Method and tool for manufacturing a spiral element for a scroll member used in scroll type fluid displacement apparatus

This invention relates to a scroll type fluid displacement apparatus, and more particularly to the manufacturing method and tool of the scroll member used therein.

The scroll type fluid displacement apparatus are well known in the prior art. For example, U.S. Patent No. 801,182 discloses a device including two scroll members each having a circular end plate and spiroidal or involute spiral element. The both scroll members interfit and are maintained angularly and radially offset from one another so that both spiral element contact at a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets: The relative orbital motion of these scroll members shifts the line contacts along the spiral curved surfaces and, therefore, changes the volume of the fluid pockets. The volume of the fluid pockets increases or decreases depending on the direction of the orbital motion. Therefore, scroll type fluid displacement apparatus is applicable to compress, expand or pump fluids.

Fig. 1 illustrates the basic design of the scroll member suitable for use in any of scroll type fluid displacement apparatus described in the U.S. Patent No. 801,182 and others. The basic construction of the scroll member 1 comprises a circular end plate 2 and, a wrap means or involute spiral element 3 affixed to or extending from one side surface of end plate 2. The scroll type fluid displacement apparatus includes a pair of these scroll members which interfit and are maintained angularly and radially offset from one another so as to contact at a plurality of line contacts and axial contact between both scroll members to define at least one pair of sealed off fluid pockets. In this apparatus, each sealed off fluid pocket is defined by the line contacts between interfitting spiral elements and the axial contacts between the axial end surface of spiral element and the inner end surface of the end plate. The volume of the fluid pocket is thereby defined by both line contacts and axial contacts.

The scroll member is generally formed from single piece of metal by machining process, such as milling. However, this process consumes a great deal of time and energy and, also produces large quantity of waste metal. Furthermore, when the scroll member is formed by casting or forging, and axial dimension of the spiral element is longer as possible for obtaining the large volume or higher capacity, the draft angle of mold must be made larger. The machining amount of spiral element material to form uniform wall thickness increases and thereby the large quantity of waste metal is vested. These manufacturing method also consumes a great deal of time and energy and, it has a demoralizing influence upon the accuracy of the wall dimension of the spiral element.

It is a primary object of this invention to provide an improvement in a manufacturing method of preformed scroll member used in the scroll type fluid displacement apparatus.

It is another object of this invention to provide a manufacturing method of the preformed scroll member which can reduce the production of waste metal during the finish machining operation of preformed scroll member.

It is a further primary object of this invention to provide a manufacturing tool for forming preformed scroll member used in the scroll type fluid displacement apparatus.

It is another object of this invention to provide the manufacturing tool which achieves the dimensional accuracy without the great deal of time in finish operation of the preformed scroll member.

A manufacturing method of preformed scroll member used in a scroll type fluid displacement apparatus according to this invention provides one molding member which has an involute groove and another involute groove at its side surface. The sectional configuration of the first involute groove is formed in wedge-shape and, sectional configuration of the second involute groove is formed substantially in rectangular-shape.

An insertion member with wedge-shape cross section is disposed within the first involute groove for filling up the space of the groove. A metal of which the spiral element of preformed scroll member is made is fullfilled in the second involute groove for metal forming.

After metal forming, the insertion member is removed from the first involute groove and the formed metal member is taken out from the second involute groove. The preformed scroll member with rectangular cross section is thereby obtained.

Another aspect of this invention provides another molding member which has a circular indentation at its axial end surface. This molding member is disposed on the end surface of first molding member for covering the both involute grooves. The space of indentation consists of the forming space. Therefore, metal filling up the forming space of indentation forms the end plate of preformed scroll member.

Still another aspect of this invention is that the first molding member has a plurality of holes each of which is placed on the locus of involute curve and connects between the bottom surface of first involute groove and opposite side surface of first molding member. The insertion member has a plurality of pins at the axial end surface thereof. When the insertion member is disposed in the first involute groove, each of the pins is inserted in the each hole of the molding member and the axial outer end portion of pin extends from the hole. The insertion member is, therefore, easily removed from the first involute groove by pushing up the pins.

A manufacturing tool of preformed scroll member includes a first molding member which comprises an end plate portion and two involute wall elements. The two involute wall elements parallely extend so that two involute grooves are defined between the both involute wall elements. One of the two involute groove has a wedge-shaped sectional configuration and, other groove has a substantially rectangular-shaped sectional configuration. An insertion member is removably disposed within the one of two involute grooves. A second molding member has a circular indentation at one side surface opposite to the involute wall element. The second molding member is disposed on the first molding member and connected to the first molding member when casting the molten metal.

On metal molding, the rectangular-shaped groove in which the metal is disposed can not expand, and therefore, the forming metal which makes the spiral element of preformed scroll member keeps the rectangular-shaped sectional configuration.

Another aspect of this invention is that a plurality of holes are formed in the end plate portion of first molding member and, a plurality of pins which project axially from the insertion member are inserted in the holes. The removal of the insertion member is, therefore, easily operated by pushing the pins.

Further objects, features and other aspects of this invention will be understood from the following detailed description of preferred embodiment of this invention referring to the annexed drawings.

Fig. 1 is a perspective view of the scroll member of a basic design;

• Fig. 2 is an exploded perspective view of the manufacturing tool according to this invention;
• F_ig. 3 is a perspective view of the first molding member used in the manufacturing tool of Fig. 2;
• Fig. 4 is a perspective view of the second molding member used in the manufacturing tool of Fig. 2;
• Fig. 5 is a sectional view illustrating the connecting situation of the first and second molding members; and
• Fig. 6 is a perspective view of the first molding member according to another embodiment of the invention.

