EP0085279B1

EP0085279B1 - Directional control valve to obtain in a hydraulic appliance the alternative motion of a piston operating to charge and fire a tool, specially suitable for hydraulic hammers

Info

Publication number: EP0085279B1
Application number: EP82830014A
Authority: EP
Inventors: Mauro Vitulano
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-01-22
Filing date: 1982-01-22
Publication date: 1986-07-09
Also published as: DE3271910D1; ATE20647T1; EP0085279A1

Abstract

The directional control valve to apply to a hydraulic appliances working with uncompressible fluid, is composed of a cylindrical valve i.e. a sleeve 5 sliding in a cylindrical chamber 1, that acts as a cylinder to the piston 7 when its outside part B, or also its intermediate part A in an execution suitable to different application, penetrates inside the sleeve 5 or comes out of it. The control valve action is caused by the hydraulic fluid when the piston moves so that it comes out or by the fluid which the piston presses when, being the exhaust ports still opened, it moves in order to penetrate into the sleeve valve 5. The axial travel reversals of the control valve start every time the piston, by its circular edge 7c, gets a tightness touch with distributor's circular edge 5d. This control valve permits large tightnesses of exhaust and supply ports of hydraulic fluid so that the piston 7 avoid to do this by means of its lateral surfaces, as other control valve, and therefore the device is not subjected to wear. For its simplicity and very good functionality this directional control valve cuts manufacturing and maintenance costs; it can be, moreover, applied both to free gas recharging hammers and hammers directly actuated by under pressure hydraulic fluid.

Description

The invention relates to a directional control valve, that is a device making use of a sleeve valve to supply or return incompressible fluid from a cylinder, e.g. of a hydraulic hammer, in which a piston operating to charge and fire a tool has to be effected to an alternate motion. There is a large number of directional control valves for hydraulic appliances, using a cylindrical control valve, i.e. a sleeve coaxial to the cylinder in which the piston moves.
This, actuated by the hydraulic fluid alternately, opens and closes the supply and return ports for the hydraulic fluid, so that the fluid can be alternately forced on the upper or lower face of the same piston to fire it or to force it back (recharge).
These control valves, as well as being subjected to continuous and strong stresses, need complex circuits for oil discharge, little working tolerances and frontal fluid tight joints that may fail owing to abnormal wear caused by repeated impacts.
In some directional control valves, the mobile member that is the sleeve, is really struck by the same piston which acts as a shoulder, and elastic devices, as spring cushions, don't minimize the stresses the control valve is subjected to.
From US-A-4022108 a directional control valve of a hydraulically operated percussion device is known in which a sleeve-like shaped valve member responsive to the movements of the piston is contained in a pressure chamber for alternately connecting said chamber to a channel system including a high pressure and low pressure branch for conducting hydraulic pressure fluid to and from said pressure chamber.
The invention here claimed is intended to remedy these drawbacks.
The invention solves the problem of how to design a double acting directional control valve for hydraulically operated percussion devices, in which the stresses transmitted to the piston by the tool in operation subjected to an alternate motion, are not taken by the valve device, thereby averting any risk of damage to the mobile distributing valve element in the form of a sleeve-shaped slide element.
The invention solves also the problem relative to cutting the maintenance costs of the hydraulically operated percussion devices with a control system less complex, and therefore manufactured at a lower cost because of its simplicity. Two ways to carry out the invention are described in detail below with reference to the drawings in which:

Fig. 1a, is a detailed longitudinal section of a first embodiment the central valve with the sleeve-shaped distribution member closing the exhaust ports.
Fig. 1, shows the device applied to hammers with piston actuated by impact energy of free nitrogen compressed by the same piston during the recharging stroke, with piston in recharging stroke;
Fig. 2 shows the device in the same recharging stroke of the piston, moving down to close the hydraulic fluid supply port and to open the exhaust port;
Fig. 3 shows the device with piston on top dead center, closing the hydraulic fluid supply port;
Fig. 4 shows the device closing the supply port and piston in striking phase;
Fig. 5 shows a second embodiment of the device applied to a hydraulic hammer with piston actuated directly by the fluid under pressure and accumulator of nitrogen to balance pressure variations, with piston in striking phase;
Fig. 6 shows the operation of the control valve to close the supply ports of fluid under pressure;
Fig. 7 shows the device while the piston is in recharging stroke, i.e. sleeve valve member opening the exhaust ports;
Fig. 8 the device with the piston making a fluid tight seal with sleeve valve member of control valve to cause the opening of the supply port of the hydraulic fluid under pressure.

