4 BULLETIN 115, TJ. S. DEPARTMENT OF AGEICULTURE. 



Practically all gates of this type are fitted with screw and wheel 

 lift and locking devices. The locking device usually consists of some 

 form of cast-iron nut turning on the thread of the gate stem under 

 the crosshead. As the stem does not turn around but is lifted simply 

 by the threads in the wheel it is necessary only to screw the loose 

 nut to any desired point and lock it to a chain or bar connecting 

 with one standard. This prevents it being turned in either direc- 

 tion, and when the stem is raised until the nut reaches the crosshead, 

 the shutter is locked as regards further opening, but may be closed 

 partially or wholly by the consumer. Other devices used lock the 

 gate so that it can not be either opened or closed except under 

 action of the key. (See fig. 11, p. 42.) 



Most of the standards of this type of gate come in lengths of 6 

 feet unless ordered otherwise, but the writer noticed many cases 

 throughout the West where a material saving could have been exer- 

 cised by ordering shorter lengths of standard. 



The standards may be made so that they will be at right angles 

 to the connection for the pipe or at an angle of 60° or 75° with the 

 pipe. In most cases the 75° angle probably will give better results, 

 as the face then will be more nearly in conformity with the slope of 

 the bank. One manufacturer even makes a type with a slope of 45° 

 with the pipe. 



Most makers step up the gate sizes to conform to the sizes of stand- 

 ard vitrified-clay pipe beginning at 6 inches and going to 24 inches. 

 Some makers have gates for 30 and 36 inch pipe, but as a rule the type 

 is changed. 



Gates with connections for rectangular openings are for use with 

 timber or masonry tubes larger than standard sizes of pipes, as a rule. 

 The standards, locking devices, etc., are the same as on the gates for 

 pipes. These gates run in various sizes from 6 by 6 inches up to 

 several feet in either dimension. The stems and lifts vary all the 

 way from a simple handle and bar up to powerful geared rack-and- 

 pinion or screw lifts. 



The third type of gates consists of sheet-steel or cast-iron slides with 

 metal guides. They come in sizes up to about 12 feet wide and may 

 be built up from a single panel to a battery of several openings. 

 Where the masonry structure is divided into vents by masonry piers 

 each gate is a unit independent of the others. They also are designed 

 in batteries for installation as a metal unit in a gate structure with 

 walls and floor of concrete or rubble masonry. This class has a struc- 

 tural steel frame securely anchored by bolts to the floor and walls. 

 An example of this type of gate is shown in Plate V, figure 2. 



The rack-and-pinion lift is the most common type for this class of 

 gates. On the more simple ones the lever acts directly on the pinion, 

 the gate being held by a pawl. More power is secured by inserting a 

 train of gears between the lever and the rack. 



