GB2425938A

GB2425938A - Self-propelling apparatus for a vacuum cleaner

Info

Publication number: GB2425938A
Application number: GB0519739A
Authority: GB
Inventors: Joo-Sung Moon; Byung-Jo Lee; Myoung-Sun Choung
Original assignee: Samsung Gwangju Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2005-04-28
Filing date: 2005-09-28
Publication date: 2006-11-15
Anticipated expiration: 2025-09-28
Also published as: KR100667863B1; GB2425938B; AU2005209669A1; KR20060112781A; GB0519739D0; AU2005209669B2; US20060242786A1

Abstract

A self-propelling apparatus (130) for a vacuum cleaner having a cleaner body 110 pivotably mounted to a nozzle unit 120 is provided. The self-propelling apparatus 130 includes a sensor unit 300 having a wheel unit 310 that pivots in the direction opposite to that in which the vacuum cleaner moves, a connection unit 320 connected to the wheel unit and fixed to the nozzle unit 120 by one end thereof, and a switch unit 331,332 which is turned on and off by the connection unit, thereby to generate progression and retrogression signals according to the pivoting motion of the wheel unit. An interception unit 400 is provided to generate an interception signal when the cleaner body 120 is upright, and a drive unit 200 moves the vacuum cleaner 100 forwards or backwards in accordance with the progression and retrogression signals.

Description

Self-Propelling Apparatus for a Vacuum Cleaner This invention relates to a

self-propelling apparatus fbr a vacuum cleaner, the apparatus being capable of automatically driving the vacuum cleaner forwards and backwards.

US Patent Specification 6,282,747 discloses a vacuum cleaner in which, when an operator grips a handle and moves the body of the cleaner forwards or backwards, this action is transmitted to a drive module through a linkage mechanism connected to the handle so that the vacuum cleaner is automatically driven forwards and backwards. US Patent Specification 6,158,084 discloses another vacuum cleaner capab]e of automatically moving forwards and backwards as the operator's action is transmitted to a transmission through a cable connected to the handle. Japanese Patent Publication No. 115-68656 discloses a vacuum cleaner which automatically moves forwards and backwards by detecting the torque applied to a drive wheel thereby operating a drive motor for forwards and backwards movement. Using the self-propelling apparatus as described iii the above examples, once driven forwards or backwards, the vacuum cleaner concerned automatically maintains the forwards or backwards motion without further application of force. Therefore, cleaning is facilitated, even on an uneven surface, such as carpet, which tends to hinder smooth travel of a vacuum cleaner due to the high resistance generated.

However, the known vacuum cleaners disclosed in the two US Patent Specifications mentioned above have the disadvantage that, while an action force is transmitted through a connection means such as a linkage mechanism or a cable, the operator's intention to drive the vacuum cleaner forwards and backwards may not be followed or may fail. This may cause malfunction of the self-propelling apparatus, thereby reducing the reliability of the apparatus. Also, the connection means such as the linkage mechanism or the cable complicates the structure and increases the manufacturing cost of the apparatus.

Furthermore, a torque detector as employed in the vacuum cleaner of Japanese Patent Publication No. H5-68656 has the disadvantage of leading to a complex structure and a high manufacturing cost. In addition, repetitive use of the electric torque detector may reduce reliability and durability of the apparatus.

An aim of the present invention is to solve at least these disadvantages and to provide at least the advantages described below. Accordingly, a primary aim of the invention is to provide a self-propelling apparatus for a vacuum cleaner which can correctly transmit an operator's intention of moving the vacuum cleaner forwards and backwards.

A secondary aim of the invention is to provide a self-propelling apparatus for a vacuum cleaner, which apparatus has improved reliability and durability.

Another aim of the invention is to provide a vacuum cleaner with a selfpropelling apparatus having a simple structure.

The present invention provides a self-propelling apparatus for a vacuum cleaner having a cleaner body pivotably mounted to a nozzle unit, the apparatus comprising: a sensor unit mounted on the nozzle unit and having a wheel unit which is pivotable, in a direction opposite to that in which the vacuum cleaner moves, to generate progression and retrogression signals according to pivoting motion of the wheel unit; and a drive unit for moving the vacuum cleaner in response with the progression and retrogression signals.

