A pump provided with at least one rotary shaft

Abstract: A pump provided with a rotary shaft and rotary pump parts, such as a centrifugal pump comprising a shaft and an impeller (1), and with a pump housing (4). A shaft seal device (6) is arranged between the shaft (3) and the rear wall (4) of the pump housing where the shaft extends through a hole in the rear wall. The device comprises a stator ring (10) attached to the rear wall (4) by means of permanent retaining means (10,20,21), whereby a rotor ring (25) fixedly connected with rear face (1a) of the rotary pump part sealingly may abut said stator ring. An annular chamber (12) is provided between the rear wall (4) and the stator ring (10) and houses a sealing ring (13). The chamber (12) has an axial length exceeding the axial dimension (d) of the cross-section of the ring (13) and has a circumferential, essentially funnel-like, inlet passageway (8). The shaft seal requires less cleaning and is easy to dismount for cleaning without the use of tools.

Description: The invention relates to a pump of the type stated in the preamble of claim 1. US-A-4377290 discloses a shaft seal device comprising a stator ring rigidly secured in radial direction to a rear pump wall by means of a permanently mounted retaining means, where a rotor ring is fixedly connected with the rotary pump parts. The rotor ring sealingly abuts said stator ring. An annular chamber is provided between said rear wall and the stator ring and houses a sealing resilient ring such as an O-ring. The annual chamber has an axial length exceeding the axial dimension of the cross-section of the resilient ring, e.g. an O-ring. This shaft seal is not selfcleaning because there is no space for small reciprocating movements of the resilient ring. There is no easy access for the pumped fluid to the annular chamber. The object of the invention is to provide a pump of the above type where the shaft seal requires less cleaning than hitherto known and where the shaft seal is easy to dismount/mount without the use of tools when it is to be cleaned manually. The pump according to the invention is characterised in that a portion of the annular chamber is directly delimited by the rear wall, and in that the frusto-conical portion of said end collar is provided with one or more circumferential rounded projections placed at the annular opening of the annular chamber, said chamber having a length of 1.1-1.5 preferably 1.3-1.5 times the cross-sectional diameter of the O-ring. The resulting shaft seal is particularly easy to clean, as the sealing resilient ring may perform small reciprocate axial movements inside the chamber during the operation of the pump - especially because the axial length of the annular chamber exceeds the axial length of the sealing ring. The funnel-like inlet passageway ensures easy access of the pumped fluid to the chamber and the sealing ring. In other words, the sealing ring and its annular chamber are both essentially self-cleaning. As a result, the present centrifugal pump is particularly suited for the pumping of fluid foods obviously requiring a high hygienic standard. The shaft seal is moreover very easy to mount, as no special tools are required for the mounting thereof. Only the stator ring and the rotor ring need to be replaced in case the shaft seal is damaged and these parts are relatively easy to dismount/mount, as said permanent retaining means remain untouched. Moreover, according to a preferred embodiment of the invention the circumferential recess provided in the rear wall and partly defining the annular chamber as arranged adjacent an essentially frusto-conical surface on the side of the rear wall facing the impeller. Thus, it is readily obtained that circulating flows can arise in the pump medium on the delivery side of the pump (the rear face of the impeller), said flows preventing a portion of the pump medium (the foodstuff) from harmfully remaining in the same place for a long period of time. The invention is explained in detail below with reference to the drawings, in which Figure 1 illustrates an embodiment of the pump according to the invention formed as a centrifugal pump and provided with the special shaft seal, a large portion of the impeller as well as the pump housing being removed except for a small portion of the rear wall, Figure 2 is on a larger scale a view of the annular chamber in which a O-ring is arranged, and Figure 3 is a diagrammatic, cross-sectional view of a second embodiment of the pump according to the invention shaped as a rotor lobe pump. The centrifugal pump shown in Figure 1 comprises an impeller 1 provided with blades 2 and attached to a pump shaft 3. The pump shaft extends through a hole in the rear wall 4 of the pump housing. A shaft seal device 6 is mounted between said rear wall and the pump shaft. This device comprises a stator ring 10 attached to the rear wall 4, a rotor ring 25 firmly connected with the rear face of the impeller sealingly abutting the end face of the stator ring. As it appears the outer surface of the shaft 3 and the inner surface of the stator ring 10 and the rotor ring 25 respectively, are slightly spaced apart. An annular chamber 12 is provided between the rear wall 4 and the stator ring 10 and houses a sealing, resilient ring such as an O-ring 13. The axial length of the annular chamber 12 exceeds the axial dimension (in this case the diameter) d of the cross-section of the O-ring and the chamber is further provided with an essentially circumferential, funnel-like inlet passageway 14. As the axial length of the chamber 12 exceeds the cross-section of the O-ring 13, the O-ring 13 may perform quite small, reciprocate axial movements during operation of the pump, whereby the O-ring as it were acts to clean the chamber 12. The self-cleansing ensures that the pump medium (such as a fluid foodstuff) is prevented from settling permanently in corners of the chamber. As shown in Figure 2, the annular chamber 12 may be defined partly by an inner, circumferential, preferably essentially cylindrical recess 14 in the rear wall 4, partly by an outer, essentially cylindrical surface 15 on the stator ring 10 and partly by an end collar provided on said stator ring. The end face of the rotor ring 25 may abut the end face 16a of this end collar. As shown on the left-hand side in Figure 2, the cylindrical recess 14 may be rounded in the transition area 17 between the inner cylinder face of the recess 14 and the planar bottom face 18 of said recess. The rounding on the transition area 17 is usually circular. The portion of the end collar 16 of the stator ring 10 facing the cylinder face of the said ring 10 may be frusto-conical and optionally be provided with one or several circumferential, rounded projections 16b. Preferably, the annular chamber 12 has a length of 1.1 - 1.3, e.g. 1.2 - 1.3 times the cross-sectional diameter d of the O-ring. As shown in Figure 2, the circumferential recess 12 provided in the rear wall 4 may be arranged adjacent an essentially frusto-conical face 4a on the side of the rear wall 4 facing the impeller 1. The rotor ring 25 may be attached to the rear face 1a of the impeller by being inserted directly into the hub portion 41 of the impeller 1. As it appears, the rotor ring is inserted into an auxiliary recess 42 in the hub of the impeller 1, said auxiliary recess preferably being cylindrical and optionally provided with a stepped bottom 43. The rotor ring may be fixed in the auxiliary recess by means of pressing or by means of a fixing member, such as a fixing pin 44. A second sealing chamber 46 may be provided between the face 25a of the rotor ring 25 facing radially outwardly and a face in the auxiliary recess facing radially inwardly, whereby a sealing, resilient auxiliary ring such as an auxiliary O-ring 47 is inserted in said second chamber. Preferably, this sealing chamber has an axial length of 1.1 - 1.5, e.g. 1.2 to 1.3 times the axial dimension (in this case the diameter) δ of the cross-section of the auxiliary ring. The rotor ring 25 and/or the stator ring 10 may be essentially S-shaped in cross-section. The stator ring 10 may be secured to the rear wall 4 of the pump housing by means of a pot-shaped cover 19 being secured to the housing e.g. by means of screw, where a preloaded spring means 20, such as a coil spring, is arranged between cover and the stator ring 10 coaxially with the latter and pressing against an annular disc 21, which in turn presses against the end face of the stator ring 10 facing away from the impeller 1. On the side facing the end face of the stator ring, the annular disc 21 may be provided with at least one axially extending, pin-like projection 22 which may co-act with a corresponding notch in the end of the stator ring to prevent the latter from rotating, but nevertheless allowing small axial movements of the stator ring. Along its circumference, the annular disc may be provided with at two radially extending, pin-like projections (of which only one is visible at the reference numeral 21a in Figure 1) co-acting with notches or cavities (not shown) in the pot-shaped, cover-like holder member 19 such that the pressure disc 21 cannot rotate relative to the holder member 19. A drain cylinder 24 may be inserted through a central hole in the annular disc 21 and in continuation of the stator ring 10, the inner diameter of said cylinder essentially corresponding to the inner diameter of the stator ring 10, a cavity being provided between the shaft 3 and the inner face of the stator ring and the drain cylinder respectively. The drain cylinder may project outwardly through a central hole 26 in the cover 19. The drain cylinder may be secured to the stator ring 10 by pressing one or several projections 27 on the drain cylinder 24 against the stator ring 10 by means of the annular disc 21. The term "O-ring" is to be understood in the broadest sense of the word, as said ring not only may have a circular cross-section, but also a C-shaped, square or V-shaped cross-section. As shown in Figure 3, the pump may be a rotor lobe pump (a rotary gear pump). If so, two shafts 3' and 3" are arranged in the wall 4' of the pump housing. Each shaft is provided with a lobe-gear 1', 1" respectively. Corresponding to the stator ring 10 with a sealing, resilient ring 22 in Figure 1, a stator ring 10, 10' and sealing, resilient rings 22', 22" are now provided. The permanently mounted retaining means are indicated by means of the reference numerals 19', 19". A rotor ring corresponding to the rotor ring in Figure 1 is indicated by means of the reference numerals 25',25" in Figure 3. The shaft seal devices in Figure 3 act in the same manner as the shaft seal shown in Figure 1.

