Method for operating a hydrodynamic compression tool and hydrodynamic compression tool

Abstract

A method for operating a hydrodynamic compression tool (1) comprises moving a compression jaw (9) towards an abutment jaw (8) by actuating a hydraulic pump (18), counting a number (N_p) of pumping strokes of the hydraulic pump (18) from an actuation start of the hydraulic pump (18) when the piston is in the stroke start position (16), identifying a compression start condition (22) when the abutment jaw (8) and the compression jaw (9) both engage the object (11) to be compressed, determining a control parameter or compression completion criterion depending on a pumping stroke number at contact (N_p_c) consisting of the pumping stroke number (N_p) counted up to the occurrence of the compression start condition (22).

Description

“Method for operating a hydrodynamic compression tool and hydrodynamic compression tool” DESCRIPTION

[0001] The present invention relates to a method for operating a hydrodynamic compression and / or cutting tool, as well as a hydrodynamic compression tool configured to implement the method.

[0002] I n order to perform certain connection operations, for example, compressing connectors about electric cables, compressing rivets, or cutting operations, for example, cutting electric cables when installing and servicing electrical systems, hydrodynamic compression or crimping tools actuated by a motor are often used.

[0003] Such tools usually comprise an electric motor supplied by an accumulator and provided with a motor shaft connected to a transformation mechanism which transforms the rotary motion of the motor shaft into an alternating translational motion which causes, in a hydrodynamic unit connected thereto, an increase in pressure of a hydraulic fluid acting on a piston for moving the latter against the force of a return spring. The piston is in turn connected to a movable jaw (e.g., in the shape of a punch) so as to move it towards a fixed jaw of the tool during the compression operation. The jaws can be shaped and / or provided with interchangeable accessory elements so as to be adapted to a specific product, for example an electrical contact to be crimped.

[0004] Since compression tools are quite often used in outdoor environments, for example, along railways lines remote from buildings provided with a connection to the electrical grid, they require their own source of electricity, i.e., a portable electric accumulator integrated in or applied to the tool. Such an accumulator provides a limited amount of electricity which determines the autonomy, i.e., the number of compression / cutting operations executable by the tool without the need to replace the accumulator. It is thus desirable to perform the compression using electricity not exceeding that required and sufficient for the type of object, e.g., electrical contact, to be compressed by the planned compression stroke and force.

[0005] Compression tools without interchangeable compression dies are known (so-called “dieless” compression tools), which determine a predetermined or manually settable or adjustable (e.g., selecting the actuation time of the tool and the interruption time of the actuation) stroke of the jaws and a maximum compression force, or determined with the aid of sensors, for example, position sensors of the jaws or the piston (encoder) and by monitoring the pressure of the hydraulic fluid by means of a pressure sensor.

[0006] A known compression tool adapts to the size of the connector to be compressed and always applies - independently of the contact type and size - the same maximum compressionforce which when reached, causes an interruption in the compression (or crimping) cycle and a return of the piston.

[0007] A further known compression tool adapts to the size of the connector to be compressed and applies a variable maximum compression force depending on a “determination of status” by measuring the stroke distance of the piston and the pressure of the hydraulic fluid or by integrating a value of force on the stroke distance of the piston. An encoder is provided to this end, which however increases the overall axial volume of the tool.

[0008] Despite their satisfactory operation and their reliability and robustness, the “dieless” tools of the prior art still have certain drawbacks.

[0009] The known “dieless” tools applying a constant maximum compression force have the disadvantage of excessive consumption of electricity and mechanical stresses not required in case of compressions of objects (electrical connectors) of intermediate and small sizes for which smaller compression forces than the maximum compression force of the tool would be sufficient.

[0010] The known “dieless” tools adapting the compression force to the size of the object (electrical contact) to be compressed require auxiliary sensors (e.g., encoders) in order to ensure a satisfactory detection accuracy of the type or size of the object to be compressed.

[0011] A further disadvantage of the prior art is that, with the compression cycle started, it is always possible to interrupt the compression, but it is not possible to stop the compression in order to handle and inspect the connector to be compressed and then continue the compression without however having to start a new compression cycle, and thus keeping all the settings and all the parameters of the already started compression.

[0012] Therefore, it is problematic in the prior art to manually interrupt the compression of a connector at an instant in which the connector is already firmly clamped between the jaws of the tool but is not yet compressed, due to the difficulty in releasing the button of the tool at the exact instant required and due to the fact that the tool resets itself and thus loses the control parameters of the already started compression cycle.

[0013] The need is instead felt to be able to handle the object to be compressed (e.g., an electrical connector), for example to:

[0014] - position the connector in the planned position thereof before completing the compression,

[0015] - visually check the correct positioning of the connector between the two jaws,

[0016] - insert the connector on an electric cable or hydraulic pipe up to the precise position in which the connector is to be crimped on the cable or pipe, etc.

[0017] ln this context, according to the inventors, it would be innovative and advantageous tothen be able to continue the compression with the parameters already determined as a function of the first compression step up to the moment of interruption.

[0018] Therefore, it is the object of the present invention to provide a method for operating a hydrodynamic compression tool and a hydrodynamic compression tool having features such as to obviate at least some of the drawbacks mentioned with reference to the prior art.

