China
Africa
Explore chapters and articles related to this topic
Fuses and Relay Circuits
Published in Dorin O. Neacşu, Automotive Power Systems, 2020
The rotary solenoid uses a special construction able to rotate a ratcheting mechanism when power is applied. The ratchet mechanical device allows continuous rotary motion in only one direction while preventing motion in the opposite direction. When the solenoid is activated, the armature core is magnetically attracted toward the stator pole, and the disk rotates on the ball bearings as it moves toward the coil body. When power is removed, a spring on the disk rotates it back to its starting position.
Prototyping of automated systems
Published in Fuewen Frank Liou, Rapid Prototyping and Engineering Applications, 2019
A wheel provided with suitably shaped teeth, receiving an intermittent circular motion from an oscillating or reciprocating member, is called a ratchet. A ratchet can be used to move a toothed wheel one tooth at a time. A simple form of ratchet mechanism is shown in Figure 8.69. A is the ratchet wheel, and B is an oscillating lever carrying the driving pawl C. A supplementary pawl at D prevents backward motion of the wheel. Ratchets are also used to ensure that motion only occurs in one direction, useful for winding gear that must not be allowed to drop. Ratchets are also used in the free-wheel mechanism of a bicycle.
Wirework and Rigging
Published in David House, Seamanship Techniques, 2019
The lever and ratchet types, generally used for lighter work, are smaller and permit optional positioning wherever they are required. They are usually equipped with a reversible pawl system which allows the ratchet wheel to be turned in operation in either direction.
RoamFab: A Design Tool for Reconfiguring Parameterized Mechanisms to 3D Models With Structural Optimization
Published in International Journal of Human–Computer Interaction, 2022
Shijian Luo, Zhitong Cui, Jiancheng Gu, Ting Chen, Chengyi Shen, Yang Lu, Yanan Wang, Preben Hansen
Ratchet mechanisms allow rotary motion in one direction with discrete steps and prevent movement in the reverse direction, which can be used to handle loads. RoamFab offers a ratchet mechanism with an inner pawl that is squeezed when rotating by exploiting the elasticity of PLA (Figure 4). Since the pawls are the most fragile structures, we conducted a series of tests with different thickness pawls and set the minimum thickness to 1.2 mm. This size ensures that the inner pawl can be smoothly rotated and will not break without significant destructive force in the opposite direction. To increase the load the ratchet can handle in the reverse direction, the user can increase the depth of the sawtooth or the height of the ratchet wheel. The sawtooth count on the ratchet wheel can be customized for different degrees of the swing arc. As shown in Figure 4(b), we extend this primitive with a cylindrical shape for aesthetic reasons as generated in the design example of the solder spool holder (Figure 16). At the other end, symmetrical to the ratchet, we use a screw nut to prevent the pawl from getting out of the ratchet wheel.
Tissue expanders with a focus on extremity reconstruction
Published in Expert Review of Medical Devices, 2018
Abdul R. Arain, Keegan Cole, Christopher Sullivan, Samik Banerjee, Jillian Kazley, Richard L. Uhl
A disadvantage is that the ratchet cannot be reversed. If overtightened, it must be removed. The staples can be left in place while a new device is threaded through them. Another disadvantage is that after the initial stress relaxation, there is no continuous tension to promote creep. Therefore, additional expansion does not occur until the next tightening. Govaert and others in a study of 13 patients with 23 extremity fasciotomies found that the mean time from operation-to-closure was 6.3 days (range, 1–14 days) and the mean time to device removal was 16 days (range 4–23 days) [55]. Two patients developed postoperative superficial wound infections treated successfully with intravenous antibiotics and one developed a small wound dehiscence after device removal.
Comparison of musculoskeletal load using two devices for manual height adjustment of the hospital bed
Published in International Journal of Occupational Safety and Ergonomics, 2022
Sanpatchaya Sirisawasd, Sasitorn Taptagaporn, Chaweewon Boonshuyar, Poramet Earde
A ratchet is widely used in machinery and tools. The advantage of the ratchet is that its mechanism allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction [18]. From this advantage, it is possible to replace the existing hand crank of the hospital bed, but this should be as part of a mechanical box. In brief, the ratchet can rotate a nut both left and right using its side switch, and it can be used to rotate the spine with a sprocket used to rotate the shaft of the hospital bed. Therefore, it can be concluded that the ratchet is the most appropriate device to be developed as the extension device for manual height adjustment of the hospital bed.