A tape cartridge

Abstract: In a tape cartridge in which top case half (1a), bottom case half (1b) and tape guide piece (10) are separately molded, the tape cartridge is provided with a tape guide piece (10) having its upper and lower edges on the back surface provided with parallel upper and lower ribs forming recessed portions so as to avoid undesired engagement with the tape wound on the hubs.

Description: FIELD OF THE INVENTION The present invention relates to a recording tape cartridge, and more particularly to an improvement of a tape guide piece used in a three piece type tape cartridge wherein a top case half, a bottom case half and a tape guide piece are separately molded and they are assembled together. A tape cartridge of this kind is disclosed in EP-A-0 151 210. DESCRIPTION OF THE PRIOR ART An example of the three piece type tape cartridge mentioned above is shown in Fig. 1 to Fig. 3, wherein three members of a top case half 1a, a bottom case half 1b and a tape guide piece 10 are molded separately. The tape guide piece 10 has its one side (front side) formed guide ribs 16 facing to a recording and reproducing head insertion window 6 (referred to as recording head insertion window hereinafter) and guide ribs 15 and 17 facing to an erasing head insertion window 7 and a pinch roller insertion window 8 and has its other side (rear side) defined concave portions 30 on both left and right regions. The tape guide piece 10 is molded as a separate body from the tap and bottom case halves 1a and 1b in order to enhance abrasion proof property and to improve the accuracy of work of the respective guide ribs 15, 16 and 17. As means for positioning the tape guide piece 10 relative to the top and bottom case halves 1a and 1b, there are provided bosses 27 extending in a vertical direction between the guide ribs 16 and 17 with standard positioning holes 12 defined in the respective bosses 27 so as to extend in the vertical direction and a central hole 28 defined in the top and bottom case halves 1a and 1b between the bosses 27, thereby causing the bosses 27 to be inserted in installing holes 29 which are situated at positions corresponding to the conventional positioning standard holes and causing the central hole 28 to be fitted with a screw boss 22 projected on the top and bottom case halves 1a and 1b, so that the tape guide piece 10 is regulated in terms of position in the front and rear directions and left and right directions in the cartridge. In the conventional tape guide piece 10 mentioned above, since the parts of the tape guide piece 10 thinned by the concave portions 30 lacks mechanical strength, a reinforcing rib 31 is attached only at the lower end of the concave portion 30, moreover the thinned portions are reinforced by the bosses 27. In the contrivance of attaching the reinforcing rib 31 only to the lower end of the concave portion 30, the vertical cross sectional shape of the tape guide piece 10 becomes asymmetrical in connection with the top and bottom direction of the tape guide piece 10, whereby in molding the tape guide piece 10, the balance of the flow of the molten resin is harmed and there tend to occur deformation, curving, bending and torsion due to the shrinkage of the molded tape guide piece after molding. SUMMARY OF THE INVENTION An essential object of the present invention is to eliminate the drawbacks being inherent in the prior art tape cartridge mentioned above and to provide a tape cartridge which can prevent the deformation such as bending and curving of the tape guide piece, assuring enough mechanical strength and can improve the accuracy of the verticality of the tape guide piece so as to obtain an excellent tape running property. In order to accomplish the object of the present invention mentioned above, the tape cartridge is provided with a tape guide piece having its upper and lower edges on the back surface provided with parallel upper and lower ribs forming recessed portions so as to avoid undesired engagement with the tape wound on the hubs. In the arrangement mentioned above, since the cross sectional shape of the tape guide piece is symmetrical by the parallel ribs, when the tape guide piece is molded the flow of the resin can be improved, whereby deformation and bending or curving of the tape guide piece due to the shrinkage after the molding can be suppressed. In addition by providing the upper and lower ribs at the upper edge and lower edge of the tape guide piece, enough mechanical strength can be assured without specific bosses as used in the prior art, therefore it becomes possible to remove the mold in the direction perpendicular to the guide ribs on the tape guide piece when molding, whereby the guide ribs can be molded with a high accuracy. BRIEF EXPLANATION OF THE DRAWINGS Fig. 1 is an inside plan view of a conventional tape cartridge with partially cut, Fig. 2 is an exploded view of the tape cartridge shown in Fig. 1, Fig. 3 is a cross sectional view taken along the lines G-G in Fig. 1, Fig. 4 is an inside plan view of an embodiment of a tape cartridge according to the present invention with partially cut, Fig. 5 is an exploded view of the tape cartridge shown in Fig. 4, Fig. 6 is an enlarged cross sectional view showing