Paper machine having a high pressure fluid slitter with overflow compensation

A paper machine has a high pressure liquid pump for use with a liquid slitter for slitting a fiber material web. The high pressure liquid pump includes a pump shell having an axis of rotation and an annular smooth inwardly facing surface. The inwardly facing surface is configured for carrying a film of liquid thereon. A hydraulic shoe having an outer convexly curved working face is in close running engagement with the inwardly facing surface. A pivotal arm is connected with the shoe and positions the shoe relative to the inwardly facing surface. The arm is movable toward and away from the inwardly facing surface. A hydraulic pressure member is engaged with the arm for urging the shoe toward the inwardly facing surface dependent upon a hydraulic pressure therein. The pump shell is driven about the axis of rotation, thereby continuously moving the inwardly facing surface of the pump shell past the shoe and continuously forming a hydraulic wedge of high-pressure liquid between the inwardly facing surface and the working face.

BACKGROUND OF THE INVENTION 
1. Field of the Invention. 
The present invention relates to high-pressure, low-delivery liquid pumps 
used in paper machines for waterjet cutting or slitting a continuous 
traveling fiber material web, such as a paper web. 
2. Description of the Related Art. 
Waterjet cutters or slitters are used in a paper machine to cut a traveling 
fiber material web. A moving high-pressure stream of liquid which is used 
for cutting affords advantages in that the liquid can be ordinary water 
without additives. The cutting operation is dust-free and does not create 
dust problems which result in creating wear in machinery, pollution of the 
air and health hazards. Waterjet cutting is advantageous in that it does 
not require space-consuming and complex cutting equipment, and the 
mechanism can be easily operated and controlled for a variety of cutting 
conditions with variations in speed and thickness of material and other 
variations which must be encountered in commercial cutting operations. 
However, to provide a continuous supply of water in very small quantities 
at very high pressures such as used in paper web cutting, the reliable 
operating life of most conventional pumps is severely limited. Pressures 
in the range of 10,000 psi to 60,000 psi must be available at very small 
delivery quantities of water and such pumps frequently have an operating 
life on the order of only 250 hours without requiring shutdown and 
attention. Further, such pumps require parts with critical tolerances and 
the moving parts must be carefully and precisely machined. Also, 
conventional pumps are generally mechanically complex and many are 
unreliable in applications where the fluid is water and cannot contain 
rust inhibitors. 
U.S. Pat. No. 4,239,448 (Graf), now expired, describes a high-pressure, low 
delivery liquid pump for use in a paper machine which is simple, effective 
and reliable. A hydraulic wedge is created between a hydraulic shoe and a 
rotating inwardly facing surface of a pump shell. A fluid passage having 
an inlet at the working surface of the shoe transports high-pressure 
liquid away from the hydraulic wedge to a cutting head of a slitter. 
The high-pressure, low delivery liquid pump described by Graf '448 requires 
a control system to ensure that the liquid within the pump adjacent to the 
pump shell is kept at a relatively small predetermined level. The fluid 
passage only draws away a relatively small amount of water under high 
pressure from the hydraulic wedge. If too much water is introduced into 
the pump, the hydraulic shoe must "push" the excess water ahead of the 
shoe as the pump shell rotates. The excess water is not actually 
immediately used since it is not in the high-pressure region of the 
hydraulic wedge, and substantially adds to the power requirements to drive 
the rotation of the pump shell. The necessary increased power in turn 
decreases the efficiency of the pump and increases the cost to operate the 
pump. It is therefore necessary to provide a relatively complicated and 
expensive control system to control the water flow into and operation of 
the pump. 
What is needed in the art is a high-pressure, low delivery liquid pump for 
use in a paper machine which maintains necessary input power at a minimum 
by removing excess or overflow water from the pump without the need for a 
complex and expensive control system. 
