US3357451A

US3357451A - Speed and directional control valve for double-acting lift cylinder

Info

Publication number: US3357451A
Application number: US458123A
Authority: US
Inventors: Francis H Tennis
Original assignee: Hydraulic Unit Specialties Co
Current assignee: Koehring Co; Hydraulic Unit Specialties Co
Priority date: 1965-05-24
Filing date: 1965-05-24
Publication date: 1967-12-12
Anticipated expiration: 1984-12-12

Description

Dec. 12, 1967 SPEED AND DIRECTIONAL D UBLE-ACTING LI Filed May 24, 1965 O F. H. TENNIS CYLINDER NTROL VALVE FOR 3 Sheets-Sheet l RESERVOIR F. H. TENNIS 3357451 SPEED AND DIRECTIONAL CONTROL VALVE FOR DOUBLE-ACTING LIFT CYLINDER 3 Sheet5 sheet 2 Dec. 12, 1967 Filed May 24, 1965 "35? arl/:15H: Tam-us ai* wm N" Dec. 12, F. H TENNIS SPEED AND DIRECTIONAL CONTROL VALVE FOR DOUBLE-ACTING LIFT CYLINDER Filed May 24, 1965 3 Sheets-Sheet i United States Patent O 3,357 451 SPEED AND DHQECTIOAL CONTROL VALVE FR DOUBLE-ACTING LIFT CYLINDER Francis H. Tennis, Hartland, Wis., assignor to Hydraulic Unit Specialties Company, Pewaukee, Wis., a corporation of Wisconsin Filed' May 24, 1965, Ser. No. 458,123 3 Claims. (Cl. 137-596) ABSTRACT F TIE DISCLOSURE This invention relates to control valves for double-acting hydraulic lift cylinders of the type generally employed to raise and lower a load such as the fork of a lift truck or the boom of a front end loader, for example; and it has more particular reference to improvements in control valves for effecting raising of the fork at different speeds by its cylinder.

A control valve which has been used for that purpose is disclosed in my copending application Ser. No. 230,524, led Oct. 15, 1962 and now abandoned. The control valve of that application has a pair of service passages which are respectively connectable with the head and rod ends of a double-acting lift cylinder, Iand a valve element or spool that is shiftable in the valve body from a neutral position to each of two defined normal operating positions to enable either service passage to be communicated with supply passage means and the other service passage to be communicated with exhaust passage means. In each of these operating positions, source fluid flows from the supply passage means to the selected service passage vthrough a load-holding check valve common to both service passages.

The valve spool is also shiftable to a second pair of delined operating positions to effect either high speed lowering or high speed raising of the load. In the iirst of these high speed positions, the valve element communicates the head and rod connected service passages with one another through an exhaust passage in the valve body and isolates them from the supply passage means. Hence, fluid exhausting from the head end of the lift cylinder is recirculated back to the rod end of the cylinder to allow the load to descend freely and rapidly by its own weight.

In the fast raise position of the valve spool, both service passages are closed cfr from the exhaust passage means and are communicated with one another and with the supply passage means through connecting branches of the latter. Accordingly source fluid flows to the head end of the lift cylinder along with exhaust uid expelled from the rod end of the cylinder, to raise the load at a fast rate.

In both of these high speed positions of the valve spool, fluid expelled from one end of the cylinder is fed back into its other end through passages in the valve body that bypass the load holding check valve mentioned previously. In other words, the load holding check valve is fully operative in only the two normal operating positions of the valve element. This situation is of little or no concern in the high speed lower position of the valve element at which the load is intentionally lowered at a fast rate and the operator is ordinarily able to slow and stop the descent of the load at the desired level.

The situation that obtains when the valve element is in its high speed raise position, however, can be quite objectionable. At such times, the head and rod connected service passages in the valve body, though communicated with the upstream portion of the supply passage means through the conventional load holding check valve, are also communicated with one another through branches 0f the supply passage means which are downstream from the load-holding check valve. As a result, if the pump or the prime mover driving the same should fail in the fast raise position of the valve spool, the load on the cylinder can cause objectionably high pressures to be substantially instantaneously built up in the cylinder. This, of course, gives rise to the possibility of damage occurr-ing to the system.

