GB2180981A - Record player sub-chassis - Google Patents

Abstract

A record player turntable 4 and a pick-up arm 8 are supported on a sub-chassis 2 resiliently mounted on a main chassis I so as to isolate the turntable and pick-up from vibration. As a result of the phono-cartridge II tracking the record 5 acoustic energy in the form of vibration of many different frequencies is produced. This vibration is transmitted by the pick-up arm 8 into the sub-chassis main structure, IO. Attached to the main structure of the sub-chassis are extending weaker elements IOA, which are tuned to resonate at the various frequencies present in the main structure. The use of these weaker elements provides a method for acoustic energy, present in the sub-chassis, to dissipate very rapidly preventing energy increasing in magnitude, whilst allowing the main structure of the sub-chassis to remain rigid. <IMAGE>

Description

SPECIFICATION Record player sub-chassis This invention relates to a record player sub-chassis.

This is a member used to supporttheturntable and the pick-up. It is resiliently mounted on a main chassis, which can also constitute a casing of a record player, so asto isolate the turntable and pick-up arm from vibrations which may be transmitted to the main chassis through the surface on which it is resting.

It is of importance that the sub-chassis be of rigid construction between the turntable and the pick-up arm in orderto prevent any movement relative to each other. Forthis reason sub-chassis have conventionally been structures made of strong rigid material such as steel, heavy gauge metal sheet, laminated cellular materials or metal and plasticsheetlaminates.

The purpose ofthe record player isforthe pick-up to trace the grooved surface of a disc record located on the revolving turntable. This produces acoustic energy (vibration) which is channeled to the subchassis to be dissipated. The acoustic, or mechanical energy produced by the pick-up can vary in both frequencyand amplitude depending ontheformedirre- gularitieswithin the grooved surface of the disc record. The acoustic energy is dissipated by either heat orsound. Sub-chassis made of metal sheets and laminates dissipate energy into heat by molecularfriction within the material. This takes a period oftime which is unacceptable, allowing acoustic energy levels to increase. Sub-chassis of cellular construc- tion dissipate energy both by heat and sound.The energy is transferred mostly into heat bytheforementioned method, howeverwhere energyamplitude is sufficiently large cell walls are excited into movement producing low level sound. Energy dissipation isquickerbythis method, but still un satisfactory forthree reasons. These are: (1) Cellular materials have both ends ofthe cell wall fixed. Obstructed movement results and ac ousticenergydissipation hamperedunacceptabley by this restriction.

(2) Cell walls of uniform thickness will resonate at approximatelythe same frequency. As the energy to be dissipated has many differentfrequencies, dissipation becomes selective allowing acoustic energy levelsto increase at otherfrequenciesun- acceptabley.

(3) As the cell walls, usually held within a laminate, flexthe rigidity required from the sub-chassis is lost.

This invention provides a record playercomprising aturntable and meansforsupporting a pick-up, both mounted on a common sub-chassis which is resiliently mounted on a main chassis and is formed at least partly ofweaker elements extending from the main structure.

The use of weaker extending elements enables acoustic energy to be dissipated from the sub-chassis still allowing the sub-chassis to retain its required rigidity.

The weaker elements could, in practice have the resemblance of spikes, although different shaped elements could be used providing they have a lower rigidity than the main structure.

Only one end of the extending elements is fixed, the other end being free to move without restriction, thereby achieving a high degree of energydissipation. Furthermore the weaker extending elements can be tailored to various dimensions, this allowing them to be tuned to resonate, and hence dissipate at the wide range of frequencies present in the subchassis. The sub-chassis should preferably be manufactured complete with weaker extending elements in one piece without dislocation between the main structure and the extending elements.The subchassis can be conveniently made by moulding, preferably aluminium alloy, although other materials such as different metals, plastics or glass are also suitable.Asub-chassis mayalso be formed byfabrication, the weaker elements being attached to the main structure bya suitable method, such as weld- ing, adhesives, press fitting or screwing into place.

The weaker elements can be of a different material than the main structure allowing greaterflexibility in manufacture.

One way in which the invention may be performed will now be described with reference to the accompanying drawing, which is a diagramatic representation shown partly in vertical cross-section and partly in elevation of partofa record pl ayer constructed in accordance with the invention.

Referring to the diagram the illustrated record playercomprisesa mainchassislwhichalsoforms an outer casing. A sub-chassis 2 is resiliently mounted on the main chassis 1. In the illustrated example the resilient mounting is provided by compression springs 3 but in an alternative arrangement the subchassis could be suspended on tension springs or rubbertiesfrom suitable points on the main chassis.

Aturntable4,supporting a disc record is fixed to a spindle 6, which in turn locates into a journal bearing 7 attached to the sub-chassis 2. The turntable rotates underthe influence of a drive belt, (not shown) passing around the periphery ofthe turntable 4A. A pick-up arm 8 is fixed, preferably directly too, the sub-chassis structire 10 by bolts 9 or other suitable method as rigidly as possable so that acoustic energy transmitted from the phono-cartridge 11 by the pick-up arm 8 will transfer into the subchassis 2 unimpeded.

Once the acoustic energy is within the main structure 10 ofthe sub-chassis the extending weakerel- ements resembling spikes 1 OA respond to the acoustic energy by vibrating and hence dissipating the acoustic energy in theform of sound propagation.

twill be appreciated that the illustrated apparatus is only one example of many ways in which the invention may be implemented and different forms of pick-up, turntable, sub-chassis structure shape and sub-chassis suspension may be used. A record player constructed as shown in the diagram has however proved in comparison tests with other conventional record playersto provide a remarkable and immediately noticeable advance in reproduction quality.

Claims (1)

1. (1) Arecord playercomprising aturntableand meansforsupporting a pick-up, both mounted on a common sub-chassis which is resiliently mounted on a main chassis and is formed at least partly of weaker elements extending from the main structure.

   (2) A record player according to claim 1 in which the weaker element extending from the main structure has the resemblance of a spike.

   (3) A record player according to claim 1 in which the weaker extending elements are attached to the main structure by one end only.

   (4) A record player according to claim 1 in which there is no disclocation between the main subchassis structure and the weaker element.

   (5) A record player according to claims 1, 2 and 3 in which a sub-chassis with weaker extending elements is manufactured in metal.

   (6) A record player according to claim Sin which the metal is an aluminium alloy.

   (7) A record player according to claims 1,2 and 3 in which a sub-chassis is manufactured from plastic.

   (8) A record player according to claim 7 in which the plastic is a thermoplastic.

   (9) A record player according to claim 7 in which the plastic is a thermosetting polymer.

   (10) A record player according to claims 1,2 and 3 in which a sub-chassis is manufactured in glass.

   (11) A record player according to claim 10 in which the glass is a liquid glass resin.

   (12) Arecord player according to claim 1 in which the weaker extending elements are of a different mat erialtothatofthe main structure.

   (13) A record player according to claims 1,2 and 3 in which the weaker extending elements are fastened to the main sub-chassis structure.

   (14) A record player according to claim 13 in which fastening is achived by welding.

   (15) A record playeraccording to claim 13 in which fastening is achived by adhesives.

   (16) Arecord playeraccording to claim 13 in which fastening is achived by press fitting into the main structure.

   (17) Arecordplayeraccordingtoclaim 13in which fastening is achived by screwing into place.

   (18) A record player according to any one or all of the preceding claims numbered 1 to 17.

   (19) A record player substantially as described with reference to the accompanying drawing and substantially as illustrated therein.