DE3815129A1 - Guide device for a rotation hoop knife - Google Patents

Abstract

A guide device for the rotation hoop knife (2) of a rotation hoop knife splitting machine consists of two guide strips (49, 50) which have inclined front surfaces (47, 48), with which they bear against correspondingly shaped run-on surfaces (45, 46) of a stop body (43). The guide strips (49, 50) also rest on the rotation hoop knife (2). They are in each case connected to a leaf spring (53, 54), on which a pretensioning force is exerted via a pressure strip (55). This pretensioning force is distributed uniformly onto the two guide strips (49, 50) and, at the inclined run-on surfaces (45, 46), is converted into a force component which is normal to these run-on surfaces and a force component which stands vertically on the plane of the rotation hoop knife (2). By means of the latter force component, the rotation hoop knife (2) is always guided exactly centrally, and there is no change to this even after relatively long operation as the guide strips (49, 50) are worn uniformly. Even in the event of non-uniform wear, however, the leaf springs (53, 54) ensure that the rotation hoop knife (2) is guided centrally (Fig. 5). <IMAGE>

Description

The invention relates to a guide device for a band knife, especially for a band knife splitting machine for soft materials such as leather or the like, with at least two Guide strips on the top and bottom of the Band knife rest.  

Band knife splitting machines are used to make soft, mostly flat workpieces in a plane parallel to their To split main surface. For this purpose, they instruct themselves closed, revolving band knife, which in the Usually runs over two disks, one of which is powered is. The workpiece is then parallel to the band knife on this to moved so that the desired cut can be made can. The feed movement of the workpiece can automatically e.g. B. happen by means of guide rollers. The cut is in usually in the upper run of the band knife, the so-called Workspace.

Such band knife splitting machines are of particular importance for the leather industry that uses it to make leather in two or split up multiple layers. Mostly one is this Shift committee while the other is being processed; however, when using very thick leather, one can Splitting into several reusable layers is desirable be. These band knife splitting machines find further applications when splitting skins, rubber, plastic and the like

To ensure a clean cut and fraying of the workpiece and the formation of unclean surfaces avoid, it is essential that the cutting edge of the band knife always in very sharp, d. H. good condition is held. It is therefore usually in the lower range Belt of the band knife, the so-called return run, one Grinding device arranged. This consists of two loops discs, each of the upper and the lower cutting edge can grind the cutting edge of the band knife as well as the associated brackets and drive devices.  

An essential requirement for such a grinding device consists of a symmetrical grinding of the cutting edge the band knife, d. H. the upper and the lower cutting edge should have the same cutting edge angle and the same chamfer width be sanded. This requirement can only be met if you always sharpen the band knife in an exact centered position is supplied, even after a long time Operating time. The band knife can also be used after a few Do not move the operating time out of its centered position.

The band knife is therefore before entering the grinding machine direction guided by a guide device. Such one Guide device is for example from DE-OS 21 44 133 known. The guide device described therein includes two guide rails mounted on guide plates. These guide plates are against each other by a single one Tilt point pivotally mounted, which includes a connecting element serves, which is fixed in operation with the lower guide plate is connected and has a head part, which in a pan-shaped recess of the upper guide plate is. The required preload on the two guide plates against each other is applied by springs or the like. The Band knife is clamped between the two guide strips.

Such a device ensures exact guidance of the band knife. However, it is structurally very complex and can be constant for a long period of operation Position the band knife, but not for it exactly centric positioning. Adjustment means for displacement the band knife level, in order to possibly achieve a centering, are not provided. This is with a guiding device  of the type shown in DE-OS 21 44 133 also not required, since it is a guide device for the Area of work flow, d. H. to guide the band knife before entering the workpiece.

For guidance in the area of the grinding device, however, is one exact centric guidance required. The present invention is therefore the object of a guide device to create the one with the simplest design Precise centric guidance even after a long period of operation of the band knife allowed. This task is with a leader device of the type mentioned solved by that the guide rails one against the level of Band knife have inclined front surface with which they are attached correspondingly shaped ramp surfaces of at least one stop body and that both guide rails with one in essentially the same size, in the direction of the stop body acting prestressing force.

The base body is preferably the stop body Grinding device used. This alone is the fiction appropriate guide device mechanically much easier and therefore cheaper than the known guide device, since no guide plates and expensive storage options for which they are required. Rather, besides that Guide rails themselves and means to do this with a leader no additional parts required. The prestressing force exerted on the guide rails, which in A plane acting parallel to the band knife plane is used on the inclined run-up surfaces of the stop body in two components  disassembled, one of which is perpendicular to the inclined casserole surface stands and the other perpendicular to the band knife level, d. H. the latter force component acts directly on the tape knife and leads this. Once the band knife is centric is set, this centering remains even after a longer period Reliable operating life, because of the essentially equal preload on both guide rails these are also subject to the same amount of wear. Self but if there is uneven wear should, the more worn guide bar the preload force on the inclined contact surface of the stop body continues until they are reliably in contact again stands with the band knife, and because of the essentially The band knife is located at symmetrical prestressing forces in this case, too, in an exactly centered position.

Although the guide device according to the invention in the first Line for guiding the band knife in the area in front of the inlet is provided in the grinding device, it can of course also in the work area, d. H. before hitting the band knife on the workpiece. The invention is beyond that also not for use in the field of band knives slitting machines limited; rather, it can also be used for others Areas of mechanical engineering where comparable requirements consist of a guide device, are used. Examples include machines with an oscillating knife, Band saw machines and the like

The inclined front surfaces of the guide strips are preferred and the correspondingly inclined run-up surfaces of the stop body designed as a flat surface. These areas are special  easy to manufacture. However, there are other shapes possible; e.g. B. the inclined surfaces can also be curved, in particular be conical surfaces.

