Woodworking – Rotary cutter – Having slotted bit seat
Patent
1989-04-06
1990-05-08
Bray, W. Donald
Woodworking
Rotary cutter
Having slotted bit seat
144174, 407 41, 407 49, B27G 1300
Patent
active
049229770
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to rotary cutter heads for woodworking machinery and in particular to a novel means of blade anchorage and adjustment for such cutter heads.
BACKGROUND ART
Rotary cutters for woodworking machinery may be of one-piece construction or may be provided with removable and adjustable cutter blades. The latter form of rotary cutter is advantageous in that worn or broken blades may be replaced, and moreover the blades may be adjusted radially outwardly in blade-receiving recesses or housings in a cutter block, to compensate for blade wear. For many years the retention of such blades by wedge means has been known, with each blade and its associated wedge being received in an inwardly divergent blade-receiving recess in the cutter block. Tightening screws or bolts are provided, bearing on a side face of the wedge means, for securing the blades and wedges in position in the recesses. The wedging action is such that with increasing rotational speeds the wedges are urged outwardly by centripetal force, to bear with increasing force on the blades received in the same blade-receiving recesses. In accordance with some known cutterblock constructions, when the wedges are slackened in the blade-receiving recesses by the partial release of the tightening screws or bolts, the blades must be withdrawn axially from the block and reinserted axially in their new radially outer positions. This can be a time-consuming operation, since the wedges become loose when the blades are removed, and tend to interfere with the reinsertion of the blades. Our European Patent No. 73595 therefore proposes a modified construction in which at least one resilient means extends partially from a recess in the wedge means on slackening of the tightening screws of bolts, to hold the blade lightly in position while the screws or bolts are in their untightened condition.
A common disadvantage of the above known methods of blade mounting is the number of tightening screws or bolts to be tightened or slackened for each blade adjustment. For a cutterblock with six angularly spaded blades there may be up to seven tightening screws or bolts per blade, which means up to 42 screws or bolts to be slackened and re-tightened each blade setting or regrinding operation. This takes time and also incurs the risk that if the operator is distracted during the sequence of tightening operations, then some bolts or screws may remain slack. This is a safety hazard. Even with axially shorter cutterblocks in which there are only one or two tightening screws or bolts per wedge, the known methods of tightening the wedges incur the risk that overtightening may distort the cutterblock body. The use of a torque wrench is recommended to overcome the overtightening problem, but there is no protection against someone damaging the cutterblock body by ignoring the recommendations and overtightening.
DE 1170607B (Continental Gummi Werke) discloses a rotary cutter head with a blade 4 held in place by a wedge 3. The wedge 3 is driven outwardly in its wedging recess and into contact with the blade 4 by pressurization of a flexible and inflatable hose 2 located axially of the cutter-block 1. Because the hose 2 occupies a position axially of the cutterblock 1, there is no provision for clamping the cutterblock on an axial spindle of a rotary woodworking machine. The cutter head would therefore be end-mounted by bolts.
US 2652749 (Hagmeister) also discloses a rotary cutter head in which blades 8 are held by wedges 16 which are hydraulically actuated. The Specification contains no discussion at all of the mounting of the cutter head on a rotary woodworking machine.
US 4533287 (Hagenmeyer), on the other hand, discloses the hydraulic clamping of a cutter head 10 on a spindle of a rotary woodworking machine but utilizes conventional screw-tightenable wedges 55 to retain the blades 50 in the cutterblock 21.
None of the above three Specifications addresses the problem of potential time saving by automating the procedures of blade clamping in a manner that
REFERENCES:
patent: 4220186 (1980-09-01), Sybertz
patent: 4594928 (1986-06-01), Thomas et al.
Colton Peter
Stocker Mark A.
Willbond Andrew D.
Bray W. Donald
Wadkin PLC
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