GB2352609A

GB2352609A - Insulated transmission and damping means for an electric hedge cutter.

Info

Publication number: GB2352609A
Application number: GB9926381A
Authority: GB
Inventors: Federico Velo
Original assignee: Valex Internat S A
Current assignee: Valex Internat S A
Priority date: 1999-07-30
Filing date: 1999-11-09
Publication date: 2001-02-07
Also published as: IT248120Y1; ITTV990038U1; FR2796805B3; FR2796805A3; GB9926381D0; ES1044636U; ES1044636Y; DE29922965U1

Abstract

A transmission assembly for an electric hedge cutter having two reciprocating blades 1, 2 being connected to cam members 3, 4. Rotary motion is provided to cams 3, 4 from an electric motor (not shown) by a pinion engaging a gear wheel 7. Gear wheel 7 having at least one circumferential cavity 71 which engages parts 71 of a body 8. Body 8 being made up of disks 81 and 82 and the gear wheel 7 being sandwiched between the two. Body 8 is made of an insulating material, hence blades 1, 2 are insulated from the motor. There are springs 10 also held within cavities 71 which act as damping means in case of momentary jamming of blades 1,2. In a second embodiment, body 8 may be made up of two disks 14, 15.

Description

2352609 MULTIFUNCTIONAL DEVICE FOR PROTECTING THE ACTION PARTICULARLY OF

PORTABLE ELECTRIC HEDGE-CUTTER EQUIPMENT AND OF THE CUTTER OPERATOR The present invention relates to a multifunctional device for protecting the action particularly of portable electric hedge-cutter equipment and of the cutter operator.

The invention, finds particular, even if not exclusive, application in the production of portable and electric equipment, aimed at trimming hedges.

Among the usual equipment for gardening, the hedge-cutter has a special importance. Created for easing the manual work of trimming and lopping, carried out traditionally by means of shears, the hedge-cutter is presently an indispensable, handy and very useful item of equipment. Said equipment, substantially, is made up of a protruding cutting bar supported by a casing, inside of which the relevant motor assembly is housed and which, being provided with a double hand grip, can be moved by the operator lapping the hedge to cut the shrubs exceeding the desired shape. The cutting element is substantially the bar which is made up of two superimposed blades, arranged to move mutually and longitudinally, which due to the interaction of their respective teeth, carry out the cutting operation.

Because of the understandable comfort, the use of electric hedge-cutter equipment, particularly with a mains supply, which substantially comprises a motor assembly having a shaft which by co-operation of eccentric components, exerts, as previously mentioned, a straight reciprocating motion to the cutting blades, has been widely spreading.

2 This equipment, especially when used under heavy working conditions, is very sensitive in certain situations, mainly in regard to the transmission assembly, because, as known, it may undergo considerable stresses which might damage it irreparably. These conditions, which cause sudden locking of the blades, are mainly due to the interception of net or of metal wire, usually use for the enclosure or support of plants. Among less usual effects, motor damage is possible, because of winding burnout.

From this it may be understood that the cost of the damage can be so considerable that replacing the equipment is the best solution.

the above described drawbacks, were easily solved, for instance by the German patent 2 340 888 (Black and Decker), which describes a friction system interposed between the blades and the motor assembly. This art allows, when the blades are in a locked condition, the motor shaft to be substantially independent, protecting the transmission assembly and also the motor.

Similar proposals, which differ in the friction system adopted, are also found in other German patents, among which 3 001 923 (Licentia), 3 310 639 (Schrock), 3 128 282 (Licentia), as well as 3 343 772 (Freund) may be mentioned as reference.

Nevertheless, the drawbacks of the known solutions, go beyond the previously considered aspects. More particularly, they might relate to the supply which, being of the mains voltage type, may cause a series of drawbacks, mainly injuries for the operator. Among these it may be mentioned that there is the possibility that the electric current may reach the cutting metal blades thereby compromising the operator's safety. This is not infrequent and may occur because of a short circuit in the motor, or because of faults inherent in the motor.

