FR2810196A1 - Portable rotary cutting machine comprises tubular body with rotary motor driving rotary blade and torque limiter between motor and blade - Google Patents

Abstract

The rotary cutting machine, called a bush cutter, comprises a tubular body (1) provided with a rotary motor (2) which drives a rigid rotary blade (3). Between the rotary motor and the cutting blade is a torque limiter (4). The torque limiter has a percussive effect which is produced in a plane parallel to the cutting blade plane of rotation.

Description

The present invention relates to a portable rotary cutter machine called a brush cutter of the type comprising a tubular body or rod provided with a rotary motor element for driving a rigid rotary cutter member of the blade or disc type, as well that a torque limiter equipping in particular such a machine.

Brushcutters of the aforementioned type are particularly dangerous when they are fitted with rigid cutting members such as blade, disc or the like. In fact, when the torque transmitted by the driving element of the brush cutter to the cutting member becomes less than the resistant torque applied to the cutting member, in particular when encountering an obstacle, such as a stone, an immediate violent reaction occurs from the entire brushcutter. This reaction can, if the operator is not wary, injure last. This reaction can result in uncontrolled and brutal movements of the brushcutter, by the breakage of the cutting member or by the breakage of all or part of the motor element incapable of reacting to a sudden stop the rotation of the member cutting. object of the present invention is to provide a portable rotary cutting machine whose design protects the user from jolts and dangerous behavior of the brushcutter when the cutting member encounters an obstacle.

Another object of the present invention is to propose a brush cutter whose design makes it possible to protect the motor element, including motor and transmission member, against any deterioration, including in the case of a sudden stop of the rotation of the member. cutting when the latter encounters an obstacle.

Another object of the present invention is to provide a brushcutter whose design allows - the user to measure the effort he exerts on the brushcutter and 'thus optimize the operation of the latter so as to limit the stress on the material.

for this purpose, the subject of the invention is a portable rotary cutter machine called a brush cutter of the type comprising a tubular body or rod provided with a rotary motor element for driving a rigid rotary cutter member of the blade type. or disc, characterized in that the rigid cutting member is detachable at least temporarily, in rotation of the driving element when the resistive torque applied to the cutting member is greater than the torque transmitted by the driving element to the cutting member so that the motor element continues to be rotated while the cutting member is immobilized by an obstacle or any resistance.

According to a preferred embodiment of the invention, this machine comprises, interposed between the rotary motor element and the rigid cutting member, a torque limiter separating, at least temporarily, in rotation the motor element and the member cutting when the resistive torque applied to the cutting member is greater than the torque transmitted by the motor element to the cutting member. The invention also relates to a torque limiter characterized in that it is arranged to be interposed between the rotary motor element and the rigid rotary cutter type blade or disc of a rotary cutting machine ce torque limiter separating, at least temporarily, in rotation the driving element and the cutting member when the resistive torque applied to the cutting member exceeds the torque transmitted by the driving element to the cutting member.

Thanks to the design of this brushcutter, repetition of the shocks of the cutting member on the obstacle is avoided thanks to the separation in rotation of the cutting member and the motor element. Likewise, protection of the motor element is ensured since the latter can continue to operate normally, including in the event of a sudden stop driving the rotation of the cutting member.

The invention will be clearly understood on reading the following description of exemplary embodiments, with reference to the accompanying drawings in which FIG. 1 represents a partial schematic view of a brushcutter according to the invention in the exploded state of the constituent elements brushcutter; 2 shows a partial schematic view of brush cutter according to the invention in the assembled state of the elements; FIG. 3 represents a partial schematic view of a brushcutter according to the invention in the unassembled state of the elements constituting it, the motor element being of the male outlet type; FIG. 4 represents a partial schematic view in a partially assembled state of the elements constituting it, the motor element being of the female outlet type; 5 shows a partial top view of the part of the torque limiter integral with the cutting member and Figure 6 shows schematically the movement of a ball of the torque limiter of Figure 5 between two successive housings.

