CN220060184U - Assembling component - Google Patents

Abstract

The utility model discloses an assembly member. The assembly member includes: the horizontal fixing part is formed by vertically abutting two square section pipes, and a separation wall is formed in the center of each square section pipe, so that any side of each square section pipe can be used for inserting a square pipe without protruding from the opposite side; the first arc-shaped connecting part is fixed below the square section pipe below; the two weight bearing pipes are fixed at two side ends of the first arc-shaped connecting part respectively with the same angle with the vertical section of the horizontal fixing part and are used for plugging a circular connecting pipe fitting for bearing the weight above; the second arc-shaped connecting part is fixed above the square section pipe above; and two weight transfer pipes which are fixed at two side ends of the second arc-shaped connecting part respectively and have the same angle with the vertical section of the horizontal fixing part and are used for plugging a circular foot pipe fitting so as to transfer the weight average from the circular connecting pipe fittings and the weight average of the weight transfer pipes to the circular foot pipe fittings.

Description

Assembling component

Technical Field

The present utility model relates to a connecting piece, and more particularly, to an assembling member for connecting and assembling furniture bars.

Background

With the improvement of life quality, people attach importance to the activity arrangement during leisure, and travel outside or enjoy barbecue fun of a home courtyard, so that the method becomes an outstanding trend. When the chair moves in the outdoor natural environment, the user can sit and lie for rest in the case of needing to stop the foot rest, and the user can put movable articles on one table, so that the oven is an indispensable tool for making delicacies. The biggest difference between the outdoor furniture and the general indoor furniture is that the former is changeable in use field and the latter is fixed, which leads to the outdoor furniture to be designed with the characteristics of easy disassembly and assembly, convenient storage, light materials and the like.

In the case of outdoor assembled tables, the table top may be constructed from alternately foldable strip aluminum metal sheets and the legs may be hollow tubes that are inserted into the slots of the table top. For the stability of the table, the legs may be connected with a transverse auxiliary bar. For the connection of the hollow tube with the auxiliary rod in different directions, special connecting members are required, or else screw locking is required between the hollow tube and the auxiliary rod. However, locking the screw is a cumbersome task, and also requires the user to carry the screwdriver with him, which is inconvenient to assemble the table. If the grooves of the screw heads wear after a long time of assembly and disassembly, the service life of the table will end. Therefore, the connecting piece between the rod pieces becomes an essential element for assembling furniture.

Different rod piece connectors are used for different assembled furniture, and the operation is reasonable but the development cost is high. Unless the sales volume of such assembled furniture is large, the development costs of the rod connection can be spread out, which would otherwise not normally be invested by the developer. As modern commodities move more and more toward diverse and small development paths, the requirement of the times of assembling furniture also needs to be met. A new form of assembly member is needed in the industry for supporting or forming part of an assembled piece of furniture with different bars, provided that the form of the support bars does not vary much, such as with standardized round bars or square bars.

Disclosure of Invention

In order to solve the above problems, the present utility model discloses an assembly member. The assembly member includes: the horizontal fixing part is formed by vertically abutting two square section pipes, and a separation wall is formed in the center of each square section pipe, so that any side of each square section pipe can be used for inserting a square pipe without protruding from the opposite side; the first arc-shaped connecting part is fixed below the square section pipe below; two weight bearing pipes with fixed circular cross section and the same angle with the vertical cross section of the horizontal fixing part and fixed to the two side ends of the first arc connecting part, the opening at the fixing part is reduced to a first round hole, and each weight bearing pipe is used for being inserted into a circular connecting pipe for bearing the weight above; the second arc-shaped connecting part is fixed above the square section pipe above; and two weight transfer pipes with fixed circular cross sections, which are fixed at the two side ends of the second arc connecting part respectively with the same angle with the vertical cross section of the horizontal fixing part, wherein the opening of the fixing part is reduced to form a second round hole, and each weight transfer pipe is used for plugging a circular foot pipe fitting so as to evenly transfer the weight from the circular connecting pipe fittings and the weight of the weight transfer pipes to the circular foot pipe fittings. The weight-receiving pipes and the weight-transmitting pipes are inclined toward the same side of the horizontal fixing portion, the inclination angle of the weight-transmitting pipes is larger than that of the weight-receiving pipes, and one assembly member can be connected with the other assembly member or a fitting connected with the square pipe by inserting the square pipe into the square pipe.

