Pump housing and a manufacturing method therefor

Abstract: A pump housing and manufacturing method therefor includes a primary molding for injecting halves of the pump housing and a secondary molding for assembling the primary molds to each other to be installed to the interior of a secondary metal mold and secondarily-molding the outer surface of the pump housing without requiring core fabrication, installation and removal steps of the injection molding. Thus, the core fabrication and core removal steps heretofore required for an inlet or undercut are unnecessary for enabling swift mass production and lowering difficulty of working to make the quality consistent and decrease inferior products, thereby reducing the manufacturing cost.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump housing and manufacturing method therefor, and more particularly to a pump housing and manufacturing method therefor, wherein a molding process of a pump housing for circulating hot water is separated into a primary molding and a second molding for improving quality of a product and reducing manufacturing cost. 2. Description of the Prior Art A pump housing of a hot-water circulating pump molded via a conventional molding method is illustrated in FIGS. 1 and 2. FIG. 1 is a plan view showing the pump housing, and FIG. 2 is a sectional view thereof. As shown in FIGS. 1 and 2, pump housing 10 has an inlet 15 for admitting a fluid, and a volute chamber 11 formed for facilitating the flowing of the admitted fluid and constantly maintaining the sum of ordinary flow rate components and an outlet 13 for discharging the admitted fluid. A whirlpooltype spiral groove 17 is formed within volute chamber 11. In association with such pump housing 10, it is impossible to finish the formation of pump housing 10 by an injection molding once due to the shape of spiral groove 17 and the streamlined structure of inlet 15 and outlet 13 for being suitable for the flowing conditions of the fluid. Therefore, a core which is a hollow bar of a metal mold is employed to perform the molding, and then removed after the molding. FIG. 3 illustrates a process for manufacturing pump housing 10 via the conventional molding method. Referring to FIG. 3, a metal mold fabricating step for forming a metal mold having the outer surface shape of pump housing 10 and a core fabricating step for forming a core constituting the interior of inlet 15, outlet 13 and volute chamber 11 should be executed in advance. After finishing the above steps, a core installing step for installing the core within the fabricated metal mold, and an injection molding step are sequentially carr ed out. After the injection molding, pump housing 10 is separated from the metal mold, and a core removing step of eliminating the core within pump housing 10 is then executed. Thus, the molding process of pump housing 10 is completed to produce completed pump housing 10. At this time, the core removing process may differ from the kinds of the core. That is, a lost core for removing the core after injection-molding pump housing 10 is classified into a casting sand lost core which uses casting sand during a casting for pulverizing to remove the core after the injection molding and a messed lost core which injects an alloy of lead and bismuth during the injection molding for melting to remove the alloy after the injection molding. The molding method of the pump housing using the lost core involves steps of the metal mold fabrication, core fabrication, core installation, injection molding and core removal to require relatively lengthy processing. Especially, the core removal step has drawbacks of taking too long time and being highly demanding job. That is, in case of the injection molding, since the messed being the alloy of lead and bismuth is applied with heat to be removed after the injection molding, so that a lot of time is required and so much cost is needed as well as the operation is laborious. For these reasons, the injection molding is not applied to general products except for products of special use. Also, in case of the casting, the casting sand lost core is broken or pulverized to be removed after the casting. Thus, so much time is required and the working is difficulty. Additionally, in overall molding process, the lost core installed to the metal mold is liable to be shaken while a liquid metal is poured to be forced out or inclined toward one side. Particularly, the casting is disadvantageous in that the lost core is moved while the casting sand is broken down. Furthermore, in spite that a core bar is inserted into the core for preventing the warping of the lost core, the lost core is warped to be deformed owing to the high temperature of the liquid metal, which in turn results in a defect of products. SUMMARY OF THE INVENTION It is an object of the present invention to provide a pump housing and manufacturing method therefor, wherein, in order to solve the foregoing