PRIOR ART
The invention is based on a hand held planer.
German Patent DE-PS 91 52 65 discloses a planer with a planer shaft that has planer blades, extending over its width, that are clamped by centrifugal force actuated clamping wedges, that is, so-called centrifugal wedges, carried by the planer shaft. The centrifugal wedges are elastically prestressed by springs and are braced in a longitudinal groove between the planer blade and the planer shaft. The higher the rotary speed of the planer shaft, the greater then force that presses the centrifugal wedges radially outward. Accordingly, with increasing rpm of the planer shaft the clamping force with which the planer blades are firmly held relative to the planer shaft increases as well. It becomes clear from this that the centrifugal wedges must be displaceable radially outward as far as their maximum clamped position in the groove if they are to achieve their optimal clamping action quickly. This requires great dimensional accuracy and high surface quality of the centrifugal wedges and longitudinal grooves. Otherwise, it would be impossible to prevent canting of the clamping wedges would become canted in the longitudinal groove before they reach the clamping position, making for an excessively low clamping force, and as a result the planer blades could change their bearing during work with the plane and be spun out of the planer shaft - with an attendant risk of injury to humans and equipment in the vicinity of the work site.
The planer shaft in the known planer has one separate longitudinal groove for each planer blade and for each associated centrifugal wedge. The longitudinal axes of the grooves extend parallel, but the transverse axes between the groove sides extend at angles to one another. This makes it still more difficult to manufacture the planer shaft or the grooves. This increases the production costs for the known planer considerably. For changing the planer blades as the blades become dull, the self-lockingly fastened centrifugal wedges must be displaced radially inward over their entire length with a special tool, counter to the spring prestressing, in order to undo the clamping and chucking action.
From European Patent Disclosure EP 0 117 991, a planer with a planer shaft comprising profile disks is known, in the longitudinal groove of which a loose centrifugal wedge is provided for clamping the planer blade. The production costs of the planer shaft and the centrifugal wedges are high, because of the requisite high dimensional accuracy. Changing planer blades is time-consuming, because the loose centrifugal wedge is wedged in self-locking fashion in the longitudinal groove opposite the planer blade and offers only a relatively small engagement face for a special tool for pushing back the centrifugal wedge. The centrifugal wedge or the planer blade is often knocked loose in order to change planer blades, but this can damage the blade or the planer shaft.
USPTO Backgrounds
USPTO Backgrounds