Hand grip strengthener and injection molding manufacturing method thereof

1 . A hand grip strengthener, comprising:

a first operation handle which comprises a first handle body;

a second operation handle which is movably coupled to the first operation handle and comprises a second handle body, wherein the first handle body and the second handle body are injection molded; and

a strength adjustment assembly arranged to generate a resistance force to a relative movement between the first operation handle and the second operation handle;

wherein the first operation handle further comprises a first gripping layer which is overmolded on the first handle body, the second operation handle further comprises a second gripping layer which is overmolded on the second handle body;

wherein the strength adjustment assembly comprises a spring element, wherein the first handle body comprises a first handle portion, a curved spring mounting portion extended from the first handle portion, and a first connecting portion, wherein the second handle body comprises a second handle portion, a base portion extended from the second handle portion and a second connecting portion which is movably connected to the first connecting portion, wherein the spring element is connected to the curved spring mounting portion and is inclinedly arranged between the curved spring mounting portion and the base portion of the second handle body, wherein the first gripping layer is overmolded on a rear side of the first handle portion, the second gripping layer is overmolded on a front side of the second handle portion;

wherein the first handle body has a first indented groove formed at a rear side of the first handle portion, wherein the first gripping layer is integrally molded on the first handle body to conceal the first indented groove.

2 . The hand grip strengthener according to claim 1 , wherein the first indented groove is an injection gate mark formed after an injection molding process of the first handle body.

3 . The hand grip strengthener according to claim 1 , wherein the second handle body has a second indented groove formed at a rear side of the second connecting portion, wherein the second indented groove is an injection gate mark formed after an injection molding process of the second handle body.

4 . A hand grip strengthener, comprising:

a first operation handle which comprises a first handle body;

a second operation handle which is movably coupled to the first operation handle and comprises a second handle body, wherein the first handle body and the second handle body are injection molded; and

a strength adjustment assembly arranged to generate a resistance force to a relative movement between the first operation handle and the second operation handle;

wherein the first operation handle further comprises a first gripping layer which is overmolded on the first handle body, the second operation handle further comprises a second gripping layer which is overmolded on the second handle body;

wherein the strength adjustment assembly comprises a spring element, wherein the first handle body comprises a first handle portion, a curved spring mounting portion extended from the first handle portion, and a first connecting portion, wherein the second handle body comprises a second handle portion, a base portion extended from the second handle portion and a second connecting portion which is movably connected to the first connecting portion, wherein the spring element is connected to the curved spring mounting portion and is inclinedly arranged between the curved spring mounting portion and the base portion of the second handle body, wherein the first gripping layer is overmolded on a rear side of the first handle portion, the second gripping layer is overmolded on a front side of the second handle portion;

wherein the first handle portion comprises a first bonding wall and a first enclosing stopper wall extended from the first bonding wall to define a first retention groove, wherein the first gripping layer is overmolded and fitted to the first bonding wall at the first retention groove.

5 . The hand grip strengthener according to claim 4 , wherein the first handle body has a first indented groove formed at the first bonding wall at an upper portion of the first handle portion adjacent to the curved spring mounting portion, wherein the first gripping layer is integrally molded on the first handle portion to conceal the first indented groove.

6 . The hand grip strengthener according to claim 4 , wherein the first retention groove is extended along a circumferential direction to occupy a quarter to three quarters of a circumference of the first handle portion.

7 . The hand grip strengthener according to claim 6 , wherein the second handle portion comprises a second bonding wall and a second enclosing stopper extended from the second bonding wall to define a second retention groove, wherein the second gripping layer is overmolded and fitted to the second bonding wall at the second retention groove, wherein the second retention groove is extended along a circumferential direction to occupy a quarter to three quarters of a circumference of the second handle portion.

8 . A hand grip strengthener, comprising:

a first operation handle which comprises a first handle body;

a second operation handle which is movably coupled to the first operation handle and comprises a second handle body, wherein the first handle body and the second handle body are injection molded; and

a strength adjustment assembly arranged to generate a resistance force to a relative movement between the first operation handle and the second operation handle;

wherein the first operation handle further comprises a first gripping layer which is overmolded on the first handle body, the second operation handle further comprises a second gripping layer which is overmolded on the second handle body;

wherein the strength adjustment assembly comprises a spring element, wherein the first handle body comprises a first handle portion, a curved spring mounting portion extended from the first handle portion, and a first connecting portion, wherein the second handle body comprises a second handle portion, a base portion extended from the second handle portion and a second connecting portion which is movably connected to the first connecting portion, wherein the spring element is connected to the curved spring mounting portion and is inclinedly arranged between the curved spring mounting portion and the base portion of the second handle body, wherein the first gripping layer is overmolded on a rear side of the first handle portion, the second gripping layer is overmolded on a front side of the second handle portion;

wherein a tapered groove is formed at a lower portion of the curved spring mounting portion, wherein the tapered groove is configured with a downwardly widened shape.

9 . A hand grip strengthener, comprising:

a first operation handle which comprises a first handle body injection molded by polypropylene, wherein the first handle body comprises a first handle portion, a curved spring mounting portion extended from the first handle portion, and a first connecting portion, wherein the first operation handle further comprises a first gripping layer which is a thermoplastic elastomer layer or thermoplastic rubber layer overmolded on the first handle portion of the first handle body, wherein the first handle body has a first indented groove formed at an upper portion of the first handle portion adjacent to the curved spring mounting portion, wherein the first gripping layer is integrally molded on the first handle portion to conceal the first indented groove which is an injection gate mark after an injection molding process of the first handle body;

a second operation handle which comprises a second handle body injection molded by polypropylene, wherein the second handle body comprises a second handle portion, a base portion extended from the second handle portion and a second connecting portion which is movably connected to the first connecting portion; and

a strength adjustment assembly which comprises a spring element, a spring driving element, and an adjustment control element, wherein the spring element is arranged to generate a resistance force to a relative movement between the first operation handle and the second operation handle, the adjustment control element is arranged to drive the spring driving element to move, so as to drive the spring element to move and deform, so as to adjust the resistance force, wherein the spring element is connected to the curved spring mounting portion and is inclinedly arranged between the curved spring mounting portion and the base portion of the second handle body.