US3449975A

US3449975A - Adjustable drive mechanism for phonographs

Info

Publication number: US3449975A
Application number: US602822A
Authority: US
Inventors: Wolfgang Hasselbach
Original assignee: Braun GmbH
Current assignee: Braun GmbH
Priority date: 1965-12-24
Filing date: 1966-12-19
Publication date: 1969-06-17
Anticipated expiration: 1986-06-17
Also published as: CH445886A; GB1121516A; DE1261333B

Description

United States Patent Int. Cl. Fllih 15/16 US. Cl. 74-193 4 Claims ABSTRACT OF THE DISCLOSURE This invention concerns a drive mechanism which includes a motor-driven stepped shaft, 'a friction transfer wheel selectively engageable with each step of the stepped shaft, and a conical roller engaging the transfer wheel and axially adjustable relative to it. This drive is particularly useful in phonograph record players.

The present invention is applicable to the drive of electro-acoustical storage units with mechanical carriers, and concerns particularly the drive mechanism of phonographs for playing disc records of different rates of revolution, which rates can be selected by means of 'a friction gear.

In sound reproduction devices, it is advantageous to be able to provide, in addition to the major speed selection, a fine adjustment for the rate of revolution of the record, in order to be able, on the one hand, to eliminate completely the influence of unavoidable manufacturing tolerances upon the number of revolutions and consequently the pitch, and, on the other hand, to offer a musician the possibility of tuning the record being played to his musical instrument.

'In addition to the fine adjustment systems operating with a braking effect, drives are known wherein a stepped shaft is carried on the motor shaft, the individual steps being of a conical shape. The friction wheel positioned between the stepped shaft and the turn-table is displaced axially along the steps by means of a suitable operating device.

Other phonographs use a conical motor shaft with various rises spaced axially, accomplishing a not very sensitive continuous adjustment of the speed by provida friction wheel which is moved therealong, driving the turntable from below.

These devices have the disadvantage that it is necessary to make a separate fine speed adjustment for each individual major speed selection, this being necessary four times in the case of a four-speed machine. Since the structural dimensions, particularly in the vertical direction, are limited in most cases, the path of adjustment for the individual stage cannot be made large enough. However, it is of advantage for the smooth operation of the device if this path is large, since the path length determines the extent of the influence on the smooth operation caused by the impact of the [friction wheel: this impact is unavoidable within certain limits.

It is a major object of the present invention to provide a variable speed drive in which the major speed adjustment may be made while maintaining constant a fivespeed adjustment. The invention overcomes noted disad- 3,449,975 Patented June 17, 1969 vantages by providing an arrangement wherein a friction 5 wheel drive element is positioned, for power-transmitting the speed, on the other hand, are accomplished by respective axial displacement of two of these engaging drive elements independently of each other.

There is shown in the single figure of the drawing an embodiment of the invention, with some parts in crosssection.

Referring now to the drawing, there is shown a motor 10 having an output shaft 11 on which is mounted a stepped shaft 12, which may have, as shown, four axially spaced steps of different diameters. The motor 10 is carried by a support 13 which may be positioned on one or another of the steps of a stepped support 14.

A friction wheel 15 is rotatably carried on a shaft 16 which is supported by a fixed frame member 17. It will be appreciated that the motor 10 and its support 13 may be positioned on any one of the steps of the stepped support 14 and that when positioned on a particular step, the stepped shaft 12 will have one or another of its steps in contact with the friction wheel 15. Thereby, for a given rotational speed of the motor 10, the friction wheel 15 will be given a selected rotational speed depending upon the position of the motor 10 on the stepped support 14 and the corresponding engagement of the friction wheel 15 with one of the steps of the stepped shaft 12. Thus, a selected rotational speed is imparted to the friction wheel 15.

In order to provide a fine adjustment for the rotational speed of a member driven by the variable speed drive mechanism of the present invention, there is provided a conical roller 18 fixed to a shaft 19 rotatably carried by the two arms of a fork 21. Attached to [fork 21 is a screw threaded member 22 'which passes upwardly through a slot 23 in a plate 24, and has threaded on it an adjusting nut 26. The back element 21a of fork 21 is inclined at the same angle as the conical roller 18, and carries nearly fiat springs 27 which are in engagement with an inclined surface 28 of a guide member 29. By manipulating the adjusting nut 26, the fork 21 and conical roller 18 carried by it will be moved vertically and somewhat horizontally, the horizontal movement being caused by the inclination of surface 28 and being permitted by the slots 23. Consequently, the conical roller 18 is caused to move so that a selected diameter of it will be in engagement with the friction wheel 15, to thereby accomplish a fine adjustment of the rotational speed of conical roller 18. A spring 31 may be provided about threaded member 22 to insure the continuous engagement of the wheel 15 and roller 18.

To the shaft 19 of conical roller 18 is fixed a pulley 32, and a belt 33 is driven by the pulley 32, belt 33 in turn driving a suitable driven element, such as a turntable (not shown), and is kept under tension by a tightener (not shown) as it is well known in the art. Consequently, while the rotational speed and position of conical roller 18 and its shaft 19 may be adjusted, the pulley 32 will be driven at which ever speed is selected by the fine adjustment due to the conical roller and by the main speed selection provided by the stepped shaft 12.

It will be apparent that the invention may be practiced other than'as disclosed'herein', and accordinglywhe'in vention is to be construed in the spirit of the application and the appended claims.

What is claimed is:

1. A variable speed drive mechanism comprising a stepped shaft having plural, axially spaced steps, a friction wheel engaging a selected one of said steps, a conical roller means engagingv said friction wheel for roration thereby, whereby said friction wheel is driven at a selected speed by said stepped shaft and said conical roller means is driven at a selected speed by said friction wheel, and means for axially adjusting said conical roller means relative to said friction wheel.

2. A variable speeddrive mechanism as set forth in claim 1, and means for axially shifting said stepped shaft and said friction wheel relative to each other to effect engagement of a selected step with said friction wheel.

I 3. A variable speed drive as set forth in claim 2, wherein said friction wheel is axially fixed.

" 4. The Variable speed" drive of claim 3T wher e in the means for axially adjusting said conical roller means relative to said friction wheel comprises means for axially moving said conical roller means into a selected position in which it is in engagement with said friction wheel.

References Cited UNITED STATES PATENTS "11/1964 Canada. ROBERT A. OLEARY, Primary Examiner.

8 WILLIAM E. WAYNER, Assistant Examiner;