EP1579786A1

EP1579786A1 - Arrangement for adjusting a back rest

Info

Publication number: EP1579786A1
Application number: EP05075668A
Authority: EP
Inventors: Wine Krol
Original assignee: Unimeta Nederland BV
Current assignee: SUN GARDEN GMBH
Priority date: 2004-03-24
Filing date: 2005-03-21
Publication date: 2005-09-28
Also published as: NL1025800C2

Abstract

Arrangement for adjusting and locking a back rest (3) of a chair (1), which arrangement comprises a first toothing (11) connected to an arm rest (2) of the chair (1) and moreover a locking element (8), connected to the chair (1) and mounted for rotation round a first shaft (9), which locking element (8) is provided with a second toothing (12) and which locking element (8) tends to swivel to a position in which the second toothing (12) engages the first toothing (11) when the arm rest (2) is moved in a first direction, in which case the second toothing (12) engages the first toothing (11), with the first toothing (11) and the second toothing (12) each having several teeth. An adjusting and locking mechanism of this type is affordable, reliable and safe. Moreover it offers the possibility of fine adjustment and the possibility of mounting the adjusting mechanism completely out of sight.

Description

The invention relates to an arrangement for adjusting and locking a back rest of a chair.
Chairs having an adjustable back rest are known. The adjusting means and locking means may be installed in a hinge between the seat and the back rest. This is usual for car chairs. This application makes great demand on the mechanism, because of the inherently large forces operating upon the construction, which must be absorbed by the locking means. In chairs with arm rests, generally another mechanism is employed. The arm rests are thereby hingedly mounted to the back rest. The arm rests are each provided with a toothing and the underframe is provided with locking bodies cooperating with it. Thereby, the arm rests may be shifted with respect to the underframe and locked in a number of discrete positions. In this way the back rest can be adjusted and can be locked in a corresponding number of discrete positions. This is usual for garden chairs. In that case the locking element is rigidly mounted to the underframe. A serious disadvantage is the risk of being trapped, for example fingers may be trapped in particular between the toothing and the locking element. Moreover the number of possible positions of the back rest is limited.
In NL 1003729 of the present applicant, an adjusting and locking arrangement is disclosed which comprises a swivelling locking element which engages a guiding body, with the locking action being based upon friction resistance. The advantage is that a continuous, stepless adjustment and locking is possible. It turns out that a locking arrangement of this type is not always reliable. The friction surfaces may get dirty, as a result of which the locking arrangement may slip. Moreover a relatively large moment of torque is needed, which implies that the hinge point of the locking element will be situated outside and/or under the arm rest, which is objectionable from an aesthetical point of view and which also carries a substantial risk that for example fingers will be trapped. Moreover it turns out that suitable materials are hard to find. The coefficients of friction of many popular synthetic materials for example will be reduced significantly as a result of creep caused by the contact pressure, and it turns out that in practice a reliable locking is very difficult to obtain. A metal like stainless steel is found to perform very well, but its application would drastically increase the cost price.
In EP2593050 a locking mechanism is disclosed which also comprises a locking mechanism provided with a swivelling locking element, in which the actual locking is based upon the engagement of a single tooth in a toothing provided for that purpose. The forces that must be absorbed by the tooth and the toothing are relatively large. Therefore the dimensions of the tooth and the toothing must be relatively large in order to keep the strain in the tooth and the toothing within limits. This implies that the number of possible discrete positions of the back rest that can be adjusted will be limited. Also in this case the hinge point of the locking element will be situated outside the arm rest, which brings along the objections from an aesthetical point of view and the substantial risk of being trapped. Obviously, there is a need for an adjusting and a locking mechanism which is affordable, reliable and safe, preferably with a possibility of fine adjustment, for which the adjusting mechanism is preferably completely out of sight. The present invention aims at providing such a mechanism.
Therefore, the invention provides an arrangement for adjusting and locking a back rest of a chair, which arrangement comprises a first toothing connected to an arm rest of the chair and moreover a locking element, connected to the chair and mounted for rotation round a first shaft, which locking element is provided with a second toothing and which locking element tends to swivel to a position in which the second toothing engages the first toothing when the arm rest is moved in a first direction. It is characterised in that the first toothing and the second toothing each comprise several teeth.
In case the arm rest is connected to the back rest, the back rest may be locked in a certain position in that way, for example because a user leans against the back rest. As the locking is based upon the mutual interlock of toothings, the requirements imposed onto the materials to be used may be reduced. Contrary to the locking element disclosed in NL1003729, the material does not need to have a high friction resistance. As the forces are spread over a number of teeth, the strain occurring in the toothings is relatively small, and for that reason the teeth and their mutual distance may be relatively small. This implies that the number of possible discrete positions of the back rest that can be selected will be large.
Also the moment of torque, necessary for the locking is relatively small, which means that the first shaft and the complete locking element and the toothings may be placed inside the arm rest, which is a significant advantage from an aesthetical point of view and which eliminates the risk of being trapped, or at least substantially reduces it. Moreover it becomes possible to use inexpensive and popular synthetic materials, because there are no high demands imposed upon the material to be used with respect to mechanical strength or friction resistance. This means that adjusting and locking means are obtained which are affordable, reliable and safe, with a possibility of fine adjustment, for which the entire adjusting mechanism may be mounted out of sight.
