Abstract:
Providing in conjunction with a large round baler is a wrapping arrangement for enveloping a large round bale with an enveloping material. The wrapping arrangement includes a propulsion element, preferably a propulsion roll, that withdraws the enveloping material from a supply, preferably in the form of a roll, and a clutch arrangement effectively connected to the propulsion element. The clutch arrangement is arranged to maintain the force acting upon the enveloping material generally at a constant level once the enveloping material is grasped by the bale during the wrapping process.

Description:
FIELD OF THE INVENTION 
     The invention concerns a wrapping arrangement for the enveloping of a bale with an enveloping material and including a propulsion element, preferably a propulsion roll that withdraws the enveloping material from a supply, preferably in the form of a roll, and a clutch arrangement effectively connected to the propulsion element, and a baler with such an arrangement. 
     BACKGROUND OF THE INVENTION 
     DE-A1-197 20 489 shows a baler for agricultural harvested crop with a station for withdrawing a band of enveloping material from a supply. The withdrawal station is provided with a brake arrangement operating on the principle of centrifugal force as a speed control arrangement, so that the enveloping material is under a predetermined tension during the wrapping of the cylindrical bale and the separating process. 
     The problem underlying the invention is seen in the fact that such an arrangement for the enveloping of a bale is very costly. 
     SUMMARY OF THE INVENTION 
     This problem is solved according to the invention, by the teaching of patent claims  1  or  9 , where the further patent claims cite characteristics that further develop the solution to great advantage. 
     In this way the invention proposes a wrapping arrangement for the enveloping of a bale with an enveloping material, with the arrangement including a propulsion element that withdraws the enveloping material from a supply, preferably in the form of a roll, and a clutch arrangement effectively connected to the propulsion element. The propulsion element is preferably a propulsion roll that can be driven in rotation. However, other configurations are also conceivable. The clutch arrangement is arranged to maintain an essentially constant level of the force applied to the enveloping material as it is grasped by the bale so that the enveloping material can envelop the bale in an optimum manner regardless of the actual circumferential velocity and thereby the force applied to the enveloping material by the bale is dependent upon the harvested crop actually processed and its condition, for example, its moisture content and/or the existing surrounding conditions. The arrangement can regulate or control the force. 
     If the propulsion element is driven at a velocity that is less than the circumferential velocity of the bale, then a stretching or tensioning of the enveloping material, which has one end grasped by the bale, can be attained so that can adhere closely to the bale. 
     As previously noted, the circumferential velocity of the bale may depend upon various different factors. Particularly, in the case of dry and/or coarse harvested crop, it frequently is far lower than usually assumed theoretically. In order to attain an adequate stretching or tensioning of the enveloping material, provision can be made for the circumferential velocity of the propulsion element to be lower than the circumferential velocity of the bale by more than 10%, but preferably by approximately 30% or even more. 
     If the clutch arrangement is configured in the form of a slipping clutch, the clutch can slip as soon as a predetermined force is applied to the enveloping material. Thereby an excessive stretching and/or loading of the enveloping material can be avoided even if the difference in the circumferential velocities is selected to be a very high value. 
     Provision can be made for the force to be defined as a fixed value. However, a flexible reaction to the actual conditions or requirements is possible, in particular if the force can be adjusted, for example, by varying the preload on the clutch arrangement. In the case of a slipping clutch, for example, a determination can be made at what force the clutch begins to slip or slips completely when the friction coefficient of the clutch is reached or is exceeded. In each case, the preload can be applied by an appropriate spring, for example, in the form of a compression spring or any other appropriate energy storage device, such as by hydraulic or pneumatic means. 
     If the clutch arrangement establishes an effective connection between a drive arrangement and the propulsion element, then the force transmitted by the clutch arrangement can be a function of the force occurring or the circumferential velocity of the bale in such a way that it opposes it selectively or permits it, so that the force applied to the enveloping material is held at least essentially constant. 
     The drive arrangement may include a gearbox or any other arrangement that is appropriate for the of force or movement. On balers to which an arrangement according to the invention will usually be applied, drives with tensioning devices are frequently found already among others in the form of chain drives and in particular belt drives. 
     If a belt drive is provided, then the clutch arrangement can interact at least with a belt drive pulley of the bet drive gearbox and permit, for example, a transmission of force or movement from the bet drive pulley to a drive shaft in such a way that the force applied to the enveloping material is held constant. 
