US3646756A - Trapezoidial scoop tube - Google Patents

Abstract

A variable speed fluid coupling having a scoop tube which has a trapezoidial fluid entrance opening such that the tube penetrates deeper into the fluid ring than conventional scoop tubes during constant speed operation; deeper penetration is believed to minimize bounce of the tube from the liquid ring. Further penetration of the scoop tube into the ring (as for deceleration) exposes relatively large areas of the opening to the fluid so that fluid ring thickness is rapidly diminished for rapid declutching of the coupling.

Description

United States Patent Langlois 51 Mar. 7, 1972 [54] TRAPEZOIDIAL SCOOP TUBE I Primary Examiner-Edgar W. Geoghegan [72] lnvemor' Henry Damn Mich Attorney-John E. McRae, Tennes l. Erstad and Robert G. [73] Assignee: American Standard Inc., New York, NY. Crooks [22] Filed: Feb. 12, 1970 ABSTRACT 21 A LN 10759 I pp 0 A variable speed fluid coupling having a scoop tube which has a trapezoidial fluid entrance opening such that the tube [52] US. Cl .60/54, 415/88 penetrates deeper into the fl id i than conventional Scoop [51] Cl 31/06 tubes during constant speed operation; deeper penetration is of Search believed to minimize bounce of the tube from the ring Further penetration of the scoop tube into the ring (as for [56] References cued deceleration) exposes relatively large areas of the opening to UNITED STATES pATENTS the fluid so that fluid ring thickness is rapidly diminished for rapid declutching of the coupling. 3,403,514 10/1968 James ..60/54 Meyer et al ..60/54 4 Claims, 5 Drawing Figures PATENTEDMAR H972 3,646,756

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Hzlvw j [MG TRAPEZOIDIAL SCOOP TUBE THE DRAWINGS FIG. I is a sectional view taken through a diagrammatically illustrated embodiment of the invention.

FIG. 2 is an enlarged sectional view of the tip area of a scoop tube employed in the FIG. 1 embodiment.

FIG. 3 is a frontal view of the FIG. 3 scoop tip area taken in the direction of arrow 2 in FIG. 2.

FIG. 4 is a frontal view of the tip area of a conventional scoop tube.

FIG. 5 is a view similar to FIG. 3 but illustrating a modified form of the invention.

FIG. I shows a fluid coupling comprising a vaned impeller carried by a power input shaft 12 which is arranged to rotate in a conventional bearing 14 suitably carried on a fixed housing wall 16. Numeral 18 refers to a conventional vaned runner facing the impeller 10 and cooperating therewith to define a conventional power-transmitting work chamber 20 of toroidial shape. Runner 18 is carried on an output shaft 22 which is arranged to rotate in a conventional bearing 24 carried by a second stationery housing wall 26.

Impeller 10 is bolted at its periphery to a scoop chamber casing 28 which surrounds the runner l8 and extends therebeyond to define a scoop chamber 30. Oil admitted to the work chamber 20 continually escapes therefrom through a clearance space 32 between the runner and casing 28 to thus form a rotating fluid ring 34 in the scoop chamber 30. The radial thickness of this fluid ring (dimension 36) is controlled by a hollow cylindrical scoop tube 38 which is mounted for movement in the direction of its axis 40. The scoop tube has no physical connection with the scoop chamber casing 28, but may instead be slidably mounted within a circular bore 42 formed through a boss 44 which projects laterally from the stationary wall structure 26.

The scoop tube extends generally parallel to the plane of the paper (FIG. 1) so that movement thereof in the arrow 40 direction causes the tube tip area 46 to move generally radially with respect to the rotational axis 48 of the coupling. The tip area of the scoop tube has a trapezoidial opening 50 facing the rotating liquid ring in the scoop chamber so that velocity pressure of the oncoming fluid drives some fluid through opening 50 and into the tube. The tube is provided with a discharge opening 52 which dumps the fluid into a fluid sump 54, as denoted by flow arrows 56. In practice the fluid coupling is housed within a stationary housing which includes a lower housing space defining the fluid sump; see for example U.S. Pat. No. 3,096,620 issued July 9, I963 to R. M. Nelden.

