Patent Publication Number: US-2022221028-A1

Title: Clamp, system and method for measuring tension in a conveyor belt

Description:
TECHNICAL FIELD 
     This application claims priority from Australian provisional patent application no. 2019901411 filed on 26 Apr. 2019, the contents of which are incorporated by reference. 
     TECHNICAL FIELD 
     The invention relates to a clamp for a conveyor belt. In particular, the invention relates to a clamp, a system and associated method for measuring tension in a conveyor belt. 
     BACKGROUND 
     Conveyor systems often require maintenance such as if the conveyor belt becomes damaged or to change rollers of the conveyor system. During such maintenance, the belt may need to be held so that tension can be removed from damaged sections to, for example, allow a new section of belt to be spliced with the existing belt or allow a roller to be replaced. Accordingly, many types of belt clamps have been developed that hold the belt to allow such maintenance to take place. 
     One example of a belt clamp includes two flat bars arranged to each transverse the belt and engage with opposing side faces of the belt, and clamps at opposing ends of the flat bars. Once the two flat bars are in position, the clamps are tightened to compress the flat bars toward one another and thereby secure the belt. More than one belt clamp may be used such as to isolate a section of the belt to be repaired. 
     A problem with such belt clamps is that the clamps are designed with a load rating relating to the inline tension of the belt. However, it is difficult to determine, and often unknown, what actual tension is being applied to the belt or the load on the clamps, in use. Accordingly, the belt clamps may unexpectedly fail due to over loading, or the high tension within the belt may damage the belt or other parts of the conveyor system. 
     The invention disclosed herein seeks to overcome one or more of the above identified problems or at least provide a useful alternative. 
     SUMMARY 
     In accordance with a first broad aspect there is provided, a clamp for measuring a tension of a conveyor belt, the clamp including a clamping portion arranged to engage with opposing faces of the conveyor belt in a clamped condition to hold the conveyor belt relative to an anchor, and a load sensing arrangement between the clamping portion and the anchor, the load sensing arrangement configured to provide a signal indicative of the tension in the conveyor belt in the clamped condition. 
     In an aspect, the load sensing arrangement includes at least one load sensor arranged to measure at least a load applied in a direction inline with the belt. 
     In another aspect, the clamping portion includes a first clamping section and a second clamping section arranged to each engage with the opposing faces of the conveyor belt in the clamped condition. 
     In yet another aspect, the first clamping section is movable relative to the second clamping section to engage with the conveyor belt in the clamped condition. 
     In yet another aspect, the load sensing arrangement is connected to the first clamping section so as to be movable therewith. 
     In yet another aspect, the load sensing arrangement includes a load sensing section between the first clamping section and the anchor, and wherein the load sensing section carries the at least one load sensor. 
     In yet another aspect, the load sensing section has a substantially dog-bone shape. 
     In yet another aspect, the load sensing section is located between the first clamping section and the anchor, and wherein the load sensing section carries the at least one load sensor. 
     In yet another aspect, the at least one load sensor is provided in the form of two strain gauges each located proximate respective opposing upper and lower surfaces of the load sensing section. 
     In yet another aspect, a free end of the load sensing section is coupled with an anchor point that is in turn coupled with the anchor in the clamped condition. 
     In yet another aspect, the second clamping section is substantially fixed. 
     In yet another aspect, the clamp includes a main body with a top and a bottom, the second clamping section being provided toward the top and the first clamping section being pivotally supported by a pivotal coupling arranged between the bottom and the first clamping section. 
     In yet another aspect, the pivotal coupling is arranged to maintain a first clamping surface of the first clamping section substantially parallel to the conveyor belt. 
     In yet another aspect, the pivotal coupling is arranged to allow the first clamping section to increase a clamping force on the belt in response to an increase in tension within the conveyor belt. 
     In yet another aspect, the pivotal coupling includes two parallel members pivotally coupled at spaced apart locations between the bottom and the first clamping section. 
     In yet another aspect, the main body includes opposing sides between the top and the bottom, one of the opposing sides having a slot in which an edge of the conveyor belt is receivable. 
     In yet another aspect, the clamp includes a retainer arranged to maintain the clamp in the clamped condition. 
