Integrated volume control and switch assembly

An integral volume control and switch assembly comprising a resilient conductive member serving for switching between a first and second switch state and a resilient tactile member serving for providing a user with a tactile feedback upon change of switch state. The resilient tactile member and the resilient conductive member are formed by separate members. Hereby the assembly can be further miniaturised without the resilient tactile member and the resilient conductive member being too small to handle in a manufacturing process. In addition, it is possible to adjust angular position of the rotatable member where switch function and tactile feedback occurs. Preferably the resilient tactile member and the resilient conductive member are spatially separated along a rotational axis of the rotatable member. The assembly according to the invention is suitable for hearing aids.

FIELD OF THE INVENTION

The present invention relates to an integrated volume control and switch assembly comprising a combined potentiometer and switch function. In particular, the assembly is suitable for use in hearing aids and portable communication devices.

BACKGROUND OF THE INVENTION

Known potentiometers may in addition to a variable resistance function have a built-in switch that provides the option of changing between first and second switch states via the potentiometer knob—typically in an extreme position of the potentiometer knob. The potentiometer may function as a volume control where the potentiometer knob upon turning in one direction decreases the volume, and finally turns off the signal and/or switches off power. Preferably, the user is provided with feedback indicating that the switch has reached an off state, e.g. light in a display or diode, a sound, a tactile mechanical resistance towards turning of the knob, or similar. In relation to volume controls for portable audio equipment feedback is often provided to the user by a tactile feedback upon turning a rotatable volume control knob to or beyond its lowermost position. Hereby, the user has a indication that the device has been switched off so as to save battery without the need for visual confirmation or feedback.

PJ 88 manufactured by the applicant is an example of a potentiometer with a built-in switch providing the user with a tactile feedback. PJ 88 is suited for miniature applications, such as a combined volume control and on/off switch in a hearing aid. PJ 88 provides a combined switch function and tactile feedback arranged by engagement of two metal springs upon interaction with a protrusion on a user rotatable part. The two metal springs are both engaged with the switch function as well as the tactile feedback function.

The combined switch and tactile feedback arrangement provided in PJ 88 has a number of disadvantages that are particularly troublesome with respect to further miniaturisation. The two metal springs are small when compared to an overall size of the potentiometer assembly. This means that the solutions are not suited for further miniaturisation, since a pure downscale of such potentiometers would include mechanical parts being too complicated to manufacture and handle in a cost efficient production process.

An additional problem with PJ 88 is that it is not possible to independently adjust an angular position of the user rotatable part where the switch function and the tactile feedback occur.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an integrated volume control and switch assembly of a simple design that provides tactile feedback to a user of the assembly in connection with the switch function. The assembly must be suited for miniature applications, such as hearing aids, and still suited for cost efficient production.

An additional object is to provide an integrated volume control and switch assembly providing independently adjustable switch and feedback functions.

The mentioned objects are complied with by providing, in a first aspect, an integrated volume control and switch assembly comprisinga base plate being penetrable by first and second conductive switch legs, the base plate further supporting a resilient conductive member adapted to establish an electrical connection between the first and second conductive switch legs in a first switch state of the assembly, and adapted to break said electrical connection in a second switch state,a variable resistance means responsive to an angular position of a rotatable member, the variable resistance means being electrically connected between third and fourth conductive legs, anda resilient tactile member adapted to provide a tactile feedback to a user at a predetermined angular position of the rotatable member, to indicate to the user, a change between the first and second switch states,
wherein the resilient tactile member and the resilient conductive member are formed by separate members.

It is understood that even though denoted “legs” the first and second conductive switch legs may be formed differently than long slim members or pins. For example the switch legs may be formed by conductive bumps adapted for soldering or they may be formed by pieces of Printed Circuit Boards (PCB), pieces of flexprint or flexible wires etc.

The invention is particularly advantageous in that it is possible to manufacture the assembly in miniature versions without the need for components being so small that they are difficult to handle in a mass production line. This is accomplished by the fact that the switch function and the tactile feedback function are formed by separate members. Hereby, the separate members can be independently positioned in the assembly thus allowing each member to be located in positions with more space available.

