Abstract:
A pump device for pumping liquid foodstuff includes a pump housing having an inlet and an outlet for pumping the foodstuff therethrough. A pump body is disposed within the pump housing having an elastic member which contains a predetermined volume of pressurized liquid. The pressurized liquid expands the elastic member from an unpressurized normal shape to a prestressed shape. The volume of liquid contained within the elastic member remains substantially fixed while the elastic member expands from its prestressed shape to a stretched shape to pump a predetermined amount of foodstuff out of the outlet.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a pump device for pumping liquid foodstuff, e.g. ketchup, mustard, sauce, dressing or similar, wherein the pump device includes a pump housing, an inlet, an outlet, a pump body and at least one pump means, wherein the pump body has an elastic member which by means of the pump means can be stretched for imparting pump movements thereon for pumping foodstuff out of the pump housing through the outlet, and wherein the elastic member of the pump body is provided to perform, through contraction, suction movements for sucking foodstuff into the pump housing through the inlet. 
     BACKGROUND OF THE INVENTION 
     A pump device for foodstuff of this type is already known from U.S. Pat. No. 4,961,508 and the object of the present invention is to improve these pump devices such that one therewith can feed or discharge exactly the same amounts of foodstuff during each portioning step. A similar pump device, but for other substances than foodstuff is known from EP 0 390 298. 
     SUMMARY OF THE INVENTION 
     In an exemplary embodiment of the present invention a pump device for pumping liquid foodstuff is presented. The pump device includes a pump housing having an inlet and an outlet for pumping the foodstuff therethrough. A pump body is disposed within the pump housing having an elastic member which contains a predetermined volume of pressurized liquid. The pressurized liquid expands the elastic member from an unpressurized normal shape to a prestressed shape. The volume of liquid contained within the elastic member remains substantially fixed while the elastic member expands from its prestressed shape to a stretched shape to pump a predetermined amount of foodstuff out of the outlet. 
     Since the pump device according to the invention is provided with said characterizing features, it is attained that one for sure can feed or discharge exactly the same amounts of foodstuff during each portioning step, and that the elastic member of a pump body forming part of the pump device is prestressed such that said elastic member can contract to the same extent after every pump movement. 
     The invention will be further described below with reference to the accompanying drawing, which is a section through the pump device according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The pump device  1  illustrated in the drawing is adapted for sucking liquid foodstuff  2 , e.g. ketchup, mustard, sauce, dressing or similar, from a foodstuff container  3  to a discharge or dispensing device  4  for discharge through said device  4 . The pump device  1  includes an inlet  5 , an outlet  6  and a pump housing  7 . The inlet  5  is through a hose  8  or similar connected to the foodstuff container  3  such that foodstuff  2  through the hose  8  can be sucked into the pump housing  7 . A non-return valve  9  can be provided on the hose  8  for allowing foodstuff  2  to be sucked from the foodstuff container  3  to the pump housing  7 , but not pressed in the opposite direction. A hose to the discharge device  4  is connected to the outlet  6  for discharge of the foodstuff  2 . A non-return valve  11  can be provided on the hose  10  for allowing foodstuff  2  to pass out from the pump housing  7  to the discharge device  4  but not in the opposite direction. 
     The pump device  1  further includes a pump body  12  with an elastic member  13  and a retaining member  14 . The elastic member  13  and the retaining member  14  can be formed in one piece of the same elastic or flexible material, e.g. elastic plastic material or caoutchouc. The elastic member  13  and the retaining member  14  preferably have the shape of an elongated tube which is open at the retaining member  14 , but closed at the opposite end. The retaining member  14  has inwardly directed retaining portions  15 , e.g. in the form of circular flanges  15 , and it is threaded onto a retaining ring  16  having corresponding retaining portions  17 , e.g. in the form of circular grooves in which the flanges  15  are sealingly engaged. 
     The pump body  12  is inserted into the pump housing  7  such that the elastic member  13  is located in such a portion of the pump housing  7  which has a larger inner diameter than the elastic member  13 , while the retaining member  14  is situated in another portion  40  of the pump housing  7  which it engages with sealing. Hereby, the retaining member  14  of the pump body  12  defines a sealing member between the pump housing  7  and the retaining ring  16 . An outer ring  18  can be provided on the retaining ring  16  and may have a groove  19  in which an outer flange  20  or a corresponding portion of the pump housing  7  is engaged. 
     The pump device  1  includes a pump means  21  which is dimensioned for displacement from a rear position BL into the elastic member  13  to a front position FL (indicated with dashed and dotted lines), at which it reaches the front portion of the elastic member  13 . Said pump means  21  has an outer piston  22  which is inserted into the retaining ring  16  and which is displaceably mounted relative thereto as well as relative to the elastic member  13 . 