problems, a molding process is classified into a primary molding and a secondary molding for improving quality of products and simplifying and facilitating a manufacturing process thereof. To achieve the above object of the present invention, a pump housing includes a left mold which is one half of a primary mold stuff formed with an inlet for admitting a fluid in one side, a volute chamber communicated with the inlet at the center and an outlet for discharging the fluid in a portion opposing to the inlet. A right mold which is the other half of the primary mold stuff united with the section of the left mold for forming an internal space of the inlet, outlet and volute chamber. Also, a secondary mold stuff is injection-molded to the outer surface of the united left mold and right mold. Here, it is preferable that a spiral groove connected to the outlet for facilitating floating of the fluid is formed in an inner wall of the volute chamber, and a plurality of projections for preventing the floating during the injection-molding of the secondary mold stuff are formed to the outer surface of the primary mold stuff. In addition, a plurality of grooves may be formed in the outer surface of the primary mold stuff for smoothly welding a liquid metal of the secondary mold stuff. Preferably, a junction portion of the left mold and right mold is provided to be formed with a guide projection at one junction end and a guide groove coupled with the guide projection in the other junction end for blocking intrusion of the liquid metal of the secondary mold stuff into the primary mold stuff. Alternatively, to achieve the above object of the present invention, a pump housing includes a left mold being one half of a primary mold stuff formed with an inlet for admitting a fluid in one side, a volute chamber communicated with the inlet at the center and an outlet for discharging the fluid in a portion opposing to the inlet. A right mold being the other half the primary mold stuff is united with the section of the left mold for forming an internal space of the inlet, outlet and volute chamber, and a spiral groove is connected to the outlet in the inner wall of the volute chamber for facilitating the floating of the fluid. The outer surface of the united left mold and right is injection-molded with a secondary mold stuff, and a plurality of projections are provided from an outer surface of the primary mold stuff for preventing the floating thereof during the injection-molding of the secondary mold stuff. A plurality of grooves formed in the outer surface of the primary mold stuff facilitate the flow of a liquid metal of the secondary mold stuff. Furthermore, a guide projection is formed to one junction end around a junction portion of the left mold and right mold for blocking intrusion of the liquid metal of the secondary mold stuff into the interior of the primary mold stuff. Then, a guide groove formed to the other junction end is fitted with the guide projection. To achieve the above and other object of the present invention, a method for manufacturing the pump housing is sequentially performed by preparing respective metal molds for injection-molding portions of a primary mold stuff formed with an inlet for admitting a fluid in one side, a volute chamber communicated with the inlet at the center and an outlet in the opposing side of the inlet for discharging the fluid, and preparing a metal mold of a secondary mold stuff injection-molded to an outer surface of the primary mold stuff. Thereafter, the primary mold stuff is molded and the secondary mold stuff is molded. Here, the step of preparing the metal mold of the primary mold stuff is preferably performed by preparing the metal mold of the left mold of the primary mold stuf, and preparing the metal mold of the mold being the other half of the primary mold stuff united with the section of the left mold for forming the internal space of the inlet, outlet and volute chamber. More preferably, the step of molding the secondary mold stuff is conducted such that the left mold is united with the right mold, the united primary mold stuff is installed to the interior of the metal mold of the secondary mold stuff, and performing the injection into a clearance between the interior of the metal mold of the secondary mold stuff and primary mold stuff. The pump housing according to the present invention described as above is formed by the primary mold stuff functioning as a core and the secondary mold stuff molded to the outer surface of the primary mold stuff to be provided as one body. The primary mold stuff is constructed by the left mold and right mold having the vertically-cut section of the inlet, outlet and volute chamber. That is, the left mold is shaped as the left side and the right mold is shaped as the right side when the center of the pump housing is vertically cut through. The left mold and right mold are separately provided from respective metal molds