EP0426928A1

EP0426928A1 - Method to automatically adjust the functional parameters of a percussion apparatus

Info

Publication number: EP0426928A1
Application number: EP89830451A
Authority: EP
Inventors: Mauro Vitulano
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-10-18
Filing date: 1989-10-18
Publication date: 1991-05-15
Anticipated expiration: 2009-10-18
Also published as: EP0426928B1; DE68928143T2; DE68928143D1; ATE154774T1; ES2103711T3

Abstract

The device exploits the striking mass rebound energy, which depends on the hardness of the material on which the tool operates.

It is based on the functioning of the device as in the European Patent No. 0085279, and in providing adequate means to vary the distributor stroke during the piston upward-moving phase, as to anticipate or to postpone the percussion phase when the tool operates respectively on a less or more hard material.

In this first case, the anticipation of the percussion stroke causes a decrease in the volume of the cylindrical chamber where the pressurized oil works and therefore, under the same power, it causes an increase in the blows frequency, if the working oil flow mantains unaltered.

Description

The present invention is applied to percussion hydraulic appliances used in both the demolition of very hard materials - such as concrete, reinforced concrete, rocks, frozen surfaces, etc. - and the digging of particularly hard soils, mine marking and extraction, etc.
In particular, it refers to those devices which - checking the high-pressure oil inlet, and low-pressure oil outlet of a hydraulic appliance - bring about the alternate movement of the mass striking the tool.
As well known, the alternate movement of the piston which strikes the tool in a hydraulic appliance or by incompressible fluid, is obtained as a distributor which alternately places the chamber over the piston, in communication with a high-pressure circuit to give it impact power, and with a low-pressure circuit to bring the piston back to the upper dead centre.
The movement towards this centre is caused by the pressure exerted by the high-pressure oil itself to the piston small ring surface, opposite to the wider circular surface which receives the working push: the latter is greater than the rear push, due to the wider surface on which the high pressure is exerted.
The commonest distributor consists of a cylindrical tubular component whose external diameter - with the adequate tolerance margin - is equal to the internal diameter of the cylinder where the piston moves: along one of its circular edges, it is connected to a ring plate like to a flange, which runs vertically into a ring chamber coaxial to the cylinder, within the limits prefixed by the height of the same ring chamber.
In some appliances, the distributor internal diameter is smaller than the piston head external diameter; in others, the internal diameter is equal to the piston head external diameter, as in the European Patent No. 0085269 by the same applicant.
In this case the piston head, instead of striking the opposite end of the tubular components forming the distributor, moves inside it, in the opposite direction: in this case, the difference between the diameter of the cylindrical chamber and that of the piston is twice the distributor radial thickness.
A common drawback to all the devices causing the piston alternate movement is the lack of capability to adapt the striking rate and power per blow to the hardness of the material to crumble in real time.
In order to avoid such drawback, some manufacturers conceived some particular devices which guarantee the blows frequency and power automatic variation according to the hardness of the materials to crumble - c.f. French Patent No. 8114043.
This is done by retrieving the tool reaction energy, that is the rebound power it undergoes, which is higher if the soil where one works is harder, in order to obtain a greater efficiency.
For this aim, the device causing the striking mass alternate movement also includes a unidirectional valve which guarantees the fluid passage from the cylindrical chamber over the piston towards the high-pressure circuit and devices which guarantee a quick, subsequent displacement of the distributor, so to rapidly interrupt the connection with the high-pressure circuit and to slowly connect the chamber placed over the piston with the low-pressure circuit.
Thus, as the unidirectional valve permits the passage of the ultracompressed fluid into the cylindrical chamber over the piston, in the fraction of time during which this chamber is isolated from both the low-pressure and the high-pressure circuits, the maximum retrieval of reaction energy should be possible; the piston greater reversal velocity would cause - for a given oil supply - a shorter duration of every cycle of the appliance, as well as an increase in the impact pressure, parallel to the increase in blows frequency.
In other words, such a device would cause an increase in blows frequency and impact power, which would be higher if the material to crumble is harder, without calling for a greater power i.e. a greater pressure of the oil to the digger or the shovel coupled to the breaker.
Vice-versa, on a more soft soil, the striking mass would work at a low velocity with a low impact power.
Such working method is irrational, as the breaking of scarcely compact soils should have a low velocity, although needing a smaller impact power: in other words, and contrarily to any logic, concrete, rocks and very hard materials would be crumbled more rapidly than normally-compact soils.
Moreover, although the appliance where the above-mentioned device is applied absorbs reaction energy, it still undergoes high strains owing to the incompressibility of the fluid.
The fact that this device increases - rather than decreasing - impact power and working velocity when the hardness of the material to crumble is greater, provokes a rapid wear of the tools.
The aim of this invention is to adapt in real time the power and frequency of a percussion appliance to the hardness of the material where it works, avoiding the above-mentioned drawbacks caused by the appliance as in the French Patent No. 8114043.
This invention - as characterized by our claims - solves the problem to vary the piston stroke and impact energy in real time, in inverse function to the blows frequency, so to adapt the latter to the resistance of the material to crumble, without varying the hydraulic power averagely absorbed by the appliance, i.e. the absorbed power.
More specifically, this invention solves the problem of working on very hard materials such as rocks, concrete, etc., with a lower frequency of greater intensity blows and - on less hard materials - with a greater frequency of lower intensity blows.
The advantages obtained through the present invention mainly consist by the fact that the supplied power maintains on an average constant and that therefore the strains that the appliance undergoes when working on very hard materials, and the consequent wear of the tools are smaller.
Moreover the appliance request a smaller working and maintenance expenditure, and operate by a greater velocity on less hard materials.
One way of carrying out the invention is described in detail below with references to drawings which illustrate only one specific embodiment, in wich:

