Sun and planet gear transmission mechanism particularly for power wrenches

DETAILED DESCRIPTION Having thus set forth and disclosed the nature of this invention, what is claimed is: 1.
A sun and planet gear transmission mechanism particularly for power wrenches comprising: a.
a power input shaft and at least two successive gear steps including a first gear step and a second gear step disposed within a gear casing, b.
each said first and second gear steps including a sun gear and at least one planet gear, c.
the sun gear of the first gear step being connected to the power input shaft and the sun gear of the second gear steps being in a fixed location within said gear casing, d.
said power input shaft being axially displaceable and said sun gear of the first gear step is disengagable with respect to the appertaining planet gear in said first gear step, and e.
coupling means located at said second gear step is effective to engage the sun gear of said second gear step when said sun gear of the first gear step is disengaged from said planet gear in the first gear step.
2.
A gear mechanism as defined in claim 1 wherein said power input shaft includes a plurality of annular grooves laterally displaced with respect to each other along the axial length of the power input shaft, said gear casing includes a stop device for engaging at least one of the annular grooves to arrest the axially displaceable power input shaft at a desired switch position within the casing.
3.
A gear mechanism as defined in claim 2 wherein a reverse stop means is disposed in said gear casing for engaging a toothing disposed along the power input shaft, one of said annular grooves being located on the input shaft within said toothing to form separated portions therein.
4.
A gear mechanism as defined in claim 2 wherein said stop device comprises a safety lock having a pin projecting resiliently into an annular groove and a handle for retracting said pin from said annular groove.
5.
A gear mechanism as defined in claim 1 wherein said input shaft includes a switch head means fixedly disposed at the outer end thereof outside said gear casing, said switch head includes a connecting means for attaching a driving mechanism