MXPA98010237A - Cavity pump progress - Google Patents

Abstract

An improved progressive cavity (PC) pump is provided. In a first aspect, the pump comprises a rotor connected to a motor via a conduit shaft which is insulated from the material flowing through the suction chamber of the pump, thereby preventing the pumped material from reaching the joints of the driving shaft through flaws in the seals. In another aspect, the pump comprising a rotor assembly comprising a rotor shaft that is joined to a rotor member by means of a connecting member characterized by a thermally induced structural failure capability that provides a fail-safe mechanism, which prevents the improper use, against overheating. In a preferred embodiment, the connecting member is made of an alloy that melts at a low temperature which becomes a liquid state at a temperature beyond which the operation of the pump can not be safe. If the pump overheats, as a result of the operation operation without fluid or dry pumping, the connecting member is melted so that the driving relationship between the rotor shaft and the rotor member ends. The improved PC pump is particularly useful for pumping explosive

Description

CAVITY PUMP P_.Q__R-.SIVA DESCRIPTION OF THE INVENTION The present invention relates to a progressive cavity pump with a tamper-proof safety feature. The invention also extends to a progressive cavity pump feature with an improved sealed flfe mechanism and rotor assembly. BACKGROUND OF THE INVENTION Eccentric screw pumps, also known as progressive cavity pumps (pe pumps), are used widely in the explosives industry due to its low pulsation flow, its low cutting product and its ability to handle products with up to 40% of globules. They are also used in the food industry in the management of sewage and in other applications where it is necessary to pump materials that have relatively high abrasiveness. A typical pump pe generally comprises a rotor mounted for rotation in a stator defining a chamber of pumping. In a typical configuration, the rotor is geometrically a large inclined helix, while the stator can be considered as a body comprising a helix of two starts with twice the inclination of the rotor. As a result, conveyor spaces (cavities) are formed in the pumping chamber between the stator and the rotor. During pumping, these cavities are filled with product and move continuously from an entrance to an exit. Due to the smooth transition from one cavity to the next, the pump supply is almost pulse free. The conveyor spaces are sealed by the interference between the rotor and the stator. The stator is usually made of an elastomeric material retained within a rigid coating, although other configurations such as an elastomeric coated rotor may be used. The volume of the cavities during their movement remains constant. Other configurations can be used in addition to a large pitch propeller rotor in a two-start propeller stator including, for example, a large inclined rotor of elliptical cross section in a triple start helix stator having one and a half times the inclination of the rotor. Due to the particular configuration of the rotor / stator, the The rotor moves radially inside the stator so that it defines an orbital motion. See, for example, Netzsch Product Catalog entitled "The New NM Series - Who would have thought you could improve NEMO" Pump? ", Netzsch Mohnopumpen GmbH, Waldkraiburg, Germany, June 1994. In a typical pump of the prior art, The rotor is driven by a drive shaft, the rotating movement is imparted to the drive shaft by an electric, hydraulic, pneumatic or other motor.To adapt to the rotor's orbital motion, the drive shaft is made of a flexible material, such as spring steel, or it can be a rigid structure with universal, mesh or bolt joints at its ends.Elastomeric seals or sheaths are provided to prevent pumped material, eg explosives, from entering the joints.Ocasionally, instead of use two separate sleeves, connect an elastomeric sleeve between the two seals and surround the shaft, and in certain configurations, a single sheath can be used, see, for example, Waite, pat American entity number 3,930,765. Preferably the joints are lubricated with oil, in which case, the seals, covers or the sleeve, besides keeping the pumped material out of the Together, they also keep the lubricant out of the pumped material. When pumps are used with explosives, they must be protected against excessive heat generation. During normal operation, the pumped material transports heat away from the pump, and thus prevents the generation of excessive heat. However, excessive heat can be generated in cases of operation without fluid and dry pumping. The operation operation without fluid (also known as pumping operation without fluid) occurs when the flow of the pump is blocked. This can occur at the outlet of the pump or downstream of the outlet. Running pumping without fluid is potentially the most dangerous condition that can exist during the pumping of explosives. If the drive motor does not stop during pumping operation without fluid, the total impulse energy supplied to the pump will be converted into heat, which will be absorbed by the trapped explosives and by the rotor and the stator. The rate of temperature increase depends on the input energy, the ability to extinguish heat and the heat dissipation of the system. When the decomposition temperature of the explosives is reached (for example, a temperature greater than about 200 ° C for emulsions), all of the explosive stock within the bomb explodes, which generally results in the destruction of the bomb. , physical damage to the surroundings and serious damage to personnel that may be near the pump. In addition, such a primary case can lead to secondary cases if the bomb fragments provide a sufficient shock momentum to detonate explosives near the bomb. The pumping incidents run without fluid in this manner without a serious concern in the explosives industry and many efforts have been spent trying to reduce the likelihood of their filing. Dry pumping occurs when a pump is rotating but there is no product available on the suction side of the stator. When a pump operates in such a dry condition, it acquires heat by friction and from the work derived from the deformation of the stator elastomer. Since there is no product available to transport the heat away, it must be adsorbed by the rotor, the stator and the thin film of explosive debris that remain inside the stator. According the temperature increases, the stator expands mainly inward due to its rigid outer confining coating. In turn, this accelerates the heating and can result in the ignition of the explosive residues in the pump. Dry pumping is generally a minor problem compared to pumping running without fluid because there are fewer explosives in the pump, but the damage is still significant. In addition, dry pumping tends to occur with \ 0 higher frequency. For example, operators working with an airtight pump should know when to try to solve the problem by simply continuing to operate the pump instead of taking time to prime the pump. Operators must also know how to inactivate security mechanisms to allow such unsafe procedures to be used. This unfortunate truth is one reason why security systems are needed that are difficult to overcome. As discussed below, the present invention solves such a problem. 20 A third dangerous condition may occur when explosives enter the joints at the ends of the drive shaft as a result of a break in the integrity of the sheath, seal or sleeve that surrounds these joints. These joints can become less effective after a prolonged period of use due to fatigue, abrasion, chemical attack or freezing. This causes a problem since the seal failure can occur without any detectable signs from the outside. Although the speeds of sliding in such joints are slow, the contact pressure between metal parts is high and this can lead to increased friction especially when the lubricant has been lost and replaced by explosives. Explosives are always sensitive to friction and can become more sensitive through crystallization and loss of water. Therefore, the friction levels in a joint can be high enough to ignite the explosives. This is dangerous and undesirable. When pumping non-explosive materials, the danger of an explosion, of course, does not exist. However, the presence of material pumped into the joints is undesirable since it shortens the life of the pump and can lead to contamination of the pumped material by, for example, metal particles and lubricants. Many approaches have been used in the prior art to solve the problems mentioned above. These approaches usually they have been of electronic nature, and have detected the lack of flow, high and / or low pressure, or the high temperature, all of which are indicators of unsafe conditions. The devices that encompass these approaches have generally been sensitive and relatively sensitive. Consequently, they have worked well in a controlled environment, but have been less resistant to failure in a difficult environment, such as in explosive pumping trucks or underground explosive loading equipment. Another drawback is that these devices are generally easy to derive. With respect to the problems associated with the operation of operation without fluid and dry pumping, a solution shown in the prior art is to provide a pump comprising a rotor member with a longitudinal cylindrical bore receiving a rotor shaft having a transverse dimension significantly smaller than the diameter of the perforation. The space between the perforation walls and the rotor shaft is filled with a fusible metal bonding material which constitutes a connection member. If the temperature inside the stator increases beyond the melting temperature of the alloy during pump operation, the alloy softens and allows the rotor shaft to rotate freely in the rotor bore (see application for published European patent 0 255 336). The accumulation in the pumped material is substantially reduced since the rotor member no longer rotates in the stator of the pump. However, this solution has drawbacks. The ability of the connecting member to transmit torque to the rotor member under normal operating conditions depends both on the bond strength of the piercing walls / connecting member and the rotor shaft / connecting member. The unifying force joining the connecting member to the associated components is solely due to the interfacial bond between the joining material from which the connecting member is made and the material of the rotor member and the rotor shaft. Such an interfacial bond is essentially a chemical bond between compatible materials. The ability of such a chemical bond to withstand shear stresses of a magnitude normally encountered during pump operation is critical to prevent premature failure of the connecting member. It is then understood that special manufacturing procedures executed with care must be followed to ensure that a bond of sufficient strength is generated between the connecting member and its associated components during the manufacture of the rotor assembly. Failure to do so may result in poor performance due to premature breakage of the joint. In some situations, even when the manufacturing processes have been carried out in a satisfactory manner, the link can be weakened with respect to time as a result of aging, repetitive cooling / heating cycles to which the connecting member is subjected when the pump starts and stops repeatedly, chemical changes in the materials that form the union, etc. In this way, the joint can break even during the normal operation of the pump as a result of the shear forces imparted by the rotor shaft.

