JPH0359499B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to tape transport systems, and more particularly, tape wound around supply and take-up hubs for transporting the tape from one hub to another while maintaining tension in the tape. The present invention relates to an apparatus for reducing tension fluctuations in a tape transport system using a peripheral drive belt that engages the outer surface of a tape transport system. A tape transport system with a peripheral belt drive is disclosed in US Pat. No. 4,172,569 to Chester W. Newell. The disclosed transport system includes a tape supply hub and a take-up hub, and the tape is transferred from the supply hub via a first redirection idler, a transducer head, and a second redirection idler. It is wound onto the winding hub. An endless drive belt loop having a thickness less than or approximately equal to the thickness of the tape engages the peripheral outer surface of the loop wound on the supply hub and the tape wound on the take-up hub. The drive belt drives the hubs around which the tape is wound, thereby transporting the tape from one hub to the other and creating tension in the portion of the tape extending between the two hubs. 1st and 2nd
The redirection idler is positioned to support a portion of the tape across the transducer head and guide the tape over the head as it is fed from one hub to the other. The belt drive is driven by a rotating drive roller that drives the tape hub, tensions the tape, and moves the tape between the two hubs. The different speeds required between the take-up and supply hub circumferences necessary to maintain tape tension are achieved by driving a rear drive belt idler via a tension belt coupled to a drive roller. be done. This is accomplished by driving the tape drive belt with a pulley that contacts the drive roller and has a larger diameter than the pulley used for the tension belt. Substantially reducing the net tension variation in the drive belt caused by changes in its curved path due to tape transport between its hubs is accomplished by mounting the hub and tape guide in specific locations. Ru. This particular location is selected to produce approximately equal and opposite path length change effects on the first and second portions of the drive belt as the tape is transported between the hubs. be done. The peripheral belt guide system provides a means for creating a speed differential at the radial centerline of the drive belt. By using a relatively stiff tape drive belt, a constant geometrical arrangement of the elements of the tape transport system allows the tape to be wrapped around the hub as it is transported from one hub to the other. Almost complete self-compensation in the drive belt path length variation effects caused by diameter variations is achieved. However, the resulting velocity at the centerline of each tape on the hub in the area where the drive belt engages the tape wound on the hub is reduced by the ratio of the radius of the belt centerline to the tape centerline. The centerline velocity difference between the belt and tape is equal only when the radii of the supply roll and take-up roll are equal, which occurs at the midpoint of tape advance. This problem of tension variation was discussed in the IEEE published in 1978.
Transactions on Magnetics, Vol.Mag−14,
No. 4, “An Improved ANSI−Compatible Magnetic” by Chester W. Newell.
(See Equation 26 therein.) Practical tape hub and tape roll radii, tape and belt thicknesses and moduli, and practically usable geometries. The variation in tape tension is typically that of a normal tape tension.
On the order of 25% or higher. Reducing this tape tension variation reduces the total amount of tension required to maintain tension in contact with the transducer head, thus reducing wear and tear on the head and tape. Tape life is extended. In a tape peripheral drive transport system having a tape supply hub and a tape take-up hub, the tape is
from the supply hub, through a first diverting element, such as an idler, through a converting head, through a second diverting element, such as an idler;
the tape is pulled to the take-up hub, where variations in tape tension due to the difference in radius relative to the belt centerline and radius relative to the tape centerline cause tape tension between the redirection idler and the tape supply roll. is reduced by introducing fixed guide friction posts located in the path. Its fixed friction guide posts are positioned to be in constant contact with the tape as it unwinds from the supply reel, and its fixed friction guide posts are positioned so that it is in constant contact with the tape as it is unwound from the supply reel, and its It is defined to be wrapped at a minimum angle and to be wrapped at a maximum angle around the post when the maximum amount of tape is wrapped around the hub. The minimum angle is an angle greater than 0 degrees and is sufficient to prevent frictional forces from disappearing. A similar geometry is provided for the tape take-up roll. As the tape in the headspan slides past its fixed post, the tension gradient is given in such a way that the tension in front of the post increases after contacting the post, and that increase parameters such as the coefficient of friction between the posts and the wrapping angle of the tape around the post.