to be assembled with each other, thereby serving as the core of the secondary mold stuff. The secondary mold stuff is injection-molded to the outer surface of the primary mold stuff as described above to unite the assembled primary mold stuff not to be separated from each other while constituting the outer appearance of the pump housing. Additionally, the method for manufacturing the pump housing according to the present invention constructed as above can be largely classified into the step of molding the pair of primary molds and the step of molding the secondary mold stuff by using the primary molds as the core. The step for molding the primary mold stuff is carried out by fabricating the metal molds of the left mold and right mold respectively constituting the vertical halves of the pump housing, and molding them by using the metal molds. The step for molding the secondary mold stuff is carried out by fabricating the metal mold of the secondary mold stuff, and insertedly installing the pair of primary molds into the metal mold of the secondary mold stuff and performing the final molding, thereby completing the pump housing. Therefore, the pump housing and manufacturing method therefor according to the present invention constructed as above can prevent the shaking of the primary mold stuff caused by the pressure of the liquid metal poured in the molding step of the secondary mold stuff, and prevent the intrusion of the poured liquid metal into the interior of the primary mold stuff. Also, the core fabrication and core removal steps heretofore needed for an inlet or undercut are not required for enabling speedy mass production and lowering the difficulty in working to make the quality consistent and decrease inferior products, thereby reducing the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS The above objects and other advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to :he attached drawings in which: FIG. 1 is a plan view showing a pump housing molded by means of a conventional molding method; FIG. 2 is a sectional view of the pump housing shown in FIG. 1; FIG. 3 shows a process of manufacturing the pump housing according to the conventional molding method; FIG. 4 shows a process of manufacturing a pump housing by means of a molding method according to the present invention; FIG. 5 is a plan view showing a pair of primary molds in the pump housing according to the present invention; FIG. 6 is a plan view showing a secondary mold stuff in the pump housing according to the present invention; FIG. 7 is a sectional view showing the left mold of the primary mold stuff shown in FIG. 5; FIG. 8 is a sectional view of the pump housing shown in FIG. 6; FIG. 9 is a sectional view showing a state that the primary mold stuff having projections is installed to the metal mold of the secondary mold stuff according to a first embodiment of the present invention; FIG. 10 is a sectional view showing a state that the primary mold stuff having grooves is installed to the metal mold of the secondary mold stuff according to a second embodiment of the present invention; FIG. 11 is an enlarged view with respect to an A portion shown in FIG. 9; and FIG. 12 is an enlarged view with respect to the groove portion shown in FIG. 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pump housing and manufacturing method therefor according to the present invention will be described in detail with reference to accompanying drawings. FIG. 4 illustrates a process for manufacturing the pump housing according to a molding method of the present invention. Referring to FIG. 4, a step for fabricating a metal mold of a primary mold stuff (hereinafter simply referred to as "primary metal mold") directs a step for fabricating the metal mold for molding half the pump housing with respect to the longitudinal direction. Then, a step for fabricating a metal mold of a secondary mold stuff (hereinafter simply referred to as "secondary metal mold") is for fabricating a metal mold constituting the outer appearance of the pump housing by being formed to the outer surface of the primary mold stuff. A molding of the primary mold stuff refers a step of molding the primary mold stuff, i.e., a left mold and right mold, by using the primary metal mold. Thereafter, the molded left mold and right mold are brought into contact with each other to be assembled. The assembled molds are inserted to be fixed to the interior of the secondary metal mold. A molding of the secondary mold stuff refers a step of completely finishing the pump housing by pouring a liquid metal between the secondary metal mold and primary mold stuff. FIG. 5 is a plan view showing the pair of primary molds of the pump housing according to the present invention. Referring to FIG. 5, primary mold stuff 102 consists of left mold 100 and right mold 101. Left mold 100 is formed with a guide projection 109 at a portion in contact with right mold 101, and a guide groove 