Transport apparatus for a single reel tape cartridge

A tape transport which is sized to fit within an 8 inch form factor or footprint, to accommodate prevailing mini/micro computer applications, and including operative components which are capable of automatically receiving IBM Corporation's 3480-type tape cartridge and the web of tape which it contains for appropriate introduction to the transport for presentation to a high performance magnetic recording head. This permits a use of the 3480 tape cartridge in a transport apparatus which is capable of fitting within an 8 inch form factor or footprint, and which is therfore acceptable for use in connection with many mini/micro computer applications, yet which is capable of providing high performance (parallel track, high transfer rate) storage and retrieval due to its compatability (and interchangeability) with the format used by the IBM Corporation in connection with its 3480 tape cartridge.

BACKGROUND OF THE INVENTION 
The present invention relates generally to the storage of data on magnetic 
recording tape, and in particular, to the storage of data on magnetic tape 
in cartridge form. 
In the course of developing various systems for the storage of data on 
magnetic recording tape, particularly off-line storage of data in the form 
of back-up storage, a variety of different formats have been developed. 
Many of these formats call for the tape to be contained in an appropriate 
cartridge, both to facilitate handling of the tape while in use, and to 
protect the tape while in storage. 
To this end, the IBM Corporation has developed a tape cartridge which is 
primarily intended for use in its Model 3480 data storage system, for the 
storage of relatively large quantities of data (on the order of 200 
megabytes). Details regarding the construction of this type of tape 
cartridge (hereinafter referred to as a 3480 tape cartridge) may be had 
with reference to U.S. Pat. No. 4,452,406. By way of general description, 
the 3480 tape cartridge is comprised of a single reel containing a 
quantity of magnetic tape and contained in a rectangular enclosure having 
dimensions on the order of 4 inches in width, 5 inches in length, and 1 
inch in height. The cartridge enclosure includes an aperture in one of its 
major faces, to receive means for rotating the reel of tape contained 
within the cartridge, and an aperture in one of its corners, for gaining 
access to the free end of the web of tape. A so-called "leader block" is 
connected to the free end of the tape, and is retained within the open 
corner of the cartridge so that it is capable of being withdrawn from and 
replaced within the cartridge by appropriate means. 
In connection with the 3480 tape cartridge, IBM Corporation has also 
developed equipment for receiving the tape cartridge and for properly 
placing the web of tape which it contains in operative association with a 
magnetic read/write head. Further details regarding such equipment may be 
had with reference to U.S. Pat. Nos. 4,432,508; 4,399,959; 4,399,936; and 
4,335,858, which illustrate various different devices which have been 
developed by the IBM Corporation to accommodate its 3480 tape cartridge. 
The 3480 tape cartridge has found wide acceptance in the industry, for a 
variety of reasons. One important reason for this is that unlike other 
types of tape cartridges which have been developed for use in the off-line 
storage of data, the IBM 3480 tape cartridge houses only a single reel of 
magnetic recording tape in a relatively small, space-efficient package. 
The resulting package is therefore conveniently stored and easily used. 
To this end, the leader block which is connected to the free end of the web 
of tape is used to introduce the web of tape to the transport apparatus 
(and the read/write head). The transport apparatus must therefore be 
provided with appropriate means for withdrawing the leader block from its 
nesting within the 3480 tape cartridge, and for threading the leader block 
(and the web of tape) through the apparatus and past the read/write head. 
Of course, means must also be provided for unthreading the web of tape 
(and the leader block) from the apparatus, and for replacing the leader 
block within its nesting in the 3480 tape cartridge. 
To this end, special means must be provided to engage the leader block 
assembly, and to guide the leader block (and the tape which follows) 
through the transport apparatus which is to operate upon the web of tape. 
This requires care in withdrawing the leader block from the tape 
cartridge, and in guiding the web of tape from the supply reel of the tape 
cartridge, past the read/write head, and into engagement with the take-up 
reel which is traditionally provided to cooperate with the supply reel in 
transporting the web of tape through the apparatus and past the read/write 
head. This necessitates the development of an appropriate path for 
threading the leader block through the apparatus, as well as means which 
have sufficient driving forces to withdraw the leader block from its 
normally seated position within the tape cartridge, and to replace the 
leader block within this normally seated position after the tape cartridge 
has been used. To meet these needs, as well as other design requirements 
regarding data density and performance characteristics, those devices 
described in the above-identified United States patents each make use of a 
leader block loading mechanism which is operated by a relatively large, 
dedicated driving motor, leading to significant demands for space and 
power, and overall cost. 
Yet another consideration is that, as with any magnetic tape recording 
apparatus, care must be taken to develop a proper tape path between the 
supply and take-up reels, and across the read/write head, to assure proper 
registration of the tape with the read/write head. To this end, those 
devices described in the above-identified patents each provide a tape path 
of significant length, to account for such potential irregularities. Also 
to be considered in this regard is that care must be taken to avoid 
undesirable contact between the oxide coating provided on the web of 
magnetic recording tape and components such as bearings and idler rollers. 
As a result of these and other design considerations, those devices which 
were originally developed to operate upon the 3480 tape cartridge were 
relatively large, cumbersome and expensive. While this was justifiable in 
connection with relatively large, mainframe computer applications, such 
design constraints tended to limit, and at times even preclude use of the 
3480 tape cartridge in connection with lower cost, minicomputer or 
microcomputer applications. Yet another limiting factor was that of space. 
It was generally impractical, and therefore undesirable, to necessitate 
the purchase of an apparatus for off-line, back-up storage or the like 
which was significantly larger than the primary equipment which the 
apparatus was to support. 
In fact, due to the prevalent use of both 8 inch and 51/4 inch magnetic 
recording (floppy) discs in connection with such applications, de facto 
standards arose for any form of storage equipment (floppy disc, hard disc, 
cartridge, etc.) which would replace or otherwise relate to such 
conventional storage means. The recognized "form factor" or "footprint" of 
a standard 8 inch magnetic recording disc calls for a container or housing 
having dimensions on the order of 8.5 inches in width, 15 inches in depth 
and 5 inches in height. The recognized "form factor" or "footprint" of a 
standard 51/4 inch magnetic recording disc calls for a container or 
housing having dimensions on the order of 53/4 inches in width, 8 inches 
in depth and 31/4 inches in height. Those devices described in the 
above-identified patents were not adaptable to such applications, limiting 
the ability to use the 3480 tape cartridge in mini/micro-computer 
applications. 
Recognizing this, efforts were made to develop tape transports which were 
capable of operating upon a 3480 tape cartridge, and which were also 
capable of being contained within the reduced form factors or footprints 
required in connection with conventional mini/micro computer systems. One 
example of this is the "Patriot" tape transport which is manufactured by 
Computer Peripherals Inc., of Norristown, Pa., which incorporates a 
modified tape path adapted to provide all of the functions necessary to 
properly interface a 3480 tape cartridge with a tape transport, in a 
housing which is sufficiently small to accommodate a 51/4 form factor. 
However, this and other devices which have been developed for this purpose 
have generally required a compromise between the overall size of the 
transport, and its overall performance, particularly in terms of the data 
transfer rates which could be achieved in connection with such systems. 
Accordingly, while providing adequate results in connection with 
relatively low performance systems, it was found that this compromise 
tended to limit the utility of such transport devices for larger systems. 
It therefore became desirable to develop a transport apparatus capable of 
accommodating the reduced form factors or footprints needed for 
conventional mini/micro computer applications, yet which could provide the 
higher performance characteristics which were necessary to satisfy the 
ever-expanding computer technology, and which was capable of operating 
upon data in the same format (parallel track, high transfer rate) as that 
used by the IBM Corporation in connection with its 3480 tape cartridge 
systems, to promote interchangeability with other systems. 
SUMMARY OF THE INVENTION 
It is therefore a primary object of the present invention to provide an 
apparatus for receiving and operating upon an IBM 3480 tape cartridge 
which is sufficiently compact for use in prevailing mini/micro computer 
applications, without an attendant attenuation in performance. 
It is also an object of the present invention to provide such an apparatus 
with appropriate means for engaging the leader block of the tape 
cartridge, and for loading and unloading the magnetic recording tape which 
it contains without compromising the performance of the tape cartridge or 
the transport apparatus. 
It is also an object of the present invention to provide such an apparatus 
with appropriate means for interfacing the web of magnetic recording tape 
with a high performance read/write head, using components capable of 
fitting within the reduced form factor or footprint which is available. 
It is also an object of the present invention to provide such means in an 
apparatus which can operate upon data (read and write) in the same format 
as that used by the IBM Corporation in connection with its 3480 tape 
cartridge systems to promote system interchangeability. 
It is also an object of the present invention to provide such means in an 
apparatus which is simple and reliable in operation, and which is cost 
effective even in connection with mini/micro computer applications. 
These and other objects are achieved in accordance with the present 
invention by providing a tape transport which is sized to fit within a 
standard 8 inch form factor or footprint, to accommodate prevailing 
mini/micro computer applications, and which includes operative components 
capable of automatically receiving a 3480 tape cartridge and the web of 
tape which it contains for appropriate application to the transport for 
presentation to a high performance magnetic read/write head. This permits 
the use of a 3480 tape cartridge in a transport which is capable of 
fitting within the standard 8 inch form factor or footprint which is 
acceptable for use in connection with many mini/micro computer 
applications, and even certain super-mini and mainframe applications, yet 
which is capable of providing high performance data management. 
