US3341400A

US3341400A - Pressure headbox for web forming machine

Info

Publication number: US3341400A
Application number: US419988A
Authority: US
Inventors: Vivian S Grater
Original assignee: Dominion Engineering Works Ltd
Current assignee: General Electric Canada Co; Valmet Montreal Inc
Priority date: 1964-12-21
Filing date: 1964-12-21
Publication date: 1967-09-12
Anticipated expiration: 1984-09-12
Also published as: FI45581C; FI45581B; SE331631B; DE1461083A1; FR1461123A; GB1109370A; NL6516647A; CH450141A

Description

Sept. 12, 1967 v. s. GRATER 3,341,400

PRESSURE HEADBOX FOR WEB FORMING MACHINE Filed Dec. 21, 1964 6 SheetsSheet 1 INVENTOR V. S. GRATER V. S. GRATER Sept. 12, 1967 PRESSURE HEADBOX FOR WEB FORMING MACHINE 6 Sheets-Sheet 2 Filed Dec 21, 1964 INVENTOR V. S. GRATER Sept. 12, 1967 v. s. GRATER PRESSURE HEADBOX FOR WEB FORMING MACHINE 6 Sheets-Sheet 3 Filed Dec. 21, 1964 III III

INVENTOR V. S. GRATER Sept. 12, 1967 v. s. GRATER 3,341,400

PRESSURE HEADBOX FOR WEB FORMING MACHINE Filed Dec. 21, 1964 6 Sheets-Sheet 4 Plzsssuee 256.

INVENTOR V. S. GRATER V. S. GRATER Sept. 12, 1967 PRESSURE HEADBOX FOR WEB FORMING MACHINE 6 Sheets-Sheet Filed Dec. 21, 1964 lNVE/VTOR V. S. GRATER FIG. 9

Sept 1967 v. s. GRATER 3,341,400

PRESSURE HEADBOX FOR WEB FORMING MACHINE Filed Dec. 21, 1964 6 Sheets-Sheet 6 FIG. 10

INVENTOR V. S. GRATER United States Patent ABSTRACT OF THE DISCLOSURE The structure of a paper machine headbox includes an encompassing reaction frame to contain working forces, particularly the pressure of stock acting against the movable portion of the headbox slice, the force transmitting members including hydraulic connecting members pressurized in response to the pressure of stock in the headbox.

This invention relates to an improved headbox of the type used to supply paper stock to a paper making machine web forming section whose configuration limits the space available for the positioning of the headbox, or whose configuration necessitates unconventional positioning of the 'headbox. Such web forming sections are shown and described in US. Patents Nos. 2,882,966, 2,995,186 and 3,056,719.

An essential requirement in the manufacture of paper is that paper stock is deposited from the headbox onto the web forming section in a stream of constant thickness across the width of the machine. Thus, an essential requirement of headbox design is that the slice lips, through which the stock flows, maintain a gap substantially parallel across the Width of the machine, under all operating conditions.

The pressure of the paper stock in the headbox, necessary to provide the required stock discharge velocity, acts on the structural members of the headboX which are conventionally the lower slice lip and apron member and the upper slice lip and roof member. When the slice lips apart and causes the gap to increase to a maximum dimension in the central unsupported portion of the slice lips and thus discharge a stream of paper stock of uneven thickness.

In conventional paper machine headboxes, where space limitations are not the major consideration, it is a simple matter to reinforce the slice lip supporting structure, and to provide pressure compensating means, such that the gap between the slice lips is maintained constant across the width of the machine.

However, in paper machines of the type shown and described in US. Patents Nos. 2,882,966, 2,995,186 and 3,056,719, it is necessary that the headboxes be positioned to eject a stream of stock in a substantially downward direction and also that the headboxes be repositioned to suit varying operating conditions, where it is necessary to eject a stream of stock onto the web forming section at different angles. Under these conditions it is not possible to provide slice lip reinforcing and pressure compensating means similar to those used on conventional stationary headboxes.

