GB2090480A

GB2090480A - Cooling electric motors in hairdryers

Info

Publication number: GB2090480A
Application number: GB8138463A
Authority: GB
Original assignee: FCF Ltd
Current assignee: FCF Ltd
Priority date: 1980-12-31
Filing date: 1981-12-22
Publication date: 1982-07-07

Abstract

A hairdryer incorporating a housing 11, an electric heater element 18, an electric motor 21 and a fan 27 driven by the motor has a motor cooling system by means of which air is blown through the motor in a direction opposite to that of the main airflow. The fan 27 produces a main airstream from an inlet end 30 to an outlet end 31/32, the air passing over the heater element 18. Some air passes through apertures 33 in an end of a support 13 for the motor 21 and flows over the housing of the motor to reach the end of the motor remote from the fan 27. This air then passes into an inlet in that end of the motor, passes through the motor, (left to right in Fig. 1), and is drawn out from the motor through apertures 34 into a low pressure area associated with the central region of the rotating fan. <IMAGE>

Description

SPECIFICATION Hairdryers The invention relates to hairdryers and is concerned particularly with an arrangement for cooling an electric motor of a hairdryer.

A typical hairdryer incorporates a housing, an electric heater element, an electric motor and a fan arranged to be driven by the motor to blow air over the heater element and so produce a stream of warm air for drying hair.

In recent years there have been tendencies to make hairdryers more compact and to use more powerful heating elements and these factors tend to increase the internal temperature of the hairdryer including that of the motor. There is also a tendency to use simple DC electric motors which tend to become unreliable when operated in an enclosed high temperature environment. The problem becomes more acute when the motor is close to the heater.

An object of the present invention is to provide a cooling arrangement for the electric motor of a hairdryer which is simple and effective.

According to the present invention there is provided ,a hairdryer incorporating a housing, an electric heater element, an electric motor and a fan arranged co-axially with the motor to be driven by the motor to blow air around the motor and over the heater element to an outlet characterised in that some of the air blown by the fan is ducted to a motor air inlet at the end of the motor remote from the fan, this air passing through the motor as a cooling air stream in a direction against the main airflow direction in the hairdryer and being extracted from the end of the motor adjacent the fan by a low pressure region formed by the fan near the centre thereof. By this arrangement, the fan intended for blowing air over the heater element also provides an airflow through the motor, which results in effective cooling of the motor.

Although a typical fan used in a hairdryer system is an axial flow fan, there is a tendency in any fan for a low pressure region to develop near its centre as a result of a centrifugal effect and advantage is taken of this fact with the present invention by drawing air out of the motor into the low pressure area.

In the kind of hairdryer in which the heater surrounds the motor, air should be supplied in one or more ducts extending between the heater and the motor to guide air from the fan to the end of the motor remote from the fan to the motor air inlet.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a cross section through a hairdryer of the invention; and Figure 2 is an end elevation of internal parts of the motor with the fan removed.

The hairdryer shown in the drawings incorporates an outer cylindrical housing 11 from which a handle 1 2 projects. The outer housing supports in its interior, an inner moulding 1 3 (best seen in Fig. 2) which supports most of the interior working parts of the hairdryer.

The inner moulding 1 3 is primarily in the form of a cylindrical part 15, with eight external ribs 1 6 which serve to locate the inner moulding within the housing 11 and are also slotted as shown at 1 7 in Fig. 1 to support a heater element 1 8 in an annular space between the housing 11 and the cylindrical part of the inner moulding. The inner moulding also has eight inwardly directed ribs 1 9 the inner ends of which engage with and support the outer casing of an electric motor 21. These ribs form eight spaces around the periphery of the motor. The space opposite the handle 12, incorporates a thermal cut-out 22 which is isolated from the motor by a transverse rib 23 but is open to the region of the hairdryer incorporating the heater element 18.

The end of the inner moulding to the right in Fig 1 incorporates a conical taper section 24 which terminates in an end face 25.

