Abstract: A wing or blade in at least two sections facing each other. Each section has a longitudinal bearing structure provided with at least one sole of which the link between the sections includes at least one first link plate linking the end of the soles of the sections facing each other. A method of producing such wing or blade.

Abstract: A flap arrangement for a wind turbine rotor blade, which includes a leading edge, a trailing edge and a chord line between the leading edge and the trailing edge, is described. The flap arrangement includes a support portion and a flap portion which is passively moveable with respect to an angle between a surface normal of a surface of the flap portion and the chord line. The support portion and the flap portion are positioned relatively to each other such that the support portion provides a limit to the movement of the flap portion. Also described are a wind turbine rotor blade including the flap arrangement and a method of enhancing the aerodynamic performance of a blade.

Abstract: A blade adjusting device for a wind turbine is connected to a plant safety chain and can open and close the plant safety chain by activating a switch. If a fault is detected in one of the blade adjusting devices, the respective control unit can open the plant safety chain. By opening the safety chain, a signal is sent to the blade adjusting devices, and so all the blade adjusting devices initiate a synchronous safety operation of at least two rotor blades when the signal is received.

Abstract: A wind turbine is disclosed having a generator and rectifier and structured to provide direct current power that in one form is medium voltage direct current (MVDC). The wind turbine includes a crowbar circuit arranged to protect from a condition such as an overvoltage. The crowbar can be activated based on a voltage measurement or rate of change of voltage. A resistor can be coupled to the crowbar to absorb excess power provided by the generator during the overvoltage condition. Individual wind turbines in a wind farm can each have individual crow bars that can be activated based on local measurement of a voltage condition. In some forms the crowbar can be coupled with a transformer, for example coupled with a tertiary winding of a three winding transformer.

Abstract: To provide a radial piston pump capable of displacement control without using an electronic control valve.

Abstract: Aircraft with an emission-free drive and method for emission-free driving of an aircraft. The aircraft includes a drive device structured and arranged to generate thrust, a lift device structured and arranged to generate lift, and a heat engine structured and arranged to convert thermal energy into kinetic energy to drive the drive device. The heat engine includes at least one flat-plate Stirling engine drivable by solar thermal radiation.

Abstract: A fluid end block for attachment to a power end of a high pressure reciprocating pump includes a main body portion having an outwardly facing body forward face, an outwardly facing body rear face opposite the body forward face, and opposing side surfaces. A web portion protrudes outwardly from the outwardly facing body forward face. The web portion may have an outwardly facing web forward face and a curvilinear side surface. The web portion may be integral with the main body portion. A plurality of bosses protrude from the web forward face and having a forward facing end. The plurality of bosses may be integral with the main body portion and the web portion. A plunger bore extends through one of the plurality of bosses configured to receive a reciprocating plunger.

Abstract: A cylinder is configured into a bottomed tubular form and includes an inner peripheral wall, an inner bottom wall, an outer peripheral wall and an intake hole and a discharge hole. The inner peripheral wall slidably guides the plunger. The intake hole and the discharge hole communicate between the inner peripheral wall and the outer peripheral wall. A pump housing includes a cylinder receiving hole that includes an inner peripheral wall, into which the cylinder is inserted. A pressurizing chamber is formed by the inner peripheral wall and the inner bottom wall of the cylinder and a distal end outer wall of the plunger.

Abstract: A pump has a pump body and at least first and second pumping elements, each pumping element including a piston defining a head-end and a rod-end. The pump receives a pressurized fluid at an inlet, and returns fluid through a drain outlet. A hydraulic distributor operates to fluidly connect the head end of an extending piston to the pressurized fluid, and the rod end of the extending piston to the drain outlet. The hydraulic distributor further connects the rod-end of a retracting piston to the drain outlet, and the rod-end of one or more retracting pistons to the drain or to a return pressure, which is lower than an extending pressure.

Abstract: An apparatus configured to hydraulically fracture an earth formation, includes a pump configured to hydraulically fracture the earth formation by pumping a fracturing liquid into a borehole penetrating the earth formation and an electric motor having a rotor coupled to the pump and a stator. A motor control center is configured to apply an alternating electrical voltage having a fixed-frequency to the stator in order to power the electric motor, wherein the apparatus and motor control center do not have a variable frequency drive.

