66 results about "Limit pressure" patented technology

A method for determining a p-V characteristic of at least one wheel brake cylinder of a brake system of a vehicle. The method includes: increasing a pressure prevailing in the wheel brake cylinder during a measurement time interval, wherein a volume variable that reflects a present volume in the wheel brake cylinder, and a pressure variable that reflects a present pressure in the wheel brake cylinder, are determined at least once during the measurement time interval, and setting the p-V characteristic of the wheel brake cylinder taking into consideration the volume variable and the pressure variable. Before the measurement time interval, during a pressure increase interval, a pressure exerted on the closed wheel inlet valve and / or the closed isolating valve is increased with an average pressure build-up gradient greater than or equal to 50 bar / second up to a limit pressure of greater than or equal to 25 bar.

The invention relates to a fault development gas storage operation upper limit pressure determination method considering an overpressure operation condition. The method comprises the following steps: 1, establishing a gas storage three-dimensional geomechanical model covering reservoir, cap strata and peripheral faults; 2, carrying out geomechanical simulation; 3, determining the shear failure resistance limit pressure bearing capacity and the tensile failure resistance limit pressure bearing capacity of the cover layer; 4, designing a gas logging permeability test experiment of the cover rock under different static confining pressures; 5, determining the gas breakthrough pressure of the cover rock under different pressure increasing coefficients; 6, determining the sealing limit pressure-bearing capacity of the capillary tube of the cover layer; 7, determining the anti-slip activation limit pressure bearing capacity and the anti-expansion fracture limit pressure bearing capacity of the fault; and 8, the operation upper limit pressure of the gas storage is determined. According to the method, the four-dimensional geomechanical model is established, the stress path of the reservoir building and gas injection process of the oil and gas reservoir is obtained through numerical simulation, and the dynamic horizontal principal stress of the reservoir building and gas injection process is calculated and determined by taking the determined reservoir top horizontal principal stress as the reference.

PROBLEM: To avoid the pressure of the actuator oil passage from becoming higher or equal to the upper limit pressure that is set depending on an individual option hydraulic actuator, during non-operation of an option operation lever, even if the actuator oil passage connected to the option hydraulic actuator is not provided with a variable relief valve. SOLUTION: It is configured to release the pressure of the actuator oil passage into the oil tank via the option control valve, the load pressure introducing oil passage, the variable relief valve, by switching the option control valve to load pressure relief positions at which the pressure of the actuator oil passage is allowed to flow into the load pressure introducing oil passage, when the pressure of the actuator oil passages exceeds the upper limit pressure during non-operation of the option operation lever; as well as by controlling the relief setting pressure of the variable relief valve connected to the load pressure introducing oil passage so as to be less than or equal to the upper limit pressure.

The utility model discloses a plug valve capable of adjusting a plug cock up and down, relates to the technical field of plug valves, and can improve the sealing performance by adjusting the up-down position of the plug cock to adapt to different working conditions. A bottom hole is formed in the bottom of the valve body, a cover plate covers the bottom hole, an adjusting bolt is arranged on the cover plate in a threaded mode, the adjusting bolt penetrates to the flow channel cavity from the outside of the cover plate, a lifting cushion block is further movably installed on the cover plate, and the lifting cushion block abuts against the top end of the adjusting bolt and abuts against the bottom of the cock. The valve rod is sleeved with a limiting gland, the limiting gland is in threaded connection with the valve deck through an adjusting stud, the valve rod is provided with a step, and the limiting gland abuts against the step in a matched mode. When the adjusting bolt is rotated, the adjusting bolt moves up and down in the cover plate, the lifting cushion block abuts against the top end of the adjusting bolt and abuts against the bottom of the plug cock, and therefore the plug cock can be driven to move up and down in the valve body, the up-down position of the plug cock is adjusted, and the sealing performance is improved.

