EP0095912B1

EP0095912B1 - Blade holding device

Info

Publication number: EP0095912B1
Application number: EP83303078A
Authority: EP
Inventors: William Blauser Attenweiler; Dineshchandra Gulabrai Punater; John Lawrence Herman
Original assignee: Harris Graphics Corp
Current assignee: Cessione am International Inc
Priority date: 1982-06-01
Filing date: 1983-05-27
Publication date: 1988-03-23
Also published as: CA1206374A; EP0095912A2; EP0095912A3; DE3376058D1

Description

The present invention relates to a device for mounting and accurately seating a perforating or cutoff blade along a cylinder such as might be used for partially or completely severing a web at a plurality of locations along its length. Such devices are particularly useful in machines for continuous printing or collating of paper webs.
One of the requirements for such blade mounting arrangements is that the blade be capable of removal, replacement and/or repositioning along the rotating blade cylinder. From time to time during the operation of the machine, it is necessary to remove the blade from the cylinder, for instance, when it may be desired to print a web without perforating or severing the same, or when replacement of the blade is necessary due to dulling or breakage of the blade.
A second requirement for such blade mounting arrangements is that the cutting edge of a perforating blade be capable of accurate seating against an anvil surface. Otherwise, an uneven perforation will result, with some sections of the perforation being too deep, or some sections being too shallow, or both. This produces variation in the tear strength along the perforation, with resultant high probability of jamming in subsequent printers or bursters. A backup or anvil cylinder may be included for providing a hardened anvil surface, or insert, or in some cases a die, to cooperate with the sharpened edge of the properly seated blade in perforating the passing web as the web moves between the rotating blade cylinder and anvil or backup cylinder.
The blade is mounted to the rotating cylinder by clamping the blade into a recess or slot cut generally lengthwise into the cylinder periphery. Typically, the recess is rectangular in cross section, and the blade may be clamped against one of the side faces of the recess, or against an intermediate supporting bar. Several techniques are available, however, for providing proper seating of the cutting edge of the blade against the anvil surface.
Typically, when a perforating blade is manufactured, it includes some variation in height from its base to its cutting edge, as well as a tendency to bow in a lateral direction. One method for seating the blade is to use a blade which has been manufactured to very close tolerances with respect to both height and bow. The cylinder is provided with a recess that has been machined also to very close tolerances with respect to a uniform and specific depth. Seating of the blade is relatively simple, since the blade is loaded into the recess, with the base of the blade bottomed along the base of the recess, and is then clamped tightly in place.
Despite the simplicity of the seating process, this technique possesses several readily apparent disadvantages. By requiring very close tolerances in manufacturing of the blades, the cost of the blades is increased significantly. Similarly, the cost of the cylinder into which the recess is cut is also increased, particularly in view of the fact that such cylinders typically have as many as eight such recesses for mounting up to eight blades at one time. Moreoever, in the event that blade height or recess depth varies even slightly from blade to blade or recess to recess, the cutting edge of a blade extending slightly further from the recess than another will be dulled relatively quickly through contact with the anvil surface.
A second technique is available, in which a blade having very loose height and bow tolerance may be used. The blade is inserted into the recess, but is not bottomed against the base of the recess, and is secured somewhat loosely along its length. The blade is then seated against the anvil surface, through a procedure known as "crash in". This procedure consists of rotating the blade cylinder and anvil cylinder, with or without a web passing therebetween at inching speed through one revolution. The cutting edge of the blade is free to move under the seating force sufficiently into the recess, at whatever locations are necessary to obtain a uniform seating of the cutting edge against the anvil. While secured somewhat loosely, the blade must be nonetheless held tight enough to hold its seated position. The apparatus is then stopped and the blade is securely clamped along its entire length to prevent slip within the recess when the apparatus is operated at higher speeds.
While this technique requires a more complicated blade seating technique, it allows the use of blades and cylinders manufactured to much looser tolerances, with substantial cost savings. A third technique, possessing some of the advantages and disadvantages of both techniques, utilizes a blade having close tolerance with respect to height only. While the blade is bottomed against the recess base, crash-in is required to remove vertical bow from the blade.
