TECHNICAL FIELD

The present invention relates to the field of pumps, in particular multi-cylinder piston pumps, i.e. comprising a plurality of pumping chambers, and equipped with automatic delivery and suction valves.

PRIOR ART

Various types of piston and multi-cylinder liquid pumps are known, such as reciprocating pumps and inclined-plate pumps in which the flow direction is controlled by automatic suction and delivery valves (essentially shaped like non-return valves).

In particular, such pumps comprise a head in which a plurality of pumping chambers are realised, the volume of which is varied by a respective pumping element, e.g. a piston. These pump chambers are in fluid communication with a suction conduit and a delivery conduit along which there is a suction valve and a delivery valve, respectively.

The suction and delivery valves are inserted in special housing seats which are at least partly made as holes starting from an outer surface of the head, in which they create an inlet opening through which the respective valve is inserted into the housing seat itself during installation or maintenance of the pump.

In particular, each housing seat comprises an abutment surface made available by a restricted portion of the hole, in an internal portion of the head and therefore downstream of the inlet opening. The valve is held in place in the seat by clamping it between said abutment surface and a plug inserted, in particular screwed, into the inlet opening.

Therefore, female threads must be made in the housing seats to accommodate plugs with a corresponding male thread.

Since this process of making threads in plugs and inlet openings lengthens production time and complicates the design, it is desirable to eliminate or at least reduce the need for plugs to be screwed into the head to hold the valves in place.

The aim of the present invention, therefore, is to at least reduce the use of such threaded plugs, within the scope of a rational and contained cost solution. The dependent claims outline preferred and/or particularly advantageous aspects of the invention.

DISCLOSURE OF THE INVENTION

In particular, the invention makes available a pump for pumping liquid comprising:

- a head in which a plurality of pumping chambers is realised, - a plurality of suction valves and a plurality of delivery valves, of the automatic oneway type, each housed in a respective housing seat realised in the head, wherein at least two housing seats are each at least partially realised in the head as a hole starting from an outer surface of the head, in which outer surface it realises an inlet opening, and which comprises a restricted section realised within the head, which restricted section makes available an abutment surface facing the inlet opening and on which the respective valve rests, said pump being characterised in that it comprises a cover fixed to the head and which closes at least said two inlet openings by tightening the suction and/or delivery valves present in the housing seats of the corresponding inlet openings closed by the cover, between the respective abutment surface and the cover itself.

In this way it is possible to hold a plurality of valves in place by means of the single cover instead of having to screw in a plug for each valve, which is both more time-consuming during assembly and more time-consuming during the machining of the head, as it is necessary to create a female thread at all the inlet openings.

According to one aspect of the invention, the cover may be made of a polymer material. This makes its production particularly fast and economical.

According to another aspect of the invention, the polymer material of the cover may comprise a polymer belonging to the polyamide family in a percentage between 30% and 70% and glass fibre in a percentage between 30% and 70%.

If the cover is made of polymer material, the pump may comprise a stiffening plate placed inside the cover.

In this way it is possible to increase the strength of a cover made mainly of polymer material anyway (more than half of the volume of the cover is made of polymer material). Preferably, the cover and stiffening plate are made by co-moulding.

In this way, the cover with stiffening bar is made in a single operation, therefore quickly, without the need to glue or weld the plate to the cover in subsequent operations.

According to a further aspect of the invention, the pump may comprise a casing in contact with the head on a side thereof opposite the cover and a plurality of fastening screws adapted to fasten the cover and the head to the casing, each of said fastening screws being provided with a shank inserted in a through manner into the cover and the head, and being provided with a threaded portion screwed into a threaded hole made in the casing.

In this way the cover is fastened with screws that would already be required to fasten the head to the casing.

In order to improve the distribution of the clamping force of the screws, the screws may also pass through a portion of the stiffening plate, creating a through hole therein.

According to yet another aspect of the invention, the head may comprise a face facing the cover provided with a flat surface in which all the inlet openings of the suction valve housing seats are realised and wherein the cover comprises a face facing the head provided with a flat surface in direct contact with the flat surface of said head face and which closes all the inlet openings realised in said head face.

The invention may further provide that between the cover and the respective valves whose inlet openings are closed by the cover there may be a spacer crossed by a delivery or suction conduit.

