BE870198A - ADDITIONAL VOLUTE ELEMENTS, ESPECIALLY FOR LIQUID PUMPS - Google Patents

Description

       

  "Complementary volute elements, in particular for

  
liquids "The invention relates to liquid pumps of the volute type, and in particular liquid pumps of this type, which can be immersed in the pumped liquid:

  
It is known that there is a category of machines generally comprising pumps, compressors and "volute" motors, in which two complementary elements of spiral shape or involute spiral, of the same pitch, are mounted on separate end plates. . These spiral elements are angularly and radially offset so as to come into contact with each other along at least two determined lines, for example, between curved spiral surfaces. Two contact lines are located approximately on one

  
radius starting from the central zone of the volutes so as to delimit one or more volumes, pockets or chambers. The angular position of these chambers varies with the relative orbital motion of the centers of the spirals and all chambers maintain the same relative angular position. When the lines

  
of contact progress along the surfaces of the volutes, the chambers formed exhibit a change in volume. In compressors and expansion motors, this results in

  
low pressure and high pressure areas, communicating with

  
outlets. In liquid pumps, the volume ratio remains constantly equal to 1. The outer and inner chambers communicate with flow ports and the liquid can flow from the inner chamber to the outside or from the outer chamber to the outlet. inside.

  
Although volute pumps have many advantages over compressors and expansion valves, these advantages consisting of reduced leakage problems and lower operating temperatures, it is not possible to achieve these advantages in practice for devices operating. satisfactorily unless such volute pumps can be operated at suitable speeds (eg at least 1800 rpm), essentially pulseless. The volute pump according to the invention comprises a device intended to suppress the pressure pulsations, or else a device intended to lower these pulsations.

  
pressure below a level above which said pulsations adversely affect the operation and efficiency of the pump. As will emerge from the following description concerning the embodiment shown in Figures 62 to 84 of the accompanying drawings, the volute pump according to the invention can be designed so as to be able to be immersed in the pumped liquid and in particular in fuel tanks for self-propelled vehicles, for example automobiles.

  
The invention therefore relates to volute elements, one of which is fixed and the other performs an orbital movement. The use of these elements in a volute pump allows

  
to operate the latter smoothly and at relatively high speeds, with maximum efficiency, so that it circulates a liquid without pulsation. In addition, the volute pump according to the invention is simple and inexpensive to manufacture and it can be made partially of plastic, for example by using techniques such as molding.

  
The invention therefore relates to a volute pump of the type described above and which, in one of its embodiments, can be immersed in the pumped liquid. This pump can be used as a fuel pump for self-propelled vehicles using light fractions of fuel oil, and it can be placed in the fuel tank so as to be isolated from the excessive temperatures which may be encountered in vehicles with exhaust gas control devices.

   The submersible pump according to the invention can deliver the fuel at high pressures; it initiates itself; it operates substantially without noise or vibrations, or variation of the delivery rate; it can run dry for a while; it does not require valves and it can ingest debris without suffering permanent damage. The volute pump described above also automatically ensures the seal between the volutes; it has a minimum of friction losses; it operates reliably for long periods of time and it

  
is inexpensive.

  
The invention therefore relates to complementary volute elements suitable for use in a liquid volute pump. These elements include a fixed element

  
volute having a central orifice for the flow of liquid and comprising a fixed end plate, a fixed involute coil of a turn and a half, fixed to a first surface of

  
the fixed end plate, and a fixed liquid transfer channel, formed in the first surface of the end plate. The other element is a volute element mounted so as to be able to perform an orbital movement relative to the fixed element under the action of a control device. It comprises a movable end plate, a movable involute turn of a turn and a half, fixed to a first surface of the movable end plate, and a movable liquid transfer channel, produced

  
in said first surface of the movable end plate. The term "mobile" denotes orbital motion. Fixed channels

  
and liquid transfer mobile are arranged and configured

  
so as to open approximately immediately after the movable coil has reached the point in its orbital cycle corresponding to the formation of three liquid chambers, separated essentially in a sealed manner from one another.

  
The invention therefore relates to a positive displacement pump

  
liquid, comprising the assembly of complementary elements

  
volute as described above, of a device applying an axial force which tends to cause the volute elements to bear axially against each other, of a coupling which maintains the volute elements in a fixed angular arrangement , a liquid inlet port and a liquid outlet port, and a device for controlling the orbital movement of the mobile element, so that the flanks of the involute turns and the associated end plates define mobile liquid pockets of variable volume, a peripheral volume surrounding these pockets and a discharge zone.

  
The invention therefore relates to a positive displacement pump

  
liquid, as defined above, can be immersed in the pumped liquid. This pump comprises a body which delimits a chamber containing the volute elements and which has, at one end, the liquid inlet orifice and, at its second end, the liquid outlet or discharge orifice. The control device comprises a motor placed in the chamber delimited by the body, between the volute elements and the second end of the body, so that the liquid discharged radially outwards by the volute elements and circulating in the pump s 'flows around the controller and maintains a predetermined hydraulic pressure inside the chamber, to constitute the element applying an axial force.

  
The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting examples and in which:

  
Figures 1 and 2 are, respectively, a plan view and an axial section of a first embodiment of a fixed volute element according to the invention, this element being particularly suitable for a volute pump in which the liquid flows inward;

  
Figures 3 and 4 are, respectively, a plan view and an axial section of an orbital scroll member for use with the fixed scroll member shown in Figures 1 and 2;

  
figures 5 to 20 are cross sections
(odd figures) and longitudinal (even figures) of the elements in fixed volute and with orbital movement shown in Figures 1 to 4, these sections showing the operation of the central discharge port of this embodiment;

  
Figures 21 and 22 are, respectively, a plan view and an axial section of another embodiment of the fixed volute element according to the invention, this embodiment being particularly suitable for a volute pump in which the liquid flows out;

  
Figures 23 and 24 are, respectively, a plan view and an axial section of the orbital scroll member for use with the fixed scroll member shown in Figures 21 and 22;

  
figures 25 to 40 are cross sections
(odd figures) and longitudinal or axial (even figures) of the elements in fixed volute and with orbital motion shown in Figures 21 to 24, these sections showing the operation of the peripheral discharge port of this embodiment;

  
Figures 41 and 42 are, respectively, a plan view and an axial section of another embodiment of the fixed volute member according to the invention, having both a central orifice and a peripheral discharge orifice and in which the liquid can flow inward or outward;

  
Figures 43 and 44 are, respectively, a plan view and an axial section of an orbital scroll member for use with the fixed scroll member shown in Figures 41 and 42;

  
figures 45 to 60 are cross sections
(odd figures) and longitudinal or axial sections (even figures) of the fixed volute and orbital motion elements shown in Figures 41 to 44, these cross sections showing the operation of the discharge ports of this embodiment when the liquid s' flows inward or outward; FIG. 61 is a longitudinal section of a volute pump for liquids according to the invention; FIG. 62 is a longitudinal section on an enlarged scale of a volute pump for liquids according to the invention, particularly suitable for use as a fuel pump for an automobile, the pump of which is submerged in the fuel; Figure 63 is a plan view of the discharge end of the pump shown in Figure 62;

   FIG. 64 is a partial longitudinal section of a variant of the pump shown in FIG. 62, this section showing a variant of the device making electrical connections with the motor and with a secondary counterweight; Figure 65 is a plan view of the discharge end of the pump shown in Figure 64; FIG. 66 is a partial longitudinal section, on an enlarged scale, of the inlet end of the volute pump according to the invention, this view showing in detail the drive and coupling device, the volute elements, the outlets and the element supporting the

  
axial load; Figure 67 is a section taken on line 67-67 of Figure 66; Figure 68 is a section taken on line 68-68 of Figure 66;

  
Figures 69, 70 and 71 are partial longitudinal sections showing three other embodiments of the pump element of Figure 66 for supporting

  
the axial load, this element being used with a separate coupling element; Fig. 72 is a partial longitudinal section showing one embodiment of an axial load bearing member and a coupling member, associated to form a sub-assembly; Figure 73 is a section taken on line 73-73 of Figure 72, showing the respective positions of the axial ball bearings used;

  
Figures 74A, 74B and 74C are, respectively, a schematic diagram, a plan view and a partial cross section showing the parameters entering into the use of the thrust ball bearings shown in Figures 72 and 73; Fig. 75 is a partial longitudinal section of another embodiment of the axial load bearing member and the coupling member, combined to form a subassembly;

  
Figures 76 and 77 are, respectively, a plan view and an axial section of the axial load support and coupling sub-assembly shown in Figure 74; Fig. 78 is a partial longitudinal section of another embodiment of the coupling and axial load support sub-assembly, in which spherical members perform the dual function of load support and coupling;

  
Figures 79 and 80 are, respectively, a plan view and a partial axial section of the coupling and axial load support sub-assembly shown in Figure 78; Fig. 81 is a partial longitudinal section showing a variant of the coupling and axial load support sub-assembly shown in Fig. 78 and in which rollers perform the dual function of load support and coupling;

  
Figures 82 and 83 are, respectively, a

  
plan view and partial axial section of the axial load bearing and coupling sub-assembly shown

  
in Figure 81; and Figure 84 is a cross section of a liquid tank in which the pump according to the invention is submerged.

  
Each sealed pocket containing a fluid and delimited inside a volute apparatus is formed by two parallel planes presented by end plates, and by two cylindrical surfaces following the involute of a circle or any other suitable curve. The volute elements have parallel axes, because this is essential to maintain a tight and continuous contact between the flat surfaces of these elements. Each sealed pocket moves between these parallel planes, as do the two lines of contact between the cylindrical surfaces. These contact lines move due to the fact that one of the cylindrical elements, for example a volute element, performs an orbital movement inside

  
of the other element. This is obtained, for example, by maintaining a first volute element in a fixed position, and by orbital movement of the other volute element. The pump according to the invention uses this mechanism to circulate the fluids and, therefore, it is called "volute pump for liquids".

