Patent Publication Number: US-2011058860-A1

Title: Support mechanism for coil tension spring

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from U.S. provisional application 61/240,529, filed on Sep. 8, 2009; the entire contents of which, are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to support mechanisms for coil tension springs. 
     BACKGROUND 
     A coil tension spring is used to urge a certain member. Such a coil tension spring includes hooks provided at opposite ends thereof, and the hooks engage with respective objects. For example, two openings may be formed in a plate-like member to allow a hook to pass therethrough. 
     However, the hook may come off when a certain external force is applied to the coil tension spring. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view illustrating the support mechanism for a coil tension spring in a first embodiment; 
         FIG. 2  is a cross-sectional view taken along A-A in  FIG. 1 ; 
         FIG. 3  is a diagram illustrating a hook coming off a support member; 
         FIG. 4  is a side view illustrating the support mechanism for a coil tension spring in a second embodiment; 
         FIG. 5  is a cross-sectional view taken along B-B in  FIG. 4 ; 
         FIG. 6  is a side view illustrating the support mechanism for a coil tension spring in a third embodiment; 
         FIG. 7  is a cross-sectional view taken along C-C in  FIG. 6 ; 
         FIG. 8  is a side view illustrating the support mechanism for a coil tension spring in a fourth embodiment; 
         FIG. 9  is a diagram illustrating the internal structure of an image forming device in a fifth embodiment; 
         FIG. 10  is an exterior view of a fixing unit in the fifth embodiment; 
         FIG. 11  is a side view of the fixing unit; 
         FIG. 12  is an exterior view illustrating the structure around stripping claws in the fifth embodiment; and 
         FIG. 13  is an exterior view illustrating the support mechanism for a coil tension spring in the fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A support mechanism in each embodiment includes a coil spring that generates a tensile force, hooks, and support members. Each of the hooks includes a first position extending from the coil spring, an open end, and a second position that is closer to the open end than the first position. Each of the support members includes a first edge facing the first position and a second edge facing the second position. 
     The second edge is convex in a direction away from the first edge, the direction crossing a plane passing through the first edge, the first position, and the second position. 
     Hereinafter, the embodiments will be described with reference to the drawings. 
     First Embodiment 
     The support mechanism for a coil tension spring in a first embodiment will be described with reference to  FIGS. 1 and 2 .  FIG. 1  is a side view of the support mechanism, and  FIG. 2  is a cross-sectional view taken along A-A in  FIG. 1 . In  FIGS. 1 and 2 , X-, Y-, and Z-axes are orthogonal to each other. 
     A coil tension spring  10  includes a coil portion  11  and hooks  12  provided at opposite ends of the coil portion  11 .  FIGS. 1 and 2  show only one of the hooks. As shown in  FIG. 1 , the hook  12  has an arc shape. The hook  12  engages with a support member  20 . 
     The support member  20  has a flat planar shape and lies in the X-Y plane. The support member  20  includes a first edge  21  and a second edge  22 . The first edge  21  and the second edge  22  are disposed inside the hook  12 . The first edge  21  faces a base end portion  12   a  of the hook  12  in the X-Y plane. The second edge  22  faces a tip end portion  12   b  of the hook  12  in the X-Y plane and is located closer to the tip end of the hook  12  than the base end portion  12   a.    
     The base end portion  12   a  and the tip end portion  12   b  are portions of the hook  12  that overlap with a plane (the X-Y plane) in which the first edge  21  and the second edge  22  lie. The base end portion  12   a , the tip end portion  12   b , the first edge  21 , and the second edge  22  lie in the same plane (the X-Y plane). 
     As shown in  FIG. 2 , the first edge  21  has a curvature concave toward the second edge  22  in the X-Y plane and comes into contact with the base end portion  12   a  of the hook  12 . The first edge  21  may not have a curvature. For example, the first edge may be formed of at least two mutually intersecting planes. 
