Stretcher frame for a stretchable carrier

Abstract

A stretchable carrier that has been provided with four straight stretcher bars that are divided in the corners by surfaces that stretch along the bisecting line of the corner between the center line of the stretcher bars that meet in the corner and at least one key fixed in a corner that is connected with both stretcher bars meeting in the said corner by means of friction effected by being jammed between the stretcher bars, whereby the top angle of the key is aimed at the corner and whereby the angle of the key is larger than the angle enclosed by the center lines of the stretcher bars meeting in the said corner. As this key is connected to the stretcher bars by this jamming and friction, the stretcher bars can be adjusted to any required dimensions without problems when connecting the stretcher bars.

Claims

1. A Stretcher frame for a stretchable carrier whereby the stretcher frame comprises: at least three longitudinal stretcher bars stretching along a straight line between corners, whereby the stretcher bars are divided in a corner by surfaces that stretch out along a bisecting line of an angle that is enclosed between a centre line of the stretcher bars meeting in the corner; and a triangular key set in the corner that is connected to both stretcher bars that meet in the said corner by means of a friction caused by the clamping between the stretcher bars and the key, whereby a top angle of the key is aimed at the corner, wherein that the key has a top angle that is larger than the angle that is enclosed by the centre lines of the stretcher bars meeting in the corner, wherein a groove is provided across an entire length of an outside side edge of the stretcher frame and at least one corner piece has been jammed into an outside groove of the stretcher bars meeting in the corner, wherein a top surface of the outside side edge has a rounded profile.

2. The Stretcher frame according to claim 1, wherein that the stretcher frame has a rectangular structure, the stretcher frame has four stretcher bars and a plurality of keys, wherein at least one of the keys has an obtuse angle.

3. The Stretcher frame according to claim 2, wherein at least one key of the plurality of keys has been fitted to each of the corners.

4. The Stretcher frame according to claim 1, wherein an inside edge of the stretcher frame has been provided with a groove and the key is jammed into the inside groove of the stretcher bar.

5. The Stretcher frame according to claim 4, wherein that the depth of the inside groove is at least twice as deep as the width of the inside groove.

6. The Stretcher frame according to claim 2, wherein the keys have been made of a wood product.

7. The Stretcher frame according to claim 1, wherein a corner piece has been fitted at each of the corners of the stretcher bars.

8. The Stretcher frame according to claim 1, wherein, at least one of the stretcher bars is made up of at least two stretcher bar sections, the stretcher bar sections are provided with a groove on an inside and outside surface starting at the joint and that the stretcher bar sections meeting at a joint have been connected by two extension elements that stretch out in a groove on the inside surface, and a groove on the outside surface.

9. The Stretcher frame according to claim 8, wherein the extension elements have been made of wood.

10. The Stretcher frame according to claim 2, wherein the stretcher frame has been provided with a reinforcement element that stretches between two parallel stretcher bars, which is located perpendicular to the parallel stretcher bars and that the reinforcement element has been connected inside the groove on the inside of the parallel stretcher bars with coupling elements.

11. The Stretcher frame according to claim 10, wherein the coupling elements have at least a first part that runs along the inside of the parallel stretcher bars and at least a second part that runs along a groove that has been made on one of the sides of the reinforcement element.

12. The Stretcher frame according to claim 11, wherein the coupling elements have an L-shaped configuration, of which one leg runs on the inside groove of the parallel stretcher bars and the other leg runs in the groove provided on one of the sides of the reinforcement element.

13. The Stretcher frame according to claim 11, wherein that the coupling elements have a U-shaped configuration, with at least two legs configured to run in the groove provided on both sides of the reinforcement element and a connecting section is placed inside the groove on the inside of the stretcher bars.

14. The Stretcher frame according to claim 11, wherein a thickness and a width of the profile of the reinforcement element generally correspond to the thickness and the width of the profile of the stretcher bars.

15. The Stretcher frame according to claim 1, wherein the stretcher bars are provided with a raised profile running along a length and a front edge of their outside surfaces.

16. The Stretcher frame according to claim 15, wherein the stretcher bars are beveled on their outside surface from front to back.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Subsequently, the present invention will be explained on the basis of the attached drawings, in which the following shall represent:

(2) FIG. 1: a diagram of a view from above of a stretcher frame according to the invention;

(3) FIG. 2: a cross cut view of the stretcher frame shown in FIG. 1;

(4) FIG. 3: a cross cut view of a first variant of the stretcher frame shown in FIG. 2.

