Abstract:
A drawing frame comprising, starting from a main frame ( 1 ), a sliding frame consisting of several actuators ( 20, 22, 23 ) arranged in a straight position on the elements drawing the sheath ( 5 ). The various actuators ( 20, 22, 23 ) are guided by slide rails ( 13, 14 ) and in particular by a pair of dihedral structures ( 7 ) for example, comprising beams ( 10, 12 ) and slides mobile by the effect of the various actuators. The drawing frame can advantageously be installed on a machine used for making silos, for sheathing fodder bales for example.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is the 35 USC 371 national stage of international application PCT/FR98/02323, filed on Oct. 29, 1998, which designated the United States of America. 
    
    
     FIELD OF THE INVENTION 
     This invention concerns a drawing frame for sheath made of plastic material such as shape-memory polyethylene, with high elastic deformation. 
     This drawing frame can be used for instance on a sheathing machine and in particular a machine for making silos, with bales of plants, fodder or other. 
     BACKGROUND OF THE INVENTION 
     This type of machine such as that described notably in the document U.S. Pat. No. 5,220,772 for round bales or EP-0 789 993 for parallelepipedic bales, comprises generally an appropriate polygonal frame, associated with a main frame whose size is such that it enables the passage of the fodder bale. This frame comprises extenders consisting—of cantilever supports on which the plastic sheath is stored and—of actuators moving said supports radially in order to increase the perimeter of said sheath sufficiently to be able to insert the bales inside said sheath. The sheath is pulled down around said bales as they are produced, thereby forming a kind of sausage. 
     In view of the radial arrangement of the extenders, the machines of this type are particularly cumbersome and, due to the presence of an immovable polygonal frame, they are not suitable for bales of different gauges. 
     SUMMARY OF THE INVENTION 
     According to the invention, the sheath is stored on supports mounted on throated arms, whereas said supports are arranged and/or guided with respect to a fixed main frame in order to form a polygonal mouth piece and whereby one of these supports is mobile, subject to displacement means that cause the perimeter of the sheath to expand at said mouthpiece, whereas said displacement means consist of actuators arranged in a straight position on each mobile support and, some of them, on the main frame, whatever the shape of said mouth piece. 
     According to a preferred embodiment of the invention, the main frame takes the form of a horizontal beam comprising, on the one hand, arranged symmetrically with respect to the vertical plane of the polygon delineated by the sheath—fixed supports integral with said beam and,—two lateral structures, articulated on said horizontal beam, close to the fixed supports, and on which structures the mobile support(s) is(are) guided and, on the other hand, actuators forming, around the mouthpiece, a closed frame on said beam, arranged in a straight position on one another, starting from said beam and on the mobile support(s). 
     Still according to the invention, in the case of a drawing frame for round bales, each lateral structure has for instance the shape of a dihedron, consisting of two beams forming slide rails that delineate an angle of approx. 120° in the case of a mouthpiece and of a hexagonal frame:—a first beam articulated at one of its ends on the horizontal beam of the main frame close to each fixed support,—a second beam mounted to run at one of its ends on the first beam, comprising a mobile support situated on the bisecting plane of the angle delineated by said first and second beams,—a slide at the end of the second beam comprising another mobile support. 
     Still according to a preferred embodiment of the invention, the hexagonal frame consists—of two lateral dihedral structures and of two actuators in each dihedron,—with the addition of an actuator extending between the ends of two lateral structures, at their upper section, interposed between the slides arranged at the ends of the second beams of said structures and—of the horizontal beam of the main frame that serves as a sixth side. 
     In the case of square bales, the drawing frame according to the invention comprises lateral structures in the form of single beams articulated on either side of the fixed lower supports, on the horizontal beam of the main frame, whereas each beam serves as a guide for a slide that is fitted with a sheath support, whereby said slides are interconnected by a horizontal actuator and are connected to the main frame each by an actuator and the frame consists therefore: of said horizontal beam, of the lateral beams and of the horizontal upper actuator. 
