GB2154154A

GB2154154A - Axial-flow filter element

Info

Publication number: GB2154154A
Application number: GB08504350A
Authority: GB
Inventors: Yuuji Ito; Tadahiko Shibata; Masahiko Sakai; Yukio Ota; Naohiko Kondo; Harukazu Matuyama
Original assignee: NipponDenso Co Ltd
Current assignee: Denso Corp
Priority date: 1984-02-20
Filing date: 1985-02-20
Publication date: 1985-09-04
Also published as: GB2154154B; GB8504350D0

Abstract

An axial-flow filter element presenting concentric circular pleats is formed from a flat sector-shaped sheet of filter medium 2, which is clamped at its apex and pressed to conform with a ridged mould 3 by lowering curved blades 4a to 4e in succession. The shaped sheet is then heat set and removed from the mould, then radially compressed until it assumes circular form (Fig 5 not shown). <IMAGE>

Description

SPECIFICATION Method for making axial-flow filter and apparatus therefor This present invention relates to a filter, particularly an axial-flow filter for filtering air or oil to remove foreign matter.

Conventionally, an axial-flow filter is made using a flexible base sheet or template having many corrugations, and to which a flat sheet of filter material is applied, the filter material being folded along the corrugations of the base sheet to produce a corrugated sheet of filter material. This method is very unreliable and time consuming; for example, it takes two minutes to produce a corrugated sheet which is about 300 mm in diameter. Also, it is impossible for manual workers in a production line to fold the corrugations uniformly so that the filters produced are of variable quality and effect. Consequently, their value is reduced.

An added complication arises due to the nature of the filter material. Because the material is soft and flexible material it is much more difficult to handle and shape than rigid and solid materials like metal or hard plastic.

One object of the present invention is to enable the rapid mass production of axial-flow filters. In accordance with the present invention, we propose making a curved corrugated sheet from a flat sheet of filter material by advancing folding blades toward a mould so as to fold the filter material over curved undulations in the mould surface. In the process, the filter material is corrugated with a certain curvature in a moment. The invention is, however, applicable for forming corrugated sheets of materials other than filter material, such as fin metallic material or plastics material.

We also propose bending the curved corrugated sheets obtained above so as to bring the ends thereof together to make as a whole a round axialflow filter.

The above two stages in production may be accomplished at high speed using machinery developed by us and may be performed one after the other in rapid succession to form an axial flow filter production line.

Features of the present invention are set forth in the appendant claims.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a flat fanshaped sheet of filter material; Figure 2 is a perspective view showing the flat sheet of Figure 1 attached to a mould; Figure 3 is a perspective view of a corrugated sheet in the mould; Figure 4 illustrates the formation of a fully rounded filter from a curved corrugated sheet; Figure 5 is a perspective view of an axial-flow filter; Figure 6 is a part cross-sectional side view of one embodiment of apparatus for making a curved corrugated sheet; Figure 7 shows a front view of a set of folding blades forming part of the apparatus of Figure 6; Figure 8 is a cross-section of a modified mould; Figure 9 is a part cross-sectional front view of apparatus for a curved corrugated sheet into a circular filter;; Figure 10 is an underside view of the apparatus shown in Figure 9; Figure 11 is a plan view of a reshaper mounted in the apparatus of Figure 9; Figure 12 shows a circular corrugated sheet produced by the apparatus of Figure 9; and Figure 13 shows a part cross-sectional front view of a modification of the apparatus shown in Figure 9.

Figure 1 shows a flat sheet 2 of filter material cut to the shape of a sector of an annulus (fan-shaped) having two curved edges 2b and two tapered side edges 2c. In one side of the sheet is a set of depressions having the same centre of curvature as the curved edges 2b. Figure 2, shows mould 3 which has, on one side thereof, an undulating surface 3a defining valleys and ridges which are curved along the length thereof and have a predetermined radius of curvature. The mould 3 is also curved at the radially inner end 3b thereof. The flat sheet 2 is fixed at the curved end 3b of the mould so that the sheet 2 is curved to form a part-conical surface inclined to the curved wavy surface 3a of the mould as shown in the Figure.A set of folding blades 4a, 4b and 4c is positioned against the sheet 2 and then moved downward to fold the sheet 2 along the upper face of the curved undulating surface 3a as shown in Figure 3 to obtain a curved corrugated sheet 2c. The curved corrugated sheet 2c thus produced is worked around a centre rod or former 5 to form the curved sheet 2c into a full circle as indicated by dotted line A in Figure 4.

When all the steps illustrated in Figures 1 to 4 are complete, and the circular corrugated sheet is reshaped, to produce finally an axial-flow filter 21 as shown in Figure 5.

