EP3555472A1

EP3555472A1 - Plunger pump provided with pumping elements driven by eccentric means

Info

Publication number: EP3555472A1
Application number: EP17832335.8A
Authority: EP
Inventors: Mauro Marchionni; Raffaele Bonifazi; Fabio Basile; Stefano MARCOLIN; Antonio Trani; Luigi DEMITRI
Original assignee: Innovation & Design Consulting Srl
Current assignee: Sdn Holding Srl
Priority date: 2016-12-14
Filing date: 2017-12-13
Publication date: 2019-10-23
Also published as: WO2018109692A1; IT201600126214A1

Abstract

Pump (1) comprising a first hollow cylindrical body (2) therein containing: a second hollow body (11) with a cylindrical outer profile and internally shaped in a cam-like manner, the second hollow body (11) being associated to drive means for the rotation thereof around a rotation axis (X); a plurality of pumping elements (10a, 10b, 10c) obtained inside a central fixed body (31). Each of the pumping elements (10a, 10b, 10c) has: a first cylinder (4) defining a chamber within which there is slidably coupled a piston (5) moving with reciprocating motion inside the first cylinder (4), the piston (5) having a housing for a plunger (6) coupled to the piston (5) and such to follow the reciprocating motions of the piston (5) within a second cylinder (7) which suctioningly receives the fluid coming from an external tank through a first duct (8), the plunger (6) causing the delivery outflow of the compressed fluid through the first duct (8) according to a direction opposite to the suctioning direction; a second duct (9) which places the first duct (8) of each pumping element (10a, 10b, 10c) in communication with an external point of delivery; a pressurisation check valve (13) present in the second duct (9). The pump has, connected to the second duct (9) upstream of the pressurisation valve (13), at least one valve for adjusting the fluid flow rate actuatable to at least partly discharge the fluid coming from the pumping elements (10a, 10b, 10c).

Description

PLUNGER PUMP PROVIDED WITH PUMPING ELEMENTS DRIVEN BY ECCENTRIC MEANS

DESCRIPTION

The present invention regards a new type of plunger pump comprising a plurality of pumping elements driven by eccentric means, particularly but not exclusively suitable for use in the diesel vehicle industry.

It is known that plunger pumps are reciprocating pumps in which the pressurisation of the fluid is obtained through a reciprocating sliding of a plunger in a cylinder.

This type of pumps belongs to the family of volumetric pumps, in which the fundamental characteristic lies in the fact that the dispensed flow rate is basically constant for each duty cycle, this mainly depending on the number of cycles carried out in the time unit.

It is also known that high pressure plunger pumps (starting from 2000 bars onwards) and with flow rates in the order of at least 1 l/min are generally difficult to obtain with a single mechanical pumping element actuated by an eccentric cam.

Furthermore, the presence of only one pumping element entails the drawback lying in the fact that achieving the aforementioned pressures and flow rate would require the use of large flywheels so as to be able to supply the fluid with the required pressure during the step in which the cam is in the thrust phase on the pumping element.

In order to overcome this drawback, a solution is to use a plurality of pumping elements, each one of which is actuated by a cam system.

Furthermore, currently in the pumps driven by eccentric means of the known type, in cases where a lower flow rate is required, there arises the need for either complex and expensive systems for the mechanical variation of the displacement capacity or for eliminating the surplus flow rate through relief valves which, by virtue of their nature, are dissipating elements and thus unacceptable from an energy point of view. Thus, the variation of the flow rate can only be obtained by varying the number of revolutions of the motor which actuates the pump.

An object of the present invention is to provide a fixed displacement pump without loss of energy, that is not subject to angular rotation speed variations within given limits and which enables obtaining a variable flow rate, should need arise.

From now henceforth, the expression "pumping element" shall be used to indicate a mechanical unit made up of:

- a cylinder provided with an inlet path for introducing a fluid coming from a tank outside the pump thereinto;

- a piston moving with reciprocating motion within said cylinder and connected to a plunger which moves inside the aforementioned inlet path coaxial to the plunger;

- a path for delivering the fluid pushed outside by the cylinder due to the action of the plunger.

The aforementioned object is attained by the present invention regarding a pump whose main characteristics are outlined in the main claim.

Further characteristics of the invention are outlined in the dependent claims. Advantageously, the pump according to the present invention provides for a plurality of pumping elements that operate sequentially with respect to each other.

