JPH055525B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method for holding successive folds, or accordion-folded folds, of high-efficiency air filter media a predetermined distance apart. It relates to a method of manufacturing a generally used type of tapered wave spacer member, in particular a method of manufacturing a tapered corrugated spacer member which is folded in a zigzag manner along parallel lines and has a larger number of V-shaped portions over a constant width at one end edge of the sheet than in the past. The present invention relates to a method of manufacturing a spacer member having a novel shape.

(Technical background of the invention and its problems) In high-efficiency air filters that are generally commercially available, the filter medium is folded in an accordion shape to form a continuous V-shaped bent body, and the outer periphery is open. It is sealed in a rectangular frame. The distance between the surfaces of adjacent bent bodies is set to a maximum value of 0.2 inch (approximately 5 mm) or less at the open end,
Further, the bent bodies are arranged to gradually come together toward the closed end. As a result, it is necessary to place spacer means between adjacent walls of each medium in order to maximize the volume of airflow through the filter and minimize the pressure drop to meet the required efficiency level.

In such filters, corrugated sheets of aluminum or other materials tapered from one edge to the other have been used for many years to provide the required spacing between the media folds. It has been used for a long time. For example, U.S. Pat.
Similar disclosures are found in US Pat. No. 3,146,197 and Barany U.S. Pat. No. 3,293,833. The present invention is most closely related to the latter patent, and relates to an improvement that reduces the degree of taper and reduces the amplitude, as described below.

The amplitude ratio, that is, V passing through the continuous bending line on each side
The straight line distance between parallel lines extending in the lateral direction of the spacer member along the two edges forming the character-shaped portion is:
It is the same as the ratio of the number of V-shaped parts within a certain width on both ends. In other words, when forming three V-shaped parts on one end edge corresponding to one V-shaped part on the other end edge, the height of the edge with a small amplitude is adjusted to keep the folded lines parallel. will be one third of the height on the large amplitude side. Similarly, if five V-shaped parts are formed on the small-amplitude side edge corresponding to one V-shaped part on the large-amplitude side edge, the ratio of both amplitudes and the V-shaped part within a certain linear distance The number of glyphs is 5:1.

5:1 in such type of tapered separator
It has long been recognized that a ratio of 3 to 1 is useful, and Barany's U.S. Pat.
No. 3,293,833 mentions that the ratio is preferably any odd number. However, it has been virtually impossible to manufacture suitable spacers with shaping rollers and blades having a ratio greater than 3 to 1 as disclosed in that patent. That is, as suggested by commonly assigned U.S. Pat. No. 3,293,833 and related U.S. Pat. No. 3,311,526, which includes a preferred embodiment of a spacer manufacturing apparatus, the number of small amplitude molded blades on each side of a large amplitude blade may be reduced. It is possible to change this ratio by simply increasing it, but attempting this in manufacturing a spacer with large amplitude bends over the required size range would result in numerous fractures and fractures along the small amplitude side edges. A crack occurred. Such fractured or cracked spacers cannot be used because the jagged sharp edges tear or puncture the filter media, rendering the entire filter assembly unacceptable.

Furthermore, in order to provide a spacer with the required rigidity and anti-flattening properties after forming the V-shaped portion, an aluminum sheet having the minimum necessary hardness to cause virtually no fracture or cracking in the formed spacer is used. It is preferable to use In the past, it has been considered inappropriate to manufacture spacers with a 5:1 taper ratio, even when using soft aluminum that can be stretched without fracture.

It is desirable that the amplitude ratio of the spacer be increased from the high side end to the low side end, and it is also desirable that the taper be as uniform as possible from one side to the other side. The V-shaped portion extending over the entire spacer from one end to the other, that is, the folded line included in the large-amplitude side edge forms such a gentle taper, while the intermediate V-shaped portion at the small-amplitude side edge forms such a gentle taper. The fold lines forming the section do not extend completely to the large amplitude side edge even when the large amplitude V-shaped section continues. In the end, in order to maximize equalization and make the taper gentler, the folding line forming the intermediate folding curve should be extended to a portion corresponding to approximately 90% of the distance between the small amplitude edge and the large amplitude edge on the small amplitude edge side. It needs to be extended.

