A gantry machine tool beam hydraulic balance mechanism and configuration method

Abstract

The present application relates to the technical field of numerical control machine tool, specifically to a gantry machine tool beam hydraulic balance mechanism and configuration method, including a column and a beam capable of lifting motion along the column, further comprising: a balance execution assembly, one end of which is connected with the column, and the other end is connected with the beam; a hydraulic supply circuit is connected in series with the balance execution assembly, and the hydraulic supply circuit is configured to supply pressure oil to the balance execution assembly, so that the balance execution assembly applies a lifting balance force opposite to the direction of gravity to the beam. Two accumulators are connected in parallel to the rod cavity oil supply main pipe, and the downlink recovers oil discharge energy storage and the uplink discharges oil flow compensation, which can suppress the switching flow pulsation and pressure peak; the variable pump start and stop are controlled by the high and low hysteresis of the pressure relay, and the pump can be stopped during the pressure maintaining period of the accumulator, reducing the continuous oil supplement heating and energy consumption; the overflow valve and the variable pump pressure cut-off double pressure limiting prevent the downlink peak overpressure.

Description

Technical Field

[0001] This invention relates to the field of CNC machine tool technology, specifically to a hydraulic balancing mechanism and configuration method for the crossbeam of a gantry milling machine. Background Technology

[0002] The crossbeam of the gantry milling machine is a large-mass lifting component. When it moves up and down along the column, its own weight is entirely applied to the drive transmission pair such as the lead screw or rack, which can easily cause uneven wear of the transmission components and a decrease in positioning accuracy.

[0003] Some technical solutions use a combination of accumulators and cylinders to lift the crossbeam to counteract its own weight. However, conventional hydraulic balance circuits rely solely on hydraulic pumps for direct oil replenishment, resulting in incomplete energy storage, pressure limiting, and locking structures. When the crossbeam is raised or lowered and the load changes, the oil in the rod chamber of the cylinder increases or decreases instantaneously. The system lacks effective buffering and flow compensation, which can easily cause pressure shocks and fluctuations, affecting the stability of the crossbeam's movement. If there is no locking mechanism when the machine stops, the high-pressure accumulator oil may backflow or depressurize, causing the crossbeam to sink. Summary of the Invention

[0004] The purpose of this invention is to provide a hydraulic balancing mechanism and configuration method for the crossbeam of a gantry milling machine, so as to solve the above-mentioned shortcomings in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a hydraulic balancing mechanism for a gantry milling machine beam, comprising a column and a beam capable of lifting and lowering along the column, and further comprising: A balancing actuator, one end of which is connected to the column and the other end of which is connected to the crossbeam; A hydraulic supply circuit is connected in series with the balancing actuator. The hydraulic supply circuit is configured to supply pressurized oil to the balancing actuator, so that the balancing actuator applies a lifting balancing force to the crossbeam in the opposite direction to its own weight, thereby offsetting 70%-90% of the crossbeam's own weight load. An energy storage buffer component is connected in parallel to the pressure oil chamber of the balance execution component to absorb flow shocks, smooth system pressure fluctuations, and compensate for internal leakage in the hydraulic supply circuit during beam lifting and reversing. The pressure monitoring component is connected to the hydraulic supply circuit to monitor the circuit pressure in real time, and triggers a pressure replenishment action when the circuit pressure drops to a set low point and stops pressure replenishment when the pressure rises to a set high point. A locking and pressure-holding assembly, connected in series in the hydraulic supply circuit, is configured to close in the shutdown state to prevent high-pressure oil backflow from the energy storage buffer assembly.

[0006] Preferably, the balancing actuator includes two sets of single-acting hydraulic cylinders, which are symmetrically arranged about the centerline of the crossbeam along its length; the cylinder body of each single-acting hydraulic cylinder is fixedly connected to the column, and the piston rod end is connected to the crossbeam through a flexible hinge structure.

[0007] Preferably, the rod chamber of the single-acting hydraulic cylinder serves as the pressure oil chamber, and the rod chambers of the two sets of single-acting hydraulic cylinders are connected in parallel to the same hydraulic supply circuit to apply symmetrical lifting balance forces to both sides of the crossbeam in the length direction.

[0008] Preferably, the hydraulic supply circuit includes: Oil tank, used to store system hydraulic oil; A hydraulic pump assembly includes an electric motor and a variable hydraulic pump driven by the electric motor, the variable hydraulic pump drawing oil from the oil tank and outputting pressurized oil; The oil supply line is connected in series with an oil suction filter, the variable hydraulic pump, and a check valve. The oil supply line downstream of the check valve branches into two lines, which are respectively connected to the rod chambers of the two sets of the balance actuators. A safety valve assembly, connected in parallel to the output of the variable hydraulic pump, is used to limit the maximum working pressure of the system. When the system pressure reaches the set maximum value, the variable hydraulic pump enters the pressure cut-off state. When the system pressure exceeds the set maximum value, the overflow is opened to reduce the system pressure.

[0009] Preferably, the energy storage buffer assembly includes at least two energy storage devices, which are connected in parallel to the oil supply pipeline branch downstream of the ball valve via a ball valve, so as to achieve communication with the rod chamber of the balance execution assembly; In response to the downward movement of the crossbeam, the rod chamber of the balancing actuator discharges high-pressure oil, a portion of which enters the accumulator to store energy, and the excess oil overflows back to the oil tank through the overflow valve with pressure limiting. In response to the upward movement of the crossbeam, the accumulator releases the stored high-pressure oil to supply the rod chamber. The accumulator provides redundant buffering capacity for the system while smoothing the flow pulsation during lifting and reversing.

[0010] Preferably, the pressure monitoring component includes a pressure relay, which is disposed on the oil supply line between the locking and pressure-holding component and the energy storage buffer component; the set low point and the set high point constitute a hysteresis interval; When the circuit pressure rises to the set high point, the pressure monitoring component sends a stop signal to cut off the motor power supply, causing the variable hydraulic pump to stop working. At this time, the high-pressure oil stored in the energy storage buffer component maintains the balance circuit pressure. When the circuit pressure drops to the set low point due to the movement of the crossbeam and internal leakage, the pressure monitoring component sends a start signal to restart the variable hydraulic pump to replenish the pressure, so that the circuit pressure rises back to the set high point.