It is the object of this invention, therefore, to provide a speed and directional control valve of the character described, but which features la single load holding check valve that functions to prevent load drop in both the normal raise and rapid raise positions of the valve spool, and in addition operates to prevent objectionably high pressures in the cylinder that heretofore were sometimes experienced in the fast raise position of the valve element.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination tand arrangement of parts substantially as hereinafter described and more particularly dened by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention, constructed according to the best mode so tar devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a longitudinal sectional View through the control valve of this invention, taken on the line 1*1 of FIGURE 2 and showing the valve spool in its neutral position;

FIGURE 2 is a sectional view taken on the plane of the line 2-2 in FIGURE 1;

FIGURE 3 is a diagrammatic section-al view like FIG- URE 1, but showing the valve spool in its slow raise posit-ion; and

FIGURE 4 is a diagrammatic sectional view similar to FIGURE 3 but showing the Valve spool in its fast raise position.

Referring now to the drawings, the numeral 5 generally designates the body of the speed and directional control valve of this invention. The valve has been shown embodied in a hydraulic system comprising a double-acting lift cylinder 6, a pump 7, and a reservoir 8 from which the pump is supplied with fluid.

The body 5 of the valve has been shown as comprising but one control section of a valve that may consist of a plurality of similar control sections connected together in a stack between manifold sections, not shown, in which the inlet and outlet of the valve are formed. It has a valve element or spool lil that can be shifted endwise in a bore 11 from a neutral position seen in FIGURE l to a rst operating position to the left of neutral to effect slow descent of a load 12, such as the fork of a lift truck or the boom of a front end loader, to which the piston rod 13 of the cylinder is operatively connected. The spool can also be shifted from its neutral position to each of two additional operating positions to the right of neutral to eect either slow or fast raising of the load 12. All of these spool positions are customarily defined by detents, not shown.

Fluid is routed to and from the cylinder in these various operating positions of the valve spool in a manner similar to that disclosed in my copending application Serial No. 230,524 tiled October 15, 1962. Source fiuid from the pump ows to the inlet of the valve assembly and then through the upstream or inlet branch 14 of a carry-over or open center passage in the body of the control section to the bore 11. When the valve spool is in its neutral position seen in FIGURE l, such iluid arriving at the bore ilows axially therein to the downstream or outlet branch 15 of the Open center passage, from whence it can flow into the inlet branch of the carry-over passage in the next adjacent control section or to the outlet of a manifold section.

For purposes of illustration, the pump delivery line 16 has been shown as connecting with the upstream or inlet branch 14 of the carry-over passage in the control section. The upstream branch 14 of the carry-over passage opens through a passageway 14' to supply passage means comprising a U-shaped bridge passage 17 having

opposite legs

18 and 19 that intersect the bore 11 at axially opposite sides of the carry-over passage. Whereas in past valves of this type source iluid was constrained to ow through a load holding check valve usually located in the passageway 14' before entering the U-shaped bridge passage, the upstream branch 14 of the carry-over passage here opens to the bridge passage 17 at a location up-y stream from a load holding check valve 20 controlling communication between the inlet passage 14 and only the leg 18 of the bridge passage. As seen best in FIGURE 2, the bight of the U-shaped bridge passage joins the

legs

18 and 19 of the bridge through bight portions 18' and 19', respectively, which are offset in the direction of the carry-over passage. Thus, the bight portion 18' extends lengthwise of the bore from its leg 18 at a location near one face 22 of the control section, while the bight portion 19 similarly extends lengthwise of the bore from its leg 19 but at a location near the opposite face 23 of the control section. The overlapping parts of these bight portions are communicated by a bore 24 which opens to the bight portion 18 through an annular valve seat 25 formed at the bottom of a counterbore 26 containing the load holding check valve 20.

As in my Patent No. 3,151,630 issued Oct. 6, 1964, the mouth of the counterbore 26 is adapted to be closed by an adjacent control or manifold section, to thus hold the check valve 20 in place without special retaining means such as threaded plugs or the like. The check valve spring 28 is also adapted to seat upon the face of the adjacent control section to thus yieldingly bias the check valve 20 to its normally closed position.

With the arrangement described, source fluid entering the upstream branch 14 of the carry-over passage can iiow directly to the leg 19 of the bridge passage 17, but such fluid must flow through the bore 24 and unseat the check valve 20 before it can enter the leg 18 of the bridge passage.

