Dumbbell with rotating grip

Abstract

A dumbbell having a shaft, first and second dumbbell heads, respectively fixedly connected to first and second ends of the shaft, a tube-shaped hollow grip rotatably arranged around the shaft having first and second ends. An inner diameter of the grip is greater than an outer cross-sectional dimension of the shaft. The dumbbell further having a first ball bearing and a second ball bearing, wherein an outer ring of the first ball bearing is connected to the first dumbbell head, and an inner ring of the first ball bearing is fixedly arranged to the first end of the hollow grip, and an outer ring of the second ball bearing is connected to the second dumbbell head, and an inner ring of the second ball bearing is fixedly arranged to the second end of the hollow grip.

Claims

1. A dumbbell comprising: a shaft having an outer cross-sectional dimension, and extending along a longitudinal axis, a first dumbbell head fixedly connected to a first end of the shaft and centered around the longitudinal axis of the shaft, a second dumbbell head fixedly connected to a second end of the shaft and centered around the longitudinal axis of the shaft, and the first dumbbell head comprises an inner side facing the second dumbbell head and an opposite outer side facing away from the second dumbbell head, and the second dumbbell head comprises an inner side facing the first dumbbell head and an opposite outer side facing away from the first dumbbell head, a tube-shaped hollow grip arranged around the shaft and centered around the longitudinal axis of the shaft, the grip having a first end and an opposite second end, and an inner diameter and an outer diameter, wherein the inner diameter of the grip is greater than the outer cross-sectional dimension of the shaft, a first ball bearing centered around the longitudinal axis of the shaft, wherein an outer ring of the first ball bearing is connected to the first dumbbell head, and an inner ring of the first ball bearing is fixedly arranged to the first end of the hollow grip, a second ball bearing centered around the longitudinal axis of the shaft, wherein an outer ring of the second ball bearing is connected to the second dumbbell head, and an inner ring of the second ball bearing is fixedly arranged to the second end of the hollow grip, and wherein the inner side of the first dumbbell head comprises a first cavity centered around the longitudinal axis of the shaft, and the inner side of the second dumbbell head comprises a second cavity centered around the longitudinal axis of the shaft, wherein the first cavity has an outer diameter which corresponds with an outer diameter of the first ball bearing and the second cavity has an outer diameter which corresponds with an outer diameter of the second ball bearing, and the first ball bearing is arranged in the first cavity and the second ball bearing is arranged in the second cavity, and wherein the first ball bearing is arranged in the first cavity by slip fitting, and the second ball bearing is arranged in the second cavity by slip fitting, wherein each slip fitting is a mechanical interface between the corresponding ball bearing and cavity characterized by an exact fit of the ball bearing into the cavity and is not a press fit between the ball bearing and the cavity.

2. The dumbbell according to claim 1, wherein the inner ring of the first ball bearing and the inner ring of the second ball bearing respectively has an inner diameter which corresponds with the outer diameter of the grip, such that the grip is fixedly arranged with its first end inside the inner ring of the first ball bearing and with its second end inside the inner ring of the second ball bearing.

3. The dumbbell according to claim 1, wherein the first dumbbell head is fixedly connected to the first end of the shaft by press fitting, and the second dumbbell head is fixedly connected to the second end of the shaft by press fitting.

4. The dumbbell according to claim 1, wherein the inner ring of the first ball bearing is fixedly arranged to the first end of the hollow grip by press fitting, and the inner ring of the second ball bearing is fixedly arranged to the second end of the hollow grip by press fitting.

5. The dumbbell according to claim 1, wherein a first wave washer is arranged in the first cavity between a bottom of the first cavity and the first ball bearing and centered around the longitudinal axis of the shaft, and a second wave washer is arranged in the second cavity between a bottom of the second cavity and the second ball bearing and centered around the longitudinal axis of the shaft.

