WO2015173618A1

WO2015173618A1 - Belt-driven volumetric pump with hollow compartments having variable geometry

Info

Publication number: WO2015173618A1
Application number: PCT/IB2015/000665
Authority: WO
Inventors: Emidio Capannelli
Original assignee: Emidio Capannelli
Priority date: 2014-05-13
Filing date: 2015-05-08
Publication date: 2015-11-19

Abstract

The object of the present invention is a belt-driven volumetric pump (1), for pumping a liquid or gaseous fluid, which envisages one or more compartments (3) carried by a belt (2) which winds on two or more pulleys (4). According to the invention, each of said compartments (3) has inner (3.1), outer (3.2) and side (5,1; 3.12) confining walls allowing it to communicate exclusively and alternatively with drawing (Amb.in) and delivery (Amb.out) environments. During the winding of said belt (2) on each of said pulleys (4), said inner (3.1) and outer (3.2) confining walls are forced to a reciprocal approach thereof up to mutually delimiting a volume (V) equal to a minimum value (V.min) whereas, during the stretching of said belt (2) between two consecutive of said pulleys (4), said confining walls (3.1, 3.2) are forced to a reciprocal distancing thereof up to delimiting a volume (V) equal to said maximum value (V.max), whereas said side confining walls (5.1; 3.12) are capable of supporting said approaching and distancing movement of said confining walls (3.1, 3.2).

Description

BELT-DRIVEN VOLUMETRIC PUMP WITH HOLLOW COMPARTMENTS HAVING VARIABLE GEOMETRY

DESCRIPTION

The present invention relates to a pump or a volumetric compressor of the type comprising a belt provided with variable volume compartments that force the transfer of a fluid from a drawing environment to a delivery environment.

Typically, the device adapted to such transfer of the fluid is called "pump" if the fluid transferred is a liquid and "compressor" if it is a gas.

Hereinafter, for convenience of description, the term "pump" shall always be used for such device, irrespectively from the fact that the fluid transferred is a liquid or a gas.

Two main classes of pumps substantially exist: the fluid-dynamic pumps and the volumetric pumps, of which some features that are interesting to highlight are listed herein. ^"

In the fluid-dynamic pumps the movement of the fluid is produced by a rotary motion induced in the same fluid. These pumps do not need check valves; the flow rate and efficiency decrease as the outlet pressure increases; if the pumped fluid is a liquid, priming is necessary, i.e. the pump must be initially filled with liquid in order to operate; they are suitable for any flow rate.

Volumetric pumps are those pumps that take advantage of the variation in volume in a chamber to cause a suction or a thrust on a fluid. In case of pumping of liquids, the flow rate delivered is independent of the head and is instead directly proportional to the rotation speed; their main characteristic may be considered as the easy adjustment of the flow rate.

Except for the Archimedes screw, suitable for high flow rates and low heads due to the considerable leakages, the volumetric pumps, of which the most known types are now listed, are suitable for lower flow rates and higher pressures than the fluid-dynamic pumps.

Piston pumps: suitable for small and medium flow rates and high heads; pulsating flow rate and pressure.

Membrane pumps: have the advantage of absolute waterproofing; are used for low and medium flow rates, and heads limited by the resistance of the material constituting the membrane, except for executions in which the membrane is driven by fluid under pressure which then, in turn, requires another pump; pulsating flow rate and pressure.

Gear pumps: are widely used for pumping lubricating oil; ensure a substantially constant flow rate, with minimum pulses.

Lobe pumps: conceptually similar to those with gears, create a reasonably continuous flow.

Vane pumps: do not require valves; have limited head due to the low resistance of the blades; are suitable for pumping liquids having a certain lubricity; have adjustable flow rate without changing the rotation speed.

Peristaltic pumps: ensure constant and easily adjustable flow rate; suitable for low flow rates and heads; particularly used in the medical field.

Volumetric pumps are then known which may be classified as of the conveying- belt type so-called "endless" (hereinafter "belt-driven pumps") where the belt rotates about two pulleys.

In two documents, these belts are characterized by having toothing between the recesses of which, having a variable volume, the fluid is transferred from the drawing environment to the delivery environment.

For example, document GB 1540908 shows a belt-driven pump having a toothing with rectangular or trapezoid teeth on the outer side that winds on two pulleys and between the recesses of which the fluid is carried. The belt absorbs the fluid in the interdental recesses when it is wound on a pulley and expels it from the same when it is stretched, but for such pump to exert a fairly effective conveying action, it is appropriate that the teeth are trapezoid and one or more semi-cylindrical guides are provided that press against the dorsal part of the belt (which rubs against them), forcing it to fold against the inside so that the trapezoid teeth close one against the other and all fluid is expelled from the interdental recesses wherein it was dragged.

In order to ensure the sealing between drawing environment and delivery environment, the belt teeth necessarily have to rub against the walls of the housing not only on the sides but also on their summit edge; there is also the rubbing against the semi-cylindrical guides; this is a source of frictions and therefore of dissipation of energy. The execution, apparently simple, requires accuracy in the making of the edge of the teeth to ensure sufficient sealing.

The flow rate, other conditions being equal, increases as the ratio between summit and base width of the teeth, but there are geometrical limits to the reduction of such ratio.

A limit of such solution is that the drive belt has a passive role for most of its path, without suction or expulsion of fluid from the interdental spaces.

Another type of toothed-belt volumetric pump is disclosed in patent GB 818091, where a V-belt with toothing on the inner side is present. In this case the interdental recesses take an open configuration, adapted to carry the fluid during the rectilinear motion and a closed configuration, adapted to expel the fluid during the rotary motion about the pulley.

This pump is of very simple execution but has the disadvantage of providing an even more limited flow rate compared to previous pump, due to the necessarily narrow interdental recesses.

Even in such case the drive belt has a passive role for most of its path.

