Patent Publication Number: US-2012038195-A1

Title: Seating furniture having movable backrest

Description:
TECHNICAL FIELD  
     The present invention relates to seating furniture, and in particular to a technology which is directed to allowing a backrest of seating furniture to support, all the time, a user&#39;s back so that a user can sit in a correct sitting posture. 
     BACKGROUND ART  
     Since lots of people spend time sitting on seating furniture such as a chair or a sofa, people suffering from an injury due to an incorrect sitting posture increase. Such injury problems occur because a user sits in an incorrect or wrong posture when sitting on seating furniture with his waists and hips not fitting closer to a backrest. 
     A lot of new chairs designed to support a user&#39;s back with the aid of movable backrest are already disclosed in the industry. One of such new chairs is disclosed in the Korean Patent Application number 10-2007-0060533. 
     The above technology is basically directed to generating a driving force with the aid of a weight when a user sits on a seat part, so a backrest moves forward, thus allowing a backrest to come into close contact with a user&#39;s back. The above construction however has some limits in application to diverse chairs because the height in an upward and downward direction is long, and furthermore there are some limits in making the outer appearance of a chair look nice. In addition, a structural stability is bad, so improvements are needed in a conventional construction. 
     DISCLOSURE OF INVENTION  
     Accordingly, it is an object of the present invention to provide seating furniture having a movable backrest which is compact-sized and is more stable than a conventional chair and can be well applied to diverse seating furniture. 
     To achieve the above object, there is provided a seating furniture having movable backrest, comprising a lower frame which is connected to a support part; an upper frame which is connected with the lower frame with an upper and lower displacement generation part being disposed between them; at least one elastic part disposed between the lower frame and the upper frame; a forward and backward movement part which is formed at the edge portions of left and right sides of the upper frame and is connected with the backrest frame and is movable in forward and backward directions; a driving force generation part allowing the backrest frame to move in a forward direction as the displacement generating owing to the down movement of the upper frame is converted into a linear movement by means of a forward and backward movement part when a certain weight is applied to a seat part engaged to the upper frame; and a switching part which becomes a half-lock state in which the backrest frame is movable only in a forward direction when a weight is applied to the seat part, and which becomes an unlock state in which the backrest frame is movable only in a backward direction when the weight having applied to the seat part is removed. 
     Preferably, the upper and lower displacement generation part is formed of a plurality of vertical slides or a plurality of foldable link plates, each of said vertical slides or said foldable link plates connecting the lower frame and the upper frame and linearly moving. 
     Preferably, the driving force generation part comprises a vertical rack gear which is vertically installed at an upper surface of the lower frame; a gear box which is engaged to the upper frame; a pinion gear which is engaged with a first shaft installed at a lower side of the gear box and then is engaged with the vertical rack gear; a vertical bevel gear which is engaged with the first shaft near the pinion gear; a spur gear which is horizontally installed in the interior of the gear box wherein a horizontal bevel gear connected with the vertical bevel gear is installed at a lower surface of the spur gear and rotates; and a horizontal rack gear which is engaged to a lower side of the backrest and is engaged with the spur gear and transfers a driving force to the backrest frame. 
     Preferably, the driving force generation part is formed of a stopper which is connected with a stop lever at one side of the spur gear, thus being selectively engaged with or disengaged from the spur gear. 
     Preferably, the switching part comprises a rotation latch which is engaged in the interior of the upper frame in forward and backward directions, thus converting a rotation direction depending on the presence of a weight at the seat part; and a latch hook which is connected with a lower surface of the backrest frame and is in a rotational operation within a limited angle range and is selectively engaged or disengaged with respect to the rotation latch. 
     Preferably, the seating furniture having a movable backrest is characterized in that the sear part is movable upward and downward with the rear end portion of the upper frame operating as a fixing part, and a pusher connected with a front end portion of the rotation latch is disposed at a lower surface of the front end portion of the seat part, thus allowing the rotation latch to rotate depending on the motion of the seat part. 
     Preferably, the pusher comprises an upper pusher which faces a lower surface of the seat part; a lower pusher of which an upper end portion is inserted through a lower side of the upper pusher and is movable, and a lower end portion is engaged with the rotation latch; and a coil spring which is disposed between the upper pusher and the lower pusher. 
     Preferably, the switching part is characterized in that a latch guide with slot formed in forward and backward directions is disposed between the rotation latch and the latch hook, and two limit pins protruded with certain intervals from each other are disposed at the latch hook, and the latch hook passes though the slot, wherein the rotation angle of the latch hook is so limited that the latch hook is limited by two limit pins. 
     Preferably, the switching part is formed of a release lever by which the rotation latch can be adjusted to an unlock state by pressing a front end portion of the rotation latch. 
     Advantageous Effects  
     In the seating furniture having a movable backrest according to the is present invention, when a user sits on a chair, a backrest automatically moves forwards and supports a user&#39;s back, which leads to a user&#39;s correct sitting posture, and the construction of a seating further is compact-sized, so the present invention might be well applied to diverse chairs such as an office chair, a student chair at a classroom or a sofa and a train chair or an airplane chair. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not imitative of the present invention, wherein; 
         FIG. 1  is a schematic partial perspective view illustrating seating furniture according to a first embodiment of the present invention; 
         FIG. 2  is a partial cross sectional view when seeing from the front side; 
         FIG. 3  is a cross sectional view when seeing from the lateral side; 
         FIG. 4  is a plane view; 
         FIG. 5  is a partial perspective view illustrating part of elements including a lower frame; 
         FIG. 6  is a cross sectional view illustrating a forward and backward moving part used in the present embodiment; 
         FIG. 7  is a partial perspective view illustrating major parts of a driving force generation part; 
         FIG. 8  is a perspective view illustrating an engaged state of a switching part and major parts; 
         FIG. 9  is a schematic cross sectional view of a chair according to a second embodiment of the present invention; 
         FIG. 10  is a schematic side view illustrating a structure of a link plate; 
       
