Rotary cutter for wood cutting machine, and device for holding cutting elements thereof

A holding device for a rotary cutter has a supporting member extending over a greater part of each cutting element and having a web and holding tongues provided with an openings for receiving tightening screws, an abutment surface for abutting the cutting element and determining a projecting length of the latter, a wearing member fixed in the body part for abutment of the rear surface of the cutting element, a locking member for fixing the wearing member, a centrifuging wedge member with a wedge surface pressing the cutting element against the wearing member, wherein the wearing member has a locking groove which is open toward the cutting element and forms the abutment surface and in which the web of the supporting member is received in a form locking manner, and the centrifuging wedge member lies with its wedge surface directly against the front surface of the cutting element.

BACKGROUND OF THE INVENTION 
The present invention relates to a holding device for mounting a 
resharpenable cutting element in a rotary cutter of a wood cutting 
machine, as well as to a rotary cutter of the latter. 
Rotary cutters and holding devices of the above-mentioned general type are 
known in the art. A known holding device has a supporting member extending 
over a greater part of the length of the cutting element and having a web 
which is small as compared with the height of the cutting element and 
provided with holding tongues extending over a part of the side of the 
cutting element and having elongated openings. Tightening screws extend 
through these openings so that the supporting member can displace somewhat 
radially over the rear surface of the cutting element and be fixed. An 
abutment surface fixedly arranged in the body part of the cutter 
determines a projecting length of the cutting element and is located so 
that the supporting member loosely lies against the same. A wearing member 
is fixed in the body part of the cutter via a somewhat radially acting 
locking member and arranged so that the cutting element abuts with its 
rear surface against the wearing member. Finally, a centrifuging wedge 
member presses against the wearing member. Such a rotary cutter and its 
holding device is disclosed, for example, in the German Gebrauchsmuster 
No. 8,002,428. The cutting element lies with its front surface loosely 
against a clamping strip which is held in the body part via a locking 
member and is actuated by a centrifuging wedge member which presses the 
clamping strip against the front surface of the cutting element and 
thereby the cutting element against the wearing member. The cutting 
element is loosely introduced, together with supporting member screwed 
therewith, into an approximately radially extending insertion slot of the 
wearing member and abuts with assured abutting face of the supporting 
member loosely against the above-mentioned abutment surface in the body 
part of the cutter. In the above-described known construction, the cutting 
element is thereby held exclusively in a force transmitting manner. In 
order to prevent that the centrifugal wedge member which is pulled 
radially outwardly under the action of the centrifugal force changes the 
position of the cutting element in the cutter body and thereby the 
projecting length of the cutting element over the outer surface of the 
body part, the clamping strip between the centrifuging wedge member and 
the front surface of the cutting element which is form lockingly fixed in 
the body part is provided. The abutment surface which supports the 
supporting member is formed as a holding strip which is screwed with the 
body part and located, as seen in radial direction, under the cutting 
element as well as the supporting element. A peripheral recess provided in 
the body part for receiving the holding device must therefore be deeper 
than the width of the cutting element in order to additionally receive the 
above-mentioned holding strip. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a rotary 
cutter and a holding device therefor, which avoid the disadvantages of the 
prior art. 
More particularly, it is an object of the present invention to provide a 
rotary cutter and a holding device which have a simpler construction . 
In keeping with these objects, and with others which will become apparent 
hereinafter, one feature of the present invention resides, briefly stated, 
in a holding device in which a wearing member has a locking groove which 
opens toward a cutting element and forms an abutment surface, so that a 
web of a supporting member for the cutting element is inserted in the 
locking groove in a form-locking manner, and the centrifuging wedge member 
lies with its wedge surface directly against a front surface of the 
cutting element. 
The form-locking connection which was provided in the prior art for the 
clamping strip is formed in accordance with the invention behind the rear 
surface of the cutting elements between the supporting member and the 
wearing member. The supporting member of the cutting element and thereby 
also the cutting element screwed therewith are held directly in a 
form-locking manner in the wearing member. The cutting element is also 
secured in a radial direction from displacement. Because of this it is 
possible in accordance with the invention to dispense with the clamping 
strip which was used in the prior-art construction and provide abutment of 
the centrifugal wedge member directly against the front surface of the 
cutting element. The inventive holding device is composed of a small 
number of parts. Because of the absence of the clamping strip for the 
cutting element, its locking member and holding strip are also dispensed 
with, and there is a possibility that the locking member which holds the 
wearing member in the body part is located completely behind the rear 
surface of the cutting element. For this purpose the peripheral recess 
which receives the holding device can be formed only with such a depth 
which is required for receiving the cutting element. There are no more 
parts which overlap the cutting element. The locking member which holds 
the wearing member can be formed in conventional manner hook-shaped and 
formed by a holding strip screwed with the body part of the cutter or 
fixed in any other way. 
