Ribbon transducers

Abstract: A ribbon transducer has the ends of its ribbon (10) held by end fixings which incorporate damping means. The end fixing may include a resilient support member (18) fixed to the ribbon (10), with the ribbon overlying a pad (22) of damping material and having its outer end held clamped, or alternatively left free.

Description: RIBBON TRANSDUCERS This invention relates to ribbon transducers, and is particularly concerned with the mounting of such transducers, for example in loudspeakers and microphones. Conventionally, ribbon transducers have simply been clamped at their ends to a rigid support. Over a period of time this rigid clamping of the ends of the ribbon can lead to fracture of the ribbon or at least to a degradation in its performance. EP-A-0116957 describes a ribbon system with separate ribbons for tweeter, mid-range and woofer, where the ribbons are each an elongate, corrugated aluminium ribbon which is set vertically and is clamped at top and bottom to a rigid, elongate frame. GB-A-1493296 describes a loudspeaker assembly with a cone diaphragm which is resiliently attached to a frame by a damper, such as silicon rubber. It is an object of the present invention to provide an improved end mounting for a ribbon transducer, particularly for a ribbon transducer to be used in a loudspeaker. In accordance with the present invention this is achieved by a ribbon transducer comprising a ribbon having two oppositely disposed ends which are fixed, and a support member at at least one end of the ribbon, characterised in that the support member is a resilient damping member affixed to the ribbon at a position spaced from the at least one end of the ribbon, and in that a grooved block or a mounting bar fixedly holds the resilient support member, thereby to create a ribbon end endwise of the fixing of the support member which will reduce cracking and avoid fracturing of the ribbon. By the provision of a damped mounting at each end of the ribbon the danger of cracking or fracturing of the ribbon is avoided or at least substantially reduced without in any way adversely affecting the performance of the transducer. In order that the invention may be more fully understood, a number of embodiments of end mounting for the ribbon of a ribbon transducer in accordance with the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is an isometric view of a preferred embodiment of end mounting; Fig. 2 is an illustration of one alternative end mounting; and, Fig. 3 is a schematic view of a further alternative end mounting. Referring first to Fig. 1, there is shown a ribbon foil 10 which constitutes the active element of a ribbon transducer, for example for a loudspeaker. The end portion of the ribbon foil 10 is clamped between a terminal block 12 and a clamping bar 14. The terminal block 12 is provided with a surface groove 16 of arcuate cross-section across its width. This groove 16 provides a seat for a support member 18. The support member 18 is made of a resilient material, for example silicone rubber, and may have a thickness of the order of 0.5mm. At one end the support member 18 is provided a bead 20 which is seated in the groove 16 as a locating means. The bead 20 may be glued in place. The other end of the support member 18 is glued or otherwise secured to the underside of the ribbon foil 10. The central portion of the support member 18 carries a foam damping pad 22 which is of generally semi-circular shape in cross-section as viewed from the side of the foil. The ribbon foil 10 passes over the damping pad 22, as shown in the drawing. This resilient/damping end mounting for the ribbon foil 10 provides the necessary security against fracture at the ends of the ribbon. Fig.2 shows one alternative mounting arrangement. Here, the support member 18 has one end glued to the ribbon foil 10, as indicated at 24. The other end of the support member 18 is rigidly fixed to a mounting bar 26. In this arrangement the end of the ribbon foil, after passing over the damping pad 22, extends freely. The portion of the foil 10 which passes over the damping pad 22 is glued to the pad. Fig. 3 shows yet a further alternative end mounting. Here the end portion of the ribbon foil 10 is turned back on itself through 180° and is secured at its end to a fixed-position block 28. The one end of the support member 18 is glued, at 24, to the ribbon foil 10 and the other end of the support member 18 is fixed to a mounting block 26. This arrangement again provides a resilient damping at the end of the ribbon foil sufficient to reduce the danger of fracture. Various other alternative methods of mounting the ribbon foil at its ends may be devised within the scope of the present invention.

Claims: A ribbon transducer comprising a ribbon (10) having two oppositely disposed ends which are fixed, and a support member at at least one end of the ribbon, characterised in that the support member is a resilient damping member (18) affixed to the ribbon (10) at a position spaced from the at least one end of the ribbon, and in that a grooved block or a mounting bar (12, 16; 26) fixedly holds the resilient support member (18), thereby to create a ribbon end endwise of the fixing of the support member which will reduce cracking and avoid fracturing of the ribbon. A ribbon transducer according to claim 1, characterised in that the support member (18) is affixed to the underside of the ribbon. A ribbon transducer according to claim 1 or 2, characterised in that the ribbon end, outwardly of the position at which the ribbon is fixed to the support member (18), towards the end of the ribbon, overlies a pad (22) of damping material held between the ribbon and the support member. A ribbon transducer according to claim 3, characterised in that the ribbon end beyond the pad (22) is held clamped by clamping means (12, 14). A ribbon transducer according to claim 4, characterised in that the clamping means (12) also provides a locating means for the support member. A ribbon transducer according to claim 2, characterised in that the ribbon end, outwardly of the position at which the ribbon is fixed to the support member, towards the end of the ribbon, is turned back on itself, and both the end of the ribbon (10) and the end of the support member (18) remote from its contact with the ribbon are fixedly mounted (26, 28). A ribbon transducer according to any preceding claim, characterised in that the support member (18) is a thin strip of material. A ribbon transducer according to claim 7, characterised in that the support member (18) has a thickness of the order of 0.5mm.

Inventors: BANK GRAHAM, PINFOLD HAROLD CHARLS, BANK, GRAHAM, PINFOLD, HAROLD CHARLS
Applicants: CELESTION INT LTD, CELESTION INTERNATIONAL LIMITED
Application year: 1990
Main classification: H04R9
IPC codes: H04R9