     Still according to the invention, the lateral structures of the drawing frame are interconnected by a kind of rudder bar that maintains each of them in such a position that they are constantly symmetrical with respect to one another and with respect to the middle vertical plane going through the longitudinal axis of the drawing frame, i.e. the insertion axis of the bales; said rudder bar has the shape of a transversal axle guided on the main frame of the drawing frame and fitted at its lateral ends with arms parallel to one another and whose end of each is integral, using an appropriate link, with the corresponding lateral structure. 
     According to another embodiment of the invention, the supports of the plastic sheath are mounted on throated arms in order to place the stored sheath on the plane of the actuators and of the slide rails, whereby each arm is integral with a slide or with the main frame and whereby each support comprises a fixed pallet in the form of a cylindrical section. 
     The invention also concerns a sheathing machine for bales of plants, that comprises a drawing frame such as described previously and a hydraulic control station of the various actuators that are power supplied from a stand-alone plant or from a plant arranged on a farming vehicle such as a tractor. 
     This drawing frame may for instance be used on a stand-alone sheathing machine, i.e. fitted with its own pusher as described in the document CA-2 111 546, as well as on a simpler machine for which the bales are pushed directly by the loading vehicle. 
     Still according to the invention, this machine comprises a main frame mounted on transport wheels and this main frame also comprises, on the silo side, i.e. of the sheathed bales, girders fitted with pad-shaped members and/or suitable wheels according to the nature of the soil, and possibly fitted with spades that maintain the machine in position and prevent it from reversing as the bales are inserted into the mouthpiece of the sheath. 
     According to another arrangement of the invention, the anchoring points of the handling actuators are multiple, so that the size of the mouthpiece and of the frame can be adapted easily to the gauge of the bales to be sheathed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be detailed further using the following description and the appended drawings, given for exemplification purposes and in which: 
     FIG. 1 is a schematic front view of the drawing frame according to the invention, for sheathing round bales; 
     FIG. 2 is a schematic view along  2 — 2  of FIG. 1; 
     FIG. 3 is a schematic front view of the drawing frame according to the invention for parallelepiped bales; 
     FIG. 4 is a schematic view along  4 — 4  of FIG. 3; 
     FIG. 5 is a simplified perspective view showing the rudder bar system that enables connecting the lateral structures of the drawing frame in order to hold them in the same position, symmetrically with respect to the middle vertical plane of the drawing frame; 
     FIG. 6 represents the drawing frame schematically as seen from above; 
     FIG. 7 represents a supporting arm on which the plastic sheath is laid; 
     FIG. 8 represents a sliding beam of the drawing frame shown on FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The drawing frame represented schematically on FIGS. 1 and 2 comprises a main frame  1  mounted for instance on wheels, whereas said main frame carries a deployable frame  2  extending from the horizontal transversal beam  3  of said main frame, on a plane that is vertical and perpendicular to the direction of introduction of the bales ‘B’ into said frame for sheathing said bales. 
     Sheathing takes place using a sheath made of plastic material such as shape-memory stretchable polyethylene, i.e. with elastic deformation. This sheath is stored on supports  4 , distributed in the angles of a polygon; it is for instance arranged in superimposed layers forming a tube with quasi-hexagonal cross-section. This type of sheath  5  sustains at least 30% elastic stretching. 
     Drawing the sheath  5  thus stored consists of radial displacement of the supports  4  and in particular, in the embodiment of FIG. 1, of the displacement of four of the supports  4 : the upper supports  41 , one situated on the right ( 41 D) and the other on the left ( 41 G) and the intermediate lateral supports  42 D and  42 G. The lower supports  43 D and  43 G are fixed; they are integral with the horizontal beam  3  of the main frame  1 , by means of the arms  6 . 
     All the supports  4  are arranged symmetrically with respect to the middle vertical plane of the main frame  1 . 
     The hexagonal frame  2  comprises in its lower section a side formed by the horizontal beam  3  of the main frame  1 . It also comprises a pair of dihedral lateral structures  7  that serve as slide rails. These structures  7 D and  7 G are formed by a first beam  10  articulated at one of its ends around an axle  11  on the beam  3  of the main frame  1 , and by a second beam  12  that is mounted to run at one of its ends on said first beam  10 , using a slide  13 . The apex angle of the dihedron is approx. 120° in the example of FIG.  1 . 
