US3892502A

US3892502A - Control of expansion ratio in rotary motors

Info

Publication number: US3892502A
Application number: US359023A
Authority: US
Inventors: Edward Pritchard
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-10-28
Filing date: 1973-05-10
Publication date: 1975-07-01
Anticipated expiration: 1992-07-01

Abstract

A rotary motor driven by a pressurised working fluid such as steam or compressed air having a series of working chambers around the periphery of the motor, an inlet port and an exhaust port oppositely disposed at the periphery of the motor for the inlet and outlet of the working fluid and a further port or ports between those ports admitting further working fluid bled from the supply to the chamber past the inlet port but before the exhaust port to significantly increase the amount of working fluid in the motor at low speeds or high load.

Description

July 1, 1975 United States Patent [1 1 Pritchard Barnes..........1.n.................. 418/138 Scott...........

S s w n w a a HBD 81 459 234 99999 HHHHH 53253 293 940 5 .5 967 3 06 I122 CONTROL OF EXPANSION RATIO IN ROTARY MOTORS [22] Filed:

2 Appl No: 359 023 Primary ExaminerJohn .l. Vrablik Attorney, Agent, or Firm-Wenderoth, Lind & Ponack Related US. Application Data ABSTRACT [63] Continuation-impart of Ser. No. 162,237, July 13, 1971, abandoned, which is a continuation of Ser. No. 869,271, Oct 24 1969, abandoned.

A rotary motor driven by a pressurised working fluid [3O] 0 ;8 ;;8 Pnonty Dam such as steam or compressed air having a series of ct. ustra 5464/68 working chambers around the periphery of the motor, an inlet port and an exhaust port oppositely disposed at the periphery of the motor for the inlet and outlet [52] US. Cl. 418/15; 418/138; 418/;

of the working fluid and a further port or ports between those ports admitting further working fluid bled from the supply to the chamber past the inlet port but before the exhaust port to significantly increase the 0 -9 8 W 8 2 o 2 5 l 0/ 8.8 N10 1400 2 .H C moo 1.l 0 m4 mhu 0 Hr a e us an .M e .mfi UN 55 amount of working fluid in the motor at low speeds or high load.

{56] References Cited UNITED STATES PATENTS 470,405 3/1892 Westfall11............................ 418/15 7 Claims, 4 Drawing Figures s latttt is .HIPWFDJUL] I975 SHEET 1 EDWARD PRITCHARD, In 6r EDWARD PRITCHARD, Inventor wwm'mm Attorneys CONTROL OF EXPANSION RATIO IN ROTARY MOTORS This application is a Continuation-in-Part of my copending application Ser. No. l62,237 filed July I3, 1971 now abandoned which is a streamlined continuation of application Ser. No. 869,271, filed Oct. 24, 1969 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to rotary motors of the type using steam or compressed air or other expansible gas or vapor. In particular the invention relates to the provision of a device for varying the expansion ratio of rotary motors of the type specified and which are not fitted with intake valves such as rotary inlet valves or inlet valves operated by means of link motions or cam shafts.

In a rotary motor or reciprocating engine which is used over a wide range of speeds as, for example, from zero to the maximum design speed, it is desirable to use a small expansion ratio or late cut-off" of the high pressure working fluid in order to obtain more positive starting, high overload torque and better smoothness on starting. A smaller expansion ratio or later cut-off" is also desirable, apart from when starting, in order to run against loads heavier than normal. Under normal loads, it is desirable to run on a higher expansion ratio (early cuboff) so as to obtain more economical use of the working fluid.

In some rotary and reciprocating engines, changes of cut-off are obtained, for example, simply by varying the arrangements of link motions or by changing the positions of cams or, on engines fitted with rotary valves, by changing the position of rotary valve sleeves.

However it is advantageous if intake valves can be eliminated and to rely solely upon porting of the rotary engine thereby reducing initial and ensuing maintenance costs.

