METHOD AND ARRANGEMENT FOR SHARPENING SAW CHAINS, WHEREBY A CONTINUOUSLY MOVING CHAIN CAUSES A TRANSVERSE MOTION OF ONE OR MORE FILES

Abstract: Fur users of motor driven saws with endless tooth carriers it is known that these teeth should be filed rather often in order to keep the saw well cutting. Auxiliary devices are known for facilitating the filing work, and also for controlling the direction of the filing, which should form a certain angle with the cross direction of the teeth. It is common for the known auxiliaries that what is filed is one temporarily fixed tooth at a time, whereby the filing work will still be time consuming and difficult. The invention provides for an entirely new principle and apparatus for a continuous filing of the teeth (18) on an endless saw cutter (7), in that a filing is effected by means of files (14) moved in a one-way motion in engagement with teeth (18) moved along the chain blade (7), said file (14) being held in a desired oblique position relative to the tooth for filing the latter under a desired cutting angle (v) and being moved in a direction oblique to the chain blade such that the file (14), during movement of the chain, will carry out a pure longitudinal displacement relative to the tooth.

Description: METHOD AND ARRANGEMENT FOR SHARPENING SAW CHAINS, WHEREBY A CONTINUOUSLY MOVING CHAIN CAUSES A TRANSVERSE MOTION OF IKE OR MORE FILES, The present invention relates to a device for sharpening the teeth of motor chain saws. Users of motor saws are familiar with the necessity of sharpening the teeth on the chain at relatively frequent intervals to maintain satisfactory cutting, and are well aware that this procedure is difficult and time-consuming, or is a source of irritation. By its nature, the problem is particularly familiar to forestry workers. Many devices have been developed to facilitate the sharpening operation, including control of the file alignment, which must be set at a certain angle ' relative to the lateral alignment of the teeth. In general, however, these known devices for controlling the forward and backward movement of the file, or even developing a rotary movement of the file, have not achieved widespread practical use. The invention is intended not merely as an 'ancillary' device, but as a genuine device for more or less automatic performance of the sharpening operation. The invention demonstrates the possibility of using a new sharpening technique, in which the file is neither traversed forward and backward nor rotated against a stationary tooth, but is traversed unidixectionally against a tooth moving along the saw chain. Thus, if the said file is held against the tooth in the desired angular position at the start of its (the tooth's) travel along the guide bar of the saw, with the fully retracted end of the file in initial engagement with the tooth, forward movement of the file in a direction perpendicular to its (the file's) longitudinal axis, in other words, a movement at an angle with respect to the guide bar, will cause the leading end of the file to move increasingly further from the guide bar, while the opposite end of the file will move increasingly closer. In other words, the file will execute a progressive longitudinal movement relative to the tooth; that is, it will automatically perform a unidirectional sharpening action as the saw chain is driven forward by the file or as the file is traversed by movement of the chain along the guide bar. While it has formerly been the practice to perform sharpening on stationary teeth, the invention simply utilises the fact that the teeth can move along the guide bar, whereby a type of dynamic sharpening is performed by the angular movement of the laterally mounted file relative to the guide bar, the file being mounted movabl in a separate driving device attached to the guide bar, while the guide bar is mounted in a file drive support frame. This ensures that the file movement itself is generated automatically and that the file is maintained at the desired sharpening angle relative to the tooth throughout the operation, Furthermore, it is not a condition that the file be moved in a direction perpendicular to its own direction, but may be positioned more or less at an angle. This means that the angle between the direction of travel of the file and the file angle should not be identical; in other words, the direction of travel of the file for a given tooth sharpening angle may be more or less at an angle to the guide bar. The greater this angle, the faster the file movement, and the shorter the file which can be used for a given sharpening 'distance'. Ideally, the width of the file path should be such that, on one side, it intersects the start of the tooth path on the guide bar and, on the other side, it intersects the end of the tooth path, ensuring that the file interacts with the tooth over its (the