fig. 1, shows the device in the stroke-end position it assumes when the percussion appliance works on soft materials;
fig. 2, shows the device in the stroke-end position it assumes when operating on very hard materials;
figures 3 to 11 show the working phases of a percussion appliance where the device according to the invention was applied, namely:

fig. 3 shows the appliance with the piston at the upper dead centre when the rebound energy is feeble, at the moment when the percussion stroke starts;
fig. 4, shows the appliance with the piston at the upper dead centre when the rebound energy is strong, at the moment when the percussion stroke starts;
fig. 5, shows the appliance with the piston during the percussion phase and the distributor moving upwards to obstruct the high-pressure oil inlet port;
fig. 6 shows the appliance with the piston at the lower dead centre;
fig. 7, shows the appliance with the piston moving upwards;
fig. 8, the anticipation of the piston-distributor contact when the rebound energy is feeble;
fig. 9, the appliance with the piston in contact with the distributor when the rebound energy is strong: the distributor is in the stroke-end position;
fig. 10, the upper dead centre when the rebound energy is feeble;
fig. 11, the upper dead centre when the rebound energy is strong.
As illustrated in figures 1 and 2, the device according to the invention consists in the combination of the means forming the distributor as in the European Patent No. 0085279 by the same applicant, with the means limiting the distributor upwards stroke during the piston upwards movement, so that the piston start of percussion is anticipated when compared to the upper dead centre, when the material hit by the tool is scarcely hard, whereas, when the material is very hard - i.e. rocks, concrete, etc. - the piston start of percussion occurs exactly at the upper dead centre: the upper dead centre is fixed by stop corner 16.
As in the European Patent No. 0085279, the distributor is made up of a cylindrical tubular component 1, one of whose ends is connected to a flange-type ring plate, which can move with the protruding part 1a having width d1, in a ring chamber having height h and width d1, equal to the width d1 of the flange protruding part.
The upwards movements of distributor 1 are caused by differences in pressure on faces 1b and 1c of distributor itself, during the down stroke of piston, the downwards movements of distributor solely by the pressure on face 1b during the up stroke of piston: this is possible because, during the upward movement, piston 3, whenever the contact occurs between its circular edge 3a and the distributor circular edge 1d, compresses the oil of the cylindrical chamber 4 which is placed over the piston surface 3b , provoking the distributor downwards movement, whereas during the blow, when the distributor is in the positions showed in figures 5 and 6, the piston provokes the distributor upwards movement when the latter circular edge 3 - moving downwards - protrudes from the distributor cylindrical cavity anc goes beyond its edge 1d, due to the effect of high pressure on the distributor edge 1c.
The annular grove 5, coaxial to the axis of the cylindrical chamber where the piston moves during the downstroke of piston, allows the oil under pressure to push on the distributor face 1c, having width d3, greater than the one of face 1b whose width d2 is smaller then d3, provoking its upward movement: this is made easier because the basis of the ring grove 2 gives a stop edge 2a having width d4, so that d3 - d4 > d2.
Duct 9 below ring grove 2, being connected to the lowpressure circuit, aims at creating the differences in downward movement when the high-pressure oil inlet ports 7a must be opened.
In accordance with the invention, the above-mentioned means are combined to means permitting different velocities of the oil outlet from the ring chamber 2c, which the protruding ring plate 1a of distributor 1 forms in the upper part of ring grove 2.
These means are made up of a gauged duct 11 having a small diameter or, in general, of a duct where a pressure valve is inserted, which communicates chamber 2c with exhaust duct 10, to bring about an exhaust velocity proportional to the pressure exerted by the distributor protruding plate 1a, that also depends on the piston rebound energy and velocity.
