US3475944A - Reverse forming arrangement and method - Google Patents

Description

Nov. 4, 1969 R. L. MARSHNER 3,475,944

REVERSE FORMING ARRANGEMENT AND METHOD Filed Dec. 30, 1966 v2 Sheets-Sheet 1 ROBERT L. MARSHNER h INVENTOR ATTORNEY R. L. MARSHNER REVERSE FORMING ARRANGEMENT AND METHOD Nov. 4, 1969 2 Sheets-Sheet 2 Filed Dec. 30, 1966 ROBERT L MARSHNER INVENTOR LL-D United States Patent 3,475,944 REVERSE FORMING ARRANGEMENT AND METHOD Robert L. Marshner, 9103 Simms Ave., Baltimore, Md. 21234 Filed Dec. 30, 1966, Ser. No. 606,069 Int. Cl. B21d 22/20 US. Cl. 72-347 11 Claims ABSTRACT OF DISCLOSURE A method and apparatus for forming a folded cup from material capable of permanent plastic deformation to a self-holding configuration, in which a mandrel having a thin flared head with an axially non-straight smoothly arcuate rim surface is employed to apply an axial reverse drawing force on a central area of a tubular cup, the thin arcuate rim zone also applying a radial restraining force to the cup during the reverse drawing and enabling ease of withdrawal of the mandrel from the cup after drawing.

This invention relates to an arrangement and method for reverse forming metallic or other permanently plastically deformable cups, and particularl cup seals which have a plurality of concentric tubular walls in an intermediate or final configuration form.

In the formation of metallic cups by reverse drawing, a problem is encountered in the extraction of the forming mandrels from the re-shaped cup after partial or full reverse drawing. This results from the radial compressive gripping action between the mandrel and the cup wall as the mandrel draws the cup material thereabout. In smaller diameter cups of one or two inches or the like or smaller in diameter this problem is not as aggravated as in larger diameter cups or cup seals, as for instance diameters of seven or eight inches or the like or larger. In the normal reverse drawing operation the mandrel is of the desired reverse drawn diameter for the cup along its effective length, even when the natural roll radius is permitted to be formed by the material during the reverse drawing operation, :and the resulting compressive gripping forces by the cup on the straight walled mandrel are quite high, particularly in the larger diameter cups, thereby posing a very substantial problem in removal of the mandrel from the reverse drawn cup. It is accordingly a major feature and advantage of this invention to provide an improved method and arrangement for forming cups or cup seals, and particularly cup seals having multiple concentric tubular walls, in which the removal of the mandrel from the cup is materially facilitated through reduction of the gripping action on the mandrel, while enabling forming of the same desired cup configuration.

Still other objects, features and attendant advantages will become apparent to those skilled in the art from a reading of the following detailed description, taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is an exploded view in perspective of an embodiment of an arrangement according to the invention,

FIGURES 2-6 are schematic illustrations of the practice of the method according to the invention,

FIGURE 7 is an illustration of a modified application of the method according to the invention.

Referring now in detail to the figures of the drawings, as shown in the exploded view of FIGURE 1 a flared headed mandrel 11 is employed to reverse draw a cup 21 which is adapted to be slidably removably disposed within a guide block 41 having a guide cap 51 removably fitting thereover for guiding of the flared headed mandrel 11 during the reverse drawing operations.

"Ice

The flared headed mandrel 11 has a flat head 13, and a reduced diameter smooth surfaced neck 15 on which is formed a threaded neck section 15a for receiving an adjustable stop nut 31, which adjustment may have an interference fit for secure adjustment. The smaller diameter end 15b of the mandrel 11 is preferably flat for advantageous application of force thereto in the forming operation on cup 21. The flared head 13 of the mandrel has a smoothly rounded annular rim 13a, and has a flat end surface 13b corresponding to the flat surface size desired in the end of the tubular portion of the cup upon completion of the reverse forming operation. In addition, the radius of curvature of the smoothly rounded annular rim 13a corresponds to the desired radius of curvature of the reverse formed cup at the zone of annular interconnection between the reverse formed cup end wall 21b (see FIG- URE 3) and the integrally adjoining inner tubular wall section 21a. This longitudinally rounded relatively thin rim configuration also aids in ease of removal, particularly when rocking removal motion is required, as later described. While other relative diameters may be employed and still yield some of the benefits of the invention, it is most advantageous and desirable that the outer diameter of the head 13 from rim-to-rim in diameter of the head 13 correspond to the diameter which will enable the cup to form a natural roll radius along the reversal zone 21] between the outer and inner cup sections 21a, 21a. This diameter for the mandrel head 13 can be determined for practical purposes by application of the following empirical formula:

where D is the original diameter of the cup 21 before the particular reverse drawing operation to be effected by the mandrel 11, t is the thickness of the tubular wall section 21a to be formed by the reverse drawing of the cup 21 by the mandrel 11, and consequently is also the diameter of the flared mandrel head 13.

