JP6844946B2 - Heat exchanger - Google Patents

Description

The present invention relates to a heat exchanger used in an air conditioner or the like.

Conventionally, the fins (radiating plates) of the fin tube heat exchanger are provided with spacers formed by cutting out a part of the fins in order to maintain an appropriate distance between the fins (for example, Patent Document 1). reference). For example, the fin 101 shown in FIG. 10 has a plurality of fitting portions 103 to be fitted with the flat tube 102, and spacers 104 are provided at the front end portion and the rear end portion of the region whose upper and lower portions are partitioned by the fitting portion 103. I have.

FIG. 11A shows a heat exchanger 100 formed in an L shape in a plan view so as to be housed in the outdoor unit housing of the air conditioner. In this type of heat exchanger 100, the assembly process of assembling the flat heat exchanger 100 with a member coated with a brazing material on the surface and the assembled flat heat exchanger 100 are put into a furnace and brazed. It is manufactured through a brazing step and a bending step of bending the brazed flat heat exchanger 100 into an L shape.

Japanese Unexamined Patent Publication No. 2012-163318

By the way, the spacer 104 is brazed to the fins 101 whose tip ends are adjacent to each other. As shown in FIG. 11B, when the flat heat exchanger 100 is bent into an L shape, the spacer 104 is bent into an L shape. At the position inside the curved portion 105, in other words, at the position where the fin spacing is narrowed during bending, the spacer 104 does not buckle partially, and as a result, the spacing between the fins 101 is constant inside the curved portion 105. Therefore, there is a problem that the heat exchange efficiency is lowered.

Therefore, the present invention has been made in view of the above problems, and is a heat exchanger provided with a spacer formed by cutting and raising a part of fins, and is inside the curved portion after L-shaped bending. It is an object of the present invention to provide a heat exchanger capable of improving heat exchange efficiency by keeping the fin spacing constant.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 is an L-shaped heat exchanger having a curved portion, which comprises a flat tube through which a refrigerant flows and the flattened portion. The fins having a fitting portion for fitting the pipes, extending in the direction intersecting the flat pipes and being laminated in the length direction of the flat pipes, and the fins formed by cutting up a part of the fins and adjacent to each other. A first spacer that maintains a distance from the fins is provided, and the first spacer is located inside the curved portion and has a buckling portion that preferentially buckles between the tip portion and the root portion thereof. It is characterized by.
According to this configuration, the first spacer buckles inside the curved portion during the bending process after brazing, so that the fin spacing inside the curved portion can be kept constant and the heat exchange efficiency can be improved. ..

According to the second aspect of the present invention, in the heat exchanger according to the first aspect, the buckling portion has the width of the fin surface most between the tip portion of the first spacer and the root portion of the first spacer. It is characterized in that it is formed by any of a narrow narrow portion, a thin portion having the thinnest plate thickness between the tip portion of the first spacer and the root portion of the first spacer.
According to this configuration, a buckling portion that reliably buckles the spacer inside the curved portion can be obtained during the bending process after brazing.

The invention according to claim 3 is the heat exchanger according to claim 1 or 2, wherein the heat exchanger is formed by cutting out a part of the fins and maintains a distance from adjacent fins. The second spacer is further provided with two spacers, the second spacer has a notch at the tip portion, and the first spacer is arranged at a position outside the flat tube after the L-shaped bending process of the heat exchanger. The second spacer is characterized in that it is arranged at a position inside the flat tube after the L-shaped bending process of the heat exchanger.
According to this configuration, the brazing area between the tip side of the second spacer and the adjacent fin is reduced as compared with the conventional case, and the brazing area is easily removed. The tip side of the two spacers will be separated from the adjacent fins, and as a result, the distance between the fins on the outside of the curved portion can be kept constant, and the heat exchange efficiency can be improved.

The invention according to claim 4 is characterized in that, in the heat exchanger according to claim 3, the notch is formed from at least one recess in the center of the tip end portion of the second spacer. ..
According to this configuration, the brazing area between the tip side of the second spacer and the adjacent fin is symmetrically reduced. Therefore, when bending after brazing, the tip side of the spacer is adjacent to the outside of the curved portion. It can be reliably removed from the matching fins.

