Abstract:
A tape cassette includes a cassette housing composed of an upper cassette part and a lower cassette part, a slider slidably attached to the cassette housing so as to open and close an opening in the lower surface of the housing, a slider lock portion provided on the lower cassette part to lock the slider at a predetermined position, and an engagement aperture bored through the slider so as to oppose an engagement portion of the slider lock portion for engagement therewith, which has an inclined portion formed at one end. Further, the tape cassette includes a protruded pin projected from the upper cassette part opposing the slider lock portion, and a spring fit around the protruded pin and interposed between the slider lock portion and the upper cassette part such that the slider lock portion is biased in a direction of engagement with the engagement aperture, wherein at least one end portion of the spring is bent toward the inside of a coil winding portion to form a pin supporting portion which is wound around the protruded pin.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a magnetic tape cassette for use with a digital audio tape recorder (DAT) or the like and, more particularly, is directed to a magnetic tape cassette in which a slider can be reliably engaged with a lower cassette part at a predetermined position. 
     2. Description of the Prior Art 
     Conventional tape recorders such as a digital audio tape recorder (DAT) or the like employ a magnetic tape cassette which is generally depicted by reference numeral  11  in FIGS. 1 to  3 , for example. 
     As illustrated, in the case of the magnetic tape cassette for the DAT, a magnetic tape T is protected not only by upper and lower cassette parts  2 ,  3  but also by a lid  7 , a slider  8  or the like in order to prevent a drop-out from occurring in a reproduced signal when the surface of the magnetic tape T is smudged by fingermarks, oily components, dust or the like. 
     A pair of reel hubs  5   a,    5   b  around which the magnetic tape T is wound is accommodated within a cassette housing  4  that is composed of the upper cassette shell or part  2  and the lower cassette shell or part  3  which are fastened together by some suitable means such as screws or the like. A transparent window  2   a  is formed on the upper cassette part  2  so that the user can visually confirm the remaining amount of the magnetic tape T wrapped around the reel hubs  5   a  and  5   b . Also, in order to prevent the magnetic tape T from being exposed through a mouth portion  6  of the cassette housing  4  when the magnetic tape cassette  11  is not in use or when the magnetic tape cassette  11  is preserved, a lid  7  is pivotally attached to the front portion of the cassette housing  4  such that the lid  7  becomes freely rotatable in the upper direction. The lid  7  is constantly spring-biased by a spring (not shown) in the direction in which the lid closes the mouth portion  6 . 
     The slider  8  is provided on the lower cassette part  3  so that it slides along the lower cassette part  3  back and forth (in the directions shown by arrows a and b in FIGS. 2A,  2 B) to thereby open and close the mouth portion  6 . The slider  8  has bored therethrough a pair of reel shaft insertion apertures  8   b ,  8   b  that communicate with a pair of reel shaft insertion apertures  3   b ,  3   b  bored through the lower cassette part  3  at the opening position of the mouth portion  6 . The slider  8  is constantly spring-biased by a slider spring S in the forward direction (in the arrow a direction (see FIG. 2A) in which the slider  8  closes the mouth portion  6 ) relative to the lower cassette part  3 . 
     When the magnetic tape cassette  11  thus arranged is not in use, as shown in FIG. 2A, the lid  7  closes the front portion of the mouth portion  6  and the slider  8  closes the lower portion of the mouth portion  6 , whereby the magnetic tape T extended within the mouth portion  6  is isolated from the outside. The reel shaft insertion apertures  3   b  of the lower cassette part  3  and the reel shaft insertion apertures  8   b  of the slider  8  are not coincident with one another and the slider  8  closes the reel shaft insertion apertures  3   b  of the lower cassette part  3 , thereby preventing the inside of the cassette housing  4  from being smudged by dust or the like. 
     When the magnetic tape cassette  11  is loaded onto a recording and reproducing apparatus such as the DAT or the like, as shown in FIG. 2B, the slider  8  is slid rearward of the cassette housing  4  (in the arrow b direction) and then held. Also, the lid  7  is rotated upwardly to open the front portion and the lower surface of the mouth portion  6 . 
