ROTARY LOBE PUMP WITH RADIAL WEARPLATE AS WELL AS A METHOD FOR REMOVING SAID WEARPLATE

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to a rotary lobe pump having at least one radial wearplate, a radial wearplate for use in a lobe pump, and a method for removing a radial wearplate from a rotary lobe pump.

Description of the Prior Art

US 5567140 describes a rotary lobe pump comprising a curved radial wearplate situated between a pump chamber wall and a rotor in the pump. Over time during use the radial wearplate wears out, e.g. due to friction from the rotor. This results in reduced sealing efficiency between the rotor and the chamber wall. The drawback of the invention in US 5567140 is that the worn out radial wearplate is not easily replaced. The replacing process demands a number of different operation steps where mistakes can happen. In US 5567140, in addition to opening the pump it is necessary also to remove the rotor from its position in order to free the radial wearplate. Such an operation is time-consuming, both for the removing- and the replacement process of said radial wearplate. A further disadvantage is that such operations due to the large number of operation steps increases the risk of possible mistakes during assembling of the pump with a new radial wearplate.

In GB-A-324817 there is described a rotary pump with a chamber having two compartments separated by rotors in the form of crescent shaped vanes which rotate in opposite directions. Bearing surfaces in the form of liner plates extend around the periphery of the vanes and the peripheral chamber walls with which the vanes cooperate. The edges of the liner plates are deformed to engage edges of the vanes and shoulders of the pump housing.

SUMMARY OF THE INVENTION

The object of the present invention is to construct a rotary lobe pump comprising radial wearplate which pump has such a construction whereby the number of operations necessary for replacing the radial wearplate is reduced in comparison to conventional rotary lobe pumps. Broadly stated the invention resides in a lobe pump including a radial wearplate that can be removed from a position between a rotor and an adjacent wall of the pump housing without requiring any axial displacement of the rotor.

Provided in accordance with a first aspect of the invention is a rotary lobe pump comprising a housing enclosing a chamber having rear end and an open front end, a cover plate arranged to close the open front end, an inlet port and an outlet port in the housing, rotors accommodated in the chamber, and at least one curved radial wearplate positioned in the chamber and comprising an inner surface, an outer surface, and a peripheral edge with straight and curved portions, characterised in that the radial wearplate is provided with a protrusion extending along at least a part of a curved edge portion.

The protrusion of the radial wearplate is situated along one part of the edge on the radial wearplate so that walls of the radial wearplate are

even and comprise no projections, and the protrusion can function as a guiding means to keep the radial wearplate fixed in a desired position. The protrusion is preferably removably engaged in a corresponding keyway provided in the chamber wall of the housing in the pump adjacent to the open front end. The radial wearplate can be slid out between the wall of the housing and the rotor without removing the rotor when it is worn out and needs to be changed.

In accordance with one embodiment of the invention the protrusion extends along a first edge portion between a third edge portion and a fourth edge portion of the peripheral edge. The first edge portion is right angled with each one of the third and fourth edge portions. Between the chamber wall and the rotor is a gap which corresponds to the thickness of the main part of the radial wearplate not comprising the protrusion. Therefore, due to the position of the protrusion the radial wearplate can be inserted one way only between the rotor and the wall of the housing. One advantage of the protrusion is that it fixes the radial wearplate to the wall of the housing via a corresponding keyway. One further advantage of the protrusion is that it stiffens the radial wearplate.

In accordance with one embodiment of the invention the protrusion projects outwardly from the outer surface of the wearplate. The protrusion is an integral part of the radial wearplate. In an alternative embodiment of the invention the protrusion is mechanically connected to the outer surface of the radial wearplate. The connection can be provided by any known method, such as e.g. gluing, welding, bolting etc. One advantage of the protrusion is that it stabilises and stiffens the radial wearplate. Another advantage is that it strengthens the curvature of the radial wearplate.

In accordance with one embodiment of the invention the protrusion is inserted between, and cooperates with the housing and the cover plate. As mentioned above the protrusion is removably engaged in a corresponding keyway in the wall of the pump housing. The keyway is positioned adjacent the open end. The keyway is a recess or notch created in the edge area of the wall of the housing adjacent the open end. The shape of the protrusion corresponds to the shape of the keyway. The protrusion is further secured by the cover plate sealing the open end and covering the protrusion.

In accordance with one embodiment of the invention the protrusion comprises a front surface adjacent to the plate, a rear surface connected to the outer surface of the wearplate, and an outer surface connecting the front surface to the rear surface, the front surface having a larger area than the rear surface. When the protrusion is positioned in the keyway and the cover plate is positioned to close the open end, the plate abuts against the front surface of the protrusion. Thus the front surface is in contact with the cover plate when the cover plate is coupled to the housing. The protrusion slidably engages into the keyway in the housing.

The protrusion and the corresponding keyway can take any geometrical form allowing them to cooperate with each other. For example, the protrusion could e.g., in a cross-section view, have one of the following geometric forms: H, Pl, λ. The keyway in the wall of the chamber will correspond to the chosen cross-section of the protrusion.

