Abstract: Wind turbine blade having at least one longitudinal hollow element that defines an aerodynamic outer surface and an inner cavity having an inner surface. The blade also comprises at least one spar (1), disposed in the inner cavity and bonded to the inner surface by at least two bonding surfaces (13) located on bonding surfaces (2) of the spar (1). The spar (1) comprises, on at least one bonding zone (2), at least three fibre fabric layers (3) and at least one central core (4) and at least one lateral core (5) disposed between the at least three fibre fabric layers (3). This makes it possible to increase the resistance to shear stresses in the adhesive bond of the spar (1) to the inner surface of the longitudinal hollow element and decrease the required amount of adhesive.

Abstract: A component for a wind turbine blade is described having a reinforced through-going aperture. The reinforcement can be provide by way of a fibre rope arranged around the periphery of the aperture, or as fibre material arranged in a radially-extending arrangement from the aperture.

Abstract: A rotor blade of a wind turbine. The rotor blade comprises at least one rotor-blade inner portion, having a region connecting to the rotor-blade hub, and at least one rotor-blade outer portion, having a rotor-blade tip, the rotor-blade inner portion and the rotor-blade outer portion each being made substantially of a fibre-reinforced plastic, and the rotor-blade inner portion and the rotor-blade outer portion being connected to each other by a connecting device. The connecting device in this case comprises an inner insert that is at least partially wrapped in the fibre-reinforced plastic of the rotor-blade inner portion, an outer insert that is at least partially incorporated in the fibre-reinforced plastic of the rotor-blade outer portion, the inner insert and the outer insert being connected to each other via a connecting element.

Abstract: A wind concentrator turbine generator has an inlet cavity to concentrate a wind flow to a nozzle aperture. One or more turbine fans are oriented within a turbine cavity such that the concentrated find flow is directed at the turbine fans. A generator is coupled to each of the one or more turbine fans. The generator is scalable from discrete power generation requirements to utility scale power generation. Larger scale generators may be connected to deliver electrical power to regional electrical power grids.

Abstract: The present invention relates to a method for controlling a wind power plant, the wind power plant comprising a plurality of wind turbine generators, each wind turbine generator comprising at least one power converter for providing active power and/or reactive power to an electrical grid, wherein the method is determining a required amount of reactive power provided by the plurality of wind turbine generators, and grouping the plurality of wind turbine generators into a first set of wind turbine generators and a second set of wind turbine generators based on a demand for reactive power; and supplying reactive power to the grid (20) from the first set of wind turbine generators and disconnecting the second set of wind turbine generators from the electrical grid (20) in response to a control demand, in order to minimize active power losses. The present invention also relates to a wind power plant arranged to perform the method.

Abstract: A wind turbine comprising a tower, a rotor including a plurality of blades, an electrical generator operatively coupled to the rotor, and a control system including an active damping module configured to monitor oscillatory motion of the wind turbine and to output a damping demand signal to damp the oscillatory motion. The control system is configured to perform a rotor imbalance determination process including: controlling the rotating frequency of the rotor so that it substantially coincides with the natural frequency of the tower, determining rotor imbalance data based on the damping demand signal and evaluating said rotor imbalance data to determine the presence of a rotor imbalance condition, and correcting the rotor imbalance condition by applying pitch control inputs to one or more of the plurality of blades so as to reduce the severity of the rotor imbalance. The invention may also be expressed as a method.

Abstract: A method is proposed for operating at least one wind turbine of a wind farm including determining wind turbine individual offset information based on reactive power provided by the respective wind turbine and reactive power provided by at least one further wind turbine of the wind farm, determining wind turbine individual control information based on the wind turbine individual offset information and wind farm specific control information, operating the at least one wind turbine according to the wind turbine individual control information. Further, a controller and a device as well as a computer program product and a computer readable medium are also provided.

Abstract: Systems, methods, and apparatuses are provided for generating clean energy. A Savonius vertical-axis wind turbine, including a shaft configured to rotate about a first axis, aerofoil blades transversely mounted with respect to the first axis, on the shaft, transversely extending outwards from the shaft to a first distance from the shaft, a generator coupled to the shaft, the generator configured to generate electricity from rotational energy of the shaft when the shaft rotates about the axis; and a first curved wind shield having a semi-circular shape defined by a curvature, each point of the curvature is a fixed second transverse distance from the shaft, the first curved wind shield positioned at the fixed second transverse distance from the rotating shaft, and the curved wind shield is rotatable about the rotating shaft, at the fixed second distance. In some embodiments, the wind shields increase productive wind circulation to the turbine blades.

