Metal deforming – By use of closed-die and coacting work-forcer – Forcing work into or within closed die; e.g. – forging
Patent
1987-03-27
1988-09-06
Bray, W. Donald
Metal deforming
By use of closed-die and coacting work-forcer
Forcing work into or within closed die; e.g., forging
72353, 72359, B21K 176, B21J 512, F16D 322
Patent
active
047683686
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the manufacture of hollow articles. The invention has been developed for the manufacture of the outer member of a constant velocity ratio universal joint of the cross-groove type. Such a joint comprises an inner member and an outer member, the outer member having an internal cylindrical surface and the inner member an external cylindrical surface which surfaces have grooves formed therein. There are two sets of, preferably, helical grooves in each member, the grooves of the two sets being helices of opposite hand. For manufacturing simplicity, the grooves are usually straight and inclined to the rotational axis of the respective joint member, instead of the truly helical. Bells are engaged in the grooves and are held in a cage, and because of the crossed configuration of the grooves the balls are held in the bisector plane of the joint as the parts of the joint articulate, to give the joint constant velocity ratio (homokinetic) properties.
Although the invention has been developed for making outer members for such cross groove constant velocity joints, it is applicable more generally to the manufacture of articles of the type, hereinafter referred to as being of the type specified, having two sets of grooves in the internal surface thereof, the sets of grooves having longitudinal axes of symmetry (as hereinafter defined) which differ (as hereinafter defined). By the longitudinal axis of symmetry of a groove, we mean the imaginary line which is equally spaced from the edges of the groove and which lies in an imaginary surface forming a continuation of the surface of the bore of the article, containing said edges.
When we say that the longitudinal axes of symmetry are the same, we mean that the loci of points moving in synchronism from the one ends of said axes of symmetry to the other bear a fixed relation to one another. Conversely, when we say that the longitudinal axes differ we mean that the loci of such moving points do not lie in a fixed relation to one another thus, for example, the axes could be on helices of different hand but the same pitch, of the same hand and different pitch, or of different pitch and hand. Some of the axes could be straight and parallel to the rotational axis of the article, while others could be helical.
At present, in the manufacture of outer members for cross-groove constant velocity ratio universal joints, blanks are made by forging, extrusion or some other metal forming method and the grooves are then machined in the blank bores. Such machining operations are expensive in time and equipment, besides necessarily involving the removal of material. It would be convenient to be able to form the grooves in the bore without removal of metal or even to make them with imprecise grooves which would require less machining than at present. However, since the longitudinal axes of symmetry of the grooves differ as defined above, a one piece tool could not be removed from the bore after the grooves have been formed therearound.
A tool, and method, for manufacturing articles of the kind specified is disclosed in GB-A-No. 2132514, which enables the machining required in the finished article to be reduced. The tool comprises intercalated portions capable of being withdrawn successively from the finished article by movement of formations on the portions along the grooves formed thereby. However, such successive withdrawal of the tool portions from the article can require very high forces which is disadvantageous.
It is an object of one aspect of the present invention to provide an improved tool for making hollow articles of the type specified, and particularly for making outer members of cross groove constant velocity universal joints, whereby machining of the gooves can be reduced or eliminated.
According to one aspect of the invention there is provided a tool for use in the manufacture of a hollow article of the type specified, by forming the material of the article about the tool and subsequently withdrawing the tool, the tool comprising a plurality of elements
REFERENCES:
patent: 4317356 (1982-03-01), Stell
patent: 4406146 (1983-09-01), Suzuki
Langford Edward A.
Morden Geoffrey A.
Bray W. Donald
PFD Limited
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