An additional advantage is that the independent switch function and tactile feedback function allow independent choice of angular position of the rotatable member for switching and for tactile feedback. Once the assembly has been designed it is possible by simple changes to adjust a relative angular position of the rotatable member where switching and tactile feedback occurs—switching and tactile feedback need not be provided at the same angular position of the rotatable member.

The integral volume control and switch assembly may have the resilient tactile member (35) and the resilient conductive member (8) spatially separated along a rotational axis of the rotatable member (40). The resilient conductive member (8) and the switch legs (2,3) may constitute separate members.

The assembly may further comprise an intermediate link (20) rigidly connected to the rotatable member (40), the intermediate link (20) comprising a protrusion (21) being adapted to engage with the resilient conductive member (8) so as to either establish or break the electrical connection between the first (2) and second (3) switch legs.

The assembly may further comprise an intermediate housing (30) part being rigidly connected to the base plate (1), the intermediate housing part (30) having a top portion aligned with the base plate (1), wherein the top portion supports the resilient tactile member (35). The top portion of the intermediate housing part (30) may comprise an indentation (32) for guiding a first part (35a) of the resilient tactile member (35).

The rotatable member (40) may comprise at least one protrusion (39) adapted to engage with an engaging part (38) of the resilient tactile member (35).

The first part (35a) of the resilient tactile member (35) may be substantially U-shaped, and said first part (35a) being substantially perpendicular to the engaging part (38).

The at least one protrusion (39) of the rotatable member (40) may be adapted to engage with the resilient tactile member (35) so as to provide an audible feedback signal in addition to the tactile feedback. The predetermined angular position of the rotatable member (40) may be different from or equal to an angular position of the rotatable member (40) causing the resilient conductive member (8) to switch between the first and second switch states.

The resilient conductive member (8) may comprise a first part (9a,9b) adapted to engage with the protrusion (21) of the intermediate link (20).

The resilient conductive member (8) may comprise a detent spring manufactured in a material selected from the group consisting of: stainless steel, spring steel, low carbon steel, metallic alloys and Palladium alloys. The resilient conductive member (8) may be manufactured monolithically.

The resilient tactile member (35) may comprise a detent spring manufactured in a material selected from the group consisting of: stainless steel, spring steel, low carbon steel, and Palladium alloys. The resilient tactile member (35) may be manufactured monolithically.

The assembly may further comprise a user operable knob (50) connected to the rotatable member (40), the user operable knob (50) comprising means for providing friction with a user's finger.

The base plate (1) may be manufactured in a material selected from the group consisting of: heat resistive thermoplastics, insulating ceramics, LCP, PVC, PE, PP, and Polyetheretherketone. The intermediate housing part (30) may be manufactured in a material selected from the group consisting of: insulating ceramics, PVC, PE, PP, and Polyamide.

The variable resistance means may comprisea substrate (10) supporting a conductive path (14) on a surface thereof, wherein a first end portion of the conductive path (14) is electrically connected to the third (11) conductive leg, anda slidable contact (22) adapted to slide along the conductive path (14) upon rotation of the rotatable member (40), the slidable contact (22) further being in electrical contact with the fourth conductive leg (13).

The variable resistance means may further comprise a fifth conductive leg (12) electrically connected to a second end portion of the conductive path (14). The substrate (10) supporting the conductive path (14) may comprise a PCB.

As described for the conductive switch legs (2,3) it is understood that the term “leg” is not limiting with respect to third, fourth and fifth conductive legs (11,12,13). These conductive legs (11,12,13) may also be shaped as for example flexible wires, flexprint or bumps etc.

An outer diameter of the assembly may be in the range 1–4 mm, preferably in the range 2–3 mm. By an outer diameter is understood an outer diameter including a suitable outer protective housing part of the volume control and switch assembly.

A total height of the assembly is in the range 1,5–4,5 mm, preferably in the range 2,5–3,5 mm.

