US2880583A

US2880583A - Hydraulic turbo-couplings

Info

Publication number: US2880583A
Application number: US387000A
Authority: US
Inventors: Sinclair Harold
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-11-06
Filing date: 1953-10-19
Publication date: 1959-04-07
Anticipated expiration: 1976-04-07

Description

April 7, 1959 H. SINCLAIR 2,880,583

HYDRAULIC TURBO-COUPLINGS I Filed Oct. 19, 1953 5 Sheets-Sheet 1 Fig.1; I

ZN VE N TOR BY ADM, 4M

ATTORNEYS.

April 7, 1959 H. SINCLAIR HYDRAULIC TURBO-COUPLINGS 3 Sheets-Sheet 2 Filed Oct. 19, 1953 5 Q: VEA/Tqg ATTORNEYS VIIIIIIIIIIIIIIIIIII United States Patent HYDRAULIC TURBO-COUPLINGS Harold Sinclair, Windsor, England Application October 19, 1953, Serial No. 387,000

Claims priority, application Great Britain November 6, 1952 6 Claims. (Cl. 60-54) with the working chamber, via an external circuit including for example a cooler to the working chamber which is provided with leak-off nozzles via which fluid passes from the working circuit to the reservoir. In this form of coupling viz., the scoop-control type, the degree of filling of the working circuit increases with the degree of insertion of the scoop-tube into the ring of liquid formed within the rotating reservoir chamber.

In the afore-mentioned form of turbo coupling there is a continuous circulation of working fluid into and out of the working chamber. During normal operation of such turbo-couplings, the driving motor (usually a squirrel cage induction motor) is started and run up to full speed with the control means set so that the working circuit of the coupling is practically empty, and the control means are thereafter operated manually or by a control servo mechanism so as to fill the working circuit and thereby accelerate the driven machine. In such cases where it is not desired to operate or control the scoop manually the control means may be set in the normal condition for filling the working circuit, so that upon running the motor up to speed the working circuit fills and the driven machine is thereby accelerated. During the time that the runner is being accelerated there is .a relatively high pressure in the duct or ducts via which fluid is fed to the working chamber, this pressure being due in part to the rapid transfer of liquid into the working chamber and circuit, and in part to back-pressure that is created within the working chamber while it is being filled and the runner is being accelerated and is overcoming the resistance of the load. The pressure in the filling ducts is high therefore when the working circuit is partially filled with the loaded runner stationary, and varies as the runner accelerates, eventually falling to a low value as the runner speed more nearly approaches the impeller speed.

In the event that the driving motor is started or restarted with the working circuit of the turbo-coupling more than say half full the pressure in the filling ducts will immediately rise to a high value and will decrease later as the runner acceleratesagainst the resistance of the load.

Normally, in the case of a coupling of the type referred to, the filling takes place .rapidly and the coupling becomes capable within a few seconds of transmitting high torque. In some cases, however, it may be undesir- Patented Apr. 7, 1959 able for the coupling to exert more than a predetermined torque during the acceleration period of the load. For example, the coupling may be interposed between a prime mover and a belt conveyor, and it may be a requirement that the tension in the belt shall not exceed a stipulated maximum value, which is not excessively greater than the normal working tension of the belt and is below the overload torque capacity of the prime mover. It may be, for example, that whereas in general conveyor practice it is permissible for the belt to experience a tension of 200% of the normal running tension, in a particular case it may be stipulated that the belt tension must not exceed say to of the normal running value during the acceleration period of the conveyor. Excessive tension will occur in the belt if the loaded conveyor is accelerated too rapidly, and it is desirable to limit the torque applied to the conveyor during acceleration so as to avoid excessive tension in the belt and thereby prolong the useful life of the belt. Furthermore it becomes practicable to use a belt having plies, at a lower cost, and it is feasible to use a drive head pulley of smaller diameter rotating at a higher speed and requiring a lower torque for a given H.P., with the result that the drive head and reduction gear are lower in cost.

The object of the invention is to provide a hydraulic turbo-coupling of the type first referred to above, comprising means whereby the torque-transmitting capability of the coupling is automatically limited, during the time that the runner is accelerating under the normal load condition, so as not to attain an excessive value.

The invention makes use of the pressure that arises in the ducts in communication with the working circuit, and in accordance with the invention means are provided which are responsive to the said pressure to exert an automatic control on said adjustable control means.

