COUNTER-ROTATING SAW BLADES

Abstract: A pair of saw blades, including two each other adjacently located saw blades (1, 2), arranged to take up a saw cut in a work piece (5) in a common and co-acting operation during rotation in relation to each other counter-rotating directions. According to the invention, the saw teeth (3, 4) of the saw blades (1, 2) are arranged with a specific inclination for each saw blade (1, 2) at the cutting edge portion for related saw teeth (3, 4), whereby the saw teeth (3, 4) in a pair of saw blades are arranged to take up contact as a first portion with a work piece with the part of each saw tooth (3, 4) that is closest to the co-acting saw blade (1, 2), thereby imposing a force arranged to displace the saw blades (1, 2) in direction towards each other. When setting the saw teeth (3, 4), the saw teeth (3, 4) of each saw blade (1, 2) are set in one side direction only, and in direction away from the plane intended to be located as an adjacent plane in relation to co-acting saw blade (1, 2). The saw blades (1, 2) forming a pair of saw blades are advantageously arranged with means only facilitating attachment of the saw blades (1, 2) in an each other adjacent relationship and with the saw blades (1, 2) in an internally correct related disposition to each other.

Description: Counter-rotating saw blades The present invention relates to two saw blades used as a pair of saw blades, arranged to take up a saw cut in a work piece as a simultaneous and co-acting operation during rotation in two counter-rotating rotary directions. It is previously known from US, A, 963520 to use two saw blades located in an adjacent position to each other, and operating in two counter-rotating rotary directions, in order to take up a saw cut in a simultaneous and co-acting operation. WO, A, 86/05727 discloses a further development of this sawing method, and shows how utilized saw blades can achieve an intermediate and internally separating gap by means of a pneu atical or hydraulical pressure applied against adjacently located surfaces of the saw blades. The latter publication also discloses that the saw blades may be driven with different speed in relation to each other, a feature that, for example, when cutting profiled sectional work pieces at an inclined angle, results in certain advantages, e.g. such as maintaining existing gap between the saw blades. As disclosed in WO, A, 86/05727, the technique of using pairs of counter-rotating saw blades involves major advantages in relation to sawing performed with one saw blade only. However, in those applications where sawing is performed utilizing a high feeding speed, the saw blades arranged as a pair may resiliently move away from each other at the outer and cutting peripheral portions, resulting in an increase of the intermediate gap therebetween. As a result, the width of the saw cut in the work piece is obviously also increased, and thus the quantity of material removed, but furthermore, the saw blades attempt to move to the left or to the right from an intended sawing line. When using a pair of counter-rotating saw blades with maximum feeding speed, which in the work piece tend to depart from an intended sawing line, e.g. in a number of adjacently located profiled sectional work pieces, no solution is known from the prior art. The object of the present invention is to disclose a pair of saw blades which facilitate maximum feeding speed, while maintaining a small separating gap at the outer portions of the saw blades. As a result, a straight line of sawing can be achieved at high feeding speeds, and the width of the saw cut can be maintained small, with a minimum of material removed in connection with the sawing operation. Furthermore, far more advantageous cutting properties are achived than those offered by means of conventional saw blades, a feature resulting in improved cutting properties and a reduced sound level in relation to prior art. A pair of saw blades according to the present invention includes two each other adjacently located saw blades, arranged to take up a saw cut in a work piece in a simultaneous and co-acting operation during rotation in relation to each other counter-rotating directions, and is mainly characterised in that the saw teeth of the saw blades are arranged with a specific inclination for each saw blade at the cutting edge portion for related saw teeth, and that the saw teeth in a pair of saw blades thereby are arranged to take up contact as a first portion with a work piece with the part of each saw tooth that is closest to the co-acting saw blade, thereby imposing a force arranged to displace the saw blades in direction towards each other. Examples of embodiments of a pair of saw blades according to the present invention will be more fully described below with reference to the accompanying drawings, in which:- Fig. 1 is a cross-sectional view of a work piece, whereagainst a pair of saw blades according to a first embodiment of the present invention are arranged with two saw teeth in contact with the work piece; Fig. 2 is a view corresponding to Fig. 1, in which the pair of saw blades constitute a second embodiment of the present invention; Fig. 3 is a side view of an embodiment of a saw blade as included in a pair of saw blades according to the present invention; Fig. 4 is a perspective view showing a suspending part of a saw, by means of which a saw blade included in a pair of saw blades is intended to be carried; Fig. 5 is a cross-sectional view of a further example of an embodiment of a pair of saw blades according to the present invention; Fig. 6 is a cross-sectional view of a pair of saw blades according to the present invention, showing a further modification; and Fig. 7 is a plan view of a saw tooth at a saw blade, modified in relation to what is shown 1n Figs. 1 and 2. With reference to Fig. 1, two saw blades 1, 2 are shown, arranged in an adjacent relationship to each other, and intended to rotate in opposed directions to each other, as indicated by arrows. In difference to conventional saw blades, each saw blade 1, 2 includes saw teeth 3, 4 having the outer and cutting edge portions