  
The expression "volute part" used in the present specification denotes the base part consisting of an end plate having the orifice (s) characterizing the invention, and an involute member which has surfaces establishing the movable lines of contact. The term "coil" is used herein to denote the involute member establishing movable contact lines. These turns have a certain shape, for example an involute of a circle (involute spiral), an arc of a circle, etc., and they have a certain height and a certain thickness. Finally, the expression "volute element" applies to the whole of the fixed or orbital movement member, of which the fixed or orbital movement part forms part.

  
When the volute apparatus is used as compressors and regulators, the turns of the volute elements can have any desired number of involute turns. However, a liquid volute pump must be designed so that each of the volute elements has a turn forming a turn and a half of an involute. This criterion is dictated by the fact that a volute apparatus intended to pump a liquid must have a compression ratio exactly equal to 1. When the compression ratio of such an apparatus is greater than 1, the retained liquid tends to be compressed. Since the liquid is essentially incompressible, any volute pump operating with a compression ratio greater than 1 tends to jam and malfunction.

   Thus, for a volute pump to have a compression ratio equal to 1, its elements must not have more than one and a half involute turns. The length of the coil makes it possible to obtain the desired continuity for the joint between the peripheral zone and the interior zone delimited between the volute elements

  
without compressing the retained fluid.

  
However, the limitation of the turns to one and a half involute turns does not make it possible to completely solve the problems raised for the manufacture of a liquid pump.

  
of the volute type, practical and efficient, since the serious problem of the pressure pulsations developed during the discharge of the liquid from the pump is not solved. These pressure pulsations result from the fact that the rate of variation of the volume of the volute pocket (central or peripheral), communicating with the discharge orifice, is greater than the rate of variation of the area of the orifice. discharge from this pocket. Therefore, the forward drive of the orbital-moving volute member causes compression of the liquid in the discharge pocket, the discharge by force of

  
this liquid through a narrow discharge opening and, consequently, the appearance of intermittent pulsations at high pressure. This pressure can be high enough to risk damaging the components constituting the volute elements.

  
In the case of small pumps of relatively low efficiency and operating at relatively low speeds, it may be possible to tolerate some pressure pulsations. However, in most applications of a

  
  <EMI ID = 1.1>

  
relatively pulsation-free and work at suitable speeds, for example at 1800 rpm or more.

  
The volute pump according to the invention performs pumping of liquids without pulsation, at relatively high flow rates, using a new arrangement of orifices. This arrangement of the orifices makes it possible to eliminate

  
the pocket relieves the pressure causing the pulsations by making the opening of the discharge orifice faster than when this opening relies only on the movement of the coil of the volute element performing an orbital movement.

  
The flow of the liquid in a volute pump being able to take place from the peripheral zone towards the interior and towards the central pocket, or else from the latter towards the exterior and the peripheral zone, the new arrangement of the orifices can be made. apply to central pocket, peripheral volume or both.

  
Figures 1 to 4 show parts in a fixed volute and in orbital movement, suitable for elements in volute for a pump in which the liquid flows from the peripheral volume inwardly to the central pocket. The fixed volute part 10 shown in FIG. 1 comprises an end plate 11 and an involute coil 12, made in one piece with the end plate or mounted on a separate member which is fixed to the inner surface 13 of the plate. extreme 11 (as described, for example, in US Pat. No. 3,994,635). The involute coil 12 begins at a contact line 14 which corresponds to a tangent

  
to the involute generator ray, and it passes through the points of contact between the involutes of the elements in fixed volute and orbital motion, so as to end in a contact line 15 which also corresponds to a tangent to the generator ray of the involute . Thus, this turn forms one and a half involute turns and it has an outer side wall or surface 16, a side wall or an inner side surface 17 and an end surface 18.

  
The end plate 11 has a central boss

  
20 which projects from the outer surface 21 and which has an annular groove 22 for containing a sealing ring when the fixed volute part is assembled in a fixed volute member of a liquid pump such as that shown in FIG. figure 61. An orifice 23 for liquid passes through the end plate 11 and the boss 20 and a transfer channel 24 is machined in the surface 13 and is in the form of a recess communicating with the orifice 23. The latter and

  
the transfer channel 24 constitutes a collector or a discharge zone. As shown in plan in Figure 1, the channel
24 has a main edge 25 which coincides with a line passing through the center 26 of the end plate 11 and parallel to the contact lines 14 and 15, and another curved main edge 27 the shape of which corresponds to that of the surface. 34 of the coil 32 involute of the volute part 30 with orbital movement (Figures 3 and 4), when the two volute parts are oriented so that the sides of the volutes come into contact at most at four points, as shown in the orientation of the turns in Fig. 5. Therefore, the curved edge 27 can be defined as following the trace of an involute turn edge of the complementary volute pieces.

   These main edges are joined by fillets 28. Although the transfer channel 24 can have a semi-circular edge instead of the involute edge 27, this involute shape is preferred because of the greater precision it provides. available at the orifices. Since the transfer channel 24 is placed inside the involute turn, it may be referred to as the "inner channel".

  
Although the orifice 23 is shown in Figures 1 and 2 in a position such that it intersects the edge
25 of the transfer channel 24, this orifice 23 can also be located at any point of the interior pocket formed by the turns of the volute parts, provided that it communicates with the channel
24 transfer and that it does not affect the shape of the coil

  
12.

  
FIGS. 3 and 4 show the part 30 in volute with orbital movement, the shape of which corresponds to that of the fixed part 10 in volute. This movable part 30 comprises an end plate 31 and an involute coil 32 which is fixed to the inner surface 33 of the end plate 31 or which is made in one piece with the latter. The coil 32 has a flank or an outer contact surface 34, a flank or an inner surface 35 and an end surface 36 of contact. It begins at a contact line 37 which corresponds to a tangent to the generating radius of the involute, it passes through the points of contact between the involutes of the parts.

  
in a fixed and mobile volute, and it ends at a contact line 38 which also corresponds to a tangent to the generating radius of the involute. A transfer channel 39 is machined in the surface 33 of the end plate of the movable volute part, so as to constitute a recess whose position and shape with respect to the fixed volute part correspond to the position and shape of the transfer channel 24 of this fixed part relative to the moving part. In other words, the transfer channel 39 has a main straight edge 40 which coincides with a line passing through the center 41 of the end plate and parallel to the contact lines 37 and
38, and a curved main edge 42 which corresponds to the partial outline of an edge 16 of the outer surface of the coil 12

  
of the fixed volute part when the volute parts are oriented so as to establish the maximum of four contact points, as shown in figure 5. These main edges

  
are also joined by rounded fillets 43. When they are associated, these channels 24 and 39 for transferring the end plates of the volute parts correspond to a first arrangement of the orifices of the device according to the invention.

  
In the case where the volute parts are made of a metal such as stainless steel, the recessed transfer channels can be made by machining. When the volute parts are made from a synthetic resin such as a polyimide, the transfer channels can be molded with the parts. In general, it is better to give

  
to these channels a depth approximately equal to the width of

  
the involute coil.

  
The manner in which the arrangement of the orifices of the volute parts shown in Figures 1 to 4 makes it possible to obtain essentially pulsation-free pumping of the liquid will be described in detail with reference to Figures 5 to 20 which show the operation of a pump in operation. volute using these volute elements and in which the liquid flows radially inward. Figures 5 to 20 show the volute parts in various positions corresponding to intervals equal to one-eighth of the orbital movement performed during a pumping cycle, the figures bearing odd numbers being sections of the turns, transverse to the axis central of the apparatus, and the figures bearing even numbers which immediately follow the odd numbers being corresponding longitudinal sections passing through the turns.

   Like reference numerals denote the same elements in Figures 5 to 20 and in Figures 1 to 4. Although the shape of the volute movable part transfer channel 39 does not normally appear on cross sections (e.g. figures 5, 7, etc.), the shape of this transfer channel is indicated in dotted lines in order to establish the position of the transverse channels in the corresponding axial sections
(eg in figures 6, 8, etc.). The boss 20 of the fixed volute part is not shown in the axial sections of Figures 6, 8, etc. to clarify more.

  
When operating the volute pump,

  
the part 30 in volute with orbital movement, mounted in a movable element in volute, is driven so as to execute an orbital movement (using a device described in more detail with regard to FIG. 61) with respect to the fixed part 10 which is mounted in a fixed volute element, the side surfaces 16 and 17, and 34 and 35 of the fixed and movable volute parts being in contact along moving lines. As described in more detail hereinafter with reference to Fig. 61, it is in fact possible that a very small clearance, for example a clearance between about 0.025 and 0.125 mm, appears between the side surfaces of the involutes.

   The end surfaces 18 and 36 of the fixed and movable scroll parts, by coming into contact with the inner surfaces 33 and 13 of the movable and fixed scroll parts, respectively, define movable pockets
50, 51 and 52, the volumes and intercommunications of which vary in order to circulate the liquid inside the pump. Liquids with viscosities much greater than those of gases and the internal volumetric ratio of the pump being equal

  
at 1 rather than greater than 1, the need for effective radial sealing between the end surfaces 18 and 36 in contact with the turns, from one pocket to the other, is not as important as in the case of compressors or of regulators. It is therefore unnecessary to use radial sealing members such as those described in the patent of the United States of America.

  
N [deg.] 3,944,636.

