EP0538123B1 - Diaphragmpump with continuously adjustable delivery between zero and a maximum value - Google Patents

Description

The present invention relates generally to the field of adjustable flow pumps and more particularly it relates to improvements made to interrupted cycle diaphragm pumps, with continuously adjustable flow between a zero value and a maximum value, according to the preamble of the claim 1.

Pumps are known in which the pumping member is driven in a reciprocating linear movement by a connecting rod-crank system with variable eccentricity driven by a rotating shaft (output of electric motor or internal combustion via a reducer gears, for example worm gear). However, the means to be used for adjusting the offset are often complex and require precise machining and complicated shapes. These means include fragile parts which limit the life of the mechanism. In addition, the size due to the presence of the stroke adjustment means is in all cases very large in relation to the size of the machine.

In addition, it is very difficult, without resorting to overly complex mechanisms, to carry out a continuous adjustment of the flow rate between a zero value and a maximum value, in particular towards low flow values.

Finally, the dead volume in the pumping head (that is to say the position, at the end of the compression stroke) of the pumping member linked to the connecting rod varies depending on the stroke amplitude used, and it corresponds substantially to the middle of the displacement (or stroke) when the flow rate is set to 0%. As the dead volume increases in the low settings, a notable drop in efficiency is often observed for low flow rates.

Furthermore, documents US-A-3 801 232 (document on which the preamble of claim 1 is based) and US-A 3 661 167 describe conventional arrangements of interrupted cycle dosing pump, comprising an eccentric rotary, a linearly movable piston which is held in contact with the eccentric by a spring, and an adjustable locking means for cyclically locking the piston over an adjustable part of its stroke.

The major drawback of these known arrangements lies essentially in the fact that the force exerted by the spring on the piston is directed in the same direction as the resistant force due to the backflow of the product displaced by the pump and is approximately of the same order of greatness as this resistant effort. As a result, the engine effort to be generated to move the pump is approximately double the delivery effort itself, which alone is useful. It is therefore necessary to have recourse to motor means which are largely oversized in relation to the delivery force, which is the only useful, hence the very high costs of manufacture and use.

• le contact du piston sur l'excentrique étant ponctuel, il en résulte une usure importante de ces pièces ;
• l'inversion cyclique de sens des efforts importants se traduit, dans les paliers, par des claquements générateurs de bruits élevés ;
• le point de contact de l'excentrique sur l'extrémité du piston se déplace transversalement sur celle-ci au cours de la rotation de l'excentrique : l'effort qui en résulte est donc excentré de façon cycliquement variable par rapport à l'axe du piston, avec pour conséquence une tendance de la pièce en mouvement alternatif à se désaxer par rapport aux organes de guidage et donc une usure supplémentaire au niveau du guidage de ladite pièce en mouvement alternatif.

In addition, these known pumps have other drawbacks, in particular:

• the contact of the piston on the eccentric being punctual, this results in significant wear of these parts;
• the cyclical reversal of direction of the large forces is reflected, in the bearings, by clicks generating high noise;
• the point of contact of the eccentric on the end of the piston moves transversely thereon during the rotation of the eccentric: the force which results therefrom is therefore eccentrically cyclically variable with respect to the axis of the piston, with the consequence of a tendency of the part in reciprocating movement to be offset with respect to the guide members and therefore additional wear in the guiding of said part in reciprocating motion.

Document EP-A-0 449 686 describes a metering pump arrangement in which the spring return system of conventional pumps is replaced by a declutching system involving a wedge effect using balls and transverse spring. However, the friction of the balls against the slides causes very significant wear and the pump thus equipped is not reliable over time.

The main object of the invention is to remedy the drawbacks of currently known devices and to propose an improved pump arrangement which not only makes it possible to continuously adjust the flow rate between a zero value and a maximum value, including for the very weak. values, but which also implements less complex and more reliable means than current pumps and above all which requires less motor power and which ultimately turns out to be more economical than current pumps.

To this end, an interrupted cycle diaphragm pump, with continuously adjustable flow rate between a zero value and a maximum value, of the type defined in the preamble, is essentially characterized, being arranged in accordance with the invention, in that the connecting rod head is provided with at least one slide (11) extending substantially in the extension of the connecting rod (5) opposite the membrane (2) and capable of supporting the above-mentioned bearing (10) with free sliding relative to the connecting rod head, and in that elastic return means (15) are provided for maintaining said bearing (10) at the bottom of the slide in the absence of antagonistic force exerted by the eccentric member on the bearing, said means elastic return acting on said bearing opposite the connecting rod.

