Magnetic tape cartridge having leader block retainer mechanism

Abstract: The improved magnetic tape cartridge (100) includes a leader block retainer mechanism that provides a positive locking function to automatically secure the leader block (101) in place in the opening (121) of the magnetic tape cartridge housing (117). The leader block retainer mechanism comprises detent members springably attached to both the top and bottom sides of the housing (117), juxtaposed to the opening (121), to engage corresponding features on the leader block (101) to resist withdrawal of the leader block (101) from the housing (117).

Description: This invention relates to magnetic recording and, in particular, to a magnetic tape cartridge that includes a leader block retainer mechanism to securely retain the leader block within the magnetic tape cartridge when the cartridge is not in use. It is a problem in the field of 1/2" single reel magnetic tape cartridges, such as IBM's 3480-type magnetic tape cartridge, to prevent the leader block from exiting the opening in the magnetic tape cartridge when the cartridge is not in use. The 3480-type magnetic tape cartridge as disclosed in EP-A-0 086 394 is an industry standard tape cartridge that consists of a substantially rectangular housing of predetermined dimensions within which is rotatably attached a single reel of magnetic tape. One end of the magnetic tape is secured to a leader block that is accessible to a tape threading arm in the tape drive via an opening in one corner of the magnetic tape cartridge housing. When the magnetic tape is completely wound on the reel in the magnetic tape cartridge, the leader block is drawn into the opening of the housing a sufficient distance to block the opening. The force required to withdraw the leader block from the tape cartridge opening depends on the length of the leader block and the size of the opening in the magnetic tape cartridge. The dimensions of the leader block and the opening in the magnetic tape cartridge are variable due to the variability of the molding and assembly processes, which results in significant departures from the nominal force required to withdraw the leader block. The existing 3480-type magnetic tape cartridge is equipped with a simple leader block latch to prevent the withdrawal of the leader block and the attached tape from the magnetic tape cartridge. This latch is an integral part of the housing and is located at the opening in the magnetic tape cartridge in a position that exposes the latch to damage. If the magnetic tape cartridge is dropped, the latch can be damaged and the magnetic tape cartridge rendered inoperable. Also, if the leader block does not fully engage this latch due to the tape threading arm failing to place the leader block fully within the housing, the leader block moves freely and, as the 3480-type magnetic tape cartridge is being handled by the user, or maintained in storage, or being shipped between locations, the leader block can inadvertently be extracted from the magnetic tape cartridge, thereby exposing a length of magnetic tape to damage. FR-A-1 311 514 discloses a magnetic tape cartridge in which a length of magnetic tape is wound on a reel hub with the free end of the tape permanently connected to a generally rectangular-shaped leader block. The cartridge completely surrounds the reel of magnetic tape except for an opening provided at one corner of the cartridge. A spring, located proximate the opening, is arranged to engage the leader block in a clamping relationship and help to retain the leader block in a position where the leader block is located in the opening. Another magnetic tape cartridge is disclosed in WO-A-93/21634 the subject matter of which is published after the priority date of the instant application (Art. 54(3) document). This document discloses a magnetic tape cartridge having a self docking leader block which makes use of guide slots formed in the interior surface of the top and bottom plates of the cartridge housing, juxtaposed to the leader block opening in the housing, to mate with corresponding projections on the leader block. The cartridge comprises a pivotable latch arm for engaging with a lateral engagement slot of the leader block. In its engagement position, a latching end of the latch arm is located in the engagement slot so that the leader block is latched in the opening of the housing. By means of a release pin of the tape drive the latch arm can be pivoted into a disengagement position in which the latching end is arranged outside the engagement slot of the leader block so that the latter can be moved out of the opening. It is the object of the present invention to provide a magnetic tape cartridge in which the leader block of the tape is prevented from inadvertently being extracted from the housing of the magnetic tape cartridge. According to the invention, this object is solved by means of a magnetic tape cartridge as defined in claim 1. The magnetic tape cartridge according to the invention is provided with a substantially rectangular housing having a top side and a bottom side parallel to each other and joined by a plurality of side walls being substantially perpendicular to the top and bottom sides. In one corner of the housing there is provided an opening so as to access to a magnetic tape wound on a single reel rotatably mounted in the housing. The free end of the magnetic tape is provided with a leader block having a first end attached to