The sensor unit may comprise a connection unit connected to the wheel unit and fixed to the nozzle unit by one end thereof; and a switch unit which can be turned on and off by the connection unit. Advantageously, the wheel unit comprises a wheel for contacting a surface to be cleaned; a housing supporting the wheel; and a shaft disposed on an upper portion of the housing, the wheel unit being pivotable by inertia and friction with the surface to be cleaned.

Preferably, the connection unit comprises a link member including a first via-hole for insertion of the shaft, and a second via-hole for pivotable mounting of the nozzle unit; a resilient member disposed between the link member and the housing, the resilient member fitting around the shaft; a first connection member fixable to the shaft through the first via- hole so as to restrain escape of the link member from the shaft; and a second connection member fixable to the nozzle unit through the second via-hole so that the link member can pivot relative to the nozzle unit.

The switch unit may comprise a first switch disposed on one side of the link member and engagable with that side of the link member thereby to generate a progression signal; and a second switch disposed on the other side of the link member and engageable with that side of the link member thereby to generate a retrogression signal. The switch unit may further comprise a switch cover for shielding and fixing the first and the second switches to the nozzle unit.

The self-propelling apparatus may further comprise an interception unit which generates an interception signal when the cleaner body is in an upright position, and wherein the interception unit comprises a lever mounted on the cleaner body; and a third switch mounted on the nozzle unit and engageable with the lever when the cleaner body is in the upright position.

The drive unit may comprise a motor mounted on the nozzle unit; and a circuit unit for processing the progression and retrogression signals so as to drive the motor forwards or backwards.

Preferably, the circuit unit is such as to process the interception signal to stop the motor.

The present invention also provides a self-propelling apparatus for a vacuum cleaner having a cleaner body pivotably mounted to a nozzle unit, the apparatus comprising: a sensor unit having a wheel unit which is pivotable in a direction opposite to that in which the vacuum cleaner moves, a connection unit connected to the wheel unit and fixed to the nozzle unit by one end thereof, and a switch unit which can be turned on and off by the connection unit, thereby generating progression and retrogression signals according the pivotal movement of the wheel unit; an interception unit for generating an interception signal when the cleaner body is in an upright position; and a drive unit moving the vacuum cleaner in accordance with the progression and retrogression signals.

The invention further provides a self-propelling apparatus for a vacuum cleaner, the apparatus comprising: a wheel unit pivotable in a first direction in response to forwards movement of the vacuum cleaner, and in a second direction in response to backwards movement of the vacuum cleaner; a first switch on one side of the wheel unit, the first switch being actuable by the wheel unit when pivoted in the first direction so that the first switch generates a progression signal; a second switch on the other side of the wheel unit, the second switch being actuable by the wheel unit when pivoted in the second direction so that the second switch generates a retrogression signal; and a motor for moving the vacuum cleaner forwards in response to the progression signal and backwards in response to the retrogression signal.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which:- Figure 1 is a perspective view of a vacuum cleaner having a self- propelling apparatus contracted according to the invention; Figure 2 is a perspective view of the nozzle unit of the vacuum cleaner of Figure 1; Figure 3 is an exploded, perspective view of a sensor unit forming part of the nozzle unit of Figure 2; Figure 4 shows a link member forming part of the sensor unit of Figure 3, the link member being disposed in a neutral position between a first switch and a second switch; Figure 5 shows the link member rotated to a first operating position in which it presses the first switch; Figure 6 shows the link member rotated to a second operating position in which it presses the second switch; and Figure 7 shows the main body of the vacuum cleaner in an upright posture in which an associated lever presses a third switch.

In the following description, the same reference numerals are used for the same elements in different drawings. The description is sufficiently detailed to provide a comprehensive understanding of the invention. Thus, it will be apparent that the invention can be carried out without all the details described. Also, well-known functions or constructions are not described in detail, since they would obscure the invention in unnecessary detail.

