Safety system for a working machine

Abstract

Described is a self-propelled working machine (1) provided with a mechanism (10) for moving a load, the self-propelled working machine comprising an activation actuator (14, 16). The force applied by the actuators (14, 16) is constrained by a predetermined maximum threshold.

Description

Technical Field

[0001] The present invention relates to an improved safety system for a self-propelled working machine.

[0002] In more detail, the present invention particularly (but not exclusively) relates to a telehandler. Background Art

[0003] There are prior art telehandlers which consist of a vehicle provided with a frame or "chassis" and movable on wheels; a cab for the operator; and a maneuvering boom which can be extended for lifting and lowering a load.

[0004] In some models the maneuvering boom is articulated directly to the chassis, while other models are provided with a platform or "turret" rotatably mounted on a chassis or "undercarriage", in which case the platform or "turret" has a cab and to which the maneuvering boom is articulated.

[0005] At the distal end of the boom are provided accessories for lifting or moving a load, such as, for example, forks, cages, winches, etc.

[0006] Telehandlers are known to be equipped with a system for limiting the longitudinal moment, which monitors the variable geometrical parameters of the machine (sliding length of the boom, lifting angle of the boom relative to the horizontal, etc.), instantaneously calculates the maximum permissible load, and determines whether there is a risk of instability.

[0007] In practice, under certain stability conditions, depending on the position of the load carried by the boom and its weight, it can be determined whether the machine is at risk of tipping over. If the working conditions are close to those where there would be a risk of instability, the movement of the maneuvering boom is automatically blocked in order to prevent the above risk.

[0008] This limiting system prevents instabilities and is not specifically designed to avoid risks of machine structural failure, since these risks will in almost all cases arise in stress conditions that only occur when the limiting system is deactivated and the machine is used to move excessive loads and / or is in a position of severe exacerbation of the longitudinal moments. For this reason, the systems usually used to limit the longitudinal moments also prevent structural yielding.

[0009] However, it has recently been noted that in specific applications and under certain operating conditions, it may happen that the risk of failure is not always automatically avoided in advance by the limiting system described above. In particular, the market currently needs to provide a machine designed based on a compromise between performance and cost, which does not allow the use of components formed by thick, heavy structures, which are expensive to manufacture. Summary of the invention

[0010] For this purpose, there is a need for a safety system which also prevents the risk of failure if the machine is placed in specific operating conditions which may not be automatically covered by the system for limiting the longitudinal moment.

[0011] The technical object underlying the present invention is to provide a self-propelled working machine and an operating method for a self-propelled working machine that meet the above-mentioned needs.

[0012] This specific technical object is achieved by the present invention as made in accordance with the attached claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Further features and advantages of the invention are more apparent in the non-limiting description of a preferred embodiment of the proposed machine, as illustrated in the accompanying drawings, in which:

[0014] - Figure 1 is a side view of a working machine according to the present invention;

[0015] - Figure 2 is a diagram showing the anti-tipping function of the safety system according to the present invention; and

[0016] - Figure 3 is the load diagram of the proposed machine. DETAILED DESCRIPTION

[0017] With reference to the accompanying drawings, reference numeral 1 denotes as a whole a self-propelled working machine made in accordance with the present invention.

[0018] The machine 1 shown in the figures is a telehandler of the so-called "fixed" type, equipped with a telescopic lifting boom 10 directly articulated to a frame 11, movable by wheels, housing a cab 12. Furthermore, the boom 10 is equipped with a loading attachment 13 at its distal end.

[0019] Optionally, the frame 11 may also be equipped with an outrigger comprising a plurality of stabilizing arms; for example, the machine 1 may be equipped with a so-called “scissor-like” outrigger.

[0020] According to some embodiments, instead of wheels, there may be tracks or other moving attachments.

[0021] The machine 1 may be provided with any propulsion system, in particular a combustion, electric or hybrid system.

[0022] The term attachment 13 denotes both means for engaging a load, such as a fork, a boom equipped with a hook, a winch, a clamp or the like, and means for lifting a person (and if necessary a load), such as a load platform.

[0023] In still more detail, the boom 10 may have, at its distal end, coupling means, also of the type commonly used in telehandlers manufactured by the Applicant, which allow the attachment 13 to be replaced and connected to the hydraulic and electronic equipment of the machine 1 .

