Abstract: A telescoping joint is used to space out ends of a string and distribute the string weight between the tie-down locations. The joint can be compressed to reduce its length but has a locking mechanism that prevents extension under tensile loading. The seals in the joint provide a longer service life due to minimization of relative movement in the expansion joint components. The locking mechanism is preferably a ratchet system that uses a body lock ring that is enabled after breaking a shear pin.

Abstract: A telescoping joint is used to space out ends of a string and distribute the string weight between the tie-down locations. The joint can be compressed to reduce its length but has a locking mechanism that prevents extension under tensile loading. The seals in the joint provide a longer service life due to minimization of relative movement in the expansion joint components. The locking mechanism is preferably a ratchet system that uses a body lock ring that is enabled after breaking a shear pin.

Abstract: An electrical receptacle for selectively receiving two prong polarized or three prong grounded electrical plugs while excluding non-polarized plugs and other foreign materials from being inserted into the receptacle apertures. The receptacle is provided with a body having an internal cavity containing an aperture shield and a locking bar. The aperture shield is biased to the closed position obstructing the receptacle aperture and is retained in the closed position by the locking bar. The locking bar shifts to the unlocked position upon the insertion of the polarized plug or a ground prong enabling the aperture shield to shift transversely to the open position in response to plug insertion.

Abstract: A device for closing female apertures in an electrical receptacle and opening those apertures responsive to mechanical engagement of a male prong of a plug, having prongs operable for insertion into the receptacle.