US3613427A

US3613427A - Forming die structure

Info

Publication number: US3613427A
Application number: US819850A
Authority: US
Inventors: Roger C Haddon
Original assignee: Aluminum Company of America
Current assignee: Alcoa Corp
Priority date: 1969-04-28
Filing date: 1969-04-28
Publication date: 1971-10-19
Anticipated expiration: 1988-10-19

Abstract

A FORMING DIE HAVING A BASE MMBER AND AN ELONGATED FORMING MEMBER SECURED TO THE BASE MEMBER, THE FORMING MEMBER HAVING AN INNER SURFACE, AN OUTER SURFACE AND A CONNECTING SHEET CONTACTING SURFACE. THE FORMING MEMBER DEFINES AN ELONGATED RECESS DISPOSED GENERALLY AT THE INTERSECTION OF THE INNER SUFACE AND THE SHEET CONTACTING SURFACE. A CYLINDRICAL ROLLER WHICH IS ROTATABLY SUPPORTED IS DISPOSED WITHIN THE RECESS. IN ONE FORM THE DIE IS PARTICULARLY SUITED TO BENDING DECORATED SHEET WITHOUT CREATING SURFACE DAMAGE. IT HAS TWO SPACED PARALLEL FORMING MEMBERS SECURED TO THE BASE MEMBER IN CHANNEL DEFINING POSITION. THE FORMING DIE MAY HAVE THE ROLLERS IN CONTACT WITH THE FORMING MEMBER WITHIN THE GENERALLY CYLINDRICAL RECESS OR MAY HAVE UNITARY OR SEGMENTED SPACER MEANS INTERPOSED BETWEEN THE ROLLERS AND THE FORMING MEMBER. THE SPACER MEANS HAS A CONCAVE SURFACE OF SUBSTANTIALLY THE SAME RADIUS OF CURVATURE AS THE ROLLER, IN CONTACT WITH THE ROLLER.

Description

on. 19, 1971 R. c. HADDON 3, 1

- FORMING DIE STRUCTURE Filed April 28, 1969 2 Sheets-Sheet 1 30 FIG. 30 y FIG. 20.

' FIG. 3.

INVEN TOR.

' l8 ROGER C. HADDON wamm Affarney zsheets -sheet 2 R- C. HADDQN FORMING DIE STRUCTURE FIG. 5.

Oct. 19, 1971 Filed April 28. 1969 FIG. 7.

I02 I04 I02 United States Patent O "ice 3,613,427 FORMING DIE STRUCTURE Roger C..I-Iaddon, Pittsburgh, Pa., assignor t Aluminum Company of America, Pittsburgh, Pa. Filed Apr. 28, 1969, Ser. No. 819,850 Int. Cl. B21d 9/10 US. Cl. 72212 Claims ABSTRACT OF THE DISCLOSURE A forming die having a base member and an elongated forming member secured to the base member, the forming member having an inner surface, an outer surface and a connecting sheet contacting surface. The forming member defines an elongated recess disposed generally at the intersection of the inner surface and the sheet contacting surface. A cylindrical roller which is rotatably supported is disposed within the recess. In one form the die is particularly suited to bending decorated sheet without creating surface damage. It has two spaced parallel forming members secured to the base member in channel defining position. The forming die may have the rollers in contact with the forming member within the generally cylindrical recess or may have unitary or segmented spacer means interposed between the rollers and the forming member. The spacer means has a concave surface of substantially the same radius of curvature as the roller, in contact with the roller.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to forming die structures and more specifically to die structures uniquely adapted to form metal sheet while avoiding damage to decorative surfaces thereof.

Description of the prior art One of the problems encountered in forming metal sheet by means of a complementary die and punch is that of avoiding surface damage to the sheet. While the problem is troublesome with respect to forming of any sheet material, this problem is particularly acute when the sheet being worked upon is a decorated or patterned sheet and the forming is effected solely or to a substantial extent by bending. The problem is present regardless of whether the bending operation is a single bending stage or a multiple bend.

As such surface damage contributes substantially to waste through rejection of the ultimate product, various means of minimizing this problem have been employed. It is known to attempt to reduce such surface dam age by use of dies made of rubber. As these dies have an extremely short die life as compared with dies made from more conventional material such as tool steel, the increase in cost of replacement is substantial.

It has also been known to attempt to minimize damage to the sheet surface by employing various types of lubricants. While such an approach tends to be helpful, it is frequently imprecise and results in a lack of product uniformity. Also, additional attention of workmen must be directed toward the provision of an adequate amount of lubricant.