arranged inclined in relation to a plane coinciding with the rotary centre of the saw blades 1, 2. Fig. 1 shows a work piece 5, two each other adjacently located saw blades 1, 2, and a saw tooth, 3 and 4 respectively, at each saw blade in contact with the work piece 5. All saw teeth 3, 4 at each saw blade 1, 2 are arranged substantially similar, i.e. having an inclination corresponding to what is shown for the cross-hatched saw teeth 3, 4. With regard to the saw blade 1, each saw tooth 3 will thus first take up contact with the work piece 5 by means of a portion adjacent to the saw blade 2, and during a continued movement of the saw blade 1, the saw tooth 3 will thus successively take up contact with the work piece 5 in its entire width in direction towards the plane of the saw blade 1 which 1s directed away from the other saw blade 2. This feature applies correspondingly to the other saw blade 2, i.e. the saw teeth 4 of same will Initially take up contact with the work piece 5 by means of a portion adjacent to the first saw blade 1, and the saw teeth 4 make thereafter successively contact in direction towards the plane of the saw blade 2 which is directed away from the first saw blade 1. The fact that each saw tooth 3, 4 in this fashion successively makes contact with the work piece, and that contact is made beginning from the portion most adjacent to the other saw blade 1, 2, results in a transverse force applied by means of the saw teeth 3, 4 in relation to the plane of the saw blades 1, 2, attempting to force the outer portions of the saw blades 1, 2 against each other. By maintaining the saw blades 1, 2 separated by application of an intermediate pneumatic or hydraulic pressure, contact between the saw teeth 3, 4 of each other adjacently located saw blades is avoided. In the embodiment shown in Fig. 1, saw blades 1, 2 are shown with the saw teeth 3, 4 completely non-set. When set saw teeth 3, 4 are desired or necessary, the setting or bending of the saw teeth 3, 4 may also be used to accomplish the technical effect described above with reference to the embodiment shown in Fig. 1. Accordingly, Fig. 2 shows how each saw blade 1, 2 can be arranged with saw teeth 3, 4 set (bent) in one direction only, that is in direction from co-acting saw blade 1, 2. As a result, each saw tooth 3, 4 will function substantially similar to the embodiment described with reference to Fig. 1, i.e. each saw tooth 3, 4 will make contact with a portion located adjacent to co-acting saw blade 1, 2, resulting in establishment of a force acting to move the saw blades 1, 2 in direction towards each other. However, since a setting operation only does not always result in such an angular extension of the free and cutting edge portions of the saw teeth 3, 4 that necessary transverse force is obtained, such a onesided setting, only performed in direction towards the side plane which is directed away from co-acti-ng saw blade 1, 2, may obviously also be combined with an inclination of the cutting contact surfaces of the saw teeth 3, 4 as described with reference to Fig. 1. With reference to the embodiments now described with regard to Figs. 1 and 2, an adjacent relationship between the peripheral portions of the saw blades 1, 2 is thus secured, independently of utilized feeding speed, and an increase of the feeding speed will only further secure that desired adjacent relationship is maintained. The fact that each saw tooth 3, 4 successively makes contact with a work piece 5 will also result in a "softer" contact, and thus a possibility to achieve an improved cutting operation, as well as a reduced sound level during a sawing operation. It should be emphasized, that a saw blade 1, 2 arranged according to the present invention is only usable in combination with a second saw blade 1, 2, and that use as single units will result in obvious disadvantages, such as that the saw blade 1, 2 will try to perform a movement in one side direction. The saw blades 1, 2 according to the invention thus require to be used in pairs, as well as application of a force acting to separate the saw blades 1, 2. If the saw blades 1, 2 according to the present invention are mounted incorrectly, non-desired effects may obviously result. In order to avoid that such a situation should arise, the saw blades 1, 2 should be arranged in such a way, that internally Incorrect mounting is avoided. This may, for example, be achieved by manufacturing the saw blades 1, 2 including such means for the attachment of the saw blades 1, 2 that an incorrect mounting is made impossible, and an example of this is shown in Fig. 3. The saw blades 1, 2 are in this case assumed to be mounted on supporting shafts including a longitudinally extending grove in each shaft, but also having an outwardly extending means extending in the same longitudinal direction. Each saw blade 1, 2 includes a centrally located hole 6 having a diameter substantially corresponding to the diameter of assciated supporting shaft, and by the edge portion of said hole 6, a member 7 is arranged directed towards the rotary center, Intended to be located in the groove existing in the supporting shaft, but also including a slot 8, intended to seize the means extending outwardly from the shaft. By choosing the angle V between the member 7 and the slot 8 exceeding or less than 180°, results on one hand in safety for the fact that each saw blade 1, 2 may only be mounted on one of the supporting shafts, but prevents on the other hand also the saw blades 1, 2 from being turned in an Incorrect relationship to each other. It should be noted, that this embodiment facilitates that the saw blades 1, 2 may be an Identical pair, which when mounted as a pair receive intended location, both with regard to working direction as well as with regard to the location of the saw teeth 3, 4, i.e. with the saw teeth located in accordance with what is shown in Figs. 1 and 2. The fact that the saw blades 1, 2 may be arranged identical is obviously a major advantage from manufacturing point of view, obviously reducing both manufacturing and storage costs. However, there 1s obviously nothing preventing the saw blades 1, 2 