Abstract:
A weight-measuring device is described that is adapted to be attached between two objects, and to be brought to a stretched state and to an unstretched state. The device may be attachable to a harness of the type which comprises a pair of shoulder strap assemblies, for example of the type used with backpacks, parachute units or similar constructed systems for holding or carrying an object or load to a person&#39;s body. The weight-measuring device comprises a force resistance element altered by the application of force thereto, and a weight indicator providing an indication of the force magnitude applied thereto.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a weight/load measuring device, and more particularly, to a weight/load measuring device that is adapted to be attached between two objects to measure the force magnitude therebetween. 
       BACKGROUND OF THE INVENTION 
       [0002]    A backpack, also known by the names “book bag”, “knapsack”, “rucksack”, “haversack”, “duffle bag”, “flying bag”, is a type of bag that comprise a harness portion and a bag portion, and is a popular and effective way to carry medium to heavy loads while walking. Backpacks were originally developed for use by the military and hikers and have, over time, become a ubiquitous load carrying device. However, while backpacks are generally considered a good load carrying devices due to the fact that they distribute weight across some of the body&#39;s largest muscles, use thereof can lead to physiological and anatomical problems, especially in cases where exceedingly large loads are carried by school children. 
         [0003]    Hereinafter in the specification and drawings all different types of bags are collectively referred to as ‘backpacks’. 
         [0004]    Medical authorities have set forth certain guidelines and recommendations to demonstrate that improper use and wearing of backpacks can lead to muscle imbalance that can result in chronic back and neck problems. A distinctly important guideline is that suspending too much weight from the shoulders over an extended period has been shown to be detrimental to the back, causing problems ranging from simple discomfort and fatigue to spinal compression, back pain and misalignment of the spine, ailments which could persist into adulthood. 
         [0005]    The problem has been aggravated in recent years, as young children have been carrying overweight backpacks. In particular, both the American Academy of Orthopedic surgeons (AAOS) and the Consumer Product Safety Commission (CPSC) warn that increasing numbers of children are suffering injuries to their backs and shoulders from improper utilization of their backpacks. Many experts recommend that a child carry no more than 15% of their body weight in a backpack to avoid increased risk of musculoskeletal injury. Children from grade school through high school are currently carrying far in excess of this amount. Excessive weight of a backpack may cause functional scoliosis or curvature of a healthy spine at any age. It is emphasized that even adults should not carry more than 25 kg in a backpack. 
         [0006]    The best way to prevent danger from overloaded backpacks is to directly determine if a particular load, in backpack being carried, is too heavy for the individual carrying it. While placing the backpack on traditional scales would be suitable for determining the weight of a backpack, scales are not always available to weigh a backpack to ensure that it is not overloaded. 
         [0007]    This problem is addressed at U.S. Pat. Application Publication No. 2005/0051586 to Siwak et al. describing a weight determining mechanism and a method for determining the weight of a piece of loaded luggage, particularly a backpack. The mechanism is generally incorporated into a carry handle of the piece of luggage allowing for it to be integral with the luggage and allowing for it to not take up additional space while allowing for quick and easy weight determinations without need for an external scale. 
         [0008]    In addition to the dangers caused by excessive backpack weight, health care professionals advise that the total load should be equally divided between the two shoulder straps to avoid orthopedic injuries associated with shifting of excessive weight to a particular right or left shoulder. It is difficult to conclude about the optimal configuration of a backpack and a harness if the carrier is unaware of the importance of weight distribution between the two shoulders. Asymmetric weight distribution induces the carrier to avoid standing in a proper upright position and thus can lead to spinal injuries, muscle strain or similar problems. In addition, overloading the wearer&#39;s shoulders can also cause local injuries, such as strain of the trapezias muscle, pinching of nerve roots near the spine, etc. 
         [0009]    Maintaining a natural posture, a person experiences a significant difference between side-to-side, and front-to-back upright stability. It is essential that a natural posture be preserved as closely as possible when carrying a backpack. For side-to-side stability the bag should be symmetrical and evenly loaded on each side. Symmetric loading is of particular importance, since, when most of the pack&#39;s weight is carried by slinging it on a single shoulder, it results in encouraging the wearer to bend sideways. Such abnormal posture is even more exaggerated when carrying a heavy backpack. To preserve the body side-to-side stability one has to consider first that there is no significant extra weight applied to one shoulder compared with the other. Imbalanced load hurts the shoulders while compressing on the shoulder and in time may also lead to circulatory or nerve disturbances. 
         [0010]    There are numerous known systems for backpacks which attempt to stabilize the load, increase comfort and enhance convenience to the carrier. For example, U.S. Pat. No. 4,217,998 to Alexander describes a device comprising a set of two elongated tubes, disposed in telescoping relation to each other with a spring-loaded push button carried by the inner tube adjustably releasably locking the tubes together so that they can have various desired combined lengths. One of the tubes has a slip resistant backpack shoulder strap connector attached at its front end and the other of the tubes has a backpack rear frame connector pivotally secured to its rear end. The improved backpack utilizes a pair of the described novel devices, connected to opposite sides of the backpack rear frame and projecting forwardly to engage the two backpack shoulder straps. Thus, the two devices are disposed on opposite sides of the backpacker. Their purpose is to shift the center of gravity and balance of the backpack from aft of the vertical midline of the backpacker when standing erect with the backpack in place, that is, from a very uncomfortable and clumsy position to a more forward comfortable position adjacent that vertical midline of the backpacker, without the backpacker having to continually tug at the backpack shoulder straps and hunch over to achieve the weight shift. 
         [0011]    U.S. Patent Application Publication No. 2004/0065708 to Amram discloses backpack that has straps which may be repositioned, removed and replaced is designed to reduce muscle strain when the bag is carried by improving the balance of the load. Re-positioning the straps can enable a person to reposition the load closer to the center of the body to reduce the leverage exerted by an unbalanced load. An additional feature is that removable straps can be interchanged or replaced inexpensively with other straps that have different colors, trademarks, advertisements, or other indicia of support or affiliation. 
         [0012]    International Patent Publication No. WO 2004/100706 to Manoni describes a balanced backpack of the type comprising bag containers supported on the shoulders of a user by shoulder straps, allowing an appropriate weight distribution, with a front-rear balance as well as a side balance, and comprising: a rear bag container associable to a bust by means of a pair of shoulder straps, said rear bag container being located symmetrically with respect to said shoulder straps; a fastening point associated to said shoulder straps and located frontally to the bust in a symmetrical position; a front bag container fastenable to said fastening point, so as to charge the associated load thereon, wherein the weight loadable in each bag container with regard to the volume of the bag containers has a rear/front ratio ranging from 2.0 to 0.8. 