     A wrapping arrangement for the wrapping of a bale can be applied in industry to balers that form bales of paper, garbage, textiles etc. But such a wrapping arrangement is particularly appropriate in an application to agricultural balers for basics of agricultural harvested crops, since these are usually coupled to a towing vehicle and must be monitored by an operator of the towing vehicle. For these operators, faulty operation of a wrapping arrangement are difficult to determine and a frequently discovered only after ejection of the bale. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The drawings show an embodiment of the invention that shall be described in greater detail in the following. 
         FIG. 1  shows a baler with a wrapping arrangement for the wrapping of a bale with an enveloping material. 
         FIG. 2  shows a more precise illustration of the wrapping arrangement of  FIG. 1 , including a clutch arrangement for the selective drive of a propulsion element. 
         FIG. 3  shows the clutch arrangement of  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 1 and 2  show a baler  10  of generally conventional configuration with a baling chamber  12 . Beyond that, there is provided a wrapping arrangement  14 , constructed in accordance with the present invention, for the wrapping of a bale  16  in the baling chamber  12  with an enveloping material  18 . 
     The baler  10  may be any known conventional configuration, that is, with a baling chamber  12  of constant or variable size, that is surrounded exclusively or in combination with belts, chains or, as shown in  FIGS. 1 and 2 , by fixed rolls  20 . 
     Such a baler  10  may be applied in agriculture for the forming of bales  16  of harvested crop such as, for example, straw, hay or grass. But an application in industrial usage is also conceivable. 
     In the present embodiment the wrapping arrangement  14  is provided on the front side of the baler  10 . The enveloping material  18  is conducted into the balling chamber  12  through a slot between two adjacent roll  20  where it is carried along by the bale  16  that has been brought into rotation. The wrapping arrangement  14  may be arranged in a central region of the baler  10  or ahead of or above the baling chamber  12 . 
     The bale  16  is wrapped by the enveloping material  18  and is thereby prevented from falling apart after leaving the baler  10 . The enveloping material  18  may consist of foil, net, woven fabric, paper or the like. 
     As can best be seen in  FIG. 2 , the wrapping arrangement  14  is provided with a housing  22 , a propulsion roll, designated in the following as propulsion element  24  and a separating arrangement  26 . The housing  22  contains a support floor  27  on which the enveloping material  18  is supported in bearings as roll  28 . The support floor  27  may also be configured in such a way that it stores several rolls  28  and/or is provided with several steps or cavities for their secure storage. 
     The propulsion element  24  is in the form of a roll and provided on its circumferential surface with a coating with a high coefficient of friction and can be brought into rotation. Initially the rotation assists in withdrawing the enveloping material  18  from the roll  28 . The roll  28  is located above the support plane of the support floor  27  and comes into contact in its operating position with the propulsion element  24  in a region that corresponds approximately to a 6 to 9 o&#39;clock position. The enveloping material  18  is withdrawn from the roll  28  by means of the propulsion element  24  and conducted into the baling chamber  12  through the slot between adjacent rolls  20 . During a proper operation, the enveloping material  18  grasped by the rotating bale  16  and envelopes it. 
     The separating arrangement  26  is provided with a knife  32  that is fastened to an arm  34  pivoting about a bearing  36  in order to enter the enveloping material  18  and to cut through the latter or to the effect its tearing off, when the wrapping process is completed. The knife  32  is pivoted by a hydraulic motor  38  that is actuated by a known control or regulating arrangement (ECU). 
     Beyond that, a further arm, which carries a belt tensioning pulley  48 , is connected to the arm  34 , with the position of the arm and, hence, the pulley  48 , also being determined by the hydraulic motor  38 . In the present embodiment a guide arrangement  51  is provided, free to pivot, about the arm  34 . Such a guide arrangement  51  can be derived from U.S. Pat. No. 6,886,307, granted May 3, 2005, whose disclosure is hereby incorporated into the present patent application. 
     If the hydraulic motor  38  is in its retracted position, as shown in  FIG. 2 , then the knife  32  is in such a pivoted position that it does not affect the course of the enveloping material  18 . Referring now to  FIG. 3 , it can be seen that the propulsion element  24  operates by means of a drive shaft  39 , with which it is rigidly connected, a clutch arrangement  41 , and with a drive belt  42 . The drive belt  42  is engaged with a first belt drive pulley  44 , that interacts with one of the rolls  20 , that can be brought into rotation by a drive (not shown), and is engaged with a second belt drive pulley  46  that is applied, free to rotate, to the drive shaft  39 . Moreover, it can be seen that the tensioning pulley  48  is disposed so that it may apply more or less pressure to an upper run of the drive belt  42  at a location between the belt drive pulleys  44 ,  46  in such a way that the drive belt  42  can be tensioned by means of the tensioning pulley  48 , in order to bring the second belt drive pulley  46  into rotation. If the tensioning pulley  48  does not apply tension to the drive belt  42 , then the second belt drive pulley  46  is not driven by the drive belt  42 . 