Preferably, the pump according to the invention is one between a multi-cylinder inclined- plate piston pump and a multi-cylinder reciprocating piston pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will be more apparent after reading the following description provided by way of a non-limiting example, with the aid of the accompanying drawings.

Figure 1 is an axonometric view of a pump according to the invention.

Figure 2 is a front view of the pump of Figure 1 .

Figure 3 is a section view according to the plane Ill-Ill of Figure 2.

Figure 4 is a section view of another embodiment of a pump according to the invention.

BEST MODE TO IMPLEMENT THE INVENTION

With particular reference to these figures, two different embodiments of high-pressure pumps according to the invention have been collectively referred to as 1 and 1 ', in particular the type with several pumping chambers 5,5', preferably adapted for pumping low- viscosity liquids, such as water.

In detail, the pump identified with 1 is an axial inclined-plate pump, e.g. provided with a rotating plate with a fixed inclination and with the cylinders fastened in relation to the casing, as will be explained in more detail below.

The pump marked 1 ' is an alternative pump to pistons, e.g. in-line. The pumps are therefore both piston pumps with multiple pumping chambers, i.e. multicylinder. When it is not necessary to differentiate between them, they will simply be referred to as “pump” or “pump 1 ,1 ' “.

Furthermore, although pumps 1 and 1 ' are piston pumps, it cannot be excluded that the object of the present invention can also be applied to diaphragm pumps.

Both pumps 1 and 1 ' are provided with automatic one-way valves, delivery and suction, to regulate the pumping flow.

The pump 1 , T comprises a casing 10,10’ which contains a mechanism for operating a plurality of pumping bodies (one for each pumping chamber 5,5’) adapted to vary the volume of the respective pumping chamber 5,5’. In the illustrated embodiment, the pumping bodies are pistons, 15 for pump 1 and 15' for pump 1 ', however, it is not excluded that the inventive concept underlying the present invention may be applied to a diaphragm pump, in which the pumping bodies are flexible membranes.

In both embodiments, the casing 10,10’ comprises a plurality of guiding cylinders 20,20', one for each piston, each adapted to guide the respective piston 15,15' along a rectilinear sliding axis in order to perform the volume variation of the pumping chamber 5,5’. In particular, each guide cylinder comprises a cylindrical internal surface, e.g. made available by a bushing, which accommodates the respective piston 15,15’ (i.e. the cylindrical lateral surface of the respective piston 15,15’) slidingly to size.

The sliding axes of the pistons 15,15’ are all parallel to one other.

The operating mechanism of the pump 1 comprises a rotating inclined plate 25, adapted to receive a rotary motion from a drive shaft external to the pump itself. The inclined plate 25 is housed in the casing 10, is rotatably associated with the casing 10 with respect to an axis of rotation X (parallel to the sliding axes of the pistons 15), and for example it comprises a flat annular surface lying on an inclined plane with respect to the axis of rotation X. In particular, the inclined plate 25 is rotatably associated by a bearing with the flange 30 rigidly fixed, for example bolted, to the casing 10.

By means of said flange it is possible to fasten the casing 10 to a motor or to a frame with respect to which the external drive shaft is rotatably associated.

Each piston 15 comprises an axial end distal from the pumping chamber 5 which is maintained in contact, by the force exerted by a respective elastic element 35 for each piston 15, on the inclined plate 25, or, as in the illustrated embodiment, on an annular guide resting on the annular flat surface of the inclined plate 25, for example by the interposition of an axial roller bearing.

Each elastic element 35 has a first end connected to the casing 10 and a second end connected to the piston 15.

The axial end of the piston distal from the pumping chamber 5 may have a convex rounded shape and the annular guide may have a flat annular surface parallel to the flat annular surface of the plate.

As a result of the rotation of the inclined plate 25 (and the thrust exerted by the elastic element) the pistons 15 are made to slide along their respective sliding axes between an upper dead centre position, in which the volume of the pumping chamber 5 is minimum, and a bottom dead centre position, in which the volume of the pumping chamber 5 is maximum.

