Device for retaining knife blades

Abstract: The present invention relates to a device for retaining knife blades for cutting, perforation or other treatment of a running web, perferably a paper web, whereby said web runs between a rotatable knife-retaining cylinder (3) and a counter pressure cylinder (5), whereby the knife blade (2) may be wedged up by means of a wedge device (K) by being brought into the slot (6) by means of the counter pressure cylinder (5). In order to permit effective wedge up of knife blades (2) in exact positions in the slot (6) even it said blades have dimensions which differ from knife blades of a certain defined dimension, the wedge device (K) comprises and/or cooperates with at least one spring means (17) disposed beside said wedge device in the slot (6) and, upon insertion of a knife blade (2) into the slot (6) for wedging up thereof by means of the counter pressure cylinder (5), compressible to a dimension which lies within such an interval that it permits insertion of those knife blades (2) into the slot (6), the dimensions of which differ from said certain, defined dimension and lie within such a certain, defined range of tolerance including said defined dimension, whereby said spring means (17), when compressed to a dimension within said interval, has such a spring force that knife blades (2) having dimensions within said range of tolerance are retained in the slot (6).

Description: The present invention relates to a device for retaining knife blades for cutting, perforation or other treatment of a running web, preferably a paper web, whereby said web runs between a rotatable knife-retaining cylinder and a counter pressure cylinder, whereby the knife blade cooperates with a wedge device which is adapted to wedge up said knife blade in a slot in the knife-retaining cylinder, whereby the knife blade can be wedged up by means of the wedge device by being brought into the slot by means of the counter pressure cylinder, whereby the wedge device cooperates with a height-adjustment device which is adapted to permit setting of said wedge device at such height in the slot that said wedge device is able to wedge up a knife blade of a certain dimension, whereby the wedge device comprises two rulers having inclined wedge surfaces relative to the blade, whereby the wedge device comprises at least one resilient means which is provided to affect the rulers in a direction relative to each other and parallel to the blade in order to retain said rulers and the knife blade in the slot until they are wedged up therein, and whereby one of the rulers is a retaining ruler including a support portion through which the knife blade displaces the retaining ruler by means of the counter pressure cylinder so that the retaining ruler is pressing the knife blade against a side wall of the slot. A device of the above type is already known from SE patent specification 8900391-7 or from the corresponding US patent specification 4 920 843 and it functions excellent if the knife blades have the required dimensions. By setting the wedge device such that its height position in the slot is adapted to the required dimension of the knife blade, efficient wedging-up of said knife blade is obtained as well as an exact predetermined position thereof. However, it has been noticed that knife blades for various reasons in some cases do not have the required dimensions, but the height thereof can vary e.g. within the tolerance interval ± 0,2 mm and/or the thickness within the tolerance interval ± 0,1 mm. If the knife blades have dimensions lying at the limits of said tolerance intervals, there is a risk that they are either not properly wedged up or that they are wedged up too high up in the slot. This can result in that these knife blades loosen from the slot or damage the counter pressure cylinder or the material to be treated. The publication EP-A-0 095 912 relates to a device for retaining knife blades with a wedge device. An elastomeric strip is mounted to a channel in such side of the ruler which is facing the knife. The elastomeric strip is engaging the knife. A problem with this construction is that there is a risk that the knife by mistake is positioned on the upper side of the elastomeric strip so that the strip prevents the knife from being displaced to the support portion. The object of the present invention is to eliminate this problems by means of a simple and reliable device. According to the invention this is arrived at essentially by providing the abovementioned device with the characterizing features of claim 1. By mounting the elastic pad in a recess in the tightening ruler so that the elastic pad will be partially located between said tightening ruler and the adjacent wall of the slot, the elastic pad can not prevent the knife from being displaced to the support portion by the pressure cylinder. The invention will