[0011] Preferably, the locking and pressure-holding assembly includes at least one set of hydraulically controlled check valves, which are connected in series in the hydraulic supply circuit on the oil supply line located between the hydraulic pump assembly and the energy storage buffer assembly; When the motor stops, the hydraulic control check valve closes, preventing the high-pressure oil in the energy storage buffer assembly from flowing back into the variable hydraulic pump, and simultaneously locking the oil in the balance execution assembly to maintain the pressure-holding position of the crossbeam when the machine stops.

[0012] Preferably, the hydraulic supply circuit further includes a cooler and a cooler bypass valve group. The cooler is installed in the return oil line and is used to forcibly cool the system return oil. The cooler bypass valve group is connected in parallel to both ends of the cooler. When the system oil temperature is lower than the set value, the bypass valve group opens to allow the return oil to bypass the cooler. When the system oil temperature is higher than the set value, the bypass valve group closes to allow the return oil to pass through the cooler.

[0013] Preferably, the flexible hinge structure is a pin hinge mechanism, which compensates for assembly coaxiality errors and angular deviations caused by beam deformation by allowing slight deflection of the pin axis, thereby eliminating the radial lateral force borne by the piston rod.

[0014] A method for configuring a hydraulic balancing mechanism for a gantry milling machine beam includes the following steps: S1. Determine the design input parameters: obtain the total weight G of the moving parts of the crossbeam or ram, the lifting drive direction, the maximum lifting stroke L, and the number and symmetrical arrangement of single-acting hydraulic cylinders. S2. Calculate the load force of a single single-acting hydraulic cylinder: Distribute the total weight of the moving parts to each single-acting hydraulic cylinder according to the number of components, and determine the maximum load force Fmax that a single single-acting hydraulic cylinder needs to withstand. S3. Determine the maximum working pressure of the system: Based on Fmax and the preset hydraulic cylinder diameter parameters, calculate the maximum working pressure of the system using the formula Pmax=Fmax / S, where S is the effective working area of ​​the piston. S4. Determine the structural parameters of the single-acting hydraulic cylinder: Based on the constraint that the maximum working pressure of the system does not exceed the preset pressure upper limit, determine the piston diameter D and the piston rod diameter d so that the working pressure of the hydraulic cylinder is in a reasonable range of 7-10MPa under the premise of meeting the load force. S5. Calculate the volume of a single-acting hydraulic cylinder: using the formula ΔV=2π×[(Dd) / 2] 2×L calculates the change in stroke volume of a single-acting hydraulic cylinder, where L is the maximum lifting stroke; S6. Determine the accumulator volume: Based on the single-acting hydraulic cylinder volume ΔV and the system working pressure fluctuation range, determine the volume of a single accumulator and the number of parallel accumulators through accumulator volume calculation software or empirical formulas, so that the total accumulator volume meets the flow compensation requirements and redundancy backup requirements for the entire stroke of the beam lifting.

[0015] In the above technical solution, the beneficial effects of the present invention are: 1. In this invention, two accumulators are connected in parallel to the oil supply header in the rod chamber. During downward movement, the accumulators recover and store energy by draining oil, and during upward movement, they release oil to replenish flow, thus smoothing out flow pulsations and pressure spikes during reversal. In conjunction with the pressure relay for high and low point hysteresis control of the variable pump, the pump can be stopped during the accumulator pressure holding period, reducing heat generation and energy consumption during continuous oil replenishment. The overflow valve and the variable pump pressure cut-off provide dual pressure limiting to prevent overpressure during downward peaks. Excess oil overflows back to the tank to absorb shocks and avoid large fluctuations in crossbeam lifting pressure.

[0016] 2. The hydraulically controlled check valve of this invention is connected in series between the pump and the accumulator. When the pump stops, it locks the rod chamber and isolates the high-pressure oil in the accumulator to prevent backflow, pressure loss and beam sinking. The two accumulators can be isolated separately, and the redundant volume is still retained even if a single accumulator fails. The return oil side cooler and bypass group control the oil temperature. Combined with standard oil tank, filter, ball valve and other components, the assembly, debugging and subsequent maintenance difficulty are reduced.

[0017] 3. The double-sided single-acting hydraulic cylinders of this invention are symmetrically arranged about the center line of the crossbeam. The piston rod is connected to the crossbeam via a flexible hinge, which can compensate for assembly coaxiality errors and micro-deformation angle deviations under cutting loads. This allows the piston rod to mainly bear axial lifting force and not radial lateral force, thereby reducing the risk of wear on the guide sleeve and seals and oil leakage.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit this disclosure.

[0019] This application provides an overview of various implementations or examples of the technology described in this disclosure, and is not a full disclosure of the entire scope or all features of the disclosed technology. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0021] Figure 1 This is a schematic diagram of the structure of the single-acting hydraulic cylinder of the present invention after being connected to the column and crossbeam; Figure 2 This is a schematic diagram of the connection between the single-acting hydraulic cylinder and the flexible hinge structure of the present invention; Figure 3 This is a top view of the single-acting hydraulic cylinder and flexible hinge structure of the present invention; Figure 4 This is a schematic diagram of the hydraulic circuit of the single-acting hydraulic cylinder of the present invention.

