EP1383702B1

EP1383702B1 - A process and device for controlling a single-acting pneumatic piston

Info

Publication number: EP1383702B1
Application number: EP02722683A
Authority: EP
Inventors: Erio Ferrari
Original assignee: Olmec Srl
Current assignee: Olmec Srl
Priority date: 2001-05-04
Filing date: 2002-03-26
Publication date: 2006-05-31
Anticipated expiration: 2022-03-26
Also published as: EP1383702A1; WO2002090236A1; ITMO20010082A1; ATE327962T1; ITMO20010082A0; DE60211882D1

Abstract

A valve group comprises: a nonnally-closed two-way, two-position delivery valve (7) which places an external source of pressurised gas in communication with a pressurisable chamber (4) of a piston; a nonnally-closed two-way discharge valve (8), which places the pressurisable chamber (4) in communication with a discharge (9); and a total discharge valve (12) which when opened contemporaneously with an opening of the discharge valve, sucks gas from the pressurisable chamber by a venturi effect. The invention can be used in a pneumatic jack of a bellows-type for raising objects, in particular for raising a side of a motor vehicle.

Description

Technical Field

The invention relates to a process and device for controlling a single-acting pneumatic piston. Specifically, though not exclusively, the invention is applicable to a bellows pneumatic piston used for lifting objects, in particular for raising one side of a motor vehicle.

Background Art

Reference is made in particular to the process recited in the preamble of the first claim.
A process of this type exists in the prior art, for example US 6,082,708 and WO 99/29616, which however include a drawback, i.e. that during the vehicle lowering stage the pressurisable chamber is never completely empty of the pressurised gas and as a result the jack is always slightly raised.
The main aim of the present invention is to provide a process for controlling a single-acting pneumatic piston which overcomes the above-described drawback. An advantage of the invention is that it provides a process which with a simple command fully and rapidly evacuates the pressurisable chamber of the pneumatic piston.
A further advantage of the process is that it is simple and economical to realise.
A further aim of the invention is to provide a control device for actuating the process of the invention which is relatively small, reliable, practical and safe.
These aims and advantages and more besides are all attained by the present invention, as it is characterised in the appended claims.

Disclosure of Invention

Further characteristics and advantages of the present invention will better emerge from the detailed description that follows of a preferred but non-exclusive embodiment of the invention, illustrated purely by way of a non-limiting example in the accompanying figures of the drawings, in which:

figure 1 shows a pneumatic jack provided with the control device of the invention;
figure 2 shows the control device of figure 1;
figure 3 is the pneumatic diagram of the control device of figure 2;
figure 4 is a front view of the valve body of the control device of figure 2;
figure 5 is a back view of the valve body;
figure 6 is a side view of the valve body;
figure 7 is a side view of the valve body, from the opposite side to the view in figure 6;
figure 8 shows section VIII-VIII of figure 6;
figure 9 is section IX-IX of figure 4;
figure 10 is section X-X of figure 8;
figure 11 is section XI-XI of figure 9;
figure 12 is section XII-XII of figure 9;
figure 13 is section XIII-XIII of figure 9.

