CA1172967A

CA1172967A - Sound reproducing apparatus

Info

Publication number: CA1172967A
Application number: CA000392504A
Authority: CA
Inventors: Maurice Hiles
Original assignee: HAMILTON KENT MANUFACTURING COMPANY Inc
Current assignee: HAMILTON KENT MANUFACTURING COMPANY Inc
Priority date: 1981-12-17
Filing date: 1981-12-17
Publication date: 1984-08-21

Abstract

ABSTRACT OF THE DISCLOSURE
Recording or reproducing apparatus such as a phonograph utilizes vibration reducing and absorbing components made in accordance with U.K. specification 1,564,195. The material is in the form of a visco-elastomeric material having liquid or liquid-like properties such as delayed recovery after compression.
The components may be used in connection with the turntable, the stylus carrying arm, as suspension components isolating electromagnetic and other components which may introduce undesired vibrations. The material finds wide application in speakers as both a vibration isolator and energy absorbant.

Description

Title: "Sound Reproducing Apparatus"

This invention concerns sound reproducing apparatus and more particularly, but not exclusively, phonograph record playing apparatus.
The theoretically ideal operation of phonograph record playing apparatus is such that the stylus engages the groove of a record and moves only in response to the spiral form of the groove and the modulations therein. However, in practice, additional movements can and frequently do occur in response to many other causes. These causes are primarily vibrations in other components of the apparatus be they mechanical such as bearings, electrical ~uch as chokes and transformers, and electromechanical such as loudspeakers. Additional undesir-able movements can result from distortions in the record itself, records not always being flat in overall form but often being warped.
Many and varied proposals have been made in relation to the reduction of undesirable movements from different causes, out few if any of these proposals are entirely successful in the respective aims.
An object of the present invention is to effect further reductions of undesirable movements. The invention in fact embraces a number of different forms associated with different causes of undesirable movements but which forms each involve the use of visco-elastomeric material to damp undesirable movements. In this connection it is to be understood that the undesirable movements are commonly of low frequency, and often large amplitude, compared to those of the stylus in tracking the groove modulations. A visco-elastomeric material in this context is one having liquid or liquid-like properties whiGh can afford damping of the former movements, but having elas-tomeric pxoperties which cause little or no distortion to the latter movements. Such material can be liquid or solid.
Examples of solid material suited to this purpose are des-cribed in United Kingdom Patent Specification No. 1,564,195 ,, i7 which are characterized by being basically elastomeric but have a delayed recovery after compression. This delayed recovery is due to liquid-like properties resulting from a polymeric structure involving short and long chains and which will tend to selectively damp movements of low frequency and large amplitude. Liquids having similar properties can be produced by extension of the processes described in said specification.
In accordance with the present invention there is provided a recording or reproducing turntable comprising a layer of visco-elastomeric material consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15%, an elongation break of at least 500~, and a recovery which is delayed after compression by at least 0.7 seconds.
These and other objects and advantages of the present invention will become more apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features herein-after fully described in the specification and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.
In said annexed drawings:

csm/~ - 2 -;7 Figure 1 is a diametrical section of a turntable in accordance with the invention;
Figure 2 is another form of turntable;
Figure 3 is a schematic illustration of a stylus arm in accordance with the present invention;
Figure 4 is a schematic illustration of the invention as a suspension component; and Figure 5 is a section through a speaker illustrating various applications of the invention.