In an advantageous development of the invention, the guide afford mechanically connected. This enables that they are subjected to a common preload, d. H. only one source of power is required, whose Force action essentially symmetrical on the two guide afford is distributed. Although here a fixed, i.e. H. the two guide rails immovably fixed against each other mechanical connection is possible in this case possible non-uniform wear of the guide afford not to be balanced. It is therefore appropriate more moderate, the mechanical connection so that the Guide rails are fixed against each other. This can be advantageous about the use of springs, in particular Leaf springs happen as fasteners. Basically a single, for example curved leaf spring is sufficient; However, it is more advantageous to have one for each guide bar provide separate leaf spring. These leaf springs can then, according to a further preferred embodiment the invention, be connected by a pressure bar on the the common preload is effective. Here is only one Power source required; at the same time the one generated by it Preload force is essentially even on both guide perform distributed, and in the event that exceptionally one the guide rails are exposed to greater wear than the other, it is under the action of the leaf spring pushed further into the stop body, so that the band knife again runs centrically. However, it should be emphasized that  Meeting these requirements doesn't necessarily mean two over one Pressure bar connected leaf springs are required; for example a lever could also be provided on both Guide rails are articulated and centered by a single one Preload is applied; other solutions of this kind stand - with knowledge of the basic idea of the invention - in the ability of constructing such guiding devices entrusted specialist.

The biasing force is preferred by one or more springs, especially compression springs. This measure continues to reduce the construction effort and thus to a simple and inexpensive solution. The guide rails itself exists due to the constant sliding contact with the band knife advantageously made of sintered metal.

Further features and advantages of the present invention result from the following description of the drawing, in which Darge the invention based on preferred embodiments represents is. It is understood that the above or below explained features not only in the specified Combination, but also in other combinations or in Unique position can be realized without the frame of the present invention.

It shows

Fig. 1 is a schematic view of a band knife splitting machine,

Fig. 2 shows a cross section through the band blade, according to the reference line II-II of Fig. 1,

Fig. 3 is a schematic representation of the feed device for the grinding wheels,

Fig. 4 illustrates the importance of the different positions of a wiper arm,

Fig. 5 shows a cross section through a guide device for the band knife,

Fig. 6 is a plan view of the back guide for the band blade,

Fig. 7 shows the back view of the guide in the direction of arrow VII of Fig. 6,

Fig. 8 is a view similar to that in Fig. 7, but in another position of the mechanical components,

Fig. 9 is a block diagram of the grinding device with associated control unit and the operating unit,

Fig. 10 is a view of the front panel of the operating unit,

Fig. 11 is a flowchart of the control unit by supplying working steps for initiation of the dressing, and

Fig. 12 is another flow chart for explaining an alternative control process.

In Fig. 1, a band knife splitting machine is generally designated 1 . This band knife splitting machine is used for splitting materials that are not too hard, such as leather, skins, rubber, plastic and the like. The material to be processed is cut parallel to its surface, so that two layers of material are formed. The splitting process is carried out by a rotating band knife. This process is particularly important for the leather industry to separate worthless leather layers or to produce several thin layers from a thick leather.

The revolving, self-contained band knife 2 runs over a drive pulley 3 and a guide pulley 4 . Band knife 2 , drive pulley 3 and guide pulley 4 move in the direction of arrows 5, 6 and 7 . The cutting edge of the band knife points towards the viewer, ie it is located on the side of the drawing plane facing the viewer.

The leather or other workpiece to be machined is inserted between two rotatable guide rollers 8 and 9 , which are usually located in front of the plane of the band knife 2 , and split by the band knife. The direction of movement of the workpiece during the splitting process is illustrated by the arrow 10 pointing in the plane of the drawing. One (or both) of the guide rollers 8 and 9 can be driven to carry out the splitting process automatically.

In order to ensure a good splitting result and in particular to prevent the workpiece from fraying or the like, the cutting edge of the band knife 2 must always be in a sharpened state. In the area of the return run 11 of the band knife 2 , two grinding wheels 12 and 13 are therefore provided, which abut the cutting edge of the band knife and regrind them. The two grinding wheels 12 and 13 are driven by a grinding device 14 . This grinding device also has other functions to be explained below.

In order to ensure that the band knife 2 is centered between the grinding wheels 12 and 13 , a guide device 15 a , 15 b is provided. This guide device also ensures that the band knife 2 can not hit or flutter what z. B. could occur during load changes and would lead to a waveform being ground in the cutting edge of the band knife.

Of course, it is also possible to arrange a further guide device on the outlet side of the grinding device (in the illustration according to FIG. 1 to the left of the grinding wheels 12 and 13 ). Likewise, guide devices can also be arranged in the area of the working strand 16 of the band knife 2 on the inlet and / or outlet side.

Fig. 2 shows a cross section through the band knife according to the reference line II-II of Fig. 1. The band knife back is designated 17 . The two cutting bevels of the cutting edge have the reference symbols 18 and 19 . To carry out a uniform cut, it is desirable that the chamfer widths b and c of the two cutting bevels 18 and 19 are the same size. Furthermore, both cutting edges should have the same cutting angle (designated α / 2 in FIG. 2). For clean guidance of the band knife, the band knife back 17 must also be supported by a back guide to be described below.

Fig. 3 shows the feed device for the grinding wheels, which are designated 20 and 21 there. These grinding wheels are driven in a manner known per se by a grinding motor via a belt drive. Belt drive and grinding motor are not shown in FIG. 3. The grinding wheels rotate in the direction of the arrows 22 and 23 and thereby grind the cutting edge of the band knife 2 . The grinding wheels are, as indicated in Fig. 1 (reference numerals 12 and 13 ), laterally offset from each other.