file's) full length and over the full length of the guide bar. Since the attraction of this sharpening principle, which is considered to be unique, at least in the present context, may possibly be lessened if only a single file is used to sharpen a single tooth per operating cycle, it should be emphasised that the system is extremely adaptable to an equally unique method employing a number of files to sharpen a number of teeth simultaneously in the dynamic sharpening process, Application of these files parallel to each other in the same direction of travel, at a pitch corresponding to that of the teeth on the chain, enables several teeth to be sharpened at the same time, greatly increasing the sharpening capacity compared with the basic version. In the preferred embodiment, the files are carried on an endless belt, on which they are mounted at a pitch corresponding to that of the teeth on the chain, the belt being of sufficient operational length to extend along the motor saw guide bar, but at an angle to the latter, so that the files on the said belt continuously engage with and sharpen the successive teeth on the chain. Provided that the system is correctly adjusted and mounted, sharpening may be carried out at a high speed, enabling all of the teeth on the chain to be sharpened in a fraction of the time normally required, However, it should be noted that this solution may also be generally attractive if it is not wished to prematurely abandon the system employing only one or a relatively small number of files, given that the purpose of using a special sharpening device is to ensure that the said file or files is or are engaged automatically with successive teeth or groups of teeth on the chain, and that sharpening can be carried out even at extremely high operating speeds, provided that complete sharpening of all or the teeth is performed automatically and in a significantly shorter time than hitherto. A very significant advantage of the invention is that the sharpening device can be attached to the motor saw itself as an accessory, normally in a passive mode, from which it may be deployed in an operational mode above or below the guide bar of the saw to interact with the chain-mounted teeth extending from the latter. The motor saw may, thereby, be equipped with an integral sharpening unit which may be used to sharpen the teeth in an extremely short time, without the least difficulty to the user, who is required only to engage and disengage the device at intervals in a relatively short time. The files may be driven at an extremely high speed by the chain saw's own motor or at a normal, slower and probably safer speed by driving the file- carrying belt by motor or manual power, for example if the resistance to movement of the toothed chain is increased. The sharpening device may also be installed inside the motor casing, in which case it may either be engaged and disengaged externally or even left in permanent engagement; sharpening may be sufficiently effective if the teeth are sharpened briefly, successively and individually. The invention is described in further detail below with reference to the appended drawings, of which Fig. 1 is a plan view of an automatic sharpening device in accordance with the invention and Fig. 2 is an elevation of the same device, The automatic sharpening device 2 used to sharpen the teeth on the chain 4 of a chain saw 6 consists of a support frame 8, the ends of which are provided with two rollers 10 supported in bearings, which rollers carry an endless beit 12 to which are attached a number of round files 14 mounted at an angle to the longitudinal axis 16 of the belt. The perpendicular distance between the round files 14 is less than the distance between the edges 26 of two successive, similarly oriented teeth 18, the angle of the files relative to the direction of travel 16 of the belt being adjusted to suit the desired sharpening angle of the cutting edges on the teeth, the normal value of which on a chain saw is approx. 30°. The support frame 8 is provided with a pivoted, adjustable bracket 20 provided with clamps 22 for clamping the guide bar 24 of a chain saw. The bracket 20 is adjustable to an angle V relative to the longitudinal axis 16 of the belt (which coincides with the direction of travel of the files). The value of the angle V is a function of the distance between the files and of the distance between two successive, similarly oriented teeth 18. The angle V, combined with the angular position of the file relative to the longitudinal axis 16 of the belt, ensures correct engagement of the files 14 with two successive, similarly oriented teeth 18 on the saw chain. The combination of the angular position of the files relative to their direction of travel and the angle of the saw chain relative to the same direction, together with the length of the files, means that at