Abstract: The wheeled pumping station includes a front axle and a rear axle with wheels that mobilize a pumping station supported via a chassis. The pumping station is enclosed within a housing. The housing supports a pump from which an intake hose descends down. The pump is wired to a powering member. The powering member is also wired to at least one solar panel provided on a top surface of the housing. The powering member is wired to a computer, GPS unit, and transceiver. The computer is able to track location and maneuver the wheeled pumping station to different locations as needed. The pump is connected to both the intake hose and an irrigation pipe such that water collected via the pump is removed from the land, and transferred via the irrigation pipe to another location.

Abstract: A dual-gauge air pump has two round dial pressure gauges that are configured in a back-to-back arrangement, i.e. 180 degrees to each other, and to rotate through 360 degrees simultaneously for a user's easy observation.

Abstract: A non-evaporable getter 1 includes a mesh 3, a frame 2 which is attached to the mesh 3 and suppresses deformation of the mesh 3, and a powder-state getter material 4 which is surrounded by the mesh 3 and the frame 2, and whose particle size is larger than a mesh opening of the mesh 3.

Abstract: An air compressor includes a rotating device pivotally connected to a piston body. The rotating device includes a gear body and a counterweight. The gear body is formed together with a counterweight, wherein the counterweight is provided with a crankshaft corresponding to the center of the gear body and a crankpin placed at a distance from the crankshaft. The counterweight is horizontally divided into two integrally formed halves, including a left half and a right half, with a common line connected between the center of the crankshaft and the center of the crankpin, wherein the left half has a weight different from the right half, so that the piston body gathers more rotational momentum from the counterweight at BDC to facilitate upstrokes, so that the piston body can conduct reciprocating motion more smoothly, and thus the service life of the air compressor can be increased.

Abstract: A gas compression system is provided. The gas compression system includes a compressor, an adsorption device, and a fluid control device. The compressor includes a first port and a second port. The adsorption device is adapted to output the high pressure hydrogen gas to the first port and absorb the low pressure hydrogen gas from the second port. The adsportion includes a first container connected to the first port or the second port, and a second container connected to the first port or the second port. The first container and the second container includes a hydrogen adsorption material adapted to release the high pressure hydrogen gas when heated, and absorb the low pressure hydrogen gas when cooled. A method of using the gas compression system is also provided.

Abstract: A simplified pump system including a bellow (310) having a suction valve (312), a stem (320), a fluid lock (330), and a tube retainer (380) having a vent element wherein the product flow into and out of a pump chamber formed by the bellow (310) and stem (320) is controlled by the suction valve (312) and fluid lock (330).

Abstract: A compressing diaphragm pump with multiple effects includes an eccentric roundel mount with three cylindrical eccentric roundels, a pump head body with three operating holes, and a diaphragm membrane with three annular positioning protrusions. A basic curved groove or other positioning structure is circumferentially disposed around each operating hole while a basic curved protrusion or other mating positioning structure is provided in the diaphragm membrane for suitably coupling with the corresponding groove or positioning structure in the pump head body upon assembly, resulting in a shortened length of moment arm from the basic curved protrusions or other positioning structures and an annular positioning protrusion, and a reduction in vibration-caused noise and resonant shaking in comparison with a conventional compressing diaphragm pump.

Abstract: A pump may have a first chamber and a solenoid coil to control movement of a first valve member. A second chamber may have a second valve member to control fluid moving into a third chamber. A first fluid passageway may link the first and second chambers, a second passageway may link second and third chambers and a third passageway may link third and fourth chambers. After pressurizing the third chamber causing fluid to flow into and leave a fourth chamber, the third chamber depressurizes due to downward movement of a plunger. Upon depressurization with a solenoid coil energized, second valve member floats and then moves against a valve seat. While the second valve member is moving toward the valve seat, the solenoid coil is de-energized causing the first valve member to move and strike the second valve member when the second valve member is moving at maximum velocity.