Source` .fluid in the bridge passage can be directed to either the head end or the rod end of the cylinder 6 under the control of the valve spool 10, through

service passages

30 and 31 respectively connected with the head and rod ends of the cylinder by

ducts

30 and 31. The inner ends of the service passages intersect the bore 11 at locations axially outwardly of the legs 18-19 of the bridge passage, between the latter and Zones of intersection between the bore and the opposite branches 32- 33 of a U-shaped exhaust passage. The bight portion 34 of the exhaust passage provides a common return passage that is communicated with a return header or carryover passage 35 in the control section. The return header, of course, is adapted to be communicated with the outlet of a sectional control valve, but for illustrative purposes, the individual branches 32-33 have been shown 4- connected with the reservoir by ducts 32-33, respectively.

The valve element or spool 10 is formed with four axially spaced

circumferential grooves

37, 38, 39 and 40. In the neutral position of the spool seen in FIGURE l, the branches 14 and 15 of the carry-over passage are communicated through the bore 11 by the groove 38; and the lands at opposite ends of the grooves 37 and 40 close off the

service passages

30 and 31 from their.adjacent exhaust passage branches 32-33 as well as from their adjacent legs 18-19 of the bridge passage 17. As a result, source fluid from the pump flows freely throughithe communicated inlet and outlet branches 14-15 of the carry-over passage in bypass relation to the service passages, and the piston in cylinder 6 can neither move up nor down.

It should here be noted that the neutral position of the spool is thus also a hold position with respect to both service passages 30-31; but for the control of a double-acting lift cylinder such as shown, the groove 40 obviously can be rnade longer to normally communicate the rod-connected service passage with its exhaust branch 33.

The valve spool can be shifted to a iirst operating position, to the left of neutral, at which the land between grooves '38 and 39 blocks communication between the carry-over branches 14 and 15, the groove 4t) communicates the rodconnected service passage 31 with its adjacent leg `19 of the bridge passage '17, and the head-connected service passage `30 is communicated only with its adjacent branch 32 of the exhaust passage through a restricted passage 42 in the valve spool. This is a slow lower position of the spool, at which source fluid entering the supply passage means comprising the upstream carry-over branch 14 and bridge passage 17 is constrained to flow to the rod-connected service passage 31 via the bight portion 19 and its leg 19 to drive the piston downwardly in its cylinder 6 at a slow rate determined by the size of the restricted passage 42 through which fluid expelled from the cylinder flows to the exhaust passage branch 32. The check valve 20 is not in the ow path along which fluid flows from the branch l114 of the carryover passage to the rod connected service passage 31.

The valve spool can be shifted a first distance to the right of neutral to the normal or slow raise position seen in FIGURE 3, or a greater distance to the right of neutral =to a fast raise position seen in FIGURE 4.

In its slow raise position, the spool closes off the head connected service passage '30 from its adjacent exhaust branch 32, while its groove 37 communicates the headconnected service passage with the leg 18 of the bridge passage 17. The spool also closes off the rod-connected service passage 31 from its adjacent leg 19 of the bridge passage, while its groove @communicates the service passage 31 with the exhaust branch 33. The land between grooves 37 and 38 blocks communication between the upstream and downstream branches 14-15 of the carryover passage and cooperates with the land between

grooves

38 and 39 to constrain source `fluid entering the branch 14 to flow to the bight portion 19 of the bridge passage 17 and past the check valve 20 to the head end of the cylinder through the groove 37 in the spool. As the piston rises in the cylinder, the fluid displaced from the rod end thereof is returned to the service passage 31 i-n the valve body, and ttlows to the exhaust branch '33 via the groove 40 in the spool.

Thus, the lload connected to the cylinder will be raised at a normal or slow rate and the check valve 20, being disposed in the path of flow of pressure uid to the head end of the cylinder, can function to block reversal of such flow. As will now be described, the check valve 20 is also operative to block reversal of dluid flow to the head end of the cylinder at times when the spool is in 4its fast r-aise position seen in FIGURE 4.