The grinding wheels are rotatably mounted on grinding arms 24 and 25 in only schematically indicated bearings 26 and 27 . The grinding arms in turn can be pivoted about fixed bearing points 28 and 29 . The grinding arms are also connected via a tension spring 32 articulated at 30 and 31 .

The feed device further comprises an adjusting spindle 33 . This adjusting spindle is driven by a DC motor M ( 34 ). The direction of rotation of this DC motor is, as indicated by the double arrow 35 , reversible.

The respective position of the adjusting spindle is detected by a potentiometer P (reference number 36 ). The rotary movement of this potentiometer is indicated by the double arrow 37 . The potentiometer 36 is preferably driven by the adjusting spindle 33 via straight spur gears, but it is of course also possible to couple the potentiometer mechanically directly to the direct current motor 34 , which works as a servomotor. In order to achieve a sufficient resolution, a 10-turn spiral potentiometer is used as the potentiometer 36 . Of course, other types of position detectors such as position sensors, speed or accelerometers can also be used, in the last two cases a simple or double integration also leads to the path.

The adjusting spindle 33 also has two cut threads 38 and 39 , one of which is a left-hand thread and the other a right-hand thread. In the exemplary embodiment shown, it is assumed that the thread 38 is a right-hand thread and the thread 39 is a left-hand thread, but the orientations of the two threads can of course also be interchanged.

On each of the two threads 38 and 39 runs a - not shown in Fig. 3 - nut. This running nut is mounted on the grinding arms 24 and 25 in a longitudinally displaceable manner by means of carriers and sliding blocks. For example, the grinding arms can be provided with a C-groove in which a sliding block runs, which is rotatably mounted on the associated running nut. When the adjusting spindle 33 rotates, the running nuts on the threads 38 and 39 move and take the respective grinding arm with them, the sliding block in the C-groove of the grinding arm moving in the longitudinal direction thereof. Provided that the thread 38 is a right-hand thread and the thread 39 is a left-hand thread, rotation of the adjusting spindle 33 in a clockwise direction leads to the upper grinding arm 24 rotating clockwise about its pivot point 28 and the lower grinding arm 25 rotates counterclockwise about its pivot point 29 . The two grinding wheels therefore move away from the band knife 2 .

By reversing the direction of rotation of the adjusting spindle 33 , ie turning counterclockwise, the grinding wheels can be advanced in the direction of the band knife. This ensures that the grinding wheels are fed absolutely evenly towards the band knife, so that the cutting edge of the same is always ground absolutely symmetrically after a single adjustment, ie with the same chamfer width and the same cutting edge angle on both sides.

The tension spring 32 , which removes the thread play between the adjusting spindle 33 and the running nuts, serves to further increase the accuracy during the infeed process. The same effect could also be achieved with a compression spring. If you do not want such extremely high accuracy, this spring can of course also be omitted.

It is understood that the linkage of the barrel nuts to the Grinding arms in such a way that the barrel nut is longitudinally displaceable is connected to the assigned grinding arm, also to others, means familiar to the person skilled in the art can be realized. For example, an essential to the barrel nut mushroom-shaped head that is formed in a longitudinal direction-extending C-groove of the respective grinding arm movable is. It would also be possible to have one on the barrel nut  pliers-shaped or self-contained profile supports arrange, this profile beam in corresponding grooves of the Grinding arm runs, includes this or has a groove itself, in which a rail formed on the grinding arm runs.

Since a grinding wheel becomes clogged with dirt and cutting particles after a certain period of operation, which leads to stumping which affects the grinding performance, the grinding wheel must be dressed from time to time. For this purpose, the grinding wheel is brought into contact with a dressing wheel, for example a diamond dressing wheel, which removes these particles. In the grinding device according to the invention for a band knife splitting machine, two dressing wheels 40 and 41 are provided for this purpose, which are assigned to the grinding wheels 20 and 21 , respectively. These dressing disks are rotatably mounted and are located at exactly the same distance from the level of the band knife 2 , ie the solder from the center of each dressing disc to the band knife level is the same length. If a dressing process is required, the grinding wheels can be brought into their dressing position, ie in contact with the dressing wheels 40 and 41 , by turning the adjusting spindle 33 . This can be done manually - for example by turning the adjusting spindle 33 by hand - or also in that the user triggers a motorized actuation of the adjusting spindle 33 by means of a corresponding input command.

In any case, it is ensured that the grinding wheels are dressed to the exact same diameter due to the symmetry of the entire arrangement, which ensures perfect symmetry of the cutting edge of the band knife 2 .

Another possibility is the automatic triggering and execution of the dressing process. In this case, the operator is completely relieved from observing the degree of dulling of the grinding wheels and from triggering and carrying out appropriate dressing processes. A control unit that does this will be described with reference to FIGS. 9 to 12.

However, the various positions of the grinding wheels or grinding arms can also be approached automatically under the control of a control unit. For this purpose, the control unit receives the signal from the potentiometer 36 , which indicates the grinding arm position. The end position of the grinding arms, ie the positions in which the grinding wheels are in contact with the band knife 2 (grinding position) or the dressing rollers 40 and 41 (dressing position) can be detected by the current consumption of the servomotor (DC motor 34 ) is measured and fed to the control unit. The control unit can even detect the grinding or dressing intensity, ie the force with which the grinding wheels are pressed against the band knife 2 or the dressing wheels 40 and 41 , by the current consumption of the grinding motor, ie the grinding wheels 20 and 21 in Rotating motor is measured. The control unit can therefore automatically move the grinding arms 24 and 25 to the grinding or dressing position and can also carry out the grinding or dressing process automatically.

