FOLDABLE HANDSAW WITH AN OPTIONAL ANGLE BETWEEN THE HANDLE AND THE BLADE

Abstract: The invention concerns a handsaw comprising a blade (2) with a tooth line (4), and a handle (1) with a handgrip part (9) and an attachment part (10) forming a blunt angle with the handgrip part. The blade can be located at different angles relative to the handle by means of a joint (11) and is provided with a number of peripherally separated recesses into which a pin (17) of a spring loaded locking mechanism can be inserted. In one out of four lockable positions the handgrip part (9) of the handle extends from the attachment part (10) to the rear with a down-ward slope relative to a conceived line L extending from the tooth line (4) of the blade. In this way the handgrip (9) gets a good distance from an adjacent support surface for a workpiece, while in another position the hand of the user can apply a rearward pulling force and get a downward force component pressing the teeth of the blade into the bottom of the sawn kerf.

Description: Fo l ab l e handsaw w i th an opt i ona l ang l e between the hand l e and the b l ade . Technical field of the invention This invention refers to a handsaw comprising an elongated blade with a line of teeth, the individual teeth of which are provided with such edges that will make sawing in a rearward direction more efficient than in a forward direction, and a handle, including an elongated handgrip of shorter length than the blade and an attachment part extending in a generally blunt angle against the handgrip and being attached to a rear portion of the blade by a joint permitting rotation of the blade relative to the handle and co-operating with a locking mechanism including a locking member insertable into one of a multitude of periferically separated recesses within a generally semi-circular rear edge part of the blade to facilitate locating of the blade in different angular positions relative to the handle, said handgrip including two side walls connected by a common back and delimiting a first slot ar- ranged to co-operate with a second slot in a tooth protector movable between an inactive position and an active position extending in the direction of the handgrip and in which position the line of teeth of the blade can be inserted into both said slots simultaneously; the handgrip merging into the attachment part by a transition portion which is narrower than the knuckle protecting rear portion of the attach- ment part; and where a first recess is located at the lower edge of the blade to lock it in a position inserted in both the handgrip and the tooth protector, while a second recess is distanced from the first recess by an angle of at least 125 degrees for locking the blade in an operative position relative to the handle. Background of the invention and state of the art By the applications of the applicant EP 0910942 A2 (priority from SE 9703788-1) and WO 99/20099 (priority from SE 9703790-7) is already known a handsaw for pruning of trees and similar, where the blade of the saw is permanently rigidly connected to the handle at a determined blunt angle in relation thereto. More specifically, the blade is fixed by means of two separate bolts to a relatively robust attachment portion, the blunt angle of which relative to the handgrip part of the handle determines the angle of the blade relative to the handgrip. In preferred embodiments of that handsaw the blunt angle between the handgrip and the attachment portion amounts to 132 degrees, although it may vary between 125 and 140 degrees. To serve as a tooth protector of and against the sharp teeth of the blade, a separate sheath is used, which is delivered and carried together with the handsaw. One disadvantage of said handsaw is precisely the need of a separate sheath or tooth protector, which makes it expensive to manufacture and is liable to become lost under various circumstances. For this reason, the applicant has developed a handsaw where the tooth protector needed is made as an integral part of the handsaw. This saw is basically designed as described in the introduction and it is further described in the patent application SE 9803675-9. On that handsaw the tooth protector is made as a lid part with a U-shaped cross section, one end of which is hingedly connected to the free lower end of the handgrip part of the handle, which has also a U-like cross section, at least partially. By means of the hinge, the lid part can be rotated between a first active position as an exten- sion of the handgrip, allowing the blade and its teeth to be inserted in the slots formed in the handgrip and the lid part by their U-shaped cross sections, and a second inactive position where the lid part encloses the handgrip. Also in that case, the handsaw is primarily intended for pruning. For that reason the handsaw is made in such a way that the blade can be located in only two different angular positions relative to the handle, specifically one operative position at an angle of 130 to 135 degrees from the handgrip, and secondly an inserted position at a very small angular difference from the handgrip with its lid part unfolded. To define those two angular positions, the rear end of the blade is provided with two recesses co-operating with the locking mechanism of the handle, specifically a first recess situated at a lower edge of the blade and a second recess at an angular distance of 130-135 degrees from the first recess. Although the improved handsaw according to SE 9803675-9 is markedly suitable for conventional garden pruning purposes