HAND TOOL

Abstract: A hand tool comprises a body (2), a handle member (3) pivotally mounted thereon and an operating member (4) which is displaceable relative to the body between a starting position and a turning position against the action of a force. The handle member (3) comprises an elbow lever element (10) which has a pivot pin (14) resting against a support (15) arranged in the body (2) and which is displaceable along the support perpendicular to the pivot pin (14). The elbow lever element (10) has a first arm (10') which is pivotable about the pivot pin (14) towards and away from the body (2), and a second arm (10") which is adapted to engage the operating member (4) whem the first arm (10') pivots in the direction of the body (2) and to move the operating member from the starting position to the turning position against the action of said force. The handle member (3) is arranged such that the elbow lever element (10), when the first arm (10') pivots in the direction of the body (2), on the one hand is pivoted about the pivot pin (14) and, on the other hand, is moved in the direction of the operating member (4) while the pivot pin rests against the support (15), whereby the moment arm (L1, L2) of the first and second arm (10', 10") perpendicular to the direction of displacement of the operating member (4) gets longer and shorter, respectively.

Description: HAND TOOL The present invention relates to a hand tool com¬ prising a body, a handle member pivotally mounted thereon and an operating member which is displaceable relative to the body between a starting position and a turning posi- tion, the displacement of the operating member from the starting position to the turning position, during use of the tool, taking place against the action of a force that increases during at least part of said displacement, and the handle member being arranged to engage the operating member so as to displace, when pivoting relative to the body, the operating member from the starting position to the turning position. An example of a known hand tool of this type is dis¬ closed in Swedish Patent Specification 8700892-6. This prior-art tool is a stapler for driving staples into an object. The operating member of the tool is a driver which engages a leaf spring and is adapted, while being displaced from a lower starting position to an upper turning position, to tension this spring, which then pro- duces the force counteracting the displacement. The stap¬ ler has in its lower portion a magazine which contains a horizontal row of releasably interconnected staples, which are urged forwards towards a firing position in the front portion of the stapler by a spring-loaded feeding mechanism. When the driver reaches its turning position, it is released, the spring giving the driver a striking motion starting from the turning position and intended to drive the front staple located in the firing position into an object. The handle member of the prior-art stapler is a straight lever. The lever is pivoted to the body of the stapler by means of a horizontal pivot pin and has a short front arm and a long rear arm, which constitutes the handle of the stapler. The front arm of the lever engages by its front end in a hole in the upper portion of the driver so as to raise the driver from the start¬ ing position to the turning position against the action of the spring when the handle, i.e. the rear arm of the lever, is urged downwards towards the body of the sta- pier. The lever is designed in such a manner that the front end of its front arm is moved out of the hole in the upper portion of the driver when the driver reaches the turning position. Then the driver is released to per¬ form its striking motion. A recess extends transversely through the body of the stapler and is defined in its upper part by a grip¬ ping surface. The handle is to be pressed downwards by hand. The thumb of one hand is placed across the handle and the other fingers of the same hand are inserted into the recess in the body, whereupon one presses the handle downwards by making a squeezing motion with the thumb pressed against the handle and the other fingers pressed against the gripping surface. In the starting position, the handle extends obliquely upwards-rearwards, the open- ing angle being relatively great. This results in the grasping opening of the hand, corresponding to the dis¬ tance between the upper side of the handle and the grip¬ ping surface, first also being large. The grasping open¬ ing of the hand decreases during the squeezing motion and is comparatively small when the handle reaches a substan¬ tially horizontal position, in which the driver is locat¬ ed in its upper turning position. The maximum squeezing power of the hand, which henceforth is called the hand power, is relatively small in a large grasping opening as well as in a small grasp¬ ing opening and is at its maximum in an intermediate grasping opening position. In the starting position of the handle, the hand power thus is fairly small so as to during squeezing, i.e. with a decreasing grasping open- ing, first increase to a maximum in the intermediate grasping opening position and, as the squeezing conti¬ nues, from this intermediate position decrease again. The condition described above is illustrated in Fig. 1, which is a diagram, in which the hand power as a function of the angle v for the pivoting of the handle from the starting position is shown for three persons having different strength. Fig. 1 also shows the press¬ ing-down power which is necessary for pressing down the handle and which is proportional to the counterforce pro¬ duced by the leaf spring, as a function of the angle v in the angular area between v=0 (starting position of the handle) and v=v^. The angle vι_ corresponds to the hori¬ zontal position of the handle, in which the driver is located in its upper turning position. Fig. 1 thus illu¬ strates