Patent Publication Number: US-8985981-B2

Title: Rotary displacement pump for pumping solids emulsions, especially liquid explosives

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit under 35 U.S.C. §371 of International Patent Application No. PCT/EP2010/063572, having an international filing date of Sep. 15, 2010, the content of which is incorporated herein by reference in its entirety. 
     FIELD 
     The present invention relates to a rotary displacement pump for pumping solids emulsions, especially liquid explosives. 
     BACKGROUND 
     From the EP 1 807 624 B1, a rotary displacement pump is known which allows for pumping flowable, relatively viscose materials in the food stuff industry, the chemical and biochemical industry, the medical industry and the cosmetic industry. Examples of materials that can be pumped by such rotary displacement pump are yoghurt, soup, sauce, mayonnaise, fruit juice, cheese material, chocolate, paint, cosmetic cream, and lipstick material. 
     Now there is a need for pumping solids emulsions, especially liquid explosives. Such liquid explosives are for example used in the mining industry in the field of tunneling and operation of quarry where such liquid explosives have to be pumped in cavities and channels in the rocks where they are ignited to explode in a controlled fashion. 
     The rotary displacement pump disclosed in the EP 1 807 624 B1 is not suitable for pumping such solids emulsions. When pumping such solids emulsions with the displacement rotary pump, the solids emulsions collect, build up and pack in certain regions of the pump which increases the friction, builds up additional pressure and heats up the pump. This results in a loss of efficiency or even a total outage of the pump. When pumping liquid explosives comprising small spherical components also referred to as prill it is this prill that collects, builts up and packs in many places of that pump, which in addition to the drawbacks as mentioned above, is dangerous to men and environment. In the worst case, the whole rotary displacement pump can explode, when the temperature within the pump rises above a critical point. 
     Currently, the pumps used for pumping such solids emulsions and liquid explosives are of bigger size and more complex design which makes their use in connection with solids emulsions and liquid explosives inconvenient and expensive and which limits the applications to situations where enough space is available for such bigger pumps. 
     SUMMARY 
     It is therefore an object of the invention to provide a rotary displacement pump of the “protruding web of rotor engaging in an engagement slot of scraper”-type allowing for a small pump size and being capable of pumping solids emulsions especially liquid explosives in an efficient and safe manner. 
     This object is attained by a rotary displacement pump for pumping solids emulsions, especially liquid explosives as defined in claim  1 . 
     Such rotary displacement pumps comprises a stator; a rotor configured to be driven by a shaft, the rotor including a shaft portion and a radially protruding web having a configuration of an undulatory disk type; a scraper having an engagement slot of predetermined radial height and predetermined axial width, the engagement slot engaging the protruding web of the rotor; the scraper being supported by a scraper guide so as to be retained in circumferential direction and to allow a reciprocating movement in a substantially axial direction; a pump housing comprising a front end plate and a rear end plate, the pump housing enclosing the stator, the rotor, the scraper and the scraper guide; the shaft extending through at least the rear end plate; the stator including a generally semi-circular arc-formed first stator member and a generally semi-circular arc-formed second stator member, the first and second stator members abutting to each other laterally along a radially outer abutment portion so as to form a stator channel through which the radially protruding web of the rotor runs and to define an enclosure that encircles a generally semi-circular arc-formed portion of the radially protruding web of the rotor; the stator, the pump housing and the scraper together with the scraper guide defining an inlet chamber and an outlet chamber, the scraper together with the scraper guide forming a partition between the inlet chamber and the outlet chamber, the inlet and outlet chambers being provided with respective inlet and outlet ports; the stator channel extending from the inlet chamber to the outlet chamber, the web of the rotor being rotatable through the inlet chamber, the stator channel, the outlet chamber and the slot of the scraper, wherein at least part of the end faces of the first and second stator members being situated in the outlet chamber are oblique so as to provide an obtuse-angled transition to the inner faces of the front end plate and the rear end plate. 
