EP0604888A1 - Pump for viscous substances with a rotary gate valve - Google Patents

Abstract

A rotary spool (1) includes openings (5) emerging on the lateral face (12) in communication with the inlet (6) and openings (5) emerging on the lateral face (13) communicating with the outlet (7). These openings (5) file past a port (4) allowing passage to and from a cylinder (2)/piston (3) assembly. <IMAGE>

Description

The present invention relates to piston pumps for very viscous materials. More particularly, it relates to the distribution members of these pumps.

In the rubber processing industry, when you want to pass unvulcanized rubber continuously through a die, to obtain a specific profile or a rubber sheet, a screw extruder is most often used . The rotation of the screw makes it possible to continuously transfer the unvulcanized rubber from an intake hatch by which it is generally introduced in the form of a plate or else in the form of a coarse strip, towards the head of the extruder, where it is pushed back under a certain pressure. The rubber then passes through an extrusion orifice of suitable shape.

This technique does not allow total control of the extruded volumes. This is why the state of the art also knows a pump for raw rubber described in patent EP 400 496. This pump uses a piston sliding in a cylinder. The admission is done through lights arranged in the cylinder at a place close to the bottom dead center of the piston stroke. The discharge of the rubber from the cylinder is done through an orifice comprising a valve. The proper functioning of such a positive displacement pump depends in particular on perfect control of the movements of the valve. This leads to prefer a controlled valve, rather than a simple ball held against its seat by a back pressure.

The object of the present invention is to perfectly control the open and closed state of the discharge orifice in a piston pump used with a material extremely viscous like unvulcanized rubber. It is necessary to guarantee this perfect closure, while guaranteeing sufficient opening of the outlet orifice, without obstructing the flow of rubber when the pump is in the delivery phase.

Another object of the present invention is to provide a passage section opening sufficient not to oppose the flow of an extremely viscous material such as unvulcanized rubber when the pump is in the intake phase or in phase exhaust.

Finally, another object of the present invention is to provide a pump having a minimum of moving parts, and the movements of which are as simple as possible to control.

According to the invention, a rotary distribution member is used which serves both to control the admission into the cylinder and to control the discharge from the cylinder.

The piston pump according to the invention has an inlet and an outlet. It comprises at least one piston sliding in a pumping chamber, between a top dead center and a bottom dead center. It comprises intake boosting organs, arranged in a supply chamber, ensuring a forced mechanical transfer of the rubber from a rubber introduction orifice arranged in the supply chamber, towards said pumping chamber, and is characterized in that it comprises a rotary distribution member inserted between said supply chamber and said pumping chamber, the distribution member comprising bores arranged and distributed to sometimes put the chamber in communication with the inlet, sometimes put the room in communication with the discharge, or to isolate the room of any communication with the inlet or the outlet, and in that it comprises means for controlling the rotational movement of the dispensing member and the synchronized movement of the piston.

According to an alternative embodiment of this pump, said pumping chamber is a cylinder in which said piston slides, the cylinder having a light disposed beyond said top dead center, used both for admission and for discharge.

According to another alternative embodiment, said piston is a plunger penetrating into said pumping chamber.

The preferred application envisaged for such a machine is a pump for raw rubber. However, other applications can be envisaged.

When the piston slides in a cylinder, thanks to the fact that the only lumen is located at the top dead center, the cylinder itself has no drilling, which means that guiding the piston poses no difficulty. It is the same light that is used for both intake and exhaust. In this way, it can be as large as necessary, until it has a section comparable to that of the cylinder. This is very favorable for a good flow of the material as well towards the interior of the cylinder on admission, as out of the cylinder during the delivery. There is no longer a compromise to be sought between admission and refoulement.

In pumping applications, it is sometimes desired to distribute the pumped material between several different pipes, while very precisely controlling the flow rate passing through each of the pipes. The invention offers the possibility of adapting the distribution member to distribute the flow output of the pump between several pipes without the need to use a separate distributor or to multiply the pumps used.

The following figures illustrate the invention and make it possible to understand its operation and to grasp all the advantages.

Figure 1 is a general diagram of the invention.

Figure 2 is a flat development of the outer surface of the dispensing member.

FIG. 3 is a flat development of the sheath corresponding to the dispensing member illustrated in FIG. 2.

