mower ( 1 ) shown in fig1 to 4 is intended to be hitched to a front hitch ( 2 ) of a tractor ( 3 ). it comprises , first of all , a first chassis ( 4 ) which is provided with a hitching device ( 5 ), by which it is hitched to said hitch ( 2 ). first chassis ( 4 ) is also provided with a body ( 6 ) which extends toward the front , considering the direction of work defined by arrow ( 7 ). at the front part of body ( 6 ) are connected an upper connecting rod ( 8 ) by means of a joint ( 9 ) and two lower connecting rods ( 10 ) by means of a respective joint ( 11 ). joint ( 9 ), by which the upper connecting rod ( 8 ) is connected to body ( 6 ) of first chassis ( 4 ), is a cylindrical joint whose geometric axis extends at least approximately horizontally and at least approximately perpendicular to the direction of work defined by arrow ( 7 ). joints ( 11 ) on the other hand , by which lower connecting rods ( 10 ) are connected to body ( 6 ) of first chassis ( 4 ), are advantageously spherical joints . said connecting rods ( 8 , 10 ) extend from first chassis ( 4 ) backward , considering the direction of work defined by arrow ( 7 ), and downward . at their respective back end , they are connected by means of joints ( 12 ), respectively ( 13 ), to a second chassis ( 14 ) which supports work elements ( 15 ). these joints ( 12 , 13 ) are also advantageously spherical joints . joints ( 9 , 11 , 12 , 13 ) are placed so that connecting rods ( 8 , 10 ) form at least approximately a parallelogram deformable in an upward direction . thanks to this connection , second chassis ( 14 ) and work elements ( 15 ) that it supports can follow in an optimal way the contours of ground ( 16 ) on which second chassis ( 14 ) is brought to slide during work . actually , the deformable parallelogram formed by connecting rods ( 8 , 10 ) makes it possible for second chassis ( 14 ) and for work elements ( 15 ) that it supports to rise and fall . moreover , it should be noted that the clearing of bumps and depressions is facilitated by the fact that said parallelogram is drawn during work . spherical joints ( 11 , 12 , 13 ) then impart to second chassis ( 14 ) and to work elements ( 15 ) that it supports , a certain mobility around a geometric axis extending at least approximately parallel to the direction of work defined by arrow ( 7 ). cylindrical joint ( 9 ), finally , is intended to absorb the lateral forces generated in a curve . in this way , second chassis ( 14 ) and work elements ( 15 ) that it supports are prevented from being displaced laterally in relation to first chassis ( 4 ) when tractor ( 3 ) negotiates a curve . second chassis ( 14 ) which supports work elements ( 15 ), is , according to the invention , composed of two structures , a first structure ( 17 ) supporting work elements ( 15 ) and a second structure ( 18 ) to which connecting rods ( 8 , 10 ) are connected . second structure ( 18 ) comprises a sleeve ( 19 ) which extends at least approximately horizontally and at least approximately perpendicular to the direction of work defined by arrow ( 7 ) and which serves as a bearing for a pin ( 20 ) defining a joint ( 21 ) with a geometric axis directed at least approximately horizontally and at least approximately perpendicular to said direction of work . second structure ( 18 ) comprises , moreover , two parallel plates ( 22 ) extending at least approximately vertically and between whose upper ends the back end of upper connecting rod ( 8 ) extends which is connected there by means of joint ( 12 ). the two plates ( 22 ) are rigidly connected to sleeve ( 19 ) and are made rigid by means of a gusset ( 23 ). at their front part , the two plates ( 22 ) are rigidly connected to one another by means of an angle iron ( 24 ) extending perpendicular to the direction of work and one ( 25 ) of whose legs extends horizontally and the other ( 26 ) vertically . second structure ( 18 ) also comprises a pin ( 27 ) extending at least approximately parallel to the direction of work . this pin ( 27 ) is fastened at its back end to sleeve ( 19 ) and goes through the vertical leg ( 26 ) of angle iron ( 24 ) to which it is fastened so that the front end of said pin ( 27 ) extends toward the front beyond said vertical leg ( 26 ). second structure ( 18 ) also comprises a fastening plate ( 28 ) that is horizontal and , considering the direction of work , extends behind sleeve ( 19 ). this fastening plate ( 28 ) is rigidly connected to said sleeve ( 19 ), and to plates ( 22 ). it is used to fasten a first housing ( 29 ), whose function will be described later , to second structure ( 18 ). as said above , sleeve ( 19 ) serves as a bearing for pin ( 20 ). in fig1 it is seen very clearly that the two ends of this pin ( 20 ) come out of sleeve ( 19 ). each of these ends goes through , respectively , first leg ( 30 ) of a clevis ( 31 ), the back end of a lower connecting rod ( 10 ) and second leg ( 32 ) of said clevis ( 31 ) which is fastened to first structure ( 17 ) of second chassis ( 14 ). in this way , first structure ( 17 ) is connected to second structure ( 18 ) by joint ( 21 ) formed by the two clevises ( 31 ) and pin ( 20 ). the ends of this pin ( 20 ) form , in addition , part of joint ( 13 ) by means of which lower connecting rods ( 10 ) are connected to second structure ( 18 ) of second chassis ( 14 ). first structure ( 17 ) of second chassis ( 14 ) which supports work elements ( 15 ), is formed by the following elements . a tubular crosspiece ( 33 ), to which the two clevises ( 31 ) described above are fastened , extends at least approximately horizontally and at least approximately perpendicular to the direction of work . at each end , tubular crosspiece ( 33 ) is connected to the upper part of a lateral sheet metal piece ( 34 ) that extends in a plane at least approximately vertical and at least approximately parallel to the direction of work . at its lower part , each of lateral sheet metal pieces ( 34 ) is fastened to the corresponding end of a stiffener ( 35 ) which carries a beam ( 36 ). this beam ( 36 ) supports work elements ( 15 ) made here in the form of rotary disks that extend above said beam ( 36 ). these disks are , in a way known to a person skilled in the art , guided in rotation in beam ( 36 ) and driven in rotation by drive elements ( not represented ) housed in said beam ( 36 ). each end disk , in addition , is surmounted by a rotary drum ( 37 ) which works with a corresponding stationary windrowing device ( 38 ) fastened to corresponding lateral sheet metal piece ( 34 ), to reduce the width of the windrow of product cut by the disks , which is deposited behind the mower . above one of rotary drums ( 37 ) a second housing ( 39 ) is provided which is fastened to tubular crosspiece ( 33 ) by means of a fastening element ( 40 ). this second housing ( 39 ) is a transmission housing known to a person skilled in the art , whose output shaft ( not shown ) extends at least approximately vertically through rotary drum ( 37 ) situated under said second housing ( 39 ), to transmit the movement to work elements ( 15 ) via the drive elements housed in beam ( 36 ). the transmission of the movement from drive source ( 41 ), consisting of the front power takeoff of tractor ( 3 ), to work elements ( 15 ) will be explained later . under tubular crosspiece ( 33 ), approximately vertically below pin ( 27 ) fastened to second structure ( 18 ), is fastened a pin ( 42 ) that also extends at least approximately parallel to the direction of work . upper pin ( 27 ), fastened to second structure ( 18 ) and lower pin ( 42 ), fastened to first structure ( 17 ) form part of a release safety device ( 43 ). the latter , seen in the direction of work , extends into the middle part of mower ( 1 ) and into the front part of second chassis ( 14 ). said release safety device ( 43 ) appears in greater detail in fig5 and 6 . in addition to the two pins ( 27 , 42 ), release safety device ( 43 ) further comprises two flanges ( 44 , 45 ) which each have a recess ( 441 , 442 , 451 , 452 ) surrounding over approximately 180 ° each of the two pins ( 27 , 42 ), which extend between the flanges ( 44 , 45 ), as well as an elastic device ( 46 ) clamping the two flanges ( 44 , 45 ) to the two pins ( 27 , 42 ). for this purpose , recesses ( 441 , 442 , 451 , 452 ) exhibit a suitable shape to work with the shape of the pins ( 27 , 42 ). said elastic device ( 46 ) is positioned between the two pins ( 27 , 42 ), but is closer to lower pin ( 42 ) than to upper pin ( 27 ). it is composed of a rod ( 47 ), which extends at least approximately perpendicular to the plane containing the two pins ( 27 , 42 ), and of an elastic element ( 48 ). one of the ends of rod ( 47 ) goes through the two flanges ( 44 , 45 ) which , for this purpose , have holes ( 49 , 50 ) with a diameter somewhat larger than the diameter of said rod ( 47 ). at its end extending outside flange ( 45 ), said rod ( 47 ) is connected to a connecting piece ( 51 ) exhibiting a convex rounded surface ( 52 ) which is in contact with flange ( 45 ). at its other end