Abstract:
For hand-operated garden shears, in particular tree-pruning shears, with a ratchet mechanism, a ratchet lever may be disposed between a hand lever and a scissor lever and the ratchet lever may engage in different latching positions according to the ratchet mechanism. A rotatable abutment surface may be provided on the hand lever and a mating bearing surface on the lever extension, or vice versa, which, at the end of an initial closing operation with the ratchet lever in a first ratchet position, may allow a continuation of the cutting operation as a direct cut without further use of the ratchet mechanism.

Description:
BACKGROUND 
     The invention relates to hand-operated shears with a ratchet mechanism. 
     Shears with ratchet mechanisms have the advantage that higher resistance forces of the material to be cut can be overcome with moderate hand force of the user than with shears with the same hand lever length without a ratchet mechanism. A design is especially customary in which in a first articulation a second hand lever and in a second articulation a second shears lever are connected to a first pivot lever that contains a first shears shaft and a first hand lever. The second shears lever contains a second shears cheek and a lever extension. The lever extension is connected via a ratchet lever to the second hand lever, whereby a first end of the ratchet lever is supported in a third articulation and the second end of the ratchet lever is supported on a ratchet structure with several ratchet steps. In a first ratchet position, in which the ratchet lever engages after the maximal opening position of the hand levers during the closing of the hand levers, the shears cheeks (e.g. blades) cannot be completely closed. The hand levers must be opened a little bit wider again after reaching the end position of a first closing operation of the hand levers, whereby the ratchet lever jumps under spring action to one of the next ratchet steps, in which in the end position of the hand lever closing operation a more extensive or complete closing of the shears cheeks is possible. Shears with such a ratchet mechanism are known, e.g. from DE 298 16 971 U1. 
     The multiple closing operations of the hand levers with partial opening to be carried out in between them are also necessary if the resistance of the material to be cut could also be overcome in a single closing operation of the hand levers, in the following as a direct cut, by the hand force that can be applied by the user on the hand levers. In such a case the multi-step cutting operation via the ratchet mechanism is unnecessarily expensive. 
     The GARDENA Comfort Ratchet Shears Smart Cut has a pivotable support lever on the second handgrip, with which support lever the end of the lever extension of the second shears lever, which end faces away from the second shears axis, can be supported against the second hand lever in a ratchet mechanism of the described type without the ratchet lever with the ratchet structure becoming effective in a force-transferring manner so that a direct cut can be carried out with an expenditure of force as in traditional garden shears. For stronger material to be cut the ratchet mechanism can be engaged by pivoting the support lever away and a cut can be made in several motions. 
     U.S. Pat. No. 6,470,575 B2 suggests, in order to avoid the multiple actuation of ratchet shears, the construction of a control cam on the lever extension facing the second hand lever, which cam is guided on two rollers arranged on the second hand lever during the closing operation carried out as a direct cut. However, this is only an attempt to optimize the expenditure of force via the course of a cutting operation during a direct cut. One according to the same principle but with a roller on the lever extension and with a control cam on the second hand lever is described in the MD 3065 F1. A distinct reduction of the required force by a multiple closing operation of a ratchet mechanism with a greater accumulative hand lever travel is not possible with these shears with control cam. 
     BRIEF SUMMARY 
     The present invention has the task of improving the handling of garden shears with a ratchet mechanism, in particular of tree-pruning shears. 
     The invention is described in the independent claim. The dependent claims contain advantageous embodiments and further developments of the invention. 
     The invention gives the user the possibility of choosing to continue a cutting operation, begun while using an initially assumed ratchet position of the ratchet mechanism, upon reaching the end of the initial closing movement associated with this initial ratchet position either as a multi-step cutting operation typical for ratchet shears and moving the hand levers back for this into the open direction, or to continue the cutting operation, begun as a ratchet cut, as a direct cut without reversing the movement of the hand levers. 
     The user can therefore decide during the cutting operation, depending on the situation, whether he wants to carry out the initial cutting procedure without using the further ratchet positions as a simple direct cut or wishes to use the ratchet function. The user can make the decision spontaneously using the resistance of the material to be cut conducted in the initial cutting operation without committing himself already before the cutting operation. In particular, the user does not need to actuate any separate actuation element that brings about the shifting between two force transmission mechanisms. 
     In a preferred embodiment of the invention there is the possibility, building on the known ratchet mechanism, which has proven itself as regards the possible reduction of force by the abutment of the abutment surface on the mating bearing surface, which abutment occurs after an initial closing operation, with the ability to loosen the ratchet engagement by continuing the closing operation of the hand levers, to continue the cutting operation without previously opening the hand levers as an uninterrupted cutting operation up to one of the next ratchet positions or preferably as a direct cut up to the complete closing of the shears cheeks and the separation of the material to be cut. In such a continuation of the cutting operation without previous partial opening of the hand levers an expenditure of force comparable to that of garden shears without ratchet mechanism is required. 