         
           
             
                 
               
                 
                     
                 
                 
                   &lt;Descriptions of major reference numerals used in the drawings&gt; 
                 
                 
                     
                 
               
              
                 
                     
                 
              
             
             
                 
                 
                 
              
                 
                     
                    10: seat part 
                    20: backrest 
                 
                 
                     
                    30: support part 
                   100: lower frame 
                 
                 
                     
                   200: upper frame 
                   300: upper and lower 
                 
                 
                     
                     
                       displacement generation part 
                 
                 
                     
                   300a: link plate 
                   310: plate unit part 
                 
                 
                     
                   320: connection bracket 
                   400: elastic part 
                 
                 
                     
                   500: forward and backward 
                   510: fixing rail 
                 
                 
                     
                       moving part 
                 
                 
                     
                   520: intermediate rail 
                   530: driving rail 
                 
                 
                     
                   540: ball 
                   531: bracket 
                 
                 
                     
                   600: backrest frame 
                   700: driving force generation part 
                 
                 
                     
                   710: vertical rack gear 
                   720: gear box 
                 
                 
                     
                   730: pinion gear 
                   740: vertical bevel gear 
                 
                 
                     
                   750: horizontal bevel gear 
                   760: spur gear 
                 
                 
                     
                   770: horizontal rack gear 
                   780: guide roller 
                 
                 
                     
                   790: stopper 
                   800: switching part 
                 
                 
                     
                   810: rotation latch 
                   820: latch hook 
                 
                 
                     
                   821: limit pin 
                   830: pusher 
                 
                 
                     
                   831: upper pusher 
                   832: lower pusher 
                 
                 
                     
                   833: coil spring 
                   840: latch guide 
                 
                 
                     
                   841: slot 
                   850: release lever 
                 
                 
                     
                     
                 
              
             
           
         
       
     
    
    