Document FR 555649 describes a chain volumetric pump guided on two toothed wheels; the ring links of the chain are interposed to links composed of pairs of cylinder/piston with the piston sliding but not extractable from the cylinder, defining variable volume compartments. In them, the fluid can be introduced, carried and expelled by the motion of the pistons inside the cylinders, so that such fluid is allowed to communicate exclusively and alternately with the extraction and intake environments of the pump. The variability of volume of the compartments is due to the fact that the links of the chain engage on one of the wheels at a distance from the centre greater than that by which they engage on the second wheel, thereby forcing the links composed of the cylinder/piston pairs to a stretching/shortening thereof.

The mechanics appears very complex and suitable, perhaps, only for lift pumps for wells.

Most types of the pumps just examined have very specific scopes of application, e.g., piston, gear, lobe, vane, external toothed belt pumps are not suitable for pumping fluids with solid particles in suspension; some types of pumps are suitable only for small flow rates or low heads; most of the types of pump requires check valves.

Moreover, the flow rate of most of such pumps is adjustable only by adjusting the rotation speed of the pumping means, as well as the maximum head of such pumps, which can reach harmful values for the integrity of the structure, can be limited only by overpressure relief valves.

The main object of the present finding is to provide a new concept belt-driven volumetric pump that at least partly eliminates the above drawbacks or functional limitations.

More particularly, the object of the present invention is to provide a type of belt- driven volumetric pump executable in a plurality of variants that make it suitable for diverse applications.

Further objects of the present invention are to provide a belt-driven volumetric pump which, depending on the variants, is particularly suitable at high flow rates and/or heads and/or does not require check valves and/or does not require accurate executions to ensure the sealing.

A further object of the present invention is to provide a belt-driven volumetric pump of simple and inexpensive execution.

A further object, achievable according to some variants of the present invention, is to provide a belt-driven volumetric pump with at least partly adjustable flow rate without changing the rotation speed of the belt.

A further object, achievable according to some variants of the present invention, is to provide a belt-driven volumetric pump with maximum head controllable without using overpressure relief valves.

A further object, achievable according to some variants of the present invention, is to provide a belt-driven volumetric pump with substantially uniform flow rate and pressure behaviour.

Further features of the present invention shall be better highlighted by the following description of a main preferred embodiment and preferred variants, in accordance with the patent claims and illustrated in the enclosed drawing tables. Such figures should be considered as having an illustrative and non-limiting purpose, in which:

- Fig. 1 schematically shows, in order to highlight some general geometrical features, a possible shape of the belt-driven volumetric pump according to the invention, viewed according to a direction parallel to the axes of the return pulleys;

- Fig. 2 shows, always according to the same view, a further possible geometrical shape of the pump according to the invention;

- Fig. 3 shows, always according to the same view, a constructive detail of the compartments that pump the fluid according to a possible variant;

- Fig. 4 shows, always according to the same view, a constructive detail of the compartments that pump the fluid according to a further variant;

- Figs. 5. a, 5.b and 5.c show, according to section planes respectively parallel and orthogonal to the axes of rotation of the pulleys, details of possible sealing means;

- Fig. 6 shows, according to a section plane orthogonal to the axis of the pulleys and two overturned sections, constructive details of variants of the channels of withdrawal of the fluid to be pumped and of delivery of the fluid pumped;

- Figs. 7.a and 7.b show, according to section planes respectively orthogonal and parallel to the axes of rotation of the pulleys, details of possible sealing means and variants of the channels of delivery of the fluid pumped;

- Figs. 8. a and 8.b show, according to a section plane orthogonal to the axis of the pulleys, details of possible sealing means and channels of delivery of the fluid pumped, alternative to the previous ones;

- Fig. 9.a shows, according to a section plane orthogonal to the axis of the pulleys and in a plan view, a variant of the pump according to the invention;

- Figs. 9.b, 9.c and 9.d show, according to section planes parallel to the axis of the pulleys, details of the variant of fig. 9. a;

- Fig. 10 shows, in a plan view, a variant of the pump according to Fig. 9.a. All the figures are schematic and not necessarily to scale, having prevalently the purpose of highlighting the geometrical relations among the parts.

It is emphasized that in the following description any spatial terms such as right/left, upper/lower etc. refer to the position of the objects in the figures. "Longitudinal" means a direction extending along the development and forward axis of the drive belt that is part of the invention; "cross" means a direction laying on the belt plane and oblique relative to said longitudinal direction but not necessarily orthogonal thereto. "Internal" to the belt means a place circumscribed by the ring formed by said drive belt.

The features of the finding shall now be described using the reference numerals contained in the figures and with particular relevance to the variants represented therein.

Fig. 1 shows a belt-driven volumetric pump 1 according to the invention, hereinafter referred to as "pump 1".

The pump 1 , provided for pumping a fluid from a drawing environment Amb.in to a delivery environment Amb.out, comprises an endless drive belt 2 (hereinafter simply "belt 2"), at least two drum pulleys 4 (hereinafter simply "pulleys 4"), whereon said belt 2 winds and a housing 5 for supporting said pulleys 4 and for possibly containing said belt 2.

It shall be specified that, while "housing" usually means a box wherein oil bathed mechanical members are confined in a substantially sealed manner, here such term simply means a supporting structure for the mechanical members that shall be described and that, only for certain variants and applications, as it will clearly appear from the description, must be confined in a sealed environment. The belt 2 drags a plurality of compartments 3, each of which is capable of varying its volume V from a maximum value V.max thereof to a minimum value V.min thereof when the portion of belt 2 whereon it is positioned is wound on one of said pulleys 4 and, vice versa, from its minimum value V.min to its maximum value V.max when the portion of belt 2 whereon it is positioned is stretched between two consecutive pulleys 4.

Each of said one or more compartments 3 is placed in connection with the drawing environment Amb.in during the step in which its volume V can increase from its said minimum value V.min to its maximum value V.max, while it is connected with the delivery environment Amb.out during the step in which its volume V can reduce from its maximum value V.max to its minimum value V.min.

According to the invention, each of said one or more compartments 3 has confining walls 3.1, 3.2, 5.1, 3.12 which confine completely each compartment 3, unless communication means 3.6^ 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10 are provided according to many alternatives that shall be shown hereinafter, which allow the said alternating connection with said drawing environment Amb.in and said delivery environment Amb.out.

Many of the reference numbers listed above, as many others later, shall be recalled as the single variants and the corresponding figures are examined.