Figure 4 is a flat development of the outer surface of the dispensing member of another alternative embodiment of the invention.
FIG. 5 is a flat development of the sheath corresponding to the dispensing member of FIG. 4.

FIG. 6 is a side view of the dispensing member illustrated in FIGS. 4 and 5.

FIG. 7 is a front view of the member shown in FIG. 6.

FIG. 8 illustrates another variant embodiment of the invention.

Figure 9 illustrates yet another alternative embodiment of the invention.

In Figure 1, we see the dispensing member 1 in rotation inside a tube, the left part 6 is the inlet, and the right part 7 is the discharge. The invention is illustrated in its application to positive displacement pumps for unvulcanized rubber.

At the intake, it can be seen that the pump comprises boosting members arranged in a supply chamber, to ensure a forced mechanical transfer of rubber from an introduction orifice 80 arranged in the supply chamber, towards the lateral face 12 of the dispensing member 1 against which the rubber is pressed under pressure. This is for example a screw 8 of the kind that is found in conventional extruders.

We see a piston 3 reciprocating in a cylinder 2. At the upper end of this cylinder 2, top dead center TDC, a light 4 provides communication between the cylinder 2 and the inlet or outlet. The dispensing member is a plug having a surface of revolution 10 (here cylindrical) and two lateral faces 12 and 13 on either side thereof. The side faces are in this example flat. The plug is rotatably mounted in a sheath whose shape corresponds to the shape of the surface of revolution 10. The sheath is here a cylinder 11. The light 4 opens into the internal surface of the sheath 11. The admission of the pump results in one 12 of the side faces and the discharge leads to the other 13 of the side faces.

The axis of rotation of the dispensing member is here perpendicular to the sliding movement of the piston 3. Holes are distributed all along the surface of revolution of the dispensing member 1. The holes take for example the form d 'recesses 5 notching one of the side faces and the surface of revolution 10. These holes pass over the light 4. They put it in communication alternately with the intake and then with the discharge. The movements of rotation of the distribution member and of translation of the piston must of course be synchronized. The reduction ratio existing between these two members depends on the number of bores arranged on the outer cylindrical surface 10 of the dispensing member 1. If for example for a piston cycle, the dispensing member makes a full turn, then there is a hole communicating towards the admission and a hole communicating towards the discharge.

Figures 2 and 3 provide a better understanding of the operation of the pump through a developed representation of the surface 10 of the dispensing member (Figure 2) and the corresponding surface of the sleeve (Figure 3). In this variant, there are two recesses communicating with the intake and two recesses communicating with the discharge.

The distribution member 12 having the appearance of a cylinder, the development of its outer cylindrical surface is a rectangle. The width D thereof corresponds to the thickness of the dispensing member 1 in the direction of its axis of rotation. In Figure 3, the edge between the two vertical lines separated by the distance D corresponds to the part of the inner surface of the sleeve 11 in contact with the dispensing member.

The length of the rectangle is 2πR, R being the radius of the dispensing member 1. The dimensions of the bore formed by the sleeve are of course identical, apart from the functional clearance.

The width 1 of the light 4 is materialized by two parallel broken lines. The development L of the light appears in FIG. 3. In FIG. 2, the slice between the two vertical lines separated by the distance 1 corresponds to the part of the exterior surface of the dispensing member which passes in front of the light 4 .

Figure 2 shows the surface of the four recesses 5, two of which communicate with the inlet on the left side of the figure, and two others communicate with the discharge on the right side of the figure.

In operation, there is relative movement of these two surfaces. Imagine that the surface shown in Figure 2 slides, for example from the bottom up, in front of the light 4 so that it passes between the two parallel broken lines drawn in Figure 2. Admission begins as soon as the light 4 and a recess 5 on the intake side slightly overlap.

Preferably, the recess 5 and the lumen 4 overlap exactly in the direction of the width of the figures to maximize the transfer of materials. This is not what is shown in schematic figures 2 and 3 in order to clearly understand the operating limits of the invention. The admission continues until the light 4 has not completely passed the first recess 5.

Between intake and exhaust, the surface 10 of the distribution member 1 obscures the light 4. To properly separate the intake from the discharge, it is therefore sufficient that the distance separating the end of the first recess 5 (corresponding to the intake) of the start of the second recess 5 (corresponding to the discharge), that is to say at least equal, and preferably very slightly greater than the length L of the light 4.

