The invention relates to a coupling comprising a first coupling member and a second coupling member, which are rotatable relative to one another about an axis of rotation of the coupling and which are electrically connectable, the first coupling member comprising an electrical contact which is capable of making contact with a ring-shaped electrical contact which engages in a ring-shaped positioning form of the second coupling member.

The invention also relates to a coupling member having a ring-shaped electrical contact, which coupling member is suitable for use in a coupling in accordance with the invention.

The invention further relates to a vacuum cleaner comprising a housing, a suction unit accommodated in the housing, and a suction tool adapted to be coupled to the housing and the suction unit via a flexible suction hose.

The invention also relates to a further vacuum cleaner comprising a housing, a suction unit accommodated in the housing, and a suction tool comprising a handle and adapted to be coupled to the housing and the suction unit via a flexible suction hose.

The invention moreover relates to a suction hose and a suction tool suitable for use in a vacuum cleaner in accordance with the invention and provided with a coupling member in accordance with the invention.

A coupling of the type defined in the opening paragraph and a vacuum cleaner of the type defined above, in which a suction hose can be coupled to a housing of the vacuum cleaner by means of such a coupling, are known from US Patent 4,550,958. The known coupling comprises two tubular coupling members which are rotatable relative to one another about an axis of rotation which coincides with a common central axis of the two coupling members. By means of the coupling a first end of a suction hose of the known vacuum cleaner can be coupled to a housing of the vacuum cleaner, which housing accommodates a suction unit. A second end of the suction hose can be coupled to a suction tool. The tubular coupling members of the known coupling, together with the suction hose,

belong to a duct through which dust and dirt particles, picked up via the suction tool, are carried off to a dust container in the housing. Since the two coupling members of the coupling are rotatable relative to one another, a user of the vacuum cleaner can clean a large area around the vacuum cleaner by means of the suction tool without a displacement of the housing of the vacuum cleaner.

The suction hose of the known vacuum cleaner includes a number of electrical conductors, enabling an electric current or voltage to be applied from the housing of the vacuum cleaner to the suction tool or from the suction tool to the housing. The suction tool has been provided, for example, with an electric motor to drive a brush, the motor bein powered from the housing via the electrical conductors of the suction hose, or with an electrical or electronic control means, electric signals from the control means being transferred to the housing via the electrical conductors of die suction hose. The electrical conductors of the suction hose can be coupled to a number of electrical contacts of the first coupling member of the coupling by means of a plug and a socket. The electrical contacts of the first coupling member bear against a number of ring-shaped electrical contacts of the second coupling member, which are disposed concentrically relative to the axis of rotation of the coupling. Thus, the electrical contacts of the first coupling member remain in contact with the ring-shaped electrical contacts of the second coupling member during any rotation of the coupling members relative to one another, thus permitting unlimited rotation of the coupling members relative to one another.

The ring-shaped electrical contacts of the second coupling member of the known coupling are each disposed in a ring-shaped positioning groove of a contact holder of the second coupling member, which holder comprises two shells. During assembly of the known coupling the ring-shaped electrical contacts are placed around the two shells of the contact holder and mounted in the positioning grooves, after which the contact holder with the ring-shaped contacts is slid around a tubular holder. The tubular holder comprises a plurality of expansion limbs by means of which the shells of the contact holder are spaced apart and the ring-shaped contacts are retained in the positioning grooves. The known coupling thus comprises a comparatively large number of parts, as a result of which it takes relatively much time to assemble the coupling.

It is an object of the invention to provide a coupling of the type defined in the opening paragraph, such that the number of parts of the coupling and the time required to assemble the coupling are limited as far as possible.

To this end, a coupling in accordance with the invention is characterized

in that the ring-shaped electrical contact is elastically deformable and engages in the ring- shaped positioning form under the influence of an elastic pretensioning force which is directed radially relative to the axis of rotation. Since the ring-shaped electrical contact is elastically deformable, the ring-shaped electrical contact can be placed simply, for example by means of an expansion tool, into the positioning form of the second coupling member without disassembling the second coupling member. The ring-shaped electrical contact is retained in the positioning form by the elastic pretensioning force, which is directed radially relative to the axis of rotation. Thus, the use of the ring-shaped electrical contact enables the second coupling member with the positioning form to be manufactured as a single integrated part by means of, for example, an injection-moulding process, so that the number of parts of the coupling and the time required to assemble the coupling are limited as far as possible.