The present invention overcomes this and other disadvantages by providing a headbox which is adjustably suspended from an overhead support structure to permit a stream of stock to be ejected downwardly, at different angles, onto a forming section, and in which deflection of the roof and apron members of the headbox, which support the slice lips, are minimized by the provision of a rectangular support frame, the plane of which is substantially normal to the direction of stock flow through the headbox, and which surrounds the apron and roof members, and is adjustable therewith. The apron member is pivotally connected in the machine width direction, at approximately quarter point positions, to one side of the rectangular support frame. The adjustable roof member is connected in the machine width direction, at approximately quater point positions, to the opposing side of the rectangular support frame by means of flexible pressure cells, such as hydraulic cylinders, to permit deflection minimizing reaction forces to be applied to the roof member in all positions of adjustment. When hydraulic cylinders are used, the pressure in the cylinders is controlled by a hydraulic circuit, in response to pressure sensing means positioned in the roof member and flush with the surface of the stock flow passage through the headboX, to provide increased or decreased reaction forces in accordance with increased or decreased pressures of stock flow through the headbox.

It is, therefore, the main object of this invention to provide a headbox which is adjustably supported from an overhead structure to eject a stream of stock substantially downwardly and which embodies means to apply reaction forces to minimize deflections in the apron and roof members, in all positions of headbox adjustment and all slice openings.

Another object of this invention is to provide a headbox in which the means to apply reaction forces includes a reaction frame surrounding the head box and in which substantially all deflections, due to the reaction forces, are absorbed by the reaction frame.

Another object of this invention is to provide a headbox, as outlined in the main objective above, in which the apron and roof member reaction forces are automatically adjusted to compensate for changes in the pressure of the stock flowing through the headbox.

Another object of this invention is to provide a headbox, as outlined in the main objective above, which incorporates a flexible plate type hinge to provide adjustment of the gap between the slice lips and to provide an obstruction free passage for the flow of stock through the headbox.

A further object of this invention is to provide a head box incorporating a flexible plate type hinge and includ ing a linkage mechanism positioned at each side of the headbox to provide for mechanical adjustment of the gap between the slice lips and to prevent any loads be ing imposed on the flexible plate hinge.

These and other objects and advantages of this invention will be further apparent by referring to the following detailed specification and figures, in which:

FIG. 1 is a side view of a headbox and supporting structure embodying the features of this invention.

FIG. 2 is a plan view of the headbox and supporting structure shown in FIG. 1.

FIG. 3 is a sectional view on 3-3 in FIG. 1.

FIG. 4 is a sectional view on 4-4 in FIG. 2.

FIG. 5 is an enlarged view of the hinge details shown encircled at 5 in FIG. 4.

FIG. 6 is an enlarged side View of the headbox and linkage mechanism shown in FIG. 1.

FIG. 7 is a sectional view on 7-7 in FIG. 6.

FIG. 8 is a sectional view on 8-8 in FIG. 6.

FIG. 9 is a sectional view on 9-9 in FIG. 6.

FIG. 10 is a schematic representation of the linkage mechanism.

FIG. 11 is a schematic representation of the linkage mechanism adjusted to provide a relatively narrow gap between the headbox slice lips.

FIG. 12 is a schematic representation of the linkage mechanism adjusted to provide a relatively wide gap between the headbox slice lips.

FIG. 13 (appearing on the same sheet as FIGS. 4 and- 5) is a hydraulic circuit diagram of the stock pressure sensing and roof member deflection compensating arrangement.

Referring particularly to FIGS. 14, the headbox and reaction frame assembly, shown generally as 21, is pivotally suspended from an overhead support structure, shown generally as 22. Overhead support structure 22 includes two support columns 23 positioned on each side of the machine, an overhead tie beam 24 connecting the upper ends of support columns 23 on each side of the machine, and an overhead support beam 25 connected to, and positioned between, each tie beam 24.