     The outer piston  22  is guided by an inwardly directed guide portion  23  and has at a front outer end an outwardly guide portion  24  which cooperates with the pump body  12  for guiding the outer end of the pump means  21  when said pump body  12  is completely or almost completely drawn or pulled out from the elastic member  13 . 
     When the pump means  21  is drawn out, the outwardly directed guide portion  24  on the outer piston  22  bumps into the inwardly directed guide portion  23  on the retaining ring  16 , whereby it is ensured that the pump means  21  can not be removed from the retaining ring  16 . 
     The pump device  1  also has a prestressing device  25  which at the illustrated embodiment includes an inner piston  26  located inside the outer piston  22 . The inner piston  26  has a front end portion  27  with a sealing device  28 , e.g. a sealing ring, which provides for sealing between the front end portion  27  of the inner piston  26  and the outer piston  22 . The inner piston  26  also has a rear end portion  29  with a retaining device  30 , e.g. a friction ring or similar, for retaining said inner piston  26  at the outer piston  22  in their intended relative position. On the rear end portion  29  of the inner piston  26  there is also provided a pressure plate  31  against which pressure is applied for insertion of the pump means  21  into the pump body  12 . 
     The prestressing device  25  is adapted to preload the elastic member  13  of the pump body  12  from a normal shape NF (shown with broken lines in the FIGURE) into a prestressed or preloaded shape FF (shown with unbroken lines in the figure). This preloading is obtained by pulling out the outer piston  22  as far as possible to the rear position BL and then by pulling out the inner piston  26  from the outer piston  22 . Through the outer piston  22 , liquid  32 , e.g. water, is then poured into the elastic member  13  until said member and the outer piston  22  are filled with liquid. Thereafter, the inner piston  26  is pressed or pushed into the outer piston  22 , which means that the inner piston  26  displaces and presses the liquid in the outer piston  22  into the elastic member  13 , which thereby is preloaded from its normal shape NF to the prestressed or preloaded shape FF. The elastic member  13  has got its predetermined preloaded shape FF when the inner piston  26  is completely inserted into the outer piston  22 , and this shape is maintained while the retaining device  30  retains the inner piston  26  in its entirety inserted position in the outer piston  22 . 
     The pump device  1  is thereby assembled and ready for use for sucking foodstuff  2  from the foodstuff container  3  and pump it through the pump housing  7  to the discharge device  4 . This is done by first sucking foodstuff  2  into the pump housing  7  until said housing is filled. Then, identical amounts of foodstuff  2  can be pumped out during each pumping step by pressing the pump means  21  inwards from the rear position BL to the front position FL. Hereby, the pump means  21  will, through the liquid, stretch the elastic member  13  from its preloaded shape FF into a stretched shape UF, whereby foodstuff  2  is pumped out from the pump housing  7  and through the outlet  6  and the discharge device  4  out of the pump device  1 . When the pump means  21  is released, the elastic member  13  will, due to its elastic properties, contract from the stretched shape UF into the prestressed or preloaded shape FF, whereby a new amount of foodstuff  2  is sucked from the foodstuff container  3  into the pump housing  7  while at the same time the pump means  21 , through the liquid, is pressed back to its rear position BL. This procedure is repeated until a sufficient amount of foodstuff  2  has been pumped out or discharged. 
     In its stretched shape UF, the elastic member  13  preferably has such an outer diameter or corresponding which is less than the inner diameter or corresponding of the surrounding portions of the pump housing  7 . Hereby, there will be a space  36  around the elastic member  13  for foodstuff  2  when said member is stretched to its stretched shape UF. 
     The outlet  6  may be provided in said portions of the pump housing  7  and since the elastic member  13  can not expand to said portions, it can not obstruct the outlet  6 . 
     The foodstuff container  3  can be of the type consisting of a flexible wall material  33 , i.e. the foodstuff container  3  may be of plastic bag type. Inside the foodstuff container  3 , on an unbroken portion of said wall material  33 , there may be provided an inner connecting means  34 . An outer connecting means  35  provided on the hose  8  or similar can be brought to penetrate the unbroken portion of the flexible wall material  33  and brought to attach to the inner connecting means  34 . After this connecting procedure, foodstuff  2  can be sucked out from the foodstuff container  3  through an inner removal or discharge passage (not shown) in the outer connecting means  35 . 
     The construction and function of the pump device described above may vary within the scope of the following claims. Thus, the elastic member  13  may be preloaded into a prestressed or preloaded shape FF in another way and with another device than the one described, the elastic member  13  may have another shape than as an elongated tube which is open in one end and closed in the opposite end, the elastic member may further be of another suitable elastic material than the one described above and the liquid may be another liquid than water.