WO2023042190A1

WO2023042190A1 - Hydraulically actuated friction clutch for operating machines

Info

Publication number: WO2023042190A1
Application number: PCT/IB2022/062608
Authority: WO
Inventors: Antonio POTIGNANO
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-03-09
Filing date: 2022-12-21
Publication date: 2023-03-23
Anticipated expiration: 2024-09-09
Also published as: IT202200004544A1

Abstract

Operating machine guided by means of a handlebar and equipped with a friction clutch actuated by means of a hydraulic actuator controlled by a clutch control lever which operates a first and a second valve, both connecting a pressure chamber of said hydraulic actuator to a drain, in such a way that the first valve is closed and the second valve is open when the clutch control lever is released, and vice versa when the clutch control lever is actuated. A safety lever controls a device apt to block said second valve in closed position when the clutch control lever is released, thereby enabling to govern the friction clutch through said clutch control lever. Said clutch control lever and said safety lever being associated with one grip of the handlebar so as to be operated together using a single hand.

Description

HYDRAULICALLY ACTUATED FRICTION CLUTCH FOR OPERATING MACHINES

TECHNICAL FIELD

The present invention relates to a self-propelled operating machine, mobile on tracks or wheels or tools, which can be hand-guided by a walking operator by means of a handlebar, and more particularly to a machine of this type provided of a hydraulically actuated friction clutch with improved controls.

BACKGROUND ART

Operating machines of the type to which the present invention relates mostly comprise a driving engine, a clutch device, a transmission for transferring the driving power of the engine to a tool and/or to an axle, provided with driving wheels, and/or to a power take-off, and a motorcycle style handlebar provided with the controls needed for the various actuations.

This type of machine includes two-wheel tractors, motor hoes, motor mowers, flail mowers, wheeled brush-cutters, motorized wheelbarrows, reversible machines provided with a rotatable handlebar that can be turned 180° in a horizontal plane, so that the machine can alternately operate, for example, as a motocultivator or as a motor mower, and any other of such operating machines that are hand-guided by means of a handlebar.

For safety reasons, current regulations impose that the machine must stop within a short lapse of time if the user abandons, for whatever reasons, the handlebar.

Various solutions have been proposed to comply with the requirements of regulations. For example, the document EP2100491B1 discloses an agricultural machine equipped with a hydraulically actuated clutch wherein the hydraulic clutch actuator is controlled through a first "safety" lever and a second "clutch" lever (both levers being placed on the handlebar in correspondence of one grip so that they can be operated together using a single hand), which are operatively associated with each other in such a manner that, to go ahead and move the machine, the user must first actuate the "clutch" lever, then the "safety" lever while keeping the "clutch" lever actuated.

The adoption of two control levers enhances the practicality of use and the acting sensitivity while working, however the user actuates the "clutch" lever with fingers of his/her left hand and the "safety" lever with the palm and thumb of the same hand; therefore, to move the machine, he/she must actuate the "safety" lever with the thumb of the left hand while keeping the "clutch" lever actuated with fingers of the same hand. This procedure involves counter-intuitive steps; besides, it is cumbersome, especially for users with small hands, and prevents from reducing the force the user must apply on the "safety" lever by increasing the travel of the lever. Accordingly, there is demand for an operating machine provided of a hydraulically actuated friction clutch with improved controls that avoid the previously mentioned shortcomings.

SUMMARY OF INVENTION

Aim of the present invention is to provide a self-propelled operating machine equipped with a hydraulically actuated friction clutch, for coupling a drive shaft of an engine to an input shaft of a transmission, characterized by an ideal arrangement of controls and an ideal logic of operation thereof.

Therefore, according to one aspect, the present invention discloses an operation method of an operating machine, hand-guided by means of a handlebar provided with grips, where a friction clutch is governed through a first clutch lever, for directly controlling the clutch, and a second safety lever for automatically disengaging the friction clutch in case of emergency, both levers being associated to one grip of the handlebar so as to be operable together using a single hand, that is the safety lever is actuated by pressing the lever against the top side of the grip with the palm and thumb of one hand, and the clutch lever is actuated by pressing the lever against the bottom side of the grip with fingers of the same hand; and in which, at the first engagement of the friction clutch following the ignition of the machine or the abandonment of the handlebar, the user must first actuate the safety lever and then, keeping the safety lever actuated, he/she must first actuate and then release the clutch lever.