Guide block 41 has a cylindrical bore 43 which terminates in a shoulder 49 at one end thereof formed by an end wall 45 having a central opening 47. The guide cap 51 has an annuar skirt 53 which is slidably removably complementary to the guide block 41. A central guide bore 55 is formed in the end wall of the guide cap 51 for guiding the reduced diameter neck 15 of the mandrel 11 in the reverse forming of the cup. In the operation of the method of the invention employing this apparatus, the cup 21 is slidably inserted into the cylindrical bore 43 in guide block 41, the cup preferably having an outer diameter D which is generally complementary to and provides an easy slip fit with the annular side wall of the cylindrical bore 43. The cup is seated with its open end 21c facing the central opening 47 in the guide block 41, and the seated edge surface abuts against the shoulder 49. Guide cap 51 is thereupon placed over the upper end of the guide block 41, with the flared headed mandrel 11 having its reduced diameter neck 15 slidably disposed in the guide bore 55, and its flared head 13 resting on the closed end wall 21b of the cup 21, as shown in FIGURE 2 The adjustable stop nut 31 may be adjusted to the desired position along the length of the threaded section 15a of the mandrel neck to provide the desired termination of motion of the mandrel and length for the inner cup tubular wall section 21a, or alternatively the flat supporting surface on which the guide block 41 is supported may in some instances serve as a stop for termination of the reverse drawing stroke motion of the cup 21, and/or for seating of the open end cup edge surface thereon.

In carrying out the method according to the invention, an axial force F is applied to the mandrel 15 as indicated 3 in FIGURES 3 and 4, and the cup 21.is thereby caused to plastically deform and roll through an annular reverse bend 21] to a reduced diameter inner tubular configuration 21a, the reduced diameter end wall 21b corresponding to the shape and size of the end of the flared head 13 of the mandrel. Force F is continued to be applied until the mandrel reaches the desired stop position, which in the case of cup seals may be at any desired intermediate position which provides a desired length for each of the outer wall 21a and inner wall 21a, such as that configuration illustrated in FIGURES 46. Upon completion of the forming motion of the mandrel the force F is removed and the guide cap 51 is removed from the guide block 41. This may normally be effected by exerting a relatively small pulling force on each of the guide cap and guide block, although in some instances it may also be desirable to exert a separating force on the reduced diameter end wall 21b in a direction toward the end cap 51 by application of a force through the central opening 47 of the guide block 41. In this separating operation the formed cup 21 is normally carried with the mandrel 11 and cap 51, as illustrated in FIGURE 5, and it thereupon remains only to exert a relatively small axial pulling force on the cup 21 in removing it from the flared head 13, or to rock the cup 21 away from the head 13 as shown in FIGURE 6. This is facilely accomplished in either case, as the compressive retaining forces are very materially reduced in the case of the head 13 as compared to the conventional straight mandrel, and also the rocking action is facilitated as will be noted by the reduced neck portion 15, whereas such cannot be effected with the normal straight sided mandrel. For instance, it has been found that an 8-inch mandrel of conventional straight walled construction requires 2 to 3 tons of removal force, whereas the extraction force with the present arrangement and method is reduced to approximately 100 pounds, and in many instances the removal of the mandrel from the completed cup form can be accomplished by hand. It will be appreciated, however, that these reduced extraction forces are only reduced to this minimum when the reversal diameter corresponds to that diameter d indicated in the equation previously discussed, whereby the reverse drawing is allowed to proceed through a natural reverse bend roll radius. Any substantial reduction of this natural roll radius formation will of course result in a tighter fit of the mandrel head within the reduced diameter tubular section, with consequent increased extraction force being required, although still being substantially less than that which would be required for a straight surfaced forming mandrel. Not only is the extraction force materially reduced by employing this invention, but also the time required to extract the mandrel is substantially reduced, and one can employ reduced capacity equipment in effecting the process, particularly the extraction aspect.

In FIGURE 7 is shown a modified application of the method, in which the adjustable stop nut 31 is adjusted to a position on the mandrel neck 15 such that the end of the reverse forming stroke occurs at an intermediate position between the ends of the final outer tubular wall section 21a, thereby providing a cup seal which when employed in an arrangement such as shown in US. Patents 3,106,131 and 3,119,302 will have a reduced expansion stroke as compared to the expansion stroke of the final cup 21 resulting from the application of the method as illustrated in FIGURE 4 in which the inner tubular section 21a is relatively longer than the final outer tubular section 21a.

It will be apparent that greater or lesser length or difference in length between the outer and inner tubular sections of the cup may be obtained as desired, and further additional smaller headed mandrels may be employed for further reverse forming the cup to a further interfolded reverse drawn position by application of the smaller diameter headed mandrel in the opposite direction against the resulting reduced diameter end wall 21b, in which case the annular bend 21 may rest against the shoulder 49 of the guide block 41, the shoulder 41 being made sufficiently wide to accommodate this engagement as may be necessary, or such may rest against the supporting surface 61, or a suitable smooth walled annular groove in the supporting surface 61 or a modified shoulder 49 to accommodate the annular bend 21) during this additional reverse forming operation.

