ELECTROMECHANICAL PULSE GENERATOR

Abstract: An electromechanical pulse generator having a purely mechanical mode of operation for microelectronic equipment, e.g. volume control in hearing aids, consisting of a housing formed by a fixed base portion (7) in which a shaft (3) is fixedly mounted and a timing wheel (1) is rotatably mounted around the shaft, said timing wheel having the form of a downward facing open cylinder and being fixedly connected to a casing which forms an external handle. The inner cylinder surface of the timing wheel (1) is provided with grooves (12) engaging with the protrusion (13) of a circular carrier (5) rotatably mounted around the shaft (3). A U-shaped contact spring (6) has members (6', 6'') which are individually imparted an oscillating movement between contact pairs A-B-C and A-D-E, respectively, by the turn of the timing wheel (1) in one or the other direction via the carrier which can only move over a pre-determined circular section, so as to generate digital pulse trains. A locking device (4, 10, 15) prevents the carrier (5) from moving beyond the pre-determined circular section and causes the protrusion (13) to continuously engage with the grooves (12) by the turn of the timing wheel (1).

Description: Electromechanical pulse generator. The present invention relates to an electromechanical pulse generator for digital voltage control in an electronic apparatus, preferably a microelectronic apparatus, such as volume control in a hearing aid. Microelectronic devices without digital voltage control for volume control in hearing aids are disclosed in e.g. DK-C-134,876 and DK-A-1229/89 which relate to volume control devices in hearing aids by use of a potentiometer path or a self-aligning miniature converter, respectively. However, the use of digital electronics is particularly desirable in microelectronic hearing aids as it allows better results to be obtained than the hitherto non-digitally controlled devices. Thus, there is a need for a voltage control device which is immediately applicable within the digital electronics field and which allows a very accurate adjustment of the parameters of a hearing aid, thus furthermore making the apparatus user friendly. Electromechanical pulse generators for digital voltage control are known from e.g. radio and television sets, in which, however, such pulse generators are provided with components of an optical, magnetic or similar character. Thus, a digital voltage control based on the light/shadow effect in an optical component incorporated in the equipment is known from e.g. the electronic equipment of radios. Due to the size of such constituent parts these electromechanical pulse generators are obviously not suitable as parts of a microelectronic hearing aid in which the total outer dimensions of the components are to be in the magnitude of 3-4 mm. In Applicant's earlier patent application DK-A-1838/90 it has been attempted to minimize equipment of this type for microelectronic use by use of an electromechanical pulse generator. However, it has turned out to be relatively difficult and complicated to manufacture and mount the pulse generator due to its relatively large number of vulnerable single components of very small size as well as the relatively large possibilities of functional errors arising during use of the pulse generator due to the complex cooperation between the single components. Finally, US-A-4,282,415 discloses another pulse generator of the said type which is also suitable for minimization. This pulse generator is i.a. characterized by having two simple switch sets which are placed symmetrically and which work in the same manner for closing an electric circuit using an impact effect, as a resilient contact member of the individual switch set is brought to abut against a fixed contact member of the switch set. However, in this construction the contact impact may have an unfavourable effect in connection with the electric circuit as the impact may produce undesired multiple activations of the circuit merely by turning of the rotor of the pulse generator a single step. Therefore, it is the object of the present invention to provide an electromechnical pulse generator with a purely mechnical mode of operation for digital voltage control in microelectronic equipment which remedies the above mentioned disadvantages of the prior art pulse generators and which is suitable for being manufactured with very small outer dimensions for an effective and flawless functioning during the life of the product while at the same time having a few, simple and mutually cooperating components, which thus also allows the pulse generator to constitute a surprisingly inexpensive product. The object is obtained by means of an electromechanical pulse generator of the type stated in the introductory part of claim 1, the characteristic features of which are stated in the charcaterizing part of the claim. The pulse generator according to the invention may furthermore contain the features stated in claims 2, 3 and 4. Thus, the features which particularly distinguish the invention from the prior art are that the pulse generator, l ke the pulse generator according to Applicant's earlier application DK-A-1838/90, can be minimized to the outer dimensions required for the microelectronic use in question and that it is a purely mechanical component having a tuning knob which can be turned endlessly in either direction and which is not provided with any form of end stop. This means that the adjustment of the hearing aid becomes independent of the absolute position of the tuning knob, as the adjustment is expressed exclusively through the relative turn of the tuning knob in relation to a basic position. One of the particularly characteristic features of the invention is therefore the U-shaped contact spring which in its neutral position is connected to one of the terminal sets of the pulse generator and which is brought to abut against a terminal in the other terminal set by activation of the circuit of the pulse generator through turning of the carrier in the pulse generator. The shift from