WO2001012937A2

WO2001012937A2 - Laser welded door hardware and method of manufacture

Info

Publication number: WO2001012937A2
Application number: PCT/US2000/022004
Authority: WO
Inventors: John Hildebrandt; Jeffrey Gilbert
Original assignee: Emhart, Inc.
Priority date: 1999-08-13
Filing date: 2000-08-11
Publication date: 2001-02-22
Also published as: AU6633200A; WO2001012937A3

Abstract

A thin-walled, laser-welded multi-piece door knob assembly (20) is disclosed in which two halves (22, 24) of a knob assembly (20) are formed by standard stamping or forming processes and an interface edge is formed thereon. The stampings are placed in abutting alignment and joined together in a welding process, which fuses the two halves together with no filler material. During the welding process, each of the knob halves (22, 24) are constrained to their nominal shape as they are held in appropriate position and rotated together on a common axis. During the welding process, the welder (52) is radially manipulated with respect to the interface edges (30, 34) to maintain a fixed distance between the welder and the knob assembly (20) regardless of the circumferential configuration of the knob assembly. Sizing fixtures (40) may be utilized to constrain the knob halves (22, 24) and facilitate loading thereof through the use of articulated holders. Upon completion of the welding process, the welded knob assembly (20) is further finished utilizing sanding and polishing steps to remove any visible weld joints. Subsequent plating, physical vapor deposition or powdered coating is used to provide the desired surface finish.

Description

LASER WELDED DOOR HARDWARE AND METHOD OF MANUFACTURE

BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates generally to door hardware, and more particularly to a multiple piece knob assembly in which the individual pieces of the assembly are fabricated using traditional sheet metal stamping or forming operations that are subsequently joined together using a welding technique such that the finished door knob assembly shows no discernable weld seam. The present invention has the advantages of achieving a desired shape through a stamping process rather than a forging process as presently used for conventional knob assembly designs. In a preferred embodiment, a two-piece knob assembly provides a thin- walled hollow knob which will work with existing lockset chassis. In an alternate preferred embodiment, a three-piece knob assembly provides a thin-walled hollow knob which will work with existing lockset chassis having a keyed lock cylinder.

The present invention also provides a method of manufacture which is readily adaptable to automation and which can be utilized to achieve a cost and time effective fabrication process. Accordingly, a knob assembly having an identical look to other solid products is provided at a lower cost and at a lighter weight. Moreover, by utilizing stainless steel stampings, the present invention provides a better base material for finishing which have been shown to have longer durability, i.e., lifetime finish applications.

These and other objects, features and advantages of the present invention will become apparent from the following description when viewed in accordance with the accompanying drawings and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A is an exploded perspective view of a two-piece knob assembly in accordance with a first preferred embodiment of the present invention;

Figure 1B is a cross-sectional view of the knob assembly illustrated in Figure 1A; Figure 2A is an alternate embodiment of a three-piece knob assembly in accordance with a second preferred embodiment of the present invention;

Figure 2B is a cross-sectional view of the knob assembly illustrated in Figure 2A; Figure 3 is a flow chart illustrating the method of manufacture for a knob assembly in accordance with the present invention;

Figure 4 is a side elevational view illustrating the sizing fixture; and Figure 5 is a top plan view illustrating a processing station in which the welding operation is performed.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figures 1A and 1B, a first preferred embodiment of the present invention includes a two-piece knob assembly 20 having a back portion 22 and a front portion 24 made from suitable stainless steel sheet metal (such as 304-2B alloy stainless) and joined using a welding process to form a thin-walled, welded knob assembly. Back portion 22 and front portion 24 may be formed by any suitable stamping or forming operation which yields the desirable geometric shape. Such operations include stamping, roll forming or draw forming. Alternately, a die casting process may be utilized to provide a thin-walled casting having the desired geometric configuration.

With reference to Figures 2A and 2B, an alternate preferred embodiment of the present invention is illustrated as a three-piece knob assembly 20' having a back portion

22', a front portion 24' and a knob cover 25'. Front portion 22' and back portion 24' are welded together. Three-piece knob assembly 20' of the alternate embodiment is adapted to receive a locking cylinder (not shown) such that three-piece knob assembly 20' may be utilized as a keyed door knob assembly. Knob cover 25' is received over a portion of back portion 22' and serves as a cosmetic cover to conceal slots 23' formed therein to accommodate the locking cylinder.

From the detailed description set forth herein, one skilled in the art will readily recognize that the method of manufacture for the multiple piece door knob assembly of the present invention, whether a two-piece door knob assembly 20 or a three-piece door knob assembly 20', are fabricated utilizing similar processing steps. Accordingly, continued description of the present invention will be made only with reference to two-piece door knob assembly 20. With particular reference to Figures 1A and 1 B, back portion 22 has a neck 26 and a dome 28 terminating at an interface edge 30. Front portion 24 is defined by a dome 32 which terminates at an interface edge 34. Back dome-shaped portion 28 is complementary to front dome-shaped portion 32 such that back interface edge 30 and front interface edge 34 may be positioned in abutting alignment. Back portion 22 is welded to front portion 24 along interface edges 30, 34 to form a welded knob assembly. A laser welding process is utilized to provide a weld seam 36 of approximately 0.020 inches wide which does not require the addition of a filler material. As presently preferred, a laser welding process or a plasma welding process may be utilized.

