US2178405A - Blower - Google Patents

Description

F. c. REGGIO Oct. 31, 1939.

BLOWER Filed June '7, 1937 5 'SheetsSheet 2 F. C. REGGIO Get. 31, 1939.

BLOWER Filed June 7, 1957 5 Sheets-Sheet 5 I INVENTOR. FED/nAA Do C'. 1?: 66/0 ATTORNEY,

Oct. 31, 1939. v FQREGGIO 2,178,405

BLOWER Filed June '7, 1957 5 Sheets-Sheet 4 N N Q N M Q Tag 15 Fc'g 12,

- INVENTOR. 'fse pMm/Da C. P566510 BY I I ATTORNEY.

Patented Oct. 31, 1939 PATENT, OFFICE BLOWER,

Ferdinando Carlo Reggie, Detroit, Mich. Application June 7, 1937, Serial No. 147,715

12 Claims.

This invention relates'to centrifugal blowers and more particularly to the type used as superchargers or scavenging blowers for internal combustion engines. In the conventional type of centrifugal blower or supercharger, the volume of air or combustible mixture delivered, the pressuresat the inlet and outlet of the supercharger, and the speed of the impeller are mutually dependent variables. In' the conventional supercharger installation, the speed of the supercharger is fixed bythe speed of the engine to which it is geared and the relation between the volume delivered and the pressure at which it is delivered is determined by the speed and physical characteristics of the engine, leaving the inlet pressure as the only means of control. In gasoline engines, a throttle in the intake passage to the supercharger is thereforegenerally used as the engine control, although this involves wasting an appreciable part of the power of the engine in drawing the mixture past the throttle.

For instance, modern aeroplane engines are commonly designed to deliver their maximum power at altitudes of six to ten thousand feet and their superchargers are geared to give the maximum allowable inletv manifold pressures at these altitudes. Obviously, when such an engine is operating at a lower altitude or at less than maximum power or both as when cruising or coming into a landing at low altitude, the throttle must be set so as to greatly lessen the How of mixture to the supercharger and most of the power supplied to the supercharger is employed to overcome the resistance of the throttle and is wasted. a

It is well known, by those skilled in the art, that the maximum power, flexibility and over-all efficiency of internal-combustion engines would be substantially improved by the adoption of a supercharger whose delivery characteristic could be controlled within wide limits without waste of power, so that the engine could be supplied with the amount of air best suited to its actual running conditions such as its speed, its load, the density of the air at the intake, temperature of the exhaust gas and exhaust valves, setting of the propeller (in the case of aircraft engines) and the like. This is particularly true in variable speed Diesel engines, especially of the two cycle type.

Gear driven superchargers have been built in which the ratio of the drive was variable, but these have not been very satisfactory because of the difliculty of shifting gears while in operation and because of the limited number of gear ratios, usually two, that can be provided without excessive weight and complication.

Other means of control have been suggested and tried out, such as returning part of the mixture from the outlet of the supercharger to the 5 inlet, but these have been found to have even greater disadvantages than the conventional throttle.

The principal object of this invention is to provide a centrifugal blower or supercharger whose 1 delivery characteristics can'bevaried independently of its rotational speed and varied continuously and with the expenditure of very little energy so that the blower may be controlled by automatic devices responsive to one or more of 15 several variables, such as load, engine speed, air density, exhaust gas temperature and the like, which aflect the operation'of an engine.

More specifically it is an. object of this invention to provide a centrifugal supercharger rotor whose diameter can be-varied, thus varyingthe capacity of the supercharger.

Another object of this invention is to provide a centrifugal supercharger rotor having slidable blades connected to revolvingweights in such a way that the centrifugal forces acting on the blades and weights will be in equilibrium at all speeds and'in all positions.

Another object of this invention is to provide a centrifugal supercharger rotor having radially slidable blades connected mom or more springs in such a way that, at the designed speed of the rotor, the centrifugal forces acting on the blades and the forces of the springs will be in equilibrium in all positions of the blades.

Another object of this invention is to provide a casing for a variable-diameter supercharger rotor and arranged so that a constant clearance can be maintained between the sides of the rotor 0 and the walls of the casing.