Referring to the drawings, Figure 1 shows a vacuum cleaner 100 comprising a cleaner body 110, a nozzle unit 120, and a self-propelling apparatus 130.

The cleaner body 110 is mounted on the nozzle unit 120 to pivot in the directions of the arrows A and B. The cleaner body 110 has, at an upper portion thereof, a handle lii provided with an on/off switch lila. The cleaner body 110 contains a dust separator 112 and a dust receptacle 113.

The nozzle unit 120 is disposed at a lower portion of the cleaner body 110 to draw in dust from a surface to be cleaned. The nozzle unit 120 comprises a lower frame 121 having a suction port 121a (see Figure 2), an upper cover 122 for shielding the lower frame, and a pair of wheels 123 rotatably mounted one on each side of the nozzle unit.

As an operator drives the vacuum cleaner 100 over the surface to be cleaned, forwards and backwards as shown by the arrows C and D, dust on that surface is drawn into the dust separator 112 through the suction port 121a, is separated in the dust separator 112, and is collected in the dust receptacle 113.

Once a force is applied forwards or backwards by the operator, the vacuum cleaner 100 is continuously propelled forwards or backwards without further application of force. To this end, the self-propelling apparatus 130 comprises a drive unit 200, a sensor unit 300, and an interception unit 400.

The drive unit 200 includes a drive part 210 and a circuit part 220. The drive unit 210 comprises a motor 211, a gearbox 212, and left and right auxiliary wheels 213a and 213b.

The motor 211 rotates the auxiliary wheels 213a and 213b forwards and backwards. The gearbox 212 decelerates the output of the motor 211 at an appropriate ratio, and transmits the decelerated speed to the auxiliary wheels 213a and 213b.

The circuit part 220 processes signals generated by first and second switches 331 and 332 (see Figure 3), which are implemented by nhicroswitches, and processes signals generated by a third switch 420 thereby to operate or stop the drive part 210. More specifically, the circuit part 220 rotates the motor 211 forwards upon transmission thereto of a signal generated by the first switch 331. As a result of a retrogression signal generated by the second switch 332 and transmitted to the circuit part 220, the motor 211 is rotated backwards. When a signal generated by the third switch 420 is transmitted to the circuit part 220, the circuit part 220 stops the motor 211 regardless of the generation of the signals by the first and the second switches 331 and 332.

Referring to Figure 3, the sensor unit 300 comprises a wheel unit 310, a connection unit 320, and a switch unit 330.

The wheel unit 310 operates in contact with the surface to be cleaned, and can pivot in response to movement of the vacuum cleaner 100 due to inertia and friction. As shown in Figures 1 and 3, for example, when the vacuum cleaner 100 moves in the direction C, the wheel unit 310 pivots in the direction of the arrow E, which is substantially opposite to the direction C. When the vacuum cleaner 100 moves in the direction D, the wheel unit 310 pivots in the direction of the arrow F, that is substantially opposite to the direction D. For this, the wheel unit 310 comprises a wheel 311, a housing 312, a shaft 313, and a wheel axle 314.

The wheel 3 11 directly contacts the surface to be cleaned. The housing 3 12 is formed as a frame of a flattened-U shape for enclosing and supporting the wheel 311 on the wheel axle 314so that the wheel can rotate about the wheel axle. The shaft 313 is disposed on an upper portion of the housing 312, and has a connection recess 3 13a for coupling with a first connection member 323 in the centre thereof.

The Connection unit 320 comprises a link member 321, a resilient member 322, the first connection member 323, and a second connection member 324. The link member 321 comprises a bent section in which a first via-hole 321a is formed, and a straight section in which a second via-hole 321b is formed. The link member 321 is connected to the wheel unit 310 by inserting the shaft 313 into the first via-hole 321a. The second connection member 324 is then inserted into the second via-hole 321b, to connect the link member 321 to the nozzle unit 120 for pivotal movement of the link member about the second connection member.

The resilient member 322 may be a coil spring disposed between the link member 321 and the housing 312, and can fit around the shaft 313. The housing shaft 313, which passes through the first via-hole 321a of the link member 321, can resiliently ascend and descend to conform with the height of the surface to be cleaned in the directions of the arrows G and H by the action of the resilient member 322.

