCB 102 is a somewhat planar member having opposite first and second surfaces 112 and 114. The PCB 102 includes a plurality of conductive contacts 118 secured or otherwise formed on the first surface 112 of the PCB 102, as best illustrated in FIGURES 3A-3C. The conductive contacts 118 may be constructed of any material or materials configured to allow electrons to flow therethrough. In one embodiment, for example, the conductive contacts 118 are constructed out of copper and plated with a noble metal, such as gold. The conductive contacts 118 may be suitably spaced apart from one another so as to electrically isolate each conductive contact 118 from the other conductive contacts 118. It will be appreciated that the conductive contacts 118 may be in electrical communication with other components (not shown) on the PCB 102 via traces (not shown) formed within the PCB 102.

Referring to FIGURES 1 and 2, the PCB 102 may also include one or more elongated openings 120 that extend from the first surface 112 to the second surface 114 of the PCB 102, thereby forming one or more slots. As will be discussed in more detail below, the openings 120 are configured to receive one or more of the retaining arms 108. It will be appreciated that the PCB 102 may be constructed of any material or materials and configured to: 1) mechanically support the components mounted thereon, such as the switch body 106; and 2) electrically isolate the electrical contacts 118 formed thereon. The PCB 102 may constitute a simple circuit of which the switch assembly 100 is a part, or the PCB 102 may be the main and/or sole printed circuit board for the associated electrical device, such as a digital multimeter, that includes the switch assembly 100. In that regard, the PCB 102 may not only form a part of the switch assembly 102, but may also provide connections between and mounting points thereon for other electrical and mechanical components.

The switch assembly 100 further includes a slide plate 104 having first and second surfaces 122 and 124, as best shown in FIGURES 2 and 3A-3C. In the embodiment shown, the second surface 124 of the slide plate 104 interfaces with and may be secured to the second surface 114 of the PCB 102. The first surface 122 of the slide plate 104, on the other hand, may include one or more contours 128, the purpose of which will be described later in more detail.

As briefly described above, the switch body 106 is movable between a first position, such as the position illustrated in FIGURE 3A, and a second position, such as the position illustrated in FIGURE 3C. To affect movement of the switch body 106, in one embodiment, the switch body 106 is coupled to an actuator 130 via a moving arm 132, as best shown in FIGURE 1. In one embodiment, the actuator 130 may be mounted on the PCB 102. In other embodiments, the actuator 130 may be mounted separate from the PCB 102. In either case, the actuator 130 may be configured to move the moving arm 132 in the directions indicated by arrow B, thereby causing the switch body 106 to also move in the directions indicated by arrow B. In other embodiments, the switch body 106 may be manually actuated between the first and second positions. Furthermore, the first and second positions may not necessarily be in a linear relationship to each other.

Returning now to FIGURES 3A-3C, there are shown cross-sectional views of the switch assembly 100, each illustrating the switch assembly in a different position. The switch body 106 defines a somewhat planar surface 134 that may interface with the first surface 112 of the PCB 102, and may be made of an insulative material(s). The switch body 106 may carry one or more conductive components, such as compression springs 136, as it moves between the first position shown in FIGURE 3A and the second position shown in FIGURE 3C. Each conductive spring 136 includes a first end 138 and a second end 140. Further, each conductive spring 136 is positioned such that the first end 138 of the conductive spring 136 may be secured to the switch body 106 and the second end 140 of the conductive spring 136 extends outwardly from the surface 134 of the switch body 106. The conductive springs 136 may be constructed from any material or materials configured to allow electrons to flow therethrough, and to provide elasticity so as to act like a spring. In one embodiment, the conductive springs 136 are copper with or without noble metal plating.

Each of the conductive springs 136 are positioned within the switch body 106 in a manner that allows the conductive springs 136 to be placed in electrical communication or electrical connection with two adjacent conductive contacts 118 when the switch body 106 is moved to the first or second position. For instance, the second end 140 of each conductive spring 136 may be configured to contact a first respective conductive contact 118 when the switch body 106 is in a first position, such as the position in FIGURE 3A, and is configured to contact a second respective conductive contact 118 when the switch body 106 is in a second position, such as the position in FIGURE 3C. Although five conductive springs 136 are shown, it is to be understood that any number of conductive springs 136 may be provided depending on the configuration of the switch assembly. In some embodiments, the conductive springs 136 may be compression springs. Non-limiting examples for the conductive springs 136 may include a hanger spring, a leaf spring, a C-shaped spring, or any other spring capable of applying a biasing force against the conductive contacts 118.

