EP0494839B1

EP0494839B1 - A bedstead of springs made with compound materials

Info

Publication number: EP0494839B1
Application number: EP92500001A
Authority: EP
Inventors: Alfonso Solans Serrano
Original assignee: Pikolin SA
Current assignee: Pikolin SA
Priority date: 1991-01-08
Filing date: 1992-01-02
Publication date: 1995-08-30
Anticipated expiration: 2012-01-02
Also published as: IE920041A1; EP0494839A1; GR3018112T3; DE69204306D1; IE69272B1; ATE126985T1; ES2046153A6; DK0494839T3; DE69204306T2; ES2027569A6

Abstract

A bedstead of springs is made from compound materials of the type made up of a frame structure and functional surface, determined by a succession of transversal springs fitted on it. The latter comprises three fundamental components made up by a special section of the spring (9), bushes (11) for embedding same in the bedstead frame (10) and supplementary caps (12) for finishing off the spring-to-bush assembly. The section making up the springs (9) adopts an inverted ''U'' shape cross section with short vertical arms with a broad horizontal stretch.

Description

This Patent of invention refers to a bedstead formed by a succession of transversal springs fitted on a frame structure. Apart from others which we shall be seeing later, this bedstead offers the special feature of its springs being made from fibre reinforced plastic materials.
Amongst the highly varied types of bedstead, those in which the functional area is formed by a series of wooden springs provided with extraordinary qualities of strength and flexibility are known in the marketplace. They offer optimum adaptation for supporting the mattress and, consequently, the person using the bed. This is why these bedsteads are so widely used, so much so that it may be stated with no doubt at all that, at the present time, they are the ideal mattress base most accepted both by users and merchants, in the manufacturing industry and even by health authorities.
The excellency of the aforementioned wooden spring bedsteads is founded, as we have said, on the qualities of the springs' strength and flexibility but it is precisely these points where the problems and disadvantages that these products suffer from lie.
In fact, for springs to act as such, it is necessary to follow a laborious manufacturing process since they are made up of a package of thin wooden strips, duly compacted and given a slight arching effect. With wood being their basic, main component, it is easy to understand that the springs are significantly affected by weather conditions such as environmental humidity, temperatures, etc. Despite the fact that, in better quality bedsteads, these springs are given a plastic protection which, apart from contributing towards raising the price of the product, also has the disadvantage of breaking because of friction or other unforeseeable causes, thus leaving the springs' wooden component uncovered. They would then unfailingly deteriorate in their functionality as time elapses.
On the basis of the prestige acquired by the aforesaid spring bedsteads, several different types have appeared in the marketplace in which endeavour has been made to avoid the laborious manufacture of the springs which have been replaced by simple cross-pieces or rigid wooden slats with which flexibility, such a determining feature of this piece of furniture, disappears, or endeavour has been made to replace the wooden springs by springs made of other materials which would provide a certain degree of flexibility, with the idea of lowering the price of the product and preventing its possible deterioration. Endeavours have also been made along these lines using metal rods and sheet, plastic materials and even combining metals with plastic.
Thus, in current state-of-the-art, we find forerunners of bedsteads made up of cross pieces of various widths obtained from simple, compact, rigid wood as well as other designs of flexible springs either made up simply of coated metal rods or metal rods supplemented by metal flat strips or metal rods or strips coated with plastic materials or, finally, by springs made with a complex structuring of areas and ribs obtained wholly with plastic materials.
Among all the aforementioned antecedents, German Patent DE-B-2 703 199 merits special attention, as it describes an elastic strip for bedstead frames made out of polyester reinforced with glass fibre. It attempts to attain the required resistance through the use of a section whose longitudinal thickness varies from a maximum at the centre to a minimum at the extremes, and whose cross-section is in the form of a conical trough.
Despite the various, praiseworthy attempts referred to, none have managed to compete in qualities with genuine wooden springs and the truth is that nobody has triumphed in this attempt.
The applicant for this Patent, who has a singular experience in this type of manufactured product through being the leading Spanish firm in spring bedstead manufacturing, is fully aware of the disadvantages that wood brings to his products and of the possible advantages that replacing wood by synthetic plastic materials could bring to his product, as a natural consequence of the physical-chemical and mechanical properties intrinsic to this kind of material.
Based on this possibility, quite some time ago, the applicant commenced profound research directed towards replacing wooden springs by sections made of plastic materials. These sections had been conceived in such a way that, whilst enjoying all the advantages inherent to the very nature of the material employed, mechanical performance and the material's behaviour on being used to make a bedstead's functional surface were at least as effective as those provided by the wooden springs which it was intended to replace. With this in mind, it was laid down that the section to be obtained would have to behave elastically in the same way as the aforementioned wooden springs, that its elastic hysteresis was less and that, finally, it would be totally stable to weather conditions.
Having initially discarded complex shape structures and metal frameworks, efforts along this line of research were directed towards achieving a type of section with a simple, adequate format sufficiently reinforced by a continuous synthetic fibre support. It would be a section which could be obtained from different thermostable plastics.
To obtain the section required, an analysis was first made in order to find out the exact stresses in quality and quantity that each area of the lamina in a bedstead is supporting. This study managed to prove that 96% of the stresses are bending and 4% compressive in nature.
As a result of the research, work and tests carried out, the spring bedstead as defined in claim 1 was developed. Three components are distinguished:

the section itself, which is actually the spring,
the bushes for fitting them into the bedstead's frame, and
the supplementary caps perfecting the spring-to-bush assembly which, in turn, contribute towards the mattress being stable on the bedstead.

The Section, which forms the spring itself, is characterized by having an inverted "U" shaped cross section with short parallel sides, compared to its central broad flat bridge. The sides, at a point nearly halfway, are angled inwards at 45º angles giving the section bevelled longitudinal edges. This section can be obtained from flat, crimped, woven, combed or braided fibres or a combination of them by subsequent combination in a suitable press-mould with any type of thermostable plastic material such as ortho- and isophthalic poliesters or any other equivalent, either alone, or with various organic and inorganic charges such as calcium phthalate, calcium carbonate, talc or others. During the process, adding small amounts of other materials such as fabrics, threads, plastic films of minimum thickness or paper, not only influence the section's behaviour, but also participate in the outside decorative finish of the spring. Proportions of 70% fibre to 30% isophthalic resin or plastic are foreseen.
The effects of the deflection required in the spring's body are a function of its length for different sizes of bedstead; it is calculated that the section obtained has a curvature between 4m and 9m radius.
The invention also provides for the possible addition of two narrow, longitudinal projections on the spring's upper surface, as a continuation of the bevels of its two short sides. These projections are angular in cross section and lead to perfect adaptation of the mattress to the bedstead and prevent it sliding.
The invention's second component relates to the bushes which fit into the bedstead's frame and house the ends of the springs, protecting them from friction and wear. Since frames are usually metal, these bushes protect the springs from damage due to movement as result of their flexing on the sharp edges of the bedstead frame.
Made of plastic, these bushes have a slotted body exactly matching the spring, onto which they fit exactly at both ends; the inside slotted end facing towards the inside of the mattress. The side faces and bevelled edges are extended and terminate in thick side lugs located in a plane perpendicular to the body. These lugs have an approximate square shape but with their outside vertices curved. This curvature is more marked at their respective upper vertices.
The supplementary caps, also made in plastic, affect not only the aesthetics of the bedstead, but contribute towards improving the anchoring of the springs to the frame and towards stabilizing the mattress on the bedstead. The supplementary caps, are shaped to form a hollow, bottomless body. They have a truncated parabola in plan view decreasing in height from the widest part, where they match the bedstead's frame, to the opposite parallel and narrower end, in which the height practically matches that of the springs. The supplementary caps at their narrowest end, which faces inwards towards the bedstead's longitudinal centre line, have a mouth coinciding in shape exactly with the section of the springs. From this mouth, three ribs begin and extend parallel towards the inside of the cap, slightly increasing their height as the cap itself does, acting as a guide and adapting to the shape of the springs which are to be located inside them. The two side ribs, which are the highest and which locate with each side of the spring, have on their inside edges small longitudinal bevelled lips that project towards the centre line, and shaped to clip onto the springs by pressure when fitted in the bedstead. The three ribs do not reach the wide end part of the cap in order to leave a clear space between these ribs and the small end pieces which, at the widest end of the cap, close it off and allow it to house and hold the spring bush side lugs.
The flexibility required on the functional surface of each type and size of bedstead is preset by the number of springs shaping it, as well as the width and thickness of them. Therefore, coefficients of flexibility and firmness are constant parameters for each bedstead made with conventional wooden springs.
We see, then, that these coefficients of flexibility and firmness, as well as their suitable regulation, constitute fundamental principles which must be taken into account in the design for the manufacture of a structured bedstead with a base formed with such springs.
When we study idea of acting on the behaviour on the functional surface of the bedstead, we find in the present state of the technology that the German Patent DE-U-8 708 221 exists and is referred to as support blocks for the slats that make up the surface of the bedstead. The aforementioned support blocks are made of elastic rubber materials and present a compressible structure that has cavities to allow the deformation required to support the weight on the bedstead. In this Patent the facility for compression or deformation of the support blocks can be eliminated by means of the insertion of plugs into the cavities of the blocks. These plugs form part of devices that slide on the slats and whose extremities carry the plugs that fit into the support block cavities to make them rigid. In this Patent, the regulation of the stiffness of the bedstead is controlled exclusively by the supports and not by the actual slats which are in fact rigid. The bedstead surface has therefore total stiffness or total flexibility, without the possibility of a gradual change from one state to the other as has been achieved in the case of our invention.
The aforementioned regulation is the objective intended and achieved, in a very simple but effective way by this invention. This is done using simple means allowing individual regulation of the coefficients of flexibility and resistance of each of the various springs making up the bedstead. This regulation can be calibrated and modified at the user's will at any time he may deem fit.
The springs protected by the invention are shaped from a special section adopting an inverted "U" shape cross section with its short parallel sides, converging inwards towards a broad central flat bridge. The proportions of these sections vary both as a function of the size of the bedsteads on which the springs are fitted and as a function of the place each spring occupies in the bedstead's frame, since bedsteads are known where their centre springs in the areas in which the bedstead has to support greater stresses are noticeably wider than springs located in areas near the bedstead's headboard and footboard.
The invention also provides for the section making up each spring to be given a slight longitudinal curvature which determines the deflection defining its flexible capacity.
Whilst being used, each spring within the bedstead's framework withstands a pressure exerted by the weight of the users and, thanks to this pressure and the spring's flexibility, the spring undergoes a deformation of its initial design which is reflected both in the arc of its longitudinal curvature and in the parallelism of the short sides, defined by the "U" cross section. The sides tend to diverge outwards in order to absorb the bending stresses supported by the spring, which totally or partially recovers the original shape as soon as the pressures being received are removed or modified by virtue of the spring's intrinsic flexibility.
From the foregoing paragraph, it can be deduced that if we limit or prevent the springs from deforming, we increase resistance to pressures and, consequently, we increase the degree of firmness of the bedstead's functional surface by a corresponding magnitude.
On the basis of this principle, this invention has provided for simple regulating elements to control the spring flexibility and rigidity. Each of these elements is made up of a totally rigid piece in a general elongated rectangular ferrule shape, having a transverse rectangular aperture that exactly conforms to the shape and cross section of the undeformed spring on which it slides. In order to facilitate its being manually moved along the spring, the regulator is reinforced in thickness on the small sides to incorporate a knurled concave outside surface.
These regulators have + and - signs engraved on their top face, which is the most visible. These signs are duly aligned in the vicinity of one of its ends and when these regulators are fitted on a bedstead spring, the + sign appears on that side of the regulator facing towards the bedstead's centre whilst the - sign is located on the side nearest the bedstead's sides.
The mission fulfilled by these regulators, on tightly enveloping the springs to which they are fitted, is to prevent divergence or deformation of the narrow side faces of the springs, and thus give greater resistence to pressure and therefore greater firmness to the bedstead's surface.
Manually operated, as we have already mentioned, these regulators are arranged preferably in pairs on each of the springs and, according to their location on them, make it feasible to set their degree of resistance.
In fact, if we locate the two regulators of the same spring in the proximity of its ends, next to the bedstead's frame where the spring is fitted and, therefore, prevented from suffering any divergent deformation of its initial state, the spring's firmness will not be changed by the action of these regulators. Since the spring in question will bend under the effects of the pressures it receives, the section will suffer the pertinent deformation along the rest of its length. This divergent deformation will be more marked in the central areas of said spring.
If we move the regulators towards the central area in the direction of the + signs engraved on their top, we lessen the length of the spring's deformable area and, therefore, we increase its resistance. This resistance will increase as the regulators are being moved to the most central position, where the maximum resistance which the springs can attain occurs.
In order for the invention to be better understood, a practical form thereof is shown in the adjoining drawings, as an example without any limiting scope.
Fig. 1 shows us two different sizes in cross section of the section making up the springs as envisaged in the Patent. The sizes of this section will naturally adjust to the requirements and features of the bedstead it is intended to make in each case.
Fig. 2 represents the bush in which the spring ends fit in front elevation, plan and rear view, as well as a detail in perspective of this piece, making it easier to understand.
Fig. 3 shows a section of the same bush through A-A' in Fig. 2.
Fig. 4 shows another section of the bush through B-B' in Fig. 2.
Fig. 5 shows two views of the supplementary cap seen in elevation from its widest end and seen in plan underneath without a bottom.
Fig. 6 is a section view of the same cap through C-C' in Fig. 5.
Fig. 7 shows two views of the cap itself enabling us to see both its external configuration and its internal structuring.
Fig. 8 and Fig. 9 give us a top and bottom view of the three basic bodies making up this invention, i.e., spring, bush and supplementary cap. Since they are all fitted and mounted on a frame that makes up the bedstead assembly, the bedstead is not shown completely in the drawing as it is deemed unnecessary, since it would be no more than a mere repetition of what is defined and represented in these drawings.
Fig. 10 represents in perspective a portion of a spring made in accordance with the invention.
Fig. 11 is a schematic representation of a spring seen from the side to show us its slight longitudinal curvature giving it its deflection "f".
Fig. 12 shows us a view through A-A' of Figure 11 when the spring is at rest.
Fig. 13 is another similar view showing the spring under pressure.
Fig. 14 shows us a plan and elevation view of a regulating element.
Figure 15 shows the same item in perspective.
Figure 16 shows a cross section through a spring coinciding with the positioning of a regulator.
Fig. 17 consists of a view in top perspective of a spring with its regulators, fitted onto a bedstead frame.
In the figures, we can see that the springs 9 are formed from an inverted "U" shaped section with short parallel sides converging inwards to form the bevel 1 joining the wide central bridge 2 which is the spring's functional surface.
The invention has slight longitudinal projections 3 on this central bridge surface 2 as can be seen specifically in Fig. 1. Their sole purpose is to improve the mattress's seating on the bedstead.
The figures also show us the special arrangement of the spring receiving bush 11 in which its slotted body 4, shaped to the shape of the springs, and the lugs 5 which emerge on both sides of its mouth can be seen.
Likewise, the cap 12 which, by means of its interior ribs 6 conforms exactly to the springs cross section, is also shown. The cap is secured to the spring with longitudinal projections 7 which extend slightly from the bottom edge of the two side 6 ribs and which are bevelled to face towards the cap's centre line.
The cap end plates 8, which partially close off the cap 12 at its widest end, can be seen in the drawings. Between the end plates 8 on the caps 12 and the interior ribs 6 of this same cap we can see a small space since the ribs 6 do not reach the cap end plates. This small space houses and holds firm the lugs 5 of the bush 11 when the assembly is fitted to a bedstead frame 10 and the caps 12 anchor the springs and form part of the contour of the bedstead's surface.
The drawings also show us how the springs 9, in their initial shape with deflection "f" (Figure 11), deform the parallelism of their narrow sides when subjected to pressure effects. This is represented by lines BC-DE and B'C'-D'E' (Fig. 12 and Fig. 13). Such deformation is conditioned and made practically impossible due to the action of the rigid regulator elements whose apertures 13 fit exactly to the cross section of the springs 9.
We can also see in the figures the concave sides of the regulators with knurling 14 to facilitate moving them by hand, as well as the + and - signs engraved on their upper face. The + sign is located on the side of the regulator facing towards the bedstead's centre line whilst the - sign faces the bedstead's outer frame.
The foregoing is a faithful description of the subject matter of this Patent, in which all those variants which do not alter the essential nature of the invention, which is defined by the Claims, can be deemed as included.

Claims

A bedstead of springs made of compound materials, of the type made of a frame structure and providing a functional surface, composed as follows:
- a succession of transversal springs fitted on a frame, using a spring section made of thermostable plastic material of any type reinforced with glass fibres or equivalent;

- bushes for the spring ends which are embedded in the bedstead frame;
characterized in that
the springs (9) have an inverted U-shaped cross section with short parallel sides relative to a broad flat central bridge (2), the free ends of the sides running parallel to each other, and the sides, at a point approximately half way between the free end and the bridge, turn inwardly at an angle of 45 degrees thus giving the section bevelled longitudinal corners (1),
the bushes (11), which are made of plastic, have a slotted body (4), the slot exactly matching the section of the spring (9) onto the ends of which they fit; at the mouth of the slot the side faces of the bushes extend laterally from the slot to form thick side lugs (5) which have an approximate square shape in plan view, but with their outside vertices being curved;
supplementary caps (12) for improving the anchoring of the springs (9) to the frame (10), said caps are made of plastic and shaped to form a hollow, shell-like body, having a truncated parabola in plan view decreasing in height from the widest part being adapted to match the lugs of the bushes, in which bushes the spring ends are embedded, to the opposite parallel and narrower part being adapted to match the spring (9) to be covered, the cap being mounted over the spring end embedded in the bush (11) and secured to it by each of two small end plates (8) at the widest end of the cap which are located between the lug (5) of the bush (11) and the frame (10), and by small longitudinal bevelled lips (7) in the supplementary cap (12) which hug the spring (9) and which are formed to abut the lugs of the bush (11).
A bedstead according to claim 1, characterized in that the supplementary caps (12), at their narrowest end which faces inwards towards the bedstead's longitudinal centre line, have a mouth coinciding in shape exactly with the section of the springs, whereby from this mouth, three ribs (6) begin and extend parallel towards the inside of the cap, slightly increasing their height as the cap itself does, acting as a guide and adapting to the shape of the springs which are to be located inside them, whereby the two side ribs, which are the highest and which locate with each side of the springs, have on their inside edges small longitudinal bevelled lips (7) that project towards the centre line and shaped to clip onto the springs (9) by pressure when fitted in the bedstead.
A bedstead according to claim 2, characterized in that the three ribs (6) do not reach the wide end part of the cap in order to leave a clear space between these ribs and small end plates (8) which, at the widest end of the cap, partially close it off and allow it to house and hold the spring bush side lugs (5).
A bedstead according to claim 1, characterized in elements provided for regulating the spring flexibility and firmness, whereby each of these elements is made up of a totally rigid piece in a general elongated rectangular ferrule shape, having a transverse rectangular aperture (13) that exactly conforms to the size and cross section of the undeformed spring (9) on which it slides, and in order to facilitate its being manually moved along the spring, the regulator is reinforced in thickness on the short sides to incorporate knurled concave outside surfaces (14).
A bedstead according to claim 4, characterized in that these spring firmness regulators have + and - signs engraved on their top most visible face, whereby these signs are duly aligned in the vicinity of one of its ends and when these regulators are fitted on a bedstead spring, the + sign appears on that side of the regulator facing towards the bedstead's centre whilst the - sign is located on the side nearest the bedstead's sides.