Patent Document

BACKGROUND 
     The invention relates generally to take-up frames and similar structures for rotating machinery bearings. In particular, the invention relates to a load indicating system for take-up frames. 
     In rotating equipment, such as conveyor belts, chain drives or other systems, bearing assemblies are provided for securing a rotating element, such as a shaft, with respect to support or stationary components. Typically, one end of the system is fixed in position, while the opposite end is moveable. For example, the fixed end may be supported on a pillow block, while structures such as take-up frames are provided on the moveable end to allow for tension adjustment. 
     Take-up frames have a framework for supporting a moveable bearing set. Specifically, the framework may include glides, or guiding rails which support the bearing set while allowing it to move within the framework. A tension or compression adjustment member, such as a threaded rod may be supported by a threaded nut. Special bearing sets may be employed, including housings adapted to receive the tension or compression adjustment member. The position of the bearing assembly is adjusted by turning the thread rod or the nut to slide the bearing set into the desired location, hereby adjusting the tension on a belt, chain, or other component supported by the take-up frame bearing. 
     Such take-up frames and bearing sets are employed to maintain tensile or compressive forces within machine systems. Upon installation, the take-up frames are situated generally parallel to the forces to be regulated, such that adjustment of the bearing set position will tend to tighten or relax a machine component fitted around an associated rotated member. For example, in belt conveyors and the like, take-up frames are often positioned on either side of a pulley. In chain drives, take-up frames may be positioned on one or both sides of an endless chain. Changes in the initial installed tensile or compressive forces may cause premature wear and require frequent component repair or replacement. Moreover, it is often difficult to judge the force or tension set via adjustment of the take-up frame both during initial installation and subsequently, as the system relaxes or wears. 
     There is a need, therefore, for arrangements that will permit measurement or feedback of forces exerted by a take-up frame. There is a particular need for relatively simple, mechanical systems that can provide such feedback in a reliable manner. 
     BRIEF DESCRIPTION 
     The present invention provides a technique for regulating forces applied to a take-up frame. The technique may be used in systems in which the take-up frame is positioned either in tension or compression, providing feedback on forces exerted on the bearing sets in either case. 
     In accordance with one aspect of the present invention a bearing take-up frame assembly is provided comprising a bearing housing configured to move within a take-up frame framework, and a force transmission member coupled to the bearing housing. The force transmission member is configured to apply force to the bearing housing. A spring member is to be compressed as force is applied by the transmission member to the bearing housing. A load indicating apparatus mechanically measures the displacement of the spring member and indicates the amount of force being applied. 
     In accordance with another embodiment of the present invention a take-up frame system is provided comprising a rotating component supported by first and second bearing sets, a first take-up frame and a second take-up frame supporting the first and second bearing sets, respectively. The take-up frames each include force transmission members coupled to the bearing sets, and spring members having an axis of displacement parallel to a longitudinal axis of the force transmission member. Force indicating mechanisms are configured to indicate the displacement of the spring members. 
     In accordance with another aspect of the invention, a method of operating a take-up frame is provided comprising reading a force indication that is obtained and provided through mechanical means. The amount of force applied is then adjusted to achieve a desired amount of force. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  illustrates a take-up frame assembly in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  is a side view of the take-up frame of  FIG. 1 , configured to provide force feedback to a user in accordance with an exemplary embodiment of the present invention; 
         FIG. 3  illustrates a load indicating plate for use in the arrangement of  FIGS. 1 and 2 , in accordance with an exemplary embodiment of the present invention; and 
         FIG. 4  illustrates steps in an exemplary method for operating a force indicating take-up frame of the type shown in the previous FIGS. in accordance with an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The techniques and apparatus described herein allow a user to reach and maintain proper tensile or compressive forces on a bearing assembly or transmission component supported by the bearing assembly. The maintenance of proper tensile or compressive forces helps to reduce unnecessary maintenance and downtime that may result from an improper or unbalanced loading of bearing housings. Proper adjustment also enhances the normal operation of components such as belt conveyors, chain drives, and so forth. 
     Turning to the drawings, and referring first to  FIG. 1 , a take-up frame assembly is illustrated as applied to lateral sides of a belt conveyor and is generally designated by reference numeral  10 . Assembly  10  includes a shaft  12  supported on both ends by bearing assemblies  14 . To maintain appropriate loading on the bearing assemblies  14  and, consequently, also the shaft  12 , each bearing assembly  14  is positioned inside a take-up frame  16 . The take-up frame  16  is mounted on a support structure  18 . The support structure  18  may be any appropriate machine support such as a stand or a support framework. 