[0022] Explanation of reference numerals in the attached figures: In the diagram: 1. Oil tank; 2. Oil level gauge; 3. Air filter; 4. Suction filter; 5. Motor; 6. Variable displacement hydraulic pump; 7. Check valve; 8. Pressure gauge switch; 9. Main pressure gauge; 10. Pressure relay one; 11. Hydraulic check valve one; 12. Hydraulic check valve two; 13. Safety valve assembly; 14. Single-acting hydraulic cylinder; 15. Accumulator; 16. Ball valve; 17. Relief valve; 18. Cooler; 19. Cooler bypass valve assembly; 20. Pressure relay two; 21. Return oil filter; 22. Column; 23. Crossbeam; 24. Flexible hinge structure. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0024] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0025] This invention provides a hydraulic balancing mechanism and configuration method for a gantry milling machine beam, applicable to CNC machine tools such as gantry machining centers and gantry milling machines that use the beam or ram as a large-mass lifting component. When the gantry milling machine beam moves up and down along the column, its entire weight is applied to the drive transmission pair such as the lead screw or rack. Long-term uneven loading will lead to accelerated wear of the transmission components and decreased positioning accuracy. This invention uses double-sided single-acting hydraulic cylinders to symmetrically lift the beam, in conjunction with an energy storage buffer assembly, a pressure monitoring assembly, and a locking and pressure-holding assembly. This not only offsets most of the beam's weight but also solves problems such as radial uneven loading of the hydraulic cylinder piston rod, oil leakage due to seal wear, and pressure impact during beam lifting and reversing. The technical solution of this invention will be described in detail below with reference to specific embodiments.

[0026] Please see Figures 1 to 4 The hydraulic balancing mechanism for the crossbeam of a gantry milling machine provided by this invention includes a balancing execution component, a hydraulic supply circuit, an energy storage and buffer component, a pressure monitoring component, and a locking and pressure-holding component. These components together constitute a complete hydraulic balancing system for the crossbeam, installed between the column 22 and the crossbeam 23 of the gantry milling machine. During normal machine operation, a lifting and balancing force is continuously applied to the crossbeam 23 to offset 70%-90% of its own weight, thereby significantly reducing the load on the crossbeam lifting drive transmission pair.

[0027] Please see Figures 1 to 2 The balancing actuator includes two sets of single-acting hydraulic cylinders 14, symmetrically arranged about the centerline of the crossbeam 23 along its length, and respectively mounted on the left and right columns 22 of the gantry machine tool. The cylinder body of each single-acting hydraulic cylinder 14 is fixedly connected to the column 22 via a mounting base, with the piston rod extending vertically. The end of the piston rod is connected to the crossbeam 23 via a flexible hinge structure 24. The rod chambers of the two sets of single-acting hydraulic cylinders 14 are connected in parallel to the same hydraulic supply circuit. When the hydraulic supply circuit supplies pressurized oil to the rod chamber, the piston rod retracts upward under hydraulic pressure, applying an upward lifting balancing force to the crossbeam 23 to offset most of its own weight. The rodless chamber of each single-acting hydraulic cylinder 14 is not connected to the oil circuit; it serves only as a volume compensation space when the piston rod retracts, or is connected to the oil tank 1 via a pipeline to replenish leaked oil. The underlying logic of the symmetrical arrangement on both sides is as follows: Since the crossbeam 23 is a long structural component, if lifting force is applied only to one side, the crossbeam 23 will bear a deflection moment about its centerline along its length, causing the guide rail pair between the crossbeam 23 and the column 22 to experience additional lateral loads, accelerating guide rail wear. Symmetrical lifting on both sides ensures balanced force at both ends of the crossbeam 23, and the resultant lifting force passes through the center of gravity of the crossbeam 23, eliminating the deflection moment and ensuring the smoothness of the lifting motion of the crossbeam 23 and the uniformity of the force on the guide rail pair. In other embodiments, for ultra-large span gantry milling machines, the balancing actuator can also adopt a scheme of arranging two sets of single-acting hydraulic cylinders 14 on each side. The four sets of hydraulic cylinders are arranged symmetrically about the centerline of the crossbeam 23 to adapt to the lifting and balancing needs of larger crossbeam masses. In this case, the rod chambers of the four sets of hydraulic cylinders are also connected in parallel to the same hydraulic supply circuit.

[0028] Please see Figures 2 to 3The flexible hinge structure 24 is a pin-hinged mechanism, with an internal pin that allows the piston rod end to deflect slightly within a certain angle range. The underlying logic of the flexible hinge structure 24 is as follows: During the assembly of the gantry milling machine, coaxiality errors inevitably exist between the column 22 and the crossbeam 23; when the crossbeam 23 bears cutting loads, its structure undergoes slight elastic deformation, resulting in a slight angular deviation between the axis of the piston rod and the hydraulic cylinder body. If the piston rod and crossbeam 23 are rigidly directly connected, the aforementioned coaxiality error and deformation angle deviation will directly translate into a radial lateral force on the piston rod. This radial force acts on the mating surface between the piston rod and the guide sleeve, causing uneven wear of the guide sleeve and simultaneously compressing the seal, causing localized stress concentration, accelerating seal failure, and ultimately leading to oil leakage. The flexible hinge structure 24 compensates for the coaxiality error and deformation angle deviation in real time by allowing slight deflection of the pin axis, ensuring that the piston rod is always subjected to force along the cylinder axis, mainly bearing axial lifting force and not radial lateral force. This fundamentally eliminates the root causes of guide sleeve wear and seal overload, significantly extending the service life of the hydraulic cylinder. In a specific embodiment, the flexible hinge structure 24 can adopt a screw outer ring ball-and-socket structure. The piston rod end is machined with external threads, and a connector with a spherical outer ring ball-and-socket is connected by the threads. A spherical inner ring that can swing at multiple angles is set inside the ball-and-socket. The spherical inner ring is connected to the mounting lug on the crossbeam 23 by a pin. The spherical inner ring can swing freely within the ball-and-socket, compensating for angular deviations in various directions, and the structure is simple and easy to maintain. In other embodiments, the flexible hinge structure 24 can also use a spherical bearing instead of a pin hinge mechanism. The spherical bearing allows for angular deflection between the inner and outer rings in any direction in three-dimensional space, and has a stronger deflection compensation capability. It is suitable for applications with low assembly accuracy requirements or large beam deformation under stress. However, the load-bearing capacity of the spherical bearing is usually lower than that of the pin hinge mechanism, and it needs to be checked according to the maximum lifting force of the hydraulic cylinder when selecting it.

