Abstract:
A back rest tilting device in a reclining chair formed of less number of parts, simple in structure, easily assembled, and well balanced in layout and energizing force. The energizing means energizing a back rest in an upright direction comprises a rotatingly energizing means with rubber torsion springs using, as a core, a laterally extending pivot shaft rotated integrally with the back rest and having an elastic body filled between an outer tube locked to a support body coaxially with the core and the pivot shaft so that the elastic body can be elastically deformed when the pivot shaft is rotated about the center axis of the outer tube to impart a returning rotating force to the pivot shaft.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a backrest-tilting device in a reclining chair in which the backrest is tilted rearwards.  
         [0002]     JP2004-49717A discloses that a rubber torsion spring is used as force-promoting unit for forcing the backrest to an upright position.  
         [0003]     In the device, a hexagonal shaft is pivotally supported through a support supported by a leg and each end of the shaft is fixed to a pair of backrest support rods supporting the backrest. A force-promoting unit for forcing the backrest towards an upright position comprises a core having a hexagonal hole through which the shaft passes; an outer tube mounted to the support and coaxial with the core; and a plurality of force-promoting units each comprising a rubber torsion spring having an elastic material filed between the core and the outer tube, the core turning with the shaft around an axis with respect to the outer tube so that it is elastically deformed to apply return-rotation force to the shaft. Radial teeth are partially formed on a disc turning together with the backrest and core, and engage with and disengage from teeth of an engage member moved by an operating member.  
         [0004]     U.S. Pat. No. 6,439,661B1 discloses that a rubber torsion spring is pivotally supported to a support as well as the above, comprising a hexagonal shaft turning together with a backrest support rod for supporting the backrest; a core having a hexagonal hole through which the shaft passes; an outer tube mounted to the support and coaxial with the core; and an elastic material filled between the core and the outer tube, the core turning together with the shaft around an axis with respect to the outer tube so that the core is elastically deformed to apply the shaft to return-turning force, an adjusting screw being provided at front lower part of the support being rotated to allow the outer tube to turn around the axis thereby adjusting initial promoting force of the rubber torsion spring.  
         [0005]     However, in such a device, the core in a plurality of force-promoting units comprising a rubber torsion spring is not the same as the shaft of the backrest support rod thereby increasing the number of parts, making the structure and assembling more complicate.  
         [0006]     Especially, in JP2004-49717A, after a plurality of force-promoting units comprising a rubber torsion spring is received in the support, the hexagonal shaft is passed through the hexagonal hole of the core of the torsion spring from the side of the support. Thereafter, the ends of the beackrest support rods supporting the backrest have to be fixed to the ends of the shaft, thereby making assembling more complicate, especially, passing the hexagonal shaft through the hexagonal hole of the core of the rubber torsion spring and requiring a lot of time.  
         [0007]     In U.S. Pat. No. 6,439,662B1, the adjusting screw is disposed in the front lower part, so that, to adjust strength of initial promoting force for the backrest, a sitting person has to stoop or to turn around to handle the adjusting screw after one leaves a chair.  
         [0008]     As promoting force becomes larger, turning resistance of the adjusting screw increases to make it more difficult to handle the screw.  
       SUMMARY OF THE INVENTION  
       [0009]     It is an object of the present invention to provide a backrest-tilting device in a reclining chair, the device being simple in structure and being able to be easily assembled.  
         [0010]     It is another object of the present invention to provide a backrest-tilting device in a reclining chair, enabling the backrest to be held at an optional angle, the device being simple in structure and being able to be assembled for a short time.  
         [0011]     It is further object of the present invention to provide a backrest-tilting device in a reclining chair, initial promoting force of the backrest being easily adjusted by turning an operating handle at the lower side of a seat even when a sitting person still sits on the seat, turning resistance of an operating shaft being not able to increase even if initial promoting force of the backrest becomes larger.  
