CA1243778A - Tape cartridge having crowned guides - Google Patents
Tape cartridge having crowned guidesInfo
- Publication number
- CA1243778A CA1243778A CA000477250A CA477250A CA1243778A CA 1243778 A CA1243778 A CA 1243778A CA 000477250 A CA000477250 A CA 000477250A CA 477250 A CA477250 A CA 477250A CA 1243778 A CA1243778 A CA 1243778A
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- Canada
- Prior art keywords
- tape
- guide roller
- magnetic tape
- operative surface
- tape guide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
ABSTRACT OF THE DISCLOSURE
A magnetic tape cartridge which utilizes tape guide rollers with crowned operative surfaces prevents migration of the magnetic tape along the operative sur-faces due to misalignment between perpendicularity of the central axis of the tape guide roller in the direction of travel of the magnetic tape. By crowning the operative surface, the distance between the opposing inner faces of the shoulders of the tape guide rollers can be expanded.
By preventing migration of magnetic tape against either of the two opposing faces of the tape guide rollers' shoul-ders, damage which could occur by contact between the edges of the magnetic tape and these faces is prevented.
Although some incidental contact between the edges of the magnetic tape and the faces on the shoulders of the tape guide rollers is normally expected in tape cartridge design, when this contact occurs at high speeds and under significant tape tension, severe damage can be caused to these edges of the magnetic tape. By crowning the opera-tive surface and widening the faces of the tape guide rollers, more misalignment from perpendicularity between the central axis of the tape guide rollers and the direc-tion of travel of the magnetic tape can be tolerated.
A magnetic tape cartridge which utilizes tape guide rollers with crowned operative surfaces prevents migration of the magnetic tape along the operative sur-faces due to misalignment between perpendicularity of the central axis of the tape guide roller in the direction of travel of the magnetic tape. By crowning the operative surface, the distance between the opposing inner faces of the shoulders of the tape guide rollers can be expanded.
By preventing migration of magnetic tape against either of the two opposing faces of the tape guide rollers' shoul-ders, damage which could occur by contact between the edges of the magnetic tape and these faces is prevented.
Although some incidental contact between the edges of the magnetic tape and the faces on the shoulders of the tape guide rollers is normally expected in tape cartridge design, when this contact occurs at high speeds and under significant tape tension, severe damage can be caused to these edges of the magnetic tape. By crowning the opera-tive surface and widening the faces of the tape guide rollers, more misalignment from perpendicularity between the central axis of the tape guide rollers and the direc-tion of travel of the magnetic tape can be tolerated.
Description
377~3 1 51,774 TAPE CARTRIDGE HAVING CROWNED GUIDES
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates generally to tape record-ing devices and, more particularly, to magnetic tape cartridges which utilize guide rollers having operative surfaces which are crowned. Although the present inven-tion may be employed for recording many types of signals in relation to time, it is particularly suitable for a tape cartridge utilized in a tape recorder that records the consumption of electric quantities, such as watt-hours, over a long period of time.
In order to conduct a time-based survey that shows the consumption of a variable quantity, such as watt-hours of electrical energy, it has been the practice to record a series of coded data pulses on survey magnetic tape. Each of these pulses represents the consumption of a predetermined amount of electric energy. Also, a series of timing pulses, which occur at regular intervals, is generally applied to the magnetic tape. When a predeter-mined survey period is completed, the survey magnetic tape
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates generally to tape record-ing devices and, more particularly, to magnetic tape cartridges which utilize guide rollers having operative surfaces which are crowned. Although the present inven-tion may be employed for recording many types of signals in relation to time, it is particularly suitable for a tape cartridge utilized in a tape recorder that records the consumption of electric quantities, such as watt-hours, over a long period of time.
In order to conduct a time-based survey that shows the consumption of a variable quantity, such as watt-hours of electrical energy, it has been the practice to record a series of coded data pulses on survey magnetic tape. Each of these pulses represents the consumption of a predetermined amount of electric energy. Also, a series of timing pulses, which occur at regular intervals, is generally applied to the magnetic tape. When a predeter-mined survey period is completed, the survey magnetic tape
2~ is removed from the survey device and the information recorded thereon can be analyzed by a computer. During the recording of data, the survey magnetic tape is run from a pay-out, or supply, reel to a take-up reel. Early models of this type of mass data acquisition equipment utilized supply reels and take-up reels that were indepen-dent from each other and required separate handling in the ' ~, ~L2~37~8 , 2 51,774 field. Examples of this type of practice can be found in U.S. Patent No. 3,059,239, which issued to Snyder and U.S.
Patent ~o. 3,1~8,329, which issued to Lenehan.
In some applications, a plurality of tracks on the magnetic tape were used, with each representing a different function of a variable ~uantity to be measured.
For example, one track can be used to record watt-hours whereas a second track can measure VAR hours supplied to the same load. This type of arrangement is disclosed in U.S. Patent No. 3,470,470, which issued to Snyder.
A significant improvement in the field of mass data ac~uisition was the incorporation of a tape cartridge in which a pay-out, or supply, reel and a take-up reel are mounted side-by-side on parallel spaced axes. Such a tape cartridge system is disclosed in U.S. Patent No.
Patent ~o. 3,1~8,329, which issued to Lenehan.
In some applications, a plurality of tracks on the magnetic tape were used, with each representing a different function of a variable ~uantity to be measured.
For example, one track can be used to record watt-hours whereas a second track can measure VAR hours supplied to the same load. This type of arrangement is disclosed in U.S. Patent No. 3,470,470, which issued to Snyder.
A significant improvement in the field of mass data ac~uisition was the incorporation of a tape cartridge in which a pay-out, or supply, reel and a take-up reel are mounted side-by-side on parallel spaced axes. Such a tape cartridge system is disclosed in U.S. Patent No.
3,602,458, which issued to Doby et al. on August 31, 1971.
When this type of cartridge unit is in its operating position, the reels are in a plane adjacent to and paral-lel to the front of the tape recorder. A pressure roller ;20 presses the tape against a capstan which is mounted separ-~;ately from the cartridge itself. A single spring provides this pressure and also holds ~the cartridge unit in its operating position while further operating a break to inhibit movement of the reels when the cartridge unit is removed from its operating position. The cartridge unit is 'ypically mounted parallel to the front of the record-ing device to facilitate inspection and manipulation of the cartridge unit.
Improvements to the concept of using a magnetic tape cartridge are disclosed in U.S. Patent No. 3,678,484, which issued to Maxwell on July 18, 1972 and U.S. Patent No. 4,162,051, which issued to Doby on July 24, 1978.
U.S. Patent No. 3,678,484 discloses a tape recorder which is provided with a removable tape cartridge unit that contains a supply reel and a take-up reel. Following the recording of electrical use data in the field, the mag-netic tape is placed in a reading device and run in a ~;24377~
3 51,774 reverse direction during translation in order to both rewind the tape and translate the digital data thereon simultaneously. U.S. Patent No. 4,162,051 discloses a load survey tape recorder that has a tape transport assem-bly, including a supply spindle assembly with a magneticbreak, and a take-up spindle assembly with a magnetic clutch. Therefore, substantially constant tensions are maintained in a recording tape as it is driven between supply and take-up reels by the magnetic retarding forces of the magnetic break and by a variable magnetic drive coupiing of the magnetic clutch.
The use of tape cartridges, instead of separate supply and take-up reels, have been used successfully in mass data acquisition systems for many years. Tapa car-tridges simplify the handling of the magnetic tape andprovide the proper alignment of the magnetic tape relative to the read and write heads of magnetic recording equip-ment which is designed to be associated with the tape cartridges. However, the effective use of magnetic tape cartridges can sometimes be adversely affected by the physical characteristics of the magnetic tape itself.