SUMMARY OF THE INVENTION 
The present invention provides an overflow passage in each shoe which is at 
the leading edge of the shoe and outside the high-pressure hydraulic wedge 
area of the shoe. Each overflow passage transports the overflow or excess 
water away from the respective shoe and out of the pump. 
The invention comprises, in one form thereof, a paper machine having a high 
pressure liquid pump for use with a liquid slitter for slitting a fiber 
material web. The high pressure liquid pump includes a pump shell having 
an axis of rotation and an annular smooth inwardly facing surface. The 
inwardly facing surface is configured for carrying a film of liquid 
thereon. A hydraulic shoe having an outer convexly curved working face is 
in close running engagement with the inwardly facing surface. A pivotal 
arm is connected with the shoe and positions the shoe relative to the 
inwardly facing surface. The arm is movable toward and away from the 
inwardly facing surface. A hydraulic pressure member is engaged with the 
arm for urging the shoe toward the inwardly facing surface dependent upon 
a hydraulic pressure therein. The pump shell is driven about the axis of 
rotation, thereby continuously moving the inwardly facing surface of the 
pump shell past the shoe and continuously forming a hydraulic wedge of 
high-pressure liquid between the inwardly facing surface and the working 
face. A high pressure passage through the shoe has an inlet positioned in 
the working face and is configured for transporting the high pressure 
liquid in the hydraulic wedge away from the shoe. An overflow passage 
through the shoe has an inlet positioned at a leading edge of the shoe 
relative to the direction of rotation of the pump shell and substantially 
outside the working face. The overflow passage is configured for 
transporting excess liquid outside of the hydraulic wedge away from the 
shoe. 
An advantage of the present invention is that excess or overflow liquid is 
transported out of the pump so that required input power is maintained at 
a minimum. 
Another advantage of the present invention is that the pump provides for 
delivery of cutting fluid such as water in low volumes at very high 
pressures and is capable of doing so over long operating periods without 
repair. 
Yet another advantage is that the pump requires a minimum of moving parts 
and a minimum of machined parts with the parts not requiring critical 
tolerances for pumping liquid in very small volumes at very high 
pressures. 
A still further advantage is that the output pressure of the pump can be 
easily controlled during operation, and the number of contacting parts are 
reduced to a minimum to reduce operating wear. 
A further advantage is that the pump is capable of an almost indefinite 
operating life because of the absence of contacting wearing parts.

Corresponding reference characters indicate corresponding parts throughout 
the several views. The exemplifications set out herein illustrate one 
preferred embodiment of the invention, in one form, and such 
exemplifications are not to be construed as limiting the scope of the 
invention in any manner. 
DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings, and more particularly to FIGS. 1 and 2, 
there is shown an embodiment of a pump 8 which includes an annular pump 
shell 10 having a smooth inwardly facing surface 11. A hydraulic shoe 12 
having a relieved leading edge 13 coacts with smooth inwardly facing 
surface 11 by being in close running engagement with inwardly facing 
surface 11 sufficiently close to create a hydraulic wedge of fluid between 
shoe 12 and the relatively moving inwardly facing surface 11. A similar 
shoe 14, also having a relieved leading edge 15, is located at a position 
diametrically opposite shoe 12. Shoes 12 and 14 in these locations balance 
the forces on pump shell 10 relative to the central axis of pump shell 10. 
It will be understood, of course, that pump 8 will operate with a single 
shoe or with additional numbers of shoes. 
The low-volume, high-pressure liquid delivery of pump 8 is obtained through 
a passage 16 for shoe 12, and a passage 18 for shoe 14. Shoe 12 has an 
inlet 17 leading into passage 16 and shoe 14 has an inlet 19 leading into 
passage 18 through which the liquid flows from the hydraulic wedge. As 
illustrated in the detailed view of FIG. 3, inwardly facing surface 11 
carries a thin layer of liquid such as water 41 which remains there due to 
rimming by centrifugal force. 