- 2a -~ 7m / . ~

Considering then specific forms of the invention:
a f~rst form as seen in Figure 1 comprises a mat 10 of visco-elastomeric material for location on the turntable 11 for ~upporting the record. Such a mat is suit~bly made of solid material according to the above specification as a circular disc of 300mm diameter and 3mm thickness except for a central area of llOmm diameter which is recessed by lmm to receive the record label, and of course a central aperture for passage of the turntable record-receiving spindle 12 therethrough.
In a modification of this mat as seen in Figure 2, an additional, upper layer 14 preferably of glass, although possibly of other rigid material, is also incorporated. The two layers 14 and 16 of this mat are suitably permanently bonded together as a laminated structure.
A second form of the invention, as seen in Figure 3, involves a paddle 18 depending from the further end portion of the stylus-carrying arm 20, the paddle being immersed in a visco-elastomeric liquid 22 held in a bath 23. Paddle arrangements are already known but employ silicone liquid which exhibits normal Newtonian physical properties whereas the presently proposed liquid is effectively non-Newtonian.
Aaso~ the present liquid will have properties less variable ~ith temperature and have low viscosity, if applied to the both before reaction such as in said specification, compared to ~ilicone liquid.
Another form of the invention, seen in Fi~ure 4, involves u~e of visco-elastomeric material in suspension components 24.
Thi~ material cn be employed as solid pads seen at 25 to replace or operate in conjunction with conventional springs.
Such pads may incorporate liquid or gas-filled cavities, typ~cally air, the cavities ma~ be vented to atmosphere or may be e~losed.

.

~ Q~7 A further form ofthe invention involves the use of pads such as just described, gaskets, or other support or encapsulation to isolate electromagnetic and other components which may introduce undesired vibrations. Such components include loudspeakers shown generally at 30 which, more specifically, can employ such visco-elastomeric material over the cabinet 31 as seen at 32, between the drive unit 33 and baffle 34 as seen at 35, between the baffle 34 and cabinet walls as seen at 36, and to support and control the cone 37 in relation to its drive unit as seen at 38.
Yet another form of the invention involves supporting the stylus-cantilever assembly by a structure of visco-elastomeric material.
While the invention has been described with more parti-cular reference to phonograph record reproducing apparatus, it will be appreciated that it is applicable in some specific forms to other sound reproducing apparatus involving common components.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A recording or reproducing turntable comprising a layer of visco-elastomeric material consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15%, an elongation break of at least 500%, and a recovery which is delayed after compression by at least 0.7 seconds.

2. A turntable as set forth in claim 1 wherein said turntable comprises a two layer laminate.

3. A turntable as set forth in claim 2 wherein said other layer is glass.

4. A turntable as set forth in claim 1 wherein said layer isolates the record from the remaining apparatus.

5. A stylus arm assembly for recording or reproducing comprising an arm, a paddle depending therefrom, said paddle being immersed in a visco-elastomeric substance which is consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15%, an elongation break of at least 500%, and a recovery which is delayed after compression by at least 0.7 seconds.

6. A stylus arm assembly as set forth in claim 5 wherein said material is a visco-elastomeric liquid.

7. A stylus arm assembly as set forth in claim 6 wherein the liquid is held in a bath.

8. In a recording or reproducing apparatus a suspended component, said suspended component being supported on pads of a visco-elastomeric substance consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15%, an elongation break of at least 500%, and a recovery which is delayed after compression by at least 0.7 seconds.

9. In recording or reproducing apparatus, a vibration reducing substance consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15%, an elongation break of at least 500%, and a recovery which is delayed after compression by at least 0.7 seconds.

10. A speaker assembly including a cabinet, said cabinet including a visco-elastomeric substance covering the walls thereof, said substance consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15%, an elongation break of at least 500%, and a recovery which is delayed after compression by at least 0.7 seconds.

11. A speaker assembly as set forth in claim 10 wherein such substance covers the interior walls of the cabinet.

12. A speaker assembly comprising a cabinet and a baffle, and a vibration reducing substance between the cabinet and baffle consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15%, an elongation break of at least 500%, and a recovery which is delayed after compression by at least 0.7 seconds.

13. A speaker assembly comprising a baffle and a drive and a vibration reducing substance between the baffle and drive consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15% an elongation break of at least 500% and a recovery which is delayed after compression by at least 0.7 seconds.

14. A speaker assembly comprising a drive and a cone and a vibration reducing substance between the drive and cone consisting essentially of a flexible polyurethane of essentially linear structure containing unsatisfied hydroxyl groups and having a compression set of less than 15% an elongation break of at least 500% and a recovery which is delayed after compression by at least 0.7 seconds.