Some newer types of magnetic tape have been developed which have a special coating applied to the non-recording side of the tape, hereinafter referred to as the back of the tape. One purpose for applying a special backing of this kind to magnetic tape is to reduce prob-lems which are related to a build-up of static electric-ity. A problem can occur when this type of coating sur-face significantly changes the physical characteristics of the magnetic tape that relate to its travel from a supply reel to a take-up reel, and vice versa, within a magnetic tape cartridge. For example, it has been observed that certain tape backing compounds exhibit a higher coeffi-cient of friction than the normal back surface of uncoated magnetic tape. Although this higher friction backing does not affect the recording capabilities of the magnetic film on the front surface of the tape, it does come into direct 377~3 " , ~ 51,774 contact with other components of the tape cartridge it-self. For example, as the magnetic tape passes from the supply reel to the take-up reel, it passes over guide rollers which are used to assure that the tape is aligned properly during its passage through an opening in the tape cartridge as the tape passes proximate either a recording or a reading head.
Tape guide rollers of many types are known to those sXilled in the art and are made in ~arious configur-ations and shapes, depending on the particular require-ments of the magnetic tape cartridge itseLf. A cartridge that utilizes tape ~uide rollers is disclosed in U.S.
~atent No. 3,46~,057, which issued to Yamamoto on August l9, 1969. Sometimes the tape guide rollers incorporate shoulders at their axial ends. Such a tape guide roller is disclosed in U.S. Patent No. 3,432,084, which issued to van den Bussche on March 11, 1969.
A tape guide arrangement which utilizes tape rollers that incorporate shoulders is also disclosed in U.S. Patent No. 3,319,014, which issued to Sugawa on May 9, 1967. A tape cartridge, or cassette, which utilizes tape guide rollers with shoulders at the axial ends of its tape guide rollers is disclosed in U.S. Patent No.
When this type of cartridge unit is in its operating position, the reels are in a plane adjacent to and paral-lel to the front of the tape recorder. A pressure roller ;20 presses the tape against a capstan which is mounted separ-~;ately from the cartridge itself. A single spring provides this pressure and also holds ~the cartridge unit in its operating position while further operating a break to inhibit movement of the reels when the cartridge unit is removed from its operating position. The cartridge unit is 'ypically mounted parallel to the front of the record-ing device to facilitate inspection and manipulation of the cartridge unit.
Improvements to the concept of using a magnetic tape cartridge are disclosed in U.S. Patent No. 3,678,484, which issued to Maxwell on July 18, 1972 and U.S. Patent No. 4,162,051, which issued to Doby on July 24, 1978.
U.S. Patent No. 3,678,484 discloses a tape recorder which is provided with a removable tape cartridge unit that contains a supply reel and a take-up reel. Following the recording of electrical use data in the field, the mag-netic tape is placed in a reading device and run in a ~;24377~
3 51,774 reverse direction during translation in order to both rewind the tape and translate the digital data thereon simultaneously. U.S. Patent No. 4,162,051 discloses a load survey tape recorder that has a tape transport assem-bly, including a supply spindle assembly with a magneticbreak, and a take-up spindle assembly with a magnetic clutch. Therefore, substantially constant tensions are maintained in a recording tape as it is driven between supply and take-up reels by the magnetic retarding forces of the magnetic break and by a variable magnetic drive coupiing of the magnetic clutch.
The use of tape cartridges, instead of separate supply and take-up reels, have been used successfully in mass data acquisition systems for many years. Tapa car-tridges simplify the handling of the magnetic tape andprovide the proper alignment of the magnetic tape relative to the read and write heads of magnetic recording equip-ment which is designed to be associated with the tape cartridges. However, the effective use of magnetic tape cartridges can sometimes be adversely affected by the physical characteristics of the magnetic tape itself.
Some newer types of magnetic tape have been developed which have a special coating applied to the non-recording side of the tape, hereinafter referred to as the back of the tape. One purpose for applying a special backing of this kind to magnetic tape is to reduce prob-lems which are related to a build-up of static electric-ity. A problem can occur when this type of coating sur-face significantly changes the physical characteristics of the magnetic tape that relate to its travel from a supply reel to a take-up reel, and vice versa, within a magnetic tape cartridge. For example, it has been observed that certain tape backing compounds exhibit a higher coeffi-cient of friction than the normal back surface of uncoated magnetic tape. Although this higher friction backing does not affect the recording capabilities of the magnetic film on the front surface of the tape, it does come into direct 377~3 " , ~ 51,774 contact with other components of the tape cartridge it-self. For example, as the magnetic tape passes from the supply reel to the take-up reel, it passes over guide rollers which are used to assure that the tape is aligned properly during its passage through an opening in the tape cartridge as the tape passes proximate either a recording or a reading head.
Tape guide rollers of many types are known to those sXilled in the art and are made in ~arious configur-ations and shapes, depending on the particular require-ments of the magnetic tape cartridge itseLf. A cartridge that utilizes tape ~uide rollers is disclosed in U.S.
~atent No. 3,46~,057, which issued to Yamamoto on August l9, 1969. Sometimes the tape guide rollers incorporate shoulders at their axial ends. Such a tape guide roller is disclosed in U.S. Patent No. 3,432,084, which issued to van den Bussche on March 11, 1969.
A tape guide arrangement which utilizes tape rollers that incorporate shoulders is also disclosed in U.S. Patent No. 3,319,014, which issued to Sugawa on May 9, 1967. A tape cartridge, or cassette, which utilizes tape guide rollers with shoulders at the axial ends of its tape guide rollers is disclosed in U.S. Patent No.
4,417,705, which issued to Keto et al. on November 29, 1983. When shoulders are used on tape guide rollers, they are generally intended to maintain tape alignment during periods of time when the take-up and supply reels are not in rotation. During the rotation of these ree]s, when tape is being transferred from the supply reel to the take~up reel, the magnetic tape is preferably not in contact with the shoulders of the tape guide rollers.
Although slight intermittent contact between the magnetic tape and the tape guide rollers will, in all probability, not damage the magnetic tape, constant rubbing contact under tension between the magnetic tape and the guide rollers can damage the edges of the tape. Tape guide rollers which do not use shoulders at the axial ends of
Although slight intermittent contact between the magnetic tape and the tape guide rollers will, in all probability, not damage the magnetic tape, constant rubbing contact under tension between the magnetic tape and the guide rollers can damage the edges of the tape. Tape guide rollers which do not use shoulders at the axial ends of
5 51,774 their operative surfaces are illustrated in U.S. Patent No. 3,217,997, which issued to Lundgren et al. on November 16, 1965 and U.S. Patent No. 3,130,933, which issued to Pillsbury et al. on April 28, 1964.
In addition to the two basic shapes of tape guide rollers disclosed in the above-mentioned patents, other shapes have been used in tape guide systems. For example, in ~.S. Patent No. 3,223,303, which issued to Hunter on December 14, 1965, conical tape guides are disclosed. Wr.en conical tape guides are used, the axis of rotation of the tape guide is generally not parallel to the axes of rotation of the supply and take-up reels.
Another type of tape guide is disclosed in U.S. Patent No.
3,320,370, that issued to Barry on May 16, 1967, which describes a recessed concave tape guide. U.S. Patent No.
3,333,753, which issued to Streets on August 1, 1967, discloses a tape guide roller which comprises two conical members that are disposed on a common axis of rotation with their bases proximate each other. This type of tape guide roller is utilized when it is beneficial to force the magnetic tape axially in one preferable direction along the axis of rotation of the tape guide.
U.S. Patent No. 3,132,788, which issued to Johnson on May 12, 1964, discloses pinch rollers, for use with a magnetic recorder, that have a diameter at the axial center of its operative surface which is larger than the dlameters at the axially outward portions of its operative surface. This increased central diameter is used to maintain a positive contact between a rotating capstan and the pressure roller. U.S. Patent No.
3,132,788 uses conventionally shaped guide rollers with a reduced diameter operative surface disposed between two guide walls, or shoulders. The spacing between the faces of the guide walls is chosen to permit the magnetic tape to move freely therebetween, but to confine the magnetic tape to a minimum amount of shifting in a direction paral-lel to the axis of rotation of the guide roller.
,
In addition to the two basic shapes of tape guide rollers disclosed in the above-mentioned patents, other shapes have been used in tape guide systems. For example, in ~.S. Patent No. 3,223,303, which issued to Hunter on December 14, 1965, conical tape guides are disclosed. Wr.en conical tape guides are used, the axis of rotation of the tape guide is generally not parallel to the axes of rotation of the supply and take-up reels.