         [0012]     It is yet another object of the present invention to provide a backrest-tilting device in a reclining chair, a pivot of a backrest support rod that supports the backrest and force-promoting unit for the backrest being easily and surely assembled to the support for a short time. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a front elevational view of a chair having an embodiment of the present invention;  
         [0014]      FIG. 2  is a side elevational view thereof;  
         [0015]      FIG. 3  is an exploded perspective view of main members;  
         [0016]      FIG. 4  is an enlarged side view of main part when the backrest is in an upright position;  
         [0017]      FIG. 5  is an enlarged side view thereof when the backrest is tilted rearwards;  
         [0018]      FIG. 6  is a plan view seen from the line VI-VI in  FIG. 4 ;  
         [0019]      FIG. 7  is an exploded perspective view of a backrest-tilting device;  
         [0020]      FIG. 8  is a central vertical sectional side view of a support;  
         [0021]      FIG. 9  is a vertical sectional front view taken along the line IX-IX in  FIG. 8 ;  
         [0022]      FIG. 10  is a vertical sectional side view taken along the line X-X in  FIG. 9 ; and  
         [0023]      FIG. 11  is a horizontal sectional plan view taken along the line XI-XI in  FIG. 8   
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0024]     As shown in  FIGS. 1-3 , a reclining chair comprises a leg  3  having five leg rods  2  radially extending and having a caster  1  at the end. At the center of the leg  3 , a telescopic post  5  having a gas spring  4  is provided, and a support  6  which supports a seat  14  is fixed at the upper end of the post  5 .  
         [0025]     The support  6  comprises a hollow rhombus-shaped support body  6   a  and a front-half upper opening is covered with an upper cover  7 . A pair of arms  6   b,   6   b  are mounted on each side of the support body  6   a  so that the upper surfaces of the ends of the arms  6   b,   6   b  are disposed at a position higher than the support body  6   a.    
         [0026]     A pivot  8  which has a rectangular shaft portions  8   a,   8   a  at each end passes through the middle of the support body  6   a.  A pair of backrest support rods  10 , 10  support the backrest  9  and have tubular portions  10   a,   10   a  at the front respectively. Tubular portions  10   a,   10   a  engage with the rectangular shaft portions  8   a,   8   a  respectively thereby rotating the pivot  8 , the backrest support rods  10 , 10  and the backrest  9  together around the pivot  8  with respect to the support body  6 .  
         [0027]     A force-promoting unit A is provided by the pivot  8  and the backrest support rods  10 , 10  to force the backrest  9  to stand up.  
         [0028]     As shown in  FIG. 3 , the force-promoting unit A comprises a rotation-promoting unit B which comprises two rubber torsion springs  11 , 11  for forcing the pivot  9  in an anticlockwise direction in  FIG. 2 ; a promoting-force adjusting unit in  FIGS. 7 and 11 ; and a gas-spring unit which includes a gas spring  12 .  
         [0029]     The force-promoting unit A will be described later. The reclining chair will be then described.  
         [0030]     The lower surfaces of the rubber torsion springs  11 , 11  are covered with lower covers  13 , 13  detachably mounted to the lower surface of the support body  6   a.    
         [0031]     In  FIGS. 3-6 , short upright arms  10   b,   10   b  are provided on the backrest support rods  10 , 10  behind the pivot  8 . To the upper ends of the standing arms  10   b,   10   b,  the rear ends of a pair of seat-support frames  15 , 15  which support the seat  14  are coupled by a shaft  16 .  
         [0032]     The front of the seat-support frame  15  has a rectangular opening, an inclined lower surface  17  and an upright wall  18  at the rear end of the inclined lower surface  17 .  
         [0033]     The inclined surface  17  is slidably disposed on an inclined surface  19  at the end of the arm  6   b  of the support  6 .  
         [0034]     Between the end of the arm  6   b  of the support  6  and the front of the seat-support frame  15 , a stopper  20  prevents the inclined surface  17  from going off the inclined surface  19 .  
         [0035]     In this embodiment, the stopper  20  comprises a slit  21  in the inclined surface  17 , and a headed shaft  22  which slidably fits in the slit  21  and has a head  22   a  wider than the slit  21 . The slit  21  and head  22  may be provided in the inclined surfaces  19  and  17  respectively. In the figure, the headed shaft  22  is rectangular, but may be circular.  
         [0036]     The slit  21  extends from the front end to the rear end and opens from the upright wall  18 . The upright wall  18  has an opening  23  which communicates with the slit  21  to allow the larger head  22   a  of the headed shaft  22  to pass through the opening  23 .  
         [0037]     The headed shaft  22  is allowed to come from the opening  23  and to slide the inclined surface  17  on the inclined surface  19  rearwards and the rear end of the seat-support frame  15  is connected to the backrest support rod  10  to allow the seat-support frame  15  to join to the support  6  and the backrest support rod  10 .  