In addition, it is possible to save further fixed positions of the grinding arms that are important for the operation of the grinding device and to move to these positions if necessary. An embodiment in which the meaning of these different "fixed positions" is explained is shown in FIG. 4. This figure shows the upper grinding arm 24 in different positions, which are designated 24 a to 24 f . The grinding arm can perform a pivoting movement about point 28 by the entire pivoting angle α , ie between the grinding position (indicated grinding wheel 20 a) and the dressing position (indicated grinding wheel 20 b) .

The end position M ₁ (grinding arm position 24 a) represents a mechanical end stop, the reaching of which can be recognized by the current consumption of the servomotor. If the grinding arm reaches this position, the grinding wheel is ground down to its minimum diameter and can no longer be dressed. Reaching this position is recognized by evaluating the current consumption of the servomotor and leads to an error display alarming the operator.

The position F ₁ (grinding arm position 24 b) denotes the so-called dressing point. All new grinding wheels are dressed to the defined diameter. This has the meaning, among other things, of ensuring after a grinding wheel change that both grinding wheels have the same diameter. They are therefore dressed for a common, equally large initial diameter.

In the area between the two positions M ₁ and F ₁ (area A _n ), the control device also stores the position at which the dressing was carried out after each dressing operation. As soon as the next dressing process is triggered, the grinding wheels are moved to this position in rapid traverse, and then the machine switches to creep speed until it is recognized by the current consumption of the grinding motor that the grinding wheels are in contact with the dressing wheels.

The position F ₂ (grinding arm position 24 c) denotes the so-called change point. In this position, the grinding wheels can be replaced because they are at a sufficient distance from both the band knife and the dressing wheels.

F ₃ (grinding arm position 24 d) denotes a position up to which rapid traverse can be made when initiating the grinding process regardless of the position of the grinding wheels in the previous grinding process. In the area between the two positions F ₃ and M ₂ (area S _n ), the control unit, on the other hand, stores the position of the grinding wheels during a grinding process and travels to this point in rapid traverse the next time a grinding process is triggered, after which the switch is made to the creep speed.

When position F ₄ (grinding arm position 24 e) is reached , the control unit recognizes that the grinding wheel is almost worn out. It gives the user a corresponding warning signal, for example by switching on a yellow light-emitting diode. When the second mechanical end stop M ₂ (grinding arm position 24 f) is reached, the grinding wheel is finally worn out and can no longer be used, which can be indicated to the user, for example, by switching on a red LED. Reaching the mechanical end stop M ₂ is in turn recognized by the current consumption of the servomotor.

The grinding wheels 20 a and 20 b indicated by dashed lines in FIG. 4 are completely worn grinding wheels, since the grinding arm (grinding arm position 24 f or 24 a) is in the mechanical end positions. These grinding wheels can no longer be dressed and can no longer be used for grinding.

As already explained with reference to FIG. 1, the band knife must be guided before entering the grinding device in order to ensure an exact and clean grinding even when there are load changes and the like. FIG. 5 shows a cross section through a guide device, designated overall by 42 , for this purpose. The band knife is also designated 2 in this figure.

The basic or supporting body of the grinding device bears the reference symbol 43 . The band knife 2 runs in a groove 44 of this base body, the groove widening in its front region into two inclined run-up surfaces 45 and 46 . The front surfaces 47 and 48 of two guide strips 49 and 50 , which are inclined at the same angle, rest against these run-up surfaces. These guide strips are made of sintered metal because their surfaces 51 and 52 rest on the band knife 2 , which can lead to considerable frictional losses during operation.

With the guide strips 49 and 50 are two leaf springs 53 and 54 in a known manner, for. B. by screwing, a related party. These leaf springs are also attached to a pressure bar 55 which is subjected to a force acting in the direction of arrow 56 . This force can be applied, for example, by a compression spring.

The guide strips 49 and 50 are once adjusted in a precisely symmetrical position against each other. This can happen, for example, through elongated holes in the screw connection. The adjustment must be made so that the guide bars 49 and 50 are in exactly mirror-symmetrical positions to the axis 57 . The band knife 2 is then exactly centered, ie it is located exactly in the middle of the groove 44 . After the adjustment process has been carried out once and the subsequent fixation, the guide strips can only be displaced against one another against the force of the leaf springs 53 and 54 . Due to the symmetrical arrangement, the pressure force (see arrow 56 ) is divided exactly between the two guide rails. Due to the inclined run-up surfaces 45 and 46 of the base body 43 , a force component acts perpendicular to the plane of the band knife, which presses the guide strips onto the band knife and gives it a quiet and precisely centered run.

Since the force exerted on both guide strips 48 and 49 is the same, the wear on the surfaces 51 and 52 is always the same. The band knife 2 therefore remains exactly centered even after a long period of operation without the need for readjustment. With increasing wear of the guide strips they move further and further into the base body 43 (to the right in the illustration according to FIG. 5), without the exact, clean and central guidance of the band knife suffering as a result.

The cutting edge of the band knife is used during operation and by grinding continuously. The width of the band knife therefore decreases continuously with increasing operating time. To the Cutting edge of the band knife still in its position  hold, the back of the band knife must therefore by a back guide mechanics are supported on the back of the belt knife constantly updates.

Fig. 6 shows the top view of such a back guide. The cutting edge 58 of the band knife 2 (the grinding point is designated 59 , the running direction of the band 60 ) wears out due to regrinding and ongoing operation. In order to keep the cutting edge in position, the back of the knife 61 must be adjusted in the direction of arrow 62 .

The back guide mechanism, which accomplishes this, comprises a back guide pin 63 , which is movable in the bore of a bearing body 64 in the direction of the double arrow 65 . In principle, the bearing body 64 can be any stationary part, for example the base body of the grinding device.