[0019] lt is a particular object of the invention to provide a method and a hydrodynamic compression tool which allow an automatic adaptation of the tool in case of a change in size of the product to be crimped.

[0020] It is a further particular object of the invention to provide a method and tool which allow the adaptation of the hydrodynamic compression tool to objects to be crimped within a broad size (diameter) range with increased accuracy in the (dimensional) identification of the object.

[0021] lt is a further particular object of the invention to provide a method and tool which allow the adaptation to objects to be compressed with different sizes by a mainly software implementation, i.e., using and processing data already available in known tools, without requiring particular structural adaptations and additional sensors.

[0022] It is a further particular object of the invention to provide a control method and a compression tool which allows easily stopping the tool during a compression cycle, handling or inspecting the object to be compressed when the tool is stopped (which in this circumstance acts as gripper which holds down the object), and then continuing the compression without resetting the tool and thus applying the operating parameters already determined depending on the first compression step.

[0023] At least some of the objects are achieved by a method for operating a hydrodynamic compression tool (1 ), said tool (1 ) comprising:- an abutment jaw (8) and a compression jaw (9) movable with respect to the abutment jaw (8) for compressing an object (11 ) positioned between the abutment jaw (8) and the compression jaw (9),- a hydraulic cylinder (12) and a piston (13) connected to the compression jaw (9) and sliding with respect to the hydraulic cylinder (12) along an actuation stroke (15) between the stroke start position (16) and a stroke end position (17),- a hydraulic pump (18) with an electric motor (6) actuatable to increase the pressure of a hydraulic fluid acting in the hydraulic cylinder (12) on the piston (13) so as to move the piston (13) from the stroke start position (16) to the stroke end position (17) and thus move the compression jaw (9) towards the abutment jaw (8), said method comprising:- moving the compression jaw (9) towards the abutment jaw (8) by actuating the hydraulicpump (18),- counting a number of pumping strokes of the hydraulic pump (18) from an actuation start of the hydraulic pump (18) when the piston (13) is in the stroke start position (16),- identifying a compression start condition (22) when the abutment jaw (8) and the compression jaw (9) both engage the object (11 ) to be compressed,- determining a control parameter or compression completion criterion depending on the pumping stroke number counted up to the occurrence of the compression start condition (22).

[0024] The idea underlying the invention is to find a parameter to be observed, precisely the number of pumping strokes of the hydraulic pump, which allows identifying or determining an end-of-compression criterion or a compression control parameter, applicable for a determined object to be compressed, without any need to detect the object itself or to detect a position of the jaws or piston, and without the need to know or measure or calculate the non-deformed size of the object (e.g., an electrical contact or cable lug, etc.) to be compressed.

[0025] The invention allows directly determining the end-of-compression criterion or the general parameter for controlling the compression as a function of an easily observable parameter, and obviating any need to associate tool properties (e.g., the constancy of the return spring, the initial and final positions of the piston) and tool status information (actual position of the piston) with properties of the object to be compressed (e.g., an object size table) and with corresponding values of the end-of-compression criterion (e.g., a table of final pressure values).

[0026] The method allows an implementation mainly or completely at a software level, and thus is suitable for different structure types and concepts of hydrodynamic compression tools, in particular dieless ones.

[0027] The method allows reducing the sensors used in the prior art for determining the position of the piston or jaws, which is no longer necessary to know.

[0028] The method allows applying an end-of-compression criterion or a general compression control parameter without the need to recognize the object, e.g., an electrical connector, a cable lug, a hydraulic connector, and without the need to determine a position of the piston or jaws during the compression process, rather to accurately determine the control parameters and compression completion criteria, for example, to adjust more finely and accurately a target pressure of the hydraulic fluid, and / or a piston target stroke and / or a target number of pumping strokes, required and sufficient for completing the compression. This simplifies the control algorithm of the compression tool, reduces the consumption of electricity and the mechanical stresses of the jaws, and increases the autonomy (number of compressions executable by a battery charge) and useful life of the compression tool.

[0029] The object of the invention is also achieved by a hydrodynamic compression tool (1 ), comprising:

[0030] - an abutment jaw (8) and a compression jaw (9) movable with respect to the abutment jaw (8) for compressing an object (1 1 ) positioned between the abutment jaw (8) and the compression jaw (9),

[0031] - a hydraulic cylinder (12) and a piston (13) connected to the compression jaw (9) and translatable with respect to the hydraulic cylinder (12) along an actuation stroke (15) between a stroke start position (16) and a stroke end position (17),

[0032] - a hydraulic pump (18) with an electric motor (6) actuatable to increase the pressure of a hydraulic fluid acting in the hydraulic cylinder (12) on the piston (13) so as to move the piston (13) from the stroke start position (16) to the stroke end position (17) and thus move the compression jaw (9) towards the abutment jaw (8),

[0033] - an electronic control circuit (10) in signal connection with the electric motor (6), said electronic control circuit (10) being configured to:- moving the compression jaw (9) towards the abutment jaw (8) by actuating the hydraulic pump (18),- count a number of pumping strokes of the hydraulic pump (18) from an actuation start of the hydraulic pump (18) when the piston is in the stroke start position (16),- identifying a compression start condition (22) when the abutment jaw (8) and the compression jaw (9) both engage the object (11 ) to be compressed,- determining a control parameter or compression completion criterion depending on the pumping stroke number counted up to the occurrence of the compression start condition (22).