When the spool -10 is shifted to its fast raise position from its slow raise position, the source fluid entering the upstream branch 14 of the carry-over passage continues to ilow through the check valve 20 .to the head- `connected service passage 30, but the land between

grooves

39 and 40 then blocks orf communication between the yrod-connected service passage 31 and its adjacent exhaust branch 33. Instead, the groove 39 communicates the rod-connected service passage 31 with its adjacent leg 19 of the bridge passage 17, so that uid exhausting from the rod end of the cylinder is fed back into the bridge passage where it -joins with the source uid entering the bridge from the upstream branch 14 of the carry-over passage and flows through the check valve 20 to the head end of the cylinder via .groove 37 and service passage '30. In other words the spool, in its fast raise position seen in FIGURE 4, communicates the headconnected service passage 30 with both the inlet passage 14 and with the rod-connected service passage 3=1, in a way that requires all lluid -owing to the head end of the cylinder to flow through the check valve 20.

The lload connected with the piston rod 13 of the lift cylinder, of course, is caused to raise at a fast rate because a greater volume of pressure fluid is fed into the head end of the cylinder than is the case in the slow raise position of the valve spool, where pump output iluid only reaches the cylinder.

It is of the essence of this invention, however, that all pressure uid delivered to the head end of the cylinder in both the slow and fast raise positions of the valve spool must flow through the check valve seat 25. Accordingly, the check valve 20 blocks reversal of low in both of those positions of the valve spool. Thus, in the event of pump failure or failure of the internal combustion engine ordinarily provided to drive the pump on front end loaders, fork lift trucks and the like, while the valve spool is in its fast raise position, the check valve 20 serves to prevent exhaust of uid from the head end of the cylinder and recirculation of such exhaust lluid back to the rod end of the cylinder, thereby assuring against sudden objectionably high presure build up in the cylinder.

From the foregoing description, together with the accompanying drawings, it will be readily apparent that this invention provides a plural speed hydraulic control valve which `features a greater degree of safety than has been obtainable with valves heretofore used to raise a load at diiferent speeds.

What is claimed as my invention is:

1. A hydraulic control valve for governing llow of pressure tluid to and from the head and rod ends of a double-acting lift cylinder, which valve is of the type characterized by a body having an inlet passage to receive pressure fluid from a source thereof, supply passage means connecting with the inlet passage, return lluid passage means, and a pair of service passages respectively adapted for connection with the head and rod ends of the cylinder, said valve being further characterized by:

(A) a valve element in the body movable to a plurality of operating positions to selectively control communication between the service passages and said supply and return passage means, one of said operating positions comprising a high speed lift position of the valve element at which both of said service passages are closed ofrr from the return passage means;

(B) said supply passage means comprising (l) a rst branch passage unrestrictedly connected with the inlet passage and adapted to have unrestricted communication with the rodconnected service passage in said high speed lift position of the valve element,

(2) a second branch passage adapted to be cornmunicated with the head-connected service passage in the high speed litt position of the valve element,

(3) and passage defining means connecting said second branch passage with the inlet passage and with the rst branch passage so that the service passages will be communicated with one another and with the inlet passage in said 5 high speed lift position of the valve element and source fluid together with fluid returning to the rod connected service passage will then flow to the head connected service passage;

(C) and a load holding check Valve located in the supply passage means between said branches there- 10 of so as to be in the path of all pressure iluid flowing to the head connected service passage either from the inlet passage or from said first branch passage.

2. A hydraulic control valve for governing flow of pressure liuid to and from the head and rod ends of a double acting lift cylinder, which valve is of the type characterized by a body having an inlet passage to receive pressure fluid from a source thereof, supply passage means connecting with the inlet passage, return uid passage means, and a pair of service passages respectively adapted for connection with the head and rod ends of the cylinder, said valve being further characterized by:

(A) a valve element in the body movable to a plurality of operating positions to selectively control communication between the service passages and said supply and return passage means, one of said operating positions comprising a high speed lift position of the valve element at which both of said service passages are closed olf from the return passage means;

(B) said supply passage means comprising a substantially U-shaped bridge passage having 1) a lirst branch which is adapted to be communicated with the head connected service passage in the high speed lift position of the valve element,

(2) and a second branch which is unrestrictedly communicated with the rod connected service passage in said high speed lift position of the valve element, said second branch being connected with the first branch through bight portions of the bridge passage and being unrestrictedly connected with the inlet passage, whereby the bridge passage communicates the service passages with one another and with the inlet passage in said high speed lift position of the valve element, and source lluid together with iluid returning to the rod connected service passage will then ow to the head connected service passage;

(C) and a load holding check valve located in said bridge passage between the branches thereof so as to be in the path of all fluid flowing to the head connected service passage from said rst branch of the bridge passage.