It will be noted that the foregoing discussion is equally applicable in the case of cut-off blades.
A number of various devices for accurately securing a blade within a recess, suitable for holding the blade both for crash-in and for clamping, are known. For instance, the blade may be placed against a side wall of the recess, and a bar inserted into the recess adjacent the blade. A plurality of bolt members are threaded into holes in the bar, extending from the side of the bar to the recess side wall opposite the blade. To clamp the blade, the bolt members are driven in a direction outwardly from the bar against the recess wall. Driving of the bolt members forces the bar tightly against the blade, thereby clamping it in place. In using such a device, the bolt members may be partially tightened, allowing the blade limited movement for seating against the anvil surface during crash-in, and then the bolt members may be completely tightened for clamping.
Several disadvantages are present in such a blade holding device. In order to provide relatively uniform clamping force on the blade, a relatively large number of the bolt members must be provided disposed along the length of the bar. Thus, the clamping operation becomes a time-consuming process. Furthermore, positioning of the bolt members for crash-in must be fairly precise, since there is a relatively narrow force range suitable for crash-in wherein the blade is held loosely enough for movement during seating but tight enought to retain the seated position. Furthermore the bolt members also must be finally tightened to a relatively uniform degree, or uneven perforation will result where the blade is inadequately clamped. Consequently, during crash-in and in clamping the blade, either a torque wrench must be used, or the operator must through experience develop a "feel" for the proper tightening of the bolt members.
In U.S. patent No. 4,131,047, issured December 26, 1978, to Schriber et al, a blade holding device is disclosed in which a wedge bar is provided for clamping the blade into the cylinder recess. The blade is placed against a side wall of the recess, and the wedge bar is provided with a vertical taper, i.e., in a radial direction with respect to the cylinder. A non-rectangular cross-sectional recess may be provided, or an intermediate member placed between the blade and the wedge bar and having a taper opposite the wedge bar may be provided, along with a plurality of bolts extending through the wedge bar and into the cylinder at the bottom of the recess. By driving the bolts, the wedge bar is forced into the recess in a direction toward the axis of the cylinder, thereby securely clamping the blade into the recess. Preloading springs may be provided to act on the wedge bar with a force sufficient to retain the blade during crash-in while allowing limited movement of the blade within the recess for seating. Following seating, the bolts are tightened to firmly secure the blade.
By providing the preloading springs for supplying sufficient clamping force for seating of the blade, the Schriber et al device eliminates the need for the operator to manipulate the bolts during the crash in process. Additionally, by providing bolts that are driven radially with respect to the cylinder, rather than disposed within the-recess, access to the bolts is facilitated. Nonetheless, the Schriber et al device utilizes a plurality of bolts to provide a relatively uniform clamping force on the blade. Moreover, since the bolts are disposed along the entire length of the wedge bar, the operator must reach along the full length of the cylinder during the clamping process. Thus, even with the Schriber et al blade holding device, the clamping process is both time-consuming and awkward to perform.
In U.S. patent No. 2,832,411, issued April 29, 1958, to Richards et al, another blade holding device is disclosed, for use in conjunction with a cylinder having a recess that is at an angle with respect to the axis of the cylinder. A pair of wedge bars, each extending for substantially the full length of the recess, are located within the recess with the blade inserted between the bars. The ends of the cylinder are provided with collars, each having a slot adjacent the recess, into which a bolt is fitted. The bolts each have a pair of flanges near the head, and when the bolts are placed into the slots, the flanges fit one on each side of the slot. Each bolt extends into a threaded bore in an end of one of the wedge bars, such that by rotating the bolts, each bar may be moved in either direction along the cylinder recess. To clamp the blade, the bolts are rotated such that the wedge bars are driven into the recess so as to wedge the blade into place. Notches or other indicia are provided along the upper surface of one of the wedge bars and the cylinder surface, so that the relative movement of the bar in relation to the cylinder for aligning the blade may be easily determined.