On the other hand, the operating mechanism of the pump 1 ’ comprises a shaft 40’ pivotally associated with the casing 10,10’ according to an axis of rotation Y (perpendicular to the sliding axis of the pistons 15’) and to which a plurality of cranks 45’ are fitted, to each of which, according to a hinge axis parallel to the axis of rotation, an axial end is hinged (distal to the pumping chamber 5) of a respective piston 15’. The operating mechanism is thus substantially a connecting rod-crank mechanism, wherein the piston 15’ is the connecting rod, the rotation of the crank causes the piston 15’ to move between a bottom dead centre position, wherein the volume of the pumping chamber 5’ is maximum, and an upper dead centre position, wherein the volume of the pumping chamber 5’ is minimum.

The pump 1 ,1 ’ comprises a head 50,50’, e.g. monolithic, fastened to the casing 10,10’ and in which the plurality of pumping chambers 5,5’ of the liquid to be pumped is realised, said chambers being made available by respective (through) holes made in the head 50,50’.

It should be noted that a monolithic body is defined as a body obtained from the solidification of a single casting or injection of material in a mould and its possible subsequent machining by removal of material.

In the preferred embodiment, the head 50,50’ is made of a polymer material, such to make the pump light, economic and quick to be manufactured.

It is not however excluded that in an embodiment not shown, the head portion 50,50’ in which the pumping chambers 5,5’ are obtained is formed by several monolithic parts made of a polymer material, fastened to one other.

At least the portion of the head 50,50’ where the cylinder is realised, i.e. where the holes are made, is made as a monolithic body.

There are preferably at least three pumping chambers.

The head 50,50’ comprises a first major face 55,55’ facing the casing 10,10’, a second major face 60,60’ facing in the opposite direction and a lateral surface 65,65’ joining the first major face to the second major face.

The first major face 55,55’ is flat and for example perpendicular to the sliding axes of the pistons. The second major face 60,60’ is also flat and, for example, perpendicular to the sliding axes of the pistons.

The lateral surface is substantially a tubular surface within which the sliding axes of the pistons are contained.

The first major face 55,55’ is in direct contact with a (flat) face of the casing 10,10’ facing the head 50,50’. In such face of the casing 10,10’ there are openings which reach the guide cylinders 20,20’ and which are crossed by the respective pistons.

In the illustrated embodiment, the head 50,50’ comprises a plurality of circular rectilinear holes (circular cross-sectional rectilinear holes) equal in number to the pumping chambers and each defining at least partially a volume of a respective pumping chamber 5,5’ of the liquid, so for example each coaxial to the sliding axis of the respective piston 15,15’ (i.e. of the guide cylinder).

The circular rectilinear holes therefore have at least one section characterised by a cylindrical inner surface forming part of the respective pumping chamber 5,5’ and within which a portion of the corresponding piston 15,15’ is accommodated.

There are more than three circular rectilinear holes, i.e. at least four, preferably there are five, and they are arranged with their respective central axes parallel to one other.

In particular, in the embodiment illustrated, the circular rectilinear holes are each made as a through hole which extends from the first face to the second face, forming a first opening 70,70’ in the first major face and a second opening 75,75’ in the second major face.

In further detail, each circular rectilinear hole comprises (i.e. is partly defined by) a tubular surface (having a cylindrical cross-section) extending from the second opening towards the inside of the head 50,50’ and terminating, downstream of said second opening towards the inside of the head 50,50’, in a portion having a restricted cross-section (i.e. identifying a residual passage section having a diameter smaller than a diameter of the second opening) or in other words having a funnel-shaped cross-section or in other words forming a step. This restricted portion comprises an (annular) abutment surface 80,80’ facing the second opening itself and coaxial to the second opening (also coaxial to the sliding axis of the respective cylinder in the illustrated embodiment).

In the illustrated embodiment, the abutment surface 80,80’ is a truncated cone shaped surface with concavity facing the second opening 75,75’, however it could also be conformed as a circular crown perpendicular to the sliding axis of the respective piston 15,15’. From the restricted portion, the cylindrical inner surface 85,85’ is derived and flows into the first opening 70,75’. In the embodiment illustrated, the diameter of the cylindrical internal surface is the minimum diameter of the restricted section, however, it is not excluded that in embodiments not illustrated such diameter of the cylindrical internal surface may be larger or smaller.