The spacer disclosed in the above-mentioned U.S. Pat. No. 3,293,833, particularly in FIG.
However, in the case of spacers that have actually been provided on the market over the past 20 years, the intermediate bending curve is approximately 30% longer than the distance between the small amplitude side edge and the large amplitude side edge. It was not possible to obtain a shape extending over 50% or more.

Therefore, in the corrugated aluminum spacer,
It has long been recognized that it is useful and desirable to taper the amplitude at one end to a desired amplitude while reducing the amplitude at the other end by about a factor of five. However, no suitable spacer of this type has ever been manufactured on a commercial scale by passing an aluminum sheet between the forming blades of a pair of rotating rollers, and then interlocking and folding the sheets. . or,
Conventionally, in actual machines, it has not been possible to obtain a desired high-hardness spacer and an intermediate fold curve that extends from the small amplitude side edge to the large amplitude side edge over about 90% of the distance between the former edge.

OBJECTS OF THE INVENTION The primary object of the present invention is to maintain the continuous pleats apart at both the upstream and downstream open ends, and to provide a greater distance from the open end to the closed end than similar prior art. It is an object of the present invention to provide a method for manufacturing a corrugated spacer for use in a high-efficiency air filter of the type made of an accordion-shaped folded medium, which has a more uniform taper leading to an angular bent part.

Another principal object of the invention is to provide a continuous V-shaped portion having a uniform width and amplitude along one edge and having a width and amplitude substantially equal to that of said V-shaped portion along an opposite edge. 1/1, and the amplitude is 0.03 to
To provide a new method for manufacturing a corrugated aluminum sheet product which is folded in a zigzag shape along substantially parallel fold lines to provide a V-shaped portion of about 0.04 inch (approximately 0.76 to 1.02 mm). be.

Another object of the present invention is to pass an aluminum sheet between the forming blades of rotating rollers and fold the sheet without a significant number of cracks, tears or breaks after forming, thereby reducing the size of the spacer compared to conventional spacers. An object of the present invention is to provide a method for manufacturing a corrugated aluminum spacer for an accordion-shaped air filter, which is provided with an amplitude bend.

Yet another object of the present invention is to have an amplitude ratio of 5:1 from the high end to the low end, such that the folded line forming the intermediate V-shaped portion at the low amplitude end extends the entire distance toward the high amplitude end. The object of the present invention is to provide a method for manufacturing a zigzag bent spacer of the type mentioned above, which has a substantially uniform taper extending over about 90 percent of the length of the spacer.

Other purposes will become apparent from the description below.

SUMMARY OF THE INVENTION In the novel filter structure and spacer configuration of the present invention, the foregoing objects are achieved by the use of a forming blade of a rotating roller through which an aluminum sheet passes, the blade having a longitudinal edge. one side is highly polished and contacts the sheet to form fold lines therein. A preferred finish for the blade edge is lap sanding to 4 to 8 microinches (approximately 0.101 to 0.204 micrometers), i.e., the surface roughness of the polished area of the blade surface is no more than 4 to 8 microinches. . The aluminum sheet is preferably initially fed from a continuous roll and is formed into a zigzag shape along two longitudinal edges with fold lines substantially parallel to each other and to the other two edges. For every zigzag bent part or V-shaped part along one end edge of these two longitudinal edges, a total of five such V-shaped parts are provided along the other end edge. Therefore, the height or amplitude of the V-shaped portion along one edge is five times the height of the V-shaped portion along the other edge.
The folding lines forming the V-shaped portion along one edge extend completely to the other edge, and the folding lines forming the four auxiliary V-shaped portions extend from the other edge toward the one edge at both ends. Extends approximately 90 percent of the edge-to-edge distance. The material of the spacer is approximately 1 to 2 mil (approximately 25.4
50.8 micrometers) thick, preferably
0.0015 inches (38.1 micrometers) thick, with an amplitude of approximately 0.3 to 0.4 inches (approximately 7.6 to 7.6 micrometers) at the small amplitude end.
10.2 mm) and a hardness of H19, such as 1145 aluminum.

A spacer manufactured in accordance with the present invention and having the shape and characteristics described above is disposed in sequence between each fold of the accordion-shaped folded filter medium. The amplitude at the low end of the spacer is one-fifth of the amplitude at the high end instead of one-third as in the best prior art.
, so that the closed end of the media folded around the small amplitude side end of the spacer extends to a more angular bend than in conventional filter assemblies of the same type. Also, the shape of the pleated walls or flanks of the media is more flattened, thereby reducing the pressure drop through the media while maintaining the same efficiency and flow rate.