         [0038]     After connection, with rearward inclination of the backrest from the upright position, the seat-support frame  15  and seat  14  supported by the frame  15  is moved downward and rearward from  FIG. 4  to  FIG. 5  while the inclined surface  17  slides on the inclined surface  19 .  
         [0039]     Then, with motion of the backrest  9  and seat  14 , angles between the back and the thigh and between the thigh and the shank of a sitting person becomes wider naturally and the shank is slowly inclined backwards around the ankle of feet which contact the floor to give natural and comfortable feeling to the person.  
         [0040]     When the backrest  9  is moved from the rearward inclined position to the upright position, the seat  14  is moved reversely to the above motion giving the person comfortability too.  
         [0041]     If the inclined surface  17  contacts the inclined surface  19  along a straight line, the seat  14  is moved down rearward with rearward inclination of the backrest  9  to change surface contact to line contact. To enable them to achieve surface contact in a wider range, the inclined surface  17  and inclined surface  19  may be preferably gently curved.  
         [0042]     The seat  14  comprises a rectangular seat frame  14   a  over which elastic seating material  14  such as elastic-fiber mesh, plain weave fabric or synthetic resin film is stretched. When the person sits down, the seating material  14   b  is stretched to allow the middle of the seat to curve down along the buttock of the person thereby achieving comfort seating capability.  
         [0043]     To allow the middle of the seat to be pressed down when one sits down, four corners of the seat frame  14   a  are raised up and supported at a position higher than the support  6  by the upper surface of the arms  6   b,   6   b  and the upright arms  10   b,   10   b  of the backrest support rods  10 , 10  to produce a space  24  in which the middle of the seat  14  can be bent down, between the lower surface of the seat  14  and the upper surface of the support body  6   a.    
         [0044]     With respect to the backrest  9  as well as the seat  14 , seating material  9   b  having similar elasticity to the seating material  14   b  is stretched over a rectangular backrest frame  9   a.    
         [0045]     The seat  14  is mounted over the seat-support frames  15 , 15  to move back and forth, which is not directly connected to this invention and omitted as to the description.  
         [0046]     In the seat  14  which does not move back and forth, the rear part of the seat  14  may be connected to the upper parts of the upright arms  10   b,   10   b  of the backrest support rods  10 , 10  and the front lower surface of the seat  14  may be mounted to the upper surfaces of the arms  6   b,   6   b  to slide back and forth.  
         [0047]     An armrest  24  is provided on each of the backrest support rods  10 , but is not connected to this invention and omitted as to the description.  
         [0048]     A force-promoting unit A will be described in detail with respect to  FIG. 3  and  FIGS. 7-11 .  
         [0049]     As shown in  FIG. 7 , the force-promoting unit A comprises the rotation-promoting unit B comprising two rubber torsion springs  11 , 11  under the support  6 ; the force-promoting unit C above the support  6 ; and the gas-spring unit D including a gas spring  12 .  
         [0050]     As shown in  FIGS. 8 and 9 , in the middle of the pivot  8 , an arm  26  extends downwards almost perpendicular to the pivot  8 . Rubber torsion springs  11 , 11  are provided respectively at each side of the arm  26 .  
         [0051]     The rubber torsion spring  11  comprises a an outer tube  27  having the pivot  8  as core coaxial therewith and fixed to the support  6 ; and a rubber  28  filled between the outer tube  27  and the pivot  8  to allow the pivot  8  to rotate around an axis with respect to the outer tube  27  to cause the rubber  28  to deform elastically to apply return-turning force to the pivot  8 .  
         [0052]     The side ends of the pivot  8  projecting from each of the rubber torsion springs  11  engage with bearings  29 , 29  respectively. A positioning protrusion  29   a  is provided in the middle of the upper surface of the bearing  29 .  
         [0053]     In  FIG. 10 , under the support body  6   a,  a semicylindrical portion  6   c  opens at the lower surface to which a pair of semicylindrical lower covers  13 , 13  are mounted with screws  30 , 30 .  
