FR2656903A1 - Progressive speed limiter of a pneumatic control cylinder - Google Patents

Abstract

This progressive speed limiter applies to a control cylinder consisting essentially of a piston (8) actuated in a chamber (7) by a pressure (P1) introduced by an intake orifice (10) and forcing air from the chamber through an exhaust orifice (11), on which an air flow rate limiter (16) is provided. According to the invention, the air flow rate limiter (16) is opened progressively and automatically by means for operating the needle valve (14), which means consist of a second cylinder or limiter cylinder (13), one piston of which is capable of moving in a chamber (19) of the cylinder (13) under the effect of a pressure (P2) which is identical to that (P1) and introduced into the chamber (19) simultaneously with the introduction of the pressure (P1) into the chamber (7a) of the control cylinder (6). The invention applies to metering pumps.

Description

PROGRESSIVE SPEED LIMITER OF A PNEUMATIC CYLINDER
ORDERED.

The present invention relates to a progressive speed limiter of a pneumatic control cylinder of the type comprising a piston capable of moving in a compression chamber, from a low rest position, to a high working position, under the effect of a pressure introduced into the chamber, through an inlet orifice situated under the piston in the low position, an exhaust orifice being disposed at the opposite part of said chamber, above the piston in the high position and comprising a flow limiter air, capable of reducing the speed of movement of the piston of the control cylinder, and constitutes' by a conduit in connection with the exhaust orifice and closed at rest by an axial needle rod whose linear movement during a adjustment varies an annular section of air passage.

These well-known air flow limiters are satisfactory, but this in a limited number of applications, because, in fact, if they allow the limitation of a speed of a jack, this is carried out constantly. , for a given and fixed adjustment of the limiter concerned.

However, there is a problem encountered in the field of packaging of liquid, fluid or viscous products, with or without pieces and which involves the use of volumetric dosers or dosing pumps, of the type comprising means of suction and delivery of the product. to be dosed according to a predetermined, precise volume.

In this type of packaging device, the difficulty essentially lies in the compromise to be found between a speed of delivery of the product into the containers, offering an acceptable production rate and a speed of delivery such that it does not cause splashes at filling. In fact, if the speed is too high, during contact of the product with the empty bottom of the container, at the start of filling, there will be rises at the edges, resulting in overflows, causing losses and soiling. This problem disappears after a start of filling phase, because after this, a certain volume of bottom product constitutes a shock absorber or a brake on the jet of product.

It is easily understood that the solution lies in a device allowing the acceleration or deceleration of the control cylinder as a function of its position and, more precisely, that of the piston of the product metering device.

A known device aims to achieve this objective and consists in slowing down the stroke of a piston of a hydraulic control cylinder arranged in series with a control member of the metering device. For this, the cylinder is made up of two variable volume chambers filled with oil, separated by a movable piston membrane, the displacement of which changes the volume of one chamber to the benefit of the other by means of a bypass tube connecting them externally.

This device is, in fact, a shock absorber, braking the movement of the piston permanently and therefore does not allow high speeds, after the initial phase because the pressure drops are very large and permanent.

A proportional control valve can be placed on the bypass tube to regulate the flow, but if, at the cost of great complexity, a desired progressive speed is obtained according to a chosen curve, it will always be a question of '' a speed regulated from an initially low speed and constituting a maximum reference speed.

The present invention aims to remedy these drawbacks and relates, for this purpose, to a progressive speed limiter of a pneumatic actuator for controlling a piston capable of moving in a compression chamber, from a low position of rest, towards a high working position, under the effect of a pressure introduced into the chamber, by an intake orifice situated under the piston in the low position, an exhaust orifice being disposed at the opposite part of said chamber , above the piston in the high position and comprising an air flow limiter, capable of reducing the speed of movement of the piston of the control cylinder, and constituted by a conduit in connection with the exhaust orifice and closed at rest by an axial needle rod whose linear movement during an adjustment varies an annular section of air passage, characterized in that the exhaust air flow limiter, of the control cylinder, comprises m automatic progressive opening control means of the needle by direct action on the latter relative to the duct, the opening being proportional to the displacement of the piston of the control jack for all or part of its stroke.

Thus, it will be obtained a gradual opening of the exhaust orifice as a function of the position of the piston of the control jack, during a phase of beginning of the metering delivery.