[0024] The boom 10 is articulated to swing vertically between a lower position (substantially horizontal) and an upper position (in which the boom 10 is close to a vertical orientation) under actuation of at least one hydraulic cylinder 14 or similar actuator. Optionally, the machine 1 may include two lifting cylinders 14 or similar actuators. Figure 1 Also shown is a compensation cylinder 15 which is hydraulically connected to an actuator for adjusting the alignment of the attachment 13 .

[0025] The boom 10 is extendable and retractable and more precisely comprises a plurality of sectors coaxial with one another and inserted one inside the other and designed to translate in the axial direction.

[0026] The extension and retraction of the boom 10 is also performed by one or more hydraulic cylinders 16 (see Figure 2 ) or other actuators, or also by telescopic cylinders (or other actuators with multiple stages).

[0027] The machine 1 also comprises an electro-hydraulic distributor 17 to which the hydraulic actuators used in the machine 1 are individually connected according to known methods. The distributors are supplied by pumps actuated by an electric motor situated on the machine 1. However, embodiments of the invention are not excluded in which one or more of the above-mentioned actuators are of the electric type instead of the hydraulic type.

[0028] However, it should be noted that the present invention can be used with different types of working machines, which are generally provided with a mechanism 10 for moving a load.

[0029] In particular, the proposed machine 1 can also be a "rotating" telehandler, ie a forklift equipped with a rotating turret, which has been mentioned during the discussion of the prior art. To simplify the description, reference will be made hereinafter mainly to the example where the proposed machine 1 is a forklift of the fixed type.

[0030] The machine 1 comprises a processing unit 2 designed to transmit control signals to a distributor according to instructions issued by an operator sitting in the cab, which distributor thus controls actuators so that the actuators operate the boom 10, the bracket, the translation motor and the attachment 13, as well as other devices included in the machine 1.

[0031] In practice, the machine 1 comprises control means available to the operator in the associated cab 12, such as joysticks, pedals, buttons, etc.; when the operator acts on these control means, the processing unit generates control signals received by the distributor which then regulates the operation of each actuator of the boom 10, the bracket, the attachment 13, etc. accordingly.

[0032] Furthermore, if necessary, the invention may include the use of a remote control comprising control means corresponding in functionality to those present in cab 12 and designed to transmit control signals to a receiver connected to the processing unit.

[0033] In practice, the processing unit 2 transmits control signals to the distributor which thus controls the hydraulic actuators of the machine 1 according to the specific conditions.

[0034] The machine 1 according to the invention is equipped with a safety system capable of preventing risks of structural yielding and preferably also risks of instability of the maneuvering boom 10. The safety system according to the invention is preferably designed so that aggravating movements of the maneuvering boom 10 that could generate risks of instability or structural risks are avoided, depending on the working conditions.

[0035] According to an important aspect of the invention, it is envisaged that, in order to guarantee structural safety, the machine 1 is configured so that the force applied by at least one of the actuators 14 , 16 for activating the maneuvering boom 10 is constrained by a predetermined maximum threshold.

[0036] To this end, the machine 1 is designed so that manipulating the boom 10 (or other load moving mechanism) applies a load moving force that is limited by a maximum threshold, at least for certain movements.

[0037] More specifically, in order to maintain the structural safety of the boom 10, only the extension actuator 16 of the boom 10 may be constrained by the above-mentioned forces. In practice, in this case, the boom 10 may apply a predetermined maximum thrust to the load, and therefore the maximum extension of the boom will be limited and will depend on the weight of the carried load; in other words, under the same load conditions, the maximum operating length allowed for the boom 10 may be less than the maximum geometric length, i.e. the maximum geometric length obtained by the full extension of each section that makes up the boom 10. In other words, the maximum threshold is selected so that the boom 10 is allowed or prevented from reaching a certain length depending on the weight of the load.

[0038] This functionality can be achieved by limiting the operating pressure of the cylinder to a predetermined maximum threshold.

[0039] In particular, this can be achieved by configuring the hydraulic circuit including the sliding cylinder 16 of the boom 10 so that the boom 10 is supplied with a working fluid whose pressure is limited to a maximum value corresponding to the above-mentioned predetermined maximum threshold.