OBJECTIVES AND ESTABLISHMENT OF THE INVENTION Therefore, it is an object of the present invention to provide a pump with improved safety features. A further object of the present invention is to provide an improved pump eg that solves more particularly the problems associated with the operation of operation without fluid, dry pumping and seal seal integrity. Another additional objective of the present invention is to provide a pump eg with improved safety features which can not be easily derived. As widely described and described herein, the invention provides a progressive cavity pump, comprising: a) a cover defining a pumping chamber, the cover includes: an inlet for admitting material to be pumped into the pumping chamber; an outlet for discharging the pumped material from the pumping chamber; b) a rotor mounted on the cover, the rotor is capable of rotational and orbital movements inside the cover to cause the displacement of the material to be pumped into the pumping chamber between the inlet and the outlet; c) a driving shaft for imparting rotary movement to the rotor; d) a sealing mechanism for isolating the drive shaft from the pump chamber, the sealing mechanism provides a means to: i) provide a rotary movement of the drive shaft; and ii) provide an orbital movement of the driving shaft. For the purpose of this specification, the term "orbital motion" is intended to designate a continuous path of the rotor member about some reference site that is located at a distance from the center line of the rotor member. The trajectory is preferably circular but may also be elliptical or in some other way. Preferably, the reference site around which the rotor moves along the continuous path is the center line of the stator. It should be noted that the position of the reference site depends on the geometry of the rotor / stator configuration and therefore may vary from the preferred embodiment. On the other hand, "rotational movement" is intended to designate an angular movement of a portion of the conductor axis around the center line of that portion. For example, the driving shaft will be considered to rotate when the The end portion of the shaft that connects to the rotor is subjected to an angular displacement occurring around the center line of the end portion, which typically coincides with the center line of the rotor. To separate the drive shaft structure from the rotor, a sealing mechanism will be used as a reference point. All structures and components connected to the drive shaft and subjected to orbital and rotary motion and which are confined within the boundary of the pump chamber shall be considered part of the rotor. On the other hand, all the components joined with the rotor, are passed through the sealing mechanism and extending outside the pumping chamber will be considered part of the driving shaft. As used in the context of the present specification, the term "insulator" and its derivatives is used to refer to the fact that the conductive axis is separated from the pumped material. This expression should not be interpreted strictly when considering that it means that the drive shaft is completely sealed or that no material will ever reach or will be in contact with the drive shaft with the drive joints but rather that the amount of material that makes contact with the conductive axis or the joints thereof is negligible in terms of the type of material that is pumped. The progressive cavity pump according to the present invention is a significant improvement over the prior art devices because it is safer to operate. The position of the drive shaft outside the pump chamber prevents the accumulation of material pumped into the joints of the drive shaft, if any, which, as discussed above, can lead to deflagration of the pump when explosive substances are processed. In the most preferred embodiment, the sealing mechanism that isolates the drive shaft from the suction chamber is a composite structure that includes a seal placement ring that surrounds the end portion of the shaft that connects to the rotor and that includes two Separate seal members, one seal member supplies the rotating movement of the drive shaft and the other seal member supplies the orbital motion of the shaft. Suitable bearings are provided for positioning the seal positioning ring concentrically around the drive shaft and for allowing rotational movement of the rotor shaft to be substantially frictionless. Towards the back of the bearings is mounted a lip seal that It makes contact with the surface of the conductive shaft to form a barrier that prevents the exit of the pumped material while rotating the drive shaft. The second sealing member, one that supplies the orbital motion of the drive shaft, includes a flexible annular barrier that spans the space defined between the seal placement ring and the pump cover. The structure of the annular barrier is such that the ring for positioning the seal can be displaced in relation to the cover, by compression / extension of the barrier. This allows the drive shaft to rotate and at the same time prevents the pumped material from leaving the suction chamber on the driver shaft side. In one variant, the composite seal includes a support ring that serves as a barrier and that is capable of rotating movement within the cover to provide orbital movement to the drive shaft. Under this form of construction, the annular barrier (the support ring) does not need to be a flexible structure. Preferably, it is made of rigid material that is more resistant than the flexible soft seal since it better resists tearing and physical impacts that may occur during pump operation. It is the rotary movement of the rigid annular barrier the which allows the driving shaft and the rotor member to seal an orbital path. It will be evident that the radius of the orbital motion (the distance between the orbital path and the center line of the pump chamber) is fixed and determined by the position of the rotor relative to the support ring. Objectively, this structure requires strict manufacturing tolerances compared to the previous mode using a flexible seal, because the geometry of the orbital trajectory is fixed and only small variations are tolerable. As is widely included and described herein, the invention also provides a progressive cavity pump wherein the sealing mechanism comprises a support ring located between the pump chamber and the drive shaft, the support ring is capable of rotational movement inside the cover; a first sealing member is eccentrically secured within the support ring, the first sealing member is concentrically located on the rotor and provides a means for housing the rotational movement of the rotor, the pump also comprises a second sealing member secured to the cover , the second sealing member is located concentrically around the support ring and provides a means to accommodate the rotational movement of the support ring, whereby: a) the orbital movement of the rotor imparts a rotational movement to the support ring; and b) the second sealing member supplies the rotational movement of the support ring. In a more preferred embodiment, the pump further comprises a first bearing means for supplying the rotational movement of the rotor within the support ring and further comprising a second bearing means for accommodating the rotational movement of the support ring within the cover. Preferably, the first and second sealing members are lip seals and the first and second bearing means are double row ball bearings. In another embodiment, the pump comprises a means for generating a radial reaction force that substantially counteracts a radial force generated by the rotor on the stator during pumping. This feature reduces stator wear. In a preferred embodiment, a bearing is provided comprising a ring concentrically mounted on the drive shaft and having a rolling surface, preferably resilient, which is continuously in contact with a portion of the cover. The bearing establishes a limit on the pressure that the rotor can exert against the stator, which limits the wear of the stator. In another aspect, the invention also provides a rotor assembly for a pump, the rotor assembly comprising: a) a rotor member including a cavity; b) a rotor shaft extending at least partially in the cavity; c) a connection member in the cavity that establishes a printing relationship between the rotor shaft and the rotor member, whereby the rotational movement imparted to the rotor shaft is transmitted to the rotor member by the intermediary of the connecting member; d) the rotor member is in an engagement condition with the connecting member; e) the connection member is capable of thermally induced structural failure to end the drive ratio when a predetermined temperature is reached. In addition, the invention provides a progressive cavity pump, comprising: a) a cover defining a pumping chamber, the cover includes: an entrance to admit material that is going to be pumped into the pumping chamber; an outlet for discharging the pumped material from the pump chamber, -b) a rotor assembly mounted on the cover, the rotor assembly comprises: i) a rotor member including a cavity; ii) a rotor shaft extending at least partially in the cavity; iii) a connection member in the cavity that establishes a conductive relationship between the rotor shaft and the rotor member, whereby the rotational movement imparted to the rotor shaft is transmitted to the rotor member by the intermediary of the connecting member; iv) the rotor member is in an engagement condition with the connecting member; v) the connection member is capable of thermally induced structural failure to terminate the conductive relationship when a predetermined temperature is reached.