According to the utility model, an elastic buckling hole is formed in the upper side wall of one end of the square section tube above, and another elastic buckling hole is formed in the lower side wall of one end of the square section tube below, wherein the elastic buckling holes are used for temporarily fixing elastic buckles on the square tube provided with the elastic buckles.

According to the utility model, the tube walls of the weight transmission tubes are respectively provided with an elastic buckling hole, and the elastic buckling holes are used for temporarily fixing the elastic buckles on the round foot tube provided with the elastic buckles.

Preferably, the weight receiving pipe and the weight transmitting pipe on the same side of the horizontal fixing part are connected and fixed by a fixing block.

According to the present utility model, an upward mark is formed on the second arc-shaped connecting portion for indicating the user to place the square section tube above upward.

According to the utility model, a first guide frame is formed at the center of the first arc-shaped connecting part, and a first semicircular groove is formed on the first guide frame, so that an elastic rope passing through two first round holes can be supported by the first semicircular groove and can not swing laterally on the first arc-shaped connecting part.

According to the utility model, the second arc-shaped connecting part is provided with a second guiding frame at the center, and a second semicircular groove is arranged on the second guiding frame, so that an elastic rope passing through two second round holes can be supported by the second semicircular groove and can not swing laterally on the second arc-shaped connecting part.

Preferably, the inner sides of the opening pipe walls of the weight-receiving pipes far from the fixing position are provided with arc surfaces, the inner sides of the opening pipe walls of the weight-transmitting pipes far from the fixing position are provided with arc surfaces, and the inner sides of the two opening pipe walls of the square-section pipes are provided with arc surfaces.

The utility model utilizes the horizontal fixing part, the weight bearing pipe and the weight transmission pipe to respectively connect square pipes (rods) or round pipes (rods) with different standardization, so that the rods can be used for supporting or forming part of the assembled furniture. The utility model uses one assembly component to meet the assembly requirement of various assembled furniture, which is the most important technical feature of the utility model, and reduces the development cost, which is the advantage of the utility model in the aspect of economy.

Drawings

The utility model will be described in further detail with reference to the drawings and the detailed description.

FIG. 1 is a perspective view of an assembled component according to an embodiment of the present utility model;

FIG. 2 is a front view of the assembled component;

FIG. 3 is a rear view of the assembled component;

FIG. 4 is a left side view of the assembled component;

FIG. 5 is a right side view of the assembled component;

FIG. 6 is a top view of the assembled component;

FIG. 7 is a bottom view of the assembly member;

FIG. 8 is a connection use of the assembly member;

FIG. 9 is another connection use of the assembly member;

fig. 10 is a perspective view of a storage chair using the assembly member;

FIG. 11 is a side view of a layer rack using the assembly member;

FIG. 12 is a perspective view of an assembled table using the assembly members;

fig. 13 is a perspective view of a connection fitting set using the assembly member.

Description of the reference numerals

1. Assembling the components;

2. a storage chair;

3. a layer rack;

4. assembling the table;

5. a hanging rack;

10. a horizontal fixing part;

11. square section tube;

11a, dividing walls;

11b, elastic buttonholes;

20. a first arc-shaped connection portion;

21. a first guide frame;

21a, a first semicircular groove;

30. a weight-receiving pipe;

31. a first round hole;

35. a fixed block;

40. a second arc-shaped connection portion;

41. a second guide frame;

41a, a second semicircular groove;

42. upward marking;

50. a weight transfer tube;

51. a second round hole;

52. an elastic buckling hole;

C. circular connecting pipe fittings;

F. round foot pipe fittings;

l, elastic buckle;

r, an elastic rope;

s1, square pipes;

s2, square pipes;

alpha, inclination angle;

beta, inclination angle.

Detailed Description

The technical solutions in the embodiments of the present utility model are clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present utility model, but the present utility model may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present utility model is not limited to the specific embodiments disclosed below.