Two of these confining walls 3.1, 3.2, 5.1, 3.12 consist of as many portions of ventral 3.1 and dorsal 3.2 bands, with reference to the position they occupy on the belt 2, which extend substantially according to the extension surface of the belt 2.

These ventral 3.1 and dorsal 3.2 bands are made of flexible elastic but, subject to a possible variant which shall be later described, substantially inextensible material and are air-tightly jointed to one another at their ends 3.3 at flexible joints 3.4 that extend throughout their width, according to a preferably but not necessarily orthogonal direction (and in any case transversal to the longitudinal direction x of the belt 2).

The median surface 3.7 and 3.8 respectively of the bands 3.1 and 3.2 is indicated, to be understood substantially as the "neutral" surface; that is, that surface not undergoing compression or tension during the expected inflection of the same bands 3.1 and 3.2.

Such ventral 3.1 and dorsal 3.2 bands are at least partly constrained to said drive belt 2; preferably the constraint is at least at the flexible joints 3.4.

The constraint and/or the shape of the ventral 3.1 and dorsal 3.2 bands is such that they are forced to a mutual distancing thereof when the portion of belt 2 whereon the corresponding compartment 3 is positioned is stretched between two consecutive pulleys 4, such distance causing the volume V of compartment 3 to take its maximum value V.max; on the other hand, when the portion of belt 2 whereon compartment 3 is wound on one of said pulleys 4, the ventral 3.1 and dorsal 3.2 bands are forced to a reciprocal approach thereof which cause the volume V of compartment 3 to take its minimum value V.min.

As to the side confining walls 5.1, 3.12 which extend substantially orthogonal to the belt plane 2, of which at least two variants are possible, they have the function of supporting the mutual approaching and distancing movement of the ventral 3.1 and dorsal 3.2 bands.

It is a consequence of all this the fact that each compartment 3 sucks fluid from the drawing environment Amb.in when its volume V increase towards V.max and expels it towards the delivery environment Amb.out when its volume V is forced towards V.min.

Named V.p = V.max - V.min the volume of fluid pumped, that is, actually expelled towards the delivery environment, V.min is the so-called "dead" or "harmful" space that contains the fluid that cannot be pushed downstream of pump 1.

Pumping "effectiveness" Eff is herein referred to as the V.p / V.max ratio; thus the pumping effectiveness Eff = 1 when V.min = 0.

Always with reference to Fig. 1, according to a first basic variant, herein referred to as "with stretched ventral bands 3.1" that is now described, the ventral bands 3.1 are constrained to the belt 2 so as to be forced to stretch when the portion of belt 2 whereon they are constrained is stretched between two consecutive pulleys 4.

Advantageously, in such case, the ventral bands 3.1 can be portions of the belt 2. As to the dorsal bands 3.2, each of them is jointed to the corresponding ventral band 3.1 so that at the flexible joints 3.4 the median surface 3.8 thereof is s far from the median surface 3.7 of the same ventral band 3.1.

As shown for example in Fig. 1, the dorsal bands 3.2 advantageously have longitudinal development greater than that of the corresponding ventral bands 3.1, such development having to be at least sufficient to make possible the winding without the same dorsal bands 3.2 being subject to stretching or the ventral bands 3.1 to crumples (however constructively simpler variants can also allow such developments as to tolerate such stretching or crumples).

During the winding of said belt 2 on each of said pulleys 4, the said approaching between the ventral 3.1 and dorsal 3.2 bands is due to the fact that the ventral bands 3.1 lay on said pulleys 4 and the dorsal bands 3.2 approach the ventral bands 3.1 while, during the stretching of the belt 2 between two consecutive pulleys 4, the portions of ventral 3.1 and dorsal 3.2 bands move away from each other by the fact that the dorsal bands 3.2 take an arched shape with curvature of radius R.a lower than the radius R.p of the pulley 4 by elastic recovery to such shape and/or by inflection for peak load due to the approach of their ends 3.3. It is now useful to make some considerations on the pumping effectiveness of the pump 1, always with reference to Fig. 1 of the theoretical geometrical configuration which, only approximately, represents a possible real situation. In Fig. 1 the ventral and dorsal bands 3.1 and 3.2 are shown of thin thickness, as actually obtainable, for example, using sheets of harmonic steel, sheets of carbon fibre or fabric-reinforced elastomer (for example, the belt known with the brand PowerGrip®), depending on the needs arising from the type of fluid to be pumped and the scope of application of the pump. The thickness of such ventral and dorsal bands 3.1 and 3.2 may be considered negligible for the purposes of the following geometrical considerations.

A compartment 3 is drawn wound on the right pulley 4 with the median surface 3.8 of the dorsal band 3.2 distant by the said constant measure s from the median surface 3.7 of the ventral band 3.1 and, therefore, arranged according to an arc of a circle.

With the symbols used in the figure, where R.p is the radius of the pulley 4 and a is the angular distance between the ends 3.3 of compartment 3, we have:

- length of the arc of a circle consisting in the ventral band 3.1 :

a.i = a · R.p;

- length of the arc of a circle consisting in the dorsal band 3.2:

a.e = a · (R.p + s);

- area of the section of compartment 3 : A.min ~ a.i^■ s.

When the same compartment 3 is positioned on a stretched portion of belt 2, the dorsal band 3.2 theoretically takes the shape of an arc of length a.e, subtended by an angle β, with bending radius R.a and rope of length a.i.

In such a situation, the compartment 3 has a section of total area A.tot constituted by the rectangle having the rope of length a.i. and rib of height s, of area A.r, as its sides, and by the circular segment of radius Ra and width β, of area A.s.

The following plane geometry relations apply (a and β expressed in radians):

- rope length: a · R.p = a.i = 2 · R.a^■ sen( /2)

- arc length: a^■ (R.p + s) = a.e = β · R.a

Given these relationships, using normal mathematical notions, and through attempts, given that we are dealing with transcendental functions, it is possible to calculate R.a and β, the radius R.p of the pulley 4, the angular distance a and the distance s being known.

Obviously a.i = a.e when s = 0.

We still have the following relations.

