The Emery rotary pump in Hiscox 539 uses four wings driven by an eccentric hollow cylinder. The inner wing pins follow a groove concentric with the outer casing, and toggle connections keep them positioned. This guided arrangement differs from a generic pump with spring-loaded radial vanes.
Emery Rotary Pump · Guided-Wing Geometry and Pocket Volumes
Explore an eccentric hollow driver with four rigid guided wings. Check offset, wing length and changing geometric pocket volumes around the casing.
Equation Used
- Casing and guide groove share center O.
- Hollow cylinder turns about eccentric center C.
- Four rigid wings maintain constant length and selected line offset.
- Selected paired inner links operate in separate axial planes.
- Port timing, sealing, leakage and delivered flow are not calculated.
Historical source gives no dimensions or performance rating. The offset range is illustrative, not a pump-sizing recommendation.
Two centers and four guided wings
The outer casing and circular inner-pin groove share center O. The hollow driving cylinder turns about a lower, offset center C. Four wings pass through the cylinder. Their inner pins follow the groove, while their outer ends follow the casing.
The source engraving shows the guide and a toggle-joint connection but does not dimension the wings, collars or links. The model uses rigid wings whose centerlines have a constant offset from O. That makes both end-contact radii compatible with one unchanging wing length.
Four swiveling slide collars, carried 90° apart on the hollow driver, accommodate the wing direction as it changes. The inner positioning links are shown as two pairs meeting at O in separate axial planes. These illustrative link dimensions explain the guided motion; the exact historical joint dimensions are not specified.
The colored spaces outside the hollow cylinder are geometric fluid pockets. Their areas change as the wings advance at unequal angular rates around O. Their combined volume stays constant.
Explore offset and pocket geometry
Change casing bore, driver offset, axial depth and driver speed. Increasing offset changes the hollow cylinder radius, its center position and the variation of the pocket volumes. The guide remains concentric with the casing throughout.
The offset control is a selected model range expressed as a percentage of casing radius. The range does not specify a recommended offset for a working pump.
Axial depth scales every pocket volume. Speed changes revolution time and the average number of wing passages per second. No pressure rating, viscous-fluid performance, oil/bilge installation or delivered flow is established by this single historical source.
Rigid-wing contact geometry
Let casing radius R=D/2 and offset e=R×offset ratio/100. The selected hollow-driver outer radius is r=R−e, placing it tangent to the casing at the bottom. Its wall thickness is 0.09R, and its collar centers lie at radius r−0.045R about C.
The inner guide radius is g=0.35R and each wing line is offset h=0.18R from O. Distances along a wing from the foot of that perpendicular are sᵢ=√(g²−h²) and sₒ=√(R²−h²). Rigid wing length is L=sₒ−sᵢ.
At driver angle θ, each collar location Dⱼ=C+(r−0.045R)[cos(θ+jπ/2),sin(θ+jπ/2)]. Its wing direction is α=atan2(Dᵧ,Dₓ)+asin(h/|D|). This places the collar on the same straight line as the inner guide pin and outer casing contact.
The area of each external pocket is obtained from its two straight wing boundaries, outer-casing arc and inner driver arc. Multiplying by axial depth gives its displayed volume. The four areas sum to π(R²−r²); their combined volume is bπ(R²−r²). Divide mm³ by 1000 for cm³.
Four wings give an average passage frequency 4n/60=n/15 per second. Their instantaneous angular speed around O varies. Average passage frequency is not a pressure-pulse measurement or a flow prediction.
Example: 240 mm casing with 20% radius offset
The casing radius is 120 mm, driver offset 24 mm and hollow-driver outer radius 96 mm. The selected guide radius is 42 mm. At 50 mm axial depth, the combined external cavity volume is about 814.30 cm³.
At 60 rpm the driver makes one revolution per second, and four wings pass a reference position per second on average. Their unequal angular spacing makes the individual pocket volumes grow and shrink while retaining the same total.
Doubling axial depth doubles all pocket volumes. Doubling bore with the same ratios quadruples volumes at unchanged axial depth. Offset changes the driving geometry but leaves the rigid wing length unchanged when casing bore, guide ratio and wing-line offset are unchanged.
Model boundaries
The source-specific feature is the guided inner wing end, not a generic spring-loaded vane. The selected collars and paired positioning links explain a feasible connection, but the source supplies no dimensions, tolerances or axial assembly details.
Contact uses thin rigid wing centerlines. Visible blade width is diagrammatic. Actual seals, tip geometry, bearing loads, wall clearances, port opening areas and leakage are not solved.
Static pocket volume and its variation do not by themselves establish delivered displacement. A practical flow calculation needs the actual inlet/outlet schedule and trapped-volume behavior. No pump pressure or efficiency rating is claimed.
Emery pump questions
Why are O and C different?
O is the center of the casing and guide groove. C is the eccentric center of the hollow driving cylinder.
Do the wings change length?
No. Their inner and outer ends remain at the two specified radii, and the selected constant line offset keeps their length fixed.
Why do pocket sizes change?
Equally spaced collars around C do not produce equally spaced wings around O. The resulting variation changes each external pocket area.
Is the total cavity volume a per-revolution delivery?
No. It is a geometric volume; actual delivery needs port timing and leakage information.
Primary reference
Gardner D. Hiscox, Mechanical Movements, Powers, Devices and Appliances, device 539, printed page 146: four wings, eccentric hollow cylinder, concentric guide pins and toggle-joint positioning connection.
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