CONTACT WELDING TOOL AND METHOD FOR OPERATING SAME

Abstract

The present disclosure sets out a contact welding tool having at least one heating element for contacting a workpiece and at least one heat source for heating the heating element, at least one heat source being an infrared radiation source emitting infrared radiation in the short-wave infrared range. The present disclosure also sets out a method for operating a contact welding tool wherein a heating element of the contact welding tool is heated by means of short-wave infrared radiation and then the heating element is brought into contact with a workpiece to be reshaped. The present contact welding tool and method can be used particularly advantageously for heat staking, for example of plastic rivets.

Claims

1. A contact welding tool, comprising: at least one heating element arranged to contact a workplace and at least one heating source configured to heat the heating element, wherein the at least one heating source is an infrared radiation source configured to emit infrared radiation in the short-wave infrared range.

2. The contact welding tool according to claim 1, wherein the infrared radiation source is an IR-A heating source.

3. The contact welding tool according to claim 1, wherein the heating element comprises a thin-walled region having at least one contact surface on a front side configured to contact the workpiece and a rear side arranged to be irradiated with IR radiation by at least one infrared radiation source.

4. The contact welding tool according to claim 3, wherein the thin-walled region comprises a sheet metal part comprising V2A steel and a wall thickness in the range of [0.5 mm to 3 mm].

5. The contact welding tool according to claim 1, further comprising at least one cooling device configured to cool the heating element and arranged to supply the heating element with gaseous and/or liquid cooling medium.

6. The contact welding tool according to claim 5, further comprising an intermediate space configured to be acted upon by the cooling medium and arranged between the IR heating radiator and the heating element, and wherein the heating element comprises a wall of the intermediate space.

7. The contact welding tool according to claim 1, wherein the heating element is configured for hot contact riveting.

8. A method of operating a contact welding tool, comprising the steps of: heating a heating element of the contact welding tool by means of short-wave infrared radiation, and bringing the heating element into contact with a workpiece to be formed.

9. The method according to claim 8, further comprising the steps of cooling the heating element, while the heating element is in contact with the then formed workpiece, by means of a cooling medium to at least a demolding temperature.

10. The method according to claim 8, further comprising the steps of passing the cooling medium through an intermediate space between the heating element and an infrared radiator configured to generate shortwave infrared radiation so as to cool the heating element.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0038] Further advantageous features and details of the various embodiments of this disclosure will become apparent from the ensuing description of preferred exemplary embodiments and with the aid of the drawings. The features and combination of features recited below in the description or in the drawings alone, may be used not only in the particular combination recited but also in other combinations on their own, without departing from the scope of the disclosure.

[0039] In the following, advantageous examples of the invention are explained with reference to accompanying figures, wherein:

[0040] FIG. 1 depicts a sectional view of a contact welding tool 1 in the form of a hot riveting tool in the area of its heating element 2. The heating element 2 has a contact area (hereinafter referred to as “bottom” 3) for contacting a workpiece (not shown).

DETAILED DESCRIPTION OF THE INVENTION

[0041] As used throughout the present disclosure, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, the expression “A or B” shall mean A alone, B alone, or A and B together. If it is stated that a component includes “A, B, or C”, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. Expressions such as “at least one of” do not necessarily modify an entirety of the following list and do not necessarily modify each member of the list, such that “at least one of “A, B, and C” should be understood as including only one of A, only one of B, only one of C, or any combination of A, B, and C.

[0042] The bottom 3 here has as its base 3a a thin wall of thickness or wall thickness d, on the front of which projects at least one suitably shaped contact projection 4. This arrangement may also be referred to as a rivet calotte base. The workpiece can be contacted only with the contact projection 4, additionally at further areas of the front side of the bottom 3, in particular with the entire front side of the bottom 3.

[0043] At least the bottom 3 comprises here of metal (alternatively, for example, of ceramic), for example, of brass, aluminum or steel, in particular stainless steel. The use of V2A steel is particularly advantageous, since V2A steel has both a fast heating curve and a short cooling time, as well as a high resistance to mechanical damage, e.g., by a glass fibre filling in the plastic of the workpiece, and also a good chemical resistance.

[0044] For example, a wall thickness d of the base 3a may be in the ranged=[0.5 mm; 3 mm], in particular in the range d=[0.75 mm; 2 mm]. The base 3a can in particular be formed as a sheet metal or be formed from a sheet metal part.

[0045] For forming the workpiece (for example, for hot welding or hot caulking), the heating element 2 can be moved against the workpiece (or vice versa) and pressed against the workpiece, as indicated by the arrow F. The workpiece may thereby be formed. The workpiece may be made of thermoplastic, possibly semi-crystalline, plastic and may be, for example, a rivet or rivet head.

[0046] A rear side of the bottom 3 or base 3a facing away from the contact projection 4 serves as a wall or boundary of an intermediate space 5 between the bottom 3 and an IR-A radiator 6 arranged at a distance therefrom. The IR-A radiator 6 is adapted to irradiate the rear side of the bottom 3 with short-wave IR radiation IR to heat the bottom 3 including its front side and the contact projection 4, for example to an operating temperature of more than 250° C., for example to 280° C. Since the base 3a is formed as a thin wall, its heat capacity is low, so that heating or reheating of the bottom 3 to the desired operating temperature by absorption of the IR radiation IR can be achieved very quickly.

[0047] Cooling of the bottom 3 to or below a desired demoulding temperature (e.g., of 100° C.) can also be achieved particularly quickly, namely by flushing the intermediate space 5 with compressed air DL after switching off or deactivating the IR-A radiator 6. The intermediate space 5 thus serves as a through-flow space. The compressed air DL can be introduced into the intermediate space 5, for example via a cooling tube 7, for example at a pressure between 4 bar and 8 bar, for example at about 6 bar. The diameter of the cooling tube 7 may be, for example, between 2 mm and 4 mm, for example at 3 mm.

[0048] At least one outlet opening in the form of a vent hole 8 is provided for venting the intermediate space 5.

[0049] The contact welding tool 1 enables particularly short cycle times or cycle times for heating the bottom 3 from the demoulding temperature to the operating temperature and back. For example, using a base 3a made of V2A steel sheet with a thickness or wall thickness of d=2 mm, heating times from a demoulding temperature of 100° C. to an operating temperature of 280° C. in the range of 20 s and cooling times back to the demoulding temperature in the range of 10 s can thus be achieved.

[0050] Since the embodiments and inventions described in detail above are exemplary embodiments, they can be modified to a large extent in the usual way by a person skilled in the art without leaving the field of invention. In particular, the arrangements and the proportions of the individual elements to each other are simply exemplary. Having described some aspects of the present disclosure in detail, it will be apparent that further modifications and variations are possible without departing from the scope of the disclosure. All matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.