3 One solution to the considered problem, was offered by US 3 625 292 (Lay). It consisted in providing a trimming or hedge-cutting system, which included a trailer-mounted part, a transmission shaft, and an electric insulating element mounted on the transmission-shaft, the insulating element having at least two opposite sides which defined between them a cavity housing a blade mounted on the insulating element by spaced fixing means.

Also the same applicant considered the problem of insulation of the cutting blades. In particular, in European patent 0 702 514 (Valex), there is described a safety transmission device, particularly for electric hedge-cutters suitable for mounting on an electric hedge-cutter machine of the type comprising an electric motor arranged inside a casing and operationally fastened to a pair of cutting and superimposed blades which reciprocally move one with respect to the other for performing the cutting operation, and a friction device located between the motor and the blades, characterised in that the friction device has electric insulating means suitable for electrically insulating the motor from the blades.

Even if the above mentioned solutions brought some certainly reliable devices, they do not take into account some aspects which from the viewpoint of safety and comfort for the operator, are presently considerable. For instance, a typical fault concerns the sudden locking of blades, which apart from the friction that might or might not occur, may cause unbalancing of the operator, with possible consequences caused by loss of control of the equipment, which may result in impact with adjacent parts or the operator to fall.

4 Still another drawback, not solved by the previous solutions, concerns the cutting operation. The range of diameters of the shrubs to be cut, which unavoidably concerns the cutting bar along its length, causes an uneven distribution of cutting forces, such that some areas are more stressed than others. This circumstance causes a persisting vibration of the equipment, which on one hand tires the operator and makes his grip unsteady, and on the other stresses the transmission assembly excessively.

From these introductory considerations, it may be understood that finding 10 some means of protecting the equipment and optimising its functioning is certainly important.

The purpose of the present invention is to obviate the above-mentioned drawbacks.

SUMMARY OF THE INVENTION

This and other purposes, are achieved by the present invention according to the features in the accompanying claims, solving the mentioned problems mentioned by means of a multifunctional device for protecting the action particularly of portable electric hedge-cutter equipment and of the cutter-operator, of the type including an electric motor, for moving by a transmission assembly, the cutting blades, each movable with respect to the other, being jointed at their ends to eccentric means which, making up a motion conversion device, co-operate with said transmission assembly, said blades being electrically insulated from the motor, and in which is provided:

- a gear wheel in mesh with a pinion, said gear wheel being provided with at least one circumferential cavity:

- at least one body, also insulating and disassembable, associated with the gear wheel, which has a corresponding protrusion engaged in the or a respective circumferential cavity; - damping means, inserted in and in contact with one end of the circumferential cavity, stressed on the other side by the protrusion of the insulating body; and a disk with projecting insertions for the closure, or partial closure of the, or the respective, circumferential cavity.

According to a further aspect, the present invention consists in a portable electric hedge-cutter including a multifunctional device as now provided.

ADVANTAGES In such a way, many advantages are obtained.

A first advantage consists in preserving the optimal functioning of the equipment, reducing wear of the motor shaft and transmission elements.

Another advantage is that in the equipment now provided, vibrations caused by the cutting action are considerably reduced in their intensity, substantially ensuring better safety for the operator when he handles the equipment and at the same time reducing his fatigue.

Further advantages are found in the insulation optimization and in general 25 in the transmission assembly safety function, which includes the operator's safety in the improvement.

Finally, from the structural viewpoint, the equipment is less complex and expensive, and furthermore it may be reduced in weight and dimension, 6 easing the production process at industrial level with a good qualitypriced ratio.

