Equipment for crawl-driving of a new press felt in a paper machine

Abstract: The invention concerns a method and a device in crawling operation of a press felt (H) in a paper machine. The press felt (H) has been passed as a closed felt loop through the nip (N) placed between the centre roll (K) and the press roll (T) in the press of the paper machine, the felt (H) being driven, during the running proper of the paper machine, by means of the nip drive (N) between the centre roll (K) and the press roll (T) of the press. When the paper machine is not being run and the nip (N) between the centre roll (K) and the press roll (T) in the paper machine is open, the felt is moved, so as to moisten the new felt (H), by means of the crawling drive by rotating the drive roll (10). The axle (10a) of the drive roll (10) is permanently connected with a drive rim (20). During crawling operation, the drive wheel (19;27a,27b...) of a hydraulic device (14,17;26a,26b...) is brought into engagement with the drive rim (20), and, when the crawling drive of the felt is not in operation, the drive roll (10) is switched to the free revolving position by shifting the drive wheel (19;27a,27b...) of the hydraulic device (14,17;26a,26b...), which drive wheel is operationally connected with the drive rim (20), apart from the drive rim (20).

Description: The invention concerns a paper machine with an equipment for crawl-driving of a new press felt. The preamble of claim 1 is based on DE-A-4 004 726.A further prior art device is disclosed in DE-A-3 506 155. The press felt is passed as a closed loop through the nip between the centre roll and a press roll in the paper machine, and the drive of the felt is produced by means of the nip drive. In connection with replacement of felt, the new felt is moistened before the start of the operation proper, and at the felt-moistening stage the felt is run with a low crawling speed by means of a separate drive gear while the press nip is open. In prior art, the drive gear has consisted of an electric motor, whose speed of rotation has been lowered by means of a reduction gear, the output shaft of said gear being further connected to a mechanical cylinder-operated coupling. Through the coupling, the movement of rotation has been transferred further to the axle of the drive roll of the felt. As the mechanism mentioned above has been formed by coupling the constructional units of the mechanism one after the other, the constructional length of the mechanism has become detrimentally long. Further, the mechanism has consisted of a number of individual components, for which reason the susceptibility of failure of the equipment has been relatively high. In connection with the cylinder operation of the coupling, separate limit detectors have been used. By means of the use of the detectors, in the prior-art solutions, switching-on of the main drive of the felt has been prevented in situations in which the auxiliary drive is still in operation. The detectors have been susceptible of contamination, in which case the data on limit positions given by the detectors have not always been reliable. In the present application, attempts have been made to find an improvement for the crawling operation of a press felt. In the application, a novel paper machine with an equipment is described, wherein the coupling and the drive gear consist of the same unit. The equipment does not comprise a separate disconnecting coupling, a separate gearbox, or a separate drive unit, but these consist of one unit. Thus, it has been possible to make the whole drive unit of simple construction and of short constructional length. Since the number of units susceptible of failure is lower, the operation of the equipment is considerably more reliable than the prior-art electro-mechanical crawling-drive system. The paper machine with an equipment in accordance with invention for crawling operation of a press felt is characterized by the features of the characterizing part of claim 1. The invention will be described in the following with reference to an embodiment of the invention illustrated in the figures in the accompanying drawings, the invention being, however, not supposed to be confined to said embodiment alone. Figure 1A shows the location of the equipment of the invention in a paper machine. Figure 1B shows an equipment in accordance with the invention for crawling operation of a press felt as viewed in the machine direction. Figure 2A shows an embodiment of the device in accordance with the invention, wherein the drive rim is rotated by means of a cam mechanism. Figure 2B shows the equipment of Fig. 2A in a position of free rotation, wherein the main drive of the press felt may be switched on. Fig. 1A shows the location of the crawling-drive roll 10 of the press felt H in the press section. When the nip N between the centre roll K and the roll T in the paper machine is open, the felt is operated by means of the drive roll 10, for example, to moisten the felt. The roll 10 is a so-called crawling-drive roll. During operation of the paper machine, the felt is operated by means of the nip N, and in such a situation the roll 10 is in a position of free rotation. Fig. 1B shows the crawling-drive device of the press felt as viewed in the machine direction. The press felt H is operated by the press-felt drive roll 10, whose axles 10a are mounted in bearings 11. The drive roll 10 receives its rotation drive directly from the drive rim 20, whose body 20a is connected to the roll 10 axle 10a. Around the equipment, there is a protective housing 13. The equipment rests on a cantilevered frame beam 12, while the frame beam 12 is attached to the frame R. Figure 2A shows an embodiment of the crawling-drive device. The drive rim 20 comprises a wave-shaped inside rim form 24. Inside the drive rim 20, there is a drive unit 25, which comprises a number of drive pistons 26a,26b..., at whose ends there are cam-wheels 27a,27b... . The rotation of the drive rim 20 is produced by passing pressurized fluid through the inlet opening to the distributor 28 and from the distributor 28 further into the cylinders 29a,29b... . Some of the drive pistons 26a,26b... are in the work stage and push the cam-wheels 27a,27b... against the drive rim 20. The cam-wheels 27a,27b... that are in the work stage force the drive rim 20 into a revolving motion. After the pistons 26a,26b... have performed their full stroke, the distributor 28, which revolves synchronously with the drive rim 20, closes the inlet of fluid into the piston 26 that has completed its work stage and opens the exhaust opening to the fluid space of said piston. In a corresponding way, the distributor 28 opens the flow passage for the pressurized fluid into the piston 26 that is in the bottom position in its cylinder. When pressurized fluid is not being passed to the distributor 28 and, through the distributor, into the pistons 26a,26b..., in the way shown in Fig. 2B, the springs 30a,30b... press the pistons 26a,26b... into their bottom positions in the cylinders 29a,29b... and keep the cam-wheels 27a,27b... placed at the ends of the pistons 26a,26b... apart from the drive rim 20. In such a case, the drive rim 20 can be rotated freely so that the system does not cause an operating resistance to the movement of rotation. The cam mechanism permits a drive system in which the drive device and the disengaging coupling constitute a single unit. When the press felt H is switched to the main drive, the fluid spaces E 1 ,E 2 at both sides of the pistons 26a,26b... are kept free of pressure. In such a case, the springs 30a,30b... press the pistons 26a,26b... to their bottom positions in their cylinders 29a,29b... and keep them there. The drive rim 20 and the press-felt H crawling-drive roll 10 connected to the rim 20 permanently by means of the body 20a can revolve freely at a high speed during normal operation of the paper machine while the felt H is driven by means of the nip N between the centre roll K and the press roll T in the press.