In accordance with one embodiment of the invention the third and the forth edge portions extend between the first and the second edge portions and are parallel with a rotor axis. In this way is the largest area

is achieved for the radial wearplate the purpose of which is to cover and protect the wall of the housing.

In accordance with one embodiment of the invention the peripheral edge has a second edge portion, opposite the first edge portion, which second edge portion has a geometrically irregular form due to at least one notch being formed in the second edge portion. The notch in the second edge portion receives a corresponding tongue of a rear wearplate. In this way the tongue locks the radial wearplate against movements around the rotor centre axis. The rear wearplate comprises a notch provided on each side of the tongue. The notches of the rear wearplate receive corresponding parts of the second edge portion of the radial wearplate. The depth of the notches corresponds to the thickness of each wearplate which it is connected with.

In accordance with one embodiment of the invention the front surface of the protrusion comprises a receiving means for receiving a releasing means, e.g. a pin or the like, for removing the radial wearpiate from the housing. The receiving means can be a hole, preferably machined in the front surface of the radial wearplate. When the radial wear plate need to be removed a pin, or the like, is positioned in the hole. The pin can cooperate with the hole in such way that they connect with each other due to friction. Alternatively the hole can be provided with internal threads, and the pin can be a screw or a bolt with corresponding threads that is screwed in to the hole. The radial wearplate is removed by pulling the pin in a direction towards the open end and parallel with the rotor axis. The radial wearplate will then be extracted from the housing in the direction towards the open front end.

Another object of the present invention is to create a radial wearplate which allows it to be releasable from the housing of a rotary lobe pump without the removal of any vital internal parts of the pump.

In accordance with another aspect the present invention provides a radial wearplate for use in a rotary lobe pump, which rotary lobe pump comprises a housing enclosing a chamber having rear end and an open front end, a cover plate for closing the open front end, an inlet port and an outlet port in the housing, and rotors positioned in the chamber, the radial wearplate comprising an inner surface, an outer surface, and a circumferential edge with straight and curved portions, characterised in that a protrusion is provided along at least part of a curved edge portion.

The radial wearplate comprises four edge portions, together making up the peripheral edge. The protrusion is situated along one of three possible edge portions. The remaining edge portion (the second edge portion) must be free from the protrusion. This is because a protrusion situated along the second or rear edge portion cannot slide out between the wall of the housing and the rotor through the gap therebetween. The width of the gap corresponds to the thickness of parts of the radial wearplate without any protrusion. In other words, the gap is too narrow to fit an edge portion comprising the protrusion. An advantage of the radial wearplate is that due to the position of the protrusion the radial wearplate can be slid into position between the wall of the housing and the rotor without removal of the rotor being necessary.

A further object of the present invention is to provide a method for removal of a radial wearplate from a rotary lobe pump without removing the rotor from its position in the pump.

In accordance with a further aspect the invention provides a method for removing a radial wearplate from a rotary lobe pump, which radial wearplate comprises an inner surface, an outer surface, a peripheral edge with straight and curved portions, and a protrusion provided along part of the edge, which rotary lobe pump comprises a housing enclosing a chamber having rear end and an open front end, a cover plate for closing the open front end, an inlet port and an outlet port in the housing, and rotors as positioned in the chamber along with the wearplate characterised in that a force is applied to the radial wearplate, which force causes the radial wearplate to move from a first position between a rotor and a chamber wall, in a direction parallel to a rotor axis, to a second position, whereby an empty space between the rotor and the wall is created, and which rotor remains in a static axial position relative to the housing during the removal of the radial wearplate.

The radial wearplate is influenced by a force whereby the radial wearplate is moved from a first position to a second position in a direction towards the open front end parallel with the centre axis. In the first position the radial wearplate is positioned between the chamber wall and the rotor which is in a static position. A force applied on to the radial wearplate causes the radial wearplate to move from the first to the second position. The second position is outside the housing and beyond its open front end. During the movement of the radial wearplate between the two positions the rotor in remains in a static position in the axial direction. Preferably the rotor is also in a rotationally static. Preferably, extending into a front surface of the radial wearplate, which faces the open end of the housing, at least one releasing means is provided as a receiving means. The releasing means simplifies the removal of the radial wearplate since they can be used for pulling the wearplate out of the housing. One advantage of the method is that it demands a minimum of

steps involving vital parts of the pump in order to remove and replace a radial wearplate in a rotary lobe pump. One further advantage is that since the method reduces the number of process steps, the time necessary for performing the operation is optimised.

The invention also provides a rotary lobe pump comprising a radial wearplate inserted between a rotor of the pump and an adjacent wall of the pump housing, wherein the wearplate is removable for replacement without requiring any axial displacement of the rotor relative to the housing, i.e. without releasing the rotor and pump housing for axial movement relative to each other to enable removal and replacement of the wearplate.