Fluid discharged into the sump is recirculated back into the work chamber 20 by means of a pump 58. Conventionally the fluid is directed through a cooler 60 (air-cooled or watercooled) for removal of the heat generated in the fluid incident to its vertical movement in the work chamber 20. As shown in FIG. I, the fluid is reintroduced into the work chamber through a line 62 connecting with axial passage 64 and radial passages 66 in the power input shaft 12. Fluid discharges from passages 66 into impeller passages 68 leading into the work chamber. The illustrated system of passages is merely one way of introducing the fluid to the work chamber; in practice various supply passage arrangements are utilized to feed the work chamber and bearings with power fluid and lubricant fluid. The conventional work fluid is oil which has lubricating qualities; therefore the same fluid can be used for transmission power and for lubrication of the bearings.

Heat generated in the fluid while in the work chamber 20 is in some cases an inverse function of the amount of fluid in the Various expedients have been suggested to minimize these pumping losses. For example, aforementioned U.S. Pat. No. 3,096,620 illustrates a diverter valve controlled by the scoop tube to vary the amount of fluid admitted to the work chamber inversely in accordance with the thickness of the liquid ring in the scoop chamber. A somewhat similar diverter valve is shown at 70 in the instant drawings. As here shown, the movable valve element comprises a plate 72 movable by or in synchronism with scoop tube 38 for apportioning the pump 58 output between line 61 leading to the work chamber and line 63 leading to the sump 54. The general operation of this valve is similar to the operation of the corresponding valve in U.S. Pat. No. 3,096,620. The present invention, as hereinafter described, may be used with or without such a diverter valve.

As previously noted, power is transmitted from the impeller 10 to the runner 20 by the helical flow of fluid denoted by flow arrows 74. The impeller vanes pump the fluidoutwardly away from rotational axis 48, and the'runner vanes transform some of the velocity energy of the fluid into rotational movement of the runner. Kinetic energy losses in the runner are manifested as a temperature increase in the working fluid. The fluid heating action requires that the working fluid be circulated through an external cooler such as cooler 60 to prevent thermal degradation of the oil. Difference between the input power and the output power at each particular filling of the work chamber represents the heat absorbed by the oil, and thus determines to a certain extent the minimum circulation rate which must be continually maintained through cooler 60 and passages 68.

It will be appreciated that centrifugal force acts similarly on the fluid in the work chamber 20 and in the scoop chamber 30 so that the radial thickness of fluid ring 34 corresponds directly with the quantity of liquid in work chamber 20 and the power transmitted by the coupling. The scoop tube 38 can be moved back and forth in the arrow 40 directions to extract fluid from the inner surface of the rotating fluid ring 34 to (I) maintain the ring at a given thickness, or (2) decrease the ring radial thickness, or (3) increase the ring radial thickness. Tube positionment depends on whether it is desired to (I) maintain a given runner speed, (2) increase the runner speed, or (3) decrease the runner speed. As previously noted, heat buildup considerations make it necessary that fluid in work chamber 20 be continuously replenished or replaced by new fluid. This requirement exists during all operational periods of the coupling so that tube 38 is required to continuously dip into the rotating fluid ring 34 to extract the over supply of fluid; the only exception would be acceleration periods during which the fluid tube 38 is withdrawn from ring 34 to permit fill-up of the work chamber.

During constant speed operations (either at full runner speed or reduced runner speeds) the scoop tube extends only a slight distance into the ring. When the automatic or manual scoop tube controller (not shown) signals an increase in runner speed the tube is moved so that its opening 50 travels radially toward the rotational axis 48. This action temporarily reduces or stops fluid flow through tube 38, thereby allowing the incoming flow through passages 68 to increase the amount of power-transmitting liquid in the work chamber. Conversely when the controller calls for a decrease in runner speed the scoop tube is moved so that its opening 50 travels radially away from the coupling rotational axis 48, thus tending to increase fluid flow through tube 38 so that fluid ring 34 has a decreased radial thickness. This manifests itself as a corresponding decrease in the amount of power-transmitting fluid in chamber 20.

FIGS. 2 and 3 show the tip area of the FIG. I scoop tube 38 in a position for extracting normal replacement fluid quantities from ring 34. FIG. 4 shows the tip area of a prior art tube that is similar to tube 38 except for the configuration of the entrance opening 50a. The tubes of FIGS. 2 through 4 are shown extended into the rotating fluid ring a distance sufficient to maintain a substantially constant ring thickness and substantially constant runner speed. Penetration of the tube to maintain constant runner speed should be sufficient to skim off liquid quantities equivalent to those being admitted through passages 68. This penetration may not be the same in all positions of the tube because the inner surface of fluid ring 34 is moving at a different linear velocities according to the ring thickness and runner rotational speed. However the penetration distances 89 and 89a shown in FIGS. 3 and 4 are representative or average for the range of different conditions.