[0029] Please see Figure 4 The hydraulic supply circuit includes an oil tank 1, a hydraulic pump assembly, oil supply lines, and a safety valve assembly 13. The oil tank 1 stores the system hydraulic oil. An oil level gauge 2 and an air filter 3 are installed on the oil tank 1. The oil level gauge 2 visually displays the hydraulic level in the tank 1, allowing maintenance personnel to replenish the hydraulic oil promptly. The air filter 3 is installed at the vent of the oil tank 1 to filter the air entering the tank, preventing external dust from contaminating the hydraulic oil and extending its service life. The hydraulic pump assembly includes a motor 5 and a variable displacement hydraulic pump 6 driven by the motor 5. The variable displacement hydraulic pump 6 draws oil from the oil tank 1 and outputs pressurized oil. The oil supply lines are connected in series with an oil suction filter 4, the variable displacement hydraulic pump 6, and a check valve 7. Downstream of the check valve 7, the oil supply lines branch into two paths, each connecting to the rod chamber of a single-acting hydraulic cylinder 14. Figure 4 As shown, the two groups of branches are represented by the RC1 symbol in groups of three.

[0030] An oil suction filter 4 is installed at the suction port of the variable hydraulic pump 6 to filter particulate impurities in the hydraulic oil, preventing impurities from entering the variable hydraulic pump 6 and causing wear. A check valve 7 is connected in series at the output end of the variable hydraulic pump 6. Its core function is to immediately close the check valve 7 when the motor 5 stops, cutting off the passage between the variable hydraulic pump 6 and the system's high-pressure pipeline, preventing high-pressure oil stored in the energy storage buffer assembly from flowing back into the variable hydraulic pump 6 through the oil supply pipeline, thus avoiding damage to the variable hydraulic pump 6 due to reverse high pressure. A safety valve assembly 13 is connected in parallel at the output end of the variable hydraulic pump 6 to limit the system's maximum working pressure. When the system pressure reaches the set maximum value, the variable hydraulic pump 6 enters a pressure cut-off state. When the system pressure exceeds the set maximum value, the safety valve assembly 13 opens to overflow, reducing the system pressure. The safety valve assembly 13 and the pressure cut-off function of the variable hydraulic pump 6 constitute dual pressure limiting protection, preventing system overpressure from damaging components. In a specific embodiment, the variable hydraulic pump 6 can be a variable piston pump. Variable piston pumps change displacement by adjusting the swashplate angle, and are characterized by high pressure, high efficiency, and long service life, suitable for the 7-10 MPa working pressure range of this invention. In other embodiments, the variable hydraulic pump 6 can also be a variable vane pump. Variable vane pumps have lower noise and smaller flow pulsation, suitable for applications with high noise requirements, but their maximum working pressure is usually lower than that of variable piston pumps, and selection needs to be verified based on the system's maximum working pressure. A pressure gauge switch 8 and a main pressure gauge 9 are also installed on the oil supply line. The pressure gauge switch 8 is opened when pressure needs to be observed and closed during normal operation to protect the main pressure gauge 9 and extend its service life. The main pressure gauge 9 is used to visually display the current system working pressure, facilitating the monitoring and maintenance personnel's understanding of the system's operating status.

[0031] Please see Figure 4The energy storage and buffer assembly includes at least two accumulators 15, which are connected in parallel to the oil supply pipeline branch pipes via their respective ball valves 16, and are connected to the rod chambers of two sets of single-acting hydraulic cylinders 14. The underlying logic of the energy storage and buffer assembly is as follows: when the crossbeam 23 is raised or lowered and reversed, the oil flow rate in the rod chamber changes abruptly. Without a buffer element, the inertia of the oil will generate pressure shock waves in the pipeline, causing large fluctuations in system pressure, affecting the stability of the crossbeam 23's movement, and in severe cases, even damaging the pipeline and hydraulic components. As a hydraulic energy storage element, the accumulator 15 utilizes the compressibility of the pre-charged nitrogen gas inside. When the crossbeam 23 moves downward, high-pressure oil is discharged from the rod chamber. A portion of the high-pressure oil enters the accumulator 15 to compress nitrogen and store energy. The excess oil overflows back to the oil tank 1 through the relief valve 17. The oil suction effect of the accumulator 15 reduces the peak pressure in the pipeline and absorbs the reversing impact. When the crossbeam 23 moves upward, the volume of the rod chamber increases and requires the replenishment of high-pressure oil. The accumulator 15 releases the stored high-pressure oil and prioritizes supplying it to the rod chamber. Before the variable hydraulic pump 6 starts to replenish the oil, it provides immediate flow compensation to the system, preventing the pressure in the rod chamber from dropping suddenly due to untimely oil supply and ensuring the continuity of the lifting balance force of the crossbeam 23. The parallel arrangement of the two accumulators 15 has a dual significance: firstly, the total volume of the two accumulators 15 can meet the flow compensation requirements of the entire lifting stroke of the crossbeam 23 and provide redundant backup volume; secondly, each accumulator 15 is connected to the pipeline through an independent ball valve 16. When one accumulator 15 fails and needs maintenance, the corresponding ball valve 16 can be closed to isolate it individually, and the system can still rely on the other accumulator 15 to maintain basic buffering and compensation functions without affecting the normal production of the machine tool. In a specific embodiment, the accumulator 15 can be a bladder-type accumulator. Bladder-type accumulators have fast response speed and reliable gas-liquid separation, making them suitable for absorbing high-frequency pressure shocks. The pre-charge pressure P0 of the accumulator 15 is set to 0.9 times the minimum working pressure P1 to ensure that the accumulator 15 can still effectively release energy when the system pressure is at the minimum working pressure. In other embodiments, the accumulator 15 may also be a diaphragm accumulator. Diaphragm accumulators are small in size and light in weight, and are suitable for installation spaces with limited space. However, their volume is usually small. If the lifting stroke of the crossbeam 23 is large, the number of parallel connections needs to be increased appropriately to meet the total volume requirements.

