Patent Application
20140352514
The present invention relates generally to devices for cutting materials, and more particularly to a device for cutting material on a material supporting surface and to a cutting unit with an oscillation drive, a holder for the oscillation drive, and a cutting knife, wherein the oscillation drive sets the cutting knife into linear oscillations along an axis of oscillation that is perpendicular to an advancing direction of the cutting knife.
Devices of the type named above are used for the cutting of cuttable material, especially of web-like or sheet-like material, for example, films, cloth, paper, cardboard, foamed material or polystyrene. Such devices are disclosed among others in the pamphlet “Technical Overview of the Digital Cutter G3” of the company Zünd Systemtechnik AG and in the pamphlet “Kombo SD” of the company Eiltron. The material supporting surface of these devices is formed by the plane upper surface of a cutting table, onto which the material to be cut is attached by aspiration using vacuum. Usually the cutting table comprises a motor-driven arch or portal which can be moved in a controlled manner perpendicularly to its longitudinal axis in the direction of the X-axis along the material supporting surface, and a motor-driven carrier on the arch or portal, which can be moved in a controlled manner in the direction of the Y-axis to travel along the arch or portal. On the carrier, one or several holders are attached for replaceable processing units or modules that can be positioned by computer-controlled drive movements of the arch and of the carrier at arbitrary locations above the material on the material supporting surface and which allow arbitrary movement paths across the material. These devices are also called cutting plotters.
As is described in the pamphlet “Kombo SD” of the company Eiltron or in the pamphlet “Modules, Tools and Applications G3 S3 Digital Cutter” of the company Zünd, in addition to milling or marking modules, the processing modules comprise a number of cutting modules or cutting units, which have either fixed cutting knives or oscillating cutting knives and may be provided with a holder for securing them to the carrier.
The cutting modules or cutting units with fixed cutting knives comprise not only those in which the cutting knife is perpendicular to the material support surface but also those in which the cutting knife is inclined in a plane that is perpendicular to its forward moving direction at an angle of 45 degrees, such as the “Passepartout Tool PPT” of the company Zünd, so that the material can be cut at a slant in the direction of movement of the knife, for example, in order to produce a V groove.
The possibility of cutting slanting cuts or V grooves is advantageous, especially in the case of large material thicknesses. However, fairly solid materials, for example, cardboard, cannot be cut with a fixed knife, when the cutting depth exceeds a certain value. Even when the material can still be cut with a fixed knife, the cutting performance is considerably less effective than in the case of cutting units with oscillating cutting knives which are set into oscillation with the aid of an electrical or pneumatic oscillation drive along an axis that is perpendicular to the advancing direction of the cutting knife.
The known electrical oscillation drives are mostly piezoelectric oscillation drives, which have a very small stroke height so that the cutting units equipped with them are not suitable for the cutting of all materials. Cutting units with pneumatic oscillation drives do not provide an exact setting of the cutting depth and require an additional compressed air supply, as a result of which the device becomes more complex and expensive.
Also, to date no cutting units with tangential knives are known with which slanted cuts can be made into the material along a movement path that is curved with respect to the material supporting surface.
The present disclosure relates to a device for cutting material on a material supporting surface, the device having at least one cutting unit which can be motor-driven in a controlled manner above and across the material supporting surface in the direction of an X-axis and a Y-axis of a Cartesian coordinate system that is parallel to the material supporting surface and which device comprises an oscillation drive and a cutting knife, wherein the oscillation drive sets the cutting knife into linear oscillations having an oscillating axis which is perpendicular to an advancing direction of the cutting knife. Furthermore, the invention relates to a cutting unit comprising an oscillation drive, a holder for the oscillation drive and a cutting knife, wherein the oscillation drive sets the cutting knife into linear oscillations along an axis of oscillation that is perpendicular to an advancing direction of the cutting knife.
Based on the foregoing background, the invention has as its object the improvement of a device and a cutting unit of the type mentioned at the outset so that with the oscillating cutting knife, slanted cuts or V-shaped grooves with a variable angle of inclination with respect to the material supporting surface can be cut into the material.
In the device according to the invention, this object is achieved by the fact that the oscillation drive together with the cutting knife, is pivotable around a pivot axis that is parallel to the material supporting surface in order to alter the angle of inclination of the oscillation axis and thus of the cuts produced in the material with respect to the material supporting surface or in order to set a desired angle of inclination with respect to the material supporting surface. The cutting unit according to the invention is characterized by the fact that the oscillation drive, together with the cutting knife, is pivotable with the respect to the holder around a pivot axis that is perpendicular to the oscillation axis.
