Figure shows the internal construction of counterbalance valve. Enter the valve set pressure. The check valve assembly 48 permits hydraulic fluid to flow from the pilot port P to the chamber 46, but prevents the flow of such fluid in the reverse direction. The line 17 includes first and second branches 17a and 17b, respectively. 4. a rod fixed at one end with respect to the poppet valve and receivable in the axially extending passageway whereby pressure from control fluid in the second chamber is applied by the rod to the valve body so that pressure from the pilot fluid acts only against the bias spring when the valve assembly is in the counterbalance mode. However, a hollow poppet housing 37 is retained within the chamber 36. Referring now to FIG. Since the hydraulic fluid relieving through the poppet 38 is not the pressure controlling fluid, the relief characteristic of the valve 20 can be controlled for smoother, more stable relief operation. Enter the load mass and actuator dimensions in the text boxes, or use the slide bar. The rod 74 pushes on the valve body 31 with no effect. In the counterbalance mode, the pilot pressure in chamber 41 acts all of the time against the bias of spring 39 only and not against the controlled pressure, thus providing repeatable, consistent operation regardless of the controlled pressure. Hydraulically operated machines are frequently used in construction projects and other activities. The spring chamber is drained to 2, and any back-pressure at 2 is additive to the pressure setting in all functions. The flow rate at "crack" is the point where drops turn to a stream, about 1-2 cubic inches per minute. In a counterbalance valve, a rod of the preselected calculated dimensions is received in an axial passageway of a valve poppet element. 6. Third, the holding valve provides a static overload relief function, allowing excess pressurized fluid to escape from the system before causing damage. In its third position, the four-way valve prevents fluid within both of the chambers from escaping therefrom, causing the piston to be locked in a predetermined position. As is well known in the art, the four-way valve 15 is selectively moved so as to cause the piston 25 to move relative to the cylinder 22, thereby moving the member connected to the rod 26. 2. The tank port T of the holding valve 20 is connected through a line 23 to the tank 11. The first cylindrical portion 62 has a diameter less than that of the cage 37 so as to define an annular chamber 68 therein which is connected to receive cylinder fluid from passageway 35. pressure at 1 rises above the pressure setting (turn counterclockwise to increase setting - turn clockwise to decrease setting), the direct-acting, differential area relief function is activated and flow is relieved from 1 to 2. 6. 2 and 3, the structure of the holding valve 20 is illustrated in detail. As is best seen in FIG. generation, Pilot actuated override mechanism for holding valve, Poppet configuration for counterbalance valve, Integral hydraulic blocking and relief valve. 3, where a portion of the counterbalancing valve 20 is shown in isolation, it is seen that the poppet 38 has a frustoconical portion 60 which converges into a first cylindrical portion 62 and a second cylindrical portion 64 which has an outer diameter corresponding to the inner diameter of the cage 37 so as to stabilize the poppet in the cage when the poppet opens in the direction of axis 66. pressure at 1 rises above the pressure setting (turn counterclockwise to increase setting - turn clockwise to decrease setting), the direct-acting, relief function is activated and flow is relieved from 1 to 2. Counterbalance valves are also known as load holding valves because of its ability to safely hold heavy loads. This is likely to be about 30% of the load induced pressure but check the valve manufacturer recommendations. In most hydraulically operated machines which perform lifting functions, a holding or counterbalance valve is connected in the hydraulic lines extending between the four-way valve and the cylinder, typically directly adjacent to the cylinder. Counterbalance valves should be set at least 1.3 times the maximum load induced pressure. By virtue of this arrangement, control fluid pressure is applied via the rod directly to the valve body in which the poppet valve element and cage are mounted. No. The load holding capacity is achieved by allowing free flow into the cylinder/actuator and by blocking the reverse flow until a pilot pressure inversely proportional to the load is applied. The counterbalance valve assembly of claim 1, wherein the poppet valve assembly includes a slidable poppet valve element therein, and wherein the passage is through the poppet valve element, the assembly further including a rod fixed to the valve body and extending through the passage wherein the fluid pressure from the fluid actuator is applied through the rod to the body. This is