3. The hydraulic control valve of claim 2, further characterized by:

(A) said U-shaped bridge passage having a bight comprising (l) a bight portion connected with each of the bridge branches and overlapping the other bight portion in spaced relation thereto, (2) and a bore connecting said bight portions at the overlap therebetween; (B) and said check valve being located in said bore.

References Cited UNITED STATES PATENTS 3,000,397 9/1961 Schmiel 137-596.13 3,255,777 6/1966 Rice et al 137-625.68 3,263,574 8/1966 Tennis 91-436 3,078,873 2/1963 Stockett 137-625.67

HENRY T. KLINKSIEK, Primary Examiner.

Claims

1. A HYDRAULIC CONTROL VALVE FOR GOVERNING FLOW OF PRESSURE FLUID TO AND FROM THE HEAD AND ROD ENDS OF A DOUBLE-ACTING LIFT CYLINDER, WHICH VALVE IS OF THE TYPE CHARACTERIZED BY A BODY HAVING AN INLET PASSAGE TO RECEIVE PRESSURE FLUID FROM A SOURCE THEREOF, SUPPLY PASSAGE MEANS CONNECTING WITH THE INLET PASSAGE, RETURN FLUID PASSAGE MEANS, AND A PAIR OF SERVICE PASSAGES RESPECTIVELY ADAPTED FOR CONNECTION WITH THE HEAD AND ROD ENDS OF THE CYLINDER, SAID VALVE BEING FURTHER CHARACTERIZED BY: (A) A VALVE ELEMENT IN THE BODY MOVABLE TO A PLURALITY OF OPERATING POSITIONS TO SELECTIVELY CONTROL COMMUNICATION BETWEEN THE SERVICE PASSAGES AND SAID SUPPLY AND RETURN PASSAGE MEANS, ONE OF SAID OPERATING POSITIONS COMPRISING A HIGH SPEED LIFT POSITION OF THE VALVE ELEMENT AT WHICH BOTH OF SAID SERVICE PASSAGES ARE CLOSED OFF FROM THE RETURN PASSAGE MEANS; (B) SAID SUPPLY PASSAGE MEANS COMPRISING (1) A FIRST BRANCH PASSAGE UNRESTRICTEDLY CONNECTED WITH THE INLET PASSAGE AND ADAPTED TO HAVE UNRESTRICTED COMMUNICATION WITH THE RODCONNECTED SERVICE PASSAGE IN SAID HIGH SPEED LIFT POSITION OF THE VALVE ELEMENT, (2) A SECOND BRANCH PASSAGE ADAPTED TO BE COMMUNICATED WITH THE HEAD-CONNECTED SERVICE PASSAGE IN THE HIGH SPEED LIFT POSITION OF THE VALVE ELEMENT, (3) AND PASSAGE DEFINING MEANS CONNECTING SAID SECOND BRANCH PASSAGE WITH THE INLET PASSAGE AND WITH THE FIRST BRANCH PASSAGE SO THAT THE SERVICE PASSAGES WILL BE COMMUNICATED WITH ONE ANOTHER AND WITH THE INLET PASSAGE IN SAID HIGH SPEED LIFT POSITION OF THE VALVE ELEMENT AND SOURCE FLUID TOGETHER WITH FLUID RETURNING TO THE ROD CONNECTED SERVICE PASSAGE WILL THEN FLOW TO THE HEAD CONNECTED SERVICE PASSAGE; (C) AND A LOAD HOLDING CHECK VALVE LOCATED IN THE SUPPLY PASSAGE MEANS BETWEEN SAID BRANCHES THEREOF SO AS TO BE IN THE PATH OF ALL PRESSURE FLUID FLOWING TO THE HEAD CONNECTED SERVICE PASSAGE EITHER FROM THE INLET PASSAGE OR FROM SAID FIRST BRANCH PASSAGE.