121results about How to "Increase the effective stroke" patented technology

The invention discloses a single-piston-rod damper and belongs to the technical field of structural vibration control devices. The single-piston-rod damper comprises a cylinder which is divided into a working chamber and a compensation chamber, the working chamber and the compensation chamber are separated from each other through a floating piston which is sealed together with the cylinder, and the working chamber is filled with shear thickening fluid (STF); one end, with the tip being connected with a working piston, of the piston rod is arranged in the working chamber in the cylinder, and the other end of the piston rod is arranged outside the cylinder and connected with an upper connecting part; and an elastic part is arranged in the compensation chamber, one end of the elastic part is connected with the floating piston, and the other end of the elastic part is connected to a rubber piston arranged at the end of the cylinder. When the shearing rate is high and the instantaneous vibration velocity in the working chamber is high, shear thickening of the STF occurs to generate damping force, so that the anti-impact vibration-reduction effect of engineering structures is achieved; and when the shearing rate is low and the instantaneous vibration velocity in the working chamber is low, the elastic part in the compensation chamber elastically compensates for the initial rigidity of the damper, so that vibration reduction and energy dissipation of the engineering structures are achieved. The single-piston-rod damper is provided with the elastic compensation chamber to provide appropriate compensation rigidity, and the anti-impact vibration-reduction effect of the damper is achieved.

The invention relates to a flat knitting machine bottom plate with motor transmission. At present, the flat knitting machine bottom plate with motor transmission which has a simple structure, a reasonable design and reliable performance does not exist. The flat knitting machine bottom plate with motor transmission comprises a bottom plate body, a left homing triangle plate, a right homing triangle plate, a left needle turning and connecting triangle plate, a right needle turning and connecting triangle plate, a left needle lifting and hanging head triangle plate and a right needle lifting and hanging head triangle plate, and is characterized by also comprising a slide plate motor, a gear, a rack, a sliding plate, a sliding plate guide seat, a needle turning motor, a needle turning cam, a fixed plate, a bearing, a silencing plate, a left fixed column, a right fixed column, a left connecting column, a right connecting column, a left pressure spring, a right pressure spring, a left positioning column, a right positioning column, a left lug, a right lug, a left reset spring and a right reset spring, wherein the left homing triangle plate and the right homing triangle plate are both movably connected to the bottom plate body, a left homing cylindrical sleeve and a right homing cylindrical sleeve respectively arranged on the left homing triangle plate and the right homing triangle plate are respectively arranged in a left chute and a right chute of the sliding plate, and the left needle turning and connecting triangle plate, the right needle turning and connecting triangle plate, the left needle lifting and hanging head triangle plate and the right needle lifting and hanging head triangle plate are all movably connected to the bottom plate body. The flat knitting machine bottom plate with the motor transmission has the advantages of reasonable design, reliable performance, stable transmission and no noise production.

The invention provides a bowed roll block fast replacing device for a rolling mill, which at least comprises a bowed roll block replacing trolley, a lifting platform and a jack, wherein the lifting platform is arranged above the bowed roll block replacing trolley and can make vertical movement relative to the bowed roll block replacing trolley; and the jack is arranged between the bowed roll block replacing trolley and the lifting platform and is used for controlling the lifting platform to ascend or descend. The bowed roll block fast replacing device for a rolling mill has simple structure, is convenient to operate, can realize the fast disassembly or assembly of bowed roll blocks of the rolling mill, greatly improves the operating efficiency, greatly lowers the labor intensity and shortens the equipment maintenance time.

The invention discloses a vertical plate feeding numerical control drill with routing. The vertical plate feeding numerical control drill comprises a rack part, an X-axis part, a Y-axis part, a Z-axis part, a drill box part, an electric box part and an operation panel part, wherein the X-axis part comprises an X-axis transverse beam, a linear guide rail group, a mounting base plate, a gear, a rack, a clamp cylinder, a clamp fixing end, a clamp moving end and a first servo motor; the Y-axis part comprises a transverse beam, a Y-axis linear sliding rail, a second servo motor, a Y-axis lead screw and a Y-axis mounting plate; the Z-axis part comprises a Z-axis mounting plate, a first Z-axis slide block, a routing electric spindle, a Z-axis lead screw, a third servo motor and a fourth servo motor; and the drill box part is horizontally arranged on the Z-axis mounting plate and comprises a vertical drill, a left-right side drill, a top-bottom side drill and a grooving saw. Multifunctional full-numerical control machining is realized on a machine, the efficiency and machining precision are improved, the cost is saved, the drill is particularly suitable for machining individualized products, and the vertical plate feeding mode contributes to chip removal and dust collection.