Referring to Fig. 2, a manufacturing tool 10 of a preformed scroll member in accordance with the present invention is shown. The tool 10 includes a first molding member 11, an insertion member 12, and a second molding member 13. First molding member 11 comprises a circular end plate portion 111 and two involute wall elements 112 and 113 affixed to or extending from one side surface of end plate 111. The second involute wall element 113 extends along the inner side surface of first involute wall element 112 to keep the space from one another. Two involute grooves 20 and 21 are, therefore, formed between both involute wall elements 112 and 113. The outer side surface of first involute wall element 112 forms. vertical surface and the inner side surface forms a tapered surface. The outer side surface of second involute wall element 113 also forms a tapered surface and the inner side surface forms vertical surface. An outer involute groove 20 is defined by the inner side surface of first involute wall element 112 and the outer side surface of second involute wall element 113, and is thereby formed in wedge-shape cross section and, an inner involute groove 21 is defined by the outer side surface of first involute wall element 112 and the inner side surface of second involute wall element 113, and is formed in a substantially rectangular-shape cross section. A plurality of holes 114 are formed in end plate portion 111 for connecting between the bottom surface of outer involute groove 20 and opposite side surface of end plate portion 111. Each of holes 114 is placed on the locus of the involute curve which defines the outer groove 20, as shown in Fig. 3. A vent hole 115 is formed on the end surface of end plate portion 111.

Insertion member 12 is disposed, for metal forming, in outer groove 20 defined by the inner side surface of first involute wall element 112 and the outer side surface of second involute wall element 113. The sectional configuration of insertion member 12 has a configuration substantially same as that of outer groove 20, i.e., wedge-shape configuration. Therefore, the open space of outer groove 20 is filled up by insertion member 12. Insertion member 12 has a plurality of pins 121 axially projecting from one end surface thereof. Each pin 121 is inserted into each hole 114 and outer end portion of pin 121 is extended from hole 114.

Second molding member 13 is disposed over the first molding member 11 for closing the opening space of both involute grooves 20 and 21. The end surface of second molding member 13 which opposes to the first molding member 11 is formed with a circular indentation 131, as shown in Fig. 4. The indentation 131 consists of molding space. A pouring gate 22 is formed in second molding member 13. In this embodiment, as shown in Figs. 2 and 4, two pouring gates 22 are formed in second molding member 13, and a circular sprue runner 221 which is connected to pouring gates 22 is formed in the bottom surface of indentation 131.

In this tool, a supporting member 14 is disposed on the outer side surface of the first involute wall element 112. When both molding members 11 and 13 are connected by a fastening member, such as bolts and nuts 15 as shown in Fig. 5, the axial end surface of supporting member 14 is fitted against the end surface of second molding member 13. The predetermined axial distance between both molding members 11 and 13 is, therefore, kept by supporting member 14.

The casting method using the above tool will be explained below.

At the first step, first molding member 11 and insertion member 12 are handled so that insertion member 12 is set in outer involute groove 20. And then, second molding member 13 is disposed on the first molding member 11 and is connected to first molding member 11 by bolts and nuts 15.

At the second step, the molten metal, such as aluminum, is poured into the space defined between both molding members 11 and 13 through pouring gate 22 and sprue runner 221 formed in second molding member 13. The space of inner groove 21 and molding space of indentation 131 are, therefore, filled up by the molten metal. The molten metal is solidified in the subsequent cooling process.

At this time, the expansion of inner groove 21 due to filling up and solidification of molten metal is prevented by insertion member 12 disposed in outer groove 20. Therefore, the sectional configuration of inner groove 21 is not changed, so that the sectional configuration of spiral element of preformed scroll member is formed in substantially rectangular-shape cross section. Furthermore, the molten metal which fills up the molding space of indentation 131 forms the end plate of preformed scroll member.

As the third step, after solidification of molten metal, the connection between both molding members 11 and 13 is released and, second molding member 13 is removed from first molding member 11. Then, outer end portions of pins 121 of insertion member 12 which are extended from holes 114 of the first molding member 11 are pushed out in the axial direction. Insertion member 12 disposed in outer groove 20 is, therefore, removed from outer groove 20. At the same time, solidified metal, i.e., the preformed scroll member is removed from inner groove 21. Since, the axial end surface of insertion member 12 is fitted against the end surface of end plate of the preformed scroll member. The preformed scroll member is thus removed from inner groove 21 of first molding member 11 by removing the insertion member 12. the preformed scroll member and insertion member 12 are removed from first molding member 11 at the same time, and therefore, removal of preformed scroll member is smoothly operated. Because the open space of outer groove 20 will be made by removal of insertion member 12, involute wall element 112 which partitions between the outer and inner grooves 20 and 21 can be radially bent, so that the space of the inner groove 21 is made larger.

Fig. 6 shows another embodiment of manufacturing tool according to this invention, in which the involute wall element is modified. The first and second involute wall elements 112 and 113 have a plurality of slits 116 at suitable involute angular positions. Both involute wall elements 112 and 113 are, thus, formed by a plurality of tongue-shaped portions. The removal of preformed scroll member is, therefore, made easier, since, each of tongue-shaped portions of involute wall element has less rigidity for easier elastic deformation and can be easily bent.

The preformed scroll member formed by above method and tool is operated in the machine working, such as the milling work, therefore, the final scroll member used in the scroll type apparatus is obtained.

As described above, since the draft angle of the mold of spiral element portion can be minimized according to this invention, quantity of waste metal which occurs at the finish working of preformed scroll member is reduced. Furthermore, time and energy for working of final scroll member is greatly reduced without the influence upon the accuracy of spiral element dimension.

This invention has been described in detail in connection with the preferred embodiment, but this is an example only and this invention is not restricted thereto. It will be easily understood by those skilled in the art that other variations and modifications can be easily made with the scope of this invention.