     With such a rotary displacement pump, solids emulsions, and especially liquid explosives can be pumped efficiently and safely. By the obtuse-angled transition of at least part of the end faces of the first and second stator members to the inner faces of the front and rear end plates, the material build up, and especially the prill build up along edges and in grooves is minimized, thereby providing for an efficient and safe operation of the rotary displacement pump when pumping solids emulsions and especially liquid explosives. It has been discovered by the inventors that it is mostly the prill that builds up and packs within the pump housing and in particular within the outlet chamber, and such prill, in addition to packing the pump housing and in particular the outlet chamber, has a disadvantageous abrasive effect. 
     The inventors of the present rotary displacement pump have made countless different modifications to different features of rotary displacement pumps until finding out that by the rotary displacement pump, as defined in claim  1 , an efficient and safe pumping of solids emulsions, and especially liquid explosives can be attained. 
     By the outlet chamber which is confined by the end faces of the first and second stator members providing an obtuse-angle transition to the inner faces of the front and rear end plates, by the pump housing, by the scraper and the scraper guide, the material built up and the packing of material can be significantly reduced which provides for improved material flow characteristics and, consequently, for an efficient and safe operation. 
     According to a first embodiment of the invention, the obtuse-angle between the end faces of the first and second stator members and the inner faces of the front end plate and the rear end plate is 120 to 160°, particularly 140 to 160°. These angles have been proven to provide for a particularly good and smooth material flow. 
     According to a further embodiment of the invention the shaft extends through both the front and rear end plates, which are provided with central openings for this purpose, and generally tube-shaped front and rear seal housing elements are provided being positioned in the recesses of the first and second stator elements. 
     These housing elements are stationary and encircle the rotating shaft/shaft sleeve elements. 
     According to a further embodiment of the invention, these seal housing elements confine the inlet and outlet chambers in a direction towards the shaft therefore provide part of the boundary of the inlet and outlet chambers. 
     According to a further embodiment of the invention, the seal housing elements are provided with at least one slot in order to reduce the pressure within the inlet and outlet chambers and in order to relieve material build up. The pumped solids emulsions will get through such slot into the interspace between the seal housing elements and the shaft/shaft sleeve elements, and material built up above the seal housing elements can be minimized. 
     According to a further embodiment of the invention, front and rear shaft sleeves attach to the rotor, wherein the front and rear shaft sleeves are situated within the seal housing elements, and wherein sealing elements are provided between the rotating front and rear shaft sleeves and the stationary seal housing elements. 
     Such sealing elements provide for a sealing between the rotating front and rear shaft sleeves and the stationary seal housing elements. However, these sealing elements are not totally tight, but allow for a pressure compensation, and a certain amount of the pumped solids emulsions can pass through the sealing elements in a forward direction out of the front end plate and in a rearward direction out of the rear end plate and can leave the pump housing that way. 
     According to a very compact embodiment of the invention, the sealing elements are provided at the inner side of the seal housing elements. 
     According to a further embodiment of the invention, the sealing elements are formed as three lip sealing rings with two interposed support rings. The two sealing rings that are situated closest to the rotor provide for a sealing to the outside, and the outermost sealing ring provides for a sealing from outside to inside. 
     According to a further embodiment of the invention, the generally tube-shaped front seal housing element and the generally tube-shaped rear housing element are of identical shape and size. 
     According to a further embodiment of the invention, the front and rear shaft sleeves are also of identical shape and size. 
     By mirroring the design of the front and rear housing elements and, preferably, also of the front and rear shaft sleeves a part commonality is attained which helps to save costs and provides a means of pressure relief at both ends of the shaft. 
     According to a further embodiment of the invention, the tip of the shaft or the front shaft sleeve and/or a front locking element that secures the front shaft sleeve to the shaft protrudes out of that front end plate, which is provided with a central opening. 