It has also been known to periodically refinish the die radius in order to remove irregularities which contribute to undesired surface defects. This form of continuous maintenance not only requires periodic shutdown of a fabricating line, but also requires the expense of the labor involved in refinishing the die.

US. Pat. 2,908,315 suggests the use of large floating 3,613,427 Patented Oct. 19, 1971 rollers disposed within V-shaped grooves in a sheet bending operation. A punch cooperates with the tworollers to establish a channel shaped bend in the metal sheet. It is noted that a minimum of scratching of the sheet will occur as the relative movement between the sheet and female die is reduced through the use of rollers. As the rollers employed in this patent are retained in operating position solely by gravity, the female die contemplated by the invention described in that patent could be employed only in a horizontal upwardly open position. Also, in view of the nature of the fit between the rollers and the grooves, a region for undesirable accumulation and entrapment of metal particles and other foreign materials is provided underneath the rollers. This material may readily be transferred from the rollers to the workpiece or create a surface defect therein through contact with the foreign material on the rollers. One additional disadvantage of the system disclosed in this patent is the need to substitute rollers each time a change in product configuration is contemplated. A further disadvantage of the system disclosed in US. Pat. 2,908,315 is that by establishing a given diameter of roller, one also freezes the flexibility with respect to depth of member which may be formed.

SUMMARY OF THE INVENTION The above enumerated problems have been solved by the die structure of this invention. The die structure of this invention provides a base member and one or more upstanding forming members secured to the base member. Each forming member has an inner surface, an outer surface and a connecting sheet contacting surface. The forming member defines an elongated recess which is disposed generally at the intersection of the inner surface and sheet contacting surface. A cylindrical roller is rotatably supported within the recess.

In the embodiment of the invention wherein a single forming member is provided the die may be effectively employed in cooperation with a suitable punch to perform wiping or single bend operations on a sheet.

In embodiments of the invention employing two forming members they may be disposed in parallel spaced relationship to cooperate vwth the base member in defining a channel shaped die structure suitable for forming simultaneous double bends in a sheet. As the height of the forming member may be determined independently of the diameter of the rollers, the depth of bend may be readily established independent of the roller diameter.

In one form of the invention the recess in the forming member is of complementary configuration to the roller and is in contact therewith. This contact provides a cleansing or wiping action to the roller and prevents pick-up of foreign materials which are potentially damaging to the sheet surface. An alternative structure contemplated by this invention provides a roller retaining insert or spacer which is received within the elongated recess of the form ing member and has a complementary concave surface in contact with the roller. This spacer is preferably made from a material having a lower coeflicient of friction than the forming member. This serves to increase the freedom of rotation of the roller.

In another form of the invention, the roller receiving spacer may be a plurality of spacer elements positioned within the recess at spaced intervals. A suitable filler material may be positioned in the gaps between spacer elements.

It is an object of this invention to provide a sheet forming die having roller elements rotatably secured thereto in such a manner as to resist scratching or defacing of the sheet surface during the forming operation.

It is another object of this invention to provide a bending die structure which is so designed as to resist accumulation of dirt at any sheet contacting roller posi tion and also to provide positive roller cleaning means to continuously remove any foreign material deposited upon the roller.

It is another object of this invention to provide a bending die adapted for variations in width or depth of a multiple bend without requiring alteration of roller size.

It is another object of the invention to provide a sheet metal bending die having relatively small roller members secured to the die in such a manner as to permit free rotation thereof and so structured as to reduce the likelihood of galling of the rollers.

These and other objects of the invention will be more fully understood and appreciated from the following detailed description of the invention on reference to the illustrations appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of one form of die structure contemplated by this invention.

FIG. 2 is a sectional elevational view of the die illustrated in FIG. 1, taken through 22, showing also a metal sheet and complementary punch.

FIG. 2a illustrates an enlarged detailed representation of the encircled portion of FIG. 2.

FIG. 3 is a sectional elevation illustrating the die structure of FIG. 2 with the metal in an intermediate stage of bending.

FIG. 4 is a sectional elevation of a modified form of die structure of this invention showing the sheet in the final bending stages.

FIG. 5 illustrates a sectional elevation of another embodiment of this invention showing a die member employed in a wiping or single bend operation.

FIGS. 6 and 7 illustrate top plan sectional views showing embodiments of the invention employing segmented roller receiving or spacer elements.