Another type of tape guide is disclosed in U.S. Patent No.
3,320,370, that issued to Barry on May 16, 1967, which describes a recessed concave tape guide. U.S. Patent No.
3,333,753, which issued to Streets on August 1, 1967, discloses a tape guide roller which comprises two conical members that are disposed on a common axis of rotation with their bases proximate each other. This type of tape guide roller is utilized when it is beneficial to force the magnetic tape axially in one preferable direction along the axis of rotation of the tape guide.
U.S. Patent No. 3,132,788, which issued to Johnson on May 12, 1964, discloses pinch rollers, for use with a magnetic recorder, that have a diameter at the axial center of its operative surface which is larger than the dlameters at the axially outward portions of its operative surface. This increased central diameter is used to maintain a positive contact between a rotating capstan and the pressure roller. U.S. Patent No.
3,132,788 uses conventionally shaped guide rollers with a reduced diameter operative surface disposed between two guide walls, or shoulders. The spacing between the faces of the guide walls is chosen to permit the magnetic tape to move freely therebetween, but to confine the magnetic tape to a minimum amount of shifting in a direction paral-lel to the axis of rotation of the guide roller.
,
6 51,774 When the axis of rotation of a guide roller is not precisely perpendicular to the direction of travel of the magnetic tape between the supply reel to the take-up reel, the magnetic tape can migrate in a direction perpen-dicular to its intended direction of travel. When thecoefficient of friction between the back side of the magnetic tape and the operative surface of the tape guide roller is small, this tendency to migrate in a direction perpendicular to its intended travel is reduced because the back side of the magnetic tape is able to maintain its proper position by sliding along the operative surface of the misaligned guide roller. Other forces which normally act on the magnetic tape, such as the tension provided by the take-up reel, will normally overcome the frictional forces of the operative surface on the back side of the tape and maintain the magnetic tape at a proper position along the tape guide rollers and, thus, the above-mentioned tendency to migrate is counteracted. However, if the magnetic tape has a backing material which exhibits a higher than normal coefficient of friction between it and the operative surface of the tape guide roller, a guide roller which is not aligned properly, in combination with this higher coefficient of friction, will cause the magnetic tape to migrate in a direction along the axis of rotation of the tape guide roller.
If the magnetic tape is permitted to migrate, as discussed above, tape damage can occur. If the tape guide roller is provided with shoulders, one edge of the magnet-ic tape will come into rubbing contact with the inner face of one of the shoulders. When this rubbing contact occurs while the tape is under tension, the magnetic tape can be severely damaged. If this migration occurs on a tape guide roller that has no shoulders, the magnetic tape can actually be forced off of the roller by the migration process. Therefore, it is beneficial to provide a magnet-ic tape cartridge with tape guide rollers that provide compensation for minor deviations between the axis of . ~Z437713
If the magnetic tape is permitted to migrate, as discussed above, tape damage can occur. If the tape guide roller is provided with shoulders, one edge of the magnet-ic tape will come into rubbing contact with the inner face of one of the shoulders. When this rubbing contact occurs while the tape is under tension, the magnetic tape can be severely damaged. If this migration occurs on a tape guide roller that has no shoulders, the magnetic tape can actually be forced off of the roller by the migration process. Therefore, it is beneficial to provide a magnet-ic tape cartridge with tape guide rollers that provide compensation for minor deviations between the axis of . ~Z437713
7 51,774 rotation of the tape guide roller and a line drawn paral-lel to the back surface of the magnetic tape and perpen-dicular to its intended direction of travel.
The present invention utilizes tape guide roll-ers which incorporate shoulders at its axial ends and a crown on its operative surface. The tape guide rollers of the present invention would normally be utilized in a tape cartridge device which has first and second tape reels that are rotatably mounted to a generally flat plate. The first and second tape reels function as supply and take-up reels. The tape guide roller of the present invention is mounted to the generally flat plate with its axis of rotation being generally parallel to the axes o~ rotation of the first and second tape reels. The tape guide roller has an operative surface shaped to receivs the magne-tic tape in rolling association therewith. The operative surface of the tape guide roller has a larger diameter at its central region than at its axial end regions. The tape guide rollers of the present invention incorporate shoulders at their axial ends of the operative surfaces.
The distance between the faces of the shoulders is slight~
ly larger than the width of the magnetic tape to be re-ceived therebetween. One or more of the tape guide roll-ers of the present invention is disposed functionally between the first and second tape reels. It should be understood that the magnetic tape, after being unwound from the supply reel, generally does not pass in a direc-tion which is directly toward the take-up reel. Instead, the magnetic tape typically passes first in a direction away from a line drawn between the axes of rotation of the supply and take-up reels. It then passes in rolling association over a tape guide roller and then past a portion of the cartridge where a read or write head can have easy access to the recording surface on the front side of the magnetic tape. After passing through this open area of the cartridge, the magnetic tape typically passes over a second tape guide roller, in rolling asso-~2~377~3
The present invention utilizes tape guide roll-ers which incorporate shoulders at its axial ends and a crown on its operative surface. The tape guide rollers of the present invention would normally be utilized in a tape cartridge device which has first and second tape reels that are rotatably mounted to a generally flat plate. The first and second tape reels function as supply and take-up reels. The tape guide roller of the present invention is mounted to the generally flat plate with its axis of rotation being generally parallel to the axes o~ rotation of the first and second tape reels. The tape guide roller has an operative surface shaped to receivs the magne-tic tape in rolling association therewith. The operative surface of the tape guide roller has a larger diameter at its central region than at its axial end regions. The tape guide rollers of the present invention incorporate shoulders at their axial ends of the operative surfaces.
The distance between the faces of the shoulders is slight~
ly larger than the width of the magnetic tape to be re-ceived therebetween. One or more of the tape guide roll-ers of the present invention is disposed functionally between the first and second tape reels. It should be understood that the magnetic tape, after being unwound from the supply reel, generally does not pass in a direc-tion which is directly toward the take-up reel. Instead, the magnetic tape typically passes first in a direction away from a line drawn between the axes of rotation of the supply and take-up reels. It then passes in rolling association over a tape guide roller and then past a portion of the cartridge where a read or write head can have easy access to the recording surface on the front side of the magnetic tape. After passing through this open area of the cartridge, the magnetic tape typically passes over a second tape guide roller, in rolling asso-~2~377~3
8 51,774 ciation therewith, and proceeds toward the take-up reel.
Therefore, in the most common application of the present invention, two tape guide rollers would be utilized.
A tape guide roller made in accordance with the present invention would therefore incorporate a shoulder at each of its axial ends and would have an operative surface located therebetween. The operative surface, over which the magnetic tape would travel, is crowned so that the portions of the operative surace which are closest to the shoulders each have a diameter which is less than that of the operative surface in its central region. This crowned surface facilitates alignment by operating to position the magnetic tape in the central portion of the operative surface and avoid contact between the edges of the tape and the inner faces of the shoulders.
A tape guide roller made in accordance with the present invention is also provided with a central opening which is concentric with its intended axis of rotation.
The central opening is generally cylindrical and shaped to receive a guide post in sliding association therein. In a typical application of the present invention, the guide post would be fixedly attached to a generally flat plate of the tape cartridge. The tape guide roller would be disposed thereon and would rotate about the central axis of the guide post.
As the magnetic tape travels from the supply reel to the take-up reel, it passes over the operative surface of the tape guide roller in rolling association therewith. The increased diameter near the central por-tion of the operative surface of the tape guide rollerdescribes a convex, or arcuate, surface that tends to maintain the position of the magnetic tape in the central portion of the operative surface between the faces of the shoulders. Because of t~is tendency to position the magnetic tape in the central portion of the operative surface, rubbing contact between the edges of the magnetic tape and the faces of the shoulders is prevented. There-L377t~
Therefore, in the most common application of the present invention, two tape guide rollers would be utilized.
A tape guide roller made in accordance with the present invention would therefore incorporate a shoulder at each of its axial ends and would have an operative surface located therebetween. The operative surface, over which the magnetic tape would travel, is crowned so that the portions of the operative surace which are closest to the shoulders each have a diameter which is less than that of the operative surface in its central region. This crowned surface facilitates alignment by operating to position the magnetic tape in the central portion of the operative surface and avoid contact between the edges of the tape and the inner faces of the shoulders.
