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BACKGROUND 
     The present disclosure relates to a device for fastening a toilet seat. 
     DISCUSSION OF THE RELATED ART 
     A toilet seat generally comprises a seat and a lid which are hingedly assembled on a bowl. The back portion of the toilet seat may be fastened to the bowl by bolts having their nuts generally located under the seating portion. A disadvantage is that the fitting and the removal of the toilet seat, particularly for the maintenance thereof, requires unscrewing and screwing the bolts, which may be uneasily accessible, the bowl being generally placed in a narrow room. Another disadvantage is that the fitting and the removal of the toilet seat for maintenance requires manipulating the bolt and the back portion of the toilet seat, which may be relatively uncleaned parts due to their location. 
     There exist toilet seats where the seat and the lid of the toilet seat are pivotally mounted on a fastening device which is fastened on two pins attached to the toilet bowl by a locking device which may be released by pressing on a button located at the back or at the front of the toilet seat. A disadvantage is that the fitting and the removal of the toilet seat for the maintenance thereof generally requires manipulating the back portion of the toilet seat. According to a variation, a protrusion may be provided at the back of the seat to press on the unlock button when the seat is up. A disadvantage then is that the unlock button is actuated each time the seat is put up, which may cause an incidental unwanted removal of the toilet seat. 
     There exist toilet seats where the toilet seat comprises, at its back portion, a magnet which cooperates with a magnet provided on the bowl to fasten the toilet seat to the bowl. A disadvantage is that, to provide a good fastening of the toilet seat to the bowl, the attractive force of the magnets used should be relatively significant, whereby removing the toilet seat may require applying a significant force. 
     It would be desirable to be able to simply fit and/or remove a toilet seat, particularly for the maintenance thereof, with no excessive effort and without having to manipulate the back portion of the toilet seat. 
     SUMMARY 
     An object of an embodiment aims at overcoming all or part of the disadvantages of previously-described toilet seat fastening devices. 
     Another object of an embodiment is for the toilet seat to be able to be fitted or removed, particularly for the maintenance thereof, with no manipulation of the back portion of the toilet seat. 
     Another object of an embodiment is for the user to be able to simply and rapidly fit and remove the toilet seat, particularly for the maintenance thereof. 
     Another object of an embodiment is for the toilet seat to be able to be fitted or removed, particularly for the maintenance thereof, with no excessive effort. 
     Thus, an embodiment provides a device for fastening a toilet seat to at least one first elements fastened to a toilet bowl, comprising a first locking part and wherein, for each back and forth motion of the fastening device relative to the bowl, the locking part is capable of alternately displacing between a first position where the first locking part cooperates with the first element and a second position where the fastening device can be separated from the first element. 
     According to an embodiment, the device comprises a support, a first arm hinged with respect to the support and stressed at a first end by a spring and intended to be stressed by the first element at a second end, the first arm cooperating with a first cam hinged with respect to the support and capable of allowing the pivoting of the first hinged locking part relative to the support, for each back and forth motion of the fastening device relative to the bowl, alternately between a first position where the first locking part partly penetrates into a first groove of the first element and a second position where the first locking part does not penetrate into the first groove. 
     According to an embodiment, the first arm is hinged with respect to the support around a first axis and the first cam and the first locking part are hinged with respect to the support around a second axis different from the first axis. 
     According to an embodiment, the first cam comprises a first groove following a closed curve. 
     According to an embodiment, the device comprises a first finger attached to the first arm and penetrating into the first groove. 
     According to an embodiment, the second axis is outside of the first curve. 
     According to an embodiment, the first locking part comprises first stressing means capable of having the first locking part pivot against the first element. 
     According to an embodiment, the first stressing means comprise a first flexible tab. 
     According to an embodiment, the device comprises a second arm hinged with respect to the support and stressed at a third end by the spring and intended to be stressed by a second element of the bowl at a fourth end, the second arm cooperating with a second cam hinged with respect to the support and capable of allowing the pivoting of a second locking part hinged with respect to the support, for each back and forth motion of the fastening device relative to the bowl, alternately between a third position where the second locking part partly penetrates into a second groove of the second element and a fourth position where the second locking part does not penetrate into the second groove. 