As the tape is unwound from the supply roll, the wrap angle is reduced at the supply side guide post. Conversely, as the tape is wound onto the take-up roll, the wrap angle increases around the take-up side guide post. At the beginning of tape advance, when the take-up roll radius is smaller than the supply roll radius, the tension in the span of the head increases. Similarly, during the later portions of the tape advance when the radius of the supply roll is smaller than the radius of the take-up roll, the tension in the span of the head decreases. This increasing/decreasing effect works in the opposite direction to the tension fluctuation caused by the difference in radius between the radial center line of the belt and the radial center line of the tape, so the introduction of this guide post cancels it out. effect is given. A tape transport system with a peripheral belt drive in which a relatively stiff belt is used for the stiffness of the tape was developed by Chester W. Newell on October 30, 1979.
Published by and Newell Research
United States Patent No. Assigned to Corporation.
No. 4172569 describes this in more detail. For convenience of understanding, reference numbers in this application are:
The same numbers as in the Newell patent are used to describe the same elements of the invention. Referring to FIGS. 1 and 2, a tape supply hub 52 and a tape take-up hub 54 are rotatably mounted to the lower plate 14 of the tape cartridge by a pair of shafts 56,58. magnetic recording tape 5
0 has a roll 60 wound around one end or first hub 52 and a roll 62 wound around the other end or hub 54. middle part 64
extends from a peripheral point 74 of tape roll 60 to a peripheral point 76 of deep roll 62 between its hubs. The intermediate portion of tape 64 is fed through a pair of diverting idlers or tape guides 78, 80 that are rotatably mounted to tape 14. The redirecting idler provides substantially frictionless guidance to the tape. The redirection idlers 78, 80 suitably align the tape headspan within the head location opening 16 to maintain proper contact with the magnetic recording head 86 when the art cartridge is installed in a recording/playback device. . A further tape support idler or post 88 attached to the lower plate 14 allows the head 86 to contact the recording tape while keeping the tape from contacting the belt drive member 18. The drive member 18 is positioned to engage a drive capstan 94 that is part of a recording/playback device.
It is rotatably attached to the lower plate 14 with a shaft. The drive member 18 has a first level of a certain diameter and a second level of a larger diameter, which provide different mechanical advantages (see FIG. 2). Drive belt 130 engages the smaller diameter level and tension belt 4
6 engages the larger diameter level. A pair of rotary belt guide members, ie, rear idlers 36 and 38, are rotatably mounted on a pair of shafts fixed to the lower plate 14. Each of these idlers has a first level 118,1 of different diameters to provide different mechanical advantages.
20 and second levels 122 and 124. An endless loop drive belt 130 connects a first level of drive members 18 and rear idlers 36,3.
8 are sent around the first level 118, 120. An endless loop tension belt 46 connects the second level of the drive member 18 and the rear idler 3.
6,38 second levels 122,124. The drive member 18 is rotated clockwise to the capstan 94.
Rotated by Drive belt 130 engages tape roll 60 between peripheral points 134 and 136, thereby defining a wrap angle around tape roll 60. The drive belt 130 is located at point 1
It engages the tape roll 62 between 38 and 140 so that the wrapping angle is similarly defined. The endless tension belt 46 is formed as a result of the difference in diameter between the first level and the second level of the drive pulley and rear idler around which the drive belt and tension belt are wound, respectively.
By effectively creating and transmitting opposing torques to the rear idlers 36, 38, the first portion 154 of the drive belt 130 and the drive belt 13
Means are provided to create a difference in tension between the second portion 158 of the second portion 158 of This results in maintenance of tension in tape 50. Drive member 18 and idlers 36, 3 as described in more detail in the Newell patent mentioned above.