     Under this condition, a tape loading guide member (not shown) on the recording and reproducing apparatus side can be inserted into the mouth portion  6  of the cassette housing  4 . Also, the reel shaft insertion apertures  8   b ,  8   b  of the slider  8  become coincident with the reel shaft insertion apertures  3   b ,  3   b  of the lower cassette half  3 , whereby reel shafts (not shown) of the recording and reproducing apparatus can be inserted into the reel shaft insertion apertures  3   b ,  8   b.    
     When the magnetic tape cassette  11  is not in use, the slider  8  is moved forwardly and held at the position at which the slider closes the mouth portion  6 . When the magnetic tape cassette  11  is loaded onto the recording and reproducing apparatus, the slider  8  is moved backwardly and then held at the position at which the slider opens the mouth portion  6 . In order to hold the slider  8  at the respective predetermined positions, two pairs of engagement apertures  8   c ,  8   c  and  8   d ,  8   d  are bored through the slider  8  at two positions in the arrow b direction in FIG. 2B and a pair of slider lock portions  3   c ,  3   c  of pin-configuration that can be engaged with the engagement apertures  8   c ,  8   c  and  8   d ,  8   d  are formed on the lower cassette part  3 . 
     As shown in FIGS. 1 and 3, the slider lock portions  3   c ,  3   c  are formed by cutting one portion of the lower cassette part  3 . These slider lock portions  3   c ,  3   c  have a spring-biasing property so that the respective engagement protrusions  3   d ,  3   d  formed on the tops thereof are constantly spring-biased so as to return to the direction in which the engagement protrusions  3   d ,  3   d  are engaged with the engagement apertures  8   c  or  8   d  of the slider  8 . In order to prevent the returning force of the slider lock portions  3   c ,  3   c  from being reduced when the lower cassette part  3  is deformed by the deterioration of the material forming the lower cassette part  3 , it is proposed that compression coil springs (hereinafter referred to as slider lock springs)  9 ,  9  be respectively interposed between the engagement protrusions  3   d ,  3   d  of the slider lock portions  3   c ,  3   c  and the upper cassette part  2 . 
     FIG. 3 of the accompanying drawings shows an example of the slider lock spring  9  that the assignee of the present application has previously proposed (see Japanese Patent Application No. 3-48741). As shown in FIG. 3, the slider lock spring  9  comprises a spring body portion  9   a  formed of a coil spring whose inner diameter is progressively increased upwardly and an elongated portion  9   b  that is linearly elongated from the upper end edge of the spring body portion  9   a . The coil spring is doubly wound around only the upper and lower end portions tightly. 
     In the slider lock springs  9 ,  9  thus arranged, the spring body portions  9   a ,  9   a  are wound around a pair of pins  2   b ,  2   b  protruded from the inner side surface of the upper cassette part  2  in response to the inner surface sides of the tops of the engagement protrusions  3   d ,  3   d  of the slider lock portions  3   c ,  3   c . The elongated portion  9   b  is welded (fixed by a caulking process) to a recess  2   d  of a fixed portion  2   c  of the upper cassette part  2 . Therefore, the slider lock springs  9 ,  9  can be prevented from disenging from the upper cassette part  2  and come in contact with the inner end faces of the engagement protrusions  3   d ,  3   d  of the slider lock portions  3   c ,  3   c  to downwardly press the engagement protrusions  3   d ,  3   d , thereby reinforcing the spring-biasing force of the slider lock portions  3   c ,  3   c.    
     The above conventional magnetic tape cassette  11 , however, suffers from the following disadvantages: 
     That is, if the spring-biasing force of the slider lock spring  9  is increased, although the returning force of the slider lock portion  3   c  is reinforced more effectively, a force (opening force) that is required to open the slider  8  must be increased because the top end faces of the respective engagement protrusions  3   d  are brought in parallel contact with the respective engagement apertures  8   c  when the engagement protrusions  3   d  of the slider lock portions  3   c  are disengaged from the engagement apertures  8   c  of the slider  8 . 