The first connection member 323 is inserted in the connection recess 31 3a of the shaft 313 through the first via-hole 32 Ia, so that the link member 321 is not released from that shaft in the direction G. The second connection member 324 is connected to the nozzle unit 120, and passes through the second via-hole 32 lb. A respective screw or a rivet may constitute the first and second connection members 323 and 324.

Figures 4 to 6 are views showing the pivoting operation of the link member 321, the cover 333 of the switch not being shown in these figures. Referring to Figures 3 and 4, the switch unit 330 is turned on and off by the connection unit 320, thereby generating the progression signal and the retrogression signal. To this end, the switch unit 330 includes the first switch 33 1, the second switch 332, and the switch cover 333.

The first switch 331 is disposed on one side of the link member 321, and has a first switch projection 33 1 a, which is normally biased to an extended position. As the wheel 311 is pivoted in the direction E about the second connection member 324, the first switch projection 331a is pressed by the side Si of the link member 321. When the first switch projection 331a is thus pressed, as shown in Figure 5, the first switch 331 is turned on to generate the progression signal, and the progression signal is transmitted to the circuit unit 220.

The second switch 332 is disposed on the other side of the link member 321, and has a second switch projection 332a, which is normally biased to an extended position. As the wheel 311 is pivoted in the direction F about the second connection member 324, the second switch projection 332a is pressed by the side S2 of the link member 321. When the second switch projection 332a is thus pressed, as shown in Figure 6, the second switch 332 is turned on to generate the retrogression signal, and the retrogression signal is transmitted to the circuit unit 220.

The switch cover 333 shields the tops of the first and the second switches 331 and 332, and fixes those switches to the nozzle unit 120. However, the first and the second switches 331 and 332 may be directly fixed to the nozzle unit 120 without the switch cover 333 being present. The switch cover 333 includes a second connection member insertion hole 333a (see Figure 3) for penetration by the second connection member 324. After inserting the second connection member 324 into the second connection member insertion hole 333a, the second connection member pivotably mounts the link member 321 to the nozzle unit 120.

The interception unit 400 comprises a lever 410 and the third switch 420 in order to generate the interception signal, as shown in Figure 2.

As shown in Figure 7, the lever 410 is mounted on the cleaner body 110, and presses the third switch 420 only when the cleaner body 110 is upright (as shown in Figure 1). However, the lever 410 does not press the third switch 420 when the cleaner body 110 is pivoted to the position shown in Figure 2 with respect to the nozzle unit 120 in the direction B. The third switch 420 is mounted on the nozzle unit 120, and is pressed by the lever 410 when the cleaner body 110 is upright, the third switch 420 having a third switch projection 420a (see Figure 7) which is pressed by the lever when the cleaner body is upright. As the third switch projection 420a is pressed by the lever 410, the third switch is turned on, thereby generating the interception signal. Upon transmission of the interception signal to the circuit unit 220, the circuit unit 220 stops the motor 211 regardless of the generation of the progression and the retrogression signals.

The interception unit 400 is not essential to the operation of the selfpropelling apparatus 130.

However, since the cleaner body 110 is usually inclined by the operator during cleaning, it is preferable to incorporate the interception unit 400 which is capable of detecting the inclination of the cleaner body 110 so that the self-propelling apparatus 130 is operated only upon detection of the inclination of the cleaner body.

The operation of the self-propelling apparatus 130 will now be described.

Referring to Figure 1, when the operator moves the vacuum cleaner 100 forwards in the direction C, the wheel unit 310 is pivoted about the wheel axle 314 and is pivoted about the second connection member 324 in the direction E, that is to say in the direction opposite to the direction in which the vacuum cleaner 100 moves, owing to the inertia and friction of the wheel unit with the surface to be cleaned. With reference to Figure 4, the link member 321 (which is connected to the wheel unit 310) is also pivoted in the direction E, thereby moving to the position shown in Figure 5 from the position shown in Figure 4. Accordingly, the side SI of the link member 321 presses the first switch projection 33la of the first switch 331.