The present invention also relates to the characteristics below, considered in isolation or in all their technically possible combinations.

According to a preferred embodiment of the invention, the means for controlling the progressive opening of the needle are constituted by a second jack or limiting jack comprising a piston of which the needle is integral and which is capable of moving in a first chamber of the cylinder under the effect of a pressure identical or proportional to that introduced into the chamber of the control cylinder, simultaneously.

According to a characteristic of the invention, a first non-return valve is arranged in communication with a second chamber of the limiter cylinder and constitutes an exhaust from the control cylinder.

According to another characteristic of the invention, the pressure is introduced upstream of the chamber of the limiting cylinder, by means of a second non-return valve open in a direction of introduction of the pressure.

However, tests have shown that the beginning of delivery, in some cases, was still carried out at too high a speed, since the piston of the limiting cylinder is only braked by its only friction in the chamber.

To remedy this, for certain applications and according to another characteristic of the invention, a second air flow limiter is arranged in communication with a downstream part of the chamber of the limiting cylinder, open in an escape direction from the pressure, so as to constitute a brake of adjustable value, to the displacement of the limiter piston where from the needle, during all or part of the stroke of the piston of the control jack.

According to another characteristic of the invention, a third non-return valve is associated in bypass with the second air flow limiter and able to allow the introduction of pressure downstream of said chamber, rather than upstream, thanks reversing means, intervening at a predetermined moment in the stroke of the piston of the limiting cylinder to constitute a braking back pressure; a third air flow limiter associated in bypass with the second non-return valve is arranged upstream of the chamber and then becomes passing in an exhaust direction, according to an adjustable value.

This characteristic makes it possible, for example, to obtain a decreasing speed of the piston of the limiting cylinder, hence the piston of the control cylinder, at the end of the stroke.

According to another characteristic of the invention, the piston of the limiting cylinder comprises, at its end opposite the needle, a collinear support member capable of cooperating, at the end of the race, with an adjustable stop of said cylinder.

According to a preferred embodiment, the needle is constituted by a cone able to allow obtaining a curve or part of a speed curve, rectilinear.

According to an alternative embodiment, the needle has a surface of revolution with a concave profile capable of making it possible to obtain a curved curve or part of a speed curve.

According to another alternative embodiment, the needle has a surface of revolution with a convex profile capable of allowing the obtaining of an inflected curve or part of the speed curve.

The description will be further illustrated without being in any way limited by the description which follows, given with reference to the appended drawings in which
Figure 1 is a schematic view in longitu section
dinal of a progressive speed limiter according to
the invention, in the start of operation position,
relative to a control cylinder to be regulated, shown
smelled on a reduced scale
Figure 2 is a schematic view of a
speed according to figure 1, represented in a phase
final operation
Figure 3 is a speed curve of the piston of the
control cylinder during the operating phases
ment of the progressive speed limiter according to the invention
tion
Figures 4, 5 and 6 respectively represent
the end of a needle with a surface of revolution at
concave, conical and convex profile; and
FIGS. 4A, 5A, 6A respectively represent the
initial speed curves obtained respectively
with a needle whose end has a surface of
concave, conical and convex profile revolution.

The installation shown in Figure 1 relates to a control assembly of a metering pump 1 essentially consisting of a cylindrical chamber 2 pierced with a suction pipe 3 and a discharge pipe 4 and in which is actuated displacement of a piston with a conical head 5, sucking or discharging the product to be metered, under the action of a control cylinder 6, acting linearly on the piston 5 of the pump 1.

The control cylinder 6 also consists in a known manner of a compression chamber 7 in which a control piston 8 can move, in mechanical connection with the piston 5 by a common axis 9, and this from a position low rest O to a high maximum working position III.

The displacement of the control piston 9 is carried out by introduction of a pressure P1 in a lower part 7a of the compression chamber 7, by an intake orifice 10 constituting a point D, located under the piston 8 when the latter is in low position O.

An exhaust orifice It constituting a point B is disposed at an upper part 7b of the chamber 7 above the piston 8, when the latter is in the maximum high position III.

The piston 8 can thus move within predetermined limits situated between a bottom dead center (PMB) for a position O of the piston 8, and a top dead center (TDC) for a position III of said piston 8.