The portable rotary cutting machine, called a brush cutter, object of the invention, comprises in itself known a tubular body or rod 1 provided (e) with an element 2 rotary drive motor 'a cutting member 3.

Rod 1 can have a large number of shapes. It is generally provided in the vicinity one of its ends (not shown), a handlebar or a handle to facilitate its gripping by the operator. The element 2 rotary motor for driving the cutting member 3 generally consists of a thermal or electric motor equipped with a flexible or rigid transmission shaft connecting said motor to the cutting member 3 fixed in exit of said tree. Examples of the design of this drive shaft have been shown in the figures. examples are however in no way limiting. The output of such a rotary shaft can be of the male type, as shown in FIG. 3, or of the female type, as shown in FIG. 4. In some cases, the rod 1 is further extended by a brushcutter head 11 . As shown in Figures 1 and 2, this head 11 substantially affects the shape of a bell defining a housing inside which can be accommodated a number of elements. The cutting member 3 in this case extends outside of said brushcutter head. This rotary cutting member 3 is a rigid member which may consist of one or more blades, or of a blade with n branches, or of discs, or alternatively of rotary plates of any shape. The general design of such a brushcutter will not be described in more detail because it is well known to those versed in this art.

Characteristically to the invention, the rigid cutting member 3 can be detached, at least temporarily, in rotation from the motor element 2 when the resistive torque applied to the cutting member 3 is greater than the torque transmitted by the element 2 motor to the cutting member 3. Thus, the motor element 2 continues to be driven in rotation while the cutting member 3 is immobilized by an obstacle or any resistance. Obviously during this rotational attachment of the cutting member 3 and the motor element 2, the cutting member 3 remains mechanically coupled by an axial connection to the motor element 2. Conversely, as soon as the resistive torque applied to the cutting member 3 becomes less than the torque transmitted by the motor element 2 to the cutting member 3, the cutting member 3 is again secured in rotation l 'element 2 engine.

In a particular embodiment of the invention, this securing in rotation of the member 3 for cutting the motor element is obtained by means of a torque limiter (4) interposed between the element 2 of the rotary motor and the rigid cutting member 3.

In the exemplary embodiments shown, this torque limiter 4 consists of an axial assembly of two parts 4A, 4B in the general form of a hub, one of which 4A is said to be integral in rotation with the motor element 2, the other 4B said driven carrying the rigid cutting member 3. Said parts 4A, 4B, thus permanently coupled via the axial assembly, are separable in rotation beyond a predetermined torque value so that the driving part 4A can continue to be driven in rotation while that the driven part 4B is immobilized by an obstacle or a resistance on the cutting member 3.

The operating principle of a torque limiter is as follows. When the cutting member 3 encounters an obstacle which becomes in opposition to its rotation, the cutting member 3 is immobilized, while the driving part 4A of the torque limiter 4 continues to be driven in rotation. When the resistive torque applied to the cutting member becomes lower than the torque transmitted by the motor element 2 the cutting member 3, the cutting member 3 is' again driven in rotation by the driving element 2. This is called resetting the torque limiter 4.

In the examples shown, at least one 4A of parts 4B of the torque limiter 4 comprises channels 6 arranged coaxially with its axis of rotation. These channels 6 house compression springs 7 and balls 8 projecting from the distal face of the hub. The other part 4B of the torque limiter forming a ball cage has a cage bottom provided on a circumference with a series of housings 9, shown as conical, capable of partially receiving the projecting part of the balls 8 carried by the other part 4A . The balls 8 are erased in the channels 6 during an untimely immobilization of any part 4A, 4B of the torque limiter 4 to allow relative angular movement of the parts 4A, 4B between them, separable in rotation beyond of a predetermined torque value.