SUMMARY OF THE INVENTION This invention has for its principal objective to provide a rotary engine of the type specified in which the expansion ratio can be varied in accordance with load and speed requirements.

With the principal objective in view there is provided according to the present invention in a rotary motor driven by a working fluid introduced through an inlet port under pressure the improvements comprising, a bleed or bypass passage leading the working fluid to a later expansion stage in the motor, thereby increasing the amount of working fluid within the motor to do work.

Conveniently a pressure sensitive valve is provided in said bleed passage, the valve being sensitive to variations in pressure of working fluid in the bypass line and the main supply line leading to the inlet port. It will be understood that the external load on the motor is proportional to the degree of pressure of working fluid in the motor. With an increase in load the pressure of working fluid in the motor must increase to maintain speed.

The bleed passage may be restricted and provided in parallel to said valve to provide a continuous flow of working fluid which is particularly effective at low motor speeds to substantially increase the amount of working fluid and decrease the expansion ratio. Alter natively the bleed restriction may be incorporated into the valve construction so that even when closed the valve continues to pass working fluid to a later expansion stage.

Said pressure sensitive valve is conveniently sensitive to working fluid inlet or expansion stage pressure, or a pressure differential between inlet and expansion stage inlet pressures. When a differential is apparent the valve is opened to transmit increased quantities of working fluid to a later stage so that effects of later cutoff are achieved. The inlet pressure represents a datum pressure and the expansion stage inlet pressure is dependant for its value upon the load on the motor. Accordingly, at low speeds and high load a pressure differential will exist across the valve to open said valve. The datum pressure and thus the pressure differential be' tween inlet and expansion stage inlet pressures may be further increased by manual control of the engine throttle, however, this aspect forms no part of the present invention.

It will be understood that according to the invention re-introduction of the working fluid may take place at several succeeding stages of expansion to a lower pressure in the motor.

A practical arrangement of the invention will be described with reference to an extensible vane or blade type rotary motor having variable volume chambers, with said blades being driven by steam or air, however, it will be understood that the invention can be applied to various types of rotary motors in which there is at least two stages of expansion of the working fluid. The arrangement is described having reference to the accompanying drawings which depicts a schematic form of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an end sectional view on line H of FIG. 2.

FIG. 2 is a sectional elevation taken on line 11-" of FIG. 1.

FIG. 3 is a sectional elevation showing a modified form of engine with a plurality of late admission ports for working fluid.

FIG. 4 is a partial sectional view of a modified pressure sensitive valve.

DETAILED DESCRIPTION OF THE INVENTION There is provided a stationary cylindrical ported chamber I. In sealing contact with said chamber 1 a plurality of blades 3 are provided which extend radially from bearing bosses 3b mounted on shaft 2 about centre 0 enabling said blades 3 to move about centre 0 independently of each other in the direction of rotation shown. The blades 3 are constructed with their inner portions and bosses 3b forked to fit inside each other along the shaft 2. The blades 3 pass through sealing segments 4a mounted in a rotatable cylindrical structure 4 which is integrally formed with an end flange 40 at the drive end and with a removable flange 4d at the opposite end. The blades 3 are stepped down at 30 in overall width (taken along the axis) to clear inner portions 4b of the end flanges of the structure 4. At the driving end of the structure 4 an output shaft 21 on centre C extends from the end flange 4c.

Shaft 2 is held into end wall 23 of chamber 1 by means of a nut 22. Output shaft 21 runs in bearings machined into an extension 24 of the opposite end wall of chamber 1.

The ports, inlet 6 and outlet 7 in the chamber 1 are placed approximately opposite one another.

It is preferred that a sufficient number of radial blades 3 are provided so that at least two expansion stages or chambers are formed before exhausting through the exhaust port 7.

Accordingly smooth running of the motor is obtained despite the lack of intake and exhaust valves as well as providing a greater expansion ratio.

