INTEGRATED WELD STOP

Abstract

A weld stop element may be used in a hot plate welding process for bonding first and second plastic components. The weld stop element includes a weld stop post positioned between ribs of one or both of the components. The weld stop post is sized such that the weld stop post is not accessible by a heating element during a heating phase of the hot plate welding process. The weld stop post defines a stop position for when the first and second plastic components are pressed together after the heating phase.

Claims

1. A weld stop element for use in a hot plate welding process for bonding a first plastic component having a plurality of first ribs with a second plastic component having a plurality of second ribs, the weld stop element comprising a weld stop post positioned between at least one of the plurality of first and second ribs, wherein the weld stop post is sized such that the weld stop post is not accessible by a heating element during a heating phase of the hot plate welding process, the weld stop post defining a stop position for when the first and second plastic components are pressed together after the heating phase.

2. A weld stop element according to claim 1, comprising at least two of the weld stop posts, one for each of the first and second plastic components.

3. A weld stop element according to claim 2, comprising a plurality of weld stop posts for each of the first and second plastic components.

4. A weld stop element according to claim 1, wherein the first and second ribs each have an outermost distal end, and wherein a stop surface of the weld stop is positioned short of the outermost distal end.

5. A weld stop element according to claim 1, wherein the weld stop post is cylindrical.

6. An assembly of two molded plastic components, each of the two plastic components comprising: a plurality of ribs on a facing side; and at least one weld stop post positioned between adjacent ones of the plurality of ribs, wherein the at least one weld stop post is positioned relative to the ribs such that a distal edge of the at least one weld stop post is short of outermost distal edges of the plurality of ribs, and wherein the facing sides of two plastic components are connected by welding.

7. An assembly according to claim 6, wherein each of the two plastic components comprises a plurality of weld stop posts respectively interposed between adjacent ones of the plurality of ribs.

8. An assembly according to claim 7, wherein the weld stop posts on one of the two plastic components correspond in number and are aligned with the weld stop posts on the other of the two plastic components when the facing sides are aligned.

9. An assembly according to claim 7, wherein the weld stop posts are cylindrical.

10. An assembly according to claim 6, wherein the at least one weld stop post on one of the two plastic components is aligned with the at least one weld stop post on the other of the two plastic components when the facing sides are aligned.

11. An assembly according to claim 6, wherein the at least one weld stop post is integral with each of the two plastic components.

12. An assembly according to claim 6, wherein a distance that the weld stop posts are short of the outermost distal edges of the plurality of ribs corresponds to an overlap distance for the plurality of ribs during welding.

13. A method of coupling two molded plastic components, each of the two plastic components including a plurality of ribs on a facing side, and at least one weld stop post positioned between adjacent ones of the plurality of ribs, wherein the at least one weld stop post is positioned relative to the ribs such that a distal edge of the at least one weld stop post is short of outermost distal edges of the plurality of ribs, the method comprising: (a) heating the facing sides of the two plastic components with a hot plate such that the outermost distal edges of the plurality of ribs begin to melt; (b) aligning the facing sides of the two plastic components; (c) pressing the two plastic components together such that the outermost distal edges of the ribs of one of the two plastic components is united with the outermost distal edges of the other of the two plastic components; and (d) limiting a relative displacement of the two plastic components in step (c) with the weld stop posts.

14. A method according to claim 13, wherein step (d) is practiced by engaging the distal edge of the at least one weld stop post of one of the two plastic components with the distal edge of the at least one weld stop post of the other of the two plastic components.

15. A method according to claim 13, wherein step (a) is practiced without heating the weld stop posts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] These and other aspects and advantages will be described in detail with reference to the accompanying drawings, in which:

[0018] FIG. 1 is a perspective view of a weld-stop element including a weld stop post according to the described embodiments;

[0019] FIG. 1A shows the height/spatial relationship between the component ribs and the weld stop posts;

[0020] FIGS. 2 and 3 are perspective views of exemplary plastic components to be welded;

[0021] FIG. 4 shows the heating phase in welding the exemplary components;

[0022] FIG. 5 shows the welding phase and the functionality of the weld stop posts during the welding phase;

[0023] FIG. 6 is a perspective view showing the exemplary components bonded to form a single unit; and

[0024] FIG. 7 is a sectional view through the top component after the welding phase.