Shoes 12 and 14 are mounted on a central stationary shaft 20. While 
advantages are attained in driving pump shell 10 in rotation about shoes 
12 and 14, it is possible to rotate pump 8 rotatably by driving shoes 12 
and 14 relative to pump shell 8. 
Shoes 12 and 14 are supported on pivotal arms 22 and 24, which are 
respectively pivoted at pins 23 and 25 on a block 21 supported on shaft 
20. Arms 22 and 24 are pushed outwardly to control the force at which 
shoes 12 and 14 are urged against inwardly facing surface 11 and hence the 
output delivery pressure of pump 8. For this purpose, hydraulic plungers 
26 and 27 push against the moveable ends of arms 22 and 24. Plungers 26 
and 27 are operated by hydraulic fluid in cylinders 28 and 29 
therebeneath. Hydraulic fluid at controlled pressure is delivered to 
cylinders 28 and 29 through radial passages 30 and 31 from axial passages 
32 and 33 leading through shaft 20 from a hydraulic pressure supply line 
34 which has a pressure control valve 34A which can be adjusted to control 
the output pressure of pump 8. 
To supply water to pump 8, axial supply passage 35 leads through stationary 
shaft 20 and radially out through an opening 36. Sufficient water is 
provided to maintain shallow film 41 against inwardly facing surface 11 
which creates hydraulic wedge 42. In addition to controlling pressure by 
regulating the hydraulic force used to pivot arms 22 and 24 and urge shoes 
12 and 14 outwardly, the speed of rotation of pump 8 also changes the 
output pressure. That is, increased speed increases the hydraulic pressure 
in hydraulic wedge 42 to increase the delivered pressure out through 
passage 16. Also, at start-up, the force on arms 22 and 24 is relieved so 
that no actual metal-to-metal contact occurs between shoes 12 and 14 and 
the inwardly facing surface 11 of pump shell 10 to avoid scoring of pump 
shell 10 and working faces 38 and 39 of shoes 12 and 14, respectively. 
While a relatively narrow shell and shoe are employed, as illustrated 
generally in FIG. 1, if a pump of increased capacity is desired, the axial 
width of the shoe and shell can be increased and a plurality of inlets 17 
and 19 can be provided instead of single inlet 17 and 19 along working 
faces 38 and 39 of shoes 12 and 14. Shoe 12 can generally be made in the 
shape illustrated or can be made with a convex shape with a radius of 
curvature smaller than inwardly facing surface 11. Shoe 12 can also be 
pivotally supported on arm 22 so that it will assume a natural position 
relative to the hydraulic forces built up between shoe 12 and pump shell 
10. 
As shown in FIG. 1, pump shell 10 is constructed in the form of an annular 
ring and disk-shaped side plates 61 and 62 are bolted together by axially 
extending through bolts 43. Plates 61 and 62 have respective hubs 46 and 
47 and within hubs 46 and 47 are supporting annular bearings, such as 
bearings 44 and 45 for hub 46. Hub 47 is provided with similar bearings, 
not shown, for rotatably supporting the shell and its carrying assembly on 
stationary shaft 20. Pump shell 10 is driven by ring gears 48 and 59. Pump 
8 is supported on side pedestals 53 and 54. Mounted at the base of 
pedestals 53 and 54 is a drive shaft 51 which is supported on bearings 55 
and 56. Drive shaft 51 carries gears 50 and 57 which through intermediate 
gear belts 49 and 58 drive ring gears 48 and 59. It will, of course, be 
understood that while dual drive trains are illustrated, a single drive 
gearing system may be employed. Drive shaft 51 is driven by an input gear 
or sheave 52 which is driven by a suitable motor (not shown). Variable 
speed control may be provided if desired by varying the drive speed at the 
motor or in the drive train. 
