Power tool with vibration damping handle

1. A power tool, comprising:

a driving force transmission mechanism that transmits a rotary driving force from a rotary drive source to operate the power tool;

a housing that receives said driving force transmission mechanism therein and provides an outer shell for the power tool;

a tail cover provided at at least a region of said housing, which region is to be held by an operator,

said tail cover comprising an elastomer member integrally formed with a resin member,

said resin member having a higher hardness than said elastomer member,

said tail cover having a bilayer formation structure with said elastomer member placed on an outer side of said resin member,

said resin member defining a portion connected to said housing,

said elastomer member defining a receiving portion, said receiving portion being one of i) a gel pack-receiving portion and ii) a viscoelastic polymer-receiving portion,

said receiving portion being composed only of said elastomer member and being free of said resin member; and

one of i) a gel pack containing a gel-like material enclosed by a resin film, and ii) a viscoelastic polymer placed between said tale cover and said housing in said receiving portion formed by said elastomer member.

2. The power tool as claimed in claim 1 , wherein:

an adjacent portion of said resin member to said gel pack-receiving portion or said viscoelastic polymer-receiving portion has a shape to provide an undercut portion, when conducting a bilayer formation with said elastomer member; and

said resin member has a shape to be fitted into a mold, when forming said resin member and said elastomer member integrally with each other to form said tale cover.

3. The power tool as claimed in claim 1 , wherein:

said resin member is provided at an adjacent portion thereof to said gel pack-receiving portion or said viscoelastic polymer-receiving portion with a slit.

4. The power tool as claimed in claim 3 , wherein:

each of said housing and said tale cover has a three-dimensional shape having a plurality of curved surfaces; and

said gel pack or said viscoelastic polymer, which is placed in a space defined by said three-dimensional shape, has notches fitting into said three-dimensional shape.

5. The power tool as claimed in claim 3 , further comprising:

an operation switch provided on a front side of the power tool to control operation thereof; and wherein: said gel pack or said viscoelastic polymer is placed to cover at least regions of a rear side and both of opposite sides of said housing in which said operation switch is provided.

6. The power tool as claimed in claim 3 , wherein:

said gel pack or said viscoelastic polymer has through-holes to prevent movement thereof between said tale cover and said housing to secure said gel pack or said viscoelastic polymer to said housing.

7. The power tool as claimed in claim 1 , wherein:

each of said housing and said tale cover has a three-dimensional shape having a plurality of curved surfaces; and

said gel pack or said viscoelastic polymer, which is placed in a space defined by said three-dimensional shape, has notches fitting into said three-dimensional shape.

8. The power tool as claimed in claim 7 , further comprising:

an operation switch provided on a front side of the power tool to control operation thereof; and wherein:

said gel pack or said viscoelastic polymer is placed to cover at least regions of a rear side and both of opposite sides of said housing in which said operation switch is provided.

9. The power tool as claimed in claim 1 , further comprising:

an operation switch provided on a front side of the power tool to control operation thereof; and

wherein:

said gel pack or said viscoelastic polymer is placed to cover at least regions of a rear side and both of opposite sides of said housing in which said operation switch is provided.

10. The power tool as claimed in claim 1 , wherein: further comprising:

projections in one of the housing and tale cover,

through-holes in the one of said gel pack or said viscoelastic polymer, the projections inserted into the through-holes to prevent movement thereof between said tale cover and said housing to secure said gel pack or said viscoelastic polymer to said housing.

11. The power tool as claimed in claim 2 , wherein:

said resin member is provided at an adjacent portion thereof to said gel pack-receiving portion or said viscoelastic polymer-receiving portion with a slit.

12. The power tool as claimed in claim 2 , wherein:

each of said housing and said tale cover has a three-dimensional shape having a plurality of curved surfaces; and

said gel pack or said viscoelastic polymer, which is placed in a space defined by said three-dimensional shape, has notches fitting into said three-dimensional shape.

13. The power tool as claimed in claim 2 , further comprising:

an operation switch provided on a front side of the power tool to control operation thereof; and wherein:

said gel pack or said viscoelastic polymer is placed to cover at least regions of a rear side and both of opposite sides of said housing in which said operation switch is provided.

14. The power tool as claimed in claim 1 , further comprising:

projections in one of the housing and tale cover,

through-holes in the one of said gel pack or said viscoelastic polymer, the projections inserted into the through-holes to prevent movement thereof between said tale cover and said housing to secure said gel pack or said viscoelastic polymer to said housing.