and to a limited extent also for certain carpentry purposes, its usefulness is limited by having only one single op- erative position. Aims and characterizing features of the invention The present invention aims at improving the handsaw described in SE 9803675-9 in such a way that it can be used efficiently not only for pruning pur- poses, but also and primarily for general carpentry purposes. One basic aim of the invention is thus to create a handsaw of the general kind described above, but possible to be used not only in such situations where the handle and the hand gripping it are clearly distanced from the work piece (as is the case when cutting separate lengths of lumber, tree branches or similar) but also for flush cutting when the handle and the hand move in the immediate proximity of a support surface (as in the case of cutting wooden laths supporting tiles on a roof). Efficient sawing and ergonomic suitability should be ensured independently of for what purpose the saw is used for a given angular setting. As an additional aspect, the invention also aims to provide a handsaw with an improved tooth protector. According to the invention, the basic aim is realised by the features mentioned in the characterizing part of claim 1. Further preferred embodiments are defined by the dependent claims. Further discussion of the state of the art The German petty patent DE 29613265 U1 describes a handsaw with a handle designed without knuckle protection, rotatable to a position obliquely upward-rearward from the rear end of the blade, in order to permit sawing through a workpiece on a supporting surface. In that case, however, the sawing capacity will be mediocre, since the handle will subject the blade to an upward force vector during every rearward sawing motion when the necessary pulling force is applied to the upwardly directed handle. Another embodiment of the saw has a knuckle protection and may be used for sawing through a workpiece on a support, but in that case the knuckle protector extends below the straight line of motion of the teeth of the blade; something that will make sawing all the way through the workpiece impossible. Through DE 198 08 705 A1 is previously known a handsaw with a blade that is adjustable in different operative positions in relation to a handle associated therewith. However, in this case the blade is mounted in a very bulky attachment part, which projects prominently below the linear motion path of the line of teeth, and consequently it is impossible to completely cut through a workpiece lying on a support surface. US 2747631 describes a handsaw comprising a handle which is built from a sturdy handgrip and a comparatively slim attachment part, and a blade con- nected to the attachment part and adjustable to different angles relative to it. In that case the different setting positions of the blade are determined by a multitude of equidistant pins located on the attachment part and penetrating a number of equidistant holes in the blade and in a locating body which is connected to the at- tachment part by a threaded bolt device pressing the blade against the attachment part. In order to adjust the blade between different angular setting positions, the locating body must be released and them remounted after the pins determining the setting positions having been inserted in the desired series of holes. More particularly, that saw does not include any locking mechanism or recess of the kind specified by the present invention, nor does it include any kind of tooth protector. A handsaw struck by the same disadvantages as the saw according to DE 29613265 U1 is also known from US 5979065. From US 2621689 is previously known a saw adjustable to a number of defined positions by a bolt device which has to be unlocked in the same way as US 2747631 and which further does not permit sawing completely through a workpiece resting on a support surface. Brief description of the accompanying drawings Among the drawings: Figure 1 is a schematic, partly sectioned lateral view showing a handsaw according to the invention, with the blade of the saw in a first operative position relative to the handle associated therewith, Figure 2 is a similar lateral view showing a tooth protector part of the handle in an extended position, Figures 3 and 4 are partial lateral views showing the handsaw with the blade in two further different operative positions, Figure 5 is a lateral view showing the blade of the handsaw in an inactive position inserted in both the handle and in the tooth protector, Figure 6 is a split perspective view showing three components of the saw handle, Figure 7 is a cross section through the handgrip part of the handle, Figure 8 is an analogous cross section through the handle showing only the tooth protector part, Figure 9 is a partially sectioned partial lateral view showing the region of the joint between the blade and the handle of the handsaw, Figure 10 is a cross section through the handle in the region of a locking mechanism, Figure 11 is an analogous cross section showing a pin part of the locking mechanism separated from the handle, Figure 12 is an enlarged partial lateral view of of the rear end portion of the blade, Figure 13 is an enlarged partial lateral view showing the type of tooth line of the blade. Detailed description of a preferred embodiment of the invention The handsaw according to the invention shown in various positions in figures 1 - 5 comprises a handle 1 , a blade 2 and a tooth protector 3.The blade 2 carries teeth 4 forming a line of teeth which preferably