Referring to FIG. I bypass or bleed fluid passes through a restricting orifice or passage 8 of a definite predetermined minimum control area in bleed line 9 leading from the main supply line 6a to a later expan sion chamber supplied by inlet pipe 16. The amount of bleed fluid is increased by opening up an additional passage area controlled by means of a pressure sensitive valve ll which may be diaphragm controlled and interconnects passage 10 to passages 9 and through needle valve 14. The diaphragm 12 may be sensitive to the pressure existing at a datum point such as at the fluid intake (not shown) or to a pressure differential such as the difference between the pressures at the intake 6 and at the point of readmission to a later expansion chamber as at pipe 16 of the working fluid as shown in FIG. 1. In this arrangement the diaphragm 11 is subjected to the pressure in passage 10 (datum pressure) on one side and the pressure in passage 13 (chamber pressure) on the other side. The diaphragm is adapted to move in response to the bias created by the pressure differential whereby the needle valve is moved to open or close passage 15. If necessary a compression spring 17 may be provided to ensure that the needle valve i4 is closed at the appropriate time.

A major controlling factor over the maximum expansion ratio on the type of rotary motor illustrated is the number of blades 3. The larger the number of blades, the greater the expansion ratio obtainable.

It will be appreciated that the bleed fluid flowing in the restricted

passage

8, 9 will have little effect at normal running speed, the volume of flow being of but a small proportion of the total flow of working fluid through the motor. Thus the bleed passage is mainly effective at starting and low speeds as desired. Also, while the restricting orifice or passage 8 is of definite predetermined controlling area, this is to be understood to be for a given set of circumstances relating to the input fluid pressure and relative size of the main supply line and the bleed or bypass line. Accordingly, it is understood that such restricting passage may be of a selectively variable type to achieve a predeterminable control area therethrough for different conditions.

Referring to FIG. 3, a modification of the embodiment described with reference to FIG. 1 is illustrated showing a plurality of bypass passages controlled by a pressure sensitive valve 11 feeding into more than one expansion stage. In this Figure similar reference numerals refer to like integers. The internal construction together with the function of the valve 11 is similar to that previously described with reference to FIG. I or alternatively similar to that described here-below with reference to FIG. 4.

The arrangement shown in FIG. 3 depicts explicitly multiple bypass of working fluid to two expansion stages enhancing the amount of late cut-off working fluid that may be supplied to the motor. Having reference to the first stage after inlet pipe 6 (reference A), two inlet pipes 16a and b are arranged to feed into this stage at the particular point in time represented by the diagram. The spacing of the inlet pipes 160, l6b, 16c and 16d is selected by the designer to achieve optimum benefit from the late admission of working fluid. For instance, the spacing of inlet pipe 16c from pipe 16a provides that chamber A will receive working fluid from all three inlets 16a, 16b and 16c for an instant in time during its passage around housing 1. Similarly chamber B would receive steam from 16b, 16c and 16d for an instant in time slightly preceding chamber A. It will be understood the phasing or spacing of the bypass inlets may be chosen according to needs and the operating conditions of the motor provided always that working fluid is not admitted when a chamber is being exhausted through port 7. The valve may operate in identical fashion to that already described with reference to FIG. 1. Namely, a diaphragm 12 is provided, which is subject to a pressure differential between working fluid pressure in expansion stages cut-off from the working fluid inlet pipe 6 and the working fluid pressure in the inlet pipe 60. In the arrangement shown in FIG. 1 the pressure sensitive valve 11 is provided in parallel circuit with bleed restriction 8 in pipe 9 leading from inlet pipe 60 to a later expansion stage.

