Fireproofing of building joints

Abstract

To provide a fire prevention structure for building joints which can be closed and held by easy work of press-fitting and engaging, and which can delay carbonization and combustion by sealing and closing both the joint through-hole and the upper and lower through-slits of a notched part without any gap due to thermal expansion in the case of a fire and without fear of falling off even if a wood member is thin, and which is extremely excellent in workability and fire prevention performance.SOLUTION: A fire-prevention structure of a building joint is constructed such that a joint through-hole 5 of a notch part 4, in which a column 1 and a transverse member 2 are connected and joined by a joint fitting 3, and an upper and a lower through-slits 12 are held in a closed state by press-fitting a joint blockage member 7 made of a thermally expandable refractory material, and both are held in a sealed closed state by thermal expansion in the event of a fire to delay carbonization and combustion.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fire prevention structure for joints in buildings, in which upper and lower through holes (joint through holes) formed in the joint parts (cutout parts) of cross members (beams) joined to columns by metal fittings, are blocked with a blocking fire-resistant material (joint blocking member) to slow down heat transfer (spread of fire) through these joint through holes in the event of a fire. [Background technology]

[0002] In wooden buildings, for example, when a wooden pillar and a cross member (beam) are joined, they are joined using metal fittings. An example of such metal fittings is disclosed in Patent Document 1.

[0003] For example, when joining a pillar and a beam with a connecting metal fitting, part of the connecting metal fitting (the connecting base part) is bolted to the pillar, and the other part (the connecting protruding plate part protruding from the connecting base part) is connected to the beam by driving a connecting fastener (drift pin) into the beam to join the pillar and beam. However, it is necessary to provide a cutout portion on the beam to accommodate this connecting metal fitting, and this cutout portion has a joint through hole that penetrates at least in the vertical direction.

[0004] When viewed from below, the joint through hole in this cut-out not only looks unsightly as the metal fittings are visible from the lower opening (joint opening) inside, but in the unlikely event of a fire, heat could be transferred from this joint through hole that penetrates in the vertical direction, accelerating the carbonization and combustion of the cross members.

[0005] For this reason, in the past, wooden blocks or fire-resistant plates have been glued into the lower part of the joint opening to block the opening and slow down the carbonization and burning of the cross members.

[0006] Meanwhile, sheets and fillers made from heat-expandable fire-resistant materials that expand in the heat of a fire are also available commercially and are used as fireproofing materials for buildings.

[0007] However, as mentioned above, simply gluing a wooden block or the like over the joint through-hole of the cutout section to close it is not only difficult to do, but there is also the risk that a fire will cause the wood around the wooden block to shrink, allowing heat to be transmitted through the gap. Also, the adhesive has a low heat resistance, so the bond may loosen, causing the wooden block to fall off and hastening carbonization and combustion.

[0008] Furthermore, even if a fireproofing material made of a heat-expandable fire-resistant material that expands due to the heat of a fire is simply filled into the opening of the joint through hole to seal it, the sealing operation is still not easy.

[0009] Moreover, in recent years, there has been a trend for wooden buildings to become taller. In the case of high-rise buildings, the number of joints between columns and beams naturally increases, which in turn results in a considerable number of joint openings that need to be blocked, as mentioned above, making construction even more difficult.

[0010] Due to this current situation, a practical fire-resistant joint structure has not yet been realized, and there has been a demand for a fire-resistant joint structure that is easy to install while maintaining fire resistance. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2020-84593 A Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made in consideration of the current situation and has resolved the above-mentioned problems, and aims to provide a fire-resistant joint structure for buildings which has an easy-to-construct structure, i.e., a structure which can be kept closed by the simple operation of press-fitting, and which can seal off at least the joint through-hole in the cut-out part without any gaps due to thermal expansion in the event of a fire, and without the risk of falling off even if the wood shrinks, thereby delaying carbonization and combustion, and which has extremely excellent construction properties and fire-resistant performance. [Means for solving the problem]