       SUMMARY OF TILE INVENTION 
       [0013]    The present invention relates to a weight/load measuring device that is adapted to be attached between two objects to measure the forces therebetween. 
         [0014]    In accordance with one aspect of the present invention, there is provided a weight/load measuring device that is adapted to be attached between two objects to measure the force magnitude therebetween, which comprises a force resistance element altered by the application of force thereto, and a weight indicator providing an indication of the force magnitude applied thereto; the device being adapted to be brought to a stretched state and to a unstretched state, so that when the weight-measuring device is in the stretched state the force resistance element is altered by the application of forces by the two objects, and when the weight-measuring device is in the unstretched state the force resistance element is not altered by the application of forces by the two objects, the unstretched state thereby improving the calibration lifespan of the force resistance element. There being indicia provided for the state of stretching of weight indicator corresponding with the weight applied thereto. 
         [0015]    The calibration lifespan of the weight-measuring device is improved by reducing the time the force resistance element is altered. 
         [0016]    Multiple weight-measuring devices may be attached to multiple objects to determine asymmetric load between the objects. For example, there may be provided a backpack fitted with two shoulder straps, each fitted with a weight-measuring device according to the invention. In the event that the measuring device indicates an asymmetric load, a user may wish to correct the imbalance. Thus, the weight-measuring device may further comprising a balancing mechanism which is adapted to change the force magnitude between the two objects to which it is attached between. The balancing mechanism may be adapted to lengthen and/or shorten the distance between the two objects, thereby changing the force magnitude therebetween. The balancing mechanism may be an integral part of the weight-measuring device. 
         [0017]    The force resistance element may be a strap which is made of an elastic material. The elastic material may be made of natural rubber, however, any suitable material may be used. 
         [0018]    The weight indicator may comprise a numerical scale associated with said force resistance element, or other indication means such as a colored scale, a scale provided with geometrical illustrations, etc. 
         [0019]    The weight measuring device may further comprise a display window for viewing the weight indicator. The display window may be fitted with a magnifying glass for improving visualizing of the scale. 
         [0020]    The two objects between which the weight-measuring device is attached may be two portions of a shoulder strap assembly of a harness. The harness may be part of a backpack or a parachute apparatus, etc. 
         [0021]    According to a further aspect of the present invention, there is provided a harness comprising a pair of shoulder strap assemblies, with each shoulder strap assembly including a weight-measuring device according to the present invention, including any one or other of the features described above. 
         [0022]    The harness may enable a user to quickly and easily provide a balance control of the shoulder strap assemblies by operation of the weight-measuring device for determining the weight load carried by each shoulder along with the total weight carried by the user and adjusting it as needed. 
         [0023]    If the harness is part of a backpack, and is secured to a user who is wearing it, the weight of the backpack carried by the user can be measured by activating both weight-measuring devices simultaneously, giving the approximate total weight of the backpack carried by the user. Additionally, activation of only one of the weight-measuring devices may display the weight carried by the corresponding shoulder strap assembly. A particular advantage of this aspect is the potential to provide easy parent awareness of the load and balance thereof caused on a child carrying such a backpack. Thereby, allowing the parent to prevent problems caused by excessive load, asymmetric strap configuration and/or inter-shoulder weight imbalance. 
         [0024]    The balancing correction can also be made by readjusting the straps in the harness via fasteners in the shoulder strap assemblies and/or by rearranging the bag&#39;s contents (i.e. shifting heavy objects from side to side). 
         [0025]    According to any of the above aspects, the weight-measuring device may also be adapted to be detachably to the objects to which it is attached, or it may be designed to be permanently attached to the two objects. 
         [0026]    There has thus been outlined, rather broadly, the more important features of the invention so that the detailed description thereof that follows hereinafter may be better understood, and the present contribution to the art may be better appreciated. Additional details and advantages of the invention will be set forth in the detailed description. 
         [0027]    The invention calls for a force measuring device for connecting force exerting points and for measuring a force therebetween, the force measuring device including a force measuring mechanism designed such that an accuracy of the mechanism in measuring a force is not diminished by the force exerting points over time. 
         [0028]    According to one of its aspects, the invention is directed to a force measuring device for connecting between force exerting points and for measuring a force therebetween, the force measuring device including a force adjustment mechanism designed for incrementally adjusting a distance between the force exerting points. 
         [0029]    The prior art provides several examples of load measuring/balancing devices. Although some of these devices can be used to measure and/or adjust load distribution in backpacks, such designs suffer from several inherent limitations. Prior art load measuring devices employ load measuring mechanism which also function in load bearing and as such, these mechanisms display a loss in measuring quality over time due to plastic rather than elastic stretching and the like. 
         [0030]    In addition, prior art devices which enable load adjusting typically use buckles and straps which cannot be adjusted via precise and incremental adjustment actions which can be accurately repeated. This limitation is particularly problematic in the case of backpacks in which precise adjustment of two straps is required for proper load adjustment. 
         [0031]    While reducing the present invention to practice and having the specific goal of traversing these limitations of prior art designs, the present inventors have designed a load measuring and adjustment device which includes an accurate load measuring mechanism which does not diminish in measurement quality over time and a load distribution mechanism which is incremental, repeatable and precise. 
