TAPE REEL FOR TAPE CASSETTE

Abstract: A tape reel structure for a tape cassette provides radially extending ribs (21) between an outer cylindrical section forming tape reel section (11) which is to have wound therearound a tape, and an inner cylindrical section (12) serving as a reel shaft boss. The ribs (21) at least have a portion extending substantially through overall length of the outer cylindrical section (11) so as to prevent radially inward deformation thereof. The ribs (21) join with the inner cylindrical section (12) at the radially inner edges. The upper end of the joining portion between the inner edge of the rib and the inner cylindrical section is at a lower elevation that the upper end of the joining portion between the outer edge of the rib and the outer cylindrical section. This height difference is effective for preventing the outer cylindrical section from forming wave-form uneveness during moulding process. The ribs extending substantially the overall length of the outer cylindrical section successfully prevents the outer cylindrical section from radially inward bending.

Description: The present invention relates generally to a tape reel structure for a tape cassette and more specifically, to a tape reel structure of a tape cassette with an improved reel flange supporting structure. More particularly, the invention relates to a tape reel structure of a tape cassette with an inner cylindrical boss section and an outer cylindrical reel section coaxially arranged in spaced apart relationship and connected by radially extending ribs. A magnetic tape cassette, such as a video tape cassette for a video tape recorder (VTR), have been disclosed in Japanese Utility model Second (examined) Publication (Jikko) Showa 57-56382. The disclosed magnetic tape cassette employs tape reels, each of which has upper and lower reel flanges. The tape reels also have coaxially arranged inner and outer sections in spaced apart relationship to each other. The inner cylindrical section serves as a boss for drivingly receiving a reel shaft of an associated tape recording and/or reproducing apparatus. The outer cylindrical section forms reel body so that a magnetic tape as a recording medium is wrapped or wound therearound. Radially extending ribs are provided between the inner and outer cylindrical sections. Such tape reels are formed of a synthetic resin by injection moulding, in which molten resin is injected into moulding dies. In this case, when the radially extending ribs extend through the overall length of the inner and outer cylindrical sections, flows of the molten resin injected through the radial centre of the reel converge at about the axial intermediate portion of the outer cylindrical section. Confluence of the molten resin flows at this position tends to form waving on the outer periphery of the outer cylindrical section. During injection moulding process, two molten resin flows are formed. The first resin flow flows radially through the portion of the die to form the lower reel flange. The second resin flow is through the upper end wall of the portion for forming the upper end wall of the inner cylindrical section and through the upper end wall of the inner cylindrical section and through the upper end portion of the rib. Part of the resin in the first flow flows along the inner and outer cylindrical sections and the ribs toward the upper end. On the other hand, part of the molten resin in the second flow flows through the inner and outer cylindrical sections and the ribs toward the lower flange. Due to the opposite flow directions of the molten resin in the first and second flows at their confluence at the axial intermediate portion, stress is created in the resin. This stress causes formation of the waving uneveness at the confluencing portion. When waving of the outer periphery of the outer cylindrical section is caused, wrinkles tend to be formed on the tape which may cause disturbance of the signal or data to be recorded on the tape. Such disturbance of the recorded signal or data will cause disturbance of reproduced image in the case of a video tape. Formation of waving uneveness on the outer periphery of the outer cylindrical section can be prevented by shortening the length of rib so as to interrupt the second flow by a discontinuity between the inner and outer cylindrical sections at the upper end thereof. In this case, however, another problem is encountered in resilient deformation at the discontinuity of the outer cylindrical section toward the inner cylindrical section when the tape is tightly wound therearound. Namely, by shortening the ribs, the upper end portion of the outer cylindrical section becomes free from inward or radial bending. This causes radially inward bending of the portion where it is not restricted by the ribs. As a result of radially inward bending at the upper portion of the outer cylindrical section, the