GB2218664A - Manufacturing multitubular sheaths - Google Patents

Abstract

A method of making a multitubular sheath, which is used to make a tubular battery plate, comprises opening tubular channels in a sheath comprising two porous fabric sheets stitched together along a number of parallel lines (4). The method comprises providing a mandrel (8) in each tube (2) of the sheath defined between the rows of stitching (4). First and second gripping means combined into a single gripper (10) are actuated to grip the tubes (2) and the mandrels (8) within them, the first gripping means gripping alternate mandrels and the second gripping means gripping the remainder. The gripper (10) advances the mandrels by a predetermined distance, then the first gripping means is disengaged, and a first series of pusher means (12) returns the released mandrels (8) to their original position and the first gripping means is then re-engaged. The second gripping means is disengaged and a second series of pusher means (14) returns the remaining mandrels to their original position. The first and second pusher means are then retracted and a portion of the fabric transverse to its length is cut off by a cutter (16). Before or after the cutting operation, the gripper (10) is disengaged and returned to its original position and the cycle is repeated. <IMAGE>

Description

MANUFACTURING MULTITUBULAR SHEATHS The present invention relates to the manufacture of multitubular sheaths of the type that is used in the manufacture of so-called tubular battery plates.

Tubular battery plates comprise a plurality of parallel tubes of porous woven or non-woven fabric, each of which contains active electrode material, lead dioxide in the case of a positive plate for a lead acid battery, and extending along the axis of each of which is a spine of lead or lead alloy. The spines are all connected together at one end of the sheath by a common top bar to which a current take-off lug is connected and the other end of each tube is closed by a plug.

The tubes are commonly constituted by two porous fabric sheets which are stitched together along a number of parallel lines and are thus initially in flat or collapsed form. It is therefore necessary to open each tube to permit it to be filled with active material and one common method of doing this is disclosed in GB 1574722. This specification describes the feeding of the initially collapsed multitubular sheath, which is impregnated with a polymer material, through two spaced pairs of cooperating drive rollers.

The first pair of rollers turns the sheath through 900 and locates a floating, circular-section mandrel of shepherds crook or walking stick shape in position in each tube. The leading handle end of each mandrel opens the respective tube upstream of the drive rollers and the straight portion of each mandrel downstream of the rollers retains each tube in a circular shape whilst it is heated to cure the polymer. The sheath then passes through the second set of downstream rollers before being cut into lengths.

Each drive roller defines a series of semicircular grooves in its periphery which together with the grooves in the opposing roller receives the uncured sheath and the floating mandrels in the case of the upstream rollers and the tubes of the cured sheath in the case-of the downstream rollers. The lands between adjacent grooves engage and squeeze the sheath along the lines of stitching for the purpose of moving it.

In order that these lands do not cut the sheath, it is essential that they have an appreciable width, typically of about 3 mm, and since the lines of stitching have a negligible width, it is found that the finished tubes have a somewhat flattened or oblate cross-section and not a truly circular shape. This is found to have disadvantages in a tubular battery plate, primarily because each tube can accommodate less active material than would be the case if the tubes were truly circular, whereby the capacity of the resultant plate is decreased.

It is therefore an object of the present invention to provide a method of manufacturing multitubular sheaths of the type referred to above in which the tubes are of substantially true circular shape or at least are substantially more truly circular than the tubes of sheaths manufactured by the known method described above.

According to the present invention a method of making a multitubular sheath for use in manufacturing a tubular battery plate comprises providing a length of porous multitubular fabric in collapsed form, providing a circular section floating mandrel within each tube, actuating first and second gripping means to grip the tubes and mandrels within them and advancing the gripping means and thus the sheath and the mandrels by a predetermined distance, releasing the first gripping means and thus certain of the mandrels, actuating a first series of pusher means to return the said certain mandrels to their original position, actuating the first gripping means and releasing the second gripping means thereby gripping the said certain mandrels and releasing the remaining mandrels, actuating a second series of pusher means to return the said remaining mandrels to their original position, retracting the first and second series of pusher means and cutting off a portion of the fabric transverse to its length.

