Abstract:
A method for forming a deep-drawn, one-piece, double-walled, cylindrical ring having tabs extending inwardly from the inner wall. The inner wall is formed and pierced to form the tabs. The outer wall is subsequently formed, or completed, to cover the tabs extending from the inner wall. In a preferred embodiment, the tab is formed with a bend by working the inner wall both outwardly and inwardly.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to deep-drawn metal stamping processes and more particularly to such processes permitting side piercing of the stamped objects. 
     Deep-drawn stamping is a well-developed and well-known art used to fabricate metal parts having significant depth. Initially flat metal stock is transferred through a series of stamping stations. Usually, the process is conducted on a transfer press having the stamping stations and a transfer mechanism for transporting the parts from station to station. 
     Deep-drawn stamping can be used to fabricate cylindrical objects having double (i.e. inner and outer) walls. However, in known deep-drawn processes, it is not possible to pierce (or otherwise work) either the inner wall or the outer wall because the double-wall structure prohibits simultaneous internal and external radial access to either wall. 
     SUMMARY OF THE INVENTION 
     The aforementioned problems are overcome in the present invention, wherein a process is provided for forming a double-wall, cylindrical object in which at least one of the walls is pierced or otherwise worked. More particularly, the process includes partially forming the object to create one of the inner wall and the outer wall, piercing or otherwise working the one wall while the one wall can be accessed internally and externally, and subsequently forming the other wall restricting internal or external access to the pierced wall. 
     In a preferred embodiments, the one wall is pierced to form a tab. In a further preferred embodiment, the tab is pushed radially inwardly to create a bent tab. 
     The present invention is a deep-drawn stamping process for forming a double-wall, cylindrical object having a pierced wall portion. The process is straightforward, efficient, and relatively inexpensive. 
     These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary perspective view of a sleeve assembly including a sleeve retainer fabricated in accordance with the process of the present invention; 
     FIG. 2 is a sectional view through the uncrimped sleeve retainer (i.e. prior to crimping onto the sleeve); 
     FIG. 3 is a perspective view showing the sleeve retainer after each forming step, or station, in the stamping process; 
     FIG. 4 is the first station drawing; 
     FIG. 5 is the second station drawing; 
     FIG. 6 is the third station drawing; 
     FIG. 7 is the fourth station drawing; 
     FIG. 8 is the fifth station drawing; 
     FIG. 9 is the sixth station drawing; 
     FIG. 10 is a plan view of the FIG. 9 piercing apparatus; 
     FIG. 11 is the seventh station drawing; 
     FIG. 12 is the eighth station drawing; 
     FIG. 13 is the ninth station drawing; and 
     FIG. 14 is the tenth station drawing. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     I. Sleeve Retainer 
     Oxygen sensors are positioned in the exhaust system of an automotive vehicle to monitor the relationship of fuel and air for optimizing engine performance and emission levels. The wiring harness extending from the oxygen sensor is connected to an on-board computer module. These wires are housed in a flexible, hollow, woven, plastic sleeve. Due to exposure to environmental conditions such as water, stones, and road debris, the sensor and harness must be protected. A metallic ring-shaped retainer is used to secure the flexible sleeve S to the oxygen sensor. 
     A sleeve retainer fabricated using the process of the present invention is illustrated in FIGS. 1 and 2 and generally designated 10. The retainer is a cylindrical, one-piece, deep-drawn, double-wall object that can be crimped onto the end of a fabric sleeve or hose S. The retainer 10 includes an inner wall 12, an outer wall 14, and a curved connecting portion 16. The free edge 20 of the inner wall 12 curves back into the retainer to facilitate installation of the retainer on a separate component (not shown), such as an oxygen sensor. 
     The inner wall 12 includes a plurality of integral tabs 30. In the preferred embodiment, four such tabs are included and are equally spaced at 90° intervals around the circumference of the inner wall 12. Each tab 30 includes a connector portion 30a integral with and generally parallel to the inner wall 12 and a bent portion 30b inclined radially inwardly from the connector portion 30a. The tabs 30 provide a retaining function when the retainer 10 is fitted over an object (not shown), such as an oxygen sensor. 