A special embodiment of a coupling in accordance with the invention is characterized in that the ring-shaped electrical contact in the ring-shaped positioning form has a diameter larger than a diameter which the ring-shaped electrical contact has in a non-loaded condition prior to mounting in the positioning form. During assembly of the coupling the diameter of the ring-shaped electrical contact is increased, for example by means of an expansion tool, after which the ring-shaped electrical contact is engageable in the positiomng form of the second coupling member. When the diameter of the ring-shaped electrical contact is increased the ring-shaped electrical contact is deformed elastically, thereby producing in the ring-shaped electrical contact a pretensioning force which is directed radially relative to a central axis of the ring-shaped electrical contact. Said pretensioning force is sustained after the ring-shaped electrical contact has engaged the positioning form, because the positioning form has a diameter larger than the diameter of the ring-shaped electrical contact in its non- loaded condition prior to mounting in the positioning form, and constitutes the pretensioning force which is directed radially relative to the axis of rotation and under the influence of which the ring-shaped electrical contact is retained in the positioning form.

A further embodiment of a coupling in accordance with the invention is characterized in that the ring-shaped electrical contact comprises a helical spring. When the helical spring is to be fitted into the ring-shaped positioning form the helical spring can be given a desired diameter in a simple and reliable manner. Since the helical spring has a plurality of continuous turns this also limits the wear of the electrical contact of the first coupling member, which occurs as it slides past the helical spring.

Yet another embodiment of a coupling in accordance with the invention is characterized in that the ring-shaped electrical contact is electrically connected to an

electrical conductor, the electrical conductor being clamped between the ring-shaped electrical contact and the ring-shaped positioning form under the influence of the elastic pretensioning force. In this way, the elastic pretensioning force, under the influence of whic the ring-shaped electrical contact is retained in the positiomng form, also constitutes a clamping force under the influence of which the electrical conductor is in contact with the ring-shaped electrical contact. Thus, the coupling does not require any further means to secure the electrical conductor to the ring-shaped electrical contact. This results in a further reduction of the number of parts required for the coupling.

A vacuum cleaner of the type defined in the opening part, in which the merits of a coupling in accordance with the invention used therein are particularly manifest, is characterized in that the suction hose can be coupled to the housing by means of a coupling in accordance with the invention.

A further vacuum cleaner of the type defmed in the opening part, wherein the merits of a coupling in accordance with the invention used therein are also particularly manifest, is characterized in that the handle of d e suction tool can be coupled to the suction hose by means of a coupling in accordance with the invention.

The invention will be described in more detail hereinafter with reference to the drawings, in which Figure 1 shows diagrammatically a vacuum cleaner provided with a coupling in accordance with the invention,

Figure 2 shows a handle of a suction tool and one end of a suction hose of the vacuum cleaner shown in Figure 1,

Figure 3 is a cross-sectional view of a coupling in accordance with the invention used in the vacuum cleaner shown in Figure 1,

Figure 4a shows diagrammatically a coupling member and a ring-shaped electrical contact of the coupling shown in Figure 3, and

Figure 4b shows diagrammatically how the ring-shaped electrical contact shown in Figure 4a is fitted around the coupling member shown in Figure 4a.

