Abstract:
The instrument package mounting apparatus comprises an axle that serves to eliminate the need to wrap a tether line about the axle. In particular, the axle comprises a cylindrical solid configured with a slot extending from the outer surface of the axle to a substantially central axis thereof, the slot being capable of receiving the tether line. Juxtaposed to this slot and located substantially centered about the substantially central axis of the axle is a rectangular shaped interior channel that functions to receive a pinch bar comprising a substantially rectangular shaped tapered bar. The tapered pinch bar is inserted into the channel formed in the axle and operates to frictionally secure the tether line and the axle. The friction to secure the tether line in the slot, as held in place by the tapered pinch bar is generated by a compression fit formed as the tapered pinch bar is inserted into the interior channel of the axle.

Description:
FIELD OF THE INVENTION 
     This invention relates to instrumentation packages, and in particular, to an apparatus for pivotally mounting an instrument package to a line, such as a balloon tether line, to enable the instrument package to freely rotate about the line. 
     PROBLEM 
     It is a problem in the field of balloon mounted instrument packages to provide an apparatus that enables a user to quickly, simply and reliably attach an instrument package to a balloon tether line in a manner that enables the instrument package to freely rotate about the line. To minimize the size of the balloon required, tether lines are typically constructed from a material with a high strength to weight ratio. However, these tether lines are susceptible to breakage from abrasion, twisting, and kinking stresses. Thus, instrument package attachment systems for tethered balloons must be lightweight, simple to operate, and yet prevent the instrument package from slipping, which causes abrasion of the tether line. The instrument package must also be free to rotate about the tether line with the wind direction to prevent the instrument package from twisting the tether line. Finally, the instrument package attachment system must be constructed with a low profile to reduce wind resistance, which could cause the instrument package to kink the tether line. 
     There have been a number of past solutions to this problem. The most effective is that disclosed in U.S. Pat. No. 5,410,918, entitled “Ambient Air Sampler.” The line attachment apparatus disclosed in U.S. Pat. No. 5,410,918 comprises a stationary axle which is secured to the tether line at respective ends of the axle. End caps fit over the ends of the axle and are received by bearings that are secured to a mounting plate on the air sampler. The bearings allow the air sampler to rotate about the end caps of the axle while the tether line is held stationary within the axle. The mounting plate includes an upper mounting arm fixedly connected to an upper cylindrical bearing and a lower spring-loaded mounting arm connected about a pivot to a lower cylindrical bearing. The spring biases the lower spring-mounted arm into a locked position to hold the axle between the two bearings. The tether line is wound about the axle and secured parallel to the length of the axle by the end caps. A helical groove formed on the outer surface of the axle guides and seats the tether line around the axle when the ends of the axle are inserted into the end caps. A slot or notch formed at each end of the axle receives the line as it exits the groove. The end caps are secured over the two ends of the axle respectively via set screws that frictionally secure the end caps to the axle. Each of the end caps are cylindrically shaped and include a slot formed in the circumference thereof to enable the axle and its attached tether line to be inserted therein and spring loaded into place. 
     Unfortunately, wrapping large diameter tether lines around the axle is difficult and time consuming. Additionally, the tension generated by a large balloon often prevents the user from gaining sufficient slack in the tether line to enable wrapping about the axle. Furthermore, the use of the end caps to both secure the tether line to the axle and provide the bearing function places a significant amount of stress on the end caps. This results in premature wear or the need to utilize expensive materials in the construction of the end caps. 