In a second aspect, the invention relates to a hearing aid comprising an integral volume control and switch assembly according to the first aspect.

In a third aspect, the invention relates to a portable communication device comprising an integral volume control and switch assembly according to the first aspect.

While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown only by way of examples. However, it should be understood that the invention is not intended to be limited to the particular embodiments disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a perspective view of selected parts of the assembly according to the invention showing from below a base plate1comprising first2and second3conductive switch legs. The first2and second3conductive switch legs penetrate the base plate1and form two terminals4,5, respectively, on an upper surface of the base plate1. It is understood that even though denoted “legs” the first2and second3conductive switch legs may be formed differently than the long slim members or pins shown in the Figures. For example the switch legs2,3may be formed by conductive bumps adapted for soldering or they may be formed by pieces of Printed Circuit Boards (PCB), pieces of flexprint or flexible wires.

The base plate1further comprises three holes6for receiving third11, fourth12and fifth13conductive legs mounted on substrate10. These legs11,12,13form the termination of the 3-pin potentiometer part of the assembly. One of conductive legs11or12may be omitted, if preferred, thus leaving the potentiometer part in a 2-pin version providing an adjustable resistance value between the two legs11,13or12,13.

The base plate1also comprises an indentation7fitted to receive and support a resilient conductive member8. The resilient conductive member8is a detent spring having a first part9cpositioned in the indentation7and second parts9a,9boriented substantially perpendicular to the first part9c. The second part9aof the resilient conductive member8is intended to co-operate with a protrusion21of the intermediate link20, in order to change switch state, i.e. establish or break the electrical connection between the two terminals4,5and hence the first2and second3conductive switch legs. The indentation7is preferably wider near the point of engagement between the resilient conductive member8and the protrusion21so as to allow bending of the first part9cof the resilient conductive member8positioned in the indentation7.

The substrate10comprises a conductive path14on a surface thereof. Third and fourth conductive legs11,12penetrate the substrate10so as to be electrically connected to opposite end portions of the conductive path14. The fifth conductive leg13is preferably positioned near the centre of the substrate10as the fifth conductive leg13is adapted to be in electrical contact with a centre mounted contact element23of a slidable contact22formed as a wiper, the slidable contact22further having a contact point24adapted for electrical contact with the conductive path14. Preferably, the substantially circular substrate10comprises an indentation16so as to let the second part9a,9bof the resilient conductive member8extend above the substrate10.

The intermediate link20has the slidable contact22rigidly mounted to its lower side. In a well-known manner the conductive legs11,12,13, the conductive path14, and the slidable contact are capable of constituting a conventional voltage divider where the rotation of the conductive wiper22provides two mutually dependent variable resistance values between the third conductive leg11and the fifth conductive leg13, and between the fourth conductive leg12and the fifth conductive leg13, respectively.

As mentioned, the intermediate link20comprises a protrusion21adapted to engage with the second part9bof the resilient conductive member8. The protrusion21is preferably manufactured in a material appropriate for the engagement with the resilient conductive member8, such as insulating ceramics, PVC, PE, PP or similar. Polyamide 6.6 with 50% glass is a preferred choice of material for the intermediate link20. Preferably, the intermediate link20and the protrusion21are manufactured, e.g. moulded, in one piece to simplify manufacturing.

An intermediate housing part30comprises a through-going opening31suited for receiving and preferably supporting the intermediate link20in such a way as to allow the intermediate link20to rotate at least part of a full revolution. The intermediate housing part30preferably comprises a U-shaped indentation32adapted to receive and support a resilient tactile member35formed as a detent spring. The leg parts of the U-shaped indentation32are wider than the bottom part of the U-shaped indentation32so as to allow bending of a first part35aof the resilient tactile member35when positioned in the leg parts of the U-shaped indentation32. The resilient tactile member35comprises a second part38oriented substantially perpendicular to the first part35a. The intermediate housing part30preferably comprises a projection part36that supports the rotatable member40. In addition, the projection part36serves as stopping means by preventing damage of the assembly that would occur by overturning the rotatable member40. As the rotatable member40is turned in one direction relative to the intermediate housing part30a protrusion39(further described in the following) of the rotatable member40will at one point of the rotation engage with the projecting part36that will thus hinder further rotation of the rotatable member40in the same direction. The same applies by rotation of the rotatable member40in the opposite direction. The intermediate housing part30also comprises an outer projection33for easy and reliable mounting/fixing of the assembly in a device, such as in a face plate of a hearing aid.

