Magnetic tape reel for computer

A reel for the magnetic tape of a computer, wherein the central part is constituted, like the side flanges, by polystyrene, which is therefore ultrasonically weldable, and these flanges are welded on said part at four spots, the ring integral with the rest of the part being connected to the web by a plurality of ribs separated from one another by spaces.

The present invention relates to a reel for the magnetic tape of a 
computer. 
A reel of this type is described in U.S. Pat. No. 3,632,053; it comprises 
two side flanges, a hub and a ring on which the tape is wound. It is well 
known that the fact of the tape tightening whilst it is being wound causes 
an extremely intense compression to be exerted on the ring. 
It is an object of this U.S. patent to avoid transmission of the 
compression both to the hub, to prevent it from tightening on the driving 
spindle, and to the flanges, to prevent their buckling. To this end, a 
clearance is provided between the ring and the flanges; these flanges are 
secured (particularly by ultrasonic welding if all the elements are made 
of polystyrene) solely to the hub, against its faces and at three points 
without interlocking: the connection between the ring and the hub is 
effected elastically by means of an intermediate ring connected 
alternately to one and the other by angularly offset ribs. 
In this way, the ring is compressed when the tape is being wound but no 
stress can be transmitted to the hub nor the flanges which therefore do 
not risk buckling. 
This reel has been constructed and tested, but has not been launched on the 
market, although there is a pressing demand. 
Contrary to the invention described in the above U.S. patent, the purpose 
of the present invention is to have all the essential components of the 
central part of the reel participate in the resistance to compression; to 
this end, a box-like or caisson structure is constituted by the hub, ring 
and the flanges, this box-structure having to be sufficiently rigid and 
undeformable to avoid the hub tightening on its driving spindle, the 
flanges buckling and the ring losing its cylindricity, whilst the tape is 
being wound. 
In accordance with the invention, the flanges are therefore welded to the 
central part in four annular zones ensuring, in two's and on each side, 
the rigid joining of the corresponding flange with the ring and the hub 
respectively in order to form a box-like structure with better resistance 
to the compression produced by the tape being wound and, to this end, each 
flange presents, on its internal face, two projecting parts each defined 
by a substantially cylindrical welding surface, these two surfaces 
cooperating with two conjugated surfaces made on the inside of the ring 
and the outside of the hub, respectively. 
According to another important feature of the invention, each flange is 
provided with a joggle, for housing the corresponding free end of the 
ring, so that a sharp edge appears between this flange and the ring.

Referring now to the drawings, FIG. 1 shows a reel which comprises a 
central part 1 made of glass-fibre filled polystyrene and two side flanges 
2, 3 also made of polystyrene which is therefore ultrasonically weldable. 
The central part 1 is monolithic (FIG. 3); it has a driving ring 4 and a 
hub 5 fast with a web 6. Between the web 6 and the ring 4 is arranged a 
free space 7 due to which it becomes possible to mould said ring without 
risk of developing cavities and therefore to obtain a winding surface 8 
which is perfectly cylindrical and having strictly straight generatrices. 
The web and ring are connected together by relatively thin ribs 9 in order 
to avoid cavities on moulding (FIGS. 2 and 3). 
The flanges 2, 3 delimit, opposite the free ends of the ring 4, joggles 10, 
11 intended for supporting said ends, recessed in the inner surface of the 
flanges. In this way, the connection of the flanges with the ring is made 
with a sharp edge (FIG. 2). To ensure that these flanges 2, 3 are 
assembled with the central part 1, ultrasonic welding is effected at four 
points 12 to 15. 
To this end, the ring 4 has projecting from its inner surface, between each 
of its free ends and the ribs 9, an annular collar 16 whose internal 
diameter is smaller than the external diameter of an annular boss 17 in 
the corresponding flange 2 or 3; in the same way, the hub 5 has projecting 
from its outer surface, near each side of the web 6, an annular collar 18 
whose external diameter is greater than the internal diameter either of an 
insert portion 19 of the flange 2 or of an annular skirt 20 of the flange 
3. 
The emission of ultrasounds is effected at the same time as the flanges are 
pressed on the central part, so that the collars 16 and bosses 17 
penetrate into each other to produce, by shearing and softening, the weld 
spots 12, 13, in the same way as the collars 18 and inset portion 19 and 
the skirt 20 penetrate into one another to produce, by shearing and 
softening, the weld spots 14, 15. 
It is important to note that a slight clearance is provided between, on the 
one hand, the ring 4 and the bosses 17, on the other hand the hub 5 and 
the inset portion 19 as well as the skirt 20 in order that the ultrasonic 
welding action be localised at the shearing zones. 
Furthermore, ribs 21 connect the boss 17 of the flange 2 to the inset 
portion 19 and other ribs 22 connect the boss 17 of the flange 3 to skirt 
20. Due to the four weld spots 12 to 15 and to ribs 21, 22, a perfectly 
rigid, assembled central part is obtained, maintaining the flanges 
strictly parallel to each other whatever the influences to which the reel 
is subjected; moreover, the winding surface of the ring 8 remains 
cylindrical and concentric to the bore of the hub 5 with great accuracy, 
its generatrices being straight. 
The improvements forming the subject matter of the present invention are 
preferably applicable to magnetic tape reels for computers.