WO2018030890A1

WO2018030890A1 - Hemming burr hole

Info

Publication number: WO2018030890A1
Application number: PCT/MY2017/050030
Authority: WO
Inventors: Kit Yoke LAM; Zi Yong TEAN
Original assignee: Daikin Research & Development Malaysia Sdn. Bhd.
Priority date: 2016-08-12
Filing date: 2017-06-23
Publication date: 2018-02-15

Abstract

A metal sheet (200) having a hole (130) formed on at least one free end (100) of the metal sheet (200), the hole (130) is punched on the free end (100) which is folded in such a way that it forms a thickened wall to accommodate a fastening member.

Description

HEMMING BURR HOLE

FIELD OF THE INVENTION This invention relates to burr hole on a metal sheet through metal stamping process, and more particularly through combined hemming and burring process.

BACKGROUND OF THE INVENTION Existing techniques used for punching a hole on the metal sheet has many drawbacks. During hemming process and punching the hole on the metal sheet, the free ends of the metal sheet tilts up easily, which causes detachment and misalignment. The hole formed on the metal sheet does not provide sufficient surface area for a screw to mount a device, which loosens the screw in the hole and functions of the mounted device will be affected. Further, a pre-cut metal sheet is used and placed on top/bottom of the free end forming double thickness and then hole is punched on it, which incurs additional cost for the pre-cut metal sheet. Furthermore, while punching the hole on the metal sheet with double thickness causes damage to punching tool. Therefore, the intention of this invention is to increase the surface area of the hole formed on the metal sheet without incurring additional costs.

SUMMARY OF THE INVENTION The present invention provides a metal sheet having hole formed on at least one free end of the metal sheet, the hole is punched on the free end which is folded in such a way that it forms a thickened wall to accommodate a fastening member.

According to an aspect of the present invention, the metal sheet is a panel or bracket.

According to an aspect of the present invention, the free end is folded by a hemming process. According to another aspect of the present invention, the hole is punched on the folded end by a punching process. According to another aspect of the present invention, the folded end is folded inwardly forming first section and second section.

According to another aspect of the present invention, the hole punched on the folded end forms the hole on the first and second sections of the folded end.

According to preferred aspect of the present invention, the metal sheet is a part of an outdoor unit of an air conditioning unit.

According to another aspect of the present invention, the folded end changes to opposite side of the punching direction during the punching on the folded end.

According to another aspect of the present invention, includes a plate to hold the folded end, to provide grip to the folded end and prevent misalignment of the folded end.

According to yet another aspect of the present invention, the folded end is folded at an angle of 180°.

According to yet another aspect of the present invention, the hole formed is a burr hole.

According to preferred embodiment of the present invention, the folded end is a flat fold. BRIEF DESCRIPTION OF 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(a), 1(b) and 1(c) illustrates perspective views of a hemmed metal sheet with a burr hole, in accordance with an aspect of the present invention;

Fig. 2 (a) illustrates the hemmed metal sheet with the burr hole as shown in the figure 1, and 2 (b) illustrates a motor fixed into the panel, in accordance with another aspect of the present invention; and,

Fig 3 illustrates an outdoor unit of an air conditioning unit with the panel as shown in figure 2, in accordance with another aspect of the present invention. DETAILED DESCRIPTION OF THE INVENTION

For a better understanding of the invention, preferred embodiments of the invention that are illustrated in the accompanying drawings will be described in detail. The words "folded", "hemmed" are interchanged throughout the document.

The words "burr hole", "burring hole" are interchanged throughout the document.

The free end of a metal sheet is folded and a burr hole is punched on the folded metal sheet to accommodate a fastening member. This enhances the strength of the burr hole to accommodate the fastening member without causing any looseness.

The metal sheets are formed into the desired shape and size of the component by stamping process according to the applicability to form desired shape panel (200) where the panel (200) can be a bracket.

Referring to figure 1 (a), (b) and (c) illustrates the hemmed metal sheet (100) with a burr hole (130). The metal sheet undergoes stamping process to form the panel (200) or bracket. The free ends of the metal sheet are hemmed to form hemmed edges. The hemmed edge can be a flat hem or a rope hem, formed by using the hemming process. Hemming is a process that bends the edge of a metal sheet to 180° or more. It serves several functions: to increase the part stiffness, to eliminate the acute edge, to improve the appearance of highly visible panel edges, and to join the inner and outer parts.