According to the present invention, it is a heat exchanger provided with a spacer formed by cutting and raising a part of fins, and it is possible to improve the heat exchange efficiency by keeping the distance between the fins of the curved portion constant after the L-shaped bending process. it can.

It is explanatory drawing which shows the structure of the air conditioner to which the heat exchanger which concerns on embodiment of this invention is applied. It is a perspective view of the outdoor unit to which the heat exchanger according to the embodiment of this invention is applied. It is an internal perspective view of the outdoor unit to which the heat exchanger according to the embodiment of this invention is applied. It is a figure which shows the heat exchanger which concerns on embodiment of this invention, (a) is a plan view of a heat exchanger, (b) is a front view of a heat exchanger, (c) is a side view of a heat exchanger. .. It is a side sectional view of the main part of the heat exchanger which concerns on embodiment of this invention. It is a figure which shows the outer spacer formed in the fin of the heat exchanger which concerns on embodiment of this invention, (a) is the side view of the main part of the fin which shows the outer spacer, (b) is the main part of the fin which shows the outer spacer. A partial perspective view, (c) is a sectional view taken along the line AA of the outer spacer, and (d) is a front view of a main part of the fin showing the outer spacer. It is a figure which shows the inner spacer formed in the fin of the heat exchanger which concerns on embodiment of this invention, (a) is a side view of the main part of the fin which shows an inner spacer, (b) is the main part of the fin which shows an inner spacer. A partial perspective view, (c) is a sectional view taken along line BB of the inner spacer, and (d) is a front view of a main part of the fin showing the inner spacer. It is an operation explanatory view of the inner spacer formed in the fin of the heat exchanger which concerns on embodiment of this invention, (a) is the front view of the main part of the fin which shows the inner spacer before bending process, (b) is bending process. The main part plan view of the fin showing the front inner spacer, (c) is the main part front view of the fin showing the inner spacer after bending, and (d) is the main part plan view of the fin showing the inner spacer after bending work. Is. It is a figure which shows the outer spacer which concerns on a modification, (a) is the side view of the main part of the fin which shows the outer spacer which concerns on the modification, (b) is the CC cross-sectional view of the outer spacer which concerns on the modification, (c). ) Is a front view of a main part of the fin showing the outer spacer according to the modified example. It is explanatory drawing which shows the spacer formed in the fin of the heat exchanger which concerns on the prior art. It is a figure which shows the heat exchanger which concerns on the prior art, (a) is a plan view which shows the heat exchanger before bending, and (b) is a plan view which shows the heat exchanger after bending.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the drawings. The same elements will be described with the same reference numerals throughout the description of the embodiments.

[Air conditioner]
FIG. 1 is an explanatory diagram showing a configuration of an air conditioner to which the heat exchanger according to the embodiment of the present invention is applied.
As shown in FIG. 1, the air conditioner 1 includes an indoor unit 2 and an outdoor unit 3. The indoor unit 2 is provided with an indoor heat exchanger 4, and the outdoor unit 3 is provided with a compressor 6, an expansion valve 7, a four-way valve 8 and the like in addition to the outdoor heat exchanger 5. There is.

During the heating operation, the high-temperature and high-pressure gas refrigerant discharged from the compressor 6 of the outdoor unit 3 flows into the heat exchanger 4 of the indoor unit 2 via the four-way valve 8. The high-pressure gas refrigerant that has exchanged heat with air in the heat exchanger 4 (condenser) condenses and liquefies. After that, the high-pressure liquid refrigerant is depressurized by passing through the expansion valve 7 of the outdoor unit 3, becomes a low-temperature low-pressure gas-liquid two-phase refrigerant, and flows into the heat exchanger 5. The refrigerant that has exchanged heat with the outside air in the heat exchanger 5 (evaporator) is gasified. After that, the low-pressure gas refrigerant is sucked into the compressor 6 via the four-way valve 8.

During the cooling operation, the high-temperature and high-pressure gas refrigerant discharged from the compressor 6 of the outdoor unit 3 flows into the heat exchanger 5 via the four-way valve 8. The high-pressure gas refrigerant that has exchanged heat with the outside air in the heat exchanger 5 (condenser) condenses and liquefies. After that, the high-pressure liquid refrigerant is depressurized by passing through the expansion valve 7 of the outdoor unit 3, becomes a low-temperature low-pressure gas-liquid two-phase refrigerant, and flows into the heat exchanger 4 of the indoor unit 2. The refrigerant that has exchanged heat with air in the heat exchanger 4 (evaporator) is gasified. After that, the low-pressure gas refrigerant is sucked into the compressor 6 via the four-way valve 8.

