Patent Publication Number: US-8113802-B2

Title: Food centrifugal pump formed by stamping and welding having a seal arrangement between the impeller and casing

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a centrifugal pump, more particular, to a food centrifugal pump for processing food formed by stamping and welding. 
     DESCRIPTION OF THE RELATED ART 
     Food centrifugal pump is a centrifugal pump product having a large market, and is widely used in industrial areas like food, beverage, beer and chemicals etc. In the prior art, the food centrifugal pump is manufactured by mean of casting. However, the casting is a process which has some disadvantages, such as high energy consuming, waste material, intensity of labor and pollution for environment. Furthermore, the pump made by casting has defects of large size, heave weight, difficulty in installation and maintaining and low efficiency etc. On the other hand, as being a kind of low-flow micro-centrifugal pump, e.g. food pump, some of components of pump can not be cast due to restriction of their structural dimension, such as an impeller which has a small flow and whose outlet has a narrow width. Therefore, the food pump formed by casting is not an ideal one at all. 
     A Chinese invention patent CN1082627 (App. No. 99111134.6) issued on Apr. 10, 2002 which disclosed a centrifugal pump formed by welding and punching metal plate and a method of manufacturing this pump, the centrifugal pump includes an inlet flange, an outlet flange, a rear cover, a casing and an impeller, there is a chamber between the casing and the impeller by punching, the chamber is radially outward and gradually enlarged along with direction of fluid flow, and a cross-section of which shows approximately semi-circle shape and is almost full-volute of 360 deg, furthermore, the casing also has an outlet end hole in oval shape, an outlet bend neck is communicated with and welded to the end hole, a cross-section of the outlet bend neck is communicated with and welded to the end hole, a cross-section of the outlet bend neck is an oval shape with variable diameter, a supporter of labyrinth ring is disposed in the casing. Although, this pump has advantages over the casting pumps, it is easy to have the impeller blocked during fluid flowing therein while the fluid is thick, due to a closed structure impeller, the passability of which is unacceptable; on the other hand, it can block the flow of fluid and make the fluid passing the casing not sanitary due to the bracket inside of the casing. Hence, this type of pump is not suitable to be used as a food pump. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to solve the foregoing problems existing in the prior art, accordingly, provides a food centrifugal pump which has the advantages of simple manufacture process, low cost, excellent fluid passablity and sanitary. 
     According to the present invention, there is provided a food centrifugal pump formed by stamping and welding, comprising a pump casing, a cover, an impeller, a shaft which is mounted in said pump casing, and a motor provided on the external of the casing, said impeller is mounted on the shaft and driven to rotate by the motor; the pump casing is provided with an inlet pipe and an outlet pipe, the impeller having a structure of half-opened type and consisting of blades, a hub and a back cover plate, the front ends of said blades is proximate to the inner side of the axial plane of said pump casing, and form end surface seal thereof; the pump casing is formed by stamping a single metal plate, a bracket for supporting the inlet pipe is provided on the outer side of the axial plane of the casing, one end of said bracket is connected to the outer side of the pump casing, the other end is engaged over and fixed on the inlet pipe. 
     The food centrifugal pump formed by stamping and welding according to the present invention also has additional technical characters as following: 
     Said blades have an integrated structure of two in one, the adjacent two said blades are manufactured from one piece of metal plate by stamping, and forming a blade body having a cross section of U-shape. 
     Each of said blades in radial direction consists of two segments circular arc with interiorly tangent. 
     Said bracket is a truncated cone in overall shape, the diameter thereof gradually increasing from front to rear, said bracket comprises a conical main body, a rear end wall integrated with said main body, a front end wall and a peripheral wall externally extending outwards from said front end wall; said rear end wall welded to the axially outer surface of said pump casing, said peripheral wall engaged over and welded to an external of the front end of said inlet pipe. 
     Said rear end wall is a vertical wall, and closely contacted and welded together with a vertical wall of the axial plane of said pump casing. The intermediate portion of the axial plane of said pump casing caved inwardly, so as to form a peripheral wall, an inclined wall and a middle wall connecting said inclined wall and said vertical wall in the middle of the axial plane; said peripheral wall engaged over and welded to the external of the rear end of said inlet pipe. 
     A width of inlet of said blades is greater than an outlet&#39;s width thereof, so as to form a sloping edge with an angle α in the front end of said blades; an obliquity angle β of said inclined wall equal to said obliquity a, so as to form said end face seal. A clearance between the front end of said blade and said inclined wall is less than 2 mm. 