     The take-up frame  16  provides a framework that allows the bearing assembly  14  to move linearly in order to adjust the tensile forces applied to the bearing assembly  14 . As will be appreciated by those skilled in the art, through appropriate adjustment of the take-up frame  16 , and consequent movement of bearing assemblies  14  on either side of the shaft  12 , the tension on belt  22  may be adjusted to a level appropriate for the anticipated loading of the take-up frame assembly  10  and the belt. Additionally, appropriate adjustment of the take-up frame  16  helps to properly situate the belt  22  on pulley  20  and avoids lateral creep. 
     In the presently disclosed technique, visual feedback of applied force allows a user to readily discern proper adjustment. Specifically, as will be described in greater detail below, a mechanical apparatus is provided to indicate force exerted on a bearing assembly  14 . 
     As mentioned earlier, each bearing assembly  14  is mounted in a take-up frame  16  so that it is able to move to adjust the tensile or compressive forces on the belt  22 . A force transmission member  24 , such as a threaded rod, for example, is attached to the bearing assembly  14 . A hex nut  26  supports the force transmission member  24  within the take-up frame  16 . As the hex nut  26  or the transmission member  24  is turned, tensile or compressive forces are adjusted. Specifically, as the hex nut  26  is tightened on the forced transmission member  24 , the bearing assembly  14  may move within the take-up frame in order to apply force to the belt  22 . Alternatively, the hex nut  26  can be loosened in order to reduce the tensile forces applied to the bearing assembly  14  and the belt  22 . Movement of the bearing assembly  14  towards the hex nut  26  is limited by an end plate  28 . The end plate  28  prevents the bearing assembly  14  from exiting the take-up frame  16 . 
     As the take-up frame  16  may be used in harsh environments, such as in food processing plants or in mining operations, a cover  30  is provided to prevent debris from coming into contact with parts of the take-up frame  16 . The cover  30  is secured to the take-up frame  16  by a slotted guidepost  32  which fits over the threaded rod and is held in place by the hex nut  26 . The cover  30  and slotted guidepost  32  may be welded together at a 90 degree angle. Additionally, a lower guide  36  and an upper guide  38  hold the cover in place, as can be seen in  FIG. 2 . A position indicating piece, such as a cone point set screw  40  is attached to the cover  30  in order to indicate movement of the cover  30  relative to the take-up frame  16 , as will be discussed in detail below. 
     A side view of the take-up frame  16  is illustrated in  FIG. 2  in accordance with an exemplary embodiment of the present invention. As can be seen in this view, the cone point set screw  40  protrudes through the cover  30  so that the cone point is directed at a load indicating plate  42  mounted on the take-up frame  16 . Movement of the cone point set screw  40  relative to the load indicating plate  42  indicates the amount of force being applied by the force transmission member  24  to the bearing assembly  14 . Specifically, the cone point set screw  40  points to imprinted or inscribed numbers on a load indicating plate  42 . 
     The load indicating plate  42  is attached to the take-up frame  16  and may have numbers imprinted, etched, or otherwise placed on it. Alternatively, markings may be made directly to the take-up frame  16  itself, however, such an embodiment may be limited in its ability to be calibrated. As illustrated, the numbers may increase in steps of 400, or in any other incremental step (typically depending upon the range of force that can be applied to the take-up frame, and the reasonable subdivisions of the range). Alternatively, the load indicating plate  42  may simply have markings to indicate relative displacement of the cover  30  to the take-up frame  16 . Furthermore, the load indicating plate  42  may have markings to indicate an ideal load level or a range of acceptability for a particular application. 
     The numbers or markings on the load indicating plate  42  correspond to an amount of tensile or compressive force applied to the bearing assembly  14  by the force transmission member  24 . As such, units corresponding to the numbers may be in Newtons, or pounds-force, for example. 
     The amount of force applied can result from, and be approximated through the use of a spring mechanism such as Belleville washers  44 . As will be appreciated by those skilled in the art, the force applied to the bearing assembly will depend upon the effective aggregate spring constant of the Belleville washers, and the compression (i.e., change in aggregate length) of the collection of washers, according to the force equation: F=Kx, where F is force, K is the aggregate spring constant, and x is the compression of the set of washers or displacement of the bearing set. The Belleville washers  44  may be positioned on the force transmission member  24  between an outboard washer  46  and an inboard washer  48 . The outboard washer  46  may be placed on the end plate  28  of the take-up frame  16 , while the inboard washer  48  is on the opposite side of the slotted guidepost  34  from the hex nut  26 . The Belleville washers  44  have specific spring constants k that can be obtained from their manufacturer. Moreover, the spring constant k can vary according to the stacking orientations of the washers. For example, the washers can be stacked in the same direction to provide a stiffer spring and maintain the constant k. The washers may also be stacked by alternating their orientation to provide a lower spring constant and greater displacement or deflection for the same applied force. Using such stacking techniques allows for specific spring constants and deflection characteristics to be achieved. The effective aggregate constant K, then is generally the combination (e.g., average) of the constants k, and is selected, along with the overall length of the collection of washers, to provide the desired tension and length adjustability ranges for the take-up frame assembly. 