[Outdoor unit]
FIG. 2 is a perspective view of an outdoor unit to which the heat exchanger according to the embodiment of the present invention is applied.
As shown in FIG. 2, the outside of the outdoor unit 3 has a case 9 having a suction port (not shown) on the back surface and an air outlet 9a on the front surface, and a leg portion 10 provided on the lower surface portion of the case 9. A fan guard 11 that covers the air outlet 9a of the case 9 and a removable cover 14 that covers the wiring connection portion 12 and the pipe connection portion 13 are provided.

FIG. 3 is an internal perspective view of an outdoor unit to which the heat exchanger according to the embodiment of the present invention is applied.
As shown in FIG. 3, the inside of the outdoor unit 3 is divided into a machine room 16 and a heat exchange room 17 by a partition plate 15. A compressor 6 and an accumulator (not shown) are arranged in the machine room 16, and a heat exchanger 5 and a blower fan 18 are arranged in the heat exchange room 17. The heat exchanger 5 has an L-shape in a plan view along the back surface and one side surface of the case 9, and heat exchange is performed between the air sucked from the suction port on the back surface and the refrigerant by the blower fan 18.

The L-shaped heat exchanger 5 is obtained by bending a flat heat exchanger 5. Specifically, an assembly process of assembling a flat heat exchanger 5 with a member coated with a brazing material on the surface, and a brazing process of putting the assembled flat heat exchanger 5 into a furnace and brazing. The L-shaped heat exchanger 5 is manufactured through a bending step of bending the brazed flat heat exchanger 5 into an L-shape. First, the flat heat exchanger 5 will be described.

[Heat exchanger]
4A and 4B are views showing a heat exchanger according to an embodiment of the present invention, in which FIG. 4A is a top view of the heat exchanger, FIG. 4B is a front view of the heat exchanger, and FIG. 4C is a heat exchanger. It is a side view.
As shown in FIG. 4, the heat exchanger 5 extends in a direction intersecting the plurality of flat pipes 19 through which the refrigerant flows, the pair of headers 20 attached to both ends of the flat pipes 19, and the flat pipes 19 and is flat. A plurality of fins 21 laminated in the length direction of the tube 19 are provided.

FIG. 5 is a side sectional view of a main part of the heat exchanger according to the embodiment of the present invention.
As shown in FIG. 5, the flat tube 19 has a flat shape extending in the air flow direction indicated by an arrow, and a plurality of refrigerant flow paths 19a orthogonal to the air flow direction are formed therein. ..

The flat tubes 19 are arranged in parallel vertically through a gap through which air passes, and both ends thereof are connected to a pair of headers 20. For example, in the heat exchanger 5 shown in FIG. 4B, a plurality of flat tubes 19 along the left-right direction are arranged in parallel in the vertical direction via a predetermined gap, and both ends of the flat tubes 19 are connected to the header 20. doing.

The header 20 has a cylindrical shape, and inside the header 20, the refrigerant supplied to the heat exchanger 5 may flow into the plurality of flat pipes 19 in a branched manner, or the refrigerant flowing out from the plurality of flat pipes 19 may flow out. Merge.

The fins 21 have a flat plate shape extending in a direction intersecting the flat tube 19 in the front view of FIG. 5, and are laminated in parallel with a gap for air to pass in the length direction of the flat tube 19. And are arranged. For example, in the heat exchanger 5 shown in FIG. 4B, a plurality of fins 21 along the vertical direction are arranged in parallel in the horizontal direction with a predetermined gap.

As shown in FIG. 5, the fins 21 are formed with a plurality of fitting portions 21a to be fitted with the flat tube 19, and the fitting portions 21a are brazed in a state of being fitted with the flat tube 19. By attaching, the fin 21 and the flat tube 19 are integrally joined. The fitting portion 21a of the present embodiment has a notched groove shape with an opening on the windward side, but may have a punched hole shape.

[Spacer]
Next, the spacers 22 and 23 of the fins 21, which are the main parts of the present invention, will be described with reference to FIGS. 5 to 8.

