Flow-through heater for heating water

Details Flow-through heater for heating water Flow-through heater for heating water

1999-11-02

2001-06-26

Wilson, Gregory (Department: 3749)

Liquid heaters and vaporizers

Tubes and connections

C122S364000, C392S480000

Reexamination Certificate

active

06250259

ABSTRACT:

This invention relates to a flow-through heater for heating water for domestic use in accordance with the prior-art portion of claim
1
.
Such a flow-through heater with a protective device is described in DE 196 05 187 A1 and used, for example, in coffee and tea makers. For normal operation such domestic appliances are equipped with a safety switch which, in cooperation with the temperature control device, interrupts the power supply to the domestic appliance under critical temperature and error conditions. This temperature protective device is, as a rule, sufficient to disconnect the appliance from the electrical supply, as on a failure of the temperature control device which is conventionally equipped with a bimetal. However, if in the presence of an adverse phase position and a defective temperature control device a short circuit occurs to the effect that heating conductor sections of a tubular heating element are electrically connected to a protective conductor, an uncontrolled heating of the tubular heating element may occur and produce an environmental hazard.
To master such an error condition, DE 196 05 187 A1 initially referred to describes a temperature fuse in which a mechanically biased conductor, which disconnects by melting of the solder, interrupts the power supply to the tubular heating element of the flow-through heater. The aforementioned solution requires, however, a special element for carrying the soldered joint and connecting with the terminal stud of the tubular heating element. In this arrangement, the connecting element is comprised of a flat soldering lug which, owing to its bigger soldering surface, establishes a fixed connection from the terminal stud to the conductor through the intermediary of the solder. Apart from additional expenditure of material, the use of such a connection element adds to the complexity of production, requiring in particular the soldering end to be of a flat and wide configuration. This presents a problem in cases where a round and relatively thin wire is employed.
It is therefore an object of the present invention to simplify the flow-through heater construction for the purposes of production without impairing the achieved level of operational reliability, while at the same time enhancing its functionality and safety.
This object is accomplished in the flow-through heater of the type initially referred to by the features identified in patent claim
1
. Soldering the conductor directly with the terminal stud of the heating element due to the special shaping of the terminal connector of the conductor eliminates the need for the connector element so far used. By shaping the conductor end as disclosed in the invention, it is possible to fill the space enclosed by the conductor end with solder fully or to the fullest possible extent, and this particularly because liquid solder is capable of covering surfaces up to a specified size (globule size), maintaining this covering position until the solder has cooled down and become hard. Furthermore, this presents an advantage in automated production for the purposes of a secure positioning. It is then also possible for the wire to embrace partially the terminal stud over one or several partial sections which then establish an intimate soldered connection with the terminal stud during soldering.
Owing to the special shaping of the terminal connector of the conductor, the soldering surface between the conductor end and the contact tab of the heater is enlarged. The present invention finds application particularly advantageously with conductors of circular cross section (claim
2
). It will be understood, however, that the use of oval or rectangular terminal studs or terminal studs of any other cross section is possible, the conductor end being then shaped to extend in conformity with the stud's outer shell surface essentially over one or several partial areas.
A round or oval wire offers, however, a connecting surface to the terminal stud which is partly closed all-round.
For production-related reasons, it is further advantageous to configure the conductor in accordance with patent claims
3
and
4
. These approaches enable the aforementioned features to be implemented particularly simply and effectively, the conductor end then embracing the shell surface of the terminal stud over a specified partial area only or engaging with its partial area the shell surface of the terminal stud wholly or, due to non-circular manufacturing tolerances, only partially.
In particular with regard to automated production and reliable placement of the conductor on the terminal stud provision is furthermore made in patent claim
5
for the soldered joint to be arranged a sufficient distance from the end of the terminal stud in the direction of the heating element, and for the conductor to be of a length not protruding beyond the end of the terminal stud.
Overall, for the solutions set forth it is advantageous if the conductor is a spring wire of round cross section.
With the features of claim
6
the number of necessary components is reduced and hence manufacture and assembly of the flow-through heater are simplified while good compliance with the predetermined breaking values under error conditions is ensured. Owing to the large-surface soldering using round wires as disclosed in the invention, a stable protective device in the form of a junction having the added function of a fusible cutout is accomplished.


REFERENCES:
patent: 4778977 (1988-10-01), Bleckman
patent: 4904845 (1990-02-01), Wonka
patent: 5150488 (1992-09-01), Salomon
patent: 5192937 (1993-03-01), Lee
patent: 5283854 (1994-02-01), Schiebelhuth
patent: 173569 (1953-01-01), None
patent: 195 05 621 (1996-08-01), None
patent: 196 05 187 (1997-08-01), None

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