     Once the spring constant K is known, the displacement of the Belleville washers  44  is all that is needed to calculate the force applied to the bearing assembly. Accordingly, an approximation of the amount of force applied to the bearing assembly  14  can be obtained by measuring the aggregate deflection or displacement of the Belleville washers  44 . Because the end plate  28  of the take-up frame  16  is fixed, and the cover  30  is attached to the opposite end of the washer stack, the aggregate displacement of the washers may be determined by measuring the amount of movement of the cover  30  relative to the take-up frame  16 . 
     It should be noted that any suitable tension or compression arrangement may be used in place of the Belleville washers shown in the figures and described here. These might include both tension and compression springs, compression members of various types (e.g., fluid cylinders), and so forth. 
     An initial calibration may be necessary to ensure accurate approximation of the force. Specifically, when installing the take-up frame assembly  10  the cone point set screw  40  and the load indicating plate  42  may need to be properly aligned. As illustrated in  FIG. 3 , the load indicating plate has adjustment slots  50  configured to allow movement of the load indicating plate  42 . Adjustment screws  52  are provided to secure the load indicating plate  42  to a take-up frame  16 . To calibrate the load indicating take-up frame, the load indicating plate  42  is moved so that the cone point set screw  40  is aligned with the zero position on the load indicating plate  42 , with the washers under substantially no compression. 
     Operation of the take-up frame assembly  10  includes the tightening or loosening of the hex nut  26 . Initially, the tightening of the hex nut  26  will only move the bearing assembly within the take-up frame  16 . Specifically, the bearing assembly will move towards the end plate  28  and remove slack from the belt  22 , or any other component supported by the bearing assembly. Eventually, the slack is removed from the belt and tightening of the hex nut  26  provides tension force to the bearing assembly  14  (i.e., preloading). As the Belleville washers  44  are compressed between the outboard washer  46  and the inboard washer  48 , displacement occurs. The displacement of the Belleville washers  44  allows the cover  30  to move parallel to the take-up frame  16 . Consequently, the cone point set screw  40  moves relative to the load indicating plate  42  and a user can easily obtain an estimation of the forces being applied to the bearing assembly. 
     Turning to  FIG. 4 , a technique of operation for a load indicating take-up frame is shown and generally indicated by the reference numeral  60 . The technique  60  includes an initial calibration as indicated at box  62 . The calibration may include moving a load indicating plate  42  into alignment with a cone point set screw as discussed above, with no preload on the assembly. 
     Once the take-up frame has been calibrated, a hex nut  28  can be tightened on a force transmission member  24  to provide tension, as indicated at block  64 . Initially, the tightening of the hex nut  26  will remove slack from a conveyor belt, chain assembly, or other system component. Once the slack is removed, tensile or compressive forces will be applied to a bearing assembly  14  within the take-up frame  16 . As the tension increases, a spring member, such as Belleville washers  44 , deforms or is displaced from an initial position. A cover  30  coupled to the spring member is displaced relative to the take-up frame  16  a distance corresponding to the displacement of the spring member. 
     A user can consult the load indicating plate  42  and obtain an approximation of the amount of tension being applied to the bearing assembly  14  in the take-up frame  16 , as indicated at block  66 . Specifically, a user can read a number value from the load indicating plate  42  that corresponds to the position of a cone point set screw  40  as discussed above. The number value correlates with the amount of force being asserted by the force transmission member  24  to the bearing assembly  14 . Because the force feedback is purely mechanical, the feedback is instant, and requires no connection to any external power source or network. 
     The ability to read the tension from the load indicating plate  42  allows a user to adjust the tension to a desired load, as indicated at box  68 . Specifically, it may be necessary to have the tension in a take-up frame  16  be equal to the tension of another take-up frame supporting a common belt or chain assembly. As discussed above, imbalance in loading may cause premature wear on parts necessitating repair or replacement. As such, the technique  60  helps to reduce downtime and repair expenses by allowing proper and balanced loading. Similarly, over time, the system components (e.g., a conveyor belt) may wear or stretch, and proper force adjustment of the system will be facilitated by the same steps summarized above. 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Technology Category: 2