These and other objects of the invention will appear from the following description, reference being made to the accompanying drawings in which- Figure 1 is a longitudinal sectional view through one of the preferred forms of the invention. I

Figure 2 is an end view of the structure shown in Fig. 1 with certain parts removed to more clearly show the internal structure.

Figures 3 to 6 are views showing the four different-forms of blade.

Fig. '7 is a section on the line 1-1 of Fig. 3.

Fig. 8 is a section on the line 8-8 of Fig. 3.

Fig. 915 a section of a portion of a modified form of the invention.

Fig. 10 is a section of a portion of another modified form.

Fig. 11 is a section of a portion of a third modification.

Fig. 12 is a section of a. portion of a fourth modification.

Fig. 13 is a section on the line I3I3 of 'Fig. 12.

Figs. 14 and 15 are respectively a side elevation and an end view of the centrifugal blower shown in Figs. 1 and 2. I

Fig. 16 is a fragmentary view of an impeller blade removed from the apparatus and showing the same in various relations with reference to the axis of the impeller.

Fig. 1''! is a fragmentary longitudinal sectional elevation of a centrifugal blower of still another modified construction.

In the preferred form of the invention, a hollow shaft I0 is formed integrally with the rotor hub II and is carried in a housing l2 by a pair of ball bearings l3. The shaft I0 may be driven in any conventional manner, as by an exhaust turbine or a gear drive from the engine, the particular form of the invention shown in the drawings being provided with a gear I4 splined on the shaft ID for this purpose.

The hub II on the end of the shaft II! is provided with eight slots I5 cut in from the end of the hub I I and all lying in planes parallel to and spaced a short distance from its axis.

A cover or end piece I6 on the hub II closes the sides of the slots I5, leaving them open at their ends, and also serves to reenforce the hub I I. The latter function is accomplished by means of an annular groove in the cover I6 which receives an annular rib or tongue H on the end of the hub II.

The eight slots I5 carry eight blades I8 which project out from the hub I I at equal distances around its periphery. The root of each of the blades I8 extends practically through the hub I I, and the end away from the projecting portion is made heavy enough so that the center of gravity of the entire blade I8 is directly opposite the axis of the hub I I when the blade I8 is in its median position.

Since the slots I5 intersect each other, it is necessary that the blades I8 can pass through each other. This is provided for by cutting away a part of the central portion of each blade so that the portion that is left of each blade passes through the cut away places in the blades which i it intersects.

The individual blades I8 have the shapes shown in Figs. 3 to 6, there being two blades of each shape. The blades are assembled with each other before being placed in the hub II, the assembling beginning with the two blades of the shape shown in Fig. 3 and proceeding by successfully inserting pairs of blades having the shapes shown in Figs. 4, 5 and 6 through the" previously assembled blades.

While-the portions of the blades that slide in the slots 'in the hub II are relatively thick, the projecting portions of the blades are made of thin sheet, as shown in section in Figs. 7 and 8, and are curved laterally to increase their rigidity and strength and to lessen the impact of the air on the blades as it enters.

The center of the hub II is occupied by a long gear l9 formed on the end of a control shaft 20 journaled in the center of the hollow main shaft III of thesupercharger. The gear I9 simultaneously engages the central portions of all the blades I8, these portions of the blades bein formed into racks 2I and being tangential to the gear I9. Thus rotation of the control shaft 20 and control gear I9 relative to the main shaft I0 will cause all the blades I8 to slide simultaneously in their slots I5, thus changing the overall diameter of the rotor. This relative rotation of the two shafts I0 and 20 is caused by the axial movement of a control sleeve 22 which fits into the hollow main shaft I0 and around the control shaft 20. For this purpose, the outside of the control sleeve 22 is provided with straight or helical splines 23 which fit splines 24 on the inside of the main shaft III while the inside of the control sleeve 22 is provided with helical splines 25 which fit helical splines 26 on the control shaft 20. Axial movement of the control shaft 20 is prevented by a collar 21 formed integral with it.. The collar 21 is held axially between a shoulder on the inside of the main shaft in and a ring 28 held by a snap ring 30 which fits into notches in the splines 24.