The invention discloses a motor over-temperature control method and system of a brake-by-wire system, and computer equipment, and the method comprises the steps: detecting the temperature, power and loop pressure state of a motor in real time, and obtaining the over-temperature of the motor according to the target request pressure and the working state of the motor; when the motor is normal and the pressure of the pressure cylinder reaches the target pressure, the pressure cylinder isolation valve is actively closed, and the motor is controlled to withdraw and release the pressure; when the motor is overheated to reduce power or the pressure of the main cylinder exceeds the limit pressure building capacity of the motor, the main cylinder loop is switched to supply pressure; according to the scheme, self-adaptive control over the motor load is achieved, overheating degradation caused by long-time high load is avoided, braking continuity and safety in different thermal states are guaranteed, and the system reliability and the braking force upper limit are improved.

The invention relates to the technical field of foundation pit engineering enclosure structure construction, in particular to an enclosure bottom anti-sedimentation limiting device, an inner cavity of a limiting bearing plate is provided with an anti-sedimentation assembly, the anti-sedimentation assembly comprises a positive and negative screw rod, the positive and negative screw rod is located in the inner cavity of the limiting bearing plate, and the surface of the positive and negative screw rod is fixedly sleeved with a rotating disc; an operation notch facilitating operation is formed in the top of the limiting pressure-bearing plate, threaded sleeves are arranged on the positive and negative threaded surfaces of the positive and negative threaded rod in a threaded and sleeving mode, push plates are fixedly arranged on the surfaces of the threaded sleeves in a sleeving mode, guide blocks are arranged at the two ends of the top of each push plate, guide grooves matched with the guide blocks are formed in the two ends of the top of an inner cavity of the limiting pressure-bearing plate, and positioning rods are arranged on the outer sides of the push plates. The push plate is driven by the positive and negative screws to drive the positioning rod to perform bidirectional displacement adjustment, multi-point active limiting of the bottom of the enclosure structure is achieved, differential settlement and horizontal displacement are effectively controlled, and the device has the advantages of being capable of being actively adjusted, convenient to install and high in adaptability.

The embodiment of the invention discloses a design method and device of an axial flow fan blade, a medium and an axial flow fan. The design method of the axial flow fan blade can comprise the steps that an initial blade model of the axial flow fan blade is obtained; based on the limit pressure difference of the suction surface and the pressure surface of the axial flow fan blade corresponding to the target noise and the limit turbulent flow separation point of the axial flow fan blade; designing an axial stacking line of the axial flow fan blade according to the limit pressure difference, and designing a circumferential stacking line of the axial flow fan blade according to the limit turbulence separation point; and updating the initial blade model by using the axial stacking line and the circumferential stacking line to obtain a target blade model, so that the noise of the axial flow fan blade corresponding to the target blade model during working is smaller than the target noise.

The invention relates to the technical field of hydrogen storage cylinder pressure relief and detection, and particularly discloses an explosion-proof gas storage cylinder ultimate pressure detection device and a pressure relief structure thereof. When the pressure in the hydrogen storage cylinder abnormally rises and reaches a critical value, the pressure relief mechanism is automatically started, and high-pressure hydrogen is guided to the limit relief connector. In the process, the pressure reducing mechanism intervenes the high-speed hydrogen flow, and the flow speed and pressure of the high-speed hydrogen flow are effectively reduced. When the pressure relief mechanism is started, the pre-fire-extinguishing mechanism is driven to perform pre-fire-extinguishing on hydrogen subjected to pressure reduction by the pressure reduction mechanism, so that controllable and ordered release of high-pressure hydrogen is realized, violent impact caused by instantaneous sudden drop of pressure is avoided, and a fire extinguishing agent can be early intervened in a release path; combustion reaction possibly caused by static electricity or an external fire source is actively inhibited, so that the risk of secondary burning explosion in the discharging process is fundamentally eradicated, and safe jump from passive pressure relief to active explosion suppression is achieved.

