EP2122167B1

EP2122167B1 - Hydraulic-electromagnetic motor pump with floating piston

Info

Publication number: EP2122167B1
Application number: EP07723275A
Authority: EP
Inventors: Marta Cassola
Original assignee: Ceme SpA
Current assignee: Ceme SpA
Priority date: 2007-03-15
Filing date: 2007-03-15
Publication date: 2011-02-23
Anticipated expiration: 2027-03-15
Also published as: ES2361503T3; TW200940833A; TWI422742B; CN101755123A; PT2122167E; EP2122167A1; WO2008110187A1; ATE499527T1; PL2122167T3; DE602007012769D1; CN101755123B

Abstract

A motor pump of the hydraulic-electromagnetic type with floating piston, comprises a container body partly delimited in its external part, by a coil, an inlet duct and an opposite outlet duct located in said body, a couple of opposite magnetic bearings spaced between them and placed between said body and coil, a delivery piston placed inside the body and sliding inside it, said delivery piston being supported by a front and a rear springs and a magnetic bushing placed in the central lower part of the container body facing the inlet duct; the magnetic bushing presents an upper tapered portion facing the delivery piston in operative conditions.

Description

The present invention refers to a motor pump of the hydraulic-electromagnetic type with floating piston.
More particularly, the present invention refers to a motor pump of the hydraulic-electromagnetic type with floating piston, particularly suitable for the use in the fluid motion, especially water.
This type of motor pumps is applied to various apparatuses such as irons, electric coffee machines, steam generators, irrigation systems and also in the automotive industry.
Motor pumps of the hydraulic-electromagnetic type (with floating piston) are known from EP1205663 , from US4749343 , from EP 1001167 , from JP11141458 and from EP0288216 . Particularly, EP1205663 discloses a motor pump of the hydraulic-electromagnetic type with floating piston having the features of the preamble of claim 1. The operation of said motor pumps is based on the presence of a coil that cooperates with a couple of magnetic bearings; the coil is electrically powered and causes the axial movement of the floating piston or delivery piston with an alternate motion. The coil is placed outside the body of the motor pump, while the magnetic bearings are positioned in an annular seat formed between the same coil and a sleeve housing said piston. Said piston is elastically supported by opposite helical springs that are alternatively compressed during the floating in order to allow the passage of the fluid from the inlet duct to the delivery one. Known valves, rings and rubber gaskets associated to the piston and to the relevant sleeve assure the seal of the fluid moving inside the body of the motor pump.
These motor pumps have an important drawback that is essentially related to the pressure level that can be obtained, considering that sometimes, for particular uses, a high fluid pressurization is required. It is known that an increase in fluid pressurization can be obtained increasing the intensity of the magnetic field by the oversizing of the coil.
This implies an unavoidable increase of the motor pump dimensions and a considerable additional cost due. to the increase of the winding coils. A greater size of the body of the motor pump in its whole sometimes is not compatible with the installation of the motor pump on the target apparatus or it requires at least structural changes of the same apparatus. Even the increase in cost is an important factor that could lead to the manufacturing of uncompetitive products.
Therefore, an object of the present invention is to remove the above-mentioned drawbacks.
More particularly, object of the present invention is the provision of a motor pump of the hydraulic-electromagnetic type as specified in claim 1 with floating piston wherein the pressure level of the delivery fluid can be increased without oversizing the coil with a subsequent increase of its dimensions and production costs.
A further object of the present invention is to provide a motor pump of the above-mentioned type that can guarantee a high resistance and reliability level in time and it is easily manufactured.
Remarkably, an object of the present invention relies in providing a motor pump with enhanced magnetic efficiency, or in other words in providing a pump with better performance with minimum magnetic material employment.
Last but not least, the present invention is intended to provide for a motor pump wherein operating noise is minimized.
According to the present invention these and other purposes (as for example stated further in this description) are obtained by a motor pump according to the attached claims.
The manufacturing and operating features of the motor pump of the present invention will be better understood from the following description wherein reference is made to the table of the attached drawings representing a preferred embodiment given by way of non-limitative example wherein:

Figure 1 is a section view of the improved motor pump of the present invention in a first operative condition (maximum upper position of the piston);
Figure 2 is a section view of the motor pump of Figure 1 in another operative condition (minimum and "zero" lower position of the piston); and
Figure 3 is a section view of the motor pump of Figure 1 in another operative condition (minimum and "non-zero" lower position of the piston).

