it is emphasized in the present description and in the claims , that the term “ fruit - bearing hedge ” designates a row or line of fruit - bearing bushes which may be of various species that are cultivated on tying wires or on stakes , such as rows of vine stock . the cutting head of the trimming machine shown in fig1 features two vertical rotating drive shafts 1 a and 1 b . each of these shafts is supported by a pivoting vertical cradle 2 a , 2 b and driven in rotation by a motor which may comprise a hydraulic motor coupled to the upper end of said drive shafts . this pivoting vertical cradle is itself suspended , in pendulum fashion known as such , on a support arm connected in an articulated manner to chassis 3 of the cutting head . on each of the vertical drive shafts 1 a , 1 b , are mounted toothed cutting disks or circular saws 4 , stacked on said shafts , at preferably even distance , on top of each other . in a manner known as such and as indicated previously , the stacks 4 a , 4 b are offset in vertical direction , so that the toothed cutting disks can mesh together when said stacks are brought together or in closed position of the cutting head . more precisely , the toothed cutting disks of the right stack 4 a and the toothed cutting disks of the left stack 4 b intersect in the horizontal plane , over a distance of several centimeters , for example over a distance of 5 cm . at least one rotating opening wheel 5 a , 5 b is mounted around each vertical shaft 1 a , 1 b , these opening wheels being driven in rotation by said shafts . the pivoting motion in the reverse direction of the supporting cradles 2 a , 2 b results in : either the bringing together of the cutting stacks in working position ; or the distancing of the latter in the position to bypass the posts p 1 of the tying wires p of the fruit - bearing hedge h . according to a characteristic disposition of the invention , each opening wheel is mounted on its drive shaft 1 a , 1 b , through the intermediary of a speed reducer coupled in rotation to said shaft . according to another advantageous characteristic disposition , these speed reducers are constituted by planetary gear train reducers . each of these planetary gear train reducers 20 includes ( fig4 and 5 ): an input sun - gear 6 driven in rotation by the shaft 1 a or 1 b together with which it rotates by means of a coupling 1 a - 6 a ; four bearings mounted on the sun - gear 6 , two bearings 7 a on the upper part and two bearings 7 b on the lower part of said sun - gear 6 ; a flange 8 mounted on the two lower bearings 7 b and to which are attached , on the one hand , a second output sun - gear 9 , by means of screws 10 , and , on the other hand , a stopping tail 11 by means of screws 12 , this stopping tail 11 taking hold on the tube 13 of polygonal ( for example four - sided ) section of the pivoting vertical cradle 2 a or 2 b of the cutting head so as to stop the rotation of the sun - gear 9 ; a star carrier 15 mounted on the two upper bearings 7 a ; and three planet gears 16 provided with a plain bearing 17 and mounted on the star carrier 15 . the planet gears are engaged , on the one hand , with the teeth of sun gear 6 and , on the other hand , with the teeth of sun gear 9 comprising a circular crown with teeth on the inside . according to a preferred method of production , the ratio of reduction of the speed reducer and , in particular , the ratio of reduction of the planetary gear train described above , is in the order of 1 : 2 . this ratio of reduction makes it possible to obtain a rotation speed between the sun gear 6 and the star carrier 15 such as v 2 = v 1 : 2 , in which : v 1 = rotation speed of the drive shafts 1 a , 1 b , v 2 = rotation speed of the opening wheels 5 a , 5 b . the star carrier 15 of the opening wheels 5 a , 5 b , which has a diameter greater than the diameter of the toothed cutting disks 4 , makes contact with and wraps itself around the posts p 1 of the tying wires p , as the trimming machine advances on the fruit - bearing hedge h with a rotation speed v 2 which will have been preset by the operator to correspond essentially to the forward speed so as not to exert any pushing or pulling force on said posts . it is clear that according to the arrangement of the planetary gear train reducer illustrated in fig4 and 5 , the opening wheels 5 a and 5 b are properly constituted by the periphery of the rotating star carrier 15 . the cutting stacks 4 a , 4 b turn at a rotation speed v 1 twice as great as the rotation speed v 2 of the opening wheels and permit high - quality trimming and fracturing of the woods and canes , as well as a good cleaning of the tying wires of the fruit - bearing hedge . for example , the cutting disks turn at 200 rpm , whereas the opening wheels turn at 100 rpm . according to another advantageous characteristic disposition of the invention , one of the faces of the opening wheel 5 a , 5 b of each stack 4 a , 4 b is fitted to constitute a counter - blade which , in the active close position of said stacks finds itself facing one of the opposite surfaces of the peripheral zone of one of the cutting disks 4 of the opposite stack 4 b , 4 a . in this way , one obtains a cooperating action between the opening wheel and the cutting disk positioned opposite with a slight offset in the vertical direction , and so the fruit - bearing hedge can be trimmed over the entire height of the stacks 4 a and 4 b . according to a method of production illustrated in fig4 and 5 , a circular counter - blade is fastened , by means of screws 19 , on the star carrier 15 of each opening wheel . the counter - blade 18 is equipped , peripherally and alternatingly , with teeth 21 and notches 22 . the periphery of each opening wheel 5 a , 5 b which may be advantageously constituted by the star carrier 15 of the reducer of the planetary gear train 20 , presents a shape that is identical to that of the counter - blade 18 . a small gap has been made between the counter - blade 18 of the opening wheels 5 a , 5 b , and the toothed cutting disk 4 placed opposite with a slight vertical offset , this gap being , for example , in the order of 10 mm . preferably , the counter - blade is positioned on the upper face of the planetary gear train reducer constituted by the star carrier 15 and it is placed opposite the lower face of the disk 4 of the opposite stack with which the counter - blade is associated . fig3 a to 3e illustrate the movement of the cutting head of a trimming machine on a row of vine stock . on fig3 a , the cutting head approaches a post p 1 of the tying wires . the cutting disks 4 of the stacks 4 a , 4 b which mesh with each other , turn at a speed v 1 , whereas the opening wheels 5 a , 5 b , turn in the same direction , at a speed v 2 which is half of v 1 . fig3 b shows how the opening wheels come into contact with the post p 1 . on fig3 c , the opening wheels roll over the post 1 , which results in the cutting disks 4 of the stacks 4 a , 4 b moving away from the post p 1 . on fig3 d , the post p 1 has been bypassed and the stacks 4 a , 4 b find themselves closer to each other under the action of the return mechanism ( not shown ) known as such . in this position the stacks mesh again with each other . fig3 e shows the cutting head moving away from the bypassed post p 1 .
device for the automatic bypassing of tying posts or stakes in fruit - bearing hedges , in particular for trimming machines featuring a working head having two vertical rotating drive shafts on which are mounted two stacks of toothed cutting disks and an opening wheel . the stacks being able to assume a position where they come closer to each other and then intersect , or a position where they get further apart where the cutting disks of each stack find themselves distanced from the cutting disks of the other stack . each opening wheel is mounted on its drive shaft through the intermediary of the speed reducer coupled to said shaft . the invention also concerns agricultural machines equipped with such a device .