Equally advantageously, the pump according to the present invention provides for that the flow rate of the fluid pumped by the pumping elements can be split through the presence of one or more flow rate adjustment valves arranged upstream of the pressurisation valve. Thus, the aforementioned delivery adjustment valves enable modulating the flow rate considering the same number of revolutions of the motor that actuates the pump, thus avoiding considerable waste of energy arising from the dissipation of the energy used to pressurise only one part of the flow rate of the fluid coming from the pumping elements.

The non-utilised flow rate is actually re-introduced into the hydraulic circuit of the pump without being pressurised.

The aforementioned flow rate adjustment means can be a plurality of manual discharge shut-off valves or, according to a preferred variant embodiment of the invention, electro-controlled valves controlled to open a given number of times during a duty cycle of the pump.

Equally advantageously, with the same number of revolutions of the motor, the pump according to the invention is capable of providing a much wider range of flow rates and pressure associated to a substantially constant power value of the motor, and this differing with respect to the prior art pumps in which a fixed flow rate value is associated to a single pressure line. Thus, being capable of providing variable flow rate values considering the same number of revolutions of the motor, the pump according to the present invention enables achieving a high efficiency of the pumping system due to the considerable reduction of energy dissipation.

This occurs given that the fluid part pumped by the pumping elements is discharged through the shut-off valves or the electro-controlled valves which are located upstream of the pressurisation valve without being pressurised due to the presence of the pressurisation valve.

This implies that the pump according to the invention enables the pressurisation valve to pressurise just the required amount of fluid, thus directly discharging (and thus without pressurising) the non-required amount of fluid through the shut-off valves or electro-controlled valves.

The aforementioned object and advantages shall be more apparent from the description of a preferred embodiment of the invention, outlined hereinafter by way of non-limiting example, with reference to the attached drawings, wherein:

- fig. 1 represents a front view of the pump according to the invention;

- fig. 2 represents a transversal cross-sectional view of the pump of fig. 1 ;

- fig. 3 represents a lateral cross-sectional view of the pump of fig. 1 ;

- fig. 4 represents a lateral cross-sectional view of a variant embodiment of fig. 3;

- fig. 5 shows an enlarged view of a detail of fig. 4.

With reference to figs. 1 -3, the pump according to the invention, indicated in its entirety with 1 , comprises a first substantially hollow cylindrical body 2, containing a second rotary body 11 therein, also curved, cylindrical-shaped and internally profiled with cams, associated to drive means (not shown in the figures) which drive the rotary body 11 in rotation through a drive shaft 2a which rotates around a rotation axis X (visible in fig. 3).

As observable in fig. 1 , the pump 1 lies on a base 3.

As observable in fig. 2, the pump 1 has, obtained inside a third fixed body 31 , a plurality of pumping elements 10a, 10b, 10c, which are three and arranged symmetrically spaced by about 120° from each other in the present embodiment. However, in a possible variant embodiment not illustrated in the figures, it cannot be ruled out that the pumping elements can be of any number other than three. Advantageously, the pumping elements 10a, 10b, 10c can have plungers with diameters different from each other and they are configured to operate sequentially. This advantageously enables optimising the operation of the system with a better modulation of the outflow rate.

With reference to fig. 2, it should be observed that each of the pumping elements 10a, 10b, 10c has a first cylinder 4 within which there is present a piston 5 which, at the axis Y thereof, has a housing for a plunger 6 which is mechanically connected to the piston 5 and moves in a second cylinder 7 communicating with a first duct 8.

When suctioning the fluid, the second cylinder 7 is the inlet path into which the fluid coming from an external tank (not shown in the figures) enters through the first duct 8.

The plunger 6 follows the reciprocating motion of the piston 5 of the pump 1 and it is driven in motion by the rotary body 11 provided with cams, which receives the motion from the drive means. Provided with the cams, the rotary body 11 is driven in rotation by the drive shaft 2a and it is integrally joined thereto.

When the rotary body 11 is in motion, as observable in fig. 2, the two cams thereof push - not simultaneously - wheels or bearings 11a which are present between the head of the piston 5 and the profile of the cam, conferring the plunger 6 a reciprocating straight motion in the chamber thereof.

The continuous contact between each wheel 11a and the profile of the cams is ensured by the spring 51 present in each first cylinder 4 and which pushes the piston 5 towards the outside.

If n is used to indicate the general number of the pumping elements of the pump according to the invention, the number of cams must always be equal to n-1 so as to prevent all pistons of the pumping elements from being actuated simultaneously, as this would lead to excessive periodic torsional stress on the drive shaft.