BRIEF DESCRIPTION OF THE DRAWING

The presented invention will now be elucidated by reference to a preferred embodiment partially illustrated schematically in the drawing. The drawing is an exploded view of a lobe pump embodying the invention and shows only details necessary for understanding the invention.

Fig 1/1 show a rotary lobe pump (1 ) comprising a housing (2), a chamber (3), end walls (4), a rear end (5), an open front end (6), and a cover plate (7) for closing the chamber (3). An inlet port (8) and an outlet port (9) are provided on the housing and communicate with the chamber (3).

Located inside the housing (2) are two rotors (10), two axles (11 ), two rear wearplates (12) and two radial wearplates (13). Each rotor (10) is splined onto a respective axle (11 ) for rotation therewith about the centre axis (14) of the axle (11). The rear wearplates (12) each comprises a hole through which a respective one of the axles (11) passes. The rear

wearplates (12) are positioned next to the rear wall (5), whereby they partly cover the rear wall (5). The two rotors (10) are placed next to each other, the chamber (3) in the housing (2) accommodating the rotors (10) being generally oblong. The end walls (4) of the chamber (3) are curved whereby the rotors (10) can rotate with a constant distance defined between each wall (4) and the radially outer part of the adjacent rotor (10). The radial wearplates (13) are positioned adjacent to the respective walls (4), whereby they cover and protect the end walls from contact by the rotors (10) when they are turning. The inlet and outlet ports (8, 9) are each situated on opposite sides of the housing between the two curved end walls (4).

Each radial wearplate (13) has an inner surface (15), an outer surface (16), a peripheral edge (17 - 20) and a rib-like protrusion (21). The surrounding edge (17 - 20) consists of four edge portions, namely; a first curved front edge portion (17); a second rear curved edge portion (18); a third edge portion (19); and, a fourth edge portion (20). The third and the fourth edge portions (19,20) which are straight and parallel to each other, interconnect the first and the second edge portions (17,18). The radial wearplate (13), like the first and the second edge portions (17, 18) is curved between the straight third and the fourth edge portions (19, 20). The protrusion (21) extends along the first edge portion (17) between the third and fourth edge portions (19,20) and projects outwardly from the outer surface (16). The curvature of the radial wearplate (13) corresponds to the curvature of the adjacent end wall (4) of the chamber (3).

The protrusion (21) comprises a front surface (22), an outer surface (23) and a rear surface (24). The front surface (22) is connected via an edge with the inner surface (15) of the radial wearplate (13). The front surface (22) connected to the outer surface (23) via an edge between the two

surfaces (22, 23). The rear surface (24), is opposite the front surface (22) and is connected to the outer surface (23) of the protrusion and to the outer surface (16) of the wearplate via edges.

The second edge portion (18) of the wearplate comprises a notch (25) centrally located therealong.

In the assembled rotary lobe pump (1) each radial wearplate (13) is positioned between an end wall (4) and the adjacent rotor (10). The protrusion (21) is releasably received in a groove (26) which extends around the edge of the end wall at the open end (6) of the housing (2). The front cover plate (7) is in contact with the front surface (21) of the radial wearplate (13) and is mechanically secured to the housing (2) via bolts (not shown), to seal the housing (2) and to anchor the protrusion in the groove (26) under the pressure applied by the plate (7) to the front surface (22) of the protrusion (21).

The second edge portion (18) of the radial wearplate (13) is partly in contact with the rear end (5) of the chamber (3) when the wearplate is fixed in position in the housing, and the notch (25) in the second edge portion (18) receives a tongue (27) which is provided along the circumference of the corresponding rear wearplate (12). The notch (25) and the tongue (27) interlock to prevent rotation of the radial wearplate (13) around the centre axis (14) of the rotor shaft. On one side, or preferably each side, of the tongue (27) a small gap is defined between the circumference of the rear wearplate (12) and the end wall (4) to receive the parts of the second edge portion (18) either side of the notch (25).

During removal of the radial wearplate (13) the cover plate (7) is removed and a force is applied to the radial wearplate (13) in a direction parallel to the centre axis (14). When sufficient force is applied, the radial wear plate will move from a first position between the end wall (4) and the rotor (10) to a second position outside the chamber (3). This movement of the radial wearplate (13) will be in an axial direction through the open end (6). During removal of the wear plate the rotor (10) remains in an axial static position. Preferably the rotor (10) is also in a rotationally static position.

The front surface (22) of the protrusion comprises a number of receiving means (28) which are preferably holes for receiving a pin (not shown in the figure), or the like. During removal of the radial wearplate (13) the above described removing force is applied to the pin or pins. With sufficient friction between the pin and the receiving means the pin can be pulled in the direction towards the open end (6) whereby the radial wearplate (13) will be extracted from the housing. Alternatively the receiving means (28) can be internally threaded and the pin can take the form of a bolt or a screw having corresponding threads whereby they interlock with each other.

The invention is not limited to the above presented embodiment and can be modified without departing from this scope of the invention as defined by the following claims.