Patent Application
20100089116
This invention relates to the method and apparatus for forming a can shell from sheet metal or sheet aluminum, for example, such as the methods and apparatus or tooling disclosed in U.S. Pat. No. 4,713,958, No. 4,716,755, No. 4,808,052, No. 4,955,223, No. 6,658,911 and No. 7,302,822. The disclosures of these patents are herein incorporated by reference to supplement the detail description of the present invention.
In such tooling assembly or apparatus, it has been found desirable for the apparatus to be constructed for use in a single action mechanical press such as disclosed in above mentioned U.S. Pat. No. 4,955,223 and U.S. Pat. No. 7,302,822 and to avoid using a double action mechanical press, for example, as disclosed in above-mentioned U.S. Pat. No. 4,716,755 and U.S. Pat. No. 6,658,911. A single action high speed press is simpler and more economical in construction and is more economical in operation and in maintenance and can be operated effectively and efficiently, for example, with a stroke of 1.75 inch and at a speed of 650 strokes per minute. There are also many more single action high speed presses in use in the field than there are double action presses.
It has also been found desirable for the apparatus or tooling assembly to incorporate an inner pressure sleeve and an outer pressure sleeve and to operate both sleeves with air pressure, but avoid actuating the inner pressure sleeve with circumferentially spaced and axially extending springs, for example, as disclosed in U.S. Pat. No. 7,302,822 or the use of circumferentially spaced and axially extending pins, for example, as disclosed in U.S. Pat. No. 4,716,755. The high speed axial reciprocating movement of the pins and the single piston which actuates the pins create undesirable additional heat, and is difficult to produce an adjustable and precisely controllable axial force on the inner pressure sleeve with the use of compression springs.
It is further desirable to have a precisely controllable constant force exerted by the outer pressure sleeve on the sheet material to avoid thinning the material between the outer pressure sleeve and the die core ring during high speed operation of the press. Precisely controllable air pressure on the inner pressure sleeve is also desirable for holding the chuckwall of the can shell while forming the countersink, panel wall and center panel of the can shell without thinning the sheet metal. In addition, it is desirable to minimize the vertical height of the tooling assembly for producing can shells in order to accommodate more single action high speed presses existing in the field and to operate at higher speeds with less heat being generated so as to avoid the use of water cooled tooling components. After reviewing the above patents, it is apparent that none of the patents provide all of the above desirable features.
The present invention is directed to improved method and apparatus or tooling for high speed production of can shells and which provide all of the desirable features mentioned above. The tooling assembly of the invention is also ideally suited for producing a can shell such as disclosed in applicant's U.S. Pat. No. 7,341,163 and in applicant's published patent application No. US-2005-0029269, the disclosures of which are also herein incorporated by reference. The method and apparatus or tooling assembly of the invention are especially suited for use on a single action press and for producing uniform and precision can shells at a high rate of speed and with the minimum generation of heat in order to avoid thermal changing of the tooling assembly during operation.
In accordance with one illustrated embodiment of the invention, a can shell is formed by a tooling assembly including an annular inner pressure sleeve which is located within an annular outer pressure sleeve, and both of the sleeves have integral pistons within corresponding annular air piston chambers. The outer pressure sleeve is supported within an annular blank and draw die secured to an upper retainer mounted on an upper die shoe of a single action press. The retainer also supports a die center piston which may be supported for relative axial movement, and the die center piston supports a die center punch within the inner pressure sleeve. The die center piston has a center portion defining an air reservoir chamber supplied with air through a port at a controlled pressure. The air reservoir chamber is connected to the air piston chamber for the inner pressure sleeve by a plurality of circumferentially spaced elongated air passages. The air piston chamber for the outer pressure sleeve is supplied with air at a controlled substantially lower pressure through a separate port in the upper retainer.
The inner pressure sleeve has an annular nose portion which normally projects from the die center piston and initiates the draw of a cup within a die cut sheet metal disk held between the outer pressure sleeve and an opposing fixed die core ring supported by a lower retainer mounted on a fixed lower die shoe of the press. The nose portion of the inner pressure sleeve and the die core ring have mating contoured surfaces which form an annular chuckwall on the disk, and the die center punch cooperates with the inner pressure sleeve to complete the drawing of the cup which is engaged by a panel punch supported within the die core ring. The panel punch has a peripheral contoured surface which forms the center panel of the shell and also the annular panel wall and the annular countersink. In another embodiment of the invention, the air piston chamber for the outer pressure sleeve is connected by an air passage extending to the air reservoir chamber so that the air piston chamber for the inner pressure sleeve and the air piston chamber for the outer pressure sleeve receive the same controllable air supply pressure, thereby avoiding the need for two different air supplies at different pressures to operate the tooling assembly on the upper die shoe.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
Referring to
Referring to
An annular outer pressure sleeve 55 is supported for axial movement within the blank and draw die 48 and includes an integrally formed piston 56 having radial plastic wear pins 57. A die center piston 60 may be supported for axial movement within the upper retainer 38 and includes a lower portion 62 which supports a die center punch 65 removably secured to the die center piston 60 by a center cap screw 66. A flat ground annular spacer 68 is positioned between the die center punch 65 and a shoulder on the lower portion 62 of the die center piston 60 to provide for precisely selecting the axial position of the die center punch on the die center piston 60. A cylindrical pressurized air reservoir chamber 70 is formed within the center portion of the die center piston 60 and is closed at the top by a threaded plug 71. The reservoir chamber 70 receives pressurized air through a port 74 formed within the retainer 38 and an aligned radial passage 76 formed within the die center piston 60.
