WO2025226230A1

WO2025226230A1 - A body frame and a range hood comprising a body frame

Info

Publication number: WO2025226230A1
Application number: PCT/TR2024/050409
Authority: WO
Inventors: Cemil GOZKENC; Batuhan GURBUZ; Huseyin AKCAN
Original assignee: Femas Metal Sanayi ve Ticaret AS
Current assignee: Femas Metal Sanayi ve Ticaret AS
Priority date: 2024-04-24
Filing date: 2024-04-24
Publication date: 2025-10-30
Anticipated expiration: 2026-10-24

Abstract

The present invention discloses a body frame (4) for range hoods that are configured to draw in the air from a cooking zone and direct it to a ventilation system, the body frame comprising a front frame portion (10), a rear frame portion (9) extending on the side opposite the front frame portion (10) in a direction essentially parallel thereto, and side frame portions (11, 12) extending mutually opposite between the front frame portion (10) and the rear frame portion (9) so as to define an interior space (15) between them. The invention further discloses a production method for providing the body frame (4).

Description

A BODY FRAME AND A RANGE HOOD COMPRISING A BODY FRAME

TECHNICAL FIELD

The present invention relates to range hoods that are configured to draw in the air from a cooking zone and direct it to a ventilation system, and more particularly to a body frame for such range hoods, the body frame comprising a front frame portion, a rear frame portion extending on the side opposite the front frame portion in a direction essentially parallel thereto, and side frame portions extending mutually opposite between the front and rear frame portions so as to define an interior space between them, and to a range hood comprising said body frame.

PRIOR ART

As is known, range hoods are configured to draw in the air from a cooking zone and guide it to a ventilation system. In the most general sense, range hoods consist of an upper housing and a lower housing. The lower housing comprises a body frame and, mounted on the body frame, a front panel, a lighting arrangement and a filter arrangement. The upper housing is provided between the lower housing and the ventilation system and directs the air drawn from the cooking zone to the ventilation system. The visually perceptible burn marks and weld seams caused by the joining process, in particular by spot-welding, at the corner regions of the body frame in the lower housing impair the aesthetic appearance of the range hood. In conventional methods, the spot-welding process is carried out on portions of the body frame that remain visible from outside. Although certain additional finishing operations such as polishing are performed to eliminate the aforementioned negative appearance, it has not been possible to eliminate the resulting adverse aesthetic appearance completely.

DE 102011083565 A1 publication discloses a mounting system for sheet-metal panels of range hoods is described. Here, side panels are mounted to a main body. The side panels have multiple flange structures that are bendable, and the side panels are joined to the main body by spot-welding in these regions.

The present invention provides a further improvement, a further advantage or an alternative to the prior art. SUMMARY OF THE INVENTION

One of the objects of the present invention is to provide a body frame whose aesthetic appearance is improved, which is easy to manufacture and has low cost, and a range hood comprising said body frame.

Another object of the present invention is to provide a production method that reduces labour costs and is easier to carry out for manufacturing a body frame for range hoods.

To achieve the aforesaid object, the present invention provides a body frame for range hoods that are configured to draw in the air from a cooking zone and direct it to a ventilation system, the body frame comprising a front frame portion, a rear frame portion extending opposite the front frame portion in a direction essentially parallel thereto, and side frame portions extending mutually opposite between the front and rear frame portions so as to define an interior space between them. According to the invention, each of the frame portions in the body frame comprises a main wall and mutually opposed horizontal walls provided so as to extend from the longitudinal edges of the main walls toward the interior space, mutually opposed vertical walls provided so as to extend from said horizontal walls toward each other and essentially parallel to the respective main wall, and the side frame portions comprise ear portions provided in a foldable manner on first vertical walls of said side frame portions so as to correspond to respective parts of second vertical walls of the front frame portion and the rear frame portion. Accordingly, the regions in which the frame portions are joined at the corner regions of the body frame are provided so as not to be visible from outside, i.e. they are concealed. Thus, the joining of the frame portions of the body frame can be performed without adversely affecting the aesthetic appearance. Furthermore, no additional part is required for joining the frame portions together. On the other hand, the total number of joining operations applied to the body frame is reduced, thereby reducing labour time and labour costs.

The term “front frame portion” herein denotes the frame portion located at the front of the body frame and to which a front panel configured so that the user can control the range hood is attached.

The term “rear frame portion” herein denotes the frame portion located on the side of the body frame opposite the front frame portion, i.e. at the rear of the body frame.