DETAILED DESCRIPTION

[0025] FIG. 1 is a perspective view of a weld stop element for use in a hot plate welding process for bonding a first plastic component 10 with a second plastic component 12. FIGS. 2 and 3 are perspective views showing an exemplary configuration of suitable first and second plastic components 10, 12. The pallet or tray in the exemplary configuration is formed by joining two pieces to into the finished product. It is desirable in some component designs to utilize separate pieces to facilitate the molding process.

[0026] Each of the first and second plastic components 10, 12 includes a plurality of ribs 14 that generally provide structural support for the resulting assembly. The weld stop element primarily includes a weld stop post 16 positioned between the ribs 14 of one or both of the first and second plastic components 10, 12. As shown in FIGS. 2 and 3, in some embodiments, each of the first and second plastic components 10, 12 includes a plurality of weld stop posts 16. If only one of the components includes the weld stop post(s) 16, the component could include an extended length post. Preferably, the weld stop posts 16 are integral with the first and/or second plastic components 10, 12.

[0027] With reference to FIG. 1A, the weld stop posts 16 are sized and/or positioned relative to the ribs 14 such that the weld stop posts 16 are not accessible by a heating element during a heating phase of the hot plate welding process. That is, in some embodiments, the weld stop posts 16 are positioned relative to the ribs 14 such that a distal edge 16A of the weld stop posts 16 is short (i.e., below for an upward facing component, or above for a downward facing component) of the outermost distal edges 14A by the distance A shown in FIG. 1A. In some embodiments, the weld stop posts 16 are cylindrical as shown, although the weld stop posts 16 could have any shape.

[0028] FIG. 4 shows a heating phase of the hot plate welding process. In this phase, both parts 10, 12 are pressed against a hot plate 18 to melt the material at the outermost distal ends 14A of the ribs 14. This phase prepares the ribs 14 for the welding phase in which the parts are bonded. Typically, the hot plate 18 is PTFE-coated for easy release of the plastic component melted material. The hot plate 18 is removed from between the parts 10, 12 after the ribs 14 (or alternative outermost surfaces) have been heated to a melting point. With continued reference to FIG. 1A, by virtue of the distance A between the distal edge 16A of the weld stop posts 16 and the outermost distal edges 14A of the ribs 14, the weld stop posts 16 are not accessible by the heating element during the heating phase and thus are not melted during the heating phase. The weld stop posts 16 remain solid and rigid. The heating plate 18 may additionally (or alternatively) include recesses in the areas adjacent the weld stop posts 16 to further separate the heat generating by the heating plate 18 from the weld stop posts 16.

[0029] In an embodiment where only one of the plastic components 10, 12 includes the weld stop posts 16, the weld stop posts 16 on the one component could extend to the supporting (horizontal) surface of the other component. In this construction, the hot plate 18 may include a cut-out through which the weld stop posts 16 would extend to prevent the weld stop posts 16 from being heated during the heating phase.

[0030] FIG. 5 shows the welding phase for the first and second components 10, 12. In this phase, the facing sides of the plastic components 10, 12 are aligned and pressed together such that the outermost distal edges 14A of the ribs 14 of both of the plastic components 10, 12 are united. In this phase, the weld stop posts 16 of the facing sides are brought into contact under slight pressure. Since the weld stop posts 16 are solid, they limit further relative movement of the components 10, 12. The solid weld stop posts 16 act as spacers or stops to maintain the relative part height of the welded components. As shown in FIG. 5, the edges 14A of the facing ribs 14 are slightly overlapped when the distal edges 16A of the weld stop posts 16 come in contact. The weld stop posts 16 prevent the parts 10, 12 from being pushed too hard against each other, which could detrimentally affect the quality of the weld.

[0031] FIG. 6 shows the finished product with the exemplary components 10, 12. After cooling, the parts 10, 12 are bonded and essentially form a single connected unit. FIG. 7 is a sectional view through the top of the assembly after the welding phase. A weld line 20 is shown for illustration purposes. In the final assembly, the first component 10 is welded to the second component 12 with the respective weld stop posts 16 in facing engagement.

[0032] The weld stop element according to the described embodiments ensures a consistent weld quality and improves the resulting part/product quality. Since the weld posts can be integrated into the plastic components, no adjustable weld stops in the weld tools are required. Set-up time and weld processing time can also be reduced.

[0033] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.