     MODES FOR CARRYING OUT THE INVENTION  
     The preferred embodiments of the seating furniture having a movable backrest (hereinafter referred to “seating furniture”) according to the present invention will be described in detailed with reference to the to accompanying drawings which are provided in relation with the preferred embodiments given as means or better understanding of the present invention, provided that the attached drawings are provided for illustrative purposes based on the technical concepts of the present invention, so it should be understood that implementations with simple design changes or substitutions with is equivalent elements of partial constructions are also included in the technical scope of the present invention. 
     First Embodiment  
     First of all, the seating furniture according to a first embodiment of the present invention will be described. Figure is a schematic partial perspective view of the same. In the first embodiment of the present invention, it is characterized that the technology of the present invention is applied to an ordinary office chair, and  FIG. 2  is a cross sectional view when seeing from the front side, and  FIG. 3  is a cross sectional view when seeing from the lateral side, and  FIG. 4  is a plane view. 
     As a way for allowing a backrest  20  to automatically move forward to support a user&#39;s backrest when a user sits on a seat part  10  belonging to a chair, there are provided a lower frame  100 , an upper frame  200 , an upper and lower displacement generation part  300 , an elastic part  400 , a forward and backward moving part  500 , a backrest frame  600 , a driving force generation part  700 , and a switching part  800 . 
     The lower frame  100  is a portion fixedly secured to a support part  30  wherein the support part  30  represents a lower side including a leg part of a chair. Here the support part  30  might have different shapes and functions depending on the kinds of seating furniture. Some of the office chairs of the present invention are provided with the functions that the height of the support part can be adjusted. In other words, it is characterized in that the length of the portion of the support part can be changed depending on the height of the user. The technology for adjusting the height of the support part belongs to a conventional art. 
       FIG. 5  is a partial perspective view illustrating partial elements of a lower frame. As shown therein, a lower frame  100  is connected with an upper side of the support part  30 , and an upper and lower displacement generation part  300  is disposed at the left and right sides of the lower frame  100 , and an upper frame  200  is disposed at an upper side of the lower frame  100  with the aid of the upper and lower displacement generation part  300 . In the present embodiment of the present invention, the upper and lower displacement generation unit  300  is characterized in that the upper frame  200  is vertically movable about the fixed lower frame  100  as a plurality of balls roll along the rail by a linear movement. For a linear sliding movement, something like a LM guide might be used. The upper and lower displacement generation part used in the present embodiment of the present invention is called an upper and lower slider which has the same construction as the forward and backward movement part. 
     At least one elastic part  400  is disposed between the lower frame  100  and the upper frame  200 , thus generating a repulsive force, preferably, a coil spring might be used. When a person sits on the seat part  10 , the upper frame  200  moves down, and the elastic part  400  is contracted, thus storing a repulsive force. In this state, when the weight is removed, the elastic part  400  recovers, thus pushing upward the upper frame  200 . 
     When a certain weight is applied to the seat part  10 , the backrest frame  600  linearly moves in a forward direction. Here, the forward and backward movement part  500  is provided for a linear movement of the backrest frame  600 . The forward and backward movement part  500  is installed at the front and back sides at an inner edge position of the left and right sides of the upper frame  200  and is connected with the backrest frame  600 . The forward and backward movement part  500  is not limited to its construction when it can move linearly. In the present embodiment, it adapts the same format as the upper and lower displacement generation part  300 . 
