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1. (WO2017097316) SHEARS
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SHEARS

The invention relates to the field of shears, in particular pruning shears or secateurs .

For cutting purposes, shears usually comprise a first shear part and a second shear part, both shear parts having a cutting blade and a shaft or lever arm which are arranged at opposite sides of a pivot. The pivot connects both first and second shear parts with each other in rotatable manner.

Shears like pruning shears or secateurs, for example known from DE 34 26 577 Al , usually comprise a spring element that provides an opening force to the first and second shear parts in order to bring the shear in an open position and thus into a position from which a following cutting movement can be started. The spring characteristics of such a spring element, for example a laminated or flat spring element, are basically determined by various parameters like length, thickness or geometry of the spring element. These parameters also limit the spring forces and lifetime of known laminated or flat spring elements.

For increasing the spring force of a thin spring element, it is known to enlarge the spring element in length or to increase the bias respectively the preload of the spring element. This has the disadvantage that the lifetime is reduced. Another possibility is to increase the width of the spring element, what is however mostly limited by the space available for mounting of the spring element in a shear. Furthermore such a modification has not the desired significant influence on the spring force. The use of spring elements comprising several flat spring elements being arranged in layers is also a known technigue, but is very expensive and also reguires an increased mounting space .

It is an object of the invention to provide a shear, in particu- lar a pruning shear or secateur that overcomes the mentioned disadvanteges .

The object is achieved by a shear, in particular a pruning shear or a secateur, according to the technical features of claim 1.

The shears according to the present invention comprises a first shear part and a second shear part, each of the first and second shear parts having a cutting blade and a shaft or lever arm which are arranged at opposite sides of a pivot. The first and the second shear parts are rotatably connected with each other by the pivot, so that the shear can be moved between an open and a closed position. The shear further comprises a laminated or flat spring element which acts upon the first and second shear parts to move the shear on to their open position so that the operator of the shear only has to perform the closing movement and therewith the cutting operation. The laminated or flat spring element comprises a first portion fixedly arranged at or allocated to the first shear part and a flexibly arranged second portion acting on the second shear part. A longitudinal portion of the laminated or flat spring element is provided with at least one corrugation extending in a longitudinal direction of the laminated or flat spring element.

In other words, the longitudinal portion comprising the corrugation respectively a groove-shaped recess shows a curved cross-section. The longitudinal direction is to be understood as a direction that leads from the first portion of the laminated or flat spring element to the second portion of the laminated spring element. The corrugation respectively a groove-shaped recess shows a curved cross-section.

A laminated or flat spring element comprising such a corrugation, thus a spring element with a profiled cross-section, has the advantage that the spring forces and lifetime of the spring element as well as the lifetime of the shear are increased. The corrugation can be inexpensively manufactured manually or by a machine using two beading rollers for pressing the corrugation into the laminated or flat spring element. Furthermore, only a small mounting space is reguired as no increase for example in length is reguired. By varying the depth, the width and the length of the corrugation, a desired spring force can be adjusted.

The longitudinal portion is preferably formed between the first and the second portion of the laminated or flat spring element. Therefore the first and the second portion also referred to as end portions of the laminated or flat spring element, are not provided with such a corrugation. This ensures that the laminated or flat spring element can be fixedly or flexibly arranged or allocated to the first and second shear part without having to consider the curved cross-section of the corrugation, but the spring element still provides the desired spring characteristics .

In principle, the corrugation present in the longitudinal portion may extend over the entire width of the laminated or flat spring element, so that a cross-section of the longitudinal portion shows a completely curved course. In a preferred embodiment, the corrugation is surrounded laterally respectively on both sides by two flat edge portions of the laminated or flat spring element extending in a longitudinal direction of the laminated or flat spring element. Thereby the corrugation turns on each side into the flat edge portions in a transition area having a curved course .

Preferably, the corrugation is formed centrally and symmetrically between the flat edge portions, so that the corrugation extends along a central longitudinal axis of the laminated or flat spring element. Therefore the spring force can be adjusted in a structural simple way by varying the depth of the corrugation.

In a preferred embodiment, the convex side of the corrugation that has a curved cross-section is arranged on a tension side of the laminated or flat spring element. The tension side is to be understood as a side of the laminated or flat spring element that is exposed to highest tensile stress under load of the laminated or flat spring element. The depression of the corrugation respectively a concave side of the corrugation is therefore arranged at a compression side. The compression side is to be un-derstood as a side of the laminated or flat spring element that is exposed to highest pressure stress under load of the laminated or flat spring element. The laminated or flat spring element is under load in a closed position of the shear, whereby it is approximately straight. The laminated or flat spring element is free of load in an open position of the shear, whereby it shows an arcuate shape.