The front edge 67 of the return bolt 63 lies against the back of the knife 61 and exerts a constant contact pressure thereon in a manner to be described. On the rear side, the return pin comprises a hemispherical extension 66 which is in contact with a first lever 68 . This lever is fixed at 69 . A nose 70 is formed on its other lever arm and bears against a cam disk 71 . The outer contour of this cam can best be seen in FIG. 7, which shows a view in the direction of arrow VII in FIG. 6.

The cam disk 71 ( FIG. 6) is rotatably mounted (bearing axis 72 ) on a bearing body 73 , which can also be the base body of the grinding device. Connected to the cam disk 71 , ie rotatable with it, is a rope pulley 74 on which a rope 75 runs. A weight 76 hangs from this rope, which is located below the drawing plane in the illustration according to FIG. 6.

The pulley 74 also has a side toothing 77 . The function of this toothing will be explained in the following.

The weight 76 keeps the rope 75 constantly under tension. Here, the cam disk 71 is exposed to a torque, ie the cam disk tries to rotate clockwise. Since its radius increases continuously during a movement in this direction, a force is constantly exerted on the nose 70 , which is communicated to the back guide pin 63 via the lever 68 and presses it against the back of the knife 61 . This force is also maintained when the cutting edge 58 of the band knife 2 wears out, that is to say when this band knife becomes narrower, since the cam disk 71 is able to maintain this pretension constantly due to its constantly increasing radius. The back guide mechanism thus has self-locking and self-adjusting properties.

Fig. 7, a view in the direction of arrow VII of Fig. 6, shows another part of the back guide mechanism, not yet shown in Fig. 6, which serves to remove the return bolt from the back of the knife when removing the machine casing, ie To take tension out of the band knife.

The cam plate 71 with teeth 77 , the first lever 68 , the rope 75 and the weight 76 correspond to the parts shown in FIG. 6. In addition, part of the machine cladding 78 can also be seen. A pressure bolt 79 is welded to this machine casing (weld seams 80, 81 ). This pressure bolt is supported on an arm of a second lever 82 . This second lever is mounted on a fixed, ie non-movable bearing point 83 . This bearing point is expediently a bearing point of the machine chassis or another, fixed part.

The other lever arm of the second lever 82 is rotatable (bearing point 84 ) connected to a third lever 85 . The bearing point 84 is a pivoting bearing point, ie it is not connected to a stationary part and can execute a pivoting movement. On a lever arm of the third lever 85 (attachment point 86 ), a tension spring 87 is articulated, the other end of which is fixed (bearing point 88 ).

The second lever arm of the third lever 85 abuts a fixed stop 89 . This lever is also provided with a pawl 90 . Fig. 8, which shows the same machine parts as Fig. 7 but in a different position, illustrates the effect of removing the machine cover. If the machine casing is moved in the direction of arrow 91 (the machine casing is no longer shown in FIG. 8), the pressure pin 79 moves to the left according to FIG. 8. This releases the second lever 82 . Under the action of the tension spring 87 , the pivotable bearing point 84 now moves to the right, the third lever 85 initially resting against the stop 89 . As soon as the pawl 90 of the lever 85 engages in the toothing 77 of the rope pulley 71 , it moves this rope disk - counter to the action of the weight 76 - counterclockwise, the lever 85 lifting off the stop 89 . The rope pulley 71 is rotated counterclockwise until the lever 82 abuts the stop 89 . Thus, the Fig. 8 shows only one intermediate state, that is, the parts will move somewhat further and the pulley 71 is further rotated counterclockwise until the lever 82 abuts the stop 89th

As can be easily visualized with reference to FIGS . 8 and 6, the rotation of the rope pulley 71 counterclockwise leads to the fact that on the first lever 68 and thus on the back guide pin 63 no more force is exerted. The knife back 61 of the band knife 2 is therefore relieved.

If necessary - e.g. B. if an old narrow is to be exchanged for a new wide band knife - the pulley 71 can now be turned by hand further counterclockwise. The third lever 85 , which is under the pretension of the tension spring 87 , ensures that the pawl 90 is constantly in meshing engagement with the toothing 77 of the rope pulley 71 , so that it is locked in each case.

When the casing is replaced, the reverse process takes place, ie the pressure pin 79 presses on the second lever 82 , which rotates clockwise, as a result of which the movable bearing point 84 (against the action of the tension spring 87 ) moves to the left in an arc. The pawl 90 disengages from the toothing 77 , and the third lever 85 comes into contact with the stop 89 .

After the release of the pulley 71 , this is rotated clockwise again by the weight 76 until the back guide pin 63 is pressed against the back of the band knife via the first lever 68 again. The state shown in FIG. 7 is thus reached again.

In Fig. 9, a block diagram of the entire Schleifvor direction is shown with the associated control units. The actual grinding device, which can be designed, for example, as shown in FIG. 3, is designated by the reference sign 92 . A control unit, which can be implemented, for example, by a microprocessor with associated hardware, but also by an analog circuit, and which comprises a memory area (in the case of an analog circuit, these memories can be capacities, for example) is designated by 93 . This control unit receives the signals of a timer 94 and can also set it. As an alternative to this, it is of course also possible to generate time signals internally in the control unit 93 .

M _Schl (reference number 95 ) denotes the grinding motor, which rotates the grinding wheels, for example by means of a belt. The control unit 93 can control the grinding motor via an actuator (not shown here) and in turn receives a signal that is proportional to the current consumption of the grinding motor (double arrow 96 ). The mechanical path, ie the mechanical connection of the armature shaft of the grinding motor to the grinding device, is symbolized by arrow 97 .

The control unit 93 controls a servomotor M _st in a comparable manner (reference numeral 98 ). The mechanical connection between the servomotor and grinding device (this can be, for example, the adjusting spindle 33 , see FIG. 3) is symbolized by the arrow 99 , and likewise the control signals of the control unit 93 to the servomotor and the feedback on its current consumption by the double arrow 100 illustrated. The control unit 93 can query the position of the grinding arms via the potentiometer 101 .

