Abstract: An auto-tentioner of timing-belt used for apparatus such as automobiles, which comprises a body, a plunger inserted into the body, a piston inserted in the pluner and protruding from the body so as to push the timing-belt, and a spring at the rear end of the body and pushing the body to the direction of timing-belt, thereby making it possible for the auto-tentioner fully to follow up the extraordinary expansion of the timing-belt.

Abstract: Two forms of a valve, both useful as a standing valve in a well conduit, permitting upward production flow and preventing downward injection flow. Both forms of this valve may also be operated as injection valves, permitting downward injection flow and preventing upward production flow. One form of the valve utilizes a ball valve for flow control and can be converted to injection only valve operation. The other form of the control valve utilizes an annular valve for flow control and cannot be converted to injection valve only operation. The annular valve and ball valve are biased closed, and both are opened for downward injection flow by increasing valve interior pressure to a pressure which will open a control check valve to permit opening flow to a pressure responsive operator. Opening pressure of the check valve is variable and may be predetermined.

Abstract: Polymers used for the control of permeability in stratified subterranean formations are gelled in a controlled manner by the use of rapid and delayed gelling agents. The polymer is first gelled lightly by the use of a rapid gelling agent which partly cross-links the polymer to produce a viscous solution which will selectively enter only the more permeable regions of the formation but can still be readily injected. A delayed cross-linking agent completes the cross-linking process after the polymer has been selectively emplaced to form a firm, full strength gel. Suitable rapid cross-linking agents may be formed by the reaction of alkalies and chromic salts at specified ratios or by the redox reduction of chromium from its higher oxidation states under certain specified conditions. Delayed cross-linking agents are exemplified by chromic salts. Polymers which may be used include polyacrylamides and polysaccharide biopolymers.