Moreover, the locking element may be provided with a for example tooth-shaped projection, which projection is shaped and located so as to cooperate with the first toothing for forcing the locking element to swivel to a position where the second toothing engages the first toothing when the arm rest is moved in a first direction. In this way, the locking element may be forced to swivel, even if the locking element is more or less obstructed in its movements, for example because of dirt or friction caused by adjacent construction parts.
Preferably, the locking element tends to swivel to a position in which the second toothing at least substantially disengages the first toothing when the arm rest is moved in a second direction. With 'at least substantially disengages' is meant in this context and in the following that the toothings may disengage to the point that they may move more or less free with respect to one another. If the arm rest is connected to the back rest, the position of the back rest may be adjusted for example forwards, because a user moves the arm rest into the second direction.
Preferably, when lifting the arm rest the second toothing will at least substantially disengage the first toothing. In this way the back rest may be adjusted backwards if the arm rest is connected to the back rest, with a user lifting up the arm rest and moving it into the first direction. As soon as the arm rest is lowered, the locking element will tend to swivel into a position in which the second toothing engages the first toothing, as a result of which the back rest will be locked again in a well defined position.
Preferably, after being assembled, the first toothing and the locking element, including the first shaft, will be positioned inside the profile of the arm rest in a mounting space provided for that purpose. In this way, the risk of being trapped, for example with a finger, is minimised. Moreover, the arrangement will be out of sight in this way. Indeed the moment of torque exerted upon the locking element will be relatively small, as the first shaft is positioned relatively close to the working surface of the toothings, but this is not a drawback as the locking is at least substantially based upon the mutual engagement of both toothings. This is unlike the locking element disclosed in NL1003729, where a relatively large momentum is needed in order to make the frictional forces large enough to obtain a sufficiently good locking.
Preferably, the toothings comprise teeth having a relatively small characteristic height, for example 2-5 millimetres. The risk of being trapped, for example with a finger, is minimised in this way.
Preferably, the toothings comprise teeth having a relatively small characteristic mutual distance, for example 3-8 millimetres. In this way it becomes possible to realise a fine adjustment.
Preferably, the toothings comprise teeth with rounded tips. This even further reduces the chance of being trapped, for example with a finger.
The locking element may be forced into a position where the second toothing engages the first toothing as soon as the arm rest approaches a first extreme position, with the aid of a guiding element provided for that purpose. In this way, the arm rest and the back rest attached to it will now be locked in the first extreme position, for example in which the back rest is as far backwards as possible, and it will be impossible to exceed this first extreme position. More in particular there is no need for a stop, which means that there is no risk of fingers being trapped between that stop and the locking element.
As soon as the locking element reaches a second extreme position, it may touch a stop, provided for that purpose. This may be necessary for subsequently further folding or collapsing the chair.
In a preferred embodiment of the arrangement according to the invention, the locking element may be rotatable over a small angle, for example 2-5 degrees, round a second axis, for example perpendicular to the first shaft. In this way the locking element may align itself, for example within a guiding element, to the position of the arm rest and the first toothing, so that small clearances and mutual rotations of the construction parts involved round the second axis may be overcome.
In a preferred embodiment of an arrangement according to the invention, the locking element and the arm rest are provided with guiding means, with guiding surfaces, for example slanting sides, which may cooperate while being mounted together. With this cooperation of the guiding surfaces, the locking element may be guided towards its correct position. While doing so, the first parts of the arm rest may temporarily be forced apart for a short while, in order to grant passage to the locking element. Subsequently, the first parts may retake their original positions with respect to each other, with the locking element clicking into the arm rest in a secured position. In this way the mounting is quick and simple, as will be explained with a reference to the figures in the following description of a possible embodiment of an arrangement according to the invention.
Preferably, the locking element comprises bevelled parts which, after being mounted inside the arm rest, engage the arm rest at a location which is in a sideward direction as remote as possible with respect to the centre line of the arm rest. In this way it is prevented that the first parts of the arm rest will be pushed apart by the mounted locking element, which would imply that the locking element could slip out of the arm rest.
In the following, the invention is elucidated with the aid of a non-limiting example of an embodiment according to the invention. Thereby shows:
Fig. 1 an example of a chair provided with an arrangement according to the invention;
Fig. 2 a cross section of an example of an embodiment of an arrangement according to the invention in a locked position;
Fig. 3 a cross section of an example of an embodiment of an arrangement according to the invention with a locking element provided with a projection according to the invention;
Fig. 4 a cross section of an example of an embodiment of an arrangement according to the invention in a first, free-running state;
Fig. 5 a cross section of an example of an embodiment of an arrangement according to the invention in a second free-running state;