  
The substantially simplified longitudinal section of Figure 6 shows the fixed volute part 10 mounted in a volute member which comprises a body plate 53 having an annular protrusion 54 whose end surface 55 assumes the function of the contact surface with which the inner surface 56 of the movable volute element 57, of which the end plate 31 forms part, establishes a movable contact in order to delimit a peripheral volume 58 in which the liquid to be pumped is introduced by entering through a peripheral orifice 59. FIG. 61 shows in more detail and with greater precision the assembly of the volute elements in a complete volute pump.

   The other even-numbered figures 8, 10 ... 20 only represent the parts of the volute parts comprising the turns and the orifices, the peripheral volume which, of course, exists, not being shown again.

  
It is assumed that the operating cycle to be described begins with the closing of the central pocket 52 to

  
a time at which the pockets 50 and 51 are also closed. The liquid is discharged by passing through the outlet manifold comprising the orifice 23 and the transfer channel 24. In this mode of operation, the central pocket 52 assumes the operation of a discharge zone. As shown in Figures 5 and 6, the pockets 50 and 51 are at their maximum volume and they are separated almost completely and hermetically from the central pocket 52, if we do not consider the small clearances between the sides of the turns and between the end surfaces of the turns and the end plates. It is first assumed that none of the transfer channels 24 and 39 is machined in the end plates.

   The effect which may result from this appears in FIGS. 7 and 8 which show the positions of the turns after one-eighth of the total orbital movement of the mobile element, the direction of movement being indicated by the broken arrow. The volume of the pockets 50, 51 and 52 begins to decrease and the liquid contained in the pump being essentially incompressible, it is forced out of the pockets 50 and
51 towards the central pocket 52 passing through the relatively narrow openings 60 and 61 resulting from the movement of the turns. In addition, the relative dimensions of the central pocket 52 and the discharge port 23 are such that this effect is accentuated. This results in the build-up of pressures producing a very detrimental effect on the volute members and the production of high pressure pulsations making the pump inefficient and noisy.

  
The presence of interior transfer channels 24 and 39 in the fixed and movable scroll members, respectively, essentially eliminates this undesirable phenomenon. As shown in Figure 8, the transfer channels are profiled and arranged so as to open almost instantaneously after the pocket 52 is closed. Thus, the channels 24

  
and transfer 39, which were closed due to the position of the coil, open with continued movement of the movable coil. Channels 24 and 39 are of a size and depth such that they enlarge openings 60 and 61 sufficiently so that the possible flow rate reaches a value which prevents pressure build-up in the pockets and allows non-pulsating flow of the liquid. in the orifice 23 (the flow of liquid being indicated by arrows in solid lines in the figures).

  
As shown in Figures 9 to 14, the transfer channels 24 and 39 remain open to allow an essentially non-pulsating flow of liquid from the pockets 50 and 51 into the pocket 52, then, when the pockets 50,

  
51 and 52 decrease in volume and constitute a single virtual central pocket, these channels still allow the liquid to flow smoothly through the discharge orifice 23. When the combined volume of the pockets 50, 51 and 52 decreases, the liquid of the peripheral volume 58 begins to penetrate into the so-called "open" pockets 65 and 66, delimited between the turns.

  
in volute. These pockets 65 and 66 are said to be "open" by the

  
that they communicate directly with the peripheral volume 58. As shown in Figures 9 and 10, during the first quarter of the orbital movement, the channels or openings

  
60 and 61 formed by the movement of the turns enlarge and the transfer channels 24 and 39 are completely open in order to

  
to allow liquid to flow freely into the central pocket 52 and into the discharge manifold. The openings

  
60 and 61 continue to enlarge until half of the orbital motion is reached, as shown in the figures

  
11 to 14. Although transfer channels 24 and 39 continue

  
in making the pockets 50, 51 and 52 communicate, they are no longer essential for conducting a large quantity of liquid and they close progressively under the effect of the movement of the mobile element in a volute. As shown in Figures 15-20, this is so until the central pocket 52 can be viewed as a separate pocket after about three-quarters of the orbital motion and the pockets "open. "65 and 66 are sufficiently closed with respect to the peripheral volume 58 to be considered as forming new outer pockets 50 and 51, communicating with the peripheral volume through openings 67 and
68 always decreasing.

  
Due to the closing of the openings 67 and 68, all of the closed pockets, including the central pocket 52, reach their maximum volume to establish the situation shown in Figures 5 and 6 and to start a new cycle.

  
As long as the openings 67 and 68 are open on the peripheral volume, the transfer channels 24 and 39 are closed. But, as indicated above, approximately at the time of closing of the three pockets, the system of orifices designed according to the invention comes into operation.

  
Figures 21 to 24 show volute parts

  
fixed and mobile, presenting the system of orifices according to the

  
vention and suitable for a volute pump in which the

  
liquid flows radially outward from the central pocket

  
laughter and peripheral volume. The fixed part 70 in volute shown in Figure 21 comprises an end plate 71 and

  
an involute coil 72 made in one piece with

  
this end plate or fixed to the inner surface 73 of said plate. The turn 72, as well as the turn 12 shown

  
in Figures 1 and 2 begins at a contact line 74 and

  
leads to a line 75 of contact and it forms a development.

  
te spanning a turn and a half. The coil 72 has an outer flank or an outer lateral surface 76, an inner flank

  
or an inner side surface 77 and an end surface

  
78. End plate 71 has a central boss 79 projecting from an outer surface 80. A liquid port 81 passes through end plate 71 and boss 79.

  
A transfer channel 85 is machined in the interior surface 73 of the end plate 71 so as to form

  
a recess. As shown in plan in figure 21, the

  
transfer channel 85 has a main inner edge 86

  
whose shape corresponds to that of the inner surface 95

  
of the involute turn 92 of the volute element 90 with orbital movement (Figures 23 and 24) when the two volute elements are oriented such that the maximum number of points

  
contact between the sides of the turns is equal to 4, as

  
shown in Figure 25. Thus, this leading edge 86, likewise

  
that the edge 27 of the inner channel 24 shown in Figure

  
1, partially follows the path of the edge of the involute coil of the corresponding volute part. The second edge

  
main or outer edge 87 of the east transfer channel 85

  
machined to follow the shape of the inner edge 86 of which

  
it is spaced radially outward. Edges 86 and

  
87 join by leaves 88. The distance between

  
the edges 86 and 87 is preferably equal to twice the thickness of the involute turn of the volute part. The

  
transfer channel 85 is therefore in the form of a curved recess, contiguous to the outer end of the turn 72 or only slightly spaced from this outer end, and

  
extending over an arc between about 45 and 90 [deg.]. The canal
As the transfer unit is located outside the involute coil, it may be designated, for convenience, "outer channel".

  
The volute part 90 with orbital movement or mobile part, shown in plan in FIG. 23 and in axial section in FIG. 24, comprises an end plate 91 and a coil

  
92 as an involute made in one piece with the end plate or fixed to the inner surface 93 thereof. This turn 92 begins at a contact line 74 and ends at a contact line 75 and forms an involute turn and a half. The coil 92 has an outer flank or an outer side surface 94 of contact, an inner flank or an inner surface 95 and an end surface 96 of contact. A channel 97

  
transfer, corresponding to the transfer channel 85 of the fixed volute part, is machined in the inner surface 93 of the end plate 91 so as to form a recess. As shown in plan in Figure 23, the transfer channel 97 has a main inner edge 98 whose shape corresponds to the partial outline of the edge of the inner surface 77 of

  
  <EMI ID = 2.1>

  
that the two volute parts are oriented in such a way that a maximum of four points of contact is obtained between the sides of the turns. The main outer edge 99 of the canal
Transfer 97 has the same profile as the main inner edge 98 and the channel is closed by fillets 100. Its shape and size correspond to those of the curved transfer channel 85 of the fixed volute element.

  
The manner in which the orifice system of the volute parts shown in Figures 21 to 24 allows for substantially pulseless liquid pumping will be described in detail in conjunction with Figures 25 to 40 which show the volute parts during pumping of liquid. a liquid radially outward. As in the case of Figures 5 to
20, Figures 25-40 show the volute parts in various positions during a pumping cycle, the odd figures showing the cross-sectional turns oriented transversely to the central axis of the apparatus, and the even figures which follow the odd figures being corresponding axial sections passing through the turns. In Figures 25 to 40, the longitudinal plane of the volute elements is rotated around the central axis from one figure to another in order to cut the

  
  <EMI ID = 3.1>

  
and their closure.

  
Similar to Figure 6, Figure 26 shows the volute parts 70 and 90 mounted in a volute pump. Thus, the fixed part 70 in volute is mounted in a plate
105 of a body which has an annular protrusion 106 having a surface 107 for contacting the interior surface 93 of a protrusion 108 of the volute movable member. A peripheral liquid volume 110 is delimited in the closed space thus obtained, and an orifice 109 (or more of these orifices) is made through the plate 105 of the body in order to establish communication between the peripheral volume 110.

  
and a liquid reservoir (not shown). In the operating cycle described below, orifice 109 assumes the function of a liquid flow collector for the peripheral discharge zone thus formed, the liquid flowing radially outward. The orifice 81 of the fixed volute element therefore constitutes the inlet manifold. The turns as positioned in Figures 25 and 26 therefore form two closed outer pockets 111 and 112 and a central pocket
113.

  
Figures 25 to 40 show in detail the operation of the orifice system according to the invention. It is assumed that the cycle begins at the point at which each of the pockets or chambers 111, 112 and 113 has just closed relative to the other pockets and has its minimum volume, immediately before enlarging. As in the case of the orifice system described above with reference to Figures 1 to 20, a slight clearance, for example between 0.025 and 0.125 mm, may be constantly tolerated between the sides of the turns in order to avoid their wear.