In another aspect, the present invention discloses a hydraulically actuated friction clutch that comprises an output part, associated to an input shaft of a transmission and including a first set of coupling members such as a pressure plate and a counter-plate, where the pressure plate is rotationally integral to the counter-plate and the counter-plate is an integral part of a clutch bell that is fixed to the transmission input shaft; and an input part, associated to a drive shaft of an engine and including a second set of coupling members such as at least one friction disk that is arranged between said counter-plate and said pressure plate and is rotationally integral to a hub fixed to the engine drive shaft. Pressure plate and friction disk are axially movable along an axis of rotation of the friction clutch, a disengagement spring positions the pressure plate in a defined initial position relative to the counter-plate. The first and the second set of coupling members are axially pressed against each other to frictionally connect the hub to the clutch bell, thereby transmitting a torque from the engine drive shaft to the transmission input shaft. A hydraulic actuator produces the force needed to press the two sets of coupling members against each other. The hydraulic actuator includes a piston arranged within a cylinder which together delimit a pressure chamber filled with hydraulic fluid. When the hydraulic fluid is pressurized, the pistons slide out of the cylinder and applies a force on a thrust bearing to compress the two sets of coupling members, the thrust bearing being in contact with the pressure plate. The hydraulic actuator is controlled through one clutch lever, associated to the handlebar, which controls a first and a second valve which are configured to selectively intercept hydraulic fluid flowing through a first and a second hole connecting the pressure chamber to a drain.

The valve control system is so arranged that, when the clutch lever is released, the first valve is in closed position and the second valve is in open position, while when the clutch lever is fully actuated, the first valve is in open position and the second valve is in closed position. Therefore, in whatever position the clutch lever is in the pressure chamber is connected to the drain, so that hydraulic fluid introduced into the pressure chamber comes out through the first or the second hole. To be able to pressurize hydraulic fluid within the pressure chamber, thereby engaging the friction clutch, a locking device is provided for blocking the second valve in closed position when the clutch lever is released.

The locking device is controlled by a safety lever associated to the handlebar. If the safety lever is kept actuated, an actuation of the clutch lever brings the second valve into closed position, but when the lever is released the second valve is retained in closed position by the locking device, so that the valve is disconnected from the clutch lever and remains in closed position. In this condition, further actuations of the clutch lever have no effect on the operating position of the second valve, as long as the safety lever is kept actuated, while the friction clutch is controlled by opening/closing the first valve through the clutch lever. If the safety lever is released, the locking device frees the second valve which, under action of a return spring, returns into open position and the hydraulic fluid contained in the pressure chamber flows rapidly out, reducing suddenly the pressure acting upon the piston, so that the disengagement spring brings the pressure plate back to the initial position decoupling the contact between the two sets of coupling members.

Further characteristics and advantages of the invention will be apparent from the following description of embodiments, given by way of example and not of limitation, with the aid of the accompanying figures of the drawings. BRIEF DESCRIPTION OF DRAWINGS

Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale so that the dimensions of some parts may be arbitrarily increased or reduced, relative to other parts in the same figure, for clarity of discussion; in which like reference numerals refer to same or similar parts throughout the various figures; and wherein:

Fig. 1 shows an example of self-propelled operating machine, according to the present invention, in a partially sectioned side view;

Fig. 2 is a schematic representation of a friction clutch, according to one embodiment of the present invention, in sectional side view;

Fig. 3 is a cross-sectional view of the friction clutch of Fig. 2, taken along section A- A;

Fig. 4 is a top plan view taken along section B-B from Fig. 3 of the valve control system and the locking device of the friction clutch of Fig. 2;

Fig. 5 is a representation of control levers on the handlebar;

Fig. 6, Fig. 7, Fig. 8, Fig. 9 are schematic representations of the valve control system and locking device of the friction clutch of Fig. 2 in the various operating positions;

Fig. 10, Fig. 11 are schematic representations of the friction clutch of Fig. 2 according to an alternate form of construction, respectively in a first (friction clutch disengaged) and in a second (friction clutch engaged) operating position;

Fig. 12, Fig. 13 are schematic representations, taken along section A-A from Fig. 2, of a further embodiment of the invention, respectively in a first (friction clutch disengaged) and in a second (friction clutch engaged) operating position.

DESCRIPTION OF EMBODIMENTS

Referring to Fig. 1, a self-propelled operating machine 10 comprises a handlebar 11 at the end of which are grips (21) and controls (22, 23), an engine 12 for producing a motive power, a transmission 13 for transferring said motive power at least to a tool 14 and/or to a power take-off 15 and/or to an axle 16 provided with driving wheels 18, and a friction clutch 19 arranged between said engine and said transmission.