The motor shaft 26 extends out through the end face 25 and supports an axial flow fan 27 comprising an inner hub 28 and blades 29.

The end of the housing 11 adjacent the fan 27 is closed off by a grid 30 which allows air to flow into the fan but protects the fan against intrustion of fingers or similar sized objects. At the opposite end of the hairdryer, an end closure 31 closes off the end of the cylindrical part of the inner moulding and is supported from the housing 11. by ribs 32 to provide an annular outlet from the hairdryer.

The conical tapered portion 24 of the inner moulding 25 has four apertures 33 shown in Fig. 2 which communicate between the region of the fan 27 and four longitudinal ducts formed between inwardly directed ribs 19.

Apertures 33 are in line with the blades 29 of the fan and in an airflow area which is converging due to the conical taper at 24. This results in a high pressure at the apertures 33 so that air enters these apertures and flows down the ducts to the downstream end of the motor 21, i.e., the end remote from the fan 27. The air flows in through apertures which are provided in the end of a typical motor for airflow purposes. This air then passes over the commutator of the motor when this is a DC motor, through a space between the armature and the stator of the motor to the end of the motor adjacent the fan 27. Apertures 34 are provided in the end face 25 and these communicate with air flow passages normally provided in the housing of a motor to allow the flow of air to escape from the motor into the central region of the fan 27.Because a low pressure area tends to develop near the axis of a rotating body due to a tendency for the body to act as a centrifugal fan, the low pressure area near the centre of the fan tends to draw air out through the end of the motor and the apertures 34, thus supplementing the flow of air. The air may then flow out radially on the motor side of the fan to join the main airstream generated by the rotation of the fan blades. Alternatively, the central boss of the fan may incorporate apertures to allow the cooling air to pass through this boss to the up-stream side of the fan.

In the kind of DC permanent magnet electric motor commonly used with hairdryers, it is conventional to provide an inlet at each end of the hairdryer and one or more outlets on the cylindrical part of the motor housing.

Rotation of the armature and commutator tends to set up some airflow by centrifugal force, drawing air in from both ends of the motor and out through the outlets in the cylindrical wall. With the present invention, use is made of the openings at both ends of the motor as inlets and outlets respectively although these were originally intended both to be inlets. Clearly, it becomes necessary to blank off the openings intended as outlets to ensure good flow through the hairdryer. This blanking can be done by means such as adhesive tape but as a further precaution, these outlets are arranged to be in sectors defined by the ribs 19 which lie between the air ducts with their inlets 33.

The hairdryer is also provided with-an on-off switch 35 and other conventional electrical components such as a rectifier assembly 36 for providing a DC supply to the electric motor when the hairdryer is operating from an AC mains supply. In use, when the hairdryer is switched on, the motor 21 drives the fan 27 and causes air to be blown over the heater element 18 to provide a stream of hot drying air from the annular outlet of the hairdryer.

Throughout the time while the motor is run ning, the cooling airflow is being passed through the motor to prevent over heating thereof.

Claims

1. A hairdryer incorporating a housing, an electric heater element, an electric motor and a fan arranged co-axially with the motor to be driven by the motor to blow air around the motor and over the heater element to an outlet, characterised in that some of the air blown by the fan is ducted to a motor air inlet at the end of the motor remote from the fan, this air passing through the motor as a cool ing air stream in a direction against the main airflow direction in the hairdryer and being extracted from the end of the motor adjacent the fan by a low pressure region formed by the fan near the centre thereof.

2. A hairdryer as claimed in Claim 1, of the kind of which the heater surrounds the motor wherein air is supplied in one or more ducts extending between the heater and the motor to guide air from the fan to the end of the motor remote from the fan and so to the motor air inlet.

3. A hairdryer as claimed in Claim 1 or Claim 2 wherein the ducting is in the form of spaced individual ducts spaced around the periphery of the motor.

4. A hairdryer substantially as hereinbefore described with reference to and as shown in the accompanying drawings.