Abstract: A device comprising a vertical axis wind turbine comprising an arm, a housing coupled to the arm, a generator housed within the housing, and a blade extending along the housing vertically.

Abstract: A condition monitoring system for a wind turbine comprises: a sensor which senses a condition of a yaw bearing; a monitor device which generates a diagnosis parameter based on a detection result of the sensor; a sensor which senses a rotating angular velocity of a nacelle and that of a main shaft; and a data server which diagnoses a failure of the yaw bearing based on the diagnosis parameter. The data server diagnoses whether the yaw bearing has a failure, based on a variation of the diagnosis parameter from an initial value thereof when the nacelle has a rotating angular velocity within a non-zero, first prescribed range and the main shaft has a rotating angular velocity within a second prescribed range.

Abstract: A thermal actuator for a rotating shaft shutdown seal that has a piston with a portion of its axial length enclosed within a chamber shell with a material that expands upon a rise in temperature. The portion of the actual length of the piston within the chamber has at least two different diameters with the larger diameter leading in the direction of travel of the piston. Upon a rise in temperature, expansion of the material surrounding the piston within the chamber creates a force on the piston in the desired direction of travel. Below a preselected temperature the piston is positively locked with a passive release when the preselected temperature is reached.

Abstract: A heat sensitive actuator utilizes a bilayer of shape memory material, each layer thermally stimulated to change shape at a different temperature, to generate two-way actuation functionality. The second layer—with higher phase-change temperature—brings up greater intrinsic force in its high temperature phase than the first, and in this way is able to be used to reset the actuator to its initial shape after being deformed by the first layer at a lower temperature.

Abstract: A pump having two pistons which are parallel and in opposition and are disposed in two, cylindrical, cavities in a pump body, including at least one inlet port and at least one outlet port connected to a rotational port-switching device which can move axially along its rotational axis and is held in abutment in the pump body by a restoring member, in the form of a spring.

Abstract: An apparatus and method according to which a fluid, such as a fracturing fluid, is pressurized. The apparatus includes a motor that produces a first rotational output including a first angular velocity, a pump operably coupled to the motor, the pump comprising a fluid end and a power end operably coupled to the fluid end, and a transmission operably coupled between the motor and the pump. The transmission receives the first rotational output as a first rotational input, the first rotational input including the first angular velocity, and converts the first rotational input into a second rotational output, the second rotational output including a second angular velocity. The power end receives the second rotational output as a second rotational input, the second rotational input including the second angular velocity. In some embodiments, the transmission is directly connected to, or part of, the pump and the motor.

Abstract: A peristaltic pump which includes: (a) a plurality of effecters, actuated in a periodic manner upon by obstructive forces of a flexible infusion tube so as flow of infusion fluid is provided along said infusion tube, the magnitude of the obstructive forces are dependent upon the displacement of the moving effecters; and (b) a plurality of balancing magnets providing balancing forces upon one or all the moving effecters, the balancing forces at each point along the path of motion of the moving effecters being of approximately equal magnitude to that of the obstructive forces at the point, such that the parasitic output due to work performed against the obstructive forces is approximately zero and yield is maximized.

Abstract: A system and method for pumping formation fluids from a well using a sucker rod pumping system that prevents the pumping system from experiencing a floating rod condition. The sucker rod pumping system comprises a pump drive system, a rod string, and a downhole reciprocating pump driven by the rod string. The pump drive system is coupled to the rod string by a bridle. In addition, the sucker rod pumping system comprises a drive control system that controls the speed of the pump drive system during the downstroke. The drive control system is coupled to a load cell configured to provide a signal representative of load on the rod string. The drive control system controls the speed of the pump drive system during the downstroke based on the load on the rod string so that the rod string does not experience a floating rod condition.

Abstract: A variable displacement pump includes: an urging mechanism which includes two spring members; an electromagnetic switching valve which is arranged to connect the second control chamber and the discharge portion in an energized state, and to connect the second control chamber and the low pressure chamber in a deenergized state; and a control valve which is actuated by the pressure of the discharge portion, and which is arranged to decrease the pressure within the second control chamber when the pressure of the discharge portion becomes equal to or greater than a predetermined pressure.