one terminal to another terminal in the electronic circuit, e.g. in a hearing aid, results in the elimination of the above mentioned negative effects of contact impact. The invention will be explained in further detail below with reference to the accompanying drawings in which Figures 1-5 diagrammatically illustrates an example of a non-limiting embodiment of the invention. Fig. 1 is a side view of an electromechanical pulse generator provided with a wheel-shaped handle or a wheel-shaped tuning knob. Fig. 2 is a pulse generator with a tuning knob having catch fans. Fig. 3 is a vertical sectional view through a pulse generator along the line III-III of Fig. 4. Fig. 4 is a horizontal sectional view through a pulse generator along the line IV-IV of Fig. 3. Fig. 5 illustrates different steps of the mechanical functioning of the pulse generator. Fig. 6 is a circuit diagram illustrating the principles of the converter functions according to the invention. Fig. 7 is a circuit diagram of e.g. the digital pulse trains generated in the circuits according to the invention. In Figures 1 and 2, which are both side views of a pulse generator which have been enlarged about 10 times, 1 designates a timing wheel which is fixedly mounted in an outer casing 2a, 2b and which is mounted rotatably around a shaft 3 (Fig. 1) which is attached in a base portion 7 on the pulse generator. Furthermore, in the base portion 7 contact members A, B, C, D and E are attached to two converters mounted in the housing, the function of which converters will be discussed below. The surrounding casing, which can be freely rotated around the shaft in both directions, may have the form of an externally knurled wheel 2a (Fig. 1) or it may be provided with catch fans 2b (Fig. 2). Figures 3 and 4 are both illustrations of the invention which have been enlarged about 20 times showing a vertical and a horizontal sectional view, respectively, through the pulse generator without the casing 2a, 2b. By means of a retention plate 14 the timing wheel 1 is mounted rotatably around the shaft 3 which is mounted in the base portion 7 in which the contact members are also mounted (in Fig. 3 only shown as A, D and E). The upper portion of the contact members projects a distance above the upward facing inner surface of the base portion. A U-shaped flat spring 6 having members 6' and 6" forms a common contact spring for the terminals and is attached to contact member A at the "lower" portion of the U and is moreover placed parallel with the horizontal surfaces of the base portion inside the housing formed by the timing wheel 3 and the base portion 7 so that the contact spring in its non-actuated position abuts on contact members B and D, whereas it can be brought to abut against contact member C and contact member E, respectively, by an outer effect, see below. A circular carrier 5 is also mounted rotatably around the shaft 3 - inside the housing and above the spring, said carrier being provided along its outer periphery with a protrusion 13 and on its downward facing surface with another circular protrusion 4 which can be moved in another circular groove 15 in the base portion 7. The central cutout 8 of the carrier and the complementary shape of the protrusion 4 and the groove 15 furthermore allow a diametrical movement of the carrier inside the housing during a certain effect which will be discussed below. The timing wheel 1, which in principle has the form of a downward facing open cylinder, is on its inner vertical cylinder surface provided with corrugated grooves 12 disposed parallel with the axis which are independently intended to hold the protrusion 13 of the carrier 5. In a cutout 9 in the carrier perpendicular to the diametrical plane in which the carrier moves, another flat spring 10, the locking spring, is placed which when pre-loaded abuts on both the shaft 3 and the shoulders 11 in the cutout 9 (Fig. 4), and which through its spring load effect maintains the protrusion 13 in a groove 12. When the protrusion 13 is maintained in a groove 12, the downward facing protrusion 4 of the carrier 5 shown in Fig. 3 can be moved to one or the other side in the groove 15 in the base portion 7 by turning of the timing wheel 1. As indicated with dotted lines in Fig. 4, the groove 4 covers about 1/5 of a circle. If the timing wheel is turned to one of the sides from the position in which the contact spring 6 is in a rest position and in which contact members 6' and 6" abut against contact member terminals B and D, thereby bringing e.g. contact member 6" to abut against terminal E, the further movement of the protrusion 4 in the direction of turning is stopped by the end stop of the groove 15 and so is also the further turning of the carrier. If turning of the timing wheel 1 proceeds, the protrusion 13 slides over the peak between the two grooves 12, as the cutout 8 and the groove 15 permit the carrier 5 to perform a corresponding diametrical movement backwards against the force of the locking spring 10. As soon as the protrusion 13 has passed the peak between two grooves, the spring 10 again pushes the carrier 5 forwards into engagement with the protrusion 13 in the subsequent groove 12. By means of the spring load effect from the member 6" in direction towards the starting position, the contact spring 6 simultaneously returns the protrusion 4 to the center position in the groove 15. Thus, a continued turning of the timing wheel 1 in the subsequent direction will result in a corresponding number of engagements of the protrusion 13 in the grooves 12 and a corresponding number of movements of the contact spring members 6' and 6" between the neutral positions AB and AD, respectively, and the activated positions AC and AE, which in practice are marked by a number of "notches" or clicks caused by the movements of the protrusion 13 into and out of the grooves 12. This mode of operation of the pulse generator and the results thereof are shown in Figures 5, 6 and 7. In Fig. 5 positions (a), (b), (c) and (d) indicate the movements of the parts of the pulse generator by turning of the timing wheel 1 in direction