- area of the circular segment: A.s = β · R.a ² - 1/2 · (a.i · R.a · cos( /2))

- area of the rectangle: A.r = a.i · s

- total area: A.tot = A.s + A.r

If the ventral and dorsal bands 3.1 and 3.2 have equal width L, then:

V.max = A.tot · L; V.min = A.r^■ L

The volume V.p pumped from each compartment 3 as it passes on the pulley 4 is equal to A.s · L, while V.min is the so-called "dead" or "harmful" space that contains the fluid that cannot be pushed downstream of pump 1.

The maximum value of a that allows the entire winding of the ventral band 3.1 on the pulley 4, before it returns to stretch, is π (see Figs. 2, 3, 4) to which, as can be verified, corresponds the maximum value that A.s can take.

With s = R.p / 10 and a = π, A.s is almost twice the section of the pulley 4

(equal to π · R.p²).

At each turn of the pulley 4, the compartments 3 that are pressed against it are 2.π/α; in this case, with a = π, two compartments 3.

Therefore the volume pumped at each pulley 4, for each turn of the same, is equal to 2 · V.p = 2 · A.s · L.

Since the same pulley can have substantially width L, it is interesting to note that, when a = π, at each turn of the pulley 4 the volume pumped V.p, as an order of magnitude, is almost four times the volume of the same pulley 4.

This dimensional feature does not appear attainable with the known pumps and belts.

Coming back to the dead space, as is known, it has negligible effects if the pumped fluid is incompressible; that is, if it is a liquid. On the other hand, it negatively affects the efficiency of the pump (more precisely a compressor, in such case) when the fluid is a gas.

Such dead space V.min, in the assumption taken of distance between ventral and dorsal bands 3.1 and 3.2 that is constant and equal to s when the first is wound on a pulley 4, is annulled only by letting s = 0 (from which A.r = 0) , but this annuls the volume of fluid pumped because also the area A.tot = A.s + A.r reduces to zero.

Apparently, therefore, the harmful space would be ineliminable unless it is slightly reduced assuming that the dorsal band 3.2 comes to touch the ventral band 3.1 in the centre (i.e. at the a/2) when this is wound on the pulley 4 but, as may be simply understood, at the expense of an insignificant value of A.tot because such dorsal band 3.2, when the ventral band 3.1 is stretched, would result in an extremely thin circular segment.

Nevertheless, despite the need to provide, in this variant with stretched bands, that the distance s between dorsal bands 3.2 and ventral bands 3.1 is > 0 at the flexible joints 3.4, the dead space can be substantially annulled by providing (as shown in Figs. 3 and 4) thickenings 3.9 or 3.10 of the ventral band 3.1 and/or of the corresponding dorsal band 3.2; such thickenings 3.9 or 3.10 extending from the median surface 3.7, 3.8 of the one towards the other of said bands 3.1, 3.2 so as to reduce up to substantially annul the dead space V.min.

In the example of Fig. 3 without any limiting intent, such thickening consists in layers 3.9 of material applied to the ventral band 3.1 and the corresponding dorsal band 3.2, respectively, each of thickness s/2 and extending with continuity from one flexible joint 3.4 to the other.

More generally, such two thickening layers 3.9 have thicknesses si and s2 also variable from point to point but such that, in each point, it is always si + s2 < s. This variant of course requires that the thickening material is sufficiently flexible.

On the other end, according to the variant shown in Fig. 4, such thickening consists in two racks 3.10 constructed both on the ventral band 3.1 and on the corresponding dorsal band 3.2, whose teeth 3.101 mutually engage when said ventral and dorsal bands 3.1, 3.2 are wound on pulley 4 (only a portion of said racks 3.10 is drawn in the figure).

This variant ensures flexibility of the bands 3.1, 3.2 and of belt 2 even if the teeth 3.101 were of inflexible material.

Such thickenings 3.9, 3.10 reduce V. MAX, the other conditions being equal, but, by substantially resetting V.min, improve the pumping effectiveness.

Coming to the side confining walls, these may consist in two flat shoulders 5.1 (see Figs. 5. a, 5.b, 7.a and 7.b) mutually enclosing the edges 3.5 of the ventral 3.1 and dorsal 3.2 bands (in such case of equal width L) at least in the portions wherein the volume V of the compartments 3 switches from its maximum value V.max to its minimum value V.min and which are sufficiently close to minimize any fluid leakage.

Optional pressing means (e.g., elastic, hydraulic or pneumatic) symbolized in the drawings by black arrows, can ensure the appropriate approach and avoid seizures in the event of a change in the width L of the ventral 3.1 and dorsal 3.2 bands for wear or thermal expansions.

This type of seal is also suitable at the highest delivery pressures generally provided for the volumetric pumps, making use of materials suitably resistant and stable for the construction of the belt 2 and the ventral 3.1 and dorsal 3.2 bands.

As can be seen in Fig. 5.c, said flat shoulders 5.1 can be combined to seal even to the edges 2.1 of the belt 2, should this not be made up of consecutive ventral bands 3.1 and had width LI different from that L of the ventral and dorsal bands 3.1, 3.2.

If the fluid contained in the drawing environment Amb.in needs to be confined, this is possible by providing that said flat shoulders 5.1 are part of the walls 5.1 of the housing 5, that extend to laterally cover the entire belt 2 and that the hubs 4.1 of the pulleys 4 are keyed on them. In this way the space 5.2 inside the belt 2 is sealed.

In accordance with a second basic variant, herein referred to as "with free ventral bands 3.1", the ventral and dorsal bands 3.1 and 3.2 and the side confining walls 3.12 (see Figs. 9.a to 9.d) constitute a continuum, consisting in as many ventral, dorsal and lateral zones 3.1, 3.2 and 3.12 of the continuous wall of portions of a tubular element 3.11 of flexible material. The compartments 3 are always separated from one another by the flexible joints 3.4 already seen that can be easily obtained with transversal welding of the tubular element 3.11.

It shall be immediately evident that, according to this variant, the distance s between median surfaces 3.5, 3.6 of the ventral and dorsal zones 3.1, 3.2 can be = 0 at the flexible joints 3.4, without this to annul the volume pumped V.p.