The control unit 93 is also connected to an operating unit 102 , which is implemented here by a front panel with corresponding buttons and displays. The arrow 103 illustrates the commands issued by the operator to the control unit and the arrow 104 shows the machine's feedback to the operator.

FIG. 10 shows there designated 105 front panel in detail. It includes a series of buttons and displays, the function of which will be described below.

With 106 a key switch is designated, which, as can be seen, can be turned into the positions "0" and "I". This key switch is used to lock a program that is running once, and therefore has a different function than the “emergency stop” switch (not shown in FIG. 10). As a rule, a grinding program can only be selected in position I of the key switch, ie by turning it to position "0" after a program has been triggered, this program is locked and can no longer be stopped by pressing other keys. To interrupt a running program, the key switch 106 must first be turned back to the "I" position.

The display elements 107 and 108 are buttons with a display function. While the parts 107 and 108 themselves represent buttons, at the same time they fulfill a display function through the integrated light-emitting diodes 109 and 110 . A membrane keyboard is particularly suitable for such a combined function, but normal mechanical switches with an integrated light-emitting diode are also available on the market.

A manual operating mode can be selected using key 108 , into which a green light-emitting diode (reference numeral 110 ) is inserted. In this operating mode, continuous grinding is triggered, ie the grinding wheels are permanently in contact with the cutting edge of the band knife. Grinding is carried out with a fixed grinding intensity. If after some time the grinding wheels with dirt and machining particles have clogged so that the grinding effect wears off, the control unit triggers a dressing process. The steps to be taken by the control unit will be explained below. After the dressing process has ended, the grinding wheels are moved back to the grinding position immediately. The whole process can be stopped by pressing the STOP button 111 with the integrated red LED 112 .

An automatic program can be started with the "AUTO" button 107 with an integrated green LED 109 . When this automatic program runs, grinding is carried out for a certain period within a specified cycle time that can only be adjusted internally by the machine. The cycle time can be 30 minutes, for example, and the grinding time 3 minutes. Since grinding is only carried out at intervals, wear is reduced or the service life of the band knife increases.

While the cycle time is only internal to the machine, i.e. H. through a Intervention in the machine itself (for example by adjusting it of a coding switch) can be adjusted by the user the possibility of the planned within this cycle time Adjustable grinding time. It also changes that Relationship between grinding and total cycle time. An increase the grinding time in relation to the total cycle time for example, be necessary when hard to split Workpieces are processed; the cutting edge of the band knife then wears out faster, so that longer regrinding is required. Conversely, a reduction in Grinding time can be useful if very soft workpieces to be edited.

For the symbolic representation of the grinding time or the relationship between grinding time and the entire cycle time, a display 113 is used , which is equipped with nine LEDs 114 to 122 . The three light-emitting diodes 114 to 116 are green in color, the light-emitting diodes 117 to 119 in yellow and the light-emitting diodes 120 to 122 in red.

When the automatic program starts, the three green LEDs 114 to 116 always light up, which corresponds to a share of the grinding time in the total cycle time of 30%. By pressing the buttons 123 and 124 , the user can change the ratio of the grinding time to the total cycle time, depending on the application. By actuating the minus key 123 , one light-emitting diode is switched off until only the light-emitting diode 114 is on, while by pressing the plus key 124 light-emitting diodes are switched on until the light-emitting diodes 114-119 are on .

In the exemplary embodiment shown, the light-emitting diode 114 can, for example, correspond to a grinding component (proportion of the grinding time in the total cycle time) of 10%. Likewise, the light-emitting diodes 115 to 119 can correspond to grinding proportions of 20%, 30%, 50%, 65% and 80%, respectively. The red LEDs 120 to 122 , which correspond to a grinding percentage of 100%, cannot be switched on by pressing the button 124 . Rather, these light-emitting diodes burn (together with the other light-emitting diodes) if "continuous looping" was selected by pressing button 108 .

The sequence of the automatic program started by pressing the button 107 can also be stopped using the STOP button 111 .

The displays 125 and 126 (with green LEDs) have a purely display function, i.e. no button function. The light-emitting diode 127 of the display 125 indicates grinding operation and the light-emitting diode 128 of the display 126 shows a dressing process in progress.

The displays 129 to 131 in turn have a double function, ie they serve both for display and as buttons. The burning of the green LED 132 belonging to the display 129 indicates that the band knife is worn out, that is to say it has been ground down to the minimum width. After pressing this button, the control unit switches off the servomotor, possibly also the grinding motor. Since the next action of the machine operator must inevitably be a change of the band knife, the light-emitting diode 132 can only be put out by pressing the buttons 130 or 131 , the function of which will be explained in the following.

By pressing button 130 (with green LED 133 ) the control unit is informed that a new, not yet sharpened band knife has been inserted. In this case, the band knife is first sharpened for a certain time, with a sharpening intensity that is higher than in automatic or manual mode. During this continuous grinding process, the light emitting diode 133 lights up. If an already sharpened new band knife has been inserted, this function can also be deactivated by pressing the button 130 again and the LED 133 can be extinguished.

The green light-emitting diode 134 finally indicates that the grinding wheels are worn out and must be replaced. After pressing button 131 for the first time, the control unit switches off the servomotor and the grinding motor. In addition, the grinding wheels are moved to the change point (see FIG. 4, change point F ₂), just like when the button 129 is pressed, so that a change of the grinding wheel is possible. After the grinding wheel change, the button 131 must be pressed again to indicate to the control unit that the change has been made. In this mode of operation, no key other than key 131 is accepted.

The displays 135 to 140 have a pure display function, ie they are not designed as buttons. They are pure "error messages".