     The second edge  22  has a curvature convex in a direction away from the first edge  21  in the X-Y plane. The second edge  22  is located at a position that does not overlap with the moving trajectory R of the tip end portion  12   b  of the hook  12  (see  FIG. 2 ). The moving trajectory R of the tip end portion  12   b  is a moving trajectory when the tip end portion  12   b  rotates in the X-Y plane with the base end portion  12   a  in contact with the first edge  21  serving as a pivot. The trajectory R shown in  FIG. 2  is a part of the moving trajectory of the tip end portion  12   b.    
     An opening or a part of a notch formed in the support member  20  may be used as the first edge  21 . Similarly, an opening or a part of a notch formed in the support member  20  may be used as the second edge. One opening may have the first edge  21  and the second edge  22 . 
     It is sufficient to provide the shapes of the first edge  21  and the second edge  22  shown in  FIG. 2 . 
     When an external force is applied to the coil tension spring  10 , the base end portion  12   a  may come into contact with the first edge  21 , and the tip end portion  12   b  may rotate in the X-Y plane with the base end portion  12   a  serving as a pivot. For example, the tip end portion  12   b  may move in the direction of arrow D 1  in  FIG. 2 . 
     The second edge  22  is off the moving trajectory R of the tip end portion  12   b , and therefore the tip end portion  12   b  does not collide with the second edge  22 . The tip end (opening end)  12   c  of the hook  12  does not ride over the second edge  22  unless the hook  12  collides with the second edge  22 . 
     Assuming that the hook  12  can collide with the edge of the support member  20 , then the deformation of the hook  12  can cause the tip end  12   c  of the hook  12  to ride over the edge of the support member  20  and then come into contact with the lower surface of the support member  20 .  FIG. 3  shows the tip end  12   c  of the hook  12  that is in contact with the lower surface  20   a  of the support member  20 . The dotted line shown in  FIG. 3  illustrates the tip end  12   c  before the tip end  12   c  rides over the edge. If the tip end  12   c  of the hook  12  comes into contact with the lower surface  20   a  of the support member  20 , the hook  12  easily comes off the support member  20 . 
     In this embodiment, since the tip end portion  12   b  of the hook  12  does not collides with the second edge  22 , the tip end  12   c  of the hook  12  is prevented from riding over the second edge  22 . The hook  12  can be prevented from coming off even when the hook  12  does not have a complicated shape. 
     The hook on the other side of the coil tension spring  10  may be designed similarly. 
     The first edge  21  and the second edge  22  may have surfaces other than curved surfaces. The first edge  21  and the second edge  22  may have a plurality of flat surfaces. 
     The first edge  21  and the second edge  22  may not lie in the same plane. The first edge  21  and the second edge  22  may be displaced relative to each other in the Z direction. 
     Second Embodiment 
     The support mechanism for a coil tension spring in a second embodiment will be described with reference to  FIGS. 4 and 5 .  FIG. 4  is a side view of the support mechanism, and  FIG. 5  is a cross-sectional view taken along B-B in  FIG. 4 . The components described in the first embodiment are denoted by the same numerals, and the detailed description thereof will be omitted. 
     In this embodiment, a support member  20  has an opening  23 . The first edge  21  is a part of the opening  23 . The hook  12  passes through the opening  23 , and the base end portion  12   a  is disposed inside the opening  23 . 
     Third Embodiment 
     The support mechanism for a coil tension spring in a third embodiment will be described with reference to  FIGS. 6 and 7 .  FIG. 6  is a side view of the support mechanism, and  FIG. 7  is a cross-sectional view taken along C-C in  FIG. 6 . The components described in the first and second embodiments are denoted by the same numerals, and the detailed description thereof will be omitted. 
     In this embodiment, a support member  20  has openings  23  and  24 . The first edge  21  is a part of the opening  23 . The second edge  22  is a part of the opening  24 . The opening  24  has a third edge  25  that faces the second edge  22 . The third edge  25  extends in a direction along the second edge  22 . The spacing between the second edge  22  and the third edge  25  is greater than the thickness of the hook  12 . 