To this end, a housing is provided which contains traditional supply and 
take-up drive mechanisms, coupled with improved means for receiving 
(loading and unloading) the 3480 tape cartridge and for accommodating 
(loading, unloading, guiding) the leader block of the 3480 tape cartridge 
and the web of tape which follows it, for appropriate presentation of the 
web of tape to a high performance magnetic read/write head. Leader block 
and tape handling are enhanced by a tape threading mechanism which 
incorporates a pair of pivotally interconnected arms which operate to 
transfer the leader block from the tape cartridge to the take-up reel in 
an efficient movement, utilizing a relatively small drive motor, and an 
improved take-up reel for properly receiving the leader block and the web 
of tape which follows it. Proper presentation of the web of tape to the 
magnetic read/write head is achieved by providing an improved tape guide 
assembly which spans the read/write head, coupled with an improved means 
for supplying compressed air to the guide assembly to properly retain the 
oxide coating on the web of tape away from the guiding surfaces without 
requiring an unduly large air supply system for this purpose. The result 
is a transport mechanism which is capable of fitting within the reduced 8 
inch form factor or footprint which is acceptable for many mini/micro 
computer applications, and even certain super-mini and mainframe 
applications, yet which has the overall performance characteristics of the 
significantly larger transport mechanisms which have previously been used 
to operate upon the popular 3480 tape cartridge. 
For further detail regarding a preferred embodiment tape transport in 
accordance with the present invention, reference is made to the detailed 
description which is provided below, taken in conjunction with the 
following illustrations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a transport 1 for receiving and operating upon an IBM 3480 
tape cartridge 2 in accordance with the present invention. To be noted is 
that the transport 1 is sufficiently compact to be received within the 
confines of a standard 8 inch form factor or footprint. 
The transport 1 generally comprises a housing 3 for containing the 
transport apparatus which serves to operate upon the tape cartridge 2 as 
will be more fully described below, and a bezel 4 having a control panel 5 
for use by the operator of the transport 1 and a slot 6 for receiving the 
tape cartridge 2. As shown in FIG. 1, the slot 6 which receives the tape 
cartridge 2 is generally horizontally oriented within the bezel 4, with 
the control panel 5 to one side, and is appropriately sized to slidingly 
receive a tape cartridge 2 within the transport 1. However, other relative 
placements for the control panel 5 and the slot 6 are also possible, if 
desired. For certain applications, it may become desirable to place the 
transport 1 in a vertical orientation. While this can be accomplished in 
straightforward fashion by rotating the transport by 90 degrees, this also 
has the effect of placing the control panel 5 (particularly any indicia 
which it carries) at an improper orientation. To accommodate this, the 
control panel 5 is preferably adjustably attached to the bezel 4, as 
follows. 
FIG. 2 shows a frame 7 which is used to develop the control panel 5. As 
illustrated, the frame 7 (shown from its rear) defines a series of 
cavities 8 for receiving switching and control devices associated with the 
transport 1, and a series of brackets 9, 10 extending from the frame 7 for 
mounting purposes. The brackets 9 are used to mount the various display, 
switching and control elements, and associated printed circuit boards, to 
the frame 7 as desired. The brackets 10 are used to secure the frame 7 
(and accordingly the control panel 5) to the bezel 4. To be noted is that 
the brackets 10 are positioned at an angle (e.g., 45 degrees) to the edges 
11 of the frame 7 so that the prongs 12 of the brackets 10 face the 
corners of the frame 7. In this manner, the mounting brackets 10 are 
positioned to engage mating corners of the bezel 4 in one of four 
orientations (corresponding to potential orientations for the transport 
1). Thus, the orientation of the control panel 5 can be matched to the 
orientation of the transport 1 by withdrawing the frame 7 from the bezel 
4, rotating the frame 7 as desired, and replacing the frame 7 (and 
accordingly the control panel 5) within the bezel 4 in its desired 
orientation. The control panel 5 (once adjusted) is then retained in its 
desired position by the brackets 10 of the frame 7 which engage the bezel 
4 as previously described. 
This arrangement not only allows the control panel 5 to be adjustably 
positioned within the bezel 4, but also permits removal of the control 
panel 5 from the transport 1 for remote operation of the unit (when 
provided with an appropriate extender cable or the like). In any event, 
the result is a compact unit which can conveniently house the control 
circuitry in close proximity to the associated controls. Suitable indicia 
(different legends, symbols, languages, etc.) are effectively applied to 
the frame 7 of the control panel 5 by fitting an indicia bearing template 
13 to the frame 7 so that the template 13 is retained in place (e.g., by 
snapping the template into appropriate slots formed in the frame). 
Adjustment and servicing is therefore easily accomplished by snapping the 
various components of the control panel 5 together as previously 
described. 
Referring now to FIGS. 3 and 4, the tape cartridge 2 generally comprises a 
quantity of tape 15 wound upon a supply reel 16 and contained within a 
housing 17. Suitable means (a geared coupling is conventionally provided 
for this purpose) are provided for placing the supply reel 16 in operative 
association with the corresponding geared, magnetic coupling of a supply 
motor 18 positioned beneath the surface 19 of the transport apparatus 20. 
A corner 21 of the housing 17 is open, and receives a leader block 25 
which is used to securely engage the free end 26 of the web of tape 15 in 
conventional fashion. As produced by the manufacturer, the inwardly facing 
surface 27 of the web of tape 15 is provided with an oxide coating for 
recording purposes. 
The tape cartridge 2 is received (through the slot 6 of the bezel 4) upon 
the loading rack 29 of a cartridge loading/unloading mechanism 30 with the 
leading edge 31 of the tape cartridge 2 facing inwardly toward the center 
of the transport apparatus 20. This operates to place the geared coupling 
of the supply reel 16 of the tape cartridge 2 in general registration with 
the corresponding coupling of the supply motor 18 of the transport 
apparatus 20, while simultaneously engaging a slot 32 which is 
conventionally provided in the leader block 25 of the tape cartridge 2 
with a guide pin 33 which forms part of a leader block loading/unloading 
mechanism 35 which will be described more fully below. The tape cartridge 
2 is initially received upon the loading rack 29 when in a stand-by 
position (see FIG. 5a), which permits the tape cartridge 2 to be inserted 
into and withdrawn from the transport 1 without interference with 
operative features of the transport apparatus 20. Thereafter, the loading 
rack 29 (and the tape cartridge 2) is lowered to an operative position 
(see FIG. 5b) in which the geared coupling of the supply reel 16 becomes 
firmly seated upon the corresponding coupling of the supply motor 18, and 
the leader block 25 becomes firmly seated upon the guide pin 33 of the 
leader block loading/unloading mechanism 35, readying the tape cartridge 2 
for operation within the transport apparatus 20. 
To this end, and referring now to FIGS. 5a and 5b, the cartridge 
loading/unloading mechanism 30 is generally comprised of the loading rack 
29, for receiving the tape cartridge 2, a linkage 36 for moving the 
loading rack 29 relative to the transport apparatus 20, and a camming 
system 37 for regulating such movement responsive to an associated motor 
38. 
The loading rack 29 is generally defined by a supportive base 39 and a tray 
40 which combine to develop a cavity 41 for slidingly receiving the tape 
cartridge 2. The tray 40 is additionally provided with various means for 
effectively receiving and interfacing with the tape cartridge 2, as 
follows. 
A spring 42 is provided in a side 43 of the tray 40 to urge the received 
tape cartridge 2 against the opposite side 44 of the tray 40 to properly 
register the tape cartridge 2 within the cavity 41 of the loading rack 29. 
Also provided in the side 43 of the tray 40 is a spring-loaded guide block 
45 for engaging the leader block 25 of the tape cartridge 2 to positively 
retain the leader block 25 against the tape cartridge 2 in the event that 
the leader block 25 is not firmly seated in the corner 21 which normally 
receives it. Thus, the spring 42 and the guide block 45 operate to place 
the features of the tape cartridge 2 in proper registration with the 
transport apparatus 20 so that these two structures will be properly mated 
following a cartridge loading operation. 
A series of switches are further associated with the tray 40 of the loading 
rack 29 to advise the control circuitry of the transport 1 of the nature 
of the particular cartridge which has been introduced to the cartridge 
loading/unloading mechanism 30. A switch 46 extends from a flange 47 
forming the innermost end of the cavity 41, and is used to detect the 
presence of a cartridge within the cavity 41 of the loading rack 29. The 
flange 47 of the loading rack 29 is additionally provided with a switch 48 
which is used to determine whether or not the "write protection" feature 
of the tape cartridge 2 (which conventionally forms part of that 
cartridge) has been selected by the user. A switch 49 extends from the 
side 44 of the tray 40, and is positioned to detect whether the cartridge 
which has been inserted into the cavity 41 of the loading rack 29 is a 
tape cartridge 2 or a cleaning cartridge of the type adapted for use in 
connection with transports of the present type. The switches 46, 48, 49 
are electrically coupled with appropriate control circuitry associated 
with the transport 1 to operate the transport 1 in accordance with the 
particular features which have been selected by the user (e.g., loading, 
either protected or unprotected, or cleaning). 
The linkage 36 is generally comprised of three interconnected links 51, 52, 
53 extending from opposite sides of the loading rack 29. The uppermost 
link 51 is pivotally connected between the innermost end 54 of the base 39 
of the loading rack 29 and a pivot block 55 fixed to the mounting surface 
50 which supports the cartridge loading/unloading mechanism 30 within the 
transport 1. The lower link 52 is pivotally connected between the 
forwardmost end 56 of the base 39 of the loading rack 29 and a pivot block 
57 which is also fixed to the mounting surface 50. A center link 53 is 
pivotally connected between central portions of the upper link 51 and 
lower link 52, as shown. The links 51, 52, 53 are mutually interconnected 
so that a force applied to the pivot 58 which connects the upper link 51 
to the loading rack 29 will operate to raise and lower the linkage 36, and 
the loading rack 29 which it supports, accordingly raising and lowering 
the tape cartridge 2 responsive to forces applied at the connection 58. 
Loading springs 59 are positioned on opposite sides 43, 44 of the loading 
rack 29 to apply forces against the lower links 52 which operate to load 
the connections 58 against a pair of cams 60 associated with the camming 
system 37 and positioned on opposite sides 43, 44 of the loading rack 29. 