Headbox and reaction frame assembly 21 is pivotally suspended from overhead support structure 22 at approximately quarter point positions to provide for minimum deflection. This is in accordance with the well known principle that the deflection of a uniformly loaded beam will be a minimum if the beam is simply supported at its quarter point positions, that is, the supports positioned a distance in from each end of the beam equal to one quarter the length of the beam.

The headbox and reaction frame assembly suspension mechanism comprises lifting jacks 26, position upon, and extending through support beam 25. Cross-shaft 27 extends between lifting jacks 26 to provide simultaneous operation for lifting and lower ing of headbox and reaction frame assembly 21. Crossshaft 28 extends between one of the lifting jacks 26 and a power source, such as hydraulic motor 29, positioned on one of the tie beams 24 and adapted to operate lifting jacks 26.

Headbox and reaction frame assembly 21 comprises two support frames 30, headbox assembly 31 and reaction frame assembly 32. Support frames are pivotally attached to lifting jacks 26 by pivot pins 33, and rigidly support headbox assembly 31, at the quarter point positions, by means of apron support member 34, central support members and roof support members 36. Reaction frame assembly 32 is slidably supported by apron support members 34 and reaction frame extension assemblies 37, which are rigidly attached to roof support members 36.

Headbox assembly 31 comprises three main portions, apron member 38, roof member 39 and inlet member 40, with the adjacent surfaces of apron member 38 and inlet member forming stock inlet passage 41, and the adjacent surfaces of roof member 39 and inlet member 40 forming stock inlet passage 42.

Cross-flow stock inlet 43 communicates with stock inlet passage 41 and is attached to the adjacent outer surfaces of apron member 38 and inlet member 40. Crossflow stock inlet 44 communicates with stock inlet passage 42 and is attached to the adjacent outer surfaces of roof member 39 and inlet member 40. It will be understood that

cross-flow stock inlets

43 and 44 are shown thus for illustration purposes only, and that other stock inlet arrangements can be embodied in the headbox assembly without departing from the spirit of this invention.

Stock inlet passages

41 and 42 converge into a common stock passage 45, which is terminated by a stock discharge slot formed by the gap 46 between apron slice lip 47 and roof slice lip 48. Stock passage basically comprises stock accelerating portion 49 adjacent the converging point of

stock'inlet passages

41 and 42, a decelerating portion 50 and a further accelerating portion 51 between

slice lips

47 and 48.

Apron member 38 forms one surface of stock passage 45 and includes apron slice lip 47. Apron member 38 is suspended from apron support members 34 and is pivotally connected at the quarter point positions to apron reaction member 52, of reaction frame assembly 32, by means of pivot pins 53. Apron reaction member 52 is designed to provide a very high resistance to bending in the plane normal to the flow of stock through the headbox and thus provides the necessary reaction to the outward loads imposed on apron member 38 by the pressure of the stock flowing through stock passage 45.

Roof member 39 embodies the means for adjustment of gap 46 between

slice lips

47 and 48 and basically comprises fixed roof portion 54, and adjustable roof portion 55 which forms the other surface of stock passage 45 and includes roof slice lip 48. This enables slice gap 46 to be varied to suit stock and product requirements. Fixed and adjustable roof portions 54 and '55, respectively, are operatively connected together by flexible plate type hinge 56. Reference to FIG. 5 shows that flexible plate type hinge 56 provides a solid connection between fixed roof portion 54 and adjustable roof portion 55, thus ensuring no obstruction to the flow of stock through stock passage 45, whilst the reduced thickness portion 57 of hinge 56 provides the required hinge flexibility.

Fixed roof portion 54 is suspended from roof support members 36, and adjustable roof portion 55 is connected to roof reaction member 58 of reaction frame assembly 32, at the quarter point positions, by means of hydraulic cylinders 59, which are required to limit the deflection of adjustable roof portion 55 and apron member 38 when acted upon by the hydraulic pressure of stock flowing through stock passage 45. By limiting this deflection the variation in gap 45, across the width of the machine, is kept to a minimum. The circuit diagram shown in FIG. 13 (detailed later in this specification) allows this deflection to be resisted automatically in response to changes in hydraulic pressure within the headbox.