[0032] Please see Figure 4The pressure monitoring component includes a pressure relay 10, which is installed on the oil supply line between the locking and pressure-holding component and the energy storage buffer component, and is used to monitor the circuit pressure in real time. The set low point and the set high point constitute a hysteresis interval. The pressure threshold of the set low point and the set high point by the pressure relay 10 constitutes the start-stop-cycle control logic of the variable hydraulic pump 6. The underlying logic of the pressure monitoring component to realize intermittent pressure replenishment control is as follows: when the circuit pressure rises to the set high point (set to 10MPa in this embodiment), the pressure relay 10 sends a stop signal to cut off the power supply of the motor 5, and the variable hydraulic pump 6 stops working. At this time, the high-pressure oil stored in the energy storage buffer component maintains the balance of the circuit pressure; when the circuit pressure drops to the set low point (set to 8MPa in this embodiment) due to the lifting and lowering movement of the crossbeam 23 and the internal leakage of the hydraulic components, the pressure relay 10 sends a start signal to restart the variable hydraulic pump 6 to replenish the pressure, so that the circuit pressure rises back to the set high point and then stops the pump again. This hysteresis control allows the variable hydraulic pump 6 to operate intermittently, rather than continuously. During the pressure holding period of the accumulator 15, the motor 5 can be stopped, effectively reducing the heat generation and energy consumption of the system during continuous operation. Furthermore, the pressure relay also has a pressure anomaly alarm function: when the circuit pressure abnormally drops below the alarm threshold due to severe leakage in the hydraulic cylinder or pipeline, the pressure monitoring component triggers an alarm in the machine tool control system, prompting maintenance personnel to handle the situation promptly and prevent the crossbeam 23 from sinking uncontrollably due to insufficient balancing pressure. In a specific embodiment, the pressure relay 10 can be a plunger-type pressure relay, which has high operating accuracy and good repeatability, suitable for precise pressure threshold control. In other embodiments, the pressure monitoring component can also use a pressure sensor in conjunction with a PLC controller to replace the pressure relay. The pressure sensor transmits the real-time pressure signal to the PLC in analog or digital form, and the PLC controls the start and stop of the motor 5 according to the set high and low threshold logic. The advantage of this scheme is that the high and low thresholds can be flexibly adjusted through the PLC program, and real-time recording and remote monitoring of the pressure curve can be achieved, making it suitable for applications requiring a high degree of system intelligence.

[0033] Please see Figure 4The locking and pressure-holding assembly includes a hydraulically controlled check valve 11 and a hydraulically controlled check valve 12. The two sets of hydraulically controlled check valves are connected in series in the hydraulic supply circuit, on the oil supply line located between the hydraulic pump assembly and the energy storage buffer assembly. The underlying logic of the locking and pressure-holding assembly is as follows: When the motor 5 is running normally, the pressure oil output by the variable hydraulic pump 6 acts on the control port of the hydraulically controlled check valve, opening the hydraulically controlled check valve and allowing the pressure oil to flow smoothly to the energy storage buffer assembly and the rod chamber of the single-acting hydraulic cylinder 14. When the motor 5 stops, the pressure at the control port of the hydraulically controlled check valve disappears, and the hydraulically controlled check valve closes. Its one-way shut-off function isolates the passage for high-pressure oil in the energy storage buffer assembly to flow back to the variable hydraulic pump 6, while simultaneously locking the oil in the rod chamber of the single-acting hydraulic cylinder 14, keeping the piston rod in its current position and preventing the crossbeam 23 from sinking due to pressure relief in the rod chamber. The purpose of setting up two sets of hydraulically controlled check valves (hydraulically controlled check valve 11 and hydraulically controlled check valve 22) is to independently lock the two oil supply branches, ensuring that both sets of single-acting hydraulic cylinders 14 can reliably maintain pressure when the machine is stopped, preventing the crossbeam 23 from tilting due to pressure loss on one side. In a specific embodiment, the hydraulically controlled check valve can be a hydraulically controlled check valve with an external vent, which is connected to the oil tank 1, ensuring that the control chamber can reliably release pressure after the machine is stopped, so that the hydraulically controlled check valve can be reliably closed when the machine is stopped. In other embodiments, the locking and pressure-holding assembly can also use an electromagnetic shut-off valve instead of the hydraulically controlled check valve. The electromagnetic shut-off valve is controlled by an electrical signal switch and can be directly linked with the machine tool control system, closing immediately when the stop command is issued, with a faster response speed. However, the hydraulically controlled check valve relies on hydraulic pressure to control the switch, requiring no additional electrical wiring, and has a simpler and more reliable structure, making it more widely used in hydraulic systems.

[0034] Please see Figure 4 The hydraulic supply circuit also includes a cooler 18 and a cooler bypass valve assembly 19. The cooler 18 is located in the return oil line and is used to forcibly cool the system return oil to prevent the hydraulic oil from accelerating oxidation and deterioration due to excessively high operating temperatures over a long period of time. It also prevents changes in the clearance of hydraulic components due to thermal expansion from affecting the sealing performance. The cooler bypass valve assembly 19 is connected in parallel across the cooler 18. When the system oil temperature is lower than the set value, the cooler bypass valve assembly 19 opens, allowing the return oil to bypass the cooler 18 and return directly to the oil tank 1, preventing the hydraulic oil temperature from being too low, which would increase viscosity and increase system starting resistance. When the system oil temperature is higher than the set value, the cooler bypass valve assembly 19 closes, and the return oil is cooled by the cooler 18 before returning to the oil tank 1, thus controlling the oil temperature within a reasonable range. In a specific embodiment, the cooler 18 can be a water-cooled plate heat exchanger, which uses machine tool cooling water to cool the hydraulic oil, resulting in high cooling efficiency and compact structure. In other embodiments, the cooler 18 can also be an air-cooled radiator, which does not require additional cooling water piping, making installation more convenient and suitable for applications where cooling water supply is not available. However, air cooling efficiency is usually lower than water cooling, and the heat dissipation area needs to be appropriately increased in high-power, high-heat-generating applications.