         [0032]    The device according to the present invention is suitable also as a ‘stand alone’ article, namely suitable for separate accessory article detachably connectable to any device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    In order to understand the invention and to see how it may be carried out in practice, several embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which: 
           [0034]      FIG. 1A  is a perspective view of a weight-measuring device according to a first embodiment of the present invention; 
           [0035]      FIG. 1B  is a perspective view of the weighing strap of the weight-measuring device illustrated in  FIG. 1A ; 
           [0036]      FIG. 1C  is a side view of the weighing strap illustrated in  FIG. 1B ; 
           [0037]      FIG. 1D  is a perspective view of a portion of the weighing strap illustrated in  FIGS. 1B and 1C  attached to a first strap; 
           [0038]      FIG. 1E  is a perspective view of the weight-measuring device illustrated in  FIG. 1A , attached between a first strap and a second strap, e.g. of a backpack; 
           [0039]      FIG. 1F  is a schematic isometric cross-sectional view of the weight-measuring device illustrated in  FIG. 1E ; 
           [0040]      FIG. 1G  is a schematic side cross-sectional view of the weight-measuring device illustrated in  FIG. 1E ; 
           [0041]      FIG. 1H  is an enlarged view of the portion marked G in  FIG. 1G ; 
           [0042]      FIG. 1I  is the same as  FIG. 1H , with a button in the housing being depressed; 
           [0043]      FIG. 1J  is a weight-measuring device of the type illustrated in  FIGS. 1A-1I , detachably/attachably articulated to a backpack; 
           [0044]      FIG. 1K  is a weight-measuring device of the type illustrated in  FIGS. 1A-1I , attached to a backpack; 
           [0045]      FIG. 2A  is a perspective view of a further embodiment of a weight-measuring device according to the present invention, including an integral balance mechanism; 
           [0046]      FIG. 2B  is a top exploded view of the balance mechanism of the weight-measuring device illustrated in  FIG. 2A ; 
           [0047]      FIG. 2C  is a bottom exploded view of the balance mechanism illustrated in  FIG. 2B ; 
           [0048]      FIG. 2D  is an assembly view of the balance mechanism illustrated in  FIGS. 2B and 2C ; 
           [0049]      FIG. 2E  is a schematic isometric cross-sectional view of the weight-measuring device illustrated in  FIG. 2A ; 
           [0050]      FIG. 2F  is an enlarged view of a portion of the weight-measuring device illustrated in  FIGS. 2A and 2E ; 
           [0051]      FIG. 2G  is a schematic sectioned side view of the weight-measuring device illustrated in FIGS.  2 A and  2 E- 2 F; 
           [0052]      FIG. 2H  is an enlarged schematic side view of the weight-measuring device illustrated in FIGS.  2 A and  2 E- 2 G; 
           [0053]      FIG. 2I  is a bottom view of the weight-measuring device illustrated in FIGS.  2 A and  2 E- 2 H; 
           [0054]      FIG. 3A  is a perspective view of a further example of a weight measuring device of the present invention, including an integral balance mechanism; 
           [0055]      FIG. 3B  is an exploded view of the weight measuring device illustrated in  FIG. 3A , excluding the straps; 
           [0056]      FIG. 3C  is an isometric cross-sectional view of the weight measuring device illustrated in  FIG. 3A  excluding the lower strap; 
           [0057]      FIG. 3D  is a plan view of the bottom housing component shown in  FIGS. 3A-3C ; 
           [0058]      FIG. 3E  is an isometric view of the bottom housing component illustrated in  FIG. 3D ; 
           [0059]      FIG. 3F  is an alternate isometric view of the bottom housing component illustrated in  FIG. 3D ; 
           [0060]      FIG. 3G  is an isometric view of the weight measuring device illustrated in  FIG. 3B , excluding the top and bottom housing element, with the elastic strap in an unstretched position; 
           [0061]      FIG. 3H  is an isometric view of the weight measuring device illustrated in  FIG. 3G , with the elastic strap in a stretched position; 
           [0062]      FIG. 3I  is an inner side view of a portion of the weight-measuring device illustrated in  FIG. 3A ; 
           [0063]      FIG. 3J  is an enlarged isometric view of a portion of the balance mechanism illustrated in  FIGS. 3A-3C ,  3 G and  3 H, when the lever is not activated; 
           [0064]      FIG. 3K  is an enlarged isometric view of a portion of the balance mechanism illustrated in  FIG. 3J , when the lever is activated; 
           [0065]      FIG. 3L  is a plan view of the device shown in  FIG. 3A , excluding the top housing component and upper and lower straps, when the strap lengthening button is not activated; and 
           [0066]      FIG. 3M  shows a plan view of the device shown in  FIG. 3L , when the strap lengthening button is activated. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0067]    The principles and operation of a backpack according to the present invention may be better understood with reference to the accompanying description and the drawings, in which embodiments of the invention are illustrated. It should be understood that these drawings are given for illustrative purposes only and are not meant to be limiting. The present invention may be embodied in many different forms and should not be constructed as limited to the embodiments set forth herein. The same reference numerals and alphabetic characters will be utilized for identifying those components which are common in the backpack and its components shown in the drawings throughout the present description of the invention. 
         [0068]    Referring now to  FIG. 1A , a first embodiment of a weight-measuring device  100  is illustrated. The weight measuring device  100  comprises a weighing strap  102 , a housing  104  through which the weighing strap  102  is slotted, a pin  106  ( FIG. 1F ) mounted inside the housing  104  and a pawl  108  ( FIG. 1F ) pivotably mounted on the pin  106  and normally biased in a clockwise direction. 
         [0069]    Turning attention now to  FIGS. 1B-1C , the weighing strap  102  comprises a force resistance element  110  in the form of an elastic portion made of natural rubber, and a plastic portion  112 , integrated through a manufacturing process or articulated thereafter. While any suitable material with elastic properties may be used for the elastic portion, during research conducted for the current invention natural rubber was shown to have advantageous qualities over other elastic materials tested. Similarly, the plastic portion need not necessarily be made of plastic, but rather must be made from a material which does not have elastic properties and does not deform under the load that the weight-measuring device  100  is expected to be subjected to. 
         [0070]    The elastic portion  110  comprises a top end  114 , an intermediate portion  116  and a bottom end  118 . The top end  114  comprises an bulging portion  120  which, referring briefly to  FIG. 1A , when the weight measuring device  100  is assembled and consequently the weighing strap  102  is inserted through the housing  104 , is anchored to the outside of the housing  104 , and is thicker than the slot  142  ( FIGS. 1F and 1G ) in the housing  104  to which it is adjacent. Reverting to  FIGS. 1B and 1C , the intermediate portion  116  is thinner than the bulging portion  120 , and when the elastic portion  110  is inserted through the housing  104 , the intermediate portion  116  slides easily through the first slot  142  ( FIGS. 1F and 1G ) to which the bulging portion  120  is anchored, for reasons which will become apparent hereinafter. 
         [0071]    The plastic portion  112  comprises a top-half section  122  integrally formed with the bottom end  118  of the elastic portion  110 , and a bottom-half section  124 . The top-half section  122  comprises two narrow columns  126  of uni-directional slanted teeth disposed along the edges thereof and a weight indicator in the form of a series of ascending numbers  128 , for indication of weight measurement, between the teeth  126 . In this respect the numbers  128  on the elastic portion  110  are distanced in a calculated manner, proportionately to the magnitude of force required to stretch the elastic portion  110  alternatively, instead of numbers there may be other indications such as drawings, colors, etc. The bottom-half section  122  comprises a coupling slit  130  in the form of a rectangular slit. 
         [0072]    Turning attention additionally to  FIG. 1D , the coupling slit  130  in this example, is used to allow connection of the weight-measuring device  100  to a first strap  132  of a harness (not shown) via a buckle  134  and a balancing mechanism in the form of a strap fastener  136 . It should be noted that the coupling element  130  may be used to attach it to the object to be measured via any standard connection components. 