Roof reaction member 58 is designed to embody less resistance to bending in the plane normal to the flow of stock through the headbox, than apron reaction member 52, and thus will deflect under highl oading from hydraulic cylinders 59 and prevent high stresses being imposed upon the headbox. The feature whereby reaction frame assembly 32 is supported vertically but allowed to slide horizontally relative to headbox assembly 21, allows the headbox and reaction frame assembly 21 to assume a balanced state, when the loads are such that roof reaction member '58 is caused to deflect.

Apron reaction :member 52 and roof reaction member 58 are connected together to form a substantially rectangular reaction frame assembly by

end members

60 and 61.

Apron reaction member 52 is arranged to be supported vertically by apron support members 34, and to be slidable relative thereto, by studs 62 which are threaded at each end, one threaded end of each stud 62 being securely screwed into apron support members 34, the other threaded ends passing through slots in apron reaction member 52 and, together with clamping plates 63 and nuts 64, slidably and securely supporting apron reaction member 52. Nuts 64 are adjusted to provide the required horizontal slidability between apron support members 34 and apron reaction member 52, whilst also providing effective vertical support.

Roof reaction member 58 is arranged to be supported verticaly by reaction frame extension 37, and to be slidable relative thereto, by lower support brackets 65. Lower support brackets are adjustably bolted to reaction frame extension 37 by bolts 66, to provide vertical adjustment for the required horizontal slidability between roof reaction member 58 and reaction frame extension 37, whilst also providing effective vertical support.

Apron member 38, roof member 39 and inlet member 40, are joined to form the complete headbox by conventional means, such as bolting.

End covers 67 and 68 are securely and rigidly bolted to the end plates of apron member 38, inlet member 40 and fixed roof portion 54, and provide end closures for

stgck inlet passages

41 and 42 and common stock passage Reference to FIG. 9 shows a detail of a seal member (on one side of the headbox), such as an air inflated rubber tube 69, positioned between the fixed end covers 67 and 68 and the end plates of adjustable roof portion 55, to prevent leakage of stock from the headbox.

Two positioning jacks 70 are mounted on brackets on columns 23, one on each side of the machine, and are pivotally connected, through links 71, to apron member 38.

Thus headbox and reaction frame assembly 21 may be lifted by means of lifting jacks 26 to extract

slice lips

47 and 48 from nip 72 between forming section rolls 73 and 74, for screen changes, maintenance, washup, etc. Lifting jacks 26 may also be used, in conjunction with positioning jacks 70, to change the angle at which stock is ejected through

slice lips

47 and 48 into nip 72.

It will be appreciated that flexible plate type hinge 56 will not have suflicient strength to constrain the internal stock pressures and to fully support adjustable roof portion 55. Thus to relieve hinge 56 of any load carrying requirements, and to provide a positive means for adjustably positioning roof portion 55, a linkage mechanism 75 is positioned on each side of the headbox. Particular reference now to FIGS. 6 to 12 shows in detail and in schematic arrangement, linkage mechanism 75 which provides a positive connection between adjustable roof portion 55 and the remainder of the headbox, and permits adjustable roof member 55 to be pivoted about main pivot pins 76 to achieve adjustment of slice gap 46. Hinge pins 76 are positioned in axial alignment with the centre of hinge reduced portion 57. Each linkage mechanism 75 comprises main pivot pin 76 which is rigidly secured to fixed end cover (67 or 68), pivot pin 77 which is rigidly secured to the end plate of fixed roof portion 54, pivit pin 78 which is rigidly attached to brackets 79 on the outer surface of fixed roof portion 54, pivot pin 80 which is rigidly attached to the end plate of adjustable roof portion 55, and pivot pin 81 which is rigidly attached to brackets 82 on the outer surface of adjustable roof portion 55.

