Abstract: A shock absorber for damping shock energy generated by downhole perforating guns or stimulation devices is described. The shock absorber includes a spring assembly including at least a first spring and a second spring, the first spring having a tension greater than the second spring; a damper assembly; and a housing retaining the spring assembly and the damper assembly and including ends adapted for connection into a casing perforation assembly. The provision of springs of increasing stiffness permits the force generated by the perforating gun to be absorbed gradually and smoothly.

Abstract: An isolation enclosure and a group of isolation enclosures useful when a relatively large containment area is required. The enclosure is in the form of a ring having a section removed so that a technician may enter the center area of the ring. In a preferred embodiment, an access zone is located in the transparent wall of the enclosure and extends around the inner perimeter of the ring so that a technician can insert his hands into the enclosure to reach any point within. The inventive enclosures provide more containment area per unit area of floor space than conventional material isolation enclosures.

Abstract: An enclosure similar to a glovebox for isolating materials from the atmosphere, yet allowing a technician to manipulate the materials and also apparatus which is located inside the enclosure. A portion of a wall of the enclosure is comprised of at least one flexible curtain. An opening defined by a frame is provided for the technician to insert his hands and forearms into the enclosure. The frame is movable in one plane, so that the technician has access to substantially all of the working interior of the enclosure. As the frame is moved by the technician, while he accomplishes work inside the enclosure, the curtain moves such that the only opening through the enclosure wall is the frame. In a preferred embodiment, where a negative pressure is maintained inside the enclosure, the frame is comprised of airfoils so that turbulence is reduced, thereby enhancing material retention within the box.

Abstract: A plug for use in plugging a glove opening of a glovebox when the glove is eplaced. An inflated inner tube which is retained between flat plates mounted on a threaded rod is compressed in order to expand its diameter to equal that of the inside of the glove opening.