     Reference will now be made to  FIG. 3 , in which the propulsion element  24 , the drive shaft  39 , the clutch arrangement  41  and the second belt drive pulley  46  are shown in an enlarged view. 
     The second belt drive pulley  46  is applied by means of a sliding bearing  50 , free to rotate, to an end region  52  of the drive shaft  39  spaced away from the propulsion element  24 . The second belt drive pulley  46  is connected to a clutch disk  56  by means of a safety device  54 , in the form of a screw, the clutch disk is also applied to the end region  52 , but is not directly connected to the drive shaft  39 . 
     The safety device  54  is inserted through a hole  58  in the clutch disk  56  and is loaded by a spring  60  in the form of a compression spring provided on the safety device  54  at a location between a head of the device  54  and the clutch disk  56 , in such a way that the belt drive pulley  46  is biased towards the clutch disk  56 . 
     Moreover, a clutch element  62  is applied to the drive shaft  39 , and is provided with a bearing region  64  that is connected, fixed against rotation, to the end region  52  of the drive shaft  39  by means of an appropriate connection  66 , for example, in the form of a feather key. 
     A clutch region  68  extends from the bearing region  64  between the belt pulley  46  and the clutch disk  56 . The clutch region  68  is provided with a high friction coating  70  on its side facing the belt drive pulley  46  as well as the side facing the clutch disk  56 . 
     For the sake of completeness it should be noted that the drive shaft  39  extends further through a bearing  72  in a side wall  74  of the baling chamber  12  and that a spacer bushing  76  is provided between the bearing  72  and the clutch element  62 . 
     In the following, the method of operation of the arrangement  14  shall be described in greater detail. For this purpose, reference is here made to  FIG. 1  as well as to  FIGS. 2 and 3 . 
     If the formation of the bale  16  in the baling chamber  12  has been completed, which can be determined in known manner by a sensor, not shown, which mechanically or optically determines the diameter of the bale  16 , for example, then the wrapping arrangement  14  is activated. This occurs in that the hydraulic motor  38  is brought into its retracted position, shown in  FIG. 2 , as controlled by the control or regulating arrangement (ECU). 
     This retraction of the hydraulic motor  38  causes the arm  34  to be swung counter clockwise about the pivot bearing  36 , which, in turn, causes to tensioning pulley  48  to effect a tensioning of the drive belt  42  so as to cause the second belt pulley  46  to be brought into rotation. 
     The belt pulley  46  in turn operates by means of the friction coating  70  facing it as well as indirectly by means of the clutch disk  56  and the friction coating  70  facing it on the clutch element  62  and carries these along or brings the clutch element  62  and with it the drive shaft  39  and the propulsion element  24  into rotation. 
     The propulsion element  24  that is now driven in rotation withdraws the enveloping material  18  from the roll  28  and conveys it in the direction of the bale  16 . The guide arrangement  51  operates here as a support in that it guides the enveloping material  18  to the bale  16 . 
     When the enveloping material  18  is grasped by the rotating bale  16 , the bale applies a force to the enveloping material  18 . Since provision has been, made for the belt drive  40  to drive the propulsion element  24  with a speed that is less than the rotational speed of the bale  16 , preferably by approximately 15% to 30% or even less, the enveloping material  18  is braked by the action of the propulsion element  24  and is thereby stretched or tensioned, regardless of the type, of harvested crop that is processed or in what condition it is. This is desirable in order for the enveloping material  18  to adhere closely to the bale  16  and enclose it tightly. 
     The clutch arrangement  41  has the effect that the force applied to the enveloping material  18  by the bale  16  and thereby the stretching of the enveloping material  18  remains constant independently of the rotational speed of the bale. If the applied force exceeds a predetermined value, then the clutch element  62  begins to slip relative to the second belt pulley  46  and the clutch disk  56  in such a way that only the predetermined force is applied to the enveloping material  18  and thereby a certain stretching of the latter is attained. 
     The force that is to be applied or the desired stretching can be charged or predetermined by tightening the safety device  54  to a greater or lesser degree into the second belt pulley  46  against the force of the spring  60  so that the clutch arrangement  41  is preloaded in the desired manner. 
     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.