     SOLUTION 
     The above described problems are solved and a technical advance achieved in the art by the present instrument package mounting apparatus for pivotally mounting an instrument package to a line. The instrument package mounting apparatus comprises an axle, a pinch bar and a pair of bearings. The axle comprises an elongated cylindrical body having an interior channel configured to receive the tether line and the pinch bar. The pinch bar is tapered and configured to insert into the channel with the tether line to frictionally secure the axle to the tether line using a compression connection created by the taper of the pinch bar as the pinch bar is inserted. A slot juxtaposed to the interior channel and extending substantially the length of the axle provides access to the interior channel for receiving the tether line. At least one end of the axle includes an aperture for insertion of the pinch bar into the channel to frictionally secure the axle to the tether line. The bearings terminate the ends of the axle to provide a rotational attachment to an instrument package. In particular a first one of the bearings is connected to a first end of the axle and a second one of the bearings is connected to a second end of the axle to provide the rotational attachment to the instrument package. The bearings permit the instrument package to freely rotate about the axle, which internally secures the tether line via that friction force generated by the tapered pinch bar. 
     In some examples of the present instrument mounting apparatus, the axle comprises a two piece axle design, wherein a first and a second segment of the axle each comprise mating segments of a cylindrical solid that define the interior channel and the slot juxtaposed to the channel. A plurality of fasteners secure the first and second axle pieces together. In addition, the respective bearing connected to each end of the axle provides further reinforcement of the connection between the first and second axle pieces. 
     In other examples of the present instrument package mounting apparatus, the axle comprises a three piece axle design. In particular a first segment, a second segment, and a third segment each comprise mating segments of the cylindrical solid that define the interior channel and the slot juxtaposed to the channel. The first segment, the second segment, and the third segment are assembled by fasteners, which are tightened to secure the second segment and third segment to the first segment. As with the prior example, the respective bearing connected to each end of the axle provides further reinforcement of the connection between the first, second, and third axle pieces. 
     A first advantage of the present instrument package mounting apparatus is that the slot and channel can be configured in a plurality of dimensions to accommodate various tether line sizes. A second advantage of the present instrument package mounting apparatus is that it receives the tether line internal to the axle. This eliminates the prior art requirements of generating enough slack in the tether line to wrap the tether line about the axle and align the tether line with the helical grooves at each end of the axle. A third advantage of the present instrument package mounting apparatus is that the axle and the pinch bar provide the attachment to the tether line thereby eliminating the need for the end caps of the prior art. A fourth advantage of the present instrument package mounting apparatus is that the tether line is frictionally secured to the axle in a substantially uniform manner along the length of the axle to eliminate stress points. A fifth advantage of the present instrument package mounting apparatus is that grooves in the channel could be used to accommodate various sizes of tether line without reconfiguration of the axle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a perspective view of an example of the present instrument package mounting apparatus; 
     FIG. 2 illustrates a cross-sectional view of the instrument package mounting apparatus of FIG. 1; 
     FIG. 3 illustrates a prior art instrument package mounting mechanism; 
     FIG. 4 is an exploded top perspective view of another example of the present instrument package mounting apparatus; 
     FIG. 5 illustrates a perspective view of the instrument package mounting apparatus of FIG. 4; 
     FIG. 6 illustrates an exploded side perspective view of the present-instrument package mounting apparatus; and 
     FIG. 7 is a flow chart illustrating the operation of an instrument package mounting apparatus according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     It is common practice to attach instrument packages to a balloon tether line to enable the balloon to transport instrument packages to a location where measurements are to be taken by the instrument packages. For example, air sampling systems are used in many applications to measure trace gases for atmospheric research. For low altitude air sampling, tethered balloons are typically used to perform air sample measurements up to 1,000 meters above the ground. The balloon is attached to a tether line that is controllably released by a winch. One or more instrument packages are attached to the tether line to perform the desired measurements. The typical tether line is made from a material that has a high strength to weight ratio to minimize the size of the balloon required. However, these tether lines are susceptible to breakage from abrasion, twisting and kinking stresses. Thus, the instrument package attachment system for tethered balloons must be lightweight, simple to operate, and yet not allow the instrument package to slip and cause abrasion of the tether line. The instrument package must also be free to rotate about the tether line with the wind direction to prevent the instrument package from twisting the tether line. Finally, the instrument package attachment system must include a low profile to reduce wind resistance, which could cause the instrument package to kink the tether line. 