In the configuration of the pump 1 shown in fig. 2, it can be observed that the pumping elements 10a, 10b, 10c operate sequentially, and precisely the pumping element 10a is in a maximum fluid compression configuration, the pumping element 10b is in an intermediate configuration between maximum compression and maximum suctioning, while the pumping element 10c is in a maximum fluid suctioning configuration. Provided with its two cams, as observable in fig. 3, the rotary body 11 , is supported by a rolling bearing 19, which can be of the ball or roller type, and by a roller bearing 20.

Still with reference to fig. 3, there should also be observed the presence of a second duct 9, which is a delivery duct that places the first duct 8 of each pumping element 10a, 10b, 10c in communication with an external point of delivery.

Though figs. 3 and 4 only show the pumping element 10a, what will be illustrated with reference thereto as concerns the aforementioned figures shall be deemed valid for the pumping elements 10b and 10c too.

It should be observed that the first duct 8, during the suctioning of the fluid by the plunger 6, becomes an inlet duct with respect to the second cylinder 7, while it instead becomes a fluid delivery duct during the discharge stroke of the plunger 6.

With reference to figs. 1 and 3, the pump 1 further comprises the cylindrical body 2 (shown in cross-sectional view in fig. 3), which is fixed and integrally joined to the base 3 (shown in fig. 1 ), to which a lid 29 is constrained through first fixing means 30.

The lid 29 in turn supports a third central fixed body 31 , in which there are obtained holes (not shown in the figures) for the passage of the fluid to be pumped and to which there is constrained, through second fixing means 32, a cap 33 into which there converges the second duct 9 for the delivery of the fluid which will then be dispensed under pressure towards the final point of delivery.

Fig. 3 also shows the presence of a pressurisation check valve 13, present in the second delivery duct 9, which is traversed by the pressurised fluid which will then be conveyed to the final point of delivery through a manifold (not shown in the figures).

As regards this, it should be observed that each pumping element 10a, 10b, 10c is provided with its own pressurisation check valve 13 (and thus also with its own delivery duct 9). Thus, the configuration shown in figs. 3 and 4, which regards the pumping element 10a only, is similar and thus also valid for the pumping elements 10b and 10c of the pump 1. The configurations of the pumping elements 10b, 10c are not illustrated so as to avoid unnecessary repetitions. According to the present invention and with reference to fig. 3, the pump 1 has a fluid flow rate adjustment valve, which is connected to the delivery duct 9 and it is actuatable to discharge the fluid, coming from the pumping elements 10a, 10b, 10c, not intended to be pressurised.

Still with reference to fig. 3, it shows a suctioning check valve 12, which suctions fluid from a tank (not visible in the figures) external to the pump 1. According to the embodiment illustrated in figs. 1 -3, and in particular with reference to fig. 1 , the valve comprises one or more shut-off valves 14, each of which is provided with an opening 15 for discharging the fluid that is not intended to be pressurised.

Each of such shut-off valves 14 can be controlled manually and it is housed in a special seat 16 illustrated in fig. 3.

The number of shut-off valves 14 used for discharging the surplus fluid will vary depending on the flow rate of the fluid intended to be discharged before being pressurised.

Given that they are adjusted manually, the shut-off valves 14 enable an adjustment of the flow rate of the On-Off type, i.e. they open or close a given number of times depending on the intentions of the operator and thus cannot be opened only partly. Thus, the use of the shut-off valves 14 will lead to a "step" adjustment of the flow rate.

Now, with reference to figs. 4 and 5, they show a preferred variant embodiment of the pump 1 according to the invention, whose difference with respect to the previous embodiment lies in that the discharge shut-off valves 14 are now replaced by electro-controlled valves 21.

Advantageously, the aforementioned electro-controlled valves 21 are shown more clearly in the detail of fig. 5, which shows that they consist of a sealing ball 22 terminating with a cylindrical rod 22a, made of ferromagnetic material, and a return spring 23 to which the ball 22 is constrained. Such valves 21 are controlled through a coil 24 which moves the ball 22 and opens and closes the electro-controlled valve 21 through a control unit (not shown in the figures). The proportionality of the electro-controlled valve 21 can be obtained by sending an On-Off signal depending on the stroke of the plunger 6, which is detected by an encoder (not shown in the figures) connected to the rotary body 11.

