Abstract:
The invention suggests a device for wrapping a bale with a wrapping sheet, which comprises one or more sensors that detect whether the bale is wrapped properly with the wrapping sheet. A baling press is equipped with such a wrapping device as well as a control or regulating unit (ECU) that receives a signal from the one or more of the sensors and acts to interrupt the wrapping of a bale in the event the signal indicates an improper wrapping process is underway.

Description:
FIELD OF THE INVENTION 
   The invention relates to a device for wrapping a bale with a wrapping sheet, comprising elements that feed the wrapping sheet to the bale, a baler comprising such a device as well as a sensor of a control or regulating system of a device for wrapping a bale with a wrapping sheet. 
   BACKGROUND OF THE INVENTION 
   DE-A1-100 11 158 reveals a baler with a device for wrapping a bale with a wrapping sheet. The wrapping sheet is pulled off a supply reel by means of an advancing roller. The device comprises a sensor, which detects whether the wrapping sheet wraps around the advancing roller and is thus not properly fed to the bale. If the sensor detects a malfunction, the wrapping process is suspended. 
   SUMMARY OF THE INVENTION 
   The object of the invention is to resolve the problem that a device for wrapping a bale suspends the wrapping process only if the wrapping sheet has already wound around the advancing roller. If however the wrapping sheet is becoming backed up, no malfunction is detected and the system can become jammed. 
   This problem is resolved by providing a device for wrapping a bale, which determines whether a wrapping sheet is present on the surface of the bale. This is an indication that the bale wrapping process is progressing properly and the wrapping sheet is not wrapped around the components of the baling press or is experiencing an undesirable obstruction. If the sensor detects that no wrapping sheet is present although the wrapping process was initiated after completion of the baling process, then the wrapping process can be interrupted and the wrapping sheet does not continue to build up and also cannot become jammed. 
   The elements that feed the wrapping sheet to the bale can be, for example, an advancing element or an advancing roller or cylinder, which pulls the wrapping sheet off a supply device, for example in the form of a reel. The use of a pressing element is also conceivable, which would move or press the wrapping sheet to the bale at the beginning of the wrapping process so the wrapping sheet can be conveyed and thus be pulled off the supply device. Beyond that or apart from that, the pressing elements can also contain a guiding element or other and/or additional transport or conveying elements. 
   If the sensor is provided downstream from the wrapping sheet feed location, it is possible to detect already shortly after the start of the wrapping process whether the wrapping process is taking place properly and whether the bale is being wrapped with the wrapping sheet. The term “downstream” from the wrapping sheet feed location should be understood to mean that the sensor is arranged shortly behind the point at which the wrapping sheet reaches the bale. 
   The sensor, however, can also be provided upstream from the wrapping sheet feed location, wherein the term “upstream” should be interpreted to mean that the sensor, in reference to the rotational direction of the bale, is arranged just prior to the location where the wrapping sheet is fed. If the sensor is installed here, it can detect whether a first layer of the wrapping sheet has been placed around the bale. If this is the case, the risk of the wrapping sheet being fed incorrectly or becoming jammed, etc., during further wrapping of the bale is very small. 
   If one sensor is provided downstream and another sensor provided upstream from the wrapping sheet feed location, the above-described benefits can be combined and it can be detected both whether the wrapping operation started properly and whether the first layer of wrapping material has been applied to the bale. 
   As a function of the sensor signal(s) supplied by the sensor(s) the supply of wrapping sheet to the bale can be controlled such that the feeding of wrapping sheet is interrupted if it is detected that the wrapping process is not conducted properly. For this purpose, it is possible that the elements no longer feed wrapping sheet and/or that the bale no longer rotates and thus no wrapping sheet, which was seized but not placed properly on the surface, is pulled off the supply device. 
   The sensor signal can, for example, activate a display or a visual and/or acoustic warning indicator, which indicates to an operator the malfunction of the wrapping process so that the operator can interrupt the wrapping operation. The sensor or the sensors however can also work in conjunction with a preferably electric or electronic control or regulating device. Such control or regulating devices are frequently already provided on baling presses or on vehicles with which balers are pulled so as to control and/or regulate additional baler functions. This control or regulating device can receive and process the sensor signal or sensor signals so that the wrapping process can be automatically suspended in case of a malfunction. The control or regulating device also enables a time component to be included, for example in such a way that the sensor signal or the sensor signals are determined after specified time intervals after the start of the wrapping operation. The time intervals should be selected such that when the system functions properly it is to be expected that the wrapping sheet has already been applied to the bale in the respective location. For this, the rotational speed of the bale or its revolutions can be taken into consideration. 