These and other advantages will appear from the following detailed description of some preferred solutions of an embodiment of the invention, with reference to the accompanying schematic drawings, the details of which are not to be considered as limiting, but only as examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an exploded view of a first assembly for the transmission of reciprocating motion to the cutting blades of equipment particularly for an electric hedge-cutter; Figure 2 shows, also exploded, a variation of the assembly as shown in Figure 1 for the transmission of reciprocating motion to the cutting blades; Figure 3 shows a cross-sectional view of the transmission assembly of Figure 1, taken along the axis A-A of Figure 4, and Figure 4 is a plan view of the reciprocating motion transmission assembly of Figures 1 and 3.

DESCRIPTION OF THE EMBODIMENT

Referring to the drawings, it may be seen that equipment, particularly of the electric hedge-cutting machine type, is made up of a casing (not shown), generally formed in a plastics material, provided with two 7 handles, near one of which control means are provided. Inside the body, an electric motor, presenting a downwardly directed pinion, is provided.

The pinion functions to transfer the rotary motion of the motor to an adjacent transmission assembly, on which a motion conversion and cut device depends downstream, causing a pair of blades (1, 2), to have a reciprocating straight motion. Said blades (1, 2), as parts of a cutting device, are superimposed, and both are positioned to protrude from the body, while being retained at one end to said motion transmission and conversion assembly. More particularly, on one side, both blades have ends, suitably shaped, which co-operate with eccentric means(3, 4) held together by suitable end plates(5, 6) by engagement of through screws (12) to make up the motion conversion and cut device.

Associated with the motion conversion and cut device is an overhanging transmission assembly comprising a gear wheel (7), provided, circumferentially, with three through cavities (71) in its flat faces; alternatively said cavities (71) may be of a blind type. In one of the two proposals, solution (A), there is connected to the gear wheel (7) an insulating body (8), Figure 1, provided with a central hole, substantially monolithically made up of two disks (81, 82) joined by a connecting neck, perimetrally of which as many ribs (83) as cavities (71) are provided on the gear wheel (7). The insulating body (8) surrounds integrally a bushing (9) and encloses the gear wheel (7), so that the latter is partially housed inside the insulating body (8), ribs (83) passing through the cavities (71). Each of said ribs (83) occupies only a part of the corresponding cavity (71), while the remaining space in the cavity serves to contain an elastic element (10), such as a helical spring or even an elastic buffer, which bears at one end on the rib (83) and at the other end on the adjacent end of the cavity (71). The stiffness of said buffers is 8 calculated so that they are only partially compressed in the usual functioning of the machine. With the purpose of closing the cavities (71) in the gear wheel (7), so that the elastic means (10) do not come out, it will be seen that the upper disk (81) of the insulating body (8) is superimposed on the upper flat face of the gear wheel and the lower face of the gear wheel is in contact with the lower disk (82), which has as many through cavities (821) as the gear wheel to allow for the insertion of the elastic means (10) into the cavities (71) of the gear wheel. The cavities (821) in the lower disk (82) of the insulating body are in turn closed by means of inserts (11), which co-operate with said cavities (821) in the disk (82).

Locking of the transmission assembly-motion conversion and cut device group, is provided by said bushing (9) which is located axially of the insulating body (8), having at its underside a stem (91) which, by a jointing pivot (13), acts as a stacking axis for the motion conversion and cut device.

The thus constructed group makes the insulating body (8), the bushing (9), the ring (11), the screws (12), and the elements of the motion conversion and cut device rigidly integral. The whole group rotates around the pivot (13), and has a reciprocating motion of limited rotation with respect to the gear wheel (7).

When the equipment is started and during the normal work conditions, the motor drive pinion transmits motion to the gear wheel (7), with which it is directly in mesh, which undergoes small relative rotations with respect to the insulating body (8), resulting from the balance between the resistance exerted by the cutting device and the reaction of the elastic elements (10). In case of locking of the cutting elements, the gear 9 wheel (7) undergoes a further rotation, or extra-rotation, relative to the insulating body (89) which is also locked.