Abstract: Disclosed are systems and methods utilizing multiple parallel pumps to deliver a mixture of the proppant and clean fluid via a manifold trailer. One method of providing a step-change in proppant concentration includes selecting a first flow rate for a first pump connected between a first input node and first output node, calculating a first transit time for a flow of a fluid at the first flow rate through a first flow path extending from the first inlet node, through the first pump, and to the first outlet node, and calculating a second flow rate for a second pump connected between the first input node and the first output node such that a second transit time for a flow of the fluid through a second flow path extending from the first inlet node, through the second pump, and to the first outlet node is equal to the first transit time.

Abstract: A method for automatic tuning of a reference model for a fracking rig pump is provided. The method includes determining, at a processor connected to a fracking rig pump, a current choke area associated with the fracking rig pump based upon at least a maximum power and a maximum pressure obtained from the fracking rig pump for a pump speed of the fracking rig pump, obtaining a pump power and a pump pressure for the current choke area based upon at least a reference model for the fracking rig pump stored in a memory device coupled to the processor, determining a pressure difference between the maximum pressure obtained from the fracking rig pump and the pump pressure, determining a power difference between the maximum power obtained from the fracking rig pump and the pump power obtained from the reference model, and providing an updated choke area to the reference model.

Abstract: An embodiment of a gear pump arrangement includes a first gear defining a first set of teeth; and a second gear defining a second set of teeth, the first set of teeth and the second set of teeth being in meshed communication such that fluid is pumped in response to rotation of the first gear and the second gear, at least one of the first set of teeth and the second set of teeth having at least one gear tooth passageway through each tooth thereby fluidically connecting opposing faces of the tooth.

Abstract: A motor pump unit comprises an electric motor and a reversible internal gear machine. The latter has a multi-part housing in which an externally toothed pinion and an internally toothed hollow gear are arranged. A free space, in which a multi-part filler element is arranged, is configured between the gears. The filler element comprises radially movable sealing segments, between which a radial gap is configured. An axially movable sealing plate is arranged between axial faces of the gears and a housing part. This has a sealing plate control groove that is open to the faces of the gears and that can be pressurized, and which is open to the radial gap and located directly opposite thereto. The pinion segment and/or hollow gear segment has a radial sealing segment control channel that can be pressurized and extends transversely, is open to the radial gap, and ends directly in the radial gap.

Abstract: Provided is a scroll compressor capable of ensuring reliability of a release valve device. The scroll compressor is provided with: an orbiting scroll having an orbiting scroll wrap; a fixed roll having a fixed scroll wrap intermeshing with the orbiting scroll wrap; a release hole formed in the fixed scroll; a housing hole communicating with the release hole and having larger diameter than that of the release hole; a valve seat member which is housed in the housing hole and has a valve seat surface; a valve plate contacting with or separating from the valve seat surface by a pressure difference; a spring for pressing the valve plate against the valve seat surface; a stopper which is equipped with the spring and secures the valve seat member; and a retainer for securing the stopper.

Abstract: An improved discharge port of a rotary screw compressor is described. A discharge port of a screw compressor generally includes a restrictive portion to help prevent a leakage of working fluid back to a suction side of the compressor. The improved discharge port is configured to have a restrictive portion with a reduced size compared to a restrictive portion of a conventional discharge port, resulting in an enlarged opening of the discharge port compared to a conventional discharge port. The improved discharge port can help discharge the compressed working fluid more quickly than a conventional discharge port, reducing and/or avoiding over-compression of the working fluid. The efficiency gained due to the enlargement of the opening may be more than the efficiency loss due to leakage of working fluid back to the suction side, resulting in a net efficiency gain of the compressor.

Abstract: A refrigerant scroll compressor for a motor vehicle air conditioning system having a fixed scroll, a orbiting scroll engaging with the fixed scroll, wherein the fixed scroll and the orbiting scroll cooperate to compress a refrigerant gas. An intermediate pressure chamber is disposed adjacent the orbiting scroll, an oil return duct provides fluid communication between the intermediate pressure chamber and a high pressure area of the refrigerant scroll compressor, and at least one intermediate pressure duct is formed in one of the orbiting scroll and fixed scroll and is in fluid communication with the intermediate pressure chamber.