The invention discloses a k-type disc proportional electromagnet, comprising an armature (2), a push rod (6) and the like, wherein the longitudinal section of the armature (2) is in a k shape, the armature (2) comprises a bottom (21), an annular side wall (20) and an outer ring (25); the end part of the annular side wall (20) is provided with a V-shaped slot (22); the gap between the annular side wall (20) and a magnetic inductive outer shell (9) forms a radial working air gap I (203); the gap between the annular side wall (20) and a magnetic inductive core column (8) forms a radial working air gap II (204); the gap between the outer ring (25) and the magnetic inductive outer shell (9) forms an axial working air gap III (201); the gap between the bottom (21) and the magnetic inductive core column (8) forms an axial working air gap IV (202); and a permanent magnet (4) is arranged between the magnetic inductive core column (8) and the magnetic inductive outer shell (9). The k-type disc proportional electromagnet has the good proportional property and other characteristics.

The present invention relates to one kind of multiple freedom flexible finger, which includes rigid bodies, front coarse rubber pipes and one constraint steel wire inside the wall of the front coarse rubber pipe. The front coarse rubber pipes and the rigid bodies are arranged alternately and connected hermetically, and each pair of one front coarse rubber pipe and one rigid body constitutes one sealed space as the first work cavity. The last rigid body is connected to the end cap through several fine rubber pipes and joints, and the fine rubber pipe and the joint constitute one sealed space as the second work cavity. The first work cavity and the second work cavity are communicated with one air pipe. One back coarse rubber pipe is connected between the last rigid body and the end cap and around the fine rubber pipes, and the back coarse rubber pipe and the fine rubber pipes constitute one space as the third work cavity communicated to atmosphere.

The invention discloses a three-directional mechanical test platform which is of a three-layer structure consisting of an upper bearing plate, a middle bearing plate and a lower bearing plate, wherein X-direction guide tracks are fixedly arranged on two sides of the lower bearing plate in the X-direction; X-direction roller rows are arranged between the middle bearing plate and the lower bearing plate; X-side roller rows are arranged between the middle bearing plate and the X-direction guide tracks; Y-direction guide tracks are fixedly arranged on two sides of the middle bearing plate in the Y-direction; Y-direction roller rows are arranged between the upper bearing plates and the middle bearing plates; Y-side roller rows are arranged between the upper bearing plate and the Y-direction guide tracks; an X loading head is fixedly connected with one side of the middle bearing plate in the X direction; a Y leading head is connected with one side of the upper bearing plate in the Y direction; a decoupling mechanism is arranged between the Y loading head and the upper bearing plate. The three-directional mechanical test platform is large in movement range, high in bearing property and high in experiment precision, three-direction independent loading can be achieved, and one-direction, two-direction and three-direction mechanical testing on an experiment object can be achieved.

The invention discloses a mass center adjustable mixed type vibration damping platform. The mass center adjustable mixed type vibration damping platform comprises top platforms, a bottom platform, vibration damping units and mass center adjusting units, the plurality of vibration damping units are obliquely arranged between the top platforms and the bottom platform, one mass center adjusting unitis arranged between each vibration damping unit and the top platform, and the mass center adjusting units and the vibration damping units are arranged in the same axial direction; the mass center adjusting units comprise upper screw rods, sleeves and connecting rods, through holes are axially formed inside the sleeves, each of the top and the bottom of each through hole is provided with a thread section, the top ends of the upper screws are connected with the top platforms, the bottom ends of the upper screws are in threaded connection with threaded sections at the tops of the through holes, the top ends of the connecting rods are in threaded connection with the threaded sections at the bottoms of the through holes, and the bottom ends of the connecting rods are connected with the vibration damping units. The mass center adjusting units can realize platform mass center adjustment and pose adjustment, so that the mass center of a rigidity center and the mass center of a vibration damping system (including a vibration damping object and a rigid pedestal) are arranged on the same vertical line, and the vibration damping and vibration isolation effect can be greatly enhanced.