         [0073]    Referring now to  FIGS. 1E-1G , the weight-measuring device  100  is shown connected between a first strap  132  (which in the context of a harness of a backpack could be referred to as a ‘bottom strap’) and a second strap  138  (which in the context of a harness of a backpack could be referred to as a ‘top strap’). The second strap  138  comprises a cavity  140 , within which a sleeve-like portion  105  of the housing  104  is inserted. The second strap  138  is attached, e.g. by sewing, around the sleeve-like portion  105  of the housing  104  within the cavity  140 , to secure the position of the housing  104  therein. 
         [0074]    The housing portion  104  comprises a first slot  142 , a second slot  144 , a depressible button  146  and a display window  148 . As mentioned above the weighing strap  102  is slotted through the housing  104 , this is accomplished via the first slot  142  and the second slot  144 . In  FIG. 1G  the elastic portion  110  of the weighing strap  102  is clearly shown to be slotted through both the first slot  142  and anchored thereto by the bulging portion  120 , while the plastic portion  112  is capable of sliding motion through the second slot  144 . The display window  148  is positioned above at least one of the series of numbers  128  and is made of magnifying glass to facilitate easy viewing thereof. 
         [0075]    The pawl  108  comprises a pivot hole  150  adapted for the insertion of the pin  106 , a pointed distal projection  152  adapted for engagement to the teeth of the narrow columns of uni-directional slanted teeth  126  on the plastic portion  112 , and a button portion  154  disposed at the end of the pawl  108  underneath the button  146  of the housing portion  104 . 
         [0076]    A pin  106  is mounted inside the housing  104  to support the pawl  108  pivotably mounted thereon. 
         [0077]    Operation of the Weight-Measuring Device: 
         [0078]    Referring first to  FIG. 1E , in operation the weight-measuring device  100  is necessarily attached between two objects. As mentioned above, in this embodiment the weight-measuring device  100  is connected between a first strap  132  and a second strap  138 . 
         [0079]    Referring now to  FIG. 1H , the pawl  108  is shown in it&#39;s normally biased position, with the distal projection  152  engaging the teeth  126 . In this position, stretching of the weighing strap  102 , created, for example, by a force exerted on the bottom-half section  124  of the plastic portion  112  by the first strap  132  in the direction of the arrow numbered  156 , or by the second strap  138  on the housing  104  in the direction opposite to arrow  156 , is arrested by the above-mentioned engagement of the distal projection  152  with the teeth  126 . To elaborate, stretching of the weighing strap  102  does not occur as the plastic portion  112  is not elastic, therefore it also does not stretch to any significant amount, and the elastic portion  110  is anchored at one end to the housing  104  and the other end to the above-mentioned engagement between the distal projection  152  and the teeth  126 . 
         [0080]    However, it should be noted that if the elastic portion  110  was in tension before the engagement between the distal projection  152  and the teeth  126 , the uni-directional nature of the teeth  126  allows the weighing strap  102  to contract, i.e. at least a portion of the elastic portion  110  and the plastic portion  112  will move in the direction opposite to the arrow numbered  156 , towards the anchored bulging portion  120 . Thus, the elastic properties of the elastic portion  110  will contract the weighing strap  102  until the elastic portion  110  is no longer stretched, thereby constituting an “unstretched mode” of the weight-measuring device  100 . 
         [0081]    Referring now to  FIG. 1I , the pawl  108  is shown in a rotated position resulting from the depression of the depressible button  146 , counter to the normally biasing force, by a user of the weight-measuring device  100 . The depressible button  146  moves the button portion  154  disposed at the end of the pawl  108  in the direction of the weighing strap  102 . In this position, the distal projection  152  disengages the teeth  126 , allowing stretching of the elastic portion  110  of the weighing strap  102 , if there are forces exerted on the bottom-half section  124  of the plastic portion  112  by the first strap  132  in the direction of the arrow numbered  156 , or by the second strap  138  on the housing  104  in the direction opposite to arrow  156 . 
         [0082]    During stretching, the plastic portion  112 , which is not elastic, does not stretch to any significant amount, however, the elastic properties of the elastic portion  110  allow stretching thereof. This stretching will allow a different portion of the elastic portion  110 , comprising at least one of the numbers  128 , to be disposed beneath the display window  148 . A user may then view the numbers  128  via the magnifying glass  148  and hence, knowing the relationship between the numerical value shown and the magnitude of stretching force required to view such number, estimate the magnitude of force and/or weight stretching the weight-measuring device  100 . This measuring position, thereby constitutes the “stretched mode” of the weight-measuring device  100 . 
         [0083]    The user then releases the depressible button  146 , which allows the pawl  108  to pivot back to its normal position and the distal projection  152  to re-engage the teeth  126 , returning the weight-measuring device  100  to the unstretched position. It should be noted that the unstretched position improves the calibration lifespan of the force resistance element/weighing strap  102  as it reduces the amount of time that the elastic portion  110  is stretched. Such stretching only occurring during measurement of the magnitude of force applied to the weight-measuring device  100 . 
         [0084]    In any case, the weight scale calibration can be checked and corrected. This may be suggested following long use, when the stretchable element may become slightly lax and overly extended to show false reading. A proper calibration can, for example, be performed while comparing indications of the weight-measuring device  100  against a known amount of weight attached to the first or second strap. Then, the numbers  128  may be corrected to reflect the weight shown. Thus, the weight-measuring device  100  will resume accuracy. 
         [0085]    Turning attention now to  FIG. 1J , there is illustrated an example of the weight-measuring device  100  being detachably attached to an object in the form of a backpack  160  comprising a harness  162  configured for securing the backpack  160  on a user. 
         [0086]    The harness  162  comprises two shoulder strap assemblies  166  (only one of which can be seen in the partial view shown). Each shoulder strap assembly  166  comprises a lower strap  168 , a first strap  132 , a lower fastener  170 , a weight-measuring device  100 , a second strap  138 , an upper strap  172  and an upper fastener  174 . The lower strap  168  extends between two ends, a first end  176  which is attached (e.g. by sewing or otherwise) to a lower portion  178  of a bag portion  164  and a second end  180  engaging the first strap  132  via the lower fastener  170 . 
         [0087]    As described in previous figures the weight measuring device  100  is attached between the first strap  132  and second strap  138 . The upper strap  172  extends between two ends, a first end  182  which is attached (e.g. by sowing or otherwise) to an upper portion  184  of the bag portion  164  and a second end  186  engaging the second strap  138  via the upper fastener  174 . The lower fastener  170  and the upper fastener  174  both comprise a pin  188 , the arrangement of which facilitates, upon removal of the pin  188 , disengagement of the straps connected via the respective fastener. However, it should be noted that any fastener or similar type device which allows the engagement and disengagement of the straps is suitable for this purpose. 