One embodiment of apparatus for performing the steps corresponding to Figures 2 and 3, is illustrated in Figures 6 and 7. The mould 3 has curved ridges 3f, 3g, 3h, 3i and 3j. The radially inner end of the sheet 2 of filter material is held against the curved end 3b of the mould 3 by a clamp 14 operated by an air cylinder 13, so that the flat sheet 2 is located in the inclined position illustrated in Figure 6 with the folding blades 4a to 4e disposed adjacent the upper surface of the sheet 2.

Each folding blade 4a to 4e is carried by the piston rod of a air cylinder 8a to 8e and all of these cylinders are supported upon a plate 7 which is slidable toward and away from a mould base 6 along guide column 12, by a hydraulic cylinder 10 mounted upon a beam 11 attached to the top of the columns 12.

When the cylinder 10 is operated to move the plate 7 downwards the folding blades in the extended position illustrated in Figure 6 approach the sheet 2 such that the folding blade 4a first folds the sheet 2 over the ridge 3f and presses it into the valley defined between the ridges 3f and 39. Fur ther movement causes the next folding blade 4b to fold the sheet 2 over the ridge 39 and so one until all of the succeeding blades 4c, 4d and 4e enter the corresponding valleys in the mould 3. As the plate 7 moves down all of the cylinders 8a to 8e, move with it so that the folding blades engage the sheet 2 in the mould one after the other and the associated piston rods are pressed into the respective air cylinders.Since the initial positions of the folding blades 4a to 4e are staggered stepwise, a single downward movement of the plate 7 causes folds to be formed in the sheet 2 consecutively and at a high speed to obtain a curved corrugated sheet 2c conforming to the mould 3. Heaters 51 are provided between adjacent folding blades so as to heat and set the folds so formed in the sheet 2 material at the crest of each of the curve ridges 3f to 3j. The mould 3 may also include a heater to heat the material in contact with the undulating mould surface 3a. Hence the sheet becomes permanently deformed and retains corrugations conforming to the mould 3 when the folding blades 4a to 4e are retracted.Although in the illustrated embodiment air cylinders (8a-8e) are used to absorb movement for the stems of the folding blades 4a to 4e, to ap ply pressure and to extend the blades once again when the plate 7 is retracted, simple springs may be used for this purpose.

The relative positions of the fixing blades 4a, 4b, 4c, 4d and 4e, sheet of filter material 2 and the mould 3 is shown more closely in Figure 7. It will be seen that the sheet 2 is held such that it is inclined above the mould presenting a part-conical surface adjacent which folding blades 4a to 4e are disposed. Each of the folding blades 4a to 4e is curved to conform with the curvature of the ridges 3f to 3j and valleys therebetween, since each blade must mate with a corresponding valley in the mould 3. The edges of the folding blades 4a to 4e are sharpened as indicated in this Figure. Also, the arcuate length of each blade corresponds to the width of the sheet 2 at that point.

In the embodiment of Figures 6 and 7, the crests of ridges 3f to 3j lie in a horizontal plane parallel to the base 6, but this is not essential. The ridges may define a surface inclined to the base 6 in which case the undulating surface of the mould 3 should be modified by making the downward slope of each ridge (3f) shorter than the upward slope thereof and the upward slope of the next (in the direction of increasing radius of curvature) ridge (3g). A mould modified as described is used to produce a corrugated sheet which is generally part-conical in form and may be used to form a dished (i.e. slightly conical) axial flow filter.In practice, such filters are preferred for use, for ex ample, in the air cleaner of an automobile since, overall, the surface of the filter is inclined to the (axial) direction of air flow therethrough producing a space through which the air can communicate with the intake system of the engine.

Figure 8 shows another embodiment of mould 3 having a mould part 31 which defines the crests of the ridges 3f to 3j, and which is movable relative to a mould base part 32 so enabling the production of various types of corrugated sheets having ridges of different heights. If desired each crest may be adjustable independently.

Since the pitch of the corrugations and hence of the folding blades 4a to 4e remains constant, the same mould may be used to manufacture various types of axial-flow filter in which the corrugations are of different heights.

The filter material 2 is preferably a three-ply material which has a top layer of coarse or low density material and a layer of middle density material intervening between the top layer and a bottom layer of high density material. In use a filter of this type of material is arranged such that the air passes from the coarse side to the high density side whereby the coarse material removes relatively large particles of foreign matter first and then filters any other unwanted materials. During manufacture as described above of a filter using such filter materials, the coarse or low density material is presented to the folding blades 4a to 4e so that the corrugated sheet produced has the coarse material on top and the high density material below.When the sheet is made conical as explained above, the coarse side is made the outer surface of the cone and the high density side is the inner side of the cone.

