TECHNICAL FIELD The present invention relates to a detachable backrest for a vehicle seat, in which the backrest comprises a headrest disposed on the backrest. The headrest...can be ...automatically released from a locking position using actuating means, whereupon the headrest, by means of a mechanism built into the headrest or the seat back, moves from a first position to a second position relative to the backrest when the backrest is tilted down in order, for example, to expand the loading space of the vehicle.

BACKGROUND ART In many vehicles there is a requirement for the passenger seats to be able to be moved or tilted in different directions in order to enlarge the loading space of the vehicle. In order further to increase flexibility in terms of utilizing the loading space, there is also a requirement in many vehicle applications for the seat back (a vehicle seat can be deemed to consist of two main parts: a seat cushion part and a seat back) to be able to be lifted fully out of the vehicle, in other words separated from the seat cushion part with which the seat back combines to make up the vehicle seat.

In most vehicles, the seats are usually provided with a headrest for the comfort and safety of the passengers, and there is generally a mechanism present in the seat for tilting the headrest forward if the seat back is to be tilted forward, since the headrest might otherwise impede the tilting movement of the seat back. In known solutions, such a mechanism comprises a part which is fixed in or below the pivot point for the seat back, in other words a part which is fixed in the seat cushion part or elsewhere in the vehicle.

One requirement is for both of the abovementioned facilities to be present in a vehicle seat, in other words for it to be possible, on the one hand, to lift out the seat back and, on the other hand, to tilt the seat back forwards. In the latter case (tilting of the backrest), a headrest disposed on the seat back should also be able to be tilted forwards, which means that the headrest- tilting mechanism must not inhibit the facility to remove the seat back in its entirety, and vice versa.

DISCLOSURE OF INVENTION The above-stated requirements are met by the present invention, in that it discloses a detachable backrest for a vehicle seat, comprising a headrest disposed on the backrest.

The backrest further comprises actuating means, by means of which the headrest is automatically released from a locking position when the backrest is tilted, whereupon the headrest, by means of a mechanism built into the headrest, moves from a first position to a second position relative to the backrest.

According to the invention, the actuating means for releasing the headrest from the locking position are disposed in the backrest and the actuating means are connected to the headrest by means of a wire extending in the backrest.

Since the backrest according to the invention accommodates all the parts, inclusive of the actuating means for the release of the headrest, the seat back can easily be lifted out of the vehicle, in other words released from the seat cushion part of the vehicle seat.

BRIEF DESCRIPTION OF DRAWINGS The invention will be described in greater detail below with reference to the appended drawings, in which Figs 1a - 1c show a vehicle seat intended to incorporate the seat back according to the invention, and Fig 2 shows actuating means for a headrest in a seat back according to the invention.

EMBODIMENTS Figs 1a-1c show a vehicle seat back 100 according to the invention and its -function. As can be . seen, .the. seat back. 100 according to the invention comprises a headrest 110, which, in Fig. 1a, is disposed in the position which it will normally have when a passenger is sitting in the seat. Suitably, this position of the headrest 110 is such that the headrest covers an upper part of the back of the vehicle seat, in other words the headrest is in a position which offers support for a head.

In the example which is shown in Figs 1a-1c, the headrest 110 is disposed around the crossbar in a bracket 101 which sticks up out of the seat back and which is indicated in Fig. 1a.

In Fig. 1 b, the seat back 100 has started to be tilted forwards towards the floor of the vehicle, for example in order to be able to increase the loading space of the vehicle. If the headrest 110 were to maintain the position from Fig. 1a, it might catch, for example, the seat cushion part of its own seat or the seat back in front and thereby impede part of the forward tilting of the seat back 100. In order to prevent this, the headrest 110 in the seat back 100 according to the invention comprises a mechanism by means of which the headrest, when the seat back 100 is tilted forward, will be swivelled out to an angular position in which the headrest 110, once the seat back 100 is tilted down, assumes a position in which the headrest juts out in front of the seat cushion part, down towards the floor of the vehicle. As an alternative, this mechanism can also be disposed in the seat back.

The start of the movement of the headrest towards the said angular position is shown in Fig. 1 b and the final position of the headrest cushion 110 in the tilted-down position of the seat back is shown in Fig. 1c.

In Figs 1a-1c, a facility has been shown for enlarging the loading space in a vehicle, namely for tilting forward the seat back in one of the vehicle seats. Another facility or requirement is for the seat back to able to be lifted fully out of the vehicle, the seat back being separated from its seat cushion part. The mechanism which is shown in Figs Ia-Ic and which executes the tilting- forward of the headrest comprises in existing solutions a part which is disposed below the pivot point of the seat back, in other words in the seat cushion part or in another part of the vehicle. In such solutions, it is impossible, in other words, to easily release the seat back in order to be able to lift it out of the vehicle.