The pivot axis of the cutting unit is preferably oriented perpendicularly to the oscillation axis of the cutting knife, so that it intersects the pivot axis at a right angle.
The oscillation drive is preferably an electrical drive, so that an exact cutting depth can be provided and the device does not need an additional compressed air supply, which makes it possible to incorporate the cutting unit even in smaller and more economical devices. Advantageously, the oscillation drive comprises an electrical drive motor with a rotating drive shaft which is connected to a knife holder that carries and guides the cutting knife linearly by means of a gear that converts the rotation of the drive shaft into an oscillating movement of the knife holder. As a result of this, an oscillating movement of the cutting knife is achieved with a stroke height of up to 2 mm, which is more than the stroke height of piezoelectric oscillation drives.
According to a preferred embodiment of the invention, the drive shaft of the oscillation drive is oriented parallel to the supporting surface, wherein its axis of rotation is aligned with the pivot axis. In order to reduce the number of movable parts and thus undesirable vibrations, the drive shaft is advantageously the motor shaft of the electrical drive motor which projects from one side of a motor housing of the drive motor. The motor shaft is supported in the usual manner within the motor housing in two bearings, however, according to a favorable embodiment of the invention, outside the motor housing and beyond the oscillation axis of the cutting knife an additional bearing is provided, in which the free end of the motor shaft is supported rotatably. The additional bearing is expediently removable.
Another preferred embodiment of the device according to the invention provides that the cutting unit is attached to a holder that can be moved in a controlled motor-driven manner in the direction of the X-axis and the Y-axis, wherein the entire cutting unit is secured or suspended replaceably, as expedient, on the carrier.
Since the distance of the tip of the cutting knife from the material supporting surface changes when the oscillation drive with the cutting knife is pivoted around the pivot axis, advantageously the height of the cutting unit with respect to the carrier can be adjusted.
The cutting knife can be fundamentally a drag knife, the cutting edge of which is directed into the advancing direction by frictional forces between the cutting knife and the material. However, preferably, the cutting knife is a tangential knife whose orientation is controlled actively during cutting so that the cutting edge is always positioned in the advancing direction. This control or alignment, which is also called tangential control or tangential feed, is performed according to another preferred embodiment of the invention with the aid of a controlled tangential or rotary drive that is arranged between the oscillation drive and the carrier. With the aid of this tangential or rotary drive the oscillation drive, together with the cutting knife, can be rotated around the oscillation axis of the cutting knife with respect to the carrier. It is thereby possible to cut the material with inclined cuts along curved movement paths.
Preferably, the cutting unit comprises a holder for the oscillation drive in which the latter is supported pivotably, so that, together with the cutting knife, a knife carrier that holds the cutting knife and a guide for the knife carrier, it can be pivoted around the pivot axis with respect to the holder to change the angle of inclination of the oscillation axis with respect to the material supporting surface.
Depending on whether the knife is a drag knife or a tangential knife driven by a tangential or rotary drive, the holder is secured either directly to the carrier or to a drive shaft of the tangential or rotary drive.
Another preferred embodiment of the invention provides that the cutting knife is secured to a linearly guided oscillating knife carrier and that a gear for converting the rotary movement of the drive shaft of the electric motor into an oscillating movement of the cutting knife comprises an eccentric ring and connecting rod drive between the drive shaft and the knife carrier. This eccentric ring and connecting rod drive comprises advantageously an eccentric ring which is fixedly attached to the drive shaft, and a connecting rod the connecting rod foot of which is pivotably hinged or articulated to the knife carrier, whereas its connecting rod head surrounds the eccentric ring. Advantageously, a roller bearing is arranged between the rotating eccentric ring and the connecting rod head. Expediently, a hard metal liner is inserted into the connecting rod foot through which a hard metal bolt extends that is connected to the knife carrier.
In order to ensure that the angle of inclination of the cutting knife can be adjusted to a desired value and does not change during the cutting, advantageously, the oscillation drive can be blocked in various arbitrary and discrete pivot positions, wherein the change of the angle of inclination can be carried out either continuously or in discrete steps. In the first case, the oscillation drive can advantageously be attached to the holder in a fixed manner using a clamping device of the cutting unit, which provides for an arbitrary change of the angle of inclination.