The utility model relates to a kind of multi-station detection devices, including workbench, first support, second support, limiting piece, pressure element, first detection piece;The first support is set on the workbench;The second support is set on the workbench and the second support is located in the side of the first support;The limiting piece is set on the second support;The pressure element is set on the second support;The pressure element is pressed tightly the limiting piece in acting end;The first detection piece is set on the workbench;Guiding rod is provided on the first support;The first detection piece corresponds with the guiding rod.Solved the positioning difference of traditional detection device, adaptation low, need multi-station adjustable limit pressure detection device.

A pumping system includes a plurality of pumps, each having an inlet and an outlet. The inlet is fluidly coupled to a hydraulic fluid reservoir. The outlet is fluidly coupled to a control pod having a valve and a pair of sensors monitoring upstream and downstream pressures of the valve. The control pod is fluidly coupled to a subsea blowout preventer. A first motor is coupled to a first pump of the plurality of pumps and sets the first pump at a first predetermined pressure. A controller is coupled to and configured to control the first motor, thereby controlling the first pump. The pumping system is configured to: engage and disengage each pump independently; and de-stroke each pump to limit pressure to the valve, when a predetermined pressure for each pump is attained, thereby reducing fluid hammer at the control pod.

The invention discloses an in-service welding burn-through prediction method and system based on radial stress, and belongs to the field of pipeline maintenance and repair. In-service welding stress distribution characteristics and a burn-through mechanism are analyzed, it is determined that in-pipe radial pressure starts to be larger than the yield strength of the inner wall of the pipeline as a burn-through critical condition, the pipeline can be burnt through only after the inner wall loses efficacy, and the radial stress value of the inner wall of the pipeline in the in-service welding process is approximately equal to the pressure of a medium in the pipeline; scientific theoretical support is provided for criterion formulation, the prediction method is further simplified on the basis, the relation between the in-pipe medium pressure and the pipeline inner wall yield strength is simplified into a design pressure-critical inner wall peak temperature relation table on the basis of the limiting working condition, a direct judgment method is established, and the prediction accuracy is improved. Engineers can judge whether the burn-through problem needs to be considered or not during construction by directly looking up the table, the critical inner wall peak temperature or the critical burn-through ultimate pressure when burn-through does not occur under the specific working condition is given, and the simplified method has better engineering application value.

The utility model relates to the technical field of air compressor accessories, and discloses a pressure-adjustable air compressor valve which comprises a valve body, an air inlet is formed in the valve body, an air outlet is formed in the valve body, an adjusting mechanism is arranged in the valve body, and a protection mechanism is arranged outside the valve body. By arranging a square rod and a top plate, a rotating disc can be conveniently rotated, so that deformation of a spring caused by rotation of the rotating disc is avoided, by rotating a hand wheel, a pressure adjusting sleeve can be conveniently lifted, so that upper limit pressure and lower limit pressure can be conveniently adjusted according to requirements, and by arranging an extension block and a positioning column, the top plate can be conveniently positioned; and under the cooperation of a nut and a second limiting block, limiting work can be conveniently conducted on a top plate, downward movement of a lifting plate is facilitated by rotating a threaded rod, and under the cooperation of an arc-shaped protection plate, shielding of a hand wheel is facilitated, so that rotation of the hand wheel due to mistaken touch is avoided.

The utility model relates to valve technical field, and disclose a kind of pressure reducing type backflow preventer, including valve body, drain valve seat, drain valve flap, long valve rod, fixed screw, valve cover, the valve body is provided with drain valve seat, the drain valve seat inside is provided with drain valve flap, the drain valve flap upper side is provided with long valve rod, the valve body upper side is provided with valve cover.The pressure reducing type backflow preventer, by first valve seat, first valve flap, first main valve rod, first spring seat, first spring and first hexagon nut are assembled to it before being loaded into valve body, subsequent and present an integral loading into valve body inside, greatly shorten assembly time, also suitable for the assembly in the valve body of smaller volume, the unique flow passage design of two-stage check valve, small flow resistance, open and close speed is fast, can effectively prevent the damage of sudden back pressure rise to valve and pipeline, limit pressure water backflow or siphon backflow, with mute function, effectively prolong the service life of valve.

