The invention relates to a device by means of which the shell surfaces of the drying cylinders in a paper machine can be machined and particularly ground' without having to detach the drying cylinders from the paper machine. It is of advantage to use this kind of device when a worn, dirty, or otherwise uneven shell surface of a drying cylinder is to be repaired by ma¬ chining.

It is known to carry out grinding by means of a method wherein a separate body beam is mounted beside the drying cylinder, and the body beam is provided with guide rails on which a grinder secured on a displacing carriage is supported for the grinding of the shell sur¬ face of the drying cylinder. The repair grinding is dif¬ ficult to carry out by means of this method, because the body beam must be steady, whereby it of necessity is heavy and the mounting thereof is both laborous and dif¬ ficult. Further, the apparatus itself is very difficult to fasten on the object to be ground. The repair grinding of the shell surface of the drying -cylinder thus takes plenty of time, and is difficult to carry out. Finnish Patent Specification 822,448 discloses a grinder the body of which is formed e.g. by a felt roll or an adjacent drying cylinder to which guide rails are attached by means of clamp frames, magnets or some other fastening means, by virtue whereof the grinder is light and the mounting thereof is fairly easy to carry out. How¬ ever, bringing the device into working order is accurate work, wherefore it often takes plenty of time, too.

Further, the prior art methods and devices for grinding a drying cylinder are disadvantageous in that the wire must be removed from the drying cylinder in

order that the grinding could be carried out, which lengthens the highly costly downtime of the paper machine.

The object of the novel machining device according to the invention is to eliminate the above-mentioned dis- advantages. For the achievement thereof the invention is characterized in that the carriage comprises a frame car¬ riage which is provided with supporting elements by means of which the frame carriage is supported both on a drying cylinder of the paper machine and on a second cylinder of the paper machine between said cylinders when the ^* de¬ vice is in operation.

By virtue of the device according to the invention the grinding work can be carried out easily and rapidly, whereby the paper machine has to be put out of operation only for a short period of time.

The invention will be described in detail in the following by means of one preferred embodiment thereof with reference to the attached drawings, wherein

Figure 1 illustrates the machining device in a side view, i.e. perpendicularly to the longitudinal axis of the drying cylinder, and

Figure 2 illustrates the machining device in a partial sectional view seen in the -•direction of the lon¬ gitudinal axis of the drying cylinder. In Figures 1 and 2 the frame carriage of the ma¬ chining device is indicated generally by the reference numeral 1. An abrasive belt grinder ( _a stone grinder is also possible) operated by a motor 2 is positioned within the frame carriage 1 and indicated generally by the refe- rence numeral 3. The position of the abrasive belt grinder 3 can be adjusted by means of a horizontal carriage 4 and a vertical carriage 5, and the both carriages are operated by their own displacing motors 6 and- 7. The abrasive belt grinder 3 is attached to the horizontal carriage 4, which is displaced on guides 8 and attached to the vertical

carriage 5. In the figures the frame carriage 1 is fitted between two adjacent drying cylinders 9 and 10 of-the paper machine, of which cylinders the upper one 9 is ex¬ posed to the grinding operation. As appears from Figure 5 1, the displacement of the frame carriage 1 in the lon¬ gitudinal direction of the drying cylinder is carried out by means of a displacing motor 11 which is separate from the frame carriage, e.g. attached to the frame of the paper machine. The displacing motor 11 operates the frame

10 carriage by means of a displacing chain 12.

The frame carriage 1 comprises two parts so that it is easy to mount between the drying cylinders 9 and 10; i.e. the frame carriage is assembled in situ of two parts which are attached to each other. The two parts of

15 the frame carriage 1 are formed e.g. in such a way that each vertical beam thereof is formed by two pieces and provided with connecting flanges 18 positioned in the lower portion of the frame carriage, whereby the flanges and the vertical beams are interconnected by means of a

20 bolted joint when the frame carriage is assembled and de¬ tached from each other when the frame carriage is dis¬ assembled. The horizontal beams of the frame carriage 1 can also be provided with connecting flanged 19 for fa¬ cilitating the mounting. It is possible to replace said 25 flanges by hinge-type joints. In view of the mounting, an alternative structure would be such that the beams of the frame carriage are e.g. telescopic, whereby the height of the frame carriage is easily adjustable. The frame carriage 1 of the machining device is arranged to

30 be supported between the drying cylinders 9 and 10 on eight supporting elements 13 and 14. The supporting ele¬ ments 13 and 14 are provided with rotating balls, roller wheels, or slide blocks so that the cylinders 9 and 10 are able to rotate during the grinding. The supporting 35. elements 14 positioned against at least the drying cy-

linder 9 are resilient, whereby the clearances of the machinery and the.irregularities..of__the_ drying cylinders do not hamper the grinding process. The relilience can be effected e.g. by means of springs, as shown in Figure 2, The control of the grinder 3 is based e.g. on the use of a laser transmitter. The laser transmitter, which is indicated by the reference numeral 16 in Figure 1, is mounted in parallel with the longitudinal axis of the drying cylinder 9. The laser transmitter 16 transmits light towards the grinder 3, to which an identifier 17 is attached, whereby an automatic control (not shown) con¬ nected to the laser transmitter determines accurately the position of the grinder, i.e. the distance thereof from the axis of the cylinder 9 to be ground, and ensures that the driving motors 6 and 7 of the horizontal and -the ver¬ tical carriage control said .carriages in such a way that the desired grinding ^' program will be carried ^' out. It is not necessary to control the .displacing motor 11 of the frame carriage 1 by means of the laser transmitter, be- cause it may rotate at a determined, preset constant speed during the entire grinding process. In place of the laser control, optical devices can be utilized in the control of the horizontal and the vertical motor 6 and 7, by means of which devices it is possible to observe the path of the grinder 3 and manually correct it, if ne¬ cessary. Alternatively, the control can be effected by means of a wire which is tightened in parallel with the longitudinal axis of the drying cylinder to be ground, whereby a sensor is utilized for maintaining the move- ment of the grinder parallel to the tightened wire.

The system according to the invention can also be carried out in such a manner that in place of a grinder, a cutter unit, e.g. a turning chisel or a milling cutter, is fastened on the horizontal carriage. By means of the cutter unit the drying cylinder can be machined extremely

rapidly. The finishing step, however, must be carried out by grinding.

It has been stated above that the machining device according to the invention is mounted between two drying cylinders of the paper machine; however, it can be alter¬ natively mounted between the drying cylinder to be ground and a felt roll of the paper machine so that the felt roll acts as the second cylinder mentioned in Claim 1. The de¬ vice can easily be constructed so that the grinder there- of can be turned towards a third or a fourth drying cy¬ linder of the paper machine, i.e. towards a cylinder on which the device is not supported, for the grinding of said cylinder (s) .

The invention has been described above only by means of one preferred embodiment thereof, and a few pos¬ sible modifications of the invention have been referred to. However, it is fully possible to realize the invention in- a slightly different way within the sphere of the in- ^' ventive idea defined in the attached claims. For instance, the frame carriage can be formed by more than two parts for facilitating the mounting thereof, and it is, of course, possible to fasten the frame carriage on more than two cylinders.