least two similarly oriented teeth on the saw chain are in engagement with the files, while two further teeth are, respectively, on the point of engagement and on the point of disengagement with the files. The files 14 used to sharpen the cutting edges 26 of the teeth 18 are round files, both ends 28 of which are tapered and smoothed to facilitate their entry in the cutter recess without damaging the tooth 18. As shown by the typical embodiment illustrated in Fig. 2, the files 14 are attached to the belt 12 by fastening devices consisting of a swan-neck stalk 30, one end of which is attached to the belt 12 and the other to the file 14, close to the mid-point. Thus, since the files are attached to the belt at this point alone, they can travel around the curved rollers without problems. The attachment between the belt or chain 12 and the stalks 30 may be of a pivoted, lockable type, enabling the files 14 to be locked in practically any random position relative to their direction of travel 16. This enables the tooth to be sharpened to a desired, optimum angle since only the angular position of the guide bar relative to the file path can be adjusted correspondingly to suit the tooth pitch. The relative settings should be adjusted so that sharpening takes place with the tooth edges. However, this does not preclude the possibility of sharpening against the edges. When setting the file angles, it is self-evident that all of the files should be set at the same angle relative to their direction of travel 16; in other words, the longitudinal axes 42 of the files must be aligned in parallel during sharpening. The tooth sharpening files which, in the foregoing, have been described as round files 1 , need not necessarily be of a round cross- section, provided that they axe of an appropriate shape in the region of interaction with the teeth. Similarly, each of the swan-neck stalks 30 may be provided with a flat file 32 aligned parallel to the round file 14 and attached to a spur-shaped stalk 34 projecting from the rear of the stalk 30 as illustrated in Figs. 1 and 2. The upper face of the fiat file is located at a suitable level and distance relative to the round file, in such manner that a chain saw drive dog 36 located between two successive teeth is dressed by the fiat file as the teeth are sharpened by the round files 14. The side of the belt 12 facing the chain 4 is enclosed by a guide in the form of a rail 38, which is provided with a slot 40 in the direction of the belt to permit passage of the file stalks 30 attached to the belt. The rail 38 is slightly curved at a curvature identical to that of the saw guide bar 24, ensuring that the files and teeth follow the same path within the sharpening range. In another embodiment of the automatic sharpening device which is not illustrated, the belt and file arrangement consist of an endless belt of a special, flexible, synthetic material carried on two rollers in similar manner to the embodiment already described. The upper face of the belt is provided with a number of angular ribs corresponding to a desired tooth sharpening angle. The top surfaces of the ribs are coated with an abrasive, such as powdered diamond or carborundum, and are otherwise of similar shape to the round and fiat files already described. In this embodiment, the flexibility of the synthetic material is utilised in combination with the facility of the ribs, which replace actual metal files, to travel over the rollers without damaging the abrasive coating since the ribs, being oblique, can fiex during this passage. Since it is obviously impossible to alter the angle of the sharpening faces relative to their (i.e. the belt's) direction of travel, it must be accepted that at least one group of teeth will be sharpened against the edges, unless an arrangement similar to the file configuration is adopted, in which the ribs are aligned in the opposite direction, enabling the opposite facing group of teeth and associated drive dogs to be sharpened. It is also possible to construct a device in accordance with the sharpening principle used in the invention, in which each group of laterally opposite teeth on a saw chain is sharpened simultaneously. An embodiment of this type consists of two belts chains 12 and files 14, the files 14 on each belt/chain being set at an individual angle relative to the direction of travel due to the addition of an upper sharpening system to sharpen the teeth at the upper side of the guide bar. The new principle of sharpening the teeth of a chain saw in a quick, simple manner may naturally be employed in other embodiments. For example, the automatic sharpening device may be mounted directly on the chain saw to enable sharpening of the teeth to be initiated by one simple operation of a handle or pushbutton. Sharpening of the teeth may also be carried out continuously while the saw is in use.