In other words, when the cutting member 3, mounted on the brush cutter, encounters an obstacle which puts it in opposition to its rotation, a blocking of the part 4B of the torque limiter 4 is observed. The pressure of the spring 7 n 'then being more sufficient to maintain the balls 8 in the housings 9 of the part 4B and thus ensure the rotational drive of the part 4B. The balls 8, pushed back into the channels 6, are driven in displacement with the part 4A on a rolling track 10 formed on the part 4B of the torque limiter 4 until they are housed in a new housing of the part 4B. This positioning of the balls 8 in the housings is only possible when the cutting member 3 is released and the pressure of the springs then compressed is sufficient to push the balls 8 back into their housings 9 and keep them there. The two parts 4A, 4B of the torque limiter 4 are then again joined in rotation to ensure the drive by rotation of the cutting member 3.

In the examples shown, the part 4B forming a ball cage of the torque limiter 4 has the general shape of a barrel. This part 4B overlaps part 4A of the torque limiter 4. Part 4A can affect a large number of shapes depending on the configuration of the output of the motor element 2.

In the examples shown in Figures 1 and 2, the rod 1 of the brush cutter is shaped at one of its ends to form a head 11 of brush cutter. This head 11 provides a housing inside which is arranged the torque limiter 4. The housing of the brushcutter head 11 is closed by a plate 12 through which projects at least part of the torque limiter 4, in particular at least part of the part 4B of the torque limiter 4, to receive the member 3 of rigid cutting. The entire torque limiter is kept inside its housing by means of sliding bearings such as ball bearings cooperating with the plate and / or the head 11. The part 4A is in turn provided with a pinion 16 engaging with a pinion 17 disposed at the end of the motor element 2 so as to drive the rotation of the part 4A of the torque limiter 4 and, consequently, the rotation of the Exhibit 4B.

In the examples shown in Figures 3 and 4, the part 4A has a tapped hollow hub to allow the screw limiter to be fixed by the part 4A of the torque limiter at the output of the motor element 2. In the case of the example shown, the element 2 rotary drive motor the cutting member 3 is in this case a rotary shaft of the type provided, at or near its end, with a shoulder 14 standard for a range of shaft diameters. The torque limiter 4, and in particular, the part 4A of the torque limiter 4, is coupled to the shaft 2 by means of a device mainly consisting of an adapter ring 13 provided on the one hand, on at least one of its front faces, of a countersink 13A, 13B dimensioned to cover by abutment the standard shoulder 14 of the rotary shaft 2 and be kept in non-sliding bearing contact under the effect of a axial compression force, on the other hand means 15 ′ coupling to one 4A of the parts 4A, 4B of the torque limiter 4 in order to secure in rotation one, 4A of the parts 4B of the torque limiter 4, ring 13 and shaft 2. In the examples shown, these fixing means 15 are constituted by a thread of the ring 13.

This part 4A of the torque limiter is further arranged to receive a shouldered screw 5, this part allowing the axial assembly of part 4A of the torque limiter 4 with part 4B of the torque limiter 4. This part 5 crosses the part 4A of the limiter, engages with a tapping of the part 4B of the torque limiter and makes' llie beyond this last part to allow fixing by screwing of the cutting member 3, in particular by means of a nut on the end of the screw, as shown in Figures 3 and 4. In this particular case the cutting member 3 and at least one, namely the part 4B, of the torque limiter 4 are coupled via at least one member 5 serving for the axial assembly of the parts 4A, 4B of the torque limiter 4 therebetween.