     It has been discovered by the inventors, that by such embodiment material built up is further mitigated and a pressure relief through the front sealing element in a forward direction can be attained. It has further been discovered that by such embodiment the drawback of a material build up and packing of material between a bushing assembly and the cover which happened when the front cover end of the shaft was closed and supported by a bushing can reliably be avoided. According to a further effect of this embodiment a certain degree of load support is achieved in addition. 
     According to a further embodiment of the invention, a security cover element is provided covering the tip of the shaft or the front shaft sleeve and/or the front locking element, wherein this security cover element has evacuation apertures, particularly radially oriented evacuation apertures in order to allow for the solids emulsions to pass through. By the provision of such security cover element injuries caused by the rotating shaft tip can be avoided. The solids emulsion can pass through the evacuation apertures which further helps avoiding material built up in the inside of the pump housing. 
     According to a further embodiment of the invention a recessed spacer element having evacuation apertures, in particular radially-oriented evacuation apertures, is provided behind the rear end plate. The evacuation apertures allow for the solids emulsion passing through which further mitigates material build up and provides for an additional pressure relief through the rear sealing element in a rearward direction. 
     According to a further embodiment of the invention, the evacuation apertures are closed by means of grating elements, in particular by means of a grating security ring. Thereby a discharge of solids emulsion can be attained, wherein at the same time injuries by people unintentionally putting their fingers through the apertures and touching the rotating shaft or shaft sleeves can be avoided. 
     According to a further embodiment of the invention, the scraper has the general form of a plate, particularly a rectangular plate, with the engagement slot formed therein. Furthermore, the width of the scraper can correspond to 65 to 75%, particularly to 68 to 72% of the width of the inlet and outlet chambers, measured from the front end plate to the rear end plate of the pump housing, so as to provide, in the extreme axial positions of the scraper, for sufficient distance between the side faces of the scraper and the front and rear end plates of the pump housing. 
     The inventors have found that by a scraper of such reduced width material built up in particular in between the side faces of the scraper and the front and rear end plates of the pump housing, in corner areas as well as in mating cavities in the pump housing can be significantly reduced which contributes to a safe and efficient operation of the pump. 
     According to a further embodiment of the invention, the scraper has the general form of plate, particularly a rectangular plate, with the engagement slot formed therein. The side faces of the scraper can be oblique with respect to an axial plane, with the rear face of the scraper oriented towards the outlet chamber having a smaller surface area than the front face of the scraper oriented towards the inlet chamber. By this feature the effect of packing solids emulsions, in particular into the space between the side faces of the scraper and the facing portions of the front and rear end plates of the pump housing, into corner areas of the outlet chamber and into mating cavities in the pump housing can be considerably reduced. This embodiment further contributes to a safe and efficient operation of the pump. 
     According to a further embodiment of the invention, the angle between the side faces of the scraper and the axial plane is in the range of 20 to 60 degrees, particularly in the range of 30 to 40 degrees. These angles have been found to be particularly advantageous. 
     According to a further embodiment of the invention, the scraper guide has a form of a recessed plate or cartridge, with the width of the recess being such that the engagement slot of the scraper in its extreme axial positions lies within this recess, thereby providing a compact and reliable construction of the scraper and scraper guide. 
     According to a further embodiment of the invention, the scraper guide can be provided with limit stops defining the extreme axial positions of the scraper. By the provision of such limit stops the limits of the movement of the scraper can be defined precisely therefore preventing misfunction. 
     According to a further embodiment of the invention, the scraper guide is supported within the pump housing between the front end and rear end plates. For this purpose at least one of the front and rear end plates can be provided with a mating cavity in order to support the scraper guide. By these features the scraper guide can be maintained in its optimum position reliably and permanently. 
     According to a further embodiment of the invention, the scraper has a radially outer guiding groove that engages with a corresponding guiding track of the scraper guide and a radially inner guiding groove engaging with corresponding circumferential portions of the seal housing elements. Thus, the scraper can be retained in a circumferential direction and allows for a reciprocating movement in a substantially axial direction. This configuration is particularly compact and stable and only requires a minimum number of parts involved. 