The control sleeve 22 is moved axially by a control rod 3| connected to its end by a ball bearing 32. The other end of the control rod 3I is square and is supported and prevented from rotating by sliding in a square hole 29 in the end plate 33 of the housing. The control rod 3| is moved endwise by a yoke 34 engaging pins 35 on the rod 3|, the yoke 34 being carried by a shaft 36 and actuated by an external control lever 31.

When the blades I8 are in their median positions with their center of gravity nearest the axis of the rotor, the centrifugal forces acting upon them will be exactly at right angles to them and will tend only tdpress them against the sides of their slots I5 without tending to move them endwise. When the blades I8 are at either side of this position, centrifugal force will act upon them obliquely and tend to move them endwise away from their median position and to rotate the control shaft 20. on the shaft 20 will be resisted by the helical splines 25 and 26 connecting it to the control sleeve 22 and will tend to move it farther away from its median position. To resist this tendency, the control sleeve 22 is provided with sev- The torque thus imposed eral weights 40 which are arranged so as to tend to move the sleeve 22 towards its median position with a force equal to that with which the blades I8 tend to move it away.

The weights 40 are carried in radial holes H in a head 42 on the end of the control sleeve 22 and bear against the inner surface of a cup-like race 43 secured to the end of the main shaft Ill. The entire assembly of head 42, weights 40 and cup 43 rotates with the shaft l0 so that the weights 40 are pressed against the cup 43 by centrifugal force. When the sleeve 22 and head 42 are in their median position, the balls or weights 40 press against the part of the race 43 having the greatest diameter and exert no force on the head 42 of the control sleeve 22. When the head 42 and the weights 40 are ,at one side of their the control sleeve towards its median position 76' can be made exactly equal to the force exerted by the blades [6 through the control shaft 28 and tending to move it out of its median position. .An analysis of the forces involved shows that, to satisfy this condition, the surface of the race 43 must be such that the centers of the balls lie on an ellipsoid of revolution, the shape and size of the ellipsoid depending upon the weights of the blades and the balls, the size of the control gear l9 and the pitches of the two pairs of splines 23 to 26. By a suitable choice of these variables, the proper shape for. the path of the centers of the balls can be made'a sphere, and the surface of the race 43 will then also be a sphere, which is relatively simple to machine.

It will be noted that, if the blades l8 are tapered as shown in the drawings, the thickness of the rotor at any given radius will change as the blades l8 are moved in and out and the diameter of the rotor varied. To compensate for this change in thickness, one side or wall 56 of the impeller casing is arranged to move in and out as the rotor diameter is decreased or increased. This is accomplishedby mounting the side 56 of the casing upon three or more short helieally splined shafts 5| rotatably carried by the front 52 of the collector chamber 53. The shafts 55 are provided with arms 54 connected to each other and to the arm 31 by suitable linkage, such as the links 54a and Bowden wire 31a, Figs. 14 and 15, so that the shafts 5| which control the position of the wall 50 are rotated simultaneously with the sliding of-the sleeve 22- which controls the position of the'blades l8.

In order to prevent leakage between the housing l2 and the movable wall 56, a bellows 56 made of leather, rubber, neoprene or other suitable material connects the two. The bellows 56 is covered by a smooth piece of sheet metal 51 to lessen the frictional resistance to the fiow of air in the housing 82. v i In the operation of the supercharger, the air leaving the blades 58 at high velocity slows down and builds up pressure in the space 58 forming the diffuser between the face 59 of the movable wall 56 and the fixed portion of housing 52. The pressure acting on the face 59 of the movable wall 58 may be balanced by the pressure acting on its back 68 which forms oneside of the collector 53. By a suitable choice of the amount by which the bellows 56 and the bellows cover 51 are set in from the edge of the movable wall 58, the total amount of one of the forces can be made whatever is desired and the two forces thus made to balance. a

For certain types'of engines, it is desirable that the blower deliver whatever volume of air the engine may require but always at substantially the same pressure. For these engines, a supercharger may be made as described above but modified so asto be self regulating. The modification, shown in Fig. 9, comprises setting the bellows 56' and bellows cover 51 in further from the outer edge of the movable wall 58' than is required to supercharger casing and the main portion of the movable wall 69 of the impeller chamber extends out radially just beyond the outermost position of the tips of the blades l8. An annular flexible wall 16 joins the edge of the movable wall 69 to the fixed portion 68 of the casing and prevents leakage at the same time that it allows relative movement therebetween.