     According to an embodiment, the first arm comprises a first toothed portion and the second arm comprises a second toothed portion, the first toothed portion meshing with the second toothed portion. 
     According to an embodiment, the second arm is hinged with respect to the support around a third axis and the second cam and the second locking part are hinged with respect to the support around a fourth axis different from the third axis. 
     According to an embodiment, the second cam comprises a second groove following a second closed curve. 
     According to an embodiment, the device comprises a second finger fastened to the second arm and penetrating into the second groove. 
     According to an embodiment, the fourth axis is outside of the second curve. 
     According to an embodiment, the second locking part comprises second stressing means capable of pivoting the second locking part against the second element. 
     An embodiment also provides a toilet comprising a bowl and a toilet seat, and a device, such as previously defined, for fastening the toilet seat to at least one first element fastened to the bowl. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings, among which: 
         FIG. 1  is a perspective view of an embodiment of a toilet; 
         FIG. 2  is a cross-section view of an embodiment of a device for fastening a toilet seat to a toilet bowl; 
         FIGS. 3 and 4  are front views of parts of the embodiment of the fastening device of  FIG. 2 ; 
         FIGS. 5A and 5B  are front views of each side of another part of the embodiment of the fastening device of  FIG. 2 ; 
         FIGS. 6A and 6B  are front views of each side of another part of the embodiment of the fastening device of  FIG. 2 ; 
         FIGS. 7A to 7E  are cross-section views of the embodiment of the fastening device of  FIG. 2  at successive steps during an operation of removing the toilet seat from a toilet bowl; and 
         FIGS. 8A to 8D  are cross-section views of the embodiment of the fastening device of  FIG. 2  at successive steps during an operation of fitting the toilet seat to a toilet bowl. 
     
    
    
     DETAILED DESCRIPTION 
     For clarity, the same elements have been designated with the same reference numerals in the various drawings and, further, the various drawings are not to scale. In the following description, expressions “substantially”, “around”, and “approximately” mean “to within 10%”. Further, adjectives “front”, “back”, “lower” and “upper” are used with respect to the usual orientation of a toilet. 
       FIG. 1  shows an embodiment of a toilet  10  comprising a bowl  12  having an internal cavity  13  and an edge forming a seating portion  14 . A toilet seat  15  is fastened to bowl  12 . Toilet seat  15  comprises a seat  16 , for example, made of a plastic material, pivotally assembled with respect to bowl  12  at the level of a fastening device  18  fastened to the back portion of bowl  12  so that seat  16  covers seating portion  14  when it is put down on bowl  12 . A lid  20 , for example, made of a plastic material, is also pivotally assembled with respect to fastening device  18  so that lid  20  covers seat  16  when it is put down on bowl  12 . When seat  16  and lid  20  are put down on bowl  12 , they close internal cavity  13  of bowl  12 . 
       FIG. 2  is a cross-section view of an embodiment of fastening device  18  in closed position. The cross-section plane is a vertical plane perpendicular to the horizontal direction oriented from front to back of toilet  10 . In  FIG. 2 , seat  16  and lid  20  are not shown. 
     Fastening device  18  comprises a cylindrical tube  24  containing a locking device  26  having an axial symmetry relative to a vertical axis C. In the following description, the elements which are symmetrical with respect to axis C are designated with the same reference numeral followed by letter “A” when the element is totally or mainly located to the left of axis C in  FIG. 2 , and followed by letter “B” when the element is totally or mainly located to the right of axis C in  FIG. 2 . 