As a result of this, the loading rack 29 can be raised and lowered 
responsive to rotation of the cams 60 about a common drive shaft 61 
responsive to rotation of the motor 38. 
In operation, and as is best shown in FIG. 5a of the drawings, the loading 
rack 29 is normally maintained in a raised position to receive a tape 
cartridge 2 through the slot 6 in the bezel 4 of the transport 1. A tape 
cartridge 2 to be operated upon is inserted into the cavity 41 of the 
loading rack 29, through the slot 6, and is properly positioned within the 
cavity 41 under the influence of the retaining spring 42. The leader block 
is effectively supported in proper position by the guide block 45, 
irrespective of whether the leader block is fully seated within the corner 
21 of the tape cartridge 2. The switches 48, 49 will determine the nature 
of the cartridge which has been inserted into the cavity 41 (e.g., write 
protected or for cleaning). The switch 46 will determine when the tape 
cartridge 2 has been fully inserted into the cavity 41 of the loading rack 
29 and is in contact with the flange 47, signifying that the tape 
cartridge 2 is positioned for a cartridge loading operation to take place. 
Cartridge loading then proceeds by causing the motor 38 to rotate the shaft 
61 in a counter-clockwise direction, lowering the connections 58 and the 
linkage 36 under the influence of the loading springs 59. The cooperating 
links 51, 52, 53 will in turn operate to lower the loading rack 29 from 
its raised position toward the lowered position which is shown in FIG. 5b, 
which operates to firmly seat the leader block 25 (previously engaged by 
the guide pin 33 when the tape cartridge 2 was received within the cavity 
41) upon the guide pin 33 of the leader block loading/unloading mechanism 
35 and to bring the geared coupling of the supply reel 16 of the tape 
cartridge 2 into contact with the corresponding coupling of the supply 
motor 18. As the loading rack 29 approaches this lowered position, a pin 
62 extending from each cam 60 is caused to contact the loading springs 59 
to positively seat the loading rack 29 in its lowermost position (resting 
the tape cartridge 2 upon the seating pegs which are conventionally 
provided for this purpose), and to ready the tape cartridge 2 for 
subsequent operations. 
Following desired operations upon the tape cartridge 2, a cartridge 
unloading procedure is then accomplished by reversing the cams 60, and 
accordingly, the movements of the loading rack 29 which were previously 
described. This is accomplished by reversing the direction of rotation of 
the motor 38, which causes the connections 58 to follow the cams 60, in 
turn raising the loading rack 29 to its uppermost position (FIG. 5a). Two 
features are particularly noteworthy in connection with this rotation of 
the cams 60. 
First, the surface of each cam 60 is provided with a compound curvature 
comprised of a minor portion 63 and a major portion 64. The minor portion 
63 of the cam 60 is configured to gradually raise the loading rack 29, 
while applying significant forces to each connection 58. This is done to 
provide the significant forces which are necessary to break the magnetic 
connection between the geared coupling of the supply reel 16 of the tape 
cartridge 2 and the corresponding coupling of the supply motor 18. 
Thereafter, the major portion 64 of the cam 60 is configured to more 
rapidly raise the loading rack 29 to its uppermost position, since 
significantly reduced forces are then required to do so. 
Second, the pivot 65 which connects each lower link 52 to the forwardmost 
end 56 of the loading rack 29 is received within a slot 66 which is 
elongated in the general (substantially horizontal) direction of the lower 
link 52, so that the loading rack 29 will be caused to assume an angle in 
the course of being transferred from its lowermost position to its raised 
position. This angle serves to reduce the forces which are needed to 
separate the geared coupling of the supply reel 16 from the corresponding 
coupling of the supply motor 18, to further assist the minor portion 63 of 
the cam 60 in performing this function. To be noted is that the elongated 
slot 66 also tends to lower the loading rack 29 in similar, angled 
fashion, easing the placement of the geared coupling of the supply reel 16 
upon the corresponding coupling of the supply motor 18 in the course of a 
cartridge loading operation. 
Upon raising the loading rack 29 to its uppermost position, steps are taken 
to continue to rotate the cams 60 responsive to continued rotation of the 
motor 38, to perform a cartridge ejecting function as follows. An ejection 
cam 67 is additionally associated with the cam shaft 61, and cooperates 
with an ejection lever 68 which is loaded against the cam 67 by an 
appropriate spring 69. The cam 67 is configured so that continued rotation 
of the motor 38 will cause the ejection lever 68 to project from the 
flange 47 of the loading rack 29, as shown in phantom in FIG. 5a, pushing 
the tape cartridge 2 from the cavity 41 which receives it, and ejecting 
the tape cartridge 2 from the slot 6 in the bezel 4. Following this 
cartridge ejection procedure, steps are taken to reverse the motor 38 to 
its center position to ready the loading rack 29 to receive another tape 
cartridge 2. Controlled positioning of the cams 60, 67 is accomplished by 
a slotted disc 70 which is also associated with the cam shaft 61 and which 
cooperates with an appropriate detection device (e.g., a photocell or 
magnetic sensor) to determine the positioning of the cams 60, 67, and 
accordingly, to regulate the above-described cartridge loading and 
unloading procedures. 
Following a cartridge loading procedure as previously described, it becomes 
necessary to withdraw the leader block 25 from the corner 21 of the 
housing 17 for transfer through the transport apparatus 20, past a 
magnetic read/write head 75 and to a take-up reel 74. The take-up reel 74 
is received upon a take-up motor 73 located beneath the surface 19 of the 
transport apparatus 20, permitting the web of tape 15 to be transported 
between the supply reel 16 and the take-up reel 74 responsive to rotation 
of the supply motor 18 and the take-up motor 73, transporting the web of 
tape 15 past the read/write head 75 to achieve desired transfers of data. 
As previously indicated, a primary object of the present invention is to 
provide a tape transport 1 which is capable of assuming an 8 inch form 
factor, yet which is capable of providing performance characteristics 
often associated with larger transport mechanisms. This enhanced 
performance is primarily the result of an enhanced tape path which is 
achieved in accordance with the present invention as will be described 
more fully below, to permit the use of a parallel, 18 track magnetic 
read/write head according to the thirteenth draft of the proposed ANSI 
X3B5 Standard for magnetic tape cartridges of the general type being 
addressed herein, i.e., the IBM 3480 tape cartridge. 
The use of such a tape cartridge in a high-performance, 
parallel-track-formatted transport capable of assuming an 8 inch form 
factor or footprint was previously not possible because of the precision 
necessary to effectively transport a web of magnetic recording tape past 
such a read/write head configuration, generally due to limitations in the 
tape paths which were previously developed for such purposes. However, use 
of such a read/write head in a transport apparatus capable of assuming an 
8 inch form factor or footprint is now permitted by providing the 
transport apparatus 20 with certain improvements, as follows. 
FIG. 6 shows components of a leader block loading/unloading mechanism 35 
which is used to transfer the leader block 25 from the tape cartridge 2 to 
the take-up reel 74 as previously described. Torque for operating the 
leader block loading/unloading mechanism 35 is provided by a motor 76 
which receives a drive coupling 77 and which in turn engages paired arms 
78, 79. The motor 76 is mounted beneath the surface 19 of the transport 
apparatus 20 so that its shaft 80 extends through the surface 19 of the 
transport apparatus 20 and into fixed engagement with the drive coupling 
77, which lies above the surface 19. 
The shaft 80 of the motor 76 also slidingly receives a bearing 81 in the 
uppermost arm 78, enabling the arm 78 to freely rotate about an axis 
defined by the center-line of the shaft 80 (the shaft 80 is further 
received by an upper support 121 which is attached to the surface 19 of 
the transport 1 and which includes a bearing 122 which operates to capture 
the upper arm 78 between the lower arm 79 and the upper support 121). 
Surrounding the bearing 81 is a flange 82 which is provided with a pair of 
slots 83a, 83b for slidingly receiving a pair of driving pins 84a, 84b 
which extend from the coupling 77, to deliver driving forces to the upper 
arm 78 as will be described more fully below. The flange 82 is associated 
with a first end 85 of the arm 78, the opposite end 86 of which is 
provided with the guide pin 33 which is used to engage the slot 32 
provided in the leader block 25 as previously described. 
The lowermost arm 79 is positioned just beneath the upper arm 78, and is 
received by the surface 19 of the transport apparatus 20 at a pivot 87 
which extends from inboard portions 88 of the lower arm 79. One end 89 of 
the lower arm 79 is provided with a pin 90 which projects from the lower 
arm 79 into a configured slot 91 provided in the underside of the upper 
arm 78. The other end 92 of the lower arm 79 is provided with a detent 93 
for avoiding contact with the bearing 81 of the upper arm 78, and a 
longitudinally extending slot 94 for receiving one of the driving pins 84b 
of the drive coupling 77. 
The leader block loading/unloading mechanism 35 shown in FIG. 6 generally 
operates to transfer the leader block 25 from the tape cartridge 2 to the 
take-up reel 74 as follows. The upper arm 78 serves as the primary means 
for accomplishing this transfer, by drawing the leader block 25 through 
the transport apparatus 20 responsive to movement of the guide pin 33 
which is provided at its end 86. The motive forces which are needed for 
this transfer are delivered to the upper arm 78 through an operative 
connection which is developed between the end 107 of the slot 83a in the 
flange 82 and the driving pin 84a of the coupling 77 which engages it. In 
transferring a leader block 25 from the tape cartridge 2 to the take-up 
reel 74, and in returning the leader block 25 from the take-up reel 74 to 
the tape cartridge 2, little energy and therefore relatively small forces 
are necessary during predominant portions of the resulting transfer path 
(shown as 95 in FIG. 7 of the drawings). However, there are two exceptions 
to this which must be accounted for. 