Referring to Fig. 1 a, the control valve includes a cylindrical sleeve-shaped distribution valve member 5, positioned in same cylindrical chamber 1 in which the piston moves.
Along one edge, the sleeve-shaped element (1) has an outwardly directed flange means 6 forming an annular rim 5a that strikes against face 1b of annular groove 1a forming an annular chamber in the wall of the cylindrical chamber 1, limiting the stroke of the sleeve element 5. This cylindrical chamber 1 having a diameter D₁, is coaxially connected to the cylindrical chamber 2A having a diameter D₄ inferior to D₁, through annular groove 3 having a diameter D₃ greater than D₁, but smaller than the diameter D₂ of the above groove 1a in order to form a second circular shoulder 4 for limiting the stroke of the sleeve 5 itself in the other direction and submit to a greater thrust the rim 5a having an area higher than the area of the opposite rim 5b of the sleeve-shaped element 5.
In the first application of the invention (Fig. 1, 2, 3, 4), in the recharge phase, (Fig. 1) the sleeve-shaped element works so that it can permit the moving up of piston 7 which has two different diameters D₇ (A) and (C) D₈, where D₇ is greater than D₈, to compress a gas (e.g. nitrogen) contained in a hermetic compression chamber 11. This is possible thanks to the sleeve-shaped element which opens inlet port of channel 8 in the same cylindrical chamber 1 and permits the application of a pressure (p1) of hydraulic fluid on annular face 7a of area A₁ of the piston causing a thrust S_i=Ai . ^p _l.
In the second phase (Fig. 2), the piston has reached almost top dead center as fixed by the shoulder 13, thereby compressing the gas contained in the chamber 11 up to the maximum pressure _P2 inferior to p_i because of the thrust 5₁ and of the area C₁ of the surface 7b greater than area A₁. Meanwhile, the sleeve-shaped element 5 is forced to move down by hydraulic fluid flowing in the annular groove 3, which can press against annular surface 5a of element 5, thereby causing a thrust higher than the one the same hydraulic fluid produces on opposite surface 5b of smaller area.
The inlet port of channel 8 is thus closed and outlet channel 9 is opened (see Fig. 3).
At this point as the thrust of high-pressure fluid on the annular surface 7a of piston 7 stops and as the cylindrical chamber 1 is connected with outlet channel 9 and 10 (Fig. 3), the piston 7, not being forced by back pressure moves down violently striking a tool 14 at a speed higher than the upstroke speed.
Piston upstroke and downstroke speed are respectively related with pump delivery capacity and with expansion speed of gas compressed in the chamber 11.
The sleeve-shaped element 5 surrounds the section A of piston 7 that enters in the chamber 1 forming a fluid tight fit.
The reversal of sliding of sleeve-shaped element 5 to open the inlet port of channel 8 takes place every time the circular edge 7c of the section A of piston 7 makes a fluid tight seal with the circular edge 7d of the sleeve-shaped element.
At this point, infact, the compression of hydraulic fluid remaining in the chamber 1 by same piston, produces a thrust on the sleeve- surface 5b; because the sleeve element 5 is opposed by no back pressure, it moves thereby opening the inlet port of high-pressure channel and closing the ports of channel 9, so that the piston can move up pushed by the pressure of fluid on the annular surface 7a.
In the application of the control valve to the percussion apparatus shown in Fig. 5, 6, 7 and 8, the piston sleeve shaped element 5 surrounds the head B of piston 7 that enters in the high-pressure chamber 1 instead of the section A. In the impact stroke (Fig. 5), the inlet ports of high-pressure channel 8 are opened while the outlet ports of low-pressure channel 9 are closed by the sleeve-shaped element 5. The piston moves down although high-pressure hydraulic fluid via channel 12 acts at the same time on the rim 7a of piston; infact, area A1 of rim 7a is smaller than area 7b of piston. Referring to Fig. 6, while piston 7 moves down, section B of the piston allows the flow of high-pressure fluid to the annular chamber 3 so that the fluid itself can press on circular surface 5a of the sleeve which, being larger than the circular surface 5b, causes a resultant thrust which moves up the sleeve until to close the ports of high-pressure channel 8 and to open the outlet ports to low-pressure channel 9. This causes the upward movement of piston 7 only because of the thrust of the hydraulic fluid on the annular surface 7a of the piston (Fig. 7).
Referring to Fig. 8, when the circular edge 7c of piston 7 comes into contact with circular edge 5d of the sleeve making a fluid tight seal, the piston 7 presses the hydraulic fluid remaining in chamber 1 thus causing a pressure on the circular surface 5b of the sleeve itself, which is not opposed by back pressure.
Sleeve 5 moves down again to open the inlet ports of high-pressure channel 8 and to permit the repeating of a new cycle.
As the sleeve 5 moves down to open the inlet ports of the fluid, the sleeve forces the fluid which is in the annular space formed under the surface 5a into little duct 15 and then via the annular recess formed by section 7d of piston 7, in the low-pressure duct 16.
To increase the impact velocity, i.e. the kinetic energy of piston 7, and for better exploitation of the capacity of the hydraulic pump, in this directional control valve according to this invention, the appliance is equipped with a pneumatic accumulator 11 a of nitrogen with a diaphragm 18 and with a sequence and velocity controlling valve 17, which exploiting the pressure decrease taking place on the beginning of recharging stroke for the higher hydraulic flow required by the recharge of accumulator 11a, at first closes and after throttles the outlet port of the low-pressure duct 10, in order to reduce the moving up velocity of the piston.
After recharging the accumulator, when the pressure of hydraulic fluid reaches the maximum value, the reaction of the spring 17a is insufficient to oppose the thrust given by the little piston 17b and therefore the outlet 17c of the valve is opened.
On the top dead centre, the piston impact is damped by the compressed fluid in the upper part of chamber 1 and being part A of piston diametrically greater than the B one to make as a shoulder, by rim 13 formed in the cylindrical chamber 2A and by the fluid contained in the same cylindrical chamber 2A.
As detailed above, the fluid-tightsurfaces of the sleeve like element 5 are very large.
The fluid-tight of inlet and outlet ports is, infact, made by the lateral outside surfaces 5e of the sleeve and 6b of flange 6 of the same sleeve.
It should be noted that before the piston reaches its top dead centre, the sleeve element 5 acts as a cylinder for piston 7, moving coaxially to it in the opposite direction, thus avoiding frontal impacts against piston 7 and consequently stresses in the sleeve element.
Moreover, in the control valve according to the invention the fluid-tight seal of the inlet and outlet ports is made only by the sleeve like element5 and is independent from the piston wear.