(Embodiments of the invention) Hereinafter, embodiments of the invention will be described with reference to the drawings.

In FIG. 1, a filter device or cartridge is indicated generally by the numeral 10 and is representative of the type of high efficiency air filter that has been in widespread commercial use for many years. It is. The filter 10 includes a frame, and the frame includes solid flat side plates 12, 1 made of wood or metal.
4, 16 and 18, forming a box shape with an open end. A continuous sheet made of a conventional filter medium and folded into an accordion shape is disposed in a sealable manner within the frame, forming a plurality of pleats extending in the front-rear direction between both open ends of the frame. . The pleated medium terminates at 20,22.

Pleated sides or flanks, indicated at 24, extend from the edge 20 to a fold 26 and are closely or sealably secured to the inner surface of the frame side plate 12. The pleated sides extending from the terminal edge 22 are similarly sealed to the frame side plate 16.
In a preferred and effective manner, the zigzag side edges of the media extending throughout the depth of the filter
For example, it is sealed to frame side plates 14 and 18 in accordance with the teachings of commonly assigned U.S. Pat. Such side edges are made of adhesive material and are marked 2.
It is embedded in the adhesive layer indicated by 8 and 30.

One or more of the above filter devices are placed within an opening in a wall, ceiling or other solid barrier with suitable airtight sealing means interposed between the filter frame and the filter frame.

Unfiltered air enters the filter from upstream, as indicated by arrow 32, to be filtered, and passes downstream, as indicated by arrow 34. Air flows between the pleats of the filter medium that open on the upstream side, passes through the pleat sides, and flows out between the pleat folds that open on the downstream side. The above is the same as the conventional configuration.

In order to maintain the desired shape of the walls of the pleated media, that is, a shape that gradually tapers from the open end to the closed end, the wave height of the corrugated sheet is increased along one edge of the sheet and decreased at the other end. It has been standard practice in industry for many years to place the sheet between each pleat of the medium. FIG. 1 shows a corrugated sheet constructed as will be described in detail below, which sheet is inserted between upstream-opening pleats indicated at 36 and downstream-opening at 38. It is inserted between the pleats shown. In FIG. 1, the spacer is shown exaggerated in size relative to the overall filter assembly for clarity of construction. In reality, for a filter assembly with a total height of 22.5 inches (approximately 57 cm), 90 to 110 pleats with typical specifications are provided, and each pleat has two pleats, one upstream and the other downstream.
Two spacers are provided. Further, the number of zigzag-shaped bent portions at the edge of one of these spacers having a large wave height is not about 12 as shown in the figure, but is actually about 50.

The structure of the spacer will be described in detail with reference to FIGS. 2 and 3. In the preferred spacer manufacturing method, a continuous strip 40 of flat aluminum sheet is fed between a pair of spaced apart rotating rollers. One roller is designated at 42 in FIG. 2, and both rollers have radially projecting and axially extending shaped blade portions, as will be explained in more detail below. According to the conventional configuration, the sheet ends are formed at edges 48, 50 before being introduced into the forming rollers.
It is folded as shown in the figure to provide a so-called "safe edge." When the aluminum sheet leaves the forming roller, it is folded in a zigzag pattern, with the fold line perpendicular to the sheet transport direction indicated by arrow 44 in FIG. After passing through the rollers, the folded sheet is cut to a required length corresponding to the width dimension of the filter assembly to be used.

As is clear from FIG. 2, both end edges 48, 50
Four auxiliary folding lines 52 are interposed between the folding lines 46 extending over the entire distance. The folding line 52
extends from edge 50 to edge 48 for a distance of approximately 90 percent of the distance between the edges, and blends into the sheet surface at its end. The details of the edge 48 of one zigzag bent portion are shown in an enlarged scale in FIG. 3, and the side of the edge 50 is shown superimposed over the same width dimension. In the figure, folding lines 46 appear on both edges, and four folding lines 52 appear on the edge 50 side at every interval of the folding lines 46. As a result, on the edge 50 side, five zigzag bent portions are provided within the same width dimension as one bent portion on the edge 48 side. The linear distance of one entire zigzag bend along edge 48 is indicated by dimension W. On the other hand, the width of one zigzag bent portion along the edge 50 is indicated by w. Further, the heights, that is, the amplitudes of the zigzag bent portions along both end edges 48 and 50 are indicated by dimensions H and h, respectively.