     In yet another aspect, the load sensing arrangement includes a communication device arranged to communicate a signal indicative of the tension to an external device. 
     In accordance with a second broad aspect there is provided, pair of clamps adapted to couple with opposing side edges of a conveyor belt, each one of the pair clamps formed in accordance with one or more aspects of the clamp described above and herein. 
     In accordance with a third broad aspect there is provided, a system for detecting load in a conveyor belt. The system including: a pair of clamps each having respective clamping portions adapted to clampingly engage with opposing side edges of the conveyor belt in a clamped condition; an anchoring arrangement arranged to couple with an anchor point of the pair of clamps to anchor the pair of clamps to a fixed structure; a load sensing arrangement including a load sensing section located between at least one of the respective clamping portions of the pair of clamps and the anchoring arrangement, each load sensing section including a load sensor and a communication device arranged to communicate a load signal; and a receiving device configured to receive the load signal so as to provide an indication of a tension in the conveyor belt in the clamped condition. 
     In accordance with a fourth broad aspect there is provided, a method for detecting load in a conveyor belt, the method including the steps of: fitting a pair of clamps to opposing edges of the conveyor belt and moving at least one of the respective clamping portions of the pair of clamps to engage with opposing side edges of the conveyor belt in a clamped condition; coupling an anchoring arrangement to a load sensing section associated with one or both of the clamping portions of each pair of clamps; transmitting, via a communication device associated with load sensors fitted to each load sensing section, a load signal; and receiving, at a receiving device, the load signal so as to provide an indication of a tension in the conveyor belt in the clamped condition. 
     In an aspect, the method further includes: determining a measured belt tension based on the load signal; and comparing the measured belt tension with a predetermined threshold belt tension; and providing an alert if the measured belt tension exceeds the predetermined threshold belt tension. 
     In accordance with a fifth broad aspect there is provided, a clamp for measuring tension of a conveyor belt, the clamp including a clamping arrangement adapted to engage with opposing faces of the conveyor belt in a clamped condition to hold the conveyor belt relative to an fixed anchor, and a load sensing arrangement associated with the clamping arrangement configured to provide a signal indicative of the tension in the conveyor belt in the clamped condition. 
     In accordance with a sixth broad aspect there is provided, a clamp for measuring a tension of a conveyor belt, the clamp including a clamping part arranged to engage with at least one opposing face of the conveyor belt in a clamped condition to hold the conveyor belt relative to an anchor, and a load sensor operatively arranged between the clamping part and an anchor point connectable to the anchor, the load sensor being configured to provide a signal indicative of the tension in the conveyor belt in the clamped condition. 
     In accordance with a seventh broad aspect there is provided, a system for measuring a tension of a conveyor belt, the system including: a clamp including a clamping part arranged to engage with at least one opposing face of the conveyor belt in a clamped condition to hold the conveyor belt relative to an anchor, a load sensor operatively associated between the clamping part and an anchor point connectable to the anchor so as to provide a signal indicative of the tension of the conveyor belt in the clamped condition; and a device adapted to receive the signal, and at least one of display a measured tension value and provide an alert if the measured tension value exceeds a predetermined value. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention is described, by way of non-limiting example only, by reference to the accompanying figures, in which; 
         FIG. 1  is a perspective view illustrating a first example one of a pair of clamps for a conveyor belt; 
         FIG. 2  is a side view illustrating one of the pair of clamps; 
         FIG. 3  is a top view illustrating one of the pair of clamps; 
         FIG. 4  is an opposing side view illustrating one of the pair of clamps; 
         FIG. 5  is a front view illustrating one of the pair of clamps; 
         FIG. 6  is a side view illustrating one of the pair of clamps with a side wall removed to reveal the clamping portion moved toward a clamped condition with a retaining mechanism fitted to limit movement of the clamping portion; 
         FIG. 7  is a side sectional view illustrating one of the pair of clamps along section A-A as shown in  FIG. 3 ; 
         FIG. 8  is another perspective view illustrating one of the pair of clamps showing the position of a load sensor; 
         FIG. 9  is an underside perspective view illustrating one of the pair of clamps showing the position of another load sensor; 