Please refer to fig. 1 to 7. Fig. 1 is a perspective view of an assembly member 1 according to an embodiment of the present utility model, fig. 2 is a front view of the assembly member 1, fig. 3 is a rear view of the assembly member 1, fig. 4 is a left side view of the assembly member 1, fig. 5 is a right side view of the assembly member 1, fig. 6 is a top view of the assembly member 1, and fig. 7 is a bottom view of the assembly member 1. The assembly 1 comprises the following functional items: a horizontal fixing portion 10, a first arc-shaped connecting portion 20, two weight receiving pipes 30, a second arc-shaped connecting portion 40 and two weight transmitting pipes 50. These visually distinguishable objects may be molded individually, joined by a process such as gluing or welding to form the assembly member 1, or may be integrally molded. In terms of materials, metals such as aluminum alloys or cast iron may be used, as well as plastics such as ABS or nylon. The strength and toughness of the product are of primary concern. The external appearance of these articles and the manner of using the assembly member 1 will be described below.

The function of the horizontal fixing portion 10 according to the utility model is to connect the design of the cross member in the piece of furniture. In use, both ends of the cross member are connected to an assembly member 1 by means of the horizontal fixing portion 10, and the weight borne by the assembly member 1 is not transferred to the cross member. Thus, the function of the cross member is to maintain the relative position between the two assembled members 1, including their longitudinal (perpendicular to the plane) members, preventing collapse of the piece of sectional furniture due to forces parallel to the ground (such as earthquakes). In this embodiment, the cross member is a square tube; in practice, the cross member may also be a square solid bar. The horizontal fixing portion 10 is formed by two square cross-section pipes 11 abutting on each other. For convenience of the following description, the square-section tube 11 in the upper position in fig. 2 is defined as an upper square-section tube 11, and the square-section tube 11 in the lower position is defined as a lower square-section tube 11. A partition wall 11a is formed at the center of each square section tube 11. The dividing wall 11a blocks connectivity between two ends of the square-section tube 11, so that either side of the square-section tube 11 can be used to insert a square tube without the square tube protruding from the opposite side, i.e., two openings of the square-section tube 11 can be separately connected to different square tubes, respectively.

In design, as shown in fig. 1, the inner sides of the pipe walls of the two openings of the square section pipe 11 are provided with arc surfaces, so that the square section pipe 11 can be smoothly guided and inserted into the square section pipe by the provided arc surfaces. Preferably, the adjacent sides of the square tube are also provided with arc surfaces. In contrast, a corresponding arc surface is also formed between the inner side surfaces of the square-section tube 11. In addition, an elastic buckling hole 11b is formed in the upper side wall of one end of the upper square section tube 11, and another elastic buckling hole 11b is formed in the lower side wall of one end of the lower square section tube 11. If elastic buckles (cambered protrusions are pressed to be sunk into the square tube and rebound after the pressure is removed) for fixing are arranged on the square tube, the elastic buckling holes 11b are used for temporarily fixing the elastic buckles on the square tube. The use of square tubes with elastic buckles has several advantages over the conventional square tubes: the elastic fastening hole 11b can replace a screw, and is used as a technology for temporarily connecting and fixing the square pipe and the square section pipe 11, and is convenient to assemble, disassemble and operate and foolproof in assembly.

The first arcuate connection 20 is a bridging design and is secured below the underlying square section tube 11. In the present embodiment, the main structure appearance of the first arc-shaped connection portion 20 is a plate-like structure having an arc edge. The first arc-shaped connecting portion 20 has a first guiding frame 21 formed at the center thereof, the first guiding frame 21 is perpendicular to the plate-shaped structure, and a first semicircular groove 21a is formed in the first guiding frame 21. The function of the first semicircular groove 21a will be described below.

The weight-receiving pipe 30 serves to connect with a pipe or solid rod which receives the weight of the upper part in the assembled furniture. Each of the weight-receiving tubes 30 has a function of fixing a circular cross section. Referring to fig. 3, the center line (shown by long dashed lines) of the weight receiving tube 30 may be fixed to both side ends of the first arc-shaped connection portion 20 at the same angle as the vertical section (shown by short dashed lines) of the horizontal fixing portion 10. The opening at the fixing location of the weight-receiving pipe 30 and the first arc-shaped connection portion 20 is reduced to a first circular hole 31. Since the weight-receiving pipe 30 is a circular pipe, the weight-receiving pipe 30 is used to insert a circular connecting pipe receiving the upper weight. The circular cross-section of the weight-receiving tube 30 is sized to conform to the circular area of the outer periphery of the circular connecting tube cross-section. The circular connecting tube may be rotated with respect to the weight receiving tube 30 without providing an elastic buckle. In fact, since one end of the circular connecting pipe member conducts pressure, the circular connecting pipe member is tightly inserted into the weight receiving pipe 30 by the pressure, and is hardly rotated by a slight external force. Similarly, the inner side of the wall of the opening tube of the weight receiving tube 30, which is far from the fixing portion, is also provided with an arc surface to facilitate connection with the circular connecting tube.