The Richards et al device reduces the number of bolts which must be manipulated during the clamping process in comparison with the devices described above. It is indicated in the patent, however, that the primary purpose of the device is to enable the angle of the blade with respect to the direction of travel of the web to be somewhat adjustable, although the device seems better suited for adjusting the distance from the blade along the cylinder periphery to a next following blade. In either case, while such a feature may be desirable in compensating for an improperly machined cylinder and/or associated gears, it requires the operator of the device during the clamping process to ensure that the blade is mounted either precisely perpendicular to the web, or precisely to the required spacing from perforation to perforation or from separation to separation. Consequently, any reduction in complexity or time obtained through use of the Richards device is lost in the necessary adjustment of the blade angle or radial position. Further, by having bolt members extending from each end of the cylinder, the operator is required to travel around the machine during the clamping process as blade angle and position adjustments are made. Finally, use of the device requires a cylinder having a recess cut an angle with respect to the cylinder axis. To use this device, then, a specially constructed cylinder must be used.
In addition, the Richards et al patent does not address the problem of holding the blade for seating during crash-in, and in fact, shows the blade bottomed on the recess base. Moreover, the Richards device possesses several disadvantages that make it impractical for use with a blade that must be seated for uniform perforation.
Because the force exerted upon the blade must be substantially uniform to ensure uniform perforation, the fit of the wedge bars into the recess must be very precise. Thus very close tolerances must be provided in the widths of the wedge bars, recess, and blade, since variations in these dimensions will produce variations in the "tightness" of the fit of the wedge bars within the recess as the bars are wedged into place, thereby producing variations in the force applied to blade. As a result, not only is manufacture of the bars, recess and blade made difficult and expensive, but the slightest mishandling of these parts during use may be sufficient to misalign them to the extent that uniform force is no longer attainable.
Further, since the range of force values acceptable for crash in is relatively narrow, careful positioning of the bars is required prior to crash-in. This requires the expenditure of significant amounts of time, use of special tools, and/or the development of special skills by the operator for proper adjustment of the bars.
US-A-3793918, which is considered to represent the closest known prior art, discloses another blade holding device comprising a multiplicity of clamp rollers distributed along the recess with their axes disposed radially of the cylinder. The rollers are loose and shiftable transversely and longitudinally in the recess, and are disposed in two longitudinal rows with the peripheries of the rollers in one row projecting between and contacting the peripheries of the rollers in the other row. By applying a compressive force to the rollers longitudinally of the recess the two rows are cammed apart transversely, thereby to exert a clamping force on the blade at a plurality of locations along the length thereof. Whilst the device is claimed to be capable of quickly, accurately and uniformly clamping the blade in its operative position, it possesses the previously described disadvantage that there is only a relatively narrow clamping force range which is suitable for crash-in wherein the blade is held loosely enough for movement during seating but tight enough to retain the seated position.
What is needed, therefore, is a blade holding device for use with a cylinder in which the blade may be clamped in a relatively quick and simple manner. Such a device should require manipulation of few parts during the clamping operation, and should not require the use of any special tools or special skills on the part of the operator. The device should enable the blade to be secured loosely into the cylinder with uniform securing force, properly seated against an anvil surface, and then tightly clamped into place. Clamping force should be uniformly applied along the length of the blade. The device should be relatively simple to manufacture, and should not require unreasonably tight manufacturing tolerances.
It is an object of the present invention to provide a device for clamping a blade to a rotary cutter cylinder by means of which the blade may be inserted into and held in place by the device so that the blade may move as necessary to seat against an anvil surface during crash-in, whilst it is held so that it will be retained in the seated position. Thereafter, the blade holding device can be tightened in order to secure the blade in the seated position.
According to the present invention, there is provided a blade holding device for use with a blade and a rotatable cylinder, the cylinder having a longitudinal recess defined in the periphery thereof parallel to the axis of the cylinder, members fittable within the recess with adjacent faces in mutual contact, such that the blade is disposed between the members and a waU of the recess, and means for performing relative movement of the members whereby the blade is clamped between the members and the recess wall, characterized in that:

said members comprise first and second wedge members fittable within the recess, each said wedge member having an inner wedge face and an outer face, each of said wedge members being tapered in a direction longitudinal along said recess;
said wedge members being insertable within the recess with said inner wedge faces in mutual contact, such that, in operation, the blade is disposed between said outer face of said first wedge member and a wall of the recess; and
said movement performing means comprise means for performing relative movement between said wedge members in a direction along the recess, said first wedge member being operative in response to said movement to apply force to the blade for retaining the blade within the recess;
means being provided for increasing said retaining force applied to the blade as a non-linear function of relative displacment between said wedge members.

In one prefered embodiment, to ensure uniform holding force against the blade for crash-in, the retaining force-increasing means includes at least one spring member disposed adjacent the outer face of the first wedge member between the wedge member and the blade. In a further preferred embodiment, a plurality of spring members may be provided in the form of Belleville disc springs, although a spring member in the form of a corrugated metal strip or elastomeric strip may alternatively be used. The disc springs may be held in relative positions, and the holding means may be a strip constructed of a resilient material having a plurality of holes along the length thereof. The disc springs are mounted one each within each hole. The first wedge member includes a relatively shallow channel defined along the length of its outer face, so that the resilient strip may be mounted along the channel, whereby the disc springs may abut the blade, for example, perforating blade, when the blade and first wedge member are inserted into the recess of the cylinder.
Inclusion of the spring members provides a wide range for relative positioning of the wedge members for crash-in. Because the range of holding force exerted upon the blade for proper seating is relatively narrow, the spring members make application of the proper force easier, faster, and more precise than in previously known devices.
The spring members also allow a wider range of tolerance for the recess or slot width, wedge member width and blade thickness, and produce more uniform crash-in force along the entire length of the blade.
The relative movement of the wedge members within the cylinder recess may be performed by providing an end member mounted to one end of the cylinder adjacent the recess. The end member includes an opening therein, through which a bolt is extended. The bolt has at least one flange near its head, the flange being disposed on one side of the opening for retaining the bolt in a position relative to the end member. The bolt is further engageable with one of the wedge members, so that by rotating the bolt, the wedge member. may be move relative to the cylinder, and hence relative to the other wedge member.
The bolt may be engageable with an end of the second wedge member, and the relative movement of the wedge members is performed by moving the second wedge member along the recess. The first wedge member is captured between two end rings to prevent its movement along the recess. Additionally, at least a portion of the outer face of the first wedge member is roughened to increase the holding force on the blade or to prevent slippage of the blade within the recess.
In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which:

Fig. 1 is a perspective view of a portion of a rotary cutter cylinder showing insertion into a recess therein of a blade and the blade holding device embodying the present invention;
Fig. 2 is a plan view of the cylinder showing the blade and blade holding device in position;
Fig. 3 is a sectional view of a portion of one end of the cylinder, showing the wedging mechanism for operating the blade holding device with the blade firmly clamped in place;
Fig. 4 is a view similar to Fig. 3 showing the operation of the wedging mechanism and with the blade in position for seating within the recess;
Fig. 5 is a graph showing the load applied to the perforating blade as a function of displacement of a wedge member along the recess, and as a function of the compression of the wedge members and spring members across the recess;
Fig. 6 is an enlarged cross-sectional view of a segment of the cylinder, taken generally along line 6-6 of Fig. 3;
Fig. 7 is a view similar to Fig. 6, taken generally along line 7-7 of Fig. 4;
Fig. 8 is a perspective view of a portion of a wedge member, showing an alternative embodiment for the spring member; and
Fig. 9 is a cross-sectional view similar to a portion of Fig. 6, showing a further alternative embodiment for the spring member.