In this specification, the term "gear condition" is intended to designate an arrangement in which the rotor member or rotor shaft is mechanically interconnected with the connecting member so that torsional moment transmission is presented without being supported some or only partially relying on the junction on the surface of the connecting member / rotor member or the connecting member / rotor shaft. For example, a mechanical interengagement is obtained between the connecting member and the rotor member by providing a member with a projection received in a contact recess in the other member. In a specific example that should not be interpreted in a limiting manner, the rotor shaft includes a series of longitudinally extending projections running along the entire length of the shaft that are distributed at regular angular intervals. These projections form teeth that engage mechanically with the material of the connecting member. In a similar way, the material of the connecting member that fills the spaces between the projections on the rotor shaft also forms teeth that mate with those projections. The coupling between the connecting member and the rotor shaft in this manner is similar to a groove connection between the rotor member and the connection member. In this example there is a double coupling condition, specifically between the rotor member and the • connection member, and between the rotor shaft and the connection member. To create a condition of engagement between the connecting member, the rotor member or the rotor shaft, intercoupling projections / recesses may be used, as described above, which, however, do not need 4fc to be found all along the connection member. The projections / recesses may extend along only a portion of the length of the connecting member. The number and spacing of the projections / recesses may also vary without departing from the spirit of the invention. One possibility is to use a projection formed on the connecting member received in a contact recess on the rotor member and ^ • ^ use another projection formed on the connection member received in a contact recess on the rotor axis, or vice versa. Another possibility to establish a condition of engagement between the connecting member and the rotor shaft is to use a rotor shaft having a noncircular cross section at least along a portion of its length. For example, you can use a square, polygonal axis, triangular or oval. A slightly different possibility is to use a rotor shaft that is not rectilinear. A section of the shaft is positioned at an angle relative to the rest of the shaft to generate a mechanical coupling with the connecting member. In a specific example, the shaft may include a longitudinally extending main portion terminating with a transverse piece forming projections that contact the material of the connecting member. Another possibility that one can consider is to form the rotor shaft as a helix or, in general, with a helical structure. Another additional possibility would be to consider providing a rotor shaft which is of circular transverse exception but which is located eccentrically within the cavity of the rotor member. The term "thermally induced structural failure" refers to the ability of the material forming the connecting member to lose or at least partially its structural integrity so that it is no longer capable of communicating rotary motion from the rotor shaft to the operating member. rotor. In a preferred embodiment, the connecting member is fabricated from a low temperature portion alloy which is converted to a liquid state when its temperature exceeds the melting point. In this stage, the rotor shaft rotates freely within the accumulated liquid alloy and rotary motion is not communicated to the rotor member. Preferably, the material must be eutectic or substantially eutectic. A bismuth alloy, preferably composed of 55.5% bismuth and 44.5% lead, has been found satisfactory. There are other possibilities, for example, the connecting member can be manufactured as a particulate structure, the particles are retained in an alloy matrix that melts at a low temperature or, in general, a material that disintegrates or converts to the liquid phase. a given temperature. Below the given temperature the connection member behaves as a unitary structure. However, when the pump overheats, the bond between the particles is broken and released to move relative to each other. Therefore, the rotor shaft and the rotor member are decoupled from each other. The possibility of using materials or structures to fabricate the connecting member so that it weakens sufficiently at a predetermined temperature can also be considered so that the rupture of the structure of the connection member thereto is no longer capable of transmitting rotary movement to the rotor member and which, however, causes the connecting member to melt.