The vacuum cleaner 1 shown in Figure 1 comprises a plastics housing 3, which can be placed on a surface 7 by means of a number of wheels 5. The housing 3 accommodates an electrically drivable suction unit 9, which is shown only diagrammatically in Figure 1. The vacuum cleaner 1 further comprises a suction tool 11 comprising a suction

nozzle 13, a metal wand 15, and a handle 17. The handle 17 of the suction tool 11 is coupled to a flexible suction hose 21 of the vacuum cleaner 1 by means of a first coupling 19, while the suction hose 21 is detachably coupled to a suction port 25 of the housing 3 by means of a second coupling 23. The suction port 25 opens into a dust container 27 of the vacuum cleaner 1, which is connected to the suction unit 9 via a filter 29. In operation the suction unit 9 generates a partial vacuum in the dust container 27, the suction hose 21 and the suction tool 11, as a result of which dust and dirt particles present on the surface 7 are carried off to the dust container 27 via the suction nozzle 13 of the suction tool 11 and the suction hose 21. As is shown in Figure 1, the handle 17 carries a control means 31 for the suction unit 9, enabling a user of the vacuum cleaner 1 to adjust the suction power of die suction unit 9. The control means 31 comprises, for example, a variable resistor, not shown in Figure 1, which can be controlled by means of a slide control 33. As is shown in Figure 2, the control means 31 is electrically connectable to the suction unit 9 by means of two electrical conductors 35a, 35b situated in two ducts 37a, 37b formed diagonally relative to one another in a jacket of the suction hose 21.

As is further shown in Figure 2, the first coupling 19, which couples the handle 17 to the suction hose 21, comprises a tubular first coupling member 39 secured to the handle 17, and a tubular second coupling member 41 secured to the suction hose 21. The coupling members 39 and 41 of die first coupling 19 are rotatable relative to one another about an axis of rotation 43 of the first coupling 19, which axis coincides with a common central axis of the tubular coupling members 39 and 41. As a result of the rotatability of the coupling members 39 and 41 relative to one another the suction tool 11 has a high manoeuvrability. Figure 3 shows the coupling members 39 and 41 of die first coupling 19 in a cross-sectional view. As is shown in Figures 2 and 3, die second coupling member 41 comprises a cylindrical union 45 having a central axis which coincides with the axis of rotation 43. The union 45 is connected to an end 49 of the suction hose 21. A flexible plastics sleeve 51 is fitted around the end 49 of the suction hose 21 and has cutouts 53 and bevelled locking projections 55. The bevelled locking projections 55 are each surrounded by a C-shaped cutout 57 in the sleeve 51, permitting them to be bent relative to the sleeve 51 in a radial direction with respect to the axis of rotation 43. In the assembly shown in Figure 2 the union 45 and die sleeve 51 are rotatable relative to one another about the axis of rotation 43, while the sleeve 51 is axially slidable over die suction hose 21 up to an annular stop 59

of the union 45. The first coupling member 39 comprises a bushing 61 having an inner diameter which substantially corresponds to an outer diameter of die sleeve 51. In the assembly shown in Figure 3, where the two coupling members 39 and 41 have been coupled to one andier, the locking projections 55 of the sleeve 51 engage in openings 63 in the bushing 61, as a result of which the sleeve 51 is retained axially and in the direction of rotation relative to the first coupling member 39. The union 45 of the second coupling member 41 is then axially retained substantially without any clearance between the sleeve 51 and a further annular stop 64 in die bushing 61 of me first coupling member 39, as a result of which the second coupling member 41 is axially retained relative to die first coupling member 39 and die coupling members 39 and 41 are rotatable relative to one another about the axis of rotation 43. The first coupling 19 wim die coupling members 39, 41, the locking projections 55 and the openings 63 provides a permanent coupling of the handle 17 to die suction hose 21. It is to be noted that the first coupling 19 may alternatively be constructed as a detachable coupling. The first coupling 19 men comprises, for example, only a single flexible locking projection 55 for cooperation with only a single opening 63, permitting a user of the vacuum cleaner 1 to uncouple the handle 17 and die suction hose 21 by bending the single locking projection 55 towards the axis of rotation 43 and subsequently taking the coupling members 39, 41 apart.