The utility model relates to a kind of high-reliability pressure-limited pressure cooker exhaust structure, including pressure-limiting valve and exhaust pipe, the outer thread is only set in the gas outlet end outer periphery of exhaust pipe, the small diameter size of the outer thread is greater than the non-gas outlet end size of exhaust pipe, the pressure-limiting valve includes coaxially arranged inner valve body and outer valve body, the outer valve body is fixedly sleeved in the outer periphery of the inner valve body, the inside of the inner valve body is formed with accommodating cavity, the bottom of the inner valve body is provided with the opening being communicated with accommodating cavity, the opening is fixedly provided with insert, the center of the insert is provided with the internal thread being matched with the outer thread, valve tip is fixedly arranged in the accommodating cavity, the gas outlet end of exhaust pipe is inserted into accommodating cavity. After using such scheme, the risk that pressure-limiting valve is accidentally dropped due to snap spring fatigue or improper operation is fundamentally eliminated by using thread structure, and the safety and connection reliability are greatly improved.

The application discloses a long-term service performance evaluation method of a flexible composite pipe, and comprises the following steps: obtaining the limit pressure of the flexible composite pipe at the current service time and the limit time required to reach the limit pressure; obtaining the safe working pressure of the flexible composite pipe under the specific working condition environment at the long-term service time and the residual service time; establishing a linear relationship between the working pressure and the service time through the above parameters; selecting at least one test time between the limit time and the residual service time, and obtaining the maximum working pressure at the test time according to the linear relationship; loading the test time and the maximum working pressure at the test time on the flexible composite pipe to perform a survival test, if the survival test is passed, the flexible composite pipe meets the long-term service requirement, otherwise, the flexible composite pipe does not meet the long-term service requirement. The method reduces the workload, is high in operability, and can quickly respond to the long-term service performance of the flexible composite pipe under different working condition conditions in an oil and gas field.

This application discloses a limiting locking mechanism and an aircraft, relating to the field of limiting structure technology. The limiting locking mechanism includes a limiting pressure bar, a pre-tightening device, and a pressure-bearing structure. One end of the limiting pressure bar constitutes an actuating part, and the other end constitutes a limiting part. The limiting pressure bar rotates around a first horizontal axis. The distance between the first horizontal axis and the actuating part is greater than the distance between the first horizontal axis and the limiting part. The pre-tightening device applies an upward force to the actuating part to drive the limiting part downward to the limiting area. The pressure-bearing structure moves along a first horizontal path to the limiting area to push the limiting part to overcome the force of the pre-tightening device and rotate upward. The first horizontal path is parallel to the first horizontal axis. The pressure-bearing structure of this solution can overcome the pre-tightening force of the limiting pressure bar and enter the pre-tightening area with a relatively small driving force, reducing the requirements for the power source. Moreover, the limiting pressure bar can apply a large compressive force to the pressure-bearing structure after it enters the pre-tightening area, ensuring the stability of the limiting constraint.

A vacuum pump (10) with a housing (12) that defines a working chamber (14) and with a rotor (24) rotatably mounted in the housing (12) about a rotor axis (22) and carrying at least one vane (26) that is movably mounted in the radial direction, wherein the vane (26) has a transverse extension (d1) and divides the working chamber (14) into a suction side (34) with a suction inlet (32) and a pressure side (28) with a pressure outlet (33), characterized in that the housing (12) has at least one oil outlet (36, 52) opening into the working chamber (14), which is separate from the pressure outlet (33) and is closed by a pressure relief valve (38, 46), wherein the pressure relief valve (38, 46) assumes an open position when a limit pressure prevailing in the working chamber (14) above a nominal pressure is exceeded, and that the transverse extension (d1) of the wing (26) is so large that when the wing passes the oil outlet (36, 52), the oil outlet is closed by the wing (26),so that there is no fluid connection between the suction side (34) and the pressure side (28) via the oil outlet (36, 52).