The term “side frame portions” herein denotes the frame portions extending between the front frame portion and the rear frame portion and interconnecting the front and rear frame portions. In a possible embodiment of the invention, mutually corresponding ear portions shaped and dimensioned according to the ear portions are provided on the sides of the second vertical walls of the front frame portion and the rear frame portion that are close to the ear portions. Thus, the ear portions can be folded onto the corresponding ear portions which are provided on the second vertical walls and are shaped and dimensioned according to the ear portions. In a possible embodiment of the invention, the ear portions are arranged so as to be able to move from a first position, in which they are essentially perpendicular to the corresponding ear portion, into a second position, in which they are essentially parallel to the corresponding ear portion.

In a possible embodiment of the invention, a relief cut-out is provided on a folding axis between each ear portion and the corresponding first vertical wall. As a result, the transition of the ear portions from the first position into the second position is facilitated, and the external force to be applied to the ear portion during assembly is reduced.

In a possible embodiment of the invention, a fixed ear portion configured as the mirror image of the ear portion with respect to the folding axis is provided on the parts of the first vertical walls near the ear portions. Consequently, after the folding operation of the ear portion, separation of the ear portion from the first vertical wall is prevented, and adequate connection of the ear portion to the first vertical wall along the folding axis is ensured.

In a possible embodiment of the invention, when the respective ear portion is in the second position, at least one recess provided in the main walls of the front frame portion and the rear frame portion allows external access to the respective ear portion for joining the respective ear portion to the respective corresponding ear portion. Thus, during assembly it is possible to access the ear portion from outside for the joining operation, in particular for a spot-welding operation.

In a possible embodiment of the invention, each side frame portion has two ear portions for connection to the respective corresponding ear portion of the front frame portion and two ear portions for connection to the respective corresponding ear portion of the rear frame portion. Thus, the bent parts of the frame portions can easily be joined to one another at the corner regions by only eight joining operations.

In a possible embodiment of the invention, the rear frame portion comprises a first rear frame section and a second rear frame section arranged opposite one another and joined together by at least one frame-connecting portion. Thus, after all joining operations on the body frame have been completed, the body frame becomes a closed geometric frame structure. The term “frame-connecting portion” herein denotes a frame portion to which a joining operation, in particular a welding operation, is applied.

In a possible embodiment of the invention, an upper second vertical wall in the rear frame portion and a lower second vertical wall on the opposite side thereof each comprise a frame-connecting portion. Thus, the first rear frame section and the second rear frame section are strongly connected to each other.

In a possible embodiment of the invention, the body frame is manufactured from sheet-metal material, in particular from stainless-steel material. Thus, a body frame resistant to wear, abrasion and corrosion is provided. In a possible embodiment of the invention, the range hood comprises a lower housing including a body frame. Consequently, a range hood comprising the above-mentioned technical advantages of the body frame is provided.

To achieve the aforesaid object, the present invention also provides a production method for providing a body frame for a range hood. The production method comprises the steps of:

• obtaining the frame portions by bending the relevant bending portions of a sheet-metal plate so as to form a main wall, horizontal walls and vertical walls;

• bending the relevant ear portion provided on the first vertical walls in the side frame portions by applying an external force so as to correspond to the relevant corresponding ear portions provided on the front frame portion or the rear frame portion;

• joining mutually corresponding ear portions and corresponding ear portions to one another by a joining operation; and

• obtaining a closed geometric frame structure by joining, by at least one frame-connecting portion, the first rear frame section and the second rear frame section that form the rear frame portion.

Thus, no additional part is required during assembly, and it is sufficient to carry out only eight joining operations at the corner regions of the bent parts of the frame portions. Consequently, labour costs are reduced and a production method that is easier to implement is provided. Moreover, the joining operation is carried out so as not to be visible from outside, and a body frame with improved aesthetic appearance is obtained.

In a possible embodiment of the invention, the joining operation of the ear portions and the corresponding ear portions is a welding operation, in particular a spot-welding operation. Thus, the ear portions and the corresponding ear portions, which have a plate-like form, are easily joined to each other by applying pressure and heat to the welding region by means of an electric current.

In a possible embodiment of the invention, the joining operation of the ear portions and the corresponding ear portions is carried out by means of a pair of joining elements configured to supply an electric current, in particular a pair of copper-alloy electrode elements, a first joining element being provided so as to pass through the interior space defined by the frame portions and contact the corresponding ear portion, and a second joining element being provided so as to pass through the relevant recess in the front frame portion or the rear frame portion and contact the ear portion. Accordingly, the spot-welding operation is carried out in the interior of the body frame so as not to be visible from outside, and a body frame with improved aesthetic appearance is obtained.