The pressure sensitive valve may be modified as shown in FIG. 4 by the provision of a non-closable valve and

valve seat

14, 14a. All other parts ofthe valve lla are identical in construction to that previously described with reference to FIG. I. The seat includes small slots or recesses 14b spaced therearound through which working fluid may pass even when valve element 14 is in engagement with the seat 140. Accordingly, lifting of the valve element 14 off its seat merely allows for an increase in flow of fluid into line I5 and thence to a later expansion chamber. It is preferred but not essential that valve Ila be utilised in feeding working fluid to a plurality of later expansion stages as shown in FIG.

I claim:

I. In a rotary motor driven by expansion of a compressible working fluid introduced from a working fluid inlet supply line under pressure through an inlet port of the motor into a first expansion stage, said motor having at least one additional expansion stage between said first expansion stage and an outlet port spaced from said inlet port, the improvement in a motor control system associated therewith comprising:

a bleed passage means connected to said working fluid inlet supply line for continuously transmitting additional working fluid to said at least one additional expansion stage thereby increasing the amount of working fluid within the motor to do work;

said bleed passage means having therein a restriction having a predeterminable minimum fluid passage control area;

a pressure sensitive valve in a passage connected in parallel to said restriction, between said at least one expansion stage and said working fluid inlet supply line;

said restriction forming means for automatically passing to said at least one additional expansion stage a continuous flow of working fluid in predetermined amounts effective at low motor speeds; and

said pressure sensitive valve providing means for automatically passing increased amounts of working fluid to said at least one additional expansion stage during periods of abnormal load.

2. The improvement claimed in claim 1, further comprising plural restrictions and plural pressure sensitive valves for connecting said working fluid supply with a plurality of said additional expansion stages to continuously pass progressively introduced amounts of said additional working fluid to progressively expanding volume stages.

3. The improvement claimed in claim 1 wherein said pressure sensitive valve comprises a valving member and a diaphragm operably connected with said valving member, one side of said diaphragm being operably connected to said working fluid inlet supply line and the other side of said diaphragm being operably connected to an additional expansion stage, said diaphragm being automatically movable at said periods of abnormal load from a first closed valve position to a second position opening said valving member to allow said passage therethrough of said increased amounts of working fluid,

4. In a rotary motor driven by expansion of compress ible working fluid introduced from a working fluid inlet supply line under pressure through an inlet port of the motor into a first expansion stage, said motor having at least one additional expansion stage between said first expansion stage by said inlet port and an outlet port of the motor spaced from said inlet port, the improvement in a motor control system associated therewith comprising:

a bleed passage means interconnecting said at least one additional expansion stage and said working fluid inlet supply for continuously transmitting additional working fluid to said additional expansion stage thereby extending the effective cut-off point for admission of working fluid and reducing the effective expansion ratio, and

said bleed passage means having provided therein pressure sensitive valve means for automatically controlling flow of working fluid through said bleed passage means, said pressure sensitive valve means comprising a valving member and a diaphragm operably connected with said valving member, one side of said diaphragm being operably connected to said working fluid inlet supply line and the other side of said diaphragm being operably connected to an additional expansion stage, said diaphragm being automatically movable upon an increased load on said motor from a first position to a second position opening said valving member to allow passage through said bleed passage means of additional working fluid.

5. In a control system for rotary expansion motors having a plurality of expansion stages, a pressurized working fluid supply means adapted to be connected by a working fluid inlet supply line to an expansion stage of the motor, and at least one additional expansion stage of the motor, the improvement comprising:

bleed passage means for pressurized working fluid connectable between said at least one additional expansion stage and said inlet supply line, said bleed passage means including restriction means have a predeterminable minimum control area for continuously passing a bypass flow of the working fluid from said inlet supply line to said at least one additional expansion stage;

a second passage connected in parallel to said bleed passage means and connectable between said at least one additional expansion stage and said working fluid inlet supply line; and

a pressure sensitive valve means connected in said second passage, said valve means being responsive to changes of pressure difference between a point downstream of said restriction means and the said working fluid inlet supply line, for passing corresponding additional working fluid to said at least one additional expansion stage.