[0035] Please see Figure 4 The oil tank 1 is also equipped with a pressure relay 20 and a return oil filter 21. The pressure relay 20, installed on the oil tank 1, is used for auxiliary monitoring of the pressure inside the oil tank 1. It can promptly respond to pressure changes within the oil tank 1 and feed the signal back to the machine tool's control system, triggering an alarm. The return oil filter 21, also installed on the oil tank 1, is used to filter the hydraulic oil returning along the overflow valve 17.

[0036] Please see Figures 1 to 4 The following provides a detailed description of the complete working process of the hydraulic balancing mechanism for the gantry milling machine beam of the present invention.

[0037] System pressure build-up and replenishment phase: After the machine tool is powered on, motor 5 starts and drives variable hydraulic pump 6 to rotate, drawing oil from oil tank 1 through suction filter 4 and outputting pressurized oil. The pressurized oil passes through check valve 7, hydraulically controlled check valve one 11, hydraulically controlled check valve two 12, and ball valve 16 to simultaneously pressurize the rod chambers of two accumulators 15 and two sets of single-acting hydraulic cylinders 14. The piston rod retracts upward under hydraulic pressure, applying a lifting balance force to the crossbeam 23. As the pressure in the rod chamber and accumulator 15 continues to rise, when the circuit pressure reaches the set high point of 10MPa, the pressure relay activates, cutting off the power to motor 5, and variable hydraulic pump 6 stops working. Thereafter, the high-pressure oil stored in accumulator 15 maintains the balance circuit pressure, and the system enters the pressure holding state.

[0038] During the downward movement of the crossbeam 23: The crossbeam 23 is driven downward by the lifting drive mechanism. The piston rod of the single-acting hydraulic cylinder 14 extends as the crossbeam 23 descends, reducing the volume of the rod chamber and discharging high-pressure oil. The ball valve 16 remains open, and a portion of the discharged high-pressure oil enters the accumulator 15 to compress nitrogen and store energy. The circuit pressure increases with the increase in oil discharge. When the pressure exceeds the set value of the relief valve 17, the excess high-pressure oil pushes open the relief valve 17 and overflows back to the oil tank 1, limiting the downward peak pressure within the set value of the relief valve 17, absorbing the reversing impact, and preventing system overpressure.

[0039] During the upward movement of the crossbeam 23: The crossbeam 23 is driven upward by the lifting drive mechanism. The piston rod of the single-acting hydraulic cylinder 14 retracts as the crossbeam 23 rises, increasing the volume of the rod chamber and requiring the replenishment of high-pressure oil. The accumulator 15 prioritizes releasing the stored high-pressure oil to supply the rod chamber, and the pressure inside the accumulator 15 decreases as the oil discharge increases. When the circuit pressure drops to the set low point of 8MPa, the pressure relay activates, starting the motor 5 to drive the variable hydraulic pump 6 to replenish the pressure, causing the circuit pressure to rise back to the set high point of 10MPa before stopping the pump again. This cycle repeats to maintain the stability of the lifting balance pressure of the crossbeam 23.

[0040] During the shutdown and pressure holding phase: When the machine tool stops, the motor 5 is de-energized, the variable hydraulic pump 6 stops running, the control chamber pressure of the hydraulic control check valve 11 and the hydraulic control check valve 22 disappears, the two sets of hydraulic control check valves close, and the passage for high-pressure oil in the energy storage buffer assembly to flow back to the variable hydraulic pump 6 is isolated. At the same time, the oil in the rod chamber of the two sets of single-acting hydraulic cylinders 14 is locked, so that the piston rod is kept in the current position. The crossbeam 23 remains at the current height position in the shutdown state and does not sink.

[0041] Please see Figures 1 to 4 In an optional embodiment of the hydraulic balancing mechanism for the gantry milling machine beam provided by this invention, the cylinder diameter and rod diameter of the single-acting hydraulic cylinder 14 in the balancing actuator can be adjusted according to the specific mass of the machine beam. In the above embodiment, taking a total beam mass of 20,000 kg and a configuration of one set of hydraulic cylinders on each side as an example, the piston diameter D is 125 mm, the piston rod diameter d is 60 mm, and the effective oil inlet area S of the rod chamber is approximately 0.009439 m². 2 The system operates at a pressure range of 7-10 MPa and has a balance force range of approximately 70,000 N-94,000 N, which can offset 70%-90% of the crossbeam's own weight. For heavy-duty gantry milling machines with larger crossbeam masses, the total lifting force can be increased by increasing the cylinder diameter or the number of hydraulic cylinders on one side to meet the balance requirements of crossbeams of different tonnages.

[0042] In one optional embodiment of the hydraulic balancing mechanism for the gantry milling machine beam provided by this invention, the application scenarios of this mechanism are not limited to the gravity balancing of the gantry milling machine beam, but can also be adapted to the self-weight balancing scenario of the gantry milling machine ram's Z-axis. When the ram makes a vertical feed motion along the beam, its self-weight also acts entirely on the Z-axis feed transmission pair. The hydraulic balancing mechanism of this invention can apply a lifting balancing force to the ram by adjusting the installation direction of the single-acting hydraulic cylinder 14 and the connection position of the flexible hinge structure 24, so as to counteract the load of the ram's self-weight on the Z-axis transmission pair. The principle is exactly the same as that of beam balancing, and it has wide process adaptability.

[0043] Please see Figures 1 to 4 The following provides a detailed description of the configuration method of the hydraulic balancing mechanism for the gantry milling machine beam of the present invention.

[0044] S1. Determine the design input parameters: Obtain the total weight G of the moving parts of the crossbeam or ram, the lifting drive direction, the maximum lifting stroke L, and the number and symmetrical arrangement of the single-acting hydraulic cylinders 14. In a specific embodiment, a symmetrical scheme with a total crossbeam mass G=20000kg, a maximum lifting stroke L=1200mm, and a set of single-acting hydraulic cylinders 14 arranged on each side is used as an example for calculation and explanation.

