12 



Ward's Patent for Improvements 



or straps^ of the breadth of about one-sixth part of the 

 diameter of the cylinder of the pump. I prefer leather of 

 ox-hide, such as is used for straps for working machinery. 

 Such bands are united by sewing, and also with the well- 

 known cement of isinglass or fish-glue dissolved in weak 

 spirit, or are united by other suitable means, so as to form 

 a continuous circle of about the same diameter as the 

 pump cylinder, but considerably conical, so as to facilitate 

 the bending hereinafter mentioned. The bands of leather, 

 after being softened by water and placed upon a block of 

 similar size to the piston, are then bent and contracted so 

 that about one-third part of the breadth may fit the 

 cylinder and the other two-third parts may be attached to 

 the piston, and secured by plates of metal screwed to the 

 main part of the piston, but which screws being slightly 

 loosened would allow the leather to be driven outwards, 

 or towards the sides of the cylinder, after a portion of the 

 said packing has become worn. The shaving off the hair 

 side of the leather will much facilitate the forming it into 

 the required shape, and also the cutting out gaps or 

 notches where the screws or bolts will be required to pass. 

 After the leathers are put into the required form, they 

 should be well saturated with neat's-foot oil, or similar 

 unctuous matter. The edge of the leather band being 

 thus turned will form a portion of concave surface which, 

 being well supplied with oil or other suitable lubricating 

 matter, will fit for the cylinder so as to be air-tight, and 

 yet move with very little friction. Although it is well 

 known that the leathers of the pistons of pumps con- 

 structed in a similar manner to that hereinbefore described, 

 become the tighter the greater the pressure they are ex- 

 posed to, yet the packing of the piston of a large air- 

 pump must either be made somewhat more tight than 

 advantageous, or when the pressure of the air on which it 

 is acting is slight, the air will be liable to pass before the 

 leather expands so as to fit the side of the cylinder. 

 I therefore insert a series of springs, formed by cutting 

 gaps or notches in plates of very thin steel, similar to 

 what is manufactured for making steel pens, forming 

 the segments of a circle, and then bending the parts 

 left to a similar form with relative portions of the 

 bands of leather hereinbefore described, so that the 

 springs, after being tempered, may be inserted between 

 the band of leather and the plates which fix it on the 