The utility model discloses a rapid temperature and pressure joint for an experiment, and aims to solve the problem that the conventional joint is inconvenient to disassemble and assemble. According to the technical scheme, the connector is characterized by comprising a connector body, the tail of the connector body is provided with a head connector, the head connector is connected with a high-pressure and low-pressure filling opening of the automobile air conditioner, the side wall of the connector body is provided with a pressure connector, and the pressure connector is provided with a pressure sensor communicated with the pressure connector; the pressure sensor is provided with a pressure measuring pipe connector detachably connected with the pressure connector, the inner wall of the pressure connector is fixedly connected with a hollow cylindrical sealing clamping piece, and the diameter of the pressure measuring pipe connector is smaller than the diameter of the inner ring of the sealing clamping piece. A limiting device used for limiting the pressure measuring pipe connector is arranged in the pressure connector. According to the utility model, the plugging installation of the pressure measuring pipe joint is realized through arranging the sealing clamping piece and the limiting device, so that the installation of the pressure sensor is more convenient.

The application relates to the field of regulating valve testing, and discloses a regulating valve pressure measuring equipment for an air conditioner dehumidifier, which comprises a workbench and three pressure measuring box bodies arranged on the top of the workbench, the three pressure measuring box bodies are a high-temperature box, a low-temperature box and a normal-temperature box, pressure measuring mechanisms are arranged in the high-temperature box, the low-temperature box and the normal-temperature box, the pressure measuring mechanism comprises a storage structure arranged at the bottom of the pressure measuring box body and used for placing a regulating valve, the inner walls of the pressure measuring box body are provided with sealing structures used for sealing the end of the regulating valve, the sealing structure comprises a sealing head, the sealing head can move in the pressure measuring box body, the end of the regulating valve placed on the storage structure can be sealed, and a first pipeline interface used for connecting a test pipeline is arranged on one side of the pressure measuring box body. Double measurement is used for verification, so that the test result is more accurate. The limit pressure value when the regulating valve is deformed or damaged can be measured by continuously filling gas, and the limit pressure resistance of the regulating valve can be known.

The application provides a method and device for calculating the working gas amount of an underground gas storage which is increased due to an increase in the upper limit pressure, the method comprising: splitting the underground gas storage into a plurality of gas storage units with each gas injection well as the center of each gas storage unit; simulating the operation of each gas injection well in each gas storage unit to obtain the bottom hole pressure resistance value of each gas injection well; determining the stratum radius influenced by each gas injection well in each gas storage unit according to the bottom hole pressure resistance value of each gas injection well, the operation parameters of the underground gas storage and the target upper limit pressure of the underground gas storage; determining the increased working gas amount of each gas storage unit and the increased working gas amount of the underground gas storage according to the stratum radius and the target upper limit pressure. By splitting into the gas storage units with the gas injection well as the center, the stratum radius influenced by each gas injection well is determined independently, the problem of pressure imbalance does not need to be solved, and the working gas amount of the underground gas storage which is increased due to an increase in the upper limit pressure can be accurately determined.

The present invention discloses a pliers automatic handle sleeve machine, including a limit pressure plate, a cylinder, a turntable and a chassis, wherein a servo motor is installed inside the chassis, a turntable is installed at the output end of the servo motor, and a fixed arm is evenly welded on the top of the turntable, and a main shaft is welded at the middle position of the top of the turntable, a cylinder is evenly fixed on the main shaft, and a support plate is welded on the top of the fixed arm. The present invention is equipped with a servo motor, a silencer shell, a turntable, a guide block and a guide groove, so that when the device is used, the servo motor can be started to drive the turntable to rotate, so as to realize the processing operations of different stations, and when the turntable moves, the guide block at its bottom will slide inside the guide groove, and then the sliding connection structure of the guide block and the guide groove is used to improve the stability of the turntable during operation and avoid rollover, and at the same time, the silencer shell and the vacuum reserved cavity and sound-absorbing mineral wool arranged thereon are used to achieve a better noise reduction function.