The second arcuate connection 40 is also a bridging design and is secured over the square section tube 11 above. In the present embodiment, the main structure of the second arc-shaped connecting portion 40 has the same appearance as the first arc-shaped connecting portion 20, and is a plate-shaped structure having a circular arc edge. The second arc connecting portion 40 has a second guiding frame 41 formed at the center thereof, the second guiding frame 41 is perpendicular to the plate structure, and a second semicircular groove 41a is formed in the second guiding frame 41. The function of the second semicircular groove 41a will be described below.

The weight transfer tube 50 is used to connect with a weight supporting foot tube or solid bar in an assembled piece of furniture. Each of the weight transfer tubes 50 has a fixed circular cross section. Similarly, the center line of the weight transfer tube 50 is also fixed to both side ends of the second arc-shaped connection part 40 at the same angle with the vertical cross section of the horizontal fixing part 10. In the present embodiment, the angle between the weight transfer tube 50 and the horizontal fixing portion 10 is substantially equal to the angle between the weight receiving tube 30 and the horizontal fixing portion 10, and may be different in practice. The opening at the fixing location of the weight transfer tube 50 and the second arc-shaped connection portion 40 is reduced to a second circular hole 51. The weight transfer tubes 50 are also round tubes, so that each weight transfer tube 50 can be used to plug in a round foot tube to evenly transfer the weight from the round connecting tubes to the round foot tubes. The circular cross-section of the weight transfer tube 50 is sized to conform to the outer peripheral circular area of the circular foot tube cross-section. If the circular foot tube is rotated relative to the weight transfer tube 50, the assembled furniture is in an unstable state and may collapse upon external force. Therefore, the circular foot pipe must be provided with elastic buckles for fixing the relative positions between the circular foot pipe and the weight receiving pipe 50. In order to connect with the elastic buckle of the circular foot pipe, the pipe walls of the two weight transmission pipes 50 are respectively provided with an elastic buckle hole 52, and the elastic buckle holes 52 can be used for temporarily fixing the elastic buckle on the circular foot pipe provided with the elastic buckle. Similarly, the inner side of the wall of the weight transfer tube 50, which is far from the fixed part, is provided with an arc surface to facilitate connection with the circular foot tube.

Referring to fig. 5, a design feature of the present utility model is that the weight receiving pipes 30 and the weight transmitting pipes 50 are inclined toward the same side (left side in fig. 5) of the horizontal fixing portion 10, and the inclination angle α of the weight transmitting pipes 50 is larger than the inclination angle β of the weight receiving pipes 30. In fact, when the assembly member 1 is used on an assembled piece of furniture, it is generally at the side of the assembled piece of furniture. Therefore, the inclination direction is towards the side edge of the assembled furniture, the bottom of the installed round foot pipe fitting is far away from the center of the assembled furniture, and the capability of resisting external force dumping below the assembled furniture is also increased. Because of the design of the inclination angle beta, the circular connecting pipe fitting also extends upwards from the position of the assembling component 1 in a slight inclination way, and the structural volume of the upper part of the assembled furniture is increased. However, the tilting resistance of the whole assembled furniture is generally increased due to the fact that the tilting angle beta is smaller than the tilting angle alpha.

It is noted that damage may occur due to collision between the weight receiving pipe 30 and the weight transfer pipe 50 on the same side of the horizontal fixing portion 10. Therefore, the weight receiving pipe 30 and the weight transmitting pipe 50 on the same side of the horizontal fixing portion 10 are connected and fixed by the fixing block 35. The fixing block 35 is a solid block that seals the space between the weight receiving pipe 30 and the weight transmitting pipe 50 on the same side. In addition, since the weight receiving pipe 30 has the same appearance as the weight transmitting pipe 50 with only a slight difference in inclination, there is a possibility that the assembly member 1 is turned upside down during the operation of the assembly work, resulting in trouble that the assembly member must be disassembled and then re-passed. For this purpose, an upward mark 42 is formed on the second arc-shaped connecting portion 40 for indicating to the user to place the square-section tube 11 above upward.