One portion of the leader block transfer path 95 in which significantly 
increased forces are required is to positively withdraw the leader block 
25 from its nesting 97 within the corner 21 of the tape cartridge 2, as 
well as to replace the leader block 25 within this nesting 97 prior to 
removal of the tape cartridge 2 from the transport 1. To provide the 
increased motive forces which are necessary, without necessitating an 
increase in the size of the motor 76 (which can otherwise be kept 
relatively small), the lower arm 79 is configured to assist in both the 
withdrawal of the leader block 25 from the tape cartridge 2, as well as 
its replacement within the tape cartridge 2, by imparting a levering 
action to the resulting assembly. This is generally accomplished by 
rotating the driving pin 84b within the slot 94 of the lower arm 79, 
rotating the lower arm 79 about the pivot 87. This in turn develops a 
lever which operates to amplify the forces which are produced at the drive 
pin 90, "snapping" the leader block from its nesting 97 during a tape 
threading operation, and "snapping" the leader block back into its 
nesting 97 following a leader block unloading procedure. 
The other portion of the leader block transfer path 95 in which properly 
directed forces are required involves unloading of the leader block 25 
from the take-up reel 74, to positively unseat the leader block 25. The 
forces which are necessary to accomplish this are provided by the pre-load 
spring 100a of a spring-pin clutch 100 which is pivotally connected 
between the upper arm 78 and the drive pin 84a, and which serves to apply 
sufficient forces to the leader block 25 to withdraw the leader block 25 
from the take-up reel 74 in the course of a leader block unloading 
procedure. 
Further detail regarding each of these operations is provided below, with 
reference to FIGS. 7 to 11 and 13, which illustrate a typical leader block 
loading/unloading procedure. 
FIG. 7 illustrates a transport 1 having a tape cartridge 2 seated within 
its cartridge loading rack 29, and ready (loading rack 29 lowered) for a 
leader block loading operation (structural detail of the remainder of the 
cartridge loading/unloading mechanism 30 has been deleted for illustrative 
purposes only). It will be understood that resulting from such placement, 
the guide pin 33 of the leader block loading/unloading mechanism 35 will 
be seated within the slot 32 of the leader block 25, ready for a leader 
block loading procedure to commence, but that the leader block 25 will be 
nested in the corner 21 of the tape cartridge 2 so that the tip 101 of the 
leader block 25 is retained behind a flange 102 in the cartridge housing 
17, securing the leader block 25 in its stored position. 
As previously indicated, the amount of force required to snap the leader 
block 25 from its nesting 97, by causing the tip 101 of the leader block 
25 to pass the flange 102 of the housing 17, will generally be 
significantly more than that which the motor 76 is capable of providing to 
the upper arm 78 of the leader block loading/unloading mechanism 35 (to 
permit the use of a motor 76 which is reduced in size for reasons 
previously described). However, the lower arm 79 is available for this 
purpose, as follows. 
Rotation of the coupling 77 causes the driving pins 84a, 84b to advance in 
a counter-clockwise direction within the slots 83a, 83b of the upper arm 
78. As a result of this, the driving pin 84b applies a motive force to the 
slot 94 of the lower arm 79, causing the pin 90 of the arm 79 to rotate 
(also counter-clockwise but on a much smaller radius) about the pivot 87. 
This in turn forces the pin 90 of the lower arm 79 against the sloping 
edge 103 of the slot 91 provided in the upper arm 78, urging the end 86 of 
the upper arm 78 away from the tape cartridge 2. The resulting mechanical 
advantage operates to amplify the forces produced at the drive pin 90 (in 
effect amplifying the forces produced by the motor 76), which are then 
sufficient to cause the tip 101 of the leader block 25 to pass the flange 
102 of the housing 17, releasing the leader block 25 from the tape 
cartridge 2. To be noted is that during this operation, and so that the 
appropriate mechanical advantage can be developed, the coupling 77 and the 
driving pins 84a, 84b will be caused to proceed through an angle of 
rotation which is larger than that which is appropriate for the upper arm 
78. This is accommodated by the slots 83a, 83b and the spring-pin clutch 
100, which combine to effectively decouple the upper arm 78 from the 
driving pins 84a, 84b while the drive pin 90 is acting upon the upper arm 
78 as previously described. 
Such counter-clockwise movement of the coupling 77 causes the lower arm 79 
to rotate to the position 105 which is shown in FIG. 8. This permits the 
driving pin 84b to pass from the slot 94 in the lower arm 79, and continue 
its counter-clockwise rotation. What is more, in the course of this 
rotation (which is only on the order of 15 degrees of movement of the 
coupling 77), the pin 90 is caused to move along the slot 91 of the upper 
arm 78, until the pin 90 comes into general alignment with an opening 106 
provided in the slot 91 which extends laterally to the exterior of the 
upper arm 78. This motion serves to disconnect the upper arm 78 from the 
lower arm 79 so that the upper arm 78 is then free to rotate (beyond the 
limited movement of the lower arm 79) in a counter-clockwise direction 
resulting from contact between the driving pin 84a of the coupling 77 and 
the end 107 of the slot 83a in the upper arm 78 (to reduce potential 
timing problems, the slot 83b is preferably elongated relative to the slot 
83a so that rotation of the upper arm 78 results only from contact between 
the driving pin 84a and the slot 83a). To be noted is that the spring-pin 
clutch 100 operates to maintain the proper orientation of the slot 91 in 
the upper arm 78 relative to the pin 90 in the lower arm 79 during this 
transfer in control of the upper arm 78 from the drive pin 90 to the 
driving pin 84a, resulting from the pre-load of the spring 100a which is 
connected between the end 108 of the spring-pin clutch 100 and the pivot 
block 113 of the upper arm 78. A spring 109 (see FIG. 6) is provided to 
retain the disengaged lower arm 79 in this position, for subsequent 
engagement during return of the leader block 25 to the tape cartridge 2 as 
will be described more fully below. 
The arm 78 is then caused to proceed through an arcuate transfer path 95 
(referring to FIG. 9) extending from the corner 21 of the tape cartridge 2 
to the take-up reel 74, under the influence of the motor 76. To be noted 
is that the motor 76 is fully sufficient to provide the relatively small 
torque which is necessary to accomplish this latter transfer. 
As is conventional, the take-up reel 74 includes a nest 110 which is 
configured to slidingly receive the leader block 25 and complete the 
periphery of the hub 115 of the take-up reel 74. To prepare the take-up 
reel 74 to receive the leader block 25, steps are taken to properly orient 
the nest 110 (using techniques which are otherwise known) so that 
continued counter-clockwise rotation of the upper arm 78 will bring the 
engaged end 111 of the leader block 25 to the nest 110 of the take-up reel 
74 (referring to FIG. 10 of the drawings), eventually causing the end 111 
to enter the nest 110. This continues until such time as the leader block 
25 is caused to fully seat within the nest 110 (referring to FIG. 11 of 
the drawings), so that the trailing end 112 of the leader block 25 is in 
general alignment with (and therefore completes) the periphery of the hub 
115 of the take-up reel 74. 
It has been found that the orientation of the leader block 25 which results 
from the relationship between the engaged slot 32 of the leader block 25 
and the web of tape 15 which extends from the leader block 25, is not 
ideally suited to entry of the nest 110 as the leader block 25 approaches 
the take-up reel 74. For this reason, and with reference to FIG. 12 of the 
drawings, the flanges 116, 117 of the take-up reel 74 are provided with 
correspondingly configured tracks 118 which operate to initially receive 
the leader block 25 and to thereafter guide the leader block 25 into the 
nest 110. This is accomplished by causing the side edge 119 of the leader 
block 25 to pass along the tracks 118 (see FIG. 10), in turn causing the 
leader block 25 to rotate from its initial position, as received prior to 
entering the nest 110, to a position (generally radial) which is 
appropriate for proper entry into the nest 110. To be noted is that this 
is accomplished without requiring additional guides or other structures to 
properly insert the leader block 25 into its nesting, at 110. Also to be 
noted is that the opposed tracks 118 are enlarged in relation to the 
distance between the flanges 116, 117 to assist passage of the leader 
block 25 into the nest 110 while assuring that the web of tape 15 which 
follows is properly received between the flanges 116, 117 during 
subsequent tape transport (to reduce tape pack slippage). 
This, in turn, serves to complete the leader block loading operation, 
readying the transport apparatus 20 for further data processing. It is 
preferred that during such operations, contact between the guide pin 33 
and the slot 32 of the leader block 25 should be kept to a minimum, if not 
avoided, and it is therefore preferred to provide a relatively wide 
tolerance between the guide pin 33 and the slot 32 to avoid contact 
between these components when the leader block 25 remains seated within 
the nest 110. 
This continues until such time as the transfer of data which is desired is 
completed, and a leader block unloading operation is to take place. This 
is initiated by rotating the coupling 77 in a clockwise direction, causing 
the driving pin 84a to apply a compressive force to the end 108 of the 
spring-pin clutch 100. Resulting from this, a reactive force is applied by 
the opposite end of the spring-pin clutch 100 to the pivot block 113 on 
the upper arm 78. This force causes the upper arm 78 to rotate in a 
clockwise direction, withdrawing the leader block 25 from the nest 110 and 
causing the leader block to progress toward the tape cartridge 2, along 
the transfer path 95, responsive to continued clockwise rotation of the 
upper arm 78. To be noted is that the tracks 118 also operate to 
facilitate a controlled withdrawal of the leader block 25 from the hub 115 
of the take-up reel 74 by properly orienting the leader block 25 for 
eventual return to the tape cartridge 2. 
Referring to FIG. 13 of the drawings, this will continue until such time as 
the leader block 25 is positioned just outside of the corner 21 of the 
housing 17, and is ready for reinsertion into its nesting 97. In the 
course of reaching this position, the opening 106 in the slot 91 of the 
upper arm 78 will engage the pin 90 of the lower arm 79, and the pin 84b 
of the coupling 77 will engage the slot 94 of the lower arm 79. To be 
noted is that the spring-pin clutch 100 and the spring 109 operate to 
correctly position the upper arm 78 relative to the lower arm 79 in the 
course of this transfer. This will in turn cause the lower arm 79 to 
rotate in a generally clockwise orientation with respect to the pivot 87, 
in turn causing the pin 90 to engage the sloping edge 120 of the slot 91. 