111 is formed in a corresponding portion of right mold 101 to be fitted with guide projection 109. When left mold 100 and right mold 101 are assembled by being engaged with each other in this manner, the internal room of pump housing 300, i.e., an inlet, an outlet and a volute chamber, is completed. A plurality of projections 113 protrude from the outer surface of left mold 100 and right mold 101 for preventing the floating of primary mold stuff 102 in the secondary molding step. It is good enough for projections 113 to have a predetermined projecting height and place on the outer surface without being greatly spaced apart from one another. FIG. 6 is a plan view showing the secondary mold stuff of the pump housing according to the present invention. Referring to FIG. 6, secondary mold stuff 200 having a predetermined thickness is formed to the outer surface of assembled left mold 100 and right mold 101 to constitute pump housing 300. FIG. 7 is a sectional view showing left mold 100 of primary mold stuff 102 shown in FIG. 5. That is, FIG. 7 illustrates the formation and connection of a flow passage forming the interior of pump housing 300. In FIG. 7, inlet 105 for admitting hot water is formed to the right side, and volute chamber 107 having an upper portion connected to inlet 105 is formed to the certral portion. A spiral groove 106 for facilitating the flow of the hot water is formed in the sidewall of volute chamber 107. Outlet 103 for discharging the hot water is formed to the last portion of spiral groove 106. Volute chamber 107 serves for smoothing the flow of the hot water and making the sum of ordinary flow rate components constant. The bottom of volute chamber 107 is open to be communicated with an interior of a pump when pump housing 300 is coupled to a body (not shown) of the pump. FIG. 8 is a sectional view of pump housing 300 shown in FIG. 6. As shown in FIG. 8, secondary mold stuff 200 having a predetermined thickness is injection-molded to the outer surface of left mold 100. In other words, secondary mold stuff 200 is formed to left mold 100, thereby completing pump housing 300. FIG. 9 shows a first embodiment of the present invention which illustrates a state that the primary mold stuff having projections 113 is installed to secondary metal mold 130. As shown in FIG. 9, secondary metal mold 130 is fabricated to mold the outer appearance of pump housing 300, and the interior thereof is provided for being inserted with pair of left mold 100 and right mold 101 which are assembled by being brought into contact with each other. A prescribed clearance 137 is formed between secondary metal mold 130 and primary mold stuff 100 & 101 for being admitted with the liquid metal of secondary mold stuff 200. Plurality of projections 113 directing toward secondary metal mold 130 are formed from the outer surface of primary mold stuff 100 & 101. An ingate 132 for supplying the liquid metal into clearance 137 is installed into secondary metal mold 130. Ingate 132 may number one or at least two in accordance with the size and injection conditions of pump housing 300. When the liquid metal of secondary mold stuff 200 is poured after left mold 100 and right mold 101 are installed to the interior of secondary metal mold 130, left mold 100 and right mold 101 are liable to be shaken by the pouring amount of the liquid metal. For preventing the shaking, an auxiliary metal mold 134 is fixedly installed to the rear plane of ingate 132 within left mold 100 or right mold 101. FIG. 10 which illustrates a secondary embodiment of the present invention is a sectional view showing a state that primary mold stuff 100 & 101 having grooves 145 is installed to secondary metal mold 130. As shown in FIG. 10, secondary metal mold 130 and auxiliary metal mold 134 are the same as those shown in FIG. 9 except that projections 113 are not formed to the outer surface of left mold 100 and right mold 101 but plurality of grooves 145 are provided. Grooves 145 serve for receiving the liquid metal along them to facilitate welding of secondary mold stuff 200 to primary mold stuff 102. FIG. 11 illustrates an enlarged sectional view with respect to a portion A of FIG. 9. As shown in FIG. 11, left mold 100 is formed with guide groove 111 in the portion in contact with right mold 101, and guide projection 109 is formed to the corresponding portion of right mold 101. Guide projection 109 and guide groove 111 are closely united with each other without involving any gap to block the intrusion of the liquid metal into the interior of primary mold stuff 102. FIG. 12 illustrates an enlarged sectional view with respect to the groove portion of FIG. 10. Here, respective grooves 145 are engraved to have a predetermined depth within a range of not piercing through the thickness of primary mold stu f 102. Grooves 145 are consistently distributed across the outer surface of primary mold stuff 102, and, as required, may be formed to the outer