Abstract: In accordance with one embodiment, the gear pump comprises a first gear meshed with a second gear as well as a housing, in which the gears are supported. The housing includes a first void, which at least partly adjoins a first side surface of the first gear, and a second void, which at least partly adjoins a second side surface of the first gear. The gear pump further comprises a fluid intake channel configured to direct fluid towards the gears, wherein at least one deflector is arranged within the fluid intake such that an incident fluid flow is diverted towards the first void as well as to the second void.

Abstract: A compressor may include a non-orbiting scroll, an orbiting scroll, a driveshaft and an Oldham coupling. The orbiting scroll meshingly engages the non-orbiting scroll. The driveshaft includes a crankpin engaging the orbiting scroll and driving the orbiting scroll in an orbital path relative to the non-orbiting scroll. The Oldham coupling may include an annular body and a plurality of first keys extending from the annular body and slidably received in slots formed in the orbiting scroll. Each of the first keys may include a first post and a first cap covering at least a portion of the first post. The first posts may be integrally formed with the annular body from a first material. The first caps may be attached to the first posts and formed from a second material.

Abstract: A centrifugal pump for delivering coolant in vehicles and providing a centering of a pump impeller and a dampening of motor vibrations. The centrifugal pump having a pump housing consisting of a pump head, which forms a single part with a suction nozzle, a discharge nozzle, a spoke, and a bearing support, in which a counter bearing is mounted, in which a first region of a shaft is supported, around which a pump impeller is rotatably mounted via a slide bearing secured in the pump impeller, the spoke retaining the bearing support in a central position within the pump head and having a containment shell, which separates a wet chamber from a dry chamber and in which a second region of the shaft is supported. The invention seeks to solve the problem of providing in a generic centrifugal pump.

Abstract: A low emission, high efficiency Gas Turbine engine operating on a combination of Natural Gas and Bio Gas as fuel, driving either a high efficiency turbo-blower or a high efficiency Turbo Pump system combined with heat recovery systems and in other embodiments is provided a generator of electricity or providing evaporative cooling from using the remaining waste heat in the exhaust gas.

Abstract: Disclosed is an embodiment of a dual seal arrangement for the high-speed shaft of a supercharger with a centrifugal compressor and a mechanical speed step-down transmission to the shaft. A ring located about the shaft splits the rotational speed of the shaft between two seals, so that each seal spins at a speed of roughly half the speed of the shaft. The arrangement can also be used to split the shaft speed between two bearings in the same manner. The high-speed shaft may also have a turbine attached, to form a driven turbocharger.

Abstract: A fan noise suppression circuit may be coupled between a power source and a power input to at least one fan. The fan noise suppression circuit may include an adjustable current source coupled to the power source. The adjustable current source may provide a voltage output and a current output based on a power output of the power source. The fan noise suppression circuit may include a feedback controller coupled to an output of the adjustable current source. The feedback controller may be configured to compare the voltage output to a reference voltage and provide an error value to the adjustable current source, wherein the adjustable current source may adjust the current output based on the error value.

Abstract: The present invention proposes an electric blower which can strongly hold and fix a sleeve onto a frame, and eventually provide high reliability. An electric blower 1 includes a centrifugal fan 2; a shaft 9 installed integrally rotatably with the centrifugal fan 2; a sleeve 16; a bearing 17 provided in the sleeve 16 and adapted to rotatably support the shaft 9; a diffuser 6 provided with a through hole 21 in which the sleeve 16 is fixed; a recess 41 provided in an outer circumferential surface of the sleeve 16; and a stopper 43 filling a gap between the diffuser 6 and the recess 41 and adapted to harden and thereby prevent the sleeve 16 from being detached from the through hole 21.

Abstract: A centrifugal ceiling fan adapted to evenly ventilate and heat its surrounding area. The fan comprises a casing defining a top, a side, and a bottom. The air inlet is provided in the top and the air outlet comprises a first passage provided in the side and a second passage provided in the bottom, and a central dome for regulating the flow of air between the first passage and the second passage to a desired proportion. The fan comprises a centrifugal propeller having blades which are curved and have a variable width such that rotation of the centrifugal propeller causes air to be received from said air inlet and to be pushed from said air outlet in substantially all directions between the first direction and the second direction. The dome comprises a heat source for heating air pushed downward from the bottom. Whereby, unheated air is pushed sideways and heated air is pushed downward and for evenly ventilating and heating a room in which the centrifugal ceiling fan is installed.