Entrance opening 50 of the FIG. 3 tube has a trapezoidial shape defined by relatively short arcuate outer boundary wall 80, relatively long inner boundary wall 82, and two side boundary walls 84 which flare away from one another in the direction of the inner wall 82. Wall 80 is preferably no longer than one-half the length of wall 82, and each wall 84 is preferably at least as long as wall 82. Numerals 85 through 89 represent equal area sections of the opening 50 subdivided into horizontal parallel slices normal to the direction of tube 38 as it moves in and out of the fluid ring. Area 85 has the greatest thickness in the arrow 40 direction, area 86 has an intermediate thickness in the arrow 40 direction, and areas 87 and 88 have the smallest thickness in the arrow 40 direction. The fact that these four equal flow areas have different thicknesses means that tube 38 must move different incremental distances in different stages to provide a given increase or decrease'in tube flow. For example, initial penetration of the tube into the fluid ring produces only a slight flow of liquid into the tube. As the tube penetrates further into the ring the flow area increases at a progressively increasing rate so that during the final stages the tube is handling fluid quantities that are disproportionate to the extent of the tube penetration.

In an installation wherein tube 38 is required to handle a maximum flow of 500 gallons per minute the opening 50 might have a total flow area of about 3 square inches; wall 82 would be on the order of 2 inches long, arcuate wall 80 would be on the order of l inch long, and each wall 84 would be on the order of 2% inches long. The first 20 percent of the penetrating movement, as denoted by arrows 89, may be sufficient for the tube to then receive about 40 gallons per minute, the next l5 percent of the penetrating movement may be sufficient for the tube to accept an additional 80 gallons per minute, and so on. The final 20 percent of penetration denoted generally by arrow 88 may be sufficient for the tube to accept an additional 130 gallons per minute. In its illustrated position the tube provides sufiicient penetration to just balance the flow through passages 68 into the work chamber at steady run conditions. With such a balanced flow the runner will operate at a constant speed, either fully clutched or at any given percent slip. Further penetration into the fluid ring, as for example denoted by numerals 85 and 86 will provide normal deceleration of the runner. Full penetration of the scoop tube will provide rapid deceleration, terminating eventually in a declutching action.

One reason for the FIG. 3 configuration of the entrance opening 50 is to permit a substantial penetration of the tube into the liquid ring before appreciable flow through the opening. With such an arrangement the scoop tube enjoys a substantial penetration into the ring under constant speed conditions. It is believed that this penetration tends to stabilize the scoop tube against erratic bouncing movements into and out of the fluid ring. Another reason for the FIG. 3 configuration is that it makes large flow areas available for rapid declutching or deceleration.

FIG. 4 illustrates a conventional scoop tube having an elliptical fluid entrance opening 50a. The tube is illustrated in a position for accepting approximately the same quantity of oil as the FIG. 3 tube. The FIG. 4 tube penetrates the oil ring to the extent denoted by dimension 89a. This dimension is about 50 percent less than the corresponding penetration dimension 89 of the FIG. 3 tube. The lesser penetration of the conventional scoop tube is believed to be a cause of instability noted during use of the conventional tube.

It is believed that with the comparatively slight penetration 89a of the conventional tube during constant speed operation there is a tendency for the liquid ring to produce transitory upsetting forces on the tube in the arrow 40 direction. Thus, should the position of the tube or the thickness of the ring instantaneously cause a slight decrease in penetration it is believed that the tube can wholly or substantially leave the liquid surface 92, whereupon the liquid surface can act somewhat in the nature of a solid skin to resist new penetration of the tube into the liquid. An increased control force must then be exerted on the tube in the arrow 40 direction to overcome this skin resistance. Eventually the increased control force will effect penetration of the tube into the liquid ring, but the increased force will apparently cause the tube to overshoot and to penetrate too far into the liquid. The result is a hunting action of the tube which manifests itself as vibrational tube motion and undesirable coupling operation.

