GB1574666A

GB1574666A - Vacuum cleaner

Info

Publication number: GB1574666A
Application number: GB9402/78A
Authority: GB
Original assignee: Fisker and Nielsen AS
Current assignee: Fisker and Nielsen AS
Priority date: 1977-03-11
Filing date: 1978-03-09
Publication date: 1980-09-10
Also published as: IT1103653B; DK108077A; NL181708C; DK144552C; DE2809153A1; SE7802699L; DK144552B; DE2809153C2; NL181708B; SE439428B; NL7802554A; IT7809365A0

Description

(54) A VACUUM CLEANER (71) We, A/S GISKER & NIELSEN, a company organized under the laws of Denmark, of No. 30, Peter Bangsvej, 2000 Copenhagen F, Denmark, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a vacuum cleaner comprising a casing provided with an opening for the inflow of dust-laden air and a discharge opening for filtered air, a motorfan unit mounted within the casing and having an air inlet opening and an air outlet opening, a dust separating filter element located between the inflow opening of the casing and the air inlet opening of the motorfan unit, and a sealing element between the downstream side of the filter element and said air outlet opening.

Vacuum cleaners of the kind referred to are known in which the sealing element between the suction side and the delivery side of the fan is located such that the filtered air discharged from the fan flows in contact with a substantial portion of the inner wall of the vacuum cleaner housing.

With increasing power consumption of the fan motor, dictated by the desire for a high suction capacity, the temperature of the discharge air, which also serves to cool the motor and the fan increases. The temperature may become so high that it causes burns to an operator unintentionally or inadvertently touching the casing. If the vacuum cleaner casing and/or parts secured thereto, such as electric component parts, are made of materials which are only moderately temperature resistant, such as plastics, the high temperature of the discharge air may lead to softening of the materials resulting in permanent deformations and deterioration.

For remedying this drawback it has been proposed in our British Patent Specification No; 1,541,664 that the sealing element between the suction and delivery side of the fan may be tubular and arranged between the air outlet opening of the motorfan unit and the discharge opening of the casing in such a way that it surrounds an air outflow passage from the fan and separates this passage from the surrounding space within the casing, which space communicates freely with the downstream side of the filter element. In this way it can be ensured that after having passed the filter element the relatively cool air can flow in contact with the entire inner surface of the casing except a small area immediately surrounding the discharge opening so that the casing wall is efficiently cooled by that air due to the circulating flow thereof through the above-mentioned space which surrounds the motor-fan unit.

In our prior British Patent Application No. 48384/77 (Serial No. 1,574,165) there is described a vacuum cleaner of similar design as in Patent Specification No. 1,531,664 and wherein a temperature sensor is mounted in the space between the vacuum cleaner casing and the motor-fan unit. The sensor operates to open a normally closed valve when the temperature within the space exceeds a predetermined value whereby ambient air can flow into the space. This protects the vacuum cleaner from damage due to excessive temperatures, especially in case the suction conduit becomes unintentionally closed or choked so that the normal flow of air through the vacuum cleaner is entirely or substantially discontinued. The opening of the valve creates an alternative flow path for cooling air to the motor and the fan.

The location of the temperature sensor in that space, to which ambient air shall be drawn in when the valve opens, is evidently advantageous from a constructional point of view, but it has been found to result in a rather slow response of the sensor to increased temperature of the discharge air.

A reason for this is that during normal operation the sensor is located in the pre yiously mentioned circulating flow of relatively^ cool filtered air, and when the temperature of the discharge air increases, the sensor is primarily heated by radiation from the surrounding walls, in particular the Outer wall of the motor-fan unit. This means that- when the temperature of the discharge air rises steeply, the temperature of the sensor increases substantially slower than that of the air, and for ensuring the opening of the valve at a given temperature of the discharge air the actuating temperature of the sensor has to be chosen a good deal lower. A low actuating temperature involves, however, in particular at high ambient temperature such as in the tropics, the risk thatthe sensor may cause the valve to open in situations- where this is not required.