With reference to the above-mentioned figures, the motor pump of the present invention, marked in its whole with 10 in Figure 2, comprises: an inlet duct 44'; an opposite outlet duct 36; a container body 12 which is partly delimited, in its external part, by a coil 14; a couple of opposite magnetic bearings 46, 46' that are spaced between them and placed between the body 12 and the coil 14; a delivery piston 16 that is placed in the body 12, slides in it and it is elastically supported by a front helical spring 20 and by a rear helical spring 20'.
In front of the piston 16, in the part facing the delivery duct 22, a seal valve 24 of the delivery piston 16 is commonly placed.
The seal valve 24 cooperates with a support bearing 28 and with a rubber gasket 30 that is elastically tensioned by a further helical spring 32.
The spring 32 and, partly, the rubber gasket 30 are housed inside a seat of the delivery duct 22 whose diameter is fit to house the ensemble formed by the rubber gasket 30 and by the helical spring 32 and it is generally higher than the one of the outlet duct or hole 36 of the delivery duct 22.
A locking ring 38 having a flanged configuration and engaging with a matching part (e.g. via a snap-on fitting or the like) that is threaded in the outer part of the container body 12 is put on said duct 22.
The tubular-shaped container body 12, comprises a front part with a higher diameter that faces the outlet duct 36; an adjacent intermediate part with a lower diameter than the one of the front part itself delimiting the sliding axial chamber of the piston 16 and a terminal part 44 whose diameter is lower than the one of the intermediate part that defines the inlet duct 44'.
The opposite magnetic bearings 46 and 46', that may be mutually spaced with the use of a spacing element if necessary, are fit on the external side surface of the intermediate part of the body 12; the coil 14 is in its turn fit on the body 12 so that it can comprise bearings 46, 46'.
The coil 14 is stabilized with means that are for instance made of a shaped elastic ring that matches with a face of the coil and a shoulder placed on the body 12 between the front part and the intermediate part with a lower diameter that matches with the opposite face.
Inside the container body 12 in the central-lower part facing the inlet duct 44', a magnetic bushing 52, preferably made of steel with a low magnetic residual content, is advantageously placed.
Advantageously, the magnetic bushing 52 presents an upper tapered portion 52' facing the delivery piston 16 in operative conditions; at the same time, the delivery piston 16 presents a tapered lower inner portion 16'.
In a particularly efficient embodiment of the present invention, the lower inner portion 16' is counter-shaped to said upper tapered portion 52': this is evident in figure 2, wherein it is shown that the slopes of the two mutually facing tapered portions are equal.
The external side surface of said magnetic bushing 52 has differentiated diameters and defines a rear area that faces the duct 44' with a diameter that is equal or slightly lower than the internal one of the intermediate part of the body 12 and an adjacent front area facing the outlet hole or duct 36 with a lower diameter.
Referring to the annexed figures, the rear area and the front area of the magnetic bushing 52, with different diameters, form a matching shoulder for the rear spring 20', and the lower end of the magnetic bushing 52 matches with the body 12 in the intermediate part near the narrowing of the terminal part 44 that defines the inlet duct 44'.
The axial sliding return of the piston 16 is obtained by means such as the couple of helical springs 20 and 20' previously described that cooperate with the piston.
Powering of the coil 14 is obtained, for example, by a couple of electric connections of the fast-on type.
The motor pump object of the present invention is highly efficient thanks to the presence of the magnetic bushing 52: more in detail, the magnetic bushing 52, that is aligned with the sliding axis of the piston 16 with one of its ends, is located close to the piston (and therefore at a lower distance between the latter and one of the two magnetic bushings 46, 46'), so it can be dynamically placed in the position reached by the piston 16 during the loading of the rear spring 20' (generally near the terminal part 44 of the body 12).
The interaction between the bushing 52 and the two bearings 46, 46' creates a magnetic field whose intensity is higher than the one of the two bearings 46, 46' only and it therefore increases the magnetic attraction force exerted on the piston 16 and the one exerted on the fluid going out of the delivery duct 22.
With the use of the bushing 52, in the event of keeping the efficiency level that would be created only with the two bearings 46, 46', it is obviously possible to reduce the number of wirings of the coil 14 with considerable production savings.
For the purposes of the present invention, the magnetic bushing 52 is preferably made of steel with a low magnetic residual content.
According to a further advantageous feature of the present invention, the motor pump may also comprise spacer means operatively acting between the delivery piston 16 and the magnetic bushing 52, so as to keep a minimum non-zero distance between the piston 16 and the bushing 52 during oscillatory motion of the piston 16 itself.
In other words, the presence and function of the just cited spacer means is directed to avoid mutual contact of the piston 16 and of the bushing 52 during the highfrequency oscillation of the piston 16: by avoiding such repeated contact, a significant noise suppression during motor pump operation is achieved.
From a structural standpoint, the spacer means may be realized in many ways, provided that they fulfill the just described technical task: for example, the spacer means may comprise the rear spring 20' (whose elastic constant may be suitably chosen) and/or means for imparting a predetermined pre-load to the rear spring 20' itself.
From a geometric standpoint, the distance between the piston 16 and the bushing 52 may be measured at correspondingly coaxial points on the sloped/tapered surface, or it may be measured between two coaxial points located on the central portion of the facing surfaces of the piston 16 and of the bushing 52.
In fact, referring to figures 2 and 3, it can be seen that even when the tapered portions 16' and 52' are in mutual contact, the "central portions" of the piston and of the bushing are kept at a "non-zero" distance.
According to the present invention, the spacer means may be set into operation independently from the shape of the piston 16 and/or of the bushing 52; more in particular, the just described spacer means may be present in a motor pump even if the lower inner portion 16' and/or the upper tapered portion 52' are not present.
The invention achieves significant advantages.
First of all, thanks to the presence of the tapered portions, magnetic coupling of the piston 16 and of the bushing is even more enhanced, and therefore a higher performance level is easily attained.
At the same time, the peculiar geometry of the just cited tapered portions allows a better interfacing of the mobile parts of the pump (with respect to the "fixed" parts), and thereby reduces mechanical stresses and wearing.
Furthermore, the mutual interfacing of tapered portions causes a significant decrease of the "ram effect" any time that the piston comes close to the bushing, harmonizing delivery pressure and flow.
The motor pump manufactured according to the above description does not imply impediments or additional costs caused by the size increase of the coil and of the relevant wiring coils, while the magnetic bushing 52 can be easily obtained and installed at a low cost.
Last but not least, it is to be noted that the cooperation between the spacer means and the peculiar shape of the magnetic bushing and of the delivery piston greatly reduce noise generation, thanks to avoiding repeated contacts between these two pieces of the device.