(5) FIG. 4: a diagram perspective view of the stretcher frame shown in FIGS. 1 and 2;

(6) FIG. 5: a diagram perspective view of a second variant of the stretcher frame shown in FIGS. 1, 2 and 4;

(7) FIG. 6: a diagram perspective detail view of a third variant of the stretcher frame shown in FIGS. 1, 2 and 4;

(8) FIG. 6A: a detailed view corresponding to FIG. 6 of a specific construction of the variant shown in the figure; and

(9) FIG. 7: a view from above of the variant shown in FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

(10) The current invention concerns a stretcher frame for stretching a carrier, which could be both a length of canvas, linen or printed synthetic material. Such a stretcher frame, when adjustable, is also known as a wedge frame. FIG. 1 shows such a stretcher frame indicated as a whole by the number 1. The stretcher frame consists of four stretcher bars 2, that have each been cut off from a wooden profile with a mitred end. Instead of wood another wood-like material such as MDF or plywood may be used, but it is also possible that synthetic materials or aluminium is used. As a result of the mitring the four stretcher bars form a rectangle when they are connected at their mitred surfaces as is customary. Other shapes however are not excluded. According to the invention, the four stretcher bars 2 are each provided with an inside groove 3 on the inside surface, as can be clearly seen from FIG. 2. Furthermore the four stretcher bars 2 have all been provided with an outside groove 4 on their outside surface.

(11) At the corners, where the stretcher bars 2 meet, mainly triangular keys 5 have been placed in the inside groove 3 of the stretcher bars 2. This situation is shown in FIG. 4. The thickness of these keys 5 is such that the keys 5 are jammed inside the inside grooves 3. The keys have the shape of a trapezium whereby the top angle is slightly larger than 90, in fact about 98. The two other angles of the triangle are about 41. As a result of the obtuse angle at the top it is possible to slightly move the angle between the stretcher bars 2 connected by the said key 5 whilst still keeping them connected. The keys are preferably made of an impact-resistant wood product such as plywood or MDF; after all the keys are mostly wedged into place with blows of a hammer, so that they should be capable of withstanding these blows.

(12) To further strengthen the joint between the two stretcher bars 2 meeting in the corner, corner pieces 6 have been inserted, again at the corners, in the outside grooves 4. These corner pieces 6 are L-shaped, but their shape may also differ if the angle between the stretcher bars 2 deviates from 90. Here too preferably impact resistant wood-like materials are used. In this application too, a wood-like material has the added advantage of a larger friction coefficient when combined with the wood-like material of the stretcher bars 2.

(13) FIG. 2 shows a cross cut view of such a stretcher bar 2. Hereby it is notable that on the front surface that is pointed towards the carrier to be stretched, the stretcher bar has been provided with a round profile 7 towards the edge of the outside surface. This round profile creates a distance between the carrier, such as a painting canvas, and the actual stretcher frame, thereby preventing the inside edges of the stretcher frame coming into contact with the carrier which would make them visible.

(14) FIG. 3 shows a variant of the stretcher bar show in FIG. 2. This stretcher bar 12 has a larger thickness, which makes it suitable for larger stretcher frames and larger carriers. Because such a thick stretcher frame, if it would not be viewed straight at its main surface, would be rather conspicuous, the outside surface of the stretcher bar 12 has been bevelled to the inside.

(15) When constructing the stretcher frames the stretcher bars are sawn off from profile material. In order to be able to make use of any remainder pieces the profile sections can be lengthened by applying extension elements 8, that can be set into the outside groove and the inside groove of the stretcher bars and fixed there by using adhesive, as is shown in FIG. 5. For the construction in FIG. 5 the joint surface between the sections of stretcher bar stretches perpendicular to the length of the stretcher bar sections. The joint between both stretcher bar sections would become stronger, however, if the interface surface between both sections would stretch out at an angle because this would increase the contact surface.

(16) Apart from applying a thicker and stronger stretcher frame it is also possible to strengthen the stretcher frame by using a reinforcement element 9 that connects two opposing stretcher bars 2. FIG. 7 shows such a configuration. Furthermore two extra reinforcement elements 19 are shown here that each stretch between a reinforcement element 9 and a stretcher bar 2. The manner in which the reinforcement elements 9 are connected to the stretcher bars is shown in FIG. 6. At the crosscut end of a reinforcement element 9 a U-shaped coupling element 10 has been fitted of which the legs 10a stretch out into the grooves 11 that are provided for in the reinforcement element 9. The coupling piece 10b of the coupling element 10 sticks out from the reinforcement element 9 and, when placing the reinforcement element 9 in the stretcher frame, coupling piece 10 stretches out into the inside groove 3 of the stretcher bar 2. It speaks for itself that the other side of the reinforcement element 9 has a similar construction. Thereby the coupling element 10 is preferably glued to the reinforcement element 9 with adhesive. When the carrier has to be stretched on the stretcher frame at a later stage, then it is necessary not to join the coupling elements to the stretcher bars with glue.

(17) FIG. 6A shows a situation whereby the U-shaped coupling element 10 has been replaced by two L-shaped coupling elements 20. This construction makes it possible for these dimensions to make use of the corner pieces 9 for the coupling elements 20.

(18) From FIG. 7 it further appears that between the reinforcement element 9 and the parallel stretching stretcher bars 2 extra reinforcement elements are inserted that are also connected by means of coupling elements. Hereby use is made of the grooves present in the reinforcement elements of which the dimensions should preferably correspond to the grooves in the stretcher bars. This further offers the possibility to use the same profiles for the reinforcement elements as for the stretcher frames, although if the profile was provided with a round profile 7, this would have to be removed before the profile could be used as a reinforcement element.

(19) It will be clear that numerous variations can be added to the above constructions within the framework of the claims and that the measures of different constructions can be combined in many ways.