The grinding of wooden frames causes problems since the grain fiber directions of the longitudinal and transverse wooden parts of the frame are different, and it is desirable that the upper surface of a frame wooden part not be ground transversely to its fiber direction.
To avoid this disadvantage, band grinding machines are already known in which for a cross-grinding, a transverse band assembly and a broad band assembly are arranged behind one another in the advancement direction. The transverse band first grinds the top of the entire frame. The broad band assembly has two pressure shoes or pressure bars arranged parallel to the advancement direction which are adjustable transversely to the advancement direction so that the broad band can targetly be pressed against the longitudinal wooden parts of the frames to be ground. Therefore, the grinding tracks produced on the wooden longitudinal parts by the transverse band can be removed. A disadvantage of this solution is, however, that the grinding band of the broad band assembly is worn only locally.
In a further known cross-grind grinding machine, the broad band by means of an electronically controlled multiple member pressure bar is pushed downwardly in areas corresponding to the longitudinal wooden pieces. Also in this case, there arises the disadvantage that the broad band is only locally worn. Moreover, problems arise in the adjustment of the grinding width to the actual longitudinal wooden piece width, since the individual pressure elements of the pressure bar cannot be made as small as desired and, therefore, the danger exists that the longitudinal wood pieces are either not ground up to their longitudinal edges or that the longitudinal edges are ground round.
The invention has as its object the provision of a band grinding machine of the aforementioned kind which permits a desired grinding of the work piece parts parallel to their grain fiber directions with optimal utilization of the used grinding means.