6. In a rotary motor driven by expansion of a compressible working fluid introduced from a working fluid inlet supply line under pressure through an inlet port of the motor into a first expansion stage, said motor having at least one additional expansion stage between said first expansion stage and an outlet port spaced from said inlet port, the improvement in a motor control system associated therewith comprising:

a bleed passage means connected to said working fluid supply for continuously transmitting additional working fluid to said at least one additional expansion stage, thereby increasing the amount of working fluid within the motor to do work;

a pressure sensitive valve in a passage between said at least one additional expansion stage and said working fluid inlet supply line;

said restriction forming means for automatically passing to said at least one additional expansion stage a continuous flow of working fluid in predetermined amounts effective at low motor speeds;

said pressure sensitive valve including a valving member and a diaphragm connected with said valving member, said valving member being permanently open to form said restriction and being operative in response to pressure of working fluid on said diaphragm to increase the area of said restriction; and

said pressure sensitive valve providing means for automatically passing increased amounts of working fluid to said at least one additional expansion stage during periods of abnormal load,

7. In a control system for rotary expansion motors having a plurality of expansion stages, a pressurized working fluid supply means adapted to be connected by a working fluid inlet supply line to an expansion stage of the motor, and at least one additional expansion stage of the motor, the improvement comprising:

a pressure sensitive valve means connected in said second passage, said pressure sensitive valve means comprising a valve housing having an operating fluid inlet passage to receive operating fluid from said working fluid inlet supply line, a discharge or from said outlet passage, said chamber enclosing a portion of said movable valving member which is remote from the end portion cooperable with said outlet passage, a flexible diaphragm disposed within said chamber and connected to said valving member to help in the movement thereof, and a fluid passage opening connected with said chamber and adapted to be connected via a fluid conduit with a pressure datum for the operating fluid to provide pressure changes against said diaphragm.

Claims

1. In a rotary motor driven by expansion of a compressible working fluid introduced from a working fluid inlet supply line under pressure through an inlet port of the motor into a first expansion stage, said motor having at least one additional expansion stage between said first expansion stage and an outlet port spaced from said inlet port, the improvement in a motor control system associated therewith comprising: a bleed passage means connected to said working fluid inlet supply line for continuously transmitting additional working fluid to said at least one additional expansion stage thereby increasing the amount of working fluid within the motor to do work; said bleed passage means having therein a restriction having a predeterminable minimum fluid passage control area; a pressure sensitive valve in a passage connected in parallel to said restriction, between said at least one expansion stage and said working fluid inlet supply line; said restriction forming means for automatically passing to said at least one additional expansion stage a continuous flow of working fluid in predetermined amounts effective at low motor speeds; and said pressure sensitive valve providing means for automatically passing increased amounts of working fluid to said at least one additional expansion stage during periods of abnormal load.

3. The improvement claimed in claim 1 wherein said pressure sensitive valve comprises a valving member and a diaphragm operably connected with said valving member, one side of said diaphragm being operably connected to said working fluid inlet supply line and the other side of said diaphragm being operably connected to an additional expansion stage, said diaphragm being automatically movable at said periods of abnormal load from a first closed valve position to a second position opening said valving member to allow said passage therethrough of said increased amounts of working fluid.

4. In a rotary motor driven by expansion of compressible working fluid introduced from a working fluid inlet supply line under pressure through an inlet port of the motor into a first expansion stage, said motor having at least one additional expansion stage between said first expansion stage by said inlet port and an outlet port of the motor spaced from said inlet port, the improvement in a motor control system associated Therewith comprising: a bleed passage means interconnecting said at least one additional expansion stage and said working fluid inlet supply for continuously transmitting additional working fluid to said additional expansion stage thereby extending the effective cut-off point for admission of working fluid and reducing the effective expansion ratio, and said bleed passage means having provided therein pressure sensitive valve means for automatically controlling flow of working fluid through said bleed passage means, said pressure sensitive valve means comprising a valving member and a diaphragm operably connected with said valving member, one side of said diaphragm being operably connected to said working fluid inlet supply line and the other side of said diaphragm being operably connected to an additional expansion stage, said diaphragm being automatically movable upon an increased load on said motor from a first position to a second position opening said valving member to allow passage through said bleed passage means of additional working fluid.