In accordance with another advantageous of the present invention, a 
permanent magnet is arranged in the locking zone of the wearing member so 
that the web of the supporting member abuts against the permanent magnet. 
Thereby, the cutting element, the supporting member and the wearing member 
are inserted into or removed from the body part of the cutter as a set. At 
the same time, the cutting element which is screwed with the supporting 
member can be easily separated from the wearing member, for example for 
sharpening of the cutting element. During grinding process the assembly of 
the cutting element and the supporting member remains maintained. The 
setting of the sharply ground cutting element is performed by a special 
setting device, wherein the web of the supporting member forms a reference 
edge. For setting, the tightening screws are somewhat released and after 
the adjustment of the cutting element are again fixedly tightened. 
In accordance with yet another advantageous feature, the centrifugal wedge 
member abuts against the front surface of the cutting element via a 
releasably connectable wearing strip. The wearing strip is independent of 
the length of the produced chips can be easily exchanged. 
The holding device in accordance with the present invention is basically 
suitable for a tooth (comb) cutter or so-called double tooth (comb) 
cutter; however, it is also suitable for a cutter with a throughgoing 
cutter edge. In this case, the wearing member may be provided with an 
insertion slot in which rectangular scratcher plates are inserted in a 
form-locking manner and retained by the cutter element. Each scratcher 
plate has a pin extending beyond both sides of the former and engaging in 
an insertion groove of the wearing member, the groove being opened toward 
the cutting element. 
The holding device in accordance with the present invention is also 
designed for switching from the tooth cutters to cutters with throughgoing 
cutting edges. The new holding device provides for a high adjustment 
accuracy for the cutting element and leads to lower additional costs for 
grinding of the cutting element. The wearing member arranged behind the 
cutting element can simultaneously serve as a scratcher support. 
The novel features which are considered as characteristic for the present 
invention are set forth in particular in the appended claims. The 
invention itself, however, both as to its construction and its method of 
operation, together with additional objects and advantages thereof, will 
be best understood from the following description of specific embodiments 
when read in connection with the accompanying drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT 
A rotary cutter and a holding device for holding a plurality of cutting 
elements in a body of the rotary cutter is shown in the drawing, wherein 
one of the cutting elements is illustrated and identified by reference 
numeral 1. The cutting element 1 has in the shown embodiment a 
throughgoing (uninterrupted) cutting edge. 
The holding device includes a supporting member identified by reference 
numeral 2 and extending over a greater part of the length of the cutting 
element. It has a web 2a which is small as compared with the height of the 
cutting element and is provided with holding tongues 2b. The tongues 
extend over a part of the height of the cutting element and has elongated 
openings 3, as can be seen from FIG. 3. Tightening screws 4 extend through 
the elongated openings 3 so that the supporting member is displaceable 
over a rear surface 1b of the cutting element 1 substantially in radial 
direction and fixable. 
A holding member 6 is screwed by a screw 6' in a body 5 of the cutter and 
has a hook-shaped locking part 7. A wearing member 8 engages in the 
locking part 7. The cutting element 1 abuts with its rear surface 1b 
against the wearing member 8. The wearing member 8 has a locking groove 9 
which opens toward the cutting element 1. The web 2a of the supporting 
member 2 is inserted into the locking groove 9 in a form-locking manner. 
The term "form-locking" is utilized here to identify an interengaging 
connection in which shapes of respective members complement each other. 
The locking groove 9 forms an abutment surface 9a for the web 2a of the 
supporting member 2 and thereby determines a projecting length of the 
cutting edge of the cutting element beyond the outer surface of the body 
part of the cutter. A permanent magnet 10 is arranged in the locking 
groove 9. The above-mentioned web 2a of the supporting member 2 freely 
abuts against the permanent magnet 10. 
The wearing member 8 has moreover insertion slots 11. Rectangular chip 
breakers 12 are inserted in the insertion slots 11 in a form locking 
manner. The chip breakers 12 are retained in the insertion slots 11 by the 
cutter 1. Each scratcher plate 12 has a pin 13 extending outwardly beyond 
the same at both its sides. The wearing member 8 has, on the other hand, 
insertion grooves 14 which are open toward the cutting element 1. The 
above-mentioned pins 13 engage in the insertion grooves 14, as can be seen 
from FIG. 2. 
The holding device further has a centrifuging wedge member 15 which lies 
against a front surface 1a of the cutting element 1 via a wearing strip 16 
releasably connected with the centrifugal wedge member 15. The centrifugal 
wedge member 15 presses the cutting element 1 with its rear surface 1b 
against the wearing member 8. The wearing strip 16 of the centrifuging 
wedge member 15 is formed wedge-shaped in its region which faces toward 
the cutting edge of the cutting element 1. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
rotary cutter and a holding device therefor, it is not intended to be 
limited to the details shown, since various modifications and structural 
changes may be made without departing in any way from the spirit of the 
present invention . 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of the present 
invention.