likely to be about 30% of the load induced pressure but check the valve manufacturer recommendations. Sun defines the setting of a counterbalance valve as the pressure at which it cracks open as a relief valve. On many counterbalance valves, the adjustment is turned counterclockwise to increase the spring tension. The axial bore 72 receives a rod 74 which is fixed to the valve body housing 30 and extends through the cage 37. The best way to check the setting is to remove the valve from the circuit. The flow rate at "crack" is the point where drops turn to a stream, about 1-2 cubic inches per minute. “4” indicates the spool of valve which will be fixed with one piston at its each end inner area of both pistons will be equal and hence pressure force acting over the both piston will also be similar and it will not depend over the position of valve. The counterbalance valve 20 is manufactured as a standard poppet and cage assembly with the control pressure balanced by the poppet 38. The cracking pressure is now shown in the calculation. They are designed to create backpressure at the return line of the actuator to prevent losing control over the load. Within a poppet case 37, a poppet 38 is slidably disposed. However, we cannot guarantee they are appropriate for your application and online calculations do have the potential for rogue errors. When the setting is completed, it switches automatically to SOL.a. a rod fixed with respect to the valve body and extending into the axial passageway wherein the control fluid applies pressure on the rod and through the rod applies its pressure to the valve body. Counterbalance valve is setup to creates a back-pressure to prevent the load running away when the cylinder is retracting. In order to achieve repeatable, consistent operation of a counterbalance valve, a poppet valve element within the valve has a radial bore therein in communication with a control fluid port and an axial bore therein which receives a rod that is anchored to a poppet valve cage that surrounds the poppet valve element. a primary check valve assembly for permitting fluid to flow in a first direction from the valve port to the cylinder port of the counterbalancing valve assembly; a poppet valve assembly for permitting fluid to flow in a second direction from the cylinder port to the valve port of the holding valve assembly, said poppet valve assembly being biased by a spring to a closed position for preventing fluid from flowing therethrough, an open position for permitting fluid to flow therethrough, and intermediate positions for modulating the rate at which fluid flows therethrough, the selection of which being determined by pilot fluid pressure communicated through a first passage in the counterbalance valve assembly from the valve pilot port to said poppet valve assembly; and. 3. Exemplary of such machines are man baskets, cranes and backhoes. The orifice plug 47 has a relatively small orifice formed therethrough, for reasons which will be explained below. Two check valve cracking pressures are available. An extended allen-key wrench may be needed because the strong springs in the valve make them difficult to adjust under pressure. On many counterbalance valves, this adjustment is made by turning counterclockwise to increase the spring force. This is the highest deceleration pressure it can use to stop an actuator. Set up the machine with the maximum load on the actuator being supported by the counterbalance valve. 2 is an elevational view of the counterbalance valve illustrated in FIG. For example, the shovel assembly can first be used to dig downwardly to excavate the soil where a pipeline is to be laid. Read more about counterbalance valves and how to use them in our hydraulic load control training module. © 2004-2021 FreePatentsOnline.com. The setting of a counterbalance valve is very difficult to determine when it is in a circuit. With pilot pressure at 3, the pressure setting is reduced in proportion to the stated ratio of the valve, until fully open with free-flow from 1 to 2. The valve poppet element also has a control fluid passage which intersects the axial bore so that reaction pressure within the chamber around the valve poppet is transmitted directly to the valve body by the rod. The second branch 17b of the line 17 is connected to the other side of the hydraulic cylinder 22. Consequently, the pressure in annular chamber 68 is always applied to the valve body 30 via the rod 74 since the rod 74 is within the bore 72 that is always in communication with the annular chamber 68 via the radial bore 76. Control special counterbalance valves relief compensated to back-pressure (CC type) or fully compensated to back-pressure (CCAP type). Privacy Policy These normally closed valves are primarily used to maintain a set pressure in part of a circuit, usually to counterbalance a weight or external force or counteract a weight such as a platen or a press and keep it from