FIG. 8 illustrates a sectional elevational view of a modified form of spacer member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more specifically to the drawings, with particular reference to FIGS. 1 and 2, there is illustrated a die structure having a base member 2 with a pair of forming members 4 secured to the base member 2 and upstanding therefrom. The forming members 4, in the form illustrated, are disposed generally perpendicular to the base member 2 and are positioned in parallel spaced relationship with respect to each other. The forming members 4 each have an inner surface 6, an outer surface 8 and a connecting sheet contacting surface 10. The forming members each have a generally cylindrical re cess defining wall 16 disposed generally at the intersection of inner surface 6 and connecting sheet contacting surface 10.

The forming members 4 cooperate with the base member 2 to define a generally channel shaped die opening 18. The recess defining walls 16 are positioned in overlying spaced relationship with respect to the base member 2 and are disposed on opposed sides of the entrance to the die opening 18.

A substantially cylindrical roller member 20 is received within the recess defined by wall 16. In the form illustrated, a spacer member 22 is interposed between wall 16 and roller 20. Both the roller 20 and the spacer member 22 are continuous and substantially coextensive with the recess defined by wall 16. The spacer member has a concave surface 24 of substantially the same diameter as the roller 20 which is in substantially continuous contact with the roller 20 over a substantial portion of the roller surface. it is generally preferred that this contact exist over approximately /2 or a major portion of the roller circumference. The spacer member 22 also has a convex surface in contact with wall 16.

As is shown in FIG. I, opposed ends of rollers are rotatably journaled within openings in end walls or plates 32. The rollers are, therefore, positioned in the entrance to die opening 18, are secured to the forming member 4 but are journaled for free rotation therein. As is shown in FIG. 2a the contact between roller 20 and spacer 22 is such that no meaningful voids which could facilitate the accumulation of metal particles or other potentially harmful foreign materials are present. This not only reduces the likelihood of galling of the rollers through contact with such materials, but also reduces the likelihood of impairment of the surface characteristics of the metal sheet being formed. As a result of the freedom of rotation provided at the entrance to die opening 18, the metal being moved over the rollers 20 is subjected to rolling frictional contact with the roller rather than sliding frictional contact with a rigid die portion. This reduced force also contributes to the reduced likelihood of sheet or die surface damage.

Another feature of this invention, as is illustrated in FIG. 2a, is the provision of a roller wiping or cleaning structure. Insert or spacer 22, in the form illustrated, contacts the roller 20 substantially continuously within the recess between initial contact point 34 and terminal contact point 36 along surface 24. Any dirt which might be picked up on the exposed surface 38 of roller 20 will upon continued rotation of the roller 20 be brought into contact with initial contact point 34 which will restrain the dirt particles against continued movement with the roller and will thereby provide a wiping action which frees the dirt from the roller. Terminal contact point 36 prevents entry of air-borne materials into the space between the roller and the spacer member 22.

In the emobdiment shown in FIG. 4 a slightly different form of roller die structure is illustrated. The roller 20 is in direct contact with the recess defining wall 16 of forming member 4. (For clarity of illustration, a slight space between roller 20 and wall 16 has been shown.) The configuration of wall 16 is complementary with respect to the surface of roller 20 with contact being substantially continuously maintained from initial contact point 40 through terminal contact point 42. While this form eliminates the need for use of spacing member 22, this benefit is somewhat reduced by the need for more precise machining of wall 16.

Another form of die assembly is shown in FIG. 8 wherein roller 20 is received within spacer member 50. Forming member 4 has a generally rectangular recess defined by

surfaces

52, 54. A complementary rectangular surface is provided in spacer member 50. Spacer member also has a curved surface 56 in substantially continuous contact with roller 20. By employing this configuration in spacer member 50 the amount of precision machining required to establish a roller receiving recess within forming member 4 is greatly reduced.

Referring now more specifically to FIGS. 2 through 4, it is seen that a sheet or plate 60 is positioned on sheet contacting surface 10 of forming members 4. While it will be appreciated that the die of this invention may be employed with sheet material of various gauges including foil, sheet and plate, for simplicity of disclosure, reference will be made herein to the sheet contacting surface. A punch 62 is positioned on the opposite side of the sheet from the forming member 4. FIG. 2 illustrates the apparatus prior to the initiation of bending, FIG. 3

shows an intermediate stage with a portion of sheet m0ving over the rollers 20 as the punch 62 moves into the die opening 18 and FIG. 4 shows the punch, die and formed sheet in a final forming position.