The resulting levering action again operates to provide sufficient force 
to cause the tip 101 of the leader block 25 to pass the flange 102 of the 
housing 17, returning the leader block to its seated position within the 
tape cartridge 2. The tape cartridge 2 is then ready for ejection from the 
transport 1, as previously described. 
FIG. 14 shows an alternative embodiment leader block loading/unloading 
mechanism 35' which may be used to transfer the leader block 25 from the 
tape cartridge 2 to the take-up reel 74. Torque for operating the leader 
block loading/unloading mechanism 35' is again provided by a motor 76'. 
However, in this case the motor 76' is mounted to a raised portion 124 of 
the surface 19 of the transport apparatus 20, as shown in phantom in FIG. 
4 of the drawings, which places the support for the motor 76' within the 
curve of the lower arm 79' and in close proximity to the upper arm 78' of 
the alternative embodiment leader block loading/unloading mechanism 35'. 
This has been found to be particularly beneficial in reducing the 
cantilevered length of the shaft 80' of the motor 76', eliminating the 
need for the upper support 121 which is used to properly support the 
leader block loading/unloading mechanism 35. 
The shaft 80' of the motor 76' engages a coupling 125. The top of the 
coupling 125 defines a bearing 126 for receiving a first end 127 of the 
upper arm 78' so that the upper arm 78' is free to rotate between the top 
of the coupling 125 and a finishing cap 128, and about an axis defined by 
the center-line of the shaft 80' (and the coupling 125). The opposite end 
86' of the upper arm 78' again includes the guide pin 33 for engaging the 
leader block 25 of the tape cartridge 2. To be noted is that the bearing 
126 develops a broad support area for receiving the end 127 of the upper 
arm 78', so that the upper arm 78' is less subject to drooping or play due 
to wear. Also extending from the top of the coupling 125 is a driving pin 
130, which is received by a slot 131 formed in the end 127 of the upper 
arm 78' to deliver driving forces to the upper arm 78' as will be 
described more fully below. 
The lower arm 79' is again positioned just beneath the upper arm 78', and 
is pivotally associated with the surface 19 of the transport apparatus 20, 
at 87. The end 89' of the lower arm 79' is again provided with a pin 90' 
which projects from the lower arm 79' into a configured slot 91' provided 
in the underside of the upper arm 78'. However, the other end 129 of the 
lower arm 79' is now fitted with a follower 132 for engaging a camming 
track 133 formed in the bottom of the coupling 125. To be noted is that 
this arrangement operates to remove the lower arm 79' from between the 
upper arm 78' and the coupling 125, which permits the supporting portion 
124 of the surface 19 to be raised closer to the coupling 125, and which 
in turn allows the cantilevered length of the shaft 80' to be reduced as 
previously described. 
The leader block loading/unloading mechanism 35' shown in FIG. 14 generally 
operates to transfer the leader block 25 from the tape cartridge 2 to the 
take-up reel 74 as follows. The upper arm 78' again serves as the primary 
means for accomplishing this transfer, by drawing the leader block 25 
through the transport apparatus 20 responsive to movement of the guide pin 
33. The motive forces which are needed for this transfer are delivered to 
the upper arm 78' through the operative connection which is developed 
between a pair of springs 134, 136 associated with the upper ar 78' and 
the driving pin 130 of the coupling 125 which engages them. As before, in 
transferring a leader block 25 from the tape cartridge 2 to the take-up 
reel 74, and in returning the leader block 25 from the take-up reel 74 to 
the tape cartridge 2, little energy and therefore relatively small forces 
are necessary during predominant portions of the resulting transfer path 
(shown as 95' in FIG. 15 of the drawings). However, the following two 
exceptions must again be accounted for. 
To provide the increased motive forces which are required to positively 
withdraw the leader block 25 from its nesting 97 within the corner 21 of 
the tape cartridge 2, as well as to replace the leader block 25 within 
this nesting 97 prior to removal of the tape cartridge 2 from the 
transport 1, without necessitating an increase in the size of the motor 
76', the lower arm 79' again operates to assist in both the withdrawal of 
the leader block 25 from the tape cartridge 2, as well as its replacement 
within the tape cartridge 2, by imparting a levering action to the 
resulting assembly. This is generally accomplished by rotating the 
coupling 125 so that the track 133 will act upon the follower 132 which 
extends from the lower arm 79', rotating the lower arm 79' about the pivot 
87. This again develops a lever which operates to amplify the forces which 
are produced at the drive pin 90', "snapping" the leader block from its 
nesting 97 during a tape threading operation, and "snapping" the leader 
block back into its nesting 97 following a leader block unloading 
procedure. 
The other portion of the leader block transfer path 95' in which properly 
directed forces are again required is to assure proper unloading of the 
leader block 25 from the take-up reel 74, to positively unseat the leader 
block 25. The forces which are necessary to accomplish this are provided 
by a leaf spring 134 associated with the upper arm 78', which serves to 
apply sufficient forces to the leader block 25 to withdraw the leader 
block 25 from the take-up reel 74 when this becomes necessary. 
Further detail regarding these operations is provided below with reference 
to FIGS. 15 to 19, which illustrate a typical leader block 
loading/unloading procedure. 
FIG. 15 illustrates a transport 1 having a tape cartridge 2 seated in the 
cartridge loading rack 29, and ready (loading rack 29 lowered) for a 
leader block loading operation (further detail regarding the cartridge 
loading/unloading mechanism 30 is again deleted for purposes of 
illustration). As before, the amount of force required to snap the leader 
block 25 from its nesting 97 will significantly exceed the amount of 
energy which the motor 76' is capable of providing to the upper arm 78' of 
the leader block loading/unloading mechanism 35'. However, the lower arm 
79' is again available for this purpose, as follows. 
Rotation of the coupling 125 in a counter-clockwise direction causes the 
follower 132 to progress along the configured portion 135 of the track 133 
which is shown in FIG. 14a, in turn causing the lower arm 79' to rotate 
the drive pin 90' (also counter-clockwise but on a much smaller radius) 
about the pivot 87. This operates to force the pin 90' of the lower arm 
79' against the edge of the slot 91' provided in the upper arm 78', urging 
the end 86' of the upper arm 78' away from the tape cartridge 2. The 
resulting mechanical advantage operates to amplify the forces produced at 
the drive pin 90' (accordingly amplifying the forces produced by the motor 
76'), which are then sufficient to cause the tip 101 of the leader block 
25 to pass the flange 102 of the housing 17, releasing the leader block 25 
from the tape cartridge 2. During this operation, the coupling 125 and the 
driving pin 130 will be caused to proceed through an angle of rotation 
which is larger than that which is appropriate for the upper arm 78', 
again so that the appropriate mechanical advantage can be developed. This 
is accommodated by the slot 131 formed in the upper arm 78', which 
operates to effectively decouple the upper arm 78' from the driving pin 
130 while the drive pin 90' is acting upon the upper arm 78'. 
This counter-clockwise movement of the coupling 125 causes the lower arm 
79' to rotate to the position 105' which is shown in FIG. 16, and to bring 
the driving pin 130 into contact with a driving spring 136 associated with 
the upper arm 78'. In the course of this rotation (which is again on the 
order of 15 degrees of movement of the coupling 125), the pin 90' is 
caused to move along the slot 91' of the upper arm 78', until the pin 90' 
is brought into general alignment with the opening 106' provided in the 
slot 91' which extends laterally to the exterior of the upper arm 78'. 
This motion serves to disconnect the upper arm 78' from the lower arm 79' 
so the upper arm 78' is then free to rotate (beyond the limited movement 
of the lower arm 79') in a counterclockwise direction, toward the take-up 
reel 74. 
Continued movement of the upper arm 78' is accomplished through continued 
rotation of the driving pin 130 (by the coupling 125) against the driving 
spring 136, causing the leader block 25 to proceed through the arcuate 
transfer path 95' (referring to FIG. 17) which extends from the corner 21 
of the tape cartridge 2 to the take-up reel 74, under the influence of the 
motor 76'. During this period, the follower 132 is caused to progress 
along constant radius portions 137 of the track 133 (see FIG. 14a), 
transferring control of the upper arm 78' from the drive pin 90' to the 
driving pin 130 while simultaneously maintaining the lower arm 79' in 
proper position for subsequent engagement during return of the leader 
block 25 to the tape cartridge 2 as will be described more fully below. To 
be noted is that the motor 76' is again fully sufficient to provide the 
relatively small torque which is necessary to accomplish this transfer, 
and that the configured tracks 118 of the take-up reel 74 will again 
assist in properly delivering the leader block 25 to the nest 110 formed 
in the hub 115 of the take-up reel 74 (FIG. 18) as previously described. 
A typical leader block unloading operation is initiated by rotating the 
coupling 125 in a clockwise direction, so that the driving pin 130 will 
apply a compressive force against the leaf spring 134. This force causes 
the upper arm 78' to rotate in a clockwise direction, withdrawing the 
leader block 25 from the nest 110 and causing the leader block 25 to 
progress toward the tape cartridge 2, along the transfer path 95', 
responsive to continued clockwise rotation of the upper arm 78'. The 
tracks 118 again operate to facilitate a controlled withdrawal of the 
leader block 25 from the hub 115 of the take-up reel 74 in the course of 
this transfer. To be noted is that the leaf spring 134 will operate to 
provide sufficient force to withdraw the leader block 25 from the nest 
110, even in the event that these two structures have come to stick to one 
another resulting from operation of the transport 1, due to continued 
compression of the leaf spring 134 by the driving pin 130. In extreme 
circumstances, it is even possible for the driving pin 130 to travel the 
length of the slot 131, contacting the end 138 of the slot to positively 
withdraw the leader block 25 from the nest 110. In such cases, the leaf 
spring 134 will operate to return the upper arm 78' to its correct 
alignment relative to the coupling 125, to properly align the upper arm 
78' (the slot 91') for proper engagement by the lower arm 79' (the pin 
90') as the leader block 25 approaches the tape cartridge 2. 
