Abstract: A folding stage includes a folding linkage with cross members and a center lock. The center lock has a handle below the cross members and off to the side of the cross members to prevent pinching of operators' hands and fingers. The folding linkage folds from a use position wherein stage decks are horizontal to form a stage surface to a storage position wherein the bottom of the stage decks oppose one another. In the fully folded position, stage support legs are angled inward slightly. Casters mount at an oblique angle to the telescoping legs and are moved closer to the telescoping legs to decrease the moment of inertia about the legs while maintaining sufficient contact with the floor. Torsion bars mount at the pivoting access of the frame and the telescoping legs to control folding speed. The folding portions of the frame and decks have a center of gravity which is aligned with the pivoting access to decrease the moment of inertia about the pivoting axis.

Abstract: A folding stage (20) includes a folding framework (22) supporting stage decks (24). The stage is supported on a caster frame (38) including casters (26) for moving the stage from location to location in a folded position. Inner legs (32) and outer legs (34) support the stage in the unfolded position and fold against decks (24) in the storage position. A folding linkage (30) directs and controls folding between a use position and a folded storage position.

Abstract: Mounting system for substantially increasing the wear life of a screen panel which is adapted to be vibrated, utilizes elastomeric material, such as urethane, to isolate the vibrating mechanism from direct contact with the screen panel. An elastomeric wear strip is bonded to screen wires on the underside of the screen panel. A recessed channel formed in the bottom of the wear strip is adapted to engage an upper contact surface of a rigid vibrating bar member, while the side edges of the channel extend downwardly over the sides of the rigid vibrating bar member to prevent abrasive material which has passed through slots in the screen panel from entering the contact area between the recessed channel and the upper contact surface. The upper contact surface of the vibrating bar member is preferably covered with elastomeric material and crowned so as to cause the screen panel to become curved when its side edges are forced down by a pair of hold-down bars.

Abstract: Improved packer assembly for sealing a well screen to a casing avoids contamination problems of expandable lead packers and the abrasion of self-sealing packers which can be rendered ineffective before they reach their intended depth. A pair of annular end members, adapted to be threaded to the well screen and to the drill stem, are joined by a compressible, tubular metal portion. When the well screen is at its intended depth, a swedge dropped against the upper end member of the packer assembly will compress the ends of the tubular metal portion toward each other while the intermediate portion expands into sealing relation with the casing. The seal can be enhanced by applying rings or layers of elastomeric material to the tubular metal portion.

Abstract: Filament reinforced cylindrical plastic screens having open slots defined by their surface wires which are of substantially different widths can be produced on a single helically finned mandrel. The slot widths are varied in accordance with the amount of wire-forming material placed in the generally V-shaped grooves defined by the mandrel fins. The grooves have a double relief angle so that the lower support portions of the surface wires will be formed so as to have a slightly tapered, radially elongated cross-section and the upper portions of the wires will have their sides at a substantially greater relief angle. This relationship permits a relatively small change in the total height of the wires to have a substantial effect on the width of the top portion of the wires, and thus, on the width of the slot openings which can be formed between adjacent wires.

Abstract: Economical plastic well screens having good hydraulic performance can be produced by the method of the present invention wherein a sheet having a large plurality of V-shaped slots is injection molded, is roll-formed into a cylindrical shape, and then has its longitudinal edges bonded to each other. The resistance of the screen to collapse and tensile forces can be enhanced by the addition of ribs in one or two directions. Also, the sheet can be rolled in one direction or another to vary the slot direction or to permit flow from inside to outside as well as the conventional outside to inside.

Abstract: Filament reinforced cylindrical plastic screens having open slots defined by their surface wires which are of substantially different widths can be produced on a single helically finned mandrel. The slot widths are varied in accordance with the amount of wire-forming material placed in the generally V-shaped grooves defined by the mandrel fins. The grooves have a double relief angle so that the lower support portions of the surface wires will be formed so as to have a slightly tapered, radially elongated cross-section and the upper portions of the wires will have their sides at a substantially greater relief angle. This relationship permits a relatively small change in the total height of the wires to have a substantial effect on the width of the top portion of the wires, and thus, on the width of the slot openings which can be formed between adjacent wires.

Abstract: A fiber reinforced plastic well screen including a slotted central section and unslotted end fitting portions is formed by manipulating a single bundle of resin-coated filaments longitudinally and circumferentially relative to a mandrel. The mandrel has a series of helically grooved segments which cooperate with each other to cause the filament bundle to form the slotted central section. Longitudinal wraps, which are looped under tension from one end of the mandrel to the other in the region between each adjacent pair of segments, are intimately bonded to all of the helical circumferential wraps which form the central section as well as those that form the end fitting portions. One removable end cap portion of the mandrel is preferably externally threaded to produce an integral internal thread in the formed well screen. A tubular internal sleeve portion of the mandrel is removable to permit the helically grooved segments to be collapsed inwardly after the well screen is cured.

Abstract: Vent cap assembly for a monitoring well permits venting from a well riser pipe while positively preventing contamination of the well by vandals. Tabs having apertures are integrally attached to the pipe and to an axially elongated vent cap. A padlock may be placed through the apertures to prevent unauthorized removal of the cap, but whether or not the cap is locked, the tab on the riser pipe causes the inner end surface of the cap to be spaced slightly above the riser pipe to insure that venting will always be possible.

Abstract: Improved method of joining a rigid thermoplastic fitting to a rigid thermoplastic well screen having longitudinal support rods utilizes pressure and friction generated heat to bond a reduced diameter tubular, rigid thermoplastic sleeve portion of the fitting to the inner surface of the screen. The method permits the joining, without the use of solvents, of screens and fittings of PVC, polypropylene, or ABS, for example, which have the same outer diameters. The sleeve portion of the fitting has an outer diameter which is greater than the inner diameter of the well screen. The assembly method requires that the parts to be mated be rotated rapidly relative to each other as they are forced axially into interfering, telescopic engagement. The overlapping members are fused along a generally conically tapered plane with the material which is melted during rotation being deposited in the circumferential spaces between the screen's support rods.