Fig. 1 shows a portion of a typical rotary cutter cylinder 10 to which may be mounted a blade 12 of any length up to and including the length of the cylinders. Blade 12 is shown as a perforating blade, but alternatively may be a cutoff blade. The cylinder 10 includes a longitudinal recess 14 defined along the periphery of cylinder 10. Recess 14 is preferably rectangular is cross-section, and as seen in Fig. 6, includes a base 15 and opposed walls 16 and 18. Referring back to Fig. 1, blade 12 may be inserted into recess 14 of cylinder 10 for mounting, although blade 12 is not bottomed against base 15, allowing space both for crash-in and storage of blade 12 when not in use. Blade 12 is held in position by the blade holding device 20 embodying the present invention.
Blade holding device 20 includes a pair of wedge members 22 and 24. Each wedge member 22 and 24 has an inner wedge face 23 and 25, respectively, and an outer face 26 and 27, respectively. As may be seen in Fig. 2, wedge members 22 and 24 are tapered in a direction longitudinally along the recess 14. Further, wedge members 22 and 24 are insertable into recess 14 of cylinder 10 with wedge faces 23 and 25 in mutual contact, such that the blade 12 may be held between outer face 26 of wedge member 22 and wall 16 of recess 14. Wedge member 24 is moved relative to wedge member 22, applying a wedging force against both walls 16 and 18 of recess 14, thereby clamping blade 12 into position.
The means for effecting movement of wedge member 24 with respect to wedge member 22 may be seen in Fig. 1, 3 and 4. Wedge member 24 is provided with a threaded bore 28 in one end thereof. Bolt 29, engageable with bore 28 includes a head 30 and a pair of flanges 32 and 34. An annular collar 36 attached to one end of cylinder 10 by a plurality of bolts 38 includes notch 40, communicating with recess 14 of cylinder 10. When wedge member 24 is inserted into recess 14, and bolt 29 is threaded into bore 28, notch 40 provides for extension of head 30 of bolt 29 beyond collar 36, so as to allow manipulation of bolt 29 from a position adjacent one end of cylinder 10.
Notch 40 of collar 36 includes a relatively shallow portion 42 having a groove 44 defined therein. A retaining member 46, having a groove 48, is mounted to relatively shallow portion 42 by a pair of bolts 50. Grooves 44 and 48 cooperate to define a hole, and bolt 29 is fittable within the hole such that flanges 32 and 34 are disposed on each side of the hole. Grooves 44 and 48 are sized accordingly such that flanges 32 and 34 retain bolt 29 within the hole but bolt 29 is freely rotatable within the hole.
In the alternative, of course, it will be recognized that bolt 29 may have a single flange, with the single flange and bolt head 30 cooperating at opposite ends of grooves 44 and 48 for retention of bolt 29 within the hole defined by grooves 44 and 48.
The operation of bolt 29 for moving wedge member 24 relative to wedge member 22 may be seen by comparing Figs. 3 and 4. Fig. 3 illustrates the wedge members 22 and 24 wedged into recess 14 of cylinder 10 such that blade 12 is securely held between outer face 26 of wedge member 22 and wall 16 of slot 14. To release blade 12, head 30 of bolt 29 is gripped by an appropriate tool (not shown) and bolt 29 is rotated in the direction indicated by arrow 52 in Fig. 4. It will be noted from arrow 52 that bolt 29 and bore 28 are provided with left-handed threads, and bolt 29 may have multiple start threads for faster movement of bolt 29 along bore 28, and hence, faster operation of the blade holding device 20. By rotating within threaded bore 28 of wedge member 24, bolt 29 draws wedge member 24 in a direction toward collar 36, as indicated by arrow 53. As wedge member 24 is drawn toward collar 36, wedge members 22 and 24 no longer apply wedging force to the walls of recess 14, and blade 12 is released and may be removed.
It will be recognized that to move wedge member 24 for clamping blade 12 into recess 14, the opposite of the operation described above is performed. Bolt 29 is rotated in a direction opposite to that indicated by arrow 52, thereby moving wedge member 24 away from bolt 29. Wedge members 22 and 24 apply a wedging force to the walls of recess 14, clamping blade 12 into place.
During either of these operations, wedge member 22 remains stationary within recess 14, retained by collar 36 and an annular end ring 54 mounted to the opposite end of cylinder 10 from collar 36.
It can easily be seen that the force or load applied to blade 12 by blade holding device 20 is dependent upon compression of wedge members 22 and 24 across recess 14, which in turn is dependent upon the displacement of wedge member 24 along recess 14. Accordingly, as an aid to the operator of the device 20 in positioning wedge member 24 relative to wedge member 22, which remains stationary, each wedge member is provided with marks, notches or other indicia 55 to present a visual indication of their relative movement.
To facilitate the movement of wedge member 24 relative to and in contact with wedge member 22 and recess 14, any appropriate solid lubricant may be applied to the wedge face 25 and outer face 27 of wedge member 24.
