Patent GB-514420-A (GB)
Title: Improvements in or relating to centrifugal blowers or compressors
IPC: F04D29/28
Filed: 1938-06-07
Abstract: 514,420. Centrifugal blowers; fluid-pressure servo-motors; linkwork. REGGIO, F. C. June 7, 1938, Nos. 16975 and 16976. Convention dates, June 7, 1937 and May 7, 1938. [Class 110 (i)] [Also in Group XXIX] To continuously vary the pressure characteristic or ratio of a centrifugal blower for precompressing the scavenging or supercharging air or mixture of internal-combustion engines, means are provided for continuously varying the effective external diameter of the impeller. With tapered impeller blades, the walls of the casing may be simultaneously adjusted' to maintain a constant spacing. The angle of the diffuser blades may also be simultaneously-adjusted. In one form, Fig. 1, the driving gear 14 is splined to a hollow shaft 10 carrying the rotor hub 11 in which are mounted four pairs of blades 18 with lateral teeth engaged by a pinion 19 on a control shaft 20. This shaft has helical splines engaging a control sleeve 22 splined to shaft 10 and moved by a rod 31 and control lever 37. Sleeve 22 carries weights 40 bearing against a race 43 and tending to move the sleeve 22 towards its median position with a force equal to that with which the blades 18 tend to move it away, the race 43 being suitably shaped. In a modification, Fig. 12 (not shown), the weights 40 are carried by control shaft 20 which is formed as a sleeve engaged by helical splines on control rod 31, rod 31 having a second set of splines engaging within shaft 10. With a constant-speed supercharger, the weights 40 and race 43 may be replaced by a helical spring around shaft 10. One wall 50 of the casing is adjusted to the position of blade 18 by helically splined shafts 51 actuated by arms 54 coupled to lever 37, a bellows 56 preventing leakage. To make the blower self regulating, Fig. 9, the bellows 56<1> is set in farther from the ,outer edge of the movable wall 50<1> and a spring 62 is provided so that alteration of pressure in chamber 53<1> will move wall 50' and, through the arms 54<1> and lever 37, will adjust the diameter of the impeller. The diffuser may have vanes 71, Fig. 14, mounted on shafts 72, 73, the latter having a screw connection with an arm 120 carried by the adjustable wall 50 so that the angle of the vanes is varied with the position of the wall. An annular flexible wall 56<2> joins wall 50 to the fixed wall 68. The walls 50 may be adjusted by'the vanes 71 in which case the shafts 72 have pinions 75<1> engaging a toothed ring 112, one shaft 72 being also coupled by rod 118 to the control lever 37. Lever 37 may be operated by a pressure regulator comprising a sealed metallic bellows 138 with spring and a bellows 140 connected by duct 142 with the discharge volute. These bellows act on a lever 146 coupled to a manual control 160 and to a slide valve 148 in a servo-motor 150 using compressed fluid such as oil from an engine-driven pump. Each impeller blade 48, Fig. 17, may consist of thin sheet material, such as laminated steel, with a lateral curvature, the blades being secured to a central drum and passing through guides so that their free ends extend substantially radially, rotation of the drum winding the blades in and reducing the outer diameter of the impeller. The guides may extend as central ribs along the whole radial development of the blades which in this form are not curved laterally, although the guides may have a slight curvature, and such an impeller may be used with a doubleinlet blower. Fig. 31 shows a shrouded impeller with pairs of flexible blades 184 guided between elements 11', 46 carried by the impeller side walls 170 grooved at 186 to receive the blades 184 which are secured to the drum 48'.