Referring to FIG. 19 of the drawings, rotation of the upper arm 78' will 
continue until such time as the leader block 25 is positioned just outside 
of the corner 21 of the housing 17, and is ready for reinsertion into its 
nesting 97. In the course of reaching this position, the opening 106' in 
the slot 91' of the upper arm 78' will engage the pin 90' of the lower arm 
79', and the follower 132 of the lower arm 79' will be returned to the 
configured portion 135 of the track 133. Continued clockwise rotation of 
the coupling 125 will cause the follower 132 to traverse the configured 
portion 135 of the track 133, which will in turn cause the lower arm 79' 
to rotate the drive pin 90' in a generally clockwise direction with 
respect to the pivot 87, and against the edge of the slot 91'. This 
levering action will again operate to provide sufficient force to cause 
the tip 101 of the leader block 25 to pass the flange 102 of the housing 
17, returning the leader block to its seated position within the tape 
cartridge 2. The tape cartridge 2 is accordingly made ready for ejection 
from the transport 1, as previously described. 
The leader block loading/unloading mechanism 35' operates to develop a 
highly controlled means for transferring the leader block 25 between the 
tape cartridge 2 and the take-up reel 74. For example, it is important to 
reduce potential impacts upon the reducing gears of the motor which 
operates the mechanism, to maximize its service life. The leader block 
loading/unloading mechanism 35' generally operates to reduce impacts upon 
the motor gears, at each end of the mechanism's travel by permitting an 
appropriate overtravel of those components of the mechanism which might 
tend to produce such undesirable impacts, as follows. 
Following a leader block loading operation, steps are taken to decouple the 
upper arm 78' from the driving pin 130 by lengthening the slot 131 which 
receives it (as well as the track 133 of the coupling 125). Accordingly, 
when the upper arm 78' comes to a stop (and the motor 76' is shut off), 
continued rotation of the motor 76' and coupling 125 is permitted to avoid 
an adverse impact upon the motor gears. This continued rotation is limited 
and controlled by the driving spring 136, which operates to receive the 
driving pin 130 and resist its counter-clockwise progression (as shown in 
phantom at 140 in FIG. 18) until power to the motor 76' is discontinued, 
and to thereafter return the driving pin 130 to its nominal position 
relative to the upper arm 78'. A stepped reaction is preferably provided 
for this purpose by providing a knee 141 in the spring 136 which, 
following contact with the edge 142 of the upper arm 78', serves to 
increase the reactive force which is then applied to the then-rotating 
driving pin 130. 
Power to the motor 76' is discontinued responsive to a flag 146 which 
extends from the upper arm 78', and which operates in combination with an 
interrupt sensor 147 which is fixed upon the transport apparatus 20, as 
follows. Just before the leader block 25 becomes seated within the nest 
110 of the take-up reel 74, the flag 146 operates upon (interrupts a beam) 
the interrupt sensor 147. A suitable time delay is then allowed to be 
certain that the leader block 25 has become fully seated, at which time 
electrical power to the motor 76' is discontinued and the motor 76' is 
stopped (or in the process of being stopped) by the driving spring 136, as 
previously described. The energy which is stored by the driving spring 136 
then acts to rotate the driving pin 130 (clockwise) back to a neutral 
position (where no forces are exerted on either of the springs 134, 136). 
This, in turn, allows the guide pin 33 of the upper arm 78' to "float" 
freely within the slot 32 of the leader block 25 so that no contact forces 
(and therefore no wear) occur at this interface during subsequent rotation 
of the take-up reel 74. 
In the course of a leader block unloading operation, steps are taken to 
stop the motor 76' as the follower 132 leaves the configured portion 135 
of the track 133, which generally corresponds to a seating of the leader 
block 25 in its nesting 97, and a dwell zone 143 is provided in the track 
133 (see FIG. 14a) to permit an appropriate overrun of the motor 76' 
following its shut-down. The dwell zone 143 is preferably increased to a 
sufficient length to receive the follower 132 without requiring a 
carefully timed shut-down of the motor 76'. Moreover, because the dwell 
zone 143 is radial to the center of the coupling 125, no motion of the arm 
79' is produced while the follower 132 traverses this zone. 
Power to the motor 76' is again discontinued responsive to a flag 148, 
which in this case extends from the coupling 125, and which again operates 
upon (interrupts the beam) the interrupt sensor 147. As the follower 132 
enters the dwell zone 143, the flag 148 is caused to interact with the 
interrupt sensor 147 (see FIG. 19), which in turn operates to discontinue 
the power to the motor 76'. Appropriate dynamic braking is then applied to 
the motor 76' to stop the motor while the follower 132 lies within the 
dwell zone 143. 
To be noted is that the leaf spring 134 will generally apply an undesirable 
resistive force to the driving pin 130 (and accordingly the motor 76') 
when seating of the leader block 25 within the nesting 97 of the tape 
cartridge 2 is in progress (and when increased operating forces are 
required). However, this potentially adverse affect is reduced because the 
forces involved are then being applied in a direction which is generally 
tangent to the direction of motion of the driving pin 130. 
In the course of a leader block unloading procedure, it becomes necessary 
to ensure that the leader block 25 has been properly seated in the nesting 
97 irrespective of its broad tolerances, and that the guide pin 33 is 
returned to the position which is proper for accepting another tape 
cartridge after operations upon the tape cartridge 2 have been completed. 
A spring-loaded overdriving feature is therefore provided as follows, with 
reference to FIG. 14a of the drawings. In the event that the leader block 
25 becomes fully seated in the nesting 97 before the coupling 125 has had 
an opportunity to complete its intended rotation (to draw the follower 132 
fully along the configured portion 135 of the track 133), a spring loaded 
gate 145 is provided to allow the driving pin 130 to pass from the 
configured portion 135 of the track 133 to the dwell zone 143 (to complete 
the unloading operation as previously described without an undesirable 
impact upon the gears of the motor 76') by rotating out of the way as 
shown in phantom in FIG. 14a, at 144. The shape of the active region 
represented by the configured portion 135 of the track 133 serves to 
produce a maximum required motion at the peak 149, which then backs off 
before the dwell zone 143 is entered. 
To further assist in reducing impacts upon the motor's gears during the 
above-described leader block loading and unloading operations, steps are 
preferably taken to reduce the voltage (then at a maximum) which is 
ordinarily applied to the motor 76' during the predominant portions of its 
travel to a decreased level slightly before the end of its travel in the 
course of a leader block loading or unloading procedure. This operates to 
reduce the speed of the motor 76' at the end of its anticipated travel, 
further assisting in reducing the forces which are applied to the motor 
gears. This is accomplished in otherwise conventional fashion, using the 
available Hall effect sensors of the motor which determine the approximate 
position of the upper arm 78' in the course of its operation. 
The leader block loading/unloading mechanism 35' also operates to 
effectively locate the various components of the mechanism for proper 
operation as previously described. Specifically, the track 133 operates to 
maintain the lower arm 79' in proper position to receive the upper arm 78' 
during a leader block unloading operation, without the need for a 
retaining spring such as the spring 58 of the lower arm 79, and assures 
that the drive pin 90' is moving under control as it engages and 
disengages the slot 91' of the upper arm 78' (by controlling movement of 
the follower 132 within the track 133 fully along its travel through the 
configured region 135). This operates to minimize impacts and assure a 
continuous motion of the leader block 25 in both directions. 
As previously indicated, in order to provide a transport apparatus 20 which 
is capable of fitting within an 8 inch form factor or footprint yet which 
is capable of providing performance characteristics generally associated 
with somewhat larger equipment, it is not only necessary to provide an 
appropriate leader block loading/unloading mechanism but also to provide 
an improved tape path which is capable of properly guiding the web of tape 
15 within the transport apparatus 20 despite the relatively short tape 
transfer path which is available. A variety of features are provided for 
this purpose. 
For example, one important aspect of proper tape path control within the 
transport apparatus 20 relates to the manner in which the web of tape 15 
is wound upon the take-up reel 74. Important in this regard are the manner 
in which the leader block 25 is seated within the nest 110, as well as 
packing of the web of tape 15 upon the hub 115 of the take-up reel 74. The 
transport apparatus 20 of the present invention is therefore provided with 
a take-up reel 74 which is specially configured to accommodate these two 
needs, with reference to FIG. 20 of the drawings. 
Generally speaking, the take-up reel 74 is comprised of a hub 115 and 
spaced flanges 116, 117 as previously described. A variety of resilient 
materials may be used to form these various structures. 
It is important to properly configure the nest 110 which receives the 
leader block 25 so that the leader block 25 is securely received within 
the nest 110, and so that the end 112 of the leader block 25 will properly 
correspond with the periphery 150 of the hub 115. The reason for this is 
to make sure that these two structures co-terminate with one another to 
avoid discontinuities at this interface which could cause irregular 
packing of the web of tape 15. 
Potential defects are minimized by providing a nest 110 for the leader 
block 25 which is not only correspondingly configured to the leader block 
25, but which further includes an entranceway, at 151, which is provided 
with an opposing pair of cantilevered arms 152 positioned at the periphery 
150 of the hub 110. This results in an appropriately configured nest 110 
which is capable of slidingly receiving the leader block 25 during initial 
leader block loading, but which is later capable of closing down upon the 
seated leader block 25 as the web of tape 15 is wound upon the hub 115. 