The width in a transverse direction of the second portion of the laminated or flat spring element is preferably smaller than the width of the longitudinal portion. The longitudinal portion may turn into the second portion in a rounded edge region under an angle, that is preferably greater than 90° and smaller than 180°, thus under an obtuse angle.

In a preferred embodiment, the spring characteristics of the laminated or flat spring element is only adjusted by profiling of the cross-section as the thickness of the laminated or flat spring is constant at least in the longitudinal section. Therefore the corrugation and the flat edge portions have the same thickness, what simplifies the manufacture of the spring element but also results in a strong spring element.

In order to fix the first portion of the laminated or flat spring element to the first shear part and to prevent an axial movement of the laminated or flat spring element, first support- ing means are provided supporting the laminated or flat spring element in a first axial direction to prevent a movement of the laminated or flat spring element towards the pivot . Said firs supporting means comprise an end section of the shaft or lever arm of the first shear part and at least a part of the first portion of the laminated or flat spring element. The end section of the shaft or lever arm of the first shear part and the first portion of the laminated or flat spring element interact with each other in the direction of the longitudinal axis of the 1am-inated or flat spring element respectively of the shaft or lever arm. In a further preferred embodiment, the interacting part of the first portion is formed as hook. Therefore the part of the first portion is preferably bent over a rounded angle and forms for example at least approximately a right angle, for reducing the danger of fracture of the laminated or flat spring element.

In order to prevent a twisting, bending and/or a movement in a lateral and/or radial direction of the second portion of the laminated or flat spring element that is flexibly arranged and acting on the second shear part and also the entire laminated or flat spring element, second supporting means are provided for supporting at least the first portion of the laminated or flat spring element in a radial and/or lateral direction. The second supporting means comprise at least one lateral bearing or con-tact surface that is oriented parallel to the longitudinal axis of the laminated or flat spring element. The lateral bearing or contact surface may comprise a lateral surface of the shaft or lever arm of the first shear part and/or an inner surface of a handle that is connected with or allocated to the shaft or lever arm of the first shear part in a mounted state. The laminated or flat spring element leans again these bearing or contact surfaces, so that its movement in lateral or radial direction is prevented.

In a preferred embodiment, at least the first portion of the laminated or flat spring element is at least partially arranged in a channel or groove being formed at an inner surface of a handle. Such an arrangement offers enough space for encasing the first portion of the laminated or flat spring element, so that movement in nearly all lateral or radial directions is prevented and a firm fixation of the laminated or flat spring element is provided. The shear therefore is of high guality and ensures a long lifetime.

A further advantageous embodiment provides that the lever arm of the second shear part is shaped by providing a fulcrum which is located in close distance to the pivot and interacting with the second portion of the laminated or flat spring element for moving the shears onto an open position. The laminated or flat spring element is constantly pressing against the fulcrum so as to perform the spring force onto the second shear part for opening the shear. The fulcrum may have a rounded contact surface to allow a sliding movement of the second portion of the spring element .

The invention will be described more fully in detail hereinafter with reference to the accompanying drawings, in which

Fig. 1 is a side view of a secateur in a closed condition;

Fig. 2 the secateur of Fig. 1 in a view from above;

Fig. 3 the secateur of Fig. 1 in a sectional view along the line A - A according to Fig. 2;

Fig. 4 the secateur of Fig. 1 in a front perspective view with a laminated spring in an exploded view;

Fig. 5 the secateur of Fig. 1 in a rear perspective view with removed handles; and

Fig. 6 the secateur of Fig. 1 in the sectional view of Fig. 3, but in an open position,

Fig. 7 the laminated spring element in a sectional view along the line B - B according to Fig. 4.

A secateur 1 as shown in particular in Fig. 1 is composed of a first and a second shear part 3, 3 ' which are made of metal and are connected to each other by means of a pivot 7 being e. g. a screw and a respective screw nut or the like. Each of the first and second shear parts 3, 3 ' comprise a lever arm 5, 5', each thereof being assembled with a handle 9, 9' made of plastics or rubber for grasping and operating the secateur 1. Furthermore, each of the first and second shear parts 3, 3 ' comprise a cutting blade 11, 11 'at their front end. Both lever arms 5, 5' and cutting blades 11, 11' are arranged on opposite sides related to the pivot 7, that connects the first and second shear part 3, 3 'rotatably .

Fig. 1 to 5 shows the secateur 1 in an idle or closed position.