The pump 1 , 1 ’ comprises a plurality of annular gaskets adapted to circumferentially seal- ingly embrace the piston 15,15’, i.e. each piston 15,15’, to prevent pumping liquid leakages from the pumping chamber 5,5’ towards the casing 10,10’ through the first opening. In particular, the pump 1 , 1 ’ comprises a high-pressure gasket, housed in the head 50,50’, and a low-pressure gasket, housed in the casing 10,10’. In particular, they are housed in an annular body 90 partly contained in a seat realised in the head 50,50' and partly in a seat realised in the casing 10,10’. Due to the seat in the head 50,50’, in the illustrated embodiment the cylindrical inner surface does not reach up to the first opening, an enlarged portion, i.e. an annular groove, extends from the cylindrical inner surface, which makes the seat available for the annular housing body of the gaskets and defines the first opening.

The pump 1 ,1 ’ includes a plurality of suction valves 95, one for each pumping chamber 5,5’, and a plurality of delivery valves 100, one for each pumping chamber 5,5’.

These valves are of the automatic one-way (non-return) type and allow the direction of flow to and from the respective pumping chamber 5,5’ to be defined. In particular the suction valve 95 allows the flow only to the pumping chamber 5,5’ and the delivery valve 100 allows the flow only from the pumping chamber 5,5’. It is specified that automatic valve refers to a valve configured to open automatically allowing fluid communication, between two environments between which it is interposed, when a pre-set difference between the pressures in both environments divided by the valve itself is reached. Specifically, automatic valves do not exploit electromechanical operating mechanisms but only differences in pressure. In detail, each of these valves comprises a mobile shutter which is pushed by an elastic element against an annular housing surface, made available by an annular body provided with a through hole coaxial to the annular housing surface, so as to achieve a hermetic seal therewith. The elastic element is held in place, e.g. by a retaining body (cage) that can be fastened to the annular body. However, such a retaining body is not strictly necessary. When the pressure difference overcomes the force of the elastic element, the shutter moves away from the housing seat and the fluid is free to pass through the annular housing surface.

Each suction valve 95 comprises an inlet mouth and an outlet mouth, which is in fluid communication with the pumping chamber 5,5’, and each delivery valve 100 comprises an inlet mouth, which is in fluid communication with the pumping chamber 5,5’, and an outlet mouth.

The pump 1 ,1 ’ comprises a respective housing seat for each suction valve 95 made directly in the head 50,50’, for example it is at least partially (e.g. entirely) made as a hole (in direct fluid communication with the pumping chamber 5,5’) starting from an outer surface of the head 50,50’, in which outer surface it realises an inlet opening, and which comprises a restricted section realised inside the head 50,50’, which makes available an abutment surface 80,80’ facing the inlet opening and on which the suction valve 95 rests. In the illustrated embodiment, the outer surface corresponds to the second major face 60,60’ of the head, the housing seat hole corresponds to the cylindrical rectilinear hole, the housing seat inlet opening corresponds to the second opening 70,70’ and the abutment surface corresponds to the abutment surface 80,80’.

In this way the suction valve 95 is inserted into the second opening 70,70’ and pushed until it abuts on the abutment surface 80,80'. In particular, the annular body in the case of delivery valves and the elastic element or retaining body in the case of suction valves are place on the abutment surface 80,80’.

In the embodiment illustrated, the suction valves are therefore positioned coaxial to the sliding axes of the respective pistons, in detail, the elastic elements generate a force in the direction of the sliding axis.

The pump 1 ,1 ’ then includes a suction channel for distributing the liquid to be pumped to the cylinders, which distributes the liquid from an inlet mouth to the respective delivery valves. In the pump 1 , such channel comprises a first section 105 which is substantially coaxial to the axis of rotation of the plate and from which conduits 1 10 branch off to the seats of the suction valves.

In the pump 1 the suction channel comprises a first section 105’ transverse to the sliding axes of the cylinders, from which conduits 1 10’ branch off transverse to the first section and to the axes of the cylinders, distributing the liquid to be pumped to the respective suction valves.

The pump 1 ,1 ’ comprises a respective housing seat for each delivery valve 100 made directly in the head 50,50’ and of an opening in an outer surface of the head 50,50’, in particular in the side surface, which flows externally to the head 50,50’ and which is closed by a delivery plug 1 15,1 15’ screwed to the head 50,50’ and configured to keep the respective delivery valve 100 in position in its housing seat.