According to the invention, a progressive speed limiter 12 designated as a whole is disposed on the exhaust orifice 11 of the control cylinder 6 and is capable of reducing the speed V of movement of the control piston 5 relative to a speed maximum reference value communicated by pressure P1.

The progressive speed limiter 12 is constituted by a second cylinder 13 or limiting cylinder comprising means for controlling the progressive and automatic opening of an axial needle rod 14, the linear displacement of which varies the annular section of air passage between the end of said needle 14 and a conduit 15 of the limiting cylinder 13, to constitute a first air flow limiter 16, the opening of which will be proportional to the displacement of the piston 8 of the control cylinder 6, for all or part of its stroke, thanks to said progressive opening means of the needle 14.

The progressive opening means consist of a piston 17 of the limiting cylinder 13 secured to the needle 14 by an axis 18, which piston 17 is capable of moving in a first chamber 19 of the cylinder 13 under the effect of a pressure P2 identical to that P1 introduced into the chamber 19, simultaneously with the pressure P1 at D and thus gradually causing the opening of the first air flow limiter 16, and the introduction of released air, into a second chamber 20 of the jack 13, isolated from the first 19 by an O-ring 21 surrounding the axis 18, before exhaust by a first non-return valve 22 constituting an exhaust point A.

The pressure P2 is applied to a point C of a second non-return valve 23 for introduction into said chamber 19 in a part 19a upstream of the latter and of the piston 17 and exerts an axial thrust on the piston 17 in a direction F1.

The axial displacement of the piston 17 in the chamber 19 causes a discharge of air which it is advantageous here to control so as to brake, more or less, the movement of said piston 17 of the limiting cylinder 13 hence the piston 5 of the cylinder control 6; this so as to allow a chosen speed curve to be obtained (FIG. 3), a first progressive phase of which goes from O to I corresponds to the positions O and I respectively of the control piston 8, the pump piston 5 and the piston limiter cylinder 17 (Figure 1).

This first phase corresponds in fact to the action of the first air flow limiter 16 beyond which the air passage rate is maximum there and corresponds to a second stable phase of the speed curve going from I to II corresponding to the working positions I, II of the same pistons 8, 5 and 17 above.

Additional braking means for the piston 17 of the limiting cylinder 13 are constituted by a second air flow limiter 24 constituting a point F, arranged in communication with a downstream part 19b of the chamber 19 of the limiting cylinder 13, open in one direction pressure escape, so as to constitute a brake of adjustable value, to the movement of said piston 17, during all or part of the stroke of the control piston 8, in this case for the portions of curves O, I and I, II (Figure 3).

In other words, the portion O, I is obtained by the action of the flow limiter 16 associated with that of the flow limiter 24, acting against the thrust exerted for the introduction of the pressure P2 at C As for the portion I, II, it results only from braking only due to the action of the flow limiter 24, the limiter 16 then being completely on.

Another characteristic of the invention makes it possible to obtain a speed of deceleration of the control piston 8 in a final delivery phase illustrated in FIG. 3 by the portion of the speed curve II, III, corresponding to the positions II, III of the pistons 8, 5 and 17 respectively of the control cylinder 6, of the pump 1 and of the limiter cylinder 13 (Figure 2).

The means for obtaining this braking, while the first flow limiter 16 is in full opening, consist in reversing the direction of introduction of the pressure P2 into the chamber 19 of the limiting cylinder 13, that is to say that instead of being introduced upstream (C) by the chamber part 19a, it will be introduced downstream (F) by the chamber part 19b, this thanks to inversion means 25, intervening at a predetermined time the stroke of the piston 17 of the limiting cylinder 13 from which the piston 8 of the control cylinder 6, to constitute a braking back pressure. To authorize this reversal, a third non-return valve 26 is associated in bypass with the second air flow limiter 24 and is open in a reverse direction of introduction of the pressure P2 into the chamber part 19b. air flow 27 is associated in bypass with the second non-return valve 23 and becomes conducting in an exhaust direction, the non-return valve 23 being blocked in this direction.

The pressures P1 and P2 come from a pressure generator P and are derived respectively towards a distributor of control cylinder DVC and towards a distributor of limiting cylinder DVL, the latter comprising the reversing and information means (not shown). ).