     The initial cutting procedure can be carried out with relatively low force by the ratchet lever that always engaged into the first catch step after the complete opening of the hand levers. Upon the contacting of the abutment surface on the mating bearing surface the resistance of force offered to the user rises suddenly. If the expenditure of force seems too high to the user for the continuation of the closing operation he can go directly into the ratchet cutting mode without any other requirement in that he again partially opens the hand levers until the ratchet lever advances to a further ratchet step. 
     One of the two surfaces of the abutment surface and the mating bearing surface can, advantageously, have a convex curvature and the other surface can have a curved, concave curvature that is less in comparison to the latter, as a result of which the so-called Hertzian pressing on the quasi-punctual contacting of the two surfaces can be held low. 
     The surface of at least one of the two adjacent surfaces can be worked in a friction-reducing manner, in particular it can be provided with a friction-reducing coating or covering. The geometries of the abutment surface and the mating bearing surface can be shaped in such a manner that the force transmitted between the two surfaces favours the relative shifting of the two adjacent surfaces during the progressing closing operation. 
     It is especially advantageous to design the relative movement between the abutment surface and the mating bearing surface, that rest on one another in a shifting position during the continuation of the cutting operation of the hand levers in the direct cut mode, as a rolling of a surface on another one. To this end the abutment surface is advantageously constructed on a mechanical element that can rotate at least in a limited manner. The abutment surface is, advantageously, convexly curved away from the point of rotation and preferably designed as a circumferential surface of a rotatably supported roller. The mating bearing surface is then, advantageously, designed concavely curved away from the abutment surface, as a result of which the Hertzian pressing at the contact point of an abutment surface and mating bearing surface can advantageously be kept low. 
     The abutment surface can be arranged on the lever extension and the mating bearing surface on the second hand lever or vice-versa. The engagement structure can be arranged on the lever extension or on the second hand lever. 
     The invention is illustrated in detail in the following using preferred exemplary embodiments with reference made to the illustrations, in which 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows initially wide-open shears, 
         FIG. 2  shows the shears at the end of the initial closing operation, 
         FIG. 3  shows the shears in a more advanced cutting stage. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a lateral view, i.e. viewed in the axial direction of the articulations of the shears, of shears in an initial open position. The shears contain a first shears lever S 1  that contains a first handgrip H 1  and a first shears cheek B 1 , e.g. first blade. The first shears cheek B 1  can also be designed in particular as the anvil of anvil shears. A first articulation point G 1  and a second articulation point G 2  are provided on the first shears lever. 
     A second hand lever H 2  is connected in a first articulation at the articulation point G 1  to the first shears lever. A second shears lever S 2  is connected at the articulation point G 2  in a second articulation to the first shears lever S 1 . The second shears lever S 2  contains a second shears cheek B 2 , e.g. second blade, and a lever extension FO facing away from the latter relative to the second articulation point G 2 . In a third articulation point G 3  a ratchet lever RH is articulated with a first end to the second hand lever H 2 . On the opposite second end of the ratchet lever RH the ratchet lever RH is supported via an engagement element, for example, a pin ST, on a catch structure RS comprising several catch steps R 1 , R 2 , R 3 , R 4 . 
     The catch structure RS is constructed in a customary design as an opening through a plate forming the second shears lever S 2 . The ratchet lever RH is pressed in the direction of the catch steps R 1 , R 2 , R 3 , R 4  of the catch structure RS, thus, clockwise in  FIG. 1 , by a spring SP that can be, for example, a traction spring to the first hand lever H 1  or a leg spring supported on the second hand lever H 2 . 
     In the position of the shears with wide-open shears mouth between the shears cheeks B 1  and B 2  shown in  FIG. 1 , the pin ST lies as engagement element of the ratchet lever RH in the first catch step R 1  of the catch structure RS. The geometry of the quadrilateral consisting of the first articulation point G 1 , second articulation point G 2 , pin ST, and third articulation point G 3  is decisive for the transfer of force of a user for moving the two hand levers H 1  and H 2  onto one another into a cutting force on a material to be cut SG between the shears cheeks B 1  and B 2 . The degree of the transfer of force can be influenced by the geometry of the lengths of the sides of this quadrilateral. In the case of a pin ST resting in another catch step R 1 , R 2 , R 3 , R 4  the geometry of the quadrilateral and therefore the degree of the transfer of force are changed. 
     If the hand levers H 1  and H 2  are moved toward one another by a force of a user, in particular a user force acting on the second hand lever H 2  is transferred via the ratchet lever RH, which is loaded by pressure, into the first catch step R 1 , e.g. groove, of the catch structure RS and is converted into a torque of the second shears lever S 1  about the second articulation point G 2 . The material to be cut SG is supported at this time on the first shears cheek B 1  taken to be the shears anvil and the polished second shears cheek B 2  cuts into the material to be cut. The closing operation can be continued during the transfer of force via the ratchet lever RH into the first catch step R 1  to the position shown in  FIG. 2  in which the second shears cheek B 2  has penetrated into the material to be cut SG and has separated it, but only partially. The lever extension FO lies in this position of the shears with a mating bearing surface GF on an abutment surface AF that is given by the circumferential surface of a roller RO rotatably supported on the second hand lever H 2 . 