The invention belongs to the technical field of nuclear power, and particularly relates to a method and device for determining the limit pressure-bearing performance of a pit defect of a heat transfer tube of a steam generator. According to the method for determining the limit pressure-bearing performance of the pit defect of the heat transfer tube of the steam generator, the maximum pressure allowed to be borne by the heat transfer tube with the pit defect can be rapidly, reasonably and conservatively calculated, and rapid evaluation can be provided for state monitoring and operation evaluation of the nuclear power steam generator. By means of the method, the ultimate bursting pressure calculation method for the pit type defect of the heat transfer pipe can be optimized, and the bursting pressure of the heat transfer pipe with the pit defect can be represented more accurately. Therefore, the influence of the pit defect on the bearing capacity of the heat transfer tube is effectively identified in heat transfer tube integrity evaluation, and the failure risk of the heat transfer tube is reduced.

The utility model relates to a motor shell convenient for storing a pipeline, and relates to the technical field of motor shells, the motor shell comprises a shell sleeve, the shell sleeve is provided with a threading through hole for a wire to pass through, and the shell sleeve is provided with a limiting pressing piece for fixing the wire at the threading through hole. The electric wire penetrating out of the threading through hole is limited and fixed through the limiting pressing piece, so that the electric wire can be conveniently stored.

The utility model relates to the technical field of corrugated pipe detection, in particular to a corrugated pipe compressive strength detection device which comprises a base, a supporting frame, a pressure applying rod, a pressure applying plate, a pressure sensor, a limiting pressure cover, a limiting supporting plate and a measuring mechanism, the supporting frame is fixedly arranged on the upper surface of the base, and the pressure applying rod is fixedly arranged at the top of the supporting frame; the pressure applying plate is fixedly arranged at the telescopic end of the pressure applying rod, and the pressure sensor is fixedly arranged at the bottom of the pressure applying plate. The problem that the corrugated pipe pops up and falls off due to uneven stress and the elasticity of the corrugated pipe in the pressing process is avoided, the elastic deformation quantity of the corrugated pipe when the corrugated pipe is pressed to be damaged is effectively measured, the performance of the corrugated pipe can be known conveniently, large elasticity can be generated when the corrugated pipe is broken, and the reliability of the corrugated pipe is improved. The measuring mechanism can be quickly locked when the measuring mechanism is quickly accelerated under the influence of elastic force, so that the accuracy of a measuring result is ensured.

The application relates to the technical field of hydrogen storage cylinder pressure relief and detection, and particularly discloses an anti-explosion gas storage cylinder limit pressure detection device and a pressure relief structure thereof. When the pressure in the hydrogen storage cylinder abnormally rises and reaches a critical value, the pressure relief mechanism is automatically started to guide the high-pressure hydrogen gas to a limit relief joint. In the process, the pressure relief mechanism intervenes in the high-speed hydrogen gas flow to effectively reduce the flow rate and pressure of the hydrogen gas. When the pressure relief mechanism is started, the pre-fire extinguishing mechanism is driven to pre-extinguish the hydrogen gas after the pressure relief of the pressure relief mechanism, controllable and orderly relief of the high-pressure hydrogen gas is realized, violent impact caused by instantaneous pressure drop is avoided, and the early intervention of the fire extinguishing agent in the relief path can actively inhibit the combustion reaction caused by static electricity or external fire sources, so that the secondary explosion risk in the relief process is fundamentally eliminated, and the safety is greatly improved from passive pressure relief to active explosion suppression.

A disclosed sampling device for mine gas concentration detection comprises a sampling sleeve and a first piston rod, a first spring is arranged between the first piston rod and the sampling sleeve, a limiting assembly is arranged at the top of the sampling sleeve, and a movably connected second piston rod is arranged in the first piston rod; the first piston rod is movably installed in the sampling sleeve, the limiting assembly comprises a limiting pressing rod, a rotating shaft, a torsion spring and a sealing cover, the limiting assembly is installed at the top of the sampling sleeve and used for limiting movement of the first piston rod, an air inlet nozzle is arranged at the bottom of the sampling sleeve, and an exhaust nozzle communicated with the air inlet nozzle is arranged at the bottom of the side end face of the sampling sleeve. A movably-connected valve rod is arranged at the bottom of the side end face of the sampling sleeve. The device has the advantages of being simple in structure, convenient to operate and capable of completing sampling and pre-exhausting operation with one hand, and the problems that an existing device is complex in valve, inconvenient to operate, prone to misoperation and capable of limiting field adjustment through double-hand operation are solved.