[0040] In more detail, the circuit also comprises the above-mentioned distributor 17 and this distributor may be designed to supply the cylinders with a working fluid whose pressure is limited to a maximum pressure value less than the maximum value at which the cylinders 16 can operate.

[0041] For example, a maximum internal pressure valve of the circuit, located inside the distributor, can be calibrated to define the maximum pressure value of the fluid supplied to the extension cylinder 16 .

[0042] Embodiments are also possible in which the pressure limitation is achieved by calibrating or configuring other parts of the hydraulic circuit (such as, for example, the extension cylinder 16 or a suitable valve) to obtain the above-mentioned maximum threshold value.

[0043] It should also be noted that if two or more hydraulic cylinders 16 (or generally two extension actuators) are provided, the limitation of pressure (or thrust in any case) to one hydraulic cylinder may be equal to or different from the limitation of pressure to another hydraulic cylinder, regardless of how this is achieved. Similarly, in the case of a telescoping cylinder, or in any case of an actuator having multiple stages, each stage may have a different thrust threshold, such as a different maximum pressure.

[0044] Thanks to this advantageous feature, the risk of structural yielding of the boom 10 can be avoided, since the stress on the boom 10 depends on the weight of the load and on the extension of the boom, i.e. on the length of the boom 10 itself, which, in practice, corresponds to the distance between the load and the hinge (or other reference) joining the boom 10 to the frame 11.

[0045] To this end, by limiting the thrust of the extension cylinder 16 in the manner described above, the maximum permissible extension of the boom 10 can be reduced proportionally as the weight of the load increases. This prevents mechanical stress on the boom 10 from becoming detrimental to its structural resistance.

[0046] In practice, after reaching the predetermined pressure limit, even if the operator acts on the control device to continue extending the boom 10, the boom will not extend further and the load remains stationary; in this condition, the operator can retract the boom 10 but cannot extend it further.

[0047] If the load to be moved is limited, the maximum force that the boom 10 can exert in the push mode can also allow it to be extended up to the maximum possible or "geometric" length of the boom, i.e. the design length. In the case of heavy weights, the constraints on the push force can reduce the length, which can reach a maximum operating length that is less than the maximum possible length.

[0048] It should be noted that the maximum threshold value of the load-moving force is predetermined and defined at the design level of the machine 1 .

[0049] It should be noted that this result can be obtained automatically even without the use of sensors and electronic controllers; however, the use of sensors connected to a processing unit also allows for finer adjustments, or to check actual operating conditions, or as feedback.

[0050] Thanks to this feature, the invention allows to offer on the market a telehandler designed with a good compromise between performance and cost, without risking structural safety. In fact, as will be shown below, while illustrating the possible operation of the invention, when using that type of machine 1, operating conditions may exist in which there is no risk of overturning, but the stresses of the boom 10 may become excessive. In those cases, the system for limiting the longitudinal moments will not automatically block the deteriorating movement of the boom 10; however, this type of machine 1 is also safe from a structural point of view, thanks to the force constraints applied to the maneuvering boom 10 described above.

[0051] As mentioned above, the safety system according to the invention can also be designed to prevent the risk of instability.

[0052] The system comprises means 3 for detecting the position and weight of the load and also comprises an electronic processing unit 2 (in Figure 2 ), the electronic processing unit is connected to the detection device and further comprises: a checking module 21, configured to compare the weight of the load with a predetermined reference value selected based on the position of the load; and a limiting module 22, configured to generate at least one limiting signal suitable for limiting the movement of the moving mechanism 10 of the machine 1 after the comparison by the checking module.

[0053] Generally speaking, it should be noted that in this specification, the processing unit 2 is presented as being subdivided into a plurality of independent functional modules, which is only for the purpose of describing the functions clearly and completely.

[0054] In practice, the processing unit 2 may comprise a single electronic device, also of the type commonly present on machines of this type, such as a control unit, suitably programmed to carry out the functions described; the various modules being able to correspond to hardware units and / or software forming part of the programmed device.

[0055] Alternatively or additionally, these functions can be performed by multiple electronic devices, and the above-mentioned functional modules can be distributed on these electronic devices.