A first ring-shaped groove 67 and a second ring-shaped groove 69, which are disposed concentrically relative to the axis of rotation 43, have been formed in an outer wall 65 of the union 45 and constitute positioning forms for a first ring-shaped electrical contact 71 and a second ring-shaped electrical contact 73, respectively. As is shown in Figures 2 and 3, die ring-shaped electrical contacts 71 and 73 each comprise a helical spring 75, 77 of phosphor-bronze mounted in die grooves 67, 69 in a manner to be described hereinafter. The helical springs 75, 77 have been expanded in a radial direction relative to die axis of rotation 43 and are retained in the grooves 67, 69 by a radially directed elastic pretensioning force which exists in the helical springs 75, 77 and which is associated with said expansion.

As is shown in Figure 2, die electrical conductor 35a in die suction hose 21 is electrically connected to the first ring-shaped electrical contact 71 in die second coupling member 41 and the electrical conductor 35b is electrically connected to die second ring-shaped electrical contact 73. As Figure 2 shows, die duct 37a for die electrical conductor 35a terminates in a slot 79 formed in die second ring-shaped groove 69 and in a ridge 81 between die first and the second ring-shaped groove 67, 69. The slot 79

communicates with a hook-shaped slot 83 in the first ring-shaped groove 67, and under d e influence of die elastic pretensioning force in the helical spring 75 one end of die electrical conductor 35a is clamped between the helical spring 75 and a number of knurls 85 formed in e groove 67. The duct 37b for the electrical conductor 35b terminates in a hook-shaped slot 87 in die second ring-shaped groove 69 and under the influence of die elastic pretensioning force in me helical spring 77 one end of die electrical conductor 35b is clamped between me helical spring 77 and a number of knurls 85 formed in die second ring-shaped groove 69.

As is further shown in Figures 2 and 3, die bushing 61 of the first coupling member 39 has a first opening 91 and a second opening 93. A first electrical contact 95 of die coupling member 39 is located in the first opening 91 and a second electrical contact 97 of the coupling member 39 is located in the second opening 93. The electrical contacts 95 and 97 each comprise a flexible lug 99, 101 of phosphor-bronze. As Figure 3 shows, the lug 99 of die first electrical contact 95 is pretensioned against the first ring-shaped electrical contact 71 of die second coupling member 41 and die lug 101 of d e second electrical contact 97 is pretensioned against die second ring-shaped electrical contact 73 of die second coupling member 41. This pretension in die lugs 99, 101 provides an adequate contact-engaging force between me electrical contacts 95, 97 of the first coupling member 39 and the electrical contacts 71, 73 of the second coupling member 41. By means of strip-shaped electrical conductors 103a, 103b die lugs 99, 101 are connected to me control means 31 in d e handle 17, die strip-shaped conductors 103a, 103b each extending in a duct 105a, 105b of d e handle 17. The control means 31 in the handle 17 is thus electrically connected to die suction unit 9 via the strip-shaped conductors 103a, 103b, the electrical contacts 95, 97 of die first coupling member 39, the ring-shaped electrical contacts 71, 73 of the second coupling member 41, and die electrical conductors 35a, 35b in die suction hose 21. Since die ring-shaped electrical contacts 71, 73 are disposed concentrically relative to the axis of rotation 43, the electrical contacts 95, 97 of die first coupling member 39 remain in contact with the ring-shaped electrical contacts 71, 73 of die second coupling member 41 when die coupling members 39 and 41 of die first coupling 19 are rotated relative to one ano er during use of die vacuum cleaner 1. This permits an unlimited rotation of die coupling members 39, 41 relative to one anodier about me axis of rotation 43.

Figure 4a shows die union 45 of die second coupling member 41 and die helical spring 77 of die second ring-shaped electrical contact 73 prior to assembly of the first coupling 19. The second ring-shaped groove 69 of die union 45, which constitutes a ring- shaped positioning form for the ring-shaped electrical contact 73, has an outer diameter O-