       FIG. 6  is a cross sectional view illustrating a forward and backward movement part  500  used in the present embodiment. The upper and lower displacement generation part  300  has the same construction as the forward and backward movement part  500  provided that the lengths of the same are different from each other. As shown therein, the forward and backward movement part  500  is provided with a fixing rail  510  fixed at the upper frame  200 , and the fixed rail  510  has a certain length matching with the forward and backward length of the upper frame  200 . An intermediate rail  520  shorter than a driving rail  530  is formed at an inner side of the fixing rail  510 , and the driving rail  530  is engaged into the interior of the intermediate rail  520 . Meanwhile, a plurality of balls  540  are disposed at the intermediate rail  520  and roll while coming into contact with the fixing rail  510  and the driving rail  530 . In addition, the upper frame  200  is connected to the bracket  531  engaged with the driving rail  530 , so the backrest frame  600  can linearly move by receiving a driving force from the driving force generation part  700 . In other words, as the backrest frame  600  linearly moves in the forward and backward directions, the intermediate rail  520  and the driving rail  530  move concurrently with respect to the fixed rail  510 . In particular, the driving rail has longer moving distance than the moving distance of the intermediate rail. The forward and backward movement part with the above mechanism is commercially available and has a known element. 
     The driving force generation part  700  will be described.  FIG. 7  is a partial perspective view illustrating major parts of a driving force generation part. 
     In the driving force generation part  700 , weight is applied to the seat part  10  engaged to the upper frame  200 , and the upper frame  200  moves down. The movement is converted into a linear movement by the front and back movement part  500  by using the displacement occurring during the above down movement, thus allowing the backrest frame  600  move forward. 
     In more details, the structure of the driving force generation part  700  will be described. 
     The driving force generation part  700  comprises a vertical rack gear  710 , a gear box  720 , a pinion gear  730 , a vertical bevel gear  740 , a horizontal bevel gear  750 , a spur gear  760 , and a horizontal rack gear  770 . The vertical rack gear  710  is vertically installed at an upper surface of the lower frame  100  and is engaged with a pinion gear  730  which will be described later. The gear box  720  is installed at the upper frame  200 , and a first shaft s 1  is horizontally installed at a lower side belonging to the gear box  720 , and a pinion gear  730  and a vertical bevel gear  740  is installed at the first shaft s 1 . The pinion gear  730  is engaged with the vertical rack gear  710 , and the pinion gear  730  and the vertical bevel gear  740  integrally rotate. 
     In addition, the spur gear  760  horizontally laying down in the interior of the gear box  720  is drivingly installed at a portion higher than the vertical bevel gear  740 . The horizontal bevel gear  750  engaged with the vertical bevel gear  740  is engaged to the lower surface of the spur gear  760 . Through the above engaging relationship, when the upper frame  200  moves down, the pinion gear  730  rotates along with the vertical rack gear  710 , and its rotational force is transferred to the horizontal bevel gear  750  via the vertical bevel gear  740 , thus allowing the spur gear  760  start rotating. 
     As the upper frame  200  moves down, a driving force generating owing to the displacement allows the spur gear  760  to rotate. There is further provided a horizontal rack gear  770  for transferring the rotational force of the spur gear  760  to the backrest frame  600 . The horizontal rack gear  770  is installed with its upper end being engaged to a lower side of the backrest frame  600  and is disposed at front and back sides, thus linearly moving as the spur gear  760  rotates, by which the backrest frame  600  can move. More preferably, there is provided a guide roller  780 , which rotates in contact with the outer side (opposite side where the gear teeth are formed), at one side of the upper surface of the gear box  720  so that the horizontal rack gear  770  can precisely engage with the spur gear  760 . Since the relatively longer horizontal rack gear  770  is supported by the guide roller  780  at the point where it is engaged with the spur gear  760 , a precise engagement between the spur gear  760  and the horizontal rack gear  770  is obtained, thus obtaining a desired reliable driving force transfer. 
     More preferably, a stopper  790  is provided at the driving force generation part  700  in order to fix the backrest frame  600  at a certain position by forcibly preventing the rotation of the spur gear  760 . The stopper  790  is connected with the stop lever  791 , thus being engaged or disengaged from the spur gear  760  by means of an operation of the stop lever  791 . In other words, when the stopper  790  is engaged with the spur gear  760 , even when the weight applied to the seat part  10  is removed, the backrest frame  600  does not move backward, staying at the moved position. The stopper  790  is connected rotatable at one side of the gear box  720  and is engaged with an end portion of the stop lever  791 , so an intermittent operation with the spur gear  760  is obtained by lifting-up or lifting-down the stop lever  791 . 