Abstract: A system and method for detecting the rotation breakaway of a spacer from a compressor rotor disk are disclosed herein. The method includes detecting a disk sensed feature and a spacer sensed feature on the compressor rotor disk and the spacer respectively. The method also includes comparing the timing between the two to a predetermined threshold to determine whether the relative position of the spacer to the compressor rotor disk exceeds a predetermined amount. The predetermined amount may be selected to determine whether an imbalance, rubbing, or binding can occur in the gas turbine engine or to determine whether anti-rotation features have been broken.

Abstract: A submersible well pump assembly has upper and lower seal sections connected between the pump and a motor. The seal sections have drive shafts with thrust runners that engage thrust bearing bases. The upper drive shaft will undergo a limited amount of downward movement toward the lower drive shaft in response to wear of the upper thrust bearing base. A spring between ends of the drive shafts transfers a portion of the down thrust on the upper drive shaft to the lower drive shaft prior to the limited amount of downward movement of the upper drive shaft toward the lower drive shaft being reached. A rigid stop member in the coupling transfers down thrust directly from the upper drive shaft to the lower drive shaft, bypassing the spring, only after the limited amount of downward movement of the upper drive shaft toward the lower drive shaft has been reached.

Abstract: An arrangement of an impeller (1) on an electrical motor, in particular on an external rotor motor (8), whereby the torque of the motor is transferred to the impeller (1) by means of a torsion-proof connection between the rotor (8) of the motor and the impeller (1) and/or its impeller hub (3), is characterised in that the connection of the impeller (1) to the motor (8) results from physical and/or chemical interactions between an adhesive medium (10) and the contact surfaces (5) of the impeller hub (3) and of the motor (8), which face each other, whereby the adhesive medium (10) fills, at least partially, an intermediate space (9) that is formed between the impeller (1) and the motor (8) by the given play.

Abstract: A forward curved blower wheel has fan blades having relatively small leading edge blades angles and a relatively lengthy mean camber lines. The blower wheel also comprises leading edge notches adjacent its blower wheel inlet. The leading edge notches eliminate buffeting that would occur with such blades if such notches were not present.

Abstract: The variable pitch propeller assembly includes a hub. The variable pitch propeller assembly also includes a plurality of propeller blade assemblies spaced circumferentially about the hub. Each of the plurality of propeller blade assemblies configured to rotate a respective propeller blade. The variable pitch propeller assembly also includes a hydraulic fluid port assembly integrally formed and including at least three hydraulic fluid ports configured to receive respective flows of hydraulic fluid from a stationary hydraulic fluid transfer sleeve. The variable pitch propeller assembly also includes a pitch actuator assembly coupled in flow communication with at least three hydraulic fluid ports through respective hydraulic fluid transfer tubes. The pitch actuator coupled to the plurality of propeller blade assemblies to selectively control a pitch of the propeller blades. The pitch actuator assembly includes a travel stop configured to limit a rotation of at least one of the pitch actuator assemblies.

Abstract: A compressor device for a turbocharger. The compressor device includes a compressor housing and a separate snorkel member which are provided separately and then connected together. The compressor housing has two air passages separated by a partition wall, while the snorkel member similarly has two separate air ducts separated in part by a partition wall. The two components have mating fittings to connect them together.

Abstract: A sealless magnetic drive pump features in improving the stiffness of a stationary shaft. More particularly, the metal magnetic drive pump has an anti-corrosion casing liner. The magnetic drive pump is used in manufacture processes related to corrosive fluid. The pump is especially used in a highly corrosive and high-temperature (up to 200° C.) condition to improve the stiffness of a front support. The stationary shaft includes a metal front support integrated with the pump casing at a pump inlet and encapsulated with a resin enclosure made of a fluoropolymer; a rear shaft seat positioned on a sealed bottom side of a containment shell for offering auxiliary support for the stationary shaft; an impeller including a channel for reducing an inlet flow velocity to offer a low NPSHr.