be further described below with reference to the accompanying drawings, wherein figure 1 is a perspective view of two cylinders, of which one cylinder is provided with knife blades retained by a retaining device according to the invention; figure 2 is a partial sectional view of the retaining device of figure 1; figure 3 is a cross-sectional view of the retaining device of figure 2 at a location where said device comprises height-adjustment or height-setting means; figure 4 is a cross-sectional view of the retaining device of figure 2 at a location where said device comprises a spring means according to the invention; figure 5 is a schematic view of the retaining device before wedging up the knife blade; figure 6 is a schematic view of the retaining device with wedged up knife blade with a certain, defined height; and figure 7 is a schematic view of the retaining device with the knife blade wedged up with a greater height. The retaining device 1 shown in the drawings is adapted for retaining a knife blade 2 on a rotatable knife-retaining cylinder 3. The knife blade 2 is adapted for cutting, perforation or other treatment of a running web 4, preferably a paper web, which e.g. runs through a printing press (not shown). The web 4 runs through a space between the knife-retaining cylinder 3 and a rotatable counter pressure cylinder 5 and is shown with dashed and dotted lines in figure 1. The knife-retaining cylinder 3 has a number of slots 6, normally six, wherein knife blades are wedged up by means of a wedge device K. The wedge device K may e.g. comprise a retaining ruler 7 which is adapted to retain the knife blade against one side wall 8a of the slot 6. The wedge device K may also comprise a tightening ruler 9 disposed beside the retaining ruler 7 and adapted to engage the opposite side wall 8b of the slot 6. The retaining ruler 7 has a wedge surface 10 facing the tightening ruler 9 and extending in a direction sloping downwards relative to the slot 6. In other words, the wedge surface extends such that it, seen from above and downwards, approaches the side wall 8a of the slot 6. The wedge surface 10 of the retaining ruler 7 cooperates with a corresponding wedge surface 11 on the tightening ruler 9. The wedge surface 11 also extends in a downwardly inclined direction relative to the slot 6 and also approaches the side wall 8a of said slot seen from above and downwards. The retaining ruler 7 includes a support portion 12 through which the blade 2 displaces the retaining ruler 7 during an adjustment manoeuvre. This support portion 12 may be provided on different portions of the retaining ruler 7 and may have various designs. A suitable position for the support portion 12 is down below on the retaining ruler 7 as shown in e.g. figure 2. The support portion 12 may further preferably be a flange protruding laterally from the retaining ruler 7, extending along the entire length thereof and having a width less than the thickness of the knife blade 2. The wedge device K cooperates with a height-adjustment or height-setting device H which is adapted to permit setting of said wedge device K at such a height in the slot 6 that said wedge device is capable of wedging up a knife blade 2 of a certain defined dimension. This height-adjustment device H may include or consist of one or more screws 13 which are screwed into the tightening ruler 9 and protrude downwards as legs through which the tightening ruler 9 engages the bottom 14 of the slot 6 or eventually a protective strip 15 disposed on the bottom 14 of the slot 6 and made of a harder material than the material in the knife-retaining cylinder 3. The heads of the screws 13 are accessible from above so that the screws can be screwed down or up with a tool, whereby the tightening ruler 9 can be lowered or raised in the slot 6. In order to ensure that the rulers 7, 9 and knife blade 2 remain in the slot 6 until they are wedged up therein, resilient means 16 are provided to affect the rulers 7, 9 vertically relative to each other. These resilient means 16 (there are preferably a plurality thereof) are compressible by manually displacing the retaining ruler 7 upwards relative to the tightening ruler 9 until the total width of both rulers 7, 9 and the blace 2 is less than that of the slot 6. The rulers 7, 9 with the blade 2 are in this condition insertable into the slot 6, whereafter whey are released. Thereby, the resilient means 16 will displace the retaining ruler 7 relative to the tightening ruler 9, which means that the total width of said rulers 7, 9 and the knife blade is increased until they are fixed in the slot 6. The resilient means may consist of helical compression springs 16 which down below engage the retaining ruler 7 and on top engage the tightening ruler 9, but said resilient means may alternatively consist of springs of another type. The knife blade 2 is wedged up by