[0056] Generally speaking, the processing unit 2 may have one or more microprocessors or microcontrollers for executing instructions contained in the memory module, and the above functional modules may also be distributed on multiple local or remote computers based on the network architecture that accommodates them.

[0057] As already explained, according to an embodiment of the invention, in which the machine is a telehandler 1, for example, the above-mentioned moving mechanism comprises a manipulating boom 10, which can be raised and lowered under the actuation of a first actuator 14; for example, the above-mentioned lifting cylinder can be extended and retracted under the actuation of a second actuator 16 (for example, a lifting cylinder). In this case, the operation of the first actuator 14 and the second actuator 16 is affected by the limit signal generated by the processing unit 2.

[0058] In more detail, if the first actuator 14 and the second actuator 16 are of the hydraulic type, the machine 1 comprises a hydraulic distributor 17 which may be designed to regulate the operation of the two hydraulic actuators 14 , 16 after receiving a limiting signal from the processing unit 2 .

[0059] Preferably, the aforementioned predetermined reference value is a threshold value and the limiting module 22 is configured to limit the movement of the boom 10 towards a position of deterioration of the longitudinal moment of the machine 1 if the measured weight corresponds to the threshold value, in order to avoid a situation where a risk of overturning may occur.

[0060] The term "deteriorated position" means that in this position the tipping moment, in particular the longitudinal moment of the machine 1, is increased compared to the previous position adopted by the load. A greater extension of the boom 10 or a lowering of the boom 10 may increase the moment in the indicated direction.

[0061] As is known, the longitudinal moment of the machine can be defined relative to an ideal axis of rotation which passes through the front wheels or, if present, through the front carrier.

[0062] Preferably, the limiting module 22 is configured to prevent the boom 10 from moving the load to a deteriorated position after verifying that the weight reaches a threshold value, it being noted that this threshold value is associated with the position. In other words, a plurality of threshold values, different or equal, are defined for a plurality of different positions that the load can adopt when moving in space by the boom 10. In practice, a matrix or vector of threshold values ​​to which the weight is compared is defined. These threshold values ​​are preferably weight values.

[0063] To this end, when the weight corresponding to the threshold reaches the position associated with the threshold, the load remains stationary even if the operator acts on the control device to lower or move the load away by rotating or extending the boom 10 downward. The operator can only raise the boom 10 or reduce the extension amount. On the other hand, if the weight of the load is less than the threshold, the limiting module does not issue a limiting signal and thus does not automatically prevent the movement of the boom 10. Stopping the movement of the boom 10 towards the deteriorated position is a type of movement limitation of the preferred boom 10, but other types of movement limitations can also be applied.

[0064] In practice, the processing unit 2 can include a memory module 23 that records different reference values ​​of the weight of the load for the different positions that the load can adopt in space, so as to define the above-mentioned matrix (or vector). The detection means 3 allow the weight of the load being lifted to be measured and the position to be detected instantaneously. Based on the instantaneous position detected, the checking module 21 compares the weight of the load with the reference weight and, if they are equal, the limiting module 22 emits a limiting signal that affects the movement of the boom 10 in a limiting sense.

[0065] The blocking of the movement of the boom 10 actuated by the safety system is referred to as a movement "cut-off" or "stop." In addition to stops, other types of movement restrictions are possible.

[0066] According to a preferred aspect of the invention, the above-mentioned reference value is independent of the angular position of the maneuvering boom 10. In other words, the reference value varies as the linear distance of the load relative to a predetermined reference (e.g. the distance along a horizontal plane or in any case a plane parallel to the ground) varies. To this end, as described in more detail below, the stop of the movement of the boom 10 generated by the processing unit 2 is "vertical", i.e. the stop is defined on a vertical plane in space so that the load cannot exceed this vertical plane. In more detail, the above-mentioned distance may be the projection along a horizontal plane of the distance between the position of the load and the position of the hinge 18 joining the boom 10 to the frame 11. The above-mentioned detection device may comprise one or more of the following components: a pressure sensor 31 of the hydraulic lifting cylinder 14 of the boom 10, a length sensor 32 determining the instantaneous length of the boom 10, and an angle sensor 33 detecting the angular position of the boom 10 (see Figure 2 ). In more detail, the lifting cylinder 14 can be equipped with two sensors 31 detecting the pressure, one sensor being located at the base and the other being located at the piston. If there are two lifting cylinders 14, each lifting cylinder can have two sensors 31 positioned in the manner described. The length sensor 31 can be a cable winding sensor, which can also be combined with an angle sensor 33.