[0034] According to a further aspect of the invention, a hydrodynamic compression tool (1 ) comprises:

[0035] - an abutment jaw (8) and a compression jaw (9) movable with respect to the abutment jaw (8) for compressing an object (1 1 ) positioned between the abutment jaw (8) and the compression jaw (9),

[0036] - a hydraulic cylinder (12) and a piston (13) connected to the compression jaw (9) and translatable with respect to the hydraulic cylinder (12) along an actuation stroke (15) between a stroke start position (16) and a stroke end position (17),

[0037] - a hydraulic pump (18) with an electric motor (6) actuatable to increase the pressure of a hydraulic fluid acting in the hydraulic cylinder (12) on the piston (13) so as to move the piston (13) from the stroke start position (16) to the stroke end position (17) and thus move the compression jaw (9) towards the abutment jaw (8),

[0038] - an electronic control circuit (10) in signal connection with the electric motor (6), saidelectronic control circuit (10) being configured to:- move the compression jaw (9) towards the abutment jaw (8) by actuating the hydraulic pump (18),- identify a compression start condition (22) when the abutment jaw (8) and the compression jaw (9) both engage the object (1 1 ) to be compressed,- in a control mode selectable by the user, automatically switch OFF the hydraulic pump (18) and / or automatically stop the jaws (8, 9) in response to the identification of the compression start condition (22).

[0039] The object 1 1 is thus clamped between the jaws 8, 9 without yet being compressed, allowing a visual inspection and / or positioning of the object 11 using the tool 1 itself as a gripper or helping hand tool to hold down the object 11 .

[0040] ln order to better understand the invention and appreciate the advantages thereof, a description of non-limiting exemplary embodiments is provided below, with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of a hydrodynamic compression tool according to an embodiment;- Figure 2 is a further perspective view of the compression tool in Figure 1 ;- Figure 3 is a longitudinal section view of the hydrodynamic compression tool in Figure 1 ;- Figure 4 shows a work head of the compression tool in Figure 3 with a piston in a stroke start position, and with a relatively large object to be compressed positioned in an abutment jaw of the work head;- Figure 5 shows the work head of the compression tool in Figure 3 with the piston in a compression position, in which a compression jaw (punch) of the work head partially penetrates the object to be compressed positioned in the abutment jaw;- Figure 6 shows the work head of the compression tool in Figure 3 in a compression start position (22) in which the compression jaw (punch) and the abutment jaw both jointly come into a first engagement contact with the object (here, relatively small) to be compressed;- Figure 7 shows the same situation in Figure 6, in which the object engaged by the abutment jaw and the compression jaw is of intermediate size;- Figure 8 shows the same situation in Figure 6, in which the object engaged by the abutment jaw and the compression jaw is relatively large;- Figure 9 is an exemplary diagram of the trend of the electric current absorbed by the hydraulic pump (in the ordinate) as a function of the number of pumping strokes or as a function of the pumping time (in the abscissa) during a step of actuating the hydraulic pump in the event of actuation without a load (in the absence of an object to be compressed);- Figure 10 is an exemplary diagram of the trend of the electric current absorbed by the hydraulic pump (in the ordinate) as a function of the number of pumping strokes or as a function of the pumping time (in the abscissa) during a step of actuating the hydraulic pump in the event of compression of objects having different sizes;- Figure 11 shows an exemplary function of direct dependency of an end-of-compression criterion (e.g., a target pressure pT) or a general control parameter and the number of pumping strokes N_p or the pumping time T_p up to the condition of first contact with the object to be compressed, according to an embodiment;- Figure 12 shows certain significant steps of a method for operating a compression tool, according to embodiments, in which said steps can be performed according to one or more individual sequences of steps or according to combinations of sequences of steps as indicated by the arrows between the step blocks of the method.

[0041] Description of the compression tool

[0042] With reference to the drawings, a hydrodynamic compression tool 1 comprises a housing 2 with a central handle-shaped portion 3 and a coupling portion 4 for the preferably snap-on connection of a replaceable and rechargeable electric battery 5, at the rear end of tool 1 , for example.

[0043] The compression tool 1 comprises an abutment jaw 8 (or fixed jaw) and a compression jaw 9 (or movable jaw) movable with respect to the abutment jaw 8 for compressing an object 1 1 positioned between the abutment jaw 8 and the compression jaw 9.

[0044] The compression tool 1 further comprises a hydraulic cylinder 12 and a piston 13 accommodated in the hydraulic cylinder 12, as well as (optionally) at least one return spring 14 which elastically pushes piston 13 to a stroke start position 16 with respect to the hydraulic cylinder 12. Piston 13 is connected to the compression jaw 9 and can translate with respect to the hydraulic cylinder 12 along an actuation stroke 15 between the stroke start position 16 and a stroke end position 17.

[0045] The compression tool 1 further comprises a hydraulic pump 18 with an electric motor 6 powerable by battery 5 through an electronic control circuit 10 having a switch on which a manual operation button 7 acts, arranged adjacent to handle 3. The hydraulic pump 18 is actuatable to increase the pressure of a hydraulic fluid acting in the hydraulic cylinder 12 on piston 13 so as to move piston 13 from the stroke start position 16 to the stroke end position 17 and thus move the compression jaw 9 towards the abutment jaw 8.