Referring to Figs. 2 to 5, a hydraulically actuated friction clutch 19, according to one exemplary embodiment of the present invention, has an input part, which can be associated with a drive shaft 24 of the engine to introduce a torque, and an output part, which can be associated with an input shaft 25 of the transmission to extract a torque. The input part and the output part are supported by a flange 26 and a casing 27, rigidly fixed to each other, and the whole clutch assembly is associate with a portion of said engine by means of said flange. The output part comprises at least a bell 31, coupled with said input shaft 25, a pressure plate 32, which is integral in rotation with the bell and axially displaceable along an axis of rotation 20 of the friction clutch, and a disengagement spring 33 for positioning the pressure plate in a defined initial position relative to the input part and output part.

The input part at least comprises a toothed hub 41, coupled to said drive shaft 24, and at least one friction disk 42, arranged between said pressure plate and a counter-plate 43 of said bell, which is mounted to the toothed hub so as to be integral in rotation with the toothed hub and axially movable along said axis of rotation of the friction clutch.

The pressure plate is displaceable axially to press said at least one friction disk together with the counter-plate, to thereby connect frictionally the input part to the output part in order to transmit a torque from the engine drive shaft to the transmission input shaft. The force needed to compress the pressure plate together with the friction disk and the counter-plate is generated by a hydraulic actuator which comprises a cylinder 51 and a piston 52, the piston being arranged within the cylinder. Preferably, said piston is an annular piston and said cylinder is an annular cylinder rigidly secured to said flange 26. The annular cylinder and piston, together, delimit a pressure chamber 53 filled with hydraulic fluid. The engagement of the friction clutch is achieved by pressurizing the hydraulic fluid in the pressure chamber so as to force the annular piston to slide out of the annular cylinder, so that the annular piston applies a force on a thrust bearing 54 which is in contact with the pressure plate. A hydraulic pump (not shown) provides for pressurizing the hydraulic fluid. Pressure chamber 53 communicates with a delivery duct (not shown) of pressurized hydraulic fluid and is connected to a drain through a maximum pressure valve (not shown), and a first 55 and a second 56 hole. A first 57 and a second 58 valve are configured to intercept hydraulic fluid flowing through said first and a second hole, respectively. Said first and second valve are rotary, or in any case mobile, distributors 57, 58 which are made to rotate by a clutch lever 22, associated to one grip 21 of the handlebar 11, by means of a cable 28 and a first 61 and a second 62 actuation lever, of the first 57 and the second 58 rotary distributor respectively, that are partially interconnected through a rod 63 (or a wire). Rotary distributors, actuation levers, and interconnecting rod are so arranged that when the clutch lever is released the first rotary distributor intercepts the flow (valve in closed position) through the first hole and the second rotary distributor allows the flow (valve in open position) through the second hole, and when the clutch lever is fully actuated the first rotary distributor allows the flow (valve in open position) through the first hole and the second rotary distributor intercepts the flow (valve in closed position) through the second hole. Preferably, whenever the user actuates the clutch lever, the first rotary distributor starts to allow the flow through the first hole when the second rotary distributor starts to intercept the flow through the second hole, and vice versa when the user releases the clutch lever.

The two rotary distributors are associated with return springs 64, 65 that take care of bringing back distributors to a starting position when the user releases the control lever, that is, the first distributor in closed position and the second distributor in open position. The actuation levers are "partially interconnected" in the sense that when the clutch lever is actuated the first actuation lever acts on the second actuation lever through rod 63 so as to place the second rotary distributor in closed position, but when the clutch lever is released the second actuation lever is free from constrain with rod 63 and is brought back into open position by its return spring.

A locking device 70 performs the task of blocking the second rotary distributor in closed position, so as to intercept the flow through the second hole when the clutch lever is released. According to the representative architecture of Figs. 2-5, the locking device comprises a sliding body 71, a support element 72, and an engaging element 73 that performs the task of locking the sliding body 71 to the support element 72. The sliding body 71 can slide in a housing 74 fixed with respect to the seat 75 of said second rotary distributor; it is subjected to return action of a retraction spring 85 and is provided with a detent 76, which can be a protruding dog that is shaped and sized to be engaged in contact by a portion of the engaging element, a notch that is recessed into the sliding body and is shaped and sized to receive in it a portion of the engaging element, or any other means apt to engage the engaging element. By way of example, and not limitation, support element 72 may be a plate 77 which is an integral part of, or rigidly fixed to the actuation lever 62 of said second rotary distributor; or a first and a second circular plate, integral part of, or rigidly fixed to the actuation lever 62, which are concentric about a rotation axis, identical to the rotation axis of said second rotary distributor, and centered on main lying planes that are perpendicular to the same rotation axis, so as to be parallel and to delimit a cavity inside which is mounted the engaging element, etc.

