WO1991016542A1

WO1991016542A1 - Peristaltic pump with retractable pressing members

Info

Publication number: WO1991016542A1
Application number: PCT/NL1991/000060
Authority: WO
Inventors: Antonius Jacobus Van Den Bos; Arie Jan Pijl
Original assignee: Bredel Exploitatie B.V.
Priority date: 1990-04-12
Filing date: 1991-04-12
Publication date: 1991-10-31
Also published as: NL9000867A

Abstract

A peristaltic pump with a closed housing in which is provided a support track (4) arranged concentrically around a central axis as well as a tube (5) bearing on the support track (4). The peristaltic pump comprises a drivable rotor (6) equipped with pressing members (7) spaced in circumferential direction, which pressing members (7) can squeeze shut the tube (5) locally (at 8). The pressing members are connected to the rotor (6) by means of a connecting mechanism (13, 14) which is maintained in the operative or pumping position by means of a tension spring. During operation of the pump, by means of a radially movable cam disc the connecting mechanism (13, 14) can be brought into a position where the pressing members (7) do not squeeze shut or deform the tube (5) and the tube can permit a cleaning fluid to pass through it.

Description

Title: Peristaltic pump with retractable pressing members.

The invention relates to a peristaltic pump comprising a closed housing provided with a support track arranged concentrically around a central axis and a pump tube bearing against the support track, a drivable rotor equipped with successive interspaced pressing members which can squeeze shut . the tube locally. ■

Such a peristaltic pump is known from Netherlands patent specification 178,711. hen using such a peristaltic pump, for instance in the food or pharmaceutical industry, it is necessary to regularly clean the interior of the tube and the installation connected to it, for example by passing a liquid cleaning agent through the tube at high velocity at a temperature of approx. 120°C. For proper cleaning, it is required that the flow velocity of the cleaning liquid be about 2.5 m per second. In order to achieve such a flow velocity of the cleaning liquid, it is necessary to rotate the pump rotor at a very high speed and this speed, added to the relatively high temperature of the cleaning liquid, has a very adverse influence on the life of the tube. The tube, made of rubber and provided with reinforcement layers, can properly tolerate a temperature of approx. 80°C during operation of the pu p. Local compression of the tube at higher temperatures and high speeds increases the rate of wear of the tube to a very considerable extent. It has already been proposed to partly disassemble the peristaltic pump to clean it, by temporarily removing the pressing members from the pump, so that during the cleaning operation the tube is not cσcnpressed anymore. This solution has a major drawback-in that it lengthens the period during which the installation for preparing food, with the peristaltic pump incorporated therein, is inoperative. The object of the invention is to provide a peristaltic pump in which these drawbacks are overcome. To that effect, the peristaltic pump according to the invention is characterized in that the pressing members are each connected to the rotor by means of a connecting mechanism that can be operated during operation of the pump, for bringing the pressing members into an inoperative position.

By operating the connecting mechanism, optionally by remote control, the pressing members can be brought from the operative position into the inoperative position during operation of the pump, so that while the pump continues to operate, the cleaning liquid can be passed through the tube of the pump at the appropriate temperature and at the desired flow velocity. After cleaning, the pump can be brought into the operative position again by operating the connecting mechanism in the opposite direction. Cleaning the production installation can thus be performed in a shorter time because partial disassembly of the pump can be omitted.

The connecting mechanism is preferably in the form of a toggle joint consisting of two links, one link being pivotally connected to the rotor and the other link being pivotally connected to the pressing member, while a tension spring acts on the connecting pivot of the two links, which spring draws the connecting pivot substantially radially inwardly against a hub mounted on the rotor.

By means of the connecting mechanism as described hereinabove, the pressing members can be maintained in a stable operative position and the toggle joint remains in the inwardly angled position, the tension spring preventing the toggle mechanism from moving into a radially outwardly angled position as a result of centrifugal forces. This last position can be realized by means of a radially movable cam disc provided within the pump housing, adapted to cooperate with a follower roller projecting outside the plane through the links and mounted adjacent the connecting pivot. By moving the cam disc in radial direction, the follower roller and hence the toggle joint mechanism, is forced to take the outwardly angled position, whereby the pressing members bear on the tube in slipping contact therewith subject only to the spring pressure.

One embodiment of the peristaltic pump according to the invention will now be further described, by way of example, with reference to the accompanying drawings, in which

Fig. 1 is a side elevational view of the pump housing with the cover removed, shown in an operative position;

Figs 2-4 show different positions of a pressing member being brought into its inoperative position; Figs 5-6 are schematic sections of the peristaltic pump taken on the line of action of the cam disc adjusting mechanism. Fig. l shows •a pump housing l provided with two connection stubs 2,3, of which one (2) forms the delivery side of the peristaltic pump and the other (3) forms the suction side. Arranged in the pump is a circular support track 4 with a pump tube 5 bearing thereon. Arranged centrally of the tube 5 is a rotor 6 provided with two diametrically opposite pressing members 7 which can compress the tube 5 as indicated at the pressure point 8. The rotor 6 rotates counterclockwise and thereby with a certain pressure forces out the liquid disposed in the tube 5 downstream of the pressure point 8, viewed in the direction of rotation, via the connection stub 2, while the part of the tube disposed upstream of the pressure point 8 is being filled via the connection stub 3 with liquid to be subsequently forced out. Each pressing member 7 is formed by a support 10 having secured thereto by means of a screw connection (not shown) a pressure pad 11 which is usually made of aluminum or plastics and has radial dimensions such that the tube 5 can be accurately squeezed shut, as indicated at pressure point 8. One end 12 of the support 10 is pivoted to a disc-shaped rotor member 9, while the other end is connected to the rotor member 9 through two links 13,14. The link 13 is pivotally connected to the support 10 at 15 and the link 14 is pivotally connected to the rotor member at 17. in the middle, the two links 13,14 are interconnected by a connecting pivot 16. The toggle joint formed by the links 13,14 is retained in the inwardly angled position by means of a tension spring 18, whose one end is connected to the connecting pivot 16 and whose other end is connected near, or possibly to, the pivot 12. In the operative position of the pressing member the connecting pivot 16 traverses a circle of a radius Rl, running over a circular hub 19 of the rotor member 9. Figs. 2-4 show in what manner the pressing members can be brought into the inoperative position. As appears from Fig. 2, a cam disc 22, which during normal operation of the pump (Fig. 1) lies in the centre of the rotor and fully within the circumference of the control disc 19, has been moved outwardly in radial direction by means of a control member, for instance a hydraulic cylinder 24 (Fig. 5) , whose line of action is- indicated at 21 in Fig. 2. After the cam disc 22 has moved outwardly in radial direction, a follower roller 23, arranged in alignment with connecting pivot 16, will engage the sloping flank of the cam disc 22 at some point during rotation of the rotor 6. Upon further rotation of the rotor 6, the follower roller 23 is urged outwardly still further until it reaches the position shown in Fig. 3, where the toggle joint mechanism consisting of links 13,14 is in the outwardly angled position, and, thus, the connecting pivot 16 is located outside the connecting line extending through the pivots 15 and 17. In that position the tension spring is extended. The connecting pivot 16 now lies on a circle with a radius R2.

Upon continued rotational movement of the rotor, the connecting pivot 16 and the follower roller 23 disposed on the same shaft come clear of the cam disc 22 (see Fig. 4) . In that position, the pressure pad 11 of the pressing member 7 is in contact with the outer wall of the tube 5. The tension spring 18 attempts to draw the connecting pivot 16 inwardly in radial direction, but is unable to do so when the pressure pad 11 is in contact with the tube. Upon further rotation, the pressure pad 11 shifts over the wall of the tube 5 without being able to compress this tube. Accordingly, no pumping action occurs. As soon as the rotor 6 has again reached a position where the pressure pad 11 is no longer in contact with the tube 5, the tension spring 18 can cause the toggle joint mechanism 13,14 to move inwardly again. This inward movement is converted into an outward movement again as soon as the follower roller 23 comes into contact again with the sloping flank of the cam disc 22 (Fig. 2) . It is desirable to choose the line of action 21 of the hydraulic cylinder 24 and the external shape of the cam disc 22 such that the follower roller 23 rolls over the cam disc 22 during that portion of the path of travel of a pressing member where the pressure pad 11 is clear of the tube 5.

Figs. 5 and 6 show a schematic section of the peristaltic pump, taken on the line of action 21 of the hydraulic cylinder 24. According to Fig. 5, the follower roller 23 and the connecting pivot 16 are at a distance Rl from the axis of the pump and the tube 5 is compressed by the pressing members of the rotor 6. The hydraulic cylinder 24, having the plunger 25 projecting therefrom and the cam disc 22 connected to the end thereof, is mounted on the cover 26 of the pump housing 1.

In Fig. 6 the plunger 25 of the hydraulic cylinder 24 is retracted, the cam disc 22 having been displaced outwardly in radial direction, and the follower roller 23 traverses a path disposed at a distance R2 from the axis of the pump housing l. In that position, the pressing members 7 are retracted and the tube 5 is not compressed when the pressing members are retracted.

Claims

£ 2_IM£

1. A peristaltic pump comprising a closed housing provided with a support track arranged concentrically around a central axis and a pump tube bearing against the support track, a drivable rotor equipped with successive interspaced pressing members which can squeeze shut the pump tube locally, characterized in that said pressing members (7) are each connected to the rotor (6) by means of a connecting mechanism (13,14) that can be operated during operation of the pump, for bringing said pressing members (7) into an inoperative position.

2. A peristaltic pump according to claim l, characterized in that the connecting mechanism comprises a toggle joint consisting of two links (13,14), of which one link (14) is pivotally (17) connected to the rotor (6) and the other link (13) is pivotally (15) connected to the pressing member (7), while a tension spring (18) acts on the connecting pivot (16) of the two links (13,14), said spring (18) drawing the connecting pivot (16) inwardly in substantially radial direction against a hub (19) mounted on the rotor (6) .

3. A peristaltic pump according to any one of claims 1-2, characterized in that within the pump housing (1) a cam disc (22) is arranged, capable of moving in radial direction (21) and adapted to cooperate with a follower roller (23) projecting outside the plane through the links (13,14) and arranged adjacent the connecting pivot (16) .

4. A peristaltic pump according to claim 3, characterized in that during operation of the pump the cam disc (22) is located within the circumferential circle of the hub (19) and, when the cam disc (22) has moved radially outwardly, the connecting pivot (16) is forced outwardly by the follower roller (23) into a position where the connecting pivot (16) is located beyond the connecting line through the pivoting points- of attachment (15,17) of the two links (13,14) of the connecting mechanism.

5. A peristaltic pump according to any one of claims 1-4, characterized in that the cam disc (22) is connected to the plunger (25) of a hydraulic cylinder (24) which is operable in two directions and is mounted on the cover (26) of the pump housing (1) .

6. A peristaltic pump according to any one of claims 1-5, characterized in that the line of action (21) of the hydraulic cylinder (24) and the shape of the cam disc (22) are chosen such that the connecting mechanism (13,14) is forced into the inoperative position at the moment when a pressing member (7) comes clear of the tube (5) .