The length of the spacer member over one zigzag-shaped bend along the edge 48, that is, the length measured along the path from the fold line 46 to the fold line 46'' via the fold line 46' in FIG. It is called "length". Importantly, the length of one entire zigzag fold at edge 48 should be exactly the same as the length of five zigzag folds at edge 50 as shown. Therefore, the angles of the bent portions along the two edges are set to be slightly different. For example, the angle A of the large amplitude bend is approximately 110
degree, the angle a of the small amplitude bend is approximately 91 degrees.

The cooperation between the film media and the spacers will be clear from FIGS. 4 and 5. First, the air flows through the high-amplitude zigzag bend of the spacer 36 between the media surface upstream of the filter device 10 and the pleats of the media that open upstream of the filter device 36, as shown by arrow 54. It flows into the triangular passageway between. After passing through the wall of the filter medium, the air exits via a passage between the medium wall and the spacer 38 opening downstream, as indicated by arrow 56. The filter medium is folded around the spacer at the low amplitude edge 50. The bends of the upstream and downstream media are designated 58 and 60, respectively. As shown in enlarged detail in FIG. 4A, both ends of the bent portion of the medium are provided in a square shape. Note that it has been found that such a shape is preferable compared to an acute bent part. Both height and width are 24 inches (approximately 60 cm)
For a typical filter device with external dimensions of 12 inches (approximately 30 cm) deep, 22.
Preferably, there are 105 pleats within a 5 inch dimension. Such a filter device has a thickness of approximately 0.015 inch (approximately 0.4 mm) and an external dimension of 3/32 inch (approximately 2.4 mm) at the bent end.
It is preferred to use a filter medium of . As previously mentioned, the amplitude at the lower end of the spacer shown in Figure 4A is 0.03 to 0.04 inches (approximately 0.7 to 1 mm), typically 0.036 inches (approximately 0.9 mm), and this is shown as dimension h in Figure 3. Indicated. Therefore, the external dimension of the filter medium at the bent end is set to be approximately 2.6 times h as shown in FIG. 4A. Since the thickness of the medium at the lower end is approximately half the amplitude of the zigzag bend (0.5h), the space between the medium and both spacers is approximately 1.5h in total at the bent end.
The pleated portion of the medium is in contact with the spacer over a short distance from the bent end.

The forming blade and forming roller will be described in detail with reference to FIGS. 6 to 9. A roller 62 is disposed directly opposite the roller 42 and rotatable about an axis parallel to the roller 62 . roller 42,
62 is identical in all respects and includes a forming blade supported on rollers. The blade is disposed in a groove formed on the outer periphery of the roller parallel to the roller axis to support the blade. Regarding the arrangement of such blades and the rotatable arrangement and driving of rollers, see the aforementioned US Pat. No. 3,311,562. However, in the present invention, the shaped blades include a first predetermined shape blade 64, a second predetermined shape blade 66, and a first predetermined shape blade 64 formed into three unique shapes shown separately in FIGS. 8a, 8b, and 8c. It consists of a third blade 68 having a predetermined shape.

The folding lines formed on the spacer, including the amplitude and period of the folding lines that give the final shape of the spacer, are determined according to the blade shape and the distance between the axes of the rollers. Then, by the blade 64, as shown in FIG.
A folding line 46 is formed that extends all the way from one side to the other side of the spacer as shown in FIG. blade 6
6 are arranged on both sides of the blade 64, and the blade 6
Adjacent two of the blades 66 are located between each pair of blades 66. The blades and rollers shown in Figures 6 to 9 have a high amplitude dimension (g) of 0.165 inch (approximately 4 mm) and a small amplitude dimension (h) of 0.036 inch (approximately 0.9 mm).
mm), angles A and a are 109°33' and 90°20', respectively;
The period (W) of one V-shaped part at the high amplitude side edge is 0.48
inch (approximately 12 mm), the period (w) at the edge of the small amplitude side is
It is designed for use in manufacturing 0.090 inch (approximately 2.3 mm) spacers.