The engaging element 73 comprises a pawl 78 having a proximal end 81 hinged to a pin 79 fixed to said support element, and a moving, distal end 82 which is biased by a biasing spring 83 to pivot toward engagement with the detent 76 and is held by a second pin 80. The pawl may generally have a rectangular plan profile with a bevelled distal end 82. It is also envisaged that the engaging element 73 take on other forms, such as a sprag or a strut movably mounted within a recessed notch of the support element, a hook which goes to hook the detent, a spring latch provided with a bevelled extremity and sliding within a housing fixed on the support element, etc. The biasing spring 83 may be a torsion spring, a coil spring, a constant force spring, or any other element capable of providing lift to a distal end of the engaging element so as to bias this end toward engagement with the detent 76.

Besides, although shown hinged to a pin fixed to the support element, it is envisioned that the engaging element 73 may be mounted to the sliding body while the detent is part of the support element. It will be apparent that arrangement and geometry of engaging element 73, including its corresponding support element 72 and the sliding body 71, can be varied from that which are shown in the drawings, depending on how the locking device is designed.

A safety lever 23, associated to said grip 21 so as to be operable together with the clutch lever using a single hand, controls the locking device through the cable 29 by acting on the sliding body 71 which can move so as to place the detent 76 in a first position P or in a second position P'.

Figures 5, 6, 7, 8 and 9 illustrate how the present invention works, according to what has previously been described in relation to the said exemplary embodiment of the invention.

The operating machine, after being ignited and prior to being put into operation, is in a stationary position with the engine running but disconnected from the transmission, being that the friction clutch has the following configuration: the clutch lever 22 is in a released position L, so that the first rotary distributor 57 is in closed position and the second rotary distributor 58 is in open position; the hydraulic pump injects pressurized hydraulic fluid into the pressure chamber, but the hydraulic fluid just injected comes out through the second hole 56, so that piston 52 does not move the pressure plate 32 from its initial position; and the safety lever 23 is in a released position S, so that the detent 76 is in the first position P (Fig. 6) in which it is out of engagement with the pawl 78.

To move the machine and go ahead, the user must actuate in succession the safety lever and then the clutch lever. By bringing the safety lever into an actuated position S', the detent 76 moves to the second position P' (Fig. 6). By bringing the clutch lever into an actuated position L', the first rotary distributor 57 is placed in open position (through the cable 28 that rotates the first actuation lever 61) and the second rotary distributor 58 is placed in closed position (through the rod 63 that rotates the second actuation lever 62). Also in this condition, the machine does not move, due to the first rotary distributor in open position which allows the flow through the first hole from which the hydraulic fluid comes out.

However, when the second actuation lever 62 rotates (r), the support element 72 also rotates, so that the pawl 78 goes into contact with the edge 84 of the detent 76 that forces the pawl to rotate around the pin 79, as seen in Fig. 7, to the point where, at an angle of rotation a just below 90°, the distal end 82 makes contact with the edge 84, as seen in Fig. 8. Beyond this threshold, the distal end of the pawl is free from constrain with the edge 84 of detent and, biased by the spring 83, performs a rotation 6 so as to return to its initial position and, when the clutch lever is released, the distal end 82 goes into abutment against the side of the detent 76, as seen in Fig. 9, and the pawl 78 catches between the detent and the support element 72, thereby locking the support element to the sliding body 71, such that the second actuation lever is prevented to rotate for bringing back the second rotary distributor into open position when the clutch lever is released. In this condition, there is no connection between the clutch lever and the second rotary distributor and further actuations of the clutch lever have no effect on the operating position (that is, valve in open position or valve in closed position) of the second rotary distributor, that remains in closed position as long as the user keeps the safety lever in the actuated position S'.

From such a configuration, by releasing the clutch lever, preferably gradually as in the normal use of a motor vehicle, the first hole 55 will also be closed by the first rotary distributor, forcing the hydraulic fluid to stay in the pressure chamber. Thus, the pressure in the pressure chamber increases (up to a value allowed by the maximum pressure valve) forcing the piston 52 to slide out of the cylinder 51 so as to apply an engagement force on the thrust bearing and the pressure plate, thereby engaging the friction clutch. In this condition, that is with the clutch lever released and the safety lever actuated, the rotary motion of the engine shaft is transmitted to the transmission and therefore to implements and/or to axle and driving wheels.

