GB2058411A

GB2058411A - Speed Control System for Spool Drive of Magnetic Tape Apparatus

Info

Publication number: GB2058411A
Application number: GB8025646A
Authority: GB
Original assignee: Voxson SpA
Current assignee: Voxson SpA
Priority date: 1979-09-07
Filing date: 1980-08-06
Publication date: 1981-04-08
Also published as: ES494659A0; IT7950205A0; ES8104616A1; DE3032273A1; JPS5647943A; FR2465291A1; IT1203243B

Abstract

A magnetic tape transport arrangement particularly for a magnetic tape cassette recorder comprises a member sensing the tape running speed arranged to control through a feedback circuit an electric motor mechanically coupled with the tape take up or winding coil. Sensing of the tape running speed is accomplished by measuring the angular velocity of an idle mounted capstan associated with sensors of its angular velocity which control a feedback circuit which acting on the motor associated with the take up coil varies its speed maintaining the magnetic tape linear velocity constant.

Description

SPECIFICATION Improvement in Tape Transport Systems for Magnetic Tape Recorders and Reproducers, Particularly of the Cassette Type This invention relates to improvement in tape transport systems for magnetic tape recorders and reproducers, particularly of the cassette type.

Specifically, this invention relates to a tape transport system for the type of equipment mentioned above, in which the tape transport occures by applying a motive force directly on the reel hubs, rather than by the conventional arrangement of capstan and pressure roller.

By the system according to this invention there can be eliminated a large number of kinematic motions necessary for the correct tape transport, driving of the take up or winding reel hub, and the mechanisms necessary for the tap fast forward.

According to this invention provision is made for a tape transport arrangement comprising a member sensing the tape running speed arranged to drive through a feedback circuit and electric motor mechanically coupled with the tape take up or winding reel, the arrangement being such that, by presetting a reference, a difference circuit senses shifting of the tape running speed with respect to that designed controlling the rotation speed of the motor mechanically coupled with the said take up reel.

This invention will be now disclosed with reference to its preferred embodiments, which are intended to be illustrative but not restrictive and on the basis of the figures shown in the attached drawings, in which: Figure 1 shows the tape transport general arrangement according to this invention Figure 2 schematically shows a first embodiment of the tape running speed sensing systems; Figure 3 shows a member associated with the structure shown in Figure 2; Figure 4 shows a modification of a detail in Figure 2; Figure 5 shows a further modification of a detail in Figure 2; and Figure 6 shows the system block electric diagram in accordance with the-invention.

With reference to Figure 1 the system general mechanical arrangement is shown in accordance with the invention. A magnetic tape cassette assembly labelled 1 is kept in position by way and means not shown on a deck 2. The magnetic tape cassette 1 includes two magnetic tape windings or reels 3, 4 centred on hubs 5, 6. Assuming that the tape moves in the direction shown by the arrows, hub 6 is set up to transport by rotation the reel or winding 4 by means of a pulley 7 coupled with a belt 8 and a motor 9. The magnetic tape in its path between return rollers 10, 11 is engaged between an idle mounted capstan 12 and a pressure roller 13.

According to the invention the arrangement is such that the capstan 12 transported in rotation by the tape translating motion provides a signal proportional to its angular velocity and consequently in a closed loop feedback circuit drives motor 9 so as to cause the transport speed to be constant and corresponding to that designed.

In Figures 2, 3, 4 and 5 there are shown several exemplificative solutions for sensing the angular velocity of capstan 12 in direct relationship to the running speed of the tape which is engaged between the said capstan 12 and the pressure roller 13, kept in contact by elastic means which are not shown.

Capstan 12 is idle mounted on a bushing 14 and is integral with a low inertia disk fitted, as shown in Figure 3, with light and dark sectors alternatively laid out regularly along the disk periphery. A transmission-type opto-electronic sensor 16 senses the light and dark marks laid out on disk 15 periphery to provide a train of pulses which is in direct relationship to the tape running speed.

Evidently, the arrangement could take the configuration shown in Figure 4 in which provision is made for an opto-electronic reflection type sensor 17 or the arrangement shown in Figure 5, in which capstan 12 is associated with a ferromagnetic material toothed wheel 18 arranged in conjunction with an electromagnetic sensor 19 of a known type which provides a train of pulses correlated with the traversing speed of the wheel 18 teeth In the proximity of its sensitive member.

In Figure 6 is shown the system simplified block diagram in accordance with the invention.

Motor M through the mechanical gears ml, m2 drives the take up coil hub MB and the angular velocity detector of capstan D producing an electric signal. It is evident that the mechanical coupling ml occurs through the magnetic tape during its motion through the system.

The signal produced by detector D after processing, if any, in a feedback network F of known type, is brought to a comparator CP in which is compared with a reference signal produced by a reference source R. The error signal drives an amplifierA which drives the electric motor M. It is evident that if motor M is a direct current motor, amplifier A will be a simple amplifier. Should motor M be an alternating current motor whose rotation speed is driven by the frequency of the supply electric current, block A will include means for the generation of a variable frequency driving energy dependent on the error signal.

It is evident that even if motor 9 mechanically coupled with the sole hub has been shown in Figure 1, it is possible, for instance to devise a similar arrangement for hub 5 also, so as to implement the functions of tape reverse or rewind, but all this falls within the common experience of an expert in the field.

This invention has been described with reference to its embodiment as presently p',eferred, but, as it will be readily understood, changes and modifications can be made in practice without departing from the scope of the appended claims.

Claims

1. Tape transport system for magnetic tape recorders and reproducers, particularly of the cassette type, characterized by the fact of comprising a member sensing the tape running speed arranged to drive through a feedback circuit an electric motor mechanically coupled with the tape take up or winding reel the arrangement being such that, by presetting a reference, a difference circuit senses the tape shifting speed with respect to that designed correspondingly controlling the rotation speed of the motor mechanically coupled with the said take up reel.

2. System in accordance with Claim 1, characterized in that the said member sensing the tape running speed comprises an idle mounted capstan engaged on tape, and associated with a member sensing the angular velocity so as to provide a signal proportional to the tape linear running velocity.

3. System in accordance with Claim 2, characterized by the fact that the said capstan is associated with a member connected to an optoelectronic detector.

4. System in accordance with Claim 2, characterized by the fact that the said capstan is associated with a ferromagnetic element connected to an electromagnetic tape detector.

5. Tape transport system for magnetic tape recorders and reproducers, particularly of the cassette type, in accordance with one or more of the above mentioned claims and substantially as illustrated and described in the Figures shown in the attached drawings.