Device for Longitudinal Cutting of Thermo-Softening Materials Into Strips

The present invention relates to the manufacture of storage batteries and more specifically it relates to a device for longitudinal cutting of a thermo-softening material into strips to make separators for the battery electrodes.

The device according to the invention can also be used for cutting thermo-softening material into strips intended for packing, winding, sewing purposes, etc.

Most effectively the present invention may be employed for automating assembly operations in the manufacture of, say, nickel-cadmium batteries with a high power capacity, containing extra-thin separators made of elastic thermo-softening materials and applied in several layers to the electrode.

One of the problems of cutting said thermo-softening material is that they are liable to be easily stretched in the course of cutting thus changing the width of the strip, so that these materials have to be cut with a little-tensioned band. In this case low-heated cutters form waves of the material in front, whereas highly-heated cutters make a wide cut and rule out stops of the moving material, since the material melts and forms a wide hole with overflows which impairs the quality of the strips and thus requires increasing the allowance for the strip width. Besides, cutting of such materials involves accumulation of melted material on the cutters, thus forming unwanted carbon deposits which impair the quality of the strips and require frequent stops of the automatic machine for cleaning the cutters.

Therefore, cutting of the separating materials and their application to the electrodes in the manufacture of storage batteries with a high power capacity (in the USSR and in prominent foreign firms) are carried out mainly by the use of manual labor or on semiautomatic equipment which is characterized by a considerable scrap or waste of the separating material. The material in this case is cut with a heated electric cutter.

Known in the prior art is a machine for longitudinal cutting of sheets into strips (see, for example, Author's Certificate No. 166458 Cl. D06 h/04, USSR, 1964) comprising a roll holder which feeds the sheet into the machine, a cutting mechanism in the form of a cutter shaft with a set of disc cutters secured on said shaft at intervals determined by the width of the strips to be cut. The machine also comprises at least one pair of pulling rollers with their rotation drive for ensuring pulling of the cut strips between the disc cutters, and a mechanism for the separate winding of adjacent strips of material on the reels of separate receiving drums. The drums are connected with the drive by friction couplings, and the axles of all the shafts and rollers are parallel to one another.

This machine cuts a sheet into strips by disc cutters using a method of mechanical separation. The machine can also be adapted for installing disc cutters heated with, say, electric current for cutting thermo-softening materials.

However, such a machine is incapable of even short-time stops since this will cause the strip edges to melt around the cutters and form a wide hole with overflows on the strip edges since the machine has no provision for lifting the cutters for the duration of a stop. As a result, this machine cannot be used to cut a thermo-softening material and the fastening of the cutters in the machine does not lend itself to periodical cleaning of the cutter blades which obviously leads to an increasingly poor quality of the produced strips.

The above described disadvantages of the prior art machine caused by a deficient design of cutter fastenings preclude its employment for cutting a thermo-softening material into separators for the battery electrodes since by virtue of its design said machine impairs the quality of electrode separation and causes an unwarranted loss of materials due to increased allowances for the width of the strips.

An object of the present invention resides in providing a simple and reliable device for longitudinal cutting of a thermosoftening material into strips. Another object of the invention resides in improving the quality of the strip edges and decreasing the consumption of the separating material.

These and other objects are accomplished by providing a device for longitudinal cutting of a thermo-softening material into strips, mainly strips of a separating material for battery electrodes comprising a roll holder with a mechanism for automatic fixing of the strip edge. A cutting mechanism with electric cutters is mounted on a common shaft, at least two pulling rollers with their rotation drive move the band in the course of cutting and deliver the cut strips on to the receiving shafts of a wind-up mechanism. The axles of the pulling rollers, roll holder and receiving shafts are parallel to one another, and the electric cutters are mounted on arms having hubs secured on a common shaft. The hubs are provided with a segment tooth on a surface face and are mounted on the shaft with the aid of an intermediate sleeve which has a mating segment tooth. Each hub is secured on the shaft along the line of cut, thus ensuring automatic lifting of the electric cutters due to interaction of segment teeth during the turning of the shaft.

The device for longitudinal cutting of a thermo-softening material into strips ensures automatic cutting of thermo-softening materials into desired width strips and their winding on reels for subsequent installation on an automatic machine for the application of separators to electrodes. Such device is intended for use in automatic battery assembly lines.

