Abstract:
A pneumatically actuated telescoping mast assembly has a mast axis and comprises a plurality of telescopically interengaged mast tubes having axially opposite ends and being axially slidable relative to one another along the mast axis between retracted and extended positions. Axially adjacent mast tubes include a stop collar held on one of the ends of each tube by a snap ring. The radially inner mast tube, of two adjacent mast tubes, includes a double wrap snap ring thereon for engaging the stop collar on the radially outer mast tube to limit relative axial displacement therebetween. The radially inner mast tube further includes a guide collar with a gasket slidably engaging the inner side of the radially outer mast tube. The mast assembly also includes an internal support collar for displacing and supporting the internal wiring used to supply power to the top of the mast assembly.

Description:
This patent application claims priority on Provisional Patent Application No. 60/332,607, filed Nov. 16, 2001. 
    
    
     The present invention relates to the art of pneumatically actuated telescoping masts for supporting a light or the like, and more particularly, to improvements in the connections between adjacent telescoping sections and the displacement of an internally coiled conductor for supplying power to the light. 
     INCORPORATION BY REFERENCE 
     Featherstone, U.S. Pat. No. 4,413,451; Hulse U.S. Pat. No. 6,290,377; and Hulse, et al. U.S. Pat. No. 5,743,635 are incorporated by reference for background information relating to pneumatically actuated telescoping masts of the character to which the invention is directed. 
     BACKGROUND OF THE INVENTION 
     Pneumatically actuated telescoping masts are well known in the art, and are, for example, mounted on the roof of a motor vehicle such as an emergency vehicle or utility vehicle. Alternatively, mounting configurations may also involve the floor of a vehicle, allowing the telescoping mast to extend through the roof of the vehicle. The mast is generally used for positioning electrical devices, such as lighting fixtures, at an elevated point above the vehicle. The effect of a lighting fixture is to light a large area around the vehicle, allowing emergency procedures to be conducted under the light, such as at accident scenes or by utility work crews during power outages, for example. Pneumatically actuated telescoping masts are particularly advantageous for such uses, because they are lightweight, compact in the retracted position, and quickly transportable to a site by the vehicles on which they are mounted. Pneumatically actuated telescoping masts are extended and retracted using air under pressure and, in a fully extended use position, are usually vertical, although they can be inclined in the use position. The vehicle on which the telescoping mast is mounted typically includes a compressor and appropriate pneumatic controls for displacing the mast sections between retracted and extended positions. The connections between adjacent telescoping sections of pneumatically actuated masts heretofore available have been difficult and time consuming to assemble. In part in this respect, certain parts of the connections are either welded or secured with numerous threaded fasteners, whereby the resulting mast is undesirably expensive to manufacture. 
     Pneumatically actuated telescoping masts include power and signal cables which extend to the payload on top of the mast. A common option in this respect is to coil the cables exteriorly about and along the mast. This approach has the virtue of accessibility and flexibility but the liabilities of exposure to physical damage and to the elements. Another option is routing a coiled cable interiorly of the mast. A problem encountered with internally routed power cables is that the coiled wire forms a weak spring. With any extended length of a coil greater than about 15 feet, the coil convolutions tend to collapse in the bottom of the mast due to the accumulated weight of the convolutions. This can result in tangling and/or snagging of the convolutions with one another when the extension moves beyond 15 feet. Also, with longer, heavier wire coils, the upper end of the cable which must support the weight of the coil therebelow is stressed by the accumulated weight of the convolutions. This can lead to breakage of the cable and requires a special connection at the cable end to preclude or minimize the likelihood of such breakage. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a pneumatically telescoping mast is provided which minimizes or overcomes the disadvantages of prior art pneumatically telescoping masts. In this respect, a telescoping mast according to the invention is comprised of component parts by which assembly of the mast is simplified, the weight of the mast is reduced and manufacturing of the mast is more economical than heretofore possible. These attributes are achieved through the provision of improved parts and structures between adjacent mast sections. The connecting components between adjacent mast sections include parts constructed of plastic, thereby minimizing weight of the mast assembly. Additionally, the attachment of collars to the tube of each mast section is simplified so as to avoid the use of numerous threaded fasteners, thereby simplifying assembly. Each of the mast sections includes an improved arrangement for halting movement of the sections when the mast assembly is fully extended. 
     In accordance with another aspect of the invention, a support arrangement is provided for an internal coiled power cable which advantageously reduces the stress on the terminal upper end of the cable and reduces the tendency of a long coil to collapse and the convolutions thereof to tangle, and/or snag during extension and retraction of the mast. 
     It is accordingly an outstanding object of the present invention to provide a pneumatically actuated telescoping mast with an improved connecting structure between adjacent mast sections. 
     A further object of the invention is to provide a mast of the foregoing character with an improved connecting structure that simplifies assembly of the mast. 
     Still a further object of the invention is to provide a mast of the foregoing character with an improved structure for halting movement of the mast sections when the mast assembly is filly extended. 
     Yet another object of the present invention is to provide a mast of the foregoing character with an internal support arrangement for a coiled, internal power cable which reduces the stress on the terminal end of the cable at the top of the mast and supports the coiled cable in a manner which reduces the tendency of the cable to collapse, tangle, and/or snag during extension and retraction of the mast. 
     Another object of the invention is to provide a telescoping mast that is more economical to manufacture than similar masts heretofore available. 
     These and other objects of the present invention will