KR100469795B1 - Wide nip press with fluctuating blanket of extended wear area and how to extend the life of the fluctuating blanket - Google Patents

Abstract

The press 20 in the form of a wide nip has a blanket 30 passing over the shoe 22, which is pressed against the backing roll 24 to form the press nip 56. The hydraulic system 70 and the controller 94 automatically continuously swing the blanket 30 laterally. As a result of this fluctuation, the high fatigue areas 58 and 59 are continuously moved over the entire surface of the blanket 30 so that the time for a particular area to be worn is minimized. The placement of the heads 38, 42 on which the ends of the blanket 30 are mounted is controlled by hydraulic pistons 60, 62 mounted between the support beam 26 and the heads 38, 42. The controller 94 operates the valve 74 to reverse the direction of movement of the blanket 30 when the sensors 92, 98 indicate that one end of the blanket 30 has reached the stops 64, 80. Let's do it. The throttle valve 86 controls the flow rate at which the hydraulic oil is supplied to the cylinders 60 and 62 for pressing the heads 38 and 42 away from the shoe 22.

Description

Wide nip presses with fluctuating blankets of extended wear zones and methods of extending the life of the fluctuation blankets

The present invention relates to a press for use in a paper machine, specifically a press employing a shoe forming a nip together with a backing roll, wherein the shoe is surrounded in a blanket, The blanket end is closed by the rotating head.

The design of paper machines has improved significantly over the past two decades. The direction of these improvements has been to increase the speed at which the web is formed and the width of the paper, thereby improving the efficiency of paper manufacturing. As the machine speed increases, the paper being formed passes more quickly through each component section of the paper machine.

In particular, the efficiency of many operations, such as drying and pressing, depends on the time the paper stays in the dryer or pressing nip. The higher speeds of modern papermaking equipment mean that individual elements, such as presses, must certainly be produced more efficiently. In the pressing section of the paper machine, the efficiency of the press has been improved through the use of new technology presses. This is most efficiently achieved by using a shoe with a concave surface opposite the backing roll. The blanket is passed over the shoe in order for the paper to pass through the nip without frictional resistance. This blanket is lubricated or cooled by oil or other lubricant that is forced between the blanket and the shoe.

One type of press using a shoe is the so-called open wide nip (registered trademark) of the type manufactured by Beloit Corporation of Beloit, Wisconsin. In this type of press, the lubrication blanket is supported on a plurality of support rolls for advancing the blanket through the nip between the backing roll and the shoe in a manner similar to the way in which conventional felt proceeds.

In some specific situations, open wide nip presses may result in oil leaking over the felt and paper when they cross the nip. In other situations it is required to place the shoe on the backing roll. When so arranged, the lubricating oil tends to flow into the paper under pressure. In this way, a press called the Closed Nip Press was developed. The closed wide nip press has a blanket whose end extends beyond the nip and shoe and sealed with a circular head. The sealing of the ends of the blanket solved the problem of lubricating oil leakage. The blanket forms a cardioid as the circular blanket deforms between the shoe and backing roll as it passes through the nip. Thus, the blanket transitions from a heart shape in the nip to a circular shape, which is necessary for mounting on the head containing the lubricant. The transition region of the blanket between the heart shape and the circular shape rotates as the blanket rotates through the nip. If the blanket is bent repeatedly, the blanket material eventually breaks down. This breakdown of the blanket is a significant cause of downtime, because a lot of capital is invested in the paper machine, and the blanket breaks significantly increase the cost of paper production.

As the blanket is moved through a closed wide nip press, the result is that the blanket is gradually lengthened in the transverse direction. In a typical wide nip press, one head or end of the blanket remains fixed while the other is floatable. Thus, the free end can move laterally to accommodate the increase in length of the blanket. The blanket gradually lengthens over the portion of the blanket passing through the nip. Thus, the end of the retained blanket is not elongated or only slightly elongated, and the area of the blanket that is fatigued by the transition between the circular end head and the heart shape remains fixed relative to the blanket.

One way to extend the life of a closed nip blanket is to move the stationary side of the blanket, for example by moving the position of the stationary side of the blanket. One known method is to install spacers against fixed stops to move the fixed end of the blanket such that the fatigue stressed area is moved relative to the fixed end. Therefore, in the conventional method, in order to change the boundary position between the blanket and the wide nip press shoe, it depends on either the adjustment of the downtime or the machine operator.

