CUTTING DEVICE FOR GARDENING AND HORTICULTURE, AND METHOD FOR PRODUCING IT

Abstract: A cutting device, for gardening and horticulture, includes: two identical blades (2, 2'), each constituted by an elongated plate-like body which has a longitudinal axis (a, a') and two asymmetrical lateral cutting regions; guiding strips (14, 15) for keeping the blades (2, 2') partially superimposed and in mutual contact so that they can slide longitudinally; and a head (4) for connection to an external motor to make the blades move in a reciprocating manner in opposite directions (F, F') on the mutual contact plane. The cutting regions of each blade are constituted by a series of equidistant recesses (5, 6; 5', 6') whose plan shape is substantially a circular arc with the concavity directed towards the median axis (a, a'); each recess has a sharp edge (7, 8; 7', 8') that covers the entire extension of the arc, increasing cutting efficiency. A method for producing a blade entails that the edge sharpening operation is performed by chip-forming machining, without using polluting abrasives and grinding wheels, with a considerable economic and environmental benefit.

Description: CUTTING DEVICE FOR GARDENING AND HORTICULTURE, AND METHOD FOR PRODUCING IT The present invention relates to a cutting device for gardening and horticulture which can be used for example for cutting hedges, bushes, shrubs, and small branches, and to a method for producing the device- Devices of this type are normally but not exclusively coupled to a portable casing that contains a motor for actuating the cutting tools. The invention relates in particular to devices that include: two identical and oppositely arranged elongated blades, in which each blade has a longitudinal median axis and asymmetrical lateral cutting regions; a guiding means for keeping the blades in mutual contact and partially face to face, so that they can slide longitudinally; and an actuation means to move the blades with a reciprocating motion in opposite directions on the mutual contact plane so as to make their lateral cutting edges interact. Examples of embodiment of these devices are described, for example, in German application DE-A-4 224 665 and in French application FR-A-2 122 473. These known devices have several advantages but also some drawbacks. A first drawback is the rather low efficiency, due to the fact that the cutting regions are constituted by approximately trapezoidal transverse teeth which have sharp edges that cover only part of the inclined sides. Another drawback is constituted by the fact that the shape and orientation of the cutting edges do not allow cutting from any position but only at certain relative angles. A further drawback is constituted by the need to frequently sharpen the blades due to the limited extent of the cutting edges. In conventional devices, blades are sharpened by using grinding wheels and abrasive tools which are expensive and have a considerable environmental impact. The abrasive materials and the binders of these tools in fact cannot be recycled and must be disposed as toxic waste. Accordingly, the cost of the sharpening operation, to which the cost of waste disposal must be added, becomes a highly significant part of the total cost of the blades. The aim of the present invention is to overcome or at least reduce the drawbacks described above by providing a cutting device for gardening and horticulture that is highly effective and has a low cost. Another object is to provide blades with extensive cutting edges and having a shape adapted for cutting from different positions with substantially constant efficiency. Another object is to provide a method for producing the device, particularly for sharpening the blades, which is cheaper and more environment-friendly than the conventional methods. This aim, these objects, and others which will become apparent hereinafter are achieved by a device of the type defined in the introduction, characterized in that both lateral cutting regions are constituted by a series of equidistant recesses that substantially have a circular arc-like shape in plan view in which the concavity is directed towards the median axis, each recess having a sharp edge that covers the entire extent of the arc. This solution allows to increase the extension of the cutting edge and accordingly to increase the efficiency of the device as a whole with respect to the prior art. Furthermore, by virtue of the circular arc-like shape it is possible to cut from several relative positions without significantly reducing the effectiveness of the device. According to the invention, a method for producing blades for the above device includes the steps of: blanking a flat metal plate of substantially uniform thickness so as to form an elongated body with two series of equidistant recesses along the opposite lateral edges and at least one pair of slotted holes arranged along the longitudinal axis of the body; sharpening the recesses so as to form cutting edges which are suitable to interact with the cutting edges of an identical oppositely arranged blade; characterized in that the recesses have a circular arc-like shape and in that the sharpening operation is performed along the entire extension of the recesses by chip-forming machining, without using polluting abrasives and grinding wheels. This sharpening operation has the advantage of considerably reducing machining costs as well as the costs for the disposal of the machining by-products, which are non-polluting. In fact, the chips produced by machining can be recovered and remelted, positively affecting the economy of the process. Further characteristics and advantages will become apparent from the following detailed description of a preferred but not exclusive embodiment of the device and of the method according to the invention, illustrated only by way of non- limitative example in the accompanying drawings, wherein: Figure 1 is a top plan view of a device according to the invention; Figure 2 is an exploded perspective view of the device of Figure l, wherein some parts are not illustrated; Figure 3 