Patent Publication Number: US-2006005350-A1

Title: Suction brush for vacuum cleaner

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application is related to copending U.S. applications entitled “Suction Brush Assembly Having Rotation Roller for Sweeping Dust,” Ser. No. 10/195,595, filed Jul. 16, 2002, and “Bendable Suction Brush for Vacuum Cleaner,” Ser. No. 10/851,080, filed May 24, 2004. 
    
    
     REFERENCE TO RELATED APPLICATION  
      This application claims priority to Korean Patent Application No. 2004-53312, filed on Jul. 9, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.  
     FIELD OF THE INVENTION  
      The present invention concerns a vacuum cleaner. More particularly, the present invention concerns an improved suction brush that adjusts to different characteristics of a cleaning surface, such as a carpet or floor, so as to enhance cleaning efficiency and accuracy.  
     BACKGROUND OF THE INVENTION  
      A vacuum cleaner generally draws in dust and contaminants on a cleaning surface using a suction force generated by the driving of a vacuum source disposed in a body of the vacuum cleaner. Referring to  FIG. 1 , the vacuum cleaner includes a cleaner body  10 , a suction brush  30 , and an extension path  20 . The cleaner body  10  accommodates a motor (not shown) generating the suction force, and the suction brush  30  is provided with an inlet  39  which faces the cleaning surface and through which dust is drawn. The dust drawn in through the suction brush  30  flows through the extension path  20  which leads to the cleaner body  10 .  
      The suction brush  30  includes an upper housing  34  and a lower housing  38  coupled by a plurality of bolts  40 . The inlet  39  is formed at the lower housing  38 , through which the dust is drawn in from the cleaning surface. The extension path  20  includes a connector  26  rotatably fit into the suction brush  30 , an extension pipe  24  that fits with the connector  26 , and a suction hose  22  that fits in the extension pipe  24  at one end and connects with the cleaner body  10  at the other end.  
      As structured and configured as above, the vacuum cleaner draws in dust and contaminants from the cleaning surface, such as a carpet or floor, while a user of the vacuum cleaner moves the suction brush  30  back and forth. However, when the suction brush  30  is moved backward, the rear end of the suction brush  30  is often lifted or spaced from the cleaning surface. With the rear end of the suction brush  30  spaced from the cleaning surface, the bottom of the lower housing  38  cannot closely contact the cleaning surface, thus bringing about loss of the suction force and deterioration of the cleaning accuracy. Also, when using the vacuum cleaner, the bottom of the lower housing  38  often directly contacts the cleaning surface, such as a floor, and thus scratches the floor.  
      In addition, since a plurality of bolts  40  are required to couple the upper housing  34  and the lower housing  38 , the manufacture costs are increased and productivity decreased due to the increased number of parts and required assembly.  
     SUMMARY OF THE INVENTION  
      To overcome the above disadvantages and problems of the conventional arrangement, there is provided an improved suction brush for a vacuum cleaner to enhance cleaning accuracy and cleaning efficiency by closely contacting a bottom plate with the cleaning surface during the cleaning operation.  
      Another aspect of the present invention provides an improved suction brush for a vacuum cleaner, which is capable of preventing a bottom plate from scratching the floor during the cleaning operation  
      Yet another aspect of the present invention provides a suction brush for a vacuum cleaner providing improved assembly without employing fastening members, such as bolts.  
      The foregoing objects are basically attained by a suction brush for a vacuum cleaner having a cover, and a bottom plate having a suction port through which dust is drawn in from a surface being cleaned by a suction force generated by a vacuum source disposed in a body of the vacuum cleaner. The bottom plate is rotatably disposed at the cover.  
      The suction brush further comprises an elastic member disposed between the bottom plate and the cover so as to elastically bias an end of the bottom plate in a predetermined direction.  
      The suction brush further comprises a bottom plate stopper disposed on at least one of the bottom plate and the cover to limit the rotation of the bottom plate. Accordingly, the bottom plate rotates within a predetermined angle.  