While the invention has been described with respect to a single embodiment and several modes of practice of the invention, it will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope or spirit of the invention. Accordingly, it is to be appreciated that the invention is not to be limited by the illustrative embodiment and mode of practice, but only by the scope of the appended claims.

That which is claimed is:

1. The method of forming a cup from material capable of permanent plastic deformation to a self-holding configuration, comprising:

applying, through the medium of an annular force-applying head of smaller axial thickness at the rim zone than in rim diameter and with an axially non-straight smoothly axially convexly arcuate rim surface, an axial reverse drawing force on a central area of the closed end of a tubular cup having one closed end and an opposite open end,

reverse drawing said cup to a depth greater than the axial rim zone thickness of said force-applying head by application of said force to a reverse drawn length substantially greater than the cup-engaging thickness of said force-applying head while applying a radial restraining force to said cup by said smoothly axially arcuate rim zone surface on said head,

and separating said head from said cup.

2. The method according to claim 1, said separation being effected by applying opposing axial separating forces on said cup and said head.

3. The method according to claim 1, said separation being effected by applying opposing axial separating forces on said cup and said head while rocking said cup to disengage it from said head.

4. The method according to claim 1, said reverse-drawing force being applied while containing the longitudinal walls of said cup within a circumscribing radial-movement-restraining surface.

5. The method according to claim 1, including terminating said reverse drawing of said cup prior to drawing of the original cup form fully into the smaller diameter reverse drawn form, to thereby form a reverse-drawn cup having an outer tubular section and an inner tubular section integrally interconnected by a smooth annular reverse bend, the inner tubular section being closed at one end,

and applying a further reverse drawing force to said inner tubular section in the opposite direction, through the medium of a force applying head as in claim 1 in which the circular area of application of the force is smaller than the closed end of said inner tubular section,

terminating application of said further reverse drawing force prior to reverse-drawing of said inner tubular section fully into the next smaller opposite reverse drawn form to thereby form a reverse drawn cup having three concentric tubular sections sequentially integrally interconnected at their opposite ends,

and removing said cup from said head by application of axial separation forces to said head and said cup.

6. The method according to claim 1, said application of reverse drawing force to said cup by said head being effected by application of force to a central area on said head of substantially smaller area than the effective reverse draw force-applying of said head to said cup, the

circumferential spatial zone surrounding and between said smaller central area of force application on said head and the larger area of head applied force being open in the zone behind said head to thereby reduce the radial gripping engagement of said cup with said head in the course of reverse drawing and to minimize the required separation force between cup and head, as well as enabling rocking of said cup on said head during removal as may be required.

7. The method according to claim 1, said reverse drawing force being applied to a central area on said closed cup end of smaller diameter d than the outer diameter D of said cup by an amount permitting formation of the natural roll radius of the cup material during said reverse drawing of the material from the original cup wall form to the inner cup wall form.

8. The method according to claim 7, said smaller diameter d being substantially where t is the thickness of said cup wall.

9. A reverse drawing arrangement for reverse drawing cups comprising:

a guide block having a cylindrical bore for receiving a cup,

a force-applying reverse-draw mandrel having a flared head at one end for applying reverse-drawing force to a cup when disposed in said bore,

said mandrel head being of smaller diameter than said cylindrical bore by an amount suflicient to enable the formation of a natural roll radius in reverse drawing a given cup within said bore,

said mandrel having a reduced diameter neck formed behind said flared head of substantially longer length than said head length,

said flared head having a rounded rim zone of smooth non-straight axially arcuate curvature and being of substantially less axial length at its rim zone than in rim diameter.

10. A reverse drawing arrangement for reverse drawing cups comprising:

a guide block having a cylindrical bore for receiving a a force-applying reverse-draw mandrel having a flared head at one end for applying reverse-drawing force to a cup when disposed in said bore,

said mandrel head being of smaller diameter than said cylindrical bore by an amount suflicient to enable the formation of a natural roll radius in reverse drawing a given cup within said bore,

said mandrel having a reduced diameter neck formed behind said flared head of substantially longer length than said head length,

said fiared head having a rounded rim zone and being of substantially less axial length at its rim zone than in rim diameter,

said mandrel having a threadedly adjustable stop formed thereon rearward of said flared head,

said guide block having a radially inwardly extending annular shoulder at one end of said bore and forming a longitudinal central opening in said guide block,

and a guide cap removably disposed on the opposite end of said guide block,

said guide cap having a central guide bore therein coaxial with said guide block bore and of complementary sliding fit with said mandrel neck for guid ing of said mandrel during application of force thereby to a cup which may be in said guide block bore.

11. An arrangement according to claim 9,

the relationship of the mandrel head diameter d rela tive to the eflective cup diameter D being substantially where t is the thickness of the cup wall to be drawn.

References Cited UNITED STATES PATENTS 830,193 9/1906 Anderson 72348 1,187,461 6/1916 Knox 72348 1,649,841 11/1927 May 72 34s 2,179,194 11/1939 Passmore 72-347 3,139,670 7/1964 George 72348 RICHARD J. HERBST, Primary Examiner

Images