Adjustable vane pump (10) with a suction side (46) and a discharge side (21), with a housing (12) and with a rotor (18) rotatably mounted in the housing (12) about a rotor axis (16) and carrying at least one vane (22) movable in the radial direction, wherein the housing (12) comprises a housing base (30) and a housing cover (26) transversely to the rotor axis (16), and wherein an adjustable cage (32) is provided in the housing (12) between the housing base and the housing cover, surrounding the rotor (18) together with the vane (22) and adjustable transversely to the rotor axis (18), wherein the housing (12) and the adjustable cage (32) define a pressure chamber (38) fluidly connected to the discharge side (21), wherein a return element (36) is provided which forces the adjustable cage (32) into a basic end position, and wherein the adjustable cage (32) is deflected from the basic position when a limit operating quantity designed as limit pressure is exceeded in the pressure chamber (38),characterized in that the rotor is driven by an electric motor designed as a rotor drive (19), wherein the rotor drive (19) is operated in the nominal speed range (a) both when the adjustable cage (32) is in the basic end position and when the adjustable cage (32) is deflected from the basic end position, and in that adjustment of the adjustable cage (32) takes place directly depending on the pressure-side pump pressure, wherein the pressure side (21) is fluidically directly connected to the pressure chamber (38).

The utility model relates to the technical field of roots pumps, and discloses a roots pump capable of reducing pressure difference, which is characterized by comprising a front gear box and a pump shell, a front partition plate is hermetically connected between the front gear box and the pump shell, a front oil cavity is formed in the front gear box, a vacuum cavity is formed in the pump shell and comprises an air outlet, and the air outlet is communicated with the front oil cavity. In the operation process of the front-stage pump, the pressure in the vacuum cavity is quickly reduced, and the pressure in the front oil cavity is also reduced under the communication action of the first through hole and the second through hole, so that the pressure difference between the vacuum cavity and the front oil cavity is reduced, the situation that gas in the front cavity leaks towards the vacuum cavity is prevented, and the limit pressure of the vacuum cavity is prevented from being influenced; a first pressure difference one-way valve is arranged in the second through hole, when the vacuum degree in the front oil cavity reaches a certain value, a gas path between the first through hole and the second through hole can be cut off through the first pressure difference one-way valve, and oil gas in the front oil cavity is prevented from entering one side of the gas outlet.

The utility model discloses a multipurpose test fixture for a leaf spring in a locomotive brake system, which comprises a bottom plate, a supporting assembly for supporting the middle of a leaf spring body is arranged in the middle of the upper end face of the bottom plate, and a supporting and pressing assembly for supporting and pressing the right end of the leaf spring body is arranged at the right end of the upper end face of the bottom plate. The left end of the upper end face of the bottom plate is detachably provided with a limiting crimping assembly which is used for pressing the left end of the leaf spring body downwards and keeping a certain deformation distance. The device further comprises a rolling shaft assembly which is installed on an installation seat of the leaf spring body during testing. According to the utility model, three performance tests of elasticity modulus, deformation quantity and fatigue resistance can be carried out on the leaf spring, and multiple functions are realized, so that the types of clamps used in leaf spring performance tests are effectively reduced, and the cost input cost of the clamps is greatly reduced; after the leaf spring is fixed on the clamp, three performance tests of elasticity modulus, deformation quantity and fatigue resistance can be carried out in sequence, so that the labor cost is effectively reduced, the test efficiency is remarkably improved, and the requirement of large-batch delivery of the leaf spring can be met.