• la bielle a été rendue solidaire de la membrane et c'est l'élasticité et l'aptitude à la déformation de cette dernière qui rendent possibles les mouvements relatifs, en lieu et place de la liaison articulée employée jusqu'à présent ;
• la liaison entre l'excentrique et la tête de bielle s'effectue à travers un palier, donc sur la totalité d'une surface circulaire, en lieu et place du contact ponctuel mobile des agencements antérieurs ;
• la position originale attribuée aux moyens de rappel élastique fait que l'effort développé par lesdits moyens ne se cumule pas avec l'effort résistant de refoulement : dans le sens de la compression, l'effort moteur doit vaincre l'effort résistant de refoulement seul tandis que, dans le sens de l'aspiration, l'effort moteur doit vaincre l'effort des moyens de rappel seul ; les moyens moteurs peuvent ainsi être plus petitement dimensionnés, et donc être moins encombrants et surtout moins onéreux aussi bien à la fabrication qu'à l'entretien ;
• d'une façon générale, l'équilibrage dynamique des pièces en mouvement est meilleur que dans les machines antérieures et il en résulte de meilleures conditions de fonctionnement, une usure moindre et des vibrations moindres, d'où un bruit moindre de fonctionnement.

Thanks to such an arrangement, all the parts subject to wear in the previous pumps have been either discarded or improved:

• the connecting rod has been made integral with the membrane and it is the elasticity and the ability to deform the latter which make possible the relative movements, instead of the articulated connection used until now;
• the connection between the eccentric and the connecting rod head is effected through a bearing, therefore over the whole of a circular surface, in place of the mobile point contact of the previous arrangements;
• the original position assigned to the elastic return means that the force developed by said means does not accumulate with the resistant discharge force: in the direction of compression, the motor force must overcome the resistant pressure force alone while, in the direction of suction, the motor force must overcome the force of the return means alone; the drive means can thus be smaller in size, and therefore be less bulky and above all less expensive both for manufacturing and for maintenance;
• in general, the dynamic balancing of moving parts is better than in previous machines and this results in better operating conditions, less wear and less vibrations, resulting in less operating noise.

Only the contact between the movable stop and the bearing surface of the connecting rod is still subject to wear; however, this wear is easily compensated for by recalibrating (using a Vernier system that can be operated from the outside) without the need to dismantle the pump. Note however that, due to the lower effort due to the particular positioning of the elastic return means, the wear-generating effort is reduced to a third or a quarter of what it was in previous pumps: the duration of operation between settings is then increased correspondingly.

Finally, it will be noted that, unlike the systems used up to now, the pump arranged in accordance with the invention implements a real bi-crank system, which is a simpler mechanical structure than the previous systems.

• une portée d'appui solidaire de la bielle,
• une butée déplaçable apte à coopérer avec la portée d'appui lors du mouvement de la bielle lorsque la bielle a parcouru une fraction souhaitée de sa course, et
• des moyens de commande pour déplacer la butée et l'amener dans une position correspondant à un débit souhaité de la pompe.

Advantageously, in a simple embodiment, the adjustment means comprise:

• a bearing surface integral with the connecting rod,
• a movable stop capable of cooperating with the bearing surface during the movement of the connecting rod when the connecting rod has traveled a desired fraction of its travel, and
• control means for moving the stop and bringing it to a position corresponding to a desired flow rate of the pump.

In this case, the bearing surface can be supported by the slide at the free end thereof and in the extension of the connecting rod. To obtain a more compact structure, it is then desirable for the arrangement to be such that the bearing surface constitutes a displacement stop for the sliding bearing. Still with the same concern of simplifying the structure, the elastic return means can bear on the bearing surface.

• la glissière comprend deux tiges de glissière supportées par la tête de bielle et écartées l'une de l'autre en s'étendant dans le prolongement de la bielle,
• la portée d'appui est une pièce rigide s'étendant transversalement à la bielle et fixée aux extrémités libres respectives des deux tiges de glissière,
• le palier coulissant est bridé à libre coulissement sur les deux tiges de glissière, et
• les moyens de rappel élastique comprennent deux ressorts en hélice entourant respectivement les deux tiges de glissière et interposés entre le palier et la portée d'appui.