The resilient conductive member8is formed as a separate member from the contact parts4,5with which the resilient conductive member8is adapted to engage. If preferred, the switching mechanism according to the invention may be arranged so that the resilient conductive member8can be formed integral with one of the contact parts4,5and consequently integral with one of the conductive switch legs2,3.

A rotatable member40is rigidly connected to the intermediate link20in order to transfer rotational displacement of the rotatable member40to the intermediate link20. Preferably, the rigid connection is established by designing the rotatable member40and the intermediate link20to be combined or forced together in a locking engagement. Alternatively, the rotatable member40and the intermediate link20are joined by welding, gluing or similar. Rotation of the rotatable member40and the intermediate link20is preferably performed around a substantially central axis of the assembly. Preferably the fifth conductive leg13is also positioned in the axis of rotation.

A knob50for user friendly interaction may be provided on top of the rotatable member40so as to allow a user to easily operate the assembly. The knob50is preferably joined to the rotatable member40by fastening on a central projection41of the rotatable member40and an indentation42of the rotatable member40, e.g. by a locking engagement or similar methods. The knob50shown has a number of wings adapted to provide sufficient friction to a user's finger during operation. The knob50may be omitted if preferred or made integral with the rotatable member40.

FIG. 2shows a different perspective view of selected parts of the assembly according to the invention. Bottom part of the rotatable member40comprises an opening adapted to fit to a top of the intermediate link20. The rotatable member40also comprises a protrusion39adapted to engage with the second part38of the resilient tactile member35upon rotation of the rotatable member40. It is apparent that an angular position of the tactile engagement relative to an angular position of the top member40where a change of switch state occurs can be chosen with a high degree of freedom. Thus, a timing experienced by the user between change of switch state and tactile feedback upon rotation of the rotatable member40can be varied. This timing corresponds to an angular difference of the rotatable member40between the point of engagement of the protrusion39and the second part38of the resilient tactile member35versus the point of engagement of the protrusion21of the intermediate link20with the second part9bof the resilient conductive member8.

The angular difference between change of switch state and tactile feedback can be adjusted on the shown embodiment in several ways. For example the rotatable member40may be turned into another angular position when locked into engagement with the intermediate link20. Another way to adjust the switch function in relation to the tactile feedback is by providing a rotatable member40with its protrusion39positioned at another angular position relative to its locking mechanism for engagement with the intermediate link20. Still another way of adjusting the switch function in relation to the tactile feedback is by providing an intermediate link20with its protrusion positioned at another angular position relative to its locking mechanism for engagement with the rotatable member40.

The detailed kind of engagement between the protrusion39and the second part38of the resilient tactile member35can be performed in a variety of ways and a variety of tactile and also acoustic effects experienced by a user can be obtained. Due to the fact that the tactile feedback arrangement, formed by the resilient tactile member35and the protrusion39, is separated from the switch arrangement formed by the protrusion21of the intermediate link20actuating the second part9bof the resilient conductive member8, a variety of different schemes for timing of tactile feedback relative to the electrical switch function can be provided. Only a few examples will be given below.

In a first embodiment of the engagement between the protrusion39and the second part38of the resilient tactile member35the protrusion39has a slope as viewed in a profile view that bends the second part38of the resilient tactile member35away from its equilibrium position upon engagement. The engagement provides the user with an increasing mechanical resistance towards rotation of the rotatable member40depending on the rate of increase of the slope and a stiffness of the resilient tactile member35. In particular the stiffness of the second part38of the resilient tactile member35but also a stiffness of the first part35aof the resilient tactile member35influences the mechanical resistance that will be experienced by the user. Preferably, the slope of the protrusion39has a linear slope, but as an alternative to a linear slope, the slope might have a concave shape, a convex shape, a step-ladder shape, or similar. Preferably, a surface of the protrusion39is coated or treated to facilitate different kinds of engagement with the second part38of the resilient tactile member35.