With reference to the figures, 1 denotes in its entirety a pneumatic jack for raising objects, comprising a single-acting pneumatic piston 2 comprising a bellows 3 made of a deformable material which delimits internally thereof a pressurisable chamber 4 which can be placed in connection with an external source of pressurised gas (for example, a compressed-air plant). An upper end of the bellows 3 is predisposed using known ways for raising an object, in particular for lifting a side of a motor vehicle in a workshop.
The jack 1 is provided with a handle 5 bearing a control device 6 for the single-acting pneumatic piston, which is actuated, preferably manually, by an operator. The control device 6 operates between the pressurised gas source and the pressurisable chamber 4.
The control device 6 comprises a normally closed two-way delivery valve 7 which on command places the external pressurised-gas source in communication with the pressurisable chamber 4 of the piston.
A normally-closed two-way discharge valve 8, places the pressurisable chamber 4 in communication with a discharge 9.
An auxiliary discharge conduit 10 has an intake zone 11 which on command can be connected to the pressurisable chamber 4. A venturi depression can be induced in the auxiliary discharge conduit 10.
A normally-closed two-way total discharge valve 12 is predisposed on the auxiliary discharge conduit 10 between the gas source and the intake zone 11.
A discharge pipe 13, on which the discharge valve 8 operates, communicates with the pressurisable chamber 4 on one side and with the intake zone 11 on the opposite side.
The delivery valve 7, the discharge valve 8 and the total discharge valve 12 are associated to a valve group comprising a valve body 14 in a single block, as shown in the figure, or can be assembled on different blocks which can then be assembled together and interfaced.
The valve block 14 comprises: an inlet mouth 15 for pressurised air which is connectable to a compressed-air plant; a first cavity 16 opening into a delivery mouth 17 for connecting to the pressurised chamber 4 of the piston; a second cavity 18 opening into a discharge mouth 19 on which a discharge silencer 27 operates; a first seating 20 for the delivery valve 7 and a second seating 21 for the discharge valve 8; and a third seating 22 for the total discharge valve 12. The first cavity 16, which is located between the first seating 20 and the second seating 21, houses an overpressure safety valve 28.
Further, various connection conduits are afforded inside the valve body 14: a first conduit 23 which inter-connects the first seating 20, the first cavity 16, the second seating 21 and the second cavity 18; a second conduit 24 which inter-connects the inlet mouth 15, the first seating 20 and the first cavity 16; a third conduit 25 which interconnects the first seating 20 and the third seating 22; and a fourth conduit 26 which interconnects the third seating 22 and the second cavity 18. The third conduit 25 and the fourth conduit 26 are staggered with respect to the first conduit 23 an the second conduit 24. A transversal conduit 30 connects the third conduit 25 with the third seating 22. A transversal conduit 30 connects the fourth conduit 26 with the third seating 22. A transversal conduit 31 connects the fourth conduit 26 with the second cavity 18. The fourth conduit 26 is obliquely located. A transversal conduit 32 connects the third conduit 25 with the first seating 20.
The second cavity 18 houses a venturi device, of known type and not illustrated., which is predisposed to induce a venturi effect in the intake zone 11.
The open ends of the conduits indicated by 23, 25, 26, 29, 30, 31 and 32 are closed by caps 3 3.
The delivery valve 7, discharge valve 8 and total discharge valve 12 are normal two-position two-way intercept valves, which are manually opened by means of a push-button, and which automatically close by means of a return spring when no thrust is present.
The delivery valve 7 in the closed and open positions respectively opens and closes the first conduit 23 and the second conduit 24.
The discharge valve 8 in the closed and open positions respectively closes and opens the first conduit 23.
The total discharge valve 12 in the closed and open positions respectively closes and opens a connection between the third conduit 25 and the fourth conduit 26.
In operation the control device 6 activates a process for controlling the single-acting pneumatic piston 2, in which process the pressurisable chamber 4 of the piston is cyclically subjected to a delivery stage, during which the piston 2 raises an object, in which stage the chamber 4 receives a pressurised gas coming from a source thereof, and a discharge stage, in which the pressurised gas is evacuated from the chamber 4 and the object is lowered under the pressure of its own weight.
During the discharge stage, in order to obtain full lowering of the object, gas is sucked from the chamber 4 by a venturi effect. This venturi effect is obtained by means of a gas flow generated by effect of an opening of the total discharge valve 12, thus placing the auxiliary discharge conduit 10 in communication with the source of pressurised gas. The pressurised gas generates a flow through the conduit 10 and, in particular, through the venturi device predisposed in the intake zone 11 in order to activate the suction. During the completion of total discharge, the intake zone 11 is placed in communication with the pressurisable chamber 4 through the discharge valve 8, which is left open for the purpose.
For using the jack, the operator first positions the jack below the object to be raised, then he activates the lifting operation by pressing the button of the delivery valve 7. The compressed air passes through the valve body 14 and is forced into the pressurisable chamber 4; in particular it passes through the inlet mouth 15, the delivery valve 7 housed in the first seating 20, the second conduit 24 and the delivery mouth 17. When the button is released, the delivery valve 7 returns into the closed position, stopping the piston 2 from rising while maintaining the pressure in the chamber 4.
When the piston 2 is to be lowered, the operator first presses the control button of the discharge valve 8, the chamber 4 is placed in communication with the discharge 9; thus the piston 2 partially descends, facilitated by the downwards action of the weight of the raised object. In a second stage of the lowering operation, the operator contemporaneously presses the discharge valve 8 and the total discharge valve 12; in this configuration the intake zone 11 is activated and communicates with the chamber 4, a suction action is begun of air from the chamber 4, causing the piston 2 to be completely lowered. When the control button of the discharge valve 8 is released, the piston 2 stays in the completely lowered position and is ready for the next work cycle. Pressing only the total discharge valve 12 button does not in any way affect the position of the piston 2.
A further embodiment of the invention could combine the functions of the discharge valve and the total discharge valves, by providing a single two-position four-way valve, with a return spring. The four ways are equivalent to the two valves 9 and 12 in the illustrated embodiment, associated two by two and arranged along the discharge conduit and the total discharge conduit. A first position is the closure position, a second position a position of opening of the discharge conduit and the auxiliary discharge conduit. The button activating the descent of the piston 2 at the same time also activates the venturi effect suction.
A still further embodiment might include a four-way valve (as in the above-described further embodiment) but with three positions, i.e. a first position in which the discharge conduit and the auxiliary discharge conduit are closed, a second position in which only the discharge conduit is open and a third position in which both the discharge conduit and the auxiliary discharge conduit are open.