This is accomplished by forming the cantilevered arms 152 of a resilient, 
elastically deformable material (i.e., of appropriate elasticity and 
having a geometric cross-section of appropriate rigidity) so that as the 
web of tape 15 is wound upon the hub 115, compression of the cantilevered 
arms 152 at the periphery 150 will cause lateral faces 153 of the 
cantilevered arms 152 to deflect inwardly, engaging terminating portions 
154 of the leader block 25 and completing the periphery 150. Preferably, 
this is accomplished by configuring each of the cantilevered arms 152 to 
progressively and continuously decrease in thickness (and stiffness) from 
the hub 115 to the lateral faces 153, to uniformly and progressively 
collapse the cantilevered arms 152 down upon the terminating portions 154 
of the leader block 25. In this fashion, it is possible to develop an 
interface between the leader block 25 and the hub 115 which is virtually 
free of discontinuities, and which actually serves to uniformly locate 
(center) the leader block 25 within the nest 110. 
To be noted is that the inherent resiliency of the cantilevered arms 152 
also serves to facilitate the release of the leader block 25 from the nest 
110 of the hub 115, by causing the lateral faces 153 to separate from the 
terminating portions 154 of the leader block 25, in turn releasing the 
leader block 25 for removal from the nest 110 as previously described. Of 
course, a certain degree of sticking between the leader block 25 and the 
nest 110, particularly between the lateral faces 153 of the cantilevered 
arms 152 and the terminating portions 154 of the leader block 25, will 
also be accommodated by the spring-pin clutch 100 of the leader block 
loading/unloading mechanism 35 and the leaf spring 134 of the leader block 
loading/unloading mechanism 35', which also serve to break this contact 
and free the leader block 25 for withdrawal from the nest 110. 
Yet another aspect of proper tape path control is that of tape packing upon 
the hub 115. Again for the purpose of minimizing irregularities, it is 
important for the web of tape 15 to be packed upon the hub 115 of the 
take-up reel 74 so that the resulting pack remains balanced (round) and 
consistently positioned upon the take-up reel 74. To this end, the hub 115 
of the take-up reel 74 is provided with a honey-comb structure 155 which 
permits a uniform and limited, yet controlled deformation (collapse) of 
the hub 115 responsive to packing of the web of tape 15 upon it. This 
permits a marginal deformation of the hub 115 to adjust to mechanical 
tolerances within the system, as well as non-uniform tape tensions. More 
importantly, this permits the hub 115 to collapse uniformly (maintaining a 
cylindrical shape), avoiding the tendency for the web of tape 15 to ride 
up on the tape pack due to non-uniformity. The honey-comb type structure 
155 preferably takes the form of a plurality of radially projecting ribs 
156 which terminate in a plurality of sectors 157 which extend to the 
periphery 150 of the hub 115. These structures serve to provide adequate 
support for the web of tape 15 which is received upon the hub 115, while 
permitting the limited deformation (collapsibility) which is desirable for 
enhanced tape packing. 
Yet another important consideration relates to the overall tape path for 
the transport apparatus 20, and the configuration of the magnetic 
read/write head 75 and the tape guides which surround it to assure an 
appropriate tape wrap about the head 75 within the confines of the 
available tape path. To correctly establish these factors, a head/guide 
assembly 160 is provided which essentially operates to define the tape 
path for the transport apparatus 20. Referring to FIG. 21 of the drawings, 
the head/guide assembly 160 is generally comprised of a right guide 161 
(FIGS. 22 and 23) and a pair of left guides 162, 163 (FIGS. 24 and 25) 
Which are positioned on opposite sides of the head 75 and which are 
mounted to a common plate 165. Common mounting of these components is 
preferable for ease of set-up and subsequent servicing since the necessary 
adjustments for the head 75 can be made separately from the transport 
apparatus 20, prior to replacing the assembly within the transport 
apparatus 20 after any necessary adjustment and/or servicing has been 
completed. To be noted is that the head/guide assembly 160 is also well 
adapted to moveable head assemblies, in addition to the fixed head 
assembly which has been selected for illustration in the drawings. In 
either case, the read/write head 75 is preferably mounted to the plate 165 
by an adjustable skew plate 166 to facilitate adjustments of head wrap, 
squareness and azimuth. 
Each of the guides 161, 162, 163 generally takes the form of an air bearing 
and is therefore a hollow structure. A preferred construction for this 
purpose is to provide a hollow body 167 formed from graphite filled 
plastic, which is in turn covered by a correspondingly curved metal foil 
168. The metal foil 168 is provided with a series of apertures 169 for 
metering compressed air to the surface of the guides 161, 162, 163, to 
effectively space the web of tape 15 from the surface of the guides 161, 
162, 163 in conventional fashion. The metal foil 168 is also provided with 
appropriate means for locating the structure and to provide a low 
impedance ground path (for static discharge). For example, the metal foil 
168 can be provided with a depending tab 170 (see FIG. 25) for locating 
the metal foil 168 and for electrically connecting the metal foil 168 with 
the mounting plate 165 (developing the desired low impedance ground path) 
through a coil spring which surrounds the depending tab 170 and extends to 
the mounting plate 165 (to eliminate the need to manufacture the depending 
tab to close tolerances). Alternatively, the metal foil 168 can be 
provided with a raised portion 171 (see FIG. 23), preferably on the order 
of 20 mils, for assuredly contacting one of the tabs of the corresponding 
guide spring (to be described below) for the guide (which is in turn 
grounded by its mounting hardware). The raised portion 171 is preferably 
located in a region of the corresponding guide which would not be used to 
guide the web of tape 15. 
Conventional practice in manufacturing the metal foil 168 is to etch the 
desired foils (and apertures) from a flat substrate, and to then form 
(curl) the etched foils for application to the correspondingly curved 
guide bodies (the hollow body 167). However, it has been found that this 
procedure can lead to certain adverse conditions in the resulting foils. 
First, such foils tend to yield at differing rates along cross-sections 
which contain the apertures 169 and cross-sections which do not, causing 
the foils to become faceted when formed. This can lead to difficulties in 
properly supporting the web of tape 15. Second, the edge of an aperture 
169 can become locally raised above the radial surface of the curved foil 
168, creating a sharp discontinuity at this location. Such conditions can 
lead to damage of the oxide coating provided on the web of tape 15 (and a 
loss of data) in the event that the guide (air bearing) becomes unable to 
support the web of tape 15. This problem is overcome by altering the 
process which is used to form the foils 168, such that the desired foils 
are etched (following their exposure to appropriate artwork) from a 
substrate which is first curled to develop the radius which is appropriate 
for application to the corresponding hollow bodies 167. 
A reference surface 173 is developed on the mounting plate 165 which 
receives the guides 161, 162, 163, to properly guide the web of tape 15 
through the head/guide assembly 160. To minimize wear at this reference 
surface 173, resulting from movement of the tape edge across it, the 
reference surface 173 is preferably coated with a hard material such as a 
nitride of titanium or silicon to reduce such wear. Of course, this 
surface may first be prepared, as appropriate, to receive the hard 
material coating, including necessary surface finish and edge rounding, as 
desired. Alternatively, this reference surface may be developed by bonding 
ceramic inserts (preferably formed of an oxide of aluminum such as 
monocrystalline or polycrystalline alumina) to the mounting plate 165, 
which are then machined to their required size and finish. To be noted is 
that if these ceramic inserts are used as the reference surface, the low 
resistance ground path which is to be developed for the foils 168 must be 
established through the guide springs located over the guides 161, 162, 
163, since the depending tab 170 will no longer be able to access the base 
material of the mounting plate 165. 
To further enhance alignment of the web of tape 15 within the head/guide 
assembly 160, a series of compliant guide springs 175 are provided along 
upper and lower portions of the guides 161, 162, 163. The purpose of the 
guide springs 175 is to exert a controlled force on the web of tape 15 
which is perpendicular to the reference surface 175, to hold the web of 
tape against the reference surface 173 using the minimum amount of force 
possible to reduce wear at this interface. 
The potential for misalignments of the web of tape 15 will be greatest at 
the outboard edges 176 of the head/guide assembly 160, which receive the 
web of tape 15 from the supply reel 16 and the take-up reel 74, 
respectively. The head/guide assembly 160 of FIG. 21 is therefore 
configured to apply the greatest amount of retaining forces in these 
regions, to assure proper registration of the web of tape 15, and to apply 
lesser forces for this purpose toward the center of this guiding 
structure. To develop these varying forces, the right guide 161 and the 
left-most guide 163 are preferably provided with guide springs 175 which 
have a variable spring rate which progressively increases toward the 
outboard edges 176. 
This is accomplished by forming the guide springs 175 from a thin sheet of 
resilient material (either a metal or a composite metal and plastic) which 
is coated with an appropriate surface material (such as a nitride of 
titanium or silicon) to reduce wear, or which is alternatively provided 
with ceramic pads (again preferably formed of an oxide of aluminum such as 
monocrystalline or polycrystalline alumina) bonded to its contacting 
surfaces, and which has a rim 177 of varying width (thickness) which 
increases (preferably linearly) toward the outboard edges 176 to develop 
the variable spring rate which is desired to achieve proper tape guidance 
in accordance with the present invention. Variations in the spring rate 
provided by the guide springs 175 are also capable of being developed by 
varying the width of the ribs 178 associated with the guide springs 175 
(as shown in FIGS. 21 and 23 of the drawings) to provide an increased 
stiffness according to the thickness of the ribs 178. As shown in FIG. 26, 
the guide springs 175 can also be configured to (preferably linearly) 
diverge slightly (varying the distance between opposing guide springs 175) 
toward the outboard edges 176, to in essence gather the web of tape 15 for 
proper presentation to the remainder of the tape guiding assembly, without 
buckling, by forming a dimple 179 in the guide spring 175 (shown in 
phantom in FIG. 21) for contacting the surface of the guide which receives 
it. Protruding tabs 180 are additionally provided to aid in threading the 
web of tape 15 along the transfer path 95, 95', by directing the upper 
edge of the web of tape 15 under the guide springs 175, and to prevent 
discontinuities (sharp edges) from being located in the same plane as the 
top edge of the web of tape 15 (which could cause damage to the top edge). 
