Patient auxiliary moving device for emergency department
By introducing motor drive power wheels and buffer stop mechanisms into the patient assisted mobile device of the emergency department, the problem of large resistance to the device in bumpy or uphill sections is solved, and labor-saving implementation and stability are achieved, ensuring the smooth progress of patient examination and treatment.
Patent Information
- Application Number
- CN202510807211.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-17
- Publication Date
- 2025-08-05
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The emergency department patient assisted mobile device has great resistance to the implementation of bumpy or uphill sections and has a heavy weight, which affects the speed of nursing staff and the difficulty of escorting, and delays the examination and treatment time of critically ill patients.
A patient-assisted mobile device including a mobile base, a bed frame, a bidirectional threaded rod, an internal threaded cylinder, a universal wheel and an intelligent drive mobile mechanism is designed to provide power by using a motor-driven power wheel, combining a buffer and a stop mechanism to reduce push resistance and improve stability.
It has achieved labor-saving implementation in bumpy or uphill sections, improved the operation convenience of nursing staff and patient comfort, and reduced the delay in examination and treatment time.
Smart Images

Figure CN120420164A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of auxiliary movement of patients in an emergency department, and in particular to a patient auxiliary movement device used in an emergency department. Background Art
[0002] During emergencies, some patients cannot move on their own. In order to facilitate patient examination and treatment, auxiliary mobility devices can help patients move more effortlessly, reduce the labor intensity of medical staff and reduce the risk of secondary injury to patients. The transfer beds commonly used in emergency departments usually need to have a lifting function to adapt to the docking requirements of beds, operating tables or examination equipment of different heights.
[0003] For example, the patent with publication number CN212490443U discloses a trolley for transferring patients in a ward, including a transfer trolley frame, a transfer trolley mattress provided on the end face of the transfer trolley frame, and frame guardrails symmetrically provided on the end face of the transfer trolley frame and based on the transfer trolley mattress as the axis, frame support rods are vertically installed at the four corners of the bottom of the transfer trolley frame, the bottom of the frame support rod is sleeved inside the mounting sleeve, a shock-absorbing spring is provided inside the mounting sleeve and below the frame support rod, a universal wheel is connected to the bottom of the mounting sleeve by bolts, and a slide groove is provided at the center of the right side wall of the transfer trolley frame, and by arranging a compression structure on the transfer trolley and adding a shock-absorbing structure to the support rod, the transfer trolley can compress the patient's incision and play a buffering and shock-absorbing effect, thereby avoiding the possibility of the patient's incision breaking during the transfer process, causing secondary injury to the patient.
[0004] For example, the patent with publication number CN213047845U discloses a bedridden patient transfer device, which includes a trolley, a combined bed board and a flat slide. The height of the trolley is equal to the height of the bed. Two longitudinal slides are provided on the top plate of the trolley. The combined bed board is located on the top plate. The combined bed board consists of a symmetrical outer bed board and an inner bed board. The bottom surface of the outer bed board and the bottom surface of the inner bed board are respectively provided with guide rails adapted to the slides. The flat slide is an accessory of the trolley and is used in conjunction with the guide rails. A quick docking device is provided between the outer bed board and the inner bed board. The device has a simple structure, quick docking and easy disassembly, which increases the comfort of patients and greatly reduces the labor intensity of medical workers. It has the characteristics of ensuring the safety of patient transfer and improving the efficiency of medical work.
[0005] For example, the patent with publication number CN220632370U discloses an emergency transport cart, which relates to the technical field of emergency transport carts, including: a transport cart body, a fixing mechanism connected to the transport cart body, and an opening and closing mechanism connected to the transport cart body; through the mutual cooperation between the transport cart body, the fixing mechanism and the opening and closing mechanism, the patient's body can be bound by the fixing mechanism without affecting the transportation of the patient during emergency treatment, and the opening and closing mechanism can be used to lift or push the mechanism for transportation according to different situations, thereby preventing the patient from being unable to be transported due to environmental factors such as the layout of the building during transportation. Some examination departments in the hospital are far away from each other, and some examination departments may not be in the same building. When emergency nursing staff push the mobile device to assist in moving patients, the pushing resistance is large on bumpy or uphill sections, and the mobile device is heavy, which affects the pushing speed of the nursing staff, making escort more difficult and delaying the examination and treatment time of some critically ill patients. In addition, the buffering capacity of some mobile devices is weak, and the ups and downs of pushing on bumpy sections are large, which will cause patients to feel dizzy, nauseous, dizzy and other discomforts, which is not conducive to patient treatment.
