ELASTIC ELEMENT STRUCTURE FOR THE RETENTION RATCHET GEAR IN MAGNETIC TAPE CASSETTES

Abstract: The present invention relates to an elastic element structure for the reel retention ratchet gear in magnetic tape cassettes which comprises an elastic lamina (1) with elongated extension defining a central portion (10) for coupling to a magnetic tape cassette (5) and two opposite branches (15) acting, at their free end (17), on the respective thrust arms (20) of the reel retention ratchets (21). The peculiarity of the invention resides in the fact that it comprises, at said free ends (17), shapings adapted to generate a thrust component in the direction of elastic preloading of said elastic lamina (1) upon the insertion of said ratchets (21) in said cassette (5) along a direction substantially coinciding with their axis of oscillation.

Description: The present invention relates to a magnetic tape cassette comprising an elastic element structure for the reel retention ratchet gear. As is known, in magnetic tape cassettes, in particular in so-called videocassettes, a ratchet gear is used which is constituted by a pair of ratchets oscillating about an axis substantially parallel to the axis of rotation of the reels, which are pushed elastically against a toothed flange of the reel, so as to prevent the rotation of the reels, when the cassette is not inserted in the recording or playback device, to prevent the rotation of said reels in the direction of unwinding of the tape from the reel. Various types of elastic elements are currently used which are constituted, for example, by an elastic leaf spring having a lower flap for coupling to the cassette shell, to the side whereof two elastic arms are provided which act with a thrusting action on the thrust branches of the ratchets. This type of solution has, first of all, the disadvantage of not allowing packaging of the elastic laminae in reels, since the presence of the small plate arranged to the side of the elastic arms does not allow the possibility of unwinding in a tape-like manner the various elastic elements. Another disadvantage resides in the fact that the elastic preloading to be imparted to the elastic arms which thrust the ratchets must be performed, during the step of assembly of the cassette, by performing a composite movement during the insertion of the ratchets in the cassette, which slows down all the steps of automatic assembly of the cassette components. To obviate these disadvantages, springs for videocassette ratchet gears have already been introduced which are substantially constituted by an elongated elastic lamina which is provided with a central portion, associable with the cassette structure, from which there extend two elastic arms, inclined with respect to the central portion, which act with a thrusting action against the ratchets. This solution allows to package the various elastic elements in a continuous tape, but is not conducive to advantages regarding the elastic preloading of the laminae, which still require a composite movement of insertion of the ratchets. To try to limit this disadvantage, ratchets have been introduced which, in their lower part of the thrust arm which engages with the elastic lamination, are provided with a bevel in the shape of an inclined plane, so that the insertion of the ratchet along the direction of oscillation of the ratchet itself creates a component which elastically compresses the elastic lamina. This solution, though valid from many points of view, has the disadvantage of possibly creating particles which come loose from the thrust arm and may remain free within the cassette with the possibility of damage of other component elements. The elastic laminae are in fact generally obtained by punching and have burr at their free edges which may scrape the plastic material which constitutes the ratchets, removing particles of plastic which, by coming loose and remaining within the cassette, may create a severe detriment to the good quality of the cassette. Also known from US-A-4,195,797 is a reel retention ratchet gear having an elastic lamina as defined in the preamble part of claim 1 The aim proposed by the invention is to eliminate the above described disadvantages by providing an elastic element structure for the reel retention ratchet gear in magnetic tape cassettes, which allows to obtain the elastic preloading of the laminae which act on the ratchets, without having to resort to a composite movement of insertion of the ratchet and without running the risk of scraping or in any way abrading the surface of the ratchet, with consequent outward dispersion of plastic particles. Within the above described aim, a particular object of the invention is to provide an elastic element structure which may be packaged in a tape-like manner, thus having the possibility of winding in a reel a large number of elastic elements. Another object of the present invention is to provide an elastic element structure which is configured so as to eliminate practically completely all of the punching burr which normally occurs during the step of punching of the individual elastic laminae from a metallic tape or band. A further object of the present invention is to provide an elastic element structure which, though being obtainable with a reduced use of material, is capable of giving the greatest assurances of reliability and safety in use. Not least object of the present invention is to provide an elastic element structure which is easily manufacturable from elements and materials commonly available on the market and which furthermore is competitive from a merely economical point of view. The above described aim, as well as the objects mentioned and others which will become apparent hereinafter, are achieved by a magnetic tape cassette comprising an elastic lamina as defined in claim 1. Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of a structure of an elastic element structure for the reel retention ratchet gear in magnetic tape cassettes and the like, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a schematic plan view of a magnetic tape cassette with the cover removed, highlighting the positioning of the elastic element according to the invention, inside the cassette; figure 2 is a sectional view of the cassette, highlighting the detail of the elastic element acting on the ratchets; figure 3 is a schematic perspective view of a ratchet; figure 4 is a detail view of the ratchet gear of a cassette with a ratchet inserted and with the other ratchet in the process of being inserted; figure 5 is a schematic view of the step of punching the individual elastic laminae starting from a metallic band; figure 6 is a partial sectional view, in greatly enlarged scale, of the elastic element according to the invention, highlighting the central portion and one of the arms which act elastically on the ratchets; figure 7 is an end view of the elastic element; figures 8 and 9 are schematic views in succession of the step of insertion of a ratchet with consequent elastic preloading of the lamina at the moment of the insertion of the ratchets on their oscillation pivot; figures 10 and 11 are views of two different embodiments of the free end portion of the elastic lamina taken along the line X-X of figure 6; figure 12 is a view of an elastic lamina with smooth central portion. With reference to the above described figures, the elastic element structure for the reel retention ratchet gear in magnetic tape cassettes comprises an elastic lamina which is generally indicated by the reference numeral 1, which substantially has a predominantly elongated extension. The elastic lamina 1 is obtained, as shown in figure 5, by punching from a metallic band or tape, generally indicated by the reference numeral 2, and is shaped, as will become apparent hereinafter, so as to have no particular punching burr. The elastic lamina 1 has a central portion 10 in which insertion coupling means may be provided, constituted for example by an indentation or possibly a hole 11 with beading, which has the function of providing the element for insertion coupling to a corresponding support 12 which is defined by the cassette, generally indicated by the reference numeral 5. From the central portion 10 there extend two opposite branches, both indicated at 15, which are connected to the portion 10 by means of a first folding line 16; the branches 15 are inclined with respect to the plane of arrangement of the portion 10 and connect, at the other end, to a terminal portion 17, possibly connected by means of a second folding line 18, so that the terminal end has a greater inclination with respect to the central portion 10. The terminal portions 17 act by contact on the thrust arm 20 of ratchets, generally indicated by the reference numeral 21, which are rotatable about pivots 22 defined by the cassette and having an axis substantially parallel to the axis of rotation of the reels 23. The ratchets 21 have an engagement arm 25 which couples with the set of teeth 26 defined by the lower flange of the cassette reel. In a per se known manner, the thrust arms 25 have the function of locking the rotation of the reels, when these are not used, in the direction of unwinding of the magnetic tape, while they allow the winding, with a practically ratchet-like coupling between the end of the thrust arm and the set of teeth 26. The particularity of the invention resides in the fact that the terminal portions 17 of the elastic lamina have a convexity, indicated at 30, on the face directed towards the ratchets 21. This convexity is extremely important since it defines, on the edges of the elastic laminae, guiding portions which, upon the insertion of the ratchets 21 with a movement along the direction coinciding with the axis of oscillation of said ratchets, generate a thrust component on the elastic lamina which in practice performs the elastic preloading of said lamina. As schematically indicated in figures 8 and 9, by introducing the ratchets with a substantially vertical motion the lower edge of the ratchets couples with the region proximate to the edge of the lamina which is arranged in practice with an inclined plane, and generates a thrust component on the lamina which elastically preloads the same. This type of coupling furthermore prevents the possible burr which may be present on the edges on the terminal portions from scraping the plastic material which constitutes the ratchets, with the possibility that particles of plastic material may become loose and dispersed in the cassette. For the sake of descriptive completeness, it should be furthermore added that the central portion 10, on the sides orthogonal to the sides from which the laminae extend, is provided with expansions 40 which allow in practice to package the various laminae in the manner of a tape which can be wound in reels; as the lamina is then gradually inserted, by means of an automatic machine, on the cassette, the individual lamina is punched in each instance, said expansions constituting an element which facilitates the grip for their insertion. Another important aspect of the invention resides in the fact that the elastic lamina has a width which decreases starting from the central portion towards the free end, this occurring since the resisting section useful for the bending torque can decrease as one approaches the free end of said lamina where contact with the ratchet gears occurs. This arrangement allows to obtain a significant saving in material, since it is possible to adopt a configuration, schematically indicated in figure 5, with a substantially rectangular central portion 10 from which there extend said arms with progressively decreasing width so as to obtain with a punching operation the execution of a plurality of laminae with no burr whatever, since the region which is provided between two mutually side-by-side arms in practice constitutes the useful region for the provision of an arm of another row of laminae. To what has been described it should be furthermore added that said convexity may be obtained by means of an inverted-V configuration, as indicated in figure 10 by the numeral 30a, or possibly with a rounded configuration, indicated at 30b in figure 11. In practical use, therefore, once the elastic lamina is positioned at the support 12 of the cassette it is sufficient to introduce the left and right ratchets 21 with a substantially vertical translatory motion, so that the lower edge of the thrust arm of the ratchet couples with the edge part of the convexity of the terminal portion, so that the successive step of introduction of the ratchet causes, automatically, the elastic compression of the spring, that is, its preloading, without resorting, as can be observed in current methods, to composite insertion movements. Another important aspect of the invention resides in the fact that the configuration adopted for the lamina allows its production in tapes wound in reels, and consequently more easily used on automatic machines, and furthermore allows to obtain the punching while minimizing burr.