5. In a control system for rotary expansion motors having a plurality of expansion stages, a pressurized working fluid supply means adapted to be connected by a working fluid inlet supply line to an expansion stage of the motor, and at least one additional expansion stage of the motor, the improvement comprising: bleed passage means for pressurized working fluid connectable between said at least one additional expansion stage and said inlet supply line, said bleed passage means including restriction means have a predeterminable minimum control area for continuously passing a bypass flow of the working fluid from said inlet supply line to said at least one additional expansion stage; a second passage connected in parallel to said bleed passage means and connectable between said at least one additional expansion stage and said working fluid inlet supply line; and a pressure sensitive valve means connected in said second passage, said valve means being responsive to changes of pressure difference between a point downstream of said restriction means and the said working fluid inlet supply line, for passing corresponding additional working fluid to said at least one additional expansion stage.

6. In a rotary motor driven by expansion of a compressible working fluid introduced from a working fluid inlet supply line under pressure through an inlet port of the motor into a first expansion stage, said motor having at least one additional expansion stage between said first expansion stage and an outlet port spaced from said inlet port, the improvement in a motor control system associated therewith comprising: a bleed passage means connected to said working fluid supply for continuously transmitting additional working fluid to said at least one additional expansion stage, thereby increasing the amount of working fluid within the motor to do work; said bleed passage means having therein a restriction having a predeterminable minimum fluid passage control area; a pressure sensitive valve in a passage between said at least one additional expansion stage and said working fluid inlet supply line; said restriction forming means for automatically passing to said at least one additional expansion stage a continuous flow of working fluid in predetermined amounts effective at low motor speeds; said pressure sensitive valve including a valving member and a diaphragm connected with said valving member, said valving member being permanently open to form said restriction and being operative in response to pressure of working fluid on said diaphragm to increase the area of said restriction; and said pressure sensitive valve providing means for automatically passing increased amounts of working fluid to said at least one additional expansion stage during periods of abnormal load.

7. In a control system for rotary expansion motors having a plurality of expansion stages, a pressurized working fluId supply means adapted to be connected by a working fluid inlet supply line to an expansion stage of the motor, and at least one additional expansion stage of the motor, the improvement comprising: bleed passage means for pressurized working fluid connectable between said at least one additional expansion stage and said inlet supply line, said bleed passage means including restriction means have a predeterminable minimum control area for continuously passing a bypass flow of the working fluid from said inlet supply line to said at least one additional expansion stage; a second passage connected in parallel to said bleed passage means and connectable between said at least one additional expansion stage and said working fluid inlet supply line; and a pressure sensitive valve means connected in said second passage, said pressure sensitive valve means comprising a valve housing having an operating fluid inlet passage to receive operating fluid from said working fluid inlet supply line, a discharge or outlet passage in said housing adapted to connect to said at least one additional expansion stage, a valving member movable within said valve housing and having a portion at one end to close and open said discharge or outlet passage, said valving member having surface means against which said operating fluid engages to effect opening of said valve discharge passage responsive to an increase in the fluid pressure entering said valve housing inlet passage from said working fluid inlet supply line, said valve means further including a chamber defined by a part of said valve housing at a portion spaced from said outlet passage, said chamber enclosing a portion of said movable valving member which is remote from the end portion cooperable with said outlet passage, a flexible diaphragm disposed within said chamber and connected to said valving member to help in the movement thereof, and a fluid passage opening connected with said chamber and adapted to be connected via a fluid conduit with a pressure datum for the operating fluid to provide pressure changes against said diaphragm.