Claims

1. Directional control valve to obtain in a hydraulic appliance, the alternate motion of a piston to charge and fire a tool, specially suitable for hydraulic hammers, the hydraulic appliance having either a piston (7) fired directly by high-pressure incompressible fluid, i.e. oil, or a piston which is fired by a gas, i.e. high-pressure nitrogen pre-compressed by the same piston (7) in the recharging stroke, the control valve including a cylindrical chamber (1) having an annular groove (1a) coaxial to the piston and a cylindrical sleeve-like slide element (5) moving alternately in the said chamber to open or to close a high-pressure channel port and a low-pressure channel port of the fluid, said sleeve-like slide element (5) having an internal diameter of D₄ and a flange means (6) with an external diameter of D₆ to restrict coaxial movements of the said valve in the said annular groove 1a, characterized in that the port of said high-pressure channel is located in said cylindrical chamber (1) and in that the sleeve-like element (5) surrounds the side surface of the piston section on which operates the high-pressure of said incompressible fluid or said gas, said section of piston having a diameter of D₇ sufficient to form a substantially fluid-tight fit in the said sleeve-like slide element (5), the inversion of movements of the sleeve coaxial to the piston and to the cylindrical chamber, to close the port of said high-pressure channel and to open the port of said low-pressure channel, or vice versa, to open the port of high-pressure channel and to close the low-pressure channel one, taking place every time the leading circular edge (7c) of the section of the pressure actuated piston makes a fluid tight seal with the inner surface ofthesleeve-like slide element (5) without knocking against it, the coaxial movements of the piston and of the element (5) being opposed, said sleeve-like element acting as a liner of the cylindrical chamber (1) in which the section of the pressure actuated piston enters.

2. Directional control valve as claimed in claim 1, characterized in that the sleeve-like slide shaped element (5) is not arranged to be transported by the piston, its movements being caused only by the pressure of incompressible fluid acting in chamber (1).

3. Directional control valve as claimed in claim 2 wherein said cylindrical chamber (1) including said coaxial annular groove (1a), said inlet port of high pressure channel and said outlet port in said low-pressure channel, is adjacent to an annular chamber (3) having diameter D₃ greater than diameter A₁ of chamber (1) to apply directly the pressure of fluid on the surface of a rim (5a) of sleeve shaped element (5).

4. Directional control valve as claimed in claim 3, characterized in that the fluid-tight closing of said inlet port of said high pressure channel is effected by the outside surface of the sleeve shaped element in fluid-tight fit with the surface of said cylindrical chamber (1), i.e. only by the side surface of same sleeve element without affecting the piston.