Another preferred embodiment of the invention provides that the angle of inclination of the cutting knife can be altered even during the advancing movement of the knife across the material support surface. Advantageously, this is done with the aid of a computer-controlled actuating drive, which is expediently attached in a fixed manner to the holder and moves the oscillation drive with respect to the holder in a controlled manner around the pivot axis.
By pivoting of the oscillation drive around the pivot axis, the tip of the cutting knife does not only move in the direction of the Z-axis of the Cartesian coordinate system of the material support surface, either away from it or towards it, but also in the direction of the X-axis and, in the case of a rotation of the cutting knife around the rotary axis of the tangential or rotary drive, also moves in the direction of the Y-axis away from the desired movement path. Therefore another advantageous embodiment of the invention provides that the device has means for compensation of these movements in the direction of the X-, Y- and Z-axes.
To compensate for the movement in the direction of the Z-axis, in the first a.m. case the holder and in the last a.m. case the tangential or rotary drive can be adjusted in height with reference to the carrier so that a change of the position of the tip of the cutting knife as a result of the pivoting movement can be compensated. Expediently, the compensation is carried out automatically as a function of the particular pivoting angle using a computer-controlled actuating drive.
On the other hand, the compensation of the movement of the tip of the cutting knife in the direction of the X- or Y-axis, which is caused by the pivoting of the oscillation drive, is achieved preferably by an appropriate control of a drive of the arch or of the carrier respectively in order to move the arch or the carrier respectively for compensation by a corresponding amount into the opposite direction.
In the following the invention will be explained in more detail with the aid of a practical example shown in the drawing.
The device 10 shown in the drawing serves for the processing of material 12 by cutting, especially of layered material or plate-shaped material which has at least one plane surface for laying onto a flat support and which can be cut by a cutting knife, like cardboard, cork, foamed material, polystyrene, reboard or other sandwich slabs.
As shown best in
Furthermore, the device 10 has an arch or portal 22 which extends in a vertical distance from the material supporting surface 20 across the supporting or cutting table 14 and can be moved back and forth by a controllable portal drive (not shown) on tracks 24 or other linear guides in the direction of a horizontal X-axis of a Cartesian coordinate system that is parallel to the material supporting surface 20. The arch or portal 22 supports a carrier 26 for a cutting unit 30, which can be moved back and forth by a controllable carrier drive (not shown) on tracks 28 or other linear guides in the direction of a horizontal Y-axis of the Cartesian coordinate system. The cutting unit 30 can be removed from the carrier 26 so that in case of need it can be replaced by another processing unit, for example, a milling unit or marking unit.
The cutting unit 30 comprises a cutting knife 32, a knife holder 34, a linear guide 36 for the knife holder 34, an oscillation drive 36 for driving the knife holder 34 in an oscillating manner, a gear 38 arranged between the oscillation drive 36 and the knife holder 34, a tangential or rotary drive 44 for active alignment of the cutting knife 32, and a holder 40 that connects the oscillation drive to a drive shaft 42 of the tangential or rotary drive 44.
With the aid of the oscillation drive 36 and of the gear 38, the cutting knife 32 can be set into linear oscillations, the oscillation axis 46 of which is perpendicular to the advancing direction of the cutting knife 32, that is, the direction in which the cutting knife 32 moves across the material supporting surface 20 through the material 12 to be cut. When the cutting knife 32 cuts the material 12 along a cutting plane that is perpendicular to the material supporting surface 20, as represented in
As shown best in
The oscillation drive 36 comprises an electric drive motor with a cylindrical motor housing 54 and a motor shaft 56 that is supported within the motor housing 54 in two roller bearings (not visible). The motor shaft 56 comprises two shaft ends 58, 60, each of which projects from one of the two opposite ends of the motor housing 54. The shaft end 60 on the side of the gear 38 is supported with its free end in another roller bearing 62, so that the motor shaft 56 is rotatably supported in a total of three roller bearings. The roller bearing 62 is inserted into a recess that is coaxial to the rotary axis of the motor shaft 56 the recess being arranged in a removable bearing cover 64, which is fastened tightly with set screws 66 to the adjacent end of the motor housing 54. The roller bearing 62 can be lubricated through a bore 68 in the middle of the bearing cover 64.