Please refer to fig. 8, which illustrates a connection usage of the assembly member 1. The use mode can be applied to a combined table for connecting a plurality of table legs and is used for connecting non-side table legs. The square pipe S1 with the elastic buckle L is inserted into the opening at the left side of the square section pipe 11, and the square pipe S1 is plugged into the opening of the square section pipe 11 only by pressing the elastic buckle L until the elastic buckle L is sprung out from the elastic buckle hole 11b to be fixed. The right opening of the square section tube 11 is inserted with a square tube S2 without an elastic buckle L. The two weight receiving pipes 30 are respectively connected to a circular connecting pipe C without the elastic buckle L, and the circular connecting pipe C can be connected to a folding table (not shown) to receive a part of the weight of the table and the weight thereon and transmit the weight to the assembly member 1. The two weight transfer pipes 50 are respectively inserted with a round foot pipe fitting F with an elastic buckle L, and the insertion method is the same as that of the square section pipe 11. In this way, the assembly 1 is able to continuously guide the weight from the weight-receiving pipes 30 on average to the circular foot tubes F.

Turning to fig. 9, another way of connecting the assembly 1 is shown. Some assembled furniture with simple assembled elements usually use elastic ropes to connect two connecting rods and pass through the connecting device for convenience in storage and avoiding rod loss. In this way, when the assembly is to be performed, the elastic rope is contracted, and the two connecting rods are respectively inserted into the connecting device by force. When the connecting rods are to be disassembled, the two connecting rods are pulled out from the connecting device by applying force, the elastic ropes are stretched, and then the two connecting rods are stored side by side. The connecting rod is attached to the connecting means all the time because of the elastic cord, the difference being only whether or not it is fixedly connected to the connecting means at a specific angle. The utility model has the same design. Two weight transfer tubes 50 in fig. 9 are illustrated as an example. As described above, the second guide frame 41 is formed at the center of the second arc-shaped connection portion 40, and the second guide frame 41 has the second semicircular groove 41a. Therefore, an elastic string R (shown in fig. 9 with a black thick line, the position of which is indicated by a broken line in the weight transfer tube 50) passing through the two second circular holes 51 can be supported by the second semicircular groove 41a without any lateral swing on the second arc-shaped connecting portion 40. If the elastic cord R swings sideways, it is easily worn. Similarly, the first guide frame 21 formed at the center of the first arc-shaped connection part 20 has a first semicircular groove 21a, so that the elastic string passing through the two first circular holes 31 can also be braced through the first semicircular groove 21a without any lateral swing on the first arc-shaped connection part 20.

The manner of application of the assembly 1 will be described below in terms of several assembled pieces of furniture.

Please refer to fig. 10, which is a perspective view of the storage chair 2 using the assembly member 1. The assembly component 1 is arranged below the canvas of the chair surface and is used as a connecting device for bearing the weight of a human body and connecting the chair legs. The square tube S2 connects the two assembly members 1.

Please refer to fig. 11, which is a side view of the layer frame 3 using the assembly member 1. As can be seen from fig. 11, the circular foot pipe member F as a cabinet foot extends downward and outward from the assembly member 1 due to the inclination of the weight transfer pipe 50, increasing the stability of the shelf 3. At the same time, the circular connecting pipe member C extends obliquely upward due to the inclination of the weight receiving pipe 30, increasing the lateral length of the upper cabinet and also increasing the overall volume of the shelf 3. This is also the design reason for the same inclination of the weight-receiving tube 30 and the weight-transmitting tube 50 towards the horizontal fixing portion 10.

Please refer to fig. 12, which is a perspective view of the assembled table 4 using the assembly member 1. According to the present utility model, one assembly member 1 can be connected to another assembly member 1 by inserting square pipes into square section pipes 11. In this example, the assembly table 4 uses 3 assembly members 1, the left assembly member 1 and the middle assembly member 1 are connected to each other by connecting the respective square cross-section tubes 11 and the two square tubes S2, and the middle assembly member 1 and the right assembly member 1 are also connected to each other by connecting the respective square cross-section tubes 11 and the two square tubes S2. Thus, the circular foot pipe F connected below the assembly member 1 forms 6 feet of the assembled table 4.