Thus in the method in accordance with the present invention the multitubular fabric is not moved continuously as in the known method but is moved in a plurality of sequential steps. Instead of engaging the multitubular fabric along the lines of stitching or the like, each tube is engaged by gripping means which are then advanced so as to advance the mandrel and the multitubular fabric.If one were to attempt to return all the mandrels simultaneously to their original position the multitubular fabric would also be returned to its original position and thus in the method of the present invention the first gripper means is released and those mandrels which are engaged by it are then returned to their original position by first pusher means whilst the sheath is retained stationary by maintaining the engagement of the second gripper means with certain of the tubes of the sheath and thus the mandrels within them. T'a first gripper means is then actuated again and the second gripper means released and the remaining mandrels are then returned to their original position by a second series of pusher means.

Due to the fact that there is no engagement with the multitubular sheath along the lines of stitching the circular section mandrels produce a truly circular shape of the resultant tubes whereby these tubes can accommodate an amount of active material which is 10% or more greater than that in the sheaths produced by the known method referred to above.

It will be appreciated that it is not crucial which of the mandrels are initially returned and which are subsequently returned but in the preferred embodiment the said certain mandrels constitute every alternate mandrel which does of course mean that the remaining mandrels also constitute every alternate mandrel.

It is preferred that the first and second gripping means are situated one behind the other in the direction of the length of the mandrels and are connected together and thus advanced and retracted in unison.

The gripping means may take various forms and it may even be possible not to use a direct contact with the sheath but to use electromagnetic gripping means which attract the mandrels within the tubes and thus grip the sheath between the mandrels and the gripping means. However, it is preferred that each of the first and second gripping means includes a gripping member which extends across the width of the sheath and is connected to be moved vertically by respective actuating means between an engaged and a released position, each gripping member affording a plurality of engaging areas arranged to engage the said certain mandrels or the said remaining mandrels when in the engaged position, the said engaging areas being interspersed with areas which do not engage the said remaining mandrels or the said certain mandrels, respectively, when in the engaged position.The first and second gripping means may include a common stationary surface on the side of the sheath remote from the gripping members.

The first and second pusher means preferably comprise elongate bars, e.g. circular bars whose diameter is the same as that of the mandrels, whose length is substantially equal to the said predetermined distance.

Further features and details of the invention will be apparent from the following description of one specific embodiment which is given with reference to the accompanying drawings, in which: Figure 1 is a highly diagrammatic plan view of an apparatus for carrying out the method in accordance with the invention; and Figure 2 is a vertical sectional view transverse to the length of the fabric through the machine of Figure 1.

Referring firstly to Figure 1, a multitubular fabric defining a plurality of tubes 2 is formed in collapsed form by providing a plurality of spaced rows of parallel stitching 4 in two superposed, elongate sheets of woven, knitted or non-woven fabric of organic polymer material, preferably a polyester or polyamide material. The elongate or continuous collapsed multitubular fabric, which is shown in Figure 1 as having only five tubes but in pracice may have many more, typically 15, is then fed to the apparatus illustrated in Figure 1 and is initially preheated in a preheating zone 6 to a temperature above its melting point, e.g. to a temperature of 110 to 1200C.

