CHAPTER III 



LOCK GATES AND VALVES. 



GATES. 



Miter-gates. The gates used for closing each end of a lock usually consist of a 

 pair of symmetrical leaves, movable about a vertical axis, shutting against each other 

 at one end and against the miter-sills at the bottom, and abutting against the hollow 

 quoins at the other end. That part fitting into the hollow quoin is called the heel, 

 while the opposite end is called the toe, and in old construction, where a post formed 

 each side of the gate-frame, they were called respectively the heel- or quoin-post and the 

 toe-post. The gates rest on shoes which turn upon pivots or pintles at the bottom of 

 the heel portions, and they are held vertical by means of collars or anchor-bars fast- 

 ened to the top of the masonry, and passing around pins in the bonnets or tops of the 

 gate-heels. A roller has sometimes been placed on the bottom of the gate near the toe, 

 traveling on the floor and relieving the strain on the anchors. The gates are usually 

 operated by means of spars or chains, or both, connecting with the top of the gate near 

 the toe and with suitable capstans located on the walls. 



The recesses for mitering gates should always be at least one foot longer than the 

 gates when these are open, and should afford a clearance of about a foot behind them 

 to allow space for floating sticks and debris, which would otherwise hinder them from 

 opening fully. 



The lap of the gate on the miter-sill may be made from 4 to 6 inches, and the clear- 

 ance between the bottom beam and the floor may be 6 inches or more. 



Single Swinging Gates may be seen on many of the older locks of narrow width, 

 but they are rarely applied to the locks used in river improvement. They are prac- 

 tically a single leaf of the miter-gate. Usually they have a balance-beam extending 

 back over the wall and serving as a lever for their movement. At the toe they are 

 supported against a shoulder in the wall. 



Rolling Gates are in use in Europe and on the upper Ohio River in America. In 

 the locks on this stream, where the chambers are no feet in width, the gates are sup- 

 ported on a heavy track, and present an appearance not unlike a long box -car. When 

 not in use they are rolled back into recesses in the bank. There are, of course, two 



gates, one at each end of the lock. Each is about 14 feet high, and about the same 



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