The display 135 shows the wear of the grinding wheels. The yellow LED 141 lights up when the grinding wheels are almost worn out. This corresponds to reaching point F ₄ in Fig. 4. Accordingly, the red LED 142 lights up when the grinding wheels are completely worn, ie when the mechanical end stops M ₁ or M ₂ ( Fig. 4) are reached. In the latter case, ie when the grinding wheels are completely worn out, they are moved to the change point F ₂ and the machine switches off. In this mode, it only accepts pressing the grinding wheel change button 131 .

The red LED 143 of the warning indicator 136 lights up when the machine cover is removed. If the key switch 106 is in the "0" position, the machine switches off in this case. However, if the key switch is in the "I" position, the machine continues to run. This is necessary for test and maintenance purposes, for example.

As the back guide bolt is removed from the band knife back when the machine cover is removed. ie the back guide is deactivated (cf. FIGS . 6 to 8), in this case the red light-emitting diode 144 of the display 139 also lights up. This display generally signals ineffective back guidance.

The display 137 serves to signal a falling battery voltage. The yellow LED 145 lights up when the voltage falls below a first threshold value, and the red LED 146 when a second, lower threshold value (minimum voltage) is undershot. In the latter case, the grinding motor is switched off and the servomotor is moved to the last reference point after the end of any dressing process that may still be running. A further program start is no longer possible, but the machine continues to run to recharge the battery.

The display 138 signals that the dressing disks are worn. This condition can be recognized by a sharp increase in the current of the grinding motor during the dressing process. In this case, the grinding wheels are moved to position F ₂ (change point, see Fig. 4) and the machine switches off. After the dressing disks have been changed, the red light-emitting diode 147 can only be extinguished by pressing the button 131 .

The red light-emitting diode 148 of the display 140 finally signals that the flat belt of the grinding motor has broken or is not in place. In this case, the grinding wheels are moved to a reference point and the grinding motor is switched off. Replacing a flat belt can be entered by pressing key 129 or key 131 .

Both in automatic and in manual operation occurs for some time the grinding wheels become dull due to clogging with dirt and cutting particles. This leaves the Grinding effect after. The grinding wheels must then be dressed will.  

Fig. 11 shows an example of a flowchart, how the control unit can determine when a dressing is required or when to trigger this. The control loop, starting with the "START" instruction 149 , is run through at regular intervals during the grinding process. First, the current consumption I _{akt of} the grinding motor is queried (reference numeral 150 ). The grinding intensity can be calculated from this current consumption (reference symbol 151 ); Since the grinding intensity is usually proportional to the current consumption of the grinding motor, this calculation step can u. U. also omitted. The current grinding time Δ t is then calculated (reference numeral 152 ), ie the grinding time that has elapsed since the last dressing process. This can be done, for example, by constantly storing the total grinding time and by forming the difference from the last dressing time, which was also stored. It is easier, however, if a memory, in which the current grinding time is stored, is set to zero with every dressing process and then incremented continuously during grinding. In this case, the calculation specified in block 152 is reduced to the mere query of this memory.

It should be emphasized that when determining the current grinding time, only those times may be included in which grinding was actually carried out. In automatic mode in particular (after pressing key 107 , see Fig. 10), grinding is not continuous, but only at intervals. In this case, operating times in which grinding has not been carried out may not be taken into account when calculating the current grinding time, since the grinding wheels are not in operation during these times and therefore no dulling can occur.

In the next step (reference number 153 ) the product

P = Δ t · S _nude,

ie the product of the current grinding time and the current grinding intensity. This product serves as an indicator of the degree of bluntness of the grinding wheels, ie as an indicator of when the next dressing process is required. In query 154 , this product is therefore compared with a stored maximum value P _max . If the product is equal to or greater than this maximum value (path 155 ), a dressing process is triggered (reference number 156 ). At the same time, in order to calculate the current grinding time in the next period, it is stored that a dressing process has been triggered, for example by storing the time of the dressing process or by resetting a memory in which the current grinding time is recorded.

The dressing process is skipped (reference number 157 ) if the product P has not yet reached the maximum value. The flow chart ends at 158 .

The control steps shown in FIG. 11 must be carried out at regular intervals during grinding. This can also be the case when there is no grinding process in progress, but it is not necessary since in this case the grinding wheels cannot become dull, which could necessitate a dressing process.

The time signal required to calculate the current grinding time Δ t can be generated in various ways.

For example, the control unit can signal a external or internal timer received. If the central is controlled by a microprocessor, the Time generation in other ways, e.g. B. by counting of interrupt cycles. In the case of an analog one Control can have a corresponding value z. B. in a capacitor get saved.

To drive the grinding wheels in the grinding or dressing position, a mechanism of the type shown in FIG. 3 is particularly expedient, since the control unit there can automatically perform these operations by actuating the servomotor 34 and no user intervention is required.

Of course, it is also possible to simplify the flow diagram shown in FIG. 11 in such a way that only the current grinding time, that is to say elapsed since the last dressing, is taken as the criterion for initiating the dressing process. This is particularly useful if you are mostly driving with a fixed, ie constant, grinding intensity. In this case, the control process is simplified to query or calculate the current grinding time Δ t and then compare it with a stored value t _max , the maximum grinding time. A dressing process is initiated when the current grinding time reaches or exceeds this maximum value. In this case, too, only those times may be used to calculate the current grinding time in which grinding was actually carried out, ie no operating times - such as those e.g. B. occur in automatic mode - in which was not ground.

If automatic mode has been selected, i. H. if not permanent is ground, it is also useful to once as necessary dressing not carried out immediately, but first a grinding process that may be running to finish. Since the grinding times in automatic mode are relatively short (about 10 seconds to 4 minutes) this means there are no disadvantages to fear. On the other hand the process is greatly simplified because after completion of the grinding process sufficient time for dressing Available.

