Grinding process and control device for a knife shaft

Details Grinding process and control device for a knife shaft Grinding process and control device for a knife shaft

2002-06-27

2003-12-09

Paladini, Albert W. (Department: 2125)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Product assembly or manufacturing

C083S364000, C083S370000, C451S010000, C451S045000, C451S242000, C451S397000

Reexamination Certificate

active

06662072

ABSTRACT:

This is a U.S. original application which claims priority on French patent application No. 0108833 filed Jul. 4, 2001.
FIELD OF THE INVENTION
The present invention relates to a process for grinding a knife shaft and the control device linked to the implementation of the process. The knife shaft is used in a machine intended for cutting sheets of material into strips, for example, sheets of paper, plastic, plates of photosensitive film or any other material having the form of thin sheets.
BACKGROUND OF THE INVENTION
In the photographic industry, to obtain several strips of photosensitive film from an initial strip of large width, slitters are used comprising many rotary knives mounted in spaced apart manner on a first knife shaft, and many counter-knives mounted on a second knife shaft, with the strip to be cut running between these two rows of knives and counter-knives. In place of knife shafts, independent units can be used carrying the knives or counter-knives. It is necessary that the knives and counter-knives be sharpened regularly to maintain a good quality of cut on the edge of the cut strips.
There already exist many means that enable the taking into account of the sharpening done on the knives of various slitters, by compensating dimensionally using appropriate means, for the loss of material due to the sharpening of one or more knives. These compensation means enable sufficiently good control of the cutting process to be kept over time, following successive sharpening of the knives. This control of the cutting process produces a sufficiently good cutting quality of the cut strips and little dimensional variability of these cut strips. However, this dimensional variability remains excessive compared with the specifications of film strips used in the photographic industry.
U.S. Pat. No. 4,592,259 describes a method and means for adjusting the relative positioning of the slitter knives of a strip cutting apparatus; in order to obtain a correct relative position of the knives one with another, and between each of the cutting units taking these knives; the cutting units can move on slides. Electrical and mechanical means enable automatic compensation for the dimensional variations of thickness of the knives in time. These compensations produce adjustments of the position of the cutting units one with another on their slides. The objective is to obtain a constant and specified distance between the cutting edges of two successive knives, by comparison with a standard reference value recorded in a memory, and corresponding, for example, to the thickness of a new blade. This invention enables a constant distance between the knives to be obtained, but this concerns knives belonging to slitters or carriages that are independent one from another as to their relative movements on their respective slides. In other words, the overall geometry of the cutting means modifies according to the dimensional variations of the knives, to keep constant the distance between the cutting units and therefore between the cut edges of the knives.
U.S. Pat. No. 4,607,552 describes an apparatus enabling automatic control of the position of many slitters that cut a moving strip. Electronic control means enable, from the measurement of wear of the cutting blades of each slitter, calculation of the dimensional compensation to correctly reposition the blade, relative to the strip to be cut and to the part acting as the counter-knife. This apparatus thus enables compensation of the wear of each of the slitter's blades, independently one from another.
The object of the invention disclosed in U.S. Pat. No. 5,097,732 has certain similarities with that of U.S. Pat. No. 4,607,552. A numerical control device enables the measurement and control of the interval between the cutting units of a slitter having many cutting units. The objective of the invention is to be able to move many cutting units simultaneously to a preset position. Then after this movement of the cutting units, the respective adjustment of the contact pressures of the upper and lower knives is carried out.
U.S. Pat. No. 4,072,887 discloses an apparatus enabling the movement of mobile elements, especially a first pair of circular cutting blades working together having their axes parallel, into a new position, through a translation according to the axis of the circular cutting blades. The apparatus enables the repositioning, using appropriate measuring means, of successive pairs of blades located side by side on independent units, compared with the first pair of blades moved.
European Patent Application 0,602,655 describes a sharpening method for circular cutting blades attached to a shaft. This invention especially aims to not remove the blades from the same knife shaft to sharpen them and so avoid inducing causes of error and thus dimensional variations linked to the remounting operation of these blades on their shaft after their sharpening. The sharpening operation described in this invention especially enables, from the knife shaft comprising its blades to be sharpened and mounted between points on a grinder, to plunge one or more rotating grinding wheels towards the edges of the blades by ensuring the movement of the grinding wheel with a numerically controlled programmed device. This is in order to sharpen successively or simultaneously the cutting blades of the same shaft without removing the blades. The final objective being to improve the lateral and radial run-out of the blade cutting edges by increasing the precision obtained on the cut strips of product. However, the result obtained as to the strip widths of product cut with the knife shafts sharpened according to this sharpening method remains unsatisfactory.
French Patent Application 9912181 relates to a device and a process to position many knives mounted on a first knife shaft in relation to many counter-knives mounted on a second knife shaft of the same strip slitter. This does not enable ensuring especially the dimensional constancy or reproducibility of the pitch on a given slitter.
All the means described in the above mentioned documents are based on principles and means of control or measurement enabling the positioning or repositioning one against the other, of cutting units or slitters comprising knives, to compensate for example for the parameters of variability of the cutting process. The purpose of this is to conserve overall control of the process. In the case of slitters, an important variability parameter of the known process is the wear of the knife blades used on these machines. This phenomenon can be controlled by acting on certain physical components of the slitter, for example, by moving them one in relation to the others to compensate for example for the wear of the knives. It is possible on the same slitter to change, for example, the type of manufacture and proceed to remove the knives corresponding to a first type of manufacture to replace them by other knives corresponding to a new planned manufacture. Then later, for example, all or part of the knives corresponding to the first type of manufacture may be reused. In this case, appropriate control and measuring means enable the control and repositioning if necessary of the knives one in relation to the others; but the guarantee of the reproducibility of the axial pitch between the knives is not assured when sharpening; consequently the quality of the cut obtained by a good correspondence or good pairing of the respective knives of the two knife shafts working together to cut, for example, the same strip of material is not assured. In other words, the means used in the prior art mentioned enable control of the cutting process but without controlling the reproducibility or the variability of the cutting pitch of the knife shaft.
SUMMARY OF THE INVENTION
An object of the present invention is to control the evenness of sharpening the knife shafts of the same slitter, and more precisely pairs of knife shafts equipped with knives, so that over time and with successive sharpening or grinding, these knife shafts

Affiliated with

Also associated with

Rating

Grinding process and control device for a knife shaft does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Grinding process and control device for a knife shaft, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Grinding process and control device for a knife shaft will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3170043