In order that the invention may be clearly understood and readily carried into efiect, it will now be described in more detail with reference to the accompanying drawings, in which:

Fig. 1 is a plan view, partly in section, of a hydraulic turbo coupling of the scoop control type incorporating the invention,

Fig. 2 is an end view of the coupling,

- Fig. 3 is an enlarged detail view showinga loadlimiting valve,

Fig. 4 shows graphs illustrating the change in runner speed and torque output when the coupling is started. from rest, and

Fig. 5 shows a modification of the arrangement of Figs. 1 and 2.

Referring to the drawing, the coupling is of the type provided with a rotating reservoir chamber 1, leak-off nozzles 2 for exhausting working fluid to the reservoir chamber 1, and a scoop-tube 3 in the reservoir chamber 1, adapted to transfer fluid from the reservoir chamber 1 to the working chamber, in which are disposed a vaned impeller 4 and a vaned runner 5. The runner element is preferably provided, as described in my co-pending application Serial No. 138,543, now Patent No. 2,687, 013 of Aug. 24, 1954, with inter-vane pockets some of which, as disclosed by section planes containing the axis of rotation of the coupling, differ in shape from others of the inter-vane pockets, the coupling also including "a baffle 6 (see U.S. patent specification No. 2,301,645) which may have a ratio of 1.4 as between its external diameter and the inner profile diameter. Title/scooptube 3, which is preferably slidable longitudinally as .described in U.S.v patent specification No. 2,264,341 is provided with an angularly movable control .lever I by means of which the scoop-tub-3 can be moved between its fully inserted and fully retracted positions. In Fig.

2 the lever 7 is in its extreme right-hand position which corresponds to full insertion of the scoop-tube 3. The coupling may also be provided with spring-loaded centrifugally operated load-limiting valves 8, which may be ball valves or double-beat poppet valves or piston type valves fully or partially balanced for hydraulic pressure, as described in the specification of my copending application Serial No. 334,804. The valve shown on an enlarged scale in Fig. 3 comprises a ball 30 adapted to co-operate with a valve seat 31. During normal rotation of the coupling the ball 30 is urged on to its seat 31 by centrifugal force, whereas when due for example to an undesirable increase in the load, the impeller speed falls below a predetermined value, the ball 30 is urged away from its seat 31 by a spring 32 thereby enabling working fluid to empty from the working chamber at a relatively rapid rate. If desired the separate leak-off nozzles 2 may be omitted, a duct 33 in the body of the valve 8 enabling working fluid to fiow from the working circuit to the reservoir chamber at a restricted rate when the ball 30 is on its seat 31.

The control lever 7 is connected by a link 9 to the piston rod 10 of a piston 11 which is disposed in a cylinder 12 fixed to a bracket 13 on a non-rotatable part of the coupling. A weight 14 tends to maintain the piston 11 at or near one end of the cylinder 12, the weight 14 being carried by an arm 15 fixed to a sprocket 16 which is rotatably mounted on a shaft 17 carried by arms 18 on bracket 13. The sprocket 16 is coupled to control lever 7 by a sprocket chain 19, connected to a link 20 on the lever 7. In the position of the piston 11 as shown the control lever 7 assumes the position (as shown) in which the scoop-tube 3 is fully inserted. In the coupling illustrated, working fluid picked up by the scoop-tube 3 is transferred via passage 22 to a cooler (not shown) and returns from the cooler to the coupling via passage 23. The end of the cylinder 12 to the right of piston 11 is connected by a conduit 21 to the passage 23.