is straight and in its details complies with what is shown in figure 13. As is set forth by this figure, the line of teeth includes sets of two different tooth types 5, 6, some of which are longer than others. More particularly, the tooth line includes sets of two or more long teeth 5 separated by a short set tooth 6. Each long tooth 5 is ground with a rear cutting edge 7 with a rake angle α equal to 12 degrees, while the relief angle β of every front cutting edge equals 24 degrees. The cutting edges are sharply ground and terminate at a sharp point. Since the rake angle α is considerably smaller than the relief angle β, the rear cutting edges 7 will cut considerably more aggressively than the front cutting edges 8; which in practical applications means that the main part of the sawing action is performed when the blade is pulled rearwards. The shorter tooth 6 between adjacent sets of longer teeth 5 is ground with a top relief angle γ which may be about 32 degrees. The long teeth can have a length of 4.8 mm, where the difference in length between long and short teeth may be 0.8 mm. After grinding of respective cutting edges, the short teeth 6 are set to improve chip removal. Despite most of the sawing action being performed by the rearwardly directed, aggressive cutting edges 7 when the saw is pulled in a rearward direction, a definite sawing action is also performed by the less aggressive cutting edges 8 in association with pushing the saw in a forward direction. The handle 1 as shown in figures 1-5 comprises an elongated handgrip 9 as well as an attachment part (10 as a whole), which basically extends in a blunt angle to the handgrip 9 and onto which the blade 2 is attached, specifically by means of a joint 11. Said blunt angle is defined as the angle where a basically flat or linear top surface 12 cuts a conceived centre line 13 through the handgrip 9. In the embodiment shown, this blunt angle amounts to approximately 135 degrees, but may be in the region 130-140 degrees. A rear portion 14 without teeth of the blade 2 is inserted in an open slot 15 in the attachment part 10, see figures 9-11 , and is attached to this by the joint 11 , which may be realised as a simple pin or bolt extending across the slot 15. To lock the blade in a desired position a locking mechanism 16 is provided, comprising a cylindrical pin 17 with a head 18. The pin 17 is located in a bore 19 extending through the attachment part 10, specifically at right angle to the slot 15. The pin 17 is in a known way provided with two axially separated constrictions 20,21 with different size diameters. As shown in figures 6 , 9 and 12, the rear end portion 14 of the blade 2 is essentially semi-circular, where in the semi-circular peripheral re- gion 22 are cut four separate recesses 23, 24, 25, 26, the locations of which are described below. Each such recess has a partially circular shape, the diameter of which corresponds to the diameter of the larger constriction 21 of the pin 17. The pin 17 is normally held in an outer end position by a spring 27, with the larger constriction 21 in the same level as the slot 15, whereby the pin locks the blade in a desired angular position when it engages with one of the recesses 23-26. When the blade is to be released to be rotated, the pin 17 is pressed into the bore 19 against the force of the spring 27 to a position where the narrower constriction 20 is located in the plane of the slot 15. This constriction 20 has a diameter small enough in comparison to the depth of the actual recess to create a distance be- tween the pin and the recess, allowing the blade to be rotated away from the actual recess. Referring to figure 12, this shows the locations of the recesses 23-26. The first recess 23 is located at a straight edge portion 28 which at one end meets the tooth line 4 and at its opposite end merges into the semicircular edge 22. Specifi- cally, the recess 23 is located near the transition between the straight edge 28 and the semi-circular edge 22. As clearly shown by the drawn figure, the straight edge portion 28 is located at a distance from a conceived line L forming an extension from the tips of the teeth, and pointing slightly upward away from the tooth line. The actual distance between the conceived extension line L and the front end of the straight edge 28 is about 8 mm when the height of the teeth 4 is 4.8 mm as said above. A second recess 25 which determines the most common operative position of the blade is peripherally separated from the first recess 23 by an angle of about 134 degrees. According to the invention, a third recess 26 is also provided, separated from the second recess 25 by about 40 degrees. Further, between the first and second recesses 23, 25 is provided a fourth recess 24 separated from the first recess by about 99 degrees. The latter angle is shown as δ in the figure, and the angles between the other couples of recesses are shown as ε and ζ respectively. While the angle δ in this embodiment is shown as 99 degrees, it may have any value within the range 95-105 degrees. Analogously, the angle ε may be other than 35 degrees but within the range of 30-40 degrees, and the angle ζ may be within the range of 35-45 degrees. In all cases the total angle between the first and third recesses 23, 26 should be within the range 170-180 degrees. In the shown preferred embodiment the total angle between the first and third recesses 23, 26 amounts to 176 degrees. In figure 12 the blade 2 has an upper edge 29. In the rear region of the blade this upper edge 29 is approximately