Method of making a cam shaft

Claim 1

A method of making a cam shaft (10) from a plurality of lobes (14) having apertures (16) and spaced along the longitudinal axis of a hollow tubular shaft (12), said method comprising inserting the hollow tubular shaft (12) through the apertures (16) of the lobes (14); orientating each of the lobes (14) axially and radially with respect to the longitudinal axis of the shaft (12), and providing liquid under pressure within the shaft to expand the wall thereof into engagement with the apertures of the lobes (14) to fixedly secure the lobes radially on the shaft, CHARACTERISED BY flaring the opposed longitudinal ends (20, 22) of the shaft (12); inserting first and second plug means (40, 46) into fluid sealing engagement with the respective interiors of said flared ends (20, 22) to seal the interior of the shaft (12) filled with liquid, said first and second plug means (40, 46) engaging with the flared ends of the shaft (12) to prevent axial and radial movement thereof and to determine the positioning of the longitudinal axis of the tubular shaft (12) at the ends thereof with respect to the exterior profiles of the lobes (14), and longitudinally displacing a ram (54) through one said plug means and within the liquid in the interior of the shaft to increase the hydraulic pressure of the liquid within the interior of the shaft (12) between the first and second plug means (40, 46) so that the wall of the shaft (12) expands into simultaneous engagement with the apertures of the lobes (14) spaced along the shaft as well as expanding the shaft outwardly in between the lobes thereby fixedly securing the lobes axially as well as radially on the shaft.

Claim 5

A method as claimed in any one of the preceding claims further characterised by finishing the exterior circumferences of the lobes (14) to closer tolerances than the interior apertures and radially positioning the exterior surfaces of the lobes (14) relative to the longitudinal axis of the shaft without reference to the position of the interior apertures.

Claim 6

A method as claimed in any one of the preceding claims further characterised by releasing the shaft (12) from the apparatus and removing the flared ends (20, 22) from the shaft (12).

Claim 7

A method as claimed in any one of the preceding claims which comprises flaring an end of the shaft (10) by engagement of the respective plug means therewith.

Claim 8

An apparatus (24) for making a cam shaft (10) from a plurality of lobes (14) having apertures (16) and spaced along the longitudinal axis of a hollow tubular shaft (12), and which comprises a restraining means (26, 28) for surrounding the hollow shaft (12) and lobes (14): means for sealing liquid within the shaft and means for pressurising said liquid to expand the tubular shaft into engagement with the lobes to fixedly secure the lobes radially on the shaft CHARACTERISED IN THAT the sealing means comprises a first plug means (44) for sealing engagement with a first longitudinal end (20) of the shaft (12), said first end (20) being provided with a flared profile and a second plug means (46) for sealing engagement with the second longitudinal end (22) of the shaft (12), said second end (22) being provided with a flared profile, said first and second plug means (44, 46) being mounted with respect to the restraining means (26, 28) and profiled for sealing engagement with the interior of the respective first and second flared ends (20, 22) of the tubular shaft (12) to restrain the shaft from axial and radial displacement and to determine the location of the longitudinal axis at the ends of the shaft with respect to the peripheral profiles of the lobes, and pressurising means by which hydraulic pressure is developed, said pressurising means comprising a ram (54) longitudinally displaceable through one said plug means (44, 46) for longitudinal displacement in the interior of the shaft (12) to develop hydraulic pressure in said liquid between the first and second plug means (20, 22) for expanding the wall of the shaft simultaneously into engagement with the apertures of the lobes (14) spaced along the shaft as well as expanding the shaft outwardly in between the lobes thereby fixedly securing the lobes axially as well as radially on the shaft.

Claim 13

An apparatus as claimed in any one of claims 9 to 12 further characterised by said restraining means (24) including upper and lower halves (26, 28) with each of said halves including a plurality of said plates (34), fastening means (78) for clamping each half (26, 28) in mating engagement with the other half.

Claim 16

An apparatus as claimed in any one of claims 9 to 15 further characterised by each of said plates (30, 32, 34) including a tube recess (72) axially adjacent to lobe recesses (38) within which the lobes are to be received and positioned and for disposition in radially spaced relationship to the exterior of the shaft (12) to limit radial expansion thereof.

Claim 17

An apparatus as claimed in any one of claims 9 to 16 further characterised by the restraining means (24) comprising upper and lower halves (26, 28) and at least one of said upper and lower halves (26) or (28) including a channel member having a central trough (58) supporting the plates (30, 32, 34).

Claim 19

An apparatus as claimed in any one of claims 8 to 18 further characterised by the second plug means (46) comprising a base (48) and a frusto conical sealing member (50) for both flaring and sealing the second end (22) of the hollow tubular shaft (12), said ram (54) being disposed within said frusto conical sealing member (50).