[0067] Additionally or alternatively, there can also be sensors applied to the rear axle of the machine which directly or indirectly detect the reduction in load, such as, for example, load cells or telemeters.

[0068] Furthermore, if the machine 1 is equipped with a stand, the processing unit 2 can also be configured to limit the movement of the mobile mechanism 10 also based on the information that the stand is placed on the ground and, if necessary, also based on, for example, the position of the stand (if it is of the pull-out type) relative to the extension degree. In this case, dedicated sensors will be provided to detect these situations.

[0069] The processing unit 2 may include a calculation module 24 configured to calculate the weight and position of the load based on the parameters obtained from the detection device. In more detail, the memory module 23 may contain information related to the weight and position of the center of gravity of the boom 10 and the attachment mounted at the end of the boom. In this case, based on the parameters related to the boom 10 and the attachment 13 included in the memory module, the calculation module 24 is configured to determine the reaction force vector of the lifting cylinder 14 based on the measurement of the pressure sensor 31 and thus calculate the weight of the load.

[0070] The computing module 24 may be configured to determine the position of the load (relative to a predetermined reference, such as a hinge between the boom 10 and the frame 11 ) based on the signals generated by the length sensor 32 and the angle sensor 33 .

[0071] The following is based on Figure 3 Describing a possible operation of the invention, the figure shows an example of a load diagram defined by the safety system of a machine 1 .

[0072] As is known, the load diagram of a telehandler defines defined areas of space around the machine 1 within which movement of the load by maneuvering the boom 10 is safe without risk of instability. The definition of these areas is determined based on the weight of the load.

[0073] exist Figure 3 In the example of , the diagram comprises a first zone Z1 delimited by the perimeters P, Q, R, T1, in which the processing unit 2 ensures that the anti-instability limitation function of the safety system does not intervene. In fact, the first zone Z1 comprises the positions adopted by the load when the boom 10 moves towards the vertical direction, that is, the positions adopted under conditions of low risk to longitudinal stability.

[0074] However, in the first zone Z1 , the “hydraulic stop” of the safety system, ie the function for limiting the thrust of the boom 10 described above, intervenes.

[0075] In fact, since the limitation of the longitudinal moment does not intervene in the first zone Z1 (except, as will be seen, at line T1), even in the case of significant loads, the extension of the boom 10 is not automatically limited by the processing unit 2. However, thanks to the advantageous feature of limiting the thrust of the boom 10 in the manner described above, an excessive extension of the boom 10 is completely prevented, which could cause stresses in it that could be dangerous for its integrity.

[0076] The second zone Z2 is defined by a first "vertical stop". The movement of the boom 10 is prevented when a load of a certain weight (1200 kg in this example) reaches the first stop line T1, which corresponds to a reference value associated with the linear distance of the above-mentioned load, which reference value is recorded in the above-mentioned memory module 23. For example, the distance considered can be the distance between the hinge 18 of the boom 10 and the first stop line T1, but it is also possible to adopt a reference point for calculating the position of the stop lines T1, T2, T3, ... In practice, the operator is not allowed to move a load with a weight in the second zone Z2.

[0077] The same logic also applies to the other zones Z2, Z3, Z4, ... which can only be reached by crossing further stop lines T2, T3, T4 with progressively lighter loads.

[0078] The invention also relates to a method of operating a working machine 1 , which may be configured as described above, including one or more optional aspects thereof.

[0079] The method consists in constraining the force applied by the moving mechanism 10 for moving the load to a predetermined maximum threshold value. In this way, the "hydraulic stop" described above is obtained. In the case of a telehandler, if the machine 1 is equipped with an extendable and retractable maneuvering boom 10, the force for the extension of the boom 10 may then be limited by a predetermined maximum threshold value. Preferably, hydraulic cylinders 16 may be provided for the extension and retraction of the boom 10; in this case, a predetermined maximum threshold value is set at the working pressure of the cylinders 16 to define the maximum longitudinal operating extension allowed for the boom 10 as a function of the load.