the magnetic tape and a second end having a leader block retrieval slot attached thereto. The leader block further comprises first and second retainer engagement surfaces opposite to each other and both located between the first and second ends. The first retainer engagement surface is adjacent to and in a parallel plane as the top side of the housing while the second retainer engagement surface is adjacent to and in a parallel plane as the bottom side of the housing. Moreover, the magnetic tape cartridge includes a leader block retainer means formed as part of the housing and surrounded by at least one of the top side and the bottom side thereof. The leader block retainer means is located adjacent to the opening of the housing and is operable to resist extraction of the leader block from the housing by independently engaging at least one of the first and second retainer engagement surfaces of the leader block. The leader block retainer mechanism of the tape cartridge of the present invention provides a positive locking function that automatically mechanically secures the leader block in place in the opening of the magnetic tape cartridge housing. The leader block can not be withdrawn therefrom by the tape drive or by a user without the application of a force of predetermined magnitude to the leader block. The leader block retainer mechanism preferably comprises a plurality of detent springs, located on the top and bottom of the inside of the magnetic tape cartridge housing, juxtaposed to the leader block opening in the magnetic tape cartridge housing. The detents are engagable with corresponding features on the leader block to prevent its extraction from the magnetic tape cartridge housing. These corresponding features also act as guides for accurately threading the magnetic tape into the tape drive takeup reel. One embodiment uses a pair of detent springs, one located on each of the top and bottom of the inside of the magnetic tape cartridge housing juxtaposed to the leader block opening in the magnetic tape cartridge housing, to provide additional reliability since the loss of one detent spring does not cause inoperability of the retainer mechanism. In addition, the detent springs can preferably be manufactured as an integral part of the magnetic tape cartridge housing molding operation. The invention will be described in more details in connection with a preferred embodiment shown in the drawing, in which: Figure 1 illustrates, in perspective view, the magnetic tape cartridge and the leader block retainer mechanism of the present invention; Figure 2 illustrated in perspective view the details of a leader block; and Figures 3 and 4 illustrate top and end views of the leader block retainer mechanism of the present invention. One type of computer system tape transport presently in use makes use of magnetic tape cartridges, having the form factor known as the IBM 3480-type magnetic tape cartridge form factor, as the data storage media. Figure 1 illustrates a perspective view of a 1/2" single reel magnetic tape cartridge 100 equipped with the leader block retainer mechanism of the present invention, while Figures 3 and 4 illustrate top and end views of the same mechanism. The magnetic tape cartridge 100 consists of a substantially rectangular exterior housing 117 that has a front side 104, that includes an opening 121 through which a tape drive accesses the magnetic tape 108 contained therein. The magnetic tape cartridge 100 is inserted into the tape drive in direction F, front side 104 first. The magnetic tape cartridge 100 contains a single supply reel 115 on which the magnetic tape 108 is wound in a counterclockwise direction. A drive spindle (not shown) is attached to the bottom side of tape supply reel 115 to engage the supply reel drive mechanism in the tape drive. As viewed in Figure 1, the magnetic tape cartridge 100 includes the opening 121 in the right side of the front 104 of the cartridge housing 117 through which the tape drive tape threading mechanism accesses the magnetic tape 108. Access to magnetic tape 108 is provided by a leader block 101 attached to one end of the magnetic tape 108 that is stored in the magnetic tape cartridge 100. The left front corner 105 of the front side 104 of the exterior housing 117 optionally can be angled or include a recess in order to mechanically denote the proper orientation of the magnetic tape cartridge 100 for loading into a tape drive. Leader block 101 is shown in perspective view in Figure 2. Magnetic tape 108 has a first end which extends through the opening 121 in the magnetic tape cartridge 100 to enable the associated tape drive to extract magnetic tape 108 from the magnetic tape cartridge 100 by means of leader block 101 which is attached to magnetic tape 108. Leader block 101 has a top side 211, a bottom side 212, a front side 213, a back side 214, a first side end 215 and a second side end 216. The top 211 and bottom 212 of leader block 101 include a first retaining projection 221 and a second retaining projection 222, respectively, which are semicylindrical ridges located on top side 211 and bottom side 212 of leader block 101. Leader block 101 also includes a tape threading arm socket 219 located on the front side 213 thereof juxtaposed to the first side end 215, which tape threading arm socket 219 is adapted to receive a tape threading arm pin. The tape threading arm socket 219 comprises a substantially semicylindrical socket extending from the top 