Abstract: A sealless magnetic drive pump features in improving the stiffness of a stationary shaft. More particularly, the metal magnetic drive pump has an anti-corrosion casing liner. The magnetic drive pump is used in manufacture processes related to corrosive fluid. The pump is especially used in a highly corrosive and high-temperature (up to 200° C.) condition to improve the stiffness of a front support. The stationary shaft includes a metal front support integrated with the pump casing at a pump inlet and encapsulated with a resin enclosure made of a fluoropolymer; a rear shaft seat positioned on a sealed bottom side of a containment shell for offering auxiliary support for the stationary shaft; an impeller including a channel for reducing an inlet flow velocity to offer a low NPSHr.

Abstract: A fan may be designed for the strategic diversion of moisture through or around a housing enclosing a controller and/or a motor. The enclosure may include one or more paths for directing moisture away from the controller or the motor. For instance, the housing may include a gap between a support structure and the housing for preventing moisture from entering the housing. The housing may also include a hollow structure for directing fluid through the housing. Additionally, the housing may include one or more channels, raised walls, gutters, and shields for preventing fluid, such as liquid water, from entering an enclosure for the controller or motor.

Abstract: A containment case includes a fan assembly including a hub having a plurality of fan blades extending radially outward between radially inward blade roots and radially outward blade tips. Containment case includes a radially outer shell circumscribing fan assembly and having a first radially inner surface and a radially outer surface, an inner structure having a second radially inner surface extending along first radially inner surface, and a trench extending circumferentially along second radially inner surface into inner structure from second radially inner surface. The trench is approximately axially aligned with the fan assembly. The containment case also includes, within the trench, a trench filler layer configured to dissipate impact energy from a released fan blade and having a plurality of sheets including a fibrous composite material having a plurality of fibers fabricated within each sheet, where the sheets are coupled together into a repeating pattern of hollow units.

Abstract: A fan assembly includes a fan having an outlet side, a fan duct positioned at the fan outlet side, and a hollow cylindrical chamber positioned within the fan duct, wherein the chamber has two closed ends, a cylindrical side wall, and an inlet port. The dimensions of the chamber are determined to suppress one or more noise frequencies emitted by the fan. In one example, one or more dimensions of a chamber disposed in an outlet duct of an axial fan is automatically adjusted to suppress a noise frequency that is a function of a rotational speed of the axial fan.

Abstract: A fan according to the present invention includes: a main plate fixed to a rotation axis of a driving device; a shroud including an air inlet; and an impeller including n blades between the main plate and the shroud, tip ends of leading edges of the respective blades arranged along a circle around the rotation axis, wherein all of the attachment pitch angles a are different angles, and the blades are arranged so that, in the attachment pitch angles ?, attachment pitch angles on both sides of an attachment pitch angle ?m are a combination of other than an attachment pitch angle ?m?1, which is the next smallest angle in order of magnitude of angle to the attachment pitch angle ?m, and an attachment pitch angle ?m+1, which is the next largest angle in order of magnitude of angle, to the attachment pitch angle ?m.

Abstract: An auxiliary shaft seal flushing system of a centrifugal pump and an axial flow pump, comprising a main running pump and a standby pump which are provided with a same shaft seal flushing system respectively, the shaft seal flushing system of the main running pump and that of the standby pump being connected in parallel to form a common shaft seal flushing system.

Abstract: An actuator controller for actuating an actuator which can be operated fluidically, having a feed line for an inflow of the working fluid to an actuator connector and having a discharge line for an outflow of the working fluid to a fluid outlet, wherein the feed line is assigned a feed line valve and the discharge line is assigned a discharge valve, which valves are configured in each case to influence a volumetric fluid flow at the actuator connector, and having a control device for actuation of the feed line valve and the discharge valve. A throughflow sensor is arranged in a line section between the discharge valve and the fluid outlet, which throughflow sensor is configured for determining a volumetric fluid flow in the discharge line and for providing a throughflow signal.

Abstract: To provide a hydraulic drive system for a work machine capable of securing a favorable operability in the case where hydraulic fluid discharged from a hydraulic actuator is regenerated for driving other hydraulic actuator.

Abstract: A Hydraulic Manifold Control Assembly for use in connection with surface blowout preventers and diverter control systems. Said Hydraulic Manifold Control Assembly incorporates design elements and methods which reduce overall envelope dimensions, improving maintenance accessibility, thereby reducing overall installation and manufacturing time and ultimately contributing to a more robust, cost effective end-product. Said design elements and methods include: the use of intrinsically safe I/O modules and components; the employment of a removable valve assembly rack installation method; the use of a removable face plate for identification of flow control valves; the implementation of a digital automatic diverter sequence; the use of integrated manifold assemblies; and the integration of a wide-range function count.