The first switch 331 then generates the progression signal and, as shown in Figure 2, the progression signal is transmitted to the circuit unit 220. The circuit unit 220 drives the motor 211 in the forwards direction. Forwards rotation of the motor 211 is transmitted to the left and the right auxiliary wheels 213a and 213b, thereby propelling the vacuum cleaner 100 forwards in the direction C. Thus, once movement in the direction C is initiated by the operator, the vacuum cleaner 100 can be kept moving in the direction C by the self- propelling apparatus 130, without the operator having to propel the vacuum cleaner forwards.

If the operator forcibly seizes or stops the vacuum cleaner 100 from moving forwards in the direction C, the link member 321 is pivoted in the direction F from the position shown in Figure 5 to the position shown in Figure 4, so that the first switch projection 331a is no longer pressed. Accordingly, the first switch 331 stops generating and transmitting the progression signal to the circuit unit 220, so that the circuit unit stops drive to the motor 211, and the forwards drive to the vacuum cleaner 100 in the direction C by the self-propelling apparatus 130 is stopped.

With reference to Figure 1, when the operator moves the vacuum cleaner 100 backwards in the direction D, the wheel unit 310 is pivoted about the wheel axle 314, and is pivoted about the second connection member 324 in the direction F that is to say in the direction opposite to the direction in which the vacuum cleaner 100 moves by inertia and friction with the surface to be cleaned. With reference to Figure 4, the link member 321, which is connected with the wheel unit 310, is also pivoted in the direction F, thereby moving to the position shown in Figure 6 from the position shown in Figure 4. Accordingly, the side S2 of the link member 321 presses the second switch projection 332a of the second switch 332, so that the second switch generates the regression signal and, as shown in Figure. 2, the retrogression signal is transmitted to the circuit unit 220, so that the circuit unit drives the motor 211 backwards. Backwards drive of the motor 211 is transmitted to the left and the right auxiliary wheels 213a and 2l3b, thereby propelling the vacuum cleaner 100 backwards in the direction D. Thus, once movement in the direction D is initiated by the operator, the vacuum cleaner 100 can be kept moving in the direction by the self-propelling apparatus 130, without the operator having to keep propelling the vacuum cleaner 100 backwards. If the operator forcibly seizes or stops the vacuum cleaner 100 from moving backwards in the direction D, the link member 321 is pivoted in the direction E from the position shown in Figure 4 to the position shown in Figure 6, so that the second switch projection 332a is no longer pressed.

Accordingly, the second switch 332 stops generating and transmitting the retrogression signal to the circuit unit 220, so that the circuit unit stops driving the motor 211, and the backwards running of the vacuum cleaner 100 in the direction D by the self-propelling apparatus 130 is stopped.

When the cleaner body 110 is in the upright position as shown in Figure 7, the lever 410 presses the third switch projection 420a. The third switch 420 then generates the interception signal. As the interception signal is transmitted to the circuit unit 220, the circuit unit stops the motor 211 regardless of the generation of the progression and the retrogression signals of the first and the second switches 331 and 332. Therefore, the vacuum cleaner 100 is not automatically moved forwards and backwards upon initial application of the force of moving the vacuum cleaner forwards and backwards.

As will be apparent, the operator's action for moving the vacuum cleaner 100 forwards or backwards is transmitted through the wheel unit 310 which is in direct contact with the surface to be cleaned. Accordingly, the operator's intention can be correctly delivered, thereby improving reliability.

Moreover, since the sensor unit 300 is a mechanical unit, reliability and durability thereof can be enhanced in spite of repeated use.

Furthermore, since the structure does not demand a dedicated connection member, such as a linkage mechanism or a cable, or a torque detector, a simplified structure and low manufacturing cost can be implemented.

While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made.

Claims

1. A self-propelling apparatus for a vacuum cleaner having a cleaner body pivotably mounted to a nozzle unit, the apparatus comprising: a sensor unit mounted on the nozzle unit and having a wheel unit which is pivotable, in a direction opposite to that in which the vacuum cleaner moves, to generate progression and retrogression signals according to pivoting motion of the wheel unit; and a drive unit for moving the vacuum cleaner in response with the progression and retrogression signals.