     There is a slide  14  at the end of the second beam  12 . 
     The movement of the first beam  10  around its axle  11  is for example limited by stops  15  that are integral with the main frame  1  and situated on either side of said beams  10 ; other means will also be detailed below in relation to FIG.  5 . 
     The support  42  (D and G) is integral with the second beam  12  and in particular its slide  13  using a radial arm  16 . This arm  16  is situated more or less on the middle plane of the dihedron formed by the structures  7 . 
     The support  41  (D and G) is integral with the slide  14  using a radial arm  17  that is situated on a plane that delineates an angle of approx. 60° with the second beam  12 . 
     The movement of the different supports  41 G,  42 G and their counterparts  41 D and  42 D, is provided by actuators arranged in a straight position on the one hand, on the arms  16  and  17  that carry respectively said supports  41  and  42  and, on the other hand, on the beam  3 . 
     There is a first actuator  20  parallel to the first beam  10 ; this actuator is articulated around an axle  21  from the beam  3  of the main frame  1 . After this actuator  20 , there is a second actuator  22 . Both these actuators  20  and  22  are integral with the arm  16  that carries the support  42  and they form together an angle similar to that of the dihedron formed by each structure  7 . The actuator  22  is also integral with the arm  17  that carries the support  41 . The arms  17  mounted on the slides  14  of the dihedrons  7 D and G, are interconnected by an actuator  23  that extends horizontally above the main frame  1 . 
     The actuators  22  and  23  are arranged in a straight position on each arm  17 , on the right and on the left. 
     The different actuators  20 ,  22  situated on the right and on the left and the upper actuator  23  form a polygonal loop that is closed on the beam  3 . Such an assembly provides better balance of the loads when the sheath  5  is extended by the supports  4 , and formation of a mouthpiece with regular shape, a shape that is established once the actuators have reached the end of their travel and are locked in that position. 
     These actuators are power-supplied from a control station that is not represented, which comprises either a stand-alone hydraulic power plant or an appropriate link that is connected to the hydraulic unit of a farming tractor. 
     The drawing operation takes place once and for all after the sheath has been placed on the supports  4 . The supports  41 ,  42 ,  43  are held in spread position by the actuators  20 ,  22 ,  23  until the sheath  5  has been reeled completely. During the sheathing operation, the drawing frame is totally passive; the various actuators are pressurised, blocked and the supports  41 ,  42  are in extended position, locked by said actuators. 
     FIG. 2 shows schematically the main frame  1  carried by pads or wheels  24  with, possibly, spades  25  serving as a reverse-locking device. Each lower support  43  is integral with the transversal beam  3  of the main frame  1 . It is topped with the support  42  arranged halfway up the frame and the support  41 , both situated in the upper section. The different supports  43 ,  42 ,  41  are carried respectively by throated arms  6 ,  16  and  17  to enable installation and storage of the sheath  5 . These throated assemblies will be detailed below in relation to FIG.  7 . 
     Still on FIG. 2, we can see the first beam  10  articulated on the beam  3  of the main frame  1 , and the second beam  12 . 
     The first beam  10  can be associated with a stiffener  30  that extends from the upper end of said beam, up to an articulation axle  31  arranged on the main frame  1 . This stiffener  30  enables stiffening the drawing frame and limiting the deflection of its upper section, notably when unreeling the sheath  5 . 
     We also find, on the same transversal plane as that of the beams  10  and  12 , the actuators  20 ,  22  and  23 . 
     FIG. 3 shows an embodiment variation of the drawing frame, more particularly suitable for sheathing bales in the form a rectangular parallelepiped whose cross-section is square or rectangular. 
     This drawing frame demonstrates the same technology as that developed on FIG. 1 for round bales. For this drawing frame, the lateral structures  7  simply consist of beams  10  forming slide rails for slides  14 ′. The slides  14 ′ are interconnected at their upper section by means of an actuator  23  and they are connected to the beam  3  of the main frame  1  by means of lateral actuators  20 . 