     Referring to FIGS. 1-3, the instrument package mounting apparatus  100  comprises an axle  101  a pinch bar  103 , a first bearing  115  and a second bearing  116 . The axle  101  comprises an elongated cylindrical body having defined therein an interior channel  106  and slot  107  juxtaposed to the channel  106 . In some examples of the present instrument package mounting apparatus  100 , the axle  101  could be constructed from a single piece of stock configured with the channel  106  and the slot  107 . In other examples of the present instrument package mounting apparatus  100 , the axle  101  could comprise a first segment  108  and a second segment  109  that comprise mating segments of a cylindrical solid to form the axle  101 . The portion of the cylindrical solid that each of the first  101  and second  102  axle segments implement result in the slot  107  that extends along the length of the axle  100  from the outer surface of the axle  100  to a substantially central axis  110 . The slot  107  is configured to receive a tether line  111 , illustrated in FIG. 2, internal to the axle  101 . Juxtaposed to the slot  107  and located substantially centered about the axis  110  of the axle  101  is the rectangular shaped interior channel  106  that functions to receive the pinch bar  103 . The pinch bar  103  comprises a substantially rectangular shaped solid that is tapered along its length so that it forms a compression fit with the interior channel  106  when the pinch bar  103  is inserted into the channel  106 . Operationally, the pinch bar  103  is inserted into the channel  106  and serves to secure the tether line  111  via frictional force created by the compression fit. Fasteners  112 - 114  provide the connection between the first segment  108  and the second segment  109 . Advantageously, the two piece axle design comprising the first segment  108  and the second segment  109  significantly reduces the manufacturing technology required to produce the axle  101 . 
     The ends of the assembled first segment  108  and the second segment  109  of the axle  101  are terminated by respective bearings  115  and  116 . The bearings  115  and  116  include a slot, e.g.  127 , that aligns with the slot  107 , formed by the first segment  108  and the second segment  109 . The slots, e.g.  127  in the bearings  115  and  116  in combination with the slot  107  permit the tether line  111  to be received in the channel  106  during attachment of the instrument package mounting apparatus  100  to the tether line  111 . Fasteners  117 - 120  provide the connection between the bearings  115  and  116  and the axle  101 . The bearings  115  and  116  provide a rotational attachment to the instrument package mounting mechanism  300 , illustrated in FIG.  3 . In particular the bearings  115  and  116  insert into the first and second axle mounts  301  and  302  and freely rotate therein. It should be noted that the instrument package mounting mechanism  300  connects to the mounting plate on an instrument package in a conventional manner with the upper mounting arm  303  fixedly connected and the lower spring-loaded mounting arm  304  pivotally connected to the mounting plate. Thus, the first and second bearings,  115  and  116 , in combination with the axle mounts  301  and  302  form a rotatable bearing mechanism to enable the instrument package to freely rotate about the axle  101 . The axle  101  in turn securely holds the tether line  111  via the friction force generated by the tapered pinch bar  103  inserted into the channel  106 . 
     FIGS. 4 and 5 illustrate another example of an instrument package mounting apparatus  400  according to the present invention. It is anticipated however, that one skilled in the art will recognize numerous other examples in accordance with the principles described below, and thus, the following examples are for the purpose of illustration and not limitation. Those skilled in the art will also appreciate that various features described below could be combined with the above described embodiment to form multiple variations of the invention. 