Claims

A process for controlling a single-acting pneumatic piston (2) in which a pressurisable chamber (4) of the piston (2) is cyclically subjected to a delivery stage, associated in particular with a raising of an object, in which the pressurisable chamber (4) receives a pressurised gas coming from a pressurised gas source, and a discharge stage, associated in particular with a lowering of the object, in which the pressurised gas is evacuated from the pressurisable chamber (4), characterised in that during the discharge stage the gas is removed from the pressurisable chamber (4) by means of a venturi effect.
The process of claim 1, wherein the venturi effect is obtained by means of a flow of gas generated by effect of an opening of an auxiliary discharge conduit (10) which is connected with the pressurised gas source and which is placed in communication with the pressurisable chamber (4) during the discharge stage.
A device for controlling a single-acting pneumatic piston (2), comprising:
a normally-closed two-way delivery valve (7) which on command places a source of pressurised gas in communication with a pressurisable chamber (4) of the piston; in particular for raising an object;

a normally-closed two-way discharge valve (8) which on command places the pressurisable chamber (4) in communication with a discharge (9), in particular for lowering the object;

characterised in that it comprises an auxiliary discharge conduit (10) having an intake zone (11) which is connectable on command to the pressurisable chamber (4), in which a depression can be generated by a venturi device predisposed in said intake zone.
The device of claim 3, comprising a normally-closed two-way total discharge valve (12) which is located on the auxiliary discharge conduit (10) between the pressurised gas source and the intake zone (11).
The device of claim 3 or 4, comprising a discharge conduit (13) on which the discharge valve (8) operates, which discharge conduit (13) communicates with the pressurisable chamber (4) at one end thereof and with the intake zone (11) at another end thereof.
The device of any one of claims from 3 to 5, wherein the delivery valve (7), the discharge valve (8) and the total discharge valve (12) are incorporated in a valve group comprising a valve body (14) which affords: an inlet mouth (15) for the pressurised air; a first cavity (16) terminating in a delivery mouth (17) for connecting to the pressurisable chamber (4) of the piston (2); a second cavity (18) terminating in a discharge mouth (19); a first seating (20) for the delivery valve (7); a second seating (21) for the discharge valve (8); a third seating for the total discharge valve (12); and a plurality of connection conduits including: a first conduit (23) inter-connecting the first seating (20), the first cavity (16) the second seating (21) and the second cavity (18); a second conduit (24) which interconnects the inlet mouth (15), the first seating (20) and the first cavity (16) with the delivery mouth (17); a third conduit (25) which interconnects the inlet mouth (15), the first seating (20) and the third seating (22); a fourth conduit (26) which interconnects the third seating (22) and the second cavity (18).
The device of claim 6, wherein: the delivery valve (7) in the closed and open positions respectively closes and opens the second conduit (24); the discharge valve (9) in the closed and open positions respectively closes and opens the first conduit (23); the total discharge valve (12) in the closed and open positions respectively closes and opens a connection between the third conduit (25) and the fourth conduit (26).
The device of clam 6 or 7, wherein the third conduit (25) and the fourth conduit (26) are staggered with respect to the first conduit (23) and the second conduit (24).
The device of any one of claims from 6 to 8, wherein the intake zone (11) is arranged in the second cavity (18).
The device of any one of claims from 6 to 9, wherein the first cavity (16) is a seating for a safety valve (28).
A pneumatic jack for raising objects, comprising a bellows (3) made of a deformable material which internally delimits a pressurisable chamber (4) connected to a pressurised gas source, an upper end of the bellows (3) being operatively associable to an object to be raised, characterised in that the jack comprises a device (6) according to any of the claims from 3 to 10, operating between the pressurised gas source and the pressurisable chamber (4).