Abstract:
A steering ring core is fabricated by telescopically assembling into a ring a plurality of arcuate alternating solid connecting elements and tubular steering ring elements and welding radiating spoke elements at their outer ends to the solid connecting elements. The steering ring elements are secured to the connecting elements by squeeze-forming respective portions of the steering ring elements into external indentations formed in the connecting elements.

Description:
This is a continuation of application Ser. No. 730,573, filed May 6, 1986, which was abandoned upon the filing hereof. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a metal core for a steering wheel, to be used for automobiles, and more specifically to a steering wheel core in which a plurality of metal pipe core elements in circular arc form are connected by connecting metal core elements of a prescribed number whereby a ring core is formed, and spoke cores are connected at respective radially outer ends to the connecting core elements of the ring core and at respective radially inner ends to a boss plate. 
     2. Description of the Prior Art 
     In such a steering wheel metal core of the prior art, a part of a ring core is formed a by pipe so as to make the metal core lighter in weight, a plurality of pipe core elements in circular arc form are connected by connecting core elements of a prescribed number, and thereby a ring core is formed. In this case, connection of the pipe core elements with the connecting core elements has been performed in a process in which the pipe core elements are arranged outside the connecting core elements and end circumferential surface of each pipe core element is welded to each connecting core element. 
     However, simultaneous welding of the whole circumference at ends of the pipe core elements is difficult because the welding may be obstructed by other portions. Consequently, the whole circumference is divided into three or the like during the welding. For example, when the ring core is composed of the three pipe core elements, the connecting core elements also become three in number and each pipe core element is welded at both ends. That is, the six portions must be welded by dividing in three respectively and therefore the process number becomes large for the connection. 
     Since welding is utilized in order to connect the pipe core elements to the connecting core elements, both core elements cannot be connected to each other if both are made of different materials, for example, if the connecting core elements are made of iron and the pipe core elements are made of aluminium to make the core metal lighter in weight. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a metal core for a steering wheel in which caulking (i.e. squeeze-forming, such as crimping) is utilized in order to connect the pipe core elements with the connecting core elements. The number of process required for manufacturing the ring core is not large, and the pipe core elements and the connecting core elements can be connected to each other even if both of the types of core elements are made of different materials. 
     The above object can be attained by the invention in that each recess is formed in a connecting core element at a connecting portion radially outside of which a respective pipe core element is to be arranged. That pipe core element is arranged outside the connecting portion of the respective connecting core element and caulked (i.e. squeeze-formed) into the recess of the connecting portion, and as a plurality of the pipe core elements in circular arc form are connected in a like manner, a ring core is formed. 
     Further in a steering wheel metal core according to the invention, when a pipe core element is caulked (i.e. squeeze-formed) into the recess portion in a respective pipe core element, the end of the pipe core element may be narrowed smoothly in a tapered or curved surface manner towards the outer circumferential surface of the recess so as to form the ring core. In such constitution of the ring core, when a coating layer of soft plastic material is formed on outer circumference of the ring core by means of injection molding after formation of the steering wheel metal core, the molding material flows smoothly over all of the outer circumference of the ring core, thereby generation of an uneven luster or a weld mark on the outer surface of the coating layer can be reduced. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a plan view of a steering wheel metal core of a first embodiment of the invention; 
     FIG. 2 is a sectional view taken in line II--II of FIG. 1; 
     FIG. 3 is a partial sectional view of a steering wheel metal core of a second embodiment; and 
     FIG. 4 is a partial sectional view of a steering wheel metal core of a third embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In a first embodiment as shown in FIG. 1 and FIG. 2, a steering wheel metal core 1 comprises a boss plate 6 of iron, three flat spoke cores 5 of iron welded at their radially inner ends with the boss plate 6, and a ring core 2 welded with radially outer ends of the spoke cores 5. 
     The ring core 2 is composed of three pipe core elements (i.e. ring core elements) 3 in circular arc form and three solid connecting core elements 4 to connect the pipe core elements 3 into ring form. The radially outer end of each spoke core 5 is welded with each connecting core element 4. Each pipe core element 3 is made of aluminium in consideration of lightening in weight, and each connecting core element 4 is made of iron in consideration of welding with the respective spoke core 5. 
     Each connecting core element 4 is formed as an arcuate member, provided on its opposite arms 4b, 4b near both ends thereof with radially outwardly opening recesses (i.e. indentations) 4a of annular groove form, two per end. The ends of each pipe core element 3 are arranged radially outside the portions of the respective connecting core elements where the recesses 4a are provided and caulked (i.e. squeeze formed) into the portions including the recesses, through the mouths of the recesses, thereby fixedly connecting the pipe core elements 3 to the respective connecting core elements 4. 
     Each connecting core element 4 has the four recesses 4a having sides 4c which diverge outwardly to respective mouths 4d and therefore use of the three connecting core elements 4 requires squeeze-forming actions to be performed at twelve sites. In order to manufacture the ring core 2, the pipe core elements 3 are arranged radially outside the portions of the respective connecting core elements where the recesses 4a, thereby assembling the pipe core elements and the connecting core elements 4 into ring form. The connecting core elements are then caulked (i.e. squeeze-formed) to a corresponding jig, in one caulking operation. Thus, the number of process steps needed for manufacturing the ring core 2 may be reduced and the cost is lowered. 
     Since caulking (i.e. squeeze-forming) is utilized to connect the pipe core elements 3 with the connecting core elements 4, both types of core elements can be fixedly connected to each other even if they are made of different materials. 
     After the ring core 2 is manufactured as above described, the ring core 2, the boss plate 6 and the spoke cores 5 are set into a prescribed jig in a conventional manner, and each spoke core 5 is welded at its respective ends with the boss plate 6 and the connecting core element 4 of the ring core 2, thus further completing manufacture the steering wheel metal core 1. 
     Although each connecting core element 4 in the first embodiment is formed near both ends with recesses 4a of annular groove form at two portions per end, the recesses 4a may be formed at one portion per each end as long as the pipe core elements 3 can be securely connected by squeeze-forming, to the respective connecting core elements. 
     Referring to the second embodiment shown in FIG. 3, each connecting core element 14 may be formed on outer circumference near both of its ends with recesses 14a being not in annular form but sunk at prescribed portions. Each pipe core element 13 may then be arranged outside the sunk portions on respective connecting core elements and caulked (i.e. squeeze-formed) therewith so as to form a ring core 12. 
     Further, referring to the third embodiment shown in FIG. 4, when a pipe core element 23 is to be caulked (i.e. squeeze-formed) at both ends, it may be narrowed smoothly in a tapered or curved surface manner to the outer circumferential surface of a respective recess 24a of a respective connecting core element 24 so as to form a ring core 22. In such a type of construction, if a coating layer of soft plastic material is formed by injection molding on outer circumference of the ring core 22 after forming the steering wheel metal core, the molding material flows smoothly towards the outer circumference of the ring core 22 so that the generation of an uneven luster or a weld mark on the outer surface of the coating layer can be reduced. 
     In addition, although a circular cross-section is shown in the drawings for the pipe core elements 3, 13, 23 and the connecting core elements 4, 14, 24 of the first through third embodiments, it may be square or trigonometric other than circular. 
     Although the connecting core elements 4, 14, 24 disclosed in the first through third embodiments preferably is solid, it may be hollow as long as the welding with the spoke core can be performed satisfactorily.