The functioning of the electro-controlled valves 21 will be illustrated more in detail hereinafter.

Advantageously, such electro-controlled valves 21 can be timed and thus the period of opening thereof can be adjusted using a special control unit (see above).

Operatively, the pump 1 operates as follows.

The pump 1 , represented in fig. 3, suctions the fluid from an external tank (not shown in the figures) through the suctioning check valves 12.

The fluid is thus introduced into the duct 8 and conveyed into the chamber consisting of the latter part of the inlet duct (which serves as a suctioning duct in this case).

The plunger 6 initially provides for suctioning the fluid and then pushing it outside towards the first duct 8 (which serves as a delivery duct in this case). At this point, if the entire flow rate of the fluid pumped by the pumping element 10a through the first duct 8 (which serves as a delivery duct in this case) must be pressurised, the entire fluid is directly sent towards the pressurisation check valve 13 and subsequently conveyed outside towards the final point of delivery. The shut-off valve 14 is obviously closed in this case.

Otherwise, if the entire flow rate of the fluid towards the final point of delivery is not to be pressurised, then the surplus part of the fluid flow rate is discharged previously by opening one or more of the shut-off valves 14.

Given that the shut-off valves 14 are arranged upstream of the pressurisation valve 13, the fluid is directly delivered to the discharge through the discharge openings 15. This advantageously avoids pressurising the fluid flow rate not required by the final point of delivery and thus avoiding unnecessary dissipation of energy.

The shut-off valves 14 can be actuated manually in On-Off mode, and thus part of the delivery fluid flow rate is discharged by opening one or more of the aforementioned shut-off valves 14.

As regards the electro-controlled valves 21 , they operate as follows.

With reference to figs. 4 and 5, in order to allow the inflow of the fluid in the direction shown by the arrow F1 , the coil 24 is not energised and the ball 22 is pushed by the pressure of the fluid downwards to the dashed position 22b (see fig. 5), opening the gap 25. Thus, the fluid flows into the first duct 8 overcoming the low resistance of the spring 23 and it is conveyed towards the pumping element 10a. With reference to fig. 4, should one intend to discharge the fluid through the electro-controlled valve 21 , when the fluid pumped by the pumping element 10a is discharged towards the first duct 8 (which becomes a delivery duct in this case), the coil 24 is energised so that the sealing ball 22 always remains distant from the seat thereof. This occurs in that the electromagnetic field to which it is subjected overcomes the resistance of the spring 23.

Thus, the fluid flows into the electro-controlled valve 21 according to the direction of the arrow F3 and flows outside according to the direction of the arrow F4.

Still with reference to fig. 4, when one wants to pressurise the entire pumped fluid so that it is discharged through the pressurisation valve 13 according to the direction of the arrow F6, the coil 24 of the electro-controlled valve 21 is no longer energised. Thus, the sealing ball 22 is pulled upwards by the spring 23 according to the direction indicated with the arrow F5 up to being positioned in the seat thereof and closing the gap 25 once again thus preventing the fluid from flowing through it.

Advantageously, through a control unit (not shown in the figures), the electro- controlled valves 21 can be timed and the frequency at which they open during a duty cycle of the pump 1 can set a priori.

Equally advantageously, the electro-controlled valves 21 , which serve both as fluid suctioning and discharge valves, can be opened proportionally through, for example, an encoder.

Given that the fluid is discharged without being pressurised, energy dissipation is now basically nullified, in that now, substantially, the total energy used in the pump according to the invention substantially coincides with the energy required to compress the required fluid flow rate which will then be conveyed to the final point of delivery.

In the light of the above, the pump according to the invention is deemed to attain the pre-set objects.

The object of providing a fixed displacement pump without loss of energy and without varying the rotation speed, from which a variable flow rate can be obtained if required, is attained.

The fact that in the pump according to the invention the diameters of the pumping elements are different from each other and that the flow rate of the delivery fluid can be controlled through the electro-controlled valves enables adjusting the pump in a very accurate manner. In particular, a pump according to the invention, for example actuated by a standard 5.5 kw motor, may operate with a range of flow rates between 0 and 4.6 l/min and with variable pressure up to 4,000 bars, maintaining the power almost constant.

Given that the expression of the power is equivalent to the product of the torque for the angular speed, and it is thus a function of the angular speed, this implies that the flow rate and the pressure of the fluid can be modulated at will, maintaining the angular speed of the motor which starts the pump constant. This becomes very important in industries such as the automotive industry, in particular in diesel vehicles that use the "common rail" system.