The abovementioned mechanism which ensures that the headrest is swivelled out to the position shown in Fig. 1c can be realized in many different ways within the scope of the invention. The principle is, however, that the headrest, by means of a tilting mechanism, can move between a first (Fig. 1a) and a second position (Fig. 1c), in which the headrest is locked in the first position by a mechanism (not shown) for locking and releasing the said lock. A number of solutions to the realization of such a mechanism are known and will not be further described here. Similarly, nor will the mechanism which produces the tilting of the headrest be further described here.

The essential point is that the locking and release mechanism of the headrest (which might be an integrated part of the tilting mechanism of the headrest), using actuating means, can be released from the said locking position and can hereupon assume a second position, for example that which is shown in Fig. 1c.

It should be pointed out that the first position from which the headrest is released by means of the invention may in principle be any position whatsoever, which is also applicable to the second position, the essential point being that the invention allows the release of a headrest from a first position and its movement into a second position.

According to the invention, the actuating means for releasing the headrest from the locking position are disposed in the backrest and are shown symbolically in Figs Ia-Ic, denoted by the numeral 120.

According to the invention, the release mechanism which is present for releasing the headrest from the locking position can be actuated for release purposes by means of an external tensile force, for example by means of a wire running in the backrest 100 from the release mechanism of the headrest to the actuating means 120.

Fig. 2 shows an example of an embodiment of the external actuating means 120; the means 120 suitably comprise a housing 125. The wire 130 runs into the housing 125 and is there fastened to a first arm 135, which first arm 135 is disposed pivotably about an axis 140.

The actuating means 120 further comprise a second arm 145, which, when actuated by a user, makes the first arm 135 pivot about the axis 140, thereby producing a pulling action in the wire 130.

The second arm 145 will be actuated when the seat back is tilted, suitably by it running through the housing 125 such that one end of the arm is perceived by a user as a knob or a pin. This knob or pin then becomes all that the user sees of the actuating means 120, the rest can be inserted in the seat back. Suitably, the second arm 145 extends through the housing and is inserted by its other end in a recess in the first arm 135.

Suitably, the actuating means 120 further comprise a first spring 150, disposed such that its spring action endeavours to counteract the action of the second arm 145 upon the first arm 135.

The device might also comprise a second spring (not shown in Fig. 2). This second spring, too, would then be disposed in the housing 125 and would endeavour to return the arm 145 relative to the housing, in other words assist the first spring 150.

With renewed reference to Figs 1 b and 1c, the working of the invention can now be explained in further detail: the actuating means are shown symbolically in Figs 1a-1c, denoted by 120. In these pictures, only a part of the arm 145, protruding beyond the housing 125, is shown. It should be emphasized that neither this part of the arm nor some other part of the actuating means 120 engages in the bottom of the seat, but runs completely free from the seat bottom.

When the seat back 100 is tilted forward by a user, the actuating means 120 can be disposed such that, upon forward movement of the seat back, they pass against a cam 122 disposed in the body of the vehicle, whereupon the protruding part of the arm 145 will gradually be forced more and more into the housing 125 and will press upon the first arm 135, thereby causing the latter to rotate about the axis 140.

That the arm is gradually pressed more and more in as the seat back 100 is tilted forwards is due to the fact that the tilting movement is not a linear movement, but a swivel movement about a centre of rotation 127, indicated in Figs 1a-1c.

This, in turn, causes the wire 130 to be pulled in a direction away from the headrest, a release/trip mechanism in the headrest releasing the headrest from a locking position and making the headrest assume the position shown in Fig. 1c. When the seat back 100 is raised, by manual force, the means or the mechanism 120, with the aid of the spring 150, will bring about slackening of the wire, which enables the headrest to be returned, suitably by manual force, to the position shown in Fig. 1a.

It has therefore been possible, by means of the invention, to offer a seat back for a vehicle seat which can accommodate a headrest with headrest- tilting mechanism, in which the seat back, moreover, can be detached from the seat cushion part without hindrance from the headrest-tilting mechanism.

An alternative to the arm 145 being pressed in as a result of passing against a cam or some other part disposed in the body of the vehicle is to make a user press in the "knob", the arm 145, manually. Other solutions can also be envisaged, the important point being that the mechanism 120 is subjected to a force which presses in the arm 145.