The device permits cutting of thin low-strength separating materials for storage batteries with a high specific capacity, e.g. for the batteries employed in aviation, electromobiles, etc., ensuring a high quality of the cut strips and economy of the separating material applied to the electrodes due to the fact that the arms carrying electric cutters are provided with hubs having a segment tooth on a surface face. The hubs are mounted on the shaft with the aid of an intermediate sleeve placed along the line of cut, thus ensuring the automatic lifting and withdrawing of the electric cutters from the cutting zone.

Besides, such fastening arrangement of the electric cutters enables any one of said electric cutters to be shifted over to an inoperative position for cleaning it of deposits without disturbing the initial setting of the width of the strips being cut.

The construction of the fastening arrangement of the electric cutters also allows the device to be quickly reset for cutting strips of a different width by partial replacement of some electric cutters with cutters brought from the inoperative position and set in advance for a new cutting width which makes it possible to use the device according to the present invention both in large and small-scale production.

Now the invention will be described in detail by way of examples with reference to the accompanying drawings, in which:

FIG. 1 is a schematic general view of the device for longitudinal cutting of a thermo-softening material into strips; and

FIG. 2 is an enlarged fragmentary view, in perspective, showing the fastening unit of an electric cutter on a shaft.

A design of the device for longitudinal cutting of a thermo-softening material into strips, for example, of a separating material for battery electrodes embodies a cutting mechanism comprising three electric cutters. However, the number of cutters can be changed at will to suit the required number of strips to be cut.

The device for longitudinal cutting of a thermo-softening material into strips comprises a roll holder 1 (FIG. 1) with a roll of band 2 of a thermo-softening separating material, said holder feeding the band 2 into the cutting mechanism for subsequent cutting of it into strips. It is recognized that as a practical matter, the roll holder 1 should be provided with a mechanism (not shown in the drawings) for automatic fixing of the edge of the moving band 2.

Installed along the direction of movement of the band 2 through the device, parallel to the axis of the roll holder are at least 3 rods 3 for guiding the band 2 into the cutting mechanism.

The cutting mechanism contains a support 4 installed between and above the two rods 3 which are positioned next along the movement of the band 2 so as to make the band 2 turn around the support 4 at equal angles at both the entrance and the exit.

Mounted above the support 4 is a shaft 5 with electric cutters 6 secured on arms 7. The shaft 5 is connected with a drive 8 for lifting the electric cutters 6. The drive turns the shaft 5 through a preset angle right and left. When the shaft 5 occupies the extreme right position the electric cutters 6 rest on the support 4 through the band 2 of the material being cut.

Two pulling rollers 9 and 10 installed near the cutting mechanism parallel to the rods 3 and support 4 are connected to their rotation drive which moves the band 2 of the thermo-softening material through the cutting mechanism. The roller 10 is coated with rubber while the roller 9 has a smooth metal surface. In practice the rotation speed of the roller 9 should be 5-10% higher than that of the roller 10 so as to ensure continuous tensioning of the strips of the band 2 on the rubber-coated surface of the roller 10 due to the slipping of the band over the surface of the roller 9. Each electric cutter 6 (FIG. 2) has the form of a metal disc with an electric spiral element embedded inside (not shown in the drawing) and a protective housing 11. The electric cutter 6 and the protective housing 11 are fastened in the center part of the arm 7 which has a hub 12 at one end and a weight 13 at the other end. The hub 12 of the arm 7 is freely mounted on an intermediate sleeve 14 and bears against the sleeve's shoulder 15.

The hub 12 has a segment tooth 16 at an end and the sleeve 14 at the same end has a ring 17 with a tooth 18, said ring being fastened on the sleeve 14 by means, such as screws. A locking screw 20 passing through the tooth 18 and sleeve 14 connects the sleeve 14 rigidly with the shaft 5 through a slot 21.

Coming off the roll, the band 2 of the thermo-softening separating material (FIG. 1) moves around the rods 3 and support 4, passes under the electric cutters 6 which cut it into strips 22, 23, the latter being delivered by the pulling rollers 9, 10 to the receiving shafts of the strip wind-up mechanism (not shown in the drawings). The arm 7 (FIG. 2) with the electric cutter 6 has a working position "A" and an auxiliary position "B" to which the electric cutters 6 are automatically shifted by the drive 8 (FIG. 1) which turns the shaft 5 through a preset angle in either direction. The arm 7 with the electric cutter 6 can also be shifted manually to an inoperative position "C" (FIG. 2) so as to bear against a support rod or tie 24, for example when it becomes necessary to clean the cutter blade.