An annular inner pressure sleeve 80 is supported for axial movement within the outer pressure sleeve 55 and includes an integral piston 82 confined within an annular air piston chamber 84 defined axially between the piston 82 and a radial shoulder 86 on the lower portion 62 of the die center piston 60. The air piston chamber 84 receives pressurized air through a plurality of three circumferentially spaced air passages 88 which extends axially from the shoulder 86 to the air reservoir chamber 70 within the die center piston 60. Suitable two piece air seal rings are carried by the piston 82 of the inner pressure sleeve 80 and also the piston 56 of the outer pressure sleeve 55 as well as by the upper portion of the die center piston 60. The piston 56 of the outer pressure sleeve 55 is confined within an annular air pressure chamber 89 which extends to a stop shoulder 90 and connects with an annular air chamber 91. The chambers 89 & 91 receive pressurized air through a port 92 in the retainer 38.
The tooling assembly 35 also includes a fixed annular lower retainer 94 which is mounted on a stationery lower die shoe 95 of the single action press. The lower retainer 94 supports a fixed die core ring 98 having an annular upper portion 99 and also supports a fixed annular retainer 102 which confines an annular cut edge die 105. A flat annular ground spacer 107 is secured to the retainer 102 to confine the cut edge die 105 and provides for precisely positioning the cut edge die axially with respect to the upper annular portion 99 of the die core ring 98. An annular lower pressure sleeve 110 is positioned between the cut edge die 105 and the upper portion 99 of the die core ring 98 and has an integral piston 112 supported for axial movement within an annular pressurized air pressure chamber 114 defined between the lower retainer 94 and die core ring 98. The chamber 114 receives pressurized air through a port (not shown) with the lower retainer 94.
A circular panel punch 118 is confined within the upper portion 99 of the die core ring 98 and is secured for axial movement with a panel punch piston 122 supported within a stepped cylindrical bore 123 formed within the die core ring 98. A flat annular ground spacer 126 is positioned between the panel punch 118 and the panel punch piston 122 to provide for precisely positioning the panel punch 118 axially on the piston 122. Suitable two piece air seal rings are carried by the lower pressure sleeve piston 112 and the panel punch piston 122 to form sliding airtight seals. An axially extending air pressure passage 127 is formed within the center of the panel punch piston 122 and receives pressurized air through a cross passage 128 and an annular chamber 129. The passage 127 provides a jet of pressurized air upwardly through a center opening 131 within the panel punch 118 for holding the shell 15 against the outer pressure sleeve 55 as the sleeve moves upwardly near the end of the pressed stroke, as shown in
Referring to
Referring to the enlarged fragmentation views of
The panel punch 118 has a flat top circular surface 163 surrounded by a tapered on frusto-conical surface 164, a substantial cylindrical surface 166 and an outer tapered or frusto-conical surface 168 which opposes the end surface 144 on the nose portion 140 of the inner pressure sleeve 80. As shown in
As shown in
When the upper die shoe 40 of the single action press arrives at the bottom of its downstroke (
As the die shoe 40 starts the upstroke (
The construction and operation of the tooling assembly 35 or 35′ has been found to provide the important and desirable features and advantages set forth above on page 1. For example, the compact tooling assembly is adapted to be operated on a single action mechanical press, and the reduced overall height of the tooling assembly enables the tooling assembly to be used in most single action high speed presses existing in the field. As another important advantage, the air reservoir chamber 70 and the set of circumferentially spaced air passages 88 within the die center piston 60 provide for using lower pressure air within the piston chamber 84, and the lower pressure air on the piston 82 of the inner pressure sleeve 80 reduces the generation of heat in the upper portion of the tooling assembly during high speed operation so that the tooling assembly produces more uniform and precise shells.
The pressurized air within the reservoir 70 and within the passages 88 also perform as air springs. These air springs not only reduce the generation of heat, but also provide for precisely selecting the resilient force exerted on the piston 82 of the inner pressure sleeve 80 to assure the desired precise clamping force on the disk 170 by the inner pressure sleeve 80 against the fixed die core ring 98. The tooling assembly 35 also permits the use of the lower pressure plant supply air, such as 80 to 90 p.s.i., to the piston 56 of the outer pressure sleeve 55, and the precisely controlled lower air pressure on the outer pressure sleeve avoids stretching of the sheet metal as the sheet metal slides between the outer pressure sleeve 55, the die core ring 98 and the blank and draw die during formation of the cup portion C.
A further advantage is provided by the normal projection of the nose portion 140 of the inner pressure sleeve 80 below the die center piston 65 so that the nose portion initiates the forming of the cup portion C, as shown in
While the apparatus or tooling assemblies herein described and their method of operation constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to the precise tooling assemblies and method steps described, and that changes may be made therein without departing from the scope and spirit of the invention as defined in the appended claims.