First, let it be assumed that the turbo coupling is employed for driving a belt conveyor. For this purpose, an AC. squirrel cage electric motor or other prime mover having a constant speed characteristic is coupled to the input or impeller shaft of the coupling, and the output or runner shaft 24 is coupled to the belt driving means. By way of example, it may be required that the maximum tension to which the belt may be subjected is 140% of the normal operating tension, and that this maximum tension is so little above the tension required for overcoming the load plus friction that an accelerating time of say seconds has to be allowed for bringing the conveyor up to full speed, for example 600 ft. per minute, in order to avoid excessive tension in the belt during the acceleration period. Initially, when the motor and turbo coupling are stationary, the greater part of the oil in the turbo coupling is in the lower half of the reservoir chamber 1, and the scoop-tube 3 is in the fully engaged position. When the motor is switched on, it attains full speed in a few seconds, since initially it is free from load apart from the inertia of the rotating parts, and the oil in the rotating reservoir chamber 1 forms into a thick annulus which submerges the end of the fully engaged scoop-tube 3. The latter immediately begins to transfer fluid from the reservoir chamber 1 to the working circuit of the coupling via the cooler, at a high rate, which if allowed to continue would fill the working circuit too rapidly, and the high output torque of the turbo coupling would impose an excessive tension on the conveyor belt. However, as soon as sufficient fluid enters the working circuit the pressure in the filling duct 23 together with the back-pressure in the Working chamber create a high pressure of say to lbs. per sq. in. in the duct 23. This pressure is transmitted to the right-hand side of piston 11, which is thereby moved against the resistance due to the weight 14 to move the control lever 7 in the direction (to the left in Fig. 2) in which the scoop-tube 3 is partially retracted, until the control lever abuts against a travellimiting stop 24. The partial retraction of the scooptube 3 due to this pressure results in the working chamoer being filled more slowly than would be the case if the scoop-tube 3 were kept fully engaged during the whole of the filling period. During the acceleration period of the runner 5, while the slip in the coupling is pro gressively falling from to nearly 5%, the high pressure condition in the filling duct 23 retards the filling operation, and thus serves suitably to prolong the acceleration period. During the prolonged acceleration, the pressure on the piston 11 maintains the scooptube 3 partially retracted, though to a gradually lessening degree, whereby the torque transmitted by the coupling is limited to a safe value while the conveyor is accelerating. I

The full line curve of Fig. 4 shows the relation between time in seconds (abscissa) and torque output in kilowatts (ordinate) of a coupling according to the invention when starting a load from rest. The chain-line curve shows the relation between the time (abscissa) in seconds and the runner speed (ordinate) in revolutions per minute.

By suitably varying the weight 14, and the angular setting of the arm 15 and hence its effective length, the characteristic relating the biassing force and the position of the piston 11 against the pressure in the filling duct 23 may be varied.

If desired, instead of the weight 14 there may be employed one or more springs which exert a biassing force on the piston 11. Such a modification is illustrated in Fig. 5, in which a compression spring 35 is housed in the cylinder 12 and tends to urge the piston 11 to the position in which the control lever 7 is in the position corresponding to full insertion of the scoop-tube.

The automatic control of the position of lever 7 in accordance with the pressure in duct 23 can also be employed to provide substantially constant runner or output speed, when connected to a load having a suitable torque/speed characteristic, when there are variations in the impeller or input speed. Assuming for example that the speed of the impeller is varied from an idling speed of 500 r.p.m. to a full load speed of 1500 r.p.m., it will be apparent that the oil flow through the leak-ofl? nozzles 2 via the scoop-tube 3 and cooler back into the working circuit will be low at the idling speed, and will rise progressively with the speed, so that at 1500 r.p.m. the oil flow will have increased to say three times the idling flow. In consequence, there will be a pressure in the duct 23 that will vary with the oil flow, and will increase normally as the speed of the input shaft of the turbo coupling increases. With the input shaft at idling speed, the oil pressure is low, hence the scoop tube 3 is fully engaged. When the input speed is increased, the oil pressure rises and the scoop-tube 3 is partly retracted. Further increase of speed will cause the scoop-tube 3 to be still further retracted, and the net result will be that the slip in the coupling will be increased as the speed of the input shaft rises. By suitably proportioning the weight 14 and arm 15, or the equivalent control spring 35 (Fig. 5) the coupling may be arranged to have a substantially constant output speed characteristic. This will be achieved both when increasing and decreasing the speed of the input shaft, but owing to the natural time delay in emptying and filling the working circuit, it is necessary that the rate of change of speed of the input shaft should be not too fast; for example, 15 to 20 seconds over the speed range from 500 to 1500 rpm.

Iclaim: I

l. A hydraulic turbo coupling comprising a vaned impeller element and a vaned runner element defining a working chamber, a reservoir mounted for rotation with one of said vaned elements, means providing restricted communication between said working chamber and said reservoir, an adjustable scoop tube having a scoop orifice disposed in said reservoir, a filling duct for feeding working liquid picked up by said scoop tube to said working chamber, a liquid pressure operated servo motor coupled to said scoop tube, and a duct interconnecting said filling duct and said servo motor to enable working liquid at the pressure in said filling duct to serve as operating medium for said servo motor.