The apparatus shown in Figures 9 and 10 for forming the curved corrugated sheet into an axialflow filter, comprises a table 23 which is supported on a stand 24 and upon which the curved corrugated sheet is located in contact with a centre rod or former 52. A contouring belt 5 which is curved at the initial position as shwon in Figure 10, embraces the periphery of the curved corrugated sheet and is made of a spring material and flexible so that it is able to flex when the ends of the contouring belt 5 are moved toward the centre rod 52.

Each end of the contouring belt 5 is held by a holder 6 on top of which is a cam follower 7. The holder 6 is on a guide bar 8, the ends of which are supported by guide bar holders 9a and 9b having can followers 16, 10a, and 10b. A cam plate 11 fixed to the base plate 22, has three cam grooves 12a, 12c and 12b receiving respectively the cam followers 10a, 7 and 10b and cam follower 16 engages in a slot 15 in a lever 13 which is pivoted about a pin 14. The lever 13 is rotated by a gear 17 meshing with another gear 21 driven by the output shaft of an air cylinder 20. A coil spring 18 exerts a tensile force on the cam follower 10b.

When the air cylinder 20 is energized to drive the gears 21 and 17 each of the levers 13 is rotated counter clockwise (in Figure 10) causing associated cam follower 136 to move along the slot 15 in the lever 13. The guide bar holder 9a thus moves counter-clockwise following slot 22a formed through the base plate 22 as shown in Figure 10.

The holder 9b on the other hand, is biased by the coild spring 18 toward the rotational centre of the lever 13. Rotation of the lever 13 also causes the cam follower 10b to travel along the cam groove 12b. Since the cam follower 16 is guided by the slot 15, the holder 9b is biased toward the rotational centre of the lever 13 and the length of the guide bar 8 is fixed, the position and the direction of the guide bar 8 is determined by the angular position of the lever 13. The position and the direction of the cam follower 7 (i.e. the belt holder 6) is also determined according to the angular position of the lever 13.When each belt holder 6 has moved along the cam groove 12c to the final position (shown dotted in Figure 10) such that each guide bar 8 reaches the vertical position (also shown dotted in Figure 10), the ends of the curved corrugated sheet meet to form a circular axial-flow filter with reduced diameter. The cam followers and cam grooves are arranged to ensure that the ends of the belt 5 trace a line such that the curved corrugated sheet 2c is made smaller and simultaneously made circular.

A ram pusher 26 operated by an air cylinder 28 which is supported by a stay 27 fixed to the base plate 22 passes through an aperture 29 to push the now circular corrugated sheet, down onto a reshaper 30 comprising two divided rotors 32 having semi-circular teeth 33 and rotated by pins 37 engaging slots 36 at the ends of the rotors 32. When the air cylinder 38 is actuated, the pins 37 are rotated by gears 35, the semi-circular teeth 33 on the rotors 32 initially in the position shown in Figure 11, rotate toward each other, so that the triangular space shown in Figure 11 is filled with the semicircular teeth 33. At this time, the upper or the other ends of the semi-circular teeth 33 are positioned as indicated by dotted line in Figure 11.

When the rounded corrugated sheet is pushed into the reshaper 30, the grooves therein mate with the semi-circular teeth in their initial positions, reg istering the centre hole of the round corrugated sheet on the centre guide pin 31. At this stage the ends of the rounded corrugated sheet do not meet to form a perfect circle as shown in Figure 12 and this imperfection is corrected when the rotors 32 or semi-circular teeth 33 are rotated as indicated by the arrows in Figure 11. After the reshaping, the reshaper 30 containing the corrugated sheet is retracted by operation of the slide plate 39, so that it could be placed on the following step.

Another embodiment of apparatus for forming a curve corrugated sheet into a circular axial flow filter, shown in Figure 13, has a contouring belt 5 which embraces the periphery of the curved corrugated sheet (as shown in Figure 9) and two or more additional contouring belts 5b and 5c with associated belt holders 6b and 6c and cam followers 7b and 7c which engage with corresponding cam grooves 12cb and 12 cc. The plurality of contouring belts (5, 5b and 5c) is advantageous in that, they can grasp more valleys of the curved corruga- tion 2c. This construction is especially suitable when a number of valleys or ridges are made in one curved corrugation. The number of contouring belts of course depends on the particular corrugated sheet or axial-flow filter desired.It has been found that five contouring belts are suitable for making an axial-flow filter with nine ridges or valleys. The ram 26 must avoid a plurality of contouring belts 5, 5b and 5c, therefore it has two slits therein to successfully push down the circular corrugated sheet made therebelow.