In order to shift gear or to engage/di sengage implements all that is needed is to act upon the clutch lever to disengage the friction clutch, actuate the desired controls, and then release the clutch lever, always keeping the safety lever actuated.

If the user, for whatever reason, abandons the handlebar and thus releases the safety lever, starting from the condition described above, the sliding body moves back to first position P, under action of a retraction spring 85, freeing the pawl from constrain with the detent to thereby free said support element to move with respect to the sliding body; therefore, the return spring 65 will make the second rotary distributor to rotate in order to allow flow through the second hole. In this configuration, the pressurized hydraulic fluid contained in the pressure chamber will flow rapidly out reducing suddenly the pressure acting upon the piston 52, so that the disengagement spring 33 brings the pressure plate back to the initial position decoupling the contact between pressure plate, friction disk, and counter-plate. Therefore, abandoning the handlebar completely stops the machine, both the movement of the machine and the rotation of implements, whilst the engine stays in motion. In order to resume work, the user must carry out a double action: actuating the safety lever; actuating and then releasing the clutch lever. Advantageously, the clutch can also function as an automatic brake to reduce the stopping time of the machine and implements operated thereby; to this end there is a contrast element 99 consisting of a ring of wear-resistant material. When the pressure plate is not pressed together with the friction disk and the counter-plate, the disengagement spring 33 pushes the pressure plate against ring 99, braking the load actuated by the clutch.

In an alternate form of construction of the above-described embodiment, according to the representative architecture of Figs. 10-11, the clutch lever 22 controls said first rotary distributor 57 by means of a first cable 86 and said second rotary distributor 58 by means of a second 87 and a third cable 88 which comprise an inner wire slidably received within an outer sheath. The locking device 70 comprises a base 89 that can be fixed to said handlebar or to the machine body. Said base supports the sliding body 71 and the engaging element. The support element consists of a slider 66 that is provided with a recessed notch or a cavity 67 within which the pawl 78 is hinged to the pin 79, while the biasing spring 83 biases the distal end 82 of the pawl out of the cavity 67 toward engagement with the detent 76. The inner wire 47 of the second cable 87 is longitudinally delimited by a first terminal that is connected to said clutch lever, and by a second terminal, at opposite side from the first terminal, which is connected to a first end portion 68 of the slider designed to house said second terminal. The inner wire 48 of said third cable 88 is longitudinally delimited by a first terminal that is connected to a second end portion 69 of the slider designed to house said first terminal, and by a second terminal, at opposite side from the first terminal, which is connected to said second actuation lever 62. The slider 66 is slidingly movable, within a housing 44 on said base, in two opposite directions along a longitudinal axis 49. The clutch lever 22 controls said second actuation lever, and thus said second rotary distributor 58, by means of the combination formed by said second cable, slider, and third cable. The sliding body 71 and the slider 66 are so arranged that the axes of sliding 40, 49 thereof are inclined to one another so as to form an acute angle P on a plane containing both axes. The engaging element may be provided with a spring acting on the slider 66 to help the reversal thereof after releasing the clutch lever. The locking device works in the same way as described above with reference to Figs. 6-9, but its operation is different in that the slider 66, that practically replaces the support element 72, makes a translational movement along the axis 49 instead of a rotation movement. As described above, by bringing the safety lever into the actuated position S', the detent 76 moves from the position P to the position P'. By bringing the clutch lever into the actuated position L', the slider 66 makes a slide movement from an initial position C to a final position C so that the distal end 82 of the pawl 78 comes into abutment against the side of the detent 76 and the pawl catches between the slider and the detent, thereby locking the slider to the sliding body and, consequently, blocking the second rotary distributor into closed position. Figure 10 shows the locking device 70 in an initial rest position with safety lever released, sliding body having the detent in the position P, and slider 66 in the initial position C, while the friction clutch is disengaged. Figure 11 shows the locking device 70 in locking position, with safety lever actuated, sliding body having the detent in the position P', slider in the final position C, and the pawl caught between the detent and the slider, while the friction clutch is engaged.