[0013] The gist of the present invention will now be described with reference to the accompanying drawings. The present invention relates to a fireproof joint structure for a building, in which a column 1 or a horizontal member 2 and a horizontal member 2 are connected and joined by a metal joint 3, and a joint through hole 5 that penetrates in the vertical direction of a cutout portion 4 formed in the horizontal member 2 to accommodate the metal joint 3 is closed by a joint closing member 7, so that carbonization and combustion in the event of a fire are delayed, The cutout portion 4 has the joint through hole 5 penetrating in the vertical direction, and a vertical through slit 12 communicating with the joint through hole 5, penetrating in the vertical direction, and into which a connecting protruding plate portion 10 is inserted, the connecting plate portion 10 protruding from the connecting base portion 9 of the connecting fitting 3 and connected to the cross member 2 by a connecting stopper 11. The joint closing member 7 is made of a heat-expandable fire-resistant material that expands due to heat during a fire. attitude and a joint through hole closing part 8 formed in a shape that closes at least one of the upper and lower joint openings 6 of the joint through hole 5, the joint through hole closing part 8 of this joint closing member 7 made of a heat-expandable fire-resistant material being press-fitted into the joint opening 6 of the joint through hole 5 to keep the joint opening 6 in a closed state, and being configured so that in the event of a fire, the joint through hole 5 is kept sealed and closed by thermal expansion, thereby retarding carbonization and combustion.

[0014] Also, in a joint fireproof structure for a building, a column 1 or a horizontal member 2 and a horizontal member 2 are connected and joined by a metal joint 3, and a joint through hole 5 penetrating in the vertical direction of a cutout portion 4 formed in the horizontal member 2 to accommodate the metal joint 3 is blocked by a joint closing member 7, so that carbonization and combustion in the event of a fire are delayed. The cutout portion 4 has the joint through hole 5 penetrating in the vertical direction, and a vertical through slit 12 communicating with the joint through hole 5, penetrating in the vertical direction, and into which a connecting protruding plate portion 10 is inserted, which protrudes from a connecting base portion 9 of the metal joint 3 and is connected and fixed to the horizontal member 2 by a connecting stopper 11, and the joint closing member 7 is made of a heat-expandable fire-resistant material that expands with the heat of a fire. attitude and a joint through hole closing part 8 formed in a shape so as to close at least one of the upper and lower joint openings 6 of the joint through hole 5, and a slit closing part 14 formed in a shape so as to close at least one of the upper and lower slit openings 13 of the upper and lower through slits 12 or in a shape so as to be inserted and disposed in the upper and lower through slits 12. The joint through hole closing part 8 of the joint closing member 7 made of a thermally expandable fire-resistant material is press-fitted into at least the joint opening 6 of the joint through hole 5, so that the joint opening 6 is held in a closed state, and the slit closing part 14 is held in a state so as to close the slit opening 13 of the upper and lower through slits 12 of the cross member 2 or in a state so as to be inserted and disposed in the upper and lower through slits 12. In the event of a fire, the joint through hole 5 and the upper and lower through slits 12 are thermally expanded to keep them sealed and closed, and carbonization and combustion are delayed.

[0015] The joint through hole closing portion 8 of the joint closing member 7 which is integrally formed from the heat-expandable fire-resistant material and is elastically deformable is formed in a shape that closes the joint opening 6 below the joint through hole 5 by press-fitting into the joint opening 6, and the slit closing portion 14 is formed in a shape that is inserted and disposed below the vertical through slit 12 of the cross member 2, so that the joint opening 6 below the joint through hole 5 and the slit opening 13 below the vertical through slit 12 are kept sealed and closed by thermal expansion during a fire, thereby retarding carbonization and combustion. This relates to a joint fire prevention structure for a building as described in claim 2.

[0016] The present invention also relates to a fire protection structure for a building joint as described in any one of claims 1 to 3, characterized in that the joint closing member 7, which is formed integrally from the heat-expandable fire-resistant material and is elastically deformable, is provided with a protrusion 15 for maintaining the press-fit engagement, and the press-fit engagement is maintained by this protrusion 15 being elastically deformed and pressed into contact.

