GB2329949A - A shaft for centering and engaging one or more tubes - Google Patents

Abstract

A shaft (1, Fig 1) for centering and engaging tubes 9, 10 of different diameters comprises a plurality of cavities 4 disposed circumferentially of the shaft, each cavity containing a movable pin 6 surrounded by a movable collar 3, means 2 being provided for moving each pin and collar radially outwardly against the tubes. The collars 3 are capable of moving a first distance beyond the circumference of the shaft; the pins 6 are capable of moving a second distance beyond the first distance. The shaft centers a first tube 9 by means of the collars 3 and pins 6 and centers a second tube 10 of a larger diameter by means of the pins 6. The same shaft can thus be used for tubes of different diameters.

Description

A shaft for the centering and engaging of one or more tubes The present invention concerns a shaft for the centering and engaging of tubes and in particular an expanding shaft for centering and engaging tubes which may be of different diameters and/or which are turning at high speed.

Tubes are commonly used in many industrial applications to quickly wind laminar material such as paper, plastic sheeting, tapes and the like or threads or similar on tubular cores or tubes. These tubes may each have slightly different internal diameters.

In such applications, the tubular cores are usually inserted on pneumatic shafts for the centering and engaging of the cores. In some instances, the cores or tubes are rotating at high speed due to the winding mechanisms coupled to the centering shafts.

Hitherto, it has not been possible to couple two tubes of slightly different diameter on the same shaft. In particular, the use of an existing expanding pneumatic shaft does not permit effective engaging of the larger diameter tube on said shaft when it is rotating at very high speed. In order to achieve such coupling, it has been necessary to use a separate shaft with a specific diameter for each tube.

The present invention aims to overcome the aforesaid disadvantage.

Particularly, it is an object of the present invention to realise an expanding shaft capable of centering and engaging tubes having different diameters.

It is another object to provide a shaft which enables cores, of different diameters, all to be engaged effectively, even though the shaft is rotating at high speed.

According to the present invention, there is provided a shaft (1) for centering and engaging tubes (9,10), comprising: a plurality of hollows (4) disposed circumferentially of said shaft; a plurality of movable elements (3,6), each element inserted in a respective hollow (4); means (2,7,8) for moving radially said movable elements (3,6) against said tube (9,1( characterized in that said movable elements (3,6) comprise: a plurality of rods (3), each rod disposed in a respective hollow (4), capable of moving a first distance beyond the circumference of the shaft; a plurality of pins (6), each pin disposed in a respective rod (3), capable of moving a second distance beyond the first distance.

An embodiment of the present invention will now be described with reference to the accompanying drawings, of which: Figure 1 shows a longitudinal partial cross-section of the shaft broken in the middle; Figure 2 shows a perpendicular section of said shaft; Figure 3 shows a partial longitudinal section of the shaft having rods and pins in an off-position; Figure 4 shows a perpendicular section corresponding to Figure 3; Figure 5 shows a partial longitudinal section of the shaft whilst engaging a tube of a smaller diameter; Figure 6 shows a perpendicular section of Figure 5; Figure 7 shows a partial longitudinal section of the shaft whilst engaging a tube of a larger diameter; and Figure 8 shows a perpendicular section of Figure 7.

As shown in Figures 1 and 2, there is shown a shaft 1 which is designed to center and engage tubes 9, which may have different diameters, preferably axially with the axis of the shaft and the tubes may be so firmly engaged that the tubes remain centered even with high rotational speeds.

The shaft comprises a plurality of longitudinal air chambers 2. The shaft also includes a number of hollows 4. The hollows are T shaped and within each hollow, there is arranged a respective rod 3. The rods 3 have bases 31 against which the air chambers act.

Preferably the rods 3 are made of aluminium and have a height equal to the depth of the hollows.

The rods are disposed equi-angularly and in this embodiment there are 5 rods in a set arranged around one circumference of the shaft and several sets are arranged at equal distances along the length of the shaft.

Within each rod, there is formed a receiving hollow 5. The receiving hollows are radially disposed with respect to the axis of the shaft. The receiving hollows are T shaped in cross-section. In each receiving hollow is disposed a pin 6. The pins are preferably made of brass. The pins 6 are capable of moving in the radial direction with respect to the axis of the shaft and have a flanged base 61 with which the pins seat themselves within each receiving hollow 5.