     According to a further embodiment of the invention, the material of the scraper is chosen with a melting temperature below the critical temperature of the pumped product. If the temperature within the pump housing rises due to dead heading, dry running, mechanical binding or another cause, the engagement slot in the scraper that mates with the rotor will deform and enlarge, thus reducing friction and preventing additional pressure and heat built up. This embodiment contributes for further safety of the pump operation. 
     The present invention also relates to the use of a pump, as described and defined above, for pumping solids emulsions of any kind and in particular for pumping liquid explosives. As described above, the inventors have found out that by a pump having a design as defined in the appended claims, such difficult and dangerous materials can be pumped safely and efficiently. 
     The invention will now be described in greater detail referring to the embodiments described in the following and shown in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded view of a rotary displacement pump according to an embodiment of the invention showing the parts involved; 
         FIG. 2  shows a perspective view of a front cover provided with a front stator/liner element of the rotary displacement pump of  FIG. 1 , according to an embodiment of the invention; 
         FIG. 3  shows a perspective view of the scraper element of the rotary displacement pump of  FIG. 1 , according to an embodiment of the invention; 
         FIG. 4  shows a perspective view of the scraper element of the rotary displacement pump of  FIG. 1 , according to a further embodiment of the invention; and 
         FIG. 5  shows a perspective view of the rotary displacement pump of  FIG. 1  in its mounted state with an upper left quadrant part being cut off. 
     
    
    
     DETAILED DESCRIPTION 
     The terms “front” and “back/rear” are to be understood in the forthcoming figures with respect to the axis of the shaft  8 , the terms “left” and “right” are to be under-stood in the forthcoming figures with respect to the axis of the shaft  8 , when seen from the back (substantially right-hand in  FIG. 1 ) to the front (substantially left-hand in  FIG. 1 ) of the shaft  8 , such that the parts of the pump that lie, with respect to the shaft  8 , on the closer side to the viewer in  FIG. 1  are positioned “left” and the parts of the pump that lie, with respect to the shaft  8 , on the farther side from the viewer in  FIG. 1  are positioned “right”. 
       FIG. 1  shows an entire rotary displacement pump  2  comprising a pump part  4  or pump proper  4  and a support part  6 . 
     At the right-hand side of  FIG. 1 , an end portion of a shaft  8  protrudes from the support part  6 . A drive motor, not shown, typically an electric motor serves to apply torque to the shaft  8 , either by being directly or through a coupling coupled to the shaft  8  or for example through a gear or a pulley etc. The support part  6  comprises a support part housing  10  in which appropriate roller bearings (not shown) for the shaft  8  can be provided. 
     The support part housing  10  has a substantially cylindrical shape, and the front end of the support part housing  10  is encircled and fixed by a mounting frame  12  that has a lower mounting plate in order to fix the entire rotary displacement pump  2  to an appropriate base. At the left and right sides of the frame part of the mounting frame  12  there are provided mounting pins  14  protruding out of the front side of the mounting frame  12  in a forward direction in order to engage with corresponding holes in the spacer ring  22  and the tubular cylindrical body  34  (to be described in further detail later) and to join the support part  6  and the pump part  4  firmly together. The middle to front portion of the shaft  8  is provided with axially extending recesses that engage with corresponding protrusions of the disk member  42  (described in further detail later), and, if appropriate, with other rotating parts of the pump part  4 . The tip of the shaft  8  is tapering. 
     A disk member  42  is keyed to the shaft  8  and rotates with the shaft  8 . In the following, the disk member  42  will be referred to as “disk  42 ”. The shaft  8  and disk  42  are part of a rotor. The disk  42  comprises a radially protruding web having an axial thickness and predetermined outer diameter. The web has a rear surface and a front surface. If one follows, for example with a fingertip the front surface, along the circle line of the outer diameter, the fingertip will describe a curved sinus-type line seen in radial view (not necessarily in the strict mathematical sense), undulating with respect to a middle plane intersecting the axis of the shaft  8  at a right angle. Along a 360° circle there are two full periods of the sine curve, i.e. the first time from completely left-hand in  FIG. 1  to completely right-hand in  FIG. 1  and back. The same description as made with respect to the front face applies to the rear face as well. For simplicity, this undulating form of the web of the disk  42  is not depicted in the figures. 