According to such variant the compartments 3, when not adhering to a pulley 4, must be free to take a natural shape thereof corresponding to a volume V equal to V.max, by exclusive elastic recovery of any deformation.

In this variant the ventral and dorsal zones 3.1, 3.2 of each compartment 3 have substantially the same longitudinal development and their natural shape is such as to keep them spaced apart from each other when the corresponding compartment 3 is between two pulleys 4.

For this purpose, the tubular element 3.11 is constrained to the belt 2 in such a way that said ventral 3.1, dorsal 3.2 and side 3.12 zones are as much as possible free from tensile stresses exerted by the same belt 2.

Preferably the tubular element 3.11 is therefore constrained to the belt 2 at a side zone 3.12, so that also the ventral zones 3.1 can assume an arched shape inwards of the belt 2, non subject to driving.

Preferably the constraint between the belt 2 and the tubular element 3.11 is only at the flexible joints 3.4.

Preferably a further belt 2 is provided, placed at the other side zone 3.12.

Advantageously, the pulleys 4 have a barrel shape (see Fig. 9.d) so that, when a compartment 3 is dragged on a pulley 4, the corresponding tubular element 3.11 can squeeze on it completely. As a consequence V.min = 0.

The variant "with free ventral bands 3.1 " has the advantage of a great constructive simplicity but has limitations of use due to the maximum thermal and mechanical stresses of the suitable elastomeric materials.

The variant "with stretched ventral bands 3.1" may, instead, envisage the use of materials with higher mechanical and physical characteristics.

From the operating principles standpoint it can be substantially said that, in the variant "with stretched ventral bands 3.1 ", the pumping effect is due to the fact that the dorsal bands 3.2 are pulled to approach the corresponding ventral bands 3.1 during the winding on the pulley 4 of cylindrical surface; whereas in the variant "with free ventral bands 3.1 " the ventral zones 3.1 are pushed towards the dorsal bands 3.2 by virtue of the barrel shape of the pulley 4.

Coming now to the communication means 3.6, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10 for the suction and expulsion of the fluid, also for them the pump 1 according to the invention envisages many possible variants, illustrated in Figs. 5 to 8.

According to a possible variant when the space 5.2 inside the belt 2 coincides with the drawing environment Amb.in (see Figs. 5. a to 5.c), said communication means 3.6, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10 comprise a through hole 3.6 made on said ventral band 3.1 in the proximity of the front end 3.3, where front means the end 3.3 that reaches a pulley 4 first during the feeding of the belt 2.

Through such hole 3.6, the fluid is sucked from the drawing environment Amb.in starting from the moment in which, as the ventral band 3.1 leaves a pulley 4, the corresponding compartment 3 begins to increase its volume V towards V.max.

As for the expulsion of the fluid towards the delivery environment Amb.out, this, in turn, can be obtained according to a number of sub-variants, all having in common the fact that the delivery environment Amb.out coincides with the cavity 4.2 which:

- is located inside each pulley 4;

- is put into communication with the downstream system (not shown) through at least one duct 4.3 made through at least one of the hubs 4.1 of the pulleys 4; - is capable of being put into communication, also, with the compartments 3 through channels 4.4 extending from it up to the surface of the pulley 4 where they come to communicate with the holes 3.6;

- is provided with sealing means 4.6 (see Fig. 5.b) or 4.7 (see Fig. 7.a) or 4.8 (see Fig. 8. a), which prevent the return of the fluid towards the drawing environment Amb.in.

These channels 4.4 (see Fig. 5.b) may be arranged radially at an angular distance γ equal to a so that each hole 3.6 faces one of the channels 4.4 when the corresponding compartment 3 reaches the pulley 4.

This requires two conditions:

- the angle α = γ must be a sub-multiple of the round angle; this implies that the length a.i. of the ventral bands 3.1 is a sub-multiple of the circumference of the pulley 4;

- any sliding of the belt 2 with respect to the pulley 4 must be prevented so as not to produce, during rolling of the belt 2, an offset between each channel

4.4 and the corresponding hole 3.6; this is resolved for example by providing a rack on the belt 2, which engages on a toothed wheel associated with the pulley 4.

These channels 4.4 may alternatively be arranged in any angular position provided that they ensure the said communication with the holes 3.6 for example:

- or because sufficiently thick and/or of sufficiently wide section to ensure that at least one of them faces a hole 3.6 (see Fig.7.a),

- or because they lead to a groove 4.5 made on the external surface of each pulley 4, whereon, in turn, said holes 3.6 face to (see Fig. 8.b).

As for the sealing means 4.6 or 4.7 or 4.8, even here many alternatives are possible; for example:

- each channel 4.4 (see Fig. 5.b) is provided with a check valve 4.6 (for example with elastic sheets) at its outlet point towards the cavity 4.2 of the pulley 4; - the inner surface 4.9 of the pulley 4 (see Figs. 7.a and 7.b) is a cylindrical surface 4.9 coupled to seal with a pin 4.7 which closes the outlet of the channels 4.4 at least when their inlet loses contact with the ventral bands 3.1, while has recesses 4.10 communicating with said cavity 4.2 and with the outlet of the channels 4.4, leaving it free when the inlet of the same channels

4.4 is in contact with the holes 3.6;

- each channel 4.4 (see Fig. 8.a) is closed, at its inlet point on the external surface 4.11 of the pulley 4.2 and when loses contact with the corresponding hole 3.6, due to the fact that said external surface 4.11 is coupled to seal with a cradle 4.8 which extends angularly substantially throughout the portion of said external surface 4.10, which is free from the belt 2, and by such at least a width as to cover said channels 4.4.

The communication means 3.6, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10 are provided with through holes 3.6 at the ventral bands 3.1 and all require retaining means 4.6 or 4.7 or 4.8 inside pump 1.

According to a variant, possible when the side confining walls consist of the two flat shoulders 5.1, said communication means 3.6, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10 can be avoided, with considerable construction simplification, by providing the inlet and the outlet of the fluid from each compartment 3 through passages 5.3, 5.4 (see Fig. 6) made on the same flat shoulders 5.1 and capable of being put into communication with said compartments 3.