of the arrow. In (a) the pulse generator is in its neutral position with the members of the contact spring 6 abutting against terminals B and D and the protrusion 4 in a center position in the groove (not shown) in the base portion. In (b) the carrier 5 together with the timing wheel 1 are turned to the left, thereby causing the protrusion 4 to push the left member of the contact spring 6 to abut against terminal E. Switch No. 2 shown in Fig. 6 consequently shifts from the neutral position (A-D) to the activated position (A-E). In (c) the turning of the timing wheel 1 proceeds, but due to the stop in the base portion for the protrusion 4, the carrier 5 does not move, and the protrusion on the periphery of the carrier slides over the peak between two grooves in the timing wheel, thereby causing the carrier to be pushed diametrically backwards against the force of the spring 10. In (d) the carrier returns to its starting position, as the protrusion on the periphery of the carrier is pushed into the subsequent groove on the inner surface of the timing wheel 1 due to the spring load effect of the spring 10 and at the same time the spring power in the left member of the contact spring 6 pushes the protrusion 4 back into the center position so as to re-abut against terminal D. Thus, each time the protrusion 13 passes from one groove to another, switch No. 2 represented by terminals A, D and E will perform a switch function and produce a pulse train corresponding to the number of peaks between the grooves which the protrusion 13 passes. This pulse train is used e.g. for digital voltage control in the form of a reduction in the signal volume in a hearing aid. Switch No. 1 represented by terminals A, B and C in Fig. 6 will be similarly activated by turning of the timing wheel in the opposite direction and cause a digital voltage control for an increase in volume. The courses of the pulse trains are shown in Fig. 7 which at the top depicts the pulse trains by activation of switch No. 1 with terminals B and C and which at the bottom depicts the pulse trains for switch No. 2 with terminals D and E. As mentioned above, each switch has the form of a resilient member of the contact spring 6 attached to terminal A and mutual to both switches. As will also appear from Fig. 7, the non-activated spring member will be in a neutral position during the rotational movement of the timing wheel.

Claims: P a t e n t C l a m s 1. An electromechanical pulse generator for digital voltage control in an electronic apparatus, preferably a microelectronic apparatus, such as a volume control in a hearing aid, consisting of a non-electrically conductive housing having a fixed base portion (7) in which outward projecting electrically conductive contact members or terminals (A, B, C, D and E) are mounted, a vertical shaft (3) mounted in the base portion (7) and a timing wheel (1) mounted rotatably around the shaft, said timing wheel being fixedly mounted in an outer casing (2), c h a r a c t e r i z e d in that the vertical inner surface of the timing wheel (1) is provided with grooves (12) disposed parallel with the axis, the profiles of the grooves forming a sinus-like curve, that a circular carrier 5 is also rotatably mounted around the shaft (3) inside the housing having its rotational movement to either side of the shaft beyond a certain circular section limited by a stop device (15) formed in the base portion, and being at its outer periphery provided with a rounded protrusion (13) which engages with the corrugated grooves (12) on the inside of the timing wheel (1), that the circular carrier (5) is furthermore mounted around the shaft (3) in a manner so as to cause the carrier to perform a diametrical movement inside the housing when the protrusion (13) passes the peak between two adjacent grooves (12) during a rotational movement of the timing wheel (1) and consequently is pushed back and carried forward for re-engagement between the protrusion (13) and the subsequent groove of a locking spring (10) mounted in a cavity (9) inside the carrier (5), and that inside the housing between the carrier (5) and the base portion (7) a U-shaped contact spring (6) is attached to terminal A in a manner which through a rotational movement of the carrier allows the member of the spring (6', 6") to be brought from a resting abutment against terminal B and terminal D, respectively, into an activating abutment against terminal C and terminal E, respectively, by a protrusion (4) parallel with, the shaft 3 on a surface of the carrier (5). 2. An electromechanical pulse generator according to claim 1, c h a r a c t e r i z e d in that the corrugated grooves (12) on the inner surface of the timing wheel (1) are formed in such a manner that they together with the protrusions (4, 13) on the carrier (5), and the locking spring (10) by continued turning of the timing wheel (1) to one side or the other, respectively, impart an oscillating movement to one or the other spring member (6', 6") 5 between the respective terminal pairs B-C and D-E for an alternating contact between the terminals of the individual pair of terminals and terminal A, thereby generating pulse trains through the contact impacts for a digitally controlled voltage increase or voltage decrease in the apparatus. 10 3. An electromechanical pulse generator according to claims 1 or 2, c h a r a c t e r i z e d in that the stop device (15) in the base portion (7) is constituted by a groove for the protrusion (4) of the carrier, and that the groove has a length which allows the 15 protrusion to move only inside a circular section corresponding to about 1/5 of the circumference of the carrier. 4. An electromechanical pulse generator according to claims 1-3, c h a r a c t e r i z e d in comprising two switches in the form of 20 terminal pairs B-C and D-E, respectively, which are individually connected to a common end terminal A by one and the same contact spring (6). 25 30 iύ

Inventors: MOELLER NIELS THOR, MOELLER, NIELS, THOR
Applicants: MICROTRONIC AS, MICROTRONIC A/S
Application year: 1991
Main classification: H01H19
IPC codes: H01H19