Control mechanism for raising and lowering window covering

Abstract

A control structure for a window covering includes a base, a revolving wheel having an axial post, a restriction means including a bushing fitting around the axial post, a transmission member provided on a side of the bushing, and at least one pawl connected to the axial post. The revolving wheel is connected to the base. The restriction means has at least one cutting groove. The transmission member has at least one abutting portion on an inner wall thereof. The pawl is pivotable within a width of the cutting groove. When the revolving wheel is rotated forward, an end of the pawl passes through the cutting groove to mesh with the abutting portion. When the revolving wheel is rotated backward, the pawl disengages from the abutting portion, and the transmission member is rotatable relative to the revolving wheel. Whereby, it could prevent generating noise while operating the window covering.

What is claimed is: 
     
       1. A control structure for raising and lowering a window covering which includes a headrail, a bottom rail, and a shade material and a shaft, wherein the shade material is provided between the headrail and the bottom rail, and is expanded or collapsed by a the shaft provided in the headrail; the control structure comprising:
 a base provided in the headrail; 
 a revolving wheel connected to the base, wherein the revolving wheel is rotatable forwards and backwards, and has an axial post; 
 a transmission member connected to the shaft and provided on the axial post, wherein the transmission member has an abutting portion on a wall thereof, and is adapted to be connected to the shaft; 
 a pawl pivotally provided between the transmission member and the axial post; and 
 a restriction means, positioned between the transmission member and the axial post of the revolving wheel, allowing the pawl to mesh with the abutting portion or to disengage from the abutting portion; 
 wherein, when the revolving wheel is rotated forward, the pawl pivots until the pawl meshes with the abutting portion and continues meshing with the abutting portion through the restriction means; and when the revolving wheel is rotated backward, the pawl pivots until the pawl disengages from the abutting portion and remains disengaged from the abutting portion through the restriction means. 
 
     
     
       2. The control structure of  claim 1 , wherein the transmission member comprises a cover; the restriction means comprises a bushing provided in the cover and fitting around the axial post, wherein the bushing has a cutting groove; one end of the pawl is pivotally provided on the axial post, while another end of the pawl extends thereof therefrom and passes through the cutting groove; wherein, when the revolving wheel is rotated forward, the pawl pivots until the another end of the pawl passes through the cutting groove, and the another end of the pawl continues meshing with the abutting portion; when the revolving wheel is rotated backward over a longer distance than the bushing is, the pawl pivots into the cutting groove, and the another end of the pawl disengages from the abutting portion and remains disengaged so that the cover is freely rotated relative to the revolving wheel by a weight of the shade material through the shaft. 
     
     
       3. The control structure of  claim 2 , wherein the axial post of the revolving wheel has an engaging groove, wherein the engaging groove has a curved bottom; the pawl has a root located in the engaging groove, and a shape of the root matches a shape of the curved bottom of the engaging groove, so that the pawl is adapted to pivot within a width of the cutting groove, and whereby the another end of the pawl operably extends to pass through the cutting groove. 
     
     
       4. The control structure of  claim 2 , wherein the bushing further has a notch; the axial post of the revolving wheel has a prominent rib provided thereon; the prominent rib engages with the notch of the bushing, and pushes against one of two sidewalk of the notch along with a forwards or backwards rotation of the revolving wheel to rotate the bushing. 
     
     
       5. The control structure of  claim 4 , further comprising a spring fitting around the bushing, wherein the base has an axial bore, and the axial post of the revolving wheel passes through the axial bore; the axial bore of the base has a flange at a front edge thereof; one end of the spring pushes against the flange, while another end thereof extends into the notch to hook the prominent rib. 
     
     
       6. The control structure of  claim 1 , wherein the transmission member comprises a cover; the restriction means comprises a bushing provided in the cover and fitting around the axial post, wherein the bushing has a cutting groove; the axial post of the revolving wheel has an engaging groove; the pawl is pivotally provided on the bushing, and is adapted to pivot in the cutting groove; the pawl has a guide portion and a mesh portion on two opposite sides thereof; wherein, when the revolving wheel is rotated forward, the pawl pivots until the guide portion and the mesh portion extend through the cutting groove, the guide portion of the pawl stays in the engaging groove and the mesh portion of the pawl continues meshing with the abutting portion so that rotation of the revolving wheel rotates the cover; when the revolving wheel is rotated backward for a longer distance than the bushing is, the pawl pivots so that the guide portion and the mesh portion of the pawl enter the cutting groove, the guide portion of the pawl leaves the engaging groove, and the mesh portion disengages from the abutting portion; the cover bearing the weight of the shade material through the shaft is freely rotated relative to the revolving wheel at this time. 
     
     
       7. The control structure of  claim 6 , wherein the bushing further has a notch; the axial post of the revolving wheel has a prominent rib provided thereon; the prominent rib engages with the notch of the bushing, and pushes against one of two sidewalls of the notch along with a forwards or backwards rotation of the revolving wheel to rotate the bushing. 
     
     
       8. The control structure of  claim 7 , further comprising a spring fitting around the bushing, wherein the base has an axial bore, and the axial post of the revolving wheel passes through the axial bore; the axial bore of the base has a flange at a front edge thereof; one end of the spring pushes against the flange, while another end thereof extends into the notch to hook the prominent rib. 
     
     
       9. The control structure of  claim 6 , wherein the pawl is pivotally provided on the bushing through an axial member, wherein the axial member is located closer to the mesh portion than to the guide portion. 
     
     
       10. The control structure of  claim 1 , wherein the transmission member comprises a rotating plate, and one side of the rotating plate has a rib formed as the abutting portion; the restriction means comprises a bushing located on the side of the rotating plate, wherein the bushing includes a bore corresponding to the rib; one end of the pawl is pivotally provided on the axial post, while another end thereof operably extends and passes through the bore; when the revolving wheel is rotated forward the pawl pivots until the another end of the pawl passes through the bore and engages the rib; when the revolving wheel is rotated backward over a longer distance than the bushing is, the pawl pivots until another end of the pawl enters the bore and disengages from the rib so that the rotating plate bearing the weight of the shade material through the shaft is rotated freely relative to the revolving wheel. 
     
     
       11. The control structure of  claim 10 , wherein the axial post of the revolving wheel has an engaging groove recessing into one end surface of the axial post and having a curved bottom; an inner wall of the bushing has a top plate provided thereon; the bore is provided on the top plate; the pawl has a root located in the engaging groove, and a shape of the root matches a shape of the curved bottom of the engaging groove, so that the pawl is adapted to pivot within a width of the bore, and thereby the another end of the pawl is operably extended to pass through the bore. 
     
     
       12. The control structure of  claim 11 , wherein the bushing further has a notch; the axial post of the revolving wheel has a prominent rib provided thereon; the prominent rib engages with the notch of the bushing, and pushes against one of two sidewalls of the notch along with a forwards or backwards rotation of the revolving wheel to rotate the bushing.