US20130061728A1

US20130061728A1 - Draw punch and method of making different shaped cutouts

Info

Publication number: US20130061728A1
Application number: US13/699,713
Authority: US
Inventors: K.N. Prabakar
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-05-28
Filing date: 2011-05-25
Publication date: 2013-03-14
Also published as: WO2011148393A1

Abstract

A draw punch assembly for making one or more desired cutouts in a work piece is disclosed. The draw punch assembly includes a draw punch with a peripheral cutting edge on an outer surface and a bending edge on an inner surface, and a die with a shaped cavity for receiving a slug, where the slug is a cutout portion of the work piece. The die and the draw punch maintain a pre-defined clearance with respect to each other during operation.

Description

TECHNICAL FIELD

The invention relates generally to a draw punch and more specifically to a punch and a die for making different shaped cutouts on a work piece and for removing slug from the work piece like sheet metal and the like.

BACKGROUND

Metal working methods involve several techniques like punching, coining, bending, and several other ways of modifying metal raw material to yield the desired shapes. In punching, typically a punch press is used to push a punch through a material and into a die to create a hole or a cutout in the workpiece. A scrap slug from the hole is deposited into the die in the process. Depending on the material being punched this slug may be recycled and reused or discarded. The different cutouts shapes that are desirable include both round and non-round shapes like square, oval, elongated rectangular and trapezoidal openings, for example, to receive connector sockets in computer housings, and punches have been developed to meet these applications.
In the current techniques, the hole walls usually are not neatly cut and show burnished area, rollover, and cause die break and must often be further processed. The slug usually causes a jam when the punch is being removed from the die after the cutting process, and removal of the slug from the die is often difficult and time-consuming. Frequently, another tool such as a screw driver is used to free the punched slugs. Further, because of the jam the threads on the bolts used to align the work piece, die and punch are damaged and need to be replaced frequently. Further the punch may itself break while the slug is being removed from the die.
Splitter punch is one technique which attempts to address the slug removal problem to some extent by splitting the slug during the cutting process so that it breaks into smaller pieces and can be removed easily.
U.S. Pat. No. 4,905,557 discloses one such splitter punch that includes peripheral cutting edges and lateral cutting edges. The peripheral edges of the punch cut a slug in the desired shape, while the lateral edges cut transversely from one peripheral edge to an opposite peripheral edge, thereby splitting the slug. Lateral cutting edges and peripheral cutting edges at their juncture provide pyramidal cutting sections which initially pierce the workpiece and initiate lateral slug splitting. This split grows from the slug periphery toward the center. Splitting is complete before a substantial portion of the slug periphery is cut. Though the split type punches address the slug removal problem to some extent, it is desirable that the slug is not split so that it can be used for some other applications.
Other draw punches, for example the embodiment of the U.S. Pat. No. 5,543,722 cause undesirable high force requirements when applied to non-round openings for punching with slug splitting.
Further, there are several applications where large diameter holes are needed in the sheet metal, for example for the electrical panels, the prior art punches currently do not have the ability to make large diameter cutouts, since there is no close tolerance between bolt and the draw punch.
Thus there is a need for a draw punch that obviates the problem in the prior art related to slug splitting, slug removal, high force requirements, and is also able to make cut-outs of any desirable diameters, and shapes.

BRIEF DESCRIPTION

In one aspect, the invention provides a draw punch assembly for making one or more desired cutouts in a work piece. The draw punch assembly includes a draw punch with a peripheral cutting edge on an outer surface and a bending edge on an inner surface, and a die with a shaped cavity for receiving a slug, where the slug is a cutout portion of the work piece. The die and the draw punch maintain a pre-defined clearance with respect to each other during operation.
In another aspect the invention provides a method for making one or more desired cutouts in a work piece. The method includes providing the draw punch assembly as disclosed herein above, aligning the draw punch, the work piece, and the die; moving the draw punch towards the die; shearing the work piece by the draw punch to yield the one or more desired cutouts and a slug; bending a slug to obtain bended slug during the shearing; and receiving the bended slug in the shaped cavity of the die.

DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagrammatic representation of an exemplary embodiment of the draw punch assembly for making a round shaped cutouts;

FIG. 2 and FIG. 3 are different views of the draw punch assembly of FIG. 1;

FIG. 4 is a diagrammatic representation of an exemplary embodiment of the draw punch assembly for making square shaped cutouts;

FIG. 5 and FIG. 6 are different views of the draw punch assembly of FIG. 4;

FIG. 7 is a diagrammatic representation of a flypress adaptation of the draw punch assembly of FIG. 1; and

FIG. 8 is a diagrammatic representation of a flypress adaptation of the draw punch assembly of FIG. 4.

DETAILED DESCRIPTION

As used herein and in the claims, the singular forms “a,” “an,” and “the” include the plural reference unless the context clearly indicates otherwise.
As used herein a work piece is a sheet metal piece including a fabricated and powder coated readymade panel.
As used herein a draw punch is a machine tool used to cut holes in a work piece. The draw punch as used herein includes a manually operated hand tool and a flypress adaptation.
As used herein a die is a specialized tool that is a counterpart for the draw punch used cut a work piece, the die is customized to the shape of the desired cutouts.
As used herein a slug is a cutout portion of the work piece, usually treated as scrap or waste or may be recycled.
An exemplary embodiment includes a draw punch assembly for making one or more desired cutouts in a work piece. In one example the draw punch assembly includes a draw punch with a peripheral cutting edge on an outer surface and a bending edge on an inner surface. The dimensions and configuration of the said draw punch are predetermined to get the exact required dimensions in the cutout so that there is no need for further rework which is usually a big disadvantage in the prior art draw punches. Advantageously the dimensions of the draw punch can be configured for making different standard size of cutouts by proper nesting with the help of the auto cad drawing printouts and templates.
The draw punch assembly further includes a die with a shaped cavity for receiving the slug. During operation, the die and the draw punch maintain a pre-defined clearance with respect to each other as the draw punch is slowly moved closer to the die. The shape of the cutting edge and the bending edge of the draw punch and the clearance between the draw punch and the die enables the slug portion of the work piece to slowly shear and bend and helps in pushing the slug into the shaped cavity of the die. Further the clearance between draw punch and the die is obtained by accommodating very close tolerance between a bolt that is used to align the draw punch, die and work piece, and the draw punch.
It will be further appreciated by those skilled in the art that the peripheral cutting edge and the bending edge of the draw punch bends the slug in the cutting process so that it does not jam inside the cavity of the die.
It may be appreciated by those skilled in the art that compared to prior art draw punches, there is no split in the slug as obtained from the different embodiments of the invention. The slug is a single piece like a washer with a center hole.
It would also be appreciated by those skilled in the art, that the draw punch assembly can be configured and dimensioned to cover different shaped cutouts, for example, but not limiting to standard square/rectangular cutouts dimensions like 45×45 mm 45×92 mm 92×92 mm, 33×33 mm, 68×68 mm and 135×135 mm or around dimension like 16 mm, 19 mm, 22.5 mm, 29.5 mm and 31.5 mm can be easily made so that most of the digital and analog, electric and electronics meters, PG glands, push buttons, lamps can be easily fitted with these cutouts, without any scratches on the surface either on the instrument or on the panel surface.
An exemplary embodiment of the draw punch assembly 10 as a circular assembly for making a round shaped cutout is shown in FIG. 1. The circular draw punch 12 has a peripheral cutting edge 14 on an outer surface 16 and a bending edge 18 on an inner surface 20. The circular assembly further comprises a circular die 22 with a circular shaped cavity 24, also sometimes referred to as slug cavity, a bearing 26 and a bolt 28. It would be appreciated by those skilled in the art, that the bolt 28 along with bearing 26 ensures smooth rotation of the draw punch so that axial force can be applied to the draw punch to cut the work piece smoothly, slowly and steadily. Cutting edge of the punch enables the slug portion of the cutout to bend and make to fall towards the shaped cavity of the die.
FIG. 2 and FIG. 3 show a front view 30 and a side view 32 respectively for the circular assembly of FIG. 1.
FIG. 4 is another exemplary embodiment of the draw punch assembly 34 for non circular cutouts. In many applications the cutouts needed are non-round, for example square, oval, elongated rectangular and trapezoidal openings for installation of electrical meters and process meters, MCB's, cooling fans especially on powder coated wired panels i.e. after bending and powder coating of panels. The exemplary embodiment 34 is shown for square shaped cutouts, and those skilled in the art will understand that the same principles can be used for fabricating draw punch assembly for other non-circular shapes like rectangular, oval, trapezoidal etc.
The non circular assembly 34 includes a non-circular draw punch 36, for example a square shaped draw punch with a peripheral cutting edge 38 on an outer surface 40 and a bending edge 42 on an inner surface 44.