Still using the foregoing arrangements, a concrete embodiment of a pump according to the invention can combine the following additional arrangements:

• the slide comprises two slide rods supported by the connecting rod head and spaced from one another by extending in the extension of the connecting rod,
• the bearing surface is a rigid piece extending transversely to the connecting rod and fixed to the respective free ends of the two slide rods,
• the sliding bearing is clamped free sliding on the two slide rods, and
• the elastic return means comprise two helical springs respectively surrounding the two slide rods and interposed between the bearing and the bearing surface.

Finally, it may be advantageous for the means for controlling the movable stop comprising a threaded rod rotating in a fixed threaded bore, the end of the threaded rod constituting or supporting the stop.

Thus, in accordance with the invention, a pump, in particular a metering pump, is formed, the flow rate of which is adjustable, entirely continuously, between a zero flow rate and a maximum flow rate, the continuity of the existing adjustment even for very low flow rates.

The diaphragm always occupies the same position at the end of the compression stroke whatever the set flow rate and the problems of a variation in dead volume and a drop in efficiency at low flow rates, presented by previous pumps, no longer arise. .

Finally, the mechanical structure of the entire pump remains simple, including with regard to the flow control means, and not very subject to wear, which has a beneficial influence on the manufacturing and maintenance costs. The pump motorization can be less powerful, and therefore less costly.

The invention will be better understood on reading the following detailed description of a preferred embodiment given solely by way of non-limiting example. In this description, reference is made to the appended drawing in which the single figure is a side view, casing removed, of an interrupted-cycle diaphragm pump arranged according to the invention.

In a suction-discharge chamber 1 (only suggested in FIG. 1), a hollowed-out part of the wall thereof receives a deformable membrane 2 secured in leaktight manner by its peripheral edge 3 to a casing 4. The center of the membrane 2 is secured (optionally with freely rotating articulation) to one end of a connecting rod 5, the other end of which is coupled, by means indicated below, to an eccentric wheel 6 in continuous rotation. The eccentric wheel 6 is integral with a rotating shaft 7 which is driven by motor means, for example by means of a worm reducer (suggested in the drawing by its axis 8 and its casing 9) and gear straight (not visible, wedged on the shaft 7).

With the wheel 6 is associated an external bearing 10 with bearings, the outer shell of which fits between two arms or slide rods 11 supported by and integral with the connecting rod 5, said slide rods extending parallel to the axis of the connecting rod 5. The connection of the slide rods 11 to the connecting rod is in the form of a semicircular part 12 attached to the end of the connecting rod or forming an integral part of it, the bearing 10 being able to be housed in the rounding of the part 12 (position shown in the figure). The bearing 10 is equipped with two diametrically opposite flanges and respectively surrounding the slide rods 11 with free sliding; these two flanges can be joined in the form of a single support plate 13 engaged in free sliding on the rods 11.

The free ends of the slide rods 11 are braced by a connecting piece 14 of which another function will appear later, the piece 14 being located at a distance from the bearing 10 and / or from the support plate 13 when the bearing 10 is in contact of the rounded part 12. The part 14 can thus also constitute an end-of-travel stop when the bearing 10 moves.

Finally, two helical springs 15, surrounding the rods 11 respectively, are interposed between the support plate 13 and the connecting piece 14 to push the bearing 10 against the rounded piece 12 in the absence of an antagonistic force generated by the eccentric wheel 6.

In the extension of the connecting rod and opposite the connecting piece 14 extends a threaded rod 16 rotating in a threaded bore 17 passing through the wall of the casing 4. The internal end 18 of the threaded rod 16 constitutes a movable stop ( the rotation of the rod 16 resulting in its axial displacement) capable of cooperating with the connecting piece 14 secured to the connecting rod 5 and which, as such, serves as a bearing surface for said connecting rod. An external handle 19 makes it possible to turn the threaded rod 16. To block the threaded rod 16 in any desired axial position, it is possible to provide locking means with an eccentric ring 20, which surrounds the threaded rod and which can be actuated in rotation by a button. grip 21.

The operation is as follows.