If the secateur is not in use, it is necessary to secure the idle or closed position. Therefore, an

interlocking element 13 is arranged at the handle 9' of the second shear part 3 ' which is movable in a longitudinal direction of the handle 9' . The interlocking element 13 is composed of a manipulator for shifting 13' and a latch 13'', the latter one interacting with a notch 15 arranged at the lever arm 5 of the first shear part 3 when the secateur 1 is in the idle or closed position. Moving the interlocking element 13 in the opposite longitudinal direction with removing the latch 13 ' ' from the notch 15 causes the secateurs 1 to pass on to their open or operational position as illustrated with Fig. 6. As being best illustrated with Fig. 3, when the secateurs 1 are closed again and a cutting operation is executed, a first stopper element com-posed of a hexagon head screw 17 with short thread projection screwed into a screw socket arranged at the handle 9 of the first shear part 3 is provided, with the handle 9' of the second shear part 3 ' striking against the top side of the hexagon head screw 17 thereby defining the stop of the cutting operation. At an end portion of handle 9 ' of the second shear part 3 ' an eyelet 19 is provided for allowing a hanging and storing of the secateur 1, e.g. at a wall hook.

A cutting operation with the secateurs 1 is usually started when the secateurs 1 are in an open position, in particular in a fully open position as illustrated with Fig. 6, by pivoting the first and second shear parts 3, 3' which are connected by the pivot 7. The operator performs a closing movement via the handles 9, 9' onto the cutting blades 11, 11' using the leverage effect for operating a high cutting force. The fully open position is defined by a bottom side 21 of the cutting blade 11' of the second shear part 3 ' striking against a second stopper element being a protrusion 25 arranged at the handle 9 of the first shear part 3. Said bottom side 21 faces the cutting edge 23 of the cutting blade 11 ' of the second shear part 3 ' .

The open position for starting the cutting operation is reached by means of an opening force generated by a spring element which may be a laminated spring element 27, as illustrated with Figs. 3 to . The laminated spring element 27 is arranged at the handle 9 of the first shear part 3 and fixed in radial and/or lateral directions at a first portion 27 ' of the laminated spring element 27 by a respective groove 31 provided at an inner surface of the handle 9. A second portion 27' ' of the laminated spring element 27 and a longitudinal section 39, formed between the first portion 27' and the second portion 21' ', is in a flexible arrangement in order to perform the spring force onto the second shear part 3', thereby passing through a spring excursion which is defined by the range between the open and the closed position. In order to allow the laminated spring element 27 to perform the excursion, a respective space or clearance 29 is provided at handle 9. The clearance 29 is limited by clearance sides 29', 29' ' being present in the handle 9.

As illustrated in particular in Fig. 4 and Fig. 7 (cross-section) the longitudinal section 39 of the laminated spring element 27 is provided with a corrugation 41 that extends in a longitudinal direction of the laminated spring element and parallel to the lever arm 5. The longitudinal section 39 further comprises two flat edge portions 43', 43' ' also extending in the longitudinal direction and surrounding the corrugation 41 laterally. The corrugation 41 merges on its both sides into the flat edge portions 43', 43' ' in rounded transition areas 45', 45' '. The corrugation 41 is formed centrally between the flat edge portions 43', 43' ' and symmetrically around a central longitudinal axis M of the longitudinal portion 39.

The corrugation 41 is formed as a through-shaped recess having a convex side 47 and a concave side 49. The convex side 47 is ar-ranged on a tension side, the concave side 49 is arranged on a compression side of the laminated spring element 27, as can best be seen in Fig. 7. Therefore the convex side 47 of the corrugation 41 is present on the upper side of the laminated spring element 27 when the secateur 1 is in an assembled state, in other words oriented in direction towards the lever arm 5 'of the second shear part 3 ' . The thickness D of the laminated spring element 27 is constant in the longitudinal section 39, so that the corrugation 41 and the flat edge portions 43', 43'' have the same thickness D.

The width of the second portion 27 ' of the laminated or laminated spring element 27 is smaller than the width of the longitudinal portion 39. This is realized in that the longitudinal portion 39 turns into the second portion 27 ' ' in a rounded edge region under an angle that is greater than 90°and smaller than 180°. Therefore the second portion 27'' that is flexibly arranged and acting on the second shear part 3' presses against said second shear part 3 ' respectively a fulcrum 33, with its entire surface, so that the possibility of tilting of the second portion 27 ' ' and the laminated spring element 27 is reduced.

Fig. 6 illustrates the laminated spring element 27 in its nearly unstressed state which is obtained in the fully open position of the secateur 1. In this respect, although the laminated spring element 27 is shown with a rectilinear illustration, the ex-ploided view of Fig. 4 reflects the laminated spring element 27 in its stressed state, which in particular is taken when the secateur 1 is in its closed position. In the unstressed position, the laminated spring element 27 adopts a bent shape having a big and constant radius (see Fig. 6) . As can be understood from Fig. 6, the first portion 27' of the laminated spring element 27 which is arranged in the groove 31 is shown with a rectilinear arrangement in order to fit into the rectilinear groove 31, however, when disassembled from the groove 31 the first por-tion 27 ' of the laminated spring element 27 follows the radius of curvature of the second portion 21 ' ' . When mounted in the groove 31, the straightened first portion 27 ' thus performs a clamping force onto the groove limitations or walls, thereby supporting a fixing and keeping in position of the laminated spring element 27.

