Plumbing elbow

A pipe system has an elbow 70 with a snake-passing opening 72 (FIG. 3) that is normally closed by a plug 88, with the walls of the snake opening and plug constructed to avoid harmful wear during use of the snake. The elbow forms a nipple 82 that surrounds the snake opening. The nipple has threads (102, FIG. 4) on its outside so snake-caused wear does not initially occur in the threads. The snake opening has an axis 108, and the plug middle forms a cup 112 that extends axially inward to block a majority of the volume within the inner end of the nipple.

BACKGROUND OF THE INVENTION

Household sinks usually have a U-shaped pipe that forms a trap, and have an elbow that follows the trap and a horizontal pipe section that follows the elbow. U.S. Pat. No. 3,168,104 shows an elbow that has a snake opening through which a “snake” can be inserted to clean out a stoppage such as a stoppage in the horizontal pipe section or in other pipe sections connected thereto. A plug closes the snake opening when a snake is not inserted. The elbow commonly has a nipple with internal threads, and the plug can be threaded into the nipple to close it. This results in one spot on the threads of the nipple being exposed to wear by the snake during use of the snake. The snake typically has a rough surface to help it loosen debris, and this rough surface can wear an end of the nipple threads and lead to leaking water. An elbow that provided the advantages of an elbow of the prior art but which avoided concentrated wear that could lead to water leakage, would be of value, especially where plastic pipes are used.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, an elbow is provided, which has a snake opening with an axis, which avoids concentrated wear that can cause leakage. The elbow has a nipple with nipple threads on the radially outer surface of the nipple. As a result, the nipple threads are initially not worn by vigorous use of the snake. The plug has threads on the radially inner surface of the plug. If there is wear at the axially outer end of the nipple, this does not result in wear of a thread, which could cause leakage.

The plug has a plug middle that extends axially inward and that covers almost all volume within the nipple. This avoids creation of a “dead space within the elbow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a prior art elbow pipe arrangement10which is commonly present under sinks of homes. The arrangement includes a U-shaped pipe12with one primarily vertical end14that connects to a sink outlet, and an opposite primarily vertical end16that connects through an elbow30to a primarily horizontal segment20of a drain pipe22that leads to a drain. The arrangement also includes an elbow30with a primarily right angle bend (30° to 60°).

The elbow30includes a snake opening32and a plug34that can be removed and reinstalled on the elbow.FIG. 2shows the plug removed so a cleanout snake40can be installed though the opening. The snake can be directed into horizontal or vertical pipe sections16or20, but usually enters the horizontal pipe section. The snake is usually made of steel, with grooves42that result in a rough surface to remove dirt and debris that might clog the pipe arrangement.

One problem that is encountered with the prior art arrangement ofFIG. 2is that continued use of the snake can result in wear of the walls of the elbow snake opening32. Such wear is especially likely at the lower side of the snake opening at an axially outward O location44where the snake passes across the lower side of the snake opening threads50. The elbow of the prior art has internal threads50, and the plug34that can cover the opening has threads54on the outside of the plug. The elbow usually forms a nipple60with internal threads, and the plug screws into the nipple.

If one side of an opening thread or one side of a plug thread is worn away, then water can leak though that opening. If the elbow is made of a material that is much softer than steel, such as a common plastic (e.g. polyvinyl chloride), then the danger of leakage by thread wear is even greater.

In accordance with one embodiment of the invention, application provides an elbow70of the type shown inFIG. 3, where the elbow has threads74on the outside surface76of the elbow nipple. The snake opening72has an opening axis80(also called a nipple axis) and is formed with a nipple82and with nipple threads74on the radial outside of the nipple82. The plug88has a ring84with an outer surface87in the form of a hexagon so a wrench can be used to turn the plug. Plug threads86on the plug88lie on the inside surface of the ring84which threadably receives the nipple82by the nipple threads74being threaded to the plug threads86. Accordingly, the plug threads86are inner threads and the nipple threads74are outer threads. The plug88has a cover89that extends across the top of the ring84closing it so as to effect closing of the snake opening72when the plug88is threaded down on the nipple82.

When the plug88is removed and a snake is moved back and forth in the elbow opening, wear occurs primarily at the location90which is at the lower side of the nipple inside surface, near the axially outer O end of the nipple. The location90can be thickened as to90tto provide an additional volume that can be worn.

One problem that can arise with the design ofFIG. 3is that a large dead space92is left under the plug88. Such dead space should be minimized to minimize the build-up of slime etc.FIG. 4shows another elbow pipe arrangement, in which the nipple100that lies about the snake opening does not have threads on the inside surface of the nipple. The nipple threads102lie on the outside of the nipple as outer threads and the plug104has plug threads106that face radially inwardly as inner threads and defining a threaded inside surface, towards the opening axis108(also called the nipple axis). However, to minimize dead space, applicant constructs the plug with an inwardly projecting cup112which fills the dead space. The plug construction also allows a seal ring to be located at114on or below an inward facing surface of the nipple or on the outward-facing smooth surface of the cup. The cup112includes an inwardly I projecting hollow cylinder116and a largely radially (to axis108) inner wall120that is preferably concavely rounded on its inner surface122.

The plug104also has the ring84with an outer surface87in the form of a wrench-engaging surface so that a wrench can be used to turn the. However, instead of a cover89across the top of the plug as in the version ofFIG. 3, the plug104has a plug middle comprising a cup112having a cylindrical wall121forming the inwardly (I) projecting hollow cylinder116that extends axially inward co-axially with the nipple axis108and concentrically with and radially inwardly spaced from the threaded inside surface with the inner threads106and terminating with the inner wall120closing the bottom of the cup112. The plug middle is formed integrally with the ring84by attachment at an outer end of the cylindrical wall121to a rim portion123that is attached to the ring84.

Thus, the invention provides an elbow pipe arrangement that includes an elbow with an access opening for passing a cleanout snake and a plug for normally keeping the opening closed, which minimizes snake-caused wear. The opening has an axis and has threads on the radially outer side of the opening, while the plug has threads on the radially inner side of the opening. The elbow forms a nipple and the opening threads lie on the outer side of the nipple. A dead space that lies within the nipple is largely blocked by a cup-shaped portion (the inwardly projecting hollow cylinder116) of the plug that projects into the dead space.