In order to form a V-shaped portion with the same amplitude along the edge 50, the shapes of the three types of blades 64, 66 and 68 have a height at one end (a first height) as shown in FIGS. 7 and 8. The dimensions a1 and b shown in Figure 8
1 and c1) are all the same, and the lower edges of the blades 64, 66, and 68 (as shown in FIG. Since the lower end edge in the longitudinal direction shown in FIG.
It protrudes over the same distance from the outer periphery of No. 2. In addition, as shown in FIG. 8, three types of blades 64,
Total length in the longitudinal direction of the upper edges of 66 and 68 l1, lb
and lc are the same (la=lb=lc). To form a high amplitude (height H in FIG. 3) V along the edge 48 of the spacer, the blade 64 is extended from one end 64 ₁ (first height a1) as shown in FIG. 8a. It is evenly tapered to the other end 64 ₂ to a larger height (second height a2). On the other hand, as shown in FIG. 8b, the blade 66 has a constant height (first height b1) from one end ₆₆₁ to a portion ₆₆₂ that is about 80% of the total length in the longitudinal direction of the upper edge of the blade.
from this part 66 ₂ to the other end 66 ₃ of the smaller height (third height b2) (20 of the remaining total length).
percent) tapered. Also, 8th c.
As shown in the figure, the blade 68 has one end 68 ₁ (first
A portion 68 ₂ (first height c
A tapered portion forming a first angle (for example, 0°18') is provided to a fourth height (c2) smaller than 1, and further from this portion ₆₈₂ to a smaller height (fifth height c3).
It is tapered to the other end ₆₈₃ (the remaining 20 percent) at a second angle (eg, 1°17') that is greater than the first angle. And the blade 66,
68, about 20% of the total length in the longitudinal direction of the upper edge toward the large amplitude edge (part 66 ₂ to the other end 6
As shown in FIG. ₂ , the folding line 52 is assimilated into the sheet surface 12 from the edge ₄₈ to approximately 10% of the total width of the spacer _, as shown in FIG. can be done. As shown in FIG.
The rollers are aligned in the rotational direction so that they are located at the closest position between the rollers 8 and 8.

The shapes of the three types of blades 64, 66, and 68 are such that the blades 66, 68 have approximately 20% of the total length in the longitudinal direction of one edge of the blade at one end (between part 66 ₂ and the other end 66 ₃ , and between part 68 ₂ and the other end). end 68
They all have the same cross-section except that they are strongly tapered over a length of ₃ mm, and their preferred shape is shown in FIG. The blade is 0.010 inches (approximately 0.25 mm) at a 45° angle from the parallel sides as shown.
and each side of the taper smoothly transitions to a parallel side at a radius of 3/16 inch (approximately 4.8 mm). For a blade with the geometry described above, the preferred roller diameter is 2.855 inches. A groove with a width (blade thickness) of 0.047 inches (approximately 1.2 mm) and a depth of 0.177 inches (approximately 4.5 mm) is formed on the roller along its axial length. If the groove spacing is set to 3°36', 100 grooves will be provided, and 20 blades 64 and 40 blades 66, 68 each.
is held within the groove. These blades are retained in a known manner by removable end caps, allowing them to be replaced individually in the event of wear or damage. The distance between the axes of the rollers is the same as that used in a filter device having 105 medium pleats in a length of 22.5 inches (approx. inch (approximately 4 mm), and the small amplitude value is 0.036 inch (approximately 0.9
mm)), it is set to 3.055 inches (approximately 78 mm). The dimension of the spacer can be changed between a slightly larger amplitude and a slightly smaller amplitude by adjusting the distance between the axes, and is suitable for a filter device having, for example, 90 to 110 filter medium bends. is provided.

An important feature is that all blade surfaces in contact with the aluminum sheet are ground, e.g.
Finished with an accuracy of 0.204 micrometers).
This allows a 1.5 mil (approximately 38 micrometer) thick sheet of acceptable hardness to be approximately 0.035 mm thick without cracking or breaking.
It becomes possible to manufacture spacers with a taper as small as an inch (approximately 0.9 mm).