      The suction brush further comprises a bottom plate fixing unit disposed between the cover and the bottom plate to selectively fix the bottom plate to the cover. The bottom plate fixing unit has a foot switch rotatably disposed in the cover, an operation knob exposed to the outside through an opening in the cover, a first locking part, a brush plate rotatably disposed in the cover to rotate in association with the foot switch, and a second locking part to lock and unlock the brush plate with the first locking part in a complementary manner.  
      Consistent with the above aspect of the present invention, the suction brush for the vacuum cleaner has a cover, a bottom plate rotatably disposed at the cover, and a bottom plate fixing unit disposed between the cover and the bottom plate. The bottom plate fixing unit has a foot switch rotatably disposed in the cover and a brush plate rotatably disposed in the cover to rotate in association with the foot switch. The foot switch has an operation knob exposed to the outside so that the user can rotate the foot switch. A first locking part is formed on both ends of the foot switch. A second locking part is formed at the brush plate in correspondence with the first locking part. When the second locking part rotates in association with the rotation of the first locking part, the brush disposed at a front part of the brush plate protrudes with respect to the cover. An elastic member is interposed between the front part of the brush plate and the bottom plate so as to press together the front part of the brush plate and the bottom plate.  
      The user can select a rotation mode and a stationary mode of the bottom plate through the operation knob. If the user selects the rotation mode, the front end of the bottom plate is biased downwardly by the elastic member and the rear end is supported by the bottom plate stopper. When a rear side of the suction brush separates apart from the cleaning surface, the bottom plate rotates and closely contacts the cleaning surface due to the suction force between the cleaning surface and the bottom plate and the force applied on the suction brush by the user.  
      When the user selects the stationary mode and rotates the foot switch by using the operation knob, the first locking part presses downward onto the second locking part so as to rotate the brush plate downwardly. The brush at the front end of the brush plate protrudes downwardly from the bottom plate. Since the suction brush is supported by a wheel at the rear end and the brush, the cleaning is performed with a predetermined gap from the cleaning surface. Accordingly, the cleaning surface, such as a floor, is not scratched. In addition, as the brush plate rotates downward, the elastic member presses the front end of the bottom plate downwardly. Thus, the front end of the bottom plate is supported by the elastic member, and the bottom plate stopper at the rear end of the bottom plate is supported by the end of brush plate support ribs formed at the cover so that the bottom plate is fixed with respect to the cover.  
      The foot switch, the brush plate, and the bottom plate, respectively, have a rotary axis. The cover is provided with support ribs having an axis hole corresponding to the rotary axis. The rotary axis and the support ribs are sloped so that the rotary axis is smoothly inserted into the axis hole. As constructed above, the assembly of the suction brush is improved and the number of the parts is reduced without having to use additional fastening means, such as bolts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
      These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawing figures of which:  
       FIG. 1  is a perspective view of a conventional vacuum cleaner,  
       FIG. 2  is a perspective view of a suction brush of a vacuum cleaner according to an embodiment of the present invention, showing the suction brush assembled;  
       FIG. 3  is an exploded view of the suction brush of the vacuum cleaner illustrated in  FIG. 2 ;  
       FIGS. 4A and 4B  are partial elevational views, respectively, of the suction brush taken in section along the lines  4 A- 4 A and  4 B- 4 B of  FIG. 3 ;  
       FIG. 5  is a perspective view of the bottom plate of the suction brush illustrated in  FIG. 3 ;  
       FIG. 6  is an elevational view of the suction brush taken in section along the line VI-VI of  FIG. 3 ;  
       FIG. 7  is an elevational view of the suction brush taken in section along the line VII-VII of  FIG. 3 ;  
       FIGS. 8A and 8B  are side elevational views of the suction brush of the vacuum cleaner with a portion of the suction brush removed according to an embodiment of the present invention; and  
       FIGS. 9A and 9B  are side elevational views of the suction brush of the vacuum cleaner with a portion of the suction brush removed according to an embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION  
      Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the drawings.  
      Referring to  FIGS. 2 and 3 , a suction brush for a vacuum cleaner according an exemplary embodiment of the present invention includes a cover  100  forming a upper casing, a bottom plate  150  rotatably fixed under the cover  100 , a bottom plate fixing unit  300 , a wheel  418 , and a wheel shaft  420 . The bottom plate fixing unit  300  is rotatably disposed between the cover  100  and the bottom plate  150 . The unit  300  allows selection between rotating or fixating of the bottom plate  150  depending on the type of a cleaning surface, such as a carpet or a floor. The wheel  418  and the wheel shaft  420  are rotatably fixed to a rear end  102  of the cover  100 .  