A plurality of vanes H are situated in the diffuser, each vane H being carried by short shafts 12 and I3 journaled in the casing members 61 and 68 forming the walls of the diffuser. The outer shaft 13 of each vane projects through the casing member 68 and into an arm 74 carried by the movable wall, 69 of the impeller "chamber. The shaft I3 and the hole'in the arm 14 which receives it are provided with interengaging helical spl nes 15 so that, as the position of the wall 69 is varied, the angle of the vanes II will also be varied. The vanes H improve the emciency of the diffuser in converting the velocity of the air discharged at the periphery of the impeller into pressure. It is convenient to change the angle of the vanes in accordance with the change in the d ameter of the impeller in order to obtain the best eficiency, since vanes having an angle designed for use with an impeller of given diameter are not equally emcient with an impeller of a different diameter.

'Movement of the wall 68 is controlled bymeans similar to those used in the form of the invention shown in Fig. 1 such as multiple-threaded shafts l8 which screw into sockets '78 on the movable wall 69 and are carried by brackets 88 fixed to or formed integrally with one section 68 of the casing. The shafts '18 are connected by arms 8| and suitable linkage to the mechanism for varying the diameter of the rotor so that the proper clearance is maintained between thebe. employed than the arrangement shown in Fg. 1. One such means is shown in Fig. 11.

In this arrangement, the blade control shaft 85 is journalled in the hollow main shaft 86 and its outer end is supported by a bushing 81 held in the end of the shaft 86 by a snap ring 88. A

helical spring 89 lies around the control shaft 85 and has its ends 90 and 9! fixed to the control shaft 85 and the bushing 81 respectively. The bushing 81 is prevented from turning with respect to the main shaft 86 by a lug 92 fitting into a slot in the wall of the main shaft 88.

The spring 89 is fitted so that it is under no stress when the blades and the control shaft 85 are in their median position so that it will resist rotation of the control shaft'in either direction relative to the main shaft with a force directly proportional to the angle of rotation. Since, at a constant speed of the supercharger rotor, the force exerted by the blades on the control shaft 85 is directly proportional to their displacement and the consequent angular displacement of the control shaft 85 from their median position, equilibrium will be secured at all positions of the blades.

The diameter of the rotor is controlled by a control rod 93 having a square portion passing through a square hole in the bushing 81 and a helically splined portion 94 engaging helical splines on the interior of the control shaft 85. The axial position of the control rod 93,-which determines the relative angular positions of the control shaft 85 and the main shaft 86, is adjusted through a ball bearing 95 and other associated mechanism similar to that shown in Fig. l.

Arrangements similar to that shown in Fig. 11 may be constructed to automatically vary the rotor diameter with the speed. To do this, the blades should be arranged so that the center of gravity of each blade'moves onlyon one side of the axs of the hub, as it is shown, for instance, in Fig. 16 where the displacement of blade I8a is such that its center of gravity moves between the two extreme positions I8g and I8g. In other words, the center of gravity of each blade must never be allowed to reach the neutral position, the position directly opposite the axis, at which centrifugal force acts perpendicular to the blade and does not tend to slide it endwise. Thus centrifugal force will always tend to move each blade in the same direction, irrespective of its position, and the spring, or other resilient means, must be arranged to act always in the opposite direction. By proper design of the spring and its connection to the blades, the force exerted by it on the blades will be in stable equilibrium with the centrifugal forces at different positions of the blades at different speeds and there will be a position of equilibrium at every speed.