Each possible embodiment disclosed in this description can, unless technically incompatible, be combined with any other possible embodiment disclosed herein. DESCRIPTION OF THE FIGURES

The sole purpose of the figures briefly described hereinafter is to facilitate a better understanding of the present invention; they are not intended to define the scope of protection or to serve as a basis for interpreting said scope in the absence of the description.

• Figure 1 : an isometric view of a range hood comprising the body frame subject to the invention.

• Figure 2: an isometric view of the body frame subject to the invention.

• Figure 3: another isometric view of the body frame subject to the invention.

• Figure 4: an enlarged isometric view showing the first side frame portion of the body frame subject to the invention, with the main wall of the front frame portion omitted and with one ear portion in the first position and another ear portion in the second position.

• Figure 5: an enlarged isometric view showing the first side frame portion and the front frame portion of the body frame subject to the invention.

• Figure 6: an enlarged isometric view showing the joining of the ear portions and the corresponding ear portions.

• Figure 7: an enlarged isometric view showing the frame-connecting portions of the rear frame portion.

• Figure 8: a diagram showing the production steps of the production method for providing a body frame.

DETAILED DESCRIPTION

In this detailed description, the subject matter of the invention is explained solely by way of examples that have no limiting effect and serve only to facilitate better understanding of the subject.

Figure 1 shows a perspective view of a range hood (1 ) comprising the body frame (4) subject to the invention. The range hood (1 ) is configured to draw in the air from a cooking zone and direct it to a ventilation system (not shown in the figures). Said cooking zone may be a region in a kitchen where a cooking process can be performed with appliances such as a hob or a stand-alone cooker. In its broadest form, the range hood (1 ) consists of an upper housing (2) and a lower housing (3). The lower housing (3) comprises a body frame (4), a front-panel arrangement (8), a lighting arrangement (6) and a filter arrangement (7) mounted on the body frame (4). The front-panel arrangement (8) has a front panel (5) on which control elements, in particular control knobs, are provided and by means of which the suction levels of the range hood (1 ) can be adjusted. The front panel (5) is provided so as to extend longitudinally on the lower housing (3). The lighting arrangement (6) comprises at least one lighting element, such as a lamp or an LED. More than one lighting arrangement (6) may be provided in the range hood (1 ); by way of example, two lighting arrangements (6) are shown in Figure 1. The filter arrangement (7) comprises at least one filter. Said filters are able to separate grease particles from the air drawn from the cooking zone. By way of example, the filter arrangement (7) shown in Figure 1 comprises three filters. Preferably, the filter arrangement (7) is provided between opposing lighting arrangements (6). The upper housing (2) is the portion provided between the lower housing (3) and the ventilation system and guides the air drawn from the cooking zone to the ventilation system. The upper housing (2) is connected to the lower housing (3) from a central part thereof. The lower housing (3) and the upper housing (2) are in fluid communication with each other; that is, the air drawn in by the lower housing (3) is directed to the ventilation system via the upper housing (2). As can be seen in Figure 1 , the front panel (5), the lighting arrangement (6) and the filter arrangement (7) are supported by the body frame (4).

With reference to Figures 2 and 3, the body frame (4) subject to the invention comprises a front frame portion (10), a rear frame portion (9) extending opposite the front frame portion (10) in a direction essentially parallel thereto, and mutually opposed side frame portions (11 , 12) extending between the front frame portion (10) and the rear frame portion (9). That is, a first side frame portion (11 ) and a second side frame portion (12) extend opposite each other. The frame portions (9, 10, 11 , 12) are provided so as to define an interior space (15). The body frame (4) has an essentially rectangular periphery. The body frame (4), which has an essentially rectangular periphery, is obtained by bending it at corner-bending portions (16) so as to have four sides. Each of the frame portions (9, 10, 11 , 12) in the body frame (4) has a main wall (19). The main walls (19) are provided so as to give the body frame (4) a depth. Each of the main walls (19) comprises mutually opposed horizontal walls provided so as to extend from the longitudinal edges of the respective main wall (19) toward the interior space (15) — namely an upper horizontal wall (20) and a lower horizontal wall (21 ). In each frame portion (9, 10, 11 , 12), two horizontal walls (20, 21 ) extending longitudinally in the respective frame portion are present. The horizontal walls (20, 21 ) are obtained by bending the main wall (19) inwardly at a horizontal-bending portion (17). The horizontal walls (20, 21 ) are provided so as to extend essentially perpendicular to the respective main wall (19). Each frame portion (9, 10, 11 , 12) further comprises mutually opposed vertical walls (22a, 22b, 23a, 23b) provided so as to extend from the respective horizontal walls (20, 21 ) toward each other. Said vertical walls (22a, 22b, 23a, 23b) are provided so as to extend essentially parallel to the respective main wall (19) — in other words, the vertical walls (22a, 22b, 23a, 23b) are provided so as to extend essentially perpendicular to the respective horizontal walls (20, 21 ). The vertical walls (22a, 22b, 23a, 23b) are obtained by bending the respective horizontal walls (20, 21 ) toward each other at a vertical-bending portion (18). Each side frame portion (11 , 12) has an upper first vertical wall (22a) and a lower first vertical wall (22b). Each of the front frame portion (10) and the rear frame portion (9) has an upper second vertical wall (23a) and a lower second vertical wall (23b).