[0045] S2. Calculate the load force of a single-acting hydraulic cylinder: Distribute the total weight of the moving parts to each single-acting hydraulic cylinder 14 according to the number of components, and determine the maximum load force Fmax and minimum load force Fmin that each single-acting hydraulic cylinder 14 needs to withstand. The underlying logic of this step is that the design goal of the hydraulic balancing mechanism is to offset 70%-90% of the crossbeam's own weight, not 100%, retaining 10%-30% of the self-weight as the effective load of the crossbeam lifting drive mechanism, to ensure that the drive mechanism is always under load during the lifting process, avoiding backlash or creeping phenomena in the transmission pair due to complete unloading. In a specific embodiment: Fmin=20000×9.8×70%÷2≈68600N, Fmax=20000×9.8×90%÷2≈88200N.

[0046] S3. Determine the system's maximum working pressure: Based on Fmax and the preset hydraulic cylinder diameter parameters, calculate the system's maximum working pressure using the formula Pmax=Fmax / S, where S is the effective working area of ​​the piston, i.e., the annular area of ​​the rod chamber S=π×[(D / 2)]. 2 -(d / 2) 2 The constraint in this step is that the system's maximum working pressure does not exceed the preset pressure limit (usually 10 MPa). If the calculated Pmax exceeds the pressure limit, the piston diameter D needs to be increased or the number of hydraulic cylinders increased, and the calculation iteration needs to be repeated until Pmax is within a reasonable working range of 7-10 MPa. In a specific embodiment, D=125mm, d=60mm, and S≈0.009439m are taken. 2 Pmax = 88200 ÷ 0.009439 ≈ 9.34 MPa, which is within the reasonable range of 7-10 MPa.

[0047] S4. Determine the structural parameters of the single-acting hydraulic cylinder: Based on the constraint that the system's maximum working pressure does not exceed the preset pressure upper limit, determine the piston diameter D and piston rod diameter d, ensuring that the hydraulic cylinder's working pressure is within a reasonable range of 7-10 MPa while meeting the load requirements. The selection of the piston rod diameter d must simultaneously meet the piston rod's compressive stability requirements. Calculate the slenderness ratio of the piston rod based on the maximum lifting stroke L and the piston rod diameter d to ensure that the piston rod does not experience compressive instability at its maximum extension length.

[0048] S5. Calculate the volume of a single-acting hydraulic cylinder: using the formula ΔV=2π×[(Dd) / 2] 2 The volume change ΔV of the rod chamber of a single-acting hydraulic cylinder 14 within its maximum lifting stroke L is calculated using the formula ×L. In a specific embodiment, ΔV = 2 × 3.14 × [(0.125 - 0.060) / 2] 2 ×1.2=2×3.14×(0.0325) 2×1.2≈7.9L. This volume change ΔV is the core input parameter for determining the accumulator volume. Its physical meaning is that during the full stroke lifting and lowering process of the crossbeam 23, the maximum volume of oil that each single-acting hydraulic cylinder 14 needs to suck in or discharge in the rod chamber must be covered by the effective volume of the accumulator 15 to ensure that the accumulator 15 always has effective buffering and compensation capabilities during the full stroke lifting and lowering process of the crossbeam 23.

[0049] S6. Determine the accumulator volume: Based on the single-acting hydraulic cylinder volume ΔV and the system working pressure fluctuation range, determine the volume of each accumulator 15 and the number of parallel connections using accumulator volume calculation software or empirical formulas. This ensures that the total volume of accumulators 15 meets the flow compensation requirements and redundancy backup requirements for the entire lifting stroke of the crossbeam 23. The pre-charging pressure P0 of accumulator 15 is set to 0.9 times the minimum working pressure P1, i.e., P0 = 0.9 × P1. In a specific embodiment, P1 = Fmin / S ≈ 68600 ÷ 0.009439 ≈ 7.27 MPa, P0 = 0.9 × 7.27 ≈ 6.54 MPa; P2 = Pmax ≈ 9.34 MPa. Based on the accumulator volume calculation software, the effective volume of the accumulator is approximately 30L. Using an empirical coefficient for redundancy, a single accumulator 15 has a volume of 80L. Two accumulators 15 are connected in parallel. The total effective volume meets the flow compensation requirements and redundancy requirements for the entire lifting stroke of the crossbeam 23. The system operating pressure range is 7-10 MPa. In other embodiments, if the mass of the machine tool crossbeam or the lifting stroke changes, the parameters can be recalculated according to the above steps. The volume of a single accumulator 15 and the number of parallel accumulators can be flexibly adjusted based on the calculation results to adapt to the balancing requirements of different specifications of gantry machine tools.

[0050] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A hydraulic balancing mechanism for a gantry milling machine beam, comprising a column and a beam capable of vertical movement along the column, characterized in that, Also includes: The balancing actuator has one end connected to the column and the other end connected to the crossbeam; A hydraulic supply circuit is connected in series with the balancing actuator. The hydraulic supply circuit is configured to supply pressurized oil to the balancing actuator, so that the balancing actuator applies a lifting balancing force to the crossbeam in the opposite direction to its own weight, thereby offsetting 70%-90% of the crossbeam's own weight load. An energy storage buffer component is connected in parallel to the pressure oil chamber of the balance execution component to absorb flow shocks, smooth system pressure fluctuations, and compensate for internal leakage in the hydraulic supply circuit during beam lifting and reversing. The pressure monitoring component is connected to the hydraulic supply circuit to monitor the circuit pressure in real time, and triggers a pressure replenishment action when the circuit pressure drops to a set low point and stops pressure replenishment when the pressure rises to a set high point. A locking and pressure-holding assembly, connected in series in the hydraulic supply circuit, is configured to close in the shutdown state to prevent high-pressure oil backflow from the energy storage buffer assembly.

2. The hydraulic balancing mechanism for the crossbeam of a gantry milling machine according to claim 1, characterized in that, The balancing actuator includes two sets of single-acting hydraulic cylinders, which are symmetrically arranged about the centerline of the crossbeam along its length. The cylinder body of each single-acting hydraulic cylinder is fixedly connected to the column, and the piston rod end is connected to the crossbeam via a flexible hinge structure.