Claims: PATENT CLAIMS 1. Method of sharpening teeth on a basically eadless saw, particularly the teeth on a motor chain saw, characterised in that sharpening is carried out by means of a file (14) traversed unidirectionaily over a tooth (18) as the saw (7) moves longitudinally, a straight file (14) being held in a desired angular position against the tooth (18) at the beginning of its (the tooth's) path of travel, with the fully retracted end of the file in initial engagement with the tooth, so that horizontal, rectilinear travel of the file (14) at an angle to the orientation of the saw will cause the leading end of the file (14) to move increasingly further from the saw (7), while the opposite end of the file (14) will simultaneously move increasingly closer to the saw (7), causing the file (14) to execute a progressive, longitudinal movement relative to the tooth (18), thereby performing an automatic, unidirectional sharpenmg action as the tooth (18) is driven forward by the traversed file (14) or as the file is traversed by movement of the saw (7). 2. Method in accordance with patent claim 1, characterised in that sharpening of several teeth is performed simultaneously. 3. Device (2) for performing the method in accordance with patent claim 1, characterised in that it consists of a belt (12), chain or disc to which are attached a number of files (14) and means (10, 22) for clamping the saw (7) at an angle relative to the direction of travel of the aforementioned files (14), which files are traversed at an angle to the saw teeth as the latter execute a forward or backward movement at a speed synchronous with the speed of forward travel of the files. 4. Device (2) in accordance with patent claim 2 whereby the saw (7) moves in a non-rectilinear manner, characterised in that it includes means (38) of guiding the file chain so that its movement corresponds to that of the saw (7). 5. Device (2) in accordance with patent claim 3 or 4, character¬ ised in t the files (14) are mounted on the belt/chain (12) at an angle relative to their direction of travel (16). 6. Device (2) in accordance with any of patent claims 3-5, char¬ acterised in that it consists of two belts or chains (12) provided with files (14), the files on each belt or chain being mounted at an individual angle to the direction of travel (16), in such manner that the files (14) on each belt or chain can simultaneously sharpen a group of laterally opposite teeth (18) on each of the respective file paths on a saw (7). 7. Device (2) in accordance with any of patent claims 3-6, characterised in that the ends of the files are tapered. 8. Device (2) in accordance with any of patent claims 3-6, intended especially for sharpening the teeth (18) on a chain saw (6), c h a r a c t e r i s- e d in th t the belt (12), in addition to the tooth sharpening files (14), is also provided with fiat files (32) for simultaneous dressing of the chain drive dogs (36). 9, Device (2) in accordance with any of the patent claims, char¬ acterised in that the files (14) are attached to the belt or chain (12) by such means that the files can be locked at angles or in angular positions relative to their direction of travel (16), in such manner that the files (14) can sharpen left and right-facing teeth (18) respectively on a saw (7), 10. Device (2) in accordance with any of patent claims 1-9, characterised in that the means (20, 22) employed to clamp the saw (7) at an angle relative to the direction of travel (16) of the files are pivoted and can be locked in a horizontal plane. SUMMARY Users of motor-driven saws employing endless, toothed saw chains are familiar with the need to sharpen the teeth at regular intervals to maintain satisfactory cutting performance. Devices to facilitate the sharpening operation, including control of the file alignment, which must be set at a certain angle relative to the lateral alignment of the teeth, are ___nown. A common feature of these known devices is the fact that they sharpen one stationary tooth at a time, making the procedure time-consuming and difficult. The invention is based on a completely new sharpening principle and device for continuous sharpening of the teeth (IS) on an endless saw (7), the sharpening operation being carried out by traversing a file (14) unidirectionally across a moving tooth (18) on the saw (7), which file (14) is mounted at a desired angle relative to the tooth, such that the tooth is sharpened at a desired angle (V), and at an angle to the direction of travel of the tooth, such that the file (14) executes a longitudinal movement relative to the tooth as the saw (7) is operated.

Inventors: SPANG KAARE, SPANG, KAARE
Applicants: SPANG KAARE, SPANG, KAARE
Application year: 1995
Main classification: B23D63
IPC codes: B23D63