In order to effectively achieve an adequate weld seam, the dimensional tolerancing between back interface edge 30 and front interface edge 34 must be such that any gap occurring therebetween is less than approximately 0.005 inches. The welding process used to join together back portion 22 and front portion 24 fuse the two halves together without any filler material and provides a weld seam having a slightly raised profile. Any remaining visible evidence of weld seam 36 is removed by a sanding or polishing operation. A desired color and or finish may also be applied to door knob assembly 20.

The method of manufacture for knob assembly 20 will now be described. Each step in the method of manufacture is set forth in sequential order in flow chart 100. The fabrication process of the present invention contemplates an automated system in which multiple knob assemblies are transported to a series of processing stations during the manufacture thereof. In this regard, the present invention may incorporate a transport system which includes multiple sizing fixtures interconnected to form a conveyor capable of being driven to transport knob assembly 20 to the processing stations. The manufacturing process begins by forming back and front portions 22, 24 as represented at Blocks 102, 104 which are then loaded into sizing fixtures 40 as represented at Blocks 106, 108. Back portion 22 and front portion 24 of knob assembly 20 may be formed utilizing any well known stamping or forming process. One skilled in the art will recognize that during this process certain temporary deformations or variations in the shape, particularly at interface edges 30 and 34, may be experienced such that the desired geometric shape is not maintained. Accordingly, subsequent processing steps may be utilized to ensure that the proper geometric shape of back portion 22 and front portion 24 are attained.

With reference now to Figure 4, sizing fixture 40 is adapted to clamp and securely hold back portion 22 in the desired geometric shape. Sizing fixture 40 includes a pair of die halves 42, 44 which are positionable relative to one another for clamping back portion 22 therein. Each die half has an inner surface 46 formed therein which is complementary to the exterior surface of back portion 22 to hold such portion in the proper geometric shape. An adjustable stop 48 may be provided between die halves 42, 44 to ensure that the proper geometric configuration is maintained. While Figure 4 only illustrates a sizing fixture for back portion 22, one skilled in the art will readily recognize that a similar sizing fixture may be utilized in conjunction with front portion 24.

Die halves 42, 44 are movable between an open position for loading knob portion 22 therein and a closed position for securely clamping knob portion 22. Interface edge 30 extends slightly above the upper surface of die halves 42, 44 to permit access thereto during subsequent processing steps. Once loaded into the sizing fixtures 40, knob portion 22 may be transported to an interface edge finishing station in which interface edges 30,

34 are finished to provide appropriate dimensional tolerancing to ensure a quality laser weld as represented at Blocks 110, 112.

More specifically, sizing fixture 40 is transported to an edge finishing station where it is appropriately located therein. For example, a bottom edge of back portion 22 may be positioned on a datum surface of the edge finishing station such that back interface edge

30 of back portion 22 is presented for edge finishing. An edge finishing tool engages and machines interface edge 30 by trimming, grinding, sanding or milling to the proper geometric dimensions. A similar process may be utilized on front portion 24. Next, back portion 22 and front portion 24 are transported to a weld processing station as represented at Block 114. Initially, at the weld processing station, back portion 22 and front portion 24 are positioned relative to one another such that the interface edges 30, 34 are positioned into abutting alignment. In order to ensure that an adequate weld seam 36 is attained, a gap of no more than 0.005 inches between back interface 30 and front interface 34 can exist.

With particular reference to Figure 5, a preferred embodiment of weld processing station 50 is illustrated and incorporates a laser welder 52. One skilled in the art should readily recognize that weld processing station 50 represents a multi-function CNC machine capable of precisely positioning back portion 22 relative to front portion 24, while at the same time providing synchronized rotation of knob assembly 20 relative to the laser welder 52 which is employed to weld the two components together. The manufacturing process of the present invention appropriately aligns the interface edges 30, 34 of back and front portions 22, 24, appropriately positions the laser welder 52 at the proper distance(d) relative to the knob assembly, and precisely rotates the knob assembly relative to the energy generated by laser welder 52 to achieve the desirable weld seam. Furthermore, when configurations such as the egg-shaped knob assembly illustrated and described herein are manufactured, laser welder 66 must be manipulated or articulated along the axis A-A of its laser beam to maintain the precise radial distance (d) at the focal length with respect to interface edges 30, 34 of knob assembly 20. In this regard, laser welder 66 moves radially toward or away from knob assembly 20 as knob assembly 20 rotates for creating weld seam 36 along the entire circumference of knob assembly 20.