     In the present embodiment, the driving force generation part is formed of a plurality of gears, but it is obvious that it alternatively might be formed of a belt or a chain. 
     The switching part  800  will be described.  FIG. 8  is a perspective view illustrating an engaged state of the switching part and the major elements of the present invention. The construction of the same will be described along with  FIGS. 2 through 4  and  8 . 
     The switching part  800  is configured in such a way that when a user sits on a seat part  10 , and weight is applied to the seat part  10 , the backrest frame  600  remains in a half-lock state in which the backrest frame  600  can move only forward. When the weight is removed from the seat part  10 , it becomes unlocked so that the backrest frame  600  can move backward. In other words, as a user sits on the seat part  10 , the backrest frame  600  moves forward by means of the driving force generation part  700 . At this time, the switching part  800  does not have any limits with respect to the forward movement of the backrest frame  600 ; however it limits the operation in such a way that when the backrest frame  600  comes into contact with a user&#39;s back, its backward movement is limited so that the backrest frame  600  cannot move backward from the then current position, which state is called a half-lock state. Even when a users body slightly moves or a users weight loses for a second by a certain reason, the backrest frame  600  can be prevented from moving unexpectedly. 
     When a user gets up from the sit state, since the external force applied to the seat part  10  becomes zero, the upper frame  200  moves upward, so a force is generated from the driving force generation part  700 , thus allowing the backrest frame  600  to move backward. Since the backrest frame  600  is supposed to move back toward the original position, the switching part  800  becomes an unlock state, thus not limiting the backward movement of the backrest frame  600 . 
     The switching part  800  will be described in more details. Along with the rotation latch  810  and the latch hook  820 , the rotation latch  810  is installed in the interior of the upper frame  200  in rotatable states in forward and backward directions. The rotation latch  810  is installed in parallel with the forward and backward movement part  500  is installed at one edge side of the upper frame  200  and is supported to be rotatable at front and back end portions. When a weight is applied to the seat part  10 , the rotation latch  810  rotates inwardly, and when the weight is removed, it rotates outwardly. 
     The latch hook  820  is connected to a lower surface of the bracket frame  600 ; however it might be installed in a such a way to rotate within a limited angle range, thus being engaged to the rotation latch  810  or disengaged from the same, so the forward or backward or only backward movements of the backrest frame  600  can be limited. As shown in the drawings, the latch hook  820  is formed to have a sharp end, thus being engaged with the toothed rotation latch  810 . When the latch hook  820  is engaged with the rotation latch  810 , the backrest frame  600  does not move backward. 
     The rotation of the rotation latch  810  is determined depending on whether or not the weight is applied to the seat part  10 . The interrelationship between the rotation latch  810  and the seat part  10  will be described. 
     In the present embodiment, the rear end portion of the seat part  10  is engaged with a rear end portion of the upper frame  200  in such a way that the front end portion of the seat part  10  can move upward and downward. When a person sits on a seat part  10 , the front end portion of the seat part is pressed down and moves downward. Since a pusher  830  is provided at an end lower surface of the front side of the seat part  10 , with the pusher being connected with the front end portion of the rotation latch  810 , the rotation direction of the rotation latch  810  can be determined depending on the motion of the seat part  10 . 
     The detailed construction of the pusher  830  connected with the rotation latch  810  is as follows. 
     The pusher  830  consists of an upper pusher  831  and a lower pusher  832 , and a coil spring  833  is disposed between the upper and lower pushers  831  and  832 . The upper end portion of the upper pusher  831  faces the lower surface of the seat part  10 , and the upper end portion of the lower pusher  832  is movably inserted into the lower end portion of the upper pusher  831 , and the lower end portion of the lower pusher  832  is connected with the front end portion of the rotation latch  810 . In other words, the upper end portion of the lower pusher  832  is inserted into the upper pusher  831  with the coil spring  833  being disposed between them. When a weight is applied to the seat part  10 , the upper pusher  831  is pressed, and moves downward. At this time, force is applied via the coil spring  833 , and then the lower pusher  832  is pressed, and the rotation latch  810  rotates inwardly. When the rotation latch  810  rotates internally, the switching part  800  becomes a half-lock state, and since the latch hook  820  is not engaged with the rotation latch  810 , the backrest frame  600  can move forwardly; whereas after the backrest frame  600  is moved forwardly and is fixed temporarily, the latch hook  820  keeps being engaged with the rotation latch  810 , thus limiting the backrest frame  600  from moving backward. 