     The pump proper  4 , in the following referred to simply as “pump  4 ”, comprises a pump housing  24  having the following the main parts: a tubular cylindrical body  34  provided at its rear end with a circular, rear end plate (not visible in  FIG. 1 ), a circular front end plate  56 , an inlet pipe socket/inlet port  26  provided with an inlet port flange  28 , and an outlet pipe socket/outlet port  30  provided with an outlet port flange  32 . The inlet and outlet ports  26 ,  30  are welded to the tubular cylindrical body  34 . 
     The axis of the inlet and outlet ports  26  and  30  intersect at 90°. Accordingly, the tubular cylindrical body  34  has two openings corresponding to the diameter of the inlet and outlet ports  26  and  30 . 
     The body  22 , the end plates and the inlet and outlet ports  26 ,  30  consist of stainless steel. 
     A stator lines the lower half of the inside of the housing  24 . The stator consists of a generally semi-circular arc-formed rear stator member  40  and of a generally semi-circular arc-formed front stator member  48 , that can be formed separately as in the  FIG. 1 , or integrally with the front end plate and, respectively the rear end plate. The stator elements can be formed as liner elements fixed in the pump housing  24 . They can be made of plastics material, particularly polyamide. 
     Taking reference to  FIG. 2 , the front stator member  48  abuts with its outer surface (the term outer is to be understood with respect to the disk  42 ) against the ring-formed inner face  90  of the front end plate  56 . In a radial sectional cut, the front stator member  48  has the profile of an “L”/a reversed “L” with the radially oriented portion of the profile forming an radial wall  70  for the web  42  and with the axially-oriented portion of the profile forming a circumferential wall  68  for the web  42 . Accordingly, the inner end (the term “inner” is to be understood opposite to the term “outer”, see above) of the circumferential wall  68  forms a lateral abutment face  74  that abuts in the mounted state to the opposite lateral abutment face of the rear stator member  40 . 
     The face of the circumferential wall  68  that is oriented towards the shaft axis forms a stator channel bottom face  76  and the inner face of the radial wall  70  forms a lateral stator channel face  78 . 
     Appropriate sealing means sealing the outer face  72  of the front stator element  48  to the lower half of the inside of the tubular cylindrical body  34  can be provided (not shown). 
     Following a central opening  92  of the rear end plate  56  there is a recess provided in the front stator element  48  so that the shaft  8  can extend through both the central opening  92  and the central recess. 
     The upper left end face of the generally semi-circular arc  48 , which is designated with reference numeral  80  in  FIG. 2 , is straight and extends horizontally. It forms the inlet chamber bottom  80 . 
     The upper right end face of the generally semi-circular arc  48 , comprises a straight, horizontal end face of the circumferential wall  68  forming a straight outlet chamber bottom part  84  and a oblique end face of the radial wall  70  forming an oblique transition portion  82  of the outlet chamber to the ring-formed inner face  90  of the front end plate  56 . 
     The same description as made with respect to the front stator element  48  applies in an analogous manner to the rear stator element  40 . Generally speaking, the rear stator member  40  is a mirror-image to the front stator member  48 , and the rear stator member  40  butts with its outer surface to the ring-formed inner surface of the rear end plate of the pump housing  24 . 
     Taking reference to  FIG. 1  again, there are provided, in the upper part of the inside of the pump housing  24 , an inlet chamber adjacent to the inlet port  26  and an outlet chamber adjacent to the outlet port  30 . The inlet chamber is provided in the upper left quadrant of the inside of the pump housing  24  that is located closer to the viewer of  FIG. 1  and the outlet chamber is provided in the upper right quadrant of the inside of the pump housing  24  that is located farther from the viewer of  FIG. 1 . 