from being manufactured in different right and left types in relation to each other, which with reference to Fig. 3 for example may involve that the centrally located hole 6 in two co-acting saw blades 1, 2 are arranged having different diameter, or that the angle V is choosen differently for such a pair of saw blades. These features can obviously also be combined. There are obviously also other possible ways to secure a predetermined internally related location of two saw blades 1, 2 forming a pair of saw blades, e.g. by arranging one or a number of means as guiding and/or supporting means for each saw blade by the saw in which the saw blades 1, 2 are intended to be used. Fig. 4 shows an example of such an embodiment, including a discshaped member 9, intended to be driven by a saw motor in a certain rotary direction, and including a number of pin-shaped members 10, 10 " , 10", located irregular in relation to each other, arranged to facilitate insertion into correspondingly located through holes in a saw blade 1, 2, and to carry and impose a rotary movement on the saw blade 1, 2. In the embodiment shown, the irregular location of the pin-shaped members 10, 10 " , 10" has been accomplished by different internal angular relationships, indicated as VI and V2, but also other alternatives exist, e.g. by arranging at least one of the pin-shaped members 10, 10 " , 10" at a different distance from the rotary center in relation to remaining pin-shaped members 10, 10 " , 10". If at least one of the pin-shaped members 10, 10", 10" is arranged having an individual diameter, and corresponding holes in the saw blade 1, 2 are adjusted accordingly to the pin-shaped members 10, 10 " , 10" used, the requirement of an irregular location of the pin-shaped members 10, 10 " , 10" can be disregarded. The alternatives stated with reference to Fig. 4 may also be combined as desired, and further modified, e.g. by replacing the pin-shaped members 10, 10 " , 10" with means having a different configuration, in which case of the holes taken up in the saw blades are modified with regard to shape to facilitate co-action. Also the embodiments discussed with reference to Fig. 4 facilitate use of identically arranged saw blades 1, 2, with safety for correct mounting. As previously mentioned, it is obviously also possible to use saw blades 1, 2 having individually different features, if desired. Further alternative solutions, which result in security for correct mounting, also exist. Accordingly, the saw blades 1, 2 may be arranged having at least one outwardly directed portion from one side surface, which secures correct location. As a first example of such an embodiment, two saw blades 1, 2 are shown in Fig. 5, having in direction from each other centrally located embossed portions 11, 11 " . Such an arrangement makes it impossible to mount the saw blades 1, 2 Incorrectly. Fig. 6 shows a cross-sectional view of a portion of two saw blades 1, 2 of the type arranged with through holes, which, during the rotary movement of the saw blades 1, 2, result in an increased air pressure between the saw blades 1, 2, in order to accomplish and maintain a separating gap therebetween. By arranging such holes as outwardly embossed channels 12, 12" in the saw blades 1, 2 will on one hand result 1n an improved fan action and thus an improved air supply to said gap, and on the other hand in outwardly extending means, which prevent the saw blades 1, 2 from being incorrectly mounted, since said channels 12, 12 " also serve as a distance means, which prevent the saw blades from being mounted in a close relationship. All embodiments described with reference to Figs. 3 - 6 thus facilitate possibility to use identical saw blades 1, 2 in a pair of saw blades, secure correct mounting of the saw blades 1, 2, and facilitate also a restricted movement of the saw blades 1, 2 in direction to/from each other. The examples of embodiments of saw teeth 3, 4 described with reference to Figs. 1 and 2 result on one hand in that the saw blades 1, 2 during a sawing operation try to maintain an adjacent relationship to each other, but facilitate also on the other hand good cutting properties, due to the "soft" and successive contact established by each saw tooth 3, 4 and a work piece 5. Shown and described saw blades 1, 2 are only intended to serve as examples of embodiments of saw blades 1, 2 that can be used to form a pair of saw blades according to the invention, since, as previously mentioned, further modifications obviously can be carried out, and an example of such a further modification is shown in Fig. 7. Said figure intends to disclose the possibility to attach, for example, cutting members 13 of hard carbide or other material to the saw teeth 3 of a saw blade 1, and this is shown in conjunction with a set saw tooth 3 of the type previously discussed with reference to Fig. 2. Such a cutting member 13 is advantageously as shown arranged having a larger width extension than the width of the supporting saw tooth 3, and as a result, safety is obtained against formation of a non-machined central strip during a sawing operation, which coul d enter between the saw blades 1, 2. As shown, the cutting member 13 extends in direction towards the plane located adjacent a co-acting saw blade in the pair of saw blades. Cutting members 13 of a similar type can also be used for a non-set saw blade 1, 2 of the type described with reference to Fig. 1, and for such a purpose, the cutting members 13 are advantageously arranged with a l arger width extension than the width of the supporting saw teeth 3, 4, and extending in direction away from co-acting saw blade included in the pair of saw blades. Such an embodiment woul d result in advantages otherwise obtained by means of a setting operation. It shoul d al so be mentioned, that combinations of the embodiments shown in Figs. 1 and 2 obviously al so are possible, i .e. with alternating set and non-set saw teeth 3, 4. The present invention is thus not restricted to shown and described embodiments, since obviously further modifications can be carried out within the scope of the inventive thought and the following claims.