With reference to figures 12-13, in a further embodiment of the invention, said second valve is a slide valve 60 in which a spool (or slide) 90 is axially movable within a housing hole 91, the movement of said spool being controllable in two opposite directions by the clutch lever 22 through the cable 28 and a secondary cable 92 (or a leverage) which is linked to the actuation lever 61. The spool 90 is associated with a spring 93 that takes care of bringing back the spool to the starting position when the user releases the clutch lever. The locking device consists of a chamber 94, which is defined by the inner surface 95 of the housing hole 91 and by an end portion 96 of the spool 90; and of a third valve 97, which is a rotary, or in any case mobile, distributor that is made to rotate by safety lever 23 and associated with a return spring 98 that takes care of bringing back the valve to the starting position when the safety lever is released. The chamber 94 is connected to pressure chamber 53 through a first duct 45 and to said drain through a second duct 46, and the end portion 96 is arranged so as to seal the chamber 94 in the axial direction. The third valve 97 is configured to intercepts hydraulic fluid flowing through the second duct 46 in such a way that when the safety lever is released it allows the flow through the duct, while when the safety lever is actuated, it intercepts the flow through the duct. The locking device works as follows. By actuating the safety lever, the third valve 97 intercepts the flow through the second duct, therefore, while the clutch lever is being actuated, the end portion 96 of the spool 90 sucks hydraulic fluid from the pressure chamber 53 into the chamber 94, and when the clutch lever is released, the pressurized hydraulic fluid is forced to stay in the chamber, thereby locking the slide valve 60 in closed position. If the user releases the safety lever, the third valve 97 frees the second duct 46 thus allowing flow through the duct, so that hydraulic fluid contained in the chamber 94 can flow out under action of the return spring 93 that brings the spool 90 back to the initial position. Figure 12 shows the locking device in an initial rest position with the third valve 97 in open position and the slide valve 60 in open position, while the friction clutch is disengaged. Figure 13 shows the locking device in locking position with the third valve 97 in closed position, the slide valve 60 in closed position, the chamber 94 is filled with hydraulic fluid to thereby locking the slide valve 60 in closed position, while the friction clutch is engaged.

The embodiments of the invention also comprise alternate forms of construction.

In a first alternate form of construction (not shown in the drawings), friction clutch 19 is a cone clutch in which said input part is constituted by a cone body, associated with drive shaft 24 so as to be integral in rotation with this drive shaft and axially displaceable along the axis of rotation 20 of the friction clutch, and said output part is constituted by a cone cup integral with the input shaft 25. The cone cup is provided with an internal frustum-conical surface that surrounds an external frustum-conical surface of the cone body. The two frustum-conical surfaces are configured to frictional engage each other. The piston 52 is configured to apply an engagement force on a thrust bearing that is in contact with the cone body; said disengagement spring 33 is configured to position the cone body in a defined initial position relative to the cone cup.

In a second alternate form of construction (not shown in the drawings), friction clutch 19 is a dry- or wet-operating multiplate friction clutch in which the friction disk 42 is a plurality of friction disks, each one having the same characteristics of friction disk 42 in any of the above-described aspects, and the friction clutch also comprises one or more intermediate plates, axially alternately arranged with the disks of said plurality of friction disks, which are integral in rotation with the bell 31 and axially movable along the axis of rotation 20 of the friction clutch.

The embodiments provided in the above description and illustrated in the accompanying drawings are examples given for explanatory purposes only and it will be apparent, to those skilled in the art, that various modifications and equivalent embodiments can be made, all falling within the inventive concept as defined in the summary of the invention and, therefore, without forsaking the ambit of protection of the appended claims.

Claims

1 . Operating machine comprising a handlebar provided with grips, an engine for producing a motive power, and a transmission for transferring said motive power at least to an axle or to a tool, the operating machine includes a friction clutch (19), arranged between the engine and the transmission, for connecting and disconnecting a drive shaft (24) of the engine with at least one input shaft (25) of the transmission, the friction clutch comprises:

- an output part constituted at least by a bell (31), which is integral with said input shaft (25), and a pressure plate (32) which is integral in rotation with the bell and axially displaceable along an axis of rotation (20) of the friction clutch;

- an input part constituted at least by a toothed hub (41), which is integral with said drive shaft (24), and a friction disk (42) which is arranged between said pressure plate and a counter-plate (43) of said bell and is mounted to the toothed hub so as to be integral in rotation with the toothed hub and axially movable along said axis of rotation of the friction clutch;