[0006] In response to the above problems, there is an urgent need to carry out innovative designs based on the existing emergency department patient auxiliary mobility devices. Summary of the Invention
[0007] The purpose of the present invention is to provide a patient-assisting mobility device for the emergency department, so as to solve the problem raised in the above-mentioned background technology that when emergency nursing staff push the mobility device to assist in patient movement, the pushing resistance is large on bumpy or uphill sections, and the mobility device is heavy, which affects the pushing speed of the nursing staff, makes escorting difficult, and delays the examination and treatment time of some critically ill patients.
[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a patient-assisting mobile device for an emergency department, comprising a mobile base and a bed frame mounted on the mobile base for lifting and lowering, a soft cushion being installed on the bed frame, a bidirectional threaded rod being rotatably connected to the mobile base, an external threaded sleeve of the bidirectional threaded rod being provided with an internal threaded cylinder, a mobile frame being fixedly installed on the internal threaded cylinder, a supporting rotating rod being rotatably connected to the mobile frame, the other end of the supporting rotating rod being rotatably connected to the bed frame; four sets of universal wheels are installed on the bottom of the mobile base, and a protective cover is fixedly installed on the mobile base, and intelligent driving and stopping moving mechanisms are provided in the protective cover and the mobile base.
[0009] Preferably, the moving mechanism includes a rectangular frame embedded in the moving base, a guide seat is fixedly installed in the rectangular frame, a lifting frame is longitudinally slidably connected to the guide seat, and a power wheel is rotatably installed in the lifting frame; the power wheel is arranged in the middle position of the four sets of universal wheels, and a plurality of anti-slip grooves are provided at equal angles on the outer circumferential surface of the power wheel.
[0010] Preferably, a motor is fixedly mounted on the lifting frame, and a belt drive is installed between the output end of the motor and the power wheel.
[0011] Preferably, a cylinder is fixedly installed in the protective cover, an output end of the cylinder is connected to a drive frame, and the drive frame is fixedly installed on the lifting frame.
[0012] Preferably, the moving mechanism also includes a cylindrical rod fixedly installed in the rectangular frame, a bogie is provided on the outside of the cylindrical rod, and a stop column is fixed on the side of the bogie close to the ground; two stop columns are symmetrically arranged about the axis of the rectangular frame, and the power wheel is arranged in the middle position of the two stop columns.
[0013] Preferably, a sliding seat is provided on the driving frame for transverse sliding, and a sleeve rod is fixedly installed on the bottom of the sliding seat; a convex rod is fixed on one end of the bogie away from the stop column, and the sleeve rod is rotatably sleeved on the outside of the convex rod.
[0014] Preferably, a guide rod is fixedly mounted on the inner wall of the rectangular frame, a clamping block is slidably engaged with the guide rod, and the clamping block is fixedly mounted on the driving frame.
[0015] Preferably, the protective cover is further provided with a buffer mechanism for supporting and buffering the vibration force pushed by the moving device.
[0016] Preferably, the buffer mechanism includes a support column rotatably installed in the protective cover, the upper end surface of the support column is telescopically connected to the buffer column, and the buffer column is rotatably pressed onto the bottom of the bed frame; the outside of the buffer column and the support column are fixedly sleeved with a disc, and the buffer column and the disc outside the support column are elastically connected with a buffer spring, and the buffer spring is sleeved on the outside of the buffer column.
[0017] Preferably, the rotating end of the support column is connected to a gear along the axial direction, and the bottom of the gear is meshed with a rack; the rack is fixedly connected to a lifting transmission frame, and the lifting transmission frame is fixedly connected to the sliding seat.