A tape guide roller made in accordance with the present invention is also provided with a central opening which is concentric with its intended axis of rotation.
The central opening is generally cylindrical and shaped to receive a guide post in sliding association therein. In a typical application of the present invention, the guide post would be fixedly attached to a generally flat plate of the tape cartridge. The tape guide roller would be disposed thereon and would rotate about the central axis of the guide post.
As the magnetic tape travels from the supply reel to the take-up reel, it passes over the operative surface of the tape guide roller in rolling association therewith. The increased diameter near the central por-tion of the operative surface of the tape guide rollerdescribes a convex, or arcuate, surface that tends to maintain the position of the magnetic tape in the central portion of the operative surface between the faces of the shoulders. Because of t~is tendency to position the magnetic tape in the central portion of the operative surface, rubbing contact between the edges of the magnetic tape and the faces of the shoulders is prevented. There-L377t~
9 51,774 fore, even if the post about which the tape guide rollerrotates is not precisely perpendicular to the direction of travel of the magnetic tape, the magnetic tape will not tend to migrate along this axis of rotation and possibly damage the edges of the tape by rub~ing against the faces of the shoulders. During periods when the tape is not being transferred from the supply reel to the take-up reel, the shoulders of the tape guide rollers will tend to captivate the tape in a position which will not permit severe migration of the magnetic tape away ~rom 'he de-sired position for future use in writing or reading maa-netically stored data on the tape.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully under-stood from a reading of the description o~ the preferred embodiment along with the drawings in which:
Figure 1 illustrates a magnetic tape cartridge which utilizes tape guide rollers made in accordance with the present invention;
Figure 2 illustrates a tape guide roller made according to principles known by those sXilled in the art;
Figure 3 shows a tape guide roller made in accordance with the present invention;
Figure 4 illustrates a magnetic tape moving in sliding relation with a tape guide roller made in accord-ance with principles known to those skilled in the art;
Figure 5 illustrates a magnetic tape moving in sliding contact with a tape guide roller made in accord-ance with the present invention; and Figure 6 illustrates a tape guide roller made in accordance with the present invention associated with a tape reel and a length of magnetic tape.
DESCRIPTION OF THE PREFERRED E BODIMENTS
The present invention relates generally to magnetic tape cartridges and, more particularly, to tape guide rollers which are used to maintain the proper later-al positioning of the magnetic tape as it travels ~rom a supply reel to a take-up reel.
~7 ~
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully under-stood from a reading of the description o~ the preferred embodiment along with the drawings in which:
Figure 1 illustrates a magnetic tape cartridge which utilizes tape guide rollers made in accordance with the present invention;
Figure 2 illustrates a tape guide roller made according to principles known by those sXilled in the art;
Figure 3 shows a tape guide roller made in accordance with the present invention;
Figure 4 illustrates a magnetic tape moving in sliding relation with a tape guide roller made in accord-ance with principles known to those skilled in the art;
Figure 5 illustrates a magnetic tape moving in sliding contact with a tape guide roller made in accord-ance with the present invention; and Figure 6 illustrates a tape guide roller made in accordance with the present invention associated with a tape reel and a length of magnetic tape.
DESCRIPTION OF THE PREFERRED E BODIMENTS
The present invention relates generally to magnetic tape cartridges and, more particularly, to tape guide rollers which are used to maintain the proper later-al positioning of the magnetic tape as it travels ~rom a supply reel to a take-up reel.
~7 ~
10 51,774 A magnetic tape cartridge 10 which utilizes the tape guide rollers of the present invention is illustrated in Fig. 1. As can be seen in Fig. 1, the magnetic tape 12 passes over a pressure roller 14 and is guided by the tape guide rollers, 16 and 18, between the tape reels 20 and 22. During a recording operation, the tape 12 leaves the supply, or pay-out, reel 20, travels in the recording direction Dl and enters ~he take~up reel 22. The tape guide rollers, 16 and 18, are rotatably mounted on posts 17 and 19, respectively. The pressure roller 14 is mo~mt-ed for rotation on a slide 24. ~he slide 24 is mounted for reciprocation toward or away from the tape 12 which extends between tape guide rollers 16 and 18.
The magnetic tape cartridge 10 which is illu-strated in Fig. 1 is used herein as an illustration of the use of the tape guide rollers of the present invention.
The tape cartridge 10 is described in greater detail in U.S. Patent No. 3,678,484.
In a tape cartridge as illustrated in Fig. 1, the slide 24 is generally mounted in such a way so it is free to move in a reciprocating manner between two guide ribs 30 and 32 which form a part of the cover 34. A screw 36 is inserted into a post that is riveted to the plate 38. The screw 36 extends through an elongated slot 40 which is formed in the slide 24. Attached to one end of the slide 24 is a brake block 42. This brake block 42 engages the rims of the reels, 20 and 22, when the car-tridge unit is not disposed within the frame of a record-ing device. ~ coil spring 44 is compressed between the brake block 42 and a portion of the cover 34 ~or the purpose of biasing the brake block 42 and the slide 24 toward ~he magnetic tape 12 which extends between the tape guide rollers 1~ and 18. Thus, the spring 44 urges the brake block 42 into braking engagement with the tape reels, 20 and 22.
.,~,;~, 1377~3 ~, .
The magnetic tape cartridge 10 which is illu-strated in Fig. 1 is used herein as an illustration of the use of the tape guide rollers of the present invention.
The tape cartridge 10 is described in greater detail in U.S. Patent No. 3,678,484.
In a tape cartridge as illustrated in Fig. 1, the slide 24 is generally mounted in such a way so it is free to move in a reciprocating manner between two guide ribs 30 and 32 which form a part of the cover 34. A screw 36 is inserted into a post that is riveted to the plate 38. The screw 36 extends through an elongated slot 40 which is formed in the slide 24. Attached to one end of the slide 24 is a brake block 42. This brake block 42 engages the rims of the reels, 20 and 22, when the car-tridge unit is not disposed within the frame of a record-ing device. ~ coil spring 44 is compressed between the brake block 42 and a portion of the cover 34 ~or the purpose of biasing the brake block 42 and the slide 24 toward ~he magnetic tape 12 which extends between the tape guide rollers 1~ and 18. Thus, the spring 44 urges the brake block 42 into braking engagement with the tape reels, 20 and 22.
.,~,;~, 1377~3 ~, .
11 51,774 As the magnetic tape passes from the supply reel 20 to the take-up reel 22, it extends in rolling associa-tion with the tape guide rollers, 16 and 18. These tape guide rollers, 16 and 18, maintain the lateral position o~
the magnetic tape 12 as it passes over the pressure roller 14. It is important that the magnetic tape 12 be in a proper lateral position as it passes proximate the opening 46 in the tape cartridge 10 because it is at this posi-tion, proximate the pressure roller 14, that the read and/or write heads will be in contact with the magnetic tape 12.
The take-up reel 22 is driven by a drive wheel mechanis~ (not illustrated in Fig. 1) which has a plural-ity of pins that are shaped to be received by the holes 48 that are distributed uniformly about the axis of the hub of the take-up reel 22. Similarly, holes 49 in the hub of the supply reel 20 are shaped to receive pins of another drive wheel (not illustrated in Fig. 1) for rewinding the tape 12 from the take-up reel 22 to the supply reel 20.
In normal operation, when the tape cartridge 10 is placed in a recording device that is in the field for the purpose of mass data acquisition, virtually all of the magnetic tape 12 is disposed on the supply reel 20.
During the recording operation, the magnetic tape moves slowly in the direction indicated by Dl from the supply reel 20 to the take-up reel 22. The winding of the mag-netic tape on the take-up reel 22 is generally very slow since its speed needs to be only high enough to move the tape sufficiently for the recording of sequential elec trical use data. After a predetermined period of time, for example a month, the tape cartridge 10 would typically be removed from the recording apparatus and taken to a central location where the recorded data can be read and translated. During this reading operation, the tape which is stored on the take-up reel 22 is transferred, at a much higher rate, to the supply reel 20 as the tape is being read in the reverse direction. This specific operation is 37~1 3
the magnetic tape 12 as it passes over the pressure roller 14. It is important that the magnetic tape 12 be in a proper lateral position as it passes proximate the opening 46 in the tape cartridge 10 because it is at this posi-tion, proximate the pressure roller 14, that the read and/or write heads will be in contact with the magnetic tape 12.