8, when the tape is transported between the first and second hubs, the drive belt portions 154, 1
58 is selected to keep net tension variations to a minimum. This is achieved by selecting a fixed position that produces approximately equal and opposite drive belt length change effects on the first and second drive belt sections as the tape is transported between the hubs. will be accomplished. This method is based on drive belt section 154 or
34 and 136 and the drive belt section 15
8 or between 138 and 140. The angular velocity here refers to the angular velocity at the center line of the drive belt in the radial direction. The tape speed in the area of tape roll 60 where the drive belt is engaged is less than the speed of the drive belt portion between 134 and 136. Also, the tape speed in the area of tape roll 62 where the drive belt is engaged is:
138 and 140 is less than the speed of the drive belt section. The speed mentioned here is
The speed at the radial centerline of the tape and the speed at the radial centerline of the drive belt. On the other hand, the angular velocity of the drive belt section between 134 and 136 is equal to the angular velocity of the tape in the region of tape roll 60 that the drive belt section engages. Also, the angular velocity of the drive belt section between 138 and 140 is equal to the angular velocity of the tape in the region of tape roll 62 that the drive belt section engages. However, the radius from the center of each hub 52, 54 to the centerline of the belt is greater than the radius from the center of each hub 52, 54 to the centerline of the tape in the area that the belt engages. Therefore,
The speed of the drive belt section is greater than the tape speed in the area that the drive belt engages. The radius of the supply roll pack 60 is the same as that of the take-up roll pack 62.
, the difference between the speed of the drive belt section between 134 and 136 and the speed of the tape that the drive belt section engages is equal to
140 is equal to the difference between the speed of the drive belt section and the speed of the tape that the drive belt section engages. The variation in tape tension as a function of the proportion of tape at the take-up hub is typically shown in the graph of FIG. This plot has an ANSI (American
National Standard Institute) Standard number X3B5/
A 7518 tape cartridge, driven by a 0.076 mm thick and 2.66 mm wide polyimide belt, removed 0.025 mm thick and 6.35 mm wide Mylar tape every 90 meters of drive. The average tension is 70.87 grams and the graph in Figure 3 shows that there is a percentage of tension variation of up to 35%. Referring again to Figure 1, additional friction posts
300 is located in the tape path between the redirection idler 78 and the supply roll. The attached friction post is positioned in constant contact with the tape as it is unwound from the hub 52.
The tape defines a minimum wrap angle around the post when a minimum amount of tape is wrapped around the hub, and a minimum wrap angle around the post when a maximum amount of tape is wrapped around the hub. Specify the maximum wrapping angle. This minimum angle works at any angle greater than 0 degrees and is sufficient to prevent frictional forces from disappearing. Preferably, the minimum and maximum wrap angles around the first and second posts are 5
It should be within a maximum of 90 degrees. A similar post 301 is positioned between the take-up side diversion idler 80 and the take-up roll 62. When a tape with tension T is fed through a fixed guide post in the headspan, the slope of the tension △Tx is determined after the tension T in front of the post contacts the post by the following equation:
It is set in such a way that it is increased to Tx. Tx/T=e〓〓 ^x or Ax=T/Tx=1/e〓〓 ^x …(1) Here, μ is the friction coefficient between the tape and the post, and θx is the friction coefficient of the tape supply roll. is the wrap angle corresponding to any particular value of radius x, and Ax is the "multiplier" of the post tension based on the headspan tension T. On the ^“ upstream” side of the system, for corresponding values of the take-up roll radius Tx′= ^e〓〓x ′…(2). The net "magnification" of the upstream and downstream posts 300, 301 based on the tension of the tape in the headspan is: A=Ax Ax'=e〓(θx'-θx) (3). As can be seen, at the beginning of the tape advance, where the take-up radius is smaller than the feed radius, θx<θx' or A>1, ie the tension in the headspan increases. Similarly, during the latter half of tape advance, θx>θx'A<1 and the tension in the headspan decreases. This increase/decrease effect as the tape is being fed from the supply roll to the take-up roll acts in the opposite direction of, and thus has the effect of counteracting, the tension variation shown in FIG. Example: In the specific example of a 1/4 inch ANSI comparable cartridge (Figures 1 and 2):
Posts of convenient size and location provide values for θx and θx' as shown in FIG.