Downstream of the preheating zone 6 each tube 2 contains a floating, elongate, circular-section mandrel 8. Situated adjacent the portion of the sheath which contains the mandrels are first and second gripping means, which will be described in more detail below and which are combined into a single gripper 10 which extends across the full width of the fabric and is movable between the position shown in solid lines in Figure 1 and the position shown in dotted lines in Figure 1. The method of the present invention will be described starting from the point at which the leading or right-hand ends of the mandrels are situated adjacent the position A in Figure 1 and the gripping bar 10 is in its left-hand position in Figure 1: The first and second gripping means are actuated to grip all the mandrels in the tubes and thus the multitubular fabric also.The first gripping means is constructed to grip only every alternate mandrel and the second gripping means is constructed to grip only the remaining mandrels. The gripper 10 is then advanced to the right as seen in Figure 1 into the position shown in solid lines and all the mandrels and thus the tubes around them are advanced by the same distance so that their leading end is adjacent the position B. The first gripping means, which engages, say, the two outer and the central mandrels, is then released but the second gripping means is left in position gripping the two remaining mandrels.First pusher means, which comprise a plurality of elongate circular section rods 12 and which are connected together and in alignment with the tubes containing the mandrels which have been released by the first gripping means, are then advanced into the tubes which have been released by the first gripping means and engage the mandrels within them and return them to the original position, namely the position A. The first gripping means is then reactuated to grip its associated mandrels and tubes and the second gripping means is then released whereby the mandrels within the second and fourth tubes are free to move. Second pusher means comprising two circular section bars 14 are then advanced into the second and fourth tubes and return the mandrels within them to their original position also.The first and second pusher means 12 and 14 are then retracted to their original position, i.e. the position illustrated in Figure 1. A single multitubular sheath of predetermined length is then cut from the continuous multitubular fabric at the position A by a hot wire cutter 16. Before or after such cutting the second gripping means is released and the gripper 10 is returned to its original position, i.e.

the left-hand position in Figure 1, and the first and second gripping means is reactuated to grip all the mandrels. The cycle is then repeated indefinitely.

Upstream of the left-hand position of the gripper bar 10 the multitubular fabric is heated to a temperature of e.g. 110 to 1200C in a heating zone 18.

This heating is performed whilst the tubes are occupied by the floating mandrels and causes the polymer material, preferably a thermoplastic phenyl formaldehyde resin or a polyester or polyacrylic resin, e.g. polymethylmethacrylate, with which thr sheath is impregnated to flow and then set in the desired truly circular shape. As mentioned previously, before the tubes are entered by the floating mandrels they are subjected to a preheating in the zone 6 to soften the resin-impregnated fabric and thus facilitate the entry of the mandrels into them.

The first and second gripping means may take many forms but, as mentioned above, in this embodiment they are incorporated into a single gripper 10. As shown in Figure 2, the gripper 10 comprises a flat table 20 which is mounted to slide parallel to the length of the mandrels on two elongate slide guides 22 and is connected to be moved along these guides by an actuator 24 which is of the type comprising a stationary cylinder containing a pneumatically or hydraulically actuated piston which does not have a piston rod but is connected to the table 20 by a coupling 26 which passes through a slot in the cylinder, which slot is provided with a sliding seal (not shown). Situated above the table 20 are two gripping bars 28, of which only one is shown and which are situated behind one another in the direction of the length of the mandrels.In its lower surface each gripping bar affords a plurality of arcuate grooves 30 and each pair of such grooves 30 is separated by a respective rectangular groove 32 of rather greater depth. The spacing of adjacent pairs of arcuate grooves 30 is wice the spacing of the adjacent mandrels and thus when each gripping bar 28 is moved downwardly every alternate mandrel is engaged by the arcuate recesses 30 whilst the intervening mandrels are accommodated in a non-engaging manner within the rectangular grooves 32. It will of course be appre iated that the grooves 30 and 32 are offset from one another by one pitch in the two adjacent gripping bars 28. Each gripping bar 28 is provided with two engaged position in which it engages and grips every alternate mandrel.When one or both gripping bars 28 is moved by its respective actuators 30 into the engaging position it presses the associated mandrels against the table 20, with the interposition of the fabric of the associated tubes, and thus prevents movement of the mandrels and thus the associated tubes relative to the gripper. If the gripper is moved by the actuator 24 along the guides 22 when the gripping bars are in the engaged position the mandrels and thus the tubes are of necessity moved with it.