[0046] A maximum pressure valve 19 is arranged in a hydraulic fluid return duct 21 which connects the hydraulic cylinder 12 to a tank 20 of the hydraulic pump 18.

[0047] The hydraulic pump 18 thus pumps the hydraulic fluid from tank 20 into the hydrauliccylinder 12 to cause piston 13, along with the compression jaw 9, to advance until reaching, in the hydraulic cylinder 12, a predetermined maximum pressure of the hydraulic fluid or until the electric motor 6 is switched OFF. Upon reaching the maximum pressure, the maximum pressure valve 19 (safety valve) automatically opens the return duct 21 to discharge the pressure fluid from the hydraulic cylinder 12 into tank 20.

[0048] General description of the method for operating the compression tool

[0049] In order to facilitate the adaptation of the compression tool and process to a plurality of different products to be compressed or cut, in particular to a plurality of electrical contacts or cable lugs having different outer sizes, for example, with non-deformed outer sizes of 13 mm, 19.6 mm or 27.2 mm, the method for operating the hydrodynamic tool 1 comprises the steps of:- moving the compression jaw 9 towards the abutment jaw 8 by actuating the hydraulic pump 18,- optionally, detecting the pressure p of the hydraulic fluid acting on piston 13,- counting a number N_p of pumping strokes of the hydraulic pump 18 from an actuation start of the hydraulic pump 18 when the piston is in the stroke start position 16,- identifying a compression start condition 22 (or first engagement contact) when the abutment jaw 8 and the compression jaw 9 both engage the object 1 1 to be compressed,- determining a control parameter or compression completion criterion depending on a pumping stroke number at contact N_p_c consisting of the pumping stroke number N_p counted up to the occurrence of the compression start condition 22.

[0050] ldentifying the compression start condition (22)

[0051] According to an embodiment, the method and / or electronic control circuit 10 identifies the compression start condition (22) by:

[0052] - detecting the supply current I of the electric motor 6 and comparing the detected supply current with a threshold current value l_s, and

[0053] - if the detected current I of the electric motor 6 is equal to or greater than the threshold current value l_s, determining the occurrence of the compression start condition (22).

[0054] The threshold current value l_s is selected:

[0055] - greater than a maximum idle current value I_max1 of the hydraulic pump 18 in the idle operating mode, i.e., during an advancement of piston 13 between the stroke start position 16 and the stroke end position 17 without contact of the jaws 8, 9 with each other and without contact of the jaws 8, 9 with the object 11 to be compressed, and

[0056] - less than a minimum end-of-compression current value I_min1 of said objects 11 , preferably of an object 11 having smaller size and deformation stroke for which thecompression method and / or tool 1 is provided.

[0057] The threshold current value l_s is thus representative of a sudden increase in the mechanical resistance against the advancement of piston 11 or against the approximation of the jaws 8, 9 to each other with respect to a situation of idle operating mode, and thus indicative of a first contact with the object 1 1 to be compressed.

[0058] According to an embodiment, the threshold current value l_s is predetermined and constant. This reduces the signal processing time and simplifies the control algorithm.

[0059] Alternatively, the threshold current value l_s is dependent (e.g., linearly dependent) on the pumping stroke number N_p or on a pumping time value T_p counted from the activation of the hydraulic pump 18 with the piston 13 in the stroke start position.

[0060] This allows standardizing the difference between the threshold current value l_s and a current value I during the idle operating mode, increases the algorithm response speed, and increases the determining resolution of the end-of-compression criterion or of the control parameter for objects 1 1 with small size differences.

[0061] According to an embodiment, the method and / or electronic control circuit 10 identifies the compression start condition (22) by:

[0062] - detecting the supply current I of the electric motor 6,

[0063] - determining a gradient of the detected current dl / dt, and

[0064] - comparing the gradient dl / dt of the detected current with a threshold gradient value or with a reference gradient value, for example, a predetermined gradient value or a gradient value calculated in a determining step preceding the current determining step,

[0065] - if the gradient dl / dt of detected current I is equal to or greater than the threshold gradient value or the reference gradient value, determining the occurrence of the compression start condition (22).

[0066] According to an embodiment, the method and / or the electronic control circuit 10 identifies the compression start condition (22) based on a gradient or value of pressure p of the hydraulic fluid detected by the pressure sensor 23.

[0067] For example, the method and / or electronic control circuit 10 identifies the compression start condition (22) by:

[0068] - detecting the pressure p of the hydraulic fluid and comparing the detected pressure p with a threshold pressure value p_s, and

[0069] - if the detected pressure p is equal to or greater than the threshold pressure value p_s, determining the occurrence of the compression start condition (22).

[0070] According to an embodiment, the method and / or electronic control circuit 10 identifies the compression start condition (22) by:

[0071] - detecting the pressure p of the hydraulic fluid, and

[0072] - determining a gradient dp / dt of the detected pressure p,

[0073] - comparing the gradient dp / dt of the detected pressure p with a threshold gradient value or with a reference gradient value, for example, a predetermined gradient value or a gradient value calculated in a determining step before the current determining step,

[0074] - if the gradient dp / dt of the detected pressure p is equal to or greater than the threshold gradient value or the reference gradient value, determining the occurrence of the compression start condition (22).

