EP0231194B1

EP0231194B1 - Pump

Info

Publication number: EP0231194B1
Application number: EP19850906096
Authority: EP
Inventors: Eric Bruce
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-11-21
Filing date: 1985-11-20
Publication date: 1989-01-18
Also published as: EP0231194A1; WO1986003255A1; SE8405849D0; DE3567702D1; AU5194286A

Abstract

A peristaltic pump is provided with an annular displacing means (9) in the pumping space inside a flexible pumping element (8) and with means of propulsion (11, 12) to impart on the displacing means a rolling movement in the pumping space while said displacing means is at the same time being pressed against the inside of the flexible pumping element, consecutive parts of the pumping element thus being peristaltically compressed. Said annular displacing means (9) is provided with elevations (13) directed outwards in the form of ridges or suchlike and spaced along the periphery of the displacing means, the distance between adjacent elevations being several times the arc length of the individual elevations, the pumping element thus being compressed locally in the region of the elevations. Further, the relation of the circumference of the displacing means to that of the curve along which it rolls is such that the elevations are displaced a certain distance per turn, the points of engagement being identical at a certain frequency.

Description

TECHNICAL SCOPE

The invention relates to a peristaltic pump of the type stated in the prior-art part of claim 1, i.e. a displacement pump comprising a pump housing enclosing a space delimited by side walls and a mantle wall; a pumping element influenced by peristaltic displacements and arranged in said space with an inlet at one end and an outlet at the other and with the outer periphery of said element contacting the mantle wall of said space at least along a sector thereof, at least the inwardly facing part of that sector of said element which maintains said contact consisting of a flexible material which permits said element to be compressed under the influence of a force directed radially outwards against the inside of said element; an annular displacing means in said space inside said flexible pumping element, the circumference of said displacing means being smaller than that of the curve along which it rolls; and means of propulsion to impart on said annular displacing means a rolling movement in said space, said displacing means concurrently being pressed against the flexible inside of said part of said sector of said pumping element, thus bringing about peristaltic compression of successive parts of said sector of said pumping element between said annular displacing means and said mantle wall of said space.
A peristaltic pump of this kind is in particular disclosed in SE-A-357801.
The invention also relates to pumping systems where the peristaltic pump is used to pump a working medium, which drives one or several further displacement pumps, also being parts of said system. This concept also includes improvements of the second displacement pump, said improvements by themselves being usable in other contexts than in combination with the peristaltic displacement pump.

BACKGROUND ART

Peristaltic pumps are known in a large number of embodiments. The Swiss Patent No. 482 922 and the British Patent No. 1 539 823 constitute examples of known designs. These and other peristaltic pump designs have in common that the flexible pumping element are being worked upon in a manner causing strong wear by that element which for each turn is pressed against the inside of the pumping element along the entire length thereof within the section in question. The displacement is accomplished by a combination of pressure, directed radially outwards, and rolling, but includes also a non-negligible amount of sliding against the flexible pumping element. All these factors contribute to the intense wear on the flexible pumping element, which is normally a piece of tubing, thus considerably shortening the working life of the flexible pumping element.
In order to prolong the working life of the pump, special materials have been developed in certain instances at high costs. In other cases, complex displacing heads have been developed or lubrication introduced to lessen the wear on the flexible pumping element, which is generally a piece of tubing. Improvements have been achieved by including the annular displacement means mentioned in the preamble, generally known as a planetary ring. Such pump designs are presented for example in the abovementioned Swedish Patent No. 357 801 and in the Swedish Patent Application made public No. :84 01777-1. The improvements brought about by the introduction of the planetary ring does not, however, seem to have satisfactorily eliminated the problems of attrition.
Yet another reason for the destruction of the flexible pumping element of known peristaltic pumps is that particles in the medium pumped is pressed into the tubing material, when the tube is compressed. This is presumably due to the fact that the compression takes place at a considerable portion of the length of the pumping element, which makes it difficult for solid particles of the pumped medium to be displaced from the compression zone, instead being trapped therein and being pressed into the tubing material, thereby causing heavy wear on the material.
Among the known displacement pumps may also be mentioned pumps of the kind comprising a first chamber provided with check valves at the inlet and outlet permitting the pumped medium to flow through the first chamber, a second chamber, a flexible impermeable wall separating the first chamber from the second, and at least one fitting at the second chamber through which to admit and discharge a working medium during working and return strokes, respectively, thus making said flexible wall during the working stroke to expand into the first chamber there to displace a corresponding amount of the pumped medium which is discharged through the outlet valve, and during the return stroke to make the flexible wall withdraw, thus sucking in a corresponding amount of pumped medium through the inlet valve into the first chamber, the least volume of the first chamber being set by a perforated rigid wall inside the flexible wall. Such a pump is described in US-A-1'852 242 and a similar design is described in FR-A-2 439 313. A drawback of displacement pumps of the kind described is that the flexible wall is not pre-tensioned, which makes it function less well during the return stroke, this in turn making it less suited for being combined with the peristaltic pump according to the invention, and also makes it work outside the ideal elastic working region of the elastic material of which the flexible wall is made.