In a resting state, as shown in Figures 3 and 4, the bases 31 of the rods 3 and the flanged bases 61 of the pins 6 rest against the upper surface of the air chambers 2.

Compressed air is fed to the air chambers 2 by way of an axial duct 7 and then distributed to radial ducts 8.

A tube 9, about which the laminar material is to be wound needs to be fed onto the shaft. Obviously, the external diameter of the shaft is smaller than the internal diameter of the tube.

In the off position, the rods 3 are depressed such that their heads 32 are preferably flush with the external surface 11 of the shaft. The pins 6 are also depressed such that their heads 62 are preferably flush with the external surface 11.

With the tube 9 arranged around the shaft, compressed air is fed into the air chambers 2 which inflates longitudinally as shown in Figures 5 and 6. The air chambers push the bases 31 of the rods 3. The upper surface 32 is pushed against the internal surface 91 of the tube 9. This leads to the centering and engaging of the tube 9.

In addition, the flanged bases 61 of the pins 6 receive a pushing force which is less than the pushing force at the bases 31 of the rods 3. Accordingly, The pins 6 remain flush with the rods 3 and so the heads 62 are flush with the internal surface 91 of the tube 9.

In summary, a tube with a relatively small diameter is centered and engaged principally by the rods 3 whilst the pins 6 only indirectly co-operate in this function.

Figures 7 and 8 show a tube 10 being centered and engaged with a relatively larger diameter. In this case, even though a pneumatic force is applied by the compressed air in the chamber 2, the furthest extent of the rods 3 is such that their radial expansion does not bring their heads 32 into contact with the internal surface 101 of the tube 10. Nonetheless, the pneumatic force exerts on the flanged bases 61 of the pins 6 which enables the heads 62 to protrude compared to the rods 3 and so the heads 62 contact the internal surface 101 of the tube 10. This enables a tube with a relatively large diameter to be centered and engaged by the shaft according to the present invention.

In summary, rather than the rods centering and engaging the tube, the pins center and engage the tube by protruding from the rods.

It is clear that the present invention provides a fast and safe operation of centering and engaging tubes, irrespective of differences in diameter.

The preceding description has been given by way of example only and it will be appreciated by a person skilled in the art that modifications can be made without departing from the scope of the present invention. For example, the shape and number of active elements may vary. In particular, the number and shape of the rods and pins according to need. It is also to be appreciated that the mechanism for moving the rods and pins might not just be based on pneumatic force and other forces can be envisaged.

Claims (9)

Claims:

1. A shaft (1) for centering and engaging tubes (9,10), comprising: a plurality of hollows (4) disposed circumferentially of said shaft; a plurality of movable elements (3,6), each element inserted in a respective hollow (4); means (2,7,8) for moving radially said movable elements (3,6) against said tube (9,10) characterized in that said movable elements (3,6) comprise: a plurality of rods (3), each rod disposed in a respective hollow (4), capable of moving a first distance beyond the circumference of the shaft; a plurality of pins (6), each pin disposed in a respective rod (3), capable of moving a second distance beyond the first distance.

2. A shaft as claimed in claim 1, in which said hollows (4) are disposed in the external surface of the shaft.

3. A shaft as claimed in claim 1 or 2, in which said hollows are disposed equi-angularly.

4. A shaft as claimed in claim 3, in which said hollows are disposed at regular intervals along the length of the shaft.

5. A shaft as claimed in any one of the preceding claims, in which each of said rods (3) has a T shaped cross-section with a base (31) and is arranged in the respective hollow (4) such that the base (31) is next to said moving means (2,7,8).

6. A shaft as claimed in any one of the preceding claims, in which each of said pins (6) has a T shaped cross-section with a flanged base (61) and is arranged in said rod (3) such that the base (61) is next to said moving means (2,7,8).

7. A shaft as claimed in any one of the preceding claims, in which said moving means comprises ducts (7,8) coupled to at least one air chamber (2), all for receiving compressed air and said chamber being arranged to apply a force to said moveable elements (3,6).

8. A shaft as claimed in any one of the preceding claims, in which said rods (3) and pins (6) are used to center a tube (9) of a first diameter and said pins (6) are used to center a tube (10) of a diameter larger than the first diameter.

9. A shaft substantially as hereinbefore described and with reference to any one of the accompanying Figures.