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US-12617113-B2 - Knife holder for cutting machines

US12617113B2US 12617113 B2US12617113 B2US 12617113B2US-12617113-B2

Abstract

A knife holder for cutting machines, with a cutter head ( 1 ) for holding a knife ( 2 ) and a positioning device ( 3 ), wherein the positioning device ( 3 ) can be driven in a drive direction ( 4 ) between a standby position and a cutting position, and comprises a spring ( 5 ), with which the positioning device ( 3 ) is applied against the drive direction ( 4 ), wherein the spring ( 5 ) generates a reset force having a negative force characteristic curve in the drive direction ( 4 ).

Inventors

  • Hans Dunn

Assignees

  • DIENES WERKE FUR MASCHINENTEILE GMBH & CO. KG

Dates

Publication Date
20260505
Application Date
20230405
Priority Date
20220405

Claims (12)

  1. 1 . A knife holder assembly for cutting machines, the knife holder assembly comprising: a cutter head ( 1 ) for holding a knife ( 2 ); and a positioning device ( 3 ), wherein the positioning device ( 3 ) comprises: a piston apparatus ( 7 ) configured to drive the knife a drive direction ( 4 ) between a standby position and a cutting position, and a spring ( 5 ), wherein the spring applies a reset force against the piston apparatus while the knife is in the cutting position, wherein the spring ( 5 ) generates the reset force having a negative force characteristic curve in the drive direction ( 4 ), such that the reset force generated by the spring acting transversely to a longitudinal axis of the spring and against the piston apparatus ( 7 ) diminishes with an increasing travel distance in the drive direction ( 4 ) from the standby position to the cutting position and wherein the longitudinal axis of the spring ( 5 ) is aligned at an angle ( 6 ) of 30° to 80° relative to the drive direction ( 4 ) when the knife is in the standby position.
  2. 2 . The knife holder assembly according to claim 1 , wherein the spring ( 5 ) is arranged and/or designed in such a way that the reset force having the negative force characteristic curve corresponds to the progression of a force characteristic curve generated by a drive of the positioning device ( 4 ) in the drive direction ( 4 ).
  3. 3 . The knife holder assembly according to claim 1 , wherein the reset force generated by the spring ( 5 ) also includes a force direction inclined to the drive direction ( 4 ).
  4. 4 . The knife holder assembly according to claim 3 , wherein the spring ( 5 ) counteracts a torque generated in the cutting position by pressing the knife ( 2 ) against a counter knife ( 13 ).
  5. 5 . The knife holder assembly according to claim 1 , wherein the spring ( 5 ) is a helical spring.
  6. 6 . The knife holder assembly according to claim 1 , wherein the piston apparatus ( 7 ) is pressurizable.
  7. 7 . The knife holder assembly according to claim 6 , wherein the spring ( 5 ) acts on the piston apparatus ( 7 ) on a side facing away from a pressurizable side.
  8. 8 . The knife holder assembly according to claim 7 , wherein the piston apparatus ( 7 ) comprises two membranes ( 8 . 1 , 8 . 2 ), between which a pressurized fluid can be introduced.
  9. 9 . The knife holder assembly according to claim 8 , wherein the two membranes ( 8 . 1 , 8 . 2 ) have different sized active surfaces.
  10. 10 . The knife holder assembly according to claim 8 , wherein the piston apparatus ( 7 ) has a multipart piston head ( 9 . 1 , 9 . 2 ), and the membranes are fixed in place by the multipart piston head ( 9 . 1 , 9 . 2 ).
  11. 11 . The knife holder assembly according to claim 6 , wherein the piston apparatus ( 7 ) has a piston rod designed as an axis ( 10 ), and the axis ( 10 ) is at least axially movably mounted by means of a bearing ( 11 ).
  12. 12 . The knife holder assembly according to claim 1 , wherein the knife holder assembly further comprises a lowering device ( 12 ) for the cutter head ( 1 ), wherein the lowering device is configured to move the cutter head ( 1 ) in a direction orthogonal to the drive direction ( 4 ).

Description

RELATED APPLICATION This application claims priority to EP patent application No. 22166663.9, filed on Apr. 5, 2022. The entirety of this application is incorporated herein by reference. SPECIFICATION The present invention relates to a knife holder for cutting machines, with a cutter head for holding a knife, in particular for holding a circular knife, and a positioning device for the cutter head, wherein the positioning device can be driven in a drive direction between a standby position and a cutting position in particular by means of a pneumatic drive, and comprises a spring, with which the positioning device is applied against the drive direction. Usually, the spring preloads the positioning device, and hence the knife, in the standby position, while the positioning device, and hence the knife, can be transferred from the standby position into the cutting position along a straight line in the drive direction by a pneumatic drive. Such a knife holder is known from DE 102 60 031 B3. Also known from this publication is that the positioning force acting in the drive direction by way of the pneumatic drive diminishes as the delivery path increases. The spring acting exclusively against the drive direction according to DE 102 60 031 B3 further strengthens this effect, since the reset force generated by the spring grows as the delivery path increases. Therefore, depending on how large the positioning path from the standby position into the cutting position is, various cutting forces can be present when applying the knife against a lower knife. In order to overcome this disadvantage, DE 102 60 031 B3 proposes that a piston surface of a positioning piston have a cross section which varies in different piston positions. In such a design, there is also a high space requirement in the drive direction. Therefore, the object of the present invention is to indicate an alternative for how the cutting force can be held as constant as possible along the drive direction. The knife holder with the features in claim 1 indicates one way of achieving this object. Additional solutions and advantageous further developments of the knife holder are explained in the dependent claims and in the description above and below, wherein individual features of the advantageous further developments can be combined with each other in a technically reasonable way. In particular, the object is achieved by a knife holder with the features mentioned at the outset, wherein the spring forms a negative force characteristic curve in the drive direction. In other words: The basic idea of the invention provides that the spring be arranged and/or designed in such a way that the (reset) force that is generated by it and acts against the drive direction diminishes with an increasing travel distance. As a result, the (delivery) force that is in particular generated by a pneumatic drive and diminishes with an increasing travel distance is compensated by the spring in such a way that a cutting force generated when the knife contacts a counter knife is nearly constant at least over large distances along the drive direction. Therefore, the cutting force is identical regardless of the distance between the standby position and the cutting position. In particular, the spring is arranged and/or designed in such a way that a progression of the negative force characteristic curve corresponds to the progression of a force characteristic curve generated by an in particular pneumatic drive of the positioning device in the drive direction. The invention also makes it possible to reduce the width of a knife holder (i.e., in the drive direction), as a result of which the adjustment range could in turn be increased given the same width. Therefore, the arrangement (in particular a degree of inclination) and design of the spring (in particular the spring constant) are selected in particular so that the force characteristic curve diminishes in the drive direction to the same extent as the characteristic curve of the force exerted by the (pneumatic) drive of the positioning device, which in particular has a membrane. In particular, the knife holder has an attachment device, for example with which the knife holder can be fastened to a traverse of a cutting machine. The knife holder can comprise a lowering device, with which the cutter head can be moved in particular toward and away from a lower knife in a lowering device. If the knife holder comprises a lowering device, the straight drive direction of the positioning device is orthogonally aligned to the lowering device. The positioning device can be used to set the knife in its axial direction on a cutting edge of a lower knife along a straight line. Therefore, the invention preferably relates to the kind of positioning device with which a circular knife can be fed to a cutting edge of a lower knife in an axial direction of the circular knife. In particular, the invention also relates to a cutting machine with a traverse, to