(The value of θx' is a mirror image of θx.) The tension canceled when 20% of the tape is at the take-up hub is -0.232 ounces. With tape tension at the center point of 2-1/2 ounces, the tension at the headspan with the above values of x and x' is 2.268/2.500 =
2.268 oz for a tension increase ratio of 0.907. To counteract this, the post should give a multiplier of A=1/0.907=1.102. From Equation 3, we obtain A=e〓(θx′−θx)=1.102. Substituting this value for θx' and θx at the 20% point and solving the equation gives the desired coefficient of friction for complete cancellation at μ=0.263. Regarding other ratios,

[Table] For optimal cancellation, those values are, on average,
It is given by μ average = 0.253. The measured coefficient of friction between a 5/16 inch diameter polished steel rod and, for example, Maxell 35/180B magnetic tape is μ=0.26. Using a 5/16 inch polished steel post, the resulting modified tension is:

[Table] The tension width △T before correction is 0.870 ounces (approximately 23.9 g) and 2-1/2 ounces (approximately
70.9g) is 35% of the average tension. The tension width ΔT after modification is 0.049 ounces, which is 2% of the average tension of 2-1/2 ounces. In this particular example given, the tension variation was reduced from 35% to 2%. Although this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be apparent to those skilled in the art that various changes in form and detail can be made without departing from the spirit and scope of this invention. Understand that it can be done.

[Brief explanation of drawings]

FIG. 1 is a top view of the tape transport system of the present invention embodied in a magnetic tape cartridge. FIG. 2 is a front view of the cartridge shown in FIG. 1. FIG. 3 is a graph plotting the variation in tension in ounces as a function of the ratio of tape wound on the take-up hub for a typical tape drive belt. In the figure, 50 is a tape, 52 is a supply hub,
54 is a take-up hub, 60 is a supply roll, 62 is a take-up roll, 36 and 38 are rear idlers, 46 is a tension belt, 130 is a drive belt, 18 is a drive member, 78 and 80 are direction changing idlers, 3
0,301 indicates a friction post.

Claims (1)

[Claims] 1. A tape supply hub and a tape take-up hub,
The tape is routed from the supply hub, through a first diverting element, through a transducing head location, through a second diverting element, and to a take-up hub, where it is wound around the tape supply hub. an endless drive belt loop having a stiffness at least equal to the stiffness of the tape; and an endless drive belt loop having a stiffness at least equal to the stiffness of the tape; The drive belt drives the first part of the tape wrapped around the supply hub.
and a second periphery of the tape wound on the take-up hub to drive the hub on which the tape is wound thereby transporting the tape from one hub to the other, and a belt drive member for driving the drive belt; a belt guide member for guiding the drive belt; and a first peripheral engagement portion of the tape and a second peripheral engagement portion of the tape. means for creating a tension differential in the drive belt between a joint, and the first and second tape guide diversion elements are positioned to support a headspan of tape, thereby In a tape transport system that guides an intermediate portion of tape through a converting head location as the tape is transported from one hub to another, the a first fixed friction post positioned in the path of the tape, said first post positioned in constant contact with the tape as the tape is unwound from the supply hub, and wherein said tape defines a minimum wrap angle around the post when a maximum amount of tape is wrapped around the hub, and a maximum wrap angle around the post when a maximum amount of tape is wrapped around the hub. defining a hanging angle, said minimum angle being sufficient to prevent frictional forces between the surfaces of the tape and the post being greater than 0 degrees; and said second deflection element and further comprising a second fixed friction post located in the path of the tape between the take-up rolls, the second post being in constant contact with the tape as it is wound onto the take-up hub. , the tape defines a minimum wrap angle around the post when a minimum amount of tape is wrapped around the hub, and a maximum amount of tape is wrapped around the hub. defining a maximum wrap angle around the post when the tape is in contact with the post, and the minimum angle is an angle greater than 0 degrees to prevent frictional forces between the tape and the post surface from disappearing; A tape transport system, characterized in that it is sufficient for. 2. The method of claim 1, wherein the first and second posts each consist of a polished rod having a coefficient of friction (μ) between the tape and the post in the range of 0.2 to 0.3. Tape transport system. 3. The tape transport system of claim 1, wherein the minimum and maximum wrap angles around the first and second posts are within a range of 5 degrees to a maximum of 90 degrees. 4. said first and second posts each consist of a polished rod having a coefficient of friction (μ) between the tape and the post in the range of 0.1 to 0.3;
2. The tape transport system of claim 1, wherein the minimum and maximum wrap angles about the first and second posts are within a range of 5 degrees to 90 degrees.