, où n est le nombre d'évidements utilisés à l'admission (ou au refoulement), donc ici n = 2.If we assume that the movement of the piston 3 from its top dead center to its bottom dead center is exactly symmetrical to the movement from the bottom dead center to the top dead center, and that the movement of the distribution member 1 is a rotation at constant speed, the admission is done during half of the cycle and the delivery is done during the second half of the cycle. For the developed representations of Figures 2 and 3, we must therefore respect the following relationship: $\text{n (A + B + 2L) ≦ 2 π R}$

, where n is the number of recesses used at admission (or at refoulement), so here n = 2.

In addition, to correctly ensure the separation of the intake and the discharge, the distance separating each time the end of the intake recess from the start of the exhaust recess and vice versa must be at least L.

For a rubber pump having a booster screw 8 at the inlet, the simplest embodiment of the invention consists in making the screw 8 and the dispensing member integral. In Figure 1, we see that the booster screw 8 is in direct engagement with the dispensing member 1, whose axis of rotation coincides with that of the screw 8. If we have two crank turns of the piston 3 a feeding screw turn 8, then one realizes on the member distribution 1 two recesses 5 at the inlet and two recesses 5 at the outlet.

The shape of the light 4 can be adapted as a function of considerations relating to the flow of the material to be pumped, and / or as a function of considerations relating to the machining of the parts. This shape can approach, or even correspond to the shape of cylinder 2. Only the length L of the light in the direction of development must be chosen or adjusted according to the length in the direction of development of the holes made on the surface of the distribution body. Apart from these constraints, the invention offers the possibility of adopting multiple variants of shapes.

Figures 4 and 5 are also diagrams giving a developed representation of the dispensing member (Figure 4) and the corresponding sleeve (Figure 5). The distribution unit has four intake holes and four delivery holes. The intake holes are all produced by recesses 5 opening on the lateral face 12 at the periphery 13 thereof (see FIGS. 6 and 7).

In this variant embodiment, the distribution member makes it possible to distribute the flow discharged by the pump between two different pipes. This is why one of the lateral faces (here, that 13 corresponding to the discharge, which is that shown in FIG. 6) has several concentric and separate tracks (here, two), each track being in communication with a pipe. different, each track communicating with at least one hole. It is of course possible to produce concentric tracks on the intake side or on the exhaust side according to the desired use for the pump.

The term "track" means the arrangement in a circle, that is to say always at the same radial level, of the outlet orifice of all the holes intended to collect (intake) or conduct (discharge) the material to or from the same pipeline.

On the discharge side, three recesses in the form of a recess 5 were arranged, quite similar to the recesses on the intake side, all three ending at the periphery of the face 13, which constitutes a first track allowing the collection of the material. in the non-moving space in rotation. A fourth hole 5R extends into a pipe 51, internal to the dispensing member, which leads to an orifice 52 constituting a second track, concentric with the first. In this case, the pumped material is distributed in a ratio of 3/4 - 1/4 between two different delivery pipes: a first annular collector collects the material at the periphery of the lateral face 13 of the distribution member, and a second collector, radially inside the first, collects the material discharged through the pipe 51.

In FIG. 8, another alternative embodiment of a pump for raw rubber is shown, in which a plunger 9 can penetrate a pumping chamber 90. The pumping chamber 90 appears twice, associated each time with the piston 9 in a different phase of operation, as will be explained below. Here again, the dispensing member is a plug 1 ′ having a surface of revolution 100 and two lateral faces 12 and 13 on either side thereof. The side faces are flat. The plug 1 'is rotatably mounted in a sleeve 11' whose shape corresponds to the shape of the surface of revolution 100. The pumping chamber 90 opens onto the surface of the sleeve 11 '. The intake of the pump ends at one 12 of the side faces and the discharge ends at the other 13 of the side faces.

The plug, seen in radial section, has the appearance of an "H" whose transverse branch 15 includes the axis of rotation of the plug, the sheath forming a protrusion penetrating between the vertical branches 16 of the "H". The pumping chamber 90 is constituted by a channel parallel to the axis of rotation of the plug, produced in said protuberance 11 right through it, and the holes 91, 92 are arranged in the vertical branches of the "H" , on either side of the transverse branch 15.