         [0088]    When the backpack  160  is carried or worn by a user, the weight load applied to the each of the strap assemblies  166  can be measured or estimated by the user via operation of the weight-measuring device  100  as described above. It should be noted that force applied to the weight-measuring devices  100  on each of the shoulder strap assemblies  166  may be measured separately or simultaneously, allowing the option to measure the load carried by each shoulder strap assembly. Additionally the load of each strap assembly and hence the amount of force measured by the weight-measuring devices  100  may be balanced through lengthening or shortening the first straps  132  via the strap fasteners  136 . In this example, the weight-measuring device can be attachably detached from the backpack  160  via the lower fastener  170  and upper fastener  174 . This may be done, for example, when the backpack is put in the laundry. 
         [0089]    Turning attention now to  1 K, the weight-measuring device  100  may, alternatively, be fixedly attached to a harness  190  having a shoulder strap assembly  192  only comprising the elements shown in  FIG. 1E . In such case the first strap  132  extends between a lower portion  178  of the bag portion  164  and the coupling slit  130  of the weighing strap  102 , and the second strap  138  extends between an upper portion  178  of the bag portion  164  and is attached to the housing  104  as described above. 
         [0090]    Turning attention to  FIGS. 2A to 2I , there is illustrated an example of a weight-measuring device generally designated  200  which has an integral balancing mechanism  202  ( FIGS. 2B and 2D ), thus removing the need for a strap fastener  136  (shown in connection with the previous embodiment) or similar external balancing mechanism. 
         [0091]    Focusing first on  FIGS. 2B-2D , the balancing mechanism  202  comprises an outer strap  204 , an inner strap  206  slidingly disposed inside the outer strap  204 , a rotary sprocket wheel  208  mounted on the inner strap, a rotary spring and lock  210  mounted in the sprocket wheel  208 , and a rotary wheel  212  engaging the rotary spring and lock  210 . 
         [0092]    Notably, the only differences between the weight-measuring device  100  of the previous embodiment and the weight-measuring device  200  of the present embodiment is that the plastic portion  112  of the weighing strap  102  has been replaced by the outer strap  204  and an inner strap  206 , and there has been the addition of elements related to the balancing mechanism  202 , namely four elements, being the rotary sprocket wheel  208 , a rotary spring and lock  210 , a rotary wheel  212  and a sleeve element  230  ( FIG. 2A , to be further described hereinafter). 
         [0093]    The outer strap  204  comprises a first end  214 , a large slot  216 , a first coupling aperture  218 , and a second end  220 . The first end  214  engages the elastic portion (not shown) of the weighing strap (not shown) in the same manner as the previous embodiment. The large slot  216  is designed to fixedly receive the inner strap  206 . The aperture  218  is to allow the outer strap  204  to be coupled to another object, in the current example to a first strap  222  ( FIG. 2A ). 
         [0094]    The inner strap  206  comprises a longitudinally oriented slot  224  having a row of teeth  226  along one of the longitudinal edges thereof, and a second coupling aperture  228 . The aperture  228  allows the inner strap  206  to be coupled to a sleeve element  230 , seen for example in  FIGS. 2A and 2E . The sleeve element slides over the outer strap  204  and is present to prevent objects coming between the inner strap  206  and the outer strap  204 . 
         [0095]    The rotary sprocket wheel  208  ( FIG. 2C ) comprises a floor  232 , a pinion gear  234  integrally formed in the floor  232  having teeth adapted for engagement with the row of teeth  206  of the inner strap  226 , and an upwardly extending lip  236  having a serrated inner edge  238 . At the assembled position the floor  232  of the rotary sprocket wheel  208  is flush with the corresponding surfaces of the inner and outer straps  206  and  204 , respectively. 
         [0096]    The rotary spring and lock  210  is adapted to sit inside the lip  236  of the rotary sprocket wheel  208  and comprises ( FIG. 2B ) a bottom portion  240 , a top portion  242 , a curved slot  244 , a hook shaped slot  246 , an upper annular protrusion  248 , a side rim  250 , and a side protrusion  252 . 
         [0097]    The rotary wheel  212  comprises a top surface  254 , a gripping rim  256 , a central aperture  257  adapted to receive the annular protrusion  248  of the rotary spring and lock  210 . The rotary wheel  212  is further formed with a bottom surface  258 , a first cylindrical protrusion  264  adapted to be received into the curved slot  244  of the rotary spring and lock  210 , and a second cylindrical protrusion  262  adapted to be accommodated within the hook shaped slot  246  of the rotary spring and lock  210 . 
         [0098]    In  FIGS. 2E-2H  internal views of the assembled mechanism are shown. As can be seen the top surface  254  of the rotary wheel  212  is partially embedded within a second strap  266 , to which the weight-measuring device  200  is attached, but remains capable of rotational movement within the second strap  266 . The gripping rim  256  has a non-smooth surface and protrudes outwardly from the sides of the second strap  266 , as seen best in  FIG. 2I . 
         [0099]    In the assembled position the rotary wheel  212  is engaged to the rotary spring and lock  210  via the following connection points: the central aperture  256  engages the annular protrusion  248 , the first cylindrical protrusion  264  is inserted into the curved slot  244 , and the second cylindrical protrusion  262  is inserted into the hook shaped slot  246 ; the rotary spring and lock  210  sits inside the rotary sprocket wheel  208  and rotates therewith when the side protrusion  252  engages the serrated inner edge  238 . Notably this only occurs when the rotary wheel  212  is rotated in one direction. The rotary sprocket wheel  208  is mounted in the inner strap  206  via the pinion gear  234  which engages the row of teeth  226  thereof; rotation of the pinion gear  234  causes the teeth thereof to engage with the row of teeth  226  of the inner strap  206 . 
       In Operation: 
       [0100]    A user may shorten the distance between the first strap  222  and the second strap  266  by rotating the rotary wheel  212  in a counter-clockwise direction with his fingers. The rotation of the rotary wheel  212  moves the second cylindrical protrusion  262  into the end portion of the hook shaped slot  246 , expanding the hook shaped slot and thereby causing the side protrusion  252  to engage the serrated inner edge  238  of the rotary sprocket wheel  208 , which is consequently rotated. Thus the pinion gear  234  engages the inner strap  206  causing the first strap  222  and the second strap  266  to be contracted together. Thus, the length of the straps may be adjusted and balanced. 
         [0101]    Additionally, the second cylindrical protrusion  262  remains in the end portion of the hook shaped slot  246  causing the first strap  222  and the second strap  266  to be locked in the adjusted position. 