With reference to Figure 4, in the preferred embodiment of the invention, the first vertical walls (22a, 22b) comprise ear portions (25) provided in a foldable manner so as to correspond to respective parts of the second vertical walls (23a, 23b) of the front frame portion (10) and the rear frame portion (9). Furthermore, on the sides of the second vertical walls (23a, 23b) of the front frame portion (10) and the rear frame portion (9) that are close to the ear portions (25), a corresponding ear portion (24) is provided that is shaped and dimensioned according to the ear portions (25). In the view shown in Figure 4, one of the ear portions (25) is in a first position in which it has not yet been folded onto the corresponding ear portion (24). In the first position, the ear portion (25) is provided so as to be essentially perpendicular to the corresponding ear portion (24). In the view shown in Figure 4, another of the ear portions (25) is in a second position in which it has been folded. In the second position, the ear portion (25) is provided so as to be essentially parallel to the corresponding ear portion (24). The ear portions (25) are arranged so as to be able to move from the first position, in which they are essentially perpendicular to the corresponding ear portion (24), into the second position, in which they are essentially parallel to the corresponding ear portion (24). When an external force (F) is applied to the ear portion (25) that is in the first position in Figure 4, the ear portion (25) is bent in a bending direction (BY) and is folded so as to be essentially parallel to the corresponding ear portion (24), i.e. it moves into the second position. That is, the ear portion (25) is folded onto the corresponding ear portion (24) by rotating about a folding axis (y) through an angle of approximately 90°. In the second position, the ear portion (25) can bear against the corresponding ear portion (24). The transition of the ear portions (25) from the first position into the second position applies to all the ear portions located on the body frame (4). In the preferred embodiment of the invention, a relief cut-out (26) is provided on the folding axis (y) between the ear portions (25) and the corresponding first vertical wall (22a, 22b). Owing to said relief cut-out (26), the transition of the ear portions (25) from the first position into the second position is facilitated. Furthermore, on the parts of the first vertical walls (22a, 22b) that are close to the ear portions (25), a fixed ear portion (29) is provided so as to be symmetrical to the ear portions (25) with respect to the folding axis (y). By virtue of the fixed ear portion (29), separation of the ear portion (25) from the corresponding first vertical wall (22a, 22b) after the folding operation is prevented, and adequate attachment of the ear portion (25) to the corresponding first vertical wall (22a, 22b) along the folding axis (y) is ensured. On the other hand, in the preferred embodiment of the invention, each side frame portion (11 , 12) has two ear portions (25) for connection to the corresponding ear portion (24) of the front frame portion (10). In addition, each side frame portion (11 , 12) has two ear portions (25) for connection to the corresponding ear portion (24) of the rear frame portion (9). With reference to Figure 5, after all the ear portions (25) have moved from the first position into the second position, the ear portions (25) and the corresponding ear portions (24) are ready for a joining operation, in particular a spot-welding operation. When the respective ear portion (25) is in the second position, at least one recess (13) provided in the main walls (19) of the front frame portion (10) and the rear frame portion (9) allows external access to the respective ear portion (25) for joining the respective ear portion (25) to the respective corresponding ear portion (24). As can be seen in Figures 2 and 3, the recess (13) is provided on the respective main wall (19) so as to correspond to the pair consisting of the respective ear portion (25) and the respective corresponding ear portion (24). Preferably, four recesses (13) are provided in each of the rear frame portion (9) and the front frame portion (10). As can be seen in Figure 6, a second joining element (510) can pass through the respective recess (13) and reach the respective ear portion (25). After the joining operation of all pairs of ear portions (25) and corresponding ear portions (24) located on the body frame (4) is completed, a final joining operation is performed on the rear frame portion (9), thereby making the body frame (4) ready to be mounted on the range hood (1 ). As can be seen in Figure 7, the rear frame portion (9) has a first rear frame section (27) and a second rear frame section (28) disposed opposite each other and joined to each other by at least one frame-connecting portion (14). The term “frame-connecting portion” denotes a portion to which a joining operation, in particular a welding operation, is applied. In the preferred embodiment of the invention, an upper second vertical wall (23a) in the rear frame portion (9) and a lower second vertical wall (23b) on the opposite side thereof each comprise a frame-connecting portion (14). Thus, the first rear frame section (27) and the second rear frame section (28) are strongly connected to each other, thereby preventing possible mechanical separation. The body frame (4) subject to the invention, as described in detail above, is manufactured from sheet-metal material, in particular from stainless-steel material.