2. Apparatus as claimed in claim 1, wherein the sensor unit comprises: a connection unit connected to the wheel unit and fixed to the nozzle unit by one end thereof; and a switch unit which can be turned on and off by the connection unit.

3. Apparatus as claimed in claim 2, wherein the wheel unit comprises: a wheel for contact with a surface to be cleaned; a housing supporting the wheel; and a shaft disposed on an upper portion of the housing, and wherein the wheel unit is pivotable by inertia and friction due to contact of the wheel unit with the surface to be cleaned.

4. Apparatus as claimed in claim 3, wherein the connection unit comprises: a link member including a first via-hole for insertion of the shaft, and a second via- hole for pivotable mounting to the nozzle unit; a resilient member disposed between the link member and the housing, the resilient member fitting around the shaft; a first connection member fixable to the shaft through the first via-hole so as to restrain escape of the link member from the shaft; and a second connection member fixable to the nozzle unit through the second via-hole so that the link member can pivot relative to the nozzle unit.

5. Apparatus as claimed in claim 4, wherein the switch unit comprises: a first switch disposed on one side of the link member and engagable with that side of the link member thereby to generate a progression signal; and a second switch disposed on the other side of the link member and engageable with that side of the link member thereby to generate a retrogression signal.

6. Apparatus as claimed in claim 5, wherein the switch unit further comprises a switch cover for shielding and fixing the first and the second switches to the nozzle unit.

7. Apparatus as claimed in any one of claims I to 6, further comprising an interception unit which generates an interception signal when the cleaner body is in an upright position, and wherein the interception unit comprises: a lever mounted on the cleaner body; and a third switch mounted on the nozzle unit and enagageable with the lever when the cleaner body is in the upright position.

8. Apparatus as claimed in any one of claims I to 7, wherein the drive unit comprises: a motor mounted on the nozzle unit; and a circuit unit for processing the progression and retrogression signals signal so as to drive the motor forwards or backwards.

9. Apparatus as claimed in claim 8 when appendant to claim 7, wherein the circuit unit is such as to process the interception signal to stop the motor.

10. A self-propelling apparatus for a vacuum cleaner having a cleaner body pivotably mounted to a nozzle unit, the apparatus comprising: a sensor unit having a wheel unit which is pivotable in a direction opposite to that in which the vacuum cleaner moves, a connection unit connected to the wheel unit and fixed to the nozzle unit by one end thereof, and a switch unit which can be turned on and off by the connection unit, thereby generating progression and retrogression signals according the pivotal movement of the wheel unit; an interception unit for generating an interception signal when the cleaner body is in an upright position; and a drive unit moving the vacuum cleaner in accordance with the progression and retrogression signals.

II. A self-propelling apparatus for a vacuum cleaner, the apparatus comprising: a wheel unit pivotable in a first direction in response to forwards movement of the vacuum cleaner, and in a second direction in response to backwards movement of the vacuum cleaner; a first switch on one side of the wheel unit, the first switch being actuable by the wheel unit when pivoted in the first direction so that the first switch generates a progression signal; a second switch on the other side of the wheel unit, the second switch being actuable by the wheel unit when pivoted in the second direction so that the second switch generates a retrogression signal; and a motor for moving the vacuum cleaner forwards in response to the progression signal and backward in response to the retrogression signal.

12. Apparatus as claimed in claim 11, further comprising a circuit unit for processing the progression and retrogression signals, and for transmitting the progression and retrogression signals to the motor.

13. Apparatus as claimed in claim 11 or claim 12, further comprising a third switch for generating an interception signal when the vacuum cleaner is in an upright position.

14. Apparatus as claimed in claim 13, wherein the arrangement is such that the motor stops moving the vacuum cleaner in response to the interception signal regardless of the generation of the progression and retrogression signals.

15. A vacuum cleaner, substantially as hereinbefore described with reference to, and as illustrated by the drawings.

15. A self-propelling apparatus for a vacuum cleaner, the apparatus being substantially as hereinbefore described with reference to, and as illustrated by the drawings.