- an actuating hydraulic device comprising a hollow cylinder (51) and a piston (52), the piston being linked to said pressure plate and at least partially slidably disposed in the hollow cylinder; a pressure chamber (53), defined by said hollow cylinder, said piston, and a closed end of the hollow cylinder, is filled with a hydraulic fluid and connected to a drain through a maximum pressure valve;

- a disengagement spring (33) that exerts a force on said pressure plate so as to produce a disengagement force for the friction clutch;

- a hydraulic pump for pressurizing said hydraulic fluid;

- a control lever (22) of said actuating hydraulic device, the control lever being mounted on said handlebar in correspondence of one (21) of said grips;

- a flange (26) and a casing (27), which can be rigidly fixed to each other, for supporting the friction clutch and associating the same with a portion of said engine; wherein said hollow cylinder is rigidly secured to said flange and said piston is slidable in said hollow cylinder along a portion of the hollow cylinder between a first retracted position, which is correlated to a minimum volume of said pressure chamber, and a second advanced position which is correlated to a maximum volume of the pressure chamber; wherein the engagement of the friction clutch is achieved by introducing pressurized hydraulic fluid into said pressure chamber so as to force said piston to slide out of said hollow cylinder to said second advanced position, so that the piston transfers an engagement force to said pressure plate ensuring that said friction disk is compressed together with the pressure plate and said counter-plate of said bell for common rotation in order to transmit the motion from said drive shaft of said engine to said input shaft of said transmission; and wherein the operating machine is characterized in that:

- said control lever controls said actuating hydraulic device by means of a first valve (57), which is configured to intercept hydraulic fluid flowing through a first hole (55) connecting said pressure chamber to said drain, and by means of a second valve (58) which is configured to intercept hydraulic fluid flowing through a second hole (56) connecting said pressure chamber to said drain; where said first valve is in closed position if it intercepts the hydraulic fluid flow through said first hole, and it is in open position if it allows this flow; and where said second valve is in closed position if it intercepts hydraulic fluid flow through said second hole, and it is in open position if it allows this flow;

- said control lever controls said first and second valve in such a way that said first valve is in said closed position and said second valve is in said open position if said control lever is placed in a released position (L), and said first valve is in said open position and said second valve is in said closed position if said control lever is placed in an actuated position (L');

- a safety lever (23), mounted on said handlebar in correspondence of said grip (21), controls a locking device (70) to retain said second valve in said closed position when said control lever is released from said actuated position to said released position, the locking device can be placed at least in two positions: a resting position, correlated to a released position (S) of the safety lever, in which said second valve is in said open position if the control lever (22) is in the released position (L) and in said closed position if the control lever is in the actuated position (L¹); and a locking position, correlated to an actuated position (S') of the safety lever, in which, after an actuation of the control lever (22) which has placed said second valve in said closed position, when the control lever is released to said released position the second valve is retained in closed position, so that the second valve is disconnected from the control lever and remains in closed position, and further actuations of the control lever have no effect on the position of the second valve, as long as the safety lever is kept in the actuated position (S').

2. Operating machine as claimed in claim 1, wherein said locking device (70) comprises:

- a sliding body (71) which is provided with a detent (76) and subjected to return action of a retraction spring (85), the sliding movement of the sliding body being controlled by said safety lever;

- a support element linked to an actuation member of said second valve; - an engaging element, which is movably mounted on said support element and configured to selectively engage said detent of said sliding body; and wherein said sliding body is configured to move between two positions: a first position (P), which corresponds to said resting position of said locking device and whereat said engaging element is not able to engage said detent, thereby allowing said support element to move freely with respect to the sliding body; and a second position (P¹), which corresponds to said locking position of said locking device and whereat, when said second valve is placed in said closed position, the engaging element engages the detent so as to lock the support element, and thus said actuation member of said second valve, to the sliding body.

3. Operating machine as claimed in claim 2, wherein said engaging element comprises:

- a pawl (78) having a proximal end hinged to a pin (79) fixed to said support element;

- a biasing spring (83) that biases a distal end (82) of the pawl toward engagement with said detent.

4. Operating machine as claimed in claim 3, wherein:

- said first and second valve are a first (57) and a second (58) rotary distributor which are associated with return springs (64, 65);

- said first rotary distributor (57) is controlled in rotation by said control lever by means of a cable (28) and a first actuation lever (61);

- said second rotary distributor (58) is controlled in rotation by said control lever by means of said actuation member, said actuation member being a second actuation lever (62) that is partially interconnected to said first actuation lever through a rod (63);

- said sliding body (71) slides in a housing (74) which is fixed with respect to the valve seat (75) of said second rotary distributor (58);

- said support element is constituted by a plate (77) which is rigidly attached to said second actuation lever (62) and on which said pawl is hinged to said pin.