Abstract: A compressor is provided that may include a passage separator provided between an electric motor drive and a compression device to separate a refrigerant passage from an oil passage. The passage separator may include a first partition wall and a second partition wall. The first partition wall may be disposed between an inner circumferential surface of a casing and a discharge hole of the compression device, and the second partition wall may be disposed between the discharge hole and a balance weight. Accordingly, the refrigerant passage may be separated from the oil passage between the compression device and electric motor drive, thereby efficiently recovering oil to an oil storage space.

Abstract: A pump drive for an extracorporeal blood pumping system including an adjustable drive magnet. The pump drive may be coupled to a blood pump which includes a pump impeller. The pump drive may include a stepper motor for dynamically adjusting the position of the drive magnet. The position of the drive magnet may be varied to vary the distance between the drive magnet and an impeller magnet of the pump impeller. Adjusting the position of the drive magnet may include dynamically adjusting the drive magnet and may include axially moving the drive magnet to thereby vary a magnetic attraction force between the drive magnet and the impeller magnet which may thereby minimize forces acting on one or more bearings of a pump impeller.

Abstract: A fan damping device for adjusting magnetic resistance includes: a support frame, a fan wheel, a ring-shaped magnetic core, a magnetic control unit, and a control unit. The fan blades of the fan wheel can provide air resistance, and the magnetic control unit and the control unit provide adjustable magnetic resistance. By such arrangements, resistance can be increased without increasing the size and weight of the present invention. Besides, the resistance is adjustable as desired to improve convenience of use.

Abstract: A turbo compressor includes: a compressor casing which accommodates impellers compressing gas by rotation; and a motor casing which accommodates a motor rotating the impellers, wherein the motor casing has a cylindrical main body part having a larger diameter than a mounting flange provided in the compressor casing, and the compressor casing and the motor casing are connected through an adapter member.

Abstract: The present invention illustrates an electric fan includes a motor, a rotatable disc and a fan blade. The motor has a driving shaft extended outwardly, the rotatable disc is connected with an end of the motor, and a fan shaft is pivotally connected on the rotatable disc and obliquely disposed relative to the driving shaft. The fan blade is disposed on the fan shaft. A connecting member is disposed between the driving shaft and the fan shaft. The rotatable disc is driven by a driving device to drive the fan shaft to rotate about the driving shaft, so as to expand a blowing range of airflow generated by the fan blade.

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 method for fan speed control for a condenser fan in an air conditioning system includes determining a refrigerant condition at an inlet of a compressor by a condenser fan speed control module; determining a refrigerant condition at an outlet of the compressor by the condenser fan speed control module; determining a parabolic curve of a relationship between an air conditioning system performance metric and a speed of the condenser fan based on the determined inlet condition and the determined outlet condition by the condenser fan speed control module; identifying an optimum condenser fan speed based on a vertex of the parabolic curve by the condenser fan speed control module; and controlling the speed of the condenser fan to meet the optimum fan speed by the condenser fan speed control module.

Abstract: A manufacturing technique for impellers for a centrifugal rotating machine is provided. The impeller is made by composition of single vanes pieces that fit to the hub or directly to the rotor shaft by welding, friction welding or a mechanical locking system. The manufacturability of the segments is easy fast and cheap and make it possible to use advanced manufacturing technologies like additive manufacturing of the type of Direct Metal Laser Melting.

Abstract: A modular fan assembly includes a center hub assembly and a first blade attached to the center hub assembly. The center hub assembly includes a first plate having an outer edge, and a second plate having an outer edge. The first blade has a mounting pad and a working portion. The mounting pad is positioned in between the first plate and the second plate. The working portion extends beyond the outer edges of the first and second plates of the center hub assembly. A thickness of the first blade is smaller proximate the outer edge of the first plate than at the mounting pad to create a first gap between the first blade and the first plate at the outer edge of the first plate.

Abstract: In one aspect, a centrifugal blower assembly is provided. The centrifugal blower assembly includes a housing defining an interior space and an impeller configured to channel an airflow within the interior space. A motor is coupled to the impeller and configured to rotate the impeller about an axis. The centrifugal blower also includes a plurality of mounting arms. Each mounting arm of the plurality of mounting arms includes a first end coupled to the housing and a second end coupled to the motor. Each mounting arm of the plurality of mounting arms has a cross-sectional profile that comprises a portion of an airfoil shape.