[0075] Counting the number N_p of pumping actions, i.e. pumping strokes

[0076] According to an embodiment, the method and / or the electronic control circuit 10 determines the number N_p of pumping strokes by the steps of:

[0077] - with piston 13 in a stroke start position 16, resetting the pumping stroke number N_p to an initial value equal to zero (N_p = 0),

[0078] - upon the activation of the hydraulic pump 18 with piston 13 in the stroke start position 16, identifying the completion of each single pumping stroke performed,

[0079] - at each completion of single pumping stroke, increasing the pumping stroke number N_p by 1 (N_p(n)= N_p(n.i) + 1 ).

[0080] ldentifying the completion of the individual pumping stroke comprises, for example, detecting:

[0081] - a characteristic variation of electric current I of motor 6,

[0082] - a feature of the electrical supply signal of motor 6,

[0083] - an angular position signal of a rotor of motor 6,

[0084] - a characteristic variation of the pressure p of the hydraulic fluid detected by the pressure sensor 23,

[0085] or receiving a feedback signal provided by the hydraulic pump 18.

[0086] Determining control parameters and / or compression completion criteria

[0087] With reference to determining a control parameter or a compression completion criterion, for example, the method can comprise the steps of:- determining a target pressure pT of the hydraulic fluid depending on the pumping stroke number at contact N_p_c, and, for example- interrupting the actuation of the electric motor 6 upon reaching the determined target pressure pT of the hydraulic fluid (end-of-compression criterion in terms of force or pressure).

[0088] Alternatively or in addition, the method can comprise the steps of:- determining a target spring force S_T of the return spring 14 depending on the pumping stroke number at contact N_p_c, in which said values of target spring force S_T can, forexample, express corresponding piston or jaw target positions pos_T indicative of a target measurement of the compressed object 1 1 , and, for example- interrupting the actuation of the electric motor 6 upon reaching the target spring force S_T of the return spring 14, in which the force of the return spring is detectable, for example, by means of a force sensor (end-of-compression criterion in terms of final size of the compressed object).

[0089] Alternatively or in addition, the method can comprise the steps of:- determining a target number N_p_T of pumping strokes of the hydraulic pump 18 (or a corresponding number of revolutions of the electric motor 6), for example a number counted starting from the compression start condition (22), depending on the pumping stroke number at contact N_p_c, and, for example

[0090] - interrupting the actuation of the electric motor 6 upon reaching the target number of pumping strokes (or engine revolution number) N_p_T (end-of-compression criterion in terms of energy or overall deforming work).

[0091] A direct relationship or direct functional dependency between the counted number N_p_c of pumping strokes and the end-of-compression criterion simplifies the operating algorithm of the compression tool 1 and reduces the sensitivity thereof to imperfections, for example, fluctuations and noise of the pressure detection signal, variability of the elastic constant of the return spring 14 between different compression tools 1 , variations in temperature and viscosity of the hydraulic fluid, variations in temperature and current absorption of the electric motor 6.

[0092] According to a further embodiment, the method comprises the steps of:

[0093] - counting the number of pumping strokes of the hydraulic pump 18 from the compression start condition (22) (instant of first contact of the object 11 with both jaws 8, 9) up to reaching the determined value of target pressure pT,

[0094] - comparing the counted number of pumping strokes with a predetermined number of pumping strokes expected (expected pumping cycle number) to reach the determined value of target pressure pT, for example, the aforesaid target number N_p_T of pumping strokes,

[0095] - if the difference between the counted number of pumping strokes and the predetermined number of expected pumping strokes is less than a threshold value, returning a “compression successful” message,

[0096] - if the difference between the counted number of pumping strokes and the predetermined number of expected pumping strokes is greater than the threshold value, returning a “compression failed” message, or a message of anomaly.

[0097] Stop tool function

[0098] According to a further aspect of the invention, in a control mode selectable by the user,the method comprises and / or the electronic control circuit 10 of tool 1 automatically switches OFF the hydraulic pump 18 and / or automatically stops the jaws 8, 9 in response to the identification of the compression start condition (22) so that the object 11 is clamped between the jaws 8, 9 but not yet compressed, allowing a visual inspection and / or a positioning of the object 11 using the tool 1 itself as a gripper or helping hand tool to hold down the object 11 .

[0099] This function allows, for example, clamping an electrical connector between the jaws 8, 9 of tool 1 without having to simultaneously hold an electric cable positioned in the electrical contact, and then inserting and positioning the electrical connector on the electric cable with the aid of tool 1 .

[0100] According to an embodiment, in response to a user command to continue the compression, the method comprises and / or the electronic control circuit 10 restarts the actuation of the hydraulic pump 18, and therefore the movement of the compression jaw 9 towards the abutment jaw 8, and completes the compression of object 11 .

[0101] ln this operating mode, the completion of the compression of object 11 occurs as a function of the control parameter or the compression completion criterion previously determined and saved during a preceding step of the same compression operation.

[0102] This obviates the compression anomalies observable in the tools of the prior art in the event of the interruption of the actuation and subsequent reset of the tool.