It preferred, however, the use of an alloy that melts at low temperature, because the material of the connecting member becomes a liquid that offers only minimal resistance to the axis of rotation. It will be apparent that any significant amount of resistance generated to the rotary shaft can have the effect of continuing to drive the rotor member, which of course is undesirable. In a preferred embodiment, the rotor assembly further comprises a means for preventing contact of the rotor shaft with the rotor member in the face of the structural failure of the connection member and, more preferably, the means for preventing contact consists of bushings. located on each end of the rotor shaft. In a further aspect, the rotor assembly further comprises a means for preventing the longitudinal displacement of the rotor member relative to the rotor axis in the face of structural failure of the connecting member and, preferably, the means for preventing longitudinal displacement of the member of the rotor. The rotor consists of a sphere located in the cavity of the rotor member.

Other objects and features of the invention will become apparent with reference to the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The following is a description of a mode of a preferred embodiment, in which reference is made to the following drawings, in which: Figure 1 is a vertical longitudinal cross-sectional view of the pump eg with improved safety features, according to a first aspect of the present invention. Figure 2 is a vertical longitudinal cross-sectional view of a pump pe in accordance with the present invention, detailing a first embodiment of the sealing mechanism and improved rotor assembly. Figure 3 is a vertical longitudinal cross-sectional view of a pump pe according to a first aspect of the present invention detailing a second embodiment of the sealing mechanism.

Figure 4 is a vertical longitudinal cross-sectional view of a pump pe according to a first aspect of the present invention detailing a third embodiment of the sealing mechanism and also detailing the axis supporting the roller. Figure 5 is a cross-sectional view taken along lines 5-5 of Figure 4, showing a third embodiment of the sealing mechanism. Figure 5a is a cross-sectional view similar to that of Figure 5 illustrating the support ring in a different angular position. Figure 6 is a cross-sectional view taken along lines 6-6 of Figure 4 showing the shaft bearing the bearing. Figure 7 is a cross-sectional view taken along lines 7-7 of Figure 2 showing a rotor assembly according to another aspect of the present invention. Figure 8 is a cross-sectional view similar to that of Figure 7 showing a preferred rotor assembly.