   The sensor can be a sensor of any suitable kind. When using two or more sensors, it is also possible to combine different types of sensors. For example, mechanical sensors, ultrasound, infrared, proximity sensors, etc., can be employed. In particular the use of optical sensors, especially a color or contrast sensor, offers the additional benefit that the actual rotating speed of the bale can be determined in connection with markings or different colors, etc., which are provided at or on the wrapping sheet. This speed can be compared, for example, to the theoretical rotating speed, which is determined by the speed of the power take-off shaft of the driving vehicle, thus allowing conclusions of the bale&#39;s slippage. This in turn allows the wrapping sheet supply or the duration of the wrapping process, etc., to be adjusted. 
   In a conventional baling press the sensors are directed at a circumferential surface of the bale. However it is also conceivable to provide sensors that detect whether, in the case of appropriately designed balers, the lateral surfaces of the bale are also covered with the wrapping sheet. Moreover, sensors can be provided, which are directed at the edges of the bale and for example detect whether a wrapping sheet of a corresponding shape has been placed over the edges of the bale. 
   A device for wrapping a bale can be used in the industry on baling presses that form bales from paper, waste products, textile materials, etc. Such a device however is also particularly suited for use in an agricultural baler for bales consisting of agricultural crops since these are generally attached to a tractor and have to be monitored by the operator of said tractor. Malfunctions of a wrapping device are difficult for an operator of a towing tractor to detect and are frequently not noticed until the bale is ejected. 
   A sensor for a control or regulating device of a device for wrapping a bale can also be retrofitted on such a device or be made available as a spare part. This is easily possible since the sensor detects whether the wrapping sheet is present on a surface of the bale. It is therefore not necessary to place the bale on certain components of the device or modify components such that they work in conjunction with the sensor or are suited to accommodate it. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawing represents an exemplary embodiment of the invention, which is described more closely in the following. 
     The sole FIGURE is a schematic right side view of a large round baler. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawing, there is shown a large round baler  10  of essentially conventional design having a baling chamber  12 . Beyond that, in accordance with the present examples, a device  14  is provided for wrapping a bale  16 , that has been formed in the baling chamber  12 , with a wrapping sheet  18 . 
   The baler  10  can be of a familiar design, i.e., wherein the baling chamber  12  is of constant or variable size, which is surrounded exclusively, or in combination, by belts, chains, or, as shown in the embodiment, by rollers  20 . 
   The baler  10  can be used in agriculture for forming bales  16  from crops, such as e.g. straw, hay or grass. A use in industrial areas however is also conceivable. 
   The device  14 , in the present embodiment, is provided on the front of the baler  10 . The wrapping sheet  18  is fed through a gap between two adjacent rollers  20 , which defines a wrapping sheet feed location  21  to the baling chamber  12 , from where it is conveyed by the rotationally offset bale  16 . The device  14  can be arranged in a central area of the baler  10  or also in front of or above the baling chamber  12 . 
   The bale  16  is bound by means of the wrapping sheet  18 , thus preventing it from falling apart after leaving the baler  10 . The wrapping sheet  18  can be a film, net, tissue, paper or the like. 
   The device  14  comprises a housing  22 , feed elements  24  that feed the wrapping sheet  18  to the bale  16  or, for example, an advancing element designed as an advancing roller and a severing device  26 . The housing  22  contains a floor  27 , on which the wrapping sheet  18  is stored as a reel  28  or supply device. The floor  27  can also be designed such that it holds several reels  28  and/or contains steps or troughs to secure their storage. 
   The advancing element or the devices  24  are included on its circumferential surface with a coating with a high coefficient of friction and can be rotationally offset. The rotation initially aids in pulling the wrapping sheet  18  off the reel  28  and in building up tension during the wrapping process due to a restrained rotating motion. The reel  28  is located above the resting surface of the floor  27  and, in its operating state, rests against the devices  24  with an area that corresponds roughly to a  6  to  9  o&#39;clock position. The devices  24  pull the wrapping sheet  18  off the reel  28  and guide it through the gap or feed location  21  between the adjoining rollers  20  into the baling chamber  12 . During proper operation, the cooperative action of the rotating bale  16  and the bale-forming rollers  20  results in the wrapping sheet  18  being carried along by the rotating bale  16  so that the bale  16  becomes wrapped by the sheet  18 . 