During crash-in of blade 12 for proper seating within recess 14 to provide a uniform perforation or severing of a web passing along cylinder 10, force must be applied to blade 12 by the blade holding device 20 within a relatively narrow range of forces so that blade 12 is held loosely enough to permit seating, yet tightly enough to retain the seated position prior to final clamping. In order to expand the range of positions of wedge member 24 relative to wedge member 22 and recess 14 wherein force within the crash-in range is applied to blade 12, a relatively shallow channel 56 is defined along the length of the outer face 26 of wedge member 22, as seen in Fig. 1. A plurality of Belleville disc springs 58 are disposed along channel 56, and are held in relative position by a rubber strip 60. Rubber strip 60 includes a plurality of holes defined along its length, such that each spring 58 may be mounted within one of the holes and retained thereby. Springs 58 may be held into the holes of strip 60 either by cementing them in place, such as with a rubber cement, or molding the strip 60 about the springs 58 so that they are retained in place. Strip 60 is preferably mounted to channel 56 by a rubber cement material.
As seen in Figs. 6 and 7, during clamping of blade 12, springs 58, held in place by strip 50, are gradually compressed against blade 12 as wedge member 24 is wedged into recess 14. Once springs 58 are compressed to the point at which surfaces 61 of wedge member 22 are in contact with blade 12, however, further movement of wedge member 24 results in blade 12 being clamped essentially by the wedge members 22 and 24 directly.
Surfaces 61 may be roughened or knurled to provide increased holding force, by friction, for the blade 12 to prevent its slippage within recess 14.
The operation of springs 58 for providing relative ease in positioning wedge member 24 for crash-in of blade 12 may be seen by referring to Fig. 5, showing a plot of the load (force per unit length) placed upon the blade 12 by the blade holding device 20 as a function of the displacement of wedge member 24 along recess 14, and as a function of the compression of wedge members 22 and 24 and springs 58 across recess 14. It will be recognized that the values presented along the load axis of Fig. 5 are pertinentto blades and blade holding devices in general, independent of their length, and values presented along the compression axis are similarly independent of the angle formed between the wedge face 25 and outer face 27 of the wedge member 24. Values presented along the displacement axis of Fig. 5, however, are dependent upon the wedge member angle, and specific values in Fig. 5 are based upon an exemplary angle of 1°. It will be nonetheless understood that the shapes and relationships of the curves presented are correct for any angle.
It has been found experimentallythatthe proper load to be placed upon blade 12 for satisfactory crash-in is within the approximate range of 41.25 to 84.83 Kg/cm (231 to 475Ibs.lin.), indicated in Fig. 5 by arrow 64. Forfinal clamping of blade 12, a load of at least 250 Kg/cm. (1400 ibs./in.) must be applied, indicated at 66.
In the absence of springs 58, the load produced by deflection of wedge member 24, corresponding to direct compression of wedge members 22 and 24, follows the linear Hooke's law relationship for compression of an elastic body, with wedge members 22 and 24 having an effective force constant of 35154 Kg/cm² (500,000 Ibs./in.²), and is shown as curve 68 of Fig. 5. For crash-in, wedge member 24 must be moved between approximately 0.76 and 1.52 mm. (.03 and .06 inches) to produce a load on blade 12 within the appropriate range. It can easily be seen, however, that positioning of wedge member 24 must necessarily be relatively precise, i.3., to within a range of .76 mm. (.03 inch), in order to achieve the proper crash-in load. With such a small range, even indicia 55 are of relatively little help for proper positioning. Thus, special tools for adjusting bolt 29 must be used or the operator of the device 20 must develop special skills or expertise.
When springs 58 are provided as illustrated generally in Fig. 1, the displacement of wedge member 24 produces the load values indicated by curve 70 in Fig. 5. Initially, only springs 58 actually contact blade 12, as seen in Fig. 7, and as wedge member 24 is moved, springs 58 compress against blade 12. Springs 58 have a significantly lower force constant (or, more properly here, a spring constant), approximately 6679 Kg/cm² (95,000 Ibs./in²), than wedge members 22 and 24, and the initial portion of curve 70, indicated at 72, has a proportionately reduced slope.
Once springs 58 are compressed such that surfaces 61 of wedge member 22 contact blade 12, indicated at point 74 on curve 70, further displacement of wedge member 24 causes increases in the load on blade 12 to be applied by wedge members 22 and 24 directly. Accordingly, the final portion 76 of curve 70 is of the same slope as curve 68.
The effect of springs 58 upon the operation of blade holding device 20 for applying crash-in force to blade 12 may be appreciated by considering the crash-in load range 64. To apply the proper load, wedge member 24 must be moved between approximately 3.56 and 7.11 mm (.14 and .28 inches), or within a range of 3.56 mm. (.14 inch), as indicated at 77. Thus, a relatively broad range of positions is available for wedge member 24, making the use of indicia 55 much more practical and helpful. Since positioning of wedge member 24 is no longer so critical, no special tools or operator expertise is required for operating blade holding device 20.