Referring now to FIG. 5, another form of the die of this invention is illustrated. In this form of the invention a female die is disposed in overlying relationship with respect to a punch 72 and a sheet 74 is interposed. The original position of forming member 76, which is secured to press crossbeam 82, and sheet end 74a are illustrated by the dotted line. The final position of the forming member 76 and sheet end 74a are illustrated by a solid line. In this form of the invention a single forming element is provided in order to form a single bend by wiping end portion 74a of sheet 74 downwardly. This may be accomplished by moving the forming member 76 downwardly While restraining the underlying punch against movement.

It is noted that in this form of the invention the roller 78 extends inwardly toward the sheet 74 a distance R greater than the inner surface 80 of forming member 76. In general, the exposed surface 84 of roller 78 will terminate in relatively close proximity to the planes of one or both of inner surface 80 and sheet contacting surface 86. It is preferable, however, in order to minimize the likelihood of damaging contact between the sheet and surfaces 80, 86 to so position the roller that it extends outwardly beyond one or both of

surfaces

80, 86 by a finite distance.

In connection with the spacer member 22 it is preferable to have a longitudinally continuous member which is coextensive in length with the recess in forming member 4 and is also continuous in a transverse direction and coextensive with recess defining wall 16. This spacer member 22 serves to maintain the roller 20 in non-contacting position with respect to wall 16. This reduces the likelihood of wear of wall 16 of forming member 4 through moving contact with roller 20. Also, the spacer member may advantageously be manufactured from a material having a reduced coeflicient of rolling friction with respect to the roller 20 with the material of the forming member. The reduced coefficient of friction provides for increased free rotation of the rollers and improved performance thereof. One of the preferred materials for such use is Teflon which has the desired hardness and lubricating properties. A number of other suitable plastic materials may also be advantageously employed. Another suitable material is a plastic filled with particles of molybdenum disulfide. To provide effective contact with the roller the circumferential extent of contact between the spacer member 22 and roller 20 is preferably about 180 or more. The transverse extent of spacer member contact will, therefore, preferably be over a major portion of the roller.

It will be appreicated that the freedom of rotation of the rollers may be improved even more by employing segmented spacer elements 90, as is shown in FIG. 6. These elements reduce the amount of surface to surface contact with roller 20. In the form illustrated in FIG. 6 the elements 90 which are of substantially the same circumferential extent as spacer member 22 are secured within inwardly directed curved embossments transversely positioned on the recess defining wall 16. In order to maintain the self-cleaning feature of this invention it is preferred to employ a filler material 96 in the intervals disposed between the spacer elements 90. This material 96 prevents entry of foreign materials into the recess. Any suitable material such as felt for example, may be employed for this purpose. As is also shown in FIG. 6, the roller 20 has a necked-in terminal extension 98 which is rotatably secured within bearing 109 which in turn is supported in an opening in end wall or plate 32.

Another form of segmented spacing elements 102 is illustrated in FIG. 7. In this form the spacing elements 102 are positioned within curved recesses transversely positioned in surface 16. This results in gaps 104 of reduced size as compared to those shown in FIG. 6. In this illustration no filler material is provided in gaps 104.

The rollers of this invention will generally be made of hardened and ground steel which may, if desired, be provided with a suitable protective coating. As the rollers will be inserted into the die at a position where a rigid die would normally have a radius, the rollers will generally be relatively small. A preferred size for most bending dies is about to 1 inch in diameter.

In conventional generally channel shaped bending dies, it is customary to provide for adjustability of the width of channel opening 18. One conventional means of accomplishing this is by employing shims (not shown) disposed at the exterior of inner surface 6. While the forming memher in the forms illustrated herein has been shown as a generally solid member, it will be appreciated that it may be assembled from a number of elements, some of which may be shim elements adapted to be removed or inserted in order to adjust the width of channel opening 18. It will be appreciated that the roller assembly of this invention is adapted for use with such adjustable dies, without requiring removal or substitution of roller members. This adjustment may, therefore, be effected independently of the structure of this invention which is compatible with such adjustment.

The roller assembly of this invention is such that the depth of forming or bending which may be effected within a given die is not directly related to the roller diameter. It is, therefore, another advantage of this invention that either the diameter of the rollers or the depth of channel opening 18 may be altered independently of each other.

It will be appreciated that the die structure of this invention may be advantageously employed with dies for various types of forming of various types of sheet including undecorated sheet, textured sheet or sheet which has a decorative coating or film as provided by painting, anodizing or lamination. The rollers are rotatably secured within a recess in the die. The die structure is so configurated as to resist entry of dirt, metal particles and other foreign materials into the region between the roller and the forming member. In addition, structural means are provided to cleanse the roller by wiping as it rotates to thereby remove foreign particles therefrom. This results in resistance to galling of the roller as well as surface damage to the sheet being formed.