   As previously, if it is assumed that the end plates 71 and 91 do not have curved transfer channels, it appears that the liquid contained in the pockets
111 and 112 is subjected to a constantly increasing pressure as the volute movable member is driven in the direction indicated by the broken arrows in Figures 25 and 26. This is due to the fact that the openings 115 and 116 ( figure 27), resulting from the displacement of the movable coil 92 relative to the fixed coil 72, are not large enough to allow the flow of the liquid from the pockets 111 and 112 in the peripheral zone 110 at a rate preventing the pressure of the liquid pockets 111 and 112 to rise excessively. This results in the appearance of pressure pulsations and ultimately deterioration of the volute organs.

  
However, in the presence of the transfer channels 85 and 97, additional liquid flow openings form almost instantaneously after the closure of the pockets 111, 112 and 113. Thus, the transfer channels 85 and 97 are added to the. openings 115 and 116 resulting from the movement of the orbital coil relative to the fixed coil and they eliminate any unwanted pressurization of the liquid which could cause pressure pulsations.

  
As shown in Figures 27 to 32, the channels

  
85 and 97 of transfer close when the element in volute with orbital movement reaches the three-eighth of its orbit because, at this moment, it is no longer essential that the channels be added to the openings 115 and 116 which almost reach their maximum. The central pocket 113 obviously occupies an increasingly large part of the volume previously forming part of the pockets 111 and 112, which ensures sufficient control of the pressure of the liquid prevailing in the central pocket.
113 when an additional quantity of liquid enters it.

  
It should be noted with regard to the figures that, when the operating cycle takes place, the pockets as described with regard to FIGS. 25 and 26 are less and less well defined, a part of each of the pockets 111 and 112 no longer being able to be distinguished from the central pocket 113 '. However, for clarity, the reference numerals of Figures 25 and 26 are used in Figures 27 to 40 and in the specification.

  
of these figures.

  
The openings 115 and 116 formed between the turns
72 and 92 remain at their substantially maximum dimension while pumping continues for three quarters of the cycle, as shown in Figures 35 and 36. This allows channels 85 and

  
97 transfer to remain really closed, that is to say inoperative. Finally, during the last quarter of the cycle (figures 37

  
to 40), the small volume of liquid remaining in the pockets 111

  
and 112 is transferred to peripheral volume 110 and, at the end

  
cycle, channels 115 and 116 are closed. As can be seen from FIGS. 33 to 40, the transfer channels 85 and 97 remain closed, because the system of orifices resulting from the movement of the orbital coil relative to the fixed coil makes it possible to obtain a discharge and a flow of the liquid without pulsation. At the end of the cycle, the pockets 111, 112 and 113 are hermetically separated from each other, as shown in FIG. 25, in order to be able to start another cycle.

  
It emerges from the foregoing description of the operation of the orifice system according to the invention that the liquid transfer channels are arranged and configured so as to open approximately immediately after the involute coil with orbital motion has reached the point in its orbit for which three liquid pockets, almost totally separated, are formed, and also so as to remain open at least until the openings, resulting from the movement of the orbital coil and establishing communication with the discharge zone (whether central or peripheral), are large enough to prevent the appearance of any sensitive pressure pulsations inside the pump.

  
In many applications, it is preferable to use liquid volute pumps designed for

  
radially outward oriented flow rather than those designed for inward oriented flow. The hydraulic pressures prevailing in outward flow pumps can be used to hold the volute elements together and thereby make operation more efficient. In addition, it is possible to increase the cross section of the discharge passage by using several orifices spaced apart along the peripheral zone if desired. These factors can more effectively reduce or eliminate

  
the flow pulsations using the orifice system according to the invention.

  
Figures 41 to 44 show another embodiment according to the invention in which the end plates of the volute members have a central (interior) channel and a peripheral (exterior) transfer channel. The fixed volute part 120 shown in Figures 41 and 42 comprises an end plate 121 and a turn 122 extending over one and a half involute turns, as is the case of the volute parts shown in Figures 1 and 2 and on the figures
21 and 22. The volute part 120 has a central orifice
123, a central transfer channel 124, forming a recess

  
and having the same shape as the channel 24 shown in Figure 1, and a peripheral transfer channel 125, forming a recess and having the same shape as the channel 85 shown in Figure 21. Likewise, the volute part 130 to orbital motion shown in Figures 43 and 44 has an end plate
131 and a turn 132 extending over one and a half involute turns, as is the case of the volute parts shown in Figures 3 and 4 and in Figures 23 and 24. The part 130 has a central channel 133 of transfer and a peripheral transfer channel 134, having the same size and shape as the channels shown, respectively, in Figures 3 and 23.

  
Figures 45 to 60 are sections analogous to those of Figures 25 to 40, the longitudinal planes of even-numbered figures, for example of Figures 46, 48, etc., being gradually rotated to clearly show the transfer channels in the open position . A liquid volute pump comprising the volute parts shown in Figures 41 to 44 can be used to circulate the liquid radially inward, from the peripheral volume to a central discharge area, or radially outward, from the central pocket to a peripheral discharge zone. The cycle of operations shown in Figures 45 to 60 illustrates the first of these modes of operation, i.e. radial inward flow.

   However, Figures 45 to 60, taken in a different order, can also be used to illustrate the operation of the orifice system when pumping according to the second mode, that is to say radially outwards, as described below. Therefore, to use Figures 45 to 60 to illustrate the two modes of operation, the flow of liquid in the first mode, that is, inward area, is indicated by an arrow referenced by the number "1" surrounded by a circle and followed by a letter ^, b ... h, these letters indicating in order and in steps of an eighth of an orbit, the operation of the pumping cycle as shown in the previous figures. The second operating mode, that is to say in outward flow, is indicated by an arrow referenced by the number "2" surrounded by a circle. <EMI ID = 4.1>

  
indicate the sequence of pumping cycle operations. In the latter case, the figures must be considered without taking into account the order of their numbering, as indicated below.

  
The volute elements of Figures 41 to 44 are

  
  <EMI ID = 5.1>

  
in the same manner as described with respect to Figure 26, and the same reference numerals are used to identify the same parts. As shown in Figure 45, it can be assumed that the cycle begins when the outer pockets 135

  
  <EMI ID = 6.1>

  
The following description relates to the first mode of operation, namely the mode in which the liquid flows radially inward.

  
As shown in Figures 45 to 56 and as

  
it emerges from a comparison of these figures with figures 5

  
  <EMI ID = 7.1>

  
of orifices comprising only central transfer channels. Thus, in a fluid pump comprising the volute parts

  
  <EMI ID = 8.1>

  
ter central openings 0 and 141 resulting from the movement of the coils end of production of a rapid flow and without pulsa-

  
  <EMI ID = 9.1> transfer pherics are not necessary and they remain inoperative during the first five-eighth of the pumping cycle, because the peripheral openings 142 and 143 resulting from the movement of the turns are suitable for the admission of liquid into the volutes . However, during the movement of the movable volute element between the five-eighth and three-quarters

  
from its orbit (figures 55 to 58), the mobile coil has moved so as to open the peripheral channels 125 and 134 of, transfer in order to increase the flow of the liquid in these peripheral channels towards the open pockets 144 and 145 located

  
  <EMI ID = 10.1>

  
sea these last. Penetrating an additional amount of liquid into pockets 144 and 145 has the effect of making the flow of liquid through the volutes smoother and therefore more uniform. As shown in Figures 57 to 60, the peripheral transfer channels 125 and 134 remain open and work until the end of the cycle, that is to say until the instant of closing of the pockets 135 and 136. (figures 45 and

  
46).

  
To follow the operation of the orifice system according to the invention in its second mode, that is to say when

  
  <EMI ID = 11.1>

  
necessary to first consider figures 45 and 46, then to follow the figures in pairs, in reverse order, of the figures

  
59 and 60 up to figures 47 and 48. The peripheral channels
125 and 134 transfer are added to the peripheral openings
142 and 143 at the end of the discharge of the liquid (figures 59 and

  
  <EMI ID = 12.1>
-suèdes Figures 27 to 30. During this period of the operating cycle, the central pocket 137 in fact includes the pockets
135 and 136, so that no communication problem between <EMI ID = 13.1> situation continues (figures 55 and 56 to figures 47 and 48)

  
and, as the central openings 140 and 141 formed by the turns continue to decrease, the role of the open central transfer channels 124 and 133 in ensuring smooth flow

  
and without pulsation of the liquid through the inlet hole 123 and the central pocket 137 in the pockets 135 and 136 becomes more

  
more importantly. When these pockets are closed, as shown in Figures 45 and 46, the volute turns have executed another cycle and they occupy a position corresponding to the discharge of the liquid in the peripheral volume 138 upon reopening of the peripheral channels 125 and 134 transfer.

  
Although it is possible to operate the volute elements shown in Figures 1 through 4 and those shown in Figures 21 through 24 in the radial inward flow mode or in the radial inward flow mode. 'outside, in most applications and in particular in the case of large volute devices, operating at relatively high speeds, it is preferable to use the volute elements shown in Figures 41 to 44, c' that is, elements having both central or interior and peripheral or exterior transfer channels. FIG. 61 is a longitudinal section of a liquid volute pump comprising the volute parts and the orifice system according to the invention.

   The volute elements shown include volute parts of Figures 42 through
44, at the point of their pumping cycle shown in figures
51 and 52. Figure 61 uses for the identification of the pockets and members of the fixed and movable volute elements, the same reference numerals as those used in Figures 41 to
44, 51 and 52.