DISCLOSURE OF THE INVENTION

A first object of the invention is to provide a peristaltic pump the flexible pumping element of which does not suffer the same degree of wear that conventional comparable pumps do, and therefore has a considerably longer working life.
Another object of the invention is to provide a pumping system comprising both a pump for a working medium in which is generated a pulsating fluid pressure by said pump and a number of displacement pumps.
A third object of the invention is to provide an improved displacement pump of a non-peristaltic type, which is well suited to function jointly with preferably one or several peristaltic pumps.
According to the invention a peristaltic pump is characterized in that the annular displacing means is provided with outwardly directed elevations in the form of ridges or suchlike, spaced along the periphery of the annular displacing means, the distance between adjacent elevations being several times the arc length of each individual elevation, said elevations being intended to be pressed against the flexible pumping element so that said element is locally collapsed in the area of the said elevations, and that the relation between the circumference of the annular displacing means and that of the curve along which it rolls is such that the said elevations are displaced for a certain distance per turn, the point of engagement against the flexible pumping element thus being the same only after a number of turns, which distributes the wear caused by the elevations on the flexible pumping element over a larger area and reduces attrition, this in turn increasing the working life of the pumping element.
Typical of an application of this peristaltic pump is that the pump is being used as a working pump to create a pulsating fluid pressure in a second displacement pump of the kind also described above. In accordance with the invention, a characteristic of an improvement of this second displacement pump is that the flexible wall of this pump is pre-tensioned. A characteristic of the function of the peristaltic displacement pump when used in conjunction with a second displacement pump, there to create a pulsating fluid pressure, is that its inlet opening is closed, a vacuum thus forming in the inlet chamber during the working stroke, said chamber being refilled with working medium during the return stroke and said vacuum cooperating with the pre-tensioned element of said second displacement pump.
Further advantages and characteristics and aspects of the invention will become apparent from the appended claims and the following description of preferred embodiments.

BRIEF DESCRIPTION OF DRAWINGS

In the following description of some preferred embodiments, reference will be made to the attached drawings, wherein