The invention discloses an intelligent self-energized absorber which comprises a piston, a piston rod, an outer cylinder and an inner cylinder. The piston rod is fixedly connected to the inner side of the outer cylinder, the piston is located inside the inner cylinder and is capable of moving up and down relative to the inner cylinder, a ball shaft sleeve is embedded on the inner wall of the outer cylinder, the outer wall of the inner cylinder is vertically sleeved with a plurality of piezoelectric rings, and the inner cylinder is then arranged in the ball shaft sleeve of the inner wall of the outer cylinder in a sleeved mode. Electrorheological elastic bodies are filled in the space, located above and below the piston, in the inner cylinder, and the electrorheological elastic bodies, the piezoelectric rings and an electronic control module are electrically connected. Energy generated by vibration of vehicles can be obtained, vehicle vibration information can be collected, the captured energy is used for supplying power for the electrorheological elastic bodies, the vibration information is used for self-adaptive control, different voltages are provided to control the damping of the electrorheological elastic bodies according to different road conditions, the absorber is made to meet the vibration reduction demands of the different road conditions, and therefore the riding comfortableness and the handling stability of vehicles can be improved.

The invention provides a method and system for protecting trains against collisions. According to the method and system, the mode that a train hook energy absorbing structure, an anti-crawling energy absorbing structure and a train deformation energy absorbing structure act successively is not adopted any more, but the anti-crawling energy absorbing structure acts firstly. The length of an energy absorbing pipe in the system for protecting the train against collisions is not limited by the position of train hooks any more, so that the length of the energy absorbing pipe is significantly increased, energy absorbed by the anti-crawling energy absorbing structure can be significantly improved compared with the prior art, more collision kinetic energy can be dissipated when collisions happen, and the safety of the trains is remarkably improved. According to the anti-crawling energy absorbing structure, the energy absorbing ratio is large, the effective travel is long, the influence of load conditions on deformation is small, and the energy absorbing characteristic under different collision conditions is stable. When the energy absorbing structures are triggered by accident, a telescopic drive structure can drive the energy absorbing pipe to retract back into a train body conveniently in a direct one-key control mode, and the effect that the trains can be normally coupled through the train hook is ensured.

A prestretching and energy sucking device for seat belt has said seat belt and two prestretching mechanisms. At elast one contact-type trigger is arranged on the seat frame, and connected to a controller via pull string. When the controller is at the first position, a pin can be inserted in the hole of movable element and the locked seat belt is at normal fixed position. When the controller is at the second position, the pin can be drawn out of the hole and the seat belt is stretched by prestretching mechanism.

The invention discloses a long nut reverse planet pin roller lead screw. The long nut reverse planet pin roller lead screw is characterized in that a lead screw, pin rollers and a retainer are assembled to form a virtual outer thread, the virtual outer thread and a long nut form a pair of virtual threaded transmission pair, the lead screw and the long nut are provided with multi-start triangular threads, the angle between the sides is 90 DEG, gears are arranged at the two ends of the lead screw, the planet pin rollers are dentoform single-start threads with radians (the sides of the planet pin rollers are convex), cylindrical pivots and gears are arranged at the tail ends of the pin rollers, the transmission ratio of the number of the gears at the ends of the pin rollers and the number of the gears at the ends of the lead screw is the same as the ratio of the number of the starts of the threads, the pivots are mounted in the holes of the planet retainer and distributed at equal distance, axial movement and peripheral movement are guaranteed not to happen between the lead screw and the pin rollers, the planet retainer is kept floating on the lead screw, an axial locking nut is fixed with a cotter pin, and the tail end of the long nut is in threaded connection with a feedback connecting shaft. According to the invention, the long nut reverse planet pin roller lead screw is small in size, long in travelling distance and high in strength, can meet the requirements of application working conditions for great thrust and small size, and is suitable for integrated electromechanical actuators.

The invention discloses a truss mechanical arm device for an intelligent production line. The truss mechanical arm device comprises a transverse beam main body, wherein at least two supporting stand columns are mounted at the bottom end of the transverse beam main body; an X-axis horizontal movement unit is arranged along the axial direction of the transverse beam main body; the X-axis horizontalmovement unit is provided with a sliding seat which can move horizontally; a Z-axis movement unit which can move vertically is mounted at the outer side of the sliding seat; the Z-axis movement unit comprises a Z-axis main body; and a grasping mechanism for grasping materials is mounted at the lower end of the Z-axis main body. The truss mechanical arm device provided by the invention aims at replacing manual operation with efficient and rapid automatic machines and conveniently improving the running precision and the running efficiency.