The gear 38 has a gear housing 70, which consists of an upper part 72 arranged in extension of the motor housing 54 and a lower part 74 that protrudes downwardly. Both parts are connected to each other to form one piece. The gear housing 70 is fastened with set screws 76 to the adjacent end of the motor housing 54. The upper part 72 of the gear housing 70 is arranged between the end of the motor housing 54 and the bearing cover 64, where it partly overlaps a lower part of the end of the motor housing 54 and abuts the holder 40 with an abutment face 77 on the motor side. The upper part 72 surrounds a stepped bore 78, which is coaxial with the motor shaft 56, which extends to the adjacent end of the motor housing 54 and which is closed on its end facing away from the motor housing 54 by the bearing cover 64. The lower part 74 of the gear housing 70 surrounds a stepped bore 80, which is open toward the bottom and which is coaxial with the oscillation axis 46. The lower part 74 opens into the stepped bore 78 within the upper part 72 and is closed at its upper end above the motor shaft 56 by a plate 82.
The gear 38 is a crank mechanism for converting the rotation of the motor shaft 56 into an oscillating movement of the knife holder 34 along the oscillation axis 46. Within the gear housing 70 the gear 38 comprises an eccentric ring 84 that is arranged on the shaft end 60 between the adjacent end of the motor housing 54 and the bearing cover 64 in extension of the oscillation axis 46. The eccentric ring 84 has an inner cylindrical surface that is concentric to the rotational axis of the motor shaft 56 and an outer cylindrical surface that is eccentric to the rotational axis of the motor shaft 56. The eccentric ring 84 is fixedly attached to the motor shaft 56 so that it rotates together with the motor shaft 56.
Furthermore, the gear 38 comprises a connecting rod 86 which is made in one piece from light metal. The connecting rod 86 has a connecting rod head 88 surrounding the eccentric ring 84 and a connecting rod foot 90 which is articulated to the knife holder 34. Between the connecting rod head 88 and the eccentric ring 84 there is a closed needle bearing or ball bearing 92, the inner ring of which is pressed onto the cylindrical outer peripheral surface of the eccentric ring 84 whereas the outer ring is pressed into an eye of the connecting rod head 88. In order to accommodate the needle bearing or ball bearing 92, the width of the connecting rod head 88 is larger than that of the rest of the connecting rod 86 and of the connecting rod foot 90 in the axial direction of the motor shaft 56, as shown best in
The knife guide 36 consists of a cylindrical tube that is open at both ends, which is coaxial to the oscillation axis 46 and is inserted from below into a widened part of the stepped bore 80 and fixedly attached.
The knife holder 34 is a hollow cylindrical piston made of light metal, which is guided within the hollow cylindrical knife guide 36 so that it can move in the direction of the oscillation axis 46, wherein its outer peripheral surface slides during the oscillation movement with a slight clearance on the inner peripheral surface of the knife guide 36. For lubrication of these sliding surfaces a transverse bore 96 is provided, which extends through a wall of the lower part 74 of the gear housing 70, a wall of the hollow cylindrical knife guide 36 and a wall of the hollow cylindrical knife holder 34.
The knife holder 34 is provided on its open upper end with a transverse bore which is perpendicular to the oscillation axis 46. A holding bolt 98 made of hard metal is pressed into the transverse bore. The bolt 98 extends through a hard metal sleeve 100 in the connecting rod foot 90 of the connecting rod 86, which protrudes from above through the hollow cylindrical knife guide 36 a little distance into the open upper end of the knife holder 34.
As shown in
In order to facilitate the introduction of cuts into the material 12, where the cuts have a cutting face that is inclined with respect to the material supporting surface 20 at an acute angle, for example, 45 degrees or 60 degrees, the oscillation drive 36, together with the gear 38, the knife guide 36, the knife carrier 34 and the knife 32 can be pivoted with respect to the holder 40 around a pivot axis 106 that is parallel to the material supporting surface 20. The pivot axis 106 is aligned with the rotary axis of the motor shaft 56 and is perpendicular to the oscillation axis 46 of the cutting knife 32. In order to set a desired angle of inclination of the oscillation axis 46 of the cutting knife 32, additionally the oscillation drive 36 together with the components 32, 34, 36 and 38 can be positioned at any desired angular position with respect to the holder 40.
In the case of the cutting unit 30 in
In the cutting unit 30 in
For this purpose, the holder 40 comprises a plate-shaped projection 124 protruding sideways above the clamping ring 108 into which a step motor 126 is inserted so that it cannot rotate. The step motor 126 drives a pinion 128 which engages with a toothed-ring 130. The toothed ring is attached to the motor housing 54 so that it cannot rotate with respect to the motor housing 54 and is coaxial with the pivot axis 106. In order to set a desired angle of inclination of the oscillation axis 46, the step motor 26 can be driven in a controlled manner after the set screw 112 has been loosened in order to rotate the motor housing 54 in the through-opening 110 until the desired angle of inclination is reached.
