EP1598306A1 - Control device for the lowering of a hydraulic jack - Google Patents

Abstract

The jack has a control device with a primary channel (20) connecting a chamber to a reservoir, and closed by a primary valve (I) allowing the passage of a fluid from the chamber to the reservoir. A lateral channel (21), connecting the chamber to the reservoir is closed by a secondary valve (II) allowing the fluid passage. The channel (21) has a section allowing a shaft to descend under its weight when the valve (II) is open. The primary channel has a dimension such that the primary valve can be open under a maximum action of about 20 daN permitting to oppose the pressure exerted by the fluid on the primary valve when the jack supports a load.

Description

The present invention relates to a hydraulic jack allowing lifting heavy loads from the ground.

A hydraulic jack is a well known lifting device and widely used to lift loads of several tons.

A hydraulic jack usually includes a sole intended to come on a bearing surface, a column connected to the sole, a cylindrical shaft slidably mounted on the column and delimiting with it a chamber of a jack. The actuation of the jack is done by a pump provided with a valve sucking an incompressible fluid into a reservoir for feed the cylinder chamber.

The pump is usually operated by a lever whose Alternative actions feed the chamber with fluid. This being incompressible, there is a relative movement of the shaft with respect to the column. Therefore, an object placed at the top of the drum or resting on a tab secured to the barrel is raised relative to the surface on which rest the jack.

To get the jack back down, the pump flap is open and the fluid contained in the cylinder chamber is forced back into the tank.

The universally used system consists of a button that he turn in one direction to open the flap and control the descent, and in the other direction to close the flap and stop the descent. This system works perfectly but it raises an important problem of security.

Indeed, in case of incident, the operator may be in the inability to turn the knob to stop the descent. It can thus be find stuck under the raised object, without being able to interrupt the descent jack.

An object of the present invention is to propose a jack hydraulic system whose descent in charge is interrupted as soon as a operator stops his action on a descent control device and whose descent in the absence of charge is carried out under the action of the gravity.

• une semelle destinée à venir sur un surface d'appui,
• une colonne liée à la semelle,
• un fût cylindrique montée coulissant sur la colonne et délimitant avec celle-ci une chambre, et
• une pompe susceptible d'aspirer un fluide incompressible contenu dans un réservoir et de le refouler dans la chambre de manière à déplacer le fut par rapport à la colonne et ainsi à soulever une charge en appui sur le fût.

In a manner known per se, the hydraulic jack comprises:

• a sole intended to come on a support surface,
• a column linked to the sole,
• a cylindrical barrel slidably mounted on the column and delimiting therewith a chamber, and
• a pump capable of sucking an incompressible fluid contained in a reservoir and pushing it back into the chamber so as to move it relative to the column and thus to lift a load bearing on the shaft.

According to the invention, the jack comprises a control device including a small section primary canal, connecting the chamber to the tank, closed by a primary valve allowing the passage of fluid from the chamber to the reservoir, the primary channel presenting a dimension such that the primary valve can be opened under an action maximum of 15 to 20 daN to oppose the pressure exerted by the fluid on the primary valve when the jack supports a charge and a secondary channel connecting the chamber to the closed tank by a secondary valve allowing the passage of fluid from the chamber to the tank, the secondary channel having a section allowing the drum to descend under its own weight when the secondary valve is open.

Thus, the idea underlying the invention is to provide in the jack a primary channel of small diameter between the tank and the chamber; this primary channel is closed by a primary valve allowing the flow of the fluid between the chamber and the reservoir by opposing the flow in sense opposite. This primary valve is normally pressed against its seat by the pressurized fluid contained in the chamber. It should be noted that the fluid contained in the chamber is subjected to very high pressures up to 300 bar when the jack is loaded. Despite of this very strong pressure exerted on the valve closing the channel of small diameter, it is possible with a moderate action of about 15 daN, ie the average strength that an operator is able to exert manually, open this primary valve. This opening causes a micro leakage of the fluid contained in the chamber to the reservoir and, therefore, a descent of the jack. On the other hand, as soon as the action on the valve stops, this one resumes its closed position since the fluid contained in the chamber subjected to the pressure of the load supported by the jack solicits automatically against his seat. The descent of the jack is then interrupted as soon as the action on the flap stops. This point is extremely favorable from the point of view of the safety of operators since as soon as the jack down control action ceases, the descent of the cry ceases. This is a considerable advantage over hydraulic jacks known whose descent can not be interrupted without an action positive of an operator on the descent control member.

The invention also makes it possible to solve the problem that may occur produce when the jack is in a configuration in which the chamber is filled with fluid (in other words, the jack is in the extended position), an action on the primary valve does not make it possible to lower the no load applied to the jack. It turns out that it counts given the small size of the primary canal connecting the chamber to the reservoir when it is opened by the valve, the jack has not come back down under the action of gravity. The secondary channel, which is section important, allows to create a leakage flow, ensuring the descent of the jack on the sole action of gravity.