         [0054]     The rubber torsion springs  11 , 11  engage in the recesses  31 , 31  between the semicylindrical portion  6   c  and the lower cover  13 , 13 . The bearings  29 , 29  are held between the semicylindrical portion  6   b  and the lower covers  13 , 13  in  FIG. 10 . The side ends of the pivot  8  from the bearings  13 , 13  passes through semicircular cut-away portions  33 , 34  between the semicylindrical portion  6   b  and the lower covers  13 , 13  in  FIG. 9 . Thus, the pivot  8 , a pair of rubber torsion springs  11 , 11  and outer bearings  29 , 29  are stored between the semicylindrical portion  6   b  of the support  6  and lower covers  13 , 13 .  
         [0055]     The lower end of the gas spring  12  is joined to the lower end of the arm  26  suspending between the lower covers  12  and  13 , with a shaft  35 .  
         [0056]     The front upper end of the gas spring  12  is coupled to the front middle portion of the support body  6   a  with a head cover  36  and a shaft  37 .  
         [0057]     Pressing a knob  38  at the front end of the gas spring  12  to a active position allows the gas spring  12  to extend elastically by gas pressure and force of an auxiliary spring. Returning the knob  38  to a passive position does not allow the gas spring  12  to retract.  
         [0058]     In the head cover  36 , to an operating lever  39  pivotally secured to the middle of the upright arm  10   b  of the right backrest support rod  10 , a running lever  42  is connected via a wire  41  extending through the flexible outer tube  40 . The operating lever  39  is pulled up to allow the running lever  42  to push the knob  38  to the active position, while a hand is released of the operating lever  39 , returning force of the knob  38  to the passive position allows the running lever  42  and operating lever  39  to return the original passive position. A spring (not shown) for returning to the passive position may be provided on the operating lever  39 .  
         [0059]     The outer tube  40  is fixed at one end to the inner surface of the upright arm  10   b  of the backrest support rod  10  and at the other end to the head cover  36  to enable the wire  41  passing through the outer tube  40  to move smoothly in an axial direction.  
         [0060]     The gas spring  12 , arm  26 , shafts  35 , 37  and head cover  36  constitute the gas spring unit D which assists force of the rotation-promoting unit B and enables the backrest  9  to be held at an optional angle by switching the knob  38  to the passive position.  
         [0061]     In  FIG. 11 , the promoting-force adjusting unit C for adjusting initial promoting force of the rotation-promoting unit B comprises an operating shaft  46  pivotally secured in the middle of the support body  6 a, having a normal thread  43 , a reverse thread  44  and an operating handle  45  projecting from the support body  6   a;  a pair of movers  49 , 50  having female thread bores  47 , 48  engaging with the normal and reverse threads  43 , 44  respectively; a connecting rod  52  the rear end of which is coupled to a shaft  51  connecting the outer tubes  27 , 27  of the rubber torsion springs  11 , 11  to each other; and a pair of links  54 , 55  each of which is coupled at the rear end to each of the movers  49 , 50  with a vertical shaft  53  and at the front end to the front end of the connecting rod  52 , rotation of the operating shaft  46  enabling the links  54 , 55  to open and close to move the connecting rod  52  back and forth thereby turning the outer tubes  27 , 27  around an axis.  
         [0062]     In the embodiment, the front end of the connecting rod  52  is supported by the support body  6   a  to slide back and forth. A side projection  52   b  is provided at the front end of a base portion  52   a  of the connecting member  52 . The front end of each of the links  54 , 55  contacts an inner corner between the side projection  52   b  and the base portion  52   a  to enable the front end to turn around a vertical axis.  
         [0063]     Force of the rubber torsion springs  11 , 11  enables the connecting rod  52  to pull back any time, and the front ends of the links  54 , 55  are always positioned inner than between the rear ends, so that the front ends of the links  54 , 55  are not released from the inner corners between the side projection  52   b  and the base  52   a.    
         [0064]     However, the front ends of the links  54 , 55  may be pivotally secured to the front end of the connecting rod  52  with a shaft (not shown) in parallel with the shaft  53  connecting the rear ends of the links  54 , 55  to the movers  49 , 50 .  
         [0065]     Rotation of the operating shaft  46  by the operating handle  45  allows the movers  49 , 50  to move towards and away from each other thereby moving the connecting rod  52  back and forth to enable the outer tubes  27 , 27  to turn around a pivotal axis, so that initial force of the rotation-promoting unit B and whole force of the backrest  9  reduces and increases.  