      The cover  100  is provided with a first bottom plate rotary axis  152  for fixing the bottom plate  150  at the inner sidewalls of the cover  100 . Two second bottom plate support ribs  157  are provided with a second bottom plate axis hole  158  corresponding to a second bottom plate rotary axis  156  ( FIG. 5 ). The second bottom plate rotary axes  156  are positioned coaxially with respect to the first bottom plate rotary axis  152 . A suction duct  108  is formed between the second bottom plate support ribs  157 , and is in fluid communication with an extension pipe connector  500 . An opening  104  is formed at an upper side of the cover  100  for receiving an operation knob  314 . Four brush plate support ribs  384  are formed in the cover  100  for rotatably fixing a brush plate  350 . Each brush plate support rib  384  is provided with a brush plate axis hole  380  ( FIG. 4B ). Two foot switch support ribs  336  are formed in the front of the brush plate support rib  384  for rotatably fixing a foot switch  310  to the cover  100 . Each foot switch support rib  336  is provided with a foot switch axis hole  334  into which a foot switch rotary axis  330  is inserted, which will be described below. At the rear end of the cover  100 , a wheel receiving part  400  is formed for receiving the extension pipe connector  500  and the wheel  418 . The wheel receiving part  400  is provided with a wheel shaft hole  410  for a lateral insertion of the wheel shaft  420 . An axis hole (not shown) is formed at a front end of the extension pipe connector  500  corresponding to the wheel shaft hole  410 . The wheel shaft  420  penetrates through the axis hole and the wheel shaft hole  410  so that the extension pipe connector  500  and the wheel  418  are rotatably fixed at the cover  100 .  
      Both sidewalls of the bottom plate  150  are provided with a first bottom plate axis hole  154  corresponding to the first bottom rotary axis  152 . The first bottom plate axis hole  154  fits with the first bottom rotary axis  152  formed at the inner sidewall of the cover  100  so as to enable the bottom plate  150  to rotate with respect to the cover  100 . Accordingly, even when a rear side under the suction brush separates apart from the cleaning surface, the bottom plate  150  rotates with respect to the cover  100  in close contact with the clearing surface. At the bottom of the bottom plate  150  is formed a dust transfer channel  172  leading to a suction port  176 . A spacer  174  is disposed in front and in rear of the suction port  176  for keeping a space between the bottom plate  150  and the cleaning surface. A rubber lip mount part  160  ( FIG. 5 ) is formed at the rear end under the bottom plate  150  on which a rubber lip  168  is mounted for sweeping dust and contaminants not drawn in to the suction port  176  but passing to the rear end.  
      The bottom plate fixing unit  300  includes the foot switch  310  rotatably fixed at the cover  100  and the brush plate  350  mounted in the cover  100  and under the foot switch  310  for rotating in association with the foot switch  310 .  
      The foot switch  310  is provided with the operation knob  314  at one end. The operation knob  314  is exposed through the opening  104  formed on the cover  100  so that the user of the vacuum cleaner can control the foot switch  310  from the outside. A first foot switch stopper  324  is formed at a rear end of the operation knob  314  for limiting excessive rotation of the foot switch  310 . A first locking part  318  is formed at the other end of the foot switch  310  and extends downwardly from the operation knob  314 . The first locking part  318  is a rib extending downwardly from under the operation knob  314  at the other end of the foot switch  310 . Each end of the foot switch  310  is provided with a foot switch rotary axis  330 . The foot switch rotary axis  330  is inserted into the foot switch axis hole  334  of the cover  100  so that the foot switch  310  is rotatably fixed at the cover  100 . The foot switch rotary axis  330  has a slope S facilitating smooth insertion into the foot switch axis hole  334 . A second foot switch stopper  328  is formed at a center of the foot switch  310  to link both ends of the foot switch  310  and to restrain the foot switch  310  from rotating in the other direction. The second foot switch stopper  328  restrains the foot switch  310  from rotating in the other direction over a predetermined angle by contacting the suction duct  108  formed at the cover  100 .  