Processing station 50 includes a first fixturing portion 54 adapted to securely clamp and appropriately position back portion 22. First fixturing portion 54 is adapted to receive a sizing fixture 40 on a rotating head assembly 56. Similarly, weld processing station 50 includes a second fixturing portion 58 adapted to securely clamp and appropriately position front portion 24 therein. Second fixturing portion 58 is adapted to receive a sizing fixture 40' on a rotating head 60. Moreover, second fixturing portion 58 is adapted to slide axially

(from left to right as viewed in Figure 5) for bringing front interface edge 34 into abutting alignment with back interface edge 30. In a presently preferred embodiment, rotating heads 56, 60 are driven by gear belts from a common drive shaft 62. Likewise, welding laser 66 is maintained on a servo-driven positioning mechanism 82 which is fully synchronized with rotation of knob assembly 20.

Synchronized rotation of back portion 22 and front portion 24 is commenced and laser welder 52 is energized to form a weld seam as represented at Block 116. Synchronized rotation is maintained as laser welder 52 moves radially inwardly and outwardly to accommodate the geometric shape of the circumferential surface of knob assembly 20 until a continuous seam weld is formed as represented in Block 118.

Upon completion of the welding step, the welded knob assembly 20 is removed from laser weld station 50 as represented in Block 120 and transported to a third processing station where welded knob assembly 20 is sanded and polished as represented in Block 122. In this regard, it is presently preferred to perform multiple finishing steps such as grinding/sanding through a range of grits and then polishing to obtain a suitable finish quality surface. Any number of presently known processing stations may be utilized in this regard including automated processing stations, as well as manual processing stations.

Once a suitable finish surface has been obtained, the welded knob assembly may be finished using any desirable finishing process as represented in Block 124. In this regard, a plating or physical vapor deposition (PVD) process may be utilized to achieve a final color. Likewise, the base knob material, stainless steel, may be polished to a suitable finish. In particular, the present invention may be provided with a polished brass or a polished stainless steel surface finish. Alternatively, the base knob material may be coated with a suitable powdered coating to achieve a different look.

While the present invention has been described with particular reference to an thin- walled, laser-welded knob assembly, having an oval or egg-shaped configuration, one skilled in the art will readily recognize that the present invention has applicability to other geometric configurations for a thin-walled, laser-welded knob assemblies including other round knob configurations, as well as lever handle configurations. Furthermore, the present invention has been described with particular reference to certain preferred embodiments for processing machinery utilized in the method of manufacture. However, one skilled in the art will readily recognize that other machinery which is adaptable to perform the stated processing steps may be utilized in practicing the present invention. Furthermore, those skilled in the art will readily recognize from the foregoing discussion and accompanying drawings and claims, that changes, modifications and variations can be made in the present invention without departing from the spirit and scope thereof as defined in the following claims.

Claims

WHAT IS CLAIMED:

1. A fabricated door knob assembly adapted to be coupled to a lockset for operating the lockset, the door knob comprising: a first shell member having a first interface edge formed thereon; a second shell member having a second interface edge formed thereon, said second interface edge being positioned in abutting alignment with said first interface edge; and a circumferential weld seam formed between said first interface edge and said second interface edge for securing said first shell member to said second shell member to form a door knob, an outer surface of said door knob having a seamless surface finish.

2. The fabricated door knob assembly of claim 1 further comprising a knob cover received over a portion of said first shell member.

3. The fabricated door knob assembly of claim 1 wherein said outer surface of said knob assembly is highly polished.

4. The fabricated door knob assembly of claim 1 wherein said outer surface of said knob assembly is chrome plated.

5. The fabricated door knob assembly of claim 1 wherein said outer surface of said knob assembly is coated with a physical vapor deposition coating.

6. The fabricated door knob assembly of claim 1 wherein said outer surface of said knob assembly is coated with a powder coating to change the color thereof.

7. A method for manufacturing a door knob assembly comprising the steps of: forming a first shell member having a first interface edge formed thereon; forming a second shell member having a second interface edge formed therein; positioning said first interface edge in abutting alignment with said second interface edge; welding said first and second interface edges together while simultaneously manipulating said first and second shell members in a synchronized manner to form a weld seam along said first and second interface edges such that said first and second shell members are secured together to form a welded door knob assembly; sanding said weld seam to provide a seamless exterior surface on said welded door knob assembly; and finishing said seamless exterior surface of said welded door knob assembly.

8. The method of claim 7 wherein the step of welding said first and second interface edges forms a weld seam which is slightly raised with respect to said exterior surface.

9. The method of claim 7 wherein the step of finishing said seamless exterior surface comprises chrome plating the door knob assembly.

10. The method of claim 7 wherein the step of finishing said seamless exterior surface comprises physical vapor deposition of a coating on the door knob assembly to change the color thereof.

11. The method of claim 7 wherein the step of finishing said seamless exterior surface comprises coating the door knob assembly with a powder coating to change the color thereof.

12. The method of claim 7 wherein the step of forming a first shell member includes forming a first shell having a neck portion and a first dome portion terminating at said first interface edge, and wherein the step of forming a second shell member includes forming a second shell having a second dome portion terminating at said second interface edge, said first dome portion being complementary to said second dome portion such that said first and second interface edges are positioned in abutting alignment to form a door knob assembly.

13. The method of claim 12 further comprising the steps of: forming a knob cover; and securing said knob cover over a portion of said first shell.