tape wound therearound may constantly subject uneven force in the direction of the width thereof. When the stress exerted by the unevenness of the force in the transverse direction of the tape becomes significant, wrinkles may be formed on the tape and cause disturbance of the signal or data to be recorded on the tape. DE-A-3,108,585 discloses a tape reel in which ribs supporting the outer reel section extend only half the height of the inner reel hub and which therefore suffers from the problem discussed above. Therefore, it is an aim of the present invention to provide a tape reel which can alleviate the aforementioned drawbacks in the background art. Another object of the invention is to provide a tape reel for a magnetic tape cassette, which will not form wrinkles of a tape. A further object of the invention is to provide a tape reel structure for a tape cassette which will never form wave-form unevenness on a tape reel section. According to a first aspect of the invention, there is provided a tape reel structure for a tape cassette comprising: a tape reel including an inner cylindrical reel shaft boss section defining at its lower end an open recess for engaging a reel shaft of a recording and/or reproducing apparatus and an outer cylindrical tape reel section, said inner and outer cylindrical sections being coaxially arranged to each other in mutually spaced relationship and a plurality of radially extending ribs extending between said inner and outer cylinder section, said ribs each having a first portion joining with the inner periphery of said outer cylindrical section and a second portion joining with the outer periphery of said inner cylindrical section; an upper reel flange to be mounted on said tape reel; and a lower flange section formed integrally with said tape reel; characterised in that said first joining portions of said ribs extend substantially through the overall height of said outer cylindrical section and have first upper ends and said second joining portions of said ribs extend substantially through the overall height of said inner cylindrical section and have second upper ends, said second upper ends being at a lower elevation than said first upper ends, and at a higher elevation than the upper end of said open recess. This axial height difference of the joining portions between the ribs and the outer cylindrical section, and between the ribs and the inner cylindrical section, may prevent resin flows from confluencing at the axial intermediate portion of the outer cylindrical section and thus prevent the flows from creating stress for causing waving unevenness on the outer periphery of the outer cylindrical section. According to a second aspect of the invention, there is provided a tape cassette including a tape reel according to the first aspect. In practice, the tape reel structure set forth above is particularly applicable for a tape reel which is formed of a synthetic resin by moulding, such as an injection moulding process. In the preferred construction, each of the ribs has an upper end including a first upper end plane lying on a first horizontal plane extending through the first upper end of the first joining portion and a second upper end plane lying on a second horizontal plane which extends through the second upper end of the second joining portion and at lower elevation than the first horizontal plane. The upper flange has a downwardly projected section having a circumferential edge substantially conforming to the upper end plane of the rib. In an alternative, each of the ribs has an upper end plane substantially lying on a horizontal plane extending through the first upper end of the first joining portion, and has the second upper end of the section joining portion at a vertical intermediate position at a lower elevation than the horizontal plane. The upper flange defines a space for receiving the upper end portion of the outer cylindrical section and the ribs. The space is defined by through openings formed through the upper reel flange. The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only. In the drawings: Fig 1 is an exploded perspective view of a tape reel to which the tape reel structure according to the present invention is applicable; Fig 2 is a cross-section of the preferred embodiment of a tape reel structure according to the invention; Fig 3 is an enlarged section of the tape reel of fig 2; and Fig 4 is a section of another embodiment of the tape reel structure. Referring now to the drawings, particularly to figs 1 and 2, a tape reel of a magnetic tape cassette, such as a VTR tape cassette, is made of a synthetic resin. The tape reel 10 has a lower reel flange 10 integrally formed with tape reel section 10a. The tape reel section 10a comprises an outer cylindrical tape reel section 11 and an inner cylindrical boss section 12. The inner cylindrical section defines a lower end opened