According to the present invention there is provided a vacuum cleaner comprising a casing provided with an opening for the inflow of dust-laden air and a discharge opening for filtered air, a motor-fan unit mounted within the casing and having an air inlet opening and an air outlet opening, a dust separating filter element located between the inflow opening of the casing and the air inlet opening of the motor-fan unit, and a sealing element between the downstream side of the filter element and said air outlet opening, wherein the sealing element is tubular and arranged between the air outlet opening of the motor-fan unit and the discharge opening of the casing so as to- -surround an air outflow passage from the motor-fan unit and to separate said passage from the surrounding space within the casing, which space communicates freely with the downstream side of the filter element, a temperature sensor being mounted in said space and arranged for actuating a normally closed valve at a predetermined temperature whereby the valve opens to permit inflow of ambient air to the space, and wherein a narrow duct extends from the interior of the motor-fan unit in the vicinity of the air outlet opening of said unit with its outlet directed towards the temperature sensor and spaced a short distance therefrom.

Due to the pressure differential between the interior of the motor-fan unit and the surrounding space, a small amount of heated discharge air flows from the interior of the unit through the narrow duct directly towards the temperature sensor, so that the temperature of the sensor follows the temperature of the discharge air with much shorter- delay than with- the previously suggested- design. As a.result thereof it has been found. possible to adjust the -temperature sensor to actuate the-opening of the valve at a sensor temperature which- is considerably higher (up to 400C higher) than with the design of Application No. 48384/77 (Serial No. 1,574,165). Since a relatively weak current of air flowing towards the sensor is sufficient the duct may be so narrow that the amount of air flowing "backwards" through the duct does not materially increase the pressure at the suction side-of the fan and- consequently does not reduce the suction capacity of the vacuum cleaner. In this connection it is advantageous that the pressure differences between the delivery and suction sides of the fan-and hence-the flow rate of the air directed against the sensor is a maximum when the suction- conduit of the vacuum cleaner is choked which is exactly the situation in which the temperature sensor shall become operative.

In a structurally simple embodiment of the invention the temperature sensor is mounted opposite the outer wall of the motor-fan unit, and the duct is provided by a bore in said outer wall.

Tests have shown- that with a duct diameter ofbetween 1 and 2mm an air stream sufficient to heat the sensor can be obtained without substantially effecting the pressure differential across the fan.

The invention will now be described in more detail with reference to accompanying drawings in which Fig. 1 is a schematic section through a vacuum cleaner embodying the invention and shown with a suction nozzle connected thereto, and Fig. 2 is a vertical section on a larger scale through that part of the vacuum cleaner hood in which the motor-fan unit, the temperature sensor and the valve controlled thereby are mounted.

The vacuum cleaner illustrated in the drawings is a so-called vertical or canister type vacuum cleaner, the - casing of which consists of three readily separable parts, i.e.

a lower part 1, which functions as a dust container, an upper part 2 and a hood 3.

As indicated in Fig. 1 the dust container is formed with socket 4 for receiving a vacuum cleaner hose 5 on the free end of which a suction nozzle or mouthpiece 6 may be mounted. Socket 4 may be forced with an inwardly protruding part to which a dust bag (not shown) may be removably secured.

A dust filter 7 made of a suitable textile material is mounted on a holder, which is clamped between the dust container 1 and the upper casing part 2.

The motor-fan unit of the vacuum cleaner is mounted in a hood 3 and comprises an electric motor 8, the stator housing of which is open at its lower end for the inflow of filtered air, a fan secured to the output shaft of the motor and comprising two series connected fan stages 9 and 10, and associated stationary vanes or baffles 11 and 12. The fan portion of the unit is surrounded by an air-tight housing 13 which at its lower end is - sealingly connected to the stator housing of motor 8, and-which at its upper endthas a centrally located air outlet opening 13, see Fig. 2.

Opening 14 is located opposite and coaxially with an air discharge opening 15 in a recessed part 16 of- the wall of hood 3.

That edge of the top wall of housing 13; which surrounds opening 14, has been upturned so as to center a sealing ring 17 having a U-shaped cross-sectional profile and'made of an elastomeric material. A suitable embodiment of the sealing ring has been described in more- detail in the afore said Patent Specification No. 1,531,664. Ring 17 provides a seal between the space 18 defined- between- the outer surface of housing 13, the inner surface of hood 3 and the outer surface of ring - 17, and the central air outflow passage 19 extending between openings 14 and 15 and defined by the inner surface of ring 17.