         FIG. 10  is a perspective view illustrating a conveyor belt fitted with a system including a clamp fitted to an edge of the conveyer belt and an anchoring arrangement to secure the clamp to a fixed structure; 
         FIG. 11  is another perspective view illustrating the conveyor belt fitted with a system including the clamp, with a side of one of the clamp removed to reveal the internal clamping portions engaged with the conveyor belt; 
         FIG. 12  is a system block diagram illustrating the load sensor arrangement of the belt clamps in communication with an external device; 
         FIG. 13  is a perspective view illustrating a second example of one of a pair of clamps for a conveyor belt; 
         FIG. 14 a    is a side view illustrating the second example of the clamp; 
         FIG. 14 b    is a side view illustrating the second example of the clamp with a cover removed to show the internal configuration thereof; 
         FIG. 15 a    is a side view illustrating the second example of the clamp with the clamping arrangement moved toward a clamped condition; 
         FIG. 15 b    is a side view illustrating the second example of the clamp with the clamping arrangement moved toward a clamped condition and the cover removed to show the internal configuration; 
         FIG. 16  is an opposing side view the second example of the clamp; 
         FIG. 17 a    is a frontend view illustrating the second example of the clamp; 
         FIG. 17 b    is a backend view illustrating the second example of the clamp; 
         FIG. 18 a    is a bottom view illustrating the second example of the clamp; and 
         FIG. 18 b    is a top view illustrating the second example of the clamp. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 to 12 , there is shown a first example of a clamp  10  for coupling with a conveyor belt  12  to determine or measure a tension of the conveyor belt  12 . The clamp  10  may be provided as part of a system  5  that includes pairs of left-hand and right-hand clamps  10  adapted to couple with opposing edges  14  of the conveyor belt  12  and an anchoring arrangement  16  to couple the pairs of left-hand and right-hand clamps  10  to an anchor  12  that may be a fixed structure such as an anchor block or a frame. The anchoring arrangement  16  may be referred to as a “chain-block”. The system  5  may further include a load sensing arrangement  22  associated with the clamp  10  that may be in communication with a remote device  74  (shown in  FIG. 12 ) that may be used to, for example, display the tension present in the conveyor belt  12 . 
     Each clamp  10  includes a clamping portion or arrangement  18  arranged to engage with opposing faces  20  of the conveyor belt  12  in a clamped condition, and in this example of the load sensing arrangement  22  is operative between the clamping portion  18  and an anchor  24  of the anchoring arrangement  16 . The load sensing arrangement  22  is configured to provide an indication of a tension in the conveyor belt  12  in the clamped condition as is further detailed below. It is noted that in the clamped condition the conveyor belt  12  is typically stationery. 
     Turning to the clamp  10  configuration in more detail, as best shown in  FIGS. 1 to 7 , the clamp  10 , more specifically the clamping portion or arrangement  18 , thereof includes a first clamping section  28  and a second clamping section  30  arranged to each engage with the opposing faces  20  of the conveyor belt  12  in the clamped condition. The first clamping section  28  and a second clamping section  30  are substantially housed by a main body  26  having a top  32 , a bottom  34 , opposing ends  36   a ,  36   b , and opposing sides  39 . 
     It is noted that in this example the end  36 a is provided by a C-section  37  arranged to facilitate a length of RHS (Rectangular Hollow Section) to pass through and be clamped via a bolt (not shown) and nut (not shown) via an aperture  41 . This purpose of the RHS is to provide a structural coupling point to enable lifting of the belt  12 , via the clamp  10 , with a belt lifter (not shown). 
     In this example, the first clamping section  28  includes a movable clamping member  40  pivotally coupled by a linkage  38  to the bottom  34  of the main body  26 . The second clamping section  30  is provided by the top  32  of the main body  26  such that in the clamped condition, the belt  12  is clamped by the first clamping section  28  pivotally elevating toward the top  32  with the first clamping section  28  being moved and the second clamping section  30  being fixed. 
     The linkage  38  is arranged to maintain a clamping surface  42  of the clamping member  40  generally parallel to the opposing faces  20  of the belt  12  (shown in  FIG. 11 ) and the clamping surface  44  of the second clamping section  30  toward the top  32 . This ensures a generally flat contact area between the clamping surfaces  42 ,  44  and the belt  12 . It is noted that in some examples, the clamping surfaces  42 ,  44  may include surface features such as ribs, teeth, grooves or serrations to increase the friction grip on the belt  12 . 