   The severing device  26  comprises a blade  32 , which is pivotably attached in order to enter the path of the wrapping sheet  18  and sever it or effect a tearing when the wrapping operating is completed. Swiveling of the blade  32  is accomplished with a hydraulic motor  38 , which is actuated by a familiar controller, such as for example, an electric or electronic control or regulating device ECU. 
   In the present example, a guiding device  40  is pivotably provided, which guides the wrapping sheet  18  towards the bale  16 . Such a guiding device  40  is revealed in U.S. patent application Ser. No. 10/462,045 filed 13 Jun. 2003. 
   Beyond that, two sensors  42  and  44  are provided in the baling chamber  12  in areas adjacent the rollers  20  arranged about the bale  16 . The first sensor  42  is provided downstream from the wrapping sheet feed location  21 , for example in the area where the wrapping material is fed. The second sensor  44  is arranged upstream from the wrapping sheet feed location  21  or in an area located behind the wrapping sheet supply area. 
   The sensors  42  and  44  each detect whether the bale  16  is wrapped with the wrapping sheet  18  in the respective area or whether, for example, as a consequence of a malfunction or insufficient wrapping sheet  18  on the supply device  28 , no wrapping of the bale  16  with the wrapping sheet  18  is taking place. 
   Both sensors  42  and  44  are connected to the control or regulating device ECU such that they transmit sensor signals, which the unit can process, and based on which the wrapping process of the bale  16  with wrapping sheet  18 , can be controlled or regulated. 
   The sensors  42  and  44  can be, for example, optical sensors, mechanical sensors, distance sensors, such as ultrasound sensors or proximity sensors, light barriers, infrared sensors or any other suitable type of sensor. A combination of different sensor types is also possible. 
   Particularly suited are optical sensors that respond to changes or differences in color or contrast. Such sensors beyond that make it possible, with a corresponding design of the wrapping sheet  18 , to determine the length of unwound wrapping sheet. For example, the wrapping sheet  18  may be provided with different colors, markings or the like at specific intervals. Moreover, it allows conclusions of the actual rotating speed of the bale by conducting parallel to this a time recording or measurement process. 
   The following shall explain the function of the wrapping device  14  in more detail. 
   When the formation of the bale  16  in the baling chamber  12  has been completed, which is detected in a known fashion with a sensor (not shown), which determines for example mechanically or visually the size of the bale  16 , the device  14  is activated. This occurs when the control or regulating device ECU selects the hydraulic motor  38  and moves it into the depicted retracted position. 
   In this position, the devices  24  are set in rotating motion. The devices  24  now pull the wrapping sheet  18  off the supply device or reel  28 . The wrapping sheet  18  approaches the bale  16  between the rollers  20 , during which process it is supported by the guiding device  40 . 
   When the device  14  functions properly, the wrapping sheet  18  is seized and conveyed by the bale  16 , causing the bale  16  to become wrapped with the wrapping sheet  18  through its own rotation. 
   The first sensor  42  downstream from the wrapping sheet feed location  21  now detects, for example optically, mechanically or in a different fashion, whether the wrapping sheet  18  is present on the bale  16  and, thus, whether the wrapping process started properly. If the sensor  42  detects that no wrapping sheet  18  is present on the bale  16 , the sensor  42  supplies a corresponding signal to the control or regulating unit ECU. The regulating unit can now suspend the wrapping operation and for example stop the bale  16  from rotating or stop the devices  24  from pulling further wrapping sheet  18  off the supply device  28 . Beyond that, it can be provided that the malfunction is indicated to an operator, for example by means of a display or another visual or also acoustic signal, to allow the operator to stop the wrapping operation. 
   If the sensor  42  supplies a signal that shows that the bale wrapping operation has started properly, the process will continue. Subsequently, the second sensor  44  detects whether the bale  16  has been wrapped entirely with a first layer of the wrapping sheet  18 . If this is the case, the bale wrapping operation continues. The end of this operation is then determined in the conventional fashion, for example, after a specified duration or by setting a specific wrapping sheet length. The determination of the wrapping sheet length may be determined by one of the sensors  42  or  44 , as described previously, or an additional sensor could be provided, which records, for example, the number of revolutions of the bale  16  or the supply device  28 . 
   If the second sensor  44  detects that no wrapping sheet  18  is present on the bale  16 , a corresponding signal is transmitted to the control or regulating device ECU, which proceeds in accordance with a corresponding signal provided by the first sensor  42 . 
   After properly concluding or ending the wrapping process, the severing device  26  is operated to cut the wrapping sheet, and the wrapped bale  16  can be ejected from the baling chamber  12  of the baling press  10  in the conventional 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.