  
The pump shown in Figure 61 between a fixed element 150 in volute consisting of a fixed plate 151 in which a fixed part 120 in volute is rigidly mounted, and an element 152 in volute with orbital movement or mobile element, consisting of a movable plate 153 in which a movable part
130 in volute is mounted rigidly. The pump also includes a coupling 154, a drive mechanism 155, a shaft and crank assembly 156, and a body 157 including a housing.
158 oil, a cooling fan 159 and a hood

  
  <EMI ID = 14.1>

  
The fixed plate 151 of the fixed volute member has an end peripheral annular portion 165 and a flange
166 facing outwards, these portions of the plate 151 forming part of the body of the apparatus. The fixed plate 151 also comprises a central end piece 167 which has a liquid channel 168 communicating directly with a central orifice 123 of the fixed volute in order to constitute a conduit which can be used for the arrival or the discharge of a liquid, depending on the type. selected operating mode. The boss 79 of the fixed volute
120 penetrates into the end piece 167 and an O-ring 169 seals them. The central end piece 167 has an internal thread 170 intended for the connection of a liquid pipe.
(not shown).

   The fixed plate 151 also comprises one or more preipherical end pieces 175 each delimiting a channel
176 liquid inlet or discharge, communicating with the peripheral zone 138 and threaded at 177 in order to allow the connection of a liquid conduit (not shown).

  
The diameter of the plate 153 of the volute and orbital motion member is large enough that this plate always protrudes beyond the inner edge of the flange 166 and thus to allow, if desired, the installation of a ring. 180 sealing oil between the plate 153 and the flange 166, in order to ensure the seal between the volute pockets and the remaining part of the apparatus. This also allows the operating mechanism and bearings to be lubricated by oil while keeping the working fluid substantially out of contact with any liquid. In applications where the pumped liquid can be used as a lubricant, the oil seal ring 180 can be omitted.

  
The body, shown generally at 157, consists of an annular projection 165 of the fixed volute member, of the flange 166, of a main part 181 which has a

  
  <EMI ID = 15.1>

  
lower oil 183. The body is hermetically secured to the volute members using flanges 166 and 182, several bolts 184, and a ring seal 185.

  
During operation, both elements

  
volute must be maintained in a fixed relative angular arrangement. This retention is provided by coupling 154. The coupling of the embodiment shown in Fig. 61 is substantially similar to that described in US Pat. No. 3,994,633 (and shown especially in Figure 14 of this patent). Thus, as shown in Figure 61, the coupling comprises a ring 190, one face of which has opposed keys 191 intended to be received and 'to slide in grooves 192 presented by the inner surface of the flange 182 of the body. The other side of the ring
Coupling 190 has a second pair of opposing keys (not shown) which seat and slide in grooves (not shown) of the volute movable member plate 153.

   United States Patent Application N [deg.] 722,713, filed September 13, 1976 in the name of John

  
E. McCullough, describes another embodiment of a suitable coupling.

  
The volute movable element 152 comprises a shaft section 195 fixed to the movable plate 153 or produced in one piece with this plate. This movable element is controlled by

  
a motor (not shown) located outside the body and able to engage with a compressor shaft 196 entering the body by passing through an oil seal 197, this shaft

  
terminating in a crank plate 198 which can be attached to the shaft 196 or made in one piece with it. This tree
196 is mounted in the body using a bearing 199 and a crank bearing 200.

  
The volute apparatus controller is described in detail in U.S. Patent Application No. 761,889, filed in the name of John E. McCullough, and is in the form a fixed stroke crankshaft mechanism. The volute movable member is attached to the drive shaft 196 by means of a bearing bracket 201 which is configured to include a counterweight 202 for compensating for the centrifugal force exerted on the volute movable member. . The bearing bracket 201 supports the shaft section 195 via a needle bearing 203 held in place by a resilient ring (not shown).

   An axial stop
205, disposed between the bearing support 201 and the outer surface of the plate 153 of the volute movable member, assumes the function of a device for applying an axial force tending to bring the end plates and the end plates closer together. ends of the turns of the two volute elements in order to ensure the desired degree of axial tightness. The axial stop
205 supports the load of the volute movable member 152 through the crankshaft bearing 200 and transmits this load to the body.

  
Main shaft 196, crank plate 198, bearing bracket 201, and counterweight 202 constitute an adjustable, fixed stroke control mechanism for the volute pump according to the invention. As indicated above, the fact that, in liquid pumps, the liquid circulated has a greater viscosity than a gas circulated in a compressor or an expander, and also the fact that the volumetric ratio is kept equal to 1, make it possible to operate with a slight play between the sides of the turns of the volute elements. This makes it possible to use a crankshaft with fixed eccentricity for the control of the movable volute element and the appearance of a predetermined play between the flanks. Thus, for the fixing of the movable element in volute

  
at the crankshaft plate 198, the position of the coil of the movable element is adjusted relative to the coil of the fixed volute element. This operation is carried out by adjusting the position of the assembly comprising the bearing support 201 and the counterweight 202 relative to the plate 198 using an axis
206 pivot and locking screws 207 (preferably four screws) which pass through oblong holes 208 of the support 201 and counterweight assembly 202 and which are screwed into the plate 198. This mechanism is shown in detail in the figure. 7 of the aforementioned patent application of the United States of America N [deg.] 761 889. In the embodiment described and shown in Figure 7 of this application, the oblong holes 208 are configured so as to allow the support assembly 201

  
and counterweight 202 to be moved over a small arc before being locked on plate 198 using screws 207.

  
Figure 61 shows an adjustable crankshaft with fixed eccentricity. It is also possible to use a fixed eccentricity crankshaft which cannot be adjusted, i.e. a crankshaft designed and constructed so that the bearing support assembly 201 and counterweight 202 is initially and securely fixed. final on plate 198

  
crank so that the desired clearance between the turns of the movable and fixed volute elements is defined. In such an arrangement, the bearing and counterweight support assembly 201

  
202 may be secured to plate 198 by two or more screws, as shown in Figure 8 of the aforementioned United States Patent Application No. 761,889.

  
It appeared that by leaving a certain clearance between the turns of the volute elements, the wear of these turns can be appreciably reduced or even eliminated, and that it is unnecessary to subject the turns to special machining. In operation, it is preferable that the clearance 100 between the flanks of the turns of the volute elements is maintained at a value between about 0.025 and 0.125 mm. The clearance between the turns can be established by one of several methods. When assembling the apparatus, a thin metal shim, having a thickness equal to that of the clearance, can be inserted between the turns, then removed after the locking screws 207 have been tightened.

   Alternatively, the radius of the orbital movement of the volute members can be measured during a test assembly and the radius of the orbital movement of the crankshaft drive mechanism can be set to this value less the desired clearance between them. flanks. For any pump

  
With a liquid of given design and size, it is generally necessary to operate the apparatus in order to determine the radius of the desired orbital motion (equivalent to the distance between the axis 210 of the apparatus and the axis 211

  
the movable element in volute), then position the support
201 bearing at a radius of orbital movement slightly smaller than that for which a linear contact between the turns appears.

  
The actual magnitude of the clearance finally tolerated between the turns normally depends, at least to some extent, on the size of the liquid pump and the viscosity of the pumped liquid. In general, the clearance is proportional to the size of the pump and the viscosity of the liquid.

  
As indicated previously with reference to the general description of the apparatus shown in Fig. 61, the lower portion 183 of the body of the apparatus includes an oil pan 158. Lubricating oil 212 from the sump 158 is drawn to the coupling 154 and to the

  
  <EMI ID = 16.1>

  
terior of the body 157, by one or more grease fingers 213 attached to the coupling. These grease fingers have a length such that they periodically immerse in the oil 212, then they rise in order to project the oil upwards, inside the body, to circulate it, the oil then returning to the sump. A channel 214 conducts some of the sprayed oil, directly into a cavity 115 in the body surrounding the crank plate and the bearing bracket, to the bearing 199. In cases where the pump is used to circulate a liquid can be used as a lubricant and where the oil seal ring 180 is not used, it is not necessary to operate the fingers 213, since the liquid normally occupies almost the entire interior volume from the body.

  
Under certain operating conditions, for example for pumping a liquid at a high temperature, it may be desirable to use an air cooling device for the body of the compressor and to cool, inside the body, the components. pump elements and the lubricating oil circulating in the body. Such a device is shown in FIG. 61. It comprises an air duct 216 which ends in a cover 217 forming an envelope. This duct is mounted so as to surround the body of the device and rests on the drive end of several fins
218 integral with the body.

   The cooling air is circulated in the duct 216 by a fan 159 which comprises several blades 219 mounted between the outer edge 220, intended to receive a belt, and the inner hub 221, receiving a shaft, of a pulley 222. The latter is fixed to the main shaft 196 by a key 223 which can be received in a groove 224 of the shaft 196. The cover 217 is fixed to the end of the fins 228 facing the volute elements and it ends in little distance from the end of the volute element in order to delimit several air exhaust openings 225 by means of which the air drawn in by the fan
159 is circulated on the body of the device, from the control end to the end comprising the elements

  
volute, then evacuated by passing through the openings 225.

  
A liquid pump similar to that shown in FIG. 61 and comprising the fixed and volute-movable parts shown in FIGS. 1 to 4 has been produced. The sealing ring 180, the lubricating fingers 213 and the cooling device of the pump. bodies have not been shown. This pump was operated at a speed of 900 rpm to operate

  
  <EMI ID = 17.1>

  
efficiency about equal to that of a gear pump having substantially the same capacity. The pump according to the invention operates smoothly and does not produce pressure pulsations.