The take-up reel 22 is driven by a drive wheel mechanis~ (not illustrated in Fig. 1) which has a plural-ity of pins that are shaped to be received by the holes 48 that are distributed uniformly about the axis of the hub of the take-up reel 22. Similarly, holes 49 in the hub of the supply reel 20 are shaped to receive pins of another drive wheel (not illustrated in Fig. 1) for rewinding the tape 12 from the take-up reel 22 to the supply reel 20.
In normal operation, when the tape cartridge 10 is placed in a recording device that is in the field for the purpose of mass data acquisition, virtually all of the magnetic tape 12 is disposed on the supply reel 20.
During the recording operation, the magnetic tape moves slowly in the direction indicated by Dl from the supply reel 20 to the take-up reel 22. The winding of the mag-netic tape on the take-up reel 22 is generally very slow since its speed needs to be only high enough to move the tape sufficiently for the recording of sequential elec trical use data. After a predetermined period of time, for example a month, the tape cartridge 10 would typically be removed from the recording apparatus and taken to a central location where the recorded data can be read and translated. During this reading operation, the tape which is stored on the take-up reel 22 is transferred, at a much higher rate, to the supply reel 20 as the tape is being read in the reverse direction. This specific operation is 37~1 3
12 51,774 disclosed in U.S. Patent No. 3,678,484. During this rewinding operation, the magnetic tape 12 passes in a direction as indicated by arrow D2 at speeds which may be in excess of 60 inches per second. This rewinding opera-tion continues until a marker, which is located near theend of the magnetic tape 12, is sensed by the reading head which is disposed proximate the pressure wheel 14. After the sensing of the tape marker, the reels, 20 and 22, are quickly stopped and the tape is once again moved in the direction indicated by Dl until the tape marker is posi-tioned beyond the reading head. During this positioning operation, the magnetic tape experiences rapid reversals of direction while it is traveling at relatively high speeds and under significant tension.
If the posts, 17 and 19, are not positioned exactly perpendicular to the plate 38 and the direction of travel of the magnetic tape 12, the magnetic tape 12 may exhibit a tendency to migrate along the operative surfaces of the tape guide rollers, 16 and 18, in a direction per-pendicular to Fig. 1 and lateral with respect to the direction of travel of the magnetic tape 12. As will be discussed in greater detail below, this lateral travel, when occurring at high speeds and high tensions, can cause damage to the edges of the magnetic tape 12 as they come into rubbing contact with the faces of the shoulders of tha tape guide rollers, 16 and 18.
Fig. 2 illustrates a tape guide roller S0 which is made according to the principles generally known to those skilled in the art. The tape guide roller 50 of Fig. 2 could be used as each of the tape guide rollers 16 and 18 of Fig. l. The conventional tape guide roller 50, shown in Fig. 2, is generally cylindrical in shape and has a central axis 52. It has an operative surface 54 which is cylindrical and concentric about the axis 52. The operative surface 54 has a constant diameter along its length. At each axial end of the tape guide roller 50, a shoulder portion is provided. These shoulders, 56 and 58 ~2~37~
,., . .~
If the posts, 17 and 19, are not positioned exactly perpendicular to the plate 38 and the direction of travel of the magnetic tape 12, the magnetic tape 12 may exhibit a tendency to migrate along the operative surfaces of the tape guide rollers, 16 and 18, in a direction per-pendicular to Fig. 1 and lateral with respect to the direction of travel of the magnetic tape 12. As will be discussed in greater detail below, this lateral travel, when occurring at high speeds and high tensions, can cause damage to the edges of the magnetic tape 12 as they come into rubbing contact with the faces of the shoulders of tha tape guide rollers, 16 and 18.
Fig. 2 illustrates a tape guide roller S0 which is made according to the principles generally known to those skilled in the art. The tape guide roller 50 of Fig. 2 could be used as each of the tape guide rollers 16 and 18 of Fig. l. The conventional tape guide roller 50, shown in Fig. 2, is generally cylindrical in shape and has a central axis 52. It has an operative surface 54 which is cylindrical and concentric about the axis 52. The operative surface 54 has a constant diameter along its length. At each axial end of the tape guide roller 50, a shoulder portion is provided. These shoulders, 56 and 58 ~2~37~
,., . .~
13 51,774 have inner faces, 57 and 59, respectively, which are proximate the axial ends of the operative surface 54 and are generally perpendicular to the central axis 52. In order to guarantee that no fillets remain in the corners 5 between the operative surface 54 and the faces, 57 and 59, a slight undercut 60 is provided proximate each of the two faces 57 and 59.
Other features of the known tape guide roller 50 are also illustrated in Fig. 2. For example, a central opening 64 is provided through the tape guide roller 50.
This central opening 64 lS generally cylindrical and is concentric about the central axis 52. Also, this central opening 64 is shaped to receive a post in rotatably slid-ing contact therewith. The post, which the central open-ing 64 is shaped to receive, is one that is similar to the posts indicated as reference numerals 17 and 19 in Fig. l.
As indicated in Fig. 2, the shoulders of the tape guide roller 50 are tapered with conical sections 66 and 68 at the outboard portions of the shoulders. The purpose of these tapered sections is to reduce the contact area between the tape guide roller 50 and the generally flat plate ~reference numeral 38 in Fig. l) of the tape cartridge. Although only one axial end of each tape guide roller 50 is in contact with the generally flat plate of the tape cartridge, both axial ends of the tape guide roller 50 are tapered so as to make the tape guide roller symmetrical and usable when aligned in either of the two opposite positions on the post. Thus, the tapered por-tions, 66 and 68, reduce the surface area of the end surfaces, 70 and 72 respectively, of the tape guide roller 50. The axial ends of the central opening 64 are also provided with bevels 74 and 76 in order to avoid the possibility of burrs which could exist from the machining process by which the tape guide roller 50 is formed.
By viewing Fig. 2 in conjunction with Fig. 1, it can be seen that the tape guide roller 50 could be placed on either of the two posts, 17 and l9, and used with the ~24377~
Other features of the known tape guide roller 50 are also illustrated in Fig. 2. For example, a central opening 64 is provided through the tape guide roller 50.
This central opening 64 lS generally cylindrical and is concentric about the central axis 52. Also, this central opening 64 is shaped to receive a post in rotatably slid-ing contact therewith. The post, which the central open-ing 64 is shaped to receive, is one that is similar to the posts indicated as reference numerals 17 and 19 in Fig. l.
As indicated in Fig. 2, the shoulders of the tape guide roller 50 are tapered with conical sections 66 and 68 at the outboard portions of the shoulders. The purpose of these tapered sections is to reduce the contact area between the tape guide roller 50 and the generally flat plate ~reference numeral 38 in Fig. l) of the tape cartridge. Although only one axial end of each tape guide roller 50 is in contact with the generally flat plate of the tape cartridge, both axial ends of the tape guide roller 50 are tapered so as to make the tape guide roller symmetrical and usable when aligned in either of the two opposite positions on the post. Thus, the tapered por-tions, 66 and 68, reduce the surface area of the end surfaces, 70 and 72 respectively, of the tape guide roller 50. The axial ends of the central opening 64 are also provided with bevels 74 and 76 in order to avoid the possibility of burrs which could exist from the machining process by which the tape guide roller 50 is formed.
By viewing Fig. 2 in conjunction with Fig. 1, it can be seen that the tape guide roller 50 could be placed on either of the two posts, 17 and l9, and used with the ~24377~
14 51,774 tape cartridge 10. The central axis 52 of the tape guide roller 50 would be coincident with the central axis of the post on which it is placed. The post would pass through the central opening 64 and the tape guide roller 50 would be able to rotate about its central axis. As the magnetic tape is wound ovér the tape guide roller 50, it would be located between the faces, 57 and 59, of the shoulders of the tape guide roller. Furthermore, the magnetic tape - would pass in rolling relation over the operative surface 54 as the tape is wound from one tape reel to the other.