FIG. 6 is a view showing an outer spacer 22 (second spacer) formed on the fin of the heat exchanger according to the embodiment of the present invention, and FIG. 6A is a side view of a main part of the fin showing the outer spacer 22. (B) is a perspective view of a main part of the fin showing the outer spacer 22, (c) is a sectional view taken along the line AA of the outer spacer 22, and (d) is a front view of the main part of the fin showing the outer spacer 22. FIG. 1 is a view showing an inner spacer 23 (first spacer) formed on the fins of the heat exchanger according to the embodiment of the present invention, and (a) is a side view of a main part of the fin showing the inner spacer 23, (b). ) Is a perspective view of a main part of the fin showing the inner spacer 23, (c) is a cross-sectional view taken along the line BB of the inner spacer 23, and (d) is a front view of the main part of the fin showing the inner spacer 23.
As shown in FIGS. 5 to 7, the fins 21 are formed by cutting out a part of the fins 21 in order to maintain an appropriate distance between adjacent fins 21 (for example, 1 mm to several mm). Types of spacers 22 and 23 are provided.

The outer spacer 22 is provided at a position outside the curved portion when the flat heat exchanger 5 is bent into an L shape, in other words, at a position where the fin spacing is widened during the bending process. The outer spacer 22 is provided on the front end side (windward side) of the region where the upper and lower parts are partitioned by the fitting portion 21a.

The inner spacer 23 is provided at a position inside the curved portion when the flat heat exchanger 5 is bent into an L shape, in other words, at a position where the fin spacing is narrowed during the bending process. An inner spacer 23 is provided on the rear end side (leeward side) of the region where the upper and lower parts are partitioned by the fitting portion 21a. The positions and numbers of spacers 22 and 23 can be appropriately changed.

The spacers 22 and 23 can maintain an appropriate distance between the fins 21 by abutting the tip surfaces thereof on the surfaces of the adjacent fins 21. On the other hand, when the spacers 22 and 23 are fitted into the cut-up holes 24 and 25 of the adjacent fins 21, not only the distance between the fins 21 cannot be maintained properly, but also the subsequent correction takes time, so that the spacers 22 and 23 are cut. It is required to prevent the spacers 22 and 23 from being fitted into the raising holes 24 and 25.

As shown in FIGS. 6 and 7, the spacers 22 and 23 of the present embodiment have the first sides 22a and 23a (width dimensions W1 and W3) on the root side and the second sides 22b and 23b (width dimensions) on the tip side. W2, W4) and the opposite side sides 22c, 23c connecting the end points of the first sides 22a, 23a and the end points of the second sides 22b, 23b are provided, and the second side is provided with respect to the first side 22a, 23a. By lengthening the 22b and 23b, the fitting of the adjacent fins 21 into the cut-up holes 24 and 25 is suppressed. Hereinafter, the differences between the outer spacer 22 and the inner spacer 23 will be described in detail.

[Outer spacer 22]
As shown in FIG. 6, the outer spacer 22 has a first side 22a (width dimension W1) on the root side, a second side 22b (width dimension W2) longer than the first side 22b on the tip side, and a first side. It has opposite side sides 22c that linearly connect the end points of 22a and the end points of the second side 22b, and is basically inverted trapezoidal, but at the tip of the outer spacer 22 (second side 22b). Is formed with a notch 22d.

The notch 22d is for reducing the contact area with the adjacent fins 21 on the second side 22b of the outer spacer 22. That is, according to such a notch 22d, when the heat exchanger 5 is brazed and then bent, the brazing area of the outer spacer 22 provided at a position outside the curved portion with respect to the adjacent fins 21 is determined. Since it is reduced and the brazing peeling load (tensile load) is reduced and it becomes easy to come off, the fins 21 in which the second side 22b of the outer spacer 22 provided at the position outside the curved portion 105 is adjacent to each other during bending. As a result, it becomes possible to keep the distance between the fins 21 on the outside of the curved portion constant.