[0018] Compared with the existing technology, the beneficial effect of the present invention is that the patient-assisted mobile device used in the emergency department has four universal wheels at the bottom of the mobile base that roll accordingly during the pushing process, and the power wheels are rotated by electric drive to assist in pushing the mobile device. Medical staff only need to control the pushing direction, and the pushing is more labor-saving.
[0019] Furthermore, the protective cover and the mobile base are provided with a mobile mechanism with intelligent drive and stop, which can control the autonomous rolling of the power wheel through the motor and belt transmission. At this time, the stop column moves away from the ground, and the power wheel provides power for the mobile device to push, making the pushing more labor-saving.
[0020] When the mobile device stops, the power wheel is controlled to move upward. At this time, the stop column moves downward under the transmission action of the sliding seat, the sleeve rod and the protruding rod. The stop column is in contact with the ground, which can increase the friction between the mobile device and the ground, thereby keeping the mobile device stationary on the ground so that the patient can complete the examination stably. Medical staff do not need to control the brake structure on the universal wheel to stabilize the mobile device during operation, and operation is more convenient.
[0021] Furthermore, the protective cover is also provided with a buffer mechanism that supports and buffers the vibration force of the moving device. When the power wheel is controlled to move in contact with the ground to provide power for the moving device, the support column and the buffer column in the buffer mechanism are rotated upward and pressed against the bottom of the bed frame. During the pushing process, the elastic buffering between the support column and the buffer column can maintain the stability of the bed frame and the patient's movement, thereby improving the comfort of the patient's pushing.
[0022] When the power wheel is controlled to move upward and the stop column moves downward, the support column and the buffer column are driven to rotate downward away from the bed frame. At this time, the bottom of the bed frame is supported only by the support rotating rod. Controlling the rotation of the support rotating rod can control the lifting and movement of the bed frame within a larger range, so that the mobile device can adapt to different patients and examination equipment. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is a schematic diagram of the cushion structure of the present invention.
[0024] Figure 2 It is a schematic diagram of the bed frame structure of the present invention.
[0025] Figure 3 This is a structural schematic diagram of the mobile base of the present invention.
[0026] Figure 4 It is a schematic diagram of the cross-sectional structure of the protective cover of the present invention.
[0027] Figure 5 It is a schematic diagram of the rectangular frame structure of the present invention.
[0028] Figure 6 This is a schematic diagram of the power wheel structure of the present invention.
[0029] Figure 7 It is a schematic structural diagram of the stop column of the present invention.
[0030] Figure 8 It is a schematic diagram of the convex rod structure of the present invention.
[0031] Figure 9 This is a schematic diagram of the buffer column structure of the present invention.
[0032] Figure 10 Schematic diagram of the gear structure of the present invention.
[0033] In the figure: 1. movable base; 2. bed frame; 3. cushion; 4. two-way threaded rod; 5. internal threaded cylinder; 6. movable frame; 7. supporting rotating rod; 8. universal wheel; 9. protective cover; 91. rectangular frame; 92. guide seat; 93. lifting frame; 94. power wheel; 941. anti-skid groove; 95. motor; 96. belt drive; 97. cylinder; 98. driving frame; 10. cylindrical rod; 101. sliding seat; 102. sleeve rod; 103. protruding rod; 104. guide rod; 105. block; 11. bogie; 12. stop column; 13. support column; 131. gear; 132. rack; 133. lifting transmission frame; 14. buffer column; 15. disc; 16. buffer spring. DETAILED DESCRIPTION
[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0035] Example 1: Please refer to Figure 1-Figure 3 The present invention provides the following technical solutions: a patient auxiliary mobile device for an emergency department, comprising a mobile base 1 and a bed frame 2 mounted on the mobile base 1 for lifting and lowering, a soft cushion 3 installed on the bed frame 2, a bidirectional threaded rod 4 rotatably connected to the mobile base 1, an external threaded sleeve of the bidirectional threaded rod 4 is provided with an internal threaded cylinder 5, a mobile frame 6 is fixedly mounted on the internal threaded cylinder 5, a supporting rotating rod 7 is rotatably connected to the mobile frame 6, and the other end of the supporting rotating rod 7 is rotatably connected to the bed frame 2; four sets of universal wheels 8 are installed at the bottom of the mobile base 1, and a protective cover 9 is fixedly installed on the mobile base 1, and an intelligent driving and stopping moving mechanism is provided in the protective cover 9 and the mobile base 1.