The roller assembly of this invention may advantageously be provided with an underlying spacer member which increases the rotational freedom of the roller and effects positive wiping action to remove dirt from the roller surface. In addition, the use of such a structure reduces the amount of precision machining which must be accomplished in order to provide the elongated recess in the forming members. These spacers may be both longitudinally and transversely continuous or may be provided in the form of segmented spacer elements. The rollers are positioned within the recess and preferably project inwardly a slight distance beyond the normal radius of curvature of the die in order to reduce the likelihood of potentially destructive contact between the sheet surface and stationary portions of the forming member. In addition, the die structure of this invention substitutes the reduced rolling frictional force for sliding frictional force and thereby facilitates ease of forming. This feature also serves to reduce the tension placed upon the sheet during bending and thereby reduces the likelihood of tensile failure of the sheet. In addition, this invention may be employed with a single forming element to form a single bend or two or more forming elements.

Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that numerous variations of the details may be made without departing from the invention as defined in the appended claims.

What is claimed is:

1. A sheet forming die comprising:

a base member,

said die is a bending die,

an elongated forming member secured to said base member, said forming member having an inner surface, an outer surface and a connecting sheet contacting surface,

said forming member defining an elongated recess disposed generally at the intersection of said inner sur face and said sheet contacting surface,

a single cylindrical roller disposed within said recess,

fixed spacer means disposed within each said recess intermediate said forming member and said cylindrical roller to retain the working surface of said roller in non-contacting position with respect to said forming member,

support means rotatably securing said roller within said recess,

said die having two said forming members secured to said base member,

Said support means having journals disposed at opposite ends of each said roller,

said forming members extending upwardly from said base member in parallel spaced relationship with respect to each other to define a generally channel shaped die with said rollers disposed at the entrance in spaced overlying relationship with respect to said base member,

each said elongated recess being of generally cylindrical configuration,

said inner surface disposed at substantially right angles with respect to said sheet contacting surface,

said rollers having a diameter of about to 1 inch,

said spacer means having a plurality of back-u elements disposed within said recess at spaced intervals along the length of said recess, and

each said back-up element disposed in substantially continuous contact with a transverse section of the surface of said roller and extending circumferentially over at least a major portion of said section.

2. The bending die of claim 1 including:

felt filler members disposed within said recess at the spaced intervals between said back-up elements.

3. A sheet forming bending die comprising:

a base member,

an elongated forming member secured to said base member,

said forming member having an inner surface, an outer surface and a connecting sheet contacting surface,

said forming member defining an elongated recess disposed generally at the intersection of said inner surface and said sheet contacting surface,

a single cylindrical roller disposed within said recess,

said spacer means having an elongated friction reducing back-up member provided with a concave roller contacting surface having substantially the same radius of curvature as said roller,

said support means having journals disposed at opposed ends of said roller,

said back-up member being substantially continuous and longitudinally coextensive with said recess,

said back-up member is in substantially continuous longitudinal contacting position with respect to said roller within said recess, and

said substantially continuous contact between said backup member and said roller includes a circumferential arc of said roller of greater than 180 but less than 360, whereby said roller is rotatably secured within said recess in said back-up member and is retained in surface to surface contact therewith while having an exposed forming surface.

4. The sheet forming die of claim 3 including:

said die having two said forming members secured to said base member,

said forming members extending upwardly from said base member in parallel spaced relationship with respect to each other to define a generally channel shaped die with said rollers disposed at the entrance in spaced overlying relationship with respect to said base member, and

each said elongated recess being of generally cylindrical configuration.

5. The sheet forming die of claim 4 including said back-up member is composed of Teflon, and

said rollers have a diameter of about /8 to 1 inch.

References Cited UNITED STATES PATENTS 2,647,552 8/1953 Magnuson et al 72-213 3,457,759 7/1969 Doerr et a1 72212 FOREIGN PATENTS 1,167,640 4/1964 Germany 72-386 978,861 12/1964 Great Britain 72386 580,506 8/1958 Italy 72386 OTHER REFERENCES The Tool Engineer; Press Brake Design for Magnesium by Alfred E. Blatter; vol. 34, No. 6; June 1955, p.

RICHARD J. HERBST, Primary Examiner US. Cl. X.R.