More precisely, there may be provided,

- for the expulsion of the fluid, outlet passages 5.4 on the flat shoulders 5.1 positioned and shaped so as to create a communication exclusively between delivery environment Amb.out and compartments 3 and with which each compartment 3 comes to communicate only when it reaches the inlet position in a pulley 4 (i.e. the position where compartment 3 begins to compress); preferably such outlet passages 5.4 have axis directed as much as possible according to the longitudinal direction x of the belt 2;

- possibly, for the suction of the fluid, inlet passages 5.3 always on the flat shoulders 5.1 positioned and shaped so as to create a communication exclusively between drawing environment Amb.in and compartments 3 and with which each compartment 3 comes to communicate only when it reaches the outlet position from a pulley 4 (i.e. the position where compartment 3 begins to expand); the drawing environment Amb.in may coincide with the space 5.2 inside the belt 2 and such inlet passages 5.3 are notches on the flat shoulders 5.1 which extend from the space 5.2 to compartments 3, allowing the fluid to bypass the edges 3.5 of the ventral bands 3.1.

Combinations are possible between communication means 3.6, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10 which provide the said through holes 3.6 and the said inlet or outlet passages 5.3, 5.4.

For example the fluid may be sucked through the through-holes 3.6 on the ventral bands 3.1 and expelled through the outlet passages 5.4 on the flat shoulders 5.1, whereas the through holes 3.6 are closed when they lay on the pulleys 4 which, in such case, may be without channels 4.4.

Providing outlet passages 5.4 with axis, as said, directed as much as possible according to the longitudinal direction x of the belt 2, rather than in the radial direction to the pulleys 4 through the channels 4.4, improves the efficiency of the pump 1 because it recovers good part of the kinetic energy of the fluid, instead of dissipating it, transforming it into dynamic pressure.

Many other variants of the belt-driven pump 1 are possible without departing from the scope of the invention.

For example in order to limit the maximum delivery pressure that, otherwise, in the pump 1 of the invention (as well as in most volumetric pumps) can reach values adversely high and destructive when the fluid pumped is a liquid, the dorsal bands 3.2, which up to now have been assumed of substantially inextensible material, may instead be made of materials that allow a predetermined elastic extensibility such that, when the same dorsal bands 3.2 winds on a pulley 4, they extend by the effect of the pressure increasing the volume V of compartment 3 and consequently limit the increase of the same pressure.

According to another possible variant, (see Fig. 9. a) the expansion of each compartment 3 may be limited to volumes V < V.max. This allows at least in part a regulation of the flow rate, the rotation speed of the pulleys 4 being equal. To this end, for example the compartments 3 may pass between guiding means 5.6, when they are in the zones between two subsequent pulleys 4. Such guiding means 5.6 are shiftable in a direction orthogonal to the plane of the belt 2 and can adjustably press against the back of the dorsal bands 3.2 and, possibly, the back of the ventral bands 3.1, so as to regulate the expansion of the compartments 3.

This variant, illustrated with reference to the version of the invention "with free ventral bands 3.1 " is obviously applicable also to the variant "with stretched ventral bands 3.1 " limited to the back of the dorsal bands 3.2.

One last possibility offered by the pump 1 according to the invention is that of limiting the pulsating behaviour of the flow rate towards the delivery environment Amb.out.

It should be noted that each compartment 3 expels the fluid contained towards the delivery environment Amb.out during an expulsion step with variable flow rate with continuity from zero to a maximum and vice versa. The expulsion step, of duration At, begins substantially when the ventral band 3.1 of such compartment 3 begins to wind on a pulley 4, reaches the maximum when this ventral band 3.1 has wound by half on the same pulley 4 up to be annulled once the ventral band 3.1 is completely wound; the duration At of such step is that taken by the pulley 4 to rotate by the angular distance a.

The pulsating behaviour of the overall flow rate due to a plurality of compartments 3, may be reduced by ensuring that each compartment 3 is positioned and/or shaped so as to begin the expulsion step thereof with an offset, with respect to the expulsion step of another compartment 3, equal to a fraction of the duration of step At; in other words, by ensuring that each compartment 3 begins its expulsion step before at least another compartment 3 ends its. A first method to achieve this is to ensure that two or more compartments 3 reach corresponding two or more pulleys 4 at instants of time that are offset to each other by a fraction of the duration of expulsion step At.

In general, if the pump 1 provides for the belt 2 to wind on a number p of pulleys 4, each one is reached by a corresponding compartment 3 with a delay of Δΐ/ρ with respect to a previous pulley 4.

A second method (see Fig. 10) to achieve the attenuation of the pulsating behaviour of the flow rate is that the flexible joints 3.4 extend throughout their width according to a direction sufficiently oblique relative to the longitudinal direction x of the belt 2, so as to ensure that the expulsion step of any one compartment 3 begins before that of the previous compartment 3 has ended on the same pulley 4. In the example of Figure 10, the obliqueness is such that each flexible joint 3.4 ends, on one side, at a point 3.41 where the next flexible joint 3.4 begins.

The rolling-up of the compartments 3 about a pulley 4 according to such embodiment is practically possible provided that at least the dorsal bands 3.2 (if not also the ventral bands 3.1) have sufficient elastic flexibility and the width L of the compartments 3 is of the same order of magnitude of the longitudinal distance between two consecutive flexible joints 3.4.

Even such variant, illustrated with reference to the version of the invention "with free ventral bands 3.1 ", is obviously applicable also to the variant "with stretched ventral bands 3.1 ".

A third method to achieve the attenuation of the pulsating behaviour of the flow rate is at least that of combining the described first and second method.

From the foregoing, it appears clear that the pulleys 4 between which the belt 2 is returned can advantageously be more than two.

It is also clear that the compartments 3 may be not uniformly distributed along the belt 2, in order to meet particular requirements.

Numerous variants of the volumetric pump 1 described above are possible to the man in the art, without departing from the novelty scopes of the inventive idea, as well as it is clear that in the practical embodiment of the invention the various components described above may be replaced with technically equivalent ones: with the present invention a wide range of types of volumetric pumps 1 may be achieved, applicable to a multitude of sectors, from the recreational/educational (wherein low operating pressures and low rotation speeds can be provided) up to the engineering one, where the pressures involved and rotation speeds takes very high values (even over 100 bars and over 30,000 rpm).