Fig. 1 is a schematic cross-sectional view of the peristaltic pump, the sectional plane being perpendicular to the pump axis;
Fig. 2 is a section taken along the line II-II of Fig. 1;
Fig. 3 is a schematic cross-section in the axial plane of a second displacement pump, suited for use in conjuction with the peristaltic pump;
Figs. 3a and 3b illustrate elements of the pump of Fig. 4;
Fig. 4 is a schematic view of a pumping system comprising both a peristaltic pump and a second displacement pump; and
Fig. 5 is a schematic view of a developed form of the peristaltic pump in accordance with the invention and its use for serving four serially connected displacement pumps for the pumping of water or some other pumping medium from large depths.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to Figs. 1 and 2, a pump housing is generally indicated by reference numeral 1. This housing is in the shape of a box, with side walls 2 on each side of a pump housing body 3, said body having a cylindrical bore 4, forming a pumping space with a cylindrical mantle wall 5. Two bores 6 and 7 extend through the body 3 from the outside, tangentially into the space 4. A flexible pumping element in the form of a tube 8 extends through the bores 6 and 7 and arcuately through the space 4, in which space said tube runs adjacent the mantle wall 5 for half the circumference thereof.
The space 4 also holds a displacing means in the form of a planetary ring 9. The diameter of this ring is considerably less than that of the mantle wall 5 and also less than that of the inside 10 facing the interior of the space 4 of that part of the tube 8 which runs adjacent the mantle wall 5. The planetary ring 9 is arranged to be rolled around the pumping space 4 by means of a central pumping axle 11. The axle 11 drives a roller 12, which is pressed against the inside of the planetary ring 9 in a manner well known in the art.
In accordance with the invention, the planetary ring 9 is provided with distinct, large elevations 13, the pitch, form, profile, and height of these elevations being such that they, as the planetary ring rotates, accomplish a suitable local compression of the tube 8 in the area where said tube runs adjacent the mantle wall 5. The elevations 13 may be attached to the planetary ring 9 in a stationary manner or flexibly or elsewise and may also, by a suitable choice of material, be made to interact with the tubing material so as to achieve the least possible wear and power consumption. The pitch and the pressure are set so that there is never less than one elevation and never more than two elevations in full engagement with the tube at any one time, i.e. collapsing it fully and preventing the return flow of the pumped medium. As the planetary ring 9 rotates, the compression in the regions of the elevations 13 will be directed radially, and at the area of contact only a slight turning will occur, the tangential forces at the same time being very small, which in turn reduces wear and resistance to rolling. Further, the relation of the circumference of the planetary ring 9 to that of the curve along which it rolls inside the pumping space 4 is such that the elevations 13 will be displaced slightly for each turn, the points of interaction of the elevations with the tube 8 being the same only after a number of turns. Thus, the wear of the elevations against the tubing is distributed over a larger area, which diminishes total wear and increases the working life of the tube. Alternatively, the lessened wear allows for a larger pump capacity as the rate of revolution may be increased and the pump size may be decreased.
Between two elevations 13 simultaneously in engagement with the tube 8 there is a cavity inside the tube. In this cavity, particles of considerable size may collect, instead of being pressed into the tubing material, which also reduces wear in comparison to conventional peristaltic pumps.
The peristaltic pump described may function as a normal pump for transportation, such as a suction pump. In such a case, the suction side 14 is connected to the volume of fluid which is to be transported, -and the discharge side 15 is connected to a transport conduit.
The pump may also be used as a source of pulsations for a second displacement pump, providing a pulsating flow of a working medium for said second pump. In such a case, the suction side 14 is closed at one end, schematically indicated by the plug 16. For each working stroke, a vacuum is created in the tube section 8' on the suction side 14, said vacuum being filled as the planetary ring 9 is at the top side of the pumping space 4. In this embodiment, the peristaltic pump may serve for example a displacement pump 17 of the kind illustrated schematically in Fig. 3. The pump 17 comprises an outer chamber 18 with rigid walls 19, the material of the walls being for example sheet metal or plastic. The outer chamber 18 is provided with a feed conduit 20 and a discharge conduit 21 with checkvalves 22 and 23, respectively. Inside the outer chamber 18 there is an inner chamber 24, formed by a rigid cylindrical body with a perforated mantle and closed ends. A connecting conduit to the inner chamber 24 is indicated by numeral 25. This connecting conduit 25 is connected to the pressure side 15 of the above described peristaltic pump. On the outside of the rigid, perforated body 26, Fig. 3a, one or several rubber sleeves 27 have been pushed. As is evident from the figures, the sleeves 27 must be expanded considerably to fit the perforated body 26. Thus, they are pre-tensioned as they assume their starting position the body 26.
Fig. 4 illustrates the use of a peristaltic pump 1' to serve a second displacement pump 17 of the type just described. The pressure side of the pump 1' is connected to the inner chamber 24 of the pump 17. During the working stroke of the peristaltic pump l' the working medium is pumped into the inner chamber 24 of the pump 17, where it expands the flexible sleeve 27 further and displaces working medium out of the outer chamber 18 through the discharge conduit 21 via check valve 23. At the same time, there is created in the tubing segment 8' on the suction side 14 of the peristaltic pump 1' a vacuum, since the inlet end is sealed off. At the return stroke, the flexible sleeve 27 springs back against the perforated body 26 and concurrently, working medium is again sucked into the suction side 14 of the peristaltic pump 1'. New working medium is sucked into the outer chamber 18 of the pump 17 , through the feeding conduit 20 via the check valve 22. During this suction stroke, the pre-tensioned sleeve 27 hence cooperates with the vacuum at the suction side of the peristaltic pump 1'. By pretensioning the rubber, it becomes possible to work within the ideal working interval of the rubber. The return force of the sleeve 27 may be set by the choice of material thickness or initial diameter so as to achieve the proper pre-tensioning according to the conditions at hand, or by applying several sleeves 27, one outside the other, as is symbolically indicated in Fig. 3b, where three sleeves 27 are'shown, intended to be put outside each other outside the perforated body 26.
The displacement pump 17 may for example be put to use in a drill hole to pump water, while the peristaltic pump 1 or 1' is placed adjacent the hole or at a distance therefrom. The pump may be driven manually, by a motor, by wind, or elsewise. When working medium is supplied from the pump 1 to the inner chamber of the pump 17, so that the elastic sleeve on the outside of the perforated body 26 expands, water is pressed in bursts via the discharge opening 21 out of the drill hole. The iterated application of working medium to the pump 17 causes a pulsating movement and a pulsating discharge of water out of the drill hole.
In Fig. 5 is illustrated a drill hole 30 in which there are arranged four serially connected displacement pumps 17 at different depths. Each one of these may be served by a peristaltic pump of the kind described with reference to Figs. 1, 2, and 4, said peristaltic pumps then being arranged to function with a suitable phase displacement in relation to each other. It is also possible to use a peristaltic pump of the kind illustrated in Fig. 5. This pump comprises four tubular elements 32 spaced along the mantle of the pumping space 4. Each tube 32 is provided with a closed suction side 33 and a pressure side 34 attached to one of the pumps 17, to pump working medium into the inner chamber 24 of this second displacement pump, Fig. 3. The four tubes 32 are acted upon by one singular planetary ring 9, of the design described with reference to Fig. 1. As this ring rotates in the pumping space 4, it will consecutively compress the four tubes 32, the four displacement pumps 17 in the drill hole 30 consecutively being activated to pump the water stepwise out of the drill hole.