For ease of manufacture, the primary canal and the secondary channel are co-axial, the primary valve and the secondary valve being arranged one behind the other and actuated by the same button button.

In a preferred embodiment, the primary valve is constituted by a ball closing the primary channel and the secondary valve is constituted by a ring in which is formed the primary channel, the ring from closing the secondary channel.

According to an embodiment characteristic, the device for control includes a cartridge embedded in a housing, arranged on the body of the pump and connected to the chamber and the receiving tank the primary valve and the secondary valve.

In addition, the cartridge has a longitudinal bore forming the secondary channel in which the rod is engaged, the piercing having a shoulder forming a seat of the secondary valve.

According to one possibility, at its opposite end to that introduction of the rod, the hole is closed by a plug against which two coaxial compression springs, one applying against the ring, the other applying against the ball.

In addition, the block has at least one radial channel opening in the secondary channel.

To insure micro leakage under load, the primary channel has a diameter of between 1 and 2.5 millimeters.

Preferably, the primary channel has a diameter of 1.2 millimeters.

Figure 1 est une vue de côté de ce cric,

Figure 2 montre le cric en coupe,

Figures 3 à 5 sont des vues en coupe selon II-II de figure 1 dans différentes positions de fonctionnement d'un dispositif de contrôle de descente de ce cric.

For a good understanding, the invention is described with reference to the accompanying drawing showing, by way of non-limiting example, an embodiment of a jack according to the invention.

Figure 1 is a side view of this jack,

Figure 2 shows the jack in section,

Figures 3 to 5 are sectional views along II-II of Figure 1 in different operating positions of a descent control device of this jack.

The jack, as shown in Figure 2, includes a sole 2, a column 3 connected to the sole 2 and a cylindrical shaft 4 mounted sliding on the column 3 and delimiting with it a chamber 5. The jack is, in addition, equipped with a pump 6 capable of sucking a fluid incompressible contained in a reservoir 8 and to repress this fluid in the The pumping of the fluid is done by means of a lever 9 whose movements can push back to the chamber, the fluid incompressible through an anti-return valve. 10. On all these points, the Jack has a very classic structure. In contrast, the jack according to the invention differs from the jacks as they exist thanks to a device allowing to lower the barrel by a so-called command of the dead man.

Referring to FIG. 1, it can be seen that a housing 11 is placed above the pump. Figure 3 shows a section of the device integrated in this housing 11.

As can be seen, this housing 11 has a hole 13 one blind connected to the tank 8 and to the chamber 5.

A tubular cartridge 15 is engaged in the bore 13; the tubular cartridge 1 5 bears against a shoulder 16 of the piercing to separate a compartment 17 located on the side of the tank and a compartment 18 located on the cylinder side.

The device comprises two valves arranged in series, namely a primary valve I and a secondary valve II respectively closing a primary channel 20 and a secondary channel 21.

As can be seen in Figure 3, the housing has a blind drilling connected to the tank and the cylinder.

A tubular cartridge 15 is engaged in the bore 13, the cartridge has a chamfer that bears against a shoulder 16 so as to separate, in a sealed manner, a zone 17 connected to the jack and an area 18 connected to the tank.

The cartridge 15 has a hole that constitutes the channel secondary 21 and a second bore of larger diameter connected to the first by a shoulder 24.

The secondary valve II is formed by a ring 25 which comes into bearing against the shoulder 24 and thus closes the secondary channel 21.

The primary valve I is, in turn, constituted by a ball 27 which closes a hole made in the ring forming the channel 20. The primary channel 20 has a very small diameter of the order of 1.2 millimeters.

A plug 28 holds a spring 30 which holds the ball 27 of the primary valve I against its seat and a spring 29 which holds the ring 25 of the secondary valve II against its seat.

For the other end of the cartridge, a pilot rod 32 is engaged in the secondary channel 21. This pilot rod 32 is equipped with a finger 34 can enter the primary channel 20 and has, moreover, a radial bearing surface 36 able to bear on the ring 25.

The pilot rod 32 has a diameter substantially equal to that of the secondary channel 21 and can slide in the latter.

It is also noted that the cartridge has two channels 37 Radials providing a connection to the tank 8.

The pilot rod 32 is equipped with a protected pusher 39 by a cowling 40.

The operation of the jack is therefore the following. To lift a load, the jack is implemented in a very classic way in actuating the lever 9 to discharge the incompressible fluid into the chamber 5 and move the barrel 4 relative to the column to lift a load that located either at a support leg 42 or directly on the upper surface of the drum 4.

When it comes to lowering the jack, the latter being in load, an operator exerts pressure on the pusher 39. The action on the push member 39 causes movement of the pilot rod 32 and causes the finger 34 comes open the primary valve I by exerting a push on the ball 27, as can be seen in Figure 4.

The very important point to emphasize is that the uprising of the ball 27 of its seat is made possible only by its very small size and by the very small section of the primary channel 20; this one has a diameter of 1.2 millimeters.