which is larger than a diameter D ₂ that the helical spring 77 has in a non-loaded condition prior to assembly of the coupling 19. In me present example D, is approximately 40 mm, D ₂ is approximately 30 mm, and die phosphor-bronze helical spring 77 has a wire thickness of approximately 0.6 mm. Figure 4b shows diagrammatically an expansion tool 107 by means of which the helical spring 77 is fitted in me groove 69 of e union 45. The expansion tool 107 has a plurality of, for example three or four, parallel pins 109, whose distances relative to one anodier are adjustable. The helical spring 77 is placed around die pins 109 of die expansion tool 107, after which the distances between the pins are increased, as a result of which me diameter of die helical spring 77 is increased, thereby subjecting die helical spring 77 to elastic deformation. When ie diameter of die deformed helical spring 77 is larger than the diameter D,, the helical spring 77 is placed around die groove 69, after which the expansion tool 107 is removed and die helical spring 77 engages in me groove 69. Since the diameter D, of the groove 69 is larger than the diameter D ₂ of the helical spring 77 in its non-loaded condition, die helical spring 77 has an elastic pretensioning force while in the groove 69. This pretensioning force is directed radially relative to die axis of rotation 43, so that d e helical spring 77 is held in the groove 69 by the pretensioning force.

Since die helical spring 77 is simply mounted in me groove 69 by means of the expansion tool 107, the union 45 of die second coupling member 41 need not be disassembled in order to enable die helical spring 77 to be mounted. The union 45 of the second coupling member 41 can thus be manufactured as a single integrated part by means of, for example, an injection-moulding process, diereby minimizing the number of parts to be assembled for die first coupling 19. Since me elastic pretensioning force in die helical springs 75, 77 is also used as a clamping force for the ends of die electrical conductors 35a, 35b, die first coupling 19 does not require any further means for securing die conductors 35a, 35b to die helical springs 75, 77, as a result of which me number of parts to be assembled for die coupling 19 is further reduced.

The second coupling 23, by means of which the suction hose 21 is coupled to die suction port 25 of the housing 3, is of a construction similar to that of the first coupling 19 and is not described in more detail. However, as already stated hereinbefore, the suction hose 21 is detachably coupled to die suction port 25, for which reason the second coupling 23 comprises only one locking projection 55, which can be bent towards die axis of rotation of the second coupling 23 by a user of the vacuum cleaner 1 in order to uncouple die suction hose 21 from the suction port 25.

The ring-shaped electrical contacts 71, 73 of the coupling 19, 23

described above each comprise a helical spring 75, 77. It is to be noted diat instead of die helical springs 75, 77 die coupling 19, 23 may alternatively comprise anodier elastically deformable ring-shaped electrical contact. An example of this is a strip bent into a cylindrical sleeve. In a non-loaded condition prior to mounting in the positioning form such a sleeve has a diameter smaller than the diameter of die positioning form, the ends of die strip overlapping one anodier. The length of die strip is such that die ends of die strip abut against each other after the strip has been fitted into the positioning form.

The above description relates to uses of a coupling 19, 23 in accordance widi the invention in a vacuum cleaner 1. It is to be noted that such a coupling may also be used in otiier apparatuses and devices. Such a coupling may be used, for example, in a lighting fixture, the first coupling member being secured to a base or basic part of the lighting future and die second coupling member being secured to a part of ie lighting fixture, which comprises a lamp socket and which is rotatable relative to the base or the basic part of the lighting fixture. A coupling in accordance widi die invention may also be used in, for example, a winder for electric cords, die first coupling member being secured to a base or basic part of die cord winder and die second coupling member being secured to a part of me cord winder which is rotatable relative to the base or basic part and onto which the electric cord is to be wound.

The couplings 19, 23 described hereinbefore each comprise two ring- shaped electrical contacts 71, 73 which are capable of making contact with two further electrical contacts 95, 97. It is to be noted that a coupling in accordance widi d e invention may alternatively have a different number of ring-shaped electrical contacts, for example three or more.

In die couplings 19, 23 described hereinbefore the electrical connections between the ring-shaped electrical contacts 71, 73 and die electrical conductors 35a, 35b is obtained by clamping of die conductors 35a, 35b under me influence of die elastic pretensioning force of the ring-shaped electrical contacts 71, 73. Finally, it is to be noted that die electrical connections between die conductors 33a, 33b and die ring-shaped electrical contacts 71, 73 can also be made in a different manner, for example by means of soldered joints, which are known per se and are customary.