[0017] The connecting fitting 3 is C-shaped, U-shaped or T-shaped in a plan view, with two or one of the connecting protrusion plate portions 10 protruding from the connecting base portion 9, and these connecting protrusion plate portions 10 are inserted into two or one of the vertical through slits 12 of the cross member 2 and connected and joined by the connecting stopper 11, respectively, and the joint through hole closing portion 8 of the elastically deformable joint closing member 7 formed integrally from the heat-expandable fire-resistant material is pressed into and engaged with the joint opening 6 below the joint through hole 5 between the connecting base portion 9 fixed to the inner surface of the column 1 and the end face of the cross member 2, and the slit closing portion 14 is inserted and arranged in the slit opening 13 below the vertical through slit 12 of the cross member 2. Effect of the Invention

[0018] Since the present invention is configured as described above, it has a structure that can be easily constructed, that is, a structure that can be kept closed by the simple operation of pressing in and engaging, and in the event of a fire, there are no gaps due to thermal expansion, and there is no risk of the wood falling out even if it shrinks, and at least the joint through hole in the cutout part can be sealed off to delay carbonization and combustion, resulting in a fire prevention structure for building joints that is extremely easy to construct and has excellent fire resistance. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is an oblique view of a joint closing member made of a thermally expandable fire-resistant material according to the present embodiment. [Diagram 2] 2 is a perspective view of the joint closing member made of a thermally expandable fire-resistant material of the present embodiment, seen from the opposite direction to that of FIG. 1. FIG. [Diagram 3] FIG. 2 is a plan view of a joint closing member made of a thermally expandable fire-resistant material according to this embodiment. [Figure 4] FIG. 13 is an explanatory exploded perspective view showing how a joint closing member made of a heat-expandable fire-resistant material is press-fitted into and closed off the joint opening below the joint through-hole of the joint portion of this embodiment. [Diagram 5] 13 is an explanatory oblique view of the state in which a joint closing member made of a heat-expandable fire-resistant material is press-fitted into and engaged with the joint opening below the joint through-hole of the joint portion of this embodiment to close it. FIG. [Figure 6] This is an explanatory plan view of the state in which a joint closing member made of a heat-expandable fire-resistant material is press-fitted into and engaged with the joint opening below the joint through-hole of the joint portion of this embodiment to close it. [Figure 7] This is an explanatory bottom view of the state in which a joint closing member made of a heat-expandable fire-resistant material is pressed into and engaged with the joint opening below the joint through-hole of the joint portion of this embodiment to close it. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] BEST MODE FOR CARRYING OUT THE PRESENT DISCLOSURE The preferred embodiment of the present invention will be briefly described below with reference to the accompanying drawings.

[0021] A pillar 1 and a cross member 2 (beam) or cross members 2 and 2 are connected and joined at a right angle or a specified angle by a metal joint 3, and for example, in the embodiment shown in Figures 4 to 6, a pillar 1 and a cross member 2 are joined by a metal joint 3, and a cutout 4 (joint 4) for accommodating the metal joint 3 is provided at the butt end of this cross member 2, and a joint through hole 5 that penetrates in the vertical direction is formed in this cutout. In the present invention, at least one of the upper and lower joint openings 6 of this joint through hole 5 is closed with a joint closing member 7.

[0022] Specifically, the cutout portion 4 has the joint through hole 5 which penetrates in the vertical direction, and a vertical through slit 12 which communicates with this joint through hole 5 and penetrates in the vertical direction, and into which a connecting protruding plate portion 10 is inserted and stored, which protrudes from the connecting base portion 9 of the connecting fitting 3 and is connected to the cross member 2 by a connecting stopper 11 (drift pin).The joint closing member 7 is formed, for example, as in the embodiment shown in Figures 1 to 3, from a heat-expandable fire-resistant material that expands due to the heat of a fire, and is composed of a joint through hole closing portion 8 which is formed in a shape that closes at least one of the upper and lower joint openings 6 of the joint through hole 5, and a slit closing portion 14 which is formed in a shape that closes at least one of the upper and lower slit openings 13 of the vertical through slits 12 or in a shape that is inserted and arranged in this vertical through slit 12.

[0023] Therefore, simply by press-fitting the joint through hole closing portion 8 of the joint closing member 7 made of this thermally expandable fire-resistant material into the joint opening 6 below the joint through hole 5, the joint opening 6 can be completely or nearly closed and maintained in a closed state in which it is completely closed upon thermal expansion. Furthermore, for example, as in the embodiment shown in Figures 1 to 3, the slit opening 13 of the vertical through slit 12 of the cross member 2 can be simultaneously closed by the slit closing portion 14 or the slit closing portion 14 can be maintained in a state in which it is inserted into the vertical through slit 12.