      Two brush plate rotary axes  376  are formed at the rear end of the brush plate  350 . The brush plate rotary axes  376  are inserted into the brush plate axis hole  380  ( FIG. 4B ) formed at the cover  100  so that the brush plate  350  is rotatably fixed at the cover  100 . A pair of second locking parts  358  are formed at the front of the brush plate rotary axes  376  and contact the first locking part  318 . An elastic member receiving part  210  is formed at the center of the front part of the brush plate  350  for receiving an elastic member  200 . The elastic member  200  is preferably a coil spring, but may be various elastic members with respective elasticities. The elastic member  200  is securely inserted into the elastic member receiving part  210  at one end, and is fixed at the front end of the bottom plate  150  at the other end so as to bias the bottom plate  150  in direction A. The front end of the brush plate  350  is provided with a brush mount part  368  for the mount of a brush  372 . The brush  372  is mounted at the front end of the brush plate  350  and vertically moves with respect to the cover  100  depending on the rotation of the brush plate  350 . The brush plate  350  rotates when the first locking part  318  presses and rotates the second locking part  358 .  
      Referring to  FIG. 3 , assembly of the suction brush is described according to an exemplary embodiment of the present invention. The foot switch  310  is fixed at the cover  100 . The operation knob  314  of the foot switch  310  is inserted into the opening  104 , and the foot switch rotary axis  330  is pressed and inserted into the foot switch axis hole  334  of the cover  100 . Then, the brush plate  350  is fixed at the cover  100 . The brush plate rotary axes  376  are pressed and inserted into the brush plate axis hole  380  ( FIG. 4B ) of the cover  100 . The pair of the second locking part  358  of the brush plate  350  contacts the first locking part  318  of the foot switch  310  with the brush plate  350  being fixed. The elastic member  200  is inserted into the elastic member receiving part  210  of the brush plate  350 . Finally, the bottom plate  150  is fixed at the cover  100 . The fixation of the bottom plate  150  is accomplished by pressing and inserting the first bottom plate axis hole  154  and the second bottom plate rotary axes  156  into the first bottom rotary axis  152  and the second bottom plate axis hole  158 , respectively. The elastic member  200  is pressed and contacts the front end of the bottom plate  150  with one end. Hence, the elastic member  200  biases the front end of the bottom plate  150  to rotate in the other direction B and the rear end of the bottom plate  150  is biased by a bottom plate stopper  164  ( FIG. 5 ). As structured and assembled, the bottom plate  150  maintains a level position with the cleaning surface.  
      Referring to  FIGS. 4A and 4B , the brush plate support ribs  384 , the foot switch support ribs  336 , the first bottom rotary axis  152 , and the second bottom plate support ribs  157  each have a slope S. The slope S facilitates the smooth insertion of the rotary axes  152 ,  156 ,  330 , and  376  into the corresponding axis holes  154 ,  158 ,  334 , and  380  while the bottom plate fixing unit  300  ( FIG. 3 ) is fixed at the cover  100 .  
      Referring to  FIG. 5 , the two second bottom plate rotary axes  156  correspond to the first bottom plate axis holes  154  on the same axis. The suction port  176  is formed between the second bottom plate rotary axes  156  by penetrating through the suction brush, through which dust is drawn in. The suction port  176  fluidly communicates with the suction duct  108  ( FIG. 3 ). The rear end of the bottom plate  150  is provided with the rubber lip mount part  160  protruding upward. Both ends of the rubber lip mount part  160  are provided with the bottom plate stopper  164  restraining the bottom plate  150  from rotating in the other direction B over a predetermined angle. Preferably, the rubber lip mount part  160  serves as the bottom plate stopper  164 , but it is possible to apply variations to such structure and configuration using a separate member as long as the function of the bottom plate stopper  164  is fulfilled. If the bottom plate  150  rotates to the other direction B over the predetermined angle, the bottom plate stopper  164  contacts the terminal end of the brush plate support ribs  384  formed at the rear end  102  of the cover  100  ( FIG. 3 ), and thus the bottom plate  150  is strained from rotating further to the other direction B.  