The construction of the electric cutters 6 in the form of a disc mounted on an arm with a provision for turning around its axis extends the life of the cutters before resharpening.

The drive 8 for lifting the electric cutters 6 (FIG. 1) can be mechanical, pneumatic, hydraulic, etc. though it is essential that it should be reversible and linked with a common drive through a time relay or limit switches which serve to automatically lift the cutters 6 immediately after stopping of the band 2 and restart said drive only after complete lowering of the electric cutters 6 and heating of the material at the point of cut.

The device for longitudinal cutting of a thermo-softening material into strips functions as follows. The band 2 of a thermo-softening material is moved by the pulling roller 9, 10 between the support 4 and electric cutters 6 cutting it into strips 22, 23 which are delivered into a wind-up device where they are wound on reels (not shown in the drawings).

The stopping of the rotation drive of the pulling rollers and of the band 2 over the support 4 is accompanied by a simultaneous starting of the drive 8 which turns the shaft 5 clockwise (FIG. 2). The sleeve 14 turns together with the shaft while the tooth 18 engages the tooth 16 and shifts the hub 12 together with the arm 7 and electric cutter 6 to position "B". From this position the arm 11 can be shifted by hand to position "C" when it becomes necessary, for example, to clean the blade of the cutter 6 of carbon deposits and remaining molten material. On turning the rotation drive of the pulling rollers 9, 10, first the drive 8 is started for turning the shaft 5 in the opposite (counterclockwise) direction. Turning together with the shaft 5 are the sleeve 14 and tooth 18. The weight 13 and the arm 7 also turn after the tooth 18 contacts the tooth 16 and thus rotates the hub 12 and the arm 7 which is connected thereto. The arm 7 stops moving when the cutter 6 comes in contact with the support 4 and the band 2 whereas the shaft 5 goes on rotating, and creates a clearance between the teeth 16 and 18, said clearance guaranteeing the lowering of all the electric cutters 6 mounted on the shaft 5 from position "B" to position "A" wherein they touch upon the band 2 and the support 4.

Then either a limit switch or a time relay turns on the drive 8 and the drive which moves the band 2 over the support 4 under the electric cutters 6 thus ensuring continuity of cutting of the band 2 after stopping.

The arms 7 withdrawn to the inoperative position "C" leave the operating zone of the tooth 18 and are no longer acted upon by the drive 8. This permits early setting of the device for cutting the band 2 into a number of strip widths or sizes, thereby ensuring prompt transition from one width of strips to another so that the device can be used in both large and small-scale production. To change the width of the strips the locking screw 20 is loosened and the sleeve 14 is moved to the required position on the shaft 5. Thereafter, the screw 20 is tightened on the shaft 5 so as to hold the sleeve 14 in its new position, and all of the subsequent manipulations with the arms 7 take place without disturbing the initial setting.

The device for longitudinal cutting of a thermo-softening material into strips ensures automation of the longitudinal cutting of thermo-softening bands 2 of thin low strength separating materials into strips, particularly in the mechanized application to battery electrodes by providing the cutting mechanism in the form of a plurality of arms with electric cutters 6 whose hubs 12 have a segment tooth 16 on a surface face and are mounted on the shaft 5 with the aid of an intermediate sleeve 14. The sleeve 14 has a mating segment tooth 18 and is secured on the shaft 5 along the line of cut, and it permits lifting automatically all of the electric cutters 6 from the cutting zone (position "A") on stopping of the band 2 by the interaction of the segment teeth 16, 18 caused by the drive 8 rotating the shaft 5. Automatic lifting of the electric cutters 6 (on stopping of the device) to position "B" prevents melting of the material around the heated electric cuttter 6 when the band 2 stops which improves the quality of the produced strips 22, 23 and permits decreasing the allowances for the width of the strips (intended for application to the electrodes) thus economizing the separating material.

Besides, such a construction of the fastening of the electric cutters 6 allows any one of the cutters 6 to be shifted to an inoperative position "C" for periodical removal of carbon deposits without disturbing the initial setting of the width of the strips being cut which also improves the quality of the strips 23, 24. The fastening unit of the electric cutters 6 also permits prompt resetting of the device for cutting strips of a different width by partial replacement of some of the electric cutters. This is done when the electric cutters are in the inoperative position "C" and have been reset in advance for the various new strip widths, thus enabling the device to be used both in large- and small-scale production.