both the available hand power and the required pressing-down power. The spring force and, thus, the re- quired pressing-down power increase linearly relative to the pivoting angle, whereas the hand power, as described above, first increases so as to later decrease. As is evident from the shown example, the weakest person does not have sufficient hand power to press down the handle, whereas the strongest person manages this relatively easily. Fig. 2 shows the ratio (in per cent) of the required pressing-down power to the hand power of the person of medium strength as a function of the pivoting angle v for the example shown in Fig. 1. As is evident, the person of medium strength first needs to use but a minor amount of the available hand power when pressing down the handle. Then he must gradually use a greater and greater amount of the available hand power so as to use, at the end, almost 100% thereof. Of course, this is strenuous work, but also confers the drawback that the precision, i.e. the ability to hold the stapler in the exactly correct position, is considerably deteriorated in the actual fir¬ ing moment. Therefore a more uniform utilisation of the available hand power is desirable. A special object of the present invention therefore is to provide a stapler, in which the course of the curve of the power required for pressing down the handle of the stapler corresponds more closely to the course of the curve of the available hand power in such a manner that a more uniform degree of utilisation in respect of the available hand power should be obtainable through the pivoting area of the handle. A more general object of the present invention is to provide a tool of the type mentioned by way of introduc¬ tion, in which the power required for pivoting the handle member is, in a simpler manner, adapted to the available hand power in the manner described above. This general object is achieved by a hand tool which is of the type mentioned by way of introduction and char¬ acterised in that the handle member comprises an elbow lever element, which has a pivot pin resting against a support arranged in the body and which is displaceable along the support perpendicular to the pivot pin, the elbow lever element having a first arm which is pivotable about the pivot pin towards and away from the body, and a second arm which is angled relative to the first arm and extends from the pivot pin in the direction of the ope¬ rating member to engage the operating member when the first arm pivots in the direction of the body, and to move the operating member from the starting position to the turning position against the action of said force, the handle member being arranged such that the elbow lever element, when the first arm pivots in the direction of the body, on the one hand is pivoted about the pivot pin, and, on the other hand, is moved in the direction of the operating member while the pivot pin rests against the support, whereby the moment arm of the first and the second arm perpendicular to the direction of displacement of the operating member gets longer and shorter, respec¬ tively. The invention will now be described by means of an embodiment and with reference to the accompanying draw¬ ings, in which Fig. 1 is a diagram of power, which shows the avail¬ able hand power and the necessary pressing-down power as a function of the pivoting angle of a pivotable tool handle; Fig. 2 is a diagram showing the ratio of the neces¬ sary pressing-down power to the available hand power as a function of the pivoting angle; Fig. 3 is a part-sectional side view and shows a hand tool according to the present invention, the handle of the tool being in a starting position; Figs 4 and 5 correspond to Fig. 3 but show the handle of the tool in an intermediate position and a pressed-down position; and Fig. 6 is a part-sectional perspective view and shows the handle of the tool in the starting position. The hand tool shown in Figs 3-6 is a stapler for driving staples 1 into an object (not shown). Basically, this stapler is of the same type as the prior-art stapler described by way of introduction. The inventive stapler thus comprises a body 2, a handle member 3 pivotally mounted thereon, and a driver 4 arranged in the front portion of the body 2 and adapted to drive the staples 1 one by one into an object. The driver 4 is vertically displaceable relative to the body 2 between a lower starting position (Figs 3 and 6) and an upper turning position (Fig. 5). A leaf spring 5, which extends in the longitudinal direction of the stapler, is at its rear end fixedly attached to the body 2 and engages at its front end into a lower hole 6 in the driver 4. The lower por- tion of the stapler accommodates a magazine 7, which con¬ tains a horizontal row of releasably interconnected stap¬ les 1 which are urged forwards towards a firing position in the front portion of the stapler, by a spring-loaded feeding mechanism (not shown) . The driver 4 is raised from its lower starting posi¬ tion to its upper turning position by means of the handle member 3, the spring 5 being tensioned while being bent upwards about the arcuate underside of a support member 8 fixedly arranged in the body 2. When the driver 4 reaches its upper turning position, it is released, the spring 5 giving the driver 4 a striking motion starting from the turning position and intended to drive the front staple 1 located in the firing position into an object. It should be noted that "front", "rear", "upper", "lower", "horizontal" and "vertical" as stated above and also henceforth are used with respect to the position in which the hand tool is shown in the drawings. It will be appreciated that the shown horizontal position is only one of many feasible positions of use of the tool. The handle member 3 consists of a handle 9 and an elbow lever element 10. The handle 9 is designed as a straight arm, whose cross-section is in the