211 to the bottom 212 of leader block 101. Also included in leader block 101 is a first lead-in chamfer 231 and second lead-in chamfer 232 which function to guide leader block retainer detents located on exterior housing 117 as described below. As illustrated in Figures 1A, 3 and 4, the leader block retainer mechanism includes a plurality of detent members 102 to retain leader block 101 in opening 121. In the preferred embodiment, a pair of detent members 102a, 102b, one located on each of the top 401 and bottom 402 sides of the exterior housing 117 of the magnetic tape cartridge 100 and located juxtaposed to opening 121, are used to retain leader block 101 within exterior housing 117. These detent members 102a, 102b are each attached at a first end 301 to the exterior housing 117 while the second end 302 is free to move in a direction that is perpendicular to the top 401 and bottom 402 sides of the magnetic tape cartridge exterior housing 117 to encounter the leader block 101. The detent members 102a, 102b are preferably molded as part of housing 117 in a manner to create a spring at the first end 301 attached to the top 401 side and bottom 402 side, respectively, of exterior housing 117. The detent members 102a, 102b are substantially rectangular in shape, having a curved second end 302 distal from the first end 301 thereof. The second end 302 of detent members 102a and 102b can include a semispherical projecting detent 103a, 103b to engage mating features of leader block 101, namely first and second retaining projections 221,222 and first and second lead-in chamfers 231,232 of leader block 101. The thus formed springs bias the projecting detents 103a, 103b in a position such that they encounter lead-in chamfers 231, 232, respectively, located on top 211 and bottom 212 of leader block 101 at the second side end 216 as it is being withdrawn into exterior housing 117 via opening 121. As the lead-in chamfers 231, 232 on the tape attaching first side end 216 of leader block 101 encounter the semispherical detents 103a, 103b on the second side end 302 of detent members 102a, 102b, they force the detent members 102a, 102b to move in a direction away from leader block 101 to enable leader block 101 to enter opening 121. Lead-in chamfers 231, 232 are ramp-shaped to gradually deflect detents 103a, 103b to enable leader block 101 to enter opening 121. Once leader block 101 is completely seated within opening 121 of exterior housing 117, the detents 103a, 103b seat within corresponding recesses formed by first and second retaining projections 221, 222, and first and second lead-in chamfers 231, 232 of leader block 101 to thereby remove the pressure from detent members 102a, 102b and securely hold leader block 101 in place within opening 121. As can be seen from Figures 3 and 4, the detent members 102a, 102b maintain leader block 101 in a precise vertical position therebetween as well as seating leader block 101 against leader block guide surface 130 contained within exterior housing 117 via the force exerted by detent members 102a, 102b against retaining ribs 221, 222, respectively. The action of detent members 102a, 102b thereby precisely positions leader block 101 in three dimensions as well as retaining leader block 101 within opening 121 by resisting the movement of leader block 101 via the force exerted on leader block 101 through the spring action of the detent members 102a, 102b and the pressure applied to the top 211 and bottom 212 surfaces of leader block 101 by the semispherical detents 103a, 103b of detent members 102a and 102b. For leader block 101 to be withdrawn from exterior housing 117, a force must be applied to the end of leader block 101 that is exposed through opening 121. This is typically accomplished by a tape threading arm in the tape drive engaging the threading arm slot 119 in leader block 101 and applying a force to leader block 101 to pull leader block 101 out of exterior housing 117 in the direction indicated by the arrow A on Figure 3. The magnitude of this withdrawal force must be great enough to overcome the retaining force exerted on leader block 101 by detents 103a and 103b. This force must be sufficient to overcome the biasing force of the spring formed by the detent members 102a and 102b to cause detents 103a and 103b to deflect in a vertical direction away from leader block 101 to enable the ridges of lead-in chamfers 231, 232 on the second end 216 of leader block 101 to clear the space between detents 103a and 103b. To accomplish this in a smooth manner, the detents 103a, 103b on detent members 102a and 102b are selected to be semispherical in shape to enable leader block 101 to slide between the detents 103a, 103b. It is obvious that other curvilinear or ramped surfaces can be used on both detents 103a, 103b and lead-in chamfers 231, 232 of leader block 101 to accomplish smooth movement of leader block 101 between detents 103a and 103b. The leader block retainer mechanism of this invention functions to resist the withdrawal of the leader block from the housing of the magnetic tape cartridge to prevent the inadvertent withdrawal therefrom. The use of a pair of detent members molded as part of the housing simplify the construction of this apparatus, minimizes the number of parts required and also enables the precise positioning of the detent members to precisely position the leader block within the housing when it is withdrawn into the opening as a result of the tape rewind operation.