Claims: A magnetic tape cassette comprising: reels (23) having lower flanges presenting teeth (26); ratchets (21) pivotally mounted in said magnetic tape cassette for oscillating around an axis (22) substantially parallel to the rotation axis of said reels (23) and each of said ratchet (21) having a thrust arm (20) and an engagement arm (25) for engaging said teeth (26) of said reels (23); and an elastic lamina (1) presenting two opposite branches (15) extending from a central portion (10) attached to the cassette (1), the free ends of said branches (15) elastically acting against the respective thrust arms (20) for pushing said ratchets (21) to oscillate and said engagement arm (25) into engagement with said teeth (26) of said reels (23), characterised in that said elastic lamina (1) presents at said free end of each branches (15) a shaping (30) inclined with respect to the direction of insertion of said ratchets (21) in order to be adapted to generate a component of thrust for elastically deforming said branches (15) in the direction of elastic action of said branches (15) upon insertion of said ratchets (21) in said cassette along a direction coinciding with the rotation axis of said ratchets (21). A magnetic tape cassette, according to claim 1, characterized in that said opposite branches (15) of said elastic lamina (1) are inclined with respect to the plane of arrangement of said central portion (10), said opposite branches (15) being connected to said central portion (10) at a first folding line (16). A magnetic tape cassette, according to anyone of the preceding claims, characterized in that said branches (15) of said elastic lamina (1) present at their free ends end portions (17) connected to said opposite branches (15) by means of a second folding line (18), said end portions (17) carrying said shapings (30) and having, with respect to said central portion (10), a greater inclination than said opposite branches (15). A magnetic tape cassette, according to anyone of the preceding claims, characterized in that said shapings (30) are constituted, at least in transverse cross section, by a portion convex on the side directed towards said ratchets (21). A magnetic tape cassette, according to anyone of the preceding claims, characterized in that said opposite branches (15) have decreasing width starting from said central portion (10) and towards said end portions (17). A magnetic tape cassette, according to anyone of the preceding claims, characterized in that said convexity of said shapings (30) has, in transverse cross section, a configuration in the shape of a flattened V (30a). A magnetic tape cassette, according to anyone of the claims 1 to 5, characterized in that said convexity of said shapings (30) has, in transverse cross section, a rounded configuration (30b). A magnetic tape cassette, according to anyone of the preceding claims, characterized in that said central portion (10) of said elastic lamina (1) presents at least one hole (11) having a border adapted for engagement with a support (12) defined by said cassette (5) for the coupling of said elastic lamina (1) in said cassette (5). A magnetic tape cassette, according to anyone of the preceding claims, characterized in that, expansions (40) are arranged on the sides of said central portion (10) of said elastic lamina (1) orthogonally with respect to the major direction of said opposite branches (15), for coupling to flanking laminae for the obtainment of a tape of laminae windable on a reel. A magnetic tape cassette, according to anyone of the preceding claims, characterized in that said elastic laminae (1) are obtainable by punching from a metallic tape or band (2), between the opposite branches (15) of two elastic laminae (1) arranged side by side along the extension of the tape (2), there can be formed by punching the counterposed branch (15) of a series of laminae (1) constituting another row of laminae (1).

Inventors: BORDIGNON, ABRAMO
Applicants: A.T.B. S.P.A.
Application year: 1988
Main classification: G11B23
IPC codes: G11B23