DESCRIPTION OF A PREFERRED MODALITY Referring now to Figure 1, the pump pe according to the present invention is particularly useful for pumping explosives and comprises a cover 2 having an inlet 4 and an outlet 6. The cover also comprises a stator 8 for receiving a rotor 10. helical The stator defines a pumping chamber that includes a suction chamber 11 formed downstream of the inlet 4, in the direction of displacement of the pumped material, and conveying spaces, such as the space 12, defined in the recess between the stator 8 and the rotor 10. These conveyor spaces are sealed by wave interference between the rotor and the stator. During pumping, these conveyor spaces are filled with pumped material and move continuously with a smooth transition which results in what is provided by a pump that has an operation that is almost pulse free. The rotor / stator configurations that can be used include a large-pitch propeller rotor in a two-start propeller stator that has twice the tilt of the rotor (referred to as 1/2 geometry) or a large section tilt rotor elliptical cross in a triple start helix stator that has three times the rotor inclination (referred to as 2/3 geometry). Due to the particular configuration of the rotor / stator, the rotor follows an orbital path within the stator, around the central axis of the stator (illustrated by dashed line B in Figure 4). The rotor in a pump pe with a 1/2 geometry completes one orbit per revolution of the rotor and the orbital movement in a pump pe with a 2/3 geometry of two orbits per revolution of the rotor. Other rotor / stator configurations can also be used. The stator can be of the full elastomer type, or of the uniform wall thickness type. The complete elastomer stator comprises a steel tube with a cast elastomeric coating having the desired shape. The stator of uniform wall thickness comprises an outer cover in the desired shape coated with an elastomer having the same thickness therethrough, the thickness depends on the size of the pump. Since the coating is of the same thickness through the pump, it exerts a uniform pressure on the entire contact line. Both types of stators are well known and available from different manufacturers. A person familiar with the art will also recognize that they can be using other types of stators that are within the scope of the present invention. The helical rotor 10 can be made of any suitable material such as stainless steel or aluminum with a hard coated surface, with aluminum being preferred due to its heat dissipation properties. For the reasons detailed here, it is important that the rotor possess good thermal conductivity to provide a rapid total response to excessive generation of heat within the pump due to an operation without fluid or dry pumping. Good heat dissipation properties are also important to avoid the formation of what are termed "hot spots" which are caused by excessive friction between the rotor and the stator in a particular area as a result of imperfections in the surface of the rotor or the stator The rotor 10 comprises an axis 13, the rotor 10 and the shaft 13 may consist of a single machined component or may consist of two separate elements connected together, as will be explained in more detail in the following. The rotor 10 is connected to a motor 14 using a compound driving shaft which may be constituted by a first shaft 18 and a second shaft 16. The motor may be electric, hydraulic, pneumatic or of any other type. The rotor 10 is connected to the drive shaft in any conventional manner. If desired, the rotor 10 and the drive shaft can be connected using a unidirectional locking arrangement that will be decoupled if the motor is inadvertently driven in the reverse direction, thereby avoiding any risk of creating a situation that could result in an accident. Located at each end of the second shaft 16 are the gaskets 20 and 22. These gaskets are required to allow the motor 14 to exert the required torque on the rotor and at the same time provide its orbital motion. Joints 20 and 22 may preferably be universal joints but may also be of any other type such as gears, bolts or CV joints. Contrary to the conventional pumps, in which the driving shaft is located inside the pumping chamber, the driving shaft of the pump pe of the present invention is isolated from the pumping chamber. This is obtained by a particular sealing mechanism described in greater detail in Figures 2, 3 and 4. A first embodiment of the sealing mechanism according to the invention will be described below with Refer to Figure 2. In accordance with this first embodiment, a seal positioning ring 24 is provided on the first end of the rotor shaft adjacent to the seal 20. Suitable bearings, such as the ball bearings 26 are used for mounting the ring 24 for positioning the seal on the rotor and for supplying the rotational movement of the rotor. The bearings 26 may be formed, for example, of a metal sphere within a stroke made of plastic material or plastic spheres within a metal race. The use of plastic is recommended since the pumped material can be corrosive and attack the metal. The seal placement ring itself does not rotate but follows the orbital motion of the rotor, as will be explained in the following. The seal positioning ring 24 includes a first sealing member consisting of two lip seals 28 and 29. The lip seals 28 and 29 abut against the surface of the rotor 10 and allow the rotor to rotate inside the positioning ring of seal and at the same time form a barrier to prevent the exit of the material pumped from the suction chamber 11 of the pump that forms a constituent part of the pumping chamber. If for any reason the pumped material passes beyond the lip seal 28, it will exit the positioning ring 24 seal through the radial relief slot 30 and in this way will not reach the bearings 26 or to the board 20. Other types of seals can be used additionally that allow the rotor to rotate inside the seal placement ring and at the same time prevent the pumped material from entering it. The exterior of the seal positioning ring 24 is insulated from the suction chamber by means of a second sealing member comprising a folded flexible annular barrier which spans the space between the seal positioning ring 24 and the cover. The seal placement ring does not rotate within the flexible barrier the latter provides for the orbital movement of the rotor and the compression / extension seal placement ring. In this way, the second sealing member allows the seal positioning ring 24 to follow the orbital motion of the rotor shaft and at the same time insulates the driving shaft from the suction chamber 11. For typical explosive applications, the second sealing member must be able to withstand a negative advance of approximately 9 meters of water column and a positive advance of approximately 10 meters of water column and accept a radial flexure of up to ± 8 millimeters. The type of seal that can be used as the second sealing member in the present invention is illustrated in Figure 2 and consists of an elastomeric ring 32 having a V-shaped cross section, the inner perimeter is secured to the seal positioning ring 24 by means of a suitable clamp 33 and the outer perimeter it is secured to the pump cover 2 by a suitable retaining ring 35 and screws 37. To prevent the seal positioning ring 24 from rotating inside the second sealing member due to friction between the rotor shaft 13 and the seals 28 and 29, a hollow torque arm 34 can be provided which positively immobilizes the seal positioning ring 24 preventing its rotation. The torque arm includes an elongated slot (not shown in the drawings) which slidably receives the screw 37. During the orbital movement of the seal positioning ring 24, the torque arm 34 slides on the screw 37 to authorize the orbital movement and at the same time prevent the seal placement ring from rotating. Such a torque moment arm however may not be necessary if the friction between the rotor shaft 13 and the lip seal 28 is minimal. Referring now to Figure 3, a second embodiment of the sealing mechanism is shown in accordance with invention. This second embodiment has a more compact seal design that allows to reduce the longitudinal dimension of the pump. In this second embodiment, the first and second sealing members are similar to the first and second sealing members of the first embodiment and consist respectively of a suitable lip seal 28a and a flexible annular barrier comprising an elastomeric ring 32a fixed to the ring 24a of seal placement and cover 2 by a suitable retaining ring 35a and screws 37a. In this particular embodiment, the ball bearing 26a is located in close proximity to the first sealing member (lip seal 28a) whereby it is possible to provide the seal positioning ring 24a that is shorter than the positioning ring 24a. stamp of the first modality. The seal placement ring of the second embodiment however does not comprise a radial relief slot to allow any pumped material that passes past the lip seal 28a to be evacuated. Therefore, it is preferable to provide bearings 26a that have no metal-to-metal contact for the reasons mentioned above and that also provide bearings that do not have an outer lip seal so as to allow any pumped material that passes the lip seal 28a and that reaches the bearing 26a pass therethrough without being trapped. A third embodiment of the sealing mechanism will be described below with reference to Figures 4, 5 and 5a. This particular sealing mechanism, generally referred to as the number 50, has the advantage of integrating the first sealing member that supplies the rotational movement of the rotor and the second sealing member that provides the orbital movement of the rotor in a single unit. In accordance with this modality, a first - sealing member including a lip seal 60 which is pressed into a ring 54 of supports. The lip seal 60 is located concentrically around the rotor (Figure 5) and supplies the rotational movement of the rotor. Contrary to the first and second embodiments, the support ring does not need to be a flexible structure and preferably is rigid. As shown more particularly in Figure 5, the support ring 54 is shaped such that the first sealing member 60 is located eccentrically within the support ring 54. More particularly, the support ring 54 is configured so that the first sealing member 60 will follow exactly the orbital movement of the axis 13 of rotor around the central axis of the stator (designated as B in figures 4 and 5). Thus, the lip seal 60 prevents the pumped material from entering the space between the rotor and the support ring 54. A second sealing member is also provided consisting of a lip seal 62 which is pressed into the interior of the cover 2, the lip seal 62 is concentrically located around the support ring 54 and provides rotational movement of the ring of support as explained later. The lip seal 62 prevents the pumped material from entering the space between the support ring 54 and the cover 2. To facilitate the rotational movements of the rotor shaft 13 and the support ring 54, suitable bearings are provided. A first double row ball bearing 52 'is secured to the interior of the support ring 54, an adjacent lip seal for supplying the rotational movement of the rotor shaft 13. Similarly, a second double row ball bearing 56 is secured to the interior of the cover 2 and provides the rotational movement of the support ring 54. The first and second bearings 52 and 56 are insulated from the suction chamber by first and second sealing members 60 and 62, respectively. During the operation of the pump, since the rotor shaft 13 is free to rotate within the first sealing member 60 and the first bearing member 52 and since the support ring 54 is free to rotate within the second member 62 of With the sealing and the second bearing member 56, the orbital motion of the rotor shaft 13 will impart a rotational movement to the support ring 54 (see FIG. 5a) with the consequence that the sealing mechanism will provide both rotational and orbital movements of the shaft. rotor and at the same time isolate the drive shaft from the suction chamber. Although this third embodiment has been described with the use of double row ball bearings, it is possible to use other types of bearings such as single ball bearings or double or single roller bearings. In another embodiment (not shown), an additional row of adjacent lip seals of the lip seals 60 and 62 and a conduit between the two seal rows that allow any pumped material passing past the first row can also be provided. of seals leave the sealing mechanism without reaching the second row of stamps (similar to the first modality illustrated in figure 2). Since any pumped material that can pass beyond the lip seal 60 and 62 will reach the bearings 52 and 56, it is preferable in this third embodiment to provide bearings that have no contact with metal for the reasons mentioned in the foregoing. Similarly, it is preferable that these bearings are not composed of integrated seals to prevent the material from being trapped inside the bearings. Any material that passes past the bearings will exit the pump through the radial slot 30 'and will not reach the driver shaft. It has been noted by the inventor that placing pump seals out of the suction chamber sometimes can result in premature wear of the stator, particularly in the area adjacent to the suction chamber (defined for purposes of the present specification as the "stator input") and especially in the case of elastomeric stators. Without wishing to be bound by any particular theory, it is considered that this premature wear is the result of the excessive radial force applied by the rotor against the stator, particularly in the area of the suction chamber 11. In reality, the pressure of the material in the pump output generates a force in the rotor that tends to move the rotor to the right, as seen in figure 4, for example. This force is counteracted by an opposing force acting on the rotor and generated by the driving shaft. Due to the angular relationship between the rotor and the drive shaft, this opposing force has a horizontal component and a radial component. The radial component of this force leads to an increased pressure in the rotor / stator interconnection, particularly in the area of the stator input, which can result in accelerated stator wear. The importance of the radial component of the opposing force will depend on the angle of the driving shaft in relation to the longitudinal axis of the rotor and the distance between the stator entrance and the first joint of the driving shaft. Generally, a larger angle or greater distance will result in a more important radial component. To avoid premature wear of the stator entrance, the user faces two choices. The first solution, commonly implemented in the prior art, is to place the gasket as close as possible to the stator entrance. However, this solution has drawbacks described in the above. A second possibility is to provide a long conductive shaft, to reduce the angle of Driver / rotor shaft. Although this solution allows to isolate the driving shaft of the suction chamber, has the disadvantage of increasing the longitudinal dimension of the pump pe. As shown in Figures 4 and 6, to prevent premature wear of the stator inlet in a pump pe having a drive shaft isolated from the suction chamber, a bearing is provided which will allow the radial component of the force to be captured by the pump cover, instead of acting on the elastomeric coating of the stator. As shown more particularly in Figure 4, the bearing 70 is located between the sealing mechanism and the gasket 20. The bearing 70 is constituted by an inner race 72 secured to the rotor shaft 13, an outer race 76 which continuously makes contact with the inside of the cover 2 so that the radial component of the force will be captured by the cover 2 instead of the stator entrance, and balls or rollers 74 between the two strokes to reduce the friction. As a result of the orbital movement of the rotor, the outer race 76 of the bearing 70 will rotate against the inner cylindrical surface 3 of the cover which in turn will generate a reaction force that will cancel out the radial component acting on the rotor.