     II. Stamping Process 
     The process of the present invention is illustrated in FIGS. 3-14. Although the process is described in conjunction with a sleeve retainer, the process has applicability to wide variety of components. FIG. 3 shows the retainer after processing at each stage or station of the manufacturing process. FIGS. 4-14 illustrate the die sets used at each stage. The die sets are utilized is a conventional transfer press (not shown). The fabrication of the dies and their utilization in a press is well within the ability of one skilled in the art based on the present disclosure. 
     As previously mentioned, FIG. 3 illustrates the retainer 10 following processing at each station illustrated in FIGS. 4-14. A hyphenated suffix is used in each of the reference numerals in FIG. 3 to illustrate the corresponding figure station number. For example, the designating numeral 10-4 identifies the sleeve 10 as it exits the FIG. 4 station. 
     Turning to FIG. 3, the designating numeral 10-B identifies the blank from which the retainer is fabricated. The blank is cut from stock supplied to the process from a coil. 
     The FIG. 4 station operation is referred to as &#34;blank and cup&#34; because it cuts the blank 10-B from the stock and initially forms it into a cup. This station results in the partially formed retainer 10-4. 
     The FIG. 5 station is the first &#34;drawing,&#34; resulting in the partially formed retainer 10-5. Drawing increases the height of the cylindrical wall. 
     FIG. 6 illustrates the station in which the &#34;finish draw&#34; is performed resulting in the partially formed retainer 10-6. 
     FIG. 7 illustrates the first &#34;reverse draw&#34; station in which the inner wall 12 is partially formed resulting in the partially formed retainer 10-7. This station is referred to as reverse drawing because the closed end of the cylindrical material is drawn upwardly inside the drawn outer wall 14. 
     FIG. 8 illustrates the &#34;bottom pierce&#34; station wherein the bottom B is removed from the piece resulting in the partially formed retainer 10-8. The removed bottoms B are discarded. 
     FIG. 9 illustrates the &#34;side pierce&#34; station, and FIG. 10 is a plan view of the cam-actuated piercing mechanism in that station. As shown in FIG. 9 and at 10-9 in FIG. 3, a portion of the inner wall 12 of the sleeve may be freely radially accessed from both the interior and exterior sides of the wall. Such free access permits metal working operations to be performed on the inner wall at this point. Specifically as illustrated in FIG. 9, the inner wall is pierced to form tabs 30. Access to the interior side of the wall is important to support the inner wall during piercing. Access to the outside of the wall is necessary to enabling the piercing punch to extend through the wall. 
     As illustrated in FIGS. 9 and 10, the punches P are cam-actuated. The punches P are extended radially inwardly after the support die D has been inserted into the piece. While the punching operation removes material, leaving the tabs 30 defined. The punches P first push radially inwardly to form the tabs and then is pulled outwardly. The tabs 30 are pulled outwardly from the inner wall as the punches P are retracted resulting in the outwardly extending tabs 30 of the partially formed retainer 10-9. 
     FIG. 11 illustrates the &#34;extrude&#34; step wherein the free end of the inner wall is curved inwardly to produce the rounded edge 20 (see FIG. 2 also), resulting in the partially formed retainer 10-11. 
     FIG. 12 illustrates the &#34;tab form&#34; operation wherein the tabs are bent inwardly from the inner wall 12. The cam-actuated die pushes the tabs radially inwardly. The supporting die D-12a and pushing die D-12b cooperate to form the bend in the tab that separates the connector portion 30a and the bent portion 30b (see also FIG. 2). 
     FIG. 13 illustrates the &#34;re-reverse draw&#34; step wherein the inner wall 12 is re-drawn to the same height as the outer wall 14. This step completes the re-reverse process resulting in the partially formed piece 10-13 wherein the inner and outer walls are axially coextensive. After this step, the outer wall prohibits free radial access to the outer side of the inner wall. 
     Finally, FIG. 14 illustrates the &#34;trim out&#34; station wherein the waste flange is removed from the free end of the outer wall 14 resulting in the finished product 10 or 10-14. 
     The present invention provides a metal-forming process for forming a double-wall cylindrical object and for performing metal-forming operations on either or both of the cylindrical walls. The present invention therefore permits the fabrication of a wide range of metal components not previously possible, or possible only with significant difficulty. Therefore, the present invention enables a broader range of components to be fabricated more efficiently and less expensively than previously known in the art. 
     The above description is that of a preferred embodiment of the invention. Various changes and alterations can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law, including the doctrine of equivalents.