As mentioned above, the first and second pusher means constitute elongate circular section bars which are aligned with respective tubes of the sheath. The length of these bars is substantially the same the predetermined distance by which the gripper 10 is moved and their diameter may be substantially the same as that of the mandrels or rather less. It will of course be appreciated that it is not essential that the pushing means constitutes circular bars and that these may have any shape which enables them to fit within the tubes and to exert the necessary force on the mandrels.

The first and second pushing means may be advanced and retracted by any appropriate means but for reasons of economy of space it is preferred that these means constitute a respective cylinder which accommodates a piston rod-less piston similar to the actuator 24.

In the embodiment described above the tubes, and thus the mandrels also, are of conventional shape, i.e.

round. It will, however, be appreciated that the present invention may find particular application in the manufacture of multitubular sheaths with rectangular or square tubes because in this case it is impractical to engage the sheath along the lines of stitching.

Claims (4)

1. A method of making a multitubular sheath for use in manufacturing a tubular battery plate which comprises providing a length of porous multitubular fabric in collapsed form, providing a circular section floating mandrel within each tube, actuating first and second gripping means to grip the tubes and the mandrels within them and advancing the gripping means and thus the fabric and the mandrels by a predetermined distance, releasing the first gripping means and thus certain of the mandrels, actuating a first series of pusher means to return the said certain mandrels to their original position, actuating the first gripping means and releasing the second gripping means thereby gripping the said certain mandrels and releasing the remaining mandrels, actuating a second series of pusher means to return the said remaining mandrels to their original position, retracting the first and second series of pusher means and cutting off a portion of the fabric transverse to its length.

2. A method as claimed in claim 1 in which the said certain mandrels constitute every alternate mandrel.

3. A method as claimed in claim 1 or 2 in which the first and second gripping means are situated one behind the other in the direction of the length of the mandrels and are advanced and retracted in unison.

4. A method as claimed in claim 3 in which each of the first and second gripping means includes a gripping member which extends across the width of the fabric and is connected to be moved vertically by respective

4. A method as claimed in claim 3 in which each of the first and second gripping means includes a gripping member which extends across the width of the fabric and is connected to be moved vertically by respective actuating means between an engaged and a released position, each gripping member affording a plurality of engaging areas arranged to engage the said certain mandrels or the said remaining mandrels when in the engaged position, the said engaging areas being interspersed with areas which do not engage the said remaining mandrels or the said certain mandrels, respectively, when in the engaged position.

5. A method as claimed in claim 4 in which the first and second gripping means include a common surface on the side of the sheath remote from the gripping members.

6. A method as claimed in any one of the preceding claims in which the first and second pusher means comprise elongate bars whose length is substantially equal to the said predetermined distance.

7. A method as claimed in any one of the preceding claims in which the fabric is impregnated with a polymer material and is heated over a proportion of its length whilst the mandrels are within the tubes.

8. A method as claimed in any one of the preceding claims in which the fabric is preheated over a proportion of its length prior to the mandrels entering the tubes.

9. A method of making a multitubular sheath for use in me:ufacturing a tubular battery plate substantially as specifically herein described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. A method of making a multitubular sheath for use in manufacturing a tubular battery plate which comprises providing a length of porous multitubular fabric in collapsed form, providing a circular or recttngular section floating mandrel within each tube, actuating first and second gripping means to grip the tubes and the mandrels within them and advancing the gripping means and thus the fabric and the mandrels by a predetermined distance, releasing the first gripping means and thus certain of the mandrels, actuating a first series of pusher means to return the said certain mandrels to their original position, actuating the first gripping means and releasing the second gripping means thereby gripping the said certain mandrels and releasing the remaining mandrels, actuating a second series of pusher means to return the said remaining mandrels to their original position, retracting the first and second series of pusher means and cutting off a portion of the fabric transverse to its length.

2. A method as claimed in claim 1 in which the said certain mandrels constitute every alternate mandrel.

3. A method as claimed in claim 1 or 2 in which the first and second gripping means are situated one behind the other in the direction of the length of the mandrels and are advanced and retracted in unison.