[0103] Description of the control circuit 10

[0104] The electronic control circuit 10 comprises a processing unit (CPU), an (internal or external) memory associated with the processing unit (CPU), a communication interface associated with the processing unit (CPU) and adapted to receive (pressure, electric parameter values) signals from the pressure sensor 23 and from electric parameter sensors and to transmit control signals to the electric motor 6. The control circuit 10 further comprises a computer program loaded in the memory and configured to carry out the processing of the signals and the operations required to implement the method for operating tool 1 . The control circuit 10 is connected to battery 5 (when battery 5 is coupled to tool 1) and could also have its own battery, possibly adapted to be charged when the control circuit 10 is connected to battery 5.

[0105] According to an embodiment, tool 1 comprises a user interface 24 with a display connected to the electronic control circuit 10, which is configured to cause, by means of such a user interface 24, a display and selection of control parameters of the compression tool 1 .

[0106] Advantageously, the memory of the electronic control circuit 10 is sized to store the detected and processed data of more than 200,000 compression cycles.

[0107] The electronic control circuit 10 is configured to execute the steps and functionsdescribed in relation to the method for operating the compression tool 1 , which functions are therefore integrated in the compression tool 1 so as to be automatically executable or in response to user commands, and are not repeated herein for conciseness.

[0108] The operation of the compression tool 1 is described below.

[0109] Pressing the operation button 7 actuates a microswitch of the electronic control circuit 10, which starts the electric motor 6 and simultaneously starts receiving and processing the electric signals indicative of the individual pumping strokes and the pressure of the hydraulic fluid. The control circuit 10 is configured so that the electric motor 6 remains ON only when the operation button 7 is pressed down, and therefore is automatically switched OFF with the release of such an operation button 7. Piston 13 starts advancing “idle” (without a load), approximating the abutment jaw 8 and compression jaw 9 to object 11 . The instance in which object 11 is engaged (compression start condition (22)), it causes a resistance to a further approximation of the jaws, which causes a significant increase in the current absorbed by motor 6 and the detected pressure p of the hydraulic fluid. The control circuit 10 determines the value of target pressure pT as a function of the number N_p of pumping strokes counted up to the occurrence of the compression start condition (22).[001 10]When the detected pressure p reaches the value of target pressure pT, the electronic control circuit 10 automatically switches OFF the electric motor 6. Now the operation button 7 can be released.[001 11 ]For the return of piston 13 to the stroke start position 16 thereof (jaws open), tool 1 can comprise a member or button 25 (Figure 1 ) for manual operation, or alternatively, means for automatically operating a general discharge valve or the maximum pressure valve of the hydraulic fluid from the hydraulic cylinder 12 into tank 20 of the hydraulic pump 18.[001 12]Possibly, the member 25 for activation of the discharge valve or maximum pressure valve, and the motor operation button 7 are configured so that with member 25 actuated, button 7 is locked and cannot be pressed down or operated in order to prevent the electric motor 6 from being switched ON during the return of piston 13 to the stroke start position 16. Alternatively, the member 25 for activating the discharge valve or maximum pressure valve, and the motor operation button 7 can be pressed simultaneously. In this case, the pump conveys the hydraulic fluid and the discharge valve recirculates it in the tank.[001 13]ln case of voluntary interruption (by deactivating the electric motor 6 by releasing the operation button 7) or an automatic interruption of an incomplete compression cycle, it is advantageous to store the previously processed parameters so as to resume the compression from the point of voluntary or automatic interruption.[001 14]ln case of voluntary interruption (by deactivating the electric motor 6) of an incompletecompression cycle, it is also advantageous to short circuit the electrical contacts of motor 6 so as to lock it in the interruption position in which it was deactivated, with a braking effect against movements out of the position of interruption.List of reference signs hydrodynamic compression tool 1 housing 2 handle 3 battery coupling portion 4 electric battery 5 electric motor 6 operation button 7 abutment jaw 8 compression jaw 9 electronic control circuit 10 object 11 hydraulic cylinder 12 piston 13 return spring 14 actuation stroke 15 stroke start position 16 stroke end position 17 hydraulic pump 18 maximum pressure valve 19 tank 20 return duct 21 compression start condition 22 pressure sensor 23 user interface 24 with display return member 25 pressure p of the hydraulic fluid target pressure pT number N_p of pumping strokes number N_p_c of contact pumping strokes supply current Ithreshold current value l_s maximum idle current I_max1 minimum end-of-compression current I_min1 pumping time T_p gradient dl / dt of the detected current pressure threshold value p_s pressure gradient dp / dt target pumping stroke number N_p_T target position pos_T target spring force S_T

Claims

CLAIMS1. A method for operating a hydrodynamic compression tool (1 ), said tool (1 ) comprising:- an abutment jaw (8) and a compression jaw (9) movable with respect to the abutment jaw (8) for compressing an object (11 ) positioned between the abutment jaw (8) and the compression jaw (9),- a hydraulic cylinder (12), a piston (13) and at least one return spring (14) which elastically pushes the piston (13) to a stroke start position (16) with respect to the hydraulic cylinder (12), wherein the piston (13) is connected to the compression jaw (9) and can translate with respect to the hydraulic cylinder (12) along an actuation stroke (15) between the stroke start position (16) and a stroke end position (17),- a hydraulic pump (18) with an electric motor (6) actuatable to increase the pressure of a hydraulic fluid acting in the hydraulic cylinder (12) on the piston (13) so as to move the piston (13) from the stroke start position (16) to the stroke end position (17) and thus move the compression jaw (9) towards the abutment jaw (8), said method comprising:- moving the compression jaw (9) towards the abutment jaw (8) by actuating the hydraulic pump (18),-counting a number (N_p) of pumping strokes of the hydraulic pump (18) from an actuation start of the hydraulic pump (18) when the piston is in the stroke start position (16),- identifying a compression start condition (22) when the abutment jaw (8) and the compression jaw (9) both engage the object (11 ) to be compressed,- determining a control parameter or compression completion criterion depending on a pumping stroke number at contact (N_p_c) consisting of the pumping stroke number (N_p) counted up to the occurrence of the compression start condition (22).