Abstract: A fan assembly and a method of assembling a diffuser collar in the fan assembly are disclosed. The fan assembly includes an impeller including a plurality of blades. The impeller has an impeller diameter. A duct is configured to receive an outflow provided by the impeller. The duct has a duct exit diameter that is larger than the impeller diameter. The fan assembly further includes a diffuser collar extending from the impeller toward a duct exit. The diffuser collar is configured and arranged to radially expand the outflow provided by the impeller. The diffuser collar has a first diameter at a first edge disposed a first distance from the impeller. A contour extends from the first edge toward a second edge having a second diameter. The second edge is disposed a second distance from the impeller. The first distance is smaller than the second distance, the first diameter is smaller than the second diameter, and the first and second diameters are smaller than the duct exit diameter.

Abstract: A hydropneumatic device having pressure a working part with a working piston guided in the working part and an intensifier part with an intensifier piston guided in the intensifier part. A connecting section for a hydraulic connection of the working part and of the intensifier part provides a connecting line for passage of hydraulic fluid between the working part and the intensifier part. The connecting section includes an adapter component which can be mounted on the working part and the intensifier part, and in the interior of which the connecting line is formed. In the mounted state of the adapter component, an opening, which is provided at the side on the working part, of a hydraulic chamber of the working part is connected, via the connecting line, to an opening, which is provided at the side on the intensifier part, of a hydraulic chamber of the intensifier part.

Abstract: A pressure accumulator has at least one accumulator housing (103) with at least one connection (111; 113) for a pressure medium (149), especially in the form of a fluid that can be accumulated in the accumulator housing (103). A filling material (119) that has hollow chambers or that forms at least one hollow chamber for accommodating at least part of the pressure medium (149) introduced into at least sections of the accumulator housing (103). An interior (117) of the accumulator housing (103) is completely filled with the filling material (119) to such an extent that the filling material (119) contacts the entire surface of a wall (120) of the accumulator housing (103).

Abstract: A separating device for fluid media receivable in a working housing (1). A separating piston (3) is inside the working housing (1) and separates two media compartments (5, 7) from one another in a media-tight manner. The separating piston (3) is provided along its external circumference with a guide (19). During a transversing movement of the separating piston (3) inside the working housing (1), the guide bears slidably on the housing inner wall (21) and is an integral component of the separating piston (3).

Abstract: A control device controls a hydraulic cylinder unit having a piston. The device receives a setpoint variable and an actual variable and determines, based on a difference between the setpoint variable and the actual variable, a preliminary manipulated variable for valves of the hydraulic cylinder unit. The setpoint variable and the actual variable relate to a position of the piston or a force applied by the piston. Linearization factors are determined dynamically as a function of the actual position of the piston and working pressures on both sides of the piston and a hydraulic fluid tank/pump. Definitive manipulated variables to control the valves are determined from the preliminary manipulated variable and the linearization factors. With the linearization factors, a ratio of the piston adjustment speed to the difference between the setpoint variable and the actual variable is independent of the actual position of the piston and the working pressures.

Abstract: A fluid system for a machine that includes a linkage. The fluid system includes an actuator, an accumulator, a pilot circuit, and a pressure reducing valve. The actuator is configured to manipulate the linkage. The accumulator is configured to store a fluid discharged by the actuator under pressure. The pilot circuit is fluidly coupled to the accumulator and is configured to receive the fluid from the accumulator. Further, the pressure reducing valve is positioned between the accumulator and the pilot circuit to regulate the pressure of the fluid delivered to the pilot circuit from the accumulator.

Abstract: Systems and methods for providing a soft robot is provided. In one system, a robotic device includes a flexible body having a fluid chamber, where a portion of the flexible body includes an elastically extensible material and a portion of the flexible body is strain limiting relative to the elastically extensible material. The robotic device can further include a pressurizing inlet in fluid communication with the fluid chamber, and a pressurizing device in fluid communication with the pressurizing inlet, the pressurizing device including a reaction chamber configured to accommodate a gas-producing chemical reaction for providing pressurized gas to the pressurizing inlet.