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of an air filter assembly using a spacer formed by the method of the present invention, and FIG. 2 is a bending process for forming a tapered spacer of the filter assembly of FIG. 1. 3 is a plan view of the aluminum sheet or aluminum film strip in FIG. 3, and FIG. 4 is a partially enlarged view of a spacer formed as shown in FIG. 1, FIG. 4A is a partially enlarged view of FIG. 4, FIG. 5 is a partially enlarged perspective view of the filter medium and spacer, and FIGS. 6 and 7. The figures are enlarged sectional views of the forming blade and roller taken along lines 6-6 and 7-7 in Figure 2, respectively, and Figures 8a, 8b and 8c are used for the rollers in Figures 6 and 7. FIG. 9 is a side view showing three types of shaped blades, and FIG. 9 is a partially enlarged end view showing each blade in detail. 10... Filter, 36... Spacer, 42, 62
...Roller, 46, 46', 46''...Folding line, 48,
50... Opposing edge, 52... Auxiliary folding line, 58, 60
...Folded portion of medium, 64, 66, 68...Blade.

Claims (1)

Claims: 1. From an aluminum sheet about 1 to 2 mils (about 25.4 to 50.8 micrometers) thick, folded in a zigzag pattern and having a series of V-shaped sections along each of its longitudinal edges. all the folding lines are substantially parallel to each other and perpendicular to the longitudinal edges, and the number of V-shaped portions within a certain distance along the first edges of the longitudinal edges is The fold line is one-fifth of the number within the certain distance along the two edge edges, and the fold line forming the V-shaped portion along the first edge extends entirely between the first and second edge edges. Manufacturing a corrugated spacer for a bent air filter, wherein a folded line extending and forming an auxiliary V-shaped portion along the second edge extends a predetermined distance from the second edge toward the first edge. In the method, (a) a plurality of elongated molded blades having first, second, and third predetermined shapes are provided, and (b) one of the longitudinal edges of each of the blades and an adjacent portion thereof are (c) a pair of cylindrical rollers with a surface roughness of 4 to 8 inches (approximately 0.101 to 0.204 micrometers); (d) Attach the other of both ends along the longitudinal direction to grooves formed at the same depth and at equal intervals on the outer periphery of the roller;
All of the edges of the blades along the one longitudinal direction are formed at one end at the same first height from the edge of the other longitudinal direction, and (e) the first predetermined shaped blade has: An edge along the one longitudinal direction of the blade is evenly tapered from the one end to the other end, and a second height greater than the first height from the edge along the other longitudinal direction at the other end. (f) the blade having the second predetermined shape is formed such that the one longitudinal edge of the blade is about 75 to 80% of the length of the longitudinal edge from the one end to the second predetermined shape; are formed parallel to each other at the first height up to the section and taper from the section toward the other end, where the edge along the one longitudinal direction extends from the edge along the other longitudinal direction. formed at a third height smaller than the first height, (g)
The third blade having a predetermined shape has an edge along the one longitudinal direction of the blade at a first angle from the one end to a portion of about 75 to 80 percent of the length of the edge along the longitudinal direction. tapered, and in the region, the one longitudinal edge is formed at a fourth height smaller than the first height from the other longitudinal edge, and larger than the first angle. tapered from the portion to the other end at a second angle, and at the other end, is formed at a fifth height smaller than the first height from an edge along the other longitudinal direction; one blade having a predetermined shape is arranged between two blades having a second predetermined shape, and each blade having a second predetermined shape is interposed between the two blades having a predetermined shape.
(i ) The pair of rollers are disposed so as to be rotatable about parallel shafts, and the axes of the pair of rollers are located on a straight line passing through the axes of the pair of rollers, and these rollers are sandwiched between the axes of the pair of rollers. The two blades facing each other are linearly separated by a distance that is less than half the distance between the protruding edges from the peripheral surface of the roller, and further, the pair of rollers rotate at the same speed and in opposite directions when viewed from the same end side. when the blade of the first predetermined shape provided on one of the pair of rollers passes between two adjacent blades of the third predetermined shape provided on the other of the pair of rollers. (j) the sheet passes between the rotating rollers according to the linear distance between the axes of the pair of rollers, the angular spacing of each blade, and the first to third predetermined shapes; A method of manufacturing a corrugated spacer for a folded air filter, characterized in that the V-shaped portion is formed in the sheet when it comes into contact with the one longitudinal edge of the blade. 2. The method of manufacturing a corrugated spacer according to claim 1, wherein the finishing is performed by lap finishing.