Rolls-royce Corporation

Allwood, Searle & Timney (holdings) Limited

John G Searle

Frederick J Harris

Arnold J Pratt

John P Searle

John G Beresford

Variable amplitude, linear reciprocation of an output ram is produced by converting rotary motion into linear motion using a swash plate connected by a bending element to drive a crank. The rotary prime mover and swash plate are mounted on a pivotable frame so as the axial throw of the swash plate is determined by the angular offset of the rotational axes of the swash plate and crank. When the axes are coincident the throw, and therefore the ram stroke, is zero but progressive angular displacement produces a progressively increased stroke. Thus, the frequency of reciprocation is determined by the angular speed of the prime mover, and the stroke is controllably variable between maximum and zero.

Friction welding apparatus

The frictional loads involved in a friction welding operation, for joining metal parts, may be several tons and the mass of the welding apparatus is correspondingly large. Thus, in addition to the energy which is converted into heat at the weld interface a substantial amount of work has to be done simply to overcome the inertial loads of the apparatus. An inertial load cancelling system is proposed in which a double acting gas spring arrangement is coupled to the welding oscillator output so that the work done in overcoming the inertia of the apparatus is returned to the system when the oscillator motion is reversed at the ends of each stroke. Thus, after the initial system input the oscillator has only to supply work to overcome internal frictional and that converted to frictional heat at the weld joint interface.

In a friction bonding operation the friction generating and weld forming forces are usually applied perpendicular to the joint faces. Thus, whenever the joint angle changes to component cassette part of the welding machine must be reset to a new angular orientation. This situation arises in the manufacture of a compressor BLUM (Bladed drUM) for a gas turbine engine, where the blades in successive stages are set at different HADE angles. The invention provides an improved component cassette in which the HADE angle is ignored. The cassette is interlocked with the workplace holder to provide a closed force loop to contain out-of-plane forces while retaining sufficient degrees of freedom to allow the friction generating and welding movements to proceed unimpeded.

Friction welding tooling

A new method of friction welding, particularly suitable for manufacturing BLISKS and BLUMS for gas turbine engine rotors, in which the disc or drum rotor is angularly reciprocated while the airfoil blades are pressed radially against the rotor circumference. A machine for carrying out the method has a workpiece holder and a counterbalancing member mounted for angular reciprocation and coupled together by torque transfer means to constitute a resonant system. In operation the machine is driven at or near its natural frequency of oscillation. The natural frequency can be tuned by adjusting the stiffness of the torque transfer means. The machine also includes a drive mechanism.

Friction welding

Holding means for a component in a friction welding operation consists of a hollow cassette which is open at one end. The component is inserted into the cassette through an aperture at the open end that is shaped to frictionally engage a thickened portion of the component with a force greater than forces transmitted to the component during a friction welding operation. The component is pressed into the cassette to a predetermined depth so that a portion of it protrudes and forms the weld interface. Material upset during the welding operation may be sheared by increasing the weld generating force to overcome the frictional holding force so the end face passes over the weld region.

A component holder for a friction welding apparatus has upper and lower clamp members which can be urged towards each other in order to clamp between them a component to which second or further components are to be friction welded. The first component is held in the component holder substantially entirely by friction clamping forces. The component holder is particularly suited to use with friction welding apparatus in which the component holder is carried by an angularly reciprocable workpiece mounting member.

A workpiece holder for angularly reciprocatory friction welding apparatus includes clamp members for clamping the workpiece to a mounting table. The height and circumferential position of a drum is adjustable to facilitate blade attachment in manufacture of a blum. Means are also described for reinforcing the drum during blade attachment in order to absorb welding forces which might otherwise distort the drum surface.

The present invention consists in the apparatus for use in welding a first component and a second component together by friction welding, comprising drive means operative to generate reciprocatory movement, a component holder operative to hold said first component, linking means operative to transmit reciprocatory movement from the drive means to the component holder so that in operation said first component performs reciprocatory heat-generating movement, pressure means operative to exert pressure on the component holder so that in operation said first component also performs welding movement, the linking means being such as to accommodate that welding movement during friction welding and the pressure means being such as to accommodate that heat-generating movement during friction welding. The pressure means preferably comprises ram means operative to apply force to a non-reciprocating head which is connected to the component holder through flexible connecting means enabling heat-generating movement of the holder to be accommodated. The connecting means may comprise one or more hinged links but preferably comprises one or more flexible elements. These flexible elements may comprise flexible rods or bars but preferably comprise flexible blades so orientated as to prevent movement of the component holder in a direction transverse to its heat-generating movement. Movement of the head in a direction parallel with the reciprocatory heat-generating movement of the component holder is preferably resisted by guide means which nevertheless permits the head with the component holder to perform welding movement. The guide means is preferably constituted by roller means preloaded to prevent backlash or rattling in use.

In a known method of friction welding two workpieces together, one workpiece is reciprocated relative to the other while the workpieces are pressed together. When sufficient frictional heat has been generated, relative movement is caused to cease and the workpieces become welded. Apparatus for carrying out that method comprises power-driven reciprocatory means which carries the reciprocating workpiece. To balance the reciprocatory means there are counterweights which move in the opposite direction to the reciprocatory means. Each counterweight is constrained by guide means to move along a rectilinear path. Each counterweight is coupled to the reciprocatory means by reversing means, which comprises a pivoted rocker, first linking means and second linking means. Each linking means may be constituted by a flexible blade which is anchored in a non-pivotal manner to the reciprocatory means, the rocker or the counterweight, as the case may be.

Growing community of inventors

Cannock, United Kingdom

John G Searle