Claims: C L A I M S 1. Pair of saw blades, including two each other adjacently located saw blades (1, 2), arranged to take up a saw cut in a work piece (5) in a simultaneous and co-acting operation during rotation in relation to each other counter-rotating directions, characterised in that the saw teeth (3, 4) of the saw blades (1, 2) are arranged with a.specific inclination for each saw blade (1, 2) at the cutting edge portion for related saw teeth (3, 4), and that the saw teeth (3, 4) in a pair of saw blades thereby are arranged to take up contact as a first portion with a work piece with the part of each saw tooth (3, 4) that Is closest to the co-acting saw blade (1, 2), thereby imposing a force arranged to displace the saw blades (1, 2) in direction towards each other. 2. Pair of saw blades according to claim 1, characterised in that the saw teeth (3, 4) of each saw blade (1, 2) are set in one side direction only, and in direction away from the plane Intended to be located as an adjacent plane 1n relation to co-acting saw blade (1, 2), and that said setting is carried out with regard to at least certain of the saw teeth (3, 4) included in a saw blade (1, 2). 3. Pair of saw blades according to any one of claims 1 and 2, characterised in that cutting members (13) are attached against the saw teeth (3, 4), preferably having a larger width extension than the saw teeth (3, 4) and with an extension in direction away from only one side plane of each saw blade (1, 2). 4. Pair of saw blades according to any one of claims 1 - 3, characterised in that the saw blades (1, 2) forming a pair of saw blades are arranged with means (6, 7, 8) which co-act with means arranged by the saw in which the saw blades (1, 2) are intended to be attached, which only facilitate attachment of the saw blades (1, 2) in an each other adjacent relationship with the saw blades (1, 2) in an internally correct related disposition to each other. 5. Pair of saw blades according to claim 4, characterised in that each saw blade (1, 2) includes a centrally located hole (6), intended to facilitate insertion of a supporting shaft, and that at least two means (7, 8) for interconnection with the supporting shaft are arranged by the edge portion of the hole (6), preferably located with an internal angular relationship (V) exceeding, or smaller than, 180°. 6. Pair of saw blades according to any one of claims 4 and 5, characterised in that each saw blade (1, 2) is arranged with a number of through holes, located with an internal configuration and/or design and shape only facilitating interconnection with co-acting means (10, 10 " , 10") extending from the saw whereagainst attachment is intended to be performed when the saw blades (1, 2) are located in a predetermined and operative internal relationship. 7. Pair of saw blade according to any one of claims 4 - 6, characterised in that each saw blade (1, 2) includes a centrally located portion (11, 11 " ) extending in a plane separated from the plane of the saw blade (1, 2), and that said centrally located portions (11, 11") are extending in a from each directed relationship when attached into a co-acting position. 8. Pair of saw blades according to any one of claims 4 - 7, characterised in that each saw blade (1, 2) includes outwardly embossed portions (12, 12 " ) extending from an outer plane, preferably arranged to form in direction towards the rotary direction open channels. 9. Pair of saw blades according to any one of claims 1 - 8, characterised in that the saw blades (1, 2) forming a pair of saw blades are substantially identical. 10. Pair of saw blades according to any one of claims 1 - 8, characterised in that the saw blades (1, 2) forming a pair of saw blades are non-identical.

Inventors: GEBELIUS SVEN RUNO VILHELM, GEBELIUS, SVEN, RUNO, VILHELM
Applicants: GEBELIUS SVEN RUNO VILHELM, GEBELIUS, SVEN, RUNO, VILHELM
Application year: 1988
Main classification: B23D45
IPC codes: B23D45, B27B5