After springs 58 are compressed such that surfaces 61 of wedge member 22 contact blade 12, further displacement of wedge member 24 causes the load to increase as shown by portion 76 of curve 70. Since portion 76 has a significantly increased slope compared to portion 72, relatively little additional displacement is necessary to apply the final clamping load to blade 12.
An additional, if not more important, advantage may be obtained through use of the spring members as provided in any of the embodiments disclosed above. In the absence of spring members, very close tolerances must be provided to insure the uniformity of the widths of the wedge members 22 and 24, the recess 14, and blade 12, with the attendant high cost and extreme care required in handling these parts. Otherwise, because of the relative rigidity of wedge members 22 and 24, variation in these dimensions may produce areas along blade 12 of varying load exerted thereon, resulting in uneven perforation or severing of the web. The required tolerance may be seen from Fig. 5. The compression range within the crash-in range where wedge member 22 and 24 are used without springs 58, shown on curve 68 as range 69, is between .0127 and .0254 mm (.0005 and .0010 inch). If the tolerance on any one or a combination of wedge members, blade or recess is such that any area along blade 12 is compressed outside this range, load applied will be outside the crash-in range, seating may not be accurate, and the resulting perforation or severing may be uneven. Thus, the tolerance required is .0254-.0127 mm.=0.0₁₂₇ mm (.0010 inch-.0005 inch=.₀₀₀₅ inch).
Due to the relative flexibility imparted to the blade holding device 20 by inclusion of one or more spring members, however, these tolerances may be relaxed. As shown at 77 along curve 70 of Fig. 5, when springs 58 are used, the compression range of wedge members and springs is between .061 and .127 mm. (.0024 and .0050 inch). Thus, inclusion of springs 58 allows wedge member, blade and recess tolerance to be increased to .066 mm (.0026 inch), a five-fold increase, with resulting significant cost savings in manufacture.
A number of alternative embodiments for the spring members may be used in place of springs 58 and rubber strip 60, each having the same operation as the embodiment just disclosed and producing a load-displacement curve of the same shape as curve 70. In Fig. 8, a single corrugated metal strip 78 is provided, fittable within channel 56 of wedge member 22. In Fig. 9, a continuous elastomeric strip 80 is used, mounted to channel 56 by a rubber cement material. A series of slightly compressible rollers or balls may be placed between the wedge members 22 and 24. Of course, it will be recognized that numerous other alternatives exist and may be used as well.
It will also be recognized that spring members may be used that are characterized by a non-linear compression-load relationship. Such an embodiment will produce a curve somewhat different from curve 70, in that the portion corresponding to portion 72 will not be linear, but will nontheless result in expansion of the compression and displacement ranges for crash-in, thereby obtaining the same advantages.
It is common practice to rotate the cylinder 10 on occasion when it'is desired not to perforate or sever the web. In such a case, the blade holding device 20 is unclamped, blade 12 is bottomed against recess base 15 so that the cutting edge of blade 12 is below the surface of cylinder 10, and the device 20 is reclamped. In the event device 20 is inadvertently left unclamped, however, a means for retaining wedge members 22 and 24 within recess 14 when unclamped is provided. In addition to collar 36 mounted to one end of cylinder 10, the annular ring 54 is provided at the opposite end seen in Fig. 2. Ring 54 is attached to cylinder 10 by a plurality of screws 86 (only one shown) and is of a radial width less than the depth of recess 14. A retaining pin 88 is mounted near the lower end of each of wedge members 22 and 24, such that when wedge members 22 and 24 are inserted into recess 14, retaining pins 88 extend from recess 14 under the ring 54. When cylinder 10 is rotated with wedge members 22 and 24 unclamped, retaining pins 88 cooperate with ring 54 to hold the wedge members in place. A similar retaining pin 88 is provided at the opposite end of wedge member 22, and is inserted into a half-slot (not shown) defined within collar 36. It will be seen that no retaining pin is required for the opposite end of wedge member 24, due to its engagement with bolt 29.
The device hereinbefore described and illustrated enables the blade to be initially secured sufficiently to allow it to seat against an anvil surface, and then be clamped to secure the blade for perforation of a web. The device exerts a uniform crash in or clamping force along the entire length of the blade. Furthermore, the device is relatively quick and simple to operate, is relatively easy to manufacture, and may be applied to cylinders having a standard configuration for the recess defined therein.
While the form of device herein described constitutes a preferred embodiment of this invention, it is to be understood that the invention is not limited to this precise form of device, and that changes may be made therein without departing from the scope of the invention as defined in the appended claims.