Claims

1. A pump of the peristaltic type, i.e. a displacement pump (1, 1', 31), comprising a pump housing enclosing a pumping space (4) delimited by side walls and a mantle wall (5); a pumping element (8) influenced by peristaltic displacements and arranged in said spce (4) with an inlet (14) at one end and an outlet (15) at the other end, and with the outer periphery of said element contacting said mantle wall of said space at least along a segment thereof, at least that inwardly facing part of said segment of said element which maintains said contact consisting of a flexible material permitting said element to be compressed under the influence of pressure applied radially outwards against the inside of said element; an annular displacing means (9) in said space inside said flexible pumping element, the circumference of said displacing means being smaller than that of the curve along which it rolls; and means of propulsion (11, 12) to impart on said annular displacing means a rolling movement in said space, said annular displacing means concurrently being pressed against the inside _Qf said segment of said flexible pumping element, thus bringing about peristaltic compression of successive parts of said segment of said flexible pumping element between said annular displacing means and said mantle wall (5) of said space, characterized in that said annular displacing means (9) is provided with outwardly directed elevations (13) in the form of ridges or suchlike, spaced along the periphery of said annular displacing means, the distance between adjacent elevations being several times the arc length of each individual elevation, said elevations being intended to be pressed against the flexible pumping element so that said element is locally collapsed in the area of the said elevations, and that the relation of the circumference of the annular displacing means to that of the curve along which it rolls is such that the said elevations are displaced for a certain distance per turn, the point of engagement against the flexible pumping element thus regularly being the same after a number of turns, which distributes the wear caused by the elevations on the flexible pumping element over a larger area and reduces attrition, thereby increasing the working life of the pumping element.

2. Pump according to claim 1, characterized in that it is a working pump in a pumping system comprising at least one second displacement pump (17), the first-mentioned pump being intended to create a pulsating pressure in a working medium for the said second displacement pump, the suction side of the first-mentioned pump being sealed off, a partial vacuum thereby being created at the suction side of said first-mentioned pump during the working stroke thereof.

3. Pump according to claim 1, characterized in that two of the said elevations of the displacing means jointly completely close the pumping element.