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(11) | EP 2 027 949 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 153(4) EPC |
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| (54) | IMPROVED METHOD AND TOOL FOR PRODUCING CONVOLUTED TUBES APPLICABLE TO STEERING COLUMNS AND UNIVERSAL JOINTS |
| (57) The invention refers to the manufacturing procedure for a convoluted tube (26) using
a tube (28) which has previously been fitted with recesses (18) obtained by turning
(14) and applying a tool (25) formed by a holder (10) equipped with discs (22) at
regular distances, an inner surface (22a), operating in combination with a support
(21) which is fitted inside the tube (14) to be then subjected to a compression force
on the end from the head (27) of the support (21). |
FIELD OF THE TECHNIQUE.
[0001] More specifically the invention refers to the design and characteristics of a machined tool formed by equally spaced rings on a holder and to the manufacturing process used for this tool to obtain a convoluted tube from a conventional tube.
SCOPE OF THE INVENTION.
[0002] The invention has the aim of obtaining convoluted tubes from a conventional tube used in the manufacture of steering columns and universal joints by the automobile sector on cars and similar vehicles with a double cardan shaft. The process places a previously machined tube to produce recesses on its side surface inside a tool to change the aforementioned normal tube into a convoluted tube.
STATE OF THE ART.
[0003] A known technique for manufacturing convoluted tubes is the hydrolining process. This process is expensive and technologically complex in which the tube has to be successively extracted until the required wall thickness is achieved.
[0004] The use of convoluted tubes in the manufacture of steering columns and universal joints is based on achieving significant improvements in safety against front or side impacts on cars. Convoluted tubes are normally used in this areas as they have two positive affects on energy absorption via the a steering column in the event of an impact:
- Bending due to the lateral bending forces produced in the event of an impact, preventing these forces being transmitted to the driver via the tube.
- Compressing as a result of frontal compression forces produced in the event of an impact, preventing these forces being transmitted to the driver.
DISCLOSURE OF THE INVENTION.
[0005] The invention comprises the tool, formed by a support containing rings located at equal distances on a holder, which is used in the manufacture of the convoluted tube and its characteristic features, and the tube's manufacturing process using the aforementioned tool after the tube has been previously rebated into slots located at predetermined gaps.
[0006] The tool used is the combination of a support fitted with the relevant head which fits inside the tube to be transformed and a set of discs surrounding the tube to be transformed supported by a holder a predetermined spaces. The ends of these discs are applied to the tube to be transformed to allow the corresponding slots to be folded when a compression force is applied to the aforementioned rebated tube to obtain the convoluted tube.
DESCRIPTION OF THE FIGURES.
[0007] A numbered list of the main parts in the invention is given below. These are shown in diagrams attached to this report:
(10) Support.
(11) Volute.
(12) Inner diameter of tube (14).
(13) Outer diameter of recessed areas.
(14) Rebated tube.
(15) Height of recess.
(16) External radius of the volute (11).
(17) Width of volute.
(18) Recesses.
(19) Diameter of tube (14).
(20) Thickness of recesses (18).
(21) Support.
(22) Internal parts.
(22a) Inner surface of rings (22a).
(23) Lugs.
(24) Width of recesses (18).
(25) Tool.
(26) Convoluted tube.
(27) Head.
(28) Starting tube.
Figure 1 is a front view in elevation of a longitudinal section in elevation of a starting tube (28) after the first machining on a lathe or similar machine transforming the tube (14), before it is attached to the support (21).
Figure 2 is a front view in elevation of a longitudinal section of a starting tube (28) after the volutes (11) have been made in its wall and after being subjected to an axial compression force forming a tube(14) with recesses (18).
Figure 3 is a front view in elevation of a longitudinal section of a starting tube (28) to which the tool (25) has been applied tom manufacture the aforementioned convoluted tubes (26).
Figure 4 is a front view in elevation of a longitudinal section of a starting tube (28) which is transformed after machining the tube (26), in accordance with Figure 2.
DESCRIPTION OF AN EMBODIMENT OF THE INVENTION.
[0008] In order to better understand the invention, the starting tube before machining (28) is shown, see Figure 4, and after machining showing recesses in the form of rebated slots (18), the tube (14), after making the slots (18) in it. This is subjected to an axial compression force forming the convoluted tube (26), see Figure 2.
[0009] In one of the preferred set ups for this invention and as shown in Figure 3, the tool (25) is formed by a support (21) with a holder (10) on its periphery. The support (21) is surrounded by a succession of rings (22) aligned and spaced at equal distances, held to the lateral surface of the aforementioned holder (10), and fitted onto the aforementioned support (21). The head (27) is located on one of its sides using external lugs (23) on the holder (10).
[0010] The support (21), shown in Figure 3, is formed by a cylindrical body ending in a head (27) at one of its ends.
[0011] Machining the tube (28) starts with rebating the lateral surface on a lathe or similar machine to obtain recessed slots (18) on its lateral surface, then being fitted inside the tool (25) and its support (21), see Figure 3.
[0012] Turning the tube (28) transforms the said smooth tube (28) into a recessed tube (18) with a height of (15) and width of (24), which is called the rebated tube (14), see Figure 1.
[0013] The axial movement of the rings (22) in its inner parts (22a) supporting the lateral surface of the tube (14) and their recesses (18) as shown in Figure 3, transforms the machined tube (14) see Figure 1, into a convoluted tube (26), see Figure 2.
[0014] The result of the axial movement of the rings (22) and its inside (22a) on the recesses (18) on the lateral surface of the tube (24) in the tool (25), from the compression force on the end of the support (21), forms the volutes (11) as shown in Figure 2. The width of the volutes (11) shall be (17), see Figure 2 and their size will depend on the compression force applied on the end of the support (21), in addition to the type of material used for the aforementioned tube(28) and its thickness (20), in the recessed area (18).
[0015] It is possible, using the aforementioned manufacturing process, for convoluted tubes (26) to have the number of volutes (11) required and to move them to vary the gaps between the recesses (18). The external diameter of the volute (11) and its width (17) may be modified to match the final design of the tool (25) in which the invention is applied.
[0016] To form the volutes (11) in the tube (28), in accordance with one of the aims of the invention, the manufacturing process involves the following operations in order to obtain the convoluted tube (26):
- Turning the tube (28) rebating its lateral surface to a height "d" (13), and a width "a" (24) at regular intervals until the machined tube is obtained (14).
- Attaching the machined tube (14) inside the support (21).
- Attaching a tool (25) formed by a support (21) for the head (27) inside which is holder (10) is fitted comprising rings (22) at predetermined distances, the inner surfaces of which (22), (22a) wrap around the lateral surface of the tube (14), in its recesses (18).
- Prior to attaching the tool (25) the distance between rings (22) is determined for the lateral surface of the holder (10).
- Compression pressure applied to the end of the tube (14) by the support (21) and its head (27) forming the convoluted tube (26).
- Turning a tube (28) until rebates or recessed slots (18) are obtained with a width of (24) and height of (15), resulting in a machined tube.
- Attaching the tube (14) in a tool (25) with a support (21) onto which the holder (10) is fitted comprising rings (22) at predetermined distances, the ends of the rings (22), (22a), pressed onto the surface of the tube (14) and the rebates or recessed strips (18).
- Prior to attaching the tube (14) in the tool (25) the distance between rings (22) is determined for the lateral surface of the holder (10).
- Supplying a compression pressure onto the end of the tube (14), fitted into the tool (25) via the head (27) of the support (21), forming a convoluted tube (26), when the recesses (18) are bent on the lateral surface of the tube (14) and changing them into volutes (11), in the resulting convoluted tube (26).