When the stop 18 is located outside the path of the connecting rod head (set of members 10 to 15) associated with the eccentric wheel 6, that is to say the threaded rod being unscrewed (moved to the right, as shown in the figure), the connecting rod 5 is freely driven by the eccentric wheel over the whole of each rotation thereof. The membrane 2 is then animated by an alternating back-and-forth movement, the extreme positions of which correspond to the two dead centers (left and right in the figure of the reciprocating movement). The amplitude of this movement is proportional to the eccentricity of the wheel 6. The pump flow is then at its maximum value.

If now, by rotation of the threaded rod 16, the stopper 18 is moved to the left, the connecting piece 14 strikes this stopper after having traversed a fraction of the stroke of the connecting rod which is a function of the axial position of the stopper . The connecting rod 5 is then blocked in its axial movement, while, under the thrust of the eccentric wheel 6 driven by the shaft 7, the bearing 10 completes its movement by sliding on the slides 11, with compression of the springs 15, in the direction of the connecting piece 14. The diaphragm 2 is therefore driven only during a fraction of the stroke of the connecting rod and the flow rate of the pump is established at a value corresponding to said fraction of stroke, in other words at the axial position. of the stop.

By moving the stopper as far as possible, the connecting rod remains locked in the neutral position on the left (in the figure), and the diaphragm is no longer driven. The pump flow is zero, while the drive shaft 7 continues to rotate, driving the bearing 10.

In all cases, whatever the effective stroke of the connecting rod 5, the diaphragm 2 always occupies the same axial position when the connecting rod is in left dead center (in the figure). The dead volume of the pump therefore remains constant whatever the flow rate of the pump, including for low flow rates or zero flow.

Claims (8)

1. Diaphragm pump with a continuously adjustable delivery between zero and a maximum value, comprising:

   - a continuously rotating eccentric drive member (6),

   - a connecting rod (5) having, at one end, a big end (11-14) fitted with a bearing (10) receiving, so as to rotate freely, the eccentric drive member (6), and the other end of which is coupled to a central area of the diaphragm (2),

   - releasable coupling means for selectively coupling the said big end to the eccentric drive member (6) during a continuously adjustable desired portion of travel, and

   - adjustment means (16-19) for continuously adjusting the desired portion of travel of the connecting rod (5) between two extreme positions, these adjustment means (16-19) comprising movable stop means (18) suitable for cooperating with a bearing surface (14) integral with the connecting rod (5); characterised in that the big end is provided with at least one guide (11) extending substantially in line with the connecting rod (5) opposite the diaphragm (2) and suitable for supporting the above-mentioned bearing (10) so as to slide freely with respect to the big end, and in that elastic return means (15) are provided to hold the said bearing (10) at the bottom of the guide in the absence of any opposing force exerted by the eccentric member on the bearing, the said elastic return means acting on the said bearing in the opposite direction to the connecting rod.
2. Pump according to Claim 1, characterised in that the adjustment means comprise:

   - a bearing surface (14) integral with the connecting rod (5),

   - -a movable stop (18) suitable for cooperating with the bearing surface (14) during the movement of the connecting rod when the connecting rod has travelled the said desired portion of its travel, and

   - control means (16, 17, 19) for moving the stop (18) and bringing into a position enabling it to limit the travel of the connecting rod to the said desired portion.
3. Pump according to Claim 2, characterised in that the bearing surface (14) is supported by the guide at the free end of the latter and in line with the Connecting rod.
4. Pump according to Claim 3, characterised in that the bearing surface also constitutes a movement stop for the sliding bearing.
5. Pump according to Claim 3 or 4, characterised in that the elastic return means bear on the bearing surface.
6. Pump according to Claim 5, characterised in that

   - the guide comprises two guide rods (11) supported by the big end and separated from each other whilst extending in line with the connecting rod,

   - the bearing surface (14) is a rigid piece extending transversely to the connecting rod (5) and fixed to the respective free ends of the two guide rods (11),

   - the sliding bearing (10) is secured (13) so as to slide freely on the two guide rods (11), and

   - the elastic return means comprise helical springs (15) surrounding respectively the two guide rods (11) and interposed between the bearing (10) and the bearing surface (14).
7. Pump according to any one of Claims 2 to 6, characterised in that the means for controlling the movable stop comprise a threaded rod (16) turning in a fixed threaded bore (17), the end of the threaded rod constituting or supporting the stop (18).
8. Pump according to Claim 7, characterised in that it also includes locking means (20) suitable for locking the threaded rod (16) in any desired axial position.

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