# Patent

## Title
Heater for vacuum cleaners

## Abstract

A heater for fluids including a housing made of a non-metallic material and having an internal cavity. The housing has an inlet and an outlet, each of which are in fluid communication with the internal cavity. An elongated electrical heating element is disposed within the cavity for heating fluid flowing through the cavity. The heating element has a generally circular cross-sectional shape and has a U-shaped portion disposed in the cavity. The electrical heating element has electrical connectors at opposite ends extending through the housing. The electrical heating element has a titanium outer surface.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a continuation-in-part of U.S. application Ser. No. 09/827,232, filed Apr. 5, 2001, the entire contents of which are incorporated by reference.


BACKGROUND OF THE INVENTION
Various vacuum cleaners have been developed that include a reservoir that holds cleaning fluid. The cleaning fluid is heated and deposited on the floor surface to be cleaned where it contacts a rotating brush of the vacuum cleaner. The cleaning fluid, dirt, and other material is then vacuumed from the floor surface. Heaters used for such vacuum cleaners are exposed to a harsh environment due to the caustic nature of the cleaning solution that flows through the heater, such that the heating elements may corrode or otherwise degrade. Also, such heaters are prone to lime buildup on the heating element that may reduce the effectiveness of the heater.
SUMMARY OF THE INVENTION
One aspect of the present invention is a heater for fluids including a housing made of a non-metallic material and having an internal cavity. The housing has an inlet and an outlet, each of which are in fluid communication with the internal cavity. An elongated electrical heating element is disposed within the cavity for heating fluid flowing through the cavity. The heating element has a generally circular cross-sectional shape and has a U-shaped portion disposed in the cavity. The electrical heating element has a titanium outer surface and includes electrical connectors at opposite ends extending through the housing.
Another aspect of the present invention is a heater for fluids including a housing made of a non-metallic material and defining a sidewall and an internal cavity and an opening through the sidewall. An elongated electrical heating element is disposed in the internal cavity, and has opposite ends extending through the sidewall. A metallic member is disposed at the opening in the housing, and has an inner surface exposed to the internal cavity. A temperature sensor is operably coupled to the metallic member to determine the temperature of the metallic member.
Yet another aspect of the present invention is a vacuum cleaner including a frame, a powered rotating brush, a suction unit, and a fluid container for liquid cleaning solution. A fluid conduit is provided for transport of liquid cleaning solution from the fluid container to an area adjacent the rotating brush. The vacuum cleaner further includes a heater operably connected to the fluid conduit for heating fluid flowing therethrough. The heater includes a housing defining an internal cavity and a heating element is disposed within the internal cavity of the housing. The heating element includes a titanium outer surface that contacts liquid cleaning solution in the housing.
These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially schematic view of a vacuum cleaner including a reservoir for liquid cleaning solution and a heater according to one aspect of the present invention;
FIG. 2 is an exploded perspective view of the heater of FIG. 1;
FIG. 3 is a perspective view of the heater in an assembled condition; and
FIG. 4 is a cross-sectional view of the heater.



DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in FIGS. 1 and 2. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.
With reference to FIG. 1, a vacuum cleaner 1 generally includes a frame 2, a fluid reservoir 3, and a vacuum system 4. A fluid conduit assembly 5 includes a pump 6 that deposits fluid 7 from the reservoir 3 adjacent a powered rotating brush 8. A pump 9 generates a vacuum in conduit 10 to pull the fluid 7, dirt, and other debris from the floor surface 11 and into a storage container or bag 12. The frame 2, fluid reservoir 3, conduit assembly 5, and vacuum system 4 may be of various known designs, and will therefore not be described in more detail herein.
A heater 15 according to one aspect of the present invention may be utilized to heat the cleaning fluid before the fluid is deposited adjacent the powered brush 8. With further reference to FIG. 2, the heater 15 includes a housing 16 that is made of a polymer material. The housing has a generally oval cross-sectional shape defining sidewalls 17 and 18 (see also FIG. 4). An electrical heating element 20 is generally U-shaped including elongated parallel portions 21 and 22, a curved portion 23, and includes electrical connectors 24 at the opposite ends 25 and 26 of heating element 20. The heating element 20 preferably has a titanium outer sheath, a stainless steel inner sheath, a dielectric powder material, and an inner heating wire substantially as described in the above-identified U.S. patent application Ser. No. 09/827,232, entitled ELECTRIC WATER HEATER.
A cup-shaped metal member 28 includes an end portion 29 that is received in opening 27 of housing 16 when assembled. A ring-like gasket 30 is made of a high temperature silicone rubber material, and provides a watertight seal between the cup-shaped metal member 28 and the housing 16. Opening 27 is defined by an outer cylindrical surface 31 and inner cylindrical surface 32. The inner cylindrical surface 32 has a diameter that is less than that of the outer cylindrical surface 31, and a tapered step 33 extends between the outer cylindrical surface 31 and the inner cylindrical surface 32. The tapered step 33 has a frusto-conical shape. When the cup-shaped metal member 28 is assembled to the housing 16, the gasket 30 is compressed against the tapered step 33, thereby deforming the gasket 30 and wedging it into tight contact with the cup-shaped metal member 28 and surfaces 31, 32 and 33 of housing 16. The metallic member 28 may be made of anodized aluminum or other suitable material having sufficient heat-transfer and corrosion resistance properties.
A thermostat 35 has an end 39 that is held in contact with inner surface 40 of metal member 28 by a clip 34. When assembled, screws 36 extend through openings 37 in clip 34, openings 38 in metal member 28, and into openings 41 in housing 16 to thereby retain the end 39 of thermostat 35 in contact with inner surface 40 of metal member 28. The screws 36 also compress the gasket 30 to provide a watertight seal between the metal member 28 and housing 16. Because the metal member 28 readily conducts heat, the end 39 of thermostat 35 is kept at substantially the same temperature as fluid flowing within the housing 16. In this way, the thermostat 35 is protected from the potentially caustic fluid, yet is still maintained at substantially the same temperature as the fluid in the housing 16. A thermal cutout assembly 43 includes an electrical connector 44 that connects to the thermostat 35, and a second electrical connector 45 that connects to an electrical connector 24 of heating element 20. The thermal cutout assembly 43 includes a thermal cutout 46 that shuts off the heater element 20 when the temperature of the thermostat 35 is at or above a preselected temperature. The thermal cutout 46 thereby prevents overheating of the heating element 20 and associated components if fluid flow through the heater 15 is stopped, or if the fluid otherwise reaches too high of a temperature. The thermal cutout 46 and related electrical components are of a known design, such that these components will not be described in detail herein.
Housing 16 has a first end 50 having a first opening 51 and a second opening 52, each of which include an outer cylindrical surface 53, tapered step 54 and inner cylindrical surface 55. When assembled, the end portions 25 and 26 of heating element 20 extend through openings 51 and 52, and ring-like silicone rubber gaskets 56 fit tightly against the surfaces 53, 54 and 55 to thereby provide a waterproof seal. A cover 57 includes first and second openings 58 and 59 through which the ends 25 and 26 extend, and the cover 57 includes connectors 60 that extend around lip 61 of housing 16 to thereby tightly retain the cover 57 on the housing 16.
A pair of barbed fluid connectors 62 and 63 may be formed at the first end 50 of housing 16. With reference to FIG. 4, housing 16 includes a divider wall 64 that forms a generally U-shaped internal cavity 65 having generally parallel first and second portions 66 and 67. A polymer cover 69 closes off the open second end 70 of housing 16, and may be welded thereto. End 68 of divider wall 64 is spaced apart from cover 69 to form a gap 71 interconnecting the first and second portions 66 and 67 of internal cavity 65. This arrangement causes the fluid 7 in housing 16 to flow in a generally U-shaped pattern, such that the fluid 7 is heated by the heating element. As illustrated in FIG. 3, barbed fluid connectors 72 and 73 may alternately be positioned at an end sidewall portion 74 of housing 16.
The heater of the present invention may be fabricated in a very cost-effective manner, and the titanium heating element alleviates lime buildup and other problems associated with known heaters. Furthermore, the cup-shaped metal member and thermostat provide for accurate determination of the temperature of the fluid in the housing, despite the fact that the housing does not readily transfer heat. Still further, the silicone rubber fitting arrangements provide for a very secure watertight interconnection where the various components extend through the housing sidewalls. The silicone rubber accommodates differences in thermal expansion between the various components, such that a watertight seal is maintained across a range of operating conditions and temperatures.
In the foregoing description, it will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims by their language expressly state otherwise.

## Claims

1. A heater for fluids, comprising:
a housing made of a non-metallic material and having an internal cavity and an inlet and an outlet, each of which are in fluid communication with the internal cavity, the housing having an opening therethrough; 
an elongated electrical heating element disposed within the cavity for heating fluid flowing through the cavity, the heating element having a generally circular cross-sectional shape and having a U-shaped portion disposed in the cavity and having electrical connectors at opposite ends of the electrical heating element extending through the housing, the electrical heating element having a titanium outer surface; 
a metallic member disposed at the opening and having an inner surface that is exposed to the cavity; 
a sensor operably connected to the metallic member to determine a temperature of fluid in the housing.