       FIG. 6  illustrates the foot switch  310  in association with the brush plate  350 . Referring to  FIG. 6 , the first locking part  318  rotates within a predetermined range by the operation knob  314  and between first and second positions P 1  and P 2 . The first position P 1  refers to a position of the first locking part  318  when the foot switch  310  is restrained from further rotation in one direction C. The foot switch  310  is restricted from rotating further in one direction C because the second foot switch stopper  328  ( FIG. 3 ) contacts the suction duct  108 . The second position P 2  refers to a position of the first locking part  318  when the foot switch  310  is restrained from further rotation in the other direction D. The foot switch  310  is restrained from rotating further to the other direction D because the first foot switch stopper  324  contacts the cover  100 . The second locking part  358  includes a first contact part  360  contacting the first locking part  318  when the first locking part is at the first position P 1 , and a second contact part  362  contacting the first locking part  318  when the first locking part  318  is at the second position P 2 . The second contact part  362  is above the first contact part  360  so that the end of the first locking part  318 , which is in contact with the first contact part  360 , contacts the second contact part  362  when the first locking part  318  moves from the first position P 1  to the second position P 2 . The first locking part  318  presses downward onto the second locking part  358  so that the brush plate  350  rotates downwardly around the brush plate rotary axes  376 .  
       FIG. 7  illustrates the wheel shaft  420  fixed at the cover  100 . Referring to  FIG. 7 , one side of the wheel shaft  420  is provided with a locking projection  424  on the outer circumstance of the wheel shaft  420 . A locking recess  414  is formed at an inner side of the wheel shaft hole  410  of the rear end of the cover  100  in correspondence with the locking projection  424 . As shaped and configured above, the extension pipe connector  500  is inserted into the rear end of the cover  100  and the wheel  418  is fixed in the wheel receiving part  400 . Then, the wheel shaft  420  is inserted into the wheel shaft hole  410  formed at the cover  100  and the extension pipe connector  500  ( FIG. 3 ), thus rotatably fixing the extension pipe connector  500  and the wheels  418  at the cover  100 . The locking projection  424  of the wheel shaft  420  is coupled to the locking recess  414  of the wheel shaft hole  410  of the cover  100 . With this simple locking structure, the wheel  418  and the extension pipe connector  500  are rotatably connected to the suction brush. Thus, the assembly of the suction brush is improved and the number of the parts is reduced.  
      As seen in  FIGS. 8A and 8B , the bottom plate  150  rotates in the rotation mode or is fixed in the stationary mode with respect to the cover  100 . While cleaning on the cleaning surface, such as a carpet, a user operates the vacuum cleaner in the rotation mode because the bottom plate  150  is not in close contact with the cleaning surface since the rear end of the suction brush is spaced from the cleaning surface. Accordingly, the user selects the rotation mode to obtain the close contact of the bottom plate  150  with the cleaning surface. The bottom plate  150  rotates with respect to the cover  100  in the rotation mode even if the rear end of the suction brush is spaced from the cleaning surface. In contrast, the cleaning surface, such as a floor, may be scratched due to direct contact with the bottom plate  150 . In order to maintain a proper gap between the bottom plate  150  and the cleaning surface to avoid scratching, the user operates the vacuum cleaner in the stationary mode with the brush  372  extending downwardly from the front end of the suction brush and with the front end of the suction brush being against the cleaning surface and the rear end of the suction brush being supported by the wheel  418 .  
       FIG. 8A  illustrates the rotation mode of the bottom plate  150  with respect to the cover  100 , and the  FIG. 8B  illustrates the stationary mode. Referring to  FIG. 8A , the second foot switch stopper  328  ( FIG. 3 ) is biased by the suction duct  108  ( FIG. 3 ) and restrained from rotating to the other direction C ( FIG. 6 ). The first locking part  318  at the both ends of the foot switch  310  contacts the first contact part  360  of the second locking part  358  formed at the both sides of the brush plate  350 . The front end of the bottom plate  150  is biased downwardly by the elastic member  200  and the rear end is supported because contact of the bottom plate stopper  164  with the terminal end of the brush plate support ribs  384 . The front end of the brush plate  350  is biased upwardly by the elastic member  200  and the rear end is supported since the first contact part  360  of the second locking part  358  is supported by the first locking part  318 .  