[0024] In other words, simply by pressing the joint through hole closing portion 8 of the joint closing member 7 made of a heat-expandable fire-resistant material into the joint opening 6 of the joint through hole 5, in other words, by simply pushing it in by hand, the joint closing member 7 can be engaged and fixed in a closed state, making this closing operation easy and speedy, and at the same time, as in the embodiment shown in Figures 1 to 3, the upper and lower through slits 12 of the cutout portion 4 can also be held in a closed state by the slit closing portion 14 or held in an inserted and arranged state.

[0025] In the unlikely event of a fire, the joint closing member 7 (the joint through hole closing portion 8 and the slit closing portion 14) will thermally expand, thereby keeping at least the joint through hole 5 sealed and preventing it from falling off.Then, the vertical penetration points of the cutout portion 4 are sealed, slowing down carbonization and combustion, thereby achieving a joint fire prevention structure with excellent workability and fire resistance. EXAMPLES

[0026] Specific embodiments of the present invention will now be described with reference to the drawings.

[0027] In this embodiment, the end of the cross member 2 (beam) is butted against the side surface (inner surface) of the column 1, and the two are connected and joined with a metal joint fitting 3 that is U-shaped when viewed from above, and this joint fitting 3 has a connecting base part 9 in the center of the U-shaped shape when viewed from above, and connecting protruding plate parts 10 on both ends. That is, the connecting base part 9 is connected to the column 1, and the connecting protruding plate parts 10 are inserted and arranged in the upper and lower through slits 12 formed in two places of the cutout part 4 of the cross member 2 (beam), and the connecting fasteners 11 (drift pins) are used to connect and fasten the column 1 and the cross member 2 (beam).

[0028] In this embodiment, the cutout 4 provided at the butt end of the cross member 2 (beam) is cut slightly shorter in the center between the vertical through slits 12, and is shaped to be slightly spaced from the side of the column 1, and a joint through hole 5 that penetrates in the vertical direction is formed between the center end face of the cutout 4 of the cross member 2 (beam) that faces the connecting base portion 9 of the connecting metal fitting 3 in a spaced state and the side of the column 1. As shown in Figures 4 and 5, the vertical width of the connecting metal fitting 3 is formed shorter than the vertical width of the cross member 2 (beam), and when the connecting metal fitting 3 is stored in the cutout 4 and joined, it is joined at a position that leaves a space above and below. The joint through hole that vertically penetrates this vertical space 5 In this embodiment, a joint through hole closing part 8 of a joint closing member 7 is press-fitted into the joint opening 6 below the joint through hole 5, and a slit closing part 14 of the joint closing member 7 is inserted into the upper and lower through slits 12 to close the joint through hole 5.

[0029] The joint closing member 7 is made of a heat-expandable fire-resistant material that expands with heat. For example, it expands in a temperature range of 200 degrees or more, expands 10 times at 400 degrees, and expands 13 times at 600 degrees, and is capable of retaining its shape even in a high-temperature environment, is elastically deformable, and uses a lightweight material with a specific gravity of about 1.4 times. (As an example, Vantect (registered trademark) manufactured by IIDA Sangyo Co., Ltd. can be used.) By using such a heat-expandable fire-resistant material, the joint closing member 7 expands in the event of a fire, completely sealing off the joint through hole 5 and the upper and lower through slits 12, and it is possible to delay the decrease in strength of the cutout portion 4 due to thermal deterioration.

[0030] 1 to 3 show the specific shape of joint closing member 7 made of thermally expandable fireproof material of this embodiment, and this joint closing member 7 has a one-part configuration in which a joint through hole closing part 8 formed in a shape conforming to the shape of the joint opening 6 of joint through hole 5, in other words, a shape having a volume sufficient to close this joint opening 6, and two slit closing parts 14 formed in a shape to be inserted into slit openings 13 of two vertical through slits 12 into which connecting protruding plate parts 10 protruding from connecting base part 9 of said joint fitting 3 are inserted, are integrally molded. Also, the distance between the slit closing parts 14 is formed to be the same dimension as the distance between the pair of vertical through slits 12. With this type of joint closing member 7, when the joint through hole 5 is viewed from above, as shown in Figure 6, it appears to be blocked by a joint through hole closing part 8, and when the joint through hole 5 is viewed from below, as shown in Figure 7, the joint through hole 5 cannot be observed and a slit closing part 14 is inserted into the upper and lower through slits 12.

