Lockable Valve for Hydraulic System

Heavy equipment of the earth moving type or framing type is normally left at the end of a working day in the open at or near the place it has been used. These machines are too heavy and move too slowly to consider driving them to a garage, warehouse, or other building for safekeeping overnight. Such machines are always equipped with an ignition lock but thieves have become adept at bypassing a locked ignition and in readily being able to start the engine of such a vehicle. In more recent times there has been a marked increase in the theft of these heavy equipment vehicles and this had led to the consideration of other means for securing such vehicles from theft. It is an object of this invention to provide a means for blocking the main hydraulic fluid line to prevent its use in moving any of the auxiliary equipment of the vehicle. Thus, in case of a bulldozer the heavy blade could be left on the ground and this would prevent movement of the vehicle even though the ignition were bypassed. In other types of vehicles it would be an added delaying deterrent which might frustrate the thief and cause him to cease further attempts at stealing the vehicle because it would take too much time to make it operate properly.

This invention provides a lockable valve in a hydraulic system comprising a valve body, a cylinder, a piston in the cylinder, and spaced inlet port and two outlet ports entering the valve body communicating with the cylinder, one of such outlet ports leading to a bypass line and the other of such outlet ports leading to an operational hydraulic cylinder. The piston is slidable in the cylinder to selectively close either of such outlet ports. A manually lockable means is provided in the valve to lock piston in the position in which the outlet port to the hydraulic cylinder is closed; and the means is spring biased to close the outlet port leading to the bypass line and to open the outlet port leading to the hydraulic cylinder when the lockable means is unlocked. In one specific embodiment of this invention the piston comprises two spaced heads and the outlet ports are positioned in accordance with the spacing between the piston heads such that when one head covers one outlet port the other of the two outlet ports is open and the inlet port is located between the two outlet ports.

The novel features believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a schematic illustration of a hydraulic system employing the lockable valve of this invention;

FIG. 2 is a front elevational view of the lockable valve of this invention;

FIG. 3 is an end elevational view of the lockable valve of this invention;

FIG. 4 is a cross section view taken along line 4--4 of FIG. 3.

In FIG. 1 there is shown a simplified schematic illustration of a hydraulic system that may be employed on any of several types of equipment. In all such systems the hydraulic fluid is pressurized by means of pump 10 through an inlet line 17 via control valve 12 to a hydraulic cylinder 13 that may be attached between the frame and any piece of auxiliary equipment mounted with respect to the frame, e.g., a bulldozer blade, a backhoe, etc. The manually operated valve 12 provides the control by which the operator of the equipment can admit fluid to hydraulic cylinder 13 to cause the relative movement of auxiliary equipment with respect to the frame as desired. In order to complete the circuit of hydraulic fluid which is under pressure, the fluid returns from the hydraulic cylinder 13 to a sump 11 which then serves as the feed to pump 10. In the system of the present invention a lockable valve 16 is connected in the line 17 between the manually operated control valve 12 and the pump 10. Lockable valve 16 includes two outlet ports 19 and 20 through which the incoming fluid from line 17 via inlet port 18 can be directed to either of the two outlet lines 14 or 15. Line 14, communicates via manually operated valve 12 to hydraulic cylinder 13. Line 15 serves as a bypass which leads directly to sump 11. Thus, if valve 16 is set to connect inlet line 17 to bypass line 15, the hydraulic fluid will merely circulate through the sump 11 and pump 10. If valve 16 is set to connect inlet line 17 with outlet line 14, the fluid will flow through valve 12 to cylinder 13 for operation of the equipment and then return to sump 11.

The details of construction of the lockable valve 16 in accord with this invention are clearly depicted in FIGS. 2-4. The valve 16 includes a valve body 22 having an inlet port 17, two outlet ports 14 and 15 and a manually operated lock 21. In order to follow the same general arrangement as shown in FIG. 1, line 14 leads to an operating hydraulic cylinder 13, and line 15 is the bypass line leading directly to sump 11. Lock 21 in FIG. 2 is in the unlocked position in which the piston portion 40 protrudes outwardly from valve body 22. In the locked position lock 21 is pressed inwardly and locked so that the key end 40 is substantially flush with the valve body end 42. Lock 21 is any type of manually operated lock, the variety shown here being a key operated lock as illustrated by key slot 37. A combination lock or other type lock may be employed so long as the operator is able to lock or unlock it and the lock body can be pressed inwardly into body 22 and the barrel 40 is sufficiently long to accommodate the throw of the valve piston 50.

The cross sectional view shown in FIG. 4 will more clearly disclose the preferred embodiment of this invention. Valve body 22 contains a cylinder 23 which communicates with the outside of valve body 22 by means of inlet port 18 and two outlet ports 19 and 20. Inlet port 18 is joined to inlet line 17 of FIG. 1 while outlet ports 19 and 20 are respectively joined to line 14 which leads to an operating hydraulic cylinder and to bypass line 15.

