GB1585096A

GB1585096A - Material treatment apparatus

Info

Publication number: GB1585096A
Application number: GB2526176A
Authority: GB
Original assignee: Spooner Edmeston Engineering Ltd
Current assignee: Spooner Edmeston Engineering Ltd
Priority date: 1977-06-17
Filing date: 1977-06-17
Publication date: 1981-02-25

Description

(54) IMPROVEMENTS IN MATERIAL TREATMENT APPARATUS (71) We, SPOONER EDMESTON ENGIN EERING LIMITED, a British Company, of Moorland Engineering Works, llkley, West Yorkshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to float treatment apparatus for treating a floating web of material.

The float treatment apparatus of the invention employs a nozzle assembly provided with what may be called a Coanda nozzle, i.e.

a nozzle in which the discharged gaseous medium flows over an extended lip surface of the nozzle between the extended surface and the adjoining surface of the web being treated and which is caused to cling to such extended surface by the so-called Coanda effect. Provided that dimensions and pressures are suitably chosen, the web of material will float relatively stably on the nozzle at a short distance from the extended surface. The present invention is, however, not concerned with the theory of operation of the nozzles but with float treatment apparatus employing a particular nozzle construction found to work effectively in practice.

Float treatment apparatus according to the invention comprises a lower bank of Coanda nozzles and an upper bank of high velocity gaseous medium discharge nozzles adapted to direct the gaseous medium so that it impinges against the upper surface of the web, each Coanda nozzle comprising a slot one lip of which has a rounded edge blending with a generally flat support surface which stands proud of the other nozzle lip so that the gaseous medium which is blown out of the slot blows along said support surface.

Each Coanda nozzle may comprise an elongate box defining a pressure chamber and having at least one of said slots therein, and a profiled bar attached to the box and having a rounded edge which accurately defines said lip of the slot.

Preferably the profiled bar is an extruded bar such that said rounded edge required no machining.

Advantageously there is a pair of parallel slots, that lip of each of which, which is remote from the other slot, being defined by a rounded edge of a respective profiled bar.

Conveniently the adjacent lip of the pair of slots are defined by a further medial bar which is attached to the box and which may also be profiled.

The invention is further described, by way of example, with reference to the drawings of which Figures 1 and 2 accompany the provisional specification and Figure 3 accompanies this complete specification. In the drawings: Figure 1 is a diagrammatic longitudinal section view of gaseous medium float treatment apparatus fitted with gaseous medium discharge nozzle assemblies according to the invention; Figure 2 is a sectional view through one of the nozzle assemblies drawn to a larger scale; and Figure 3 is a sectional view illustrating a modification to the nozzle assemblies.

Figure 1 of the drawings shows only a portion of treatment apparatus according to the invention. It may for example be a float drier for drying both sides of a printed or coated web of material 10, such as paper. The nominal path of the paper 10 is shown by a straight line drawn in full. The actual path of the paper is likely to vary but will normally be somewhat wavy path as indicated by a dotted line 10a.

A bank of nozzle assemblies 11 is provided below the web 10, the nozzle assemblies 11 being attached to an upper wall 12 of a lower plenum chamber 13. A bank of upper nozzle assemblies 14 is disposed above the web 10, the nozzle assemblies 14 being attached to a lower wall 15 of an upper plenum chamber 16.

The lower nozzle assemblies 11 combine Coanda nozzles which serve to support the web 10 in a contactless stable manner as well as to blow heated gaseous medium from the plenum chamber 13 in contact with the lower surface of the web 10. One of the nozzle assemblies 11 will be described more fully with reference to Figure 2. Each upper nozzle assembly 14 comprises an elongate box extending transversely of the web 10 over the full width of the web. A pressure chamber 17 within each nozzle box 14 receives pressurized heated gaseous medium from the plenum chamber 16 through apertures (not shown) in the wall 15. The lower face of each nozzle box 14 is defined by a continuous perforated wall 18 common to all of the nozzle boxes 14.A large number of small perforations in the wall 18 serves to discharge the gaseous medium from the pressure chamber 17 so that it impinges directly against the web 10 as indicated by the arrows 19. Relatively fewer but larger openings in the wall 18 between adjoining nozzle assemblies 14 allow the spent gaseous medium above the web 10 to flow away into exhaust chambers 20 as shown by arrows 21. The exhaust chambers 20 are defined between the walls of adjoining nozzle boxes 14 and lead transversely of the web to suitable discharge passages.