     In this example, the linkage  38  includes two linkage members  45  that are arranged in a parallel spaced relationship between upper pivots  48  at the clamping member  40  and corresponding lower pivots  50  at the bottom  34 . The arrangement the linkage  38  allows the clamping member  40  to be “floating” and increase its clamping force when the belt  12  is relatively tensioned as is further detailed below. Further, importantly, the “floating” of the clamping member  40  allows the force, namely shear force, to be transferred to the clamping member  40  and load sensing section  58  thereby allowing a measurement indicative of the belt tension/load. 
     As aforesaid, the clamp  10  may be provided as pairs of left-hand and right-hand clamps  10  and an appropriate one of the opposing sides  39  of the main body  26  includes an opening  54  in the form of a slot  56  to allow the opposing edges  14  of the belt  12  to be received between the first clamping section  28  and the second clamping section  30 . The main body  26  includes an internal wall  52  that provides an end of travel stop  55  to hold the first clamping section  28 , more specifically the movable clamping member  40 , in an initial position that is aligned with the slot  56  to allow the opposing edges  14  of the belt  12  to be received and located prior to the first clamping section  28  and the second clamping section  30  being relatively moved to the clamped condition. The initial condition is shown best in  FIG. 7 . 
     The clamp  10  may further include a retaining or locking mechanism  51 , best shown in  FIG. 6 , to hold the clamp  10  in the clamped condition. In this example, the retaining mechanism  51  includes a threaded bolt  53  that engages with a knob  57  of one of the linkage members  45 . However, other arrangements are possible. It is noted the arrangement of the retaining mechanism  51  holds the linkage members  45  against movement back toward the initial condition. However, the linkage members  45  are not locked from movement further toward the clamped condition and thereby remain able to “float” and responsive to an increase in clamping force. 
     Turning now to the load sensing arrangement  22  in more detail and referring to  FIGS. 7, 8, 9, 11 and 12 , the load sensing arrangement  22  includes a load sensing section  58  that has one or more load sensors  59  fitted thereto. The load sensing section  58  is fitted between the clamping member  40  of the first clamping section  28  and an anchor point  17  that is coupled with the anchoring arrangement  16 , in use. In this example, the load sensing section  58  has a dog-bone shaped cross section with opposing sides  62 , a top face  64 , a bottom face  66 , opposing ends  69  and a waist  71  between the opposing ends  69 . However, in other examples, the load sensing section  58  may have alternative shapes that achieve a similar purpose. 
     The one or more load sensors  59  are provided in the form of resistive strain gauges  68  fitted to the waist  71  at the top face  64  and the bottom face  66 , respectively. However, the one or more load sensors  59  may be placed elsewhere as appropriate. The resistive strain gauges  68  are oriented lengthwise along the load sensing section  58  between the opposing ends  69 . It is noted that the load sensing section  58  and the clamping member  40  may be formed as a single part such as being machined from a single piece of metal. 
     The anchor point  17  is connected to a free end  78  of the load sensing section  58  and is the coupled to a tether  80  of the anchoring arrangement  16 . In this example, the anchor point  17  is pivotally coupled to the free end  78  and may be provided in the form of a D-ring, shackle or the like. 
     In this example, the strain gauges  68  are arranged in a half bridge configuration and are wired as two quarter bridges. However, other suitable arrangements may be utilized. Both strain gauges  68  are connected to a communication device  70 , as shown in  FIG. 12 . The communication device  70  may be fitted to the clamp  10  and electrically connected to the strain gauges  68 . In other examples, the communication device  70  may be removable or remote to the strain gauges  68 . 
     The communication device  70  may be provided in the form of a microcontroller  72  with a Bluetooth™ chip to allow for wireless communication with Bluetooth™ enabled devices. Such devices may include remote receiving devices  74  such a smart phones or tablets  76 . However, other forms of wired and wireless communication and corresponding receiving devices may be utilized. 
     It is noted that the two quarter bridge strain gauges in conjunction allow measurement of force along the belt line by subtracting the bending element of strain from the total and using that resultant as the horizontal force element. Accordingly, the “tension” in the belt may be determined and monitored. 