Common screw member 83 is rotatably mounted in clevis 83a which is pivotally mounted on pivot pin 76 and contains two threaded portions 84 and 85, the pitch of threaded portion 85 being twice that of threaded portion 84. Nut 86, having pivot pin 87 mounted thereon, is positioned on thread 84, and nut 88 having pivot pin 89 mounted thereon is positioned on thread 85. Pivot pin 87 is operatively connected to pivot pins 77 and 80 by

links

90 and 91, respectively. Pivot pin 89 is operatively connected to pivot

pins

78 and 81 by

links

92 and 93, respectively. Pivot pins 76, 80 and 81, are also interconnected by link 94.

Particular reference to FIGS. 10, 11 and 12 shows, schematically, the operation of linkage mechanism 75.

In any given position, such as the position shown in full lines in FIG. 10, the pivot pins assume a geometric arrangement in which the triangles formed by

pivot pins

76, 77 and 87; 76, 80 and 87; 76, 78 and 89; 76, 81 and 89; are similar triangles. Thus when the fixed physical length between pivot pins 76 and 77 is arranged to be half of the fixed physical length between pivot pins 76 and 78 and, similarly, when the fixed physical length between pivot pins 76 and 80 is arranged to be half the flxed physical length between pivot pins 76 and 81, it will be seen that rotation of common screw 83 will cause

nuts

86 and 88, and thus pivot pins 87 and 89, respectively, to move to positions 87a and 89a, and the links will assume the geometric positions indicated by the broken lines, with pivot pin 76 remaining as the common centre of rotation for both geometric arrangements.

Reference to FIG. 11 shows a schematic arrangement of headbox 31 with linkage 75 adjusted to provide a minimum slice gap 46. This corresponds to the full line geometric arrangement in FIG. 10. In FIG. 11 the gap 95, between fixed roof portion 54 and adjustable roof portion 55, is shown as being parallel.

, Reference to FIG. 12 shows a schematic arrangement, similar to FIG. 11, but in which linkage 75 has been adjusted, by rotation of common screw member 83, to provide a maximum slice gap 46a. This corresponds, though less exaggerated, with the broken line geometric arrangement in FIG. 10. In FIG. 12 the gap 95 is now shown to be substantially closed at the outer end and adjustable roof portion 55 is pivoted about flexible hinge 56 to provide the increased slice opening 46a.

It will thus be seen that rotation of common screw member 83 changes the geometric arrangement of the links and, due to the fixed pivot points, causes adjustable roof portion 55 to pivot about pivot pin 76 and hinge 56. It will also be seen that the link 94, interconnecting pivot pins 76, and 81, prevents any loads being transferred to hinge 56.

It will be a simple mechanical expedient to provide for simultaneous operation of common screw member 83, for maintenance of a parallel slice gap, etc., although each linkage 75 may be operated separately, if required.

FIG. 13 shows a hydraulic circuit diagram of the apparatus for sensing the pressure of the stock flowing through common passage 45 and for increasing or decreasing the fluid pressure in cylinders 59 to compensate for any changes in the stock pressure and thus to maintain a balanced state with the headbox structure in a condition of minimum deflection.

Piezo-electric crystal 96 is mounted in adjustable roof portion 55 flush with the surface of common stock passage 45. Piezo-electric crystal 96 is sensitive to changes in pressure and will thus sense-changes in the pressure of the stock flowing through passage 45, which will produce corresponding changes in the capacitance of piezo-electric crystal 96. Piezo-electric crystal 96 is connected to an amplifier 97. An input reference voltage is fed to amplifier 97 and the capacitance changes in piezo-electric crystal 96 are amplified and reflected as changes in the voltage fed to servo valve 98.