According to the present invention, shoes 12 and 14 each include at least 
one overflow passage 70 which is configured for transporting overflow or 
excess liquid outside of the area of hydraulic wedge 42 away from 
respective shoes 12 and 14. Overflow passage 70 has an inlet 72 which is 
positioned adjacent to a leading edge 13 or 15 of a respective shoe 12 and 
14, relative to the direction of rotation of pump shell 10. Each inlet 72 
is positioned outside of the area of the working face of shoes 12 and 14, 
so as not to draw high pressure liquid away from hydraulic wedge 42 or 
between working face 38 or 39 and inwardly facing surface 11 of pump shell 
10. Each overflow passage 70 in shoes 12 and 14 is connected via a 
flexible coupling, such as a flexible hose 74, to a respective radial 
passage 76 and axial passage 78. Flexible hoses 74 allow relative 
rotational movement while still maintaining fluid interconnection between 
arms 22 and 24 and block 21. As shown in FIG. 3, it is possible for an 
excess amount of water to build up ahead of shoes 12 and 14, e.g., at the 
start-up of pump 8 or if the supply of water into pump 8 is not precisely 
controlled. Overflow passages 70 transport the excess water way from shoes 
12 and 14 and out of pump 8. Overflow passages 70 therefore prevent "water 
logging" of pump 8 and maintain the power input requirements necessary to 
rotatably drive pump shell 10 at a minimum. 
In the embodiment of pump 8 shown in FIGS. 1-4, inlet 72 of each overflow 
passage 70 has a substantially oval cross-sectional shape which is 
intended to provide a larger surface area for drawing excess water into 
overflow passage 70. However, it will be appreciated that the particular 
cross-sectional shape and/or size of inlet 72 may vary, and/or the number 
of inlets and/or overflow passages 70 associated with each shoe 12 or 14 
may vary. For example, referring to FIG. 5, there is shown another 
embodiment of a hydraulic shoe 80 including an overflow passage 82 having 
four inlets 84 connected therewith via a common axial passage 86. 
In operation, water is placed in a limited amount within pump shell 10, and 
pump 8 is brought up to an operating speed without applying radial outward 
force on arms 22 and 24 carrying shoes 12 and 14. When an operating speed 
is reached, shoes 12 and 14 are forced outwardly by hydraulic plungers 26 
and 27 and a hydraulic wedge 42 is built up at leading edge 13 and 15 of 
each of shoes 12 and 14. The water is relatively incompressible so that at 
the high pressure developed, it flows out through inlet 17 in shoe 12 
through passage 16 which connects through a connecting line 37 to a 
passage 39 and delivery line 40 leading through shaft 20. Line 37 is 
flexible, and the other shoe 14 is provided with a similar flexible line 
37 connecting between passage 18 to a passage 38 and delivery line 40 
leading through shaft 20. If an overflow or excess amount of water is 
built up ahead of shoes 12 and/or 14, the excess water is transported into 
overflow passages 70 through inlets 72 positioned at the leading edge of 
each shoe 12 and 14 outside the area of hydraulic wedge 42. A variation in 
hydraulic output pressure can be accomplished by changing the speed of 
rotation of pump shell 10, and/or by changing the force applied to pivot 
arms 22 and 24 outwardly and hence the force with which shoes 12 and 14 
are pressed outwardly toward inwardly facing surface 11 of pump shell 10. 
Thus, there is provided a high-speed pump 8 where there are no rubbing 
parts and the only substantially moving parts are pump shell 10 which is 
supported on dual bearings at each side. Pressures such as needed for 
high-speed and high-pressure water cutting are attained through a pump 
which has an operating life that far exceeds most conventional pumps. 
While this invention has been described as having a preferred design, the 
present invention can be further modified within the spirit and scope of 
this disclosure. This application is therefore intended to cover any 
variations, uses, or adaptations of the invention using its general 
principles. Further, this application is intended to cover such departures 
from the present disclosure as come within known or customary practice in 
the art to which this invention pertains and which fall within the limits 
of the appended claims.