The notch 22d provided in the outer spacer 22 of the present embodiment is formed from one recess (for example, an inverted trapezoidal recess) at the center of the second side 22b. According to such a notch 22d, the height of the outer spacer 22 in which the brazing area between the tip portion (second side 22b) of the outer spacer 22 and the adjacent fin 21 passes through the center of the tip portion (second side 22b). It is reduced symmetrically with respect to the straight line M parallel to the brazing direction. As a result, in the bending process after brazing, the tip end side of the outer spacer 22 can be reliably removed from the adjacent fins 21 on the outside of the curved portion 105.

[Inner spacer 23]
As shown in FIG. 7, the inner spacer 23 includes a first side 23a (width dimension W3) on the root side and a second side 23b (width dimension W4) longer than the first side 23b on the tip side. Although it is common with the outer spacer 22, it differs from the outer spacer 22 in that it has a buckling portion 23d that buckles by an external force between the first side 23a (root portion) and the second side 23b (tip portion).

FIG. 8 is an explanatory view of the operation of the inner spacer formed on the fin of the heat exchanger according to the embodiment of the present invention before and after bending the heat exchanger, and FIG. 8A is a fin showing the inner spacer before bending. (B) is a plan view of the main part of the fin showing the inner spacer before bending, (c) is a front view of the main part of the fin showing the inner spacer after bending, and (d) is a bending work. It is a main part plan view of the fin which shows the rear inner spacer.
As shown in FIG. 8, the buckling portion 23d buckles between the first side 23a and the second side 23b when a buckling load is applied to the inner spacer 23. That is, according to such a buckling portion 23d, at the time of bending after brazing the heat exchanger 5, as shown in FIGS. 8 (c) and 8 (d), the position is inside the curved portion 105. The inner spacers 23 provided in the above will buckle without detaching from the adjacent fins 21, and as a result, the distance between the fins 21 inside the curved portion 105 can be made constant.

As shown in FIGS. 7 and 8, the buckling portion 23d provided on the inner spacer 23 of the present embodiment is narrowed down to be narrower than the first side 23a and the second side 23b, and the width of the inner spacer 23 is the narrowest. It is formed by a narrow portion (a portion having a width dimension W5). Specifically, the side side 23c of the inner spacer 23 has a first side side 23e that rises vertically from the cut end of the first side 23a and a second side that bends inward at a right angle from the tip of the first side side 23e. It is provided with a side side 23f and a third side side 23g that extends from the inner end of the second side side 23f so as to extend outward and reaches the end point of the second side 23b. A narrow portion (portion having a width dimension W5) serving as a buckling portion 23d is formed between 23f and the third side side 23g. According to such a buckling portion 23d, when the heat exchanger 5 is brazed and then bent, the inner spacer 23 provided at a position inside the curved portion is buckled along the virtual buckling line L. It becomes possible to make it.

The buckling portion 23d of the present embodiment is narrowed down to be narrower than the first side 23a and the second side 23b and is formed by the narrowest narrow portion of the inner spacer 23. A buckling portion is formed by a thin portion having a thin plate thickness along the virtual buckling line L instead of the narrow portion having the narrowest spacer surface width along the virtual buckling line L perpendicular to the height direction. May be good. Specifically, a hole or a thin wall portion is provided on the surface of the spacer along the virtual buckling line, or a groove (V cut or the like) is provided on the side 23c along the virtual buckling line L. May be good.

According to the embodiment of the present invention described above, the heat exchanger 5 has a flat pipe 19 through which a refrigerant flows and a fitting portion 21a for fitting the flat pipe 19 and intersects the flat pipe 19. The outer spacer 22 and the inner spacer 23 are formed by cutting out a part of the fins 21 and are formed by cutting out a part of the fins 21 and are formed so as to maintain a distance between the plurality of fins 21 extending in the direction and being laminated in the length direction of the flat tube 19. And, since the notch 22d is provided at the tip of the outer spacer 22, the brazing area between the tip side of the outer spacer 22 and the adjacent fin 21 is reduced as compared with the conventional case. Therefore, during the bending process after brazing, the tip end side of the outer spacer 22 is separated from the adjacent fins 21 on the outside of the curved portion 105, and as a result, the distance between the fins 21 on the outside of the curved portion 105 is kept constant. , The heat exchange efficiency can be improved.