The non circular draw punch assembly further includes guide pins 46, which help to slide the draw punch 36 along the guide pins to move it closer to a non circular die 48. For square shaped cutouts, the die 48 is square shaped with a square shaped cavity 50. Similarly, for other shaped cutouts, the die and shaped cavity will be of the corresponding shapes. Other components of the non circular assembly include a guide pin mounting plate 52, screws 54 for attaching the guide pin mounting plate with the die, bearing 56, bolt 58 and dowel 60 to help in aligning the different components of the draw punch assembly. Guide pins in the die helps to slide the draw punch so that it ensures equal clearance, which is allows for smooth cutting to avoid any misalignment between the die and the draw punch.
In use, the draw punch 36 and die 48 are axially aligned with the work piece (not shown) located there between, and the draw punch 36 and die 48 are brought closer and closer together with the help of guide pins 46 until the punch is tightened to the work piece. In the process the work piece is sheared by cutting edge 38 of the draw punch 36. As the draw punch 36 moves closer to a correspondingly shaped cavity 50 of the die 48, the curved shape or the bending edge 42 of the draw punch 36 bends the slug after cutting, so that it falls easily into the shaped cavity 50 of the die. It would be appreciated by those skilled in the art that as explained hereinabove, with the use of these embodiments, there is no splitting of the slug which is a common problem in the prior art draw punch tools. Also it would be appreciated by those skilled in the art that the perimeter (cutting length) of the cutting edge is lesser than that is provided in the prior art draw punches. This advantageously results in increasing the life of the draw punch and bolts, and decreases the time consumed for single punching operation because the travel distance between the die and draw punch is less as compared to the prior art draw punch tools.
Further as shown in FIG. 4, a particular working embodiment of the invention includes legs 62, which comprises radial bending surface 64 and the cutting edge 38 is U-shaped and one side 66 of the U-shape of the draw punch is deeper compared to other side 68 which enables much lesser punching force at the end of the cutting and also it enables more bending of the slug for easy removal from the shaped cavity.
It may be further noted that the radial inner surface 66 of the legs 62 of the draw punch 38 are set to an angle transverse to the direction of the punch motion, and not perpendicular. This further facilitates the bending of the slug while cutting and also reduces the required punching force by providing localizing cutting rather than cutting around entire periphery simultaneously. Thus, the peripheral edges cuts a slug in a desired shape for ex: rectangular, square, trapezoidal, circular etc., and the bending surface bends the slug part transversely from one corner from the corner of the slug there by makes the slug bend according to the curvature of the inner radial surface of legs of draw punch.
The present embodiments of the invention reduce punch force requirements, provide a clean cutout and a readily removable bended slug. This is in contrast with the prior art draw punch tools where the cutting edge causes undesirable high force requirements when applied to non round openings for punching.
Further, the cutting edges cut right angle patterns onto the work piece, to initially pierce the work piece and bend the slug, this bending of slug grows from corners of the legs towards the center of the draw punch. This priority cutting arrangements assures that, the slug is adequately supported at the periphery while it is being bended.
In one specific embodiment, equal clearance is provided between die and draw punch which helps in equal distribution of shearing force along the four sides of the square/rectangular cutouts.
FIG. 5 and FIG. 6 show a front view 70 and a side view 72 respectively for the non-circular assembly of FIG. 4.
In the different embodiments described herein, the die and draw punch may be fabricated from a special alloy tool steel to get excellent edge holding properties, abrasion resistance and dimensional stability. High working hardness of the die and draw punch may result in the slight wearing out of the guide pins and bolts while sliding, but this will not affect the tool life since only the bolts and guide pins are the wear out parts, and are easily replaceable.
Some specific embodiments include draw punches as hand tools and other embodiments working as fly press on the same principles. The hand tool version of the draw punch as disclosed herein do away with the need for any electric or pneumatic drive attached to the operation so that even an ordinary layman can easily use this tool safely without any risk even at the site. It will also be understood by those skilled in the art that embodiments of the draw punch assembly as disclosed herein may also be adapted as flypress versions that will allow for making multiple cutouts with ease and efficiency. FIG. 7 and FIG. 8 show the flypress versions for a circular draw punch assembly 74 and a non circular draw punch assembly 77. Additional components like springs 78, and support plates 80 and 82 are additionally provided for these embodiments.
Thus the different embodiments of the invention are advantageous for making different shaped cutouts on work pieces, and for bending the slug which falls free in the shaped cavity of the die. Further these embodiments require low operative force and ensure extended life of the draw punch and its components.
The different embodiments are useful for electrical contractors, electrical panel fabricators, special purpose machines manufacturers, automation industry, retrofitting for the running machines, maintenance depts. and other electrical and electronics related works.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