Claims: Paper machine with an equipment for crawl-driving of a new press felt (H) through the open nip (N) between a centre roll (K) and a press roll (T) in the press of the paper machine, which nip (N) in normal operation of the press is closed for driving the press felt (H) as a closed felt loop, the equipment comprising a rotatable crawling-drive roll (10) e.g. for moistening of the new felt (H), which roll (10) is rotating freely during said normal operation, and comprising a drive rim (20) permanently connected to the axle (10a) of the rotatable drive roll (10); a drive wheel means (27a, 27b...) engageable with the drive rim (20) for revolving it; a hydraulic device (26a, 26b...) connected to the drive wheel means for engaging and disengaging the drive wheel means with the drive rim, said disengagement enabling said free rotation of the drive roll, characterized in that the drive rim (20) comprises a wave-shaped form (24), and that the hydraulic device comprises drive cylinders (29a, 29b...) which each comprise therein a drive piston (26a, 26b...) with a cam-wheel (27a, 27b...) at its end, the pistons of the cylinders being displaceable towards the drive rim (20) alternatingly, for pushing the cam-wheels into engagement with the wave-shaped form, the cam-wheels constituting said drive wheel means, and that the device comprises springs (30a, 30b...) which keep the pistons (26a, 26b...) in their cylinders (29a, 29b...) in their bottom positions when pressurized fluid is not being passed into the fluid space (E 1 ) between the cylinder bottom and the piston (26a, 26b...).

Inventors: HIRSIMAEKI MARTTI, SUVANTO LAURI, VILLA JOUKO, HIRSIMAEKI, MARTTI, SUVANTO, LAURI, VILLA, JOUKO, Hirsimäki, Martti
Applicants: VALMET CORP, VALMET CORPORATION
Application year: 1993
Main classification: D21F7
IPC codes: D21F3, D21F7