recess 13, into which extend engaging claws 14 for drivingly engaging with a reel shaft of an associated recording and/or reproducing apparatus, eg VTR. The head of the reel shaft is inserted into the recess 13 of the inner cylindrical section 12 when the tape cassette is loaded in the recording and/or reproducing apparatus. The inner cylindrical section 12 has an upper wall 15 with a centre positioning projection 26. A plurality of pins 16 disposed around a circle coaxial with the reel project from the upper surface of the upper wall 15. An upper reel flange 17 is mounted on the upper end of the tape reel section 10a. The upper reel flange 17 has a central portion 18 which is downwardly depressed so as to be projected downwardly from the lower surface of the general plane of the upper reel flange. A plurality of through holes 19 are formed in the central portion 18 of the upper reel flange 17. The pins 16 pass through the holes 19. The top end of the pins 16 are clamped by head clamping so that the upper reel flange 17 can be fixedly fastened on the top of the tape reel section 10a. As shown in fig 2, the outer and inner cylindrical sections 11 and 12 are coaxially arranged in spaced apart relationship to each other to define therebetween an annular space 20. Between the outer and inner cylindrical sections 11 and 12, a plurality of radially extending ribs 21 are formed. Each of the ribs extends radially across the annular space 21. The ribs 21 extend through substantially the overall height of the outer and inner cylindrical sections 11 and 12. The rib 21 joins to the inner periphery of the outer cylindrical section 11 at its outer vertical edge. The joining section between the inner periphery of the outer cylindrical section 11 and the outer vertical edge of the rib 21 will be hereafter referred to as the first joining section 23a. On the other hand, the inner vertical edge of the rib 21 joins with the outer periphery of the inner cylindrical section 12. The joining portion between the inner vertical edge of the rib 21 and the outer periphery of the inner cylindrical section 12 will be hereafter referred to as the second joining section 24a. The top end 23 of the first joining section 23a lies on a horizontal plane extending through the upper end of the outer cylindrical section 11. Similarly, the top end 24 of the second joining section 24a lies on a horizontal plane extending through the upper general surface of the upper wall 15 of the inner cylindrical section 12. The top ends 23 and 24 of the rib 21 are connected by a sloped section 25. The inclination of the sloped section 25 is determined so as to match with the inclination of the circumferential tapered edge of the centre portion 18 of the upper reel flange 17. As seen from fig 3, the heights of the top ends 23 and 24 of the first and second joining sections 23a and 24a are different from each other. Namely, the top end 23 of the first joining section 23a is higher than that of the top end 24 of the second joining section 24a. The outer cylindrical section 11 is discontinuous at a gap portion 30. The gap portion 30 allows communication between the outside of the tape reel section 10a and the annular space 20 so that one of a tape such as VTR tape can be inserted into the annular space. The gap portion 30 is closed by a clamper 31. The clamper 31 is designed to fixedly engage with the edges of the gap portion 30 to form part of the outer cylindrical section 11 with the outer periphery thereof circumferentially aligned with the outer periphery of the general section of the outer cylindrical section 11. When installed, the clamper grips the associated end of the tape. With the construction set forth above, the tape reel of the shown embodiment will never form the wave-form uneveness on the outer periphery of the outer cylindrical section 11 during the moulding process. Namely, during the moulding process, the flow of the molten resin which flows from the portion constituting the upper wall of the inner cylindrical section, is restricted by difference in the height of the top ends 23 and 24 of the first and second joining sections. This causes a reduction of the flow velocity of the molten resin. As a result, the outer cylindrical section 11 is formed by the resin flowing from the portion forming the lower flange. This prevents the molten resin from confluencing at the axial intermediate portion of the outer cylindrical section. Therefore, moulding stress which might otherwise form the wave-form uneveness on the outer periphery of the outer cylindrical section is avoided. In addition, since the ribs extend over substantially the overall heights of the outer and inner cylindrical section, they may successfully prevent the inner cylindrical section 11 from bending radially inward so as not to cause stress in the tape wound around the tape reel section. Therefore, even in use, wrinkles will