6. The dumbbell according to claim 1, wherein the outer side of the first dumbbell head comprises a third cavity and the outer side of the second dumbbell head comprises a fourth cavity, and the first end of the shaft comprises an outer portion with a thread wherein the outer portion protrudes in the third cavity, and the second end of the shaft comprises an outer portion with a thread wherein the outer portion protrudes in the fourth cavity, and the first dumbbell head is further secured to the first end of the shaft by a first nut engaged with the thread of the first end of the shaft, and the second dumbbell head is further secured to the second end of the shaft by a second nut engaged with the thread of the second end of the shaft.

7. The dumbbell according to claim 1, wherein the shaft is made of steel with a yield strength between 800-1000 N/mm.sup.2 and a tensile strength of 1000-1400 N/mm.sup.2.

8. The dumbbell according to claim 1, wherein the ball bearings are sealed low friction ball bearings.

9. The dumbbell according to claim 3, wherein the first dumbbell head is fixedly connected to the first end of the shaft by a press fitting force of at least 100 kN, and the second dumbbell head is fixedly connected to the second end of the shaft by a press fitting force of at least 100 kN.

10. The dumbbell according to claim 1, wherein each of the first dumbbell head and the second dumbbell head provide weight to the dumbbell that, combined with weight of the shaft, grip and first and second ball bearings, achieve a desired weight of the dumbbell.

11. The dumbbell according to claim 10, wherein the fixed connection between each of the first dumbbell head and the second dumbbell head and the shaft are press fittings.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

(2) FIG. 1 is a perspective view of a dumbbell according to the invention.

(3) FIG. 2 is a longitudinal cross section of the dumbbell of FIG. 1.

(4) FIG. 3 is a zoomed view of the connection point between a dumbbell head, a shaft and a grip on the left side of the dumbbell of FIG. 1.

(5) FIG. 4 is a cross-section of a ball bearing used in the dumbbell of FIG. 1.

(6) FIG. 5 is a cross-section of a shaft with a grip arranged on the outside of the shaft, of the dumbbell of FIG. 1.

DETAILED DESCRIPTION

(7) Briefly described, a high end dumbbell with an ergonomic and user friendly design with a long life time is disclosed.

(8) FIG. 1 shows a perspective view of a dumbbell 1 according to the invention. The dumbbell 1 comprises a first dumbbell head 31 and a second dumbbell head 32 arranged on a respective side of a grip 40. The grip 40 is in turn arranged around a shaft 20 (not visible in FIG. 1), which shaft 20 extends along a longitudinal axis X-X. Visible in the figure is also a first ball bearing 51. The constructional design of the dumbbell 1 will be further explained below.

(9) FIG. 2 shows a longitudinal cross section of the dumbbell 1 of FIG. 1. As mentioned above, the dumbbell 1 comprises the shaft 20. The shaft 20 has a cross-sectional dimension d.sub.s,outer, and extends, as mentioned above, along a longitudinal axis X-X (see also FIGS. 3 and 5). The shaft is made of steel with a yield strength between 800-1000 N/mm.sup.2 and a tensile strength of 1000-1400 N/mm.sup.2.

(10) The first dumbbell head 31 is fixedly connected to a first end 21 of the shaft 20 and is centered around the longitudinal axis X-X of the shaft 20. The second dumbbell head 32 is fixedly connected to a second end 22 of the shaft 20 and is also centered around the longitudinal axis X-X of the shaft 20. The respective dumbbell heads 31, 32 is fixedly connected to the respective end 21, 22 by press fitting, preferably by a force of at least 100 kN. The first dumbbell head 31 comprises an inner side 31a, which faces the second dumbbell head 32, and an opposite outer side 31b, which faces away from the second dumbbell head 32. And in a similar way, the second dumbbell head 32 comprises an inner side 32a, which faces the first dumbbell head 31 and an opposite outer side 32b, which faces away from the first dumbbell head 32. Further, the inner side 31a of the first dumbbell head 31 comprises a first cavity 35 which is centered around the longitudinal axis X-X of the shaft 20, and in the same way the inner side 32a of the second dumbbell head 32 comprises a second cavity 36, also centered around the longitudinal axis X-X of the shaft 20.