Thus, what is needed is a method and apparatus for extending the life of a blanket in a wide nip press.

1 is a schematic diagram of a press of the present invention showing a hydraulic system used for positioning of a press blanket,

2 is an isometric view of the press of FIG. 1,

3 is a front cross-sectional view of the press of FIG. 2.

The press according to the invention provides a continuous automatic rocking motion of the blanket of the wide nip press in the transverse direction. The first head is gradually driven by the hydraulic piston to move the position of the blanket in one direction, and the second head is then gradually driven by the hydraulic piston to reverse the direction of movement of the blanket. The rocking action continuously moves the area under high fatigue across the blanket surface, minimizing the wear time observed in any particular area. This maximizes the life of the blanket. The ends of the blanket are attached to circular rear and front heads mounted to rotate at the ends or journals of the support beam. The support beam supports the shoe and the hydraulic piston that presses the shoe against the backing roll. The blanket extends transversely beyond the end of the shoe. An extension of the blanket extending beyond the shoe is attached to the circular head. The blanket takes the form of a heart as it passes through the nip. The transition from the heart shape pressed into the nip to the circular shape held by the head causes fatigue over certain areas of the blanket. The heads are mounted to the journal to move between an inner stop and an outer stop approximately 4 inches apart transversely. The placement of the head on the journal is controlled by four front hydraulic pistons mounted between the support beam and the front head and four rear hydraulic pistons mounted between the support beam and the rear head. The front and rear pistons are connected to the hydraulic system. The hydraulic system includes a hydraulic pump for supplying a reservoir and hydraulic oil to the supply line. A throttle valve installed in the supply line controls the flow rate of the hydraulic oil flowing through the supply line. The hydraulic supply line is switched by hydraulic switches between the front and rear hydraulic cylinders. The hydraulic switch connects the hydraulic cylinders that are not being supplied to the hydraulic return line, which is in turn through the hydraulic reservoir. Sensors mounted on the hydraulic piston measure the displacement of the front and rear heads. When the sensor indicates that one end of the blanket has reached the stop, the controller operates the valve to reverse the direction of movement of the blanket. The throttle valve controls the flow rate of the hydraulic oil supplied to the cylinders, which presses the head connected to the hydraulic source away from the shoe.

As the blanket passes through the nip formed by the shoe and backing roll, the blanket is repeatedly compressed in the nip. This compression results in an increase in the longitudinal length of the blanket. The movement of the heads on the journal provides room for the blanket to increase by about 8 inches in length. The area of the blanket affected by fatigue is arranged at a distance from the ends of the shoe. As the length of the blanket increases in the transverse direction, the blanket swings left and right continuously, thereby extending the life of the blanket to the maximum.

It is an object of the present invention to provide a means for extending the life of a blanket in a closed press employing a concave shoe and a backing roll.

It is still another object of the present invention to provide a papermaking press in which a concave shoe that is in contact with the backing roll is used, and conditions for maintenance are not difficult.

It is still another object of the present invention to provide a method of operating a paper machine press in the form of a concave shoe in contact with a backing roll and using a sealed blanket, which provides an operating method for extending the life of the blanket.

Other objects, features and advantages of the present invention will become apparent when the following detailed description of the embodiments is compared with the accompanying drawings.

1 through 3 in which like reference numerals represent like elements, a press 20 formed by a shoe 22 and a backing roll 24 is shown in FIG. 3. The shoe 22 is supported on the cross beam 26 by one or more hydraulic pistons 28 which press the shoe 22 against the backing roll 24. A film of oil or lubricating fluid is provided between the blanket 30 and the shoe 22 so that the blanket 30 can move over the shoe with low resistance. The press 20 has a rear end 32 and a front end 34. The front end 36 of the blanket 30 is mounted to the front head 38, and the rear end 40 of the blanket is attached to the rear head 42. The front head 38 is separated into a front turn 44 and a front slide 46 connected by a bearing 48. The front head 38 is mounted to the front journal 16 extending from the cross beam 26 by the slide 46. The rear head 42 is similarly separated into a rotation 50 and a rear slide 52 which are connected by a bearing 54. The slide 52 of the rear head 42 moves in the rear journal 18 extending from the cross beam 26.