     The determination of the tension may be performed by the microcontroller  72  or at the receiving device  74 . In some examples, a predetermined threshold tension value may be set at the microcontroller  72  or at the receiving device  74 , and an indication or alert may be provided, such as at the receiving device  74 , if the measured tension exceeds the predetermined threshold tension. The predetermined threshold tension may, for example, be set by a user such as via the receiving device  74  for particular situations, sites and types of conveyor belt systems. Simply as an example, the predetermined threshold tension may be in the range of 1,000 kg to 10,000 kg, or other value, as required. 
     The receiving device  74  may include a screen with an interface to display the tension value or the like. Alternatively, the receiving device  74  may include an audible alert or a flashing light. The receiving device  74  may also be configured to display the current tension and the predetermined threshold tension. 
     The remote receiving device  74  may also be configured to communicate with a remote server (not shown), such an arrangement, could have, for example, application software operating on the remote receiving devices  74  that is in communication with the remote server. Other configurations may include the remote receiving devices  74  being at or part of a plant control system to provide the current tension and the predetermined threshold tension to a plant operator. Various similar configurations as also possible. 
     In use, the system  5  is fitted to a conveyor belt  12 , such as during maintenance of the belt or rollers, by firstly fitting a pair of edge clamps  10  to the opposing edges  14  of the conveyor belt  12  and relatively moving the respective clamping portions  18  of the pair of edge clamps  10  to engage with opposing side faces  20  of the conveyor belt  12  in the clamped condition. The pair of edge clamps  10  may then be retained in the clamped condition using the retaining mechanism  51 . It is noted that the clamps  10  fit the edges  14  of the belt  12  and are therefore able to be used with curved or flat sections of belt. 
     Tethers  80  of the anchoring arrangement  16  are then coupled to the anchor points  17  at the free ends  78  of each of the load sensing sections  58  of each pair of edge clamps  10 . The arrangement is such that the relative tension between the static anchoring arrangement  16  and the belt  12  causes movement of the first clamping section  28 , namely the clamping member  40 , toward the clamped condition. Once engaged and clamped onto the belt  12  such relative tension is then measurable by the load sensing arrangement  22 , namely the load sensors  59  in the form of the resistive strain gauges  68 . 
     The measured load signals are then transmitted via the communication device  70  to the receiving device  74  for viewing or monitoring. As aforesaid, such a receiving device  74  may be configured to provide an alert if the determined tension exceeds a predetermined threshold value. For example, software loaded by a processor of the receiving device  74  may monitor and compare the measured load signal with the predetermined threshold value stored in memory, and then provide an alert such as a light, message or alarm if the determined tension exceeds the predetermined threshold value. 
     The clamp  10  and parts thereof are substantially formed from metal or other suitable material. 
     Referring now to  FIGS. 13 to 18   b  there is shown a second example of the clamp  110 . The second example of the clamp  110  functions in the same way as the above described first example and may be used on the same manner with the system  5 . However, in this example some of the geometry and configuration of parts have been altered. Accordingly, all of the parts and functions are not again described here and like sequences of numerals (i.e 10, 110 or 18, 118) are used to denote like or similar parts. 
     In this example of the clamp  110 , like the first example, the clamping portion or arrangement  118  includes a first clamping section  128  and a second clamping section  130  arranged to each engage with the opposing faces  20  of the conveyor belt  12  in the clamped condition, in a similar manner to that described above in relation to the first example. The first clamping section  128  and a second clamping section  130  are substantially housed by a main body  126  having a top  132 , a bottom  134 , and opposing ends  136   a ,  136   b , and front and back sides  139   a ,  139   b.    
     In this example, the main body  126  has a different construction and shape in comparison to the first example with the opposing ends  136   a ,  136   b  being shaped plates that are interconnected by spaced apart round members  127  located toward the back side  139   a  and are shaped to support the top  132 . The round members  127  also serve as handles to allow manual handling. 
     In this example, like the first example, the first clamping section  128  includes a movable clamping member  140  pivotally coupled by a linkage  138  to the bottom  134  of the main body  126 . A cover or plate  141  is provided in this example that at least partially covers a side and bottom the movable clamping member  140  at or toward the front side  139   a . The cover  141  also may support an underside of the movable clamping member  140  to provide an end of travel stop, and also may serve a safety purpose to reduce or remove pinch points. The cover  141  is shown removed in  FIGS. 14 b  and 15 b   . Above the cover  141  and below the second clamping section  130  is defined a slot shaped mouth  156  in which the conveyor belt  12  is initially received before being clamped in the clamped condition. 