The invention discloses a mechanical linear scanning high-frequency ultrasonic diagnosis device, and relates to medical ultrasonic imaging equipment. The mechanical linear scanning high-frequency ultrasonic diagnosis device comprises a mechanical linear scanning probe and a main machine. The mechanical linear scanning probe scans a check part by dragging a high-frequency transducer to do linear reciprocating motion by a stepping motor in the mechanical linear scanning probe through a transmission mechanism; the main machine comprises a control unit, a digital signal processing circuit, an AD array, a high-voltage pulse generating emitter, a transmit-receive switch, a signal amplification circuit, a power drive of the stepping motor in the probe and the like, the control unit enables all parts to work cooperatively, and interaction with an external device is achieved. The effective stroke is long and can reach 70 percent of the external dimension of the probe.

The invention discloses a bottom uplifting device for a hydraulic support, which comprises a hydraulic support base (10) and a bottom uplifting jack (20), wherein opposite positioning bases (30) are arranged on the inner side of the hydraulic support base (10); fixed blocks (40) locked by a pin shaft are arranged in openings of the positioning bases (30); lugs (20-1) on both sides of the bottom uplifting jack (20) which are in a rectangular shape are positioned in positioning holes formed by the fixed blocks (40) and the positioning bases (30), and are embedded into the positioning holes formed by the fixed blocks (40) and the positioning bases (30); and the fixed blocks (40) are in a trapezoid shape, and the inclined plane of each fixed block faces the bottom uplifting jack (20). The bottom uplifting device has a simple structure and small occupation space, is fixed reliably and convenient to disassemble and assemble, and can meet the using requirement of the hydraulic support in a low coal seam. The invention also discloses the hydraulic support for the bottom uplifting device.

The invention discloses a support enabling switching between the horizontal watching state and the looking-up watching state to be achieved rapidly in a one-step mode and belongs to the technical field of supports for display devices such as flat televisions, flat-panel displayers and computer all-in-one machines. The support enabling switching between the horizontal watching state and the looking-up watching state to be achieved rapidly in the one-step mode is simple in structure, rapid falling and rising can be achieved, and the angles of the display devices can be changed synchronously. The support comprises a four-bar mechanism which is formed by hinging a machine frame base, an upper rocker arm, a connecting arm rod and a lower rocker arm in sequence in an end-to-end mode. The support is characterized by further comprising a telescopic rod, one end of the telescopic rod is hinged to the machine frame base, and the other end of the telescopic rod is hinged to the upper rocker arm or the lower rocker arm.

The invention discloses a special hammer device for a nuclear power station. A direct-current motor is fixedly installed on a base through a motor seat, an output rod of the direct-current motor is provided with a lifting cam, the lifting cam is in fit connection with a roller, a roller shaft of the roller penetrates through one end of an impact rod and is fixed through a bolt, an elastic washer is arranged between the bolt and the impact rod, the lower bottom surface of the base is fixedly connected with one end of a slide sleeve of the impact rod, the other end of the slide sleeve of the impact rod is provided with a cover plate, the impact rod penetrates through a soleplate and the slide sleeve of the impact rod and is vertical to the base, the inner end of the impact rod slide sleeve, which is close to the soleplate, is provided with an impact rod slide sleeve seat, the impact rod is provided with a spring retainer ring, a spring is arranged between the impact rod slide sleeve seat and the spring retainer ring and sleeved on the outer side of the impact rod, and the other end of the impact rod is provided with an impact head. The special hammer device is large in impact energy, long in maximal effective stroke of the cam, high in precision, high in impact frequency and light in weight.

The invention relates to a double-port supporting locking oil cylinder, which comprises a cylinder tube, an upper end cover, a lower end cover and a guide sleeve, wherein the upper end cylinder, the lower end cylinder and the guide sleeve are fixedly arranged on the cylinder tube, the upper end cover, the lower end cover, the guide sleeve and the cylinder tube form an accommodating cavity, a piston rod assembly is arranged in the accommodating cavity, a piston and a locking sleeve sheath the piston rod assembly from top to bottom, the locking sleeve and the cylinder tube are in interference fit, the upper end of the cylinder tube is provided with an upper oil nozzle used for controlling the action of the oil cylinder, and the lower end of the cylinder tube is provided with a lower oil nozzle used for controlling the action of the oil cylinder and unlocking the oil cylinder. The invention also relates to a control method of the double-port supporting locking oil cylinder. The double-port supporting locking oil cylinder has the advantages that an oil path is simplified, the cost is reduced, the reliability and the effective stroke are improved, in addition, the work state of the cylinder tube is better during the unlocking, and abrasion and groove forming cannot easily occur, so that the application is more convenient and reliable.

