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Triple-cylinder Two-stage Compressor with Variable Volume Ratio
Published in Hui Huang, Heat Pumps for Cold Climate Heating, 2020
The hermetic shell is filled with high-temperature and high-pressure gas refrigerant discharged out of the cylinder when the compressor is operating. The lubricant oil is stored at the bottom of the hermetic shell, with the compression mechanism (pump assembly) immersed in it. Therefore, on the one hand, the lubricant oil flows up to the lubrication points along the axial oil path in the crankshaft under the effects of the oil-paddled pump and the centrifugal force. On the other hand, the refrigerant reaches to all the lubrication parts through the gaps between vane and vane slot as well as the gaps of the sub bearing (lower bearing) under the pressure difference between the cylindrical chamber and gas refrigerant, so as to meet the lubrication and sealing requirements of compressor. Counterweights are installed on the upper and lower ends of the motor rotor to balance the unbalanced inertia force on the crankshaft of the compressor.
Earthmoving, Excavating, and Lifting Equipment Selection
Published in Douglas D. Gransberg, Jorge A. Rueda-Benavides, Construction Equipment Management for Engineers, Estimators, and Owners, 2020
Douglas D. Gransberg, Jorge A. Rueda-Benavides
Tower cranes are designed to work in congested areas. These cranes are a lifting device on top of a tower or mast. When a pick is made, the same lifting forces occur in the same manner as other cranes. Counterweight must be provided to balance the load. Compression is transferred down to the ground. The major difference, however, is that a tower is used to transfer the load to the ground instead of outriggers, tires or tracks. Lifting from up in the air can be both more demanding and complicated than lifting while sitting on the ground.
Slow down falling objects
Published in Michael Wiklund, Kimmy Ansems, Rachel Aronchick, Cory Costantino, Alix Dorfman, Brenda van Geel, Jonathan Kendler, Valerie Ng, Ruben Post, Jon Tilliss, Designing for Safe Use, 2019
Michael Wiklund, Kimmy Ansems, Rachel Aronchick, Cory Costantino, Alix Dorfman, Brenda van Geel, Jonathan Kendler, Valerie Ng, Ruben Post
Counterweights are often used as part of pulley systems, such as those used to move theatre stage sets and to give cranes a mechanical advantage. Counterweights balance heavy objects and help users hoist, suspend, and lower such objects slowly and safely without having to fight against heavy gravity loads.
Force sensorless admittance control of body weight support system
Published in Advanced Robotics, 2021
Jun Huo, Jian Huang, Xikai Tu, Zhongzheng Fu
In this section, the friction parameters identification is described at low velocity [37]. To avoid the influence of acceleration, we use counterweights as loads at a constant speed, shown in Figure 9(b). So, we can keep that and . Hence, the friction torque could be calculated in Equation (29) according to Equation (11). Let a vector z refer to a set of unknown parameters in Equation (15), shown in Equation (30), Define the force error between the plant output and the identification model output, then the parameters identification problem could be seen as an optimization problem as where, denotes the estimate of the z; is the actual force of the plant; is the estimated force of the identified model.
Analysis of unrestrained crawler-crane counterweights during tip-over accidents
Published in Mechanics Based Design of Structures and Machines, 2022
Joshua Vaughan, William Singhose, Dooroo Kim
Massive counterweights make the crane expensive, difficult to transport, and time-consuming to setup. Heavy counterweights also require extensive ground preparation to properly support the large compressive loads they generate. Therefore, crane manufacturers have developed cranes with moveable counterweights that can have substantially less mass because the weight can be moved to extended locations. A study of tip-over stability of crawler cranes with moveable counterweights indicated that tip-over stability is a complex function of the crane’s mass properties and configuration, as well as the payload mass (Rishmawi and Singhose 2015).
Gravity compensation of parallel kinematics mechanism with revolute joints using torsional springs
Published in Mechanics Based Design of Structures and Machines, 2020
Abdur Rosyid, Bashar El-Khasawneh, Anas Alazzam
When a counterweight is used to compensate the gravity, the static balance requires that the global center of mass does not change in the gravity direction. On the other hand, when springs are used for compensation, the static balance requires that the total potential energy is constant within the range of motion. An alternative yet very intuitive condition for a static balance is zero static reaction in the actuation direction at all active joints. To the authors’ knowledge, the last condition has never been employed as a tool to achieve a static balance in a mechanism despite it being more intuitive.