Further, since the notch 22d of the present embodiment is formed from at least one recess in the center of the tip portion (second side 22b) of the outer spacer 22, the notch 22d and the tip portion (second side 22b) of the outer spacer 22 are formed. The brazing area with the adjacent fins 22 is reduced symmetrically with respect to a straight line passing through the center of the tip portion (second side 22b) and parallel to the height direction of the outer spacer 22, and as a result, brazing. In the subsequent bending process, on the outside of the curved portion 105, the tip end side of the outer spacer 22 can be reliably removed from the adjacent fins 21.

Since the inner spacer 23 has a buckling portion 23d between the second side 23b (tip portion) and the first side 23a (root portion), the inner spacer 105 is inside the curved portion 105 during bending after brazing. The spacer 23 buckles without detaching from the fins 21, and as a result, the distance between the fins 21 inside the curved portion 105 can be kept constant and the heat exchange efficiency can be improved.

[Modification example]
Next, a modified example of the outer spacer 22 will be described with reference to FIG. However, the description of the embodiment is incorporated by using the same reference numerals as those of the embodiment for the parts common to the embodiment.

9A and 9B are views showing the outer spacer according to the modified example, FIG. 9A is a side view of a main part of the fin showing the outer spacer according to the modified example, and FIG. 9B is a CC cross section of the outer spacer according to the modified example. FIG. 3C is a front view of a main part of a fin showing an outer spacer according to a modified example.
As shown in FIG. 9, the outer spacer 22B according to the modified example is different from the outer spacer 22 of the embodiment in that the second side 22b of the tip portion is provided with notches 22e formed from a plurality of recesses. There is. Specifically, the second side 22b of the outer spacer 22B is provided with a notch 22e formed by arranging four triangular recesses. According to such a notch 22e, it is possible to reduce the brazing area with the adjacent fins 21 without deteriorating the function and strength as a spacer.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and modifications are made within the scope of the gist of the present invention described in the claims. It can be changed.

1 ... Air conditioner, 2 ... Indoor unit, 3 ... Outdoor unit, 4 ... Heat exchanger, 5 ... Heat exchanger, 6 ... Compressor, 7 ... Expansion valve, 8 ... Four-way valve, 9 ... Case, 9a ... Blowing Outlet, 10 ... Leg, 11 ... Fan guard, 12 ... Wiring connection, 13 ... Piping connection, 14 ... Cover, 15 ... Partition plate, 16 ... Machine room, 17 ... Heat exchange room, 18 ... Blower fan, 19 ... Flat pipe, 19a ... Refrigerant flow path, 20 ... Header, 21 ... Fins, 21a ... Fitting part, 22, 22B ... Outer spacer, 22a ... First side, 22b ... Second side, 22c ... Side side, 22d, 22e ... notch, 23 ... inner spacer, 23a ... first side, 23b ... second side, 23c ... side side, 23d ... buckling part, 23e ... first side side, 23f ... second side side, 23g ... second 3 side sides, 24, 25 ... cut-up hole, L ... virtual buckling line

Claims (4)

An L-shaped heat exchanger with a curved portion,
A flat pipe through which the refrigerant flows and
A plurality of fins having a fitting portion for fitting the flat tube, extending in a direction intersecting the flat tube, and being laminated in the length direction of the flat tube.
A first spacer formed by cutting and raising a part of the fins and maintaining a distance from the adjacent fins is provided.
The first spacer has a buckling portion that preferentially buckles between the tip portion and the root portion, and when the first spacer is placed inside the curved portion, the buckling portion is in a bent state. A heat exchanger characterized in that it takes a second posture in which the buckling portion is not bent when it is located at a position other than the curved portion. The buckling portion is a narrow portion having the narrowest fin surface width between the tip portion of the first spacer and the root portion of the first spacer, the tip portion of the first spacer and the root portion of the first spacer. The heat exchanger according to claim 1 , wherein the heat exchanger is formed by any of the thinnest portions between the two. The heat exchanger includes a second spacer formed by cutting a part of the fins to maintain a distance from adjacent fins.
The first spacer has a notch at the tip of the second spacer, and the first spacer is arranged at a position inside the flat tube after the L-shaped bending process of the heat exchanger, and the second spacer has the heat. The heat exchanger according to claim 1 or 2, wherein the heat exchanger is arranged at a position outside the flat tube after the L-shaped bending process of the exchanger. The heat exchanger according to claim 3, wherein the notch is formed from at least one recess in the center of the tip of the second spacer.

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