In a preferred embodiment, the outer race 76 of the bearing can be provided with a resilient sheath 78 to compensate for any misalignment between the central axis of the stator (discontinuous line B) and the central axis of the cover within which the bearing 70 will rotate or to compensate for any small deformation of the cover. Such a resilient surface also reduces noise and eliminates the need for lubrication. In another aspect of the invention, the pump pe comprises an improved rotor assembly designed to stop rotating automatically when a predetermined temperature is reached, to prevent heat buildup. This rotor assembly constitutes an improvement on the rotors that are currently in the prior art and particularly on the rotor assembly described and published in the application for European patent 0255336 referred to above and which uses a fusible metal bonding material. to create a joint between the rotor shaft and the rotor member. More particularly, the inventor has discovered that the problem associated with breaking the union between the shaft and the rotor can be avoided by providing a connecting member between the rotor shaft and the rotor member that rests on mechanical coupling (gear condition) with the rotor member, or the rotor member and the rotor shaft to carry out the torque transmission. In a preferred embodiment, described together with Figures 2 and 7, the improved rotor assembly comprises a rotor member 10 comprising a longitudinally extending cylindrical cavity. A rotor shaft 13 having a first end adjacent the seal 20 and a second end adjacent to the outlet end of the pump, and having a diameter that is smaller than the diameter of the cavity of the rotor member is located at the same. The plastic bushings 36, which prevent the rotor shaft from contacting the rotor member when the connection member changes from the solid state to the liquid state as explained below, are also placed near the first and second ends of the rotor shaft. The surface of the rotor shaft 13 defines a space 38 with the inner wall of the rotor member 10 (see FIG. 7). As shown more particularly in Figure 7, the inner surface of the rotor member 10 and the surface of the rotor shaft 13 comprise longitudinal projections and alternating recesses. Space 38, when filled with suitable material that forms the member of connection, will allow both the rotor member and the rotor shaft to be in a condition of engagement with the connecting member. More specifically, the material from which the connecting member is manufactured is liquefied and poured to fill the space. Upon solidification of the material, the connecting member will be generated and will establish a driving relationship between the rotor shaft 13 and the rotor member 10 without relying solely on surface adhesion, as discussed in the introductory part of this specification. The predetermined melting temperature of the material forming the connecting member will be chosen according to the nature of the pumped material. In the case of explosives, the melting temperature of the material (and of the connecting member) will be from about 20 ° C to about 40 ° C above the maximum pumping temperature (i.e., the highest temperature normally reached within the pump) but well below the decomposition temperature of the explosive which, as previously mentioned, is approximately 200 ° C for emulsions. The maximum pumping temperature for explosives sensitive without detonator is generally about 80 ° C, while it is generally about 95 ° C for detonator-sensitive explosives. The The desired melting temperature is obtained by selecting a suitable alloy of material eutectic or almost eutectic. A preferred alloy for explosive applications consists of a mixture of 55.50% Bi and 44.50% Pb and has a melting temperature of 124 ° C. Such an alloy is available from The Canada Metal Company Limited and is marketed under the trademark CERROBASE (number 5550-1). This alloy also has sufficient resistance to plastic deformation to withstand the shear stresses imparted by the rotor shaft on the material plus which have been estimated to be approximately 3.5 kg / cm2 (50 psi) in the case of a pump that It has a 2/3 geometry. Nevertheless, a person familiar with the art will recognize that other materials capable of inducing thermal structural failure will be available on the condition that they possess the required plastic deformation strength. If, as a result of the operation without fluid or dry pumping operation, the temperature inside the pump is increased, the temperature of the rotor member will also increase and the heat will be transmitted to the connecting member. When the melting temperature of the material is reached, the connecting member will melt and as a result, the conduction ratio between the rotor shaft 13 and the rotor member 10 it will end. The rotor shaft will thus freely rotate in the bushings 36 without imparting any movement to the rotor member and no significant amount of heat will be generated by the rotor member 10. This will prevent the explosives that are located inside the pump from getting more heat and therefore a possible deflagration will be avoided. The suitable seal 39, located adjacent to the bushing 36 is provided to prevent the molten material from leaving the space 38 or to prevent the pumped material from entering the space 38. The inner surface of the rotor member and the surface of the rotor shaft allow to provide a connecting member that is in a condition of engagement with the rotor shaft and with the rotor member. Therefore, the connection between the rotor shaft 13 and the rotor member 10 of the rotor assembly does not depend on the adhesion but rather depends on the resistance to plastic deformation of the material forming the connecting member, it must be understand that "plastic deformation" means a change in shape or deformation due to a prolonged exposure to tension. Although the rotor assembly of the present invention does not exclude the formation of a joint, it is not based on it.