2. The heater of claim 1, wherein:
the opening in the housing is substantially circular; and 
the metallic member is substantially cup-shaped with a portion of the metallic member disposed in the opening.

3. The heater of claim 2, wherein:
the metallic member includes an outwardly extending peripheral flange; and including: 
a ring-like gasket made of an elastomeric material disposed between the peripheral flange and the housing to form a seal.

4. The heater of claim 3, wherein:
the opening includes an outer cylindrical surface portion defining a first diameter and an inner cylindrical portion defining a second diameter that is less than the first diameter, the opening having a tapered step surface extending between the inner and outer cylindrical portions, the gasket contacting the tapered step surface.

5. The heater of claim 4, wherein:
the gasket is made of a high temperature silicone rubber material.

6. The heater of claim 2, wherein:
the heating element is disposed within the cavity with the opposite ends of the heating element extending out of a first end of the housing.

7. The heater of claim 6, wherein:
the first end of the housing defines a sidewall having a pair of end openings therethrough, each opening having a tapered sidewall step portion, the electrical heating element having end portions extending through the end openings; and including: 
a pair of ring-like elastomeric gaskets in the end openings contacting the tapered sidewall step portions of the openings and the end portions of the heating element to provide a waterproof seal.

8. The heater of claim 2, wherein:
the housing is made of a polymer material.

9. The heater of claim 8, wherein:
the housing has a main body portion having a generally oval cross-sectional shape having open opposite ends, and a pair of end caps sealingly closing off the opposite ends.

10. The heater of claim 1, wherein:
the sensor comprises a thermostat configured to turn off the electrical heating element when the thermostat is at or above a preselected temperature.

11. A heater for fluids, comprising:
a housing made of a non-metallic material and defining a sidewall and an internal cavity and an opening through the sidewall; 
an elongated electrical heating element disposed in the internal cavity and having opposite ends extending through the sidewall; 
a metallic member at the opening and having an inner surface exposed to the internal cavity; and 
a temperature sensor operably coupled to the metallic member to determine a temperature of the metallic member.

12. The heater of claim 11, wherein:
the opening in the housing is substantially circular; and 
the metallic member is substantially cup-shaped with a portion of the metallic member disposed in the opening.

13. The heater of claim 12, wherein:
the metallic member includes an outwardly extending peripheral flange; and including: 
a ring-like gasket made of an elastomeric material disposed between the peripheral flange and the housing to form a seal.

14. The heater of claim 13, wherein:
the opening includes an outer cylindrical surface portion defining a first diameter and an inner cylindrical portion defining a second diameter that is less than the first diameter, the opening having a tapered step surface extending between the inner and outer cylindrical portions, the gasket contacting the tapered step surface.

15. The heater of claim 14, wherein:
the gasket is made of a high temperature silicone rubber material.

16. The heater of claim 11, wherein:
the electric heating element has a titanium outer surface.

17. The vacuum cleaner of claim 11, wherein:
the housing is made of a polymer material.

18. A vacuum cleaner, comprising:
a frame; 
a powered rotation brush; 
a suction unit; 
a fluid connector for liquid cleaning solution; 
a fluid conduit for transport of liquid cleaning solution from the fluid container to an area adjacent the rotating brush; and 
a heater operably connected to the fluid conduit for heating fluid flowing therethrough, the heater including a housing defining an internal cavity and a heating element disposed within the internal cavity of the housing, and wherein the heating element includes a titanium outer surface that contacts liquid cleaning solution in the housing.

19. The vacuum cleaner of claim 18, wherein:
the housing has an opening therethrough; and including: 
a metallic member disposed at the opening and having an inner surface that contacts fluid in the cavity of the housing; 
a sensor operably connected to the metallic member to determine a temperature of fluid in the housing.

20. The vacuum cleaner of claim 19, wherein:
the opening in the housing is substantially circular; and 
the metallic member is substantially cup-shaped with a portion of the metallic member disposed in the opening.

21. The vacuum cleaner of claim 20, wherein:
the metallic member includes an outwardly extending peripheral flange; and including: 
a ring-like gasket made of an elastomeric material disposed between the peripheral flange and the housing to form a seal.

22. The vacuum cleaner of claim 21, wherein:
the opening includes an outer cylindrical surface portion defining a first diameter and an inner cylindrical portion defining a second diameter that is less than the first diameter, the opening having a tapered step surface extending between the inner and outer cylindrical portions, the gasket contacting the tapered step surface.