     Fastening device  18  is fastened to two elements  28 A,  28 B, for example, pins, attached to the bowl, not shown. The spacing between pins  28 A and  28 B is for example in the range from 10 cm to 25 cm. The diameter of tube  24  is a few centimeters, for example, from 2 cm to 3 cm. Locking device  26  comprises a support  29  fastened to the internal wall of tube  24 . Locking device  26  further comprises two arms  30 A,  30 B. Each arm  30 A,  30 B is mounted so as to pivot with respect to support  29  around an axis DA, DB, which is for example horizontal. Arms  30 A,  30 B are stressed by a spring  32 , for example, a helical spring, having one end maintained on a base  34  forming part of support  29 . A finger is fastened to each arm  30 A,  30 B, only finger  36 A being shown in  FIG. 2 . Each finger  36 A cooperates with a cam  38 A,  38 B mounted so as to pivot with respect to support  29  around an axis EA, EB, which is, for example, horizontal. Each cam  38 A,  38 B may pivot a locking part  40 A,  40 B, mounted so as to pivot with respect to support  29  around axis EA, EB. 
       FIG. 3  shows pin  28 A. Each pin  28 A,  28 B comprises a base  42 A,  42 B resting on the bowl, a cylindrical body  44 A,  44 B extending along an axis parallel to axis C from base  42 A,  42 B and extending in a tapered end portion  46 A,  46 B. In locked position, each cylindrical body  44 A,  44 B penetrates into an opening  45 A,  45 B provided in tube  24 . A groove  47 A,  47 B is made in cylindrical body  44 A,  44 B at the junction between cylindrical body  44 A,  44 B and end portion  46 A,  46 B. 
       FIG. 4  shows arm  30 A. Each arm  30 A,  30 B comprises an end  48 A,  48 B capable of bearing against end portion  46 A,  46 B of pin  28 A,  28 B when fastening device  18  is in locked position. Each arm  30 A,  30 B comprises a toothed wheel sector  50 A,  50 B at the end opposite with respect to axis DA to end  48 A,  48 B comprising teeth  52 A,  52 B on two rows. Toothed wheel sector  50 A of arm  30 A permanently meshes with toothed wheel sector  50 B or arm  30 B, so that arms  30 A,  30 B simultaneously pivot around axes DA, DB, the clockwise or counterclockwise pivoting direction of arm  30 A being opposite to the pivoting direction of arm  30 B and the inclination angles of arms  30 A,  30 B permanently being, in absolute value, substantially identical. Each arm  30 A,  30 B comprises a portion  54 A,  54 B having one end of spring  32  pressing against it. Finger  36 A is fastened to arm  30 A,  30 B between axis DA, DB and end  48 A,  48 B. 
       FIGS. 5A and 5B  show the two sides of cam  38 A. Each cam  38 A,  38 B comprises a guiding portion  55 A,  55 B comprising a groove  56 A having a finger  36 A capable of moving therein, only groove  56 A of cam  38 A being visible in the drawings. Groove  56 A follows a closed curve which successively comprises, in  FIG. 5A  in the counterclockwise direction, a first limiting upper position  58 A, a limiting outer position  60 A, a limiting lower position  62 A, a limiting inner position  64 A, a second limiting upper position  66 A, and a locking position  68 A. Guiding portion  55 A,  55 B is connected to a portion forming a pivot  70 A,  70 B by two connection portions  72 A,  72 B. Pivot-forming portion  70 A,  70 B comprises a cylindrical opening  71 A,  71 B of axis EA, EB. Rotation axis EA, EB of each cam  38 A,  38 B is located outside of groove  56 A. Pivot-forming portion  70 A,  70 B comprises a pin  74 A,  74 B. Each cam  38 A,  38 B comprises a flexible tab  76 A,  76 B for example extending from pivot-forming portion  70 A,  70 B and ending in a convex portion  78 A,  78 B which rubs against support  28  when cam  38 A,  38 B pivots around axis EA, EB. 