The switch body 106 may further include one or more insulative members 144. The insulative members 144 may be positioned between each adjacent conductive spring 136 so as to assist in electrically isolating each conductive spring 136. The insulative members 144 may be formed integral with the switch body 106 as illustrated in FIGURES 3A-3C, or they may be secured thereto.

Returning now to FIGURES 1 and 2, the switch body 106 may include one or more retaining arms 108 secured to or integrally formed with one of the surfaces of the switch body 106 for movably retaining the switch body on the PCB 102, as briefly described above. In the embodiment shown in FIGURES 1 and 2, each of the retaining arms 108 may include an arm portion 146 that extends along the switch assembly 100, such as along an outer edge of the PCB 102 or through one of the openings 120 in the PCB 102. A lip 148 is secured to or integrally formed with the outward end of each arm portion 146. In the embodiment shown, the lip 148 may extend in a direction that is perpendicular to the arm portion 146. As best shown in FIGURE 2, the lip 148 of the retaining arms 108 may be configured to engage with first surface 122 of the slide plate 104 in order to hold the switch body 106 on or adjacent the first surface 112 of the PCB 102.

As assembled, the retaining arms 108 hold the switch body 106 on or adjacent the first surface 112 of the PCB 102, while still allowing the switch body 106 to move along the first surface 112 of the PCB 102 between first and second positions. Additionally, the retaining arms 108 are capable of applying a suitable force to slide plate 104 to counteract the biasing force applied to the PCB 102 via the conductive springs 136. In the embodiment shown, the lip 148 of the retaining arms 108 may be configured to slide along the first surface 122 of the slide plate 120. In that regard, each lip 148 of the retaining arms 108 may be configured to slide along a corresponding contour 128 when the switch assembly 100 is moved from a first position to a second position. As each lip 148 slides along a corresponding contour 128, the amount of force applied by the conductive springs 136 on the first surface 112 of the PCB 102 is reduced in relation to the geometry of the contour. This reduction in force applied to the switch body 104 corresponds to a reduction in the amount each conductive spring 136 is compressed.

An example of an operation of switching the switch assembly 100 from a first position as illustrated in FIGURE 3A to a second position as illustrated in FIGURE 3C will now be described. In the first position illustrated in FIGURE 3A, the conductive springs 136 make electrical connection with corresponding conductive contacts 118 formed on the PCB 102. As is illustrated in FIGURE 3A, the conductive springs 136 are loaded to a compressed state so as to have a compressed length Y. As such, the compressed conductive springs 136 apply a biasing force to a surface of the corresponding conductive contact 118 for improving the electrical connection therebetween. As described above, the lip 148 of the retaining arms 108 may be configured to counteract the biasing force applied by the conductive spring 136 thereby holding the switch body 106 in position.

As the switch body 106 moves from the first position to the second position, the lip 148 of the retaining arms 108 slides along the contours 128 of the sliding plate 104 as illustrated by the intermediate position in FIGURE 3B. As the lip 148 slides along the concave contour 128 of the slide plate 104, the biasing force applied by the conductive springs 136 onto the PCB 102 or the conductive contacts 118 forces the switch body 106 away from the first surface 112 of the PCB 102, thereby causing the conductive springs 136 to become less compressed, as shown in FIGURE 3B. For example, as is illustrated in FIGURE 3B, the conductive springs 136 have a compressed length Y', which is greater than the compressed length Y of the springs 136 in FIGURE 3A. As a result, the forces acting on the first surface 112 of the PCB 102 and the conductive springs 136 are reduced. In one embodiment, the conductive springs 136 may be in an uncompressed state in the position shown in FIGURE 3B or anywhere along the contour 128 path.

From the description set forth above, it should be appreciated that as the second end 140 of a conductive spring 136 slides along the first surface 112 of the PCB 102, including along a portion of the conductive contacts 118, the resulting force being applied to the second end 140 is also reduced as the contour 128 path is followed. In that regard, frictional and/or other forces applied to the second end 140 of the conductive spring 136 are also reduced. In some embodiments, this may reduce wear to the second end 140 of the conductive spring 136. Similarly, the frictional and/or other forces applied to the PCB 102 and/or the conductive contacts 118 may be reduced. In some embodiments, this may reduce wear and/or damage incurred by the PCB 102 and/or the conductive contact 118.