Cylinder 23 houses a piston 50 which slides lengthwise within cylinder 23 to various positions to accomplish the intended purposes in accord with this invention. The piston 50 comprises an inner head 24 joined to an outer head 25 by a connecting rod 26 which is considerably smaller in diameter than heads 24 or 25. The two heads 24 and 25 are spaced apart in accordance with the locations of ports 18 and 19. Although other arrangements may be provided to accomplish similar results, in accord with the preferred embodiment of this invention the ports are arranged so that inlet port 18 is positioned between the two outlet ports 19 and 20 and with the spacing between heads 24 and 25 such that each head can be positioned to cover its respective outlet port and leave the other two ports open. For example, in the position shown in FIG. 4 outer head 25 covers outlet ports 19 and inner head 24 at the same time is so positioned that both inlet port 18 and outlet port 20 are open. Thus in such position hydraulic fluid from pump 10 enters through inlet port 18 and leaves through outlet port 20 to bypass line 14 and thence recirculate through sump 11 and pump 10. The second position of piston heads 24 and 25 is accomplished by unlocking lock 21, causing the spring 29 to move piston heads 24 and 25 to the left, as viewed in FIG. 4, until inner piston head 24 covers outlet port 20. In such a position outer piston head 25 has moved sufficiently far to the left such that both inlet port 18 and outlet port 19 has uncovered. In this position hydraulic fluid from pump 10 and line 17 enters inlet port 18 and leaves outlet port 19 to operating line 14 which leads via valve 12 to hydraulic cylinder 13 and thereafter recirculates through sump 11 and pump 10. Thus, the valve of this invention is designed to operate in either of two positions of the piston 50 in cylinder 23, one in the locked position shown and the other with head 24 blocking outlet port 20 with outlet port 19 unblocked.

Both piston heads 24 and 25 are sealed by any convenient means such as O-rings 27 to prevent undue leakage of hydraulic fluid past the piston heads into the cylinder. Vent 38 is provided through the valve body end 43 communicating with cylinder 23 adjacent piston end 44 to prevent any vacuum buildup upon movement of the piston, 50 towards or away from the cylinder end 43. Piston portion or extension 28 is encircled by a helical spring 29 which is biased to force piston extension 28 to the left as shown in FIG. 4. Since piston extension 28 is connected and preferably integral with piston heads 24 and 25, any movement of piston extension 28 is directly transferred to piston heads 24 and 25. Flange 30 on piston extension 28 extends laterally therefrom and functions as a seat for one end of spring 29 while the other end is seated on a circumferential shoulder 45 formed by an enlarged bore in valve body 22 to accommodate spring 29. In bore 31 at the forward end of piston extension 28 there is fitted the body 51 of manually operated lock 21. The lock body 51 is shown to be generally cylindrical and has a locking dog 32 which projects into recess 33 in valve body 22 when in the locked position. Any movement, except for minor play between the parts is thus inhibited in either direction of motion of the piston 50. When the key is inserted into slot 37 and used to unlock the mechanism, dog 32 retracts and the compression force of spring 29 is then permitted to operate freely to cause the piston 50 to move outwardly of the valve body 22. The spring 29 forces piston head 28 carrying lock 21 outwardly to the left so that it projects beyond the end of valve body 22 to the position generally shown in FIG. 2. The amount of travel is limited by a keyway 34 cooperating with set screw 35 in valve body 22. To prevent detection and tampering by a thief attempting to break this lock, set screw 35 is preferably countersunk and the depression 52 filled with solder or the like. The outer limits of piston extension 28 are sealed against dirt entering into the mechanism and against any oil lubrication leakage by any suitable means such as O-ring 36. Lock 21 is preferably sufficiently elongated so that dog 32 will be well within the confines of valve body 22 at all times and thus substantially protected from any accumulation of dirt or debris which might interfere with the lock's working mechanism.

In the operation of the valve of this invention, it may be seen that the operator of the equipment must have not only an ignition lock key to start the engine and thereby provide power for pump 10 and for movement of the vehicle, he must also have a key to unlock the locking mechanism 21 in order to operate any of the auxiliary equipment of the vehicle. When the valve is locked in the position shown in FIG. 4, the piston heads 24 and 25 are held in the position such that hydraulic fluid from pump 10 circulates only through the bypass line 15 and is not capable of providing pressurized fluid to operate any of the auxiliary equipment. As soon as lock 21 is unlocked, the hydraulic fluid is then available to operate that auxiliary equipment. When this invention is used in connection with heavy earth moving equipment, the vehicle preferably will be locked at the end of the day with a heavy arm or blade of the auxiliary equipment resting on the ground or somehow under load, and thus serve as an anchor or deterrent against movement of the vehicle until that arm or blade is lifted or relieved from its load which cannot be accomplished until the valve of this invention is unlocked or other detrimental action is taken by the thief which would greatly impede the successful theft thereof.

It is recognized that other arrangements of piston heads and ports in the valve of this invention may be employed to accomplish a similar purpose. Preferably the use of two spaced piston heads with outlet ports on either side of the inlet port permits the objective to be accomplished with a similar valve. Furthermore even in equipment which has an automatic small bypass around the pump whenever the pressure in the hydraulic line goes beyond a maximum setting, such bypass will cause pumpe failure if the excess pressure continues beyond a small time interval. The valve of this invention protects the pump by making sure that an outlet, or momentarily both outlets, are open at all times during operation of the pump. While in theory it may be possible to merely close and open the inlet port rather than having the two outlet ports and valve heads in accord with this invention, pump safety and protection would be sacrificed.

While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.