is a sectional view taken along the plane III-III of Figure 1; Figure 4 is a perspective exploded view of the complete device of Figure 1; Figures 5 and 6 are sectional views respectively taken along the planes V-V and VI-VI of Figure 1. With reference to the above figures, the cutting device according to the invention, generally designated by the reference numeral 1, comprises a set of two perfectly identical interchangeable blades 2, 2' which are coupled and partially superimposed. Since the blades 2, 2' are identical, only the first one will be described hereinafter for the sake of brevity. The blade 2 is constituted by an elongated body, which is obtained for example from a flat metal plate of constant thickness, and has an approximately central longitudinal axis a which has an end portion 3 of constant width. The portion 3 has an enlarged head 4 with a central slot for coupling to a reciprocating actuation unit, for example of the eccentric type, which is not shown in the drawings and is of a per se known type. In the remaining part of the elongated body, the blade has, along its opposite sides, two lateral cutting regions which are constituted by two series of recesses which are designated by the reference numerals 5 and 6 respectively and have a constant longitudinal pitch p. According to the invention, the recesses have, in plan view, substantially the shape of a circular arc with a radius R and the concavity directed towards the median axis a. Each recess has a sharp edge 7, 8 that runs along the entire extension of the arc. Preferably, the angular extent of the arc is at least 180°, so as to surround on all sides a body to be cut. The recesses 5 arranged on one side of the plate-like body are offset by p/2 longitudinally with respect to the recesses 6 formed on the opposite side. Accordingly, the recesses 5 and 6 form, in the lateral edges of the body, the bottoms of two series of teeth 9 and 10 which have dull crests 11 and 12. The crests 11 are substantially straight and aligned, and the crests 12 protrude outward, approximately in a mushroom-like shape, with a substantially semicircular profile. The maximum distance H of the semicircular crests 12 from the central axis a is slightly greater than the distance K of the straight crests 11 from the same axis. Two or more elongated holes 13 are formed along the axis a and are meant for coupling to the other blade 2' . In particular, the blade 2 1 , to which the same reference numerals have been applied, with the addition of primes, to reference the corresponding parts of the blade 2, is rested on the twin blade 2 after rotating it through 180° about its own longitudinal axis a__, so as to arrange the crests 11' opposite the crests 12 and the crests 12' opposite the crests 11. In this manner, the sides of the crests 12, 12' that protrude inward can apply, during operation, an action that retains and pushes the material to be cut towards the cutting edges 8, 8' of the opposite recesses 6' , 6, ensuring high cutting efficiency. A guiding means is provided to retain the blades 2, 2' in a mutually facing position and in mutual contact with minimal clearance, so that the blades can slide and move in a reciprocating manner in opposite directions. This guiding means, which is of a per se known type, can be constituted by a pair of strips 14 and 15 made of rigid material which are arranged above and below the facing blades 2 , 2 ' and are mutually retained in a parallel arrangement by pins 16 which are constituted for example by screws 17 that pass through the elongated holes 13, 13' formed in the blades 2, 2 1 , with the interposition of bushes 18 made of antifriction material. Once the blades 2, 2' have been assembled as shown in the exploded view of Figure 2, the slots 4, 4 f are coupled to eccentrics or similar parts that move the blades in a reciprocating manner in opposite directions, as shown schematically by the arrows F, F', so as to cut the objects which become interposed between the lateral recesses. In order to produce a blade 2 it is necessary to form the elongated body by blanking, with a preformed blanking die, a flat metal plate of substantially uniform thickness. During blanking it is possible to form both the lateral recesses 5 and 6 and the slotted holes 13 arranged along the longitudinal axis a. According to the invention, the sharpening of the edges of the recesses, which is meant to form the cutting edges 7 and 8, is provided by chip-forming machining, without using polluting abrasives or grinding wheels. In particular, mechanical machining can be performed with angular or frustum-shaped milling cutters arranged coaxially in front of each recess. Furthermore, each blade can be sharpened by simultaneously machining multiple recesses, for example all the recesses of a single side, by virtue of multiple rotating milling cutters mounted on parallel axes, with considerable time saving and economy in equipment. The chips produced by milling and the coolant liquids can be easily collected and recycled, with a considerable economic and environmental benefit. In a variation of the above described method, the inclined cutting edges may be formed by using adapted separate blanking dies, instead of rotating milling cutters. The dies act during the blanking of the contour of the blade at a relative angle with respect to the plane of arrangement of the blade . The cost of sharpening, which in blades of the prior art could be approximately 50% of the total production cost, is reduced dramatically with this method, for example to approximately 10%, with an obvious effect on the final cost of the blade and therefore of the entire device. The device and the method according to the invention are susceptible of numerous modifications and variations; all the details may be replaced with technical equivalents suitable to achieve the intended aim and objects and are considered to be all equally protected. For example, the recesses and the crests of the blades may also have a shape that is slightly different from the one shown without thereby altering the resulting technical effect.