         [0102]    Notably if the rotary wheel  212  is rotated in a clockwise direction, the first cylindrical protrusion  264  contacts one of the edges of the curved slot  244  of the rotary spring and lock  210 , and the second cylindrical protrusion  262  is removed from the end portion of the hook shaped slot  246 , causing the rotary spring and lock  210  to disengage from rotary sprocket wheel  208 , and consequentially the first strap  222  disengages from the second strap  266 , thus facilitating the proper conditions for weight measurement. It should also be noted that no other components rotate, in this case, as the side protrusion  252  does not engage the serrated inner edge  238  of the rotary sprocket wheel  208 . 
         [0103]    As in the previous embodiment the weight-measuring device  200  may measure the force magnitude applied thereto by a user depressing an identical depressible button  268 . The only difference being in relation to the balancing mechanism  202  which, in unlocked position, allows the inner strap  204  and outer strap  206  to move, facilitating measurement of the force magnitude applied to the weight-measuring device  200 . 
         [0104]    Referring now to  FIGS. 3A to 3M , a further example of the weight measuring device  300  is illustrated. It should be noted that the weight measuring device  300  is similar to the previous example described, in that it is able to be incorporated into a shoulder strap assembly of a backpack (not shown) and comprises a force resistance element in the form of an elastic portion  390  connected to the shoulder strap assembly and adapted to measure the weight load thereof, and further comprises an integral balancing mechanism for lengthening and shortening the strap assembly. 
         [0105]    Turning attention first to  FIGS. 3A to 3C , a shoulder strap assembly  302  is seen with a weight measuring device  300  incorporated therein. 
         [0106]    The shoulder strap assembly  302  comprises a lower strap  304  and an upper strap  306 . The lower strap  304  extends between two ends, one end of which is attached to a lower portion of a backpack (not shown) and a second end  308  adapted to engage the weight measuring device  300  via a connecting strap portion  310  attached to the second end  308 . The upper strap  306  has two ends, one end of which is attached to an upper portion of the backpack (not shown) and a second end  312  adapted to engage the weight measuring device  300  via a cavity  314  ( FIG. 3C ) formed in the upper strap  306 . The cavity  314  may be part of the original manufacture of the backpack or a normal strap may be modified to form the cavity  314 . 
         [0107]    The weight measuring device  300  comprises a bottom housing  316  sown to the upper strap  306  and partially disposed within the cavity  314 , a weighing strap  318  partially disposed within the bottom housing  316  and the cavity  314 , a balancing strap  320  partially disposed within the bottom housing  316  and engaging the lower strap  304  and the weighing strap  318 , a pin  322  mounted on the bottom housing  316 , a ratchet mechanism  324  in the form of a pawl which is pivotally mounted on the pin  322 , a D-shaped strap shortening lever  326  pivotally mounted on the bottom housing  316 , a sprocket wheel  328  mounted on the lever  326  and adapted to engage the balancing strap  320 , a sprocket lock  330  mounted on the lever  326  and rigidly connected to the sprocket wheel  328  and adapted to engage the weighing strap  318  through an aperture  432  formed in the balancing strap  320 , a strap lengthening button  332  ( FIG. 3B ) projecting into and secured to the bottom housing  316  and adapted to engage the balancing strap  320 , and a top housing  334  snappingly attachable to the bottom housing  316  and fitted with a button  466  adapted to engage the pawl  324 . 
         [0108]    The weight measuring device  300  will now be described in more detail. 
         [0109]    Referring now also to  FIGS. 3D-3F , the bottom housing  316  comprises a housing portion  336 , and a sleeve portion  338 . 
         [0110]    The housing portion  336  comprises a floor  340 , a rim  342  extending along a peripheral portion of the floor  340 , a chamber  344  disposed in a central portion of the floor  340 , and a C-shaped lip  346  extending from a peripheral portion of the floor  340 . 
         [0111]    The rim  342  is formed with sockets  348  and sowing apertures  350 . The socket  348  are adapted to receive projections (not shown) formed on the inside of the top housing  334  for connection thereof to the bottom housing  316 . The sowing apertures  350  are used for insertion of thread therethrough to allow sowing of the bottom housing  316  to the upper strap  306 . 
         [0112]    The chamber  344  comprises a transversely oriented wall  352 , a first longitudinally oriented wall  354  extending from one corner of the transversely oriented wall  352 , and a second longitudinally oriented wall  356  extending from the other corner of the transversely oriented wall  352 , each of which projecting from the floor  340 . It should be mentioned that the first and second longitudinal walls, respectively numbered  354  and  356  are spaced sufficiently to accommodate at least a portion of the weighing strap  318 , balancing strap  320  and pawl  324  therebetween. The transverse wall  352  has a first transverse slot  358  formed therein ( FIG. 3E ), adapted for slidable insertion of a portion of the weighing strap  318  therethrough. The first longitudinal wall  354  has a rectangular cut out  360  ( FIG. 3E ) formed therein which is adapted for slidable insertion of a portion of the strap lengthening button  332  therethrough, and an O-shaped flange  362  formed thereon which is adapted for receiving the pin  322 . The second longitudinal wall  356  has an O-shaped flange  364  formed thereon which is adapted for receiving the pin  322 . 
         [0113]    It should be noted that the C-shaped lip  346  is formed integral with two sockets  348  mentioned above, one of which notably having a recess  366  thereunder and hence not extending to the floor  340  for which purpose will be described hereinafter. Additionally, the C-shaped lip  346  comprises a second transverse slot  368  (best seen in  FIG. 3B ) formed at a central portion of the lip  346 , a pair of concentric apertures  370  formed therein and disposed between the transverse slot  368  and connecting sockets  348 , a support seat  372  to be described hereinafter, and a longitudinal slot  374  formed adjacent to the recess  366 . 
         [0114]    The sleeve portion  338  comprises a floor portion  376  ( FIG. 3C ) extending to the floor  340  of the bottom housing  316 , opposing longitudinally oriented side wall portions  378  extending upwardly from the floor portion  376 , an end wall portion  380  extending upwardly from the floor portion  376  and extending between the side wall portions  378 , and a lid portion  382  attachably detachable to the side walls  378  and end wall portion  380  (in this case via fasteners  384 ) and which engages the rim  342 . The end wall portion  380  has a third transverse slot  386  ( FIG. 3C ) formed therein. There is also a fourth transverse slot  388  formed by the connecting areas of the floor portion  376 , side wall portions  378  and lid portion  382 . 
         [0115]    Turning attention now to  FIGS. 3C ,  3 G and  3 I, the weighing strap  318  comprises a force resistance element  390  in the form of an elastic portion, and a plastic portion  392 . 
         [0116]    The elastic portion  390  comprises a top end  394 , an intermediate portion  396  and a bottom end  398 . The top end  394  comprises an bulging portion  400  which, when the weight measuring device  300  is assembled and consequently the weighing strap  318  is inserted through the sleeve portion  338 , is disposed on the outside of the third transverse slot  386  ( FIG. 3C ), and is thicker than the slot  386  to prevent traversing therethrough. The intermediate portion  396  is thinner than the bulging portion  400 , and when the elastic portion  390  is inserted through the sleeve  338 , the intermediate portion  396  extends through the third and fourth transverse slots, respectively numbered  386  and  388 , without being clasped thereby for reasons which will become apparent hereinafter. 
         [0117]    The plastic portion  392  comprises a top-half section  402  integrally formed with the bottom end  398  of the elastic portion  390  (integrated through a manufacturing process or articulated thereafter), and a bottom-half section  404 . Additionally, each of the sections of the plastic portion  392  identified above have a lower face (not shown), and an upper face  406 . The upper face  406  of the top-half section  402  comprises a narrow column  408  of uni-directional slanted teeth disposed along one side thereof and a series of ascending numbers  410 , for indication of weight measurement, adjacent to the teeth  408 . The upper face  406  of the bottom-half section  404  comprises a narrow column of spaced square teeth  412  (best seen in  FIG. 3J ) disposed along one side thereof and a wide column of uni-directional slanted teeth  414  adjacent to the square teeth  412 . 
         [0118]    It should be noted that when the weight measuring device  300  is being assembled, the weighing strap  318  is inserted into the bottom housing  316  via the first, second, third and fourth transverse slots, respectively numbered  358 ,  368 ,  386  and  388 , and is anchored by the bulging portion  400  to the outside of the third transverse slot  386  ( FIG. 3C ) which, notably, is the only transverse slot that impedes the longitudinal motion of the weighing strap  318 . After insertion of the weighing strap  318  into the bottom housing  316 , the sleeve portion  338  is inserted into the cavity  314  and the bottom housing  316  is sown to the upper strap  306  via the sowing apertures  350 . 
         [0119]    As seen in  FIGS. 3A ,  3 G and  3 J, the balancing strap  320  comprises a first edge  416 , a second edge  418 , a lower end  420 , an upper end  422 , a bottom face  424  and a top face  426 . The lower end  420  has a rectangular coupling slit  428 , adapted for insertion of the connecting strap portion  310  therethrough. The connecting strap portion  310  is thus threaded through the rectangular slit and fastened to the lower strap  304 , in this example, by Velcro™ (not shown). It should be noted, however, that any fastener may be used to connect the connecting strap portion  310  to the lower strap  304 . 
         [0120]    The upper end  422  comprises a ream element  430  in the form of an integral D-shaped elastic portion, extending along the first edge  416 . The D-shaped portion  430  comprises a D-shaped slot  432  formed therein. The bottom face  424  comprises a wide column of unidirectional slanted teeth  434 , adapted for single-directional locking engagement with the wide column of slanted teeth  414  on the upper face  406  of the plastic portion  392  of the weighing strap  318  (best seen in  FIG. 3I ). The top face  426  comprises a narrow column of slanted teeth  436  formed along the first edge  416  of the balancing strap  320 , and a push bar  438  formed on and extending along the second edge  418  of the balancing strap  320 . During assembly, the balancing strap  320  is inserted into the second transverse slot  368  of the bottom housing  316  and is disposed over and engages the weighing strap  318 . 
         [0121]    Referring now to  FIG. 3H , the pawl  324  is disposed within the chamber  344  ( FIGS. 3D-3F ) and comprises a pivot hole  440  adapted for the insertion of the pin  322 , a pointed distal projection  442  adapted for engagement with the teeth of the narrow column of uni-directional slanted teeth  436  on the plastic portion  392 , and a button portion  444  disposed at the end of the pawl  324  not comprising the distal projection  442 . During assembly, the pin  322  is inserted through the O-shaped flanges  362  and  364  ( FIG. 3E ) and the pivot hole  440  in the pawl  324  to allow rotation of the pawl  324 . 
         [0122]    The D-shaped strap shortening lever  326  is pivotally mounted to the bottom housing  316  and comprises a curved gripping portion  446  and a straight portion  448 . Referring now also to  FIGS. 3D-3F , during assembly the straight portion  448  is inserted into the bottom housing  316  via the pair of concentric apertures  370  formed in the lip  374  thereof and the curved portion  446  is attached to the straight portion  448 . 
         [0123]    Reverting now to  FIG. 3J , the sprocket wheel  328  is mounted on the lever  326  via a central aperture (not shown) formed therein, and comprises teeth  450  which are adapted for engaging the narrow column of slanted teeth  436  on the balancing strap  320  and pressing the balancing strap  320  against the weighing strap  318  for locking engagement, and a moon-shaped lateral projection  452  for receiving the straight portion  448  of the lever  326 . 
         [0124]    The sprocket lock  330  comprises a rectangular slot  454  and a square-shaped tooth projection  456 . The rectangular slot  454  is adapted for tight fit insertion of the moon-shaped projection  452  when the straight portion  448  of lever  326  is received therein. The square-shaped tooth projection  456  is adapted for engagement into the narrow column of square teeth  412 , when rotated to an appropriate angle (see  FIG. 3K ). The aforementioned tight fit facilitates rotation of both the sprocket wheel  328  and the sprocket lock  330  when the lever  326  is rotated. Additionally, referring briefly to  FIG. 3D , it should be noted that the support seat  372  of the bottom housing  316  has appropriately shaped recesses for the lever  326 , sprocket wheel  328  and sprocket lock  330  to rest thereon, while still allowing rotation thereof. Furthermore, the square-shaped tooth projection  456  at all times projects through the D-shaped slot  432  arresting longitudinal motion of the balancing strap  320  in either direction. 
         [0125]    Turning attention to  FIG. 3L , the strap lengthening button  332  comprises a button portion  458 , a neck portion  460  attachable to the button portion  458  and a base portion  462  extending from the neck portion  460 . Referring now also to  FIGS. 3D-3F , the neck portion  460  is adapted for slideable motion within the longitudinal slot  374  and the recess  366  in the bottom housing  316 . During assembly, the neck portion  460  is inserted through the longitudinal slot  374  such that the base portion  462  is in contact with the push bar  438 , and the button portion  458  is subsequently attached to the neck portion  460 . It should be noted that the button portion  458  and base portion  462  are larger than the longitudinal slot  374  to prevent the lengthening button  332  from falling thereout. 
         [0126]    Reverting to  FIG. 3B , the top housing  334 , which is adapted to snappingly connect to the bottom housing  316  and cover all of the components disposed therebetween, comprises a display window  464 , a button  466  and internal projections (not seen). The display window  464  is in the form of a magnifying lens disposed above the series of ascending numbers  410  on the weighing strap  318 , enabling them to be easily read therethrough. The button  466  is disposed above and engages the button portion  444  of the pawl  324 . 
         [0127]    As described hereinbefore, the top housing  334  further comprises internal projections (not seen) formed therein for snapping connection to the bottom housing  316  via the sockets  348  formed therein. 
         [0128]    As mentioned above, the weight measuring device  300  also allows balance control via lengthening and shortening of the shoulder strap assembly  302  using elements which constitute an integral balancing mechanism. In this example the balancing mechanism is comprised of all of the elements, excluding the top housing  334 , without which the balancing would not be possible. It should be noted that as the example describes an integral balancing mechanism, some of the elements in this example have a dual function, therefore the specific elements which constitute the “balancing mechanism” are not be highlighted as such to avoid confusion, because in one state an element may operate to provide a weight determination function and in another the same element may provide the balancing function. Nonetheless, the description of the balancing operation will clarify which components provide a weighing function and which provide a balancing function. 
         [0129]    In operation, the weight measuring device  300  provides a user the ability to determine the weight load, lengthen and shorten the shoulder strap assembly  302  to which it is incorporated and thus balance inter-shoulder weight load. 
         [0130]    Regarding weight load determination, the weight measuring device  300  can be described as having an unstretched state and a stretched state. As seen in  FIG. 3G  the pawl  324  is normally biased such that the distal projection  444  engages the teeth of the narrow column of uni-directional slanted teeth  408  of the plastic portion  392  in a so called “locking action”. This normally biased position of the pawl  324  is referred to as the “unstretched state”. 
         [0131]    As the elastic portion  390  of the weighing strap  318  is anchored at the top end  394 , and the aforementioned locking action arrests stretching motion of the bottom end  398  of the elastic portion  390  via the plastic portion  392 , the locking action essentially holds the elastic portion  390  static. It is noted that the slanted teeth  408  to which the pawl  324  is connected are uni-directional, therefore the locking action only prevents stretching motion of the elastic portion  390 . Thus when there is no stretching force on the elastic portion, the elasticity of the elastic portion  390  pulls the weighing strap  318  back to an unstretched state even during the locking action. 
         [0132]    The unstretched state allows extended calibration lifespan of the force resistance element by reducing the time that the elastic portion  390  is stretched. To determine the weight load of the shoulder strap assembly  302 , the assembly  302  is carried such that a stretching force is applied to the weight measuring device  300  (not shown), for example by wearing the backpack (not shown) to which the assembly  302  is connected. A user must then push the button  316  which impacts the button portion  444  of the pawl  324  rotating it and disengaging the distal projection  442  from the slanted teeth  436  on the plastic portion  392  ( FIG. 3H ). The elastic portion  390  is thus stretched by the stretching force applied to it via the lower strap  304  and balancing strap  320  on one side, and the upper strap  306  to which it is anchored via the sleeve  338  on the other, which constitutes the so-called stretched state ( FIG. 3H ). 
         [0133]    At the stretched state the user reads the appropriate number  410  which appears through the display window  464  to gauge the weight load on the shoulder strap assembly  302 . The user then releases the button  316  and the pawl  324  returns to it&#39;s normally biased position. When the stretching force is removed from the shoulder strap assembly  302 , for example by the user putting the backpack (not seen) on the floor (not seen), the elastic properties of the elastic portion  390  return the weight measuring device  300  to the so-called unstretched state ( FIG. 3G ) as described above. 
         [0134]    Referring to  FIG. 3J , to shorten the shoulder strap assembly  302 , a user grasps the lever  326  in its normal position (as shown in  FIG. 3J , namely extending substantially parallel with the straps) and rotates the lever  326  in the direction of arrow  468 . 
         [0135]    Referring now to  FIG. 3K , the rotation results in the sprocket wheel  328  and sprocket lock  330  rotating. The sprocket wheel teeth  450  consequently pushes the slanted teeth  436  on the balancing strap  320 , which as a result slides over the plastic portion  392  of the weighing strap  318  and then locks thereto, thereby shortening the shoulder strap assembly  302 . The user then returns the lever  326  to its normal position, and may repeat the lever rotation for a further shortening action. Notably, the return movement does not provide a return motion to the balancing strap  320  due to the uni-directional nature of the slanted teeth  436  on the top face  426  of the balancing strap  320 , the slanted teeth  434  on the bottom face  424  of the balancing strap  320 , and the slanted teeth  414  on the plastic portion  392  of the weighing strap  318 . Additionally, rotation of the sprocket lock  330 , causes the square-shaped tooth  456  to engage the square teeth  412  on the plastic portion  392 , arresting the motion of the weighing strap  318 . Furthermore the square tooth  456  functions as a mechanical stop if it contacts the periphery of the D-shaped slot  432 , preventing the balancing strap  320  from entering too far into the bottom housing  316 . 
         [0136]    Referring to  FIG. 3L , to lengthen the shoulder strap assembly  302 , the user presses the button portion  458  of the strap lengthening button  332  in the direction of arrow  470 . The base portion  462  pushes the push bar  438  sideways and displaces the balancing strap  320  relative to the remainder of the components of the weight measuring device  300 , as shown in  FIG. 3M . 
         [0137]    Referring now to  FIG. 3M , in this position the narrow column of slanted teeth  436  on the balancing strap  320  is not disposed directly below the teeth  450  of the sprocket wheel  328  as shown in previous drawings and the D-shaped elastic portion  430  is compressed within the second transverse slot  368  ( FIG. 3B ). If a stretching force is then applied to the weight measuring device  300  the balancing strap  320 , which is no longer pressed against the weighing strap  318  for locking engagement, slides out of the bottom housing  316 . 
         [0138]    Similar to the shortening procedure above, the square tooth  456  functions as a mechanical stop if it contacts the periphery of the D-shaped slot  432 , preventing the balancing strap  320  from exiting the bottom housing  316 . After the button  458  is released the D-shaped elastic portion  430  spontaneously reverts to it&#39;s normal shape and pushes the balancing strap  320  back to the position shown in  FIG. 3L . In this position the sprocket wheel  328  re-contacts the slanted teeth  436  on the balancing strap  320  which re-engages the weighing strap in a locking fashion. 
         [0139]    Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations and modifications can be made without departing from the scope of the invention mutatis mutandis. 
         [0140]    For example, the device according to the present invention is suitable also as a ‘stand alone’ article, namely suitable for separate accessory article detachably connectable to any device.