Hydro-Mechanical Actuator

This invention relates to a hydro-mechanical actuator for effecting displacement of a part to be positionally adjusted. An example of the use to which such an actuator may be put is the adjustment of a roll of a rolling mill in order to set the roll gap.

British patent specification No. 1,316,959 discloses in FIG. 1 a hydro-mechanical actuator for a vertical stand of a slabbing mill employing a conventional screwdown with a hydraulic capsule interposed between the screwdown and a roll carriage; the hydraulic capsule was employed for fine modulation of the roll gap after the roll had been brought approximately to the required position by the screwdown.

While the hydro-mechanical actuator of specification No. 1,316,959 is generally satisfactory, it entails a hydraulic capsule located closely adjacent to the roll gap and to the hot metal workpiece, with the attendant fire risk resulting from component failure. Further, the capsule is in a hostile environment in that it is subjected to high pressure descaling water and the scale itself.

In one aspect the present invention provides, a hydro-mechanical actuator. The actuator has an actuating member which has a driving end for effecting displacement of a part to be positionally adjusted. A mechanical driving means causes rotation of the actuating member, without restricting its axial displacement; and an internally threaded member which is held against rotation receives a threaded portion of the actuating member so that rotation of the actuating member by the driving means results in axial movement of the actuating member. A hydraulic mechanism is provided for axially displacing the internally threaded member and hence the actuating member. In that construction, the hydraulic mechanism is separated from the internally threaded member and may be located in an entablature or other housing protecting it from accidental damage.

Other objects and advantages of the invention will become apparent from the following description with reference to the accompanying drawings, wherein:

FIG. 1 is a general side view of an adjustment mechanism for a vertical roll, which incorporates the hydro-mechanical actuator;

FIG. 2 is an axial section of the hydro-mechanical actuator in a retracted position; and

FIG. 3 is an axial section of the hydro-mechanical actuator in an extended position.

The actuator 1 shown in detail in FIGS. 2 and 3 of the drawings is intended for use as the screwdown for a vertical stand of a slabbing mill, as shown in FIG. 1, but may be employed as the screwdown for other mills and in other applications. For a vertical mill, FIG. 1, two screwdowns of actuators 1 are provided for each roll 2 which is driven by a roll drive 6, each passing through an entablature 3 and engaging the roll carriage 4 at spaced points. A pull-back piston and cylinder assembly 5 is arranged between the two screwdowns 1 and is attached to the roll carriage 4, for withdrawing the roll 2 in order to open the roll gap. The actuator 1 comprises a horizontal long stroke screw and a short stroke hydraulic capsule. Thus, referring in particular to FIGS. 2 and 3, the actuator has an actuating member 10 which is splined over its rear (left hand) half 11 and threaded over its forward (right hand) half 12, which carries a pusher 13 engaging against the roll carriage 4. The mechanical drive is through a splined sleeve 14 having a wormwheel 15 driven by a worm (not shown) which engages with the splined half 11 and which rotates the actuating member 10 without restricting its axial movement.

Mounted in the entablature 3 is a sleeve 16 in which is secured a retaining sleeve 17, having internal keys 22 engaging with an internally threaded member in the form of a nut 18 and holding the nut against rotation while permitting it to move axially. The internal thread of nut 18 meshes with the threaded part 12 of the actuating member 10, so that rotation of the latter results in its axial displacement.

The short stroke hydraulic capsule is constituted by a piston 20 surrounding the actuating member 10 without engaging it, and arranged in a cylinder 21 defined by the sleeve 16 and the rear end of retaining sleeve 17. The forward end of the piston 20 abuts against the nut 18. The hydraulic cylinder may be double acting, liquid under pressure being supplied to either end of the cylinder as required.

Displacement of the actuating member 10 is effected by rotating it through the mechanical drive 14 to bring the pusher 13 and therefore the roll to its approximate operating position. Fine adjustment or modulation is then effected by the short stroke hydraulic capsule; for example the supply of liquid under pressure to the rearward (left hand) end of the cylinder 21 drives the piston 20 to the right, axially displacing the nut 18 and hence the member 10 and pusher 13, FIG. 3. Similarly, the roll gap may be increased by reducing the hydraulic pressure when the rolling load drives the actuator member 10, the nut 18 and the piston 20 rearwardly, e.g. FIG. 2.

As will be appreciated, the hydraulic capsule is protected against descaling water and scale by being located within the entablature 3, and is displaced with the actuator member by the hot workpiece being rolled by the mill.