[0036] See also Figure 4-Figure 7 The moving mechanism includes a rectangular frame 91 embedded in the moving base 1, a guide seat 92 is fixedly installed in the rectangular frame 91, a lifting frame 93 is longitudinally slidably connected to the guide seat 92, and a power wheel 94 is rotatably installed in the lifting frame 93; the power wheel 94 is arranged in the middle position of the four sets of universal wheels 8, and a plurality of anti-slip grooves 941 are opened at equal angles on the outer circumferential surface of the power wheel 94.
[0037] See also Figure 4-Figure 7A motor 95 is fixedly mounted on the lifting frame 93, and a belt transmission 96 is installed between the output end of the motor 95 and the power wheel 94. The belt transmission 96 is provided with pulleys corresponding to the output end of the motor 95 and the rotating end of the power wheel 94. A belt is installed between the two sets of pulleys, so that the power output by the motor 95 can be transmitted to the power wheel 94 to control the rolling of the power wheel 94.
[0038] See also Figure 4-Figure 7 A cylinder 97 is fixedly installed in the protective cover 9, and the output end of the cylinder 97 is connected to a driving frame 98, which is fixedly installed on the lifting frame 93.
[0039] See also Figure 5-Figure 8 The moving mechanism also includes a cylindrical rod 10 fixedly installed in the rectangular frame 91, and a bogie 11 is provided on the outside of the cylindrical rod 10 for rotation. A stop column 12 is fixed on the side of the bogie 11 close to the ground; two stop columns 12 are symmetrically arranged about the central axis of the rectangular frame 91, and the power wheel 94 is arranged in the middle position of the two stop columns 12.
[0040] See also Figure 5-Figure 8 A sliding seat 101 is mounted on the drive frame 98 for transverse sliding movement. A sleeve rod 102 is fixedly mounted on the bottom of the sliding seat 101. A protruding rod 103 is fixed to the end of the bogie 11 away from the stop post 12. The sleeve rod 102 is rotatably mounted on the outside of the protruding rod 103. A guide rod 104 is fixedly mounted on the inner wall of the rectangular frame 91. A clamping block 105 is slidably engaged with the guide rod 104. The clamping block 105 is fixedly mounted on the drive frame 98.
[0041] When an emergency patient needs to be moved between different examination departments, the medical staff controls the patient to lie on the cushion 3 on the bed frame 2. Before pushing the bed, the medical staff controls the power wheel 94 to move and fit into the ground, controls the cylinder 97 to operate and push the driving frame 98 to move downward, and the driving frame 98 drives the lifting frame 93 and the power wheel 94 to move downward to adjust the height of the power wheel 94. At this time, the driving frame 98 drives the sliding seat 101 to move downward synchronously, and the sliding seat 101 is sleeved on the driving frame 98 and slides horizontally. The sleeve rod 102 at the bottom of the sliding seat 101 is sleeved on the convex rod 103 and rotates, which can push the convex rod 103 and the bogie 11 to rotate. The bogie 11 drives the stop column 12 to rotate upward, so that the stop column 12 moves away from the ground, keeping the mobile device in a pushable state at this time. The running motor 95 controls the power wheel 94 to rotate through the belt drive 96. On bumpy or uphill sections, the power wheel 94 provides power for the pushing of the mobile device. The medical staff only needs to correct the direction during the pushing process, which is more labor-saving.