In operation, the blanket 30 rotates on the bearings 48, 54 and passes through a nip 56 formed between the backing roll 24 and the shoe 22. The blanket moves at a speed corresponding to the speed of the roll 24 in contact. The blanket 30 can be easily curved without deformation in a single plane as a flexible sheet. In other words, the flexible sheet can be easily bent in the form of a cone curve or a series of cone curves. This form is also known as a developable surface. The shape of the blanket 30 when moving through the nip is approximately heart-shaped, which is deployable. The cylindrical ends 36, 40 of the blanket 30 are gripped by the heads 38, 42 by toroidal bladders 57. The bladder 57 is sealed tubes connected to an air source, which can be expanded to grip the blanket and to contract to release the blanket. However, due to the transition between the heart shape of the blanket 30 and the gripped cylindrical ends 36, 40, the two faces are bent simultaneously. Regions or regions 58, 59 that bend in two sides are subject to significant deformation, resulting in regions where fatigue is concentrated in the blanket. On both sides of the nip 56 are two areas that are severely fatigued: the front region 58 and the rear region 59. These areas 58 and 59 are part of the blanket 30 and are the parts where the breakdown of the blanket begins.

The blanket 30 is fatigued and pressed while passing through the nip 56. Compression or compression causes the blanket to increase in longitudinal length. In a conventional machine, one end (usually the rear end) is fixed and the front end is free to float, so that the blanket can be stretched in the transverse direction. In a conventional machine, the fixed ends were periodically moved to rearrange areas 58 and 59 that were subjected to severe fatigue. Repositioning one end distributes fatigue wear to a number of discrete locations. The best solution is to continuously move the blanket 30 laterally so that any predetermined portion of the blanket adjacent the ends 36, 40 also experiences fatigue for only a short time.

As shown in FIG. 2, the position of the front head 38 is controlled by the piston 60, and the position of the rear head 42 can be controlled by the piston 62 schematically shown in FIG. 1. . Since the heads 38 and 42 are connected by the blanket 30, only one set of pistons can control the position of the head at any given time. As shown in FIG. 1, the hydraulic control system 70 has a hydraulic supply line 78 connected to one of the front piston 60 and the rear piston 62 by a valve 74. The valve 74 is arranged such that a piston which is not connected to the supply line 78 is connected to the return line 84. The hydraulic control system 70 includes a hydraulic reservoir 82, a hydraulic pump 90 and a throttle valve 86. The pump 90 supplies hydraulic oil from the reservoir 82 to the hydraulic cylinder for moving the blanket 30. The throttle valve 86 controls the amount of hydraulic oil supplied to the piston 60 or 62 that is moving the blanket 30. Thus, the throttle valve 86 controls the speed at which the blanket 30 moves.

As shown in FIG. 1, when hydraulic oil is supplied to the piston of the front end 38, the front head moves toward the front outer stop 66 as shown in FIG. 3. Hydraulic fluid is introduced at a selected flow rate such that the head travels at substantially constant speed and traverses the distance between the stops over several hours or days. As shown in FIG. 1, the position sensor 92 of the rear head piston 62 senses when the rear head 42 approaches a predetermined distance range of the rear inboard stop 64. . When this position is reached, the controller 94 activates the solenoid 96 of the valve 74 to connect the supply line 78 to the rear piston 62 and stop the blanket from moving toward the front outer stop. And move toward the rear 32 of the press 20 instead.

When the front head 38 approaches the front internal stop 80, the front internal sensor 98 mounted on the front piston 60 sends a signal to the controller 94, which is the solenoid 96. ) Again to change the transverse direction of the blanket (30).

When the blanket 30 is first placed on the press 20, both heads 38 and 42 are positioned adjacent to the respective internal stops 80 and 64 so that the length of the blanket swinging back and forth is only about 1 inch. To be. Thus, at first the blanket changes direction very frequently. However, as the blanket 30 increases in length between the heads 38 and 42, the path of the swinging head is longer until the blanket 30 is stretched long enough to reach the outer stops 66 and 68. Lose. At that point, the external front head sensor 105 and the external rear head sensor 106 are used to control when the valve 74 is switched so that the moving direction of the blanket 30 is reversed.

The blanket shown in FIG. 3 has a four inch travel stroke between the inner stops 80 and 64 and the outer stops 66 and 68. If the blanket 30 extends beyond 4 inches, the space available for oscillation decreases until the blanket increases approximately 7 inches, then the blanket again has a swing range of about 1 inch. If there is no space for the blanket 30 to oscillate, the press 20 is deactivated and the blanket is trimmed to approximately 6 inches to swing the blanket back and forth between the backing roll 24 and the shoe 22. Is resumed.