According to the utility model, an assembly member can also be connected to the fittings to which the square tube 11 is connected by inserting it. For an example of this configuration, please refer to fig. 13, which is a perspective view of the connection fitting set using the assembly member 1. In fig. 13, in addition to the above-described assembled table 4, there are fittings connected by means of two square tubes S2, a hanger 5. The hanger 5 is used as a fitting connected to the assembled table 4, and two square pipes S2 are transversely arranged below the hanger at positions corresponding to two square section pipes 11 of the assembly member 1 on one side of the assembled table 4. When the square tube S2 is inserted into the corresponding square cross-section tube 11, the hanger 5 is stably connected with the assembly table 4.

The foregoing description is only of the preferred embodiments of the utility model, and it is apparent that the embodiments described are merely some, but not all, of the embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

Claims (10)

1. An assembled component, comprising:

the horizontal fixing part is formed by vertically abutting two square section pipes, and a partition wall is formed in the center of each square section pipe, so that any side of each square section pipe is used for inserting a square pipe, and the square pipe does not protrude from the opposite side;

the first arc-shaped connecting part is fixed below the square section pipe below;

the two weight bearing pipes are provided with fixed circular cross sections, are respectively fixed at two side ends of the first arc-shaped connecting part by the same angle with the vertical cross section of the horizontal fixing part, the opening at the fixed part is reduced to form a first round hole, and each weight bearing pipe is inserted into a circular connecting pipe fitting for bearing the weight above;

the second arc-shaped connecting part is fixed above the square section pipe above; and

Two weight transfer tubes with fixed circular cross section, which are fixed at two side ends of the second arc connecting part respectively with the same angle with the vertical cross section of the horizontal fixing part, the opening of the fixing part is reduced to a second round hole, each weight transfer tube is used for inserting a circular foot pipe fitting to evenly transfer the weight from the circular connecting pipe fittings and the weight of the weight transfer tube to the circular foot pipe fittings,

wherein the weight-receiving pipes and the weight-transmitting pipes are inclined toward the same side of the horizontal fixing portion, and the inclination angles of the weight-transmitting pipes are larger than the inclination angles of the weight-receiving pipes.

2. The assembly of claim 1, wherein an upper side wall of one end of the upper square-section tube is provided with an elastic fastening hole, and a lower side wall of one end of the lower square-section tube is provided with another elastic fastening hole, and the elastic fastening holes temporarily fix elastic fasteners on the square tube provided with the elastic fasteners.

3. The assembly of claim 1, wherein the walls of the weight transfer tubes are each provided with an elastic fastening hole for fastening an elastic fastener on a circular foot tube provided with the elastic fastener.

4. The assembly of claim 1, wherein the weight receiving tube and the weight transmitting tube on the same side of the horizontal fixing portion are connected and fixed by a fixing block.

5. The assembly of claim 1, wherein the second arcuate connection portion defines an upward indication for indicating to a user that the square cross-section tube above is to be placed upward.

6. The assembly of claim 1, wherein a first guide frame is formed at the center of the first arc-shaped connection portion, and a first semicircular groove is formed in the first guide frame, so that an elastic rope passing through two first circular holes can pass through the first semicircular groove support without swinging laterally on any of the first arc-shaped connection portions.

7. The assembly of claim 1, wherein a second guide frame is formed at the center of the second arc-shaped connection portion, and a second semicircular groove is formed in the second guide frame, so that an elastic rope passing through two second circular holes can pass through the second semicircular groove support without swinging laterally on any of the second arc-shaped connection portions.

8. The assembly of claim 1 wherein the inner sides of the open tubular walls of the weight-receiving tubes remote from the attachment are provided with arcuate surfaces.

9. The assembly of claim 1, wherein the inner sides of the open tube walls of the weight transfer tubes remote from the fixation are provided with arcuate surfaces.

10. The assembly of claim 1, wherein the inner sides of the two open tube walls of the square-section tubes are provided with circular arc surfaces.