[0031] Therefore, the attachment of the joint closing member 7 can be achieved simply by pushing the joint through hole closing part 8 of the joint closing member 7 made of a thermally expandable fireproof material into the joint opening 6 below the joint through hole 5 for press-fit engagement, and inserting the slit closing part 14 into the vertical through slit 12. In other words, the joint opening 6 is almost completely closed by the joint through hole closing part 8, and can be maintained in a closed state in which it is completely sealed when it expands thermally, and at the same time, the two slit closing parts 14 formed integrally with the joint through hole closing part 8 can be maintained in a state in which they are inserted into the two vertical through slits 12 of the cross member 2 (beam).

[0032] Therefore, in this embodiment, the joint closing member 7 made of a heat-expandable fire-resistant material can be simply pressed into the joint opening 6 of the joint through hole 5 by pressing it into the joint opening 6, in other words, by pushing it in by hand, and the joint closing member 7 can be engaged and fixed in a closed state, making this closing operation easy and quick, and at the same time, it can also be inserted and arranged into both the upper and lower through slits 12 of the cutout portion 4, and this state can be maintained.

[0033] Therefore, according to this embodiment, in the event of a fire, the joint closing member 7 will thermally expand, keeping the joint through hole 5 and the vertical through slits 12 sealed and closed, making the joint closing member 7 less likely to fall off.All of the vertical through-holes of the cut-out portion 4 are sealed and closed, thereby realizing an excellent joint fire prevention structure that can slow down carbonization and combustion.

[0034] In this embodiment, the elastically deformable joint closing member 7 is integrally formed from the heat-expandable fireproof material and has a protrusion 15 (protrusion strip) for press-fitting and holding the joint.

[0035] Specifically, as shown in Figures 1 and 2, a semicircular convex portion is integrally formed on both side surfaces of the joint through-hole closing portion 8 of the joint closing member 7 as a protrusion 15 for press-fitting and holding the engagement. Therefore, the protrusion 15 is elastically deformed and pressed into contact, so that the press-fitting and holding is ensured.

[0036] In this embodiment, the protrusions 15 are provided on the opposing outer surfaces of the joint through hole closure portion 8 so as to be pressed against the side surface of the column 1 and the central end surface of the cross member 2 (beam). The protrusions 15 are long convex portions in the width direction of the cross member 2 (beam) and are rounded in the upper and lower push-in engagement directions. Therefore, even if the surfaces of the joint through hole closure portion 8 facing the column 1 and the cross member 2 (beam) are slightly misaligned relative to the opposing surfaces of the column 1 and the cross member 2 (beam) due to manufacturing errors, etc., the push-in engagement becomes easier and the engagement can be reliably maintained in a closed state, and the engagement and closing retention is also durable.

[0037] In this embodiment, in order to improve fire resistance, a connecting hole blocking member 16 made of a heat-expandable fire-resistant material is pressed into and held in engagement with the end of the connecting hole into which the connecting fastener 11 (drift pin) of the cross member 2 (beam) is inserted, thereby blocking this as well.

[0038] 6, the metal connector 3 of this embodiment is U-shaped in plan view, but is not limited to this and may be U-shaped or T-shaped. Even if the metal connector 3 is U-shaped, a joint closing member 7 of the same shape as in the U-shaped case of this embodiment can be used.

[0039] Incidentally, the present invention is not limited to the present embodiment, and the specific configurations of each component element, such as the structure of the applied joint portion, the structure of the joint portion, the structure of the connecting fittings, etc., can be designed as appropriate. [Explanation of symbols]

[0040] 1 Pillar 2 Cross members 3. Joint fittings 4 Cutout 5 Connection through hole 6 Joint opening 7. Connection Closures 8. Connection through hole closure 9 Connection board part 10 Connection protruding plate part 11 Connection stopper 12 Top and bottom through slits 13 Slit opening 14 Slit closure 15 Protrusion 16 Connection hole blocking member