According to another characteristic of the invention, the piston 17 of the limiting cylinder 13 is extended by a support shaft 28 sliding in a bearing 29 by means of an O-ring 30. The shaft 28 has at its end 28a, opposite at the needle 14, a collinear support member 31, capable of cooperating at the end of the race with an adjustable stop 32 by screwing into a part of the casing 13a of the limiting cylinder 13.

According to alternative embodiments of the needle 14, it has a surface of revolution whose profile is such as to be able to obtain initial curves of different speed. Thus a concave profile (Figure 4) will offer a curved initial curve (Figure 4A), a conical profile (Figure 5) will offer a straight initial curve (Figure 5A) and a convex profile (Figure 6), a curve inflected initial (Figure 6A).

Of course, the present invention may find applications other than that of metering pumps.

Likewise, the control pressures may be obtained by the use of other types of fluids and the control cylinder may also be hydraulic.

Claims (10)

Claims  1. Progressive speed limiter of a pneumatic cylinder (6) for controlling a piston (8) capable of moving in a compression chamber (7), from a low rest position (O), to a position working height (III), under the effect of a pressure (P1) introduced into the chamber (7) through an intake port (10) located under the piston in the low position (O), an exhaust port (11) being disposed at the opposite part of said chamber (7), above the piston (8) in the high position (III) and comprising an air flow limiter (16), capable of reducing the speed (V) of displacement of the piston (8) of the control cylinder (6), and constituted by a conduit (15) in connection with the exhaust orifice (11) and closed at rest by an axial needle rod (14) whose linear displacement during an adjustment varies an annular section of air passage, characterized in that the limiter (16) of air flow to the exhaust, of the control cylinder (6), comprises automatic progressive opening control means of the needle (14) by direct action on the latter with respect to the duct (15), the opening being proportional to the displacement of the piston (8) of the control jack (6) for all or part of its run.  2. Speed limiter according to claim 1, characterized in that the means for controlling the progressive opening of the needle (14) are constituted by a second jack or limiting jack (13) comprising a piston (17) of which the needle is integral (14) and which is capable of moving in a first chamber (19) of the jack (13) under the effect of a pressure (P2) identical or proportional to that (P1) introduced into the chamber (7) of the jack control (6), simultaneously.  3. Speed limiter according to claims 1 and 2, characterized in that a first non-return valve (22) is arranged in communication with a second chamber (20) of the limiter cylinder (13) and constitutes an exhaust of the cylinder control (6).  4. Speed limiter according to one of the preceding claims, characterized in that the pressure is introduced upstream (19a) of the chamber (19) of the limiter cylinder (13), by means of a second check valve. return (23) open in a pressure introduction direction (P2).  5. Speed limiter according to one of the preceding claims, characterized in that a second air flow limiter (24) is arranged in communication with a downstream part (19b) of the chamber (19) of the limiter cylinder ( 13), open in a pressure release direction (P2), so as to constitute a brake of adjustable value, to the displacement of the piston (17) of the limiter (13) hence the needle (14), during of all or part of the stroke of the piston (8) of the control cylinder (6).  6. Speed limiter according to one of the preceding claims, characterized in that a third non-return valve (26) is associated in bypass with the second air flow limiter (24) and able to allow the introduction of the pressure (P2) downstream of said chamber (19), rather than upstream, by means of reversing means (25), intervening at a predetermined moment in the stroke of the piston (17) of the limiting cylinder (13) to constitute a braking back pressure; a third air flow limiter (27) associated in bypass with the second non-return valve (23) is arranged upstream of the chamber (19) and then becomes passing in an exhaust direction, according to an adjustable value.  7. Speed limiter according to one of the preceding claims, characterized in that the piston (17) of the limiting cylinder (13) comprises, at its end opposite the needle (14), a support member (31) suitable collinear to cooperate, at the end of the race, with an adjustable stop (32) of said jack (13).  8. Speed limiter according to one of the preceding claims, characterized in that the needle (14) is constituted by a cone adapted to allow obtaining a curve or part of a speed curve, rectilinear.  9. Speed limiter according to one of the preceding claims, characterized in that the needle (14) has a surface of revolution with a concave profile capable of making it possible to obtain a curve or part of a speed curve, domed.  10. Speed limiter according to one of the preceding claims, characterized in that the needle (14) has a surface of revolution with a convex profile capable of making it possible to obtain a bent curve or part of a speed curve.