It will be' found that, if a spring having a straight line characteristic, such as the one shown in Fig. 11, is used, the designer will be able to choose independently the positions of equilibrium at any two speeds because he has two variables (the rate of the spring and its initial stress) at his command. If it is desired to choose the positions which the blades will automatically assume at three or more speeds, this can be done by varying the effective spring rate, by causing the rate of the spring itself to vary as it is strained, For example, in the structure shown in Fig. 17, the outer surface of the portion of the shaft I I5 lying within the spring is tapered so that the spring will wind up on it as it is stressed and its rate will increase or the spring can be made to unwind from it so that its rate will the arms or jaws I85 which are formed integrally with the control shaft I86. When the head I82 containing the weights I84 is rotating, the weights tend to move towards the part of the wall I83 of the cavity in the head I82 which is farthest from the axis. .They therefore exert a force always tending to rotate the control shaft I86 towards its median position relative to the main shaft I88. If the wall I83 of the cavity is of the proper shape this force will be equal and opposite to the forces exerted by the blades I8 upon the'control shaft I86 and all the forces will be in equilibrium. It can be shown that each lobe of the surface I83 must be such that the path of the center of the ball I84 in contact with it is given by the equation:

where I y is the distance from the axis of the shaft I88;

0 is the value of y when the balls I84 are in their median positions;

a: is the angle in radians between the position of the control shaft I86 and jaws I85 and their median position;

and

k is a constant whose value depends upon the pitch diameter of the control gear I81 and the relative total weights of the balls I84 and the blades I8.

, It will be noted that the shape of the surfaces I83 is independent of the speed of rotation; equilibrium will therefore be secured at all speeds.

The position of the control shaft I86 is adjusted by means similar to those used in the previously described forms of the invention. A control spindle I89 is provided with helical splines I I 8 of one pitch and helical splines I I I of another pitch engaging splines on the main shaft I88 and the control shaft I86 respectively so that axial movement of the control spindle I89 changes the relative angular positions of the control shaft I86 and main shaft I88. The control spindle I89, in turn, is positioned by a mechanism identical with that employed to position the control sleeve 22 in the form of the invention shown in Fig. 1.

It may be noted that, in the form of the invention shown in Figs. 12 and 13, the axially slidable control spindle I89 is connected to both the main shaft I88 and the control shaft I86 by helical splines. By a suitable choice of the pitches of the two sets of helical splines, it is possible to eliminate or balance out certain inertia effects, When the rotor is being accelerated or decelerated, there are inertia forces in the blades having components transmitted to the control shaft, inertia forces in the control shaft, and inertia forces in the control spindle I89. All of these inertia forces form couples tending to rotate the control shaft and the axially slidable control spindle I89.

In some applications of the blower, as in certain installations with automatic control means, these forces might interfere with maintaining or securing the proper adjustment, and it is therefore desirable to avoid or eliminate these inertia effects. This can be done by properly choosing the pitches of the two sets of helical splines so that the above mentioned inertia forces and the forces transmitted by the splines balance out or neutralize. To secure this result, the ratio of the pitches of the two sets of splines should be:

where plus that portion of the moment 01 inertia of the blades which acts upon the control shaft.

control shaft I06 and control gear I01.

With the forms of the invention which are not 1 self-controlled, various control-means may be used.

1 Besides making the diameter of the rotor, and

' therefore the delivery characteristics of the blower, dependent upon engine speed as in the form described on page 4, orupon the pressure in the intake manifold or collector, as in the form shown in Fig. 9, they can, by suitable mechanism be made responsive to any one or more of any of the engine operating conditions, such as speed, load, fuel control setting, intake air pressure and vtemperature, exhaust temperature, engine temperature, and, in aircraft engines, pitch of the go propeller.

bodying the invention can be used for other pur- While the forms of the invention which have been described are single stage blowers primarily intended to be used as superchargers and as scavenging blowers, it is obvious that blowers emposes and may have several stages of which one or more may embody the invention and that they 1 may be made of any suitable material. Also, the arrangement of helical splines of difierent pitch,

of which one example is shown in Fig. 12, may be -used in'connection with other forms of blade balancing means, such as those shown in Figs. 1 and 11. In addition, it is to be understood that changes may be made in the embodiment of the 5 invention to suit different requirements; and that other changes, modifications, substitutions, additions and omissions may be made in the construction, arrangement and manner of operation of the parts, without departing from the limits or scope 40 of the invention as defined in the appended claims.

What I claim is:

1. In acentrifugal blower for supplying a compressible medium, a casing defining an impeller chamber, an impeller rotatably mounted therein,

portions of said impeller acting on said medium to impart energy thereto, and means for simultaneously adjusting the configuration of said portions and the configuration of said chamber.