     There is then the antinomy that, while the spring-biasing force of the slider lock spring  9  cannot be set to a too large a value, the small spring-biasing force of the slider lock spring  9  cannot achieve a reinforcing effect of the slider lock portion  3  sufficiently, thereby locking the slider  8  in the unstable locked condition. 
     Moreover, the above conventional magnetic tape cassette cannot overcome the shortcomings which follow: 
     Welding fixing by the caulking process) the slider lock spring on the upper cassette part is not advantageous in conformability when the magnetic tape cassette is assembled by machines or the like. 
     When the slider lock spring is of a tight-winding type, a difference between the inner diameter of the slider lock spring and the outer diameter of the pin on the upper cassette part can be reduced so that the slider lock spring can be fitted into the pin with a small pressure. Since the difference between the inner diameter of the slider lock spring and the outer diameter of the pin on the upper cassette half is set to be small, such difference is not suitable for mounting the slider lock spring that is hard to deform at the tight-winding portion of the slider lock spring. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide an improved magnetic tape cassette in which the aforesaid shortcomings and disadvantages encountered with the prior art can be eliminated. 
     More specifically, it is an object of the present invention to provide a magnetic tape cassette in which a force required to open a slider can be suppressed to be small while a spring-biasing force for reinforcing a slider block portion can be set to be large. 
     It is another object of the present invention to provide a magnetic tape cassette in which a slider lock spring can be fitted into a pin with a small pressure. 
     It is still another object of the present invention to provide a magnetic tape cassette in which a slider lock spring can be easily assembled on an upper cassette part by an automatic assembling apparatus. 
     It is a further object of the present invention to provide a magnetic tape cassette which is suitable for use with a digital audio tape recorder (DAT) or the like. 
     As a first aspect of the magnetic tape cassette according to the present invention, in order that a slider, slidably attached to a lower cassette part so as to open and close a mouth portion of a cassette housing, be locked at a predetermined position, a slider lock portion is provided on the lower cassette part, an engagement aperture that is engaged with the slider lock portion is bored through the slider and a spring is interposed between the slider lock portion and an upper cassette part to thereby spring-bias the slider lock portion in the direction in which the slider lock portion is fitted into the engagement aperture. This magnetic tape cassette further includes an inclined portion having a configuration tapered toward a cassette housing being formed on one end face of the engagement aperture bored through the slider which opposes the top of the slider lock portion of the lower cassette part. 
     As a second aspect of the magnetic tape cassette according to the present invention, in order to lock a slider slidably attached to a lower cassette part at a predetermined position, a slider lock spring, that is fitted into a pin projected from an upper cassette part, is interposed between the slider lock portion provided on the lower cassette part and the upper cassette part to thereby spring-bias the slider lock portion in the direction in which the slider lock portion is fitted into the engagement aperture. In this magnetic tape cassette, at least one end portion of the slider lock spring is bent toward the inside of a coil winding portion to form a pin supporting portion. 