parallel to the tooth line 4 and the line L extending from the tooth tips. Figures 5 and 9 show the basic geometrical shape of the attachment part 10 of the handle. In the same manner as on the handsaw described in WO 99/20099 the handgrip 9 merges into the attachment part 10 through a comparatively slender transition portion 30 which at its inner border has a softly rounded recess 31 adjoining a thickened rear portion 32 of the attachment part 10. Said rear portion 32 of the attachment part 10 serves as a knuckle guard to ensure that the hand of the user does not slip forward along the handle toward the blade. The attachment part itself is delimited by an upper side 12 and a lower side 34. In contrast to the attachment part of the saw according to WO 99/20099 (where the at- tachment part is bulkier since its upper and lower sides are basically parallel) the attachment part 10 is in this case made with a generally forward tapering shape toward a rounded end portion 35. More particularly, the upper and lower sides of the attachment part form an acute angle η with each other as seen in figure 5. In the preferred embodiment this angle η amounts to about 36 degrees (should be within the range 29-43 degrees). When in this context the term attachment part is used, it should be remembered that it consists of two halves separated by a slot 15. The technical effect of the tapering shape of the attachment part will be further described below with reference to the state of function shown in figure 4. Referring now to figures 6 - 8, these show how the handgrip 9 part of the handle consists of a rigid frame with two side walls 37 connected by a common back 36 and separated by a slot 15 which is a continuation of the slot 15 in the attachment part 10. This slot 15 will in the following be called the first slot. Analo- gously, the tooth protector element 3 comprises two side walls 38 connected with each other by a common back 39 and delimiting a second slot 40. The tooth protector 3 is characterized by having the shape of a slide located in an elongated cavity 41 within the handgrip part 9 of the handle. This slide is longitudinally dis- placeable between an inactive position shown with interrupted lines in figures 1 , 3 and 4, and an actively protective protruding position shown in figures 2 and 5. As is clearly shown in figures 7 and 8, the slide 3 has basically a generally oval cross section, corresponding to a basically oval cross section of the cavity (41). Figure 6 shows how the handle as a whole is composed from two halves 42, 43 made from a polymer material. Both these halves are made with convexly curved outsides and flat insides which are pressed together when the two halves 42, 43 are to be united by a suitable method such as gluing or welding. On the flat inside, each half 42, 43 is provided with an elongated recess 44 which is open towards the free lower end of the handgrip 9. Together, the two recesses 44 in the respective halves 42, 43 form the cavity 41 mentioned above. At the bottom of each recess is provided a groove 45 ending at a certain distance from both ends of the handgrip 9. These grooves co-operate with two retaining elements shaped as protrusions 46 located on the outside of the slide 3 close to its inner end. When the slide is pulled out to its active protecting position, the retaining elements 46 ensure that the slide is retained by the handle without being disengageable. One side of the outer end portion of the slide 3 is provided with a hinge device 47 of the kind described in WO 99/20909. As known, this hinge device comprises a generally horseshoe-shaped outer flange 48 and a narrower neck 49 between the flange and the outside of the slide. The hinge device serves to allow connecting of the saw to a garment-mounted holder clip of the kind described in WO 99/20909 which includes a keyhole-shaped recess into which the hinge device can be hooked and which allows the saw to swing relative to the holder clip, and which allows easy disconnection of the saw from the holder. One of the handgrip part halves 43 is provided with a cut-out 50 to receive the hinge device 47. This cut-out 50 is open at the free end of the handgrip and is provided with a retaining bump 51. When the slide 3 is pushed into its inner end position in the cavity 41 , the narrow neck 49 of the hinge device 47 enters the cut-out 50 and is snapped in place by the bump 51 which fits into a pit-like recess 52 in the hinge device. The described snap connection ensures that the slide is retained in the corresponding cavity when the saw is actively used for sawing. However, the snap connection does not produce a noticeable resistance to pulling the slide out to the actively protecting position shown in figures 2 and 5. Function and advantages of a saw according to the invention Figures 3 and 5 show a saw according to the invention in two different functional states, which themselves were describes in SE 9803675-9, particularly one commonly occurring operative state according to figure 3 and one state when folded together according to figure 5. In the state according to figure 3 the blade 2 and the handle 1 form a blunt angle with each other. This blunt angle is deter- mined by the location of the locking pin 17 in a recess 25 and amounts to about 134 degrees in the actually shown embodiment. As already known this angle results in efficient and ergonomically advantageous sawing. In the state shown in figure 5, the tooth protector 3 has been pulled out from the handgrip part of the handle, and the blade 2 has been