As shown in Figure 2, each lower discharge nozzle assembly 11 comprises a box 22 secured to the wall 12 of the lower plenum chamber 13.

The nozzle box 22 comprises a pair of sheet metal members 23 bent to zig-zag cross section such that a lower flange 24 is attached, e.g. by rivets, to the wall 12 and the upper flange 25 is parallel to but spaced from the wall 12. The nozzle box 22 defines a pressure chamber 26 which receives heated pressure medium from the plenum chamber 13 through openings 27 formed in the wall 12 and discharges a pressure medium through a pair of nozzle slots 28. The outer lips of the slots 28, i.e. the lips remote from one another, are defined by rounded surfaces 29 on profiled bars 30. The inner lips 31 of the nozzle slots 28 are defined by lateral edges of a medial profiled bar 32. The rounded surfaces 29 blend with flat outer surfaces 33 of the profiled bars 30.The flat outer surfaces 33 stand proud of a flat outer surface 34 of the medial bar 32 and the rounded surfaces 29 are likewise substantially proud of the flat surface 34. The pressure in the chamber 26, the width of the nozzle slots 28 and the radius of the rounded surfaces 29 are so chosen that gaseous medium blown out of the nozzle slots 28 tends to follow the rounded surfaces 29 and flow over the flat outer surfaces 33 in accordance with the Coanda effect, as shown by the arrows 35 in Figure 1. The spent gaseous medium flows away into exhaust chambers 36 which comprise the spaces between adjoining nozzle assemblies 11. The spent gaseous medium can flow laterally of the web to suitable discharge passages. The theory of the manner in which the web is supported will not be given in as much as the invention is not concerned with the theory but with the construction of the apparatus.

Referring again to Figure 2, each profiled bar 30 is secured by a row of screws 37 or the like fastening means to the flanges 25. These screws also serve for the attachment of angle members 38. The medial profiled member 32 is ofsomewhat T-shaped section and is attached to the box 11 by screws 39. By removing the screws 39 the medial profiled bar 32 can be readily removed to enable the pressure chamber 26 to be cleaned. Each angle member 38 and the medial profiled bar 32 form passages 40 for directing the pressure medium to the nozzle slots 28.

The rounded surfaces 29 have to be formed with relatively close tolerances as does the width of the nozzle slots 28. By forming the profiled bars 30 and 32 as separate members it becomes easier to meet these close tolerances without having to make the remaining parts of the nozzle box 22 to similarly close tolerances.

Advantageously the profiled bars 30 and 32 can be made of extruded sections such as extruded aluminium so that no subsequent machining is required other than cutting to length and making holes for the screws.

As shown in Figure 1, the upper nozzle assemblies 14 can be spaced much further from the nominal path of the web 10 than the distance of the stable position of the web from the lower nozzle assemblies 11. This facilitates servicing, reduces the risk of the web touching the nozzle assemblies and breaking and also reduces the risk of damage to the apparatus in the event of the web breaking and building up in the apparatus. Furthermore it facilitates threading the web through the apparatus.Typical dimensions for the nozzle assembly 11 are a slot width of 3.5 mm for each of the slots 28, an overall width of 35 mm for each of the profiled bars 33, an overall width of 23 mm for the profiled bar as measured across the surface 34, a thickness of 10 mm for each of the profiled bars 30 and a thickness of 3.5 mm for the head portion of the profiled bar 32 so that the surface 34 is recessed by 6.5 mm with respect to the surfaces 33. The radius of the rounded surfaces 29 is advantageously 6.5 mm. A typical pressure range for the pressure chamber 26 is one inch water gauge to thirty inches water gauge.