2. A hydraulic turbo coupling comprising a vaned impeller element and a vaned runner element defining a working chamber; a reservoir mounted for rotation with one of said vaned elements and adapted to contain working liquid when said vaned elements are stationary; an adjustable scoop tube having a scoop orifice disposed in said reservoir; a filling duct for said working chamber communicably connected with a passageway communicating with said scoop tube for flow of liquid from said reservoir through said scoop tube, communicating passageway and filling duct into the working chamber; and a pressure motor communicably connected with said filling duct and connected to said adjustable scoop tube to actuate the scoop tube to adjust its position within the reservoir in accordance with the pressure within said filling duct to move the scope tube from a position in which the orifice is completely immersed in the working liquid in the reservoir to a position in which the orifice is partially retracted from said working liquid in said reservoir to reduce the rate of filling of the Working chamber through said filling duct, passageway and scoop tube during the period of acceleration of said vaned runner element from an initial stationary condition.

3. A hydraulic turbo coupling comprising a vaned impeller and a vaned runner together with a casing forming a working chamber, a scoop chamber communicably connected with said working chamber for flow of working liquid from said working chamber to said scoop chamber, an adjustable scoop tube having a scoop orifice disposed in said scoop chamber, the position of which scoop tube in said scoop chamber determines the degree of filling of said working chamber, a filling duct for said working chamber communicably connected with said scoop tube, and means operable in response to an increase in the pressure of the working liquid flowing from said scoop tube through said filling duct into said working chamber for adjusting the position of said scoop tube in said scoop chamber to reduce the filling of said working chamber.

4. A hydraulic turbo coupling comprising a vaned impeller and a vaned runner together with a casing forming a working chamber, a scoop chamber communicably connected with said working chamber for flow of liquid from said working chamber to said scoop chamber, an adjustable scoop tube having a scoop orifice disposed in said scoop chamber, the position of which scoop tube in said scoop chamber determines the degree of filling of said working chamber, a filling duct for said working chamber communicably connected with said scoop tube, a cylinder communicating with said filling duct, a piston movable in said cylinder and coupled to said adjustable scoop tube, and means for exerting on said piston a bias ing force opposed to the pressure in said cylinder.

5. A hydraulic turbo coupling comprising a vaned impeller element and a vaned runner element together with a casing forming a working chamber, a reservoir mounted for rotation with one of said vaned elements, means providing restricted communication between said working chamber and said reservoir, an adjustable scoop tube having a scoop orifice normally immersed in working liquid in said reservoir, a filling duct for feeding working liquid picked up by said scoop tube to said working chamber, a liquid pressure operated servo motor coupled to said scoop tube, and a duct interconnecting said filling duct and said servo motor to enable working liquid at the pressure in said filling duct to serve as operating medium for said servo motor to withdraw said scoop tube from said working liquid, and means for exerting on said scoop tube a biasing force tending to immerse said scoop orifice in said liquid.

6. A hydraulic turbo coupling comprising a vaned impeller element and a vaned runner element together with a casing forming a Working chamber; a reservoir mounted for rotation with one of said vaned elements and adapted to contain working liquid when said vaned elements are stationery; an adjustable scoop tube having a scoop orifice disposed in said reservoir; a filling duct for said working chamber communicably connected with a passageway communicating with said scoop tube for flow of liquid from said reservoir through said scoop tube, communicating passageway and filling duct into the working chamber; and a pressure motor communicably connected with said filling duct and connected to said adjustable scoop tube to actuate the scoop tube to adjust its position within the reservoir in accordance with the pressure within said filling duct to move the scoop tube from a position in which the orifice is deeply immersed in the Working liquid in the reservoir to a position in which the orifice is partially retracted from the said immersed position to reduce the rate of filling of the working chamber through said filling duct, passageway and scoop tube during the period of acceleration of said vaned runner element from an initial stationary condition.

References Cited in the file of this patent UNITED STATES PATENTS 1,873,688 Walker Aug. 23, 1932 2,256,878 Black Sept. 23, 1941 2,264,341 Sinclair et a1 Dec. 2, 1941 2,289,440 Kugel July 14, 1942 2,299,049 Ziebolz Oct. 13, 1942 2,403,399 Reggio July 2, 1946 2,536,473 Sinclair Jan. 2, 1951 2,651,919 Venstrom Sept. 15, 1953 2,689,458 Weymann Sept. 21, 1954