The invention discloses a rotary tube-plate type heat exchanger which comprises a support column, wherein a motor box, a water inlet box, a heat exchange box and a water outlet box are supported on the support column sequentially from left to right; a drive motor is arranged in the motor box; a rotating shaft bearing is fixed in the inner walls of the motor box and the water inlet box; a water pipe bearing is arranged at the center of the right side wall of the water inlet box; an incoming water pipe penetrates in the water pipe bearing and is fixed between a fixing ring and a switchover waterinlet box; the switchover water inlet box is positioned in the water inlet box; a heat exchange pipe is positioned at the central axis of a heat exchange chamber; a switchover water outlet box is positioned in the water outlet box; a hot water outlet is formed in the bottom of the water outlet box; a return water spiral plate is fixed between heat exchange pipes in the heat exchange box; an exchange water inlet is formed in the right bottom of the heat exchange box; cleaning plates are arranged on two sides of the bottom and top of the heat exchange box. According to the rotary tube-plate type heat exchanger disclosed by the invention, the effective travel and efficiency of heat exchange are improved by use of the rotating return water spiral plates.

The invention discloses embarking equipment. A lifting mechanism is arranged between a lifting platform and a motor vehicle chassis, and the height of the lifting mechanism can be adjusted. An intermediate ladder is arranged between the lifting platform and the chassis, and passengers get on and off a ship through an overturned ladder, the intermediate ladder, the lifting platform and an accommodation ladder. The lifting mechanism adopts a scissor-type lifting mechanism to drive the lifting platform to be adjusted vertically, the take-over height range is larger, and the demand for ro-ro passenger ship take-over in the larger range is met; and meanwhile, the gradient of the accommodation ladder is reduced, so that the ship is safer and more comfortable. Double pitch oil cylinders symmetrically arranged on the two sides are adopted, the pitch smoothness is improved, and safety of the passengers during embarking and disembarking is ensured.

An air-conditioning system (2, 102)is provided for an automobile comprising an interior air-conditioning module (38, 138), which can be connected in a heat-transporting manner to at least two coolant-carrying cooling circuits of the automobile via valves (32, 52, 132, 152)(e.g., controllable or adjustable valves). A controller (64, 164) is also provided that is configured to control the valves (32, 52, 132, 152)in such a manner that those cooling circuits (4, 6, 104, 106)having the higher coolant temperature can be connected in a heat-transporting manner to the interior air-conditioning module. A method is also provided for operating an air-conditioning system (2, 102).

The invention relates to a self-lubrication module of outside loop ball screw and comprises the oil box and material containing the oil. Its features lie in: the self-lubrication module is set on the drainback system of the ball screw and introduces the lubricating oil into the drainback system through the material containing the oil to lubricate the ball directly, so the self-lubrication module has the functions of storing the lubricating oil and saving the space, guarantees the effective stroke of the ball screw, does not waste the lubricating oil by means of directly lubricating the ball, extends the useful life of the outside loop ball screw and increases the partition cycle of adding the lubricating oil.

The invention relates to a gas stove. The gas stove comprises a switch valve, wherein the switch valve comprises a valve body and a valve element rotatably arranged inside the valve body; the valve element is internally provided with an air inlet passage communicated with an air source; an inner ring fire air outlet hole and an outer ring fire air outlet hole penetrating through the side wall are formed in the side wall of the valve element, wherein the valve body, corresponding to the inner ring fire air outlet hole, is provided with an inner ring main air outlet passage and an inner ring fine tuning passage, and the valve body, corresponding to the outer ring fire air outlet hole, is provided with an outer ring main air outlet passage and an outer ring fine tuning passage. During the process of adjusting heat power, after the outer ring main air outlet passage and the outer ring fire air outlet hole are staggered, the outer ring fine tuning passage supplies gas continuously in a certain angle rotation range; after the inner ring main air outlet passage and the inner ring fire air outlet hole are staggered, the inner ring fine tuning passage supplies gas continuously, so that the whole gas flow control curve becomes more gentle, and the heat power of the gas stove is convenient for a user to control accurately.

The invention relates to an oil-well pump capable of direct flushing. The oil-well pump is underground equipment which has the effects of sand prevention, gas prevention, wax prevention and high pump efficiency and is applied to oil exploration industry. In the oil-well pump, an upper plunger piston and a lower plunger piston are equipped with sand prevention slots, can send the sands deposited in the sand prevention slots to the underside of the pump to realize sand prevention. When the plunger pistons fall to a pump-bumping position, oil pipes above and below the pump are in communicated state by a pump cavity, thereby realizing the function of direct flushing. In the oil-well pump, an oil inlet valve can be opened easily under the hydraulic feedback action, thereby increasing the fullness coefficient, reducing the bend of a sucker rod, increasing the effective stroke of the pump, preventing air lock, reducing the fatigue loss of the sucker rod, and the oil-well pump has the functions and the characteristics of gas prevention and high pump efficiency.