So as to protect the potentiometer part from dirt and moist, the intermediate link20is fitted to the opening31in the intermediate housing part30substantially water-tight. This is crucial for example for hearing aid applications where it is essential that the volume and switch assembly is capable of reliable operation in a humid environment, i.e. the assembly needs to be at least substantially sweat-tight.

In a second embodiment of the engagement between the protrusion39and the second part38of the resilient tactile member35, the protrusion39has a maximum as viewed in a profile view. In this embodiment the user experiences an initially increasing mechanical resistance towards rotation of the rotatable member40being similar to the first embodiment described above. However, as the second part38of the resilient tactile member35reaches the maximum, the mechanical resistance will decrease relatively upon further rotation of the rotatable member40, thus providing the user with a different type of tactile feedback relative to the first embodiment. Preferably, the protrusion39has more than one maximum as viewed in a profile view.

In a third embodiment of the engagement between the protrusion39and the second part38of the resilient tactile member35, the protrusion39has an abrupt or discontinuous maximum following by a steep decline as viewed in a profile view. This can be considered as a special case of the second embodiment described above. The steep decline allows the second part38of the resilient tactile member35, at least for a short period of time, to accelerate towards a stop part of the protrusion39to provide a mechanical impact by the second part38of the resilient tactile member35on said stop of the protrusion39. This mechanical impact will result in an audible sound to the user, thereby informing the user about the change of switch state of the assembly via an audible click sound. Preferably, the audible sound is combined with a mechanical tactile feedback.

Optionally, the protrusion39is specifically treated or prepared at the point of the mechanical impact to enhance the audible sound. The protrusion may e.g. be metallised or similarly. In addition, the rotatable member40and/or the knob50may be designed specifically with respect to enhance their ability to transmit vibrations resulting from mentioned impact so as to enhance the acoustic signal radiated by external elements of the assembly, such as the knob50.

As seen fromFIGS. 1 and 2, the resilient conductive member8as well as the resilient tactile member35are formed by metal wire bent into a desired shape. In this way the resilient property of the resilient members8,35is provided by a spring effect. These parts are easy to manufacture and easy to handle and fit to the remaining part of the assembly, thus facilitating the production process also in miniature versions of the assembly.

Due to its conductive function the resilient conductive member8is preferably formed by an electrically conductive material. However, the resilient members8,35may be formed by different materials. The resilient tactile member35may be formed in an electrically non-conductive material such as a polymeric material that is capable of providing a spring effect so as to provide a tactile sensation to a user upon interaction of the resilient tactile member35with the protrusion39of the rotatable member40.

Preferred materials for the resilient conductive member8is Paliney 6, i.e. a Palladium-Silver based alloy. Another suitable material for the resilient conductive member8is Hera, which is a Palladium, Copper, Silver and Nickel based alloy. The same materials mentioned for the resilient conductive member8are also suitable for the slidable contact22. The resilient tactile member35is preferably manufactured in stainless steel such as W No. 1.4310. At least the material for the resilient tactile member35must provide a spring effect. All terminals, i.e. conductive switch legs2,3as well as conductive legs11,12,13are preferably manufactured in a silver alloy plated with 2 μm gold, such as AgCu 97/3. Preferred materials for intermediate link20, intermediate housing part30, rotatable member40as well as knob50is Ultramid A3EG10, i.e. Polyamide 6.6 comprising 50% glass. Materials for the base plate1must be able to withstand heat from welding. A preferred material for the base plate1is Victrex PEEK GL30, i.e. Polyetheretherketone comprising 30% glass.