     The latch hook  820  belonging to the switching part  800  is needed to rotate within a limited angle range, so the end portions of the rotation latch  810  and the latch hook  820  can be placed to be engaged with each other. In the present embodiment, a latch guide  840  having a punched slot  841  is formed between the formed positions of the rotation latch  810  and the latch hook  820 . The latch guide  840  is installed at the upper frame  200 , and the latch hook  820  is partially inserted into and passes through the slot  841 . One limit pin  821  is formed near an end portion of the latch hook  820 , and another limit pin  821  is protruded spaced apart from the above limit pin  821 . The latch hook  820  can rotate within a limited range by means of two limit pins  821 . One limit pin  821  is disposed at left and right sides of the slot  841 . 
     More preferably, the switching part  800  might be configured in such a way that the rotation latch  810  can be adjusted to a unlock state, if necessary, so the position of the backrest frame  600  can be precisely adjusted in a state that a user sits on the chair. For the above operation, a release lever  850  is provided, which is able to allow the rotation latch  810  rotate outwardly as a front end portion of the rotation latch  810  is pressed. The operation that the rotation latch  810  moved outwardly in a state that a user sits on the chair can be obtained with the aid of the pusher  830 . The pusher  830  consists of an upper pusher  831  and a lower pusher  832  as described earlier, with a coil spring  833  being disposed between the same. Since the lower pusher  832  is movably inserted in the upper pusher  831 , when the coil spring  833  is compressed by means of the motion of the release lever  850 , the lower pusher  832  moves upward along the fixed upper pusher  831 , thus adjusting the rotation latch  810 . 
     Second Embodiment  
     Next, the second embodiment of the present invention will be described. In this embodiment, it is assumed that the present invention is adapted to the chairs used at a classroom of school. 
     Differently from the first embodiment of the present invention, there are some differences in the shape of the support part  30  and the shape of the lower frame in which the lower frame  100  is fixedly installed. In particular, the upper and lower displacement generation part  300  connecting the upper frame  200  and the lower frame  100  is formed of a plurality of foldable link plates  300   a.    FIG. 9  is a schematic cross section illustrating a chair according to the second embodiment, and  FIG. 10  is a schematic lateral view illustrating the structure of the link plate. 
     As shown therein, the link plates  300   a  are disposed in four directions, thus stably connecting the upper frame  200  and the lower frame  100  and are connected with the aid of a laterally laid-down channel-shaped plate unit part  310 , thus allowing the upper frame  200  to move upward and downward with respect to the lower frame  100 . The 90° angled connection bracket  320  is engaged to the upper frame  200  and the lower frame  100 , respectively, and the plate unit part is connected by inserting a shaft. Preferably, the size of the plate unit part  310  positioned at the upper most portion is large, and its size is getting smaller toward the lower direction, thus constituting the like plates  300   a  by which the plate unit parts  310  can be folded without any interference. Since the movement operations of the other backrest frames are same, so the detailed descriptions thereon will be omitted. 
     The seating furniture having movable backrest according to the present invention can be well adapted to an ordinary office chair as well as a chair at classroom of school, and can be adapted to a sofa and a chair of train or airplane. 
     INDUSTRIAL APPLICABILITY  
     The seating furniture having movable backrest according to the present invention is characterized in that when a person sits on a seat part, the backrest frame connected with a backrest automatically moves forward, thus reliably supporting a users back, which leads to a correct sitting posture, so the present invention can be well adapted to all kinds of chairs such as a student chair, a home chair or an office chair, etc. as well as a sofa. In the detailed application of the present invention, the present invention can be adapted to a chair of a train, a chair of an airplane or the like.