     The radial plane of said casing is cylindrical, and a tongue is disposed adjacent to said outlet pipe in said radial plane, and a discharge hole is disposed on the lowest end of said casing. 
     Said electrical motor is fixed on said casing by mean of a bracket, a front end of middle portion of said bracket formed a supporting structure for rigidly supporting said cover. 
     The food centrifugal pump formed by stamping and welding according to the present invention, firstly due to the food centrifugal pump of the present invention adopts the process of stamping and welding (wherein the main components thereof, such as the casing, the cover, the impeller, the bracket for inlet pipe, are formed by stamping and connected together by welding), it has a simple and convenient process for forming if comparing with the casting pump, so that it not only reduces the manufacture cost, but also to overcome their defects, such as pollution, high power and material consumed in casting etc.; secondly, because the pump adopts the impeller with half-opened structure, it has better fluid passability than impellers with closed structure, so that the fluid is not easily blocked during passing the impeller, even if the fluid is thick. Therefore, the food centrifugal pump is adapted to be used in multiple operation situations, to pump different kinds of liquid food and to work in reliable and efficient condition; thirdly, because the bracket of the inlet pipe is disposed on the external of the casing, not in its interior, hence, it makes more sanitary the inside of the casing and ensures the quality of the food. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and advantage of the invention will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which: 
         FIG. 1  is a front view of the food centrifugal pump according to the present invention, wherein a partial section view is adapted to show the interior structure thereof; 
         FIG. 2  is an enlarged section view of the impeller of the food centrifugal pump; 
         FIG. 3A  is a front view of the structure of the impeller&#39;s blades in  FIG. 2 , the number and distributions of the blades are illuminated; 
         FIG. 3B  is a cross-sectional view of along line B-B in  FIG. 3A , it illuminates the two in one integrated type structure of the blades; 
         FIG. 4  is an enlarged view of the bracket for outlet pipe of the food centrifugal pump; 
         FIG. 5  is an enlarged view of the casing of the food centrifugal pump in  FIG. 1 , in order to make clear, the bracket for the inlet pipe fixed to the casing is also shown; 
         FIG. 6  is view of C direction in  FIG. 5 ; it shows the installation location of the tongue. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE IVENTION 
     As shown in  FIG. 1 , the food centrifugal pump according to the present invention, comprises a pump casing  1 , a cover  2  mounted inside of said pump casing  1 , an impeller  3 , a shaft  4 , and a motor  5  provided on the external of the casing  1 , said impeller  3  is mounted on the shaft  4  and driven to rotate by the motor  5 ; the pump casing  1  is provided with an inlet pipe  11  and an outlet pipe  12 . Because the food centrifugal pump of the present invention adopts the process of stamping and welding (i.e. the main components, such as the casing, the cover, the impeller, the bracket for inlet pipe, are formed by stamping an connected together by welding), it has a simple and convenient process for forming compared with the casting pump, so that it not only reduces the manufacture cost, but also to overcome their defects, such as pollution, high power and material consumed in casting etc. 
     It is also shown in  FIG. 1 , the electrical motor  5  is fixed to the casing  1  via a bracket  6 , a front end of middle portion of said bracket  6  forms a supporting structure  61  for rigidly supporting said cover  2 . Due to the rigidly supporting of said supporting structure  21  for said cover  2 , the rigidity of the cover  2  is improved dramatically, to prevent or greatly decrease the possibility of deformation of the cover under a condition of high pressure and temperature, consequently ensure the reliability of the mechanical seal  62  in operation. 
     Referring to  FIG. 1 , the casing  1  is made of an entire metal plate by punching, a bracket  13  supporting the inlet pipe  11  provided on the outer side of the axial plane of which, one end of said bracket  13  is connected to the outer side of the pump casing  1 , the other end of which is engaged over and fixed on the inlet pipe  11 . Because the bracket for the inlet pipe is disposed on external of the casing, but not its interior, the obstacle of fluid caused by the external casing is reduced and makes more sanitary the inside of the casing and ensures the quality of the food. 