In particular, to fasten the delivery plug to the head 50,50’, the latter being made of polymer material, the invention provides for the presence of a metal insert in the head 50,50’ provided with an inner (female) thread to allow the screwing of the cap, which is thus provided with an outer (male) thread.

The housing seat of the pressure valve 100 is connected to the pumping chamber 5,5’ directly or by means of a conduit (transverse to the sliding axis as in the illustrated embodiment).

The pump 1 , 1 ’ also comprises a delivery channel 120,120’ for collecting the pumped liquid, which is in direct fluid communication with the delivery valves, and is placed downstream thereof with respect to the fluid direction when the pump is in use. For example, the delivery channel is in direct fluid communication with the outlet mouth of each delivery valve 100.

The pump comprises a cover 125,125’ (rigid) fastened to the head 50,50’ and which closes at least two inlet openings of the valve housing seats (in the illustrated embodiment it closes at least two second openings of the second face of the head 50,50’) by clamping the suction valves present in the corresponding housing seats between the respective abutment surface 80,80’ and the cover 125,125’ itself. Preferably, all the inlet openings of the suction valve seats, thus all second openings, are closed by the cover 125,125' and all the suction valves therein are clamped between the corresponding abutment surface 80,80’ and the cover 125,125’.

In the illustrated embodiment, since the distance between the abutment surface 80,80’ and the inlet opening is greater than the extension along such distance of the delivery valve 100, a respective spacer 130 is inserted between the cover 125,125’ and each delivery valve 100, which fills the space between the valve and the cover 125,125’, allowing the delivery valve 100 to be clamped between the cover 125,125’ and the abutment surface 80,80’.

In the illustrated embodiment the spacer is perforated and is part of the suction channel, as it is crossed by the pump liquid and is located upstream of the suction valve 95 with respect to the direction of flow to the pumping chamber 5,5’.

It is not excluded that in an alternative embodiment the cover 125,125’ may comprise projections that fit inside the inlet openings to replace the spacers.

At the inlet opening, a gasket (o-ring) must be provided to prevent the exit of the liquid between the head 50,50’ and the cover 125,125’, in the illustrated embodiment this gasket is in the spacer, but it could also be positioned in the cover 125,125’, or in the second face of the head 50,50’ or in the straight circular hole.

The cover 125,125’ has a first major face 135,135’ in direct contact with the second major face 60,60’ of the head 50,50', e.g. such first major face 135,135’ is flat, as is the second major face of the head 50,50’. In addition, the first major face has an extension such as to occlude all the inlet openings, i.e. all the second openings.

It is not excluded that in an alternative embodiment not illustrated the position of the delivery and suction valves may be reversed, in which case it is the delivery valves which are held in position by the cover 125,125’.

It is also not excluded that in an alternative embodiment not illustrated, the cover 125,125’ may hold both the delivery valves and the suction valves in position, in which case the cover 125,125’ must also extend to embrace to size the portion of the side surface of the head 50,50’ in which the openings are made through which the delivery valves are inserted into their respective housing seats in the head 50,50’.

Further, it is not excluded that in yet another embodiment the delivery and suction valves for each pumping chamber may form a bidirectional valve in the sense of a valve assembly having essentially a one-way (non-return) suction valve, a one-way (non-return) delivery valve and a body directly interposed between said valves and to which both said valves are attached or are otherwise in contact. In said body there is both a portion of the suction conduit which goes from the pump inlet to the suction valve, and a portion of the delivery conduit which goes from the delivery valve to the pump outlet. In this case, both the pressure and suction valves are clamped between the abutment surface of the respective pumping chamber and the cover which closes the opening of the housing seat in the head in which said valve assembly is inserted. In detail, in this case, the delivery valve, the body and the suction valve are clamped between the abutment surface and the cover.

The cover 125,125’ is fixed to the head 50,50’ in a removable manner, e.g. by means of threaded connection members. Already this fastening would be sufficient to clamp the suction valves between the cover 125,125’ and the abutment surface 80,80’. However, preferably the cover 125,125’ and the head 50,50’ are fastened together by means of the same plurality of fastening screws 140 to the casing 10,10’. In particular, each of said fastening screws 140 is provided with a shank, inserted in a through way into appropriate through holes 155,160 (aligned with each other) made in the cover 125,125’ and in the head 50,50’ respectively, and provided with a threaded end portion 145 screwed into a threaded hole made in the casing 10,10’.