Abstract: A hydraulic block includes multiple pairs of actuator ports connectable to a hydraulic actuator and a discharge oil passage for discharging work oil returned from the hydraulic actuator to the outside. The charge oil passage includes a first oil passage corresponding to a predetermined actuator port of all the actuator ports and a second oil passage corresponding to non-predetermined actuator ports other than the predetermined actuator ports. The first oil passage is disposed in parallel with the second oil passage.

Abstract: In at least some aspects, there is provided a fluidic actuator including at least one fluidic actuator segment that includes an elastic tube, having a first initial length, and a braid, having a second initial length greater than the first initial length. The braid is disposed, in a buckled state, about the elastic tube and imparts an axial force to the elastic tube.

Abstract: A hydrostatic drive includes a diesel engine and a hydrostatic adjustable machine which supplies multiple consumers in normal operation as a pump. The machine has a pressure/flow regulator to which is communicated, according to the load-sensing principle, the highest load pressure of the consumers, in particular when the machine is operated as a pump. In order to realize a start/stop function of the diesel engine, a previously charged high-pressure reservoir supplies the hydrostatic machine, which then acts as a starter motor for the diesel engine. In order to switch from pump to starter motor, the hydro-machine is adjusted over zero. In order for this switch to take place quickly and reliably, the pressure/flow regulator is deactivated by means of a switching valve and the adjustment device is supplied with an adjustment pressure medium via the switching valve, which medium is taken from the high-pressure reservoir or from an auxiliary reservoir.

Abstract: A method for facilitating the distribution of the flow of one or more streams within a bed vessel is provided. Disposed within the bed vessel are internal materials and structures including multiple operating zones. One type of operating zone can be a processing zone composed of one or more beds of solid processing material. Another type of operating zone can be a treating zone. Treating zones can facilitate the distribution of the one or more streams fed to processing zones. The distribution can facilitate contact between the feed streams and the processing materials contained in the processing zones.

Abstract: A multi-component magnetic system for joining materials together or fastening materials to a person's body is disclosed. The system is particularly useful as a closure or joining mechanism in clothing, accessories and the like.

Abstract: A modular furniture system includes a plurality of panel elements having opposing first and second major faces, a perimeter wall defining a minor face therebetween, and at least a boss aperture which passes through the first and second major faces. A panel connector has a bridging element and at least two bosses in spaced apart relationship on the bridging element, each boss being a complementary fit in the boss aperture of a respective panel element, a first fastener recess in a distal free end of each boss, and a second fastener recess opposing the first fastener recess and adjacent to a proximal end of each boss. An oversized fastener associated with each boss has a panel-retaining head and a tail which is interengagable with the panel-retaining head.

Abstract: A fiber-reinforced resin member is provided in which a non-conductive sleeve and first and second non-conductive sheets are disposed between a metal fastening member and CFRP laminate, electrical continuity between the metal fastening member and the CFRP laminate is cut off, and corrosion of the metal fastening member due to galvanic corrosion is prevented. A first annular space is formed between a first flange portion of a first member and the first non-conductive sheet, a second annular space is formed between a second flange portion of a second member and the second non-conductive sheet. Therefore, even if frayed carbon fiber sticks out from a gap between the non-conductive sleeve and the first and second non-conductive sheets, due to the first and second annular spaces being formed therein, it is possible to prevent the sticking-out carbon fiber from contacting the first and second members and providing electrical continuity.

Abstract: A fastener assembly may include a pin including a central shaft connected to a distal tip, and a grommet including at least one leg. The pin and the grommet are configured to be positioned in an expanded state in which the fastener assembly securely fastens to the component, and a retracted state in which the leg(s) is drawn toward the central shaft to reduce an axial envelope of the leg(s).

Abstract: A rectangular stage includes a deck supported by a frame and removable legs. The legs insert into a corner receiving assembly below the stage deck at each corner. The leg receiving assembly includes a cylindrical socket into which the top of the leg inserts. The leg receiving assembly also includes a retaining linkage that extends through a slot in the side of the socket and engages the leg. The retaining linkage also includes a manually actuatable latch coupled to the cam to maintain the cam in engagement with the leg.