     The instrument package mounting apparatus  400  comprises a three piece axle  400 , the first bearing  115 , the second bearing  116  and the tapered pinch bar  404 . As with the axle  100 , the bearings  115  and  116  of axle  400  provide the rotational attachment to the mounting mechanism  300 . The axle  400  comprises a first segment  401 , a second segment  402 , and a third segment  403  that form mating segments of the cylindrical solid that comprises axle  400 . The portion of the cylindrical solid that each of the first  401 , the second  402 , and third  403  axle segments implement results in slot  107  that extends from the outer surface of the axle  400  to a substantially central axis  110 . As with axle  100 , the slot  107  is configured to receive the tether line  111  internal to the axle  400 . Juxtaposed to the slot  107  and located substantially centered about the axis  110  of the axle  400  is the rectangular shaped channel  106  that functions to receive the tapered pinch bar  404  and the tether line  111 . A plurality of fasteners,  409 - 414 , secure the second  402  and the third  403  segments to the first segment  401  to form the axle  400 . 
     The first segment  401  of the axle  400  includes a plurality of grooves  405 - 407  formed in the planer surface  408 . The individual grooves  405 ,  406 , and  407  are each individually configured to receive a different size of tether line, e.g.  111 . Advantageously, this permits the instrument package mounting apparatus  400  to accommodate various tether line sizes that could be used to launch various balloon sizes. The grooves  405 - 407  mate with corresponding grooves  500 - 502  formed in the tapered pinch bar  404  to form individual cavities within the interior channel  106  that are slightly smaller than the tether line size the cavities are configured to accommodate. Operationally, the tether line  111  is received into the interior channel  106  via the slot  107  and aligned with the one of the grooves  405 - 407  dimensioned for the tether line  111 . The tapered pinch bar  404  is also inserted into the channel  106  with the mating groove e.g.  502  forming the cavity around the tether line  111 . Advantageously, the cavities engage the tether line  111  in a substantially uniform manner to eliminate stress points that could damage the tether line  111 . 
     Referring to FIG. 6, the friction to secure the axle  400  to the tether line  111  is provided by the taper of the pinch bar  404 . The first segment  402  and the second segment  403  include a sloped ramp  600  in the portion of the first segment  402  and the second segment  403  that forms the interior channel  106 . The slope of the ramp  600  corresponds to the taper of the pinch bar  404  so that when the pinch bar  404  is inserted into the channel  106  the tapered pinch bar  404  and sloped ramp  600  form a compression fit to apply the necessary frictional force that secures the axle  400  to the tether line  111 . 
     FIG. 7 is a flow chart illustrating the operation of the instrument package mounting apparatus  400  according to the present invention. Those skilled in the art will appreciate that the operation of the instrument package mounting apparatus  100  would be similar. On FIG. 7 the operation begins at step  700 . At step  701 , the tether line  111  is inserted into the interior channel  106  of the axle  400  and positioned so that the tether line is in a corresponding one of the grooves  405 - 407 . At step  702  the pinch bar is inserted into the channel  106  so that the tether line  111  is aligned with the mating one of the grooves  500 - 501  on the pinch bar  404 . During the insertion of the pinch bar  404  into the channel  106  the pinch bar  404  engages the interior ramp  600  to form the compression fit between the pinch bar  404  and the interior channel  106 . At step  703 , the pinch bar is set in the channel  106 . Setting the pinch bar  404  is representative of compressing the pinch bar into the channel  106  toward the end of the insertion to firmly seat the pinch bar in the channel and create the compression fit and friction required to secure the tether line  111  in the axle  400 . Setting the pinch bar  404  could be accomplished by any appropriate method. Some examples include without limitation, smacking the extended end of the pinch bar  404  smartly with the palm of your hand, or using a mallet or other similar device to set the pinch bar in the channel  106 . At step  704  a first end of the axle  400  is inserted into the upper mounting arm  303  that is fixedly connected and the second end of the axle  400  is inserted into the lower spring-loaded mounting arm  304  to mount the instrument package on the tether line  111 . The method ends at step  705 . 
     Those skilled in the art will appreciate variations of the above-described embodiments that fall within the scope of the invention. As a result, the invention is not limited to the specific examples and illustrations discussed above, but only by the following claims and their equivalents.