  
For some pumping operations, it is desirable for the pump to work while submerged in the circulating liquid. Although there is not, in the prior art, a significant demand for such pumps, it has recently appeared necessary to have a small pump which can be placed in the fuel tank of an automobile or any other vehicle. another self-propelled vehicle using a relatively light fraction of fuel. To be effective, such a pump must be able to be completely immersed in the fuel, for example in gasoline or diesel oil, which it must put into circulation.

   The recent need for such a pump results from the obligation to implement exhaust gas control devices, the use of which leads to the rise in the temperatures prevailing under the hood, at the location at which the Prior art fuel pumps are placed. These higher temperatures cause the formation of vapor plugs in the fuel pump, and this problem can be easily solved by placing this pump in the fuel tank, in order to protect it from excessive temperature, the prmpe then being. connected to the engine by a conduit in which it delivers the fuel.

  
Given that the implementation of a pump placed in the fuel tank of an automobile requires for an immersible liquid pump criteria as severe as those required for any conceivable use, the pump according to the invention will be described in detail. in this application.-. It is however obvious that it can be used with liquids other than fuels and in a medium other than that constituted by the pumped liquid, which can be of any suitable size, -for example of a size much greater than that required. for the installation of such a pump in an automobile fuel tank, for example.

  
In addition, the development of electronically controlled fuel metering devices intended to improve engine efficiency has placed additional demands on fuel pumps. These devices require high fuel supply pressures, such pressures not being adequately attainable by a simple centrifugal pump, i.e. by a pump of the type heretofore used in inside the tanks.

  
  <EMI ID = 18.1>

  
the fuel tank of a passenger automobile is the ability to operate in a safe and efficient manner, without maintenance for long periods, for example

  
2000 hours, delivering 84 kg or approximately 120 Liters of fuel per hour, under a gauge pressure of 0.84 bar, under the control of a direct current motor operating at a voltage of 12 volts and using a maximum current of 6 , 3 amps, and run dry in an empty tank for at least 10 minutes. In addition, such a pump must prime itself, must operate with a minimum of noise, vibration and flow variations, must be able to be introduced into the fuel tank of an automobile through the opening of 'access to this reservoir, which limits the diameter of the pump to a value not exceeding 4.76 cm, and must have a low manufacturing cost.

   It immediately appears that pumps of the commonly used types, namely centrifugal pumps or conventional positive displacement pumps, do not meet all of these criteria. It is therefore necessary to move towards another type of pump suitable for this application. It has been found that a volute type liquid pump can meet all of the above criteria and can have other very important advantages.

  
FIG. 62 shows in longitudinal section an embodiment of the liquid volute pump according to the invention, suitable for use in immersion in the fuel to be pumped. This pump has a main body
240, a liquid inlet 241, a liquid outlet 242, a volute pumping device 243, a coupling 244, a device 245 for controlling the orbital volute member, a motor 246 and a device 247 supporting a axial load. In the following detailed description of the submersible pump, it is appropriate to first describe the motor and the liquid outlet, since these elements of the pump are of more or less conventional design. The motor 246 is an electric motor comprising an armature 248 and stator magnets 249 positioned and held in the central part 250

  
  <EMI ID = 19.1>

  
a skirt 252 forming part of an end block 253 of output. The armature 248 is mounted on a drive shaft 254, as is an axial or face manifold 255 which bears against brushes-256

  
made of carbon with which an electrical contact is made through screw terminals 257, opposite and terminating outside the body of the pump (see also in figure 63).

  
The liquid outlet 242 comprises a conduit 258

  
discharge made in the extreme block 253 and a valve 259

  
retainer which prevents any flow of liquid in the opposite direction in the pump when the latter is not working and when starting. The check valve 259 shown in Figure 62 includes a ball 260 pressed against a ring 261

  
made of elastomer which is supported by a ring 262. A spring
263, held in conduit 258 by an orifice plate 264, maintains ball 260 under axial force. Spring 263

  
is obviously chosen so as to allow the valve 259 to open under a predetermined liquid pressure, for example a gauge pressure of about 0.07 bar in the case of a fuel pump mounted in the gasoline tank d 'a car. A relief valve 265 is also used. As shown in Fig. 62, this valve is similar in design to check valve 259 and includes a ball 266, a bearing ring 267, an annular support 268, a spring 269 and a perforated spring retainer plate 270. . The latter is of an appropriate force so as to maintain

  
the valve 265 in the closed position until the liquids contained in the pump body reach a predetermined maximum pressure, for example a gauge pressure of about 0.84 bar. It is obviously possible, without departing from the scope of the invention, to use any suitable form of check valve and valve for the check valve 259.

  
and the relief valve 265, the embodiments of Figure 62 being shown by way of example only.

  
The drive shaft 254 ends in a central recess 271a of the end block 253 of the output and is supported and maintained in alignment in this recess by a bearing 271. A primary counterweight 272 is mounted on the shaft 254 so as to compensate for the forces produced transversely to the axis of the pump due to the eccentricity of the elements with orbital motion. It is therefore necessary to use a secondary counterweight to achieve full dynamic equilibrium by canceling the moment resulting from the primary counterweight 272. In the embodiment shown in Fig. 62, this secondary counterweight can be obtained by the placement of weights suitably positioned on the face manifold 255, or by a suitable distribution of the masses inside the armature 248.

  
Figures 64 and 65 show another embodiment of the pump outlet end block and the electrical connections made with the motor. The extreme block
273 outlet, shown in Figures 64 and 65, is shouldered in shape and ends, inside the pump, with a skirted ring 274 sealed to the central part
250 of the body using a sealing ring 275. The ring
274 holds the magnets 249 inside the pump. The carbon brushes 276, in contact with the collector 277, are held by opposing brush holders 278 which pass through the blo &#65533; 273 from the output end and which are connected to terminals 279. The drive shaft 254 terminates in a recess
280 where it is aligned and supported by a bearing 281.

  
In the embodiment shown in Fig. 64, a separate secondary counterweight 282 is mounted on shaft 254. As shown by the plan view of Fig. 65, an outlet duct 283, provided with a check valve, and a relief valve 284, similar to the line and valve shown in Figures 62 and 63, are used in the embodiment shown in Figure 64.

  
The flow of liquid in the pump is indicated by arrows in Figure 62. The liquid arriving through the inlet 241 is pumped by the device 243 in the volute of the chamber.

  
  <EMI ID = 20.1>

  
inside the body 240, so as to flow around the motor and to exit by passing over the valve 259. The pumped liquid therefore serves to lubricate and cool the elements of the pump.

  
Figures 67 to 77 show in detail the volute pumping device, the orifice system, the device for supporting an axial load, the coupling and the control mechanism of the volute pump according to the invention, the same elements bearing the same numerical references in the various figures.

  
As shown in Figure 66, the device
Volute 243 includes a fixed scroll member 287 and a scroll member 288 performing orbital motion. The fixed member 287 includes an end plate 289 and an involute coil 290, either made integrally with the end plate or mounted on a separate member which is attached to the inner surface 291 of the end plate 289 (as described, by example, in United States Patent No. [deg.] 3,994,635 supra). Evenly spaced grooves 292 are machined into the periphery of end plate 289 to accommodate keys 293 (Fig. 66) attached to the inner wall of a bearing housing portion 251, and also to hold this element in place. volute in fixed position inside the pump.

  
The end plate 289 of the fixed volute element forms the inlet end of the pump body and it

  
has a central boss 294 (figure 66) which delimits a

  
inlet conduit 295 communicating, through a central orifice 296

  
of plate 289, with the central area of the volute pump.

  
As shown in FIG. 67, the fixed volute element 287 has an internal transfer channel 296 and an external liquid transfer channel 297, these channels being in the form of recesses, the shape and function of which are similar to those of the channels 124 and 125, respectively, shown in FIG. 41. In this embodiment, the central orifice and the internal transfer channel are merged. As a variant, the central orifice of the fixed element 287

  
volute can be circular in shape and the inner transfer channel can be configured as shown in Figure 42.

  
As shown in Figure 67, the volute movable member 288 or orbital motion member has a

  
shape similar to that of the fixed element 287. This element 288 comprises an end plate 298 and an involute coil 299 which is fixed to the interior surface 300 of the plate

  
extreme 298 or which is made in one piece with this

  
plate. The coil 299 has an outer flank or an outer side surface 301, an inner flank or an inner side surface 302 and an end surface 303. As shown in Fig. 67, the movable volute member 288 has an inner transfer channel 304. and an external channel

  
305 transfer, in the form of recesses of which

  
configuration and function are similar to those of

  
channels 133 and 124 shown in Figures 43 and 44.

  
The operation of the volute pump shown

  
in figure 62 is similar to that described above and

  
the movement of the movable element 288 in a scroll causes the formation of the movable pockets 306, 307 and 308 (figure 66), the volumes and intercommunications of which vary to cause the

  
circulation of the liquid in the pump. As shown in Fig. 66, the peripheral pump discharge zone 309 surrounds the involute coils and the end plate of the volute movable member.

  
Liquids with much higher viscosities

  
to those of the gases and the volumetric ratio of the pump being equal to 1 rather than greater than 1, it is not particularly important to ensure an effective radial seal between the pockets, at the level of the surfaces 292 and 303 by which

  
the turns come into contact. As indicated in the following detailed description of the operation of the pump, the liquid back pressure flowing in this pump is sufficient to exert the axial forces necessary to keep the turns and the end plates in contact. In addition, the radial flow of the liquid towards the outside of the pump causes

  
inside the latter, hydraulic pressures tending to cause the sides of the turns of the volute elements to be hermetically carried between them when they form lines of contact between them.

  
i

  
biles. Obtaining a pulsation-free operation of this submersible pump is achieved in the same manner as described

  
for the volute elements shown in Figures 41 to

  
60.