     The sheath  5  is arranged on supports  4  as previously: upper supports  41 D and  41 G as well as lower supports  43 D and  43 G. The supports  41 D and  41 G are integral with the slides  14 ′ using arms  17 ′. The supports  43 D and  43 G are fixed and integral with the transversal beam  3  using arms  6 . 
     In normal extended position, the frame of the drawing frame consists of the lower horizontal beam  3 , vertical lateral beams  10  and the upper actuator  23  placed horizontally. The four supports  4  are arranged in the form of a square and stretch the sheath  5  in such a position that it may receive parallelepipedic bales with square cross-section. 
     FIG. 4 shows schematically the drawing frame represented on FIG.  3 . We can see the plastic sheath  5  stretched between the supports  4  and in particular the lower  43  and upper  41  supports. The upper supports  41  are integral with the slide  14 ′ that is guided on the lateral beams  10 . 
     FIG. 5 represents schematically and in a simplified fashion, the main frame  1  of the drawing frame with the beam  3  on which are articulated the lateral structures  7  of the drawing frame according to FIG. 3 or FIG.  1 . 
     The lateral structures  7  consisting notably of the beams  10 , are integral with one another by a kind of rudder bar  32  that comprises a transversal axle  33  guided on each side of the main frame  1 . This axle  33  comprises at each of its ends, an arm  34  whose end  35  co-operates with plates  36  fixed at the lower end of the beams  10 . The end  35  has for instance the shape of an axle and co-operates with a circular orifice  37  provided at the lower end of the plate  36 , thereby forming a makeshift articulation. 
     The arms  34  are made of sheet metal and exhibit certain flexibility in order to tolerate any variation in the centre distance between the orifices  37  when the beams  10  are moving around their articulation axle  11 . 
     Thus, the lateral structures  7  of the drawing frame are interconnected via the rudder bar  32  and keep, permanently, a position that is symmetrical with respect to the vertical, longitudinal and middle plane of the drawing frame in the case of FIG. 1 as well as in the case of FIG.  2 . 
     FIG. 6 shows, as seen schematically from above, the main elements of a sheathing machine. Thus, there are the main frame  1  carried by wheels and the drawing frame of the sheath  5 , which sheath is stretched by the supports  4 . This machine comprises two slide rails  56 , integral with the main frame  1 , that serve as guides for the bale intended to run through the drawing frame and to be enveloped by the sheath  5 . 
     In order to avoid any interference between the bale and the plastic sheath  5 , additional guides  57  can be arranged halfway up, for instance at the supports  42 . The bale can also be centred at its lower section using guides  58  if the form of funnel sections that would advantageously protect the lower section of the sheath  5 . 
     The guides  58  also appear on FIG.  1  and it can be noticed that in normal active position, the sheath  5  is retracted from these guides  58 , protected against any contact with the bale B. 
     FIG. 7 shows a support  4  mounted on a throated arm  16 ,  17  or  17 ′. The support  4  has the shape of a cylindrical section whose diameter is approx. 150-250 mm for instance, making up a kind of pallet on which rests the sheath  5 . The downstream end of the support  4  is rounded in order not to tear the sheath  5  apart as it is extracted during the sheathing operation. 
     FIG. 8 shows an element of the structure  7 . This element of the structure  7  corresponds on the drawing, FIG. 1, to the beam  12 , fitted with the slide  13  and on which is fixed the arm  16  that carries the support  4 . On the flanges  60  interposed between the beam  12  and the slide  13  and in particular on one flange on which the arm  16  is mounted, we can see the bores  61  and  62  that are used for installing actuators and especially the actuators  20  and  22 . 
     The bores  61 ,  62 , as represented on FIG. 8, are two in number, or more according to the requirements, for each actuator, in order to modify the stroke of the supports  4  and to suit the mouthpiece of the drawing frame easily to the different gauges of bales to be sheathed. 
     This possibility to anchor the actuators  20 ,  22 ,  23  in different positions can be seen on the arms  6 , on the slides  13  and  14  of the drawing frame for round bales and on the slides  14 ′ of the drawing frame for parallelepipedic bales.