Fig. 6 a cross section of an example of an embodiment of an arrangement according to the invention with schematically shown a finger, put into the arrangement;
Fig. 7 a cross section of an example of an embodiment of an arrangement according to the invention with a guiding element according to the invention;
Fig. 8 a cross section of an example of an embodiment of an arrangement according to the invention with a stop according to the invention;
Fig. 9 a bottom view of an example of an embodiment of an arrangement according to the invention with a locking element according to the invention which may slightly rotate round a second axis; and
Fig. 10 two cross sections of an example of an embodiment of an arrangement according to the invention, showing part of the mounting procedure.
Fig. 1 shows an example of a chair 1 with an arm rest 2 rotatably mounted to a back rest 3. The chair 1 is provided with an arrangement according to the invention 4. With a movement 5 of the arm rest 2 with respect to the underframe 6, the back rest 3 will change its position 7. The arrangement adjusting and locking 4 is positioned entirely inside the arm rest 2 and out of sight, which reduces the chance of for example a finger being trapped.
Fig. 2 shows an arrangement according to the invention 4 in a locked position. A locking element 8 may swivel round a first shaft 9, which for example coincides with the shaft of a hinged connection between a pair of legs 10 of the chair 1. On the inside, the arm rest 2 is provided with a first toothing 11. The locking element 8 is provided with a second toothing 12 which engages the first toothing 11 so as to lock the position of the arm rest 2 with respect to the locking element 8, and therewith also the position of the back rest 3. For illustration, the forces working onto the locking element 8 are indicated.
Fig. 3 demonstrates the functioning of the arrangement 4 which is provided with a, in this case tooth-shaped, projection 13. When the arm rest 2 is moved into the indicated direction 14, the action of the projection 13, locking element 8 will be forced to swivel into the indicated direction 15, until the second toothing 12 engages the first toothing 11. In this way, locking element 8 will swivel even when hindered in its movements, for example by dirt or by friction with adjoining constructional parts.
Fig. 4 shows the arrangement 4 in a first free-running situation. When the arm rest 2 is moved into the direction indicated by 16, then locking element 8 will swivel, starting from a locked situation as shown in Fig. 2, into the direction indicated by 17, whereby the second toothing 12 and the first toothing 11 disengage. In this way the arm rest 2 together with the back rest 3 can be adjusted, in this example forwards.
Fig. 5 shows the arrangement 4 in a second free-running situation. By lifting the arm rest 2, the locking element 8 will swivel in the direction indicated by 18, whereby the second toothing 12 again will disengage the first toothing 11. In this way the arm rest 2 together with the back rest 3 can be adjusted, in this example backwards. When the arm rest 2 is dropped again, locking element 8 will swivel again to a locked position as shown in Fig. 2.
Fig. 6 shows the arrangement 4 with schematically shown a finger 19, put into the arrangement. The locking element 8 is designed and located in such a way that the chance of a finger 19 being trapped between the moving parts 2,9 respectively the toothings 11,12 is small. Moreover, the height of the teeth 20 is so small, in this example a few millimetres, and the teeth 20 have been rounded, which means that the chance of being trapped is considered to be impossible. The mutual distance between the teeth 20 is so small in this example about five millimetres, that a fine adjustment can be made.
Fig. 7 shows the operation of the arrangement 4 which is provided with a guiding element 21 which forces the locking element 8 to swivel in the direction indicated by 22 to a locked position as shown in Fig. 2, as soon as the arm rest 2 reaches an extreme position. The first extreme position corresponds in this example with an extreme backwards position of the back rest 3, where it is impossible to exceed this first extreme position. For that reason, there is no need for a stop and there is no risk of fingers being trapped between a stop and the locking element.
Fig. 8 shows the arrangement 4 in a second extreme position, in which the locking element 8 rests against a stop 23. This is necessary in order to fold or collapse the chair 1 subsequently, as usual with a chair of this type.
Fig. 9 shows a bottom view of the arrangement 4, in which it can bee seen that the locking element 8 may slightly rotate over a small angle 24, for example 2-5 degrees, round a second axis 25, in this case perpendicular to the first shaft 9. In this way, the locking element 8 and the second toothing 12 may align themselves to a position of the arm rest 2 and the first toothing 11, which means that small clearances and mutual rotations of the construction parts involved round second axis 25 can be compensated for.
Finally Fig. 10 explains the mounting of the locking element 8 in the arm rest 2. Thereby, the arm rest 2 is forced in the direction indicated by 26 over the locking element 8, for the purpose of which both parts 2,8 are provided with bevelled parts 27. In doing so, first parts 29 of the arm rest 2 will be temporarily be forced outwards, indicated by the arrows a, in order to give way to the locking element 8. Next, the first parts 29 may retake their original position with respect to each other, indicated by arrows b, after which the locking element 8 is secured into the arm rest 2. This operation takes less time and is easier than fixing the arm rests with a rotating movement onto the underframe respectively the locking means, as is usually done for this type of chair. The locking element 8 has bevelled parts 28 which, after being mounted inside the arm rest 2, may engage on the arm rest 2, preferably in a sideward direction as remote as possible with respect to the centre line of arm rest 2. In this way it is prevented that the first parts 29 of arm rest 2 will be forced apart by the mounted locking element 8, because this would set locking element 8 free, which would come out of the arm rest 2.
It will be clear that for the man skilled in the art in this field that the invention is not limited to the embodiment shown and disclosed and that within the scope of the invention still many possible variations are possible.

Claims

Arrangement for adjusting and locking a back rest of a chair, which arrangement comprises a first toothing connected to an arm rest of the chair and moreover a locking element, connected to the chair and mounted for rotation round a first shaft, which locking element is provided with a second toothing and which locking element tends to swivel to a position in which the second toothing engages the first toothing when the arm rest is moved in a first direction, characterised in that the first toothing and the second toothing each comprise several teeth.
Arrangement according to claim 1, characterised in that the locking element moreover is provided with a for example tooth-shaped projection, which projection is shaped and located so as to cooperate with the first toothing for forcing the locking element to swivel to a position where the second toothing engages the first toothing when the arm rest is moved in a first direction.
Arrangement according to claim 1 of 2, characterised in that the locking element tends to swivel to a position in which the second toothing at least substantially disengages the first toothing when the arm rest is moved in a second direction.
Arrangement according to one of the previous claims, characterised in that when lifting the arm rest the second toothing will at least substantially disengage the first toothing.
Arrangement according to one of the previous claims, characterised in that after being assembled, the first toothing and the locking element, including the first shaft, will be positioned inside the profile of the arm rest in a mounting space provided for that purpose.
Arrangement according to one of the previous claims, characterised in that the toothings comprise teeth having a relatively small characteristic height, for example 2-5 millimetres.
Arrangement according to one of the previous claims, characterised in that the toothings comprise teeth having a relatively small characteristic mutual distance, for example 3-8 millimetres.
Arrangement according to one of the previous claims, characterised in that the toothings comprise teeth with rounded tips.
Arrangement according to one of the previous claims, characterised in that the locking element is forced into a position where the second toothing engages the first toothing as soon as the arm rest approaches a first extreme position, with the aid of a guiding element provided for that purpose.
Arrangement according to one of the previous claims, characterised in that the locking element contacts a stop, provided for that purpose, as soon as the arm rest arrives at a second extreme position.
Arrangement according to one of the previous claims, characterised in that the locking element is rotatable over a small angle, for example 2-5 degrees, round a second axis, for example perpendicular to the first shaft.
Arrangement according to one of the previous claims, characterised in that the locking element and the arm rest are provided with guiding means, with guiding surfaces, for example slanting sides, which may cooperate while being mounted together.
Arrangement according to one of the previous claims, characterised in that the locking element comprises bevelled parts which, after being mounted inside the arm rest, engage the arm rest at a location which is in a sideward direction as remote as possible with respect to the centre line of the arm rest.