US2893018A - Spring mattresses, upholstery seats and the like - Google Patents

Description

July. 7,- 1959 E. H. FRISELL 2,893,018

SPRING MATTRESSEZS, UPHOLSTERY SEATS AND THE LIKE Filed Nov. 8, 1954 5 Sheets-Sheet l 'zzz 4 3 9 I Inventor EH.E z.$e-LL July 7, 1959 v E. H. FIRISELL 2,893,018

SPRING MATTRESSES, UPI-IOLSTERY SEATS AND THE LIKE Filed Nov. 8, 1954 5 Sheets-Sheet 2 9 I I I V July 7, 195-9 E. H. FRISELL 2,893,018

SPRING MATTRESSES, UPHOLSTERY SEATS AND THE LIKE.

Filed Nov. 8, 1954 5 Sheets-Sheet 5 L 12 1 I w '1 ain/Z221 U d s P o 9 2,893,018

used as a seat and bed. This factor is not satisfied by 2,893,018 present-day constructions of spring bottoms that are so SPRING MA'I'TRESSES, UPHOLSTERY SEATS AND THE LIKE Erik Hjalmar Frisell, Lidingo, Sweden, assignor to Kommanditbolaget Irving & Frisell, Nykoping, Sweden, a corporation of Sweden Application November 8, 1954, Serial No. 467,528

Claims priority, application France March 18, 1950 6 Claims. (Cl. -247) The present invention relates broadly to the art of furniture.

More particularly, this invention relates to a spring support for use in supporting mattresses, upholstered cushions or the like on beds, chairs, settees, sofas and other comparable articles of furniture.

The invention relates to such a spring support that can be used independently of any overlying cushions or mattresses.

This application is a continuation in part of my prior filed application Serial Number 215,209, filed March 13, 1951, now abandoned, and entitled Spring Mattresses, Upholstery Seats and the Like.

It has now been established that lumbago and other backaches and kindred pains very often arise from the manner in which the backbone is supported during sleep. It is a well known fact that a great number of supporting structures in beds are improper and that the backbone, when the person is at rest, in unnaturally bent or strained. This occurs because the bed is deformed in the central portion under the weight of the sleeping person so that the central portion of the body supporting surface is, somewhat like a hammock, lower in the middle than at its end. Corrective measures have been proposed such as by inserting a bed board between the mattresses and the springs. However, sleeping over a bed board is not very comfortable unless the mattress is of extra thickness and consequently very expensive. For this reason bed boards and other orthopedic appliances will be used only in cases of necessity and will not attain extensive use by the general public.

On the other hand, in practically all of thepresent bed spring constructions in which the supporting surface, in the longitudinal direction of the bedstead, is connected to end frames, which sooner or later sag, simply constructed bed springs will sag very quickly while the more expensive ones will, after use, acquire this defect, particularly if the spring frame is of the type that is used as a seat. In other words, the article of furniture is a sofa or seat that is convertible to a bed. With such underlying supports, mattresses even of the inner-spring type, are never completely rigid in the longitudinal direction and will thus conform themselves to the deformation of the bed springs. Consequently the present constructions give rise to need for a definite improvement particularly in the art of supports for mattresses and the like.

Present living conditions have a great influence on the necessity of providing more economically and structurally sound supporting structure for beds, chairs and seats. In a great number of modern homes and in practically every efiiciency apartment, convertible articles of furniture are in use, that is, those which are couches, settees ordivans in the daytime and are used as beds at night. Due to this rigorous use, the underlying supports for the seating or resting surface, particularly its end and edges, should be comfortable enough to be embodied with a frame as to form a sag in the central portion thereof after use. To withstand the rigors of double use as bed and for example couch, the structure must be such as to withstand pressure occasioned during use by heavy persons without fatiguing or unduly straining the structure and still be sufliciently comfortable as to not unduly fatigue the user.

The above mentioned factors indicate that a development along the lines of the following points is necessary, at least for beds available to the general public.

(a) A spring bottom of a bedstead, hereinafter referred to as a mattress, with absolute uniform elasticity along the whole of its supporting surface, of a structure which cannot form a sag after usage and yet which is sufficiently yieldable or in other words, soft enough to adapt itself to the contour of a recumbent human body, and

(b) A mattress of a simple and inexpensive type so as to be within the resources of the general purchasing public, yet which is essentially adapted to provide level and even support andproperly dispersed pressure. A mattress of this type will not sag or be deformed.

In order that the spring support or spring mattress of a bedstead might fulfill the aforementioned desiderata, the following point should be adhered to in constructing the same:

1) Since in sleeping the human body should rest with its middle line straight in a vertical plane, the elasticity of the supporting surface should level the height differences between different body parts so that they are all properly supported and there is no undue pressure on the hip and shoulders,

(2) In order to prevent sag after usage, the supporting surface must be entirely separated from the end beams of its frame. Only with such construction can full elasticity be attained at the head and foot ends of the structure,

(3) The supporting surface should comprise and have band-like members, transversely connected to the opposite side beams or components of the frame and independent of any connection to one another so that they can adjust themselves exactly to the contour of the body,

(4) The band-like members must be rigid in the direction transverse to their length so that the application of force or a point of stress will not force them apart so as to permit the hair-mattress or overlying cushion to be forced or pressed into the spaces between the members. This requirement excludes known constructions of steel wire or coil springs,

(5) The construction of steel bands must be such that even a strong overloading, for example, when a person will stand on one single band, will not effect permanent deformation or fatigue in the material of the band members. This drawback is present when the supporting structure for a mattress or cushion utilizes coil springs. In the proper construction when deformation even under stress has reached the maximum desired value, it should automatically, gradually limit deformation, if possible without the use of a positive stop or abutment,

(6) The supporting surface or upper surface of the structure should be elevated or raised above the beams or other frame components in unloaded condition so that the sides and ends of the surface can be yieldable. Thus a thinner cushion or hair mattress can be used and still provide for comfortable seating.

(7) The various connections between the components should be such that creaking does not occur even after long usage and thus movable connections between the components should be avoided,

that without legs, it does not weigh more than about 45 pounds,

(9) From the aesthetic viewpoint and in order to prevent wear of bed ticking, the structures should be such that a cover canbe stretched straight-over the supporting surface without the cover being stretched or slackened upon deflection of the surface,

(1-0) The construction should be simple, comprise relatively few parts, and which parts should be readily exchangeable in the event of need,

- :(ll) Cost of the structure should beeconomical so that the spring mattress with'these desirable capabilities will meet the resources of the general public.

I The supporting surface should preferably bev-planar or flat in unloaded condition since a convex surface will give rise to uncomfortable positioning of lighter body parts it they are of insufficient weight to press the 'sup-. porting surface into a horizontal plane.

. It is accordingly an object of the present invention to provide a mattress constructed with respect to the above noted viewpoints.

The spring mattress or supporting surface of this invention due tov its simplicity and ability to withstand very great pressure changes for practically an unlimited period of usage without altering its form or becoming fatigued, renders it especially suitable in the constructions of seats of various types. Accordingly the present invention provides a supporting surface that can be termed a spring mattress for use in upholstered seats, beds, settees, lounge chairs and the like, which includes a frame having opposite sides and ends, a plurality of parallel, mutually spaced band-like members connected between the opposite sides of the frame, each band-like member consisting of two resilient, curved steel bands, one at each end and an intermediate band of a less high test material that connects with the inner ends of the two steel bands. The intermediate band is non-tensible in its longitudinal directionand is straight in unloaded condition. The connection between-the curved steel bands and the frame ingludes. support members that are convexly curved on their entire surface with the convexly curved portion underlying the steel bands. The steel bands are capable of withstanding the entire springing stress upon the application of load and the convex curvature of the said supports being such as to force the steel hands into rolling engagement therewith due to. the application of load so that upon deflection ofthe bands they are supported in a manner that the elastic limits of the bands are not exceeded, their free length, being successively decreased as different portions come in contact with'the convex surface whereby upon deflection up to a certain point the upper or terminal ends of the steel bands will receive a component of movement; inward adjusted in its size, thereby establishing a condition such that the intermediate bands connected at its opposite ends to the cueved steel bands can form a downwardly extending parabolic curve. In accordance with'the modification of the invention, the curved steel bands in the area adjacent the point of connection with, the intermediate bands are provided with a convexly shaped upwardly-extended bent portion which is capable ofbeing resiliently straightened when; load is applied to the mattress and the steel band is tensioned and which bent portion uponthe relief of the load returns to its original upwardly extending form. The advantage resulting from forming the curved steel band in this manner provides an arrangement in which the sides of the spring'mattress have a fuller andjmore attractiveappearance, and further presents a structurein whieh thesupporting surface upon application'of aheayy load will be somewhat more comfortable or-softer than if the steel bands are in essential straight, since upon the app i ati o oad tot-t e ma tress the teel; ands; are. subj cted to as o aextensionstrainandia-straig t nins of the bands arises wherebyl-thedejath? oftheparabolic 4 curve of the intermediate bands must be somewhat increased under the maintenance of the absolute rigidity of the steel bands in the directions at right angles to their length.

In order to provide a strong reliable and creak-free connection between the pair of steel bands and the connecting intermediate band, the steel band on at least one side of the frame is provided at its inner end with a transversely extending slot, the adjacent end of the intermediate band being provided with a down-turned end for cooperation with the slot and also rearwardly of the down-turned end is a bent down tongue which after the down-turned end is passed through the slot in the steel band and bent'backwards the tongue is bent over the now bent back down-turned end.

Further and more specific objects will be apparent from the following description taken in connection with the ac companying drawings illustrating several embodiments and in which:

Figure 1 is a fragmentary plan view of a resilient support or mattress for a bed constructed in accordance with the invention,

Figure 2 is a transverse sectional view illustrating a side support, one curved steel band and a portion of the intermediate band before it is connected to the curved band,

Figure 3 is a fragmentary plan view of the two adjacent ends of one of the curved steel bands and a portion of the intermediate band,

Figure 4 is a longitudinal sectional view on an enlarged scale of a portion of the intermediate band and the adjacent portion of the curved steel band and illustrating the first stage of connecting the same, together,

Figure 5 is a, view similar to Figure 4 but illustrating the connection completed,

Figure 6 is a fragmentary sectional view of one side of the support or mattress in unloaded condition,

Figure 7 is a transverse sectional view illustrating a side support and connected thereto a steel band having a'convexly curved upwardly bent portion,

Figure 8 illustrates the structure of Figure 7 with the intermediate band connected thereto and in loaded condition,

Figure 9 is a transverse sectional view illustrating a tubular support and a steel band having the upwardly bent portion adjacent its outer end,

Figure 10 is a fragmentary transverse sectional view illustrating a portion of a modified construction embodying additional spring means,

Figure 11 is a transverse sectional view of one of the supports and diagrammatically illustrating one of the band-like members before assembly, in unloaded condition and during application of load,

Figure 12 is a transverse sectional view diagrammatically illustrating amattress in unloaded condition, and

Figure 13 is a similar view illustrating the mattress in loaded condition.

As shown in Figure 1', the band-like resilient supporting elements denoted at 1 which constitute the supporting surface or mattress of a bedstead are strained between longitudinal side beams 2 of the bottom frame, oneend beam 2a being illustrated. Each of the resilient members is composed of three elementsa pair of curved steel bands 3 and anv intermediate band 4 of a less high test material, for example, band iron. Each interme diate band 4 is-connected between a pair of curved steel bands. Theside beams 2 are provided with a longitudinally extending slot- 6' extending inwardly from the outer side thereof and one-end ofeach curved steel band has an angularly bent portion 5 that is apertured at 8. The bentportion 5gisinserted inthe slot 6 and a wood screw 77 fixes; each steel band: to the side beam 2 by passing through theiaperture 8, in the end- '5" of theband. The s, d.9.of; each curved-steel band isifixedtoone and ff the interme ate bands. 4.

' The opposite ends of each intermediate band 4, only one end being shown in the drawing, are provided with a down-turned end portion 10. Inwardly of the downturned end there is provided a downwardly bent tongue 11. As shown in Figure 2, the end of the intermediate band 4 is provided with two longitudinally spaced tongue members extending substantially at right angles to the plane of the band. The end portion 9 of each steel band is provided with a transversely extending slot 12 inwardly of the end and having a length that somewhat exceeds the width of the intermediate band 4. The outer end of steel band 3 is provided with a notch 13, the length of which slightly exceeds the width of the tongue 11. The construction of the mattress is effected as follows:

After the curved steel bands have been secured to the side frames 2 and the intermediate bands 4 have been connected to the curved steel bands 3 along one side of the frame, the steel bands 3 on the opposite side of the frame are bent inwardly, in Figure 2 to the right, to elfect connection of the adjacent end of the intermediate band 4 therewith. This bending and connecting action is started at one end of the frame and the first curved steel band 3, for example, at the lower left hand corner of Figure l, is bent inwardly until it is possible to insert the down-turned end portion of the band 4 in slot 12, Figure 4. At the same time, the down-turned tongue 11 fits in the notch 13 and constitutes a guide for preventing mutual displacement of the interconnected parts transversely of their length. The down-turned end portion 10 is bent back to underlie the portion of the band 3 between notch 13 and slot 12 andthen the tongue -11 is bent forwardly to underlap the bent back portion 10 as shown in Figure 5.

It is believed clear that in view of the overlapping of the tongue 11 in forming the connection between the intermediate band 4 and the pair of curved steel bands 3, each of the band-like or resilient strips 1 can be subjected to considerable extension strains Without destroying the connections. The connection is particularly strong and it does not creak when the mattress is in use. It is further clear that if for any reason it is necessary to replace either an intermediate band or a curved steel band 3, the replacement can be effected very readily by bending back tongue 11 and the end part 10 with a suitable tool to disconnect the band 4 and after that is disconnected the removal of screw 7 will permit removal of the curved steel band 3.

Each curved steel band is provided with a convex upwardly bent portion 15. The end 14 of this bent portion is so adjusted that it will almost engage the rolling curve 16 on the upper, surface of the support 2 when in fully loaded condition, Figure 8. According to the drawings, the upwardly bent convex portion is exposed to a strong extension strain when the mattress is fully loaded and this strain causes an elastic straightening of the steel bands 3. When the load is relieved the bent portion 15 returns to the original upwardly extending form.

Wooden supporting beams 2 have been illustrated in the aforedescribed forms. If desirable, tubular supports 2 can be utilized, Figure 9. These tubular beams are provided with a longitudinal slot as at 18 to receive one end of each of the steel bands 3'. The bands are provided with a down-turned bent end 17 which after insertion through the slot into the tube 2 will rest against the interior of the tube. Consequently when the bands are loaded, the offset end portion 17 will maintain them within the tube.

Figure 10 illustrates an embodiment in which the deflection of the steel bands is regulated by weaker supplementary springs or hands of a resilient, but in the directions of right angles to the length of the bands 3, rigid material. It is also possible to use less acclivity in the rolling curve 16 while the major resistance against deflection of the bands 3 is provided by the additional spring, for example, the coil spring 19 illustrated. In the form 6 shown, the side beams are provided with shouldered recesses 20 to accommodate the lower end of the springs 19. The upper ends of the springs engage beneath the band-like members 1 at the point 21.

Figure 11 illustrates one side support 2 with its rolling curved upper surface 16. The relation between the ini-' tial bending radius R of the steel band before assemblage on the support and the radius r is determined by the allowed maximum stress 7 according to the formula 2(r R in which 1. is the thickness of the steel band and E is the modulus of elasticity of the material, usually ranging between about 28,800,000 and 31,300,000 pounds per square inch. The chain-dotted curved line BC in Figure 11 shows how the end of the steel band 3 upon load is at first moved inwards a certain distance A whereby the distance between the two steel bands of a pair is reduced so that the intermediate band 4 can now form a downwardly bent parabolic curve, Figure 13. At the point C where the contact point of the band 3 against the upper curved surface 16 is about level with the upper end of the steel band 3, a further depression should force the end of the band outward, which however is not possible without a straightening of the parabolic curve and the lifting of the load as a result. Thus in the neighborhood of point C is attained a softly acting stop against further depression of the supporting plane without any sound causing engagement of parts, and an increased load involves only a poor extension strain. Even now a certain elasticity of the supporting plane remains since upon side shifting of the load, for example, if a person resting on the supporting surface turns on his side, this movement forces the parabola to assume an irregular form.

in order that the supporting surface may softly conform itself to the body form, the width of the steel springs 3 should not be larger than three inches and in order that the cushion or hair mattress be not forced into the spaces between the respective springing members 1, the longitudinal edges of these members should not be too far apart. Each band should be able to withstand about thirty-five pounds before the bottom position is reached. When a person is sitting on one side of the supporting surface, each steel band should be able to withstand at least 22-27 pounds. In order to be what is termed soft, the depression a of the side of the supporting surface should be at least %--1 inch. The maximum depth of the parabola after the end of the pair of steel bands has reached the stop position should be about 3 inches so that the supporting surface may be comfortable. These figures, which of course can be varied according to the-aim and Wishes of the producer and customer, are determinative of the shape of construction.

The depth of the parabola f, Figure 13, is determined by the value of A and L according to the formula in which the A is that distance measured in the horizontal plane which the upper part of the steel band under load moves inwards while in contact with the beam 2 and L is the length of the intermediate band 4 connecting the steel bands 3, A being chosen between A and /2 inch and L between 10 and 40 inches. Thus at the normal width of a bed at 35 inches, the value of the A equals about /3 inch at a value of about 3 inches of the parabola depth is obtained. The angle v between the extension direction of the band-like member and the horizontal plane at a stress point in the middle of the supporting surface is obtained in each depression position by the formula (1) P=Drsin v and the bending moment of the steel band 2; M="" =D.--a (see Fig. 11

'in which a is the perpendicular distance from that point at which the steel band leaves the curved surface of support 2 to that line denoted at 7', Figure 11, which indicatcs. the direction of force Dr at the point C. Upon sitting on the one side of. the supporting surface the carrying capacity of the steel band at the end or stop position is (3:) W=% (see Fig. 11)

Upon the depression of the steel bands, the -value would first gradually increase with the unchanged length ofthe outerportion of the steel band until the maximum stress reaches the value settled by the relation between radius r and R when the rolling contact with the upper surface of beam 2 begins.

After that the 'y-value is determined by the relations between radius r and. Rand shortening of the steel band by'thedegree of curvature of the rolling contact which can. be calculated for every depression or load. From the abovemoted Formulas 1 and 2, the t-value is obtained which 'givesthe supporting surface the desired capabili- From the Formula 3, one obtains the freelength of the. steel band which furnishes the softness characteri'stic'de'sired. at the side. ofthe mattress. The length (1, Figure 11, of the free end of the steel band, that is that portion between the end thereof and the initial end point of; contact, can be regulated by increasing the radius r and. R in relation to the length of the steel band.

The full line through the point B illustrates the extension ofthe steel band member 3 in an unloaded condition'.

Since the values determined by the above-mentioned calculation, especially W-value, can be modified, one has the possibility of noting the carrying capacity of the steel band during the first part of depression at a selected thickness t of the steel band so as to thereby influence the form of the curve of load.

There 'is another possibility of regulating the softness or resiliency of the supporting surface within narrow limits by turning the supporting beams 2 about their longitudinal axes and thus displacing the line D-E, Figure 11, which is always perpendicular to the horizontal, in a counterclockwise direction so as to, in accordance with the illustration of Figure 11, move the contact point of the'steel band end with the support higher up on the curved surface 16 so that one obtains a smaller a-value for the same A-value and thus resiliency is diminished. By similarly turning in a clockwisedirection, that is moving the band with the curved surface below the line passing through the center. of radius r and R, Figure 11, a larger a-value is obtained which is tantamount to a more resilient'supporting surface. This possibility, however, is limited since it can furnish too large aA-value in relation to'the a-value (depression) desired.

Theinvention thus provides a very simple manner in which to obtain a supporting surface having resilient sides above a relatively rigid bottom frame and further to conform the abilities of the supporting frame to the desires of manufacturer and customer. The springiness is completely soundless and there is no risk of a permanent deformation in the mattress or fatigue in the steel bands under rather abnormal load conditions. person may stand on a single transverse band without breaking or establishing any permanent deformation therein. An important advantage of the present invention is A rather heavy the softly and elastically limiting of the depression which isaccomplished without-any noise: produciugcontact between parts. 'Since the resilient band-like members 1-are attached to the frame independently of one another, re-' placement and exchange of parts arerendered-very easily.

As stated above, upon the load being applied to the band-like members 1,v the supports shall be such as to force the steel bands 3 into rollingengagement therewith without exceeding the elastic limits of the material of these steel bands. However, as the steel bands are exposed to a. certain fatigue strain, 'it issuitable to-dimension the steel bands so that they roll upon the supports'without exceeding the variation in the maximum strain of the steel bands inorder to avoid fatigueat'the depression of the steel bands under load. The risk of fatigue depends in essential on such a variation which is why the construction should be selected so that the maximum 'y-value, namely the maximum allowed deflection strain, is reached when the steel bands are stretched during the assembly and connection thereto of the band ironstraps 4. Consequently this maximum allowed; defiectionstrain' is not changed during usage when the steelbands rollvup on the curved surface 16 but only that portion where the steel band is exposed to strain is moved upwards along the support as the steel band comes into rolling contacttherewith.

It is further to be pointed out. that this invention comprehends an arrangement in. which the side frames 2 are jointed immediate of their length by hinges 'or thelike so that one half of the spring support can be foldedon the other. In other words,. the invention contemplates utility, in: those articles of: furniture 'known' as sofa beds or convertible chairs wherein thespring support including the band-like members v1 and side frames are foldable. Thus the frame can be divided into any number. of parts which are hingedly connected with one another.

While some embodiments ofthe-present inventionhave been set forth herein, it isto beunderstood that modifications can-be employed so long as they do not'depart' from the scope of the appended claims. If desired, one endof each intermediate band 4 can be bolted to one of the steel bands 3 and the opposite end of the intermediate band can be provided with the down-turned end portion 10 and the-tongue 11 and only one of the steel bands 3 provided with the slot 12 and the notch'13.

I give below detail characteristics of a preferred bandlike member 1 in relation to its curved supporting surface adapted for a bedstead with a width of about 35 inches measured from outer side-of left hand beamz to outer side of right hand beam 2.

The steel bands 3 are made of spring steel with arno'dulus of elasticity of E=28,845,000 pounds per square'inch, tensile strength of about 242,000 pounds per square inch and (HO-0.80% C. Hardened in oil at 1760 F.

Whole length of the steel band=4'inches.

Width of the steel band=2% inches.

Thickness of the steel baud=0.0354 inch.

Radius R (see Fig. '1l)=0.807 inch.

The intermediate band 4 is made of'coldqolled band iron, 0.20% C.

Whole length of the intermediate-band=33 inches.

Width of the intermediate band=1 A inches.

Thickness of the intermediate band= 7i inch.

Radius r (see Fig. 11) of the curvature of the supportsurface of the beams=0.63 inch.

Calculation of the v -value ofthe steel bands 3:

y =l75,000 pounds per square in'ch.

Variation of 'y-Value'at the-difierent'points of the steel bands 3duringrollin'gup on the supporting surface of the" beams should not exceed 71,20D-"-85,40'0' poundsper square inch:

The upwardly bent portion 15 (see Figures 7, 8 and 9) extends about 4 inch above the main part of the steel band 3 when the latter is fixed to the intermediate straight member 4 and the spring mattress is unloaded.

What is claimed is:

1. A resilient supporting surface for a spring mattress, upholstered furniture and the like comprising, a frame having opposite sides, a plurality of parallel, mutually spaced and laterally stilf band-like means extending between the sides of the frame and including opposite ends connected thereto, each said band-like means comprising at each end portion a curved spring steel band having an inner end, and between the respective inner ends of each opposed pair of curved spring steel bands and connected thereto an intermediate band of a less high-test material, said intermediate band being non-tensible in its longitudinal direction and straight in unloaded condition, each of the opposite sides of the frames including means providing a rigid upper convex surface extending inwardly and disposed adjacent the curved spring steel bands, the said curved spring steel bands having such strength and elastic capabilities as to withstand the entire spring stress upon application of load to the band-like means, the curved spring steel bands before assembly being pre-set to a curvature of a radii greater than the radii of curvature of the rigid upper convex surfaces of the sides of the frame, the connection between the inner ends of the curved spring steel bands and the intermediate bands being located at a point substantially inwards of the high point of curvature of the respective rigid upper convex surfaces and above the same, the connection between the outer ends of the curved spring steel band and the respective sides of the frame being located in such relation to the different radii of curvatures of the under surfaces of the curved spring steel bands and the upper convex surfaces of the sides of the frame that when assembled and in unloaded condition the under surface of each of the curved spring steel bands starts to recede from the rigid upper convex surfaces of the sides of the frame at a point on said curved upper convex surfaces that is located approximately where the curvature of the convex surfaces of the sides of the frame commences to extend upwardly and inwardly toward the vertical plane through the high point of curvature of the upper surfaces of the sides of the frame, the curvature of the convex surfaces and the curvature of the spring steel bands cooperating so that upon the application of load successive portions of the spring steel bands engage the convex surfaces from the outer portion thereof upwardly and inwardly with rolling contact without exceeding the elastic limit of the material of the curved spring steel bands to decrease the free lengths thereof so that upon deflection under load the ends of the curved spring steel bands at the points of connection with the intermediate bands receive a pro-adjusted movement inwardly so as to shorten the distance between the opposite points of connection with the intermediate bands whereby the latter form a downwardly bent parabolic curve, and said curved spring steel bands being pre-set so that during connection with the intermediate bands they reach approximately the allowed maximum deflection strain to provide the supporting surface with the desired stiffness in unloaded condition and to reduce fatigue-causing variations in strain during usage when the spring steel bands make rolling contact with the underlying convex surfaces thereby permitting a higher maximum strain and lighter weight spring steel bands and with the result that even upon application of an off-center load the rolling contact engagement of the curved spring steel band immediately commences and continues until equilibrium is reached when the pull of the spring steel bands changes its direction and thereby the nature of the rolling engagement is changed and with the lower limit of downward movement of the inner ends of the curved spring steel bands being attained when said inner ends reach a point approximately level with the last point on the respective convex surfaces engaged by the under surface of the spring steel bands during the making of rolling contact with said convex surfaces where the inward movement of the ends of the spring steel bands tends to reverse to outward movement thereby applying a stretching force on the intermediate bands.

2. A resilient supporting surface for a spring mattress, upholstered furniture and the like comprising, a frame having opposite sides, a plurality of parallel, mutually spaced and laterally stiff band-like means extending between the sides of the frame and including opposite ends connected thereto, each said band-like means comprising at each end portion a curved spring steel band having an inner end, and between the respective inner ends of each opposed pair of curved spring steel bands and connected thereto an intermediate band of a less high-test material, said intermediate band being non-tensible in its longitudinal direction and straight in unloaded condition, the opposite sides of the frames including means providing upper rigid convex surfaces extending inwardly and disposed subjacent the curved spring steel bands, the said curved spring steel bands having such strength and elastic capabilities as to withstand the entire spring stress upon application of load to the band-like means, the connection between the inner ends of the curved spring steel bands and the intermediate bands being located at a point substantially inwards of the high point of curvature of the respective rigid upper convex surfaces and above the same, the connection between the outer ends of the curved spring steel bands and the respective sides of the frame being located in such relation to the different radii of curvatures of the under surfaces of the curved spring steel bands and the upper convex surfaces of the sides of the frame that when assembled and in unloaded condition the under surface of each of the curved spring steel bands starts to recede from the rigid upper convex surfaces of the sides of the frame at a point on said curved convex surfaces that is located approximately where the curvature of the convex surfaces of the sides of the frame commences to extend upwardly and inwardly toward the vertical plane through the high point of curvature of the upper surfaces of the sides of the frame, the curvature of the convex surfaces and the curvature of the spring steel bands being different and cooperating so that upon application of load successive portions of the spring steel bands engage the convex curved surfaces from the outer portion thereof upwardly and inwardly without exceeding the elastic limit of the material of the curved spring steel bands and to decrease the free lengths so that upon deflection under load the ends of the curved spring steel bands at the points of connection with the intermediate bands receive a pre-adjusted movement inwardly so as to shorten the distance between the opposite points of connection with the intermediate bands whereby the latter form a downwardly bent parabolic curve, said curved spring steel bands in the vicinity of the points of connection with the intermediate bands having a convexly upwardly bent portion capable of being resiliently straightened at the tensioning of the spring steel bands under load and of returning to the original convexly upwardly bent form at release of the load.

3. A supporting surface as claimed in claim 2, in which end portions of the convexly upwardly bent portions of said spring steel bands remote from the points of connection with the intermediate bands are capable of being brought into engagement with the supporting surfaces under a heavy load.

4. A resilient supporting surface for a spring mattress, upholstered furniture and the like comprising, a frame having opposite sides, a plurality of parallel, mutually spaced and laterally stiff band-like means extending between the sides of the frame and including opposite ends connected thereto, each said band-like means comprising at each end portion a curved spring steel band having an inner end, and between the respective inner ends of opposed pairs of curved spring steel bands and connected thereto I1 an intermediate hand of a. lessflhigh-test -material,.:saidintermediate band being non-tensible in its. longitudinal direction and-straightiin'unloaded'condition, the opposite sides of the frames including means-providing upper convex surfaces extending inwardly and disposed subjacent the curved spring steel bands, the said curved spring steel bands having suchstrength and elastic capabilities'as to withstand the entiresprin'g stress upon application of load to the band-like means, the curvature of the'convex surfaces and the'curvature of the spring steel bands cooperating so that upon application of load successive portions of the spring steel bands engage. the curved surfaces from the outer portion thereof upwardly and inwardly without exceeding the elastic limit of the material of'the. curved springsteel bands'and-to decrease the free lengths so that upondefiection under load the'ends of the curved spring steel bands at the points oficonnection with the intermediatelbands receive a pre-adjustedmovement inwardly so as to shorten the distance between the oppositepoints of connection with the intermediate bands whereby the latter form a downwardlybentparabolic curve, at least the curved spring steel bands connected to one of the side frames having a transversely extending slot at the inner ends thereof, the adjacent end of each intermediate band having a downwardly-bent endpassed through the slot and bent back toward the opposite side of the frame and tongue means embodied with said intermediate band bent forwardly andunderlying the aforementioned bent end.

5. A supporting'surface as claimed in claim 4,.in which the tongue means are integralwith the intermediate bands and pressed out of a portion thereof rearwardly adjacent the downwardly-bent ends.-

6. A. resilient supporting, surface. for. a spring mattress, upholstered furniture and the like comprising, a frame having; opposite sides, a plurality of iparallel, mutuallyspaced and laterally stiff band-like means extending betweenthe sides of the frame and including opposite ends connected thereto, each said band-like means comprising at each end portiona curved spring steel band; having an inner-end, and

between the respective inner ends ofopposed pairs of curved spring steel bands and connected thereto an intermediate metal band, said intermediate bandbeing non- 1 2 tensible in? its longitudinal direction and straight in. unloaded. condition, the opposite sides of the'frames including means providing upper convex-surfaces extending inwardly and disposed subjacent the curved-springsteel bands, the said curved spring steel bands havingsuch strength and elastic capabilities as' to withstand'the entire spring stress upon application of load to the band-like means, the curvature of the convex surfaces and the curvature of'the spring steel bands cooperating so that upon application of load successive portions of the spring steel bands engage the curved surfaces from the outer portion thereof upwardly and inwardly without exceeding the elastic limit of the material of the curved spring steel bands and to decrease the free lengths so that upon deflection under load-the. ends of the curved spring steel bands at the points of connection with the intermediate bands receive a preadjusted movementinwardly so as to shorten the distance between the opposite points of connection with the intermediate bands whereby the latter form a downwardly bent References Cited'in the file of this patent UNITED STATES PATENTS 26,235 'Scott Nov. 22, 1859 155,530 Lord et a1. Sept. 29, 1874 2,667,916 Burd Feb. 2, 1954 FOREIGN PATENTS 53,631 Austria May 25, 1912 102,728 Great Britain Dec. 11, 1916 102,905 Germany May 3, 1899 308,973 Germany Nov. 7, 1918' 350,061 France Aug. 30, 1905

Images