1. A draw punch assembly for making one or more desired cutouts in a work piece, the draw punch assembly comprising:

a draw punch with a peripheral cutting edge on an outer surface and a bending edge on an inner surface; and

a die with a shaped cavity for receiving a slug, wherein the slug is a cutout portion of the work piece,

wherein the die and the draw punch maintain a pre-defined clearance with respect to each other during operation.

2. The draw punch assembly of claim 1 further comprising a bolt and a bearing to support the die and the draw punch.

3. The draw punch assembly of claim 1 further comprising one or more guide pins to axially align the draw punch, the work piece and the die.

4. The draw punch assembly of claim 1 wherein, the die is a circular shaped die, and the draw punch is a circular shaped draw punch.

5. The draw punch assembly of claim 1 wherein, the die is a non-circular shaped die, and the draw punch is a non-circular shaped draw punch.

6. The draw punch assembly of claim 5 wherein the non-circular shaped die and the non-circular shaped draw punch are at least one of a square shaped or rectangle shaped.

7. The draw punch assembly of claim 1 wherein the work piece is a sheet metal work piece.

8. The draw punch assembly of claim 1 wherein the peripheral cutting edge is U shaped.

9. A method for making one or more desired cutouts in a work piece, the method comprising:

providing a draw punch assembly for making one or more desired cutouts in a work piece, the draw punch assembly comprising a draw punch with a peripheral cutting edge on an outer surface and a bending edge on an inner surface, and a die with a shaped cavity for receiving a slug, wherein the slug is a cutout portion of the work piece, wherein the die and the draw punch maintain a pre-defined clearance with respect to each other during operation;

aligning the draw punch, the work piece, and the die;

moving the draw punch towards the die;

shearing the work piece by the draw punch to yield the one or more desired cutouts and a slug;

bending the slug to obtain bended slug during the shearing; and

receiving the bended slug in the shaped cavity of the die.

10. The method of claim 9 wherein the bending edge of the draw punch bends the slug.

11. The method of claim 9 wherein the one or more desired cutouts are of a shape selected from a circular, a square, a rectangular shape.