As a matter of fact, "common rail" pumps operate at very high pressures and absorb high amounts of energy when running at maximum capacity and, given that the option of splitting the fluid flow rate had never been available up to now, large amounts of energy were dissipated even when the diesel engine was used at low speed. This due to the fact that, at low speed, most of the pressurised fluid flow rate was not used in the final point of delivery and thus was re-introduced into the hydraulic circuit after being pressurised for no reason.

As a matter of fact, in the industry of the "common rail" pumps, the maximum power of the diesel cycle internal combustion engine is dispensed only in very rare cases, while power (and thus a fluid flow rate) four or five times less than the maximum power is enough in most cases.

The pump according to the invention can also be applied to the modern marine propulsions which also operate according to the "common rail" principle.

In the executive step, the pump according to the present invention may be subjected to modifications and/or variants which shall be deemed protected by the present patent should they fall within the scope of protection of the claims that follow.

Claims

1 ) Pump (1 ) comprising a first substantially hollow cylindrical body (2) therein containing:

• a second hollow body (1 1 ) with a substantially cylindrical outer profile and internally shaped in a cam-like manner, said second hollow body (1 1 ) being associated to drive means for the rotation thereof around a rotation axis (X);

• a plurality of pumping elements (10a, 10b, 10c) obtained inside a central fixed body (31 ), each of said pumping elements (10a, 10b, 10c) having:

> a first cylinder (4) defining a chamber within which there is slidably coupled a piston (5) moving with reciprocating motion within said first cylinder (4) and at the symmetry axis (Y) thereof, said piston (5) having a housing for a plunger (6) coupled to said piston (5) and such to follow the reciprocating motions of said piston (5) within a second cylinder (7) coaxial to said piston (5), said second cylinder (7) suctioningly receiving the fluid coming from an external tank through a first duct (8), said plunger (6) causing the delivery outflow of said compressed fluid through said first duct (8) according to a direction opposite to the suctioning direction;

> a second duct (9) for placing the first duct (8) of each pumping element (10a, 10b, 10c) in communication with an external point of delivery;

> a pressurisation check valve (13) present in said second duct (9), characterised in that it has, connected to said second duct (9) upstream of said pressurisation valve (13), at least one valve for adjusting the fluid flow rate, said at least one flow rate adjustment valve being actuatable to at least partly discharge the fluid coming from said pumping elements (10a, 10b, 10c).

2) Pump (1 ) according to any one of the preceding claims, characterised in that said at least one valve for adjusting the fluid flow rate is an electro- controlled valve (21 ).

3) Pump (1 ) according to claim 2, characterised in that each electro- controlled valve (21 ) comprises a coil (24) supplied by a control unit, a sealing ball (22) for the opening/closing of said valve and a spring (23) to which said ball (22) is constrained, said ball (22) being made of ferromagnetic material.

4) Pump (1 ) according to claim 2 or 3, characterised in that, when said coil (24) is not energised, said electro-controlled valve (21 ) enables the inflow of the fluid into said pump (1 ) and prevents the outflow of the pressurised fluid, the outflow of the excess fluid being enabled when the coil (24) of said electro- controlled valve (21 ) is energised and said sealing ball (22) is moved away from the seat thereof.

5) Pump (1 ) according to any one of claims 2 to 4, characterised in that said electro-controlled valves (21 ) are configured to open so that the opening frequency thereof during a duty cycle of said pump (1 ) can be adjusted by means of a control unit.

6) Pump (1 ) according to any one of claims 2 to 5, characterised in that said electro-controlled valves (21 ) are configured so that they can be timed.

7) Pump (1 ) according to any one of claims 2 to 6, characterised in that said electro-controlled valves (21 ) are configured so that they can be opened only partly.

8) Pump (1 ) according to any one of the preceding claims, characterised in that said pumping elements (10a, 10b, 10c) are configured so as to operate sequentially.

9) Pump (1 ) according to any one of the preceding claims, characterised in that each of said pumping elements (10a, 10b, 10c) has a diameter different from the others.

10) Pump (1 ) according to claim 1 , characterised in that said at least one valve for adjusting the fluid flow rate comprises one or more manually controlled shut-off valves (14).

1 1 ) Pump (1 ) according to any one of claims 2 to 10, characterised in that said electro-controlled valves (21 ) are configured to be activated selectively and that said shut-off valves (14) are configured to be opened selectively.