In an exemplary embodiment, the hemmed metal sheet (100) is formed by two or three-step process. The two-step process comprises of steps: pre-hemming bending and hemming or seaming. In pre-hemming step the free edge of the metal sheet is made to bend. In hemming or seaming step the pre-hemmed edge is further made to bend at 180°. The three step process comprises steps: stamping or piercing, pre- hemming and hemming/seaming. In first step, the metal sheet is stamped into desired shape to form the panel (200). In second step the pre-hemming bend is performed, where the free edge of the metal sheet is made to bend. In final step, the pre-hemmed edge is further made to bend completely at 180° to for the hemmed metal steel (100). The metal sheet is bended inwardly or outwardly forms thickened wall or layered structure of double thickness. The hemmed metal sheet (100) is a flat hem comprising top section layer (120) and bottom section layer (110). The top section layer (120) and bottom section layer (110) overlap on each other without any gap between these two layers. In the non-limiting embodiment, the free ends of the metal sheet are hemmed using electromagnetic process. The metal sheet is preferably an aluminium metal, however, this is applicable for all kinds of metals. In next stage, a hole (130) is punched on the hemmed metal sheet (100) using a punching process preferably using a collar punch. A pair of plates are used to hold the hemmed metal sheet (100) on two ends. The shape of the collar punch is preferably cylindrically symmetric and a burring hole is punched on the two section layers (110 and 120) of the hemmed metal sheet (100). The diameter of the burring hole (130) is configured same as the diameter of the collar punch, forming a wall in the hemmed metal sheet (100) without any scrap. The punching processes, further comprises steps of: the hemmed metal sheet (100) is placed on a stage of the collar punch, and the collar punch is properly positioned. The plates holds the edges of the hemmed metal sheet (100). When the operation is initiated, in this step, the collar punch is lowered vertically to punch the hemmed metal sheet (100) causing the hemmed metal sheet (100) to warp downward into the burring hole (130) in a circular shape. Thus forming a scrapless burr hole (130) and the wall is in the burr during the punch which protrudes outwards up to an increased height of the burr hole (130) from the bottom section layer (110) of the hemmed metal sheet (100). The collar punch is performed in such a way the direction of the hemmed metal sheet (100) changes to the opposite side of the punching direction. The burr hole (100) formed on the hemmed edge of the metal sheet is at a ratio of thickness with 0.44, thereby does not cause any damage to the collar punch. In a non-limiting embodiment, the process to form the burr hole (130) on the hemmed metal sheet (100) is not limited to the collar punch.

The burr hole (130) formed on the hemmed metal sheet (100) is to accommodate a fastening member. This approach of forming the burr hole (130), provides sufficient surface area and increase in strength of the burr hole (130) for the accommodated fastening member. Further, using this approach, the cost for the metal pre-cut can be reduced. Furthermore, these hemming and burring process are included into current 6 stage stamping processes for the motor bracket. There is no additional investment cost is required. This process can be applied to all metal parts that require to increase strength of burr hole (130). In a preferred embodiment, the panel (200) is for an outdoor unit (300) of an air conditioning unit as shown in figures 2 (a), 2 (b) and 3. The metal base sheets are formed into the desired shape and size according to the size of the component by stamping process to form the panel (200) for the enclosure of the outdoor unit (300). The stamping process also includes the hemming process and punching process.

Referring to figures 2(a) and 2(b) with regards to figure 3, the hemming burr hole is formed by three step process as explained in the previous embodiments. In the first step, the metal sheet is stamped to form the panel (200) for the outdoor unit (300) of the air conditioning unit. In second step, the pre-hemming bend is performed, where the free edges of the panel (200) is made to bend. In final step, the pre -hemmed edge of the panel (200) is further made to bend completely at 180° to form the flat hem. The flat hem is thickened wall or layered structure comprises the top section layer (120) and bottom section layer (110). In next stage, the hemmed edge of the panel (200) undergoes through the punching process. The edges of the hemmed part are held by the plates to prevent causing misalignment and also provide strong grip to the hemmed edge (100) of the panel (200). The hole is punched and extended in the burring punch part of the circular section as shown in Fig. 1(a), 1(b) & 1(c) where the burr hole (130) is formed. The pieces are firmly attached to the tip edge of the burring hole (130). Thereby, with the external force pushed on a die inner surface at the time of burring, the pieces serve as a scrap from the burring hole (130), and do not break away and fall. The pieces surrounding the burr hole (130) forms like the wall structure on the bottom section layer (110) forming increased height of the burr hole (130). The wall provides sufficient surface area for the fastening member. The hole (130) is of the diameter configured to be same as the diameter of the collar punch. The diameter of the hole can vary depending upon the punch use. As shown in the figures 2 (b) and 3, the hemmed metal sheet (100) with the burr hole (130) on the edges of the panel (200) are used to mount a motor (210) for the outdoor unit (300). The motor (210) can be mounted to the panel (200) of the outdoor unit using screws. The screw are accommodated in to the burr hole and holds the motor (210) in position tightly.

The present invention may be embodied in other specific forms without departing from its essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore indicated by the appended claims rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.

Claims

1. A metal sheet (200) having a hole (130) on at least one free end (100) of the metal sheet (200), wherein the hole (130) is punched on the free end (100) which is folded in such a way that it forms a thickened wall to accommodate a fastening member.

2. The metal sheet (200) according to the claim 1, wherein the metal sheet is a panel or bracket.

3. The metal sheet (200) according to the claim 1, wherein the free end is folded by a hemming process.

The metal sheet (200) according to the claim 1, wherein the hole is punched on the folded end by a punching process.

The metal sheet (200) according to the claims 1 to 4, wherein the folded end is folded inwardly forming first section (110) and second section (120).

The metal sheet (200) according to the claims 1 to 4, wherein the hole (130) is punched on the folded end forming the hole (130) on the first section (110) and second section (120) of the folded end.

The metal sheet (200) according to any of the preceding claims, wherein the metal sheet (200) is a part of an outdoor unit (300) of an air conditioning unit.

The metal sheet (200) according to any of the preceding claims, wherein the folded end changes to opposite side of the punching direction during the punching on the folded end.

The metal sheet (200) according to any of the preceding claims, wherein the hole (130) formed on the folded end by the punching process includes a plate to hold the folded end, provides gripping force to the folded end and prevents misalignment of the folded end.

10. The metal sheet (200) according to any of the preceding claims, wherein the folded end is folded at an angle of 180°.

11. The metal sheet (200) according to any of the preceding claims, wherein the hole (130) formed is a burr hole.

12. The metal sheet (200) according to any of the preceding claims, wherein the folded end is a flat fold.