       FIGS. 6A and 6B  show the two sides of locking part  40 A. Each locking part  40 A,  40 B comprises a pivot-forming portion  80 A,  80 B pivotally assembled with respect to support  29  around axis EA, EB. Pivot-forming portion  80 A,  80 B comprises a cylindrical portion  81 A,  81 B having cylindrical opening  71 A,  71 B of each associated cam  38 A,  38 B assembled thereto. Pivot-forming portion  80 A,  80 B extends in a head  82 A,  82 B. A recess  84 A,  84 B forming a stop is provided on one of the sides of head  82 A,  82 B. A flexible tab  86 A,  86 B extends from pivot-forming portion  80 A,  80 B. 
     Arms  30 A,  30 B and cams  38 A,  38 B may be made of polyamide. Fingers  36 A may be made of stainless steel. Locking parts  40 A,  40 B may be made of polyacetal. 
       FIG. 2  shows fastening device  18  in a locked position. In this position, finger  36 A maintained by each arm  30 A,  30 B is in the locking position  68 A of groove  56 A. Locking part  40 A,  40 B is maintained under the action of flexible tab  86 A,  86 B against pin  28 A,  28 B, head  82 A,  82 B of locking part  40 A,  40 B penetrating into notch  47 A,  47 B of pin  28 A,  28 B. 
       FIGS. 7A to 7E  are views similar to  FIG. 2  of the embodiment of locking device  18  at successive steps during a toilet seat removal operation. Only the rotating motions of arm  30 A, of cam  38 A, and of locking part  40 A are described, the rotating motions of arm  30 B, of cam  38 B, and of locking part  40 B being symmetrical with respect to axis C. Head  82 A,  82 B and groove  47 A,  47 B of pin  28 A,  28 B are shaped so that, while head  82 A,  82 B penetrates into groove  47 A,  47 B of pin  28 A,  28 B, head  82 A,  82 B remains locked in groove  47 A,  47 B in the case where tube  24  is removed from the bowl. Locking device  18  thus remains locked on pins  28 A,  28 B when only a traction is exerted on the toilet seat in vertical position. 
       FIG. 7A  shows locking device  18  after a user has, with respect to the locked position shown in  FIG. 2 , displaced tube  24  with respect to the seating portion downwards along direction C, tube  24  substantially coming into contact with bases  42 A,  42 B of pins  28 A,  28 B. This may be obtained by putting up the seat and the lid vertically and by exerting a pressure on the front portion of the seat and of the lid downwards along direction C. Head  82 A and groove  47 A of pin  28 A are shaped so that, when head  82 A penetrates into groove  47 A of pin  28 A, the efforts exerted by pin  28 A on head  82 A, when tube  24  is brought closer to the seating portion, cause the clockwise pivoting of locking part  40 A around axis EA in  FIG. 7A  until head  82 A comes out of groove  72 A. Once head  82 A has come out of groove  47 A, it keeps on sliding along cylindrical body  44 A of pin  28 A. Moreover, when tube  24  is brought closer to the seating portion, pins  28 A,  28 B exert a pressure on ends  48 A,  48 B of arms  30 A,  30 B. This causes a pivoting of arms  30 A,  30 B around axes DA and DB and compressing of spring  32 . Arm  30 A pivots clockwise in  FIG. 7A . Finger  36 A displaces in groove  56 A of cam  38 A,  38 B from locking position  68 A to the first limiting upper position  58 A. This translates in  FIG. 7A  by a clockwise pivoting of cam  38 A around axis EA. The pivoting of locking part  40 A causes the deformation of flexible tab  86 A against tube  24 . For simplification, in  FIGS. 7A, 7B, and 7C , deformed flexible tabs  86 A,  86 B are shown as crossing tube  24 . 
     As a variation, the removal of head  82 A from groove  47 A may be obtained by the pivoting of cam  38 A, which may cause a clockwise pivoting of locking part  40 A around axis EA in  FIG. 7A  to disengage head  82 A from groove  47 A, by the pressing of pin  74 A against stop  84 A of locking part  40 A. 