shape of an inverted U. The handle 9 is at its rear end pivotally connected to the body 2 in the rear portion thereof by means of a pivot pin 11 defining a horizontal pivot axis. The elbow lever element 10 has a first arm 10' and, angled thereto, a second arm 10". The angle α between the two arms 10' and 10", which suitably is 90°-130°, is about 120° in the embodiment illustrated. In the starting position of the handle member 3 (Figs 3 and 6), the first arm 10' extends obliquely upwards-backwards and the second arm 10" extends obliquely upwards-forwards. Each of the two arms 10" and 10' is, like the handle 9, an inverted U in cross-section, this U being of such a width that the first arm 10' can be received in the handle 9. The first arm 10' of the elbow lever element 10 is, at its rear end, turnably connected to the handle 9 a distance behind the free front end thereof by means of a turning pin 12 extending in parallel with the pivot pin 11. A spring 13 engages the first arm 10' and the handle 9 so as to urge them to the starting position shown in Figs 3 and 6. A support and pivot pin 14 extending in parallel with the pins 11 and 12 extends through the elbow lever element 10 in the angular portion thereof. The pin 14 rests against a horizontal support surface 15 which is formed on the upper side of the stationary support member 8. When pivoting about the pin 14, the elbow lever ele- ment 10 is movable back and forth along the support sur¬ face 15 between a rear position (the starting position shown in Figs 3 and 6) and a front position or firing position (Fig. 5). The second arm 10" of the elbow lever element 10 engages at its front end or nose in an upper hole 16 in the driver 4 so as to raise the driver from its starting position to its upper turning position when the handle 9 is pivoted from the starting position shown in Figs 3 and 6 to the horizontal position shown in Fig. 5. When the driver 4 reaches its upper turning position, the elbow lever element 10 reaches its front position or firing position, the front end of the second arm 10" being pivoted out of the upper hole 16 in the driver 4, which is then released to be fired by the tensioned leaf spring 5. A recess 17 extends transversely through the body 2 and is defined in its upper part by a downwardly facing gripping surface 18. The handle 9 should be pressed down¬ wards by hand in a prior-art manner. In the same way as in the known stapler described above, the thumb of one hand is placed across the handle 9 and the other fingers of the same hand are inserted into the recess 17, where¬ upon one presses the handle 9 downwards by making a squeezing motion with the thumb pressed against the han- die and the other fingers pressed against the gripping surface 18. In this squeezing motion, the handle 9 is pivoted counterclockwise about the pivot pin 11, which is fixed relative to the body 2, and the elbow lever element 10 is pivoted clockwise about the pivot pin 14, while this and, thus, the elbow lever element 10 are moved forwards along the support surface 15. While the handle 9 is pressed down, the driver 4 is raised from its starting position to its upper turning position, which takes place against the force of the leaf spring 5, which increases as the driver 4 is raised and, thus, the leaf spring is bent. The power by which the handle 9 is to be pressed downwards, i.e. the necessary pressing-down power, con¬ sists of the force produced by the leaf spring 5, ex¬ changed via the elbow lever element 10, plus the coun- terforce which is produced by the spring 13 and which may, however, be ignored as compared with the exchanged force of the leaf spring. The moment arm of the first arm 10' perpendicular to the direction of displacement of the driver 4, i.e. its horizontal moment arm, is designated LI in Fig. 4. The corresponding moment arm of the second arm 10" is designated L2 in Fig. 4. For the pressing-down power FI (Fig. 4) which is necessary for pressing down the handle 9, if the action of the spring 13 is ignored, F1=F2«L2/L1, wherein F2 is the spring force produced by the leaf spring 5. Since in the embodiment shown LI is greater than L2 in all the pivoting positions of the elbow lever element 10 between the starting position shown in Figs 3 and 6 and the position shown in Fig. 5, the elbow lever element 10 changes down the leaf spring force F2, i.e. FKF2. As the handle 9 is pressed down- wards and the elbow lever element 10 is thus pivoted clockwise and is displaced forwards, the moment arm LI will be longer, while the moment arm L2 will be shorter, i.e. the changing-down ratio increases. By selecting a suitable length and angular setting α of the arms 10' and 10", the pressing-down power re¬ quired for pressing down the handle 9 is adapted to the power curve of the hand in the desired manner. An example of such an adaptation is shown in Fig. 1, in which the required pressing-down power in a stapler according to the invention, as shown, follows the power curve of the hand more closely than the required pressing-down power in the prior-art stapler described above. This adaptation results, as illustrated in Fig. 2, in a more uniform uti¬ lisation of the available hand power through the pivoting area of the handle 9. It should be noted that the degree of utilisation is not in any angular position of the han- die 9 close to 100%, and that the degree of utilisation in the moment of firing (v= vτ_), where high precision is desirable, is less than 50%. It will be appreciated that the required pressing- down power can be varied still more by means of parame- ters other than the length and angle α of the arms 10' and 10". The nose angle β (see Fig. 4), i.e. the angle at the second arm front end engaging in the upper hole 16 of the driver 4, also affects the course of the curve of the required pressing-down power. When the elbow lever element 10 is pivoted and displaced, the upwardly