Claims: A pump provided with at least one rotary shaft (3,3',3") for instance a centrifugal pump or a rotor lobe pump and with a rotary pump part or parts (1,1',1") such as an impeller (1) or rotor lobes (1',1"), as well as with a pump housing (4'), and where a shaft seal device (6) is arranged between the shaft (3,3',3") and a rear wall (4) in the pump housing at the location where the shaft extends through a hole in the rear wall and where the shaft seal device comprises a stator ring (10, 10', 10'') rigidly secured in radial direction to the rear wall (4, 4') by means of permanently mounted retaining means (19,20,21,19',19"), a rotor ring (25,25',25") being fixedly connected with the rear face (1a) of the rotary pump parts, such as the impeller or the rotor lobes, and sealingly abutting said stator ring, and where an annular chamber (12) is provided between the rear wall (4,4') and the stator ring (10,10',10"), an O-ring being placed in the annular chamber (12), said annular chamber (12) having a funnel-like inlet passageway (8) which inter alia to one side is defined by an end collar (16) formed on the stator ring (10), the portion of the end collar (16) facing the annular chamber (12) being frusto-conical, characterised in that a portion of the annular chamber (12) is directly delimited by the rear wall (4,4') and in that the frusto-conical portion of said end collar (16) is provided with one or more circumferential, rounded projections (16b) placed at the annular opening of the annular chamber (12), said chamber (12) having a length of 1.1 - 1.5 preferably 1.3 - 1.5 times the cross-sectional diameter (d) of the O-ring (13). A pump as claimed in claim 1, characterised in that a circumferential recess (12) provided in the rear wall (4) and partly defining the annular chamber is arranged adjacent an essentially frusto-conical surface (4a) on the side of the rear wall (4) facing the impeller (1).

Inventors: PEDERSEN BENT, PEDERSEN, BENT
Applicants: APV FLUID HANDLING HORSENS AS, APV FLUID HANDLING HORSENS A/S
Application year: 1996
Main classification: F16J15
IPC codes: F04C27, F04D29, F16J15