       FIG. 7B  shows locking device  18  after the user has, with respect to the position shown in  FIG. 7A , started taking tube  24  away from the seating portion by displacing it upwards along direction C. This may be obtained by exerting a traction on the front part of the seat and of the lid, in vertical position, upwards along direction C. As a variation, the action of spring  32  may be such that the user does not have to or only slightly has to pull on the toilet seat. Under the action of spring  32 , arm  30 A has pivoted around axis DA in the counterclockwise direction in  FIG. 7B . Finger  36 A displaces in groove  56 A of cam  38 A from limiting upper position  58 A to a position closer to limiting outer position  60 A. Groove  56 A substantially follows, between limiting upper position  58 A and limiting outer position  60 A, an arc of a circle of axis DA. This translates in  FIG. 7B  as a maintaining substantially in angular position of cam  38 A around axis EA and also of locking part  40 A under the action of pin  74 A of cam  38 A bearing against stop  84 A of locking part  40 A. Head  82 A of locking part  40 A thus does not penetrate into groove  47 A of pin  28 A when, due to the relative displacement between pin  28 A and locking part  40 A, head  82 A is located opposite groove  47 A as shown in  FIG. 7B . 
       FIG. 7C  shows locking device  18  after the user has, with respect to the position shown in  FIG. 7B , continued taking tube  24  away from the seating portion by displacing it upwards along direction C. Under the action of spring  32 , arm  30 A has pivoted around axis DA in the counterclockwise direction in  FIG. 7C . Finger  36 A displaces in groove  56 A of cam  38 A all the way to limiting outer position  60 A. This translates in  FIG. 7C  as a maintaining substantially in angular position of cam  38 A and also of locking part  40 A under the action of pin  74 A of cam  38 A bearing against stop  84 A of locking part  40 A. 
       FIG. 7D  shows locking device  18  after the user has, with respect to the position shown in  FIG. 7C , continued taking tube  24  away from the seating portion by displacing it upwards along direction C. Under the action of spring  32 , arm  30 A has pivoted around axis DA in the counterclockwise direction in  FIG. 7D . Finger  36 A displaces in groove  56 A of cam  38 A all the way to limiting lower position  62 A. This translates in  FIG. 7D  by a counterclockwise pivoting of cam  38 A around axis EA. Under the action of flexible tab  86 A, a counterclockwise pivoting of locking part  40 A around axis EA maintaining it stopped against pin  74 A of cam  38 A is obtained. Head  82 A,  82 B being located at the level of end portion  46 A,  46 B of pin  28 A, head  82 A,  82 B does not oppose the displacement of pin  28 A. 
       FIG. 7E  shows locking device  18  after the user has, with respect to the position shown in  FIG. 7D , kept on taking tube  24  away from the seating portion by displacing it upwards along direction C. Pins  28 A,  28 B have been totally removed from tube  24 . The toilet seat is then no longer fastened to the seating portion. 
       FIGS. 8A to 8D  are views similar to  FIG. 2  of the embodiment of locking device  18  at successive steps during a toilet seat fitting operation. Only the rotating motions of arm  30 A, of cam  38 A, and of locking part  40 A are described, the rotating motions of arm  30 B, of cam  38 B, and of locking part  40 B being symmetrical with respect to axis C. 
     When the toilet seat is not connected to the seating portion, fastening device  18  is in the configuration shown in  FIG. 7E . 
       FIG. 8A  shows locking device  18  after the user has introduced end portions  46 A,  46 B of pins  28 A,  28 B into openings  45 A,  45 B of tube  24  and has started bringing tube  24  closer to the seating portion by displacing it downwards along direction C. This may be obtained by exerting a downward pressure on the front part of the seat and of the lid, in vertical position, along direction C.  FIG. 8A  shows the time when end portions  46 A,  46 B of pins  28 A,  28 B come into contact with ends  48 A,  48 B of arms  30 A,  30 B. 