In order for the blanket 30 to remain stable, it must always be in tension. The air pressure in the blanket can provide the necessary tension, usually between 0.5 and 2 psi. Since the blanket 30 always moves, slack does not easily occur in the blanket 30. If additional tension is required, the return line 84 can pass through the throttle valve 100, which controls the flow of hydraulic fluid that can be discharged from the piston that is not driven, thereby forward and backward. The tension formed between the heads can be controlled. In order to provide the throttle control valve 100 only in the return line, a series of check valves 102 and 103 and bypass line 104 are used together, so that the working oil flowing toward the reservoir 82 is reduced to Only flow through).

The hydraulic valve system 101 has a first check valve 102 arranged to allow hydraulic fluid to flow only toward the first and second hydraulic pistons 60, 62. The bypass return line 104 bypasses the first check valve 102, but the second check valve 103 disposed in the bypass return line 104 so that the hydraulic oil can flow only toward the hydraulic reservoir 82. ). Throttle valve 100 is disposed in return bypass line 104 to control the tension of the blanket.

In a conventional press using a blanket, the blanket could be displaced by 0.66 inches every 14 days. This means that about 14 percent of total wear occurred at each discrete location. By continuous fluctuation of the blanket, the amount of wear at any discontinuous position is reduced to less than 1.5 percent of the total wear.

It should be understood that the speed at which the blanket swings depends on the flow rate of the hydraulic oil supplied to the drive piston, which is either the front piston 60 or the rear piston 62. Depending on the rate of fluctuation, the blanket will preferably complete one cycle over several hours or days. The flow rate of the hydraulic oil supplied to the drive piston is controlled by the throttle valve 86, which is adjusted manually or according to a pre-programmed schedule or the flow rate selected by the operator. Can be adjusted. In a similar manner, the throttle valve 100 can be adjusted manually or by the controller 94 to control the amount of tension in the blanket.

It is to be understood that the invention is not limited to the specific structures and configurations of parts illustrated and described herein, but includes modifications within the scope of the appended claims.

Claims (9)