2. In a centrifugal blower, an impeller including tapered elements, said elements being movable in a substantially radial direction, a casing for said impeller having an axially movable member, and means for simultaneously varying the position of said elements and said member and thereby maintain a substantially constant clearance therepetween. g

3. In a centrifugal blower, an impeller having adjustable elements, a casing for said impeller having a difiuser, movable vanes in said diffuser,

and means for adjusting the angle of said vanes in accordance with the adjustment of said elements while said impeller is rotating.

4. In a centrifugal compressor, an impeller chamber, a rotatable impeller in said chamber toimpart velocity energy to a medium, a difiuser wherein velocity energy of said medium is converted into pressure, portions of said impeller having variable configuration, and means for adjusting the configuration of said portions :5 chamber to impart velocity to a medium, a difwhile said impeller is rotating to control the velocity energy imparted to said medium.

5. In a centrifugal compressor, an impeller chamber, an impeller rotatably mounted in said fuser converting velocity of said medium into pressure, said impeller comprising relatively movable elements, and means for adjustingthe relative position of said elements in said impeller while said impeller is rotating and thereby controlling the velocity imparted to said medium.

6. Ina centrifugal blower, an impeller comprising relatively movable elements, means capable of limited displacement relatively to said impeller for adjusting said elements whereby the efiective outer diameter of said impeller may be varied while said impeller is rotating, said elements' being so arranged that centrifugal force acting on said elements tends to displace said means relatively to said impeller with a magnitude proportional to the square of the angular velocity of said impeller and variable with the adjustment of said elements in said impeller, balancing means whose adjustment relative to said impeller can be varied, said balancing means tending to displace said first mentioned means with a magnitude proportional to the square of the angular velocity of said impeller and variable with the adjustment of said balancing means, and means whereby at a variation of the adjustment of said impeller elements- Simultaneously corresponds a variation of the adjustment of said balancing means such that for any angular velocity of said impeller and any adjustment of said impeller elements, said impeller elements and said balancing means tend to displace said first mentioned means with equal magnitudes and in opposite directions.

/ 7. In a centrifugal blower, an impeller comprising relatively movable elements, means capable of limited angular displacement relatively to said impeller ior adjusting said elements whereby the effective outer diameter of said impeller may be varied while said impeller is rotating, said elements being so arranged that inertia force due to angular acceleration of said impeller acting on said elements, tends to displace said means relatively to said impeller with a magnitude proportional to said angular acceleration, said first mentioned means being connected with inertia balancing means 50 arranged that inertia force due to angular acceleration of said impeller acting on said last mentioned means tends to displace said first mentioned means relatively to said impeller with a magnitude proportional to said angular acceleration whereby for any value of the angular acceleration of said impeller said elements and said inertia balancing means tend to displace said first mentioned means with substantially equal magnitudes and opposite directions.

8. A. centrifugal blower as described in claim 5,

including pressure responsive means for operather, a rotatable impeller in said chamber and comprising movable elements, the movement of said elements relative to the axis of said impeller having a radial component, means for adjusting the relative positions of said elements while said impeller is rotating, pressure responsive means connected with said adjusting means, and resilient means also acting on said adjusting means and tending to yieldingly hold said elements in a predetermined position.

11. In a centrifugal blower, an impeller chamher, a rotatable impeller in said chamber and comprising movable elements, the movement of said elements relative to the axis of. said impeller having a radial component, means for adjusting the relative positions of said elements while said impeller is rotating, a casing for said impeller having an adjustable wall, and means connecting said adjusting means and said adjustable wall for simultaneously adjusting said impeller ele-' ments and said wall.

12. In a centrifugal blower, an impeller chamber, a rotatable impeller in said chamber and comprising movable elements,-the movement of said elements relative to the axis of said impeller having a radial component, means for adjusting the relative positions of said elements while said impeller is rotating, a casing for said impeller having an adjustable wall, means connecting said adjusting means and said adjustable wall whereby said impeller elements and said wall may be simultaneously adjusted, and resilient means acting on said adjusting means and tending to yieldingly hold said elements and 10 said adjustable wall in a predetermined position.

FERDINANDO C. REGGIO.

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