LOCK VALVE WITH GROOVED PORTING IN BORE

A lock valve includes a lock valve body having a bore with a valve spool reciprocatingly received therein. There is a check valve adjacent each end of the bore. Each of the check valves has a check valve member facing the bore and resiliently biased towards a valve seat at each end of the bore. A pressure relief port communicates with the bore near the center thereof and between lands of the valve spool. A pair of spaced-apart grooves are disposed within the spool valve bore. Each groove permits fluid communication past a land of the valve spool when the valve spool is displaced towards one end of the bore by fluid pressure applied to other end of the bore so as to unseat the check valve member adjacent to the one end to the bore and allow pressurized fluid to pass from the one end of the bore, through the groove, and into the relief port.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and first toFIG. 1, this shows an improved hydraulic steering system10. The steering system10is typically used for marine steering applications, but may be used for other steering applications or other control applications. The steering system10includes a hydraulic steering cylinder12which is conventional and accordingly only described briefly herein. The cylinder12has a rod14which, in this example, extends from one end of the cylinder12and is connected to a rudder or some other steerable member such as an inboard/outboard drive or an outboard motor (not shown). The cylinder12is an unbalanced cylinder although in other embodiments a balanced cylinder may be used.

The steering system10includes a helm pump16that forms part of a helm18which is used to steer a marine vessel. In this example, the helm pump16is in the form of a manually operable rotary pump. However, in alternative embodiments, motor driven pumps or helms may be used. The helm pump16has first and second helm pump ports20and22which serve to discharge or receive fluid depending upon the direction of rotation of the helm18. The helm pump16and helm18are conventional and accordingly are not described further herein.

The steering system10also includes a lock valve24. The lock valve24includes a lock valve body26having a main bore28with a valve spool30reciprocatingly received therein and thus forming a spool valve32. The main bore28accordingly functions as a spool valve bore having first and second ends and a center. The valve spool30has first and second lands34and36separated by a narrower stem38. An annular space40is defined in the area between the stem38and the valve body26. There are projections42and44extending outwardly from opposite ends of the valve spool30. In this example, the projections are generally in the shape of truncated cones though this is not critical. Other embodiments may not have such projections.

The lock valve24also includes a pair of check valves50and70located within check valve chambers52and72respectively. The check valve chambers52and72are located at opposite ends of the main bore28and are respectively separated from the main bore28by walls54and74apart from passageways56and76. The passageways56and76extend through the walls54and74from the main bore28to corresponding check valve chambers52and72. Each of the check valves50and70respectively includes a check valve member55and75and a resilient member57and77. As described for one of the check valves50, the check valve member55is a ball which is normally biased against a valve seat at the wall54by the resilient member57which, in this example, is a coil spring. Accordingly, the check valves50and70normally block the passageways56and76. The passageways56and76may also be described as steering actuator ports of the lock valve. It will be understood that other configurations of check valves may be used in other embodiments.

The lock valve24also has a pair of cylinder ports78and80which are hydraulically connected to the cylinder12via hydraulic conduits79and81respectively. The hydraulic conduits79and81are connected to opposite ends of the cylinder12on opposite sides of a piston (not shown). The ports78and80communicate inwardly, with respect to the lock valve24, with check valve chambers52and72respectively. The lock valve24also has a pair of helm ports82and84which are hydraulically connected to the helm pump16by hydraulic conduits83and85respectively. In this example the helm ports82and84are angled and communicate inwardly, with respect to the lock valve24, with main bore28.

In normal operation, when the helm18is steered, pressurized fluid is discharged from one of the helm pump ports20or22. In the example shown inFIGS. 1,1A, and1B pressurized fluid is being discharged from the first helm pump port20. Pressurized fluid discharged from the first helm pump port20enters the lock valve24via conduit85and port84and accordingly enters the main bore28. As shown best inFIG. 1A, the fluid acts on the valve member75of check valve70so that the fluid flows through opening76and into a rod side of the cylinder12through port80and hydraulic conduit81.

The pressurized fluid also shifts the valve spool30to the left from the position shown inFIG. 1to the position shown inFIG. 1A. As shown inFIG. 1A, this causes projection42to contact the check valve member55of check valve50and moves the check valve member55away from the valve seat at the wall54, against the pressure of the resilient member57, to allow communication between the main bore28and the check valve chamber52through the passageway56. In embodiments without the projections, either the lands or ends of the spool may engage the check valve member. Thus moving the check valve member55permits a return flow of fluid from the cylinder12to pass through hydraulic conduit79, port78, check valve chamber52, passageway56, port82, and conduit83and to the helm pump16through port22.

As thus far described, the steering system10is generally conventional and it will be understood that the valve spool30is shifted to the right from the position shown inFIG. 1if the helm is steered in the opposite direction and the fluid flow is substantially the opposite as described above.

However, the steering system10further includes a pair of spaced-apart first and second trough-like grooves86and88disposed within the main bore28between the lock valve body24and the valve spool30, i.e. the grooves86and88are formed within the main bore28of the lock valve body24. As best shown inFIG. 2, the grooves86and88are spaced-apart in a direction parallel to a longitudinal, central axis90of the main bore28. It will be understood that the axis90is also a longitudinal, central axis of the valve spool30shown inFIG. 1. In this particular example, and as best shown inFIG. 3for the first groove86, each groove is in the shape of a cylindrical segment having a crescent-shaped cross section as shown at a first end87of the groove86. The end87of the groove86has an outer edge92which is a circular segment defined by the curvature of a circular wall29of the main bore28. An inner edge94of the end87of the groove86is also a circular segment defined by the curvature of the groove86. In this example, the inner edge94has a smaller radius compared to the circular wall29of the main bore28. The groove86has side edges96and98which are straight and parallel to the longitudinal, central axis90which is shown inFIG. 2. In this example, the groove86has a constant cross-section similar in shape to the end87thereof. The end87of the groove86is also perpendicular to the sides96and98of the groove86in this example. It will be understood that the other one of the grooves88has a similar structure.