The laminated spring element 27 is fixed in radial and/or lateral directions by means of the groove 31 and, at the open groove side, by means of the lateral surface of the lever arm 5. The arrangement of groove 31 and lever arm 5 establishs a space for the first portion 27 ' of the laminated spring element 27 without any clearance in order to secure firm positioning with preventing twisting or movement of the laminated spring element 27 in radial and/or lateral directions.

The laminated spring element 27 is also secured against movement in a first axial direction towards the pivot 7. Therefore a part of the first portion 27 'of the spring element is bent over a rounded corner and formed as a hook 37 angled under a right an-gle . The hook 37 abuts against an end section respectively against an end face surface of the lever arm 5 and prevents a movement of the laminated spring element 27 in the first axial direction towards the pivot.

Finally, the laminated spring element 27 is also secured in a second axial direction away from pivot 7 which movement is limited by an end wall of the groove 31 positioned in close proximity to the end section of the lever arm 5, just keeping a space for reception of the hook 37.

The laminated spring element 27 is arranged at the secateur 1 in removable and exchangeable way, so it can be substituted when it is broken. The assembling of the laminated spring element 27 is executed as indicated with Figs. 4 to 6. Initially, laminated spring element 27 is separated from the secateur 1 as illustrat- ed with Fig. 4, however, as already described, Fig. 4 shows the laminated spring element 27 in straightened state. As indicated with Fig. 5, the laminated spring element 27 is then attached to the lever arm 5 of the first shear part 3, with at least its first end portion 27 ' being oriented parallel to the axis of lever arm 5. After such arrangement, handle 9 is slid on the joining of lever arm 5 and the laminated spring element 27 ahead with its open end which is positioned ahead the space or clearance 29, i. e. handle 9 is moved from the end portion of lever arm 5 alongside the lever arm 5 until the handle 9 reaches its final position. The hook 37 encompassing the end portion of lever arm 5 guarantees that laminated spring element 27 is kept in place and not moved with the handle 9 while the latter one is slid on the lever arm 5. With such assembly, the laminated spring element 27 is also firmly fixed since the laminated spring element 27 is guided into the groove 31 at handle 9'.

The lever arm 5 ' of the second shear part 3 ' is shaped by providing a fulcrum 33 which is located in close distance to the pivot 7. The second end portion 27'' of the laminated spring element 27 is constantly pressing against the fulcrum 33 so as to perform the spring force onto the second shear part 3 ' for moving the secateur 1 into its open position in which it is ready to use. The fulcrum 33 has a rounded contact surface for smooth-ly contacting the second end portion 27 ' of the laminated spring element 27 and allowing sliding when the secateur is moved from its open to closed position and vice versa. While the secateur 1 merely opens under an angle of about 50°, the surface of the fulcrum 33 directed to the laminated spring element 27 is shaped by a turn of about 110° passing over into a recess establishing a pocket 35 into which the second end portion 27'' of the laminated spring element 27 extends when the secateur 1 is in the open position (see Fig. 6) .

The pocket 35 may be filled with a lubricant (not shown) in par- ticular with grease. The construction of the secateur 1 and its pocket 35 is designed such that it can be refilled with lubricant. During the opening movement of the secateur 1 from its closed position (see Fig. 3) to the open position (see Fig. 6) the end portion of laminated spring element 27 respectively the front end of the second portion 27 ' ' arranged opposite to the the end section forming the hook 37 respectively the first portion 27 ' is dunking into the lubricant thereby lubricating the laminated spring element 27 at its contacting surface with fulcrum 33. The lubricant may directly flow to the contacting area or it may by driven from the pocket 35 to the contacting area by low interfacial surface tension between lubricant and the surface of the laminated spring element 27.

List of reference numerals

1 secateur

3, 3' first and second shear parts

5, 5 ' lever arms

7 pivot

9, 9 ' handles

11, 11' cutting blades

13 interlocking element

13 ' manipulator

13 ' ' latch

15 notch

17 hexagon head screw

19 eyelet

21 bottom side

23 cutting edge

25 protrusion

27 laminated spring element

27', 27'' first and second portions of the laminated spring element

29 clearance

29', 29'' clearance sides

31 groove

33 fulcrum

35 pocket

37 hook

39 longitudinal portion

41 corrugation

43', 43'' flat edge portion

45', 45'' transition area

47 convex side of the corrugation

49 concave side of the corrugation

central longitudinal axis of the laminated spring element

thickness of the laminated spring element angle of the rounded edge region