Regarding the requirement of resistance to plastic deformation, the material forming the connection member must have sufficient resistance to plastic deformation so that the connection member supports the shear stresses imparted by the rotor shaft to the material during the operating conditions normal. As previously mentioned, the shear stresses imparted by the rotor shaft to the pump having a geometry of 2-3 is approximately 3.5 kg / cm2 (50 psi) and the material must withstand such stresses at the pump temperature . Therefore, care must be taken to determine if the material can withstand the stresses at the pump temperature and not just at room temperature. Suitable materials having the required resistance to plastic deformation and melting temperature can be chosen by routine testing by a person familiar with the art. Similarly, since the size of the projections or recesses that allow the connecting member to establish a conduction relationship between the rotor shaft and the rotor member, they also vary based on the plastic deformation resistance of the material, and also regular tests may be required to determine the appropriate size.

In a preferred embodiment, a rotor shaft having a diameter of 50 mm with teeth of approximately 2.5 mm in depth has been provided while the inner surface of the rotor member is also provided with teeth of approximately 2.5 mm in depth. The space between the rotor shaft and the rotor member is approximately 2 mm and the cavity is filled with CERROBASE (number 5550-1). However, it has been noted that in 1 embodiment described above, premature failure of the connecting member may be subject to conditions where the pumping temperature approaches the predetermined melting temperature of the material forming the connecting member. At temperatures below the predetermined melting temperature, the material of the connecting member can be subjected to the plastic deformation effect described above. In the embodiment shown in Figure 7, this effect of plastic deformation can lead to the loss of the gear existing between the rotor shaft and the rotor member. The observed failure is typically presented by stresses that fracture the connecting member material such that a continuous fracture is formed in the area of free space between the rotor shaft and the rotor member. When this occurs, the rotor shaft is no longer in a driving relationship with the rotor member although the connecting member material has not yet completely melted. To minimize the possibility of this type of premature failure of the connection member, the normal operating temperature of the pump, for the configuration described in Figure 7, is preferably kept sufficiently low compared to the melting point of the member material. For the pumping mode described above, wherein the clearance between the rotor shaft and the interior of the rotor member is essentially constant at about 2 mm, the operating temperatures of the pump are maintained at more than 35 ° C below the material of the connection member that has been found to essentially eliminate this problem. This allows the material of the connecting member to have sufficient resistance to plastic deformation to maintain the engagement between the rotor shaft and the rotor member. However, maintaining the pump temperature lower than, for example, 35 ° C below the melting point of the material of the connecting member, results in slow response times during periods in which a thermally induced failure of the connection member.

Fortunately, other connection member design arrangements can be used which can reduce and / or eliminate this type of premature failure of the connection member. In these embodiments, the free cross-sectional space between the rotor shaft and the rotor member is not constant. In a preferred embodiment, the largest distance of the free space (over any given cross section) is greater than 10% larger than the smallest free space distance. More preferably, the largest free space distance is greater than 50%, and more preferably greater than 100%, and even more preferably greater than 200% larger than the smallest free space distance. The modalities using this technique preferably use common geometrical shapes to obtain the desired variation in free space distance, for example, a hexagon-shaped rotor shaft, in a dodecagon-shaped interior of a rotor member, as shown in Figure 8, provides sufficient variation in free space thicknesses to provide a reduced potential for premature failure of the connecting member. In Figure 8, the rotor shaft 13 is located within the rotor member 10 and defines an area of clearance 38. It should be noted that the area of Free space 38 varies in thickness from its smallest value 38a to its largest value in 38b. In this design, the smallest cross-sectional clearance is 1.5 mm while the largest cross-sectional clearance is 5 mm, which provides an increase of 233% in free space distance. Other configurations are possible including, for example, a triangular rotor shaft in a square rotor member; an oval rotor shaft in a circular rotor member; a square rotor shaft in a circular member; or even a circular axis pre-centered in a circular member. Other configurations may also include irregularly shaped rotor shafts within irregularly shaped rotor members with the condition that the thickness of the free space varies. However, preferred designs comprise 6 to 12-sided rotor within rotor members of 8 to 14 sides where the number of sides on the rotor shaft is preferably smaller than the number of sides on the rotor member. Without joining any theory, this approach is considered to reduce the chance of premature failure because it eliminates the possibility of a continuous circular path. which is a constant distance from both the rotor axis and the rotor member. Therefore, any plastic deformation or fracture stress in one of the thicknesses of the material of the connecting member is less likely to propagate in the thicker, adjacent area of the material of the connecting member. In addition, as the material of the connection member is "soften" or begin to show a lower plastic deformation resistance near the melting temperature of the material, the material of the connecting member begins to act as a liquid of high viscosity. However, the engagement between the rotor shaft and the rotor member is maintained under these conditions by the resistance to material flow from the high free space area to the low free space area. Although a certain "flow" may occur, the rotor shaft and the rotor member are maintained in a gear condition-though the motor shaft and the motor member can move at slightly different relative speeds. In other words, the rotor shaft can move relative to the rotor member, and at the same time maintain the conductive connection with the rotor member. This conductive connection only breaks at the point where the connecting member material has been fused to the point where it becomes a "fluid" of viscosity low enough to allow the material to pass from the high free space area to a small free space area without moving the rotor member. This effect is referred to herein as a "wedge-visuosity effect", which describes the state of the gear caused by the resistance of the fluid flowing from a high free space area to a small free space area. It should be noted that the design of Figure 7 does not show this "wedge-visuosity effect" since the free space area between the rotor shaft and the rotor member is essentially constant at 2 mm and does not vary. The material contained in the "tooth" of 2.5 mm depth in the rotor shaft and the rotor member is not subjected to this viscosity-wedge effect since nothing of the material is required to flow over the induced temperature conditions for decrease the resistance to plastic deformation. Using this design modification, connection member materials can be selected which have a melting temperature of less than 20 ° C, and more preferably less than 15 ° C above the normal maximum pump pump temperatures. Using this design, it is allowed a faster response of thermally induced structural failure of the connecting member during times when the pump experiences overheating. However, it should be noted that the larger cross-sectional dimension of the rotor shaft must be smaller than the smaller cross-sectional dimension of the inside of the rotor member so that the rotor shaft does not hit the member. of rotor under thermally induced failure conditions of the connecting member. Once the connecting member has melted, the residual pump pressure acts on the rotor face at the pump outlet and can cause a longitudinal displacement of the rotor member 10 relative to the rotor shaft 13. If such occur displacement, the frictional force exerted by the tip of the rotor shaft at the bottom of the cavity of the rotor member receiving the rotor shaft can generate sufficient friction to impart a rotational movement to the rotor member. To prevent such longitudinal displacement of the rotor member and the consequent undesirable conduction coupling, a hardened sphere 40 is provided within the cavity of the rotor member, between the rotor member and the second end of the rotor shaft (see FIG. 2) . If it liquefies in addition to preventing longitudinal displacement of the rotor member, the connecting member reduces the frictional force exerted by the second end of the rotor shaft and allows the rotor shaft 13 to freely rotate within the rotor member. In a preferred embodiment, the end of the rotor shaft 13 can be provided with a hardened insert 42 to prevent the shaft from wearing out and coming out of the contact area of the rotor shaft and the sphere 40. Other devices, such as a Thrust bearing located between the rotor member 10 and the gasket 20 or between the rotor member 10 and the first end of the rotor shaft, can serve the same purpose. If desired, the pump may be equipped with a sensing device that can impel the motor to stop in the event of uncoupling of the rotor member. The above description of the preferred embodiment should not be "interpreted in a limiting manner since variations and refinements are possible which are within the spirit and scope of the present invention." The scope of the invention is defined in the appended claims and their equivalents