As explained above the method and apparatus enable the rapid and reliable mass production of axial-flow filters. In particular, it is possible to produce in the same apparatus, various kinds of axialflow filters having any number of corrugations and/or corrugations of different height.

The method disclosed is for making a curved corrugated sheet from a sheet of material, including the steps of preparing the flat sheet of material, preparing a mould having a curved wavy surface at one side thereof, fixing an end of the flat sheet to a curved end of the mould so that the flat sheet is curved and inclined with respect to the curved wavy surface of the mould, preparing a set of fixing blades each of which mates with each of the bottom edges of the curved wavy surface when moved to the wavy surface, moving the set of blades toward the way surface, and folding the fixed flat sheet continuously along said curved wavy surface to make said curved corrugation in such a manner that the blade closest to the fixed end of the flat sheet is moved first and thereafter the successive blades are moved consecutively.

In other words, it is said that a method is disclosed for making an axial-flow filter comprising the steps of preparing a flat sheet of filter material, preparing a mould having a curved wavy surface at one side thereof, fixing an end of the flat sheet to a curved end of the mould so that the flat sheet is curved and inclined with respect to the curved wavy surface of the mould, preparing a set of fixing blades each of which mates with each of the bottom edges of the curved wavy surface when moved to the wavy surface, and moving said set of blades toward the wavy surface, folding said fixed flat sheet continuously along said curved wavy surface to make a curve corrugation in such a manner that a blade closest to said fixed end of the flat sheet is moved first and thereafter the successive blades are moved consecutively, positioning a centre rod close to an inner curved end of said curved corrugation, positioning a contouring belt over an outer curved circumference of the curve corrugation, and moving said contouring belt toward the centre rod in such a manner that the belt makes a circle around said centre rod, said curved corrugation being made circular between the belt and centre rod.

Further an apparatus is disclosed for making an axial-flow filter from a flat sheet of material comprising a mould having a wavy curved surface on one side thereof which corresponds to a curved corrugation from which the axial-flow filter is made, said mould having a sloped and curved inner end, a means for fixing an end of said flat sheet with said sloped and curved inner end in such a manner that the flat sheet is curved along the inner end and slanted up continuously, a set of fixing blades located apart from the curved and slanted flat sheet, a means for moving remaining fixing blades consecutively from the one closer to said end fixing means to the one farthest from said end fixing means toward the wavy curved surface, so that said curved corrugation is made between the wavy curved surface and the fixing blades, a centre rod located close to an inner end of the curved corrugation, a contouring belt located around an outer end of the curved corrugation for embracing the same, a means for grasping each end of the contouring belt, a means for moving the grasping means along a predetermined path so that the contouring belt makes a circle round the centre rod with the curved corrugation made circular therebetween.

Claims

1. A method of making a curved corrugated sheet from a flat sheet of material using folding blades to press the sheet over undulations in a curved mould surface wherein the sheet of material is held against a curved edge of the mould surface such that it is inclined above the mould surface and the blades are advanced so as to fold the sheet initially over an undulation closest to the curved end and thereafter over successively adjacent undulations.

2. A method of making a curved corrugated sheet from a flat sheet of material comprising the steps of: applying an end of the sheet to a curved end of a mould having a curved undulating surface so that the sheet is curved and inclined with respect to the said mould surface, arranging a set of folding blades such that each blade enters between the crests of adjacent undulations when moved to the mould surface, and moving the set of folding blades toward the mould so as to engage the sheet continuously along the curved undulating mould surface such that the sheet is folded first by a blade closest to the fixed end of the sheet and thereafter by the other blades in turn.

3. A method according to claim 1 or claim 2 wherein the curved mould surface has undulations radiating outwardly from the said curved end at the inner periphery of the mould surface to an outer periphery thereof.

4. A method according to any one of claims 1 to 3 further comprising heat pressing the crests of the curved corrugations formed in the sheet.

5. A method according to any one of claims 1 to 4, further comprising heating the mould surface to set the corrugations formed in the sheet.

6. A method according to any one of claims 1 to 5 wherein the flat sheet is a fan-shaped sheet of filter material with two curved edges and two tapered side edges, one of the two curved edges being fixed to said mould.

7. A method of making an axial-flow filter comprising making a curved corrugated sheet by the method according to any one of claims 1 to 6, and shaping the curved corrugated sheet around a former engaging an inner curved edge of the sheet, so as to encircle the former.