  
The control device, the device supporting an axial compressive load and the coupling are shown in Figures 66 to 68. In the embodiment shown in these figures, the device supporting an axial compressive load comprises an axial ball thrust bearing. , generally shown at 312 and comprising several balls
313 held in the desired arrangement by two parallel rings 314 and 315 which have several holes 316 regularly spaced and configured to accommodate the balls
313. The retaining rings 314 and 315 are kept spaced apart by contact with the surface of the balls 313,

  
in order to form between them several channels 317 through which the liquid can flow radially from the peripheral zone 309

  
discharge to chamber 285 of the volute device. Most of the load exerted on the volute members is a compressive load resulting from the pressure

  
outlet and it is supported by the axial stop
312. The wear of the volute elements is therefore minimized, which increases the life of the pump. Due to the fact that the device supporting the axial load makes it possible to minimize the wear

  
scrolling elements, it is possible to operate

  
the pump according to the invention at a relatively high delivery pressure, which results in a good seal between

  
volute elements and therefore high efficiency

  
and low power consumption.

  
During operation, both elements_287

  
and volute 288 must be maintained in fixed relative angular positions and this is ensured by the use

  
of the coupling shown generally at 244 in FIG.

  
66. This coupling 244, shown in Figures 66 and 68,

  
is essentially analogous to the coupling described in

  
U.S. Patent No. 3,994,633 supra (see Figure 14 of that patent and its detailed description). Thus, as shown in Figures 66 and 68, the coupling com-

  
takes a ring 318, a first face of which has clips

  
opposing vettes 319 which fit and slide in grooves 320 of the inner surface of an annular portion,
321 of bearing housing 251. It should be noted that the

  
longitudinal section of figure 66 is made according to the

  
line 66-66 of figure 68 and that, therefore, only one

  
of the two opposite keys 319 and only one of the two grooves

  
320 are shown (see figure 62). The other face of the coupling ring 318 has two other opposing keys

  
  <EMI ID = 21.1>

  
to be housed and to slide in grooves 323 of the end plate 298 of the movable element 288 in volute. Mating
244 thus assumes the function of a spring applying an initial axial preload on the movable volute element when the pump is started.

  
As described below with reference to Figures 72 to
77, it is possible to combine the functions of the axial load bearing device and the coupling into a single subassembly of the apparatus.

  
Figures 66 and 68 show in detail the control device of the scroll member performing an orbital motion. As shown in Figure 66, the control shaft 254 is mounted in a main bearing 324 which is held in a housing 325 which, itself, is made integrally with the main outer housing 251 through an outer annular portion 321, an inner bearing housing 326 and an inner annular portion 327. The drive shaft 254 terminates in a flat end piece 328 which enters a groove 329 (Figure 68) of a yoke 330 for controlling the volute movable element. This assembly allows the mobile element to move outwards under the effect of centrifugal force and hydraulic forces, until its involute coil comes into contact with

  
the involute turn of the fixed volute element. In this position, the center 331 of the yoke 330 is spaced from the center
332 of the control shaft 254 by a distance equal to the radius

  
of the orbit followed by the volute mobile element. The control yoke 330 is mounted in a bearing 333 which is supported in a ring 334 made in one piece with the outer surface 335 of the movable member 288 in a scroll.

  
This scroll member controller establishes an all-metal path (drive yoke 330, shaft end 328, and drive shaft 254) to remove heat from bearing 330 during periods when the pump is running dry. , that is to say when the liquid in which the pump is normally submerged has been evacuated. The control device is also designed to reduce the frictional losses by positioning the bearings so as to reduce the overturning moment of the movable volute member and the loads exerted on the bearings of the motor. This arrangement increases the efficiency and service life of the pump, as well as its ability to run dry.

  
As shown in Figures 66 and 68, the outer ring 321 of the bearing housing has a number of equidistant orifices 336 allowing liquid to flow from the peripheral discharge zone 309 into the chamber 286 of the motor through device chamber 285

  
in volute.

  
Figures 69 to 72, which are partial longitudinal sections of the inlet end, comprising the volute elements, of the pump according to the invention, show three other embodiments of the device supporting an axial load, these forms of embodiment being intended for pumps comprising a separate coupling. In the embodiment shown in Fig. 69, the volute elements 287 and 288 are themselves used to support the axial load, the ends 337 and 303 of the turns 290 and 299 of the fixed and movable volute elements, respectively, supporting the charges by contact with the opposite surfaces of the end plates of the corresponding elements, that is to say, respectively, the surface 300 of the movable end plate 298 and the surface 291

  
of the fixed end plate 289. The embodiment shown in Fig. 69 is generally better suited to pumps with moderate discharge pressures.

  
FIG. 70 represents an embodiment of the device supporting an axial load, comprising an annular axial stop 338 traversed by several channels 339 oriented radially. The flat surfaces 340 and 341 of this stop 338 are in contact with the opposing surfaces 291 and

  
298 fixed and movable elements in volute, so that the axial compressive load, exerted by the pressurized liquid contained in the pump, is transmitted to this stop which is preferably made of a synthetic organic plastic material, for example a polyimide, in the case of pumps whose volute elements are also made of a synthetic plastic material.

  
Fig. 71 shows a variation of the embodiment of Fig. 70, also using an annular axial stopper which, however, is in the form of a ring 342 protruding from the inner surface 291 of the fixed volute member 287 with which this ring is made in one piece. The ring 342 is crossed by several spaced radial channels 343 establishing the necessary communication between the discharge zone 309 and the pumping chamber 285. The axial load is supported by a planar surface 187 in contact with the surface 300 of the end plate of the volute movable member.

  
Figures 72 to 74C show a variant of the pump according to the invention in which the device supporting <EMI ID = 22.1>

  
This device comprises several equidistant balls 345 held so as to be able to perform only a circular movement in circular cells 346 and 347 made in

  
the surfaces 291 and 300 of the end plates of the fixed and movable volute elements, respectively. The balls 345 are held radially and circumferentially in alignment by a retaining ring 348 which is traversed by holes 349. Figure 73 shows in a relatively schematic manner the relative positions of the cells 346 and 347 of the volute elements, at a point of the volute. orbital motion. This figure shows

  
that the centers of the cells 346 and 347 of the fixed elements and

  
mobile volute are located on circles of the same radius and

  
are in axial alignment when the cycle reaches a point at

  
which the tangents to the two volute elements are parallel.

  
  <EMI ID = 23.1>

  
  <EMI ID = 24.1>

  
by the volute movable member is shown schematically in Figures 74A to 74C. During an orbital motion, a 345 ball must be able to move a distance equal to

  
  <EMI ID = 25.1>

  
all directions from its central position, as shown in Figure 74A. It therefore appears that in the case where the depth of a cell 346 (or 347) is equal to the radius Rs of the ball, the diameter Di of the cell must be equal to D + R. However, since the depth of the cell

  
  <EMI ID = 26.1>

  
ment less than D + R. Figure 74A shows in cross section one of the cells and Figure 74B is a plan view of this cell. It is however possible, without departing from the scope of the invention, to produce the cell to a suitable diameter, so that it has a straight wall and a chamfered edge.

  
Figure 74C is a partial cross section, on an enlarged scale, of the cells and the retaining ring, showing how the end plate 298 of the movable volute member (and the involute coil integral with this plate) can freely execute an orbital movement in the fixed element in volute while remaining in the desired angular position relative to this fixed element. The balls 345 perform the same function as the multi-ball axial thrust bearing shown in Figure 66, as they support the compressive axial load exerted on the volute members and hence the embodiment of the pump shown in the figures. 72-74C has the same advantageous operating characteristics as the embodiment shown in Fig. 66.

   In the absence of a separate coupling, a spring washer 350 is mounted between the yoke 330 and the shoulder of the shaft 254, in order to exert an axial prestress on the volute elements during start-up.

  
Figures 75 to 77 show another embodiment of the pump according to the invention, in which the coupling also participates in supporting a load. This coupling, shown overall at 351, is placed between the end plates 289 and 298 of the fixed and movable volute elements. It comprises a ring 352 machined so as to include two opposed keys 353 which are intended to be housed and slide in grooves 354 machined in the surface 300 of the movable end plate 298, and two opposite keys 355, perpendicular to the keys 353 and intended to be housed and slide in grooves 356 machined in the surface 291 of the fixed end plate 289.

   As shown in Figures 76 and 77, the coupling comprises several equidistant bearing pads 357, having flat surfaces 358 and 359 which come into contact with the opposite surfaces 291 and 298 presented by the end plates of the volute elements, in order to that these studs constitute the device supporting the axial compressive load. Finally, the coupling is machined so as to have several channels 360 for the liquid flow. In addition, in the case of the variant shown in FIG. 72, an elastic washer 350 is used in order to exert an axial prestress during start-up.

  
In the embodiment of the pump shown in Figures 78-80, spherical members are used to perform both the function of supporting an axial compressive load and the function of keys in the coupling. The latter comprises a ring 361 which comprises support pads 362 and which has liquid flow channels 363, as is the case with the ring 351 shown in FIGS. 75 to 77. However, this ring 361 does not have keys. A groove 364 is machined into a surface
365 of each stud 362 oriented towards the surface 300 of the movable end plate 298. Grooves 366 are machined in the surface 300 of the end plate, so that the shape and orientation of the axis of these grooves 366 correspond to those of the grooves 364 of the support pads.