folded into the tooth protector as well as the handle itself, thereby ensuring a good protection of and from the sharp teeth of the blade. In this state, the locking pin 17 is located in the first recess 23. A characteristic of the invention is that the third recess 26 makes it possible to locate the blade in the position shown in figure 4. In this state, the handgrip part 9 of the handle extends from the attachment part 10 rearwards in a direction obliquely downward relative to the extension line L from the tooth tips. Specifically, the handgrip 9 forms an angle of about 8 degrees (may vary within the range 6-10 degrees) with the extension line L. Since the attachment part 10 forms a blunt angle within the range 130-140 degrees relative to the handgrip 9, the rear end of the handgrip 9 will keep a distance from the extension line L in spite of the fact that the handgrip slopes downward and rearward from where its front end merges into the attachment part 10. Since the rear end in this way is kept at a clear distance from the extension line L, the handsaw can in this state be used for flush sawing, such as for crosscutting of a workpiece resting on a support surface such as a roof laths. Since the entire handgrip 9 has a good clearance from the support below, the fingers of the hand can fit around the handgrip part without rubbing against the support surface. The good clearance is greatly improved by the fact that the attachment part 10 is made with a forwardly tapering shape, as said above. This implies that the underside 34 of the attachment part in the state shown in figure 4 is localised at a notable distance from the extension line L. The same applies to the straight lower edge portion 28 behind the tooth line 4 of the blade, which in the state shown in figure 4 is localised in approximately the same plane as the underside 34 of the attachment part. In other words, a workpiece resting on a support surface can be sawn totally through with no risk that any part of the handle or the rear end portion of the blade would touch the support surface. Since the handgrip 9 is obliquely sloping downward, the sawing will be efficient not only in a forward direction but also in the more aggressive rearward direction, because the handle when pulled to the rear will be subject to not only a rearward pulling force, parallel with the line of teeth, but also a downward force vector ensuring that the line of teeth of the blade is pressed into the bottom of the sawn kerf with certain force. In the preferred embodiment of the handsaw described, which according to the invention includes a fourth recess 24 between the first and second recesses 23, 25 it is also possible to locate and lock the blade in the position shown in figures 1 and 2. In that state, the blade form an angle of about 99 degrees with the handgrip part of the handle. This functional state is especially suited for pruning purposes, with special regard to the possibility to turn the saw upside down for sawing partially through the underside of a branch as is commonly done when cut- ting thick branches. Although the saw has been turned with the teeth upwards, a considerable pulling force will still be applied to the blade since the handle forms such a steep angle with the blade. In this context it must be mentioned that the blade can easily and rapidly be relocated to the more conventional functional state shown in figure 3, namely through simply pressing the head 18 of the pin of the locking mechanism 16, whereupon the pin 17 can be relocated from the fourth 24 to the second recess 25. It should be stressed that all relocations of the blade between different positions will be carried out in the same easy way. One major advantage of the handsaw according to the invention is that it is universally useful not only for pruning but even more importantly for general carpentry purposes, especially for flush cutting as has been described above with reference to figure 4. In spite of the rather radical changes of the relative angle between blade and handle in the different positions, an efficient transfer of the user's muscular force through the handle to the blade is ensured, while at the same time the hand is protected from mechanical damage, in part by the knuckle guard of the handle, in part by the geometrical relation of the handle relative to the blade. The tooth protector described also offers a good protection for and against the teeth of the blade. It should be especially stressed that the tooth protector described permits use of the same handle of a standard design together with blades of different lengths. To adjust the useful length of the tooth protector to blades of different lengths, the only needed simple measure is to provide retaining elements 26 at suitable different distances from the free outer end of the tooth protector. Possible modifications of the invention The concept of the invention is not restricted to only the embodiment described above and shown in the figures. It is thus possible to provide the saw with a foldable tooth protector of the kind described in SE 9703788-1 instead of the longitudinally slideable tooth protector described above. Instead of assembling the handle from two halves as described, it would be possible to make it as one piece with a slot for the blade, and insert the tooth protector slide after some elastic deformation of the handgrip. The retaining elements on its outside might in such a case be conically shaped. Other modifications would also be possible within the scope of the following patent claims.