     When the parts of the pump proper  4  are assembled, the inlet chamber is confined by the inlet chamber bottoms  80  of the stator elements  40  and  48 , by the parts of the front and rear seal housings  50  and  36  lying in the upper left quadrant of the inside of the pump housing  24 , by the left sides of the scraper  44  and the scraper guide  46  and by the inner face of the upper left quadrant of the tubular cylindrical body  34 . 
     Likewise, when the parts of the pump proper  4  are assembled, the outlet chamber is confined by the straight outlet chamber bottoms  84  and the oblique transition portions  82  of the stator elements  40  and  48 , by the parts of the front and rear seal housings  50  and  36  lying in the upper right quadrant of the inside of the pump housing  24 , by the right sides of the scraper  44  and the scraper guide  46  and by the inner face of the upper right quadrant of the tubular cylindrical body  34 . 
     The hub of the disk  42  is clamped by means of a locking screw  54  in axial direction against the rear shaft sleeve  38  and against the front shaft sleeve  52  having a locking nut. The rotating rear shaft sleeve  38  is, when the parts of the pump proper  4  are assembled, situated inside the rear seal housing  36 , and, likewise, the rotating front shaft sleeve  52  is situated within the front seal housing  50 . 
     Sealing means are provided at the inner face of the shaft sleeves  38  and  50 . In the most simple form such sealing means can be provided in the form of a sealing ring or sealing lip. Such sealing means can also be provided in the form of three spaced-apart lip sealing rings with two interposed support rings  112  as can be seen in the embodiment of the rotary displacement pump  2  in  FIG. 5 . 
     As can be seen in  FIG. 1 , both the rear seal housing  36  and the front seal housing  50  are of identical shape and size, and both are provided with slots, particularly circumferentially extending slots that allow for pressure compensation between the inside and the outside of the pump housing  24 , that facilitate the cleaning and that allow for pumped material to enter in between the seal housings  36  and  50  and the shaft sleeves  38  and  52  and to and through the sea lings that are provided therebetween to an outside of the pump housing  24 . 
     Furthermore, the shape and size of the rear shaft sleeve  38  and the front shaft sleeve  52  (with the exception of the locking nut) are identical in the embodiment of  FIG. 1 . 
     Thereby the parts variety will be reduced which allows for corresponding sealing arrangements in both the front and rear directions, as seen from the disk  42 , which reduces the costs. 
     The scraper  44  has generally the configuration of a rectangular plate, but having an engagement slot into which the web of the disk  42  engages. 
     The scraper can be a unitary work piece, particularly made of polyamide. 
     Referring now to  FIGS. 3 and 4 , curved transitions  98  are provided between the narrowest portion of the engagement slot  96  and the outlet chamber-facing surface  100  that can be seen in  FIGS. 3 and 4  as well as the inlet chamber-facing surface that can be seen in  FIG. 1 . 
     The axial dimension of the engagement slot  96  at its smallest portion is just a little wider than the axial dimension of the web of the disk  42 , so that the engagement slot  96  can be placed over the web, the scraper  44  straddling the web. The curved transitions  98  take into account the curved or undulatory configuration of the web as contrasted to a plane configuration. 
     The scraper  44  according to the embodiment of  FIG. 3  as well as the scraper  44  according to the embodiment of  FIG. 4  have a reduced width, as seen in the axial dimension in  FIG. 1  from its front side end  102  (left-hand side in  FIGS. 3 and 4 ) to its rear side end  102  (right-hand side in  FIGS. 3 and 4 ). In the embodiment of  FIGS. 3 and 4  the width of the scraper  44  corresponds to 68 to 72%, particularly 71% of the distance between the inner faces of the front end plate  56  to the rear end plate. 