[0080] The method may include the following steps:

[0081] -Detect the position and weight of the load;

[0082] - comparing the weight of the load with a predetermined reference value selected based on the position of the load;

[0083] - Based on the comparison performed, limiting the movement of the above-mentioned mechanism 10 .

[0084] Preferably, the reference value is independent of the angular position of the steering boom 10 .

[0085] The proposed method may comprise further steps corresponding to the corresponding functions performed by the machine 1 according to the invention shown in the present description and comprising providing means or components of the machine 1 .

Claims

1. A self-propelled working machine (1) provided with a mechanism (10) for moving a load, the self-propelled working machine comprising at least one activation actuator (14, 16), characterized in that The force applied by the actuator (14, 16) is constrained by a predetermined maximum threshold.

2. The machine (1) according to the preceding claim, wherein: The mechanism comprises a maneuvering boom (10), and the actuators (14, 16) are designed to move the boom (10).

3. Machine (1) according to the preceding claim, wherein: The maneuvering boom (10) is extendable and retractable, and the actuator (16) is adapted to actuate the extension and retraction of the boom (10).

4. Machine (1) according to the preceding claim, wherein: The actuator is a hydraulic cylinder (16), the thrust of which is subject to a predetermined maximum pressure threshold to define the maximum longitudinal operational extension allowed for the boom (10) according to the load.

5. Machine (1) according to the preceding claim, comprising a hydraulic circuit including said cylinder (16), said circuit being configured to supply said cylinder (16) with a working fluid, the pressure of said working fluid being limited to a maximum value corresponding to said predetermined maximum threshold value.

6. Machine (1) according to the preceding claim, wherein: The hydraulic circuit comprises a hydraulic distributor (17) designed to supply the cylinder (16) with a working fluid, the pressure of the working fluid being limited by the maximum value.

7. Machine (1) according to any of the preceding claims, comprising a safety system designed to prevent the risk of instability, said safety system comprising means (3) for detecting the position and weight of said load and comprising a processing unit (2) connected to said detection means, and said processing unit in turn comprising: a checking module (21) configured to compare the weight of the load with a predetermined reference value selected based on the position of the load; and a limiting module (22) configured to generate at least one limiting signal suitable for limiting the movement of the moving mechanism (10) after the comparison by the checking module.

8. Machine (1) according to the preceding claim, wherein: The moving mechanism comprises a manipulating boom (10) which can be raised and lowered under the actuation of a first actuator (14) and can be extended and retracted under the actuation of a second actuator (16), the operations of the first actuator and the second actuator being affected by the limit signal.

9. Machine (1) according to the preceding claim, wherein: The reference value is independent of the angular position of the maneuvering boom (10).

10. Machine (1) according to the preceding claim, wherein: The first and second actuators (14, 16) are of hydraulic type, the machine (1) comprising a hydraulic distributor (17) designed to regulate the operation of the two hydraulic actuators and also designed to limit the actuation of the actuators after receiving the limiting signal from the processing unit (2).

11. A method for operating a working machine (1), the working machine being provided with a mechanism (10) for moving a load, wherein: The force applied by the mechanism for moving the load is constrained by a predetermined maximum threshold.

12. The method according to the preceding claim, wherein: The mechanism comprises a manipulator boom (10) which is extendable and retractable, the extension force of the manipulator boom being limited by the predetermined maximum threshold.

13. A method according to the preceding claim, wherein: A hydraulic cylinder (16) is provided for extending and retracting the boom (10), and wherein a predetermined maximum threshold is set for the operating pressure of the cylinder (16), thereby defining the maximum longitudinal operating extension allowed for the boom (10) depending on the load.

14. The method according to any one of claims 11 to 13, comprising the steps of: detecting the position and weight of the load; comparing the weight of the load to a predetermined reference value selected based on the position of the load; Movement of the mechanism (16) is restricted or freely permitted based on the comparison performed.

15. The method according to the preceding claim, wherein: The reference value is independent of the angular position of the moving mechanism.

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