As described in more detail in Patent Specification No. 1,531,664 there exists a substantially unimpeded flow passage internally of the vacuum cleaner casing between space 18 and the downstream side of filter 7 so that during normal operation of the vacuum cleaner there is created an internal air flow pattern as illustrated by the various arrows in Fig. 1. From nozzle 6 the dustladen air flows through hose 5, as shown by arrows 20, into dust container 1 and through filter 7, as shown by arrows 21, either directly or through the above-mentioned dust bag (not shown) when such a bag is employed. Part of the filtered air flows upwardly into space 18 towards the inner surface of hood 3, as shown by arrows 22.

in the left-hand part of Fig. 1. This current of relatively cold air reverses and moves downwardly as shown by arrows 23, whereby a certain turbulence is created in space 18.

This ensures an efficient cooling of the outer wall surfaces of hood 3 in that the circulating current picks up heat before it flows into the motor-fan unit together with the remainder of the filtered air as shown by arrows 24.

Arrows 25 in the upper part of Fig. 1 indicate the discharge of the heated air through the short and relatively narrow outflow passage 19 and discharge opening 15.

In the cooled part of the wall of hood 3 outside the recessed wall portion 16, see Fig. 2, there is mounted a valve generally designated by 26 and which is closed during normal operation of the vacuum cleaner.

Valve 26 comprises a valve part 27 formed in hood 3 and having a flat valve seat for cooperating with a valve member 28, which is integral with a downwardly extending, hollow and thin-walled valve stem 29 in which there is contained an amount of a meltable material 30 which is solid at normal opcrational temperatures, but which melts at a predetermined higher temperature.

Two relatively. stiff; though deformable ribs 31 are formed on valve part 27 on opposite sides of valve stem 29. On its outer surface the stem is formed with two saw tooth shaped projections 32 each having- a relatively - slightly. inclined upper surface and a substantially steeper lower surface. When the valve is closed as shown in Fig. 2, the upper surfaces of projections 32 engage with the lower edge surfaces of ribs 31, which thus retain valve member 28 in the closed position due to the incompressibility of the solid material 30.

When material 30 melts, the relatively thin wall of valve stem 29 and the molten material may be compressedradially under the influence of a spring 33 which biases valve stem 29 and hence valve member 28 with an upwardly directed force. At the previously mentioned predetermined temperature the valve is opened by the spring force which subsequently maintains the valve open until it is closed or reset manually when a knob 34 secured to the upper side of valve member 28 is pressed down.

When projections 32 have cleared ribs 31 during the upward movement of the valve member, valve stem 29 will reassume the configuration shown in Fig. 2 under the influence of the hydrostatic pressure of the molten material 30, possibly supplemented by the inherent resiliency of the valve stem, so that when material 30 solidifies the projections 32 have already been pressed outwardly to their initial position. When valve member 28- is then reset by means of knob 34, the projections may deflect ribs 31 outwardly, and when the ribs have sprung back, the valve member is again retained in the closed position shown in Fig. 2.

In the wall of the motor-fan unit housing 13 there is a narrow bore 35 immediately below the lower end face of valve stem 29.

During operation of the vacuum cleaner the pressure differential between the inner and outer side of housing 13 created by the rotating fan results in an outflow of air through bore 35, and since the bore is located in the vicinity of the final stage 12 of stationary vanes, the temperature of the outflowing air is substantially equal to the temperature of the air discharged through opening 15. Said location of bore 35 also ensures a high pressure differential for creating the air current, which thus even with a small diameter of the bore, e.g. 1.2 mm, is sufficient for maintaining valve stem 29 and the meltable material 30 enclosed therein at a temperature which closely follows the temperature of the discharge air.

It is thus ensured that valve 26 responds to any dangerous temperature rise of the discharge air with high accuracy and low response time and that it provides the required cooling of the vacuum cleaner casing by permitting cold ambient air to flow directly into the casing, primarily to space 18 around housing 13 of the motor-fan unit where the highest temperature prevails.