2. A method according to claim 1 , comprising identifying the compression start condition (22) by:- detecting the supply current (I) of the electric motor (6) and comparing the detected supply current (I) with a threshold current value (l_s), and- if the detected current (I) of the electric motor (6) is equal to or greater than the threshold current value (l_s), determining the occurrence of the compression start condition (22).

3. A method according to claim 2, wherein the threshold current value (l_s) is:- greater than a maximum idle current value (I_max1 ) of the hydraulic pump (18) in the idle operating mode, and- less than a minimum end-of-compression current value (I_min1 ) for which the compression tool (1) is configured, or the threshold current value (l_s) is predetermined and constant, or the threshold current value (l_s) is dependent, or linearly dependent, on the pumping stroke number (N_p) or on a pumping time value (T_p) counted from the activation of the hydraulic pump (18) with the piston (13) in the stroke start position.

4. A method according to claim 1 , comprising identifying the compression start condition (22) by:- detecting the supply current (I) of the electric motor (6),- determining a gradient (dl / dt) of the detected current (I), and- comparing the gradient (dl / dt) of the detected current (I) with a threshold gradient value or with a reference gradient value,- if the gradient (dl / dt) of detected current (I) is equal to or greater than the threshold gradient value or the reference gradient value, determining the occurrence of the compression start condition (22).

5. A method according to claim 1 , comprising identifying the compression start condition (22) depending on:- a gradient or value of the pressure (p) of the hydraulic fluid, detected by a pressure sensor (23), and / or- a difference in pressure increase for a single pumping stroke, between two consecutive pumping strokes, respectively.

6. A method according to any one of the preceding claims, comprising determining the pumping stroke number (N_p) through the steps of:- resetting the pumping stroke number (N_p) to an initial value equal to zero (N_p = 0),- upon the activation of the hydraulic pump (18) with the piston (13) in the stroke start position (16), identifying the completion of each single pumping stroke performed,- at each completion of single pumping stroke, increasing the pumping stroke number (N_p) by 1 (N_P(n) = N_p(n-1) + 1).

7. A method according to claim 6, wherein identifying the completion of the single pumpingstroke comprises detecting at least one of:- a characteristic variation of electric current (I) of the motor (6),- a feature of the electrical supply signal of the motor (6),- an angular position signal of a rotor of the motor (6),- a characteristic variation of pressure (p) of the hydraulic fluid, detected by a pressure sensor (23), or receiving a feedback signal provided by the hydraulic pump (18).

8. A method according to any one of the preceding claims, comprising:- determining a target pressure (pT) of the hydraulic fluid depending on the pumping stroke number at contact (N_p_c), and- interrupting the actuation of the electric motor (6) upon reaching the determined target pressure (pT), and / or- determining a target spring force (S_T) of a return spring (14) depending on the pumping stroke number at contact (N_p_c), said return spring (14) being connected between the cylinder and the piston and biasing the piston to the stroke start position, and- interrupting the actuation of the electric motor (6) upon reaching the determined target spring force (S_T), and / or- determining a target number (N_p_T) of pumping strokes of the hydraulic pump (18) or a corresponding number of revolutions of the electric motor (6) depending on the pumping stroke number at contact (N_p_c), and- interrupting the actuation of the electric motor (6) upon reaching the target pumping stroke number (N_p_T) or the corresponding number of revolutions of the electric motor (6) counted from the occurrence of the compression start condition (22).

9. A method according to any one of the preceding claims, comprising:- counting the number of pumping strokes of the hydraulic pump (18) from the compression start condition (22) up to reaching a determined value of target pressure (pT) depending on the pumping stroke number at contact (N_p_c),- comparing the counted pumping stroke number with a predetermined expected pumping stroke number (or expected pumping cycle number) to reach the determined value of target pressure (pT),- if the difference between the counted pumping stroke number (N_p_c) and the predeterminedexpected pumping stroke number is less than a threshold value, returning a “compression successful” message,- if the difference between the counted pumping stroke number (N_p_c) and the predetermined expected pumping stroke number is greater than the threshold value, returning a “compression failed” message or an anomaly message.

10. A method according to any one of the preceding claims, comprising:- automatically switching OFF the hydraulic pump (18) and / or automatically stopping the jaws (8, 9) in response to the identification of the compression start condition (22) so that the object (11 ) is clamped between the jaws (8, 9) but not yet compressed,- in response to a user command to continue the compression, restarting the actuation of the hydraulic pump (18) and / or restarting the movement of the compression jaw (9) towards the abutment jaw (8), and completing the compression of the object (11 ).