As the press 20 in the pressing section of the paper machine, A closed blanket 30 extending laterally in the paper machine and forming an endless loop in the paper machine longitudinal direction; Extending transversely through the looping blanket 30 and having a first journal 16 and a second journal 18 disposed at regular intervals in the transverse direction from the first journal 16. A fixed support beam 26; One or more press shoes (22) mounted on the support beam (26) and extending in the transverse direction within a looping blanket (30); Concave formed in the shoe 22 as a backing roll 24 disposed side by side at a predetermined interval with respect to the blanket 30 and the shoe 22 to form the shoe 22 and the nip 56. A backing roll (24) opposed to the surface and defining a concave surface of the shoe (22) and a nip (56) extending in the longitudinal direction; A first head 38 mounted to the first journal 16 to rotate relative to the support beam 26 and to translate along the transverse direction and to grip the first end 36 of the blanket 30. Wow; A second head 42 mounted to rotate in the second journal 18, the second head 42 mounted to translate in the transverse direction and gripping the second end 40 of the blanket 30; )Wow; At least one first hydraulic piston (60) disposed between the support beam (26) and the first head (38) to exert a lateral force; At least one second hydraulic piston (62) disposed between the support beam (26) and the second head (42) to exert a lateral force; A hydraulic system (70) having a supply line (78) and a return line (84), for supplying hydraulic oil at a selected flow rate; The first state in which the hydraulic system 70 supplies hydraulic oil to the first hydraulic piston 60 and the fluid is returned from the second hydraulic piston 62, and the hydraulic system 70 supplies hydraulic oil to the second hydraulic piston. The supply line 78 and the return line 84 are switched from the second state in which the fluid is supplied to the 62 and the fluid is returned from the first hydraulic piston 60 to oscillate back and forth along the transverse direction. Valve 74 for selectively moving the blanket 30 in the form Press comprising a. At least one first sensor (98) mounted to detect a displacement of said first head (38); One or more second sensors 92 mounted to detect displacement of the second head 42; To receive signals from the first sensor 98 and the second sensor 92 and to repeatedly reverse the movement of the blanket 30 so that the blanket 30 swings under the nip 56. Controller 94 for switching the valve 74 such that hydraulic oil flows alternately into the first hydraulic piston 60 and then into the second hydraulic piston 62. Press further comprising a. The press as claimed in claim 1, further comprising a hydraulic throttle valve (86) connected to the hydraulic system (70) and operable to adjust the amount of hydraulic oil supplied to the supply line (78). 2. The hydraulic fluid of claim 1, wherein one is connected to a hydraulic fluid line reaching the first hydraulic piston 60, and the other is a hydraulic fluid reaching the second hydraulic piston 62 after the valve 74 is switched. It is further provided with hydraulic valve systems 101 connected to the line, wherein each hydraulic valve system 101 is A first check valve 102 arranged to flow hydraulic oil only toward the hydraulic piston 60; A bypass return line 104 bypassing the first check valve 102, A second check valve 103 disposed in the bypass return line 104 to allow hydraulic fluid to flow only out of the hydraulic piston 60; Throttle valve 100 disposed in the return bypass line 104 to control the tension in the blanket 30 Press comprising a. A first inboard stop (80) mounted on the first journal (16) for limiting the movement of the first head (38) towards the shoe (22). , A first outer stop 66 mounted on the first journal 16 to limit the movement of the first head 38 away from the shoe 22; A second internal stop 64 mounted to the second journal 18 to limit movement of the second head 42 towards the shoe 22, A second external stop 68 mounted on the second journal 18 to limit the movement of the second head 42 away from the shoe 22. Press further comprising a. For extending the life of the closed blanket 30 used in a press nip 56 of the type having a backing roll 24 and a concave shoe 22 pressed against the backing roll 24. As a method, And continuously rocking the blanket (30) in the paper machine transverse direction. The method of claim 6, further comprising: detecting the lateral displacement of a first level of the blanket (30); Reversing the direction of rocking motion in response to the detected displacement of the blanket 30 Method further comprising a. The method of claim 6, wherein the step of continuously rocking the blanket 30 in the paper machine transverse direction, Pressurized hydraulic oil is used to displace the first head 38 holding the first end 36 of the blanket 30 together with the blanket 30 engaged with the head 38 in the transverse direction. Supplying to a piston (60) connected to the first head (38), In order to reverse the displacement of the head 38 and the blanket 30 engaged therewith, the supply of fluid to the piston 60 of the first head 38 is stopped and against the first head 38. Supplying pressurized hydraulic oil to a second piston (62) arranged at regular intervals and connected to a second head (42) holding the second end (40) of the blanket (30). Method comprising a. A press having a backing roll 24 and a concave shoe 22 with a concave surface pressed against the backing roll 24, the first internal stop for positioning of the first head 38 ( 80 and a first external stop 66, and a second internal stop 64 and a second external stop 68 for positioning of the second head 42. As a method for extending the life of the closed blanket 30 in which the first end 36 and the second end 40 are sealed by the first head 38 and the second head 42, Wherein the sum of the distance between the first head 38 and the first internal stop 80 and the distance between the second head 42 and the second internal stop 64 is approximately one inch; Disposing the blanket (30) between the first head (38) and the second head (40); Alternately connecting the hydraulic supply system 70 to the hydraulic pistons 60, 62 so that the blanket 30 moves toward the first head 38 and subsequently toward the second head 42; ; Controlling the movement of the blanket 30 such that the direction of movement is reversed when the second head 42 approaches the second internal stop 64 when the direction of movement is toward the first head 38; ; Controlling the movement of the blanket 30 so that the movement direction is reversed when the first head 38 approaches the first internal stop 80 when the movement direction is toward the second head 42; ; When the direction of movement is toward the first head 38, the first head 38 contacts the first external stop 66 before the second head 42 approaches the second internal stop 64. The two steps of controlling the movement of the blanket 30 are continued until the paper machine lateral length of the blanket 30 is increased to approach, after which the direction of movement is the first head side 38. When the first head 38 approaches the first external stop 66, the direction of movement is reversed, and when the direction of movement is the second head 42 side, the second head 42 is Controlling the movement of the blanket (30) such that the direction of movement is reversed when approaching the second external stop (68); When the blanket 30 extends in the papermaking machine longitudinal direction, the first head 38 and the second head 42 are separated from each of the first internal stop 80 and the second internal stop 64. Trimming the lateral width of the blanket 30 such that the sum of the distances away is approximately 1 inch. Method comprising a.