Each fastening screw then comprises a head 150, having a larger diameter than the shank, fastened to an end of the shank opposite the threaded portion. The cover 125,125’ and the head 50,50’ are thus clamped between the casing 10,10’ and the heads of the fastening screws.

The casing 10,10’, like the head 50,50’, may be made of a polymer material.

In this case, the casing 10,10’ contains inserts 165 provided with a female thread that allows the threaded portion of the screw to be tightened.

For example, the cover 125,125’ is substantially plate-shaped, in the pump 1 it is discshaped, in the pump T it is rectangular, thus depending on the conformation of the head 50,50’ and the positioning of the valves.

The cover 125,125’ may preferably be made of polymer material, e.g. from the polyamide family, preferably Nylon. In particular, the cover material is a compound comprising (i.e. made of) a polymer material, for example a polymer belonging to the family of polyamides, preferably Nylon, in a percentage between 30% and 70% with respect to the total of the compound (for example with respect to the total weight of the raw material used for the compound) and glass fibre in a percentage between 30% and 70% with respect to the total of the compound (for example with respect to the total weight of the raw material used for the compound). In the embodiment illustrated, the compound comprises (i.e. consists of) a polymer belonging to the polyamide family, preferably Nylon in a percentage of 50% of the total and glass fibre in a percentage of 50% of the total.

These materials provide sufficient rigidity and strength for the cover 125,125’.

It is not ruled out that a polyester resin, PPF (polyparaphenylenesulphide), PVDF (polyvinylidene fluoride), PP (polypropylene) or POM (polyoxymethylene) could be used as the polymer material of the cover, in alternative, less preferred embodiments.

The polymer of the cover is preferably also the polymer of which the head and casing are made.

The cover 125,125’ may comprise a stiffening plate 170,170’ placed inside the cover 125,125’ itself, for example made of a more rigid material than that of which the rest of the cover 125,125’ is made, preferably made of a metallic material (steel). The stiffening plate 170,170' is placed entirely inside the cover 125,125’, in particular between the first major face 135,135’ and an opposite second major face of the cover, without protruding through said faces.

The stiffening plate 170,170’ allows higher screw tightening torques to be achieved than if it were not used, as it improves the distribution of the force exerted on the cover 125,125’ by the screws. In particular, the plate is pierced by the through holes 155 of the cover 125,125’ into which the fastening screws are inserted. In the embodiment illustrated, the plate has such an extension that it is also completely superposed with all the second openings along a direction parallel to the sliding axes of the pistons, again in order to increase the resistance and improve the distribution of the clamping force exerted by the fastening screws.

The stiffening plate 170,170’ represents in volume, a portion less than half of the entire cover 125,125’, which is therefore mainly made of the least rigid metal, i.e. mainly of polymer material. The stiffening plate 170,170’ is substantially parallel to the first face of the cover 125,125’. The operation of the pump according to the invention is as follows.

Following the movement of the inclined rotating plate 25 in the pump 1 and of the shaft of the pump T, in one or more cylinders at the same time, the movement of the respective piston 15,15’ towards the bottom dead centre position generates a vacuum inside the pumping chamber 5,5’, which in turn causes the respective delivery valve 100 to close and the respective suction valve 95 to open. Thereafter, the liquid is sucked and reaches the corresponding pumping chamber 5,5’ crossing the respective suction valve 95. Having reached the bottom dead centre, the piston 15,15’ rises towards the top dead centre following the thrust of the rotating plate 25, generating an overpressure in the pumping chamber 5,5’ which closes the suction valve 95 and opens the delivery valve 100.

During assembly or reassembly in the event of maintenance, to install the suction valves it is sufficient for the technician to insert said valves in their respective straight circular holes, insert the hole spacers if they are necessary, position the cover 125,125’ to close the second openings aligning the screw holes and finally tighten the screws thus closing the whole pump (cover 125,125’, head 50,50’ and casing 10,10’).

The invention thus conceived is susceptible to many modifications and variants, all falling within the same inventive concept.

Moreover, all the details can be replaced by other technically equivalent elements.

In practice, any materials and also any contingent shapes and sizes may be used, depending on the needs, without departing from the scope of protection of the following claims.