BUMPER PLATES

The invention relates to a bumper plate comprising a weight core element and a rim surrounding the weight core element and that is arranged for absorbing an impact energy when the bumper plate hits the ground surface, said rim comprising a shock absorber region and a circumferential edge surrounding the shock absorber region.

Such a bumper plate is for example known from US 10010741B2, and is used for strength training and weightlifting in pairs of two, mounted on both sides of a barbell or dumbbell bar. A disadvantage of the bumper plate of US10010741B2 is that the allowed buffer length of the shock absorber region is limited, and therefor is its noise and vibration damping capacity.

It is an object of the invention to improve the above described bumper plate. In particular it may be an object of the invention to improve the stiffness of the circumferential edge of the bumper plate, resulting in a situation where the weight core element is placed in a hanging manner inside the circumferential edge, both being connected to each other by a dampening, for example elastic, material, forming the shock absorber region as mentioned hereafter.

The fact that the weight core element is suspended in a hanging manner inside the circumferential edge results in evenly distributed tensile stresses in the top halve of the shock absorber region, and results in a low bounce factor of the bumper plate as a result of mass inertia.

This object is achieved by providing a bumper plate according to the preamble that in accordance with the invention comprises a reinforcement element that is at least partly embedded in and extending along the circumferential edge, wherein the reinforcement element is made of a different material than the circumferential edge.

The reinforcement element is preferably made of a material having a stiffness that is higher than the material of which the rim is made, preferably an at least 300 times stiffer material than the rim.

The reinforcement element may be substantially ring shaped. Said reinforcement ring may have a reinforcement rib that extends substantially perpendicular from the reinforcement ring, in particular from the inner ring or main surface thereof, and is directed inwards. The ring shaped reinforcement element may thus have a substantially T-shaped transverse cross section. A thickness of the material layer of the circumferential edge at an outer side of the reinforcement element with respect to the weight core element may be between 1 and 20 mm, preferably between 4 and 10 mm, more preferably about 6 mm, i.e. a skin of 1 to 20 mm, preferably of 4 to 10 mm, more preferably of about 6 mm thickness may be formed over the reinforcement element.

By choosing a material for the reinforcement element that has a substantially higher stiffness then the material in the shock absorber region, the elliptical deformation of the rim upon ground impact will be lower, and therefore the damping stroke of the bumper plate will be longer than the example of US10010741B2, namely between 60 and 120 mm. As a result, the amount of absorbed impact energy will be higher, whereas the material stresses will be distributed better.

In an embodiment of the bumper plate according to the invention the reinforcement element is made of a metal (like for example aluminum) or plastic (like for example polybutylene terephthalate (PBT), glass filled polyamid (PA-GF), Polyoxymethylene (POM), polycarbonate (PC)). These materials allow being encapsulated in the material of the circumferential edge which may be an elastic material, while maintaining a chemical/and or mechanical bond with the material of the circumferential edge.

The reinforcement element must be as light as possible to ensure the least possible unsprung mass when impacting the ground surface during a drop. At the same time, the reinforcement element must be stiff enough to maintain a mostly round or slightly oval shape of the reinforcement element upon impact with the ground surface. This will ensure that the dampening stroke of the bumper plate is as long as possible.

In particular the reinforcement element is made of a metal or plastic that has a relatively low weight and a relatively high stiffness, compared to the material of the rim.

Practically, the metal may have a maximum density of 1500 kg/m ³ and/or a stiffness of 75 GPa.

Practically the plastic may have a density of 3000 kg/m ³ and/or a stiffness of 5 GPa.

In an embodiment of the bumper plate according to the invention the plastic is PA-GF, which chemically bonds to a variety of thermoplastic elastomers or rubbers in a moulding process.

As described above, the rim may be made of an elastic material.

For example, the elastic material may be a Thermoplastic Vulcanizate (TPV), thermoplastic urethane (TPU), or thermoplastic elastomer (TPE), styrene butadiene rubber (SBR), ethylene propylene diene monomer (EPDM), or Nitril butadiene rubber (NBR). In an embodiment of the bumper plate according to the invention the shock absorber region comprises a circumferential pattern of preferably evenly spaced ribs.

The ribs may define a polygonal pattern, such as a hexagonal pattern.

The pattern may define a radial length of between 60 - 100 mm, preferably about 80 mm.

The weight core element may be made of metal, such as for example steel or cast iron.

Such metals are relatively heavy and may thus provide sufficient weight for the bumper plate.

The bumper plate may be substantially disk shaped.

The invention also relates to a barbell, comprising at least two bumper plates according to any of the preceding claims.

The invention will be further elucidated with reference to the attached figures, in which:

FIG. l is a front perspective cross-section view of a bumper plate according to an exemplary embodiment of the invention.

Figure 1 shows a bumper plate 100 according to an exemplary embodiment of the invention. The bumper plate is disk shaped with a shock absorber region 101 in the rim 102 and a circumferential edge 112. The rim 102, in particular the circumferential edge 112 thereof, comprises a reinforcement element 103 that may be made of metal of plastic, and is encapsulated 104 inside an elastic material that forms the circumferential edge 112. In this embodiment the reinforcement element 103 is substantially ring-shaped. The reinforcement element may have a perpendicular rib 105 that extends inwards from the inner ring surface of the reinforcement element 103 to increase its ring stiffness.

The shock absorber region of the rim comprises a series of holes 106 that thereby define a pattern of ribs or walls 107. The holes pass transversely through the absorber region. The holes 106 in this example and thereby the pattern defined by the walls 107 are hexagonal, but any shape may be used. As is shown in figure 1, part of the walls 107 extend substantially radial, wherein the substantially radially extending walls 107 may be slightly declined with respect to a purely radial direction.

When the bumper plate is dropped, it hits the ground at the bottom of the outer surface 108 of the circumferential edge 112. While the reinforcement area largely remains it’s original cylindrical shape, momentum causes the weight core element 109 to continue to move downwards. During this movement, that is eccentrical with respect to the cylindrical or slightly oval shape of the rim, the radial walls 107 in the top area of the shock absorber region are stretched out in direction 110, absorbing kinetic energy of the weight core element, and decelerating the weight core element to zero velocity, after which it rebounds back upwards.

As a result of the elastic material the radial walls 107 will return to their original length after the drop. The outer diameter of the bumper plate is as such, that the distance 111 between the center of the bumper plate until the ground surface is between 215 and 230 mm.

Although the invention is elucidated above on the basis of a number of specific examples and embodiments, the invention is not limited thereto. Consequently, the scope of the invention is defined by the following claims.