     Typically, in known ratchet shears with such a construction when a mating bearing surface GF of the lever extension FO is placed on an abutment surface AF of the second hand lever H 2 , the closing movement of the hand levers H 1 , H 2  moved onto one another is reversed and the hand levers H 1 , H 2  are pivoted away from one another again, which is designated as the opening or the opening direction of the hand levers H 1 , H 2 . If the second hand lever H 2  is pivoted away again from the first hand lever H 1  out of the position sketched in  FIG. 2  when the first shears cheek B 1  remains placed on the material to be cut SG, the second shears lever S 2  remains standing on account of the second shears cheek B 2  that has already penetrated into the material to be cut SG, and the second end of the ratchet lever RH moves with the pin ST inside the catch structure RS further to the next or in general to one of the next catch steps R 1 , R 2 , R 3 , R 4  and engages under the action of the spring force, that acts clockwise in a rotary manner on the ratchet lever RH, into a catch step R 1 , R 2 , R 3 , R 4  located nearer to the second articulation point G 2 . 
     Upon another movement of the two hand levers H 1 , H 2  toward one another under the action of a user force, the ratchet lever RH is now supported on a catch step R 1 , R 2 , R 3 , R 4  closer to the second articulation point G 2  and the second shears cheek B 1  presses further into the material to be cut SG until the lever extension FO again rests with the mating bearing surface GF on the abutment surface AF of the roller RO or until the material to be cut SG has been entirely separated, which is always given when the ratchet lever RH is supported by the pin ST in the catch step R 1 , R 2 , R 3 , R 4  that is the closest to the second articulation point G 2 . 
     The invention now provides that starting from the situation according to  FIG. 2  the direction of movement of the hand lever H 1 , H 2  is not reversed in the direction of opening, but rather the closing procedure of the hand levers H 1 , H 2  moving the two hand levers H 1 , H 2  toward one another is continued in the same direction of movement. A transfer of force from the second hand lever H 2  onto the lever extension FO no longer takes place here via the ratchet lever RH between the third articulation point G 3  and the catch structure RS, but rather via the support of the roller RO, its abutment surface AF and the mating bearing surface GF on the lever extension FO. As a result of this transfer of force path another geometry of force transfer is given for the continuation of the closing procedure of the hand levers H 1 , H 2  and, associated with it, also for the continuation of the closing movement of the shears mouth between the two shears cheeks B 1 , B 2 , which geometry corresponds substantially to the transfer of force in garden shears without a ratchet mechanism. The force to be exerted by the user on the hand levers H 1 , H 2  therefore rises suddenly. If the user now applies the required greater force, that is assumed to be substantially equal to the force required for garden shears without a ratchet mechanism, the second hand lever H 2  and the lever extension FO of the second shears lever are pivoted substantially uniformly to one another onto the first hand lever H 1  and the shears mouth is completely closed up to the separation of the material to be cut SG. During this time the pin ST of the ratchet lever RH travels inside the ratchet structure, e.g. catch structure RS, along the several catch steps R 1 , R 2 , R 3 , R 4  but without fulfilling a function inside the ratchet mechanism and in particular without transferring the user&#39;s force onto the shears levers S 1 , S 2 .  FIG. 3  shows the shears in a more advanced closing state, in which the pin ST passes over the cog separating the next-to-the-last catch step R 3  from the last catch step R 4 . 
     If the user wants to continue the closing procedure as a direct cut in the situation according to  FIG. 2  but determines that he cannot apply the force required for this, he can simply pivot the two hand levers away from one another again without actuating any mechanical element in the procedure customary for the ratchet mechanism until the pin ST of the ratchet lever engages into one of the next catch steps R 1 , R 2 , R 3 , R 4  and then continue the cutting procedure with a force that is less in comparison to the direct cut, optionally even in several further steps. The user can also initially make more than one step of the multi-step ratchet cutting procedure with an opening motion between two closing motions as ratchet cut and only then move into a direct cut. 
     As is known about ratchet shears, the catch structure RS can also be constructed on the sides of the second hand lever H 2  and the ratchet lever RH can be articulated in a fixed position at a third articulation point on the lever extension FO and engage with an engagement element such as, for example, the pin ST into the catch structure RS on the hand lever H 2 . 
     Abutment surface AF and mating bearing surface GF can also be exchanged in such a manner that the abutment surface is constructed on the lever extension FO and the mating bearing surface GF on the sides of the hand lever H 1 , H 2 , for which the roller RO or another element that can rotate at least in a limited manner and carries the abutment surface AF is rotatably fastened on the lever extension FO. 
     The abutment surface AF, that rolls off on the mating bearing surface GF during the continuation of the cutting procedure as direct cut, can also be constructed only over a limited angular range about the point of rotation of a rotatable abutment element and can also deviate from the form of an exact circular arc about the point of rotation. An abutment element with limited rotation is advantageously pressed spring-loaded into a defined start position. 
     The previous features and those indicated in the claims and those that can be gathered from the figures can be advantageously realized individually as well as in various combinations. The invention is not limited to the described exemplary embodiments but can be modified in the framework of professional ability in many ways.