Claims

Belt-driven volumetric pump (1) for pumping a liquid or gaseous fluid from a drawing environment (Amb.in) to a delivery environment (Amb.out), comprising:

- a drive belt (2) dragging one or more compartments (3), each capable of changing its volume (V; V.min, V.max) from its minimum value (V.min) to its maximum value (V.max),

- at least two pulleys (4) whereon said drive belt (2) winds,

- a housing (5) for supporting said pulleys (4) and for possibly containing said belt (2),

where each of said one or more compartments (3):

- is constrained to said drive belt (2),

- is connected, through suitable communication means (3.6, 4.4, 4.5, 4.10; 5.3, 5.4) to said drawing environment (Amb.in) during the step in which its said volume (V; V.min, V.max) increases from its said minimum value (V.min) to its said maximum value (V.max), while it is connected to said delivery environment (Amb.out) during the step in which its volume (V; V.min, V.max) reduces from said its maximum value (V.max) to said its minimum value (V.min),

- is capable of expanding up to said maximum value (V.max) in the portions wherein said drive belt (2) is stretched out,

- is forced to move to said minimum value (V.min) in the portions wherein said drive belt (2) is wound on each of said pulleys (4), characterised in that

each of said one or more compartments has inner (3), outer (3.2) and side (5,1; 3.12) confining walls allowing it to communicate exclusively and alternatively with said drawing and delivery environments (Amb.in, Amb.out),

said inner (3.1) and outer (3.2) confining walls consisting respectively in ventral (3.1) and dorsal (3.2) bands:

- made of elastically flexible material,

- jointed to one another at their ends (3.3) at flexible joints (3.4) extending throughout the width of said ventral (3.1) and dorsal (3.2) bands in cross direction relative to said belt (2),

- at least partly constrained to said drive belt (2),

wherein, during the winding of said belt (2) on each of said pulleys (4), said ventral (3.1) and dorsal (3.2) bands are forced to approach reciprocally up to mutually delimiting a volume equal to said minimum value (V.min) while, during the stretching of said belt (2) between two consecutive of said pulleys (4), said ventral (3.1) and dorsal (3.2) bands are forced to a reciprocal distancing thereof up to delimiting a volume equal to said maximum value (V.max), while said side confining walls (5.1 ; 3.12) are capable of supporting said approaching and distancing movement of said ventral (3.1) and dorsal bands (3.2).

Volumetric pump (1) according to the previous claim,

characterised in that

- said ventral bands (3.1) are constrained to said belt (2) so as to be forced to stretch when the portion of said belt (2) whereon they are constrained is stretched out between two consecutive of said pulleys (4),

- said dorsal bands (3.2) are jointed to the corresponding of said ventral bands (3.1) so that at said flexible joints (3.4) the median surface (3.8) thereof is s > 0 far from the median surface (3.7) of said corresponding ventral band (3.1).

Volumetric pump (1) according to the previous claim,

characterised in that

said ventral bands (3.1) are portions of said belt (2).

Volumetric pump (1) according to the previous claim, characterised in that

said dorsal bands (3.2) have longitudinal development at least sufficiently greater than that of said corresponding ventral bands (3.1), so as to make it possible their winding on said pulleys (4) without producing their stretching or forming crumples of said corresponding ventral bands (3.1).

Volumetric pump (1) according to any claim from 2 onwards, characterised in that

thickenings (3.9, 3.10) respectively of said ventral bands (3.1) and/or of said corresponding dorsal bands (3.2) are provided,

- extending from said median surfaces (3.7, 3.8) of the one towards the other of said bands (3.1, 3.2),

- and have respectively constant or variable thicknesses si and s2 such that, in each point it is si + s2 < s.

Volumetric pump (1) according to claim 5,

characterised in that

said thickenings (3.9, 3.10) consist in layers of flexible material having constant thickness si and s2.

Volumetric pump (1) according to claim 5,

characterised in that

said thickenings (3.9; 3.10) consist in two racks (3.10):

- constructed on said ventral bands (3.1) and on the corresponding dorsal bands (3.2),

- and whose teeth (3.101) mutually engage when said ventral bands (3.1) and corresponding dorsal bands (3.2) are wound on said pulley (4).

Volumetric pump (1) according to any previous claim,

characterised in that

- said ventral (3.1) and dorsal (3.2) bands have equal width L,

- said side confining walls (5.1; 3.12) consist in two flat shoulders (5.1) mutually enclosing the edges (3.5) of said ventral (3.1) and dorsal (3.2) bands as well as the edges (2.1) of said belt (2), at least in the portions wherein the said volume (V; V.min, V.max) switches from its said maximum value (V.max), to its said minimum value (V.min),

- said flat shoulders (5.1) being sufficiently close to said edges (3.5, 2.1) to minimize any fluid leakage from said compartments (3).

Volumetric pump (1) according to the previous claim,

characterised in that

said flat shoulders (5.1)

- are part of the walls (5.1 ) of said housing (5),

- extend to laterally cover the entire said belt (2)

- have hubs (4.1) of said pulleys (4) keyed thereon.

Volumetric pump (1) according to the previous claim,

characterised in that

pressing means ensure the appropriate approach of said flat shoulders (5.1) against said edges (3.5, 2.1) of said ventral (3.1), dorsal (3.2) bands and belt (2).

Volumetric pump (1) according to claim 1,

characterised in that

- said ventral and dorsal bands (3.1, 3.2) and said side confining walls (5.1, 3.12) make up the ventral (3.1), dorsal (3.2) and side (3.12) zones of the continuous wall (3.1, 3.2, 3.12) of a tubular element (3.11) of flexible material,

- said ventral and dorsal bands (3.1, 3.2) have substantially the same longitudinal development,

- said compartments (3), when not adhering to a pulley (4), are free to take a natural shape corresponding to a volume (V) equal to said maximum value (V.max), by exclusive elastic recovery of any deformation, - said tubular element (3.11) being constrained to said belt (2) so as to allow said compartments (3) for said expansion up to said volume (V) equal to said maximum value (V.max).