In the modification shown in Figure 3, the profiled bars 30 are replaced by profiled bars 30a having angular extensions 41 which diverge from the nominal path of the web 10. This reduces the risk of the web catching on the outer edges of the nozzle boxes.

WHAT WE CLAIM IS: 1. A gaseous medium float treatment apparatus for treating a floating web of material, comprising a lower bank of Coanda nozzles and an upper bank of high velocity gaseous medium discharge nozzles adapted to direct the gaseous medium so that it impinges against the upper surface of the web, each Coanda nozzle comprising a slot one lip of which has a rounded edge blending with a generally flat support surface which stands proud of the other nozzle lip so that the gaseous medium which is blown out of the slot flows along said support surface.

2. Apparatus as claimed in claim 1 in which the slots of the Coanda nozzles are arranged in pairs, each pair being supplied from a respective nozzle box, the rounded lips of the nozzle slots of each pair being those lips remote from the other nozzle slot.

3. Apparatus as claimed in claim 2 in which

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. each nozzle box 14 is defined by a continuous perforated wall 18 common to all of the nozzle boxes 14. A large number of small perforations in the wall 18 serves to discharge the gaseous medium from the pressure chamber 17 so that it impinges directly against the web 10 as indicated by the arrows 19. Relatively fewer but larger openings in the wall 18 between adjoining nozzle assemblies 14 allow the spent gaseous medium above the web 10 to flow away into exhaust chambers 20 as shown by arrows 21. The exhaust chambers 20 are defined between the walls of adjoining nozzle boxes 14 and lead transversely of the web to suitable discharge passages. As shown in Figure 2, each lower discharge nozzle assembly 11 comprises a box 22 secured to the wall 12 of the lower plenum chamber 13. The nozzle box 22 comprises a pair of sheet metal members 23 bent to zig-zag cross section such that a lower flange 24 is attached, e.g. by rivets, to the wall 12 and the upper flange 25 is parallel to but spaced from the wall 12. The nozzle box 22 defines a pressure chamber 26 which receives heated pressure medium from the plenum chamber 13 through openings 27 formed in the wall 12 and discharges a pressure medium through a pair of nozzle slots 28. The outer lips of the slots 28, i.e. the lips remote from one another, are defined by rounded surfaces 29 on profiled bars 30. The inner lips 31 of the nozzle slots 28 are defined by lateral edges of a medial profiled bar 32. The rounded surfaces 29 blend with flat outer surfaces 33 of the profiled bars 30.The flat outer surfaces 33 stand proud of a flat outer surface 34 of the medial bar 32 and the rounded surfaces 29 are likewise substantially proud of the flat surface 34. The pressure in the chamber 26, the width of the nozzle slots 28 and the radius of the rounded surfaces 29 are so chosen that gaseous medium blown out of the nozzle slots 28 tends to follow the rounded surfaces 29 and flow over the flat outer surfaces 33 in accordance with the Coanda effect, as shown by the arrows 35 in Figure 1. The spent gaseous medium flows away into exhaust chambers 36 which comprise the spaces between adjoining nozzle assemblies 11. The spent gaseous medium can flow laterally of the web to suitable discharge passages. The theory of the manner in which the web is supported will not be given in as much as the invention is not concerned with the theory but with the construction of the apparatus. Referring again to Figure 2, each profiled bar 30 is secured by a row of screws 37 or the like fastening means to the flanges 25. These screws also serve for the attachment of angle members 38. The medial profiled member 32 is ofsomewhat T-shaped section and is attached to the box 11 by screws 39. By removing the screws 39 the medial profiled bar 32 can be readily removed to enable the pressure chamber 26 to be cleaned. Each angle member 38 and the medial profiled bar 32 form passages 40 for directing the pressure medium to the nozzle slots 28. The rounded surfaces 29 have to be formed with relatively close tolerances as does the width of the nozzle slots 28. By forming the profiled bars 30 and 32 as separate members it becomes easier to meet these close tolerances without having to make the remaining parts of the nozzle box 22 to similarly close tolerances. Advantageously the profiled bars 30 and 32 can be made of extruded sections such as extruded aluminium so that no subsequent machining is required other than cutting to length and making holes for the screws. As shown in Figure 1, the upper nozzle assemblies 14 can be spaced much further from the nominal path of the web 10 than the distance of the stable position of the web from the lower nozzle assemblies 11. This facilitates servicing, reduces the risk of the web touching the nozzle assemblies and breaking and also reduces the risk of damage to the apparatus in the event of the web breaking and building up in the apparatus. Furthermore it facilitates threading the web through the apparatus.Typical dimensions for the nozzle assembly 11 are a slot width of 3.5 mm for each of the slots 28, an overall width of 35 mm for each of the profiled bars 33, an overall width of 23 mm for the profiled bar as measured across the surface 34, a thickness of 10 mm for each of the profiled bars 30 and a thickness of 3.5 mm for the head portion of the profiled bar 32 so that the surface 34 is recessed by 6.5 mm with respect to the surfaces 33. The radius of the rounded surfaces 29 is advantageously 6.5 mm. A typical pressure range for the pressure chamber 26 is one inch water gauge to thirty inches water gauge. In the modification shown in Figure 3, the profiled bars 30 are replaced by profiled bars 30a having angular extensions 41 which diverge from the nominal path of the web 10. This reduces the risk of the web catching on the outer edges of the nozzle boxes. WHAT WE CLAIM IS:

1. A gaseous medium float treatment apparatus for treating a floating web of material, comprising a lower bank of Coanda nozzles and an upper bank of high velocity gaseous medium discharge nozzles adapted to direct the gaseous medium so that it impinges against the upper surface of the web, each Coanda nozzle comprising a slot one lip of which has a rounded edge blending with a generally flat support surface which stands proud of the other nozzle lip so that the gaseous medium which is blown out of the slot flows along said support surface.

3. Apparatus as claimed in claim 2 in which

the nozzle boxes are spaced apart to provide exhaust chambers for the gaseous medium flowing along said support surfaces.

4. Float treatment apparatus as claimed in claim 1, 2 or 3 wherein each Coanda nozzle comprises an elongate box defining a pressure chamber and having at least one of said slots therein, and a profiled bar attached to the box and having a rounded edge which accurately defines said lip of the slot.

5. Apparatus as claimed in claim 4 in which the profiled bar is an extruded bar such that said rounded edge requires no machining.

6. Float treatment apparatus as claimed in claim 1, 2 or 3, in which each Coanda nozzle comprises an elongate box defining a pressure chamber and having at least one of said slots therein, at least a portion of the box having said rounded edge thereon comprising an extruded bar.

7. Apparatus as claimed in claim 4, 5 or 6 when appendant to claims 2 or 3, in which the adjacent lips ofthe slots are defined by a further medial bar which is attached to the box.

8. Apparatus as claimed in claim 7 in which said medial bar comprises an extruded profiled bar.

9. A float treatment apparatus constructed substantially as herein described with reference to and as illustrated in Figure 1 of the drawings accompanying the provisional specification.

10. Apparatus as claimed in claim 9, in which the Coanda nozzle assembly is constructed substantially as herein described with reference to and as illustrated in Figure 2 of the drawings accompanying the provisional specification.

11. Apparatus as claimed in claim 9, in which the Coanda nozzle assembly is constructed substantially as herein described with reference to and as illustrated in the accompanying Figure 3 of the drawings.