FIGS. 3A and 3Bshow the assembly according to the invention in a first and a second switch state, respectively, both viewed in a partly cut-away section.

FIG. 3Ashows one leg9aof the first part9a,9bof the resilient conductive member8being in electrical contact with the upper contact terminal5, the contact terminal5forming an upper part of the conductive leg3. Likewise, the contact terminal4is in electrical contact with another leg9bof first part9a,9bof the resilient conductive member8, hence an electrical contact between the first2and second3conductive legs is established in this first switch state of operation. InFIG. 3Ait is also apparent how the contact part24of the wiper22co-operates with the conductive path14on the substrate10in order to establish electrical contact between a point of the conductive path14and the fifth conductive leg13. Furthermore, it is also shown how the two second parts9a,9bof the resilient conductive member8fit in the indentation16of the substrate10and extend above the substrate10to facilitate possible engagement by the protrusion21(not shown inFIG. 3A) of the intermediate link20.

FIG. 3Bshows the knob50, the rotatable member40(not visible inFIG. 3B), and the intermediate link20turned clockwise approximately a quarter of a full rotation relative to the position illustrated inFIG. 3A, and thusFIG. 3Billustrates the second switch state of operation. In the second switch state the protrusion21of the intermediate link20is engaged with the second part9aof the resilient conductive member8, thus forcing this second part9aof the resilient conductive member8away from the contact terminal5, and hence the electrical connection between the contact terminals4and5is broken in this second switch state of operation. Consequently, electrical connection between conductive switch legs2,3is broken in the second switch state.

In principle, the assembly can be brought into the same switch state by turning the rotatably mounted elements20,40and50in the opposite direction so that the protrusion21engages with the other leg9bof the second part9a,9bof the resilient conductive member8so as to break the electrical connection between the contact terminal4and the resilient conductive member8. However, preferably as described in connection withFIG. 1, the assembly is designed with appropriate stopping means, such as a projection part36, so that overturning of the knob50and consequently the rotatable member40and intermediate link20is prevented as this could damage at least the second part9a,9bof the resilient conductive member8.

FIG. 4shows a cross-sectional view through the centre of an assembled embodiment of the assembly according to the invention with the axis A of rotation indicated. In the cross-section shown inFIG. 4only three of the contacts members2,11,13are visible. The central conductive leg13penetrates the base plate1and the substrate10so as to provide electrically contact to the central part23of the wiper22. The second part9aof the resilient conductive member8extends with an end portion above the substrate10while another part9cof the resilient conductive member8resides in the dedicated indentation7of the base plate1. At the centre of the assembly the intermediate link20is rotatably mounted in the intermediate housing part30and the intermediate link20is rigidly connected with the rotatable member40. The rotatable member40is rigidly connected to the knob50. A part35aof the resilient tactile member35is shown positioned in the indentation32of the intermediate housing part30. The second part38of the resilient tactile member35can move freely in the cavity45of the rotatable member40until the second part38of the resilient tactile member35engages with a protrusion39(not visible inFIG. 4) of the rotatable member40.

As it is seen fromFIG. 4, in the engagement between the intermediate housing part30and the rotatable member40, the size of the projection36is larger than the size of the cavity45. Therefore, full rotation of the rotatably mounted parts20,40, and50is prevented. At a certain point of rotation, the projecting part36will meet a part of the cavity45of the rotatable member40being smaller than the projecting part36, and thus further rotation of the rotatable member40relative to the intermediate housing part30is hindered. InFIG. 2the rotatable member40is seen from below, and it is seen that the projecting part36will be stopped when reaching the protrusion39. However, other positions may be chosen for position of a stop member, for example so as to allow only a small fraction of a full rotation of the rotatable member40relative to the intermediate housing30.

A volume control and switch assembly according to the invention and according to the shown embodiments may be manufactured in a variety of sizes adapted to fit into different miniature applications such as portable audio devices for entertainment such as portable MP3 players, CD players or portable radios. The assembly may also be manufactured in sizes small enough to fit hearing aid applications while still acceptable with respect to large scale manufacturing.