When the switch body 106 reaches the second position as illustrated by FIGURE 3C, the conductive spring 136 may return to a more compressed state sufficient to place the conductive spring 136 in electrical connection with the conductive contact 118. In the embodiment illustrated in FIGURE 3C, the conductive spring 136 is returned to a compressed state so as to have a compressed length Y. As in the position illustrated in FIGURE 3A, each compressed conductive spring 136 in the position illustrated in FIGURE 3C applies a biasing force to a surface of the corresponding conductive contact 118. Further, as described above, the lip 148 of the retaining arms 108 may be configured to counteract the force applied by the conductive spring 136 thereby holding the switch body 106 in position on the PCB 102.

In an alternative embodiment, the slide plate 104 may be secured to the first surface 112 of the PCB 102. In this alternative embodiment, the slide plate 104 may be provided between the switch body 106 and the PCB 102. In particular, the second surface 124 of the slide plate 104 may be secured to the first surface 112 of the PCB 102, and the inner surface 134 of the switch body 106 may be on or adjacent the first surface 122 of the slide plate 104. In this embodiment, the switch body 106 may be configured to slide along the first surface 122 of the sliding plate 104. However, it will be appreciated that the contours on the first surface 122 of the slide plate 104 may be convex. As such, the convex contour portions reduce the forces applied to the PCB 102 and each conductive spring 136.

In other alternative embodiments, a cam or pivot arm may be utilized to reduce an amount of force applied to the PCB 102 by the conductive springs. That is, the cam or pivot arm may be coupled to the switch body 106 causing the switch body 106 to move away from the first surface 112 of the PCB 102 thereby reducing the amount of force being applied to the surface thereof by the conductive springs 136. In yet another alternative embodiment, the contour 128 on the slide plate 104 may be integral with the first surface 112 or the second surface 114 of the PCB 102.

Turning now to FIGURE 4, there is shown another exemplary embodiment of a switch assembly 200, formed in accordance with aspects of the present disclosure. The switch assembly 200 is substantially identical in materials and operation to many components of the previously described embodiments. However, the switch assembly 200 differs from the switch assembly 100 in some respects, as will be described in more detail below. For clarity in the ensuing descriptions, numeral references of like elements of the switch assembly 200 are similar to those used to describe the switch assembly 100, but are in the 200 reference numeral series, for the illustrated embodiment.

As best shown in FIGURE 4, which is a cross-sectional view of a switch assembly 200 in an intermediate position, the switch assembly 200 includes a PCB 202 and an insulative body, such as a switch body 206. The PCB 202 may be a PCB as described in reference to FIGURES 1-3 and includes a first surface 212 and an opposite, second surface 214. The PCB 202 further includes one or more elongate openings 272 formed therein. The one or more openings 272 may be oriented on the PCB 202 such that a longitudinal axis of the openings 272 is aligned with the direction of motion indicated by arrow B in FIGURE 4. Each of the openings 272 includes a first end 274 and a second end 276. Although six openings 272 are depicted in FIGURE 4, it is to be understood that any number of openings 272 in any orientation, such as any number of rows, may be provided in the PCB 202. For instance, in one embodiment, the PCB 202 includes ten openings formed therein, with five slots in two rows. As is illustrated in FIGURE 4, the one or more openings 272 may extend from the first surface 212 of the PCB 202 to the second surface 214 of the PCB 202, thereby forming elongated slots. In an alternative embodiment, however, the one or more openings 272 may extend from the first surface 212 partially through PCB 202. In this alternative embodiment, the openings 272 form channels, each having a bottom surface not shown in FIGURE 4.

The switch assembly 200 further includes pairs of conductive contacts 218, each pair being associated with an opening 272. In the embodiment shown, respective conductive contacts 218 may be formed at each end of the openings 272. That is, a conductive contact 218 may be formed at the first end 274 of each opening 272, and a conductive contact 218 may be formed at the second end 276 of each opening 272. The conductive contacts 218 may be constructed of any material or materials configured to allow electrons to flow therethrough. It will be appreciated that the conductive contacts 218 may be in electrical connection with other components (not shown) on the PCB 202 via traces (not shown) formed within the PCB 202. In one embodiment, the conductive contacts 218 are made of copper and plated with a noble metal, such as gold. In some embodiments, one or more edges of the conductive contacts 218 may be beveled.