Claims: A magnetic tape cartridge, comprising: a substantially rectangular housing (117) having a top side (401) parallel to a bottom side (402), said top side (401) and said bottom side (402) being joined by a plurality of sidewalls, said plurality of sidewalls being substantially perpendicular to said top side (401) and said bottom side (402), which housing (117) has an opening (121) in one corner thereof and is adapted to enclose a single reel (115) of magnetic tape (108), said reel (115) being rotatably mounted in a parallel plane between said top side (401) and said bottom side (402) and said magnetic tape (108) being provided with a leader block (101); said leader block (101) having a first end (216) and a second end (215), said first end (216) being attached to one end of said magnetic tape (108) and said second end (215) having a leader block retrieval slot (119) attached thereto, and said leader block (101) further comprising a first retainer engagement surface (221) opposite a second retainer engagement surface (222) both located between said first end (216) and said second end (215) of said leader block (101), said first retainer engagement surface (221) being adjacent to and in a parallel plane as said top side (401) of said housing (117) and said second retainer engagement surface (222) being adjacent to and in a parallel plane as said bottom side (402) of said housing (117); and leader block retainer means (102a) located adjacent to said opening (121) of the housing (117) and formed as part of and surrounded by at least one of said top side (401) and said bottom side (402) of said housing (117), and operable to resist extraction of said leader block (101) from said housing (117) by independently engaging said at least one of said first retainer engagement surface (221) and said second retainer engagement surface (222) of the leader block (101). The magnetic tape cartridge according to claim 1, characterized in that said leader block retainer means (102a) comprises: retainer arm means (102a) connected at a first end (301) to said housing (117) juxtaposed to said opening (121) and having a second end (302) operable into a first position to resist movement of said leader block (101) through said opening (121) in said housing (117). The magnetic tape cartridge according to claim 2, characterized in that said leader block retainer arm means (102a) is connected to said housing (117) at said first end (301) and provides a spring for biasing said retainer arm means (102a) into said first position wherein said second end (302) of said retainer arm means (102a) resists movement of said leader block (101) through said opening (121) in said housing (117). The magnetic tape cartridge according to claim 2 or 3, characterized in that said second end (302) of said retainer arm means (102a) includes a projection (103a) adapted to engage said first retainer engagement surface (221) of said leader block (101) to resist movement of said leader block (101) through said opening (121) in said housing (100). The magnetic tape cartridge according to any one of claims 2 to 4, characterized in that said retainer arm means (102a) is responsive to a force in excess of a predetermined magnitude applied to said leader block (101) in a direction (A) to extract said leader block (101) from said housing (117) via said opening (121) for translating into a second position to enable movement of said leader block (101) through said opening (121). The magnetic tape cartridge according to any one of claims 1 to 5, characterized by second leader block retainer means (102b) located within said housing (117) juxtaposed to said opening (121), on a second of said top and bottom sides (401,402) and operable to resist extraction of said leader block (101) from said housing (117). The magnetic tape cartridge according to claim 6, characterized in that said second leader block retainer means (102b) comprises retainer arm means (102b) connected at a first end (301) to said housing (117) juxtaposed to said opening (121) and having a second end (302) operable into a first position to resist movement of said leader block (101) through said opening (121) in said housing (117). The magnetic tape cartridge according to claim 7, characterized in that said leader block retainer arm means (102b) is connected to said housing (117) at said first end (301) and provides a spring for biasing said retainer arm means (102b) into said first position wherein said second end (302) of said retainer arm means (102b) resists movement of said leader block (101) through said opening (121) in said housing (117). The magnetic tape cartridge according to claim 7 or 8, wherein said second end (302) of said retainer arm means (102b) includes a projection (103b) adapted to engage said second retainer engagement surface (222) of said leader block (101) to resist movement of said leader block (101) through said opening (121) in said housing (117).

Inventors: HOGE DAVID THOMAS, JOHNSON MICHAEL WALTER, KONSHAK MICHAEL VAUGHN, OWENS JOHN CRAIG, RAMBOSEK GEORGE PHILIP, RIEGER THOMAS JAMES, HOGE, DAVID THOMAS, JOHNSON, MICHAEL WALTER, KONSHAK, MICHAEL VAUGHN, OWENS, JOHN CRAIG, RAMBOSEK, GEORGE PHILIP, RIEGER, THOMAS JAMES
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1993
Main classification: G11B23
IPC codes: G11B23