extending outside the other flange ( 44 ), rod ( 47 ) is provided with a stack of elastic washers ( 53 ) constituting elastic element ( 48 ) and which are clamped between said flange ( 44 ) and a washer ( 54 ) held by a nut ( 55 ) screwed onto said end of rod ( 47 ) which , for this purpose , is threaded . release safety device ( 43 ) which has just been described , in normal work , prevents the pivoting of first structure ( 17 ) in relation to second structure ( 18 ) backward around joint ( 21 ) consisting of pin ( 20 ) and clevises ( 31 ). when first structure ( 17 ) and / or work elements ( 15 ) hook a large obstacle ( 56 ) ( see fig4 ), since tractor ( 3 ) is advancing , a force then occurs which tends to separate the two pins ( 27 , 42 ) from one another . in so doing , pin ( 27 ) which is farther from elastic device ( 46 ) than pin ( 42 ), separates the two flanges ( 44 , 45 ) from one another , by compressing elastic washers ( 53 ), until it can escape recesses ( 441 , 451 ). this then makes it possible for first structure ( 17 ) and work elements ( 15 ) that it supports to pivot backward about the axis of joint ( 21 ) in relation to second structure ( 18 ). moreover , since joint ( 21 ) connecting first structure ( 17 ) to second structure ( 18 ) is at least approximately vertically above the front part of work elements ( 15 ), there is no risk that the latter penetrate into ground ( 16 ) during pivoting . between first structure ( 17 ) and second structure ( 18 ) a limitation element ( 57 ) is provided which limits the pivoting possible between said first structure ( 17 ) and said second structure ( 18 ) when safety device ( 43 ) has released ( fig4 ). each flange ( 44 , 45 ) is extended upward beyond upper pin ( 27 ) by such a distance that , when limitation element ( 57 ) stops the pivoting of first structure ( 17 ) in relation to second structure ( 18 ), pin ( 27 ) still extends between the two flanges ( 44 , 45 ) ( fig4 ). in this way , the reengaging of safety device ( 43 ) will be very easy . actually , it will be sufficient simply to back up with tractor ( 3 ) until pin ( 27 ) again extends between the two corresponding recesses ( 441 , 451 ). it should further be noted that the releasing force can be adjusted thanks to nut ( 55 ) which may be screwed more or less far on rod ( 47 ) so as to compress more or less strongly elastic washers ( 53 ). as said above , work elements ( 15 ) receive movement from a drive source ( 41 ), consisting of the front power takeoff of tractor ( 3 ), which comprises a shaft ( 58 ) whose axis of rotation is directed at least approximately parallel to the direction of work . first housing ( 29 ) which , in a view along the direction of work , extends into the middle part of mower ( 1 ), is equipped with an input shaft ( 59 ) extending backward and whose axis of rotation is also at least approximately parallel to the direction of work . this input shaft ( 59 ) of first housing ( 29 ) receives the movement of shaft ( 58 ) of the power takeoff of tractor ( 3 ) via a first telescopic drive shaft ( 60 ) with universal joints ( 61 ) whose longitudinal axis , in top view , extends at least approximately in the direction of work . moreover , as seen in fig2 in an intermediate position of the travel allowed by the deformable parallelogram , said first telescopic drive shaft ( 60 ) also extends at least approximately horizontally . first housing ( 29 ) which is an angle transmission housing is provided with an output shaft ( 62 ) whose axis of rotation extends at least approximately horizontally and at least approximately perpendicular to the direction of work . this output shaft ( 62 ) of first housing ( 29 ) is directed toward second housing ( 39 ) which comprises an input shaft ( 63 ) whose axis of rotation also extends at least approximately horizontally and at least approximately perpendicular to the direction of work . in this way , output shaft ( 62 ) of first housing ( 29 ) and input shaft ( 63 ) of second housing ( 39 ) are at least approximately parallel to one another . input shaft ( 63 ) of second housing ( 39 ) which is directed toward first housing ( 29 ), receives the movement of output shaft ( 62 ) of said first housing ( 29 ), via a second telescopic drive shaft ( 64 ) with universal joints ( 65 ). the longitudinal axis of this telescopic drive shaft ( 64 ), in top view , extends in a direction crosswise to the direction of work . moreover , it is seen from fig2 and 3 that telescopic drive shaft ( 64 ) also extends somewhat downward , given that input shaft ( 63 ) of second housing ( 39 ) is situated somewhat lower than output shaft ( 62 ) of first housing ( 29 ). the direction of this telescopic drive shaft ( 64 ) is such that the angles of the universal joints ( 65 ) are relatively small . moreover , it should be noted that these angles do not vary during normal work , since the relative position of first housing ( 29 ) in relation to second housing ( 39 ) does not vary during the adaptation of second chassis ( 14 ) and work elements ( 15 ) that it supports to the contours of ground ( 16 ). in fig2 it is also seen that the axis of rotation of output shaft ( 62 ) of first housing ( 29 ) and the axis of rotation of input shaft ( 63 ) of second housing ( 39 ) are at least approximately parallel to the geometric axis of joint ( 21 ) and extend into the vicinity of this geometric axis . moreover , the geometric axis of joint ( 21 ) extends higher and in front of the axis of rotation of output shaft ( 62 ) of first housing ( 29 ), while the axis of rotation of input shaft ( 63 ) of second housing ( 39 ) extends lower and in front of said geometric axis of rotation of output shaft ( 62 ) of first housing ( 29 ). finally , the distance between the axis of rotation of input shaft ( 63 ) of second housing ( 39 ) and the geometric axis of joint ( 21 ) is approximately equal to the distance between the axis of rotation of output shaft ( 62 ) of first housing ( 29 ) and the geometric axis of said joint ( 21 ). in this way , as appears very clearly in fig4 during the pivoting of first structure ( 17 ) and work elements ( 15 ) that it supports in relation to second structure ( 18 ) around the geometric axis of joint ( 21 ), the axis of rotation of input shaft ( 63 ) of second housing ( 39 ) comes close to the axis of rotation of output shaft ( 62 ) of first housing ( 29 ). the angles of universal joints ( 65 ) of the second telescopic drive shaft ( 64 ) thus diminish during pivoting . in this way , there is no danger of damaging the second telescopic drive shaft ( 64 ) during the pivoting allowed by release safety device ( 43 ). also , there is no risk of damaging the first telescopic drive shaft ( 60 ), since as seen very clearly in fig4 during pivoting the position of first housing ( 29 ) does not change in relation to shaft ( 58 ) of the power takeoff of tractor ( 3 ). the position of first housing ( 29 ) in relation to shaft ( 58 ) of the power takeoff of tractor ( 3 ) changes during the deformation of the parallelogram that makes possible the adaptation of the second chassis ( 14 ) and of work elements ( 15 ) that it supports to the contours of ground ( 16 ). since the length of the first telescopic drive shaft ( 60 ) can , however , be relatively long , the angles of the universal joints ( 61 ) remain relatively small . moreover , it should be noted that during the deformation of the parallelogram , input shaft ( 59 ) of first housing ( 29 ) still remains at least approximately parallel to shaft ( 58 ) of the power takeoff of tractor ( 3 ). in fig1 and 2 , it is also seen that mower ( 1 ) is provided with a lightening device ( 66 ) and with a lifting device ( 67 ). lightening device ( 66 ) comprises two draw springs ( 68 ) which , in top view , extend on both sides of upper connecting rod ( 8 ). at one of their ends , said springs ( 68 ) are connected to body ( 6 ) of first chassis ( 4 ). at their other end , said springs ( 68 ) are connected to a respective lever ( 69 ) fastened to upper connecting rod ( 8 ), in the vicinity of joint ( 9 ) by which said upper connecting rod ( 8 ) is connected to body 6 of first chassis ( 4 ). each lever ( 69 ) extends from connecting rod ( 8 ) downward and toward the front and corresponding spring ( 68 ) is connected to its front end . springs ( 68 ) thus exert , by levers ( 69 ), a torque on upper connecting rod ( 8 ), so that second chassis ( 14 ) rests less heavily on ground ( 16 ). the lightening device ( 66 ) is placed so that in the travel zone allowed by the deformable parallelogram , the lightening force remains relatively constant . lifting device ( 67 ) comprises a hydraulic cylinder ( 70 ) whose rod ( 71 ) is connected to body ( 6 ) of first chassis ( 4 ) and whose cylinder ( 72 ) is connected to the free end of a clevis ( 73 ). at its other end , clevis ( 73 ) is connected to body ( 6 ) of first chassis ( 4 ) so as to be able to turn freely around a geometric axis merged with the geometric axis of cylindrical joint ( 9 ), by which upper connecting rod ( 8 ) is connected