Gymnastics balance beam comprising a multilayer composite
A gymnastics balance beam includes a rigid elongate member of specific cross-section covered with a covering, the elongate member of specific cross-section including a planar upper surface on which is provided an elastic multilayer composite including at least two layers, namely an upper layer, and a lower layer in contact with the planar surface of the elongate member of specific cross-section. The upper layer is a layer of rubbery material and the lower layer is a layer of an elastic material of stiffness less than the stiffness of the rubbery material of the upper layer. Such a balance beam limits the risks of injury by reducing impact forces, while maintaining bearing security for gymnasts.
1. A gymnastics balance beam comprising a rigid elongate member ( 5 ) of specific cross-section covered with a cover ( 4 ), the rigid elongate member ( 5 ) of specific cross-section comprising a planar upper surface ( 51 ) on which is provided an elastic multilayer composite ( 6 ),
wherein the elastic multilayer composite ( 6 ) comprises:
an upper layer ( 61 ); and
a lower layer ( 62 ) in contact with the planar upper surface ( 51 ) of the rigid elongate member ( 5 ) of specific cross-section;
wherein the upper layer ( 61 ) is a layer of rubbery material and the lower layer ( 62 ) is a layer of an elastic material of a stiffness less than a stiffness of said rubbery material of the upper layer ( 62 ), and
wherein the upper layer ( 61 ) comprises a binder and either rubber fibers or rubber beads.
2. The gymnastics balance beam according to claim 1 , wherein the upper layer ( 61 ) is bonded to the lower layer ( 62 ).
3. The gymnastics balance beam according to claim 2 , wherein the upper layer ( 61 ) has a stress-strain characteristic in compression comprised between 0.20 and 0.40 N/mm 2 at 25% compression.
4. The gymnastics balance beam according to claim 2 , wherein the lower layer ( 62 ) comprises polyurethane foam.
5. The gymnastics balance beam according to claim 2 , wherein the lower layer ( 62 ) has a mass per unit volume comprised between 250 and 450 kg per cubic meter.
6. The gymnastics balance beam according to claim 1 , wherein the binder comprises polyurethane.
7. The gymnastics balance beam according to claim 6 , wherein the upper layer ( 61 ) has a stress-strain characteristic in compression comprised between 0.20 and 0.40 N/mm 2 at 25% compression.
8. The gymnastics balance beam according to claim 6 , wherein the lower layer ( 62 ) comprises polyurethane foam.
9. The gymnastics balance beam according to claim 1 , wherein the upper layer ( 61 ) has a stress-strain characteristic in compression being 0.30 N/mm 2 at 25% compression.
10. The gymnastics balance beam according to claim 1 , wherein the lower layer ( 62 ) has a mass per unit volume of 350 kg per cubic meter.
11. The gymnastics balance beam according to claim 1 , wherein the upper layer ( 61 ) has a stress-strain characteristic in compression comprised between 0.20 and 0.40 N/mm 2 at 25% compression.
12. The gymnastics balance beam according to claim 11 , wherein the lower layer ( 62 ) comprises polyurethane foam.
13. The gymnastics balance beam according to claim 1 , wherein the lower layer ( 62 ) comprises polyurethane foam.
14. The gymnastics balance beam according to claim 1 , wherein the lower layer ( 62 ) has a mass per unit volume comprised between 250 and 450 kg per cubic meter.
15. The gymnastics balance beam according to claim 1 , wherein the elastic multilayer composite ( 6 ) is bonded to the planar upper surface ( 51 ) of the rigid elongate member ( 5 ) of specific cross-section.
16. The gymnastics balance beam according to claim 1 , wherein the upper layer ( 61 ) has a thickness comprised between 3 mm and 20 mm.
17. The gymnastics balance beam according to claim 1 , wherein the lower layer ( 62 ) has a thickness comprised between 10 mm and 30 mm.