Servo valve 98 is positioned in the continually circulating hydraulic fluid circuit which provides the fluid pressure for hydraulic cylinders 59. Pump 99, driven by motor 100, delivers hydraulic fluid from tank 101 to pressure regulating valve 102. Pressure regulating valve 102 delivers hydraulic fluid under pressure to hydraulic cylinders 59 and also directs the continuing flow of hyraulic fluid back to tank 101, via servo valve 98 and pressure relief valve 103.

Thus, any changes in the capacitance of piezo-electric crystal 96 will be reflected as a change in the voltage feed to servo valve 98, which will open or close the fluid restriction 104 and cause a decrease or increase, respectively, in the pressure of the hydraulic fluid in cylinders 59.

It will be understood that, although this specification illustrates quarter point positioning of the reaction and supporting members, which represents the most economical manner for minimizing headbox deflections, further supporting points can be provided to further minimize deflection, depending upon headbox design considerations such as machine width, stock pressures, etc.

As an alternative execution of this invention the reaction frame assembly may be modified in shape to provide further space savings, provided its plane of maximum bending strength passes through the neutral axis of the apron member and it is pivotally connected thereto at least at the quarter point positions.

From the foregoing it is thus seen that a headbox according to the invention accomplishes all of the objects and advantages as set forth herein.

What I claim is:

1. In a headbox for the discharge of stock onto a machine web forming section, said headbox having stock inlet means, an adjustable orifice slice for discharging therethrough a web of varioble thickness and stock passage means between said inlet means and said slice, the improvement comprising reaction frame means surrounding said headbox having opposing elongated side members lying in a plane substantially normal to said stock passage means, said headbox being operatively connected to said reaction frame side members to minimize headbox deflection due to the pressure of stock flowing through said passage means.

2. The headbox as claimed in claim 1 having a hinged Wall portion of said passage to permit adjustment of the slice, pivoted extensible linkage means connecting said hinged wall portion to fixed portions of the headbox, to provide mechanical adjustment of the slice, and load bearing means connecting the opposing wall portion of the passage to the adjacent said frame side member in load transmitting relation therewith.

3. The headbox as claimed in claim 2 including at least one variable load transfer means connecting the movable wall portion of said passage to the adjacent one of said frame side members in load transfer relation therewith.

4. The headbox as claimed in claim 3 including means for sensing the fluid stock pressure in said headboX, load controlling means connected with said load transfer means,

and means connecting said pressure sensing means with said load controlling means, wherebythe transference of load from said movable Wall portion to said frame side member is regulated in accordance with the working pressure conditions in said headbox.

5. The headbox as claimed in claim 3 wherein said variable load transfer means is connected to said movable Wall portion at substantially the quarter points along the length thereof, to provide minimal intermediate deformation due to bending loads acting between said points of connection and to maintain the opening of said slice substantially parallel.

No references cited.

DONALL H. SYLVESTER, Primary Examiner.

A. C. HODGSON, Assistant Examiner.

Claims

1. IN A HEADBOX FOR THE DISCHARGE OF STOCK ONTO A MACHINE WEB FORMING SECTION, SAID HEADBOX HAVING STOCK INLET MEANS, AN ADJUSTABLE ORIFICE SLICE FOR DISCHARGING THERETHROUGH A WEB OF VARIOBLE THICKNESS AND STOCK PASSAGE MEANS BETWEEN SAID INLET MEANS AND SAID SLICE, THE IMPROVEMENT COMPRISING REACTION FRAME MEANS SURROUNDING SAID HEADBOX HAVING OPPOSING ELONGATED SAID MEMBERS LYING IN A PLANE SUBSTANTIALLY NORMAL TO SAID STOCK PASSAGE MEANS, SAID HEADBOX BEING OPERATIVELY CONNECTED TO SAID REACTION FRAME SIDE MEMBERS TO MINIMIZE HEADBOX DEFLECTION DUE TO THE PRESSURE OF STOCK FLOWING THROUGH SAID PASSAGE MEANS.