Claims

1. A fireproof joint structure for a building in which a column or a cross member and a cross member are connected and joined by a joint metal fitting, and a joint through hole that penetrates in the vertical direction of a cutout portion formed in the cross member to accommodate the joint metal fitting is closed with a joint closing member, so that carbonization and combustion in the event of a fire are delayed, The cutout portion has the joint through hole penetrating in the vertical direction, and a vertical through slit communicating with the joint through hole, penetrating in the vertical direction, and into which a connecting protruding plate portion protruding from the connecting base portion of the connecting fitting and connected to the cross member by a connecting stopper is inserted, The joint closing member is formed from a heat-expandable fire-resistant material that expands due to heat during a fire, and is configured to comprise a joint through hole closing part that is formed in a shape that closes at least one of the upper and lower joint openings of the joint through hole, the joint through hole closing part of the joint closing member made of this heat-expandable fire-resistant material is press-fitted into the joint opening of the joint through hole, keeping the joint opening in a closed state, and is configured so that the joint through hole is sealed and kept closed by thermal expansion during a fire, thereby delaying carbonization and combustion. This is a joint fire prevention structure for a building, characterized in that

2. A fireproof joint structure for a building in which a column or a cross member and a cross member are connected and joined by a joint metal fitting, and a joint through hole that penetrates in the vertical direction of a cutout portion formed in the cross member to accommodate the joint metal fitting is closed with a joint closing member, so that carbonization and combustion in the event of a fire are delayed, The cutout portion has the joint through hole penetrating in the vertical direction, and a vertical through slit communicating with the joint through hole, penetrating in the vertical direction, and into which a connecting protruding plate portion protruding from the connecting base portion of the connecting fitting and connected to the cross member by a connecting stopper is inserted, The joint closing member is made of a heat-expandable fire-resistant material that expands due to heat during a fire, and is composed of a joint through-hole closing part formed in a shape that closes at least one of the upper and lower joint openings of the joint through-hole, and a slit closing part formed in a shape that closes at least one of the upper and lower slit openings of the upper and lower through-slits or in a shape that is inserted and disposed in the upper and lower through-slits, This fireproof joint structure for a building is characterized in that the joint through hole closing portion of the joint closing member made of this heat-expandable fire-resistant material is pressed into and engaged with at least the joint opening of the joint through hole, maintaining the joint opening in a closed state, and the slit closing portion is maintained in a state in which it closes the slit opening of the upper and lower through slits of the cross member or in a state in which the slit closing portion is inserted and arranged in the upper and lower through slits, so that thermal expansion in the event of a fire keeps the joint through hole and the upper and lower through slits sealed and closed, thereby delaying carbonization and combustion.

3. The joint through hole closing portion of the joint closing member which is elastically deformable and integrally formed of the thermally expandable fireproof material is formed into a shape to be press-fitted into the joint opening below the joint through hole to close the joint opening, and the slit closing portion is formed into a shape to be inserted and disposed below the vertical through slit of the cross member, A fireproof joint structure for a building as described in claim 2, characterized in that it is configured so that during a fire, thermal expansion causes the joint opening below the joint through hole and the slit opening below the upper and lower through slits to be sealed closed, slowing down carbonization and combustion.

4. A fireproof structure for a joint in a building as described in any one of claims 1 to 3, characterized in that the joint closing member, which is formed integrally with the heat-expandable fire-resistant material and is elastically deformable, is provided with a protrusion for maintaining the press-fit engagement, and the press-fit engagement is maintained by this protrusion being elastically deformed and pressed into contact.

5. The connecting fitting is U-shaped, T-shaped or C-shaped in a plan view, and two or one of the connecting protruding plate parts are protruding from the connecting base part, and the connecting protruding plate parts are inserted into the upper and lower through slits at two or one places of the cross member, respectively, and are connected and joined by the connecting stopper, A fireproof joint structure for a building as described in any one of claims 2 and 3, characterized in that the joint through hole closing portion of the joint closing member which is integrally formed of the heat-expandable fire-resistant material and is elastically deformable is press-fitted and engaged into the joint opening below the joint through hole between the connecting base portion fixed to the inner surface of the column and the end face of the cross member, and the slit closing portion is inserted and arranged in the slit opening below the upper and lower through slits of the cross member.

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