Claims: CLAIMS 1. A handsaw comprising an elongated blade (2) with a line of teeth (4), the individual teeth of which (5,6) are provided with cutting edges (7,8) shaped to cut more aggressively in rearward than in forward motion, and a handle (1) consisting of an elongated handgrip part (9) of shorter length than the blade (2), as well as an attachment part (10) forming a blunt angle with the handgrip part and attached to the rear end portion (14) of the blade by a joint (11) which permits rotation of the blade relative to the handle and which co-operates with a locking mechanism (16) comprising a locking member (17) which can be located in one of a multitude of periferically separated recesses in the region of a generally semicircular rear edge (22) of the blade for the purpose of locating the blade at various angles relative to the handle, wherein the handgrip part (9) has two lateral walls (37) connected by a common back (36) and delimiting a first slot (15) arranged to co- operate with a second slot (40) in a tooth protector (3) which is movable between an inactive position and an active position extending in the direction of the handgrip part (9) of the handle and enabling the line of teeth (4) of the blade to be inserted into both said slots at the same time; said handgrip part (9) merging into the attachment part (10) via a transition portion (30) which is more slender than a knuckle guard formed by the rear end portion (32) of the attachment part; a first recess (23) among said recesses being located at a lower edge (28) of the blade to lock it in the position when the line of teeth is inserted in the handgrip part and in the tooth protector, while a second recess (25) located at a distance of at least 125 degrees from the first recess (23) can be used to lock the blade relative to the handle in one operative position, characterized by the blade being provided with at least a third recess (26) located at an angular distance from the first recess (23) within the range 170-180 degrees and by the blunt angle between the handgrip part (9) and the attachment part (10) of the handle being within the range 130-140 degrees, resulting in the free rear end of the handgrip part (9) being located above a conceived line L forming an extension line from the tips of the teeth (5,6) while at the same time said part sloping rearward obliquely down relative to said extension line L, when the blade is located in a position for flush sawing by locating the locking member (17) in the third recess (26), and by the attachment part (10) of the handle tapering in a forward direction from a knuckle protecting rear portion (32) to localise its lower side (34) at a distance above said extension line L, and by the first recess (23) being located in a toothless edge portion (28) at a distance above said extension line L. 2. A handsaw according to claim 1 , characterized by the blade (2) having a fourth recess (24) located between said first and second recesses (23,25). 3. A handsaw according to claim 2, characterized by a first angle (δ) between the first and fourth recesses (23,24) within the range 95-105 degrees, a second angle (ε) between the forth and second recesses (24,25) within the range 30-40 degrees and a third angle (ζ) between the second and third recesses (25,26) within the range 35-45 degrees, and the total angle between the first and third recesses (23,26) within the range 170-180 degrees. 4. A handsaw according to any one of the preceeding claims, characterized by the attachment part (10) tapering from its rear knuckle protecting portion (32) in a generally wedge-like form towards a front end (35) with rounded shape, where the angle (η) between the upper and lower sides (12,34) of the attachment part is within the range 29-43 degrees.

Inventors: LOEFGREN PER-OLOF, LOEFGREN, PER-OLOF
Applicants: KAPMAN AB, LOEFGREN PER OLOF, LOEFGREN, PER-OLOF
Application year: 2001
Main classification: B27B21
IPC codes: A01G3, B23D51, B23D61