[0042] When the mobile device is pushed to the vicinity of the medical examination equipment and needs to be stationary, the operating cylinder 97 controls the driving frame 98 to move upward, and the driving frame 98 drives the lifting frame 93 and the power wheel 94 to move away from the ground. At the same time, the sliding seat 101 is mounted on the driving frame 98 and slides. The sliding seat 101 is driven by the sleeve rod 102 and the protruding rod 103, and can drive the bogie 11 to rotate downward. The bogie 11 controls the stop column 12 to move and fit on the ground. The stop column 12 can quickly control the mobile device to be stationary on the ground through the friction between the stop column 12 and the ground, so that the patient can complete the medical examination stably.
[0043] The power wheel 94 is driven by electricity and consumes more energy. If the mobile device needs to move on a flat ground, the cylinder 97 is operated to adjust the height of the power wheel 94 and the stop column 12 so that the power wheel 94 and the stop column 12 are away from the ground. At this time, the mobile device can be moved and pushed only by the universal wheel 8, which is more energy-efficient.
[0044] Example 2: Please refer to Figures 1-4 and Figure 9 Based on the first embodiment, a buffer mechanism is also disclosed. Its specific structure is as follows: The protective cover 9 is also provided with a buffer mechanism that supports the vibration force of the buffer moving device. The buffer mechanism includes a support column 13 rotatably mounted in the protective cover 9. The upper end surface of the support column 13 is telescopically connected to a buffer column 14, which is rotatably pressed against the bottom of the bed frame 2. The buffer column 14 and the support column 13 are both fixedly mounted with a disk 15 on the outside. The disk 15 on the outside of the buffer column 14 and the support column 13 is elastically connected to a buffer spring 16, which is mounted on the outside of the buffer column 14.
[0045] See also Figure 9 and Figure 10 The rotating end of the support column 13 is connected to a gear 131 along the axial direction, and the bottom of the gear 131 is meshed with a rack 132; the rack 132 is fixedly linked to a lifting transmission frame 133, and the lifting transmission frame 133 is fixedly connected to the sliding seat 101.
[0046] When it is necessary to provide power for the pushing of the mobile device through the universal wheel 8, the driving frame 98 is controlled to move downward. At this time, the sliding seat 101 on the driving frame 98 and the lifting transmission frame 133 move downward synchronously, the lifting transmission frame 133 is raised and lowered, and the lifting transmission frame 133 moves laterally synchronously with the sliding seat 101, and the rack 132 on the lifting transmission frame 133 moves laterally. The rack 132 is meshed with the gear 131, and under the meshing transmission, it can drive the gear 131 and the support column 13 to rotate, so that the support column 13 and the buffer column 14 rotate close to the bed frame 2, and the buffer column 14 rotates and squeezes the bottom of the bed frame 2. During the pushing process, the buffering action of the buffer column 14, the buffer spring 16 and the support column 13 can keep the patient stable during the pushing process, avoiding the patient from experiencing discomfort.
[0047] When the mobile device is controlled to be stationary, the universal wheel 8 is controlled to move up and away from the ground. At this time, the driving frame 98 moves up. Under the transmission action of the sliding seat 101 and the lifting transmission frame 133, the rack 132 can be controlled to move in the opposite direction. Under the meshing transmission, the support column 13 can be controlled to rotate away from the bed frame 2. The bottom of the bed frame 2 is open, so that the bed frame 2 can be controlled to move up and down within a larger range. At this time, by controlling the rotation of the bidirectional threaded rod 4, the internal threaded cylinder 5 can be driven to move horizontally under the threaded transmission, and the two ends of the support rotating rod 7 connected between the mobile frame 6 and the bed frame 2 rotate accordingly. The rotating support rotating rod 7 can drive the bed frame 2 to move downward, thereby adjusting the height of the bed frame 2 so that the mobile device can adapt to different patients and examination equipment.
[0048] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.
