Abstract:
In an apparatus for quenching thin walled metal hollow casings ( 6 ) manufactured by blow molding, the apparatus has a molding tool ( 1 ) defining a slot or aperture ( 21 ) and a delivery system for applying a coolant to the slot or aperture ( 21 ) of the molding tool ( 1 ). In a method of applying a coolant to the external surface of a blow molded casing ( 6 ), the coolant is applied onto an external surface of the casing ( 6 ) after the casing ( 6 ) has been formed against a tool ( 1 ) which includes at least one slot or aperture ( 21 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates to an apparatus and method for quenching thin walled metal hollow casings and in particular to an apparatus and method for quenching thin walled metal hollow casings manufactured by blow molding. 
   2. Description of the Background Art 
   The inventor of the present invention has applied for a patent entitled “A method for manufacturing thin walled metal hollow casing by blow moulding” in a number of territories including U.S.A. with U.S. patent application Ser. No. 09/424,235 (now U.S. Pat. No. 6,261,392 issued Jul. 17, 2001) and Europe with European Patent Application No. 98919699.3 and the present application discloses an improvement to inventions in this general area. After considerable testing of the method disclosed in the above referenced application in combination with a review of blow molding processes described in the prior art, an improved apparatus and method have been invented which overcome a number of inherent problems with previous methods of quenching blow molded thin walled metal hollow casings. 
   The cooling processes used in methods disclosed in the prior art do not provide even cooling to the preheated casing. Cooling occurs more rapidly on regions of the external surface of the casing which are proximal to cooling channels provided on a number of the molding tools of the prior art thereby effecting the quality of the blow molded casing. The speed of the cooling process also needs to be optimized in order to improve the efficiency of the manufacturing method. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an apparatus and method for applying a cooling medium over a substantial portion of the external surface of a blow-molded casing and to improve the efficiency of such manufacturing methods. 
   Accordingly, the present invention provides an apparatus for applying a cooling medium to an external surface of a blow molded casing characterized in that the apparatus comprises a molding tool defining a slot or aperture and a means for delivering a cooling medium to the slot or aperture of the molding tool. The slot or aperture exposes a substantial portion of the external surface of the blow-molded casing and the medium is in direct contact with the surface. 
   Ideally, the tool defines a plurality of slots or apertures. This increases the surface area of the casing to which a cooling medium is directly applied. 
   Ideally, the delivery means is provided by a pipe and a dispenser. This apparatus provides a simple and cost effective method of applying gas or liquid coolant to the external surface of the casing. 
   Preferably, the delivery means has a plurality of dispensers aligned with and located adjacent the slots or apertures of the tool. This facilitates instant application of coolant to the exposed external surfaces of the casing. 
   Ideally, the tool includes a chamber in fluid communication with the slot or aperture. This allows a gas to be inserted into the chamber when used as the cooling medium. It will of course be appreciated that both gas and liquid coolants may be dispensed onto the exposed external surfaces of the casing simultaneously or in sequence. The simple pipe and dispenser apparatus housed within the chamber allows water to be initially flushed onto the casing in addition to gas being injected into the chamber. 
   Preferably, the delivery means is provided by pipes, one pipe having an inlet valve and another pipe having an outlet valve 
   Ideally, the valves are in fluid communication with the chamber. 
   In one embodiment, the tool is provided by two partible halves which combine to form a helical pipe. In this embodiment, the surface area of the tool supporting the casing is reduced to a minimum. The surface area of the tool serves only to support the desired shape of the casing. 
   Preferably, the helical pipe is hollow and transports a cooling/heating medium internally. 
   Accordingly, there is also provided a method of applying a cooling medium to an external surface of a blow molded casing characterized in that said cooling medium is delivered onto an external surface of the casing after the casing has been formed against a tool defining a slot or aperture. 
   Preferably, the cooling medium is a liquid such as water and it is sprayed/flushed directly onto exposed surfaces of the casing. 
   Ideally, the cooling medium is a gas and it is injected into a chamber of the tool. 
   Preferably, the gas is removed from the chamber of the tool by a vacuum means prior to the separation of the tool for removal of the casing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described with reference to the accompanying drawings, which show, by way of example only, two embodiments of an apparatus and method for quenching thin walled metal hollow casings manufactured by blow molding in accordance with th invention. In the drawings: 
       FIG. 1  is a schematic drawing showing a section view of the apparatus; 
       FIG. 2  is a second section view of the apparatus of  FIG. 1  during the blow molding process; and 
       FIG. 3  is a section view of a second embodiment of the apparatus in accordance with the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings and initially to  FIGS. 1 and 2 , there is shown a molding tool indicated generally by the reference numeral  1  in the form of two interacting tool halves  2 ,  3  in which are arranged respective support fingers  4 ,  5  for forming an essentially smooth cylindrical hollow casing billet  6  inserted between them which is preheated and intended to be molded against the inner walls of support fingers  4 ,  5  through the introduction of air to its interior. This hollow casing billet  6  comprises a thin-walled tube open at the ends. 