If the rebound energy is low, the distributor cannot get to the stroke-end fixed by the ring grove 2 upper head 2b, that is, it does not run the grove entire height h; therefore, the piston circular edge 3a anticipatedly touches the distributor circular edge 1d, so that the latter can move downwards, anticipatedly reopening the high-pressure oil inlet ports 7a: this brings about a decrease in the piston percussion stroke and, consequently, a decrease in the displacement, i.e. the volume of the cylindrical chamber where the pressurized oil operates, in order to push the piston downwards.
By firm power, this decrease in volume corresponds to an increase in the piston blows frquency: indeed, as the hydraulic power transmitted to the piston is equal to the oil flow Q multiplied by oil pressure p (Q x p), if the pressure and oil flow remain firm and if decreases the volume of the cylindrical chamber where the pressurized oil operates, it takes place an increase in the piston blow frequency.
When the piston rebound velocity caused by a greater hardness of the material to crumble is higher, the impulse determined by its momentum provokes a greater pressure on the distributor, which obliges the oil contained in the ring chamber 2c to completely outlet through gauged duct 11 into the low-pressure circuit, and the ring surface 1a of distributor to get in contact with the upper ring surface 2b of the ring chamber itself.
This delays the contact between the piston circular edge 3a and the distributor circular edge 1d, and obliges the piston to reach a higher position before obstructing the cylindrical chamber 4, and provoking the distributor 1 downwards displacement, necessary to obtain the opening of the high-pressure oil inlet ports.
The piston greater stroke upwards provokes an increase in the volume of the cylindrical chamber where the pressurized oil operates to push the piston downwards and, consequently, an increase in the push that the highpressure oil exerts on the piston face 3b.
This determines a greater energy in the blow transmitted to the tool and, if the power absorbed by the appliance remains constant a decrease in the blows frequency, i.e. the application of a greater percussion energy during a longer time.
The device also includes a maximum pressure valve 21, which discharges the oil into the high-pressure circuit if the piston rebound energy exceeds certain limits, so to further compress the gas contained in the accumulator 13 (i.e. nitrogen) through membranee 13a.
Valve 12 also works as a safety valve.
Figures 3 to 11 show the application of the distribution device according to the invention (EPC Rule 30a), to the percussion appliance according to the European Patent No. 0085279.
As we can observe in the above figures, the device according to the invention can be applied only to appliances of the type described in the European Patent No. 0085279, i.e. to appliances where distributor 1 moves to open or to close the high-pressure oil inlet ports 7a and the low-pressure oil discharge ports, only as an effect of the pressures transmitted by the piston movements to the distributor ring faces 1b and 1c through the oil.
In particular, it can be applied to a percussion appliance where the distributor moves in the opposite direction of the piston which runs coaxially inside it, that is downwards to open the high-pressure oil inlet ports 7a immediately after the contact between the upward-moving piston ring edge 3a and the distributor ring edge 1d or, alternatively, upwards to close these ports 7a when, during its percussion stroke, the piston ring edge 3a passes the distributor ring edge 1d.
The height h of ring grove 2 depends on either a greater or a smaller stroke allowed to distributor 1; similarly, the gauged duct 11 section or the pressure valve replacing its function, must be chosen according to the performance desired from the appliance.
As shown in figures 3 to 11, the mechanical stroke-end 16 limits the piston upwards maximum stroke.
The push for the piston upward movement is permanently applied to the ring surface 3d1 having width s, and it has an effect only when the high-pressure oil inlet ports 7a are closed.
C1 and c2 indicate the axial length of the chamber 4, which is placed above the piston head.