(11) The dumbbell 1 further comprises the first ball bearing 51 which is centered around the longitudinal axis X-X of the shaft 20. An outer ring 51a of the first ball bearing 51 is fixedly arranged to the first dumbbell head 31 by so-called slip fitting, which means that the first cavity 35 of the first dumbbell head 31 has an outer diameter d.sub.c, outer which corresponds with an outer diameter d.sub.b, outer of the first ball bearing 51, such as the first ball bearing 51 is exactly fitted into the first cavity 35. By that, there is contact between the outer ring 51a of the first ball bearing 51 and the walls of the cavity. In the same way, a second ball bearing 52 is centered around the longitudinal axis X-X of the shaft 20 and an outer ring 52a of the second ball bearing 52 is fixedly arranged to the second dumbbell head 32 by slip fitting, which means that the second cavity 36 of the second dumbbell head 32 has an outer diameter d.sub.c, outer which corresponds with an outer diameter d.sub.b, outer of the second ball bearing 52, such as the second ball bearing 52 is exactly fitted into the second cavity 36. See also FIG. 3.

(12) The tube-shaped hollow grip 40 is arranged around the shaft 20 and the grip 40 is centered around the longitudinal axis X-X of the shaft 20. The grip 40 has a first end 41 and an opposite second end 42 and the grip 40 has an inner diameter d.sub.g, inner and an outer diameter d.sub.g, outer (see also FIG. 3). The inner diameter d.sub.g, inner of the grip 40 is greater than the outer cross-sectional dimension d.sub.s,outer of the shaft 20, such as there is no contact between the shaft 20 and the grip 40.

(13) An inner ring 51b of the first ball bearing 51 is fixedly arranged to the first end 41 of the hollow grip 40, and an inner ring 52b of the second ball bearing 52 is fixedly arranged to the second end 42 of the hollow grip 40, in the same way. The method of fitting the inner rings 51b, 52b to the grip ends 41, 42 may vary and could for example be a manual fitting or press fitting or the like. To get a good and fixed attachment, the inner ring 51b of the first ball bearing 51 and the inner ring 52b of the second ball bearing 52, respectively has an inner diameter d.sub.b, inner which substantially corresponds with the outer diameter d.sub.g, outer of the grip 40, such as the grip 40 is fixedly connected with its first end 41 inside the inner ring 51b of the first ball bearing 51 and with its second end 42 inside the inner ring 52b of the second ball bearing 52.

(14) To allow a certain tolerance at production of the dumbbell heads 31, 32 and the cavities 35, 36 therein, but eliminate a possible play between the ball bearings 51, 52 and the dumbbell heads 31, 32, a first wave washer 61 is arranged in the first cavity 35 between a bottom 35a of the first cavity 35 and the first ball bearing 51 and a second wave washer 62 is arranged in the second cavity 36 between a bottom 36a of the second cavity 36 and the second ball bearing 52. Both the first wave washer 61 and the second wave washer 62 are centered around the longitudinal axis X-X of the shaft 20. A wave washer is a washer with a wave-like form, arranged to allow a certain flexibility and act as a spring-force in the axial direction, and thereby eliminate the play between the ball bearings and the dumbbell heads.

(15) The outer side 31b of the first dumbbell head 31 further comprises a third cavity 37 and the outer side 32b of the second dumbbell head 32 comprises a fourth cavity 38. These cavities 37, 38 are arranged to accommodate an extra security beyond that the press fitting fixation between the shaft 20 and the dumbbell heads 31, 32. To enable this, the first end 21 of the shaft 20 comprises an outer portion 21a with a thread, wherein the outer portion 21a protrudes in the third cavity 37 (see example FIG. 3), and the second end 22 of the shaft 20 also comprises an outer portion 22a with a thread, wherein the outer portion 22a protrudes in the fourth cavity 38. By that, the first dumbbell head 31 may be further secured to the first end 21 of the shaft 20 by a first nut 71, which is engaged with the thread of the first end 21 of the shaft 20. In a similar way, the second dumbbell head 32 may be further secured to the second end 22 of the shaft 20 by a second nut 72 engaged with the thread of the second end 22 of the shaft 20. In this way, a double security against loosened dumbbell heads is achieved.