In a variation (B), as shown in Figure 2, to the described solution (A), the insulating body (8) and the ring (11) are replaced by only two diskshaped parts (14) and (15) which are respectively superimposed on the two flat faces of the gear wheel (7) so that the gear wheel is sandwiched between the two parts. A first, upper, disk (14), made of electrically non-conductive material, in this example, which fits on the upper face of the gear wheel (7), has a hole (140) of a polygon-like shape inside which the bushing (9) is inserted. An upper face of the upper disk (14) is flat, while a lower one is formed with a neck (141) of a diameter enabling it to be inserted into the hole (72) of the gear wheel (7), which is similar to that previously described. On the same side as the neck (141), and perimetrally, the disk (14) has perpendicular ribs (142), equal in number to the number of cavities (71) in the gear wheel (7). The ribs (142) locate in the corresponding cavities (71), partially occupying the space therein, while the remaining part of the spaces in the cavities house the elastic elements (10). 20 The opposite, lower, face of the gear wheel (7) receives the second, lower, disk (15), which is substantially planar with a central hole (151) having a counter-shaped polygon-like edge complementary to the external lateral surface of the bushing (9). In this case, if the bushing (9) is not made of insulating material, the upper disk (14) must necessarily be of insulating material. One variation to the interaction between the lower disk (15) and the bushing(9), consists in providing a body with a single central hole having greater dimensions than external lateral section of the bushing (9). In this arrangement, said body is not tied to rotation with the upper disk (14) and the bushing (9), but is simply pressed against the gear wheel (7) by the lower elements of the cutting assembly stacked by the screw (12). If the blades should become locked, the body might or might not slip relative to the gear wheel according to the friction/inertia conditions.

Some variations to the solutions described, may concern the positions of the cavities (10) housing the elastic elements. For instance, the cavities, instead of being in the gear wheel (7), may be provided at the insulating body (8), either on one or on both of the body parts (14, 15), that is on the surfaces facing one or both of the gear wheel faces, which according to the arrangement would be provided, as necessary, with suitable protruding teeth.

Claims

1. Multifunctional device for protecting the action particularly of portable electric hedge-cutter equipment and of the cutter operator, of the type comprising an electric motor, for moving by means of a transmission assembly comprising a gear wheel in mesh with a pinion, cutting blades, each movable with respect to the other, being jointed at their ends to means which, providing a motion conversion device, co-operate with said transmission assembly, said blades being electrically insulated from the motor, wherein a body connected to the cutting blades is relatively integrally jointed to the gear wheel by dragging means associated with at least one of facing faces of the body and gear wheel, said means comprising at least one damping means.

2. Multifunctional device according to claim 1 wherein in the usual functioning of the device said dragging means is driven by at least one seat provided on the gear wheel without an end of stroke condition.

3. Multifunctional device according to claim 1 or claim 2 wherein the gear wheel is provided with at least one cavity, the body associated with the gear wheel has on a side thereof a projection inserted in the, or the respective, cavity, and the damping means(10) is inserted in one end of the or each cavity and is in contact with, so as to be stressed by, the projection of the body.

4. Multifunctional device according to claim 3 wherein the gear wheel is provided with said cavity or cavities at at least one of its flat faces.

5. Multifunctional device according to claim 3 or claim 4 wherein the damping means in the or each cavity is made up of elastic means.

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6. Multifunctional device according to any preceding claim wherein the body electrically insulates the blades from the motor.

7. Multifunctional device according to any preceding claim wherein the gear wheel is a monolithic insulating body centrally holed and made up of two disks jointed by a neck and perimetrally of which at least one rib is provided.

8. Multifunctional device according to claim 3, or any of claims 4 to 7 as dependent from claim 3, wherein the body provides electrical insulation, surrounds integrally a bushing (9) and encloses the gear wheel (7) which is thereby at least partially housed in the insulating body (8), with the or each projection in the, or the respective, cavity.

9. Multifunctional device according to any of claims 3 to 5 and 8, or claim 6 or 7 as dependent from claim 3, wherein the or each projection occupies only part of the, or the respective, cavity while the remaining space of the cavity contains an elastic element of the damping means.