[0049] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A patient auxiliary mobile device for an emergency department, comprising a mobile base (1) and a bed frame (2) mounted on the mobile base (1) in a lifting manner, wherein a cushion (3) is mounted on the bed frame (2), and is characterized in that: The movable base (1) is rotatably connected to a bidirectional threaded rod (4), an external threaded sleeve of the bidirectional threaded rod (4) is provided with an internal threaded barrel (5), a movable frame (6) is fixedly mounted on the internal threaded barrel (5), a supporting rotating rod (7) is rotatably connected to the movable frame (6), and the other end of the supporting rotating rod (7) is rotatably connected to the bed frame (2); Four sets of universal wheels (8) are installed at the bottom of the mobile base (1), and a protective cover (9) is fixedly installed on the mobile base (1). Intelligent driving and stopping moving mechanisms are provided in the protective cover (9) and the mobile base (1).
2. A patient-assisted mobility device for an emergency department according to claim 1, characterized in that: The moving mechanism comprises a rectangular frame (91) embedded in the moving base (1), a guide seat (92) fixedly mounted in the rectangular frame (91), a lifting frame (93) longitudinally slidably connected to the guide seat (92), and a power wheel (94) rotatably mounted in the lifting frame (93); The power wheel (94) is arranged in the middle of the four sets of universal wheels (8), and a plurality of anti-slip grooves (941) are provided at equal angles on the outer circumferential surface of the power wheel (94).
3. The patient-assisted mobility device for an emergency department according to claim 2, characterized in that: A motor (95) is fixedly mounted on the lifting frame (93), and a belt drive (96) is installed between the output end of the motor (95) and the power wheel (94).
4. The patient-assisted mobility device for an emergency department according to claim 3, characterized in that: A cylinder (97) is fixedly installed in the protective cover (9), and an output end of the cylinder (97) is connected to a drive frame (98), and the drive frame (98) is fixedly installed on the lifting frame (93).
5. The patient-assisted mobility device for an emergency department according to claim 4, characterized in that: The moving mechanism further comprises a cylindrical rod (10) fixedly mounted in the rectangular frame (91), a bogie (11) being provided on the outside of the cylindrical rod (10) and a stop column (12) being fixed on the side of the bogie (11) close to the ground; Two stop posts (12) are symmetrically arranged about the central axis of the rectangular frame (91), and the power wheel (94) is arranged in the middle of the two stop posts (12).
6. The patient-assisted mobility device for an emergency department according to claim 5, characterized in that: A sliding seat (101) is provided on the drive frame (98) in a transverse sliding sleeve, and a sleeve rod (102) is fixedly installed on the bottom of the sliding seat (101); A protruding rod (103) is fixed to one end of the bogie (11) away from the stop column (12), and the sleeve rod (102) is rotatably sleeved on the outside of the protruding rod (103).
7. The patient-assisted mobility device for an emergency department according to claim 6, characterized in that: A guide rod (104) is fixedly mounted on the inner wall of the rectangular frame (91), a clamping block (105) is slidably connected to the guide rod (104), and the clamping block (105) is fixedly mounted on the driving frame (98).
8. The patient-assisted mobility device for an emergency department according to claim 1, characterized in that: The protective cover (9) is also provided with a buffer mechanism for supporting the vibration force of the buffer moving device.
9. The patient-assisted mobility device for an emergency department according to claim 8, characterized in that: The buffer mechanism comprises a support column (13) rotatably mounted in the protective cover (9), the upper end surface of the support column (13) being telescopically connected to a buffer column (14), and the buffer column (14) being rotatably pressed onto the bottom of the bed frame (2); The buffer column (14) and the support column (13) are both fixedly sleeved with a disc (15), and the disc (15) outside the buffer column (14) and the support column (13) is elastically connected to a buffer spring (16), and the buffer spring (16) is sleeved on the outside of the buffer column (14).
10. The patient-assisted mobility device for an emergency department according to claim 9, characterized in that: The rotating end of the support column (13) is connected to a gear (131) along the axial direction, and the bottom of the gear (131) is meshedly connected to a rack (132); A lifting transmission frame (133) is fixedly connected to the rack (132), and the lifting transmission frame (133) is fixedly connected to the sliding seat (101).
Citation Information
Patent Citations
Trolley for transferring patients in ward
CN212490443U
Transferring equipment for bedridden patients
CN213047845U
First-aid transfer cart
CN220632370U