Claims

1. A blade holding device (20) for use with a blade (12) and a rotatable cylinder (10), the cylinder having a longitudinal recess (14) defined in the periphery thereof parallel to the axis of the cylinder (10), members fittable within the recess with adjacent faces in mutual contact, such that the blade is disposed between the members and a wall of the recess, and means for performing relative movement of the members whereby the blade is clamped between the members and the recess wall, characterized in that:

said members comprise first and second wedge members (22, 24) fittable within the recess (14), each said wedge member (22, 24) having an inner wedge face (23, 25) and an outer face (26, 27), each of said wedge members (22, 24) being tapered in a direction longitudinal along said recess (14);

said wedge members (22, 24) being insertable within the recess (14) with said inner wedge faces (23, 25) in mutual contact, such that, in operation, the blade (12) is disposed between said outer face (26) of said first wedge member (22) and a wall (16) of the recess (14); and

said movement performing means comprise means (29, 36) for performing relative movement between said wedge members (22, 24) in a direction along the recess (14), said first wedge member (22) being operative in response to said movement to apply force to the blade (12) for retaining the blade within the recess;

means (58, 61; 78,61; 80,61) being provided for increasing said retaining force applied to the blade (12) as a non-linear function of relative displacement between said wedge members (22, 24).

2. A blade holding device as claimed in claim 1, wherein said means for increasing said retaining force includes:

means (58) for increasing said retaining force applied to the blade (12) at a first rate in response to said relative movement between said wedge members (22, 24) up to a specific force value; and

means (61) for increasing said retaining force applied to the blade (12) beyond said specific force value at a second rate in response to said relative movement between said wedge members (22, 24).

3. A blade holding device as claimed in claim 1 or 2, wherein said means for increasing said retaining force includes at least one spring member (58) disposed in compression between one of said outer faces (26, 27) of said wedge members (22, 24) and a recess wall (16, 18).

4. A blade holding device as claimed in claim 3, wherein said at least one spring member (58) is disposed in compression between the outer face

(26) of said first wedge member (22) and the recess wall (16), with the blade (12) interposed therebetween.

5. A blade holding device as claimed in claim 4, including means (56) for retaining said at least one spring member (58) in a position relative to said first wedge member (22).

6. A blade holding device as claimed in claim 5, wherein said means (56) for retaining said at least one spring member includes a relatively shallow channel along the length of said outer face (26) of said first wedge member (22), said at least one spring member (58) being insertable within said channel, and abutting the blade when the first wedge member is inserted into the recess (14) of the cylinder (10).

7. A blade holding device as claimed in claim 2 in combination with any of claims 3 to 6, wherein said means for increasing said force at said first rate includes said at least one spring member

(58), said specific force value being defined by means (56, 61) for limiting compression of said at least one spring member (58), and wherein said means for increasing said force at said second rate includes means (56, 61) enabling said first wedge member (22) to contact the blade (12) once compression of said spring member (58) is limited by said compression limiting means (61).

8. A blade holding device as claimed in claim 6 in combination with claim 7, wherein said compression limiting means and said means enabling said first wedge member to contact the blade include said relatively shallow channel (56).

9. A blade holding device as claimed in any of claims 3 to 8, wherein said at least one spring member is a corrugated metal strip (78).

10. A blade holding device as claimed in any of claims 3 to 8, wherein said at least one spring member is a strip of an elastomeric material (80).

11. A blade holding device as claimed in any of claims 3 to 8, including a plurality of spring members (58), means (60') being provided for holding said spring members (58) in positions relative to each other.

12. A blade holding device as claimed in claim 11, wherein said spring members (58) are Belleville disc springs.

13. A blade holding device as claimed in claim 11 or 12, wherein said spring holding means (60) includes a strip constructed of a resilient material having a plurality of holes defined along the length thereof, one of said spring members (58) being mounted within each said hole.

14. A blade holding device as claimed in any preceding claim, wherein said means (29, 36) for performing relative movement between said wedge members (22, 24) includes a collar member (36) mounted to one end of the cylinder (10) adjacent the recess (14) and having an opening defined therethrough, a bolt (29) engageable with an end of one of said wedge members (22, 24) and extending through said opening, said bolt (29) having at least one flange (34) near the head (30) thereof, said flange (34) being disposed on one side of said opening for retaining said bolt (29) in a position relative to said collar member (36) to effect relative movement of said wedge members (22, 24).

15. A blade holding device as claimed in claim 14, wherein said bolt (29) is engageable with an end of said second wedge member (24).

16. a blade holding device as claimed in any of claims 1 to 14, wherein the relative movement between said wedge members (22, 24) is performed by moving said second wedge member (24) along the recess (14).