Abstract: A seat assembly configured to be employed in vehicle seats such as aircraft passenger seats. The seat assembly includes a seat frame having first and second spaced frame members and first and second spaced transverse beams. A plurality of springs positioned proximate an aft end of the seat frame generally above the second transverse beam span between the first and second frame members. A support member is attached to the plurality of springs and to a seat back attachable to the seat frame. A cushion assembly mounts on the seat frame such that the aft end rests on the plurality of springs while the forward end rests on the front transverse beam. In use, as the aft end of the cushion assembly deflects downward toward the second transverse beam the forward end simultaneously rotates around the first transverse beam.

Abstract: A mattress comprises an upper surface and a lower surface opposite the upper surface. The mattress further includes first and second opposing side surfaces extending between the upper surface and the lower surface and third and fourth opposing side surfaces extending between the upper surface and the lower surface and between the first and second opposing side surfaces. A core section is formed by the upper and lower surfaces and first and second opposing core section side surfaces and third and fourth opposing core section side surfaces and an extension extends outwardly from a side surface of the core section. The extension is fixedly connected to or integral with the core section and the extension provides the upper surface with a greater area than the lower surface. The extension is capable of supporting a user without a support structure being positioned below the extension.

Abstract: A bedding foundation having a nestably stackable spring assembly, including a border wire. The foundation's spring assembly may be nestably stacked with numerous other such assemblies for transportation, thereby avoiding the need to compress and tie the assembly for shipping. Each spring assembly includes support wires having alternating peaks and valleys along with stabilizer wires having alternating peaks and valleys. The valleys of the stabilizer wires are secured to the valleys of the support wires. The peaks of the stabilizer wires are secured to longitudinal wires extending parallel the sides of the border wire.

Abstract: A spring wire support for foundations and innerspring mattresses, and a variable spring surface deck for a foundation and variable spring surface for a mattress. The spring wire support comprises an elongated spring element enveloped in a pliant carrier, with the carrier including an attachment margin. The variable spring surface deck for a foundation comprises a plurality of the spring wire supports secured as desired to an upper surface of a foundation. The variable spring surface for a mattress comprises a plurality of the spring wire supports located between top and adjacent convolutions of rows or columns of springs of the mattress.

Abstract: A bedding foundation has a wire core which may be nestably stacked with numerous other such assemblies for transportation, thereby avoiding the need to compress and tie multiple assemblies for shipping. The wire core which includes an upper wire grid made of four distinct border wires and support wires extending between two opposing border wires. Each support wire has flattened valleys below the plane of the upper wire grid, each flattened valley being adapted to be secured to a wooden base frame. The wire cores, wooden bases and corner guards may be shipped separately.

Abstract: A bedding foundation having a nestably stackable spring assembly including a border wire having a generally rectangular cross-section. The foundation's spring assembly may be nestably stacked with numerous other such assemblies for transportation, thereby avoiding the need to compress and tie the assembly for shipping. Each foundation assembly includes a number of corrugated support wires having alternating peaks and valleys. The border wire is generally rectangular in cross-section to reduce wire costs without compromising beam strength of the border wire.

Abstract: A bedding foundation having a nestably stackable spring assembly, including a border wire having a generally rectangular cross-section. The foundation's spring assembly may be nestably stacked with numerous other such assemblies for transportation, thereby avoiding the need to compress and tie the assembly for shipping. Each foundation assembly includes a number of corrugated support wires having alternating peaks and valleys. The border wire is generally rectangular in cross-section to reduce wire costs without compromising beam strength of the border wire.

Abstract: A stackable wire core assembly for a bedding foundation which may be nestably stacked with numerous other such assemblies for transportation, thereby avoiding the need to compress and tie the assembly for shipping. The wire core assembly includes an upper wire grid, including a border wire and support wires extending between the ends of the border wire. Each support wire has resilient portions extending downwardly from the plane of the upper wire grid, each resilient portion having a flat bottom adapted to be secured to a wooden base frame and curved arms extending upwardly from opposed ends of the flat bottom.

Abstract: A stackable wire core assembly for a bedding foundation which may be nestably stacked with numerous other such assemblies for transportation, thereby avoiding the need to compress and tie the assembly for shipping. The wire core assembly includes an upper wire grid including a border wire and support wires extending between the ends of the border wire. Each support wire has resilient portions extending downwardly from the plane of the upper wire grid, each resilient portion having a flat bottom adapted to be secured to a wooden base frame and curved arms extending upwardly from opposed ends of the flat bottom.

Abstract: A stackable wire core assembly for a bedding foundation which may be nestably stacked with numerous other such assemblies for transportation, thereby avoiding the need to compress and tie the assembly for shipping. The wire core assembly includes an upper wire grid including a border wire and support wires extending between the ends of the border wire. Each support wire has resilient portions extending downwardly from the plane of the upper wire grid, each resilient portion having a flat bottom adapted to be secured to a wooden base frame and curved arms extending upwardly from opposed ends of the flat bottom.

Abstract: A hook-ended steel wire netting includes a first cross rail having a row of first sockets on its outer portion in a line along an axial direction; a second cross rail having a row of second sockets on its outer portion in a line along an axial direction; one or more longitudinal steel wires, both ends of which are hooks, a first end hook of each steel wire encloses a part of the outer portion of one of the cross rails and is secured by being inserted into one of the first sockets, and a second end hook of each steel wire encloses a part of the outer portion of one of the cross rails and is secured by being inserted into one of the second sockets.

Abstract: A mattress is provided comprising a plurality of inner coil springs and an edge support. The edge support comprises a foam border extending along the outer perimeter of the mattress and around the inner coil springs, a plurality of spaced slits inserted into the foam border, and a plurality of edge springs inserted into the plurality of spaced slits.

Abstract: A mattress spring structure (10) is provided with a strengthened central area (C) thereon to provide greater support for a user's body lumbar region when received thereon. The support is provided with a strengthening structure (30) having a continuous frame member (54) and a strengthening pattern (53). The continuous frame (54) encircles coil springs (12) over a major expanse of the mattress's central area (C); this frame is connected to mattress coils along the frames longitudinal (34, 36) and traverse (38, 40) segments. The strengthening pattern (53) has two metal bars (51, 52) arranged inside and connected to the continuous frame member (54). The strengthening pattern (53) may be connected to the spring coils (12) and contain additional metal straps (56, 59).

Abstract: A mattress spring structure (10) is provided with a strengthened central area (C) thereon to provide greater support for a user's body lumbar region when received thereon. The support is provided with a strengthening structure (30) having a continuous frame member (54) and a strengthening pattern (53). The continuous frame (54) encircles coil springs (12) over a major expanse of the mattress's central area (C); this frame is connected to mattress coils along the frames longitudinal (34, 36) and traverse (38, 40) segments. The strengthening pattern (53) has two metal bars (51, 52) arranged inside and connected to the continuous frame member (54). The strengthening pattern (53) may be connected to the spring coils (12) and contain additional metal straps (56, 59).

Abstract: A mattress having a border rod assembly and at least one central spring core. The border rod assembly having individual border rods and corner pieces fitting together to create a contiguous border around and attached to the central spring core. A resilient, polymer material is used for at least one of the individual border rods. Border rod assemblies serve a dual purpose in mattress construction, acting both as a frame to which fabrics and foams may be attached and as a support structure for the central spring core, eliminating unsightly sagging and bowing at the mattress edge. Using resilient materials for the border rods allows the mattress to be used interchangeably with adjustable and non-adjustable foundations, while retaining the rigidity and desirable structural aspects of standard steel border rod mattresses.

Abstract: A nestably stackable assembly for use in a bedding foundation. The assembly has a rectangular border wire with parallel sides and ends. Transversely spaced, parallel and longitudinally extending support wires are connected at their ends to the border wire ends. The support wires are formed so as to be generally corrugated along their lengths with peaks and valleys. The peaks are flattened at their tops, and the flattened tops are generally coplanar with a plane defined by the border wire. The valleys are vertically displaced beneath and intermediate of the flattened tops. Longitudinally spaced and transversely extending, upper connector wires are connected to the sides of border wires, and the upper connector wires are connected along their lengths to the flattened tops of the peaks of the support wires. The valleys have flattened bottoms, and adjacent pairs of the flattened bottoms of the valley are interconnected by resilient connectors.

Abstract: A bedding or seating product comprising a centrally located spring core, edge support means located around the perimeter of the spring core, filling material located above and below the spring core and an upholstered covering. The edge support may be either a string of springs, a pair of spiral edge supports or plastic edge reinforcements. The edge support means extends above and below the upper and lower surfaces of the spring core thus creating a higher peripheral edge than the central portion of the spring core. Layers of filling material are inserted over the central portion of the spring core in order to create a uniform upper and lower surface.

Abstract: A body support moveable between unfolded and folded positions comprises: serially interconnected body, cavity and seat sections defined by respective upper and lower grids and including resilient members. The body, cavity and seat sections have their upper and lower grids positioned to be substantially coplanar in the unfolded position, and the seat section overlies the body section in the folded position. The resilient members of the seat section are generally planar and are arranged in a plurality of transverse rows. The resilient members are pivotally attached to the seat section upper and lower grids such that, in the unfolded position, the resilient members of the seat section are erect and extend substantially normal to the seat section upper and lower grids, and in the folded position, the resilient members of the seat section pivot relative to the seat section upper and lower grids to bring the seat section upper and lower grids adjacent each other.

Abstract: Improved spring elements have a unique energy absorbing element that responds to applied loads to produce counter-acting forces that act to absorb the energy of the applied loading. The greater the magnitude of the applied loads, the more the counter-acting forces equilibrate, which enables the spring elements of the invention to accommodate a range of loading force magnitudes. The improved spring elements of the invention may be integrally formed of plastic, and are suitable for use in a variety of different articles of manufacture. Exemplary single- and double-configuration mattress spring, box spring and edge stiffener embodiments are disclosed.

Abstract: An inner spring core comprising a plurality of coil springs arranged in rows and columns having an improved border firmness adjuster around the periphery of the core. The improved border firmness adjuster comprises one of more inflatable pneumatic members positioned inwardly of the outer edges of the outermost coil springs in a space between two adjacent convolutions of each of the outermost coil springs. The pneumatic member or members is capable of variably adjusting the firmness of at least one edge of the mattress.

Abstract: A double structure spring mattress with hard spring mattress effect as well as soft spring mattress effect, one side of which mattress is backed by hard springs but the other side of which mattress is backed by soft springs coupled to the hard springs, is disclosed. The double structure spring mattress may be provided with a reinforcing spring for reinforcing the top and bottom edges of the mattress, which reinforcing spring is repeatedly coiled with regular intervals and formed into a zigzag shape having a plurality of coiled portions and fixed to top and bottom guide wires extending in the top and bottom edges of the mattress at the coiled portions using fixing rings. The spring mattress commonly meets taste of peoples preferred to use the hard spring mattress and taste of peoples preferred to use the soft spring mattress.

Abstract: A mattress spring clip to secure the wire of a border wire assembly to coils of adjacent coil springs in an innerspring assembly for a mattress, wherein the clip comprises a unitary length of spring bias material, such as metal having a relatively broad width, and curved to form a pair of reverse loops, each having entrances which are narrower than their respective loop pockets whereby the entrances have to spread apart for the wire of a border wire assembly to pass into one of the loop pockets and for the coil of an adjacent coil spring to pass into the other loop pocket. The entrances then snap back to their original spring biased positions to hold the wire and coil in their respective pockets.

Abstract: A modular innerspring and box spring assembly which can be put together by the end use customer from innerspring and box spring modules. An innerspring module consists of a plurality of coil springs joined together by helical wire fasteners in a generally rectangular configuration having dimensions which when assembled with other like modules in side-by-side and end-to-end relationship make up a completed modular innerspring assembly of the size and shape needed to make a twin, twin extra long, full, full extra long, queen and king size mattress. A top boundary wire assembly extends around the top peripheral edge of the completed modular innerspring assembly and a bottom boundary wire assembly extends around the bottom peripheral edge, in each case secured to adjacent coil springs by a double hook clip.

Abstract: A perimeter support spring for use in a mattress or furniture spring assembly having an array of coil springs connected with spaced parallel border wires along the perimeter of the spring array is connected between the border wires to provide supplementary support to the mattress perimeter. The support spring comprises a torsion spring member having an intermediate torsion coil, a pair of spring arms diverging from the torsion coil, and a pair of molded plastic mounting clips attached to the terminal ends of the spring arms.

Abstract: An improved spring is provided which may be used in cushions, mattresses, or box springs which includes a limiting internal member. This limiting member assist in limiting the longitudinal deflection of the springs. Also provided are snapped-fitting connections between the spring and a grid for use within a box spring. Also provided is a "floating" portion of a peripheral border wire, particularly suitable for use in a pair of box springs beneath a king-size mattress unit. Also provided is a corner guard which provided support for upholstered fabric on a box spring. Finally, an improved borderwireless mattress using a peripheral band is provided, which allows the mattress to bend more easily, without disadvantageous setting of its border wires.

Abstract: In order to provide a springing effect in correspondence with the edge of a belt frame in chairs, sofas or the like, a device is envisaged consisting of a plurality of arms, each fixed to a belt and extending from the latter in inclined position, as well as a common transverse element connecting all the arms. Due to stresses on the latter element, the arms deform the belts which cause a bending moment of elastic return.

Abstract: A bedding foundation unit having a top planar portion defined by two pluralities of spaced parallel grid wires, and a rigid frame spaced apart from the top planar portion by a plurality of modular springs. The modular springs are connected to the top planar portion in a snap-fit manner, each snap-fit end of each modular spring being held in place by three grid wires above and one grid wire below the snap-fit end.

Abstract: Disclosed herein is an automotive seat which includes a seat frame and a plurality of S-springs which are spanned between spaced two portions of the seat frame. Each spring has one U-shaped end portion. In order to tightly and unmovably connect the U-shaped end portion of each spring to selected one of the side portions of the frame, an improved spring holding structure is formed on the selected portion of the frame, which includes a tunnel portion which is integrally formed on the selected portion and two raised portions which are integrally formed on the same selected portion in a manner to put therebetween the tunnel portion. The distance between the two raised portions is substantially equal to the longitudinal length of the U-shaped end portion of the spring. The U-shaped end portion of the spring is received in the tunnel portion having its longitudinal ends respectively contacting with the two raised portions.

Abstract: A bedding mattress spring assembly comprising rows of coil springs laced together by helical lacing wires and having border wires secured around the periphery of the assembly in the top and bottom planes of the assembly. The border wires are secured to the edgemost coil springs by sheet metal clips. Extending between the border wires are edge support springs which are secured to the border wires by U-shaped channels formed in the ends of the edge support springs.

Abstract: A spring interior comprising a plurality of longitudinally extending bands of springs disposed side by side and connected together by helical lacing wires in the top and bottom faces of the bands. Each band of springs comprises a single length of wire formed into a plurality of substantially vertical coils of springs interconnected by interconnecting segments of wire located alternately in the top and bottom faces of the bands. Each interconnecting segment comprises a longitudinally extending bridging portion, a pair of transversely extending end portions, and a transversely extending support structure. The corners defined by the intersections between the bridging portions and the end portions of the interconnecting segments are radiused by radii of differing dimension so as to colinearly align the bridging portions of each band of springs.

Abstract: A limited deflection spring for use in a box spring assembly has a unitary wire body having a foot portion, an upright yieldable portion on the foot portion and a loading bearing portion at the upper end of the upright portion. The upright yieldable portion includes a pair of horizontally spaced upright columns which diverge relative to each other. Each of the upright columns is suspended between the load bearing portion and the foot portion by separate upper and lower torsion bar systems. Each of the torsion bar system includes a pair of generally horizontal torsion bars connected together by a central connecting bar. Suspension of the upright columns between separate torsion bar systems enhances lateral stability and impact load withstand capability of the spring elements. Spring elements having upwardly diverging upright columns may be mixed with elements having downwardly diverging upright columns in a box spring assembly so as to produce an optimum desired loading response in the assembly.

Abstract: A bent wire spring module embodying a clamp element at the upper end interengageable with the cross wire of a grid frame without requiring the formation of deviations in the cross wire to which it is attached.

Abstract: A foundation unit having a top bearing grid structure secured to a bottom substructure by intermediate support elements. The grid structure comprises a series of spaced longitudinal and transverse spring elements, each spring element being formed to permit elastic elongation thereof. Elastic elongation is accomplished by a series of V-shaped segments in each of the spring elements, the segments being located at the intersections of the spring elements and being joined by a clip. The support elements comprise wire elements which are L-shaped and which are composed of two planar portions connected at right angles to one another. The wire elements are located in transverse rows with the orientation of the wire elements in each row being opposite to the orientation of the wire elements in the adjacent row so that loads applied to the foundation unit are balanced.

Abstract: A box spring assembly consisting of a generally horizontal frame and a generally horizontal wire grid disposed a predetermined distance above the frame, and a plurality of grid support springs arranged between and secured to the grid and the frame so as to yieldably support the grid on the frame. Auxiliary grid crosswires formed of spring wire are incorporated in the grid to strengthen the grid and distribute bedding loads between the support springs.

Abstract: A box spring assembly includes a base frame, a top wire grid and a plurality of sinuous wire springs interconnecting the top wire grid and the base frame. The sinuous wire springs each comprise a sinuous wire strip formed into an inverted U-shaped configuration with the closed end of each U-shaped spring attached to the top wire grid and the free ends at the top of the U-shaped spring attached to the base frame.

Abstract: A bent wire soring unit for disposition between a base frame and grid frame disposed in spaced, parallel relation to each other includes a lower attaching element for attachment to the base frame and an upper attaching element for attachment to the grid frame. The lower and upper attaching elements are disposed in spaced, parallel planes and transversely-spaced, substantially perpendicular supports connect the lower and upper attaching elements such as to permit the upper and lower attaching elements to move relative to each other in response to pressure applied perpendicularly to the upper attaching elements.

Abstract: A plurality of main springs and a plurality of intermediate support springs are disposed and fixed on a rectangular base plate. Each main spring has a linear connecting rod portion and two coil spring portions such that one end of each of the two coil spring portions is coupled to a corresponding one of two ends of the first linear connecting rod portion. The main springs are disposed such that these connecting rod portions are perpendicular to each other in a matrix form. The other end of each of the coil springs is fastened to the base plate. Each intermediate support spring has a connecting rod portion and two coil spring portions. The connecting rod portion of each intermediate support spring is shorter than that of each main spring. One end of each of the coil spring portions of the intermediate support spring is coupled to a corresponding one of two ends of the connecting rod portion of the intermediate support spring.

Abstract: A furniture seat base which employs a series of front and/or back torsioned sinuous spring bands. Predetermined patterns of torsioned bands produce an interaction which generate spring dynamics designed to produce a seat unit which may be sat upon from the front, back, sides, or corners with excellent comfort characteristics. The bands are selectively supported adjacent the rails to obviate objectionable "lean-out.

Abstract: An innerspring assembly for furniture seats and backs comprising spaced, parallel, substantially rectangular top and bottom grids and tapered helical coils interposed between the grids and secured thereto, the top grid comprising pairs of spaced, parallel anchoring wires which define longitudinally and transversely-spaced seats for receiving the top loops of the coils and the bottom grid comprising anchoring crossing wires which intersect and define seats vertically below the centers of the seats of the top grid for receiving the bottom loops and wherein diametrically-opposed portions of the top and bottom loops overlie the wires of the seats and diametrically-opposed portions of the top and bottom loops at right angles thereto underlie the wires of the seats.

Abstract: An inner spring assembly embodying a generally channel-shaped border wire of the type which is provided with a continuous groove with straight sides and into which the end convolutions of the helical bedsprings of the assembly project in tangential fashion and about which the border wire is crimped to form a loose self-aligning non-rigid interconnection between springs and border wire. The border wire is formed from solid rod-like wire stock by a cold rolling operation in a shaping mill thereby obviating the necessity of resorting to machining and heat treating and eliminating waste material that is a consequence of machining. The rolling operation includes a reshaping of the solid cylindrical stock to a grooved border wire that offers a greater bending strength than like diameter solid border wire of the like weight per unit length.

Abstract: An auxiliary panel (12) for a bedding unit (10) is disclosed as including a peripheral wire (24) on the load supporting surface of the unit and a plurality of torsion bar springs (30 or 42) extending between opposite portions of the peripheral wire so as to resiliently provide increased firmness. Distal end torsion bars of each torsion bar spring are connected to the peripheral wire to provide the cooperation therebetween during use. Different embodiments of the panel incorporate sinuous wire type springs (30) and formed wire type springs (42) extending both longitudinally between opposite longitudinal portions (26) of the peripheral wire as well as laterally between opposite lateral portions (28) of the peripheral wire.

Abstract: An improved self-releasing locking unit, such as a self-releasing locking edge support, in an inner spring assembly wherein the locking unit can be employed to secure the inner spring assembly in a compressed condition during the covering of same, and which will release the inner spring assembly from the compressed condition after the covering procedure has been completed. The self-releasing locking unit comprises a hook connected to the peripheral lower frame of the inner spring assembly and a hook receiver connected to an upper portion of the inner spring assembly. The hook is biased in a first position near the lower frame and is movable to a second position wherein the hook is disposed substantially normal to the plane of the lower frame and is adapted to engage the hook when the lower and upper frames of the inner spring assembly are in a compressed condition.

Abstract: A box spring assembly which includes a generally rectangular frame, a plurality of wire springs mounted on the frame and connected to each other so as to yieldably resist downwardly directed bedding loads. Each of the springs has an elongated body portion arranged above the frame and downwardly extending end portions, each of the end portions having an upper section and a lower section which are located in planes that are upright and generally perpendicular to each other with each of the sections being comprised of integral legs arranged in a generally V-formation rotated about ninety degrees and with the included angle between the legs being less than ninety degrees. This construction enables the spring end portions to yieldably resist bedding loads with both bending and torsional stresses thereby enabling increased load-resisting capabilities in the spring end portions with a resulting efficient use of spring wire material.

Abstract: A box spring assembly with end rail spring mounting units consisting of a frame having wood side and end rails, metal cross rails, and metal end rail mounting units secured to the end rails. The mounting units locate and support some of the springs in the assembly.

Abstract: A tubular border frame for inner spring assemblies is disclosed. The border frame includes an opening defined by a pair of inwardly directed lips adapted to receive and secure the coil springs. Straight and corner connectors are provided for joining the sections of the frame to form a complete border surrounding the springs.

Abstract: The typical helical springs used to support the bed within the frame of a trampoline or the like are modified to incorporate adjustable hooks threadedly anchored within the springs at one end so that their overall length, and thus the tension on the bed, can be varied and overstretching accommodated. Two principal versions are disclosed, the more preferred one including an additional inner spring biasing the adjustable hook to a retracted position.

Abstract: A seat frame wherein erect walls constituting the peripheral wall of the seat frame are bent to form columnar reinforcement ribs, and flange portions being the upper end faces of the reinforcement ribs are formed with mounting parts for a spring base, so that even when the peripheral wall of the seat frame is subjected to an intense tensile load inwards, it is prevented from turning inwardly to be deformed or damaged.

Abstract: An improved foundation unit for a mattress or the like is provided which is firmer in the center than conventional torsion spring-type foundation units while having sufficient flexibility under normal loads and weight distribution to comfortably support a body upon an overlying mattress. The foundation unit includes a resilient border which protects the edge of an overlying mattress from damage when subject to extraordinary weight concentration and a center region formed of a plurality of cross rails cushioned at least about their upper surfaces which immediately underlie the upper surface of the unit. The cushioning elements may be thick foam housings that cover at least the upper surface of the cross rails or sinuous wire springs that extend along the length of the cross rails. The cross rails themselves preferably have a limited degree of flexibility so as to better withstand high impact loads.

Abstract: A spring foundation unit having one or more pairs of inner border members on the top and bottom surfaces of the unit. In a conventional fashion, the spring unit has a plurality of transverse rows and longitudinal columns of coil springs, and top and bottom perimeter border wires extending along the outer periphery of the unit and attached to outer coil springs of the transverse rows and longitudinal columns. The inner border members have side elements extending parallel to opposed sides of the unit, with one or more spring widths separating the side elements from the perimeter of the unit. Each side element has a free end which is attached to an end section of the perimeter border wire, and a cross-connecting element interconnecting the opposite ends of the opposed side elements of each inner border member. In one embodiment of the invention, the cross-connecting elements of each pair of inner border members are straight and have at least one spring width separating them.

Abstract: A reinforcing structure for the corners of innerspring assemblies comprising spaced parallel parts disposed diagonally across the top and bottom sides of the innerspring assembly, spring members at the opposite ends of the spaced parallel parts disposed between the top and bottom sides which yieldably resist displacement of the top and bottom sides relative to each other and clips fixing the structures to the top and bottom sides of the assembly. The spring members are torsion springs comprising a coil and angularly disposed arms and these are disposed with the arms situated in the planes of the sides and ends of the assembly. Optionally, the top and bottom parts are longitudinallly adjusted to vary the distance between the spring members.