Fig. 3 illustrates a tape guide roller 80 made in accordance with the present invention. In many re-spects, the tape guide roller 80 of Fig. 3 is similar to the tape guide roller 50 o Fig. 2. For example, it has two shoulders 56 and 58 located at its axial ends. Eur-thermore, each shoulder is beveled with a conical section, 66 and 68, to reduce the area of the contact surfaces 70 and 72. Eurthermore, a central opening 64 is provided through the center of the tape guide roller 80. This central opening 64, as discussed above, is concentric with the central axis 52 of the tape guide roller. Further-more, each axial end of the central opening 64 is provided with a bevel, 74 and 76, so as to avoid any possible burrs that may exist from the operation by which the tape guide roller 80 was made.
A significant difference between the tape guide roller 5b of Fig. 2 and the tape guide roller 80 of Fig. 3 is related to the operative surface 84. The tape guide roller 80 of the present invention incorporates an opera-tive surface 84 which is crowned as illustrated in Fig. 3.The crown surface is made with a radius of curvature, as indicated by arrow RC to describe a convex surface. The result of this crowning is that the diameter, measured perpendicular to the central axis 52, at the central portion of the operative surface 84 is larger than the diameter of this operative surace ~easured near its ends which are proximate the faces, 57 and 59, of the shoulders ~2~3~B
51,774 56 and 58, respectively. Another difference between the known tape guide roller 50 and the tape guide roller 80 of the present invention is the distance between the faces 57 and 59 of the shoulders. In a typical application, using the known tape yuide roller 50 with a magnetic tape that has a width of .2~8 inches, the width Wl would be approxi-mately .252 inches which would allow a total clearance between the faces, 57 and 59, and the edges of the mag-netic tape of approximately .004 inches. In the tape guide roller 80 of the present invention, this distance between the faces, 57 and 59, (reference W2 of Fig. 3) has been enlarged in a preferred embodiment of the present invention to .288 inches. Therefore, it can be seen that when used with identical magnetic tapes the present inven-tion utilizes tape guide rollers that provide slightlylarger clearances between the faces, 57 an~ 59, and the magnetic tape's edges. Therefore, it should be noted that the width W2 of the present invention is slightly greater than the width Wl of the prior art roller when used with the same size magnetic tape. However, it should be under-stood that this increased clearance between the faces, 57 and 5g, and the edges of the magnetic tape is provided as a matter of convenience and is not a required character-istic of the present invention. This incxeased width W2 is provided because the tape guide roller 80 of the pres-ent invention is primarily designed to be used with a magnetic tape which has a backing that exhibits a higher coefficient of friction than previousLy used magnetic tapes. Therefore, since the higher coefficient of fric-tion could tend to cause the magnetic tape to migrate morereadily than normally backed magnetic tapes, the increased clearance W2 is provided to permit more lateral movement of the magnetic tape than would normally be expected.
For purposes of more clearly illustrating the preferred embodiment of the present invention, a particu-lar combination of dimensions will be discussed below.
Howaver, it should be emphasized that these dimensions ~;~4~3778 ,.~
16 51,774 represent only one particular combination of the many possible combinations of dimensions that are possible within the scope of the present invention. These dimen-sions are being discussed herein so that the relative sizes can be appreciated and so that one particular pre-ferred embodiment of the present invention will be more specifically described. The cylindrical portions, 56 and 58, of the shoulder portions of the tape guide roller 80 have a length, indicated by Ll, of approximately .075 inches. The tapered portions of the shoulders each have lengths, L2, of approximately .1085 inches. The ov~ra'1 axial length L3 of the tape guide roller 80 is approxi-mately .655 inches and the distance W2 between the faces, 57 and 59, of the shoulders is approximately .288 inches.
With these comb~nations of dimensions, it has been empir-ically determined that a radius of curvature RC for the operative surface 84 can range from .25 inches to over 2 inches. Throughout this range of radii of curvature, the tape guide roller 80 functioned properly by aligning the magnetic tape in the central region between the faces, 57 and 59, of the shoulders. Even with rapid reversals of direction at high tape speeds, the magnetic tape was prevented from migrating significantly toward either of these two faces. Therefore, damage to the edges of the magnetic tape was prevented.
Figs. 4 and 5 illustrate the relationship be-tween the magnetic tape 12 and both the known tape guide roller 50 and the tape guide roller 80 of the present invention, respectively. By comparing Figs. 4 and 5, it can be seen that the two major differences between them are the distance between the faces, 57 and 59, of the shoulders and the shape o their operative surfaces. The operative surace 84 of the present invention is crowned so that its diameter at its axially central region is greater than its diameter at either axial end, proximate the shoulders, whereas the operative surface 54 of the prior art tape guide roller 50 has a constant diameter ~2~7~
.
17 51,774 along its length and is essentially cylindrical. When a cylindrical operative surface 54 is used, minor deviations from perpendicularity between the central axis 52 of the tape guide roller 50 and the direction of travel T of the magnetic tape 12 can cause the magnetic tape to migrate toward either one of the two faces, 57 and 59, of the tape guide rollers' shoulders. As described above, the migra-tion of the magnetic tape 12 against either of these faces, 57 or 59, can cause severe damage to the edges of the magnetic tape 12, especially when the magnetic tape 12 is moving rapidly and is under signficant tension.
In comparison, the tape guide roller 80 of the present invention, which is illustrated in Fig. 5, util-izes a crowned, or convex, operative surface 84 which tends to center the magne,tic tape 12 at a position which is generally mid-way between the faces, 57 and 59, of the tape guide roller's shoulders. Even under slight mis-alignment of the tape guide roller 80, in which the cen-tral axis 52 is not perfectly perpendicular to the direc-tion of travel T of the magnetic tape 12, this tendency ofthe crowned operative surface 84 to center the magnetic tape 12 prevents contact between the edges of the magnetic tape 12 and either of the two faces 57 or 59. Therefore, with a crowned operative surface 84, some misalignment between the perpendicularity of the central axis 52 and the direction of travel T is tolerable, whereas with a perfectly cylindrical operative surface such as known to those skilled in the art, such a misalignment could cause severe damage to the magnetic tape's edges.
Another advantage of the crowning of the opera-tive surface 8~ of the present invention is that it per-mits a wider distance to be utilized between the faces, 57 and 59, of the tape guide rollers' shoulders. Even with-out misalignment, the magnetic tape 12 would have a ten-dency to randomly position itself between the faces, 57 and 59, of the prior art tape guide roller 50. This would occur because the magnetic tape 12 would have no predeter-.
~2~37~8 18 51,77~
mined tendency to center itself midway between the faces of the shoulders. Therefore, when a perfectly cylindrical operati~e surface 54 is used, the spacin~ between the facest 57 and 59, must be limited so that the magnetic tape 12 will not wander far enough from the center portion of the operative surface 54 so as to be misaligned with respect to the read/write head of the magnetic recording equipment with which it is used. :[n contradistinction to this situation, the crowned operative surface 84 o the tape guide roller 80 tends to~ center the magnetic tape 12 between the faces, 57 and 59, without aid ~rom the faces themselves. This centering tendency permits the faces 57 and 59 to be spaced farther apart than would normally be allowable with the tape guide roller 50. Normally, the distance between the faces, 57 and 59, in a tape guide roller` ~30 made in accordance with the present invention, is chosen so as to prevent gross misalignment of the magnetic tape within the cartridge. These faces, 57 and 59, of a tape guide roller 80 made in accordance with the present invention are used primarily to prevent the mag-netic tape from being totally displaced with respect to the pressure roller (reference numeral 14 in Fig. 1), but are not placed close enough together to perform running alignment on the magnetic tape since the crowning of the operative surface 84 performs this function.