     The second clamping section  130  is provided by the top  132  of the main body  126  such that in the clamped condition, the belt  12  is clamped by the first clamping section  128  pivotally elevating toward the top  132  with the first clamping section  128  being moved and the second clamping section  130  being fixed. 
     In this example, the linkage  138  includes two linkage members  145  that are arranged in a parallel spaced relationship between upper pivots  148  at the movable clamping member  140  and corresponding lower pivots  150  at the bottom  134 . The arrangement the linkage  138  allows the clamping member  140  to be “floating” as with the first example. 
     The clamp  110  may further include a retaining or locking mechanism  151 , best shown in  FIG. 15 b   , to hold the clamp  110  in the clamped condition. In this example, the retaining mechanism  151  includes a threaded bolt  153  that engages with the movable clamping member  140  or linkage members  145 . The bolt  153  is fitted through a vertical elongate aperture  157  that allows some vertical movement of the bolt  154  when not tensioned to allow movement of the clamping member  140  and linkage members  145 . 
     When the bolt  153  is tightened, the retaining mechanism  151  holds the linkage members  145  against movement back toward the initial condition. However, the linkage members  145  are not locked from movement further toward the clamped condition and thereby remain able to “float” and responsive to an increase in clamping force. 
     Turning now to the load sensing arrangement  122  in more detail and referring to  FIGS. 14   ba  and  15   b , the load sensing arrangement  122  includes a load sensing section  158  that has one or more load sensors  159  fitted thereto. The load sensing section  158  is fitted between the clamping member  140  of the first clamping section  128  and an anchor point  117  that is coupled with the anchoring arrangement  116 , in use. 
     In this example, the load sensing section  158  has a dog-bone shaped cross section like the first example. However, in other examples, the load sensing section  158  may have alternative shapes that achieve a similar purpose. Like the first example. the one or more load sensors  159  are provided in the form of resistive strain gauges  168  fitted to the load sensing section  158 . The anchor point  117  is connected to a free end  178  of the load sensing section  158  and like the first example may be coupled to a tether  180  of the anchoring arrangement  116 . In this example, the anchor point  117  is pivotally coupled to the free end  178  and may be provided in the form of a D-ring, shackle or the like. 
     Like the first example, both strain gauges  168  are connected or associated with a communication device  70 , as shown in  FIG. 12 . The communication device  70  may be fitted to the clamp  110  and electrically connected to the strain gauges  68 . In other examples, the communication device  70  may be removable or remote to the strain gauges  168 . Accordingly, the second example of the clamp  110  may be interchanged with the first example of the clamp  10  to function in the above described system  5 . The remaining functions, such as the tension load alert to a remote device  74 , is the same as or similar to the system  5  as above described in relation to the first example, and is not again described here. 
     Advantageously, there has been described examples of a system including belt edge clamps that allow for the measuring and monitoring of the inline tension of a conveyor belt such as during maintenance. In particular, the pivotally “floating” clamping member of the clamp allows the force from the belt to be responsively transferred to the clamping member and the load sensing section carried thereby. The load sensing section, provided in this example in the shape of a “dog-bone”, carries two load sensors in the form of resistive strain gauges that allow measurement of the force along the belt line by subtracting the bending element of strain from the total and using that resultant as the horizontal force element that is indicative of the actual inline belt tension. Most advantageously, the measuring and monitoring of the tension allows an alert to be provided if the measured belt tension exceeds a predetermined threshold. 
     Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. 
     The reference in this specification to any known matter or any prior publication is not, and should not be taken to be, an acknowledgment or admission or suggestion that the known matter or prior art publication forms part of the common general knowledge in the field to which this specification relates. 
     While specific examples of the invention have been described, it will be understood that the invention extends to alternative combinations of the features disclosed or evident from the disclosure provided herein. 
     Many and various modifications will be apparent to those skilled in the art without departing from the scope of the invention disclosed or evident from the disclosure provided herein.