Volumetric pump (1) according to the previous claim,

characterised in that

said tubular element (3.1 1) is constrained to said belt (2) at one of said side zones (3.12).

Volumetric pump (1) according to the previous claim,

characterised in that

said constraint is only at said flexible joints (3.4).

Volumetric pump (1) according to claims 1 1 or 12,

characterised in that

a further belt (2) is provided, constrained at the other side zone (3.12).

Volumetric pump (1) according to any claim from 10 onwards, characterised in that

said pulleys (4) have a barrel shape.

Volumetric pump (1) according to any previous claim,

characterised in that

- the space (5.2) inside said belts (2) coincides with said drawing environment (Amb.in),

- the communication means (3.6, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10) comprise a through hole (3.6) made on said ventral bands (3.1) in the proximity of their front end (3.3).

Volumetric pump (1) according to any previous claim,

characterised in that

said delivery environment (Amb.out) coincides with a cavity (4.2) which:

- is located inside each of said pulleys (4),

- is put into communication with the downstream system through at least one duct (4.3) made through at least one of the hubs (4.1) of said pulleys (4),

- is capable of being put into communication with said compartments (3) through channels (4.4) extending from said cavity (4.2) up to the surface of each of said pulleys (4) where they communicate with said holes (3.6),

- is fitted with sealing means (4.6; 4.7; 4.8) which prevent the return of fluid towards the drawing environment (Amb.in).

Volumetric pump (1) according to claim 16,

characterised in that

- said channels (4.4) are arranged radially at an angular distance γ equal to the angular distance a of said holes (3.6), so that each of the latter faces one of said channels (4.4) when the corresponding compartment (3) reaches one of said pulleys (4),

- said a is a submultiple of a round angle,

- any sliding of said belts (2) relative to said pulleys (4) is prevented.

Volumetric pump (1) according to claim 16,

characterised in that

said channels (4.4) ensure said communication with said holes (3.6) due to the fact that they are sufficiently thick and/or of sufficiently wide section to ensure that at least one of them faces one of said holes (3.6).

Volumetric pump according to claim 16,

characterised in that

said channels (4.4) ensure said communication with said holes (3.6) due to the fact that they lead to a groove (4.5) on the external surface of each of said pulleys (4), whereon, in turn, said holes (3.6) face to. Volumetric pump (1) according to any claim from 16 onwards, characterised in that

said sealing means (4.6; 4.7; 4.8) consist of check valves (4.6) provided at the outlet point of said channels (4.4) towards said cavity (4.2).

Volumetric pump (1) according to any one of claims 16 to 19, characterised in that

said sealing means (4.6; 4.7; 4.8) are provided with a pin (4.7) which

- is coupled to seal with the cylindrical inner surface (4.9) of said pulleys (4),

- closes the outlet of said channels (4.4) at least when their inlet loses contact with said ventral bands (3.1),

- has recesses (4.10) communicating with said cavity (4.2) and with the outlet of said channels (4.4), leaving said cavity (4.2) free when the inlet of the same channels (4.4) is in contact with said holes (3.6).

said sealing means (4.6; 4.7; 4.8) are provided with a cradle (4.8) which is coupled to seal substantially with the whole portion of the outer surface (4.11) of said pulley (4) free from the belt (2) and with at least a width such that to cover said channels (4.4).

Volumetric pump (1) according to at least claim 8,

characterised in that,

for the expulsion of the fluid from said compartments (3) to said delivery environment (Amb.out), outlet passages (5.4) are provided on said flat shoulders (5.1) positioned and shaped so as to create a communication only between said delivery environment (Amb.out) and said compartments (3) and only when they reach the inlet position in one of said pulleys (4).

Volumetric pump (1) according to the previous claim,

characterised in that

said outlet passages (5.4) have the axis directed as much as possible according to the longitudinal direction (x) of said belt (2).

Volumetric pump (1) according to at least claim 8,

characterised in that

for the suctions of the fluid by said compartments (3), inlet passages (5.3) are provided on said flat shoulders (5.1) positioned and shaped so as to create a communication only between said drawing environment (Amb.in) and said compartments (3) and only when they reach the outlet position from one of said pulleys (4).

Volumetric pump (1) according to the previous claim,

characterised in that

- said drawing environment (Amb.in) coincides with said space (5.2) inside said belt (2),

- and said inlet passages (5.3) are notches (5.3) on said flat shoulders (5.1), said notches (5.3) extending from said space (5.2) to said compartments (3).

Volumetric pump (1) according to any previous claim,

characterised in that

said dorsal bands (3.2) are made of a substantially inextensible material.

Volumetric pump (1) according to any previous claim, 27 excluded, characterised in that,

said dorsal bands (3.2) are made of a material having a sufficient elastic extensibility to limit the increase of pressure in said compartments (3) to predetermined values when winding on said pulleys (4).

Volumetric pump (1) according to any previous claim,

characterised in that

means (5.6) adjustably limit the expansion of said compartments (3) to volumes V < V.max when said compartments (3) are in the zones between two subsequent of said pulleys (4). Volumetric pump (1) according to any previous claim,

characterised in that

each of said compartments (3) is positioned and/or shaped so as to begin its expulsion step before at least another one of said compartments (3) ends its.

Volumetric pump (1) according to the previous claim,

characterised in that

two or more compartments (3) reach corresponding two or more of said pulleys (4) at instants of time that are offset to each other by a fraction lasting At of an expulsion step.

Volumetric pump (1) according to any claim from 30 onwards, characterised in that

said flexible joints (3.4) extend throughout their width according to a sufficiently oblique direction relative to said longitudinal direction (x) of said belt(s) (2), so as to ensure that said expulsion step of any one of said compartments (3) begins before that of the previous one of said compartments (3) on the same pulley (4) ends.

Volumetric pump (1) according to any previous claim, excluding 32, characterised in that

said flexible joints (3.4) extend throughout their width according to an orthogonal direction relative to said longitudinal direction (x) of said belt(s) (2).