Due to the particular design of the torque limiter 4 described above, the latter has a percussion effect. This percussion effect is preferably established in a plane parallel to the plane of rotation of the cutting member 3. This percussion effect is linked on the one hand to the presence of the balls 8, on the other hand to the presence of the housings 9. The number of housings 9 of the ball cage is at least a multiple of the number of channels 6 of l other room 4A. In the examples shown, there are eight housings and four balls. The housings 9 of the part 4B forming a ball cage of the torque limiter 4 are substantially contiguous in order to obtain, when a predetermined torque value is exceeded, a percussion effect in the plane of rotation of the hub 4B member carrier cutting 3 when the hub 4B cutting member holder is immobilized by an obstacle or a resistance while the motor hub 4A continues to be driven. The operator can indeed hear a regular tac tac corresponding to the cut made at each attack of an element to be cut, such as wood, by the cutting member 3. In fact, at each cut, the resistive torque on the cutting member 3 becomes greater than the tripping torque of the torque limiter, but the inertia of the system and the operator's control automatically allow resetting. The system again acquires motor energy and works again. Conversely, if the user insists on increasing the cutting speed, the cutting member 3 locks against the element to be cut. The part 4B of the torque limiter 4 is immobilized and the part 4A of the torque limiter continues to rotate. The torque limiter 4 is then in a fully disengaged state. The torque limiter 4 returns to its normal operating cycle in which the parts 4A and 4B are integral in rotation as soon as the user maneuvers so that the resistance force of the cutting member on the element to be cut is lower. at the torque limiter tripping torque 4.

The torque limiter can therefore operate alternately according to two operating modes. In the first, the torque limiter functions like a conventional torque limiter in which, as soon as the triggering occurs, no more energy is transmitted to the part 4B secured to the cutting member 3. In the second operating mode, the torque limiter successively disengages and then strikes by resetting. In this second mode, the user perfectly masters his gesture and cuts it thanks to this alternation of disengages and percussions. In this second mode of operation, the ball alternately passes from a housing 9 to another housing 9 by traversing a raceway 10 formed between said housings. In this case, the ball comes out of its conical housing 9 from the part 4B of the torque limiter 4, moves along the raceway 10, then strikes the edges of a new housing 9 before again emerging from its housing 9 to move again along the rolling path 10 until the user has perfectly mastered his gesture. Conversely, in the first mode of operation, the ball meets its housing but does not stop there.

To accentuate this impact effect, the housings 9 of the part 4B forming a ball cage of the torque limiter 4 are connected together by an inclined rolling track 10 to cause an accelerated movement of the ball between two housings 9 successively occupied by the ball 8. The housings 9 have a high point corresponding to the side on which the ball projects from its housing and a low point corresponding to the point of entry of the ball into housing. The movement of the ball and the raceway are shown schematically in the figure. Such a percussion torque limiter allows the operator to optimize the use of the brushcutter and, consequently, to limit the mechanical stresses of the latter as much as possible.

As the embodiments above have shown, the torque limiter can be installed as an original equipment on a brush cutter. In this case, it will preferably be incorporated in the head of the brushcutter. However, for existing brushcutters on the market, the torque limiter can be incorporated into the cutting member 3 and will be arranged so that it can be secured at the output of the driving element of an existing brushcutter. Thus, the existing fleet of brushcutters may, in the same way as a new fleet of brushcutters, be fitted with a torque limiter in order to allow the user to work in optimal safety conditions.

Claims (4)