an essential portion of the tape cartridge shown in Fig. 4, Fig. 7 is a cross sectional view taken along the lines IV-IV in Fig. 6, Fig. 8 is a cross sectional view taken along the lines V-V in Fig. 6, Fig. 9 is a perspective view showing a tape guide piece according to the present invention, Fig. 10 is a cross sectional view taken along the lines VII-VII in Fig. 6, and Fig. 11 is a cross sectional view showing another embodiment of a tape cartridge according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 4, a case body 1 of a tape cartridge is formed by combining a top case half 1a and bottom case half 1b made of plastic resin into one body and fastening them by fitting screws 2 in screw bosses 22 at several positions. In the left half portion and right half portion of the case body 1, a pair of hubs 4 for winding a recording tape 3 are rotatably accommodated. The recording head insertion window 6 is opened on a front wall 5 of the case body 1 at the central portion in terms of a longitudinal direction or left and right direction of the case body 1, moreover on the front wall 5, the erasing head insertion windows 7 are opened at both sides of the recording head insertion window 6. A pair of tape guide rollers 9 are rotatably disposed at the left and right hands on the front portion in the case body 1 and a tape guide piece 10 is situated between the tape guide rollers 9. The recording tape 3 is adapted to be drawn from one of the hubs 4 toward the front of the case body 1 and advances along a tape running path between the guide rollers 9 and the front wall 5 guided by the tape guide piece 10 and taken up by another hub 4. Referring to Figs. 5 and 6, the tape guide piece 10 is molded separately from the top case half 1a and bottom case half 1b by injection molding. The tape guide piece 10 comprises a plate like base plate 14 having the same vertical height as the inner height of the case body 1 or inner height of the top case half 1a and bottom case half 1b, a pair of first guide ribs 15 forming a pair of vertical walls and projected in a symmetric manner towards the front direction from both left and right ends of the base plate 14, a pair of second guide ribs 16 projected symmetrically toward the front direction from the central portions of the base plate 14 and extending in a vertical direction and a further pair of third guide ribs 17 projected toward the front direction from the base plate 14 between the first guide rib 15 and second guide rib 16 in a symmetrical manner with their wall surfaces formed as a vertical walls. Moreover, there are formed concave portions 18 between the second guide ribs 16 and the third guide ribs 17 on the front surface of the base plate 14 in a symmetrical manner with respect to the longitudinal direction of the tape guide piece 10 so as to avoid overlapping with the standard positioning holes 12. As shown in Fig. 6, each of the concave portions 18 is defined by a flat inner bottom wall 18a and side walls 18b formed so as to expand stepwise in the right and left directions from both sides of the flat inner bottom wall 18a. As shown in Figs. 9 and 10, there are formed parallel upper and lower ribs 25 at the upper end and lower edges of the back surface of the base plate 14 corresponding to the first guide ribs 15 and second guide ribs 16 and concave portions 26 are formed between the upper and lower ribs 25 in the base plate 14 so as to prevent the recording tape 3 wound on the hubs 4 from being contacted with the base plate 14. Referring to Figs. 4 and 5, there are formed in the inner surface of the top case half 1a and bottom case half 1b, capstan insertion windows 11 facing to the erasing head insertion windows 7 and pinch roller insertion windows 8, moreover, there are formed standard positioning holes 12 at the position between the recording head insertion window 6 and the erasing head insertion window 7 and at the position between the recording head insertion window 6 and pinch roller insertion window 8 for receiving a positioning pin of a recording and reproducing device. From the inner surfaces of the top and bottom case halves 1a and 1b, projections 13 are projected at the peripheral edge portions of the standard positioning holes 12 so as to surround the standard positioning holes 12. As shown in Figs. 6 and 7, each of the projections 13 comprises a flat back wall 13a which meets with the flat bottom wall 18a of the concave portion 18 of the tape guide piece 10 and both side walls 13b which are formed stepwise so as to meet with the stepped side walls 18b of the concave portion 18. There are provided further projections 24 having piece receiving walls 21, at positions nearer to the tape guide rollers 9 on the inner parts from the erasing head insertion windows 7 and pinch roller insertion windows 8 in the inside of the top and bottom case halves 1a and 1b, in other words at positions back to and both outer sides from the projections 13. The distance between the back surface 13a of the projection 13 and the piece receiving wall 21 is set substantially equal to the thickness between the bottom wall 18a and back surface 18c of the base plate 14 at the portion corresponding to the concave portion 18. Moreover, there is formed