Fig. 6 illustrates the tape guide roller 80 of the present invention in association with a take-up reel 22. Both the take-up reel 22 and the tape guide roller 8Q
are rotatably attached to a generally flat plate 92. The function of the generally flat plate 92 could be performed by the component which is illustrated as reference numeral 38 in Fig. 1. The take-up reel 22 is driven by its hub 96 which would normally have a plurality of holes such as those illustrated by reference numeral 48 in Fig. l. The hub 96 can be made from any suitable rigid material such as moldable plastic material. The hub 96 is rotatably mounted on a sleeve bearing which has a flange 94 at one ~377~
, . ~
19 51,774 end and which is secured to the plate 92 by any suitable means, such as a screw passing through the central axis of the hub 96. The flange portion 94 serves as a rotatable support which positions the take-up reel 22 above the surface 93 of the plate 92 and reduces the frictional fGrces therebetween.
In an ideal situation, the central axis 52 of the tape guide roller 80 would be perfectly perpendicular to both the surface 93 of the plate 92 and the direction of travel Dl of the magnetic tape 12. However, in most typical situations, this perfect perpendicularit~ is not achieved. Therefore, as the take-up reel 22 rotates in the direction indicated by arrows R and the magnetic tape 12 is wound onto the take-up reel 22 in the direction indicated by arrow Dl, a deviation from perpendicularity between the central axis 52 and the surface 93 would normally cause the magnetic tape 12 to migrate in a direc-tion toward one of the two faces, 57 or 59. However, with the crowned operative surface 84 of the present invention, the magnetic tape 12 is centered in the central portion of the operative surface 84 and prevented from colliding with either cf the two faces.
The present invention has been described and illustrated with significant specificity in order to more clearly disclose its features. However, it should be understood that the novel concepts of the present inven-tion can very significantly while remaining within the overall scope of the present invention. For e~ample, the precise distance between the faces of the shoulders of the tape guide rollers can vary from those dimensions given above and the radius of curvature of the crowned operative surface, likewise, can vary significantly from the range of values discussed. Therefore, it should be understood that although the present invention has been described and illustrated with specific values, it is not to be con-sidered so limited. Furthermore, although particular recording and reading techniques were discussed in con--\ lZ~3771!~
51,774 junction with the description of the present invention's operation, it should be understood that these techniques do not limit the applications of the present in~ention and other methods are within its scope of uses.
Fig. 3 illustrates a tape guide roller 80 made in accordance with the present invention. In many re-spects, the tape guide roller 80 of Fig. 3 is similar to the tape guide roller 50 o Fig. 2. For example, it has two shoulders 56 and 58 located at its axial ends. Eur-thermore, each shoulder is beveled with a conical section, 66 and 68, to reduce the area of the contact surfaces 70 and 72. Eurthermore, a central opening 64 is provided through the center of the tape guide roller 80. This central opening 64, as discussed above, is concentric with the central axis 52 of the tape guide roller. Further-more, each axial end of the central opening 64 is provided with a bevel, 74 and 76, so as to avoid any possible burrs that may exist from the operation by which the tape guide roller 80 was made.
A significant difference between the tape guide roller 5b of Fig. 2 and the tape guide roller 80 of Fig. 3 is related to the operative surface 84. The tape guide roller 80 of the present invention incorporates an opera-tive surface 84 which is crowned as illustrated in Fig. 3.The crown surface is made with a radius of curvature, as indicated by arrow RC to describe a convex surface. The result of this crowning is that the diameter, measured perpendicular to the central axis 52, at the central portion of the operative surface 84 is larger than the diameter of this operative surace ~easured near its ends which are proximate the faces, 57 and 59, of the shoulders ~2~3~B
51,774 56 and 58, respectively. Another difference between the known tape guide roller 50 and the tape guide roller 80 of the present invention is the distance between the faces 57 and 59 of the shoulders. In a typical application, using the known tape yuide roller 50 with a magnetic tape that has a width of .2~8 inches, the width Wl would be approxi-mately .252 inches which would allow a total clearance between the faces, 57 and 59, and the edges of the mag-netic tape of approximately .004 inches. In the tape guide roller 80 of the present invention, this distance between the faces, 57 and 59, (reference W2 of Fig. 3) has been enlarged in a preferred embodiment of the present invention to .288 inches. Therefore, it can be seen that when used with identical magnetic tapes the present inven-tion utilizes tape guide rollers that provide slightlylarger clearances between the faces, 57 an~ 59, and the magnetic tape's edges. Therefore, it should be noted that the width W2 of the present invention is slightly greater than the width Wl of the prior art roller when used with the same size magnetic tape. However, it should be under-stood that this increased clearance between the faces, 57 and 5g, and the edges of the magnetic tape is provided as a matter of convenience and is not a required character-istic of the present invention. This incxeased width W2 is provided because the tape guide roller 80 of the pres-ent invention is primarily designed to be used with a magnetic tape which has a backing that exhibits a higher coefficient of friction than previousLy used magnetic tapes. Therefore, since the higher coefficient of fric-tion could tend to cause the magnetic tape to migrate morereadily than normally backed magnetic tapes, the increased clearance W2 is provided to permit more lateral movement of the magnetic tape than would normally be expected.
For purposes of more clearly illustrating the preferred embodiment of the present invention, a particu-lar combination of dimensions will be discussed below.
Howaver, it should be emphasized that these dimensions ~;~4~3778 ,.~
16 51,774 represent only one particular combination of the many possible combinations of dimensions that are possible within the scope of the present invention. These dimen-sions are being discussed herein so that the relative sizes can be appreciated and so that one particular pre-ferred embodiment of the present invention will be more specifically described. The cylindrical portions, 56 and 58, of the shoulder portions of the tape guide roller 80 have a length, indicated by Ll, of approximately .075 inches. The tapered portions of the shoulders each have lengths, L2, of approximately .1085 inches. The ov~ra'1 axial length L3 of the tape guide roller 80 is approxi-mately .655 inches and the distance W2 between the faces, 57 and 59, of the shoulders is approximately .288 inches.
With these comb~nations of dimensions, it has been empir-ically determined that a radius of curvature RC for the operative surface 84 can range from .25 inches to over 2 inches. Throughout this range of radii of curvature, the tape guide roller 80 functioned properly by aligning the magnetic tape in the central region between the faces, 57 and 59, of the shoulders. Even with rapid reversals of direction at high tape speeds, the magnetic tape was prevented from migrating significantly toward either of these two faces. Therefore, damage to the edges of the magnetic tape was prevented.
Figs. 4 and 5 illustrate the relationship be-tween the magnetic tape 12 and both the known tape guide roller 50 and the tape guide roller 80 of the present invention, respectively. By comparing Figs. 4 and 5, it can be seen that the two major differences between them are the distance between the faces, 57 and 59, of the shoulders and the shape o their operative surfaces. The operative surace 84 of the present invention is crowned so that its diameter at its axially central region is greater than its diameter at either axial end, proximate the shoulders, whereas the operative surface 54 of the prior art tape guide roller 50 has a constant diameter ~2~7~
.
17 51,774 along its length and is essentially cylindrical. When a cylindrical operative surface 54 is used, minor deviations from perpendicularity between the central axis 52 of the tape guide roller 50 and the direction of travel T of the magnetic tape 12 can cause the magnetic tape to migrate toward either one of the two faces, 57 and 59, of the tape guide rollers' shoulders. As described above, the migra-tion of the magnetic tape 12 against either of these faces, 57 or 59, can cause severe damage to the edges of the magnetic tape 12, especially when the magnetic tape 12 is moving rapidly and is under signficant tension.
In comparison, the tape guide roller 80 of the present invention, which is illustrated in Fig. 5, util-izes a crowned, or convex, operative surface 84 which tends to center the magne,tic tape 12 at a position which is generally mid-way between the faces, 57 and 59, of the tape guide roller's shoulders. Even under slight mis-alignment of the tape guide roller 80, in which the cen-tral axis 52 is not perfectly perpendicular to the direc-tion of travel T of the magnetic tape 12, this tendency ofthe crowned operative surface 84 to center the magnetic tape 12 prevents contact between the edges of the magnetic tape 12 and either of the two faces 57 or 59. Therefore, with a crowned operative surface 84, some misalignment between the perpendicularity of the central axis 52 and the direction of travel T is tolerable, whereas with a perfectly cylindrical operative surface such as known to those skilled in the art, such a misalignment could cause severe damage to the magnetic tape's edges.