to first chassis ( 4 ). clevis ( 73 ) further comprises a stop ( 74 ). thus , when oil is injected into cylinder ( 70 ), it contracts and draws on clevis ( 73 ) which pivots around the geometric axis of joint ( 9 ). when stop ( 74 ) comes in contact with the lower part of upper connecting rod ( 8 ), it drives said upper connecting rod ( 8 ) so as to pivot , which has the effect of lifting second chassis ( 14 ). in fig7 and 8 another embodiment of this invention is diagrammatically shown which differs from the one which has just been described by the arrangement of the first housing on the second structure and of the second drive shaft extending between this first housing and the second housing . actually , in this example , first housing ( 75 ) has two cylindrical bearing surfaces ( 76 ) with a common geometric axis at least approximately horizontal and directed at least approximately perpendicular to the direction of work . these cylindrical bearing surfaces ( 76 ) serve for the connection of the back end of lower connecting rods ( 77 ) similar to lower connecting rods ( 10 ) and of clevises ( 78 ) similar to clevises ( 31 ). these clevises ( 78 ) are connected to a tubular crosspiece ( 79 ) similar to tubular crosspiece ( 33 ). this tubular crosspiece ( 79 ) is part of a first structure ( 80 ) similar to first structure ( 17 ). to first housing ( 75 ) are fastened two parallel plates ( 81 ) that extend at least approximately vertically and between the upper ends of which the back end of upper connecting rod ( 8 ) extends which is connected there by means of joint ( 12 ). at their front part , the two plates ( 81 ) are rigidly connected to one another by means of an angle iron ( 82 ) similar to angle iron ( 24 ). second structure ( 83 ) thus made , similar to second structure ( 18 ), also comprises a pin ( 27 ) that is part of release safety device ( 43 ). first housing ( 75 ) comprises an output shaft ( 84 ) whose axis of rotation extends at least approximately horizontally and at least approximately perpendicular to the direction of work . first structure ( 80 ) comprises a second housing ( 85 ) similar to second housing ( 39 ), which is fastened to tubular crosspiece ( 79 ). this second housing ( 85 ) comprises an input shaft ( 86 ) directed toward output shaft ( 84 ) of first housing ( 75 ) and whose axis of rotation is merged with that of said output shaft ( 84 ). moreover , it is also seen from fig7 and 8 that the common axis of rotation of output shaft ( 84 ) of first housing ( 75 ) and of input shaft ( 86 ) of second housing ( 85 ) is also coaxial with the geometric axis of cylindrical bearing surfaces ( 76 ) of first housing ( 75 ), i . e ., on the one hand , with the geometric axis of joints ( 130 ) by which lower connecting rods ( 77 ) are connected to first housing ( 75 ) ( second structure ( 83 )) and , on the other hand , with the geometric axis of joint ( 210 ) by which first structure ( 80 ) is connected to first housing ( 75 ) ( second structure ( 83 )). a second drive shaft ( 87 ) transmits the movement of first housing ( 75 ) to second housing ( 85 ). the axis of rotation of this second drive shaft ( 87 ) is therefore also coaxial with the geometric axis of joint ( 210 ) connecting first structure ( 80 ) to second structure ( 83 ). in this way , when safety device ( 43 ) releases , and first structure ( 80 ) pivots in relation to second structure ( 83 ), no stress will occur in second drive shaft ( 87 ). while the examples of embodiment which have just been described relate to mowers intended to be hitched to the front hitch of a tractor , it is understood that the invention can also be applied to a mower hitched or pulled behind a tractor .
a mower includes a first chassis attachable to a tractor for movement in a work direction , a second chassis having first and second structures connected at a joint extending perpendicular to the work direction , and connecting rods , each having respective ends pivotally connected to the first chassis and to the second structure of the second chassis so as to form with the first and second chassis an upwardly deformable quadrilateral deformable such that the work elements may move to adapt to ground contours . a release safety device normally prevents pivoting of the first structure about the joint but permits pivoting of the first structure about the joint axis when the first structure or the working elements hooks an obstacle during movement of the mower in the work direction . this limits forces applied to the mower .