Self-tightening cover for pump

A self-tightening retaining system for securing a closure at an installed position within a bore of a housing to close the bore, said bore having screw threads along at least a portion of the bore and said closure having an internally threaded hole extending into the closure, the system comprising:

• a retaining cover for obstructing removal of said closure from said bore, the cover being receivable in the bore in a position generally adjacent the closure and having external threads interengageable with said screw threads of the bore such that the cover is rotatable relative to the housing in a tightening direction for movement of the cover into the bore toward the closure and rotatable in an opposite, loosening direction for movement of the cover out from the bore away from the closure, the cover having a central axis or rotation;
• and
• a locking device configured for being secured to the covers such that the locking device rotates together with the cover about said central axis, the locking device comprising a fastener receivable in said hole of the closure and having external threads interengageable with threads of the hole;
• wherein the threads of the cover and the threads of the fastener are spiraled in opposite directions such that when the cover rotates in the loosening direction, the fastener becomes tightened in the hole of the closure thereby stopping the rotation wherein the locking device further comprises a locking member receivable in said central opening of the cover, the locking member having a size and shape configured to form a radial abutment to an internal wall of the cover and against rotation of the cover relative to said locking device.