8. A method for making an axial-flow filter comprising the steps of applying an end of a flat sheet of filter material to a curved end of a mould having a curved undulating surface so that the sheet is curved and inclined with respect to the mould surface, arranging a set of folding blades such that each blade enters between the crests of adjacent undulations when moved to the mould surface, moving the set of blades toward the mould so as to fold the sheet continuously along the curved mould surface such that the sheet is folded first by a blade closest to the fixed end of the sheet and thereafter by the other blades in turn to form a curved corrugated sheet, positioning a centre rod or former adjacent an inner curved end of the curved corrugated sheet, applying a contouring belt over an outer curved end of the curved corrugated sheet; and moving the contouring belt to encircle the centre rod or former such that the ends of the curved corrugated sheet between the belt and the centre rod or former meet to form a circle.

9. A method of making an axial-flow filter according to claim 7 or claim 8 further comprising: introducing circular teeth between the crests of adjacent undulations in the circular corrugated sheet to reshape the abutting ends thereof.

10. Apparatus for making a curved corrugated sheet from a flat sheet of material comprising a mould having a curved mould surface with undulations corresponding to corrugations to be formed in the sheet, means for holding the sheet against an inclined curved edge of the mould surface such that the sheet conforms to the curvature of the edge and is inclined above the mould surface, folding blades arranged for pressing the sheet over the undulations in the mould surface and means for advancing the blades such that the sheet is folded initially over an undulation closest to the holding means and thereafter over successively adjacent undulations.

11. An apparatus for making a curved corrugated sheet from a flat sheet of material comprising: a mould having an undulating curved surface with a sloping and curved inner end, means for holding and end of the sheet against the sloping and curved inner end such that the sheet is curved at the said inner end and inclined above the mould surface, a set of folding blades for pressing the sheet over the undulations in the mould surface, and a means for moving the blades such that the sheet is folded first by a blade closest to the holding means and subsequently by the remaining blades consecutively from the one closer to the holding means to the one farthest from the holding means toward said wavy curved surface, so that said curved corrugation is made between said wavy curved surface and said fixing blades.

12. A method according to claim 10 or claim 11 wherein the curved mould surface has undulations radiating outwardly from the said curved edge at the inner periphery of the mould surface to an outer periphery thereof.

13. Apparatus according to any one of claims 10 to 12 wherein the blades are arranged such that a blade further from the holding means is spaced further from the mould surface, and the folding blades are mounted for movement together toward the mould surface so that each successive blade is pressed down between the crests of adjacent undulations in the mould surface.

14. Apparatus according to any one of claims 10 to 13 further comprising: a set of heaters located between the fixing blades respectively for pressing the crests of corru- gations formed in the sheet and means for heating the mould surface.

15. Apparatus for making an axial-flow filter comprising apparatus according to any one of claims 10 to 14, and means for shaping the curved corrugated sheet around a former engaging an inner curved edge of the sheet so as to encircle the former.

16. Apparatus according to claim 15 wherein the shaping means comprises a contouring belt for embracing an outer curved end of a curved corrugated sheet, the inner end of which engages the former, the belt being movable to encircle the former such that the ends of a curved corrugated sheet are drawn together and meet to form a circular corrugated sheet.

17. Apparatus for making an axial-flow filter from a flat sheet of material comprising: a mould having an undulating curved surface with a sloping and curved inner end, means for holding an end of the sheet with the sloping and curved inner end such that the sheet is curved at the inner end and inclined above the mould surface, a set of folding blades for pressing the sheet over the undulations in the mould surface, a means for moving the blades such that the sheet is folded first by a blade closest to the holding means and subsequently by the remaining blades consecutively from the one closer to the holding means to the one farthest from the holding means, a centre rod or former located close to an inner end of the curved corrugated sheet, a contouring belt embracing an outer end of the curved corrugated sheet, means for moving the ends of the belt along a predetermined path so as to encircle the centre rod or former so making the curved corrugated sheet circular therebetween.

18. Apparatus according to claims 16 or 17 further 15 comprising: a supporting belt located inside of the contouring belt to mate between the crests of corrugations in the sheet and movable with the contouring belt to bend the sheet into a circular shape.

19. Apparatus according to any one of claims 15 to 18 further comprising: a reshaper having semi-circular teeth therein for engaging the circular corrugated sheet between the crests of adjacent corrugations therein so as to reshape the abutting ends of the sheet.

20. A method of making a curved corrugated sheet substantially as hereinbefore described with reference to the accompanying drawings.

21. A method of making an axial-flow filter substantially as hereinbefore described with reference to the accompanying drawings.

22. Apparatus for making a curved corrugated sheet constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 8 and 13 of the accompanying drawings.

23. Apparatus for making an axial-flow filter, constructed 10 and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.