     As shown in  FIG. 1  and  FIG. 2 , the impeller  3  has a structure of half-opened type and consists of blades  31 , a hub  32  and a back cover plate  33 , the front ends of said blades are close to the inner side of the axial plane of said pump casing  1 , and there is an end surface seal formed therebetween. Compared with the impeller having closed structure, the impeller having the half-opened structure not only removes a front cover, so as to reduce the cost, but also improves the passability of fluid, and it is less likely to block even thick liquid passing the impeller. Therefore, the food centrifugal pump is adapted to be used in multiple operation situations, to pump different kinds of liquid food and to work in reliable and efficient condition. 
     As shown in  FIGS. 3A and 3B , in a preferred embodiment of the present invention, the blades  31  are an integrated structure of two in one, two adjacent said blades  31  are manufactured from one piece of metal plate by stamping, and form a blade body having a cross section in U-shape. Such structure of the blade can dramatically increase the rigidity and strength of half-opened impeller, so as to increase the reliability thereof in operation; on the other hand, a flat wall  311  can be joined to the back cover plate  33  is formed at the bottom between the two blades  31 , hence, the blades  31  can be easily welded to the back cover plate  33 , and the welded connection is very strong. 
     As shown in  FIG. 3A , each of said blades  31  in radial direction consists of two segments circular arc with interiorly tangent. Such structure results in efficient energy conversion with blades  31 . 
     As shown in  FIGS. 4 and 5 , in another preferred embodiment of the present invention, the bracket  13  is a truncated cone in overall shape, the diameter thereof gradually increasing from front to rear, the bracket  13  comprises a conical main body  131 , a rear end wall  132  integrated with said main body  131 , a front end wall  133  and a peripheral wall  134  externally extending from said front end wall  133 ; said rear end wall  132  is welded to the axially outer surface of said pump casing  1 , said peripheral wall  134  is engaged over and welded to an external of the front end of the inlet pipe  11 . The structure form of the bracket  13  ensures the rigidity and strength thereof, and increases the rigidity and strength of the casing  1  as well. 
     As shown in  FIG. 5 , the rear end wall  132  is a vertical wall (which is vertical to the axis of the casing), and is closely contacted with a vertical wall  14  of the axial plane of said pump casing  1  and welded together. The two vertical walls are contact welded, and there is enough contacting area between them so as to ensure the reliability of welding. 
     As shown in  FIG. 1  to  FIG. 5 , the middle portion of the axial plane of the pump casing  1  is caved inwardly, so as to form a peripheral wall  19 , an inclined wall  15  and a middle wall  16  connecting the inclined wall  15  to the vertical wall  14  in the middle of the axial plane; the peripheral wall  19  is engaged over and welded to the external of the rear end of the inlet pipe  11 . As shown in  FIG. 5 , the peripheral wall  19 , inclined wall  15  and the middle wall  16  form a structure having a substantial U-shape cross-section, such concave-convex structure is adapted to enormously increase the rigidity and strength of the casing  1 , and is also good to match with the front end of the impeller  3 . 
     As shown in  FIG. 2 , a width of inlet of the blades  31  is greater than an outlet width thereof, so as to form a sloping edge having an obliquity angle α in the front end of the blades; an obliquity angle β of the inclined wall  15  is equal to the obliquity angle α, so as to form the end surface seal, a clearance between the front end of the blade  31  and the inclined wall  15  is less than 2 mm. Hence, the good seal between the blades  31  and the inclined wall  15  is achieved, so as to prevent the leakage of the liquid. 
     As shown in  FIG. 6 , the radial plane of said casing  1  is cylindrical, and a tongue  17  which is adapted to enhance the hydraulic performance of the pump is disposed adjacent to the outlet pipe in said radial plane. A discharge hole  18  is disposed at the lowest end of said casing  1 , in the operation, the discharge hole  18  is blocked by a screw, as shown in  FIG. 6 , when the rest liquid is needed to be discharged from the casing  1 , remove the screw, then discharging the liquid by the discharge hole. 
     Because the food centrifugal pump of the present invention is made of a single metal plate by stamping and welding, thereby it overcomes the defects of high consuming power and material, intensity of labor, pollution for environment and complex installation and maintaining of the casting pump, and it also provides virtues of rational structure, good rigidity and strength, high efficiency and excellent passability. The weight of which is merely ¼ of weight of the same kind of the casting pump, and the cost thereof is only ⅔ is of the casting one, however, the efficiency thereof is higher 5-7% than the casting one. 
     Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications can be made in the embodiments without departing from spirit and principles of the invention. Such changes, alternatives, and modifications all fall into the scope of the claims and their equivalents.