facing surface of the nose slides against the upper limiting wall of the upper hole 16, which is formed in the driver 4, thus causing an extra raising of the driver 4 depend- ing on the nose angle β in addition to the raising that is directly caused by the pivoting of the elbow lever element 10, if the upwardly facing surface of the nose is inclined obliquely upwards-backwards (see Figs 3 and 4) . This extra raising in turn causes a supplementary ten- sioning of the leaf spring 5. The course of the curve of the required pressing- down power can also be affected, for instance, by a suit¬ able design of the support surface 15, which in the embo¬ diment shown is horizontal but which can also be inclined or be curved. According to an alternative embodiment, a support corresponding to the support surface 15 and intended for the pivot pin 14 consists of guiding grooves, which are arranged in the body 2 on both sides of the elbow lever element 10 for receiving one end each of the pivot pin 14. While pivoting the handle 9 counterclockwise about the pivot pin 11, the elbow lever element 10 is moved forwards by its first arm 10' being turnably connected to the handle by means of the turning pin 12. The first arm 10' can be connected to the handle 9 in some other man¬ ner. In a modified embodiment, the handle 9 abuts "loose¬ ly" against the first arm 10', which is then pressed against the underside of the handle by means of a spring. In this modified embodiment, the forward displacement of the elbow lever element 10 is carried out as the lever 9 is pressed downwards towards the body 2 by the second arm 10" being provided with laterally projecting pins, which engage in guiding grooves arranged in the body 2. In this modified embodiment, the handle 9 can be replaced by a handle which, like the handle 9, is turnably connected to the first arm 10' but which, in contrast to the handle 9, is not connected to the body 2 but is only supported by the elbow lever element 10 via the first arm 10' . The invention can, of course, be used in other types of hand tools, in which an operating member corresponding to the driver of the stapler is tensioned against the action of a spring. Moreover, the invention can be used in certain types of hand tools, in which the displacement of the operating member is carried out against the action of a force, which is not produced by a spring but in some other manner. Mention can be made of, for instance, blind riveting tools.

Claims: CLAIMS 1. A hand tool comprising a body (2), a handle mem- ber (3) pivotally mounted thereon and an operating member (4) which is displaceable relative to the body between a starting position and a turning position, the displace¬ ment of the operating member from the starting position to the turning position, during use of the tool, taking place against the action of a force that increases during at least part of said displacement, and the handle member (3) being arranged to engage the operating member (4) so as to displace, when pivoting relative to the body (2), the operating member from the starting position to the turning position, c h a r a c t e r i s e d in that the handle member (3) comprises an elbow lever element (10), which has a pivot pin (14) resting against a support (15) arranged in the body (2) and which is displaceable along the support perpendicular to the pivot pin (14), the elbow lever element (10) having a first arm (10' ) which is pivotable about the pivot pin (14) towards and away from the body (2), and a second arm (10") which is angled relative to the first arm (10' ) and extends from the pivot pin (14) in the direction of the operating member (4) to engage the operating member when the first arm (10' ) pivots in the direction of the body (2), and to move the operating member from the starting position to the turning position against the action of said force, the handle member (3) being arranged such that the elbow lever element (10), when the first arm (10') pivots in the direction of the body (2), on the one hand is pivoted about the pivot pin (14), and, on the other hand, is moved in the direction of the operating member (4) while the pivot pin rests against the support (15), whereby the moment arm (LI, L2) of the first and the second arm (10', 10") perpendicular to the direction of displace- ment of the operating member (4) gets longer and shorter, respectively. 2. The hand tool as claimed in claim 1, c h a r ¬ a c t e r i s e d in that the tool is a stapler for driv- ing staples (1) into an object, the operating member of the tool being a driving member (4) which engages a spring member (5) and is adapted, while moving from the starting position to the turning position, to tension said spring member, which thus produces said force and which is adapted to impart to the driving member (4) a striking motion starting from the turning position and intended to drive a staple (1) into the object. 3. The hand tool as claimed in claim 1, c h a r ¬ a c t e r i s e d in that the operating member (4) en- gages a spring member (5) which is adapted to produce a force counteracting the displacement of the operating member from the starting position to the turning posi¬ tion. 4. The hand tool as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that the handle member (3) comprises a handle (9) which is pivoted to the body (2), the pivot axis (11) extending in parallel with the pivot pin (14) of the elbow lever element (10), the first arm (10') being connected to the handle (9) so as to be pivoted by means thereof. 5. The hand tool as claimed in claim 4, c h a r ¬ a c t e r i s e d in that the first arm (10' ) is turn¬ ably connected to the handle (9), the turning axis (12) extending in parallel with said pivot pin (14).

Inventors: EDEHOLT HAAKAN, EDEHOLT, HAAKAN
Applicants: EDEHOLT HAAKAN, ISABERG AB, EDEHOLT, HAAKAN
Application year: 1996
Main classification: B25C1
IPC codes: B25C5