Claims

A motor pump (10) of the hydraulic-electromagnetic type with floating piston, comprising:
- a container body (12) being partly delimited, in its external part, by a coil (14);

- an inlet duct (44') and an opposite outlet duct (36) located in said body (12);

- a couple of opposite magnetic bearings (46, 46') with a space between them which fit on an external side surface of an intermediate part of the body (12); the coil (14) fitting on the container body (12) so that it comprises said magnetic bearings (46, 46');

- a delivery piston (16) that is placed inside the body (12) and slides inside it, said delivery piston (16) being supported by a front spring (20) and by a rear spring (20');

- a magnetic bushing (52) placed in the central-lower part of the container body (12) facing the inlet duct (44'),
Characterized in that the magnetic bushing (52) presents an upper tapered portion (52') facing the delivery piston (16) in operative conditions.
The motor pump according to claim 1, characterized in that the delivery piston (16) presents a tapered lower inner portion (16'), said lower inner portion (16') being preferably counter-shaped to said upper tapered portion (52').
The motor pump according to claims 1 or 2, characterized in that a lower end of the magnetic bushing (52) matches with the container body (12) in the intermediate part near a terminal part (44) that defines the inlet duct (44'), said magnetic bushing (52) interacting with the couple of magnetic bearings (46, 46') to increase the magnetic field and therefore the magnetic attraction force exerted on the delivery piston (16).
The motor pump according to anyone of the preceding claims, characterized in that said front spring (20) and/or said rear spring (20') are helical-shaped.
The motor pump according to anyone of the preceding claims, characterized in that said body (12) comprises:
- a front part with a higher diameter facing the outlet duct (36);

- an adjacent intermediate part with a lower diameter than the one of a front part delimiting a sliding chamber of the piston (16); and

- a terminal part (44) whose diameter is lower than the one of the adjacent intermediate part wherein said terminal part (44) defines the inlet duct (44').
The motor pump according to anyone of the preceding claims, characterized in that an external side surface of the magnetic bushing (52) comprises:
- a rear area facing the inlet duct (44') whose diameter is the same or is slightly lower than the internal diameter of the intermediate part of the container body (12); and

- an adjacent front area facing the outlet duct (36), whose diameter is lower,
said rear area and said front area facing the outlet duct (36) define a matching shoulder for the rear spring (20').
The motor pump according to anyone of the preceding claims, characterized in that the lower end of the magnetic bushing (52) matches with the container body (12) in the intermediate part adjacent to the narrowing of the terminal part (44) that defines the inlet duct (44'), the distance between an opposite end of said bushing (52) and the piston (16) being lower than the one between the latter and one or the other of the two magnetic bearings (46, 46') placed in the position that is reached by the piston (16) during a rear spring (20') loading step.
The motor pump according to anyone of the preceding claims, characterized in that said magnetic bushing (52) is made of steel with a low magnetic residual content.
The motor pump according to anyone of the preceding claims, characterized in that said motor pump further comprises spacer means operatively acting between the delivery piston (16) and the magnetic bushing (52) so as to keep a minimum non-zero distance between the piston (16) and the bushing (52) during oscillatory motion of the piston (16).
The motor pump according to claim 9, wherein said spacer means comprise the rear spring (20') and/or means for imparting a predetermined pre-load to said rear spring (20').