To be noted is that in this configuration, the guide springs 175 are the 
only structures which are required to properly align the web of tape 15 
for proper guidance, and that the degree of alignment which is required 
(and accordingly the amount of contact between the guide springs 175 and 
the web of tape 15) will only be so much as is required to bring the web 
of tape 15 back into its correct alignment. Otherwise, contact between the 
guide springs 175 and the web of tape 15 is kept to a minimum to reduce 
unnecessary wear. Also to be noted is that the guide springs 175, as well 
as the other aligning features associated with the head/guide assembly 
160, cooperate to permit an appropriately aligned (gathered without 
buckling) transport of the web of tape 15, which is sufficient for 
effective presentation of the web of tape 15 to a high performance 
read/write head, within the limited confines of an 8 inch form factor or 
footprint and the limited available tape path which results. 
To further regulate transport of the web of tape 15, the right guide 161 is 
provided with a pneumatically operated tape tension sensor, which monitors 
variations in pressure resulting from changes in tension in the web of 
tape 15 as the web of tape 15 is drawn across the guide 161. This is 
accomplished by measuring changes in pressure at a sense orifice 182 
provided in the metal foil 168 of the guide 161, which is operatively 
connected with a conventional solid state pressure transducer (see FIG. 
28). A similar tension sensor is also preferably provided in the 
center-most guide 162, to provide an indication of tape tension on 
opposite sides of the read/write head 75. This is done to permit the 
measured tape tension to be averaged across the head 75, and to identify 
possible sticking of the web of tape 15 at the surface of the head 75 
(e.g., during start-up). 
The left guides 162, 163 further include a vacuum loaded, double knife edge 
tape cleaner 185. Each of the knife edges 186 are formed of an 
appropriately hard material and are arranged so that their angle of attack 
with respect to the web of tape 15 will operate to remove asperities and 
inclusions in the tape surface without damaging the tape surface. A pair 
of knife edges 186 are provided to accomplish this irrespective of the 
direction in which the web of tape 15 is traveling. 
To further improve the results achievable by the knife edge tape cleaner 
185, the knife edges 186 are no longer simply positioned within a 
supporting block but rather are buried within the block and vacuum loaded 
to effectively draw the web of tape onto the knife edges 186 to ensure 
proper results irrespective of wear of the blades or potential changes in 
tape wrap responsive to variations within the transport apparatus. In 
fact, the vacuum loaded knife edge tape cleaner 185 virtually eliminates 
the need for tape wrap at the knife edges 186 (approximately one degree of 
tape wrap remains preferred to provide the contact pressures which are 
needed to remove debris), avoiding the redeposit of removed material onto 
the web of tape 15, and eliminating forces which often tended to move the 
tape away from the reference surfaces provided. Vacuum loading at the 
knife edges 186 further makes sure that the tape is properly oriented to 
the knife edges 186, without the need for constant mechanical adjustment 
of the knife edge tape cleaner 185 (to account for wear) as was previously 
required for tape cleaners of this general type. What is more, placement 
of the knife edge tape cleaner 185 between an adjacent pair of guides 
(i.e., the guides 162, 163) saves in overall space utilization, 
facilitates close control of the location of the knife edges 186, and 
assists in correcting any variations in tape guidance or control which are 
caused by operation of the knife edge tape cleaner 185. 
FIG. 27 shows an alternative embodiment head/guide assembly 160' which is 
configured to develop a modified tape path 95' (as shown in FIGS. 15 to 
19) which is capable of accommodating even greater misalignments in the 
web of tape 15 which is being presented to the transport apparatus 20. By 
locating the head 75 even farther from the tape cartridge 2, the 
head/guide assembly 160' operates to accept and guide a web of tape 15 
leaving the tape cartridge 2 which is positioned significantly off the 
nominal tape path centerline for the transport apparatus 20 (e.g., when 
the web of tape is poorly stacked on the supply reel). The head/guide 
assembly 160' also operates to place the knife edge tape cleaner 185 on 
the supply side of the head 75, permitting the web of tape 15 to be 
cleaned before it is first presented to the head 75 (and accordingly, as 
it is withdrawn from the supply reel 16), in addition to cleaning the web 
of tape 15 during rewind. 
While the majority of the components comprising the head/guide assembly 
160' otherwise substantially correspond to those of the head/guide 
assembly 160, it is to be noted that the guides 161', 162', 163' have been 
provided with guide springs 175' which are configured to apply the 
greatest amount of retaining forces to the web of tape 15 along regions of 
the head/guide assembly 160' which operate to positively support the web 
of tape 15 (i.e., inboard regions of the guides 161', 162', 163'), to 
assure proper registration of the web of tape 15, and to apply lesser 
forces for this purpose toward the outboard edges 176' of the head/guide 
assembly 160'. This approach (which is also applicable to the head/guide 
assembly 160 earlier described) is again implemented by varying the spring 
rate of the guide springs 175', using the same techniques that were 
applied in varying the spring rate of the guide springs 175 (e.g., the 
spring rate of the outboard ribs 178' being lower than the spring rate of 
the inboard ribs 178' according to differences in rib thickness, etc.). 
Compressed air for the guides 161, 162, 163 (161', 162', 163') and vacuum 
for the knife edge tape cleaner 185 is provided by an air supply system 
190 which is configured to accommodate these two needs, as well as the 8 
inch form factor or footprint which is assumed by the transport apparatus 
20. Moreover, the air supply system 190 is configured to accommodate the 
web of tape 15 both when moving and when stationary. When moving, the 
primary need is to supply sufficient compressed air to the air bearings 
(the guides 161, 162, 163 and 161', 162', 163') to support the web of tape 
15 as it passes across them, and sufficient vacuum to the knife edge tape 
cleaner 185 to properly operate as previously described. When stationary, 
the primary need is to supply sufficient compressed air to the read/write 
head 75 to prevent "tape stick" at the head 75 resulting from static 
contact between the head 75 and the web of tape 15. 
Referring to FIGS. 3, 4 and 28 of the drawings, the air supply system 190 
is generally comprised of a compressor 191 which delivers compressed air 
to a serially configured heat exchanger 192 and filter housing 193, for 
delivery to a distributing plenum 194. To be noted is that each of these 
components is sized to be retained within the enclosure of the transport 
1, accommodating the 8 inch form factor or footprint which is desired. 
Compressed air from the plenum 194 is in turn delivered to a 3-way valve 
195 which selectively communicates with a multi-tube distributor 196 which 
provides compressed air to each of the tape guides (the guides 161, 162, 
163 of FIG. 21 or the guides 161', 162', 163' of FIG. 27) or to a jet 197 
formed in the read/write head 75. A solid state pressure sensor 198 
monitors air pressure in the plenum 194 and is electrically connected (for 
feedback purposes) to the servo control 199 of the compressor 191. The 
plenum 194 additionally communicates with the multi-tube distributor 196 
through high resistance line 200. In this fashion, air withdrawn at the 
knife edge tape cleaner 185 (developing the desired vacuum for its 
operation) is delivered to the compressor 191 (preferably through a filter 
associated with the compressor), for serial transfer to and between the 
heat exchanger 192, the filter housing 193 and the plenum 194. This 
compressed air (the pressure of which is monitored by the pressure sensor 
198 and regulated by the servo control 199) is then available for supply 
to the 3-way valve 195, providing the compressed air which is needed for 
the correct transport of tape, as follows. 
When the tape is stationary, steps are taken to reduce (by approximately 
one-half) the tension in the web of tape 15 (servo-controlled in known 
fashion) since less tape tension is required during this phase of 
operation. As a result, less air pressure and flow is required to retain 
the web of tape 15 away from the guides 161, 162, 163 or 161', 162', 163'. 
Sufficient compressed air for this purpose is available from the bypass 
which is developed by the high resistance line 200, for delivery to the 
multi-tube distributor 196 which feeds the guides. The 3-way valve 195 is 
then operated to actively supply available compressed air to the jet 197 
associated with the head 75, for retaining the web of tape 15 away from 
its surface as is desired. 
When the transport of tape commences, the valve 195 is switched to direct 
compressed air to the multi-tube distributor 196 (i.e., the guides 161, 
162, 163 or 161', 162', 163'), and not the air jet 197. The increased 
amounts of compressed air which are then required during the active 
transport of tape are made available since there is no longer a need to 
divert a portion of the available compressed air to the air jet 197 
associated with the read/write head 75. 
In either case (tape stationary or moving), the compressor 191 is 
servo-controlled to properly regulate the supply of compressed air to the 
transport apparatus 20 as previously described. This is done to assure a 
proper supply of compressed air to the head 75 and the guides 161, 162, 
163 or 161', 162', 163' when the web of tape 15 is stationary, and to the 
guides when the web of tape is in transport, irrespective of the number of 
apertures 169 in the metal foils 168 of the guides which are covered at 
any given time (which will necessarily vary according to the amount of 
tape which is wound upon the supply reel 16 and the take-up reel 74). 
Generally speaking, such servo-control of the system is provided by 
varying the voltage supplied to the compressor 191 according to the 
pressure detected at the pressure sensor 198, which is dependent upon the 
number of apertures 169 which are then exposed and the tension present in 
the web of tape 15. In any event, the pressure sensor 198 (and the 
associated servo control 199) and the 3-way valve 195 combine to permit a 
relatively small compressor (needed to fit within the desired 8 inch form 
factor or footprint), which would ordinarily be insufficient for its 
intended purpose, to adequately supply the compressed air which is needed 
for proper operation of the transport apparatus 20 as previously 
described. 
Accordingly, it will be seen that the transport 1 previously described 
serves well to satisfy each of the objectives previously set forth. It 
will further be understood that the described transport 1 is capable of 
variation without departing from the spirit and scope of the present 
invention, and that various changes in the details, materials and 
arrangement of parts which have been herein described and illustrated in 
order to explain the nature of this invention may be made by those skilled 
in the art within the principle and scope of the present invention as 
expressed in the following claims.