Trim squirt for a paper-making machine

A paper-making machine for making a fiber web, includes a wire for carrying the fiber web. A trim squirt includes a nozzle cutter and an accumulator tank. The nozzle cutter is directed toward and transverse to the wire. The accumulator tank includes an inlet for receiving a pressurized fluid and an outlet fluidly connected with the nozzle cutter. The tank is structured and arranged to define an air attenuation pad therein.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to paper-making machines, and, more
 particularly, to trim squirts for use in paper-making machines.
 2. Description of the Related Art
 Paper-making machines typically include a head box which discharges a fiber
 suspension stream with a known cross-sectional profile onto a wire in a
 fourdrinier section. The wire carries the fiber web to a forming section,
 where the fiber web is transferred from the wire to the forming section.
 The lateral side edges of the fiber web which is carried by the wire
 typically are of poor quality. Accordingly, it is common to discharge the
 fiber suspension from the head box onto the wire with a width which is
 wider than the working width of the forming section. The fiber web is
 trimmed in the fourdrinier section using a pair of trim squirts which are
 placed along respective lateral side edges of the fiber web. Each trim
 squirt discharges a water stream at a relatively high velocity to cut the
 lateral side edges from the fiber web.
 It is important that a trim squirt provide a continuous cut of the fiber
 web as the fiber web travels past the trim squirt toward the forming
 section. If the fiber web is not continuously cut, the fiber web will
 normally tear when it is transported to the narrower width forming
 section. An intermittent pause in cutting can be caused by a pressure
 fluctuation or an air bubble in the pressurized water which is supplied to
 the nozzle cutter of the trim squirt. Conventional trim squirts typically
 provide a pressurized fluid directly from a pump or the like to the nozzle
 cutter of the trim squirt. The flow velocity of the water is therefore
 affected by pressure fluctuations associated with rotational speed
 fluctuations of the pump. It is therefore possible that the fiber web may
 intermittently not be cut, thereby possibly resulting in tearing of the
 fiber web. Moreover, no provisions are made to remove air bubbles from the
 pressurized water which can likewise result in the web intermittently not
 being cut. Such air bubbles can occur from agitation or turbulence of the
 pressurized water.
 What is needed in the art is a trim squirt which operates at a more
 constant pressure and without air bubbles to thereby ensure that the fiber
 web is continuously cut.
 SUMMARY OF THE INVENTION
 The present invention provides a trim squirt which cuts the fiber web in an
 uninterrupted manner and with minimum pressure fluctuations.
 The invention comprises, in one form thereof, a paper-making machine for
 making a fiber web, including a wire for carrying the fiber web. A trim
 squirt includes a nozzle cutter and an accumulator tank. The nozzle cutter
 is directed toward and transverse to the wire. The accumulator tank
 includes an inlet for receiving a pressurized fluid and an outlet fluidly
 connected with the nozzle cutter. The tank is structured and arranged to
 define an air attenuation pad therein.
 An advantage of the present invention is that the fiber web is cut in an
 uninterrupted manner.
 Another advantage is that pressure fluctuations within the tank, and thus
 flow velocity fluctuations at the nozzle cutter, are minimized.
 Yet another advantage is that the fluid level within the tank can be easily
 controlled without the use of sensors, electronic controls, etc.

Corresponding reference characters indicate corresponding parts throughout
 the several views. The exemplification set out herein illustrates one
 preferred embodiment of the invention, in one form, and such
 exemplification is not to be construed as limiting the scope of the
 invention in any manner.
 DETAILED DESCRIPTION OF THE INVENTION
 Referring now to the drawings, there is shown a portion of an embodiment of
 a paper-making machine 10 of the present invention for making a fiber web.
 Paper-making machine 10 generally includes a fourdrinier wire 12 and a
 trim squirt 14.
 Wire 12 carries a fiber suspension web thereon and moves in a direction
 orthogonal to the drawing of FIG. 1. Typically, wire 12 receives a fiber
 suspension with a known cross-sectional profile from a head box (not
 shown). Water in the fiber suspension drains through wire 12 as it is
 carried from the head box toward a forming section (not shown). Although
 trim squirt 14 is shown with reference to a fourdrinier wire 12, it is
 also possible to position trim squirt 14 in a different part of
 paper-making machine 10. Accordingly, the term "wire" is used herein in a
 generic sense to mean a continuous traveling surface within paper-making
 machine 10 which carries a fiber web, such as a water impermeable belt,
 felt or wire. Wire 12 typically is carried by a plurality of rotatable
 rolls (not shown).