     The above-mentioned and other objects, features, and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof to be read in conjunction with the accompanying drawings, in which like reference numerals are used to identify the same or similar parts in the several views. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view showing an example of a magnetic tape cassette according to the prior art; 
     FIGS. 2A and 2B are perspective views, respectively, showing the conventional magnetic tape cassette shown in FIG.  1  and to which references will be made in explaining a lower surface of the magnetic tape cassette when the magnetic tape cassette i s in use; 
     FIG. 3 is a side view showing a slider lock portion of the conventional magnetic tape cassette in a fragmentarily-enlarged scale; 
     FIGS. 4A and 4B are fragmentarily-enlarged cross-sectional views, respectively, used to explain the condition that a slider lock portion of a magnetic tape cassette according to a first embodiment of the present invention is being operated when the magnetic tape cassette is in use; 
     FIG. 5 is a plan view showing a slider of the magnetic tape cassette according to the present invention in an enlarged scale; 
     FIG. 6 is a perspective view showing an overall arrangement of the magnetic tape cassette according to the present invention; 
     FIG. 7 is a longitudinal cross-sectional side view showing the magnetic tape cassette according to a second embodiment of the present invention in a fragmentarily-enlarged scale; and 
     FIGS. 8A and 8B are respectively an enlarged plan view and an enlarged bottom view showing a slider lock spring used in the magnetic tape cassette according to the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A magnetic tape cassette according to a first embodiment of the present invention will hereinafter be described with reference to FIGS. 4A,  4 B to FIG.  6 . Throughout FIGS. 4A,  4 B to FIG. 6, parts and elements identical to those of the conventional magnetic tape cassette  11  according to the prior art shown in FIGS. 1 to  3  are marked with the same references and therefore need not be described in detail. 
     In a magnetic tape cassette  11  according to the first embodiment of the present invention, similarly to the conventional magnetic tape cassette  11  according to the prior-art example, the upper cassette part  2  and the lower cassette part  3  are combined to form the cassette housing  4 . The pair of reel hubs  5   a ,  5   b  around which the magnetic tape T is wound are accommodated within the cassette housing  4 . The window  2   a  that enables the user to visually confirm the remaining amount of the magnetic tape T is formed on the upper cassette part  2 . The lid  7  and the slider  8  for opening and closing the mouth portion  6  are formed on the upper cassette part  2  and the lower cassette part  3 , respectively. 
     In order to hold the slider  8  in either the condition that the mouth portion  6  is opened or closed, the slider lock portions  3   c  are provided on the lower cassette part  3 . Also, the engagement apertures  8   c ,  8   d  that are in engagement with the slider lock portions  3   c  are bored through the bottom portion of the slider  8 . A spring  10  is interposed between the slider lock portions  3   c  and the pins  2   b  of the upper cassette part  2  to thereby spring-bias the slider lock portions  3   c  in the direction in which they are fitted into the engagement apertures  8   c  or  8   d.    
     According to the first embodiment of the present invention, in addition to the above-mentioned arrangement, inclined portions  8   c   1 ,  8   c   1  which are inwardly tapered are formed on one end faces of the engagement apertures  8   c ,  8   c  of the slider  8  in an opposing relation to the top surfaces of the engagement protrusions  3   d ,  3   d  formed on the tops of the slider lock portions  3   c  of the lower cassette part  3 , respectively, when the slider  8  closes the mouth portion  6 . Thus, when the slider  8  is slid along the lower cassette part  3  backwardly (in the direction shown by an arrow c in FIGS.  4 A and  6 ), the engagement protrusions  3   d  of the slider lock portions  3   c  of the lower cassette part  3  can be disengaged from the engagement apertures  8   c  of the slider  8  with ease. 
     As shown in FIGS. 4A,  4 B and FIG. 5, the engagement apertures  8   c ,  8   c  are substantially square in shape and a little larger than the planar shapes of the engagement protrusions  3   d.    
     According to the first embodiment of the present invention, the inclined angles of the inclined portions  8   c   1 ,  8   c   1  are substantially the same as those of inclined surfaces  3   d   1 ,  3   d   1  formed on the top surfaces of the engagement protrusions  3   d  of the slider lock portion  3   c.    
     The magnetic tape cassette  11  according to the first embodiment of the present invention acts as follows when it is being loaded onto a recording and reproducing apparatus from its preserved state. 
     When the magnetic tape cassette  11  is preserved or not in use, the mouth portion  6  is closed by the lid  7  and the slider  8 , and as shown in FIG. 4A, a rear end face  3   d   2  of the engagement protrusion  3   d  on the lower cassette part  3  is brought in contact with the rear end of the engaging aperture  8   c  of the slider  8 , thereby holding the slider  8  ahead of the lower cassette part  3 . At that time, the reel shaft insertion apertures  3   b ,  3   b  of the lower cassette part  3  also are closed by the slider  8 . 