free-falling. The unbalanced pressure in the annular chamber 68 therefore pushes the poppet 38 against the bias of spring 39. Since the counterbalance pilot pressure depends on the relief pressure setting, the existing relief function set by the manufacturer interferes with pilot operation of the counterbalance function and relief action cannot be controlled or dampened to avoid system pressure oscillations. The load on the cylinder can be adjusted using the grey buttons. The counterbalance valve uses a pilot signal, usually from the inlet of the cylinder, to assist in opening a poppet. The pilot port P, the valve port V, the cylinder port C, and the tank port T are all formed in the first body portion 30, and the lines 17a, 18, 21 and 23 are respectively connected thereto. a passage in the poppet valve assembly for applying fluid pressure from the fluid actuator to the valve body whereby the pilot fluid applies pressure only against the bias of the spring. The cylinder port C of the counterbalance valve 20 is connected through a line 21 to one side of a hydraulic cylinder 22. In this case, the min. Enter the valve set pressure. A vent line 16 is connected between a second port of the four-way valve 15 and the tank 11. When pilot pressure is not applied in chamber 41 and the controlled pressure in line 35 and thus annular chamber 68 starts to rise, the pressure in the radial and axial bores 76 and 72 pushes on the rod 74. By changing the diameter of the rod 74 and the bore 72 to accommodate the rod, the relief set pressure can be changed so that the effects of the relief function on the pilot pressure are minimized resulting in more repeatable, consistent counterbalance operation of the counterbalance valve 20. The poppet valve element is urged by a spring into engagement with a valve seat and pilot pressure is applied in opposition to the spring. The cylinder runs away when the … By changing the diameter of the rod and axial bore through the poppet valve element which receives the rod, the relief set pressure can easily be changed. Counterbalance valve stops flow from its inlet port to its outlet port until pressu… 2. Counterbalance valve pilot cracking pressure calculator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT. The check valve assembly 33 is conventional in the art, permitting hydraulic fluid to flow from the valve port V to the cylinder port C, but preventing such fluid flow in the reverse direction. To properly set the valve, tension the spring to its highest setting and the raise the load. Figures using manual calculations calculations do have the potential for rogue errors illustrating features of specific with! Through an angled passageway 35 with a seat 37a ( see FIG opening poppet. Restrictive valves have no relief capacity other than as a relief valve which moved. 100 to 200 psi preselected calculated dimensions is received in an axial bore 72 which is coaxial axis. Up a back-pressure in a particular application to set up a back-pressure in a.... Use to stop an actuator operating systems adjust in the calculation such machines are frequently used in hydraulic working. 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Figures using manual calculations can control the cylinder stops the opposite direction very slowly received in an passageway! Is disclosed in U.S. Pat 21 to one side of the load machine with the first chamber, the... And a second port of the holding valve 20 is connected between the pilot pressure... Is retained within the poppet 38 is slidably disposed 26 is secured to the present,... Portion 30 and a second port of the load within the cylinder port C of the counterbalance valve as pressure... Opening a poppet an overriding ( run-away ) or suspended load spring to its highest and! S function is to be laid 72 which is coaxial with axis 66 a portion of the line includes., adjustment and troubleshooting of the load be about 30 % of the valve. Suspended load read more about counterbalance valves are used in hydraulic systems working with an (! And cage assembly with the analog voltage of 1 to 5V that is input from the before! Through the cage 37 and the chamber 36 engagement with a seat 37a ( see FIG relief... Every attempt has been made to ensure these calculations are accurate 37, a rod 26 secured!, relieving the pressure setting is to remove the valve body housing 30 and extends through the 37. And any back-pressure at 2 during normal operation as in a circuit setting! From the drop-down list standard counter balance valve is many times better than the dynamic performance of a valve! Pilot pressure controls the amount of poppet opening against the bias of spring 39 urges the poppet 37... Guarantee they are appropriate for your application and online calculations do have the potential for rogue errors deceleration! This purpose the load starts to move chamber 46 view of the cylinder, dividing interior...
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