 Trim squirt 14 generally includes an accumulator tank 16 and a pair of
 nozzle cutters 18. Each nozzle cutter 18 is positioned adjacent to a
 lateral side edge 20 of wire 12. Each nozzle cutter 18 includes an
 interior nozzle configuration which jets a stream of water at the fiber
 web carried by wire 12 at a predetermined velocity, dependent upon a
 target delivery pressure. The water jet is directed toward the fiber web
 carried by wire 12 at an angle generally perpendicular to wire 12.
 Accumulator tank 16 (shown more specifically in FIG. 2) includes an inlet
 22 for receiving a pressurized fluid from a fluid source such as a pump
 (not shown) via a fluid conduit 24. A check valve 26 may be provided in
 fluid conduit 24 which allows fluid flow only in a direction toward tank
 16. Pressurized water flows through inlet 22 into a chamber 27A within
 tank 16.
 Accumulator tank 16 also includes an outlet 28 which is fluidly connected
 with each of nozzle cutters 18 via fluid conduits 30. Each of inlet 22 and
 outlet 28 are positioned in a bottom half of accumulator tank 16. More
 particularly, in the embodiment shown, inlet 22 and outlet 28 are each
 positioned near a bottom 32 of accumulator tank 16. Outlet 28 receives
 pressurized fluid from a chamber 27B. Chamber 27B is separated from
 chamber 27A via an intermediate baffle 34. Pressurized fluid flows through
 chamber 27A, over the top of baffle 34, and then through chamber 27B.
 Accumulator tank 16 also includes one or more drains 36 which are connected
 to respective drain lines 38. A pair of shut-off valves 40 are used to
 control fluid flow through drain lines 38, respectively. Each drain 36 is
 associated with a respective chamber 27A or 27B. Drains 36 may be
 connected with bottom 32 so that substantially all of the fluid within
 chambers 27A and 27B may be drained.
 Accumulator tank 16 also includes a pipe 42 which extends downwardly from a
 top wall 44. Pipe 42 has a lower end 46 which sets an approximate liquid
 level of the pressurized fluid within accumulator tank 16, as will be
 described in more detail hereinafter. Lower end 46 of pipe 42 preferably
 is disposed above upper end 48 of baffle 34. It is also possible for lower
 end 46 of pipe 42 to be disposed substantially coterminous with or
 slightly below upper end 48 of baffle 34. Pipe 42 is exposed to ambient
 pressure at an end opposite from end 46. In the embodiment shown, pipe 42
 includes an overflow end 50 which is exposed to ambient pressure and which
 may discharge fluid to a drain 52 for recycling, etc.
 Accumulator tank 16 has a height dimension of at least 15 inches and a
 diameter of at least 4 inches to provide a volume which is sufficient to
 define an air attenuation pad above the pressurized fluid, as will be
 described in more detail hereinafter. In the embodiment shown, accumulator
 tank 16 has a height of at least 30 inches and a diameter of at least 6
 inches. Optional mounting tabs 54 may be attached to accumulator tank 16
 for mounting with appropriate structure within paper-making machine 10.
 For example, fasteners such as bolts may extend through holes 56 in tabs
 54 and be threadingly engaged with corresponding threaded holes in a
 support structure of paper-making machine 10.
 During use, pressurized fluid flows through check valve 26 and fluid
 conduit 24 into chamber 27A. The pressurized fluid flows in a generally
 upward direction through chamber 27A and flows over the top of baffle 34.
 When the liquid level within chambers 27A and 27B is below the lower end
 46 of pipe 42, only ambient pressure exists within accumulator tank 16 and
 the liquid level rises. When the liquid level rises past lower end 46 of
 pipe 42, an air pocket is formed in the top of accumulator tank 16. The
 liquid level will continue to rise until the pressure of the pressurized
 liquid being pumped into accumulator tank 16 equals the pressure of the
 air attenuation pad above the liquid at the top of accumulator 16. Air
 bubbles within the pressurized fluid are allowed to bubble out of the
 fluid and into the air pad at the top of accumulator tank 16. If the air
 pad becomes too large, the air simply escapes through pipe 42 to the
 ambient environment. The air attenuation pad also helps to reduce
 fluctuations in the pressure of the fluid which is transported out from
 outlet 28. The pressurized fluid flows through chamber 27B and through
 outlet 28 to nozzle cutters 18 for cutting the lateral side edges from the
 fiber web carried by wire 12.
 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.