Claims (28)

1. A rotor assembly for a pump, the rotor assembly comprises: a rotor member including a cavity; a rotor shaft extending at least partially in the cavity; a connection member in the cavity that establishes a driving relationship between the rotor shaft and the rotor member, whereby the rotational movement imparted to the rotor shaft is transmitted to the rotor member by the intermediary of the connecting member; the connection member is capable of thermally induced structural failure to terminate the drive ratio when a predetermined temperature is reached characterized in that the rotor member is in a condition of engagement with the connection member before the thermally-induced structural failure.

2. A rotor assembly, according to claim 1, characterized in that the connecting member is in a condition of engagement with the rotor shaft.

3. A rotor assembly, according to claim 1, characterized in that the distance of space The free cross section between the rotor shaft and the rotor member is not constant so as to generate a larger free space area and a smaller free space area.

4. A rotor assembly according to claim 3, characterized in that after the thermally induced structural failure, the movement of the material of the connection member from the largest free space area to the smallest free space area produces a viscosity effect. cradle.

5. The rotor assembly, according to claim 3, characterized in that the largest free space area is more than 10% larger than the smallest free space area.

6. The rotor assembly, according to claim 3, characterized in that the largest free space area is greater than 50% larger than the smallest free space area.

7. The rotor assembly, according to claim 3, characterized in that the largest free space area is more than 100% larger than the smallest free space area.

8. The rotor assembly, according to claim 3, characterized in that the largest free space area is more than 200% larger than the smallest free space area.

9. The rotor assembly, according to claim 1, characterized in that the rotor shaft has a hexagonal cross-sectional shape, and the cavity of the rotor member has a dodecahedral cross-sectional shape.

10. The progressive cavity pump, according to claim 1, characterized in that the connecting member is converted to a liquid state when the predetermined temperature is reached.

11. A rotor assembly, according to claim 10, characterized in that the rotor assembly further comprises a means for preventing rotor shaft contact with the rotor member when the connecting member is converted to a liquid state.

12. A rotor assembly, according to claim 11, characterized in that the means for preventing contact of the rotor shaft with the rotor member includes bushings located at each end of the rotor shaft.

13. A rotor assembly, according to claim 10, characterized in that the connecting member is made of a bismuth alloy.

14. A rotor assembly, according to claim 13, characterized in that the alloy is made up of 55.5% bismuth and 44.5% lead.

15. A rotor assembly, according to claim 10, characterized in that the rotor assembly further comprises a means for preventing longitudinal displacement of the rotor member relative to the rotor axis when the connecting member is liquefied.

16. A rotor assembly, according to claim 15, characterized in that the means for preventing longitudinal displacement of the rotor member includes a sphere located in the cavity of the rotor member adjacent to the tip of the rotor shaft.

17. A progressive cavity pump, comprising a rotor assembly according to any of the preceding claims, characterized in that it further comprises a cavity defining a pumping chamber, the cavity includes an inlet for admitting material to be pumped into the pumping chamber; an outlet for discharging the pumped material from the pumping chamber; and the rotor assembly is mounted on the cover. partially in the cavity;

18. A progressive cavity pump, according to claim 17, characterized in that the mounted assembly is capable of rotational and orbital movements inside the cover to cause the displacement of the material to be pumped into the pumping chamber between the inlet and the exit; the pump further comprises a drive shaft for imparting rotary movement to the derotor assembly; and a sealing mechanism for insulating the drive shaft from a suction chamber of the inlet, the sealing mechanism provides a means for providing a rotary movement of the drive shaft; and provide an orbital movement of the driving shaft.

19. A progressive cavity pump, according to claim 18, characterized in that the sealing mechanism comprises a seal positioning ring located between the suction chamber and the driving shaft; a first sealing member radially inward of the seal positioning ring and supplying the rotational movement of the rotor; and a second sealing member radially outwardly of the seal placement ring and providing the orbital motion of the rotor. "

20. A progressive cavity pump, according to claim 19, characterized in that the sealing mechanism further comprises a bearing means between the seal positioning ring and the rotor.

21. A progressive cavity pump, according to claim 19, characterized in that the first sealing member is a lip seal and wherein the second sealing member is made of elastomeric material and includes at least one crease.

22. A progressive cavity pump, according to claim 18, characterized in that the sealing mechanism comprises: a support ring located between the suction chamber and the driving shaft, the support ring is capable of rotational movement within the cover; a first sealing member mounted eccentrically within the support ring, the first sealing member is positioned concentrically with respect to the rotor and provides a means for supplying the rotational movement of the rotor; a second sealing member secured to the cover, the second sealing member is concentric with respect to the support ring and provides a means for supplying the rotational movement of the support ring, whereby the orbital motion of the rotor imparts a rotational movement to the support ring and in this way the second sealing member supplies the rotational movement of the support ring.

23. A progressive cavity pump, according to claim 22, characterized in that the first and second sealing members are lip seals.

24. A progressive cavity pump, according to claim 22, characterized in that it further comprises a first bearing means for supplying rotational movement of the rotor inside the support ring and further comprising a second bearing means for supplying the rotational movement of the second Support ring inside the cover.

25. A progressive cavity pump, according to claim 24, characterized in that the first and second bearing means are double row ball bearings.

26. A progressive cavity pump, according to claim 1, characterized in that the driving shaft places on the rotor a force having a radial component, the pump further comprises a bearing that provides a means to generate a radial reaction force that substantially counteracts the radial component.

27. A progressive cavity pump, according to claim 26, characterized in that the bearing is mounted to the drive shaft and the bearing is in rotatable engagement with the cover.

28. A progressive cavity pump, according to claim 27, characterized in that the bearing includes a resilient material, the resilient material engages with the cover during the rotational movement of the bearing.