The conventional scoop tube of FIG. 4 produces relatively large increases in tube flow during the intermediate portions of its penetrating movement. However, during the final movement toward a fully declutched condition the increase in opening area is not very great since the arcuate roof area 91 tends to unduly limit the amount of added fluid which can be handled by the tube during the final movement stage. It is believed that the configuration of the opening shown in FIG. 3 will provide an improved speed control inasmuch as final penetration of the tube will achieve a most significant deceleration effect. When the tube is controlled by a controller responding to runner speed the acceleration-deceleration movement of the tube will be less as the tube is near the control setting; consequently there should be less hunting for the control point than with the conventional tube.

It is believed that the invention can be practiced with fluid entrance opening configurations differing from that shown in FIG. 3. FIG. 5 illustrates one additional configuration that is believed feasible. FIG. 5 shows the scoop tube penetrating into the liquid ring so that its entrance opening 50b is extracting sufficient liquid to substantially balance the replenishment flow going into the work chamber through passages 68 (FIG. 1). The scoop tube is in the same operational position as the FIG. 3 scoop tube and the FIG. 4 scoop tube.

It will be noted that the FIG. 5 tube has a penetration distance 8911 that is substantially greater than the penetration distance of the conventional tube denoted by dimension 89a. This is due to the configuration of the entrance opening wherein the flaring boundary sidewalls 84b are quite close together in the areas thereof near the outer boundary wall b. It is believed that the FIG. 5 scoop tube would have a stabilized action and deceleration-acceleration capability somewhat approaching that of the FIG. 3 scoop tube.

I claim:

1. In a variable speed fluid coupling comprising a vaned impeller and vaned runner facing one another on a common rotational axis to define a power-transmitting work chamber; means for continually supplying said work chamber with new work fluid; a scoop chamber casing carried by the impeller for receiving fluid as it escapes from the work chamber; and a radially movable scoop tube extending into the scoop chamber for extracting fluid from the inner surface of the rotating fluid ring to thereby control the radial thickness of the ring and the quantity of fluid in the work chamber; said scoop tube having a fluid entrance opening in the tip area thereof facing the oncoming fluid so that velocity pressures drive fluid through the opening and into the tube: the improvement wherein the entrance opening includes a first radially outermost section having a comparatively small total area for a I given radial penetration thereof into the fluid ring, and a second radially innermost section having a substantially greater area for a given radial penetration thereof into the fluid ring; the outermost section of the scoop tube opening being of such area in relation to the flow of fluid supplied to the work chamber that the scoop tube is continually required to penetrate a substantial distance into the fluid ring to maintain the ring thickness at any given value; the aforementioned entrance opening being defined by a relatively short outer 3. The coupling of claim 2 wherein the outer boundary wall of the trapezoid has a dimension no greater than one-half that of the inner boundary wall.

4. The coupling of claim 3 wherein each side boundary wall is at least as long as the inner boundary wall.

* k I II

Claims (4)

1. In a variable speed fluid coupling comprising a vaned impeller and vaned runner facing one another on a common rotational axis to define a power-transmitting work chamber; means for continually supplying said work chamber with new work fluid; a scoop chamber casing carried by the impeller for receiving fluid as it escapes from the work chamber; and a radially movable scoop tube extending into the scoop chamber for extracting fluid from the inner surface of the rotating fluid ring to thereby control the radial thickness of the ring and the quantity of fluid in the work chamber; said scoop tube having a fluid entrance opening in the tip area thereof facing the oncoming fluid so that velocity pressures drive fluid through the opening and into the tube: the improvement wherein the entrance opening includes a first radially outermost section having a comparatively small total area for a given radial penetration thereof into the fluid ring, and a second radially innermost section having a substantially greater area for a given radial penetration thereof into the fluid ring; the outermost section of the scoop tube opening being of such area in relation to the flow of fluid supplied to the work chamber that the scoop tube is continually required to penetrate a substantial distance into the fluid ring to maintain the ring thickness at any given value; the aforementioned entrance opening being defined by a relatively short outer boundary wall at the extreme tip of the tube, a relatively long inner boundary wall spaced radially inwardly from the outer boundary wall, and two side boundary walls flaring away from one another in the direction of the inner boundary wall at an angle substantially less than 90*.

2. The coupling of claim l wherein the entrance opening has a trapezoidial shape.

3. The coupling of claim 2 wherein the outer boundary wall of the trapezoid has a dimension no greater than one-half that of the inner boundary wall.

4. The coupling of claim 3 wherein each side boundary wall is at least as long as the inner boundary wall.

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