rotating the knife-retaining cylinder 3 a so called setting turn relative to the counter pressure cylinder 5. Thereby the edge of the blade 2 will strike the counter pressure cylinder 5 or a member deposited thereon with which said blade 2 shall cooperate. Thereby, the peripheral surface of the counter pressure cylinder 5 or the member deposited thereon will press the blade 2 downwards to its cutting position. During this down-stroke pressing, the blade 2 will press the retaining ruler 7 downwards through the support portion 12, which means that the knife blade 2, by means of the rulers 7, 9 of the wedge device K, automatically will wedge up in the slot 6 with strength. In order to efficiently wedge up knife blades 2 in the slot 6 although said blades have dimensions which differ from knife blades of a certain defined dimension after which the height of the wedge device K has been set in the slot 6, said wedge device K comprises and/or cooperates with at least one spring means 17 disposed beside said wedge device in the slot 6 and compressible, upon insertion of a knife blade 2 into the slot 6 for wedging up thereof, to a dimension which lies within such an interval (e.g. 0,5 mm) that it permits insertion of those knife blades 2 into the slot 6, the dimensions of which differ from said certain, defined dimension and lie within such a certain, defined range of tolerance including said defined dimension. The spring means 17 has, when compressed to a dimension within said interval, such a spring force that knife blades 2 having dimensions within said range of tolerance are retained in the slot 6. The spring means 17 is preferably mounted in the slot 6 such that it in compressed condition occupies the width of said slot 6 between the side walls 18, 19 thereof together with the wedge device K, knife blade 2 and eventually further members disposed beside each other in the slot 6 when said knife blade 2 is wedged up therein. The spring means 17 preferably consists of such resilient material which is compressible and which essentially maintains the resilient properties obtained by the compression. The resilient material of the spring means 17 is preferably polyurethane and said spring means 17 can have the shape of an elastic strip or similar of polyurethane. The spring means 17 is arranged such that the tightening ruler 9 engages the side wall 8b of the slot 6 through said spring means 17. Furthermore, that side 9a of the tightening ruler 9 facing the side wall 8b of the slot 6 is provided with at least one recess 9b for the spring means 17, which is of such thickness that it protrudes out of said recess 9b and engages said side wall 8b of the slot 6. That portion 17a of the spring means 17 situated outside the recess 9b has e.g. a width of 0,3 - 1,0 mm, preferably about 0,5 mm. Furthermore, the spring means 17 preferably has a height which exceeds half the height of the tightening ruler 9. Additionally, a plurality of spring means 17 are preferably disposed along the tightening ruler 9, preferably on the portions thereof located between the height-adjustment screws 13 provided thereon. In fig. 5, the original shape of the spring means 17 before the knife blade 2 is wedged up in the slot 6, is shown schematically. The wedge device K is hereby, by means of the height-adjustment device H, set at a height in the slot 6 adapted for wedging up knife blades 2 of a certain, defined height X. As is shown, the spring means 17 has a width of e.g. totally 2 mm, whereby the portion 17a thereof located outside the recess 9b is e.g. 0,5 mm wide. In fig. 6, it is shown how the spring means 17 is compressed when the knife blade 2 with the height X is wedged up. As is shown, the spring means 17 has been compressed such that the portion 17a thereof located outside the recess 9b is reduced to e.g. 0,3 mm. The spring means 17 hereby exerts a substantially remaining spring force such that the knife blade 2 is retained in the slot 6. In fig. 7 it is shown that the spring means 17 has permitted a knife blade 2 with the height X + 0,2 to be wedged up in the slot 6 while maintaining the height position of the wedge device K. Here, the spring means 17 has been compressed more than in the embodiment described above, such that the portion 17a thereof located outside the recess 9b is reduced to e.g. 0,1 mm. Similarly, the spring means 17 permits mounting of knife blades 2 deviating from a certain, defined dimension regarding their height and/or width, provided the deviations in dimension lie within a certain, defined interval. The dimensions of the spring means 17 may vary in such a way that it can be compressible from its original shape to between 0,1 - 1,0 mm and/or such that it permits application and retention of knife blades 2, the height of which varies within an interval of up to e.g. ± 0,4 mm and the width within an interval of up to e.g. ± 0,3 mm.

