The invention relates to an apparatus constructed for at least reproducing signals from a magnetic tape which extends between two juxtaposed rotatable reel hubs, the apparatus comprising (i) a tape-threading device, which is movable between a thread-out position and at least one thread-in position and which in its thread-out position engages behind the magnetic tape which extends along an initial path, which tape-threading device, as it is moved from its thread-out position to a thread-in position, moves the magnetic tape out of the initial path and into an operational path, the magnetic tape being unwound from one of the two reel hubs and the other reel hub being locked against rotation, and which in said thread-in position keeps the magnetic tape in this operational path, (ii) a detection device for detecting whether the tape-threading device has reached a thread-in position, (iii) two winding mandrels which are each in driving engagement with one of the two reel hubs and which are each coaxially connected to a winding-mandrel wheel (iv) a winding-mandrel driving device which is switchable between a stationary mode and at least one drive mode and which has a drive wheel which can be brought selectively in driving engagement with one of the two winding-mandrel wheels, and (v) a braking device, which is movable between a release position and a braking position, for the winding mandrel which is in driving engagement with the reel hub from which the magnetic tape is unwound when the tape-threading device is actuated, which braking device is set to its braking position when the detection device detects that the tape-threading device has reached a thread-in position.
Such an apparatus as defined in the opening paragraph is known in many versions. For example, the Applicant has manufactured and marketed such an apparatus in the form of a video recorder under the type designation VR 6760. This known video recorder is constructed not only for reproducing but also for recording video and audio signals. In this known video recorder the braking device for braking the winding mandrel at the end of a threading process is constituted by a spring brake whose brake spring is a cantilevered blade spring which is constantly in frictional engagement with the cylindrical circumferential surface of a brake wheel which is coaxial with the winding mandrel, the desired braking action being provided by a suitable choice of the spring force of the blade spring provided as the brake spring. As a result of this construction, the braking device constantly brakes the winding mandrel which is in driving engagement with the reel hub from which the magnetic tape is unwound during threading-in, thereby exerting an additional load on the tape-threading device and constantly exerting an additional load on the magnetic tape, which is unfavourable.
Allowance is to be made for the different effects of the choice of the spring force of the brake spring in order to obtain a specific braking action. For example, the spring force chosen for the brake spring can be comparatively small, resulting in a comparatively moderate braking action during threading-in. This has the advantage that the load exerted on the tape-threading device and the magnetic tape as a result of the braking action applied to the winding mandrel is comparatively small. However, in particular when threading-in is effected with a comparatively high threading speed, which is not uncommon in order to minimise the time required for threading-in, and when consequently the reel hub from which the magnetic tape is unwound during threading-in is set into a comparatively rapid rotation and therefore has a comparatively high kinetic energy at the instant of braking, running-out of this winding mandrel owing to inadequate braking at the end of threading-in is likely to give rise to looping of the tape, which is obviously undesirable. Alternatively, the spring force selected for the brake spring may, for example, be comparatively large, resulting in comparatively strong braking during threading-in. This has the advantage that in the case of threading-in with a comparatively high threading speed the strong braking action guarantees that looping of the tape at the end of thread-in is substantially excluded, but it has the disadvantage that the tape-threading device should be comparatively rugged and that a high load is exerted on the magnetic tape during threading-in, which is obviously equally undesirable. In the known apparatus this leads to a compromise, which is neither optimum in order to minimise the load on the tape-threading device and the magnetic tape during threading-in nor in order to ensure that at the end of threading-in the reel hub from which the magnetic tape is unwound during threading-in is braked as rapidly and strongly as possible.
It is the object of the invention to preclude the above problems with an apparatus of the type defined in the opening paragraph and to provide an improved apparatus in which the construction of the tape threading device can be light and in which during threading-in the magnetic tape is loaded only gently and after threading-in, even if this is effected with a high threading speed, a rapid and reliable braking of the winding mandrel is achieved which is in driving engagement with the reel hub from which the magnetic tape is unwound during threading-in, and consequently looping of the magnetic tape is avoided with certainty.