Still referring to FIGURE 4, the switch assembly 200 includes an insulative body, such as the switch body 206 that carries one or more conductive members 236. The switch body 304 includes a somewhat planar surface 234 that interfaces with the first surface 212. The conductive members 236 may be configured to extend outwardly from the surface 234 of the switch body 206. In particular, a first portion of each of the conductive members 236 may be secured to the switch body 206 such that a second portion of the conductive members 236 extends outwardly from the surface 234 of the switch body 204. In embodiments that include a plurality of conductive members 236, such as the one shown in FIGURE 4, the conductive members 236 are positioned so as to be spaced apart from any other conductive member 236. The conductive members 236 are further positioned so as to correspond to the orientation and positioning of the openings 272 in the PCB 202. That is, each of the conductive members 236 are oriented in the switch body 206 to align with a corresponding opening 272 in the PCB 202. The switch body 206 may further include retaining arms 208 secured to or integral formed with the switch body 206 for movably retaining the switch body on the PCB 202.

In embodiments of the present disclosure, the one or more conductive members 236 may be any conductive member configured to electrically connect with a corresponding conductive contact 218 when a portion of the conductive member 236 abuts the conductive contact 218. In one embodiment, the conductive members 236 may be a spring. Non-limiting examples of the conductive members 236 may include a leaf spring, a C-shaped spring, a coil spring, or any spring or member configured to make suitable electrical contact with the conductive contacts 218. In other embodiments, the conductive members are bars, rods, etc. In one embodiment, the conductive members 236 are copper conductive members, which may or may not be plated with a noble metal, such as gold.

When assembled, as illustrated in FIGURE 4, the switch body 206 is positioned on the first surface 212 of the PCB 202, such that each of the conductive members 236 is provided within a corresponding opening 272 in the PCB 202. As briefly described above, the switch body 206 may be movably held on the PCB 202 by retaining arms 208. Depending on the location of the switch body 206 on the PCB 202, the retaining arms 208 may extend through openings in the PCB 202 similar to the openings 120 illustrated in FIGURE 1, and/or along an outer edge of the PCB 202 as illustrated by FIGURE 1. The lip 248 of each of the retaining arms 208 may be provided against the second surface 214 of the PCB 202 to hold the switch body 206 onto the surface of the PCB 202.

In some embodiments of the present disclosure, the switch body 206 may be manually actuated between first and second positions. In other embodiments, an actuator, such as actuator 130 as described in reference to FIGURE 1, may be employed to affect movement of the switch body 206 through moving arm 132 from a first position to a second position. That is, the switch assembly 200 may be configured to switch from a first state to a second state when the actuator 130 (FIGURE 1) causes the moving arm 132 to move in one of the directions indicated by arrow B.

FIGURE 4 illustrates the switch assembly 200 in an intermediate position, such that the conductive members 236 are not in contact with a respective conductive contact 218. As the actuator 130 causes the switch body 206 to move to a first position, i.e. towards the conductive contacts 218 located at the first end 274 of the openings 272, the conductive members 236 move within corresponding openings 272 until the conductive members 236 make physical contact with the conductive contacts 218 at the first end 274 of each opening 272. When the switch assembly 200 is in the first position and a portion of each conductive member 236 is in electrical connection with a corresponding conductive contact 218, the switch assembly 200 is placed in a first state.

Similarly, as the actuator 130 causes the switch body 206 to move to a second position, i.e. towards the conductive contacts 218 located at the second end 276 of the opening 272, the conductive members 236 move within the corresponding openings 272 until the conductive members 236 make physical contact with the conductive contacts 218 at the second end 276 of the opening 272. When the switch assembly 200 is in the second position and a portion of each conductive member 236 is in electrical connection with a corresponding conductive contact 218, the switch assembly 200 is placed in a second state. As will be clear to those skilled in the art, the illustrated switch assembly 200 may be modified for any number of poles. In that regard, any number of slots and any number of conductive contacts may be employed based on the intended purpose of the switch assembly.