The invention further provides a production method, described in detail above, for providing the body frame (4) subject to the invention for a range hood (1 ). As can be seen in Figure 8, the production method in its general form consists of four steps. In a first step (100), the frame portions (9, 10, 11 , 12) are obtained by bending the relevant bending portions (16, 17, 18) of a sheet-metal plate so as to form a main wall (19), horizontal walls (20, 21 ) and vertical walls (22a, 22b, 23a, 23b). In a second step (200), the relevant ear portion (25) provided on the first vertical walls (22a, 22b) in the side frame portions (11 , 12) is bent by applying an external force (F) so as to correspond to the relevant corresponding ear portions (24) provided on the front frame portion (10) or the rear frame portion (9). In a third step (300), mutually corresponding ear portions (25) and corresponding ear portions (24) are joined to each other by a joining operation. In a fourth step (400), a closed geometric frame structure is obtained by joining, by at least one frame-connecting portion (14), the first rear frame section (27) and the second rear frame section (28) that form the rear frame portion (9). Preferably, the joining operation of the ear portions (25) and the corresponding ear portions (24) is a welding operation, in particular a spot-welding operation. The joining operation of the ear portions (25) and the corresponding ear portions (24) is carried out by means of a pair of joining elements (500, 510) configured to supply an electric current, in particular a pair of copper-alloy electrode elements. A first joining element (500) is provided so as to pass through the interior space (15) defined by the frame portions (9, 10, 11 , 12) and contact the corresponding ear portion (24). That is, a first end part (501 ) of the first joining element (500) that faces the corresponding ear portion (24) contacts the corresponding ear portion (24). A second joining element (510) is provided so as to pass through the relevant recess (13) in the front frame portion (10) or the rear frame portion (9) and contact the respective ear portion (25). That is, a second end part (511 ) of the second joining element (510) that faces the ear portion (25) contacts the ear portion (25). Consequently, the ear portions (25) and the corresponding ear portions (24), which have a plate-like form, are easily joined to each other by applying pressure and heat to the welding region by means of an electric current.