Claims: Device for retaining knife blades for cutting, perforation or other treatment of a running web, preferably a paper web, whereby said web (4) runs between a rotatable knife-retaining cylinder (3) and a counter pressure cylinder (5), whereby the knife blade (2) cooperates with a wedge device (K) which is adapted to wedge up said knife blade in a slot (6) in the knife-retaining cylinder (3), whereby the knife blade (2) can be wedged up by means of the wedge device (K) by being brought into the slot (6) by means of the counter pressure cylinder (5), whereby the wedge device (K) cooperates with a height-adjustment device (H) which is adapted to permit setting of said wedge device at such height in the slot (6) that said wedge device is able to wedge up a knife blade (2) of a certain dimension, whereby the wedge device (K) comprises two rulers (7, 9) having inclined wedge surfaces (10, 11) relative to the blade (2), whereby the wedge device (K) comprises at least one resilient means (16) which is provided to affect the rulers (7, 9) in a direction relative to each other and parallel to the blade (2) in order to retain said rulers and the knife blade (2) in the slot (6) until they are wedged up therein, and whereby one of the rulers is a retaining ruler (7) including a support portion (12) through which the knife blade (2) displaces the retaining ruler (7) by means of the counter pressure cylinder (5) so that the retaining ruler (7) is pressing the knife blade (2) against a side wall (8a) of the slot (6), characterized in that the wedge device (K) comprises and/or cooperates with at least one spring means formed as an elastic pad (17) consisting of compressible resilient material, preferably polyurethane, which essentially maintains the resilient properties obtained by compression, that the elastic pad (17) is provided to occupy the width of the slot (6) together with said wedge device and the knife blade (2), that the elastic pad (17) upon insertion of a knife blade (2) into the slot (6) by means of the counter pressure cylinder (5) for wedging up said knife blade, is compressible to a dimension which lies within such an interval that it permits insertion of those knife blades (2) into the slot (6), the dimensions of which differ from said certain, defined dimension and lie within such a certain, defined range of tolerance including said defined dimension, that the elastic pad (17), when compressed to a dimension within said interval, has such a spring force that knife blades (2) having dimensions within said range of tolerance are retained in the slot (6), that the side (9a) of the tightening ruler (9) facing a side wall (8b) of the slot (6) is provided with at least one recess (9b), and that the elastic pad (17) is mounted in the recess (9b) such that it protrudes out of said recess (9b) and engages said side wall (8b). Device according to claim 1, characterized in that the portion (17a) of the elastic pad (17) situated outside the recess (9b) has a width of 0,3 - 1,0 mm, preferably about 0,5 mm. Device according to claim 1, characterized in that the elastic pad (17) has a height which exceeds half the height of the tightening ruler (9) and that a plurality of elastic pads (17) are disposed along the tightening ruler (9), preferably on the portions thereof located between height-adjustment screws (13) of the high adjustment device (H) provided thereon. Device according to any preceding claim, characterized in that the elastic pad (17) consists of an elastic strip of polyurethane which is cemented onto the tightening ruler (9). Device according to claim 1, characterized in that the spring means (17) from an original shape is compressible 0,1 - 1,0 mm, preferably 0,1 - 0,5 mm, whereby its spring tension, generated during compression, is sufficient to retain knife blades (2) the height of which varies within an interval of about ± 0,2 mm and/or the width of which varies within an interval of about ± 0,1 mm.

Inventors: LARSSON ROLF ARNE, STROEMBERG SVEN ARNE ROLAND, LARSSON, ROLF ARNE, STROEMBERG, SVEN ARNE ROLAND, STRÖMBERG, Sven Arne Roland
Applicants: LARSSON ROLF ARNE, STROEMBERG SVEN ARNE ROLAND, LARSSON, ROLF ARNE, STROEMBERG, SVEN ARNE ROLAND
Application year: 1993
Main classification: B65H35
IPC codes: B26D1, B26D7