The invention belongs to a needle valve injector for a rocket engine, and provides a needle valve injector for a variable thrust rocket engine in order to solve the technical problem of low combustion efficiency caused by poor mixing of propellants in an inner ring and propellants in an outer ring in an existing needle valve injector. The outer wall of the upper section of a needle valve cooperates with the inner wall of a shell so that the needle valve can linearly move relative to the shell, the lower section of the needle valve comprises a conical section and a column section, the small end of the conical section is connected with the column section, a gap is reserved between the outer wall of the tail end of the small end of the conical section and the shell to form an annular oxidant outlet channel, and a fuel outlet channel is formed in the side wall of the column section. A center rod comprises a connecting rod and a flow control boss, the connecting rod is connected with an upper cover, the outer wall of the flow control boss cooperates with the inner wall of the column section so that the needle valve can linearly move relative to the flow control boss, a cooling groove is formed in the side wall of the flow control boss, and the oxidant outlet channel, the fuel outlet channel and the cooling groove all communicate with a combustion chamber.

The invention discloses a novel electromagnetic type vibration isolator with the adjustable negative stiffness. The novel electromagnetic type vibration isolator comprises a stator shell (5), a mover(8) and a positive stiffness component, wherein the positive stiffness component is assembled below the mover (8) and plays a positive stiffness role for the mover (8). The novel electromagnetic typevibration isolator further comprises permanent magnets (9) arranged on the first layer and permanent magnets (9) arranged on the second layer, wherein the permanent magnets (9) are assembled on the outer side wall of the mover (8) and arranged in the longitudinal axis direction of the mover (8). The facing direction of the polarity end face of a permanent magnetic field formed by the permanent magnets (9) arranged on the first layer and the permanent magnets (9) arranged on the second layer is the radial direction, and the permanent magnets (9) arranged on the first layer and the permanent magnets (9) arranged on the second layer are opposite in polarity. The novel electromagnetic type vibration isolator further comprises a coil assembly, wherein the coil assembly is assembled on the innerside wall of the stator shell (5). The coil assembly comprises a coil (3) and coil yokes (10), wherein the winding axis of the coil (3) is the longitudinal axis, and the coil yokes (10) are arrangedat an upper coil opening and a lower coil opening of the coil. The vibration isolator is arranged based on the electromagnetic acting force among the permanent magnets and electromagnets.

The invention provides a large-length-diameter-ratio nut inverted planetary roller screw and belongs to the technical field of planetary roller screws. For the large-length-diameter-ratio nut invertedplanetary roller screw, multiple nuts are connected through screws, so that a stroke of the planetary roller screw can be effectively increased, and the processing difficulty of a large-length-diameter-ratio nut can be lowered; rollers are uniformly distributed in a circumferential direction of a screw, and convex arch-shaped outside threads of the rollers are engaged with triangular inside threads of the nuts and triangular outside threads of the screw in a point contact manner at the same time; and bare shafts at the two ends of the rollers are installed in holes which are distributed on aroller retainer in a circumferential direction at an equal interval respectively, and gears at the two ends of the rollers are engaged with a gear on the screw, and the ratio of tooth number of the gears is equal to the ratio of thread number of the gears. The large-length-diameter-ratio nut inverted planetary roller screw has the advantages of high bearing capability, long service life, good impact resistance and the like, reduces the processing difficulty and improves the production efficiency without processing the large-length-diameter-ratio nut, is suitable for the use working condition with relatively high requirements for some mounting spaces and is liable to realize a design of an electromechanical integrated linear actuator.

The invention discloses a double-layer platform leveling device. The double-layer platform leveling device comprises an upper platform, a lower platform, a jacking mechanism disposed on the lower platform for lifting the upper platform and multiple leveling legs for supporting the lower platform. According to the double-layer platform leveling device provided by the invention, a double-layer platform is adopted to realize the leveling operation, the effective stroke per unit height is increased, the problem that the installation space at the bottom of a special vehicle or a workbench is limited is solved, the occupied space is small, the synchronous jacking of the upper platform and the lower platform in the double-layer platform can ensure the concentricity, the jacking speed is high, theupper platform can achieve the leveling effect through leveling the lower platform, and the stability is good.