S

16. A vacuum cleaner substantially as herejnbefore described with reference to, and as illustrated by the drawings.

Amendments to the claims have been filed as follows

1. A vacuum cleaner having a nozzle unit, a cleaner body pivotably mounted to the nozzle unit, and a self-propelling apparatus comprising: a sensor unit mounted on the nozzle unit and having a wheel unit which is pivotable, in a direction opposite to that in which the vacuum cleaner moves, to generate progression and retrogression signals according to pivoting motion of the wheel unit; and a drive unit for moving the vacuum cleaner in response to the progression and retrogression signals.

2. A vacuum cleaner as claimed in claim 1, wherein the sensor unit comprises: a connection unit connected to the wheel unit and fixed to the nozzle unit by one end thereof and a switch unit which can be turned on and off by the connection unit.

3. A vacuum cleaner as claimed in claim 2, wherein the wheel unit comprises: a wheel for contact with a surface to be cleaned; a housing supporting the wheel; and a shaft disposed on an upper portion of the housing, and wherein the wheel unit is pivotable by inertia and friction due to contact of the wheel unit with the surface to be cleaned.

4. A vacuum cleaner as claimed in claim 3, wherein the connection unit comprises: a link member including a first via-hole for insertion of the shaft, and a second via-hole for pivotable mounting to the nozzle unit; a resilient member disposed between the link member and the housing, the resilient member fitting around the shaft; a first connection member fixable to the shaft through the first via-hole so as to restrain escape of the link member from the shaft; and a second connection member fixable to the nozzle unit through the second via-hole so that the link member can pivot relative to the nozzle unit.

5. A vacuum cleaner as claimed in claim 4, wherein the switch unit comprises: a first switch disposed on one side of the link member and engagable with that side of the link member thereby to generate a progression signal; and a second switch disposed on the other side of the link member and engageable with that side of the link member thereby to generate a retrogression signal.

6. A vacuum cleaner as claimed in claim 5, wherein the switch unit further comprises a switch cover for shielding and fixing the first and the second switches to the nozzle unit.

7. A vacuum cleaner as claimed in any one of claims 1 to 6 further comprising: an interception unit for generating an interception signal when the cleaner body is in an upright position.

8. A vacuum cleaner as claimed in any one of claims I to 7, further comprising an interception unit which generates an interception signal when the cleaner body is in an upright position, and wherein the interception unit comprises: a lever mounted on the cleaner body; and a third switch mounted on the nozzle unit and enagageable with the lever when the cleaner body is in the upright position.

9. A vacuum cleaner as claimed in any one of claims I to 8, wherein the drive unit comprises: a motor mounted on the nozzle unit; and a circuit unit for processing the progression and retrogression signals signal so as to drive the motor forwards or backwards.

10. A vacuum cleaner as claimed in claim 9 when appendant to claim 8, wherein the circuit unit is such as to process the interception signal to stop the motor.

11. A vacuum cleaner,as claimed in claim 5, wherein: the wheel unit is pivotable in a first direction in response to forwards movement of the vacuum cleaner, and in a second direction in response to backwards movement of the vacuum cleaner; the first switch is provided on one side of the wheel unit, the first switch being actuable by the wheel unit when pivoted in the first direction so that the first switch generates a progression signal; the second switch is provided on the other side of the wheel unit, the second switch being actuable by the wheel unit when pivoted in the second direction so that the second switch generates a retrogression signal; and the drive unit is a motor for moving the vacuum cleaner forwards in response to the progression signal and backward in response to the retrogression signal.

12. A vacuum cleaner as claimed in claim 11, further comprising a circuit unit for processing the progression and retrogression signals, and for transmitting the progression and retrogression signals to the motor.

13. A vacuum cleaner as claimed in claim 11 or claim 12, further comprising a third switch for generating an interception signal when the vacuum cleaner is in an upright position.

14. A vacuum cleaner as claimed in claim 13, wherein the arrangement is such that the motor stops moving the vacuum cleaner in response to the interception signal regardless of the generation of the progression and retrogression signals.