       FIG. 8B  shows locking device  18  after the user has, with respect to the position shown in  FIG. 8A , continued bringing tube  24  closer to the seating portion by displacing it downwards along direction C. When tube  24  is brought closer to the seating portion, pins  28 A,  28 B exert a pressure on ends  48 A,  48 B of arms  30 A,  30 B. This causes a pivoting of arms  30 A,  30 B around axes DA and DB and a compressing of spring  32 . Arm  30 A pivots clockwise in  FIG. 8B . Finger  36 A displaces in groove  56 A of cam  38 A from limiting lower position  62 A to first limiting lower position  64 A. This translates in  FIG. 8B  as a counterclockwise pivoting of cam  38 A around axis EA. The sliding of head  82 A on end portion  46 A of pin  28 A causes a clockwise pivoting of locking part  40 A around axis EA in  FIG. 8B . The pivoting of locking part  40 A causes the deformation of flexible tab  86 A against tube  24 . For simplification, in  FIGS. 8B, 8C, and 8D , deformed flexible tabs  86 A,  86 B are shown as crossing tube  24 . 
       FIG. 8C  shows locking device  18  after the user has, with respect to the locked position shown in  FIG. 8B , continued bringing tube  24  closer to the seating portion by displacing it downwards along direction C, tube  24  substantially coming into contact with bases  42 A,  42 B of pins  28 A,  28 B. During the relative displacement between pin  28 A and locking part  40 A, head  82 A penetrates into groove  47 A, comes out of groove  47 A, and then continues sliding along cylindrical body  44 A of pin  28 A. Further, under the action of pin  28 A on end  48 A of arm  30 A, arm  30 A has pivoted clockwise around axis DA in  FIG. 8C , further compressing spring  32 . Finger  36 A displaces in groove  56 A of cam  38 A all the way to the second limiting upper position  66 A. This causes a clockwise pivoting of cam  38 A. 
     As a variation, the shape of groove  56 A may be adapted so that cam  38 A is in a position which enables to prevent head  82 A of locking part  40 A from penetrating into groove  47 A of pin  28 A, due to the pressing of pin  74 A,  74 B of cam  38 A,  38 B against stop  84 A,  84 B of locking part  40 A,  40 B, during the relative displacement of pin  28 A relative to tube  24 . 
       FIG. 8D  shows locking device  18  after the user has, with respect to the position shown in  FIG. 8C , started taking tube  24  away from the seating portion by displacing it upwards along direction C. This may be obtained by exerting a traction on the front part of the seat and of the lid, in vertical position, upwards along direction C. Under the action of spring  32 , arm  30 A has pivoted around axis DA in the counterclockwise direction in  FIG. 8D . Finger  36 A displaces in groove  56 A of cam  38 A from second limiting upper position  66 A to locking position  68 A. This translates in  FIG. 8D  as a clockwise pivoting of cam  38 A around axis EA. Under the action of flexible tab  86 A, a counterclockwise pivoting of locking part  40 A around axis EA is obtained, which makes head  82 A penetrate into groove  47 A of pin  28 A, pin  74 A allowing the pivoting of locking part  40 A. Fastening device  18  is then locked on pins  28 A,  28 B. As a variation, the action of spring  32  may be such that the user does not have to or only slightly has to pull on the toilet seat. 
     During a removal or fitting operation, convex portion  78 A,  78 B of flexible tab  76 A,  76 B of each cam  38 A,  38 B continuously rubs against support  29 . Thereby, each cam  38 A,  38 B remains substantially motionless and does not tilt under its own weight, for example, when finger  36 A supported by each arm  30 A,  30 B is in limiting lower position  62 A. 
     Specific embodiments have been described. Various alterations, modifications, and improvements will readily occur to those skilled in the art. In particular, flexible tabs  86 A,  86 B may be replaced with helical springs.

Summary:
A device for fastening a toilet seat to at least one first element of a toilet bowl, including a first locking part and wherein, for each back and forth motion of the fastening device relative to the bowl, the locking part is capable of alternately displacing between a first position where the first locking part cooperates with the first element and a second position where the fastening device may be separated from the first element.