5. Operating machine as claimed in claim 3, wherein:

- said first rotary distributor (57) is controlled in rotation by said control lever by means of a first cable (86) and a first actuation lever (61);

- said second rotary distributor (58) is controlled in rotation by said control lever by means of said actuation member, said actuation member being a second actuation lever (62);

- said sliding body (71) slides in a housing seat (74) supported by a base (89);

- 14 - - said support element is constituted by a slider (66) sliding in a housing seat (44) supported by said base, the sliding movement of the slider being controlled by said control lever by means of second cable (87), whose inner wire (47) has a first end connected to the control lever and a second end connected to a first end portion (68) of said slider, and a third cable (88) whose inner wire (48) has a first end connected to a second end portion (69) of said slider and a second end connected to said second actuation lever (62); and wherein the axis of sliding (40) of said sliding body and the axis of sliding (49) of said slider are inclined to one another to conjointly define an acute angle (P) on a plane containing both axes.

6. Operating machine as claimed in claim 1, wherein said first valve is a rotary distributor (57) which is associated with a return spring (64) and controlled in rotation by said control lever by means of an actuation lever (61) and a cable (28), and said second valve is a slide valve (60) whose spool (90) is associated with a return spring (93) and the sliding movement of said spool is controllable in two opposite directions by said control lever by means of said cable (28), said actuation lever (61), and a secondary cable (92); wherein said locking device (70) comprises:

- a chamber (94) which is defined by an inner surface (95) of a housing seat (91) of said spool and by an end portion (96) of said spool; said chamber (94) being connected to said pressure chamber (53) through a first duct (45) and to said drain through a second duct (46), and said end portion of said spool being arranged so as to seal said chamber in the axial direction;

- a third valve (97), which is a rotary, or in any case mobile, distributor that is made to rotate by said safety lever (23) and is associated with a return spring (98); and wherein said third valve is configured to intercept the flow of hydraulic fluid through said second duct, so that said third valve allows said flow through said second duct if said safety lever is in said released position (S) and said third valve intercepts said flow through said second duct if said safety lever is in said actuated position (S').

7. Operating machine as claimed in claim 1 or 2 or 3 or 4 or 5 or 6, wherein said hollow cylinder (51) is an annular cylinder, rigidly secured to said flange (26), and said piston (52) is an annular piston.

8. Operating machine as claimed in claim 1 or 2 or 3 or 4 or 5 or 6 or 7, wherein said friction clutch is a cone clutch in which said input part is constituted by a cone body, associated with said drive shaft (24) of said engine so as to be integral in rotation with the drive shaft and axially displaceable along said axis of rotation of the friction clutch, and said output part is constituted by a cone cup integral with said input shaft (25) of said transmission, and where the cone body is provided with an external frustum-conical surface for frictional engagement with an internal frustum-conical surface of the cone cup that surrounds the frustum-conical surface of the cone body, and said piston transfers said engagement force to the cone body and said disengagement spring acts on the cone body.

9. Operating machine as claimed in claim 1 or 2 or 3 or 4 or 5 or 6 or 7, wherein said friction clutch is a dry- or wet-operating multiplate friction clutch in which said friction disk (42) is a plurality of friction disks, each one having the same characteristics of said friction disk; and the friction clutch also comprises one or more intermediate plates, axially alternately arranged with the disks of said plurality of friction disks, which are integral in rotation with said bell (31) and axially movable along said axis of rotation of the friction clutch.

10. Operation method of an operating machine comprising a handlebar provided with grips, an engine for producing a motive power, and a transmission for transferring said motive power at least to an axle or to a tool, where the operating machine includes a friction clutch (19) which is arranged between the engine and the transmission, to connect and disconnect a drive shaft (24) of the engine with at least one input shaft (25) of the transmission, and is controlled by means of a clutch control lever (22), while a safety lever (23) automatically disengages the friction clutch when released; said clutch control lever and said safety lever being associated to one (21) of said grips of said handlebar so as to be operated together using a single hand; the method being characterized in that the initial shift of said friction clutch from a disengaged state to an engaged state takes place through the steps of:

- actuating said safety lever, so as to bring the lever from a released position (S) into an actuated position (S'), and keeping this lever actuated:

- actuating said clutch control lever, so as to bring the lever from a released position (L) into an actuated position (L¹);

- releasing said clutch control lever to said released position (L).

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