Claims: CLAIMS 1. Cutting device for gardening and horticulture, comprising: — two blades (2, 2') which are identical and arranged opposite each other, each blade being constituted by an elongated plate-like body which has a longitudinal axis (a, a 1 ) and two asymmetrical lateral cutting regions; — a guiding means (14, 15, 16) for keeping said blades (2, 2 ' ) partially superimposed and in mutual contact so that they can slide longitudinally; — a connection means (4) for coupling said blades to an external actuation means that is suitable to make said blades move in a reciprocating manner in opposite directions (F, F') on the mutual contact plane; characterized in that the cutting regions of each blade are constituted by a series of equidistant recesses (5, 6; 5 1 , 6 ' ) whose plan shape is essentially a circular arc with the concavity directed towards the median axis (a, a 1 ), each recess (5, 6; 5' , 6 • ) having a sharp edge (7, 8; 7 ' , 8 ' ) that covers the entire extension of said arc. 2. Device according to claim 1, characterized in that the angular extent of said arc is at least 180°. 3. Device according to claim 2, characterized in that the recesses (5, 6; 5 1 , 6 1 ) arranged on the opposite lateral regions of said plate-like body are mutually staggered by half a pitch in a longitudinal direction. 4. Device according to claim 3, characterized in that said recesses form, along said lateral cutting regions, two series of teeth with dull crests, the crests of a first series of teeth arranged on one side of the body being straight and parallel to said longitudinal axis, the crests of the second series of teeth arranged on the other side having protrusions which are shaped approximately like a mushroom with a semicircular profile. 5. Device according to claim 4, characterized in that the maximum distance of said semicircular crests from the longitudinal median axis is slightly greater than the distance of the straight crests from the same axis. 6. Device according to claim 1, characterized in that each blade has at least one pair of elongated holes along said axis. 7. Device according to claim 6, characterized in that said guiding means comprises two rigid strips (6, 7) which act on the outer faces of said facing blades and are mutually retained by pins that pass through said elongated holes of said blades and have a smaller diameter than said holes. 8. Method for producing blades for a cutting device comprising the steps of: — blanking a flat metal plate of substantially uniform thickness, so as to form an elongated body with two series of equidistant recesses along the opposite lateral edges and at least one pair of slotted holes arranged along a longitudinal axis; — sharpening the edges of said recesses so as to form cutting edges which are suitable to interact with the edges of another oppositely arranged identical blade; characterized in that said recesses are shaped like a circular arc and in that the sharpening operation is performed along the entire extension of said recesses by chip-forming machining without using polluting abrasives and grinders. 9. Method according to claim 8, characterized in that said mechanical machining is performed with angular or frustum- shaped milling cutters which are arranged coaxially in front of each recess. 10. Method according to claim 9, characterized in that the sharpening of each blade is performed by simultaneously machining multiple recesses by virtue of multiple rotating milling cutters mounted on parallel axes. 11. Method according to claim 8, characterized in that the inclined cutting edges of said circular arc-like recesses are formed during the initial blanking of the contour of the blade by adapted blanking dies that act at an angle with respect to the plane of said blade.

Inventors: ANZOLIN BRUNO, ANZOLIN, BRUNO
Applicants: ANZOLIN BRUNO, VALEX SPA, ANZOLIN, BRUNO, VALEX S.P.A.
Application year: 1995
Main classification: A01G3
IPC codes: A01G3