     When the magnetic tape cassette  1  is loaded onto the recording and reproducing apparatus, the slider  8  is progressively moved rearward of the cassette housing  4  so that, as shown in FIG. 4B, the engagement protrusion  3   d  is progressively moved over the upper surface of the slider  8  while the inclined surface  3   d   1  is in slidable contact with the inclined portion  8   c   1  of the engagement aperture  8   c.    
     When the slider  8  finishes having moved rearward under the condition that the engagement protrusion  3   d  is moved over the upper surface of the slider  8 , the front engagement aperture  8   d  of the slider  8  and the engagement protrusion  3   d  become coincident with each other. Then, the engagement protrusion  3   d  is fitted into the engagement aperture  8   d  by the spring-biasing force of the spring  10 . 
     The slider  8  is held at the predetermined position under the condition such that the lower portion of the mouth portion  6  is opened and that the reel shaft insertion apertures  3   b ,  8   b  of the lower cassette part  3  and the slider  8  become coincident with each other. Then, the reel shafts (not shown) on the recording and reproducing apparatus can be inserted into the cassette housing  4 . 
     After a sequence of the above operation is finished, the lid  7  that closes the front portion of the mouth portion  6  is rotated upwardly to open the front portion of the mouth portion  6  and then a tape loading guide member on the recording and reproducing apparatus is inserted into the mouth portion  6 , thereby recording and/or reproducing the magnetic tape T. 
     As described above, according to the magnetic tape cassette  1  of the present invention, the front end surface of the engagement protrusion  3   d  of the slider lock portion  3   c  on the lower cassette part  3  and the inclined portion  8   c   1  formed on the front end of the engagement aperture  8   c  come in contact at each other with a predetermined angle in an opposing relation, resulting in the engagement protrusion  3   d  being readily moved toward the upper direction along the upper surface of the slider  8 . 
     Since the inclined portion  8   c   1  moves the slider  8  backwardly while controlling an amount with which the engagement aperture  8   c  and the engagement protrusion  3   d  are brought in contact with each other, it becomes possible to suppress a force that is required to open the mouth portion  6 . 
     Consequently, the spring-biasing force with which the spring  10  reinforces the slider block portion  3   c  can be set to be larger than that required by the prior art. Therefore, the spring-biasing force, which is weakened by the deformed slider block portion  3   c  when the magnetic tape cassette  1  is not in use, can be reinforced more effectively. 
     The magnetic tape cassette according to a second embodiment of the present invention will be described with reference to FIG.  7  and FIGS. 8A,  8 B, in which parts and elements identical to those of the first embodiment are marked with the same references and therefore need not be described. 
     As shown in FIG. 7, in the magnetic tape cassette  1  according to the second embodiment of the present invention, a slider lock spring  110  comprises a central spring body portion  110   a , tight-winding portions  10   b ,  110   c  respectively formed on the upper and lower portions of the spring body portion  110   a , a pin supporting portion  110   b   1  and a slider lock pressing portion  10   c   1 . The pin supporting portion  110   b   1  and the slider lock pressing portion  10   c   1  are formed by linearly elongating the upper and lower end portions of the tight-winding portions  110   b ,  110   c  toward the inside of the slider lock spring  110 , respectively. 
     Under the condition that the slider lock spring  110  is not yet assembled on the upper cassette part  2 , the pin supporting portion  110   b   1  of the slider lock spring  110  is located in the inside of the slider lock spring  110  as shown by a two-dot chain line in FIG. 8A, thereby making the inner diameter of the slider lock spring  110  smaller than the outer diameter of the pin  2   b . The slider lock pressing portion  10   c   1  also is formed about the center of gravity of the slider lock spring  110  so as to become symmetrical with the aforementioned pin supporting portion  110   b   1 . The pin supporting portion  110   b   1  can serve also as the slider lock pressing portion  10   c   1  in a function standpoint and vice versa. 