Regardless of whether the current grinding time or the product of the current grinding time and grinding intensity is used as a criterion for the need to initiate a dressing process, it is also possible to define several maximum values. For example, if it has been signaled to it by pressing button 130 ( FIG. 10) that a new band knife is to be sharpened, the control unit can automatically switch to another, likewise pre-stored maximum value.

Although the criterion shown in FIG. 11 for the need to initiate the dressing process - the product of the current grinding time and the current grinding intensity - is sufficient for many practical applications, the result is subject to an error since only the current grinding intensity is taken into account. If the grinding intensity changes significantly within an interval between two dressing processes - possibly several times - this method leads to an incorrect result. The method shown in Fig. 11 is therefore only suitable for applications in which grinding with little changing grinding intensity, z. B. in manual mode (after pressing the button 108 , see Fig. 10). However, if the grinding intensity is varied constantly (e.g. constant adjustment of the grinding intensity in automatic mode), it may be necessary to further refine the method shown in FIG. 11.

A theoretically exact value for the degree of bluntness of the Grinding wheels are obtained if as a criterion for the Initiate the dressing process constantly the product from current Grinding intensity and current grinding time is formed, d. H. if as a criterion - in infinitesimal notation - the integral

is used. Here, t bedeutet means the time of the last dressing process, t _act the current grinding time and S _act (t) the current grinding intensity. Here, too, the integration can only be extended to the times in which grinding is actually carried out. The specified integral then provides an exact value for the degree of bluntness of the grinding wheels.

In digital systems, this integral can be determined by the corresponding Sum formation to be replaced. As a criterion for the need for a dressing process then arises

The terms used here have the same meaning as explained above. T _inc is to be understood as the time interval that lies between the individual query processes. As a rule, this time interval will be constant. However, it is also easily possible to make this time interval variable. The sum S obtained is compared with a stored maximum value S _max during each query process, and in this case too - depending on the operating mode - several maximum values can be stored. The sum of the respective grinding intensities S _{act, n} to m (m corresponds to t _act in the integral representation).

FIG. 12 shows an example of a flowchart to implement this method. The control steps shown there are run through at least during grinding.

After entry (reference number 159 ), the instantaneous current consumption I _{act of} the grinding motor is first queried (reference number 160 ). If necessary, the instantaneous grinding intensity S _act (reference number 161 ) is then calculated therefrom; in the case of the proportionality of these two quantities, this step can also be omitted. At 162 , a counter n is then incremented by 1. This counter shows the number of times the flow chart has been run since the last dressing. It is reset to zero after each dressing (see below).

In step 163 , the actual sum formation is carried out. The product of the current grinding intensity S _act and time increment t _inc is added to the sum S _{n -1} that has already accumulated up to now and thus results in the sought criterion S _n .

In query 164 , the value S _n calculated in this way is then compared with a stored maximum value S _max , with different maximum values also being able to be used here, depending on the operating mode. If the criterion is not met, ie the maximum value has not yet been reached (reference number 165 ), the cycle is ended at 166 . However, if the maximum value is reached or exceeded, path 167 is embarked on, possibly after the end of a grinding process in automatic mode, ie a dressing process is triggered (reference number 168 ). The counter n is then reset to zero (reference number 169 ), and the start sum is also set to zero again for the next cycle (reference number 170 ).

The control steps shown in FIG. 12 are expediently only carried out when grinding is actually taking place, that is to say not during the times provided in the automatic program in which no grinding takes place. On the other hand, the method shown in FIG. 12 would also work if the control steps were carried out during these "off times", since in this case the grinding intensity is zero.

The method according to FIG. 12 is intended in particular for the case of a constant time increment t _inc , ie for the case that the corresponding control steps are carried out at equidistant intervals. However, it is also readily possible to work with variable time increments, ie to understand the parameter t _inc as a variable, in which case there would also be a query for the size of this parameter. Other modifications of this method that are within the scope of the inventive concept are also readily possible.

Claims (8)

1. Guide device for a band knife, in particular for a band knife splitting machine for soft materials such as leather or the like, with at least two guide strips which rest on the top or the bottom of the band knife, characterized in that the guide strips ( 49, 50 ) each have a front surface ( 47, 48 ) inclined against the plane of the band knife ( 2 ), with which they bear against correspondingly shaped run-up surfaces ( 45, 46 ) of at least one stop body ( 43 ), and that both guide strips ( 49, 50 ) with one essentially the same size, acting in the direction of the stop body ( 43 ) biasing force. 2. Guide device according to claim 1, characterized in that the inclined front surfaces ( 47, 48 ) of the guide strips ( 49, 50 ) and the correspondingly inclined run-up surfaces ( 45, 46 ) of the stop body ( 43 ) are flat surfaces. 3. Guide device according to claim 1 or 2, characterized in that the guide strips ( 49, 50 ) are mechanically connected, in particular are fixed relative to each other. 4. Guide device according to claim 3, characterized in that the guide strips ( 49, 50 ) via springs, in particular leaf springs ( 53, 54 ), are interconnected. 5. Guide device according to claim 3 or 4, characterized in that the guide strips ( 49, 50 ) are acted upon by their mechanical connection with a common biasing force ( 56 ). 6. Guide device according to claim 4 and 5, wherein the springs are leaf springs, characterized in that the leaf springs ( 53, 54 ) are connected by a pressure bar ( 55 ) on which the common biasing force ( 56 ) acts. 7. Guide device according to at least one of the previously outgoing claims, characterized in that the Preload force of one or more springs, in particular Compression springs. 8. Guide device according to at least one of the preceding claims, characterized in that the guide strips ( 49, 50 ) consist of sintered metal.