Patent Application
20070287611
The invention will now be described by way of example only, and with reference to the accompanying drawings in which:—
a presents a perspective view of a dumbbell with the number disc removed, according to yet another embodiment of the invention; and
b presents a perspective view of the dumbbell of
Referring to
The weight assembly 5 comprises an inner weight section 7, and an outer skin 8. The inner weight section 7 is preferably formed from cast iron, although other suitable materials could also be used. The outer skin 8 is preferably formed of rubber, polyurethane, or any other suitable resilient material, and is moulded over the inner weight section 7. The outer skin 8 protects the inner weight section from damage and corrosion, as well as providing an aesthetically pleasing finish. A central bore 2 is formed in the weight assembly for receiving the end portion 4 of the bar 3.
Cast iron is commonly used to form dumbbell weights, as its density enables a weight of suitable size to be achieved, while also being relatively cheap to purchase and form into the required shape. However, cast iron used to produce weight assemblies at a commercially viable cost is often not of suitable quality to enable a smooth surface finish to be achieved. Therefore, when a bore is formed in a cast iron weight to accommodate the end portion of a bar, it is not possible to provide an interference fit between the end portion and the weight, as the required tolerances cannot be achieved. In addition, the surface imperfections are such that the end portion does not sit completely flush with the inner surface of the bore. Hence, there is movement between the end portion and weight, which results in loosening of the fixings securing the weight to the bar.
To address this problem, there is provided in an embodiment of the present invention a collar 16, for receiving the end portion 4 of the bar 3. The collar 16 is located between the end portion 4, and the inner weight section 7. The collar 16 is preferably cylindrical, and surrounds the periphery of the end portion 4. Preferably, the collar 16 extends along the entire length of the central bore 2 of the weight assembly 5. The collar is preferably formed from seamless mild steel tubing, but may also be formed from any other suitable material.
In contrast to the cast iron of the inner weight section 7, the collar 16 may be easily machined to tight tolerances, and may be provided with a smooth surface finish. As such, an interference fit may be provided between the end portion 4 and the collar 16, to prevent or limit movement therebetween. In particular, the interference fit prevents relative axial and rotational movement between the end portion 4 and the collar 16. In this way, the collar 16 provides a securing member, which has the advantage of obviating the requirement for threaded fastenings.
The collar 16 is provided to prevent movement between the end portion 4 and the weight assembly 5. Therefore, as well as achieving a suitably toleranced fit between the collar 16 and the end portion 4, it is also necessary to ensure that any movement between the collar 16 and the weight assembly 5 is prevented. For the reasons discussed above in relation to the end portion 4, it is not possible to machine a bore in the inner weight section 7 suitable for providing a close fit with the collar 16. Therefore, the inner weight section 7 is formed around the collar 16 during the casting process. As such, the inner weight section 7 forms to the outer surface of the collar 16. The collar obviates the need for subsequent machining of the inner weight section 7. Furthermore, the closest possible tolerance between the collar 16 and the inner weight section 7 is achieved, which prevents lateral movement therebetween.
The collar 16 comprises a longitudinal axis, as shown by line A-A in
In an alternative embodiment, the collar 16 may be provided with projections which radially extend away from its outer surface. The projections may comprise one or more radially extending ridges arranged around the periphery and/or axially, one or more dimples, a secondary collar, or any other member which radially extends away from the surface of the collar. The collar 16 may also be provided with channels 18 extending around the outer surface in a spiral or helical formation, such that the channels 18 restrict movement in both the radial and axial directions. The collar 16 may also be provided with both projections and recessed sections. In a further alternative embodiment, the outer surface of the collar 16 may be tapered along the length of the collar 16, such that the ends of the collar 16 are both of greater diameter than some point along the length of the outer surface of the collar, or such that the ends of the collar 16 are both of lesser diameter than some point along the length of the collar 16.
A first securing member is provided to secure the weight assembly 5 to the end portion 4. The first securing member may comprise an end plate 12. The end plate 12 secures the weight assembly 5 to the end portion 4 independently of the collar 16. It is necessary to provide a securing member in addition to the collar, as for all but the lightest of weights an interference fit is not sufficient to permanently secure a weight on a dumbbell bar. Preferably, the end plate 12, comprises a load bearing plate (not shown), and an outer skin 25. The outer skin is moulded around the load plate in a similar manner to the outer skin 8 of the weight assembly 5.