Indeed, it must be borne in mind that when the jack is in charge, the fluid is subjected to a pressure of the order of 300 bars. This pressure of 300 bar applies, among other things, to the primary valve.

Nevertheless, thanks to the small size of this primary valve I, it is possible with an action of about 15 to 20 daN, ie the action manual of an operator to open the primary flap I by taking off the ball 27 from his seat. This allows leakage of the fluid contained in the chamber 5. The fluid contained in the chamber 5 escapes to the tank 8 through exhaust channels 37, for this purpose, in the cartridge 15.

As soon as the operator stops acting on the push button 39, the ball 27 is pushed back under the action of the fluid against seat and immediately stops leakage of fluid to the tank. The descent of the jack is then instantly interrupted.

It must be made clear that, given the section of the canal secondary 21, the operator with the sole force of his hand can not in any way take off the ring of the secondary valve II, since it is pressed by the fluid pressure very strongly against his seat and can not so move.

Thanks to the primary valve I closing the primary channel 20 of small section, it is possible to realize a descent control device a loaded jack that stops as soon as an action stops on it.

In the case where the jack is extended without load, that is to say that the fluid is present in the chamber 5, without supporting a load, the primary valve I provides an insufficient leakage rate. The barrel does not descend under his action of gravity.

The user then presses the pusher 39.

The pilot rod 32 bears on the ring 25 and thus opens the secondary valve II. Fluid does not exert pressure on the valve secondary II since the jack is without load.

The secondary valve II can then fade, there occurs a high leakage rate through the secondary channel 21 which is of a section much higher than that of the primary channel 20. This leakage flow important allows the jack to go down even when empty.

The invention therefore provides a jack presenting a control of descent by a dead man type pusher, since when the jack is in charge, stopping an action on this device leads to an interruption of the jack's descent.

Of course, the invention is not limited to the form of realization described above but embraces on the contrary all embodiments. Thus, the primary and secondary valves could not to be co-axial but could be parallel.

Moreover, this device can be adapted to any type of jack hydraulic.

Claims (10)

Hydraulic jack comprising: a sole (2) intended to come on a bearing surface, a column (3) connected to the sole (2), a cylindrical shaft (4) slidably mounted on the column (3) and defining therewith a chamber (5), and a pump (6) capable of sucking an incompressible fluid contained in a reservoir (8) and pushing it back into the chamber (5) so as to move the drum (4) with respect to the column and thus lift a load in bearing on the shaft (4), characterized in that the jack comprises a control device comprising: a primary channel (20) of small section, connecting the chamber (5) to the tank, closed by a primary valve (I) allowing the passage of the fluid from the chamber (5) to the reservoir (8), the primary channel (20). ) having a dimension such that the primary valve (I) can be opened under a maximum action of about 20 daN to oppose the pressure exerted by the fluid on the primary valve (I) when the jack supports a load, and a secondary channel (2) connecting the chamber (5) to the tank (8) closed by a secondary valve (II) allowing the passage of the fluid from the chamber (5) to the reservoir (8), the secondary channel (21) having a section allowing the shaft (4) to descend under its own weight when the secondary valve (II) is open. Hydraulic jack according to claim 1, characterized in that the primary channel (20) and the secondary channel (21) are co-axial, the primary valve (I) and the secondary valve (II) being arranged one behind the other and actuated by the same pilot rod (32). Hydraulic jack according to claim 2, characterized in that the primary valve (I) is constituted by a ball (27) closing the primary channel (20) and the secondary valve (II) is constituted by a ring (25) in which is arranged the primary channel, the ring (25) closing off the secondary channel (21). Hydraulic jack according to claim 3, characterized in that the pilot rod (32) has, at one of its ends, a push button (39) and at its other end a finger (34) engageable in the channel primary (21) to bear against the ball (27) forming the primary valve (I) and a bearing surface (36) engageable with the ring (25) forming the secondary valve (II). Hydraulic jack according to claim 4, characterized in that the control device comprises a cartridge (15) embedded in a housing (11), arranged on the body of the pump (6) and connected to the chamber (5) and the reservoir (8), receiving the primary valve (I) and the secondary valve (II). Hydraulic jack according to claim 5, characterized in that the cartridge (15) has a longitudinal bore forming the secondary channel (21) in which is engaged the pilot rod (32), the bore having a shoulder (24) forming the seat of the valve secondary (II). Hydraulic jack according to claim 6, characterized in that , at its end opposite to that of introduction of the rod, the bore is closed by a plug (28) against which two compression springs (29, 30) co -axial respectively applying against the ring (28) and against the ball (27). Hydraulic jack according to one of claims 5 to 7, characterized in that the cartridge has at least one radial channel (37) connecting the secondary channel. Hydraulic jack according to one of claims 1 to 8, characterized in that the primary channel (20) has a diameter of between 1 and 2.5 millimeters. Hydraulic jack according to claim 9, characterized in that the primary channel (20) has a diameter of 1.2 millimeters.

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