As viewed inFIG. 1, the first land34of the valve spool30has an inner circular edge35at a right end thereof facing the annular space40. It will be understood that the terms “right” and “left” as used in the following description are for purposes of explanation only, with reference toFIGS. 1,1A, and1B, and do not have any significance in the orientation or function of the steering system10disclosed herein. In the position shown inFIG. 1the first land34overlaps the edge92of the first end87of the first groove86so as to prevent communication between the annular space40and a portion of main bore28to the left of the land34. As shown inFIG. 1A, if sufficient pressure is generated in the main bore28to the right of the valve spool30, the valve spool30is shifted to the left until projection42presses against valve member55of the check valve50and unseats the valve as described above. However, if the pressure reaches a certain threshold level as shown inFIG. 1B, the valve spool30is displaced further to the left against the pressure of the resilient member57until the circular edge35of the first land34clears the edge92of the first groove86to the left. The edge92of the groove86, in this example, is in the form of a shoulder at the end of the groove86which extends about the main bore28a distance equal to the width of the edge92and is parallel to the circular edge35of the land34. The groove86extends to a second end93which is located to the left of the land34, from the point of view ofFIG. 1, so that circular edge35of the land34is to the right of the second edge93of the groove. Accordingly, when the circular edge35of the land34clears the edge92of the groove86to the left, an opposite circular edge33on the right end of the land34is still to the right of the second end93of the groove86. Accordingly, fluid is free to travel from the portion of main bore28to the left of land34, through the first groove86and into the annular space40. The linear increase in area of the fluid passageway occurs over a short transition distance, i.e. the slope of the linear increase in cross-sectional area is very steep.

There is a reservoir conduit43which extends from an opening45located on the main bore28to a hydraulic fluid reservoir or tank47. The opening45may be described as a pressure relief port for the lock valve24. Thus, when the pressure to the right of the valve spool30, caused by fluid discharged from the first helm pump port20of helm pump16exceeds a threshold value, fluid returning to the helm pump16through the second helm pump port22, and entering the main bore through port78and passageway56, can either return to the helm pump16through port82and conduit83or pass through the first groove86and into the reservoir47through opening45and conduit43. This allows any extra fluid volume returning to the helm pump16to return to the reservoir47.

The trough-shape of the groove86offers significant advantages. When the land34crosses the edge92of the groove86, there is a linear increase in cross-sectional area until the area is equal to the semicircular groove. This is particularly important for systems having two or more helms in parallel as shown inFIG. 10. Conventional lock valves may produce a free-wheeling condition when two or more helm pumps are connected in parallel. Restricting the return flow to the reservoir by this throttling action inhibits free-wheeling from occurring.

The operation is similar if helm pump116inFIG. 10is operated instead of helm pump16. Lock valve124for helm pump116is similar to the lock valve24for helm pump16and like parts have like numbers in the “100” series. Also inFIG. 10the helm ports are shown straight instead of angled. The reservoir conduit143for spool valve130is connected to the reservoir conduit43of spool valve30by a conduit49shown inFIG. 10.

It will be understood by a person skilled in the art that trough-shaped groove88provides similar pressure relief to the reservoir47when the valve spool30is shifted to the right due to pressurized fluid discharged from the second helm pump port22of the helm pump16. Proper functioning of the lock valves requires accurate positioning of the ports controlling discharge to the reservoir. In the past this has been achieved using holes and grooves on spools or angled holes through the main bore to provide a means to return unbalanced flow. However the lock valve disclosed herein provides a much more expedient and inexpensive way of achieving the desired accuracy.

An alternative embodiment of the lock valve24.1is shown inFIGS. 6 to 9. The lock valve24.1shown inFIGS. 6 to 9is generally similar to the lock valve24shown inFIG. 1, and like parts have been given the same reference numbers with the additional numerical designation “0.1”. However, in the embodiment shown inFIGS. 6 to 9helm ports82.1and84.1extend perpendicularly from the spool valve bore28.1instead of at angles as in the embodiment ofFIG. 1. In addition separate valve seats are used and the check valve members55.1and75.1are subassemblies with a frusto-conical portion directed towards the valve spool30.1.

With reference toFIGS. 4 and 5, these illustrate a rotary tool200for forming the trough-shape grooves accurately within the main bore28of the lock valve body26. This tool200has a circular, rotary cutter or land204located on a shaft206which is held and rotated by a rotary power mechanism. The grooves are formed by inserting the tool200into the main bore28as indicated by arrow210inFIG. 5. The tool is rotated as indicated by arrow212and pressed against the wall29of the main bore28to form the grooves. This is easier to control and achieves more accurate results compared to drilling holes in the lock valve body26to intersect with the main bore28. It should be understood however that the grooves could be produced in other ways besides the method described above. For example, the grooves could be broached or cast.

In this example the trough-like grooves are 0.008″ deep between the centers of the edges96and98shown inFIG. 3, but the dimensions could be different in other embodiments.

While preferred embodiments of the present invention have been described, it is to be understood that the embodiments described herein are illustrative only and the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalence, many variations and modifications naturally occurring to those of skill in the art from a perusal hereof. As is readily apparent the system and method of the present invention is advantageous in several aspects.