surface of primary mold stuff 102 formed with projections 113. In the pump housing and manufacturing method therefor according to the present invention constructed as above, the primary metal mold is fabricated, and the pair of left mold 100 and right mold 101 are injection-molded by the primary metal mold. Left mold 100 and right mold 101 are assembled by bringing guide groove 111 into contact with guide projection 109, which is insertedly installed to the interior of secondary metal mold 130. Thereafter, auxiliary metal mold 134 is fixed to the interior of primary mold stuff 102. Then, once the liquid metal is poured through ingate 132, the poured liquid metal is solidified while thoroughly filling up clearance 137 between secondary metal mold 130 and primary mold stuff 102. At this time, auxiliary metal mold 134 prevents the floating of primary mold stuff 102 due to the pressure of the liquid metal. When secondary mold stuff 200 is hardened to be solidified, auxiliary metal mold 134 is separated and pump housing 300 is separately detached from the interior of secondary metal mold 130. By doing so, the final pump housing 300 is obtained. Meantime, the substance of the liquid metal poured during the secondary molding is the same as primary mold stuff 102 to raise the affinity between primary mold stuff 102 and secondary mold stuff 200. As a result, in the pump housing and manufacturing method therefor according to the present invention provided as above, the shaking of the primary mold stuff caused by the pressure of the liquid metal poured during the molding of the secondary mold stuff can be prevented while blocking the intrusion of the poured liquid metal into the interior of the primary mold stuff. Furthermore, the core fabrication or core removal steps required for the inlet or undercut are unnecessary for enabling swift mass production and lowering the difficulty in working to make the quality consistent and decrease inferior products, thereby reducing the manufacturing cost. While the present invention has been particularly shown and described with reference to particular embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims: A method of manufacturing a pump housing (300) with a two layer structure, comprising the steps of: 1.1 preparing respective metal molds for molding two halves (100, 101) of a primary molded member (102) defining the first layer of the pump housing (300); 1.2 preparing a second metal mold (130) for injection molding a secondary molded member (200) defining the second layer of the pump housing (300); 1.3 molding the two halves (100,101) of the primary molded member (102), comprising an inlet (105) for admitting a fluid at one side thereof, an outlet (103) at the opposite side thereof and a chamber (107) communicating with the inlet (105) and the outlet (103); 1.4 installing the two halves (100, 101) combined with each other into the interior of the second metal mold (130) defining a core with clearance (137) between the core and the second metal mold (130); 1.5 injection molding the secondary molded member (200) by pouring liquid metal into the clearance (137). A pump housing being manufactured according to the method of claim 1, comprising: 2.1 a two layer structure, wherein the first layer is the inner layer and is defined by the two halves (100, 101) of the primary molded member (102) and the second layer is the outer layer and is defined by the secondary molded member (200); 2.2 the primary molded member (102) comprises an inlet (105) for admitting a fluid at one side thereof, an outlet (103) at the opposite side thereof and a chamber (107) communicating with the inlet (105) and the outlet (103); 2.3 the secondary molded member (200) encloses the primary molded member (102) A pump housing as claimed in claim 2, wherein a spiral groove (106) connected to the outlet (103) is formed in an inner wall of the chamber (107) for facilitating floating of said fluid. A pump housing as claimed in claim 2, wherein a plurality of projections (113) are formed in the outer surface of the primary molded member (102) for preventing the floating during the injection-molding of the secondary molded member (200) . A pump housing as claimed in claim 2, wherein a plurality of grooves (145) are formed in the outer surface of the primary molded member (102) for smoothly welding the liquid metal of the secondary molded member (200). A pump housing as claimed in claim 2, wherein one of the two halves (100,101) comprises a guide projection (109), the other comprises a guide groove (111) and the two halves (100,101) are jointed therewith, for blocking intrusion of the liquid metal of the secondary molded member (200) into the interior of the primary molded member (102).

Inventors: MOON SUNG-DAI, MOON, SUNG-DAI
Applicants: DAEWOO ELECTRONICS CO LTD, DAEWOO ELECTRONICS CO., LTD
Application year: 1996
Main classification: B22C9
IPC codes: B22D19, B22D25, B22C9, B22D17, F04D29, F04B39