The end plate 12 further comprises a central aperture 26. The end plate 12 covers a recess 21 in the outer skin 8 of the weight assembly 5, with the peripheral edge of the end plate 12 supported by the outer skin 8. The end plate 12 is further supported about the central aperture 26 by a first projection 17 extending from the end portion 4. Preferably, the first projection 17 is of reduced diameter relative to the end portion 4. A second projection 19, of reduced diameter relative to the first projection 17, extends from the first projection 17 and within the central aperture 26.
The second projection 19 may comprise a bore 15 extending through its centre, as shown in
The end plate 12 is secured to the end portion 4 of the bar 3. In one embodiment, the end plate 12 is secured to the end portion 4 by a weld 22. The weld is formed in the central aperture 26 of the end plate 12, and surrounds the second projection 19. Preferably the central aperture 26 is tapered, or counter-sunk to retain the weld more securely. The weld 26 provides a permanent fixing, and obviates the need for a threaded fastener such a locking nut. Previously, it has not been possible to use a weld to permanently fix the weight assembly of a dumbbell, as movement between the end portion of the bar and the weight assembly would result in the weld cracking. However, the present invention provides a collar 16 which is cast into, and fixed relative to, the weight assembly 5, and which provides an interference fit with the end portion 4. As such, movement between the end portion 4 and the weight assembly 5 is prevented, thereby enabling the use of welds as a permanent fixing means. In a further advantage, by obviating the requirement for threaded fastenings, it is no longer required to provide the inner weight section 7 with a recess to accommodate the fastening below the upper surface of the weight assembly 5.
In an alternative embodiment, the end plate 12 is secured by flaring the second projection member 19. The second projection is provided with a central bore. The end plate 12 is placed onto the upper surface of the weight assembly 5 such that the second projection 19 extends within the central aperture 26. A tapered tool is then inserted into the central bore of the second projection 19 and a force applied such that the end of the second projection 19 is expanded in diameter. The expanded diameter of the second projection 19 is forced against the countersunk central aperture 26 of the end plate 12, and secures the end plate 12 is position.
Threaded fastenings are commonly used in the arrangements of the prior art as they allow a torque to be applied to the fastening to urge the weight assembly against the locating means of the bar, which is not possible with a passive securing means such as a weld. This problem is overcome in the present invention using the resilient force of the outer skin 8.
During assembly of the dumbbell, the end plate 12 is placed onto the outer skin 8 such that the central aperture is aligned with the second projection 19. A force is applied to the upper surface of the end plate 12, for example using a press such as a 40 tonne press, thereby compressing the portion of the outer skin 8 supporting the end plate 12. The height of the first projection 17 is selected such that it is a predetermined distance below the upper surface of the outer skin 8, which contacts and supports the end plate 12. The outer skin 8 is compressed until the end plate 12 contacts the first projection 17. The end plate 12 is then held in place and secured to the end portion 4 with a weld, by flaring the end of the second projection 19, or by any other suitable means. When the compressive force is subsequently removed, the outer skin 8 remains compressed. Due to its resilient properties, the compressed outer skin 8 applies a force to the weight assembly to urge it against the locating member 10.
In addition to the end plate 12 and the collar 16, a third securing member 20 may be provided to secure the weight assembly 5 to the end portion 4, independently of the end plate 12 and the collar 16. The third securing member 20 is preferably a weld, such as a ring weld, which connects the end portion 4, the collar 16, and the upper surface of the inner weight section 7 of the weight assembly 5. Each of the three securing members, comprising the collar 16, the end plate 12, and the third securing member 20, secures the weight assembly 5 to the end portion 4 independently of each other. The weight assembly may therefore be secured to the end portion by one of the three securing members alone, by two of the securing members in combination, or using all three. The third securing member 20 is obscured from view by the end plate 12.
In an alternative embodiment, there is provided a recess 21 in the weight assembly 5, as shown in
It will be appreciated that in further embodiments various modifications to the specific arrangements described above and shown in the drawings may be made. For example, it is evident that the construction for securing the weights on the bar is not limited to applications in dumbbells or barbells but can also be applied to secure weights in other exercise equipment applications.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0611625.5 | Jun 2006 | GB | national |