Abstract: A power transmission assembly for a vehicle with prime mover, prime mover output shaft, and right and left traveling devices, comprises a power distribution unit that receives rotary power from the prime mover output shaft and distributes it between right and left transmission units, which each include: a center section with a closed fluid circuit, a lateral first portion, and a second portion perpendicular thereto; a hydraulic pump mounted on the first portion such that a pump shaft is parallel to the prime mover output shaft; a hydraulic motor on the second portion fluidly connected to the hydraulic pump via the closed fluid circuit, having a lateral motor shaft; and a speed reduction device on a distal side of the hydraulic motor that transmits power from the hydraulic motor to the right or left traveling device.

Abstract: The present invention discloses a liquid-driven nano-porous actuator and the application thereof, and belongs to the field of nano material actuators. According to the present invention, by changing the content of the liquid in the nano-porous material, the interface between the surface liquid of the nano-porous material and air is exchanged between flat and curved states, so as to change the compressive stress acting on the nano-porous material from the surface tension of the liquid and change the elastic deformation of the nano-porous material, thus driving the nano-porous material to contract and expand in a reversible manner and further realizing driving performance.

Abstract: A vapor transport device can include a tube, a first cap positioned at a first region of the tube, a second cap positioned at a second region of the tube, and a piston positioned between the first cap and the second cap so as to divide the tube into a first chamber of variable size that extends between the first cap and the piston and a second chamber of variable size that extends between the piston and the second cap. The vapor transport device can further include a drive shaft connected to the piston and extending through the second cap, and can also include one or more one-way valves.

Abstract: A mechanism to reduce load of a hydraulic cylinder having a body, a stem movable within the body, and a piston rod connected to the stem. The mechanism includes a mechanism body attached to the body and defining a recess, and a retainer attached to the mechanism adjacent the opening of the recess so that the retainer substantially fills the opening of the recess, and having an aperture that receives an end of the piston rod. The mechanism further includes a cap attached to the piston rod of the hydraulic cylinder within the recess, the cap having a diameter greater than the diameter of the aperture in the retainer, and a spring connected to the cap at a first end and to the retainer at a second end so that as the piston rod moves relative to the failsafe mechanism body, to reduce load transfer between the piston rod and the cylinder body.

Abstract: A piston actuator (10) includes a housing (12) having a hollow interior (12a) for enclosing a piston (14) defined by a head (14a) and a rod (14b). The piston (14) can reciprocate between first and second end limits of travel within the housing (12) and separates the housing (12) into first and second expandable fluid chambers (16a, 16b). The housing (12) has a rod-end opening (12b) at one end and a head-end opening (12c) at an opposite end. The piston (14) can include a longitudinally extending aperture (14c) formed therein with an open end (14d) facing the head-end opening (12c) of the housing (12). A magnet (18) can be supported by the piston (14) adjacent to the open end (14d) of the longitudinally extending aperture (14c) in the piston (14).

Abstract: A clip for facilitating installation of foam insulation boards in a building structure. The clip comprises a body, a spacer and a foot for holding the insulation board, and a connection region for attachment of the clip to a building structural member. The clip is designed to ensure proper ventilation and greatly easy the proper installation of rigid foam insulation.

Abstract: The invention disclosed herein generally relates to an improved clamp assembly for attaching two or more objects, such as furniture, tables, desks, dividers or other panel elements together of variable thicknesses. The elements of the clamp assembly invention generally include a clamp body with a clamp stop and clamp spine, a cross-dowel, an actuating screw and clamp lever. The clamp assembly imparts a compressive clamping force by utilizing a fulcrum-lever arrangement whereby the clamp lever is moved in an arcuate trajectory by rotating the actuating screw in the desired direction as the clamp lever pivots about a fulcrum point. This allows the user to easily place and connect various objects, such as tables, desks, courtesy and privacy panels and another desired object that the user desires to secure in a desired arrangement by imparting a compressive force to the panel element that is to be connected to another panel element.

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.