(16) FIG. 3 is showing a zoomed view of the connection point between the first dumbbell head 31, the shaft 20 and the grip 40. As understood, the constructional design is similar also for the second dumbbell head 32 on the opposite side of the shaft 20. The first ball bearing 51 is fitted to the first end 41 of the grip 40 by that the inner ring 51b of the first ball bearing 51 has an inner diameter d.sub.b, inner which substantially corresponds with the outer diameter d.sub.g, outer of the grip 40. Since the first ball bearing 51 is fixed in the longitudinal direction, it is only needed, but also an advantage, to only fit the first ball bearing 51 into the cavity 35 by slip fitting. As told earlier, slip fitting means a close to precise fit between the outer ring 51a of the first ball bearing 51 and the wall of the first cavity 35, but they are not pressed together as one “solid” unit, instead the first ball bearing 51 is slipped into the first cavity 35, but with very precise fit. This means that the grip 40 with the ball bearings 51, 52 is free rotating relative the dumbbell heads 31, 32 as well as relative the shaft 20, but with no detectable (sensed) play between the grip and the dumbbell heads 31, 32, which gives a premium feel for the product. The high performance steel and the solid fixation between the shaft 20 and the dumbbell heads 31, 32 takes care of the weight of the dumbbell heads 31, 32 and all possible shocks and forces caused by for example a drop of the dumbbell 1 on the ground. The ball bearings 51, 52 are less affected or worn by this why a good quality over time is achieved. As mentioned earlier, the inner diameter d.sub.g, inner of the grip 40 is greater than the outer cross-sectional dimension d.sub.s, outer of the shaft 20, such as there is no contact between the shaft 20 and the grip 40, why this effect is achieved. Visible in the figure is also the first wave washer 61, which is arranged in the first cavity 35 between the bottom 35a of the first cavity 35 and the first ball bearing 51, to ensure that any possible play is not sensed, as explained above. Visible in the zoomed figure is also the first nut 71, engaged with the thread of the outer portion 21a of the first end 21 of the shaft 20, and accessible from the third cavity 37 of the first dumbbell head 31. The outer side 31b of the first dumbbell head 31 also comprises a protective end cap 39 which protects the third cavity 37 and also provides a design area, preferably arranged for a printed logo or the like.

(17) FIG. 4 is a cross-section of first ball bearing 51 of FIGS. 2 and 3, and it is understood that the second ball bearing 52 is of the same kind. The first ball bearing 51 is preferably a sealed low-friction ball bearing of standard type, with the outer diameter d.sub.b, outer of the outer ring 51a and the inner diameter d.sub.b, inner of the inner ring 51b.

(18) FIG. 5 is a cross-section of the shaft 20 with the grip 40 arranged on the outside of the shaft 20 and extending along the longitudinal axis X-X of the shaft. The grip 40 is arranged around the middle part of the shaft 20, so that the first end 21 and the second end 22 of the shaft are free for the press fitting fixation of the shaft ends 21, 22 to the respective dumbbell head 31, 32. The length of the grip 40 extends between the first end 41 and the second end 42 of the shaft 40 and corresponds substantially to the distance between the two dumbbell heads, such as the first and second ends 41, 42 fits inside the respective ball bearing 51, 52. The thread of the respective outer portion 21a, 22a is not visible in the figure.

(19) Although the description above contains a plurality of specificities, these should not be construed as limiting the scope of the concept described herein but as merely providing illustrations of some exemplifying embodiments of the described concept. It will be appreciated that the scope of the presently described concept fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the presently described concept is accordingly not to be limited. Reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein and are intended to be encompassed hereby.