     The scrapers  44  of the embodiment of both  FIGS. 3 and 4  have an upper guiding groove  104  extending in an axial direction along the radially outer surface, this upper guiding groove  104  is extending between left and right upper guiding walls having a higher height in the lateral side portions and a reduced height in the middle portion. A corresponding guiding rail of the scraper guide  46  (not shown) engages into the upper guiding groove  104 . 
     Likewise, the scrapers  44  of the embodiments of both  FIGS. 3 and 4  have a lower guiding groove  106  of a rounded convex shape, this lower guiding groove  106  engaging with a corresponding circumferential portion of the seal housings  36  and  50 . 
     By the guiding grooves  104  and  106  of the scraper  44  and by the corresponding guiding rail of the scraper guide  46  (not shown) and the corresponding circumferential portions of the seal housing elements  36  and  50 , the scraper  44  is retained in the circumferential direction and a reciprocating movement in a substantially axial direction is made possible. 
     Furthermore, limit stops defining the extreme axial positions of the scraper  44  can be provided, particularly at the scraper guide  46 . Moreover, the scraper guide  46  having in the embodiment of  FIG. 1  the form of the partial cartridge has an outlet chamber oriented-surface against which the inlet chamber oriented larger surface of the scraper  44  butts and thus secures, in addition, the scraper  44  against a movement in circumferential direction. 
     The lateral side faces  102  of the scraper  44  in both embodiments of  FIGS. 3 and 4  are oblique with respect to an axial plane, wherein the angle to an axial plane is in the range of 20 to 60 degrees, in the embodiment of  FIG. 3  it is 50 degrees and in the embodiment of  FIG. 4  it is 35 degrees. 
     In the scraper  44  of  FIG. 3 , the oblique side faces  102  form a plane extending over the whole radial height of the scraper  44 , wherein in the scraper  44  of  FIG. 4  the side faces  102  are surrounded in a radially outward direction by upper side face walls  108  and in a radially inward direction by lower side face walls  110 . 
     By the reduced width of the scraper  44  and by the oblique side faces  102 , the effect of packing material into corner areas of the outlet chamber, particularly between the side faces  102  and the inner faces of the front and rear end plates is significantly reduced, which contributes to a good material flow and thus an efficient and reliable operation of the pump. 
     The scraper guide  46  is firmly mounted in the pump housing  24 , in particular between the front end plate  56  and the rear end plate. 
     Referring again to  FIG. 2 , a substantially cylindrical supporting cavity  94  is formed in the upper portion of the inner side of the front end plate  56  above the central opening  92 , this supporting cavity  94  supports and secures the scraper guide  46  when the parts of the pump proper  4  are assembled. Likewise a supporting cavity can be provided in the rear end plate (shown in  FIG. 5 ). 
     Referring again to  FIG. 1 , between the front face of the support part housing  10 /mounting frame  12  and the rear end plate of the pump housing  24  there is provided, from back to front, a shaft sleeve  16 , a rear security ring  18 , a retainer ring  20  and a spacer ring  22  with lateral evacuation apertures. 
     In the mounted state of the pump  2  that can be seen in  FIG. 5  material coming out of the pump housing  24  in a rearward direction, particularly through the sealing between the rear seal housing  36  and the rear shaft sleeve  38  can run out of these lateral evacuation apertures, wherein at the same time the grating-like rear security ring  18  prevents users from unintentionally touching the rotating shaft  8 /shaft sleeve  16 . 
     In  FIG. 5  it can further be seen that the shaft sleeves  16  and  20  attach to each other, both of them are firmly secured to the shaft  8 . 
     Further, the locking screw  54  extends through the front shaft sleeve  52  with the locking nut and is fixed in the central opening of the shaft  8  by means of threads (not shown) provided at the locking screw  54  and the central opening of the shaft  8 . By this configuration, the front shaft sleeve  52 , the disk  42 , the rear shaft sleeve  38  and the further shaft sleeve  16  are fixed firmly to the shaft  8  such that they rotate together with the shaft  8 . 