         [0066]     The operating handle  45  can be easily operated by the person who still sits, by stretching one&#39;s arm downwards of a right side.  
         [0067]     This embodiment is set such that the movers  49 , 50  move towards each other to allow the links  54 , 55  to close thereby increasing the force of the rotation-promoting unit B. Thus, forward move of the connecting rod  52  per one rotation of the operating shaft  46  gradually decreases thereby enabling the operating handle to be operated by lighter force any time without increasing rotation resistance of the operating shaft even if initial promoting force of the backrest becomes greater.  
         [0068]     In the middle of an upright arm  10   b  of a left-side backrest support rod  10 , an operating lever  56  is pivotally mounted around a longitudinal axis as well as the operating lever  39  in the middle of the upright arm  10   b  of the right-side backrest support rod  10 .  
         [0069]     The operating lever  56  is connected to a running lever (not shown) for operating the gas spring  4  in the post  5 . By turning the operating lever  56  upwards, the knob (not shown) for the gas spring  4  is pressed to the active position to allow the post  5  to extend and contract freely.  
         [0070]     Rotation of the operating lever  56  allows a knob (not shown) of the gas spring  4  to return to a passive position thereby enabling the post  5  to be held optionally.  
         [0071]     As described above, according to the embodiment, the pivot  8  of the backrest support rod  10  also acts as core of the rubber torsion spring  11  of the rotation-promoting unit B thereby reducing the number of parts, simplifying the structure and enabling the pivot  8  to be equipped to the support easily and readily.  
         [0072]     Especially, it avoids necessity for inserting a shaft into a core of a rubber torsion spring of a support thereby improving efficiency of assembling.  
         [0073]     The force-promoting unit A comprises the rotation-promoting unit B for applying turning force to the pivot  8  in a direction where the backrest  9  stands up; and the gas spring  12  which becomes stretchable by moving the knob  38  at one end to the active position and becomes rest by returning the knob  38  to the passive position, thereby forcing the backrest  9  strongly in an upright position by the rotation-promoting unit B and enabling the backrest  9  to be held optionally by the gas spring  12 .  
         [0074]     When the knob  38  of the gas spring  12  is in the active position, the rotation-promoting unit B can be additionally forced by the gas spring  12  thereby reducing the size of the rotation-promoting unit B.  
         [0075]     The sitting person can adjust strength of initial force of the backrest  9  by turning the operating handle at the lower side of the seat while one still sits.  
         [0076]     Furthermore, the rotation of the operating shaft  46  together with the operating handle  45  allows the movers  49 , 50  to move towards and away from each other and thus allows the links  54 , 55  to open and close thereby moving the connecting rod  52  back and forth and turning the outer tube  27  around the pivot  8  to make initial force of the rotation-promoting unit B weaker or stronger.  
         [0077]     Specifically, the rotation of the operating shaft  46  is converted by a pantograph mechanism to back-and-forth motion of the connecting rod  52  and then to rotation of the outer tube  27 .  
         [0078]     When it is set such that the movers  49 , 50  moves towards each other to allow the links  54 , 55  to become closer to increase force of the rotation-promoting unit B, back-and-forth movement of the connecting rod  52  is gradually reduced per one rotation of the operating shaft  46 . Thus, even if initial force of the backrest  9  becomes larger, the operating handle  45  can be always operated by almost constant force without increasing turning resistance of the operating shaft  46 .  
         [0079]     The rotation-promoting unit B which has the rubber torsion spring  11 , the pivot  8  of the backrest support rod  10  and the bearing  29  are assembled between the support body  6   a  and the lower cover  13  which are fixed to each other thereby assuring easy mounting to the support  76  for a short time surely.  
         [0080]     Various variations may be carried out without departing from the scope of claims as bellow:  
         [0081]     (i) The rotation-promoting unit B may comprise a single rubber torsion spring fixed to a pivot, or more than two rubber torsion springs around a single pivot.  
         [0082]     (ii) A torsion coil spring may be used as rotation-promoting unit B.  
         [0083]     (iii) A cross-section of the pivot  8  may be a hexagon or other non-circular shape.  
         [0084]     (iv) A support may comprise two separate parts comprising a support body and a cover (not shown). A space between the support body  6   a  and the cover has a rotation-promoting unit B and bearings which support a pivot. The side ends of the pivot projecting from the bearings put through openings between the support body and the cover.