     The third edge  25  may not extend along the second edge  22 . It is sufficient that the third edge  25  allow the displacement of the tip end portion  12   b  when the hook  12  receives an external force. 
     Fourth Embodiment 
     The support mechanism for a coil tension spring in a fourth embodiment will be described with reference to  FIG. 8 .  FIG. 8  is a side view of the support mechanism and corresponds to  FIG. 7 . The components described in the first to third embodiments are denoted by the same numerals, and the detailed description thereof will be omitted. 
     A support member  20  has the opening  24  and an opening  26 . The first edge  21  is a part of the opening  26 . The opening  26  has a first region S 1  corresponding to the opening  23  in the third embodiment and a second region S 2  extending in the X-direction. The second region S 2  extends from the first region S 1  in a direction away from the opening  24  (the second edge  22 ). 
     Since the opening  26  has the second region S 2 , the hook  12  can be easily inserted into the opening  26 . More specifically, by inserting the hook  12  along the second region S 2 , the hook  12  can be easily inserted into the opening  26 . Preferably, the maximum length of the opening  26  in the X-direction (the total length of the first region S 1  and the second region S 2 ) is greater than the maximum width of the hook  12 . 
     The length of the first region S 1  in the Y direction is greater than the length of the second region S 2  in the Y direction, and therefore the base end portion  12   a  of the hook  12  can stay in the first region S 1 . 
     Fifth Embodiment 
     A description will be given of a fixing unit including the support mechanisms in the fourth embodiment and of an image forming device including the fixing unit. 
     The image forming device in this embodiment will be described with reference to  FIG. 9 . As shown in  FIG. 9 , the image forming device  100  includes an image reading unit  110  and an image forming unit  120 . 
     The image reading unit  110  scans and reads an image of a sheet manuscript or a book manuscript. The image forming unit  120  forms a tonner image on a sheet from image data generated by the reading operation of the image reading unit  110 , from image data sent from an external device (such as a personal computer) to the image forming device  100 , or from other data. 
     The outline of copy processing will be described as an example of the processing in the image forming device  100 . 
     A pick-up roller  131  picks up a sheet in a paper feed cassette  130 , and the picked-up sheet travels along a conveying path P 1 . A plurality of rollers  132  are disposed in the conveying path P 1 , and the sheet is conveyed by the rotation of the plurality of rollers  132 . 
     The image forming unit  120  forms electrostatic latent images on the photosensitive surfaces of photosensitive drums  121 Y,  121 M,  121 C, and  121 K according to the image data generated by the reading operation of the image reading unit  110 . The photosensitive drums  121 Y to  121 K are used to transfer yellow (Y), magenta (M), cyan (C), and black (K) toner images onto the sheet, respectively. 
     Developing rollers (so-called mag rollers)  122 Y,  122 M,  122 C, and  122 K supply toner to the photosensitive drums  121 Y to  121 K having the electrostatic latent images formed thereon to develop the electrostatic latent images formed on the photosensitive surfaces of the photosensitive drums  121 Y to  121 K into visible images. The photosensitive drums  121 Y to  121 K transfer the tonner images formed on the photosensitive surfaces to an intermediate transfer belt  123  (so-called primary transfer). The intermediate transfer belt  123  rotates in the direction of arrow D 2  to convey the tonner images and transfers the tonner images on the intermediate transfer belt  123  to the sheet at a secondary transfer position T. 
     The paper sheer having the transferred toner image travels to a fixing unit  140 , and the fixing unit  140  heats the sheet to fix the toner image onto the sheet. The sheet having the fixed toner image travels in the conveying path P 1  by a plurality of rollers and is delivered to a tray  150 . A sheet conveying path P 2  is a path configured to turn upside down a sheet. 
     The fixing unit  140  will be described with reference to  FIGS. 10 and 11 .  FIG. 10  is an exterior view of the fixing unit  140 , and  FIG. 11  is a side view of the fixing unit  140 . 