      When operating the vacuum cleaner in the rotation mode over the cleaning surface such as a floor, the user presses the rear end of the operation knob  314  and changes to the stationary mode. Still referring to  FIGS. 8A and 8B , the first locking part  318  formed at the one end of the foot switch  310  and under the operation knob  314  rotates downward around the foot switch rotary axis  330 . The first locking part  318  presses the second locking part  358  while moving from the first contact part  360  of the second locking part  358  to the second contact part  362 . Thus, the brush plate  350  rotates downward around the brush plate rotary axes  376  so that the brush  372  moves and protrudes downward from under the bottom plate  150 . The elastic member  200 , which is disposed at the front end of the brush plate  350  and biases the brush plate  350  upwardly, is compressed due to the moment transferred from the first locking part  318 . With the elastic member  200  compressed, the front end of the bottom plate  150  receives a larger recovery force facing downward at the rotation mode. Accordingly, the bottom plate  150  becomes stationary since the front end is biased by the compressed elastic member  200  with greater recovery force than the rotation mode, and the rear end is fixed since the bottom plate stopper  164  is supported by the terminal end of the brush plate support ribs  384 . As a result, scratching of the floor is prevented in the stationary mode by the bottom plate  150 .  
       FIGS. 9A and 9B  are views of the bottom plate  150  rotating in the rotation mode.  FIG. 9A  illustrates that the rear end of the suction brush in complete contact with the cleaning surface. The bottom plate  150  is biased downward by the elastic member  200  at the front end, and is supported at the rear end by the bottom plate stopper  164  contacting the terminal end of the brush plate support ribs  384 . Thus, the bottom plate  150  is level with the cleaning surface.  
       FIG. 9B  illustrates that the rear end of the suction brush is spaced from the cleaning surface due to the rotation of the suction brush to a certain angle θ. The force applied on the suction brush by the user is transferred to the elastic member  200  via the cover  100 , the foot switch  310 , and the brush plate  350 . Such a force is applied in a direction of compressing the elastic member  200  downwardly. A force of the bottom plate  150  adhering to the cleaning surface by the suction force results in a moment in a clockwise direction around the rotary axes  152  and  156 . Such a moment compresses upward the elastic member  200  biased against the front end of the bottom plate  150 . Therefore, the force of the bottom plate  150  compressing the elastic member  200  upward is greater than the force of compressing the elastic member  200  downward so that the bottom plate  150  rotates in the clockwise direction and remains level with the cleaning surface. Even when the rear end of the suction brush separates from the cleaning surface due to the difference between the force direction caused by the user on the suction brush and the movement direction of the suction brush, the bottom plate  150  can maintain close contact with the cleaning surface, thus enhancing the cleaning efficiency.  
      When the rear end of the suction brush returns to its original position after being separated from the cleaning surface, the bottom plate  150  rotates in a counterclockwise direction by the elastic member  200  compressing downward on the front end of the bottom plate  150 . The bottom plate  150  rotates until the bottom plate stopper  164  contacts the terminal end of the brush plate support ribs  384 , to thus return to its original position, as shown in  FIG. 9A .  
      In light of the forgoing, even if the rear end of the suction brush is apart from the cleaning surface, the close contact with the cleaning surface is maintained, thus enhancing the cleaning efficiency. When cleaning over the cleaning surface, such as the floor, the user changes to the stationary mode. Then, a proper gap is maintained between the cleaning surface and the bottom plate  150 , to avoid scratching the cleaning surface. This is because the brush  372  moves and protrudes downward from the bottom plate  150  and supports the front end of the suction brush, and the rear end is supported by the wheel  418 .  
      Accordingly, the assembly of the parts of the suction brush improves without requiring a fastening means such as bolts because each rotary axis and each axis hole is provided with the corresponding slopes. In addition, the absence of the fastening means reduces the number of required parts.  
      While the exemplary embodiments of the present invention have been described, additional variations and modifications of the embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims shall be construed to include both the above embodiments and all such variations and modifications that fall within the spirit and scope of the invention.