     As can further be seen in  FIG. 5 , the front end of the shaft configuration, i.e. the front end of the front shaft sleeve  52  with the locking nut and the locking screw  54 , protrudes out of the central opening in the front end plate  56 . Material coming out of the pump housing  24  in a forward direction, particularly between the rotating front shaft sleeve  52  and the stationary front seal housing  50  and the sealing  112  provided therebetween can leave the pump  2  through the radial evacuation apertures in a security cover  64  that is placed before the central opening of the front end plate  56  and the front shaft sleeve  52  as well as the locking screw  54  protruding out of that central opening. The diameter of the security cover  64  is somewhat smaller than the diameter of the front end plate  56 . 
     As with the radial evacuation apertures in the spacer ring  22  the radial evacuation apertures in the security cover  64  are closed from unintentional access by a user in a radial direction by means of a security grating ring  62 . The front security ring  62  corresponds in shape and size to the rear security ring  18  which further helps to reduce the number of parts involved and thus to reduce costs. 
     Furthermore, mounting pins  58  and front cover nuts  66  are provided in order to firmly and safely fix the security cover  64  to the front end plate  56  and the front end plate  56  to the tubular cylindrical body  34 . 
     In  FIG. 5  the rear end plate  57  that is formed integral with the tubular cylindrical body  34  can well be seen. Furthermore, it can be seen that the web of the disk  42  engages with the engagement slot of the scraper  44 . In the sectional cut of the upper left quadrant of  FIG. 5  the portions of the parts lying in this quadrant and in particular the inlet port  26  and the inlet port flange  28  are omitted. Not visible in  FIG. 5  are the front and rear stator elements  40  and  48 . 
     In  FIG. 5 , the left-hand side of the cartridge-like scraper guide  46  is omitted and thus the inlet chamber facing-surface of the scraper  44  and part of the outlet chamber can be seen in axial direction before and behind the scraper  44 . 
     Furthermore, the dimension of the outlet chamber in the axial direction can be seen, from the front bottom (in axial direction) of the supporting cavity in the front end plate  56  to the rear bottom (in axial direction) of the supporting cavity in the rear end plate  57  of the tubular cylindrical body  34 . 
     By the rotary displacement pump  2  as described with respect to  FIGS. 1 to 5 , which consist of a relatively small number of parts making it cheap and easy to manufacture, solids emulsions of any kind and particularly liquid explosives can be pumped efficiently and safely. 
     List of Reference Numerals 
       2  rotary displacement pump 
       4  pump part 
       6  support part 
       8  shaft 
       10  support part housing 
       12  mounting frame 
       14  mounting pins 
       16  shaft sleeve 
       18  rear security ring 
       20  retainer ring 
       22  spacer ring 
       24  pump housing 
       26  inlet port 
       28  inlet port flange 
       30  outlet port 
       32  outlet port flange 
       34  tubular cylindrical body 
       36  rear seal housing 
       38  rear shaft sleeve 
       40  rear stator/liner element 
       42  rotor 
       44  scraper element 
       46  scraper guide 
       48  front stator/liner element 
       50  front seal housing 
       52  front shaft sleeve with locking nut 
       54  locking screw 
       56  front end plate 
       57  rear end plate 
       58  mounting pins 
       60  screws 
       62  security grating ring 
       64  security cover 
       66  front cover nuts 
       68  circumferential wall 
       70  radial wall 
       72  outer face 
       74  lateral abutment face 
       76  stator channel bottom face 
       78  lateral stator channel face 
       80  inlet chamber bottom 
       82  oblique transition portion of outlet chamber 
       84  straight outlet chamber bottom 
       86  circumferential mounting portion 
       88  apertures 
       90  ring-formed inner face 
       92  central opening 
       94  supporting cavity 
       96  engagement slot 
       98  curved transitions 
       100  outlet chamber-facing front 
       102  oblique side faces 
       104  upper guiding groove 
       106  lower guiding groove 
       108  upper side face walls 
       110  lower side face walls 
       112  lip sealing rings