REFERENCE NUMBERS

1 . range hood

2. upper housing

3. lower housing

4. body frame

5. front panel

6. lighting arrangement

7. filter arrangement

8. front-panel arrangement

9. rear frame portion

10. front frame portion

11 . first side frame portion

12. second side frame portion

13. recess

14. frame-connecting portion

15. interior space

16. corner-bending portion

17. horizontal-bending portion

18. vertical-bending portion

19. main wall 20. upper horizontal wall

21 . lower horizontal wall

22a. upper first vertical wall

22b. lower first vertical wall

23a. upper second vertical wall

23b. lower second vertical wall

24. corresponding ear portion

25. ear portion

26. relief cut-out

27. first rear frame section

28. second rear frame section

29. fixed ear portion

100. first step

200. second step

300. third step

400. fourth step

500. first joining element

501. first end part

510. second joining element

511. second end part

F. external force

BY. bending direction y. folding axis

Claims

1- A body frame (4) for a range hood configured to draw in the air from a cooking zone and direct it to a ventilation system, the body frame comprising a front frame portion (10), a rear frame portion (9) extending on the side opposite the front frame portion (10) in a direction essentially parallel thereto, and side frame portions (11 , 12) extending mutually opposite between the front frame portion (10) and the rear frame portion (9) so as to define an interior space (15) between them, characterized in that each of the frame portions (9, 10, 11 , 12) comprises a main wall (19) and, provided extending from the longitudinal edges of each of the main walls (19) towards the interior space (15), mutually opposing horizontal walls (20, 21 ), mutually opposing vertical walls (22a, 22b, 23a, 23b) are provided extending from the horizontal walls (20, 21 ) towards each other and essentially parallel to the respective main wall (19), and the first vertical walls (22a, 22b) in the side frame portions (11 , 12) comprise ear portions (25) provided in a foldable manner so as to correspond to a respective part of the second vertical walls (23a, 23b) of the front frame portion (10) and the rear frame portion (9).

2- The body frame (4) according to Claim 1 , wherein mutually corresponding ear portions (24) shaped and dimensioned according to the ear portions (25) are provided on the sides of the second vertical walls (23a, 23b) of the front frame portion (10) and the rear frame portion (9) that are close to the ear portions (25).

3- The body frame (4) according to Claim 2, wherein the ear portions (25) are arranged so as to be able to move from a first position, in which they are essentially perpendicular to the respective corresponding ear portion (24), into a second position, in which they are essentially parallel to the respective corresponding ear portion (24).

4- The body frame (4) according to any preceding claim, wherein a relief cut-out (26) is provided on a folding axis (y) between the ear portions (25) and the respective first vertical wall (22a, 22b).

5- The body frame (4) according to Claim 4, wherein a fixed ear portion (29) configured as the mirror image of the ear portions (25) with respect to the folding axis (y) is provided on the parts of the first vertical walls (22a, 22b) that are close to the ear portions (25). 6- The body frame (4) according to any one of Claims 3 to 5, wherein, when the respective ear portion (25) is in the second position, at least one recess (13) provided in the main walls (19) of the front frame portion (10) and the rear frame portion (9) allows external access to the respective ear portion (25) for joining the respective ear portion (25) to the respective corresponding ear portion (24).

7- The body frame (4) according to any preceding claim, wherein each side frame portion (11 ) has two ear portions (25) for connection to the corresponding ear portion (24) of the front frame portion (10) and two ear portions (25) for connection to the corresponding ear portion (24) of the rear frame portion (9).

8- The body frame (4) according to any preceding claim, wherein the rear frame portion (9) comprises a first rear frame section (27) and a second rear frame section (28) disposed opposite each other and joined to each other by at least one frame-connecting portion (14).

9- The body frame (4) according to Claim 8, wherein an upper second vertical wall (23a) in the rear frame portion (9) and a lower second vertical wall (23b) on the opposite side thereof each comprise a frame-connecting portion (14).

10- The body frame (4) according to any preceding claim, wherein the body frame (4) is manufactured from sheet-metal material, in particular from stainless-steel material.

11 - A range hood (1 ) comprising a lower housing (3) that includes a body frame (4) according to any preceding claim.

12- A production method for providing a body frame (4) according to Claim 1 for a range hood (1 ), wherein the production method comprises the steps of obtaining the frame portions (9, 10, 11 , 12) by bending the relevant bending portions (16, 17, 18) of a sheet-metal plate so as to form a main wall (19), horizontal walls (20, 21 ) and vertical walls (22a, 22b, 23a, 23b); bending the relevant ear portion (25) provided on the first vertical walls (22a, 22b) in the side frame portions (11 , 12) by applying an external force (F) so as to correspond to the relevant corresponding ear portions (24) provided on the front frame portion (10) or the rear frame portion (9); joining mutually corresponding ear portions (25) and corresponding ear portions (24) to each other by a joining operation; obtaining a closed geometric frame structure by joining, by at least one frame-connecting portion (14), the first rear frame section (27) and the second rear frame section (28) that form the rear frame portion (9).

13- The production method according to Claim 12, wherein the joining operation of the ear portions (25) and the corresponding ear portions (24) is a welding operation, in particular a spot-welding operation.

14- The production method according to Claim 13, wherein the joining operation of the ear portions (25) and the corresponding ear portions (24) is carried out by means of a pair of joining elements (500, 510) configured to supply an electric current, in particular a pair of copper-alloy electrode elements, a first joining element (500) being provided so as to pass through the interior space (15) defined by the frame portions (9, 10, 11 , 12) and contact the corresponding ear portion (24), and a second joining element (510) being provided so as to pass through the relevant recess (13) in the front frame portion (10) or the rear frame portion (9) and contact the respective ear portion (25).