in the bottom case half 1b a slanted wall 23 which frontwardly rises and is directed backward at position in front of the piece receiving wall 21 and there is formed in the top case half 1a a further slanted wall 23 which frontwardly downs and is directed backward at position in front of the piece receiving wall 21. The distance between the slanted walls 23 and front wall 5 is a predetermined value desired to provide the tape advancing path. When the tape guide piece 10 is mounted in the case body 1, the lower end portion of the tape guide piece 10 is fitted in the space between the projections 13 and the piece receiving walls 21 of the bottom case half 1b and the concave portions 18 of the base plate 14 are engaged with the projections 13, causing both right and left side ends of the back surface of the base plate 14 of the tape guide piece 10 to be contacted with the piece receiving walls 21. Moreover, the lower ends of the front surfaces 15a of the first guide ribs 15 are contacted with the slanted walls 23. Under such a condition, as shown in Figs. 6 and 8, the inner bottom walls 18a of the concave portions 18 contact with the back surfaces 13a of the projections 18 so that the position of the tape guide piece 10 is regulated in terms of the front direction A and the side walls 18b of the concave portions 18 contact with the side walls 13b of the projections 13 so that the position of the tape guide piece 10 in terms of right and left directions C is regulated. The regulation of the position of the tape guide piece 10 in the backward direction B is performed by contacting the back and right and left side ends of the tape guide piece 10 with the piece receiving walls 21 as shown in Figs. 6 and 7. The front surfaces 15a of the first guide ribs 15 contact with the slanted walls 23, whereby the position of the first guide ribs 15 is regulated in terms of the front direction A. The regulation of the position of the tape guide piece 10 in the vertical direction is made by clamping the tape guide piece 10 between the top case half 1a and bottom case half 1b assembled together by fastening the screws 2 into the screw bosses 22 as shown in Figs. 7 and 8. When the top case half 1a and bottom case half 1b are assembled, the top end portion of the tape guide piece 10 is fitted in the space between the projections 13 in the top case 1a and the piece receiving walls 21 and the top ends of the front surfaces 15a of the first guide ribs 15 engage with the slanted walls 23 of the top case half 1a. It may be made to extend the part 13C of the projection 13 so that when the tape guide piece 10 is temporarily assembled with the bottom case half 1b, the extended projection 13C can engage with the screw boss 22 to prevent the tape guide piece 10 from falling. In place of the trapezoidal shape in the cross section of the concave portion 26 in the back portion of the ribs 25 as shown in Fig. 6, there may be used various shape such as arcuated shape as shown in Fig. 11 or the like. It is noted that by providing the upper and lower ribs 25 at the upper edge and lower edge of the tape guide piece on both sides of the concave portion 26, enough mechanical strength can be assured without specific bosses 27 as used in the prior art, therefore it becomes possible to remove the mold in the direction E (see Fig. 10) perpendicular to the elongated direction guide ribs 15, 16 and 17 that is in the front direction, when molding the tape guide piece 10, whereby the guide ribs 15, 16 and 17 can be molded with a high accuracy without effecting any draft.. As mentioned above, according to the present invention, on the back surface of the tape guide piece on which the concave is formed to avoid undesired engagement with the recording tape wound on the hub, there is formed the upper and lower ribs 25 on the back surface of the tape guide piece 10 so as to extend in parallel along the longitudinal direction or left and right directions of the tape guide piece, it is possible to prevent deformation of the tape guide piece by a simple manner, whereby the mechanical strength can be increased and the verticality of the guide ribs 15, 16 and 17 can be improved, resulting in improving the tape advance property.

Claims: A tape cartridge comprising: a top case half (1a); a bottom case half (1b); a recording tape (3) wound on hubs (4) rotatably disposed in the chamber formed by the top case half and bottom case half and a tape guide piece (10) molded separately from the top case half and bottom case half and installed at position in front of the hubs in the top case half and bottom case half, said tape guide piece having vertical guide ribs (15, 16, 17) on its front surface and wherein its back surface is so shaped as to avoid engagement with the recording tape when fully wound on one of the hubs; characterised in that the back surface of the tape guide has horizontal ribs (25) formed at the upper and lower edge portions thereof and a recess (26) defined between the horizontal ribs.

Inventors: KAGANO SINICHI - SHIRIE KOAZA, SATO AKIHIKO, KAGANO, SINICHI 35-3, SHIRIE, KOAZA, OYAMAZAKI, SATO, AKIHIKO
Applicants: HITACHI MAXELL, HITACHI MAXELL LTD.
Application year: 1989
Main classification: G11B23
IPC codes: G11B23