When the angle of inclination of the cutting knife 32 is to be altered during a cutting operation, the clamping ring 108 remains loosened in order to be able to rotate the motor housing 54 by means of the step motor 126. On the other hand, when the cutting is to be performed with a constant angle of inclination, the set screw 112 is preferably tightened in order to reduce vibrations.
Fundamentally, the oscillation drive 36 can be turned through 360° in the through-opening 110 of the clamping ring 118 with respect to the holder 40; however, for the processing of the material 12 on the supporting surface 20, generally it is sufficient when the cutting knife 32, starting out from the state in
As a result of the pivotability of the oscillation drive 36 and of the gear 38 with respect to the holder 40, it becomes possible to provide a plate-shaped material 12 resting on the material supporting surface 20, for example, a reboard plate or a cardboard piece, with cuts 114, which are inclined with respect to the material supporting surface 20, as shown in
When two cuts 114 with opposite inclinations are made into the plate-shaped material 12, such that the lower ends of the cuts 114 come into contact somewhat above than the supporting surface 20, a groove that is open towards the top and has a V-shaped cross section can be cut out of the material 12. When the groove is straight, it is possible to tilt the parts of the plate-shaped material 12 around the base of the groove, until the surfaces of the groove abut each other. After that the two parts are inclined with respect to each other at an angle that corresponds to the opening angle of the groove cross section.
As shown best in
The holder 40 can be screwed onto the drive shaft 42 from below, as shown in
When the oscillation drive 36 is pivoted together with the gear 38, the knife holder 34 and the cutting knife 32 around the pivot axis 106, the distance between the tip 52 of the cutting knife 32 and the material supporting surface 20 will change. Furthermore, due the pivoting of the oscillation drive 36 and of the components 32, 34, 36 and 38 the tip 52 of the cutting knife 32 will deviate from the programmed movement path, which the tip 52 would follow in case of a vertical alignment of the oscillation axis 46 during the movement of the portal 22 and/or of the carrier 26, when viewed in a vertical projection.
For compensating the change of the vertical distance of the tip 52 of the cutting knife 32 from the material supporting surface 20, the level or height of the tangential or rotary drive 44 on the carrier 26 is adjustable, so that the drive 44 can be raised or lowered when there is a change of the pivot position of the cutting knife 32, as shown in
K(z)=A×(1−cos α)
where A is the vertical distance of the pivot axis 106 from the material supporting surface 20 and where α is the angle of inclination of the oscillation axis 46 of the cutting knife 32 with respect to its initial vertical position, as shown in
In order to compensate for the deviations of the tip 52 of the cutting knife 32 from the programmed movement path in the direction of the X- or Y-axis respectively, during a pivoting movement of the oscillation drive 36 around the pivot axis 106, the portal drive and/or the carrier drive are activated in order to move the portal 22 and/or the carrier 26 along the X-axis or Y-axis respectively in the opposite direction, where the movement of the portal 22 and/or the carrier 26 corresponds to the deviation. Here the degree of compensation in the direction of the X-axis, that is, the movement required of the portal 22 in the X-direction with respect to the cutting table 14, is:
K(x)=A×sin α×cos β.
The degree of compensation in the direction of the Y-axis, that is, the movement of the carrier 26 in the Y-direction with respect to the cutting table 14, which is necessary for the compensation, is:
K(y)=A×sin α×sin β,
where A is the vertical distance of the pivot axis 106 from the material supporting surface 20, where α is the angle of inclination of the oscillation axis 46 of the cutting knife 32 with respect to its initial vertical position, as shown in
With the device 10 described above, the cutting knife 32 can be driven with an oscillation frequency of 18,000 oscillations per minute and an exact piston or knife stroke of 1.6 mm. In comparison to a pneumatic cutting unit, the cut has an adjustable, constant cutting depth.
The oscillation frequency can be altered, since an rpm-controlled motor is used as the electric motor, while the piston stroke can be altered by replacing the eccentric ring 84 by another eccentric ring 84 with a larger or smaller eccentricity.
Although certain cutting devices and cutting units and features and characteristics thereof have been described herein in accordance with the teachings of the present disclosure, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all embodiments of the teachings of the disclosure that fairly fall within the scope of permissible equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 009 251.5 | Jun 2013 | DE | national |