     According to the second embodiment of the present invention, the magnetic tape cassette  1  acts as follows when the slider lock spring  110  is assembled on the upper cassette part  2 . 
     As the pin supporting portion  110   b   1  of the slider lock spring  110  is progressively and deeply inserted into the pin  2   b  from a tapered lower end edge  2   b   1  of the pin  2   b , the pin supporting portion  110   b   1  is progressively widened outwardly with a pressure to produce a spring-biasing force and the pin supporting portion  110   b   1  supports at its inside the pin  2   b  of the upper cassette part  2  with a constant spring-biasing force. Thus, the slider lock spring  110  is fitted into the pin  2   b  of the upper cassette part  2  with a small pressure. In that case, without the welding process or the like, the slider lock spring  110  is applied at its pin supporting portion  110   b   1  with a load when it is fitted into the pin  2   b  with a small pressure so that the slider lock spring  110  can be fitted into the pin  2   b  of the upper cassette part  2  easier than the conventional slider lock spring  9 . 
     When the upper and lower cassette parts  2  and  3  are fastened together, the slider lock spring  110  can be prevented from being disengaged from the upper cassette part  2 . Furthermore, after the assembly process, the slider lock pressing portion  110   c   1  constantly presses the slider lock portion  3   c  of the lower cassette part  3  in the lower direction, thereby reinforcing the downward biasing force of the slider lock portions  3   c ,  3   c.    
     As set out, according to the magnetic tape cassette  1  of the second embodiment of the present invention, if the slider lock spring  110  is solely applied to the magnetic tape cassette  1  without modifying the arrangements of the upper and lower cassette parts  2  and  3 , then the slider lock spring  110  can be fitted into the pin  2   b  of the upper cassette part  2  easily and reliably, resulting in the slider lock portion  3   c  of the lower cassette part  3  being reinforced. 
     In particular, since the slider lock spring  110  includes the pin supporting portion  110   b   1  and the slider lock pressing portion  10   c   1  that are symmetrical in shape, the top and bottom of the slider lock spring  110  need not be specified and the slider lock spring  110  becomes easy to handle. As a consequence, since the slider lock spring  110  can be fitted at its pin supporting portion  110   b   1  into the pin  2   b  of the upper cassette part  2  with a small pressure, the slider lock spring  110  can be automatically assembled on the upper cassette part  2  with ease by a machine or the like. 
     In the first embodiment of the present invention, the shape of the inclined portion  8   c   1  is not limited to the above inwardly-tapered one in cross section and any shape may be possible insofar as the engagement protrusion can be pushed over the upper surface of the inclined portion  8   c   1  with ease. 
     In the second embodiment of the present invention, the planar shape of the slider lock spring  110  may be replaced with a true circular shape or polygonal shape. Further, the shapes of the pin supporting portion  110   b   1  and the slider lock pressing portion  110   c   1  are not limited to the above straight line shapes and may be curved shapes insofar as the slider lock spring  110  can be fitted into the pin  2   b  of the upper cassette part  2  with a small pressure. 
     As set out, according to the magnetic tape cassette of the present invention, since the slider lock portion can be disengaged from the engagement aperture with ease, a force that is used to open the slider when the magnetic tape cassette is loaded onto the recording and reproducing apparatus can be suppressed to be small. There is then the effect such that a biasing force with which the slider lock spring reinforces the slider lock portion can be set to be larger. 
     Furthermore, according to the magnetic tape cassette of the present invention, since the slider lock spring need not be welded (fixed by the caulking process) on the upper cassette part, the slider lock spring can be assembled into the upper cassette part with ease. As a consequence, it becomes possible to assemble the slider lock spring into the upper cassette part more easily and reliably by an automatic assembling machine or the like. 
     Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments and that various changes and modifications could be effected therein by one skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.