Claims

1) "Device to adjust the functional parameters of a percussion apparatus, to the hardness of the material to crumble", characterized by a distributor based upon the European Patent No. 0085279, where the oil-tight chamber (2c) formed by the distributor flange-type ring protruding plate (1a) on top of the ring grove (2) of the cylinder (4), as an effect of the distributor upward movement, communicates with the low-pressure discharge circuit (10) by means of a gauged duct (11).

2) Device as in the previous claims, characterized by the combination of a distributor according to the European Patent No. 0085279, with a gauged duct (11) as in claim 1, which limits its upwards stroke in function of the more or less rebound pressure caused by the impact of the tool on the piston.

3) Device as in the previous claims, where the alternate movements of distributor (1) occur with no mechanic contact with the piston head (3), solely exploiting the differences in pushes which occur inside the cylindrical chamber (4) on the ring surfaces (1b) anb (1c), the distributor (1) moving itself in the opposite direction and concentrically to the piston head (3), and being made up of a cylindrical tubular component, one of whose ends being connected to a flange-type ring protruding plate (1a), which moves in a ring grove (2) having height (h) coaxial to the cylindrical chamber entered by the piston head, a first function of this grove being to limit the distributor maximum stroke, as the inversion of the distributor movements is caused by the contact between the piston ring edge (3a) and the distributor ring edge (1d), every time the two are in contact, so that the distributor moves downwards when the piston head gets inside it, or moves upwards when the piston head gets out of the chamber inside the distributor, a second function of the ring grove (2) being the formation of the oil-tight chamber (2c) by the ring protruding plate (1a) on top of the ring grove (2) itself as an effect of the distributor upward movement (1), the chamber (2c) itself being connected with the low-pressure discharge circuit (10) through a gauged duct (11) or any other similar means, which slowing down the velocity of discharge of the oil, causes a different position of the distributor in function of the rebound pressure in manner to anticipate or delay the contact between the edge (1d) of the distributor and the edge (3a) of the head of the piston to anticipate or to open the high-pressure oil inlet port (7a) and the corresponding closing of the low-pressure oil outlet ports (10).

4) Device as in the previous claims, characterized by the fact that the ring chamber (2c) height (h1) can vary from a maximum - which occurs when the piston rebound pressure is low - to zero - when the piston rebound pressure is high - so that, in the former case, the contact between the piston head ring edge (3a) and the distributor ring edge (1d) is anticipated in order to reduce the piston working stroke whereas, when the chamber (2c) height (h1) is equal to zero, the contact between the piston head ring edge (3a) and the distributor ring edge (1d) is delayed to increase the volume of the cylindrical chamber where the high-pressure oil must work and consequently, the piston percussion stroke.

5) Device as in the previous claims, characterized by the fact that, under the same power, the piston stroke variations - that is the variations in the volume of the cylindrical chamber where the high-pressure oil works - cause variations in the piston blows frequency in an inverse function.

6) Device as in the previous claims, characterized by the fact that the high-pressure chamber is endowed with a pressure-limiting valve (12) to discharge the oil into the high-pressure circuit, when the piston rebound pressure exceeds safety limits.

7) Device as in the previous claims, characterized by the fact that the pressurized gases accumulator (13) runs down at particular moments, synchronized with the moments of the percussion stroke start, these moments are determined by the rebound energy intensity.

8) "Percussion applicance where the blows frequency of the striking mass varies in inverse function to its impact energy, in order to operate at an averagely constant power on materials having different hardness"; this appliance being based upon the functioning of the European Patent No. 0085279, characterized by the application of a distributor (1) according to the previous claims and of a gauged duct (11) or any other similar means. to provoke an emptying velocity of the oil in the ring chamber (2c) on top of the grove (2), and consequently to limit the distributor (1) upwards movements in direct function to the piston rebound energy.