10. Multifunctional device according to claim 8 as dependent from claim 5, or claim 6 as dependent from claim 8, wherein an upper face of the gear wheel has an upper part of the body superimposed thereon and the lower face of the gear wheel is associated with a lower part of the body which provides as many through cavities as are in the gear wheel to allow the insertion of the elastic means into the or each cavity of the gear wheel.

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11. Multifunctional device according to claim 10 wherein the or each cavity of the lower part of the body is closed by a ring having a raised insert registering with the or each cavity.

12. Multifunctional device according to claim 8, claim 9 as dependent from claim 8, or either of claims 10 and 11, wherein locking of the transmission assembly, motor conversion and cutting group of components is provided by the bushing which is housed coaxially in the insulating body and has a stem which, by means of a jointing pivot, acts as a stacking axis.

13. Multifunctional device according to claim 12 as dependent from claim 11 wherein the thus locked group makes the insulating body, the bushing, the ring and the elements of the motion conversion and cut device rigidly integral.

14. Multifunctional device according to any of claims 1 to 6 wherein the body is relatively integrally jointed to the gear wheel(7) and comprises two parts respectively superimposed on the opposed flat faces of the gear wheel.

15. Multifunctional device according to claim 14 wherein at least one of the two body parts or the bushing is insulating, and one of said body parts has a neck which is inserted in a hole of the gear wheel (7) and has, perimetrally, one or more perpendicular ribs projecting from the face facing the gear wheel.

16. Multifunctional device according to claim 14 or claim 15 wherein one of the body parts provides a counter-shaped hole (140) in which a bushing is housed.

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17. Multifunctional device according to any one of claims 1 to 6 and 14 to 16 wherein the gear wheel has associated with one face a disk which is substantially flat, with a central hole (151).

18. Multifunctional device according to claim 17 wherein the disk is of insulating material.

19. Multifunctional device according to claim 5, or any of claims 6 to 9 and 11 to 18 as dependent from claim 5, or claims 10 to 13, wherein the elastic means in the or each cavity comprises a helical spring or elastic buffer which acts on and between an end of the or the respective cavity, and the projection in the, or the respective, cavity.

20. Multifunctional device according to claim 15, or any of claims 6 to 9 or 14 to 18 as dependent from claim 5, or claims 10 to 13 or 19, wherein the stiffness of said elastic means is calculated so that the means is only partially compressed in the usual functioning of the device.

21. Multifunctional device according to any preceding claim wherein the gear wheel (7) is circumferenti ally provided with through cavities opening through its opposite faces.

22. Multifunctional device according to claim 1 or claim 2 wherein the body has cavities in which are housed elastic elements of the damping means.

23 Multifunctional device wherein the cavities housing the elastic elements are provided on the body in association with one or each of the opposite faces of the gear wheel which is provided with protruding teeth engaged in the cavities.

24. Multifunctional device according to claim 22 or claim 23 wherein 5 the body provides electrical insulation.

25. Multifunctional device according to any of claims 3 to 5, 8 to 13, or 6, 7 or 14 to 20 as dependent from claim 3, wherein the cavities are at at least one of the two opposite faces of the gear wheel and are blind.

26. Multifunctional device according to any of claims 1 to 5 wherein the bushing and a ring are provided of an insulating material and the body is made of conductive material.

27. Multifunctional device according to claim 12 or claim 13 wherein the bushing and the jointing pivot make up a single group housed in a casing having end bearings for the pivot.

28. Multifunctional device for protecting the action particularly of portable electric hedge-cutter equipment and of the cutter operator, substantially as described herein with reference to Figures 1, 3 and 4 of the accompanying drawings.

29. Multifunctional device for protecting the action particularly of portable electric hedge cutter equipment and the cutter operator, substantially as described herein with reference to Figure 2 of the accompanying drawings.

30. A portable electric hedge-cutter including a multifinctional device according to any preceding claim.