1. Portable rotary cutting machine known as a brush cutter of the type comprising a tubular body or rod (1) provided with an element (2) rotary motor for driving a rigid rotary cutting member (3) of the blade or disc, characterized in that the rigid cutting member (3) can be detached, at least temporarily, in rotation from the motor element (2) when the resistive torque applied to the cutting member (3) is greater than the torque transmitted by the motor element (2) to the cutting element (3) so that the motor element (2) continues to be driven in rotation while the cutting element (3) is immobilized by any obstacle or resistance. 2. Machine according to claim 1, characterized in that it comprises, interposed between the element (2) rotary motor and the member (3) of rigid cutting, a torque limiter (4) separating, at least temporarily, by rotation of the motor element (2) and the cutting element (3) when the resistive torque applied to the cutting element (3) is greater than the torque transmitted by the motor element (2) to the element (3 ) cutting. 3. Machine according to claim 2, characterized in that the torque limiter (4) disposed between element (2) rotary motor and cutting member (3) has a percussion effect, this percussion effect preferably being established in a plane parallel to the plane of rotation of the cutting member (3). 4. Machine according to one of claims 2 and 3, characterized in that the torque limiter (4) consists of an axial assembly of two parts (4A, 4B) in the general form of hub, one (4A ) said driving integral in rotation with the motor element (2), the other (4B) said driven carrying the rigid cutting member (3), said parts (4A, 4B) being separable in rotation beyond a predetermined torque value so that the driving part (4A) can continue to be driven in rotation while the driven part (4B) is immobilized by an obstacle or resistance on the cutting member (3). . Machine according to claim 4, characterized in that the cutting member (3) and at least one (4B) of the parts (4A, 4B) of the torque limiter (4) are coupled via at least a member (5) for the axial assembly of the parts (4A, of the torque imager (4) therebetween. Machine according to one of claims 4 and 5, characterized in that at least one (4A ) parts (4A, of the torque limiter (4) comprises channels (6) arranged coaxially with its axis of rotation, these channels (6) housing compression springs (7) and balls (8) projecting from the face distal from the hub, the other part (4B) of the torque limiter forming a ball cage having a cage bottom provided on a circumference with a series of housings (9) capable of partially receiving the projecting part of the balls (8) carried by the other part (4A), the balls (8) disappearing in the channels (6) during an untimely immobilization of any of the parts 4A, 4B) of the torque limiter (4) to allow relative angular movement of the parts (4A, 4B) between separable in rotation beyond a predetermined torque value. . Machine according to claim 6, characterized in that the part (4B) forming a cage for the torque limiter (4) overlaps the 'other part (4A) of the limiter (4). 8. Machine according to one of claims 6 and 7, characterized in that the number of housings (9) of the ball cage is at least a multiple of the number of channels (6) of the other part (4A). . Machine according to one of claims 6 to 8, characterized in that the housings (9) of the part (4B) forming a ball cage of the torque limiter (4) are substantially contiguous so as to obtain, when passing 'a predetermined torque value, a percussion effect in the plane of rotation of the hub 4B) cutting member holder (3) when the hub (4B) cutting member holder is immobilized by an obstacle or a resistance while the driving hub (4A) continues to be trained. . Machine according to one of Claims 6 to 9, characterized in that the housings (9) of the part (4B) forming the ball cage of the torque limiter (4) are interconnected by an inclined rolling path (10) for cause an accelerated movement of the ball between two housings (9) successively occupied by the bil (8). . Machine according to one of claims 2 to, characterized in that the brushcutter cane (1) shaped at one of its ends to form a brushcutter head (11), this head (11) providing a housing for the 'inside which is arranged the torque limiter (4). 12. Machine according to claim 11, characterized in that the housing of the brushcutter head (11) is closed by a plate (12 through which protrudes at least part of the torque limiter (4) to receive the member (3) rigid cutting machine according to one of claims 2 to characterized in that the element (2) rotary motor 'drive of the member (3) cutting a rotary shaft of the type provided, at or at near its end, a standard shoulder (14) for a range of shaft diameters, the torque limiter (4) being coupled to said shaft (2) by means of a device mainly consisting of a ring ( 13) of adaptation provided on the one hand, on at least one of its front faces, with a countersink (13A, 13B) dimensioned to cover by abutment the standard shoulder (14) of the shaft (2) rotating and be maintained in non-sliding bearing contact under the effect of an axial compression force, aut re part of means (15) for coupling to one (4A) of the parts (4A, 4B) of the torque limiter (4) for securing in rotation one (of the parts (4A, 4B) of the torque limiter (4), ring (13) and shaft (2). 14. Torque limiter (4), characterized in that it is arranged to be interposed between the element (2) rotary motor and the member (3) of rigid rotary cutting of the blade or disc type of a portable rotary cutting machine, this torque limiter (4) separating, at least temporarily, in rotation the motor element (2) and the cutting member (3) when the resistive torque applied to the member (3) of cutting is greater than the torque transmitted by the motor element (2) to the cutting member (3).