     A heating roller  141  heats a sheet P. The heating roller  141  rotates in the direction of arrow E. A sub-roller  142  disposed above the heating roller  141  has a diameter smaller than the diameter of the heating roller  141 . 
     The heating roller  141  and the sub-roller  142  support a belt  143 . Since the rotation of the heating roller  141  is transmitted to the sub-roller  142  through the belt  143 , the sub-roller  142  rotates together with the heating roller  141 . 
     A press roller  144  presses the heating roller  141 . The press roller  144  includes a rotation shaft  144   a  and an elastic member  144   b  that covers the outer circumference of the rotation shaft  144   a . The elastic member  144   b  may be formed of, for example, synthetic resin sponge. The press roller  144  rotates in the direction of arrow F. 
     A plurality of stripping claws  145  strip the sheet P off from the press roller  144 . The stripping claws  145  are arranged in the direction of the rotation axis of the press roller  144 . 
     A support member  146  is disposed above the press roller  144  and supports the stripping claws  145 . Each of the stripping claws  145  includes a shaft portion  145   a  and rotates about the shaft portion  145   a . The rotation axis of each stripping claw  145  is disposed along the rotation axis of the press roller  144 . 
     The support member  146  has notches  146   a  supporting the shaft portions  145   a . The shaft portions  145   a  can move along the notches  146   a . When an external force is applied to the stripping claws  145 , the shaft portions  145   a  can move along the notches  146   a.    
     First hooks  147   a  on one ends of coil tension springs  147  engage with openings  145   b  of the stripping claws  145 . Second hooks  147   b  on the other ends of the coil tension springs  147  engage with support portions  146   b  of the support member  146 . Each support portion  146   b  has the openings  24  and  26  described in the fourth embodiments. 
     The coil tension springs  147  generate forces for pressing the ends  145   c  of the stripping claws  145  against the press roller  144 . The coil tension springs  147  are disposed closer to the conveying path of the sheet P than the shaft portions  145   a  of the stripping claws  145 . 
     Stoppers  146   c  of the support member  146  come into contact with the stripping claws  145  so as to prevent the ends  145   c  of the stripping claws  145  from pressing the press roller  144  more than necessary. 
       FIGS. 12 and 13  are enlarged views illustrating portions around the stripping claws  145 . 
     The support member  146  has the openings  24  and  26  described in the fourth embodiment. As shown in  FIGS. 11 and 12 , the support portions  146   b  (the openings  24  and  26 ) are disposed on the side opposite to the conveying path of the sheet P with respect to the stripping claws  145 . The openings  24  extend in the direction away from the conveying path of the sheet P. 
     When the sheet P is jammed in the fixing unit  140 , the jammed sheet must be removed. During the removal of the sheet P, an external force may be applied to the coil tension springs  147 . As described in the fourth embodiment, even when such an external force is applied to the coil tension springs  147 , the second hooks  147   b  are prevented from coming off the openings  24 . 
     A description will be given of the operation of the fixing unit  140 . 
     When a sheet P passes through the nip portion between the heating roller  141  and the press roller  144 , a toner image is fixed onto the sheet P. The belt  143  guides the sheet P after fixing to the sub-roller  142 . The sheet P is stripped off from the belt  143  near the top portion of the sub-roller  142 . 
     Even when the sheet P sticks to the press roller  144 , the ends  145   b  of the stripping claws  145  enter between the sheet P and the press roller  144  as shown in  FIG. 11 , so that the sheet P is stripped off from the press roller  144 . 
     In this embodiment, the number of the stripping claws  145  may be one or more. The stripping claws  145  may strip a sheet P off from the heating roller  141  or the sub-roller  142 . The stripping claws  145  may strip a sheet P off from at least one of the heating roller  141 , the sub-roller  142 , and the press roller  144 . The sub-roller  142  and the belt  143  may be omitted. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of invention. Indeed, the novel mechanisms and methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the mechanisms and methods described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.