Another advantage of the crowning of the opera-tive surface 8~ of the present invention is that it per-mits a wider distance to be utilized between the faces, 57 and 59, of the tape guide rollers' shoulders. Even with-out misalignment, the magnetic tape 12 would have a ten-dency to randomly position itself between the faces, 57 and 59, of the prior art tape guide roller 50. This would occur because the magnetic tape 12 would have no predeter-.
~2~37~8 18 51,77~
mined tendency to center itself midway between the faces of the shoulders. Therefore, when a perfectly cylindrical operati~e surface 54 is used, the spacin~ between the facest 57 and 59, must be limited so that the magnetic tape 12 will not wander far enough from the center portion of the operative surface 54 so as to be misaligned with respect to the read/write head of the magnetic recording equipment with which it is used. :[n contradistinction to this situation, the crowned operative surface 84 o the tape guide roller 80 tends to~ center the magnetic tape 12 between the faces, 57 and 59, without aid ~rom the faces themselves. This centering tendency permits the faces 57 and 59 to be spaced farther apart than would normally be allowable with the tape guide roller 50. Normally, the distance between the faces, 57 and 59, in a tape guide roller` ~30 made in accordance with the present invention, is chosen so as to prevent gross misalignment of the magnetic tape within the cartridge. These faces, 57 and 59, of a tape guide roller 80 made in accordance with the present invention are used primarily to prevent the mag-netic tape from being totally displaced with respect to the pressure roller (reference numeral 14 in Fig. 1), but are not placed close enough together to perform running alignment on the magnetic tape since the crowning of the operative surface 84 performs this function.
Fig. 6 illustrates the tape guide roller 80 of the present invention in association with a take-up reel 22. Both the take-up reel 22 and the tape guide roller 8Q
are rotatably attached to a generally flat plate 92. The function of the generally flat plate 92 could be performed by the component which is illustrated as reference numeral 38 in Fig. 1. The take-up reel 22 is driven by its hub 96 which would normally have a plurality of holes such as those illustrated by reference numeral 48 in Fig. l. The hub 96 can be made from any suitable rigid material such as moldable plastic material. The hub 96 is rotatably mounted on a sleeve bearing which has a flange 94 at one ~377~
, . ~
19 51,774 end and which is secured to the plate 92 by any suitable means, such as a screw passing through the central axis of the hub 96. The flange portion 94 serves as a rotatable support which positions the take-up reel 22 above the surface 93 of the plate 92 and reduces the frictional fGrces therebetween.
In an ideal situation, the central axis 52 of the tape guide roller 80 would be perfectly perpendicular to both the surface 93 of the plate 92 and the direction of travel Dl of the magnetic tape 12. However, in most typical situations, this perfect perpendicularit~ is not achieved. Therefore, as the take-up reel 22 rotates in the direction indicated by arrows R and the magnetic tape 12 is wound onto the take-up reel 22 in the direction indicated by arrow Dl, a deviation from perpendicularity between the central axis 52 and the surface 93 would normally cause the magnetic tape 12 to migrate in a direc-tion toward one of the two faces, 57 or 59. However, with the crowned operative surface 84 of the present invention, the magnetic tape 12 is centered in the central portion of the operative surface 84 and prevented from colliding with either cf the two faces.
The present invention has been described and illustrated with significant specificity in order to more clearly disclose its features. However, it should be understood that the novel concepts of the present inven-tion can very significantly while remaining within the overall scope of the present invention. For e~ample, the precise distance between the faces of the shoulders of the tape guide rollers can vary from those dimensions given above and the radius of curvature of the crowned operative surface, likewise, can vary significantly from the range of values discussed. Therefore, it should be understood that although the present invention has been described and illustrated with specific values, it is not to be con-sidered so limited. Furthermore, although particular recording and reading techniques were discussed in con--\ lZ~3771!~
51,774 junction with the description of the present invention's operation, it should be understood that these techniques do not limit the applications of the present in~ention and other methods are within its scope of uses.
Claims (6)
1. A magnetic tape delivery system, comprising:
a frame structure;
first and second magnetic tape containing reels mounted on said frame structure, said first and second tape reels having axes of rotation that are generally parallel to each other; and a guide roller mounted on an axis on said frame structure, said guide roller being disposed functionally between said first and second tape reels, said guide roller having an operative surface, said operative surface being symmetrical about the axis of said guide roller, said operative surface being convex;
said guide roller having raised portions at each end, said raised portions being spaced apart by a preselected distance, said preselected distance being greater than the width of said magnetic tape.
a frame structure;
first and second magnetic tape containing reels mounted on said frame structure, said first and second tape reels having axes of rotation that are generally parallel to each other; and a guide roller mounted on an axis on said frame structure, said guide roller being disposed functionally between said first and second tape reels, said guide roller having an operative surface, said operative surface being symmetrical about the axis of said guide roller, said operative surface being convex;
said guide roller having raised portions at each end, said raised portions being spaced apart by a preselected distance, said preselected distance being greater than the width of said magnetic tape.
2. A magnetic tape guide roller having a central axis, compris-ing:
an axially central portion defining an operative surface, said operative surface being symmetrical about the said central axis of said guide roller, said operative surface having a first diameter measured perpendicular to said central axis, said operative surface having a second diameter measured perpendicular to said central axis at a first axial end of said operative surface, said operative surface having a third diameter measured perpendicular to said central axis at a second axial end of said operative surface, said second and third diameters being generally equal to each other, said first diameter being larger than said second diameter, first and second shoulders disposed at ax-ially outward portions of said guide roller, each of said first and second shoulders having a face that is generally perpendicular to said central axis, said faces being disposed proximate the axial ends of said operative surface, and said faces being spaced apart by a distance that is greater than the width of said magnetic tape.
an axially central portion defining an operative surface, said operative surface being symmetrical about the said central axis of said guide roller, said operative surface having a first diameter measured perpendicular to said central axis, said operative surface having a second diameter measured perpendicular to said central axis at a first axial end of said operative surface, said operative surface having a third diameter measured perpendicular to said central axis at a second axial end of said operative surface, said second and third diameters being generally equal to each other, said first diameter being larger than said second diameter, first and second shoulders disposed at ax-ially outward portions of said guide roller, each of said first and second shoulders having a face that is generally perpendicular to said central axis, said faces being disposed proximate the axial ends of said operative surface, and said faces being spaced apart by a distance that is greater than the width of said magnetic tape.
3. The tape guide roller of claim 2, wherein:
said operative surface has a generally smooth convex contour.
said operative surface has a generally smooth convex contour.
4. The tape guide roller of claim 2, further comprising:
a central opening extending through said tape guide roller, said central opening being generally cylindrical and concentric about said central axis.
a central opening extending through said tape guide roller, said central opening being generally cylindrical and concentric about said central axis.
5. The tape guide roller of claim 2, wherein:
said operative surface is shaped to receive a predetermined length of magnetic tape in rolling association.
said operative surface is shaped to receive a predetermined length of magnetic tape in rolling association.
6. The tape guide roller of claim 4, wherein:
said central opening is shaped to receive a post in sliding relation therein.
said central opening is shaped to receive a post in sliding relation therein.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US59346784A | 1984-03-26 | 1984-03-26 | |
| US593,467 | 1984-03-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1243778A true CA1243778A (en) | 1988-10-25 |
Family
ID=24374831
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000477250A Expired CA1243778A (en) | 1984-03-26 | 1985-03-22 | Tape cartridge having crowned guides |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU587969B2 (en) |
| BR (1) | BR8501304A (en) |
| CA (1) | CA1243778A (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3132788A (en) * | 1961-10-25 | 1964-05-12 | Axel H Johnson | Tape transporting means for a magnetic recorder |
| US3333753A (en) * | 1965-06-17 | 1967-08-01 | Ampex | Helical scan magnetic tape apparatus with a squeeze film bearing |
-
1985
- 1985-03-18 AU AU40053/85A patent/AU587969B2/en not_active Ceased
- 1985-03-22 BR BR8501304A patent/BR8501304A/en unknown
- 1985-03-22 CA CA000477250A patent/CA1243778A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AU4005385A (en) | 1985-10-03 |
| AU587969B2 (en) | 1989-09-07 |
| BR8501304A (en) | 1985-11-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |