REINFORCED POCKET SPRING MATTRESS
A pocket spring mattress ( 1 ) comprising a plurality of double layer spring units ( 7 ) arranged in rows and columns to form a rectangular shaped mattress is provided. Each double layer spring unit ( 7 ) comprises a first pocket spring unit ( 2 a ) arranged axially onto a second pocket spring unit ( 2 b ), and each spring unit ( 2 a, 2 b) comprises a number of springs ( 3 a - b , 4 a - b ) and a fabric pocket ( 6′ ) enclosing the springs ( 3 a-b, 4 a-b). The springs ( 3 a - b , 4 a - b ) comprises reference springs ( 3 a - b ) having a first spring constant and frame springs ( 4 a - b ) having a second spring constant being greater than the first spring constant, and frame springs ( 4 a - b ) are arranged in at least one of the first and second pocket spring units ( 2 a, 2 b ) of at least one outermost row or column of the double layered spring units ( 7 ) in a configuration such that the edge of the mattress ( 1 ) is reinforced.
1 . A pocket spring mattress comprising a plurality of double layer spring units arranged in rows and columns to form a rectangular shaped mattress, each double layer spring unit comprising a first pocket spring unit arranged axially onto a second pocket spring unit ( 2 b ), and wherein each spring unit comprises a number of springs and a fabric pocket enclosing the springs, said springs comprising reference springs having a first spring constant and frame springs having a second spring constant being greater than the first spring constant, and wherein frame springs are arranged in at least one of the first and second pocket spring units of at least one outermost row or column of the double layered spring units in a configuration such that the edge of the mattress is reinforced.
2 . The pocket spring mattress according to claim 1 , wherein a series of adjacent double layer spring units are attached to each other to form an elongated spring string.
3 . The pocket spring mattress according to claim 2 , wherein each spring string is arranged side by side with another spring string forming an upper spring layer formed by the first pocket spring units, and a lower spring layer) formed by the second pocket spring units.
4 . The pocket spring mattress according to claim 1 , wherein frame springs are arranged in at least one of the first and second pocket spring units of at least two adjacent outermost rows or columns of the double layered spring units.
5 . The pocket spring mattress according to claim 1 , wherein frame springs are arranged only in the first pocket spring units of two adjacent outermost rows and columns of the double layered spring units, forming a reinforced edge around the circumference of the mattress.
6 . The pocket spring mattress according to any one of claim 1 , wherein frame springs are arranged only in the second pocket spring units of two adjacent outermost rows and columns of the double layered spring units, forming a reinforced edge around the circumference of the mattress.
7 . The pocket spring mattress according to claim 1 , wherein frame springs are arranged in the first and second pocket spring units of two adjacent outermost rows and columns of the double layered spring units, forming a reinforced edge around the circumference of the mattress.
8 . The pocket spring mattress according to any one of the preceding claim 1 , wherein the second spring constant of the frame springs is at least 15%, and preferably at least 30% higher than the first spring constant of the reference springs.
9 . The pocket spring mattress according to claim 1 , wherein a material of the fabric pocket is a nonwoven fabric material comprising thermoplastic material.
10 . The pocket spring mattress according to claim 2 , wherein each spring string comprises between 14 and 16 double layer spring units per meter of spring string, preferably 15 double layered spring units per meter of spring string and wherein each spring string is attached by means of an adhesive, preferably hot melt adhesive, side by side to another spring string.
11 . A method for manufacturing a plurality of double layer spring units arranged in a spring string configured to form a mattress according to claim 1 , wherein the method comprises the steps of:
determining if a reference wire or a frame wire is to be used to form upper spring of the first pocket spring units and if a reference wire or a frame wire is to be used to form lower spring of the second pocket spring units,
feeding the determined upper wire and the determined lower wire,
heating the determined wires,
bending the determined upper wire and the determined lower wire,
cutting each wire to form an upper spring and a lower spring,
placing each spring in a fabric pocket ( 5 ), and
sealing the pockets by means of welding forming a double layer spring unit.
12 . The method according to claim 11 , further comprising arranging the upper spring and the lower spring in a common pocket, and sealing the pocket around the springs and between the upper spring and the lower spring thereby forming one pocket for the upper layer and one pocket for the lower layer, thus forming two pocket spring units together forming the double layer spring unit.
13 . The ethod according to claim 11 , wherein the fabric material is cut to form a spring string after a predetermined number of double layered spring units are formed.
14 . The method according to claim 13 , further comprising attaching each spring string by means of an adhesive, preferably hot melt adhesive, or by ultra-sonic welding, side by side to another spring string.
15 . The method according to claim 12 , further comprising sealing the pockets by means of ultra-sonic welding.