3. The hydraulic balancing mechanism for the crossbeam of a gantry milling machine according to claim 2, characterized in that, The rod chamber of the single-acting hydraulic cylinder serves as the pressure oil chamber. The rod chambers of the two sets of single-acting hydraulic cylinders are connected in parallel to the same hydraulic supply circuit to apply symmetrical lifting balance forces to both sides of the crossbeam along its length.

4. The hydraulic balancing mechanism for the crossbeam of a gantry milling machine according to claim 3, characterized in that, The hydraulic supply circuit includes: Oil tank, used to store system hydraulic oil; A hydraulic pump assembly includes an electric motor and a variable hydraulic pump driven by the electric motor, the variable hydraulic pump drawing oil from the oil tank and outputting pressurized oil; The oil supply line is connected in series with an oil suction filter, the variable hydraulic pump, and a check valve. The oil supply line downstream of the check valve branches into two lines, which are respectively connected to the rod chambers of the two sets of the balance actuators. A safety valve assembly, connected in parallel to the output of the variable hydraulic pump, is used to limit the maximum working pressure of the system. When the system pressure reaches the set maximum value, the variable hydraulic pump enters the pressure cut-off state. When the system pressure exceeds the set maximum value, the overflow is opened to reduce the system pressure.

5. The hydraulic balancing mechanism for the crossbeam of a gantry milling machine according to claim 4, characterized in that, The energy storage buffer assembly includes at least two energy storage devices, which are connected in parallel to the oil supply pipeline branch downstream of the ball valve through a ball valve to achieve communication with the rod chamber of the balance execution assembly. In response to the downward movement of the crossbeam, the rod chamber of the balancing actuator discharges high-pressure oil, a portion of which enters the accumulator to store energy, and the excess oil overflows back to the oil tank through the overflow valve with pressure limiting. In response to the upward movement of the crossbeam, the accumulator releases the stored high-pressure oil to supply the rod chamber. The accumulator provides redundant buffering capacity for the system while smoothing the flow pulsation during lifting and reversing.

6. The hydraulic balancing mechanism for the crossbeam of a gantry milling machine according to claim 4, characterized in that, The pressure monitoring component includes a pressure relay, which is installed on the oil supply line between the locking and pressure-holding component and the energy storage buffer component; the set low point and the set high point form a hysteresis interval; When the circuit pressure rises to the set high point, the pressure monitoring component sends a stop signal to cut off the motor power supply, causing the variable hydraulic pump to stop working. At this time, the high-pressure oil stored in the energy storage buffer component maintains the balance circuit pressure. When the circuit pressure drops to the set low point due to the movement of the crossbeam and internal leakage, the pressure monitoring component sends a start signal to restart the variable hydraulic pump to replenish the pressure, so that the circuit pressure rises back to the set high point.

7. The hydraulic balancing mechanism for the crossbeam of a gantry milling machine according to claim 4, characterized in that, The locking and pressure-holding assembly includes at least one set of hydraulically controlled check valves, which are connected in series in the hydraulic supply circuit and located on the oil supply line between the hydraulic pump assembly and the energy storage buffer assembly. When the motor stops, the hydraulic control check valve closes, preventing the high-pressure oil in the energy storage buffer assembly from flowing back into the variable hydraulic pump, and simultaneously locking the oil in the balance execution assembly to maintain the pressure-holding position of the crossbeam when the machine stops.

8. The hydraulic balancing mechanism for the crossbeam of a gantry milling machine according to claim 4, characterized in that, The hydraulic supply circuit also includes a cooler and a cooler bypass valve group. The cooler is installed in the return oil line and is used to forcibly cool the system return oil. The cooler bypass valve group is connected in parallel to both ends of the cooler. When the system oil temperature is lower than the set value, the bypass valve group opens to allow the return oil to bypass the cooler. When the system oil temperature is higher than the set value, the bypass valve group closes to allow the return oil to pass through the cooler.

9. The hydraulic balancing mechanism for the crossbeam of a gantry milling machine according to claim 2, characterized in that, The flexible hinge structure is a pin hinge mechanism. The pin hinge mechanism compensates for assembly coaxiality errors and angular deviations caused by the deformation of the crossbeam by allowing a small deflection of the pin axis, thereby eliminating the radial lateral force borne by the piston rod.

10. A method for configuring a hydraulic balancing mechanism for a gantry milling machine beam, characterized in that, Includes the following steps: S1. Determine the design input parameters: obtain the total weight G of the moving parts of the crossbeam or ram, the lifting drive direction, the maximum lifting stroke L, and the number and symmetrical arrangement of single-acting hydraulic cylinders. S2. Calculate the load force of a single single-acting hydraulic cylinder: Distribute the total weight of the moving parts to each single-acting hydraulic cylinder according to the number of components, and determine the maximum load force Fmax that a single single-acting hydraulic cylinder needs to withstand. S3. Determine the maximum working pressure of the system: Based on Fmax and the preset hydraulic cylinder diameter parameters, calculate the maximum working pressure of the system using the formula Pmax=Fmax / S, where S is the effective working area of ​​the piston. S4. Determine the structural parameters of the single-acting hydraulic cylinder: Based on the constraint that the maximum working pressure of the system does not exceed the preset pressure upper limit, determine the piston diameter D and the piston rod diameter d so that the working pressure of the hydraulic cylinder is in a reasonable range of 7-10MPa under the premise of meeting the load force. S5. Calculate the volume of a single-acting hydraulic cylinder: using the formula ΔV=2π×[(Dd) / 2] 2 ×L calculates the change in stroke volume of a single-acting hydraulic cylinder, where L is the maximum lifting stroke; S6. Determine the accumulator volume: Based on the single-acting hydraulic cylinder volume ΔV and the system working pressure fluctuation range, determine the volume of a single accumulator and the number of parallel accumulators through accumulator volume calculation software or empirical formulas, so that the total accumulator volume meets the flow compensation requirements and redundancy backup requirements for the entire stroke of the beam lifting.

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