11. A method according to claim 10, wherein the completion of the compression of the object (11 ) occurs as a function of the control parameter or the compression completion criterion previously determined and saved during a preceding step of the same compression operation.

12. A method for operating a hydrodynamic compression tool (1 ), said tool (1 ) comprising:- an abutment jaw (8) and a compression jaw (9) movable with respect to the abutment jaw (8) for compressing an object (11 ) positioned between the abutment jaw (8) and the compression jaw (9),- a hydraulic cylinder (12), a piston (13) and at least one return spring (14) which elastically pushes the piston (13) to a stroke start position (16) with respect to the hydraulic cylinder (12), wherein the piston (13) is connected to the compression jaw (9) and can translate with respect to the hydraulic cylinder (12) along an actuation stroke (15) between the stroke start position (16) and a stroke end position (17),- a hydraulic pump (18) with an electric motor (6) actuatable to increase the pressure of a hydraulic fluid acting in the hydraulic cylinder (12) on the piston (13) so as to move the piston (13) from the stroke start position (16) to the stroke end position (17) and thus move the compression jaw (9) towards the abutment jaw (8), said method comprising:- moving the compression jaw (9) towards the abutment jaw (8) by actuating the hydraulic pump (18),- identifying a compression start condition (22) when the abutment jaw (8) and thecompression jaw (9) both engage the object (11 ) to be compressed,- automatically switching OFF the hydraulic pump (18) and / or automatically stopping the jaws (8, 9) in response to the identification of the compression start condition (22) so that the object (11 ) is clamped between the jaws (8, 9) but not yet compressed,- in response to a user command to continue the compression, restarting the actuation of the hydraulic pump (18) and / or restarting the movement of the compression jaw (9) towards the abutment jaw (8), and completing the compression of the object (11 ).

13. A method according to claim 12, wherein the completion of the compression of the object (11 ) occurs as a function of at least one control parameter or compression completion criterion previously determined and saved during a preceding step of the same compression operation.

14. A hydrodynamic compression tool (1 ), comprising:- an abutment jaw (8) and a compression jaw (9) movable with respect to the abutment jaw (8) for compressing an object (11 ) positioned between the abutment jaw (8) and the compression jaw (9),- a hydraulic cylinder (12), a piston (13) and at least one return spring (14) which elastically pushes the piston (13) to a stroke start position (16) with respect to the hydraulic cylinder (12), wherein the piston (13) is connected to the compression jaw (9) and can translate with respect to the hydraulic cylinder (12) along an actuation stroke (15) between the stroke start position (16) and a stroke end position (17),- a hydraulic pump (18) with an electric motor (6) actuatable to increase the pressure of a hydraulic fluid acting in the hydraulic cylinder (12) on the piston (13) so as to move the piston (13) from the stroke start position (16) to the stroke end position (17) and thus move the compression jaw (9) towards the abutment jaw (8),- an electronic control circuit (10) in signal connection with the electric motor (6), said electronic control circuit (10) being configured to:- move the compression jaw (9) towards the abutment jaw (8) by actuating the hydraulic pump (18),- count a number (N_p) of pumping strokes of the hydraulic pump (18) from an actuation start of the hydraulic pump (18) when the piston is in the stroke start position (16),- identify a compression start condition (22) when the abutment jaw (8) and the compression jaw (9) both engage the object (1 1 ) to be compressed,- determine a control parameter or a compression completion criterion depending on a pumping stroke number at contact (N_p_c) consisting of the pumping stroke number (N_p)counted up to the occurrence of the compression start condition (22).

15. A hydrodynamic compression tool (1 ), comprising:- an abutment jaw (8) and a compression jaw (9) movable with respect to the abutment jaw (8) for compressing an object (11 ) positioned between the abutment jaw (8) and the compression jaw (9),- a hydraulic cylinder (12), a piston (13) and at least one return spring (14) which elastically pushes the piston (13) to a stroke start position (16) with respect to the hydraulic cylinder (12), wherein the piston (13) is connected to the compression jaw (9) and can translate with respect to the hydraulic cylinder (12) along an actuation stroke (15) between the stroke start position (16) and a stroke end position (17),- a hydraulic pump (18) with an electric motor (6) actuatable to increase the pressure of a hydraulic fluid acting in the hydraulic cylinder (12) on the piston (13) so as to move the piston (13) from the stroke start position (16) to the stroke end position (17) and thus move the compression jaw (9) towards the abutment jaw (8),- an electronic control circuit (10) in signal connection with the electric motor (6), wherein in a control mode to be activated and deactivated by the user, said electronic control circuit (10) is configured to:- move the compression jaw (9) towards the abutment jaw (8) by actuating the hydraulic pump (18),- identify a compression start condition (22) when the abutment jaw (8) and the compression jaw (9) both engage the object (1 1 ) to be compressed,- automatically switch OFF the hydraulic pump (18) and / or automatically stop the jaws (8, 9) in response to the identification of the compression start condition (22) so that the object (1 1 ) is clamped between the jaws (8, 9) but not yet compressed,- in response to a user command to continue the compression, restart the actuation of the hydraulic pump (18) and / or restart the movement of the compression jaw (9) towards the abutment jaw (8), and complete the compression of the object (1 1 ).

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