never form on the tape. Fig 4 shows another embodiment of the tape reel structure according to the invention. In this embodiment the ribs 21 have their top edges 27 oriented at the same height as the top edge of the outer cylindrical section 11. In this embodiment, the top end 23 of the first joining section 23a resides on the top edge 27. On the other hand, the top 24 of the second joining section resides on the inner vertical edge of the rib. In the construction of fig 4, the upper end portion of the ribs 21 project at the level of the upper portion of the outer cylindrical section 11. In order to accept the upper end sections of the ribs 21, through openings 28 are formed through the upper reel flange. Similarly to the foregoing first embodiment, formation of the wave-form uneveness on the outer periphery of the cylindrical section 11, during moulding process may be successfully prevented by the height difference of the top ends 23 and 24 of the first and second joining sections. In addition, the ribs 21 also prevent the outer cylindrical section 11 from radially and inwardly bending by the pressure exerted from the tape wound therearound. Therefore, the present invention fulfills all of the objects and advantages sought therefor. While the present invention has been discussed in terms of the preferred embodiments of the invention. However, the invention may be implemented in various embodiments other than the shown embodiments and the shown embodiments can be modified in various forms. Therefore, the invention should be appreciated to include all of possible embodiments and modifications which can be implemented without departing from the scope of the appended claims.

Claims: A tape reel structure for a tape cassette comprising: a tape reel including an inner cylindrical reel shaft boss section (12) defining at its lower end an open recess for engaging a reel shaft of a recording and/or reproducing apparatus and an outer cylindrical tape reel section (11), said inner and outer cylindrical sections (11, 12) being coaxially arranged to each other in mutually spaced relationship and a plurality of radially extending ribs (21) extending between said inner and outer cylinder section, said ribs each having a first portion (23a) joining with the inner periphery of said outer cylindrical section (11) and a second portion (24a) joining with the outer periphery of said inner cylindrical section (12); an upper reel flange (17) to be mounted on said tape reel; and a lower flange section (10) formed integrally with said tape reel; characterised in that said first joining portions (23a) of said ribs (21) extend substantially through the overall height of said outer cylindrical section (11) and have first upper ends (23) and said second joining portions (24a) of said ribs (21) extend substantially through the overall height of said inner cylindrical section (12) and have second upper ends (24), said second upper ends (24) being at a lower elevation than said first upper ends (23), and at a higher elevation than the upper end of said open recess. A tape reel structure as set forth in claim 1, which is formed of a synthetic resin by moulding. A tape reel structure as set forth in claim 2, which is formed through an injection moulding process. A tape reel structure as set forth in claim 1, 2 or 3, wherein each of said ribs (21) has an upper end including a first upper end plane lying on a first horizontal plane extending through said first upper end (23) of said first joining portion (23a) and a second upper end plane lying on a second horizontal plane which extends through said second upper end (24) of said second joining portion (24a) and at lower elevation than said first horizontal plane. A tape reel structure as set forth in claim 4, wherein said upper flange (17) has a downwardly projected section (18) having a circumferential edge (25) substantially conforming to an upper end plane of said ribs. A tape reel structure as set forth in anyone of the preceding claims, wherein each of said ribs (21) has an upper end plane substantially lying on a horizontal plane extending through said first upper end (23) of said first joining portion (23a), and has said second upper end (24) of said second joining portion (24a) at a vertical intermediate position of lower elevation than said horizontal plane. A tape reel structure as set forth in claim 6, wherein said upper flange (17) defines spaces for receiving the upper end portion of said outer cylindrical section (11) and said ribs (21). A tape reel structure as set forth in claim 7, wherein said spaces are defined by through openings formed through said upper reel flange (17). A tape cassette incorporating a tape reel according to any one of the preceding claims.

Inventors: IWAHASHI, YUJI SONY MAGNETIC PRODUCTS INC
Applicants: SONY CORPORATION
Application year: 1987
Main classification: G11B23
IPC codes: G11B23