   A load bearing ball 367 (bearing member) is arranged so as to perform a mating movement in each pair of opposed grooves 364 and 366, the total depth of these grooves being slightly less than the diameter of the balls 367. The grooves 364 and 366 have a length, between edges, equal to or less than

  
  <EMI ID = 27.1>

  
way, grooves 368 and 369 (Figures 79 and 80) are machined in the surface 370 of the support pads 362 and in the opposing surface 291, presented by the end plate 289 of the fixed volute member, and balls 371 are placed so

  
to perform a mating movement in these pairs of grooves. The longitudinal axes of the grooves 368 and 369 are rotated 90 [deg.] With respect to the axes of the grooves 364 and 366. Consequently, the balls 367 and 371 support the axial compressive load exerted on the volute members and, moreover , due to their limited movement along the axes of the opposite grooves in which they are housed, these balls maintain the desired angular relationship between the fixed elements

  
and mobile in volute.

  
Figures 81 to 83 show a variant of the device for coupling and supporting an axial load shown in Figures 78 to 80. In the embodiment shown in Figures 81 to 83, rollers replace the balls as members. coupling and supporting a load. The coupling has the same general shape as that shown in Figures 78 to 80. It comprises a ring 361 on the periphery of which are regularly spaced support pads. This ring also has liquid flow channels 363. The four support pads 372, which

  
  <EMI ID = 28.1>

  
coupling members, while the other support pads 373 only assume the function of supporting an axial load. The surfaces 374 of the pads 372, oriented towards the surface 300 of the movable end plate 298, have grooves 375 and, in the same way, the surface 300 has four corresponding grooves 376, the two groups of grooves delimiting a closed track in which rollers 377 may move, as shown in Figure 83. The combined depth of grooves 375 and 376 is slightly less than the diameter of rollers 377 and the length of the stroke of the rollers

  
  <EMI ID = 29.1>

  
also feel 378 grooves machined into their surface
379 oriented towards the surface 291 of the end plate 289 of the fixed volute element. Likewise, the surface 291 presents

  
  <EMI ID = 30.1>

  
  <EMI ID = 31.1>

  
ted with respect to the grooves 375 and 376 so that the rollers 381, traversing the grooves 378 and 380, have their axes orthogonal to those of the rollers 377. As in the case of the balls 367 and 371 shown in Figures 78 and 79 , the rollers of the embodiment shown in Figures 81 and 82 perform both the functions of coupling and supporting an axial load. Figure 84 shows a use of the pump according to the invention. This pump is submerged in a liquid
382 to be pumped, contained in a tank 383, for example the fuel tank of an automobile. A pressure discharge conduit 384, attached to the outlet 12 of the pump, exits the reservoir 383 by passing through a suitable opening 385 and is connected to the desired element for receiving the liquid, for example the carburetor of the automobile.

   Likewise, these shielded electrical cables 386, connected to screw terminals 257, pass through opening 385 in order to be connected to a source of electrical energy. A filter 387 is attached to the inlet 241 of the pump in order to prevent the passage of debris which may be in suspension in the liquid or which may have settled on the bottom of the tank.

  
The pump according to the invention is self-priming and it can run dry for a relatively long period, for example 10 minutes or more, without loss of efficiency. It operates with minimal noise, vibration and variations in discharge flow, and allows debris to pass without permanent damage, due to the radial flexibility of the control system. The direction of flow of the liquid in the volute elements ensures automatic sealing between the sides of the turns of these elements and automatic radial sealing between said elements. Thus, it is not necessary, in the pump according to the invention, to mount additional members ensuring the radial seal or to mount members opposing the effect of the centrifugal forces exerted on the volute element to reciprocating motion.

  
The special liquid flow circuit inside the pump, as shown by the arrows in figure 62, ensures complete automatic lubrication of all pump elements and allows all valves to be removed, except simple ones. check valves mounted in the discharge line, and the relief valve.

  
The pump according to the invention is particularly suitable for use in the fuel tank of an automobile, particularly due to the fact that it can be made in dimensions small enough to pass through the access opening of the fuel tank. of an automobile (maximum diameter of the pump equal to 4.76 cm) and to have a pumping capacity allowing it to deliver

  
at least 84 kg of fuel per hour under a gauge pressure of 0.84 bar. In addition, the volute pump elements can be made (for example molded) from a suitable synthetic organic plastic material, resistant.

  
wear, and the other elements of the pump can be mass produced in plastics or metals compatible with the preceding plastic material, which makes it possible to realize such submersible fuel pumps at the low asking price.

CLAIMS

  
1. Complementary volute elements, intended in particular for a liquid volute pump, characterized in that they include a fixed volute element which has a central orifice for the flow of liquid and which comprises a fixed end plate, a fixed coil involute, extending over one and a half involute turns and fixed to a first surface of the end plate, and a fixed liquid transfer channel, machined in said first surface of the end plate to form a recess in this surface, another scroll element or movable element being mounted so as to be able to perform an orbital movement relative to the fixed scroll element under the control of a device, this movable element comprising a movable end plate, a movable coil

  
involute, extending over one and a half involute turns and fixed to a first surface of the movable end plate, and a movable liquid transfer channel, machined in said first surface of the movable end plate and forming a recess in this surface, the fixed and movable transfer channels being arranged and configured so as to open approximately immediately after the movable coil has reached the point in its orbit at which three substantially hermetically separated liquid peaches are formed each other.


    

Claims (1)

<EMI ID = 32.1> characterized in that the fixed transfer channel is delimited by a main edge following part of the path of the edge of the mobile coil, the mobile transfer channel being delimited by a leading edge that follows part of the path of an edge of the fixed coil. 3. Volute elements according to claim 2, characterized in that the fixed and mobile transfer channels are arranged either inside the fixed and movable turns, respectively, in which case they are delimited by another main edge which follows a straight line passing, respectively, through the center of the fixed end plate and through the center of the mobile end plate, and parallel to a contact line corresponding to a tangent to the generating radius of the fixed and mobile turns, respectively, i.e. to the exterior of the fixed and mobile turns, respectively, in which case these channels have as their other main edge a line following the same profile as the first <EMI ID = 33.1> the latter, either inside and outside the fixed and mobile turns. 4. Volute elements according to claim 3, characterized in that the depth of the transfer channels is approximately equal to the thickness of the involute turns, said other main edge of the outer transfer channel being spaced from the first cited main edge. at a distance equal to approximately twice the thickness of the turns, and this external transfer channel extending over an arc of between approximately 45 and 90 [deg.]. 5. Positive displacement liquid pump, characterized in that it comprises the complementary volute elements according to any one of claims 1 to 4, a device for applying an axial force to the volute elements in order to cause them to bear axially the 'against each other, a coupling which maintains the volute elements in a fixed angular orientation with respect to each other, liquid inlet and outlet elements, and a control device which operates the mobile element in volute an orbital movement during which the flanks of the involute turns and the end plates of the elements form mobile liquid pockets of variable volume, a peripheral volume which surrounds the pockets, and a discharge zone. 6. Pump according to claim 5, characterized in that the liquid inlet element communicates with the peripheral volume, in which case the liquid outlet element communicates with that of the pockets located inside and assuming the function of said discharge zone, either with the inner pocket, in which case the liquid outlet element communicates with the peripheral volume which assumes the function of said discharge zone. 7. Pump according to claim 5, characterized in that the control device is designed so as to cause the volute movable member to perform an orbital movement such that a small clearance is maintained between the flanks of the involute turns, in order to substantially eliminate the wear of the flanks after long operating times while maintaining the integrity of the fluid bags. 8. Pump according to claim 7, characterized in that the control device comprises a shaft rotatable about an axis and terminating in a crank plate, a shaft end which protrudes from the movable member volute and to which are rigidly fixed a bearing support and a counterweight, this shaft end being able to rotate on an axis parallel to the first axis located, but spaced from the latter by a distance equal to the radius of the orbit followed by the movable volute element, locking members rigidly fixing the bearing support and the counterweight to the crank plate, in a predetermined arrangement, in order to delimit said clearance. 9. Pump according to claim 8, characterized in that the device for applying an axial force comprises an axial stopper arranged between the bearing support and the counterweight and the end plate of the movable member in volute. 10. Pump according to claim 5, intended to be immersed in the liquid that it circulates and comprising a body which defines a chamber containing the volute elements and of which a first end comprises said liquid inlet element and of which the other end comprises said liquid outlet element, the pump being characterized in that the control device comprises a motor arranged inside the chamber, between the volute elements and said other end of the body, so that the liquid , forced radially outwards by the volute elements and passing through the pump, flows around the control device and maintains inside the chamber a predetermined hydraulic pressure ensuring the application of said axial force. 11. Pump according to claim 10 &#65533; comprising a relief valve and characterized in that the liquid outlet member comprises a discharge conduit provided with a check valve, pressure actuated and designed to allow liquid to be discharged from said chamber when the pressure is removed. pressure of this liquid, prevailing inside the pump, reaches a predetermined level. 12. Pump according to claim 10, characterized in that it comprises a device intended to support an axial compressive load. 13. Pump according to claim 12, characterized in that the coupling and the device supporting an axial compressive load constitute a single assembly assuming both functions. 14. Pump according to claim 10, characterized in that it comprises an additional device applying an axial force which tends to keep the movable volute element in contact with the fixed volute element during start-up. 15. Pump according to claim 10, characterized in that it comprises a primary counterweight which compensates for the forces generated transversely to the axis of the pump, and a secondary counterweight which cancels out the moments generated by the primary counterweight. 16. Pump according to claim 10, characterized in that the control device comprises a shaft terminated by a nozzle, and a drive yoke of the movable element in volute, parallel to the nozzle and spaced from the latter, when the pump operates at a distance equal to the radius of the orbit traversed by the mobile volute element. 17. Pump according to claim 16, characterized in that the shaft end and the yoke are made of metal and establish a metal-to-metal contact in order to constitute a path efficiently conducting the heat developed in the control device of the volute movable member, particularly when the pump is running dry.