   Channels  7 ,  8  are arranged in each half  2 ,  3  of the moulding tool  1  for the circulation of either warm or cold water through the support fingers  4 ,  5  for heating or cooling respectively of the moulding tool  1  during the moulding process. For feeding in and removing this medium, one end of the respective channel  7 ,  8  is connected partly to a first inlet pipe  9  for the heating medium that can comprise, for example, heated liquid or steam, and partly to a second inlet pipe  10  for the cooling medium that preferably comprises water. Similarly, the other end of the said channels  7 ,  8  is connected partly to a first outlet pipe  11  for the cooling medium and partly to a second outlet pipe  12  for the heating medium. The said inlet and outlet pipes also have their associated respective controlling device, not shown in the figures, for steering the flow between the first and the second inlet pipes  9 ,  10  so that one can select whether either the heating medium or the cooling medium will flow through channels  7 ,  8 . In this way, the flow through the respective channels  7 ,  8  in the moulding tool halves  2 ,  3  can very quickly be switched so that the flow very efficiently heats or cools the moulding tool  1  depending on whether the flow comprises the heating medium or the cooling medium. 
   In addition, the molding tool  1  or, more specifically, its respective halves  2 ,  3  are provided with slots or apertures  21 . A hose  22  and a number of dispensers  23  mounted on the hose are also incorporated into each half  2 ,  3  of the tool  1 . The dispensers  23  are mounted so as to align with the slots  21  and extend into the slots  21  to locate adjacent the external surface of the hollow casing billet  6 . Separable sealing rings  13 ,  13 ′ are mounted at their first and second inlet positions designated  14 ,  14 ′ for respective nozzles  15 ,  15 ′ intended for introducing the medium to the interior of the hollow casing billet  6  as well as leading this medium away via the open ends of the hollow casing billet  6 . 
   A first inlet pipe  16  for a medium is partly connected to one of the nozzles  15 , as is a second inlet pipe  17  for another medium, where in both cases, the medium preferably comprises air. The other nozzle  15 ′ is partly connected to a first outlet pipe  18  for the medium and partly to a second outlet pipe  19  for the second medium. The said inlet pipes  16 ,  17  and outlet pipes  18 ,  19  also have their associated respective controlling device, not shown in the figures, for steering the flow between the said pipes so that the alternative flow paths at the inlet respectively outlet can be selected. In addition, both nozzles  15 ,  15 ′ can, of course, be closed-off so that no medium can flow through them. 
   Referring to the drawings and now to  FIG. 3 , there is shown a second embodiment in accordance with the invention. A number of inlet hoses  22  provide cooling gas from a source (not shown) and each hose  22  is connected to an inlet valve  31  mounted in the internal cavities  41 ,  42  of the tool halves  2 ,  3 . A number of outlet valves  32  are also located in the internal cavities  41 ,  42  of the tool halves  2 ,  3  and each outlet valve  32  is mounted on an outlet hose  22 ′. The outlet hoses  22 ′ are connected to suction pumps (not shown) for removing cooling gas prior to separation of the tool  1  for removal of the casing  6 . 
   In use, the hollow casing billet  6 , is heated to quenching temperature between 775 and 1000° C. As illustrated in  FIG. 1 , the heated smooth hollow casing billet  6  is introduced between the halves  2 ,  3  of the molding tool  1  and these are pressed against each other to a position that produces a support frame. Following this, the nozzles  15 ,  15 ′ are introduced into openings at each end of the hollow casing whereby the sealing between the respective end and nozzle  15 ,  15 ′ takes place by means of the sealing rings  13 ,  13 ′. When the medium is introduced into the interior of the hot hollow casing billet  6  via nozzle  15 , as illustrated by the directional arrow in  FIG. 1 , the billet is molded against the inner walls of the support fingers  4 ,  5 . 
   To thereafter achieve a cooling that is efficient for carrying out the quenching process, the hollow casing billet  6  is quickly cooled on the outside. Cooling liquid is supplied via the hose  22  and the dispensers  23  and flushed directly onto the exposed external surface of the hollow casing  6 . Alternatively, cooling gas may be injected into the internal cavities  41 ,  42  of the tool  1  after the billet  6  has been formed against the inner walls of the support fingers  4 ,  5  (See  FIG. 3 ). At the same time, the halves  2 ,  3  of the tool  1  are cooled by an essentially cooling medium, preferably water, being led through the channels  7 ,  8  of these halves  2 ,  3 . 
   It will of course be understood that the invention is not limited to the specific details as herein described, which are given by way of example only, and that various alterations and modifications may be made without departing from the scope of the invention as defined in the appended claims.