Apparatus for traversing a workpiece with a working head

Claim 1

Apparatus for applying work to a workpiece which has at least two upstanding walls which meet one another at an inside corner, comprising: a travelling truck having support means which permit the truck to be supported for lateral relative movement along beside the walls; a working head for performing a task with respect to the walls; means mounting the working head on the travelling truck for projection and retraction of the working head with respect to the travelling truck; turret means mounted on the travelling truck for relative rotation of the truck with respect to the turret about an axis generally vertical relative to the travelling truck; at least three wall engaging means on the turret means, disposed in a pattern complementing the angularity of the walls with respect to one another, so that the truck may travel along one of the walls with a first and a second of the wall engaging means in moving contact therewith, until, as the inside corner is reached, the second of these two wall engaging means additionally contacts the other of the walls which meets at the corner, and the third of the wall engaging means contacts said other wall, and so that as the truck travels away from the corner along said other wall, the first and second of the wall engaging means are parted from said one wall and the second and third of the wall engaging means remain in contact with said other wall; mutually engaging cam and follower means mounted on the turret and working head, respectively, the cam being profiled to urge projection and retraction of the working head with respect to the travelling truck, when the three wall engaging means are in contact with said walls, according to a pattern which preserves the juxtaposition of the working head and the respective one of the walls toward and past the corner as the travelling truck is rotated, about said axis relative to the turret, through an angle matching the angle included between the two walls.