Winding – tensioning – or guiding – Reeling device – Fishing rod reel
Patent
1981-10-07
1983-11-01
Christian, Leonard D.
Winding, tensioning, or guiding
Reeling device
Fishing rod reel
360132, G03B 104, G11B 1532
Patent
active
044126638
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to a magnetic tape cassette, for example a tape recorder or video tape cassette, which is provided with an indexing device for the unwinding of the magnetic tape.
2. Prior Art
Such cassettes are practical to use but one is very poorly informed at a given moment as to the part of the tape in the course of recording or reading. Rough information is drawn from the estimation of the length of tape which remains to be wound or unwound and that is by viewing through a window provided in the case of the cassette.
A less inaccurate means consists in providing the reading and/or recording apparatus with a counter connected to the drive mechanism for the tape. Still, for the indication of the counter to have a significance, on the one hand, the tape must be unwound from its origin, on the other hand, the counter must be reset at the start of unwinding. In addition, the drive mechanism and/or the connection with the counter customarily comprises a belt drive so that slipping is inevitable on starting and stopping and the indication of the counter is in practice inaccurate and unreliable.
Indexing devices for the unwinding of the magnetic tape are also known which are integrated or secured to the cassettes themselves and which at least in theory are intended to give a very accurate indication of the unwound length of magnetic tape.
It has nevertheless been found in practice that these devices are too bulky to be integrated into a standard cassette, in particular a tape recorder cassette, or do not have a sufficient gear ratio to permit the accurate indexing of a given zone of the magnetic tape, or are formed of elements mounted so that the friction forces between these elements are very much greater than the traction force normally applied to the magnetic tape to unwind it, thereby risking the jamming of the cassette, the tearing of the tape, etc.
SUMMARY OF THE INVENTION
An object of the invention is to avoid these drawbacks and to propose to this end an indexing device for the unwinding of the magnetic tape of a cassette which comprises a two-stage reduction gear adapted to be driven by a reel of the cassette and formed of coaxial flat disks or rings nested in one another, two of these disks or rings carrying graduations adapted to pass by a window in the case of the cassette.
According to the invention, the first reduction stage of the device comprises a ring with an eccentric circular peripheral surface carrying means for rotational driving by the reel and mounted for rotation in a first circular annular gear with external gear teeth itself mounted for oscillation with play about a fixed point, and a second annular gear having internal gear teeth meshing with the external gear teeth of the first annular gear and an eccentric circular outer peripheral surface, the second reduction stage of the device comprising a third annular gear with a circular internal surface in which the second annular gear turns with play and with external teeth meshing with internal teeth of a fixed external annular gear surrounding the third annular gear.
Surprisingly it has been found that the frictional forces of these various elements are extremely small and in any event are very much less than the traction force which is normally exerted on the magnetic tape for its unwinding. It has equally been found that this indexing device was very short in height and could thus easily be integrated into the case of a standard cassette.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following description reference is made hereinbelow, by way of example, to the accompanying drawings in which;
FIG. 1 is a front view along the longitudinal edge of a cassette;
FIG. 2 is a plan view;
FIG. 3 is a view of the interior of a half case of a cassette, the reel having been removed;
FIG. 4 is a fragmentary view in plan on an enlarged scale of a half case before the mounting of the movable elements;
FIG. 5 is a sectional view taken on line 5--5 in FIG. 4;
FIG. 6 is a view on an enlarged scale
REFERENCES:
patent: 3502284 (1970-03-01), Loewenberg et al.
patent: 3734052 (1973-05-01), Feldman
patent: 3894507 (1975-07-01), Koechlin
patent: 3912194 (1975-10-01), Chan
patent: 3913200 (1975-10-01), Kossor
patent: 4217614 (1980-08-01), Balson
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