It will be appreciated that the detailed construction of the temperature controlled valve, which opens to permit the inflow of ambient air, may deviate from that shown in the drawing. For instance any of the embodiments shown in Application No.

48384/77 (Serial No. 1,574,165) may be employed. It is not mandatory that the temperature sensor and the valve are combined in a structural unit as shown in Fig. 2, even if this will generally be preferable for simplicity of design and manufacture.

WHAT WE CLAIM IS: 1. A vacuum cleaner comprising a casing provided with an opening for the inflow of dust-laden air and a discharge opening for filtered air, a motor-fan unit mounted within the casing and having an air inlet opening and an air outlet opening, a dust separating filter element located between the inflow opening of the casing and the air inlet opening of the motor-fan unit, and a sealing element between the downstream side of the filter element and said air outlet opening, wherein the sealing element is tubular and arranged between the air outlet opening of the motor-fan unit and the discharge opening of the casing so as to surround an air outflow passage from the motor-fan unit and to separate said passage from the surrounding space within the casing, which space communicates freely with the downstream side of the filter element, a temperature sensor being mounted in said space and arranged for actuating a normally closed valve at a predetermined temperature whereby the valve opens to permit inflow of ambient air to the space, and wherein a narrow duct extends from the interior of the motor-fan unit in the vicinity of the air outlet opening of said unit with its outlet directed towards the temperature sensor and spaced a short distance therefrom.

2. A vacuum cleaner as claimed in claim 1 wherein the temperature sensor is mounted opposite the outer wall of the motor-fan unit, and the duct is provided by a bore in said outer wall.

3. A vacuum cleaner as claimed in claim 1 or 2 wherein the diameter of the duct is between 1 and 2 mm.

4. A vacuum cleaner as claimed in any of claims 1-3 wherein the temperature sensor and the valve actuated by the sensor form a structural unit.

5. A vacuum cleaner substantially as described hereinbefore with reference to the accompanying drawings.

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Claims

**WARNING** start of CLMS field may overlap end of DESC **.

response time and that it provides the required cooling of the vacuum cleaner casing by permitting cold ambient air to flow directly into the casing, primarily to space 18 around housing 13 of the motor-fan unit where the highest temperature prevails.

It will be appreciated that the detailed construction of the temperature controlled valve, which opens to permit the inflow of ambient air, may deviate from that shown in the drawing. For instance any of the embodiments shown in Application No.

48384/77 (Serial No. 1,574,165) may be employed. It is not mandatory that the temperature sensor and the valve are combined in a structural unit as shown in Fig. 2, even if this will generally be preferable for simplicity of design and manufacture.

WHAT WE CLAIM IS: 1. A vacuum cleaner comprising a casing provided with an opening for the inflow of dust-laden air and a discharge opening for filtered air, a motor-fan unit mounted within the casing and having an air inlet opening and an air outlet opening, a dust separating filter element located between the inflow opening of the casing and the air inlet opening of the motor-fan unit, and a sealing element between the downstream side of the filter element and said air outlet opening, wherein the sealing element is tubular and arranged between the air outlet opening of the motor-fan unit and the discharge opening of the casing so as to surround an air outflow passage from the motor-fan unit and to separate said passage from the surrounding space within the casing, which space communicates freely with the downstream side of the filter element, a temperature sensor being mounted in said space and arranged for actuating a normally closed valve at a predetermined temperature whereby the valve opens to permit inflow of ambient air to the space, and wherein a narrow duct extends from the interior of the motor-fan unit in the vicinity of the air outlet opening of said unit with its outlet directed towards the temperature sensor and spaced a short distance therefrom.
2. A vacuum cleaner as claimed in claim 1 wherein the temperature sensor is mounted opposite the outer wall of the motor-fan unit, and the duct is provided by a bore in said outer wall.
3. A vacuum cleaner as claimed in claim 1 or 2 wherein the diameter of the duct is between 1 and 2 mm.
4. A vacuum cleaner as claimed in any of claims 1-3 wherein the temperature sensor and the valve actuated by the sensor form a structural unit.
5. A vacuum cleaner substantially as described hereinbefore with reference to the accompanying drawings.