In Figure 8, we see that the two holes 91 and 92 of the plug 1 'are diametrically opposite. In the upper part of Figure 8, there is shown the plunger 9 in the occupied position at the end of the admission. The drilling 91 is carried out on an arc of a circle of sufficient angle to put the inlet in communication with the pumping chamber 90 during the entire time during which the plunger 9 passes from TDC to TDC. In the lower part of Figure 8, there is shown the plunger 9 in the position it would occupy at the end of delivery. The bore 92 is produced on an arc of an angle sufficient to put the discharge in communication with the pumping chamber 90 during the entire time during which the plunger 9 passes from PMB to TDC.

In FIG. 8, in order not to overload the drawing, it has not been shown that the plug 1 and / or the corresponding sleeve 11 ′ are in reality produced in several removable parts so that they can be assembled as shown. These are simple technological details that the skilled person can run without difficulty.

Finally, FIG. 9 illustrates an alternative embodiment in which the recesses 5 of a 1 '' cylindrical plug, here similar in appearance to that shown in Figures 1 to 3, are always in communication with several at the same time with the intake , or respectively with the repression. We see a pumping chamber 90 opening onto the surface of the sleeve associated with the valve 1 '' in several places, here in two places 20 and 21. A plunger 9 ensures the admission and the discharge of the material into and out of the pumping chamber 90.

The present invention makes it possible to produce a distribution with a single moving part, and with a very simple movement since it is a rotation. Those skilled in the art can easily see all the possible applications, and adapt the implementation of the invention to the envisaged application.

Let us simply add that, if one wishes to avoid any pulsation of the flow rate of a pump, one can for example use two pistons and control their movement by a judiciously drawn cam. This allows each piston to print an advance at constant speed (for a constant cam control speed) when it is in the delivery phase, to ensure the immobility of the pistons when the dispensing member isolates the chamber. pumping any communication with the delivery, and ensuring the complete recoil of one piston while the other is in the delivery phase.

Claims (10)

Pump for viscous material, comprising an inlet (6) and a discharge (7), comprising at least one piston (3 or 9) sliding in a pumping chamber, between a top dead center and a bottom dead center, comprising intake booster (6), arranged in a supply chamber, ensuring a forced mechanical transfer of the rubber from a rubber introduction orifice fitted in the supply chamber, towards said pumping chamber, characterized in that '' it comprises a rotary distribution member inserted between said supply chamber and said pumping chamber, the distribution member comprising bores arranged and distributed so as to put the chamber in communication with the inlet (6), sometimes to put the chamber in communication with the discharge (7), or to isolate the chamber from any communication with the intake or discharge, and comprising means for controlling the rotational movement of the delivery member distribution and synchronized movement of the piston. Pump according to claim 1, characterized in that the dispensing member is a plug (1 or 1 ') having a surface of revolution and two lateral faces on either side thereof, the plug being rotatably mounted in a sheath of shape corresponding to said surface of revolution,
in that said chamber opens onto the surface of the sheath, in that the inlet ends at one of the side faces, and the discharge leads to the other side face. Pump according to claim 1 or 2, characterized in that said chamber is a cylinder (2) in which slides said piston (3), the cylinder (2) having a light (4) disposed beyond said top dead center, used both for admission and for discharge. Pump according to one of claims 1 or 2, characterized in that said piston is a plunger (9) penetrating into said chamber (90). Pump according to claims 2 and 4, characterized in that said plug (1 ') has, seen in radial section, the shape of an "H" whose transverse branch (15) includes the axis of rotation of the plug, the sheath forming a protuberance (111) penetrating between the vertical branches (16) of the "H", in that said chamber (90) is constituted by a channel parallel to the axis of rotation of the plug, produced in said protuberance (111 ) right through it, and in that said holes (91, 92) are arranged in the vertical branches on either side of the transverse branch. Pump according to one of claims 1 to 5, characterized in that said chamber opens onto the surface of the sleeve in several places. Pump according to one of claims 2 to 6, characterized in that at least some holes are recesses (5) cutting into one of the lateral faces and the surface of revolution. Pump according to one of claims 2 to 7, characterized in that at least one of the lateral faces has concentric and separate tracks, each track being in communication with a different pipe, each track communicating with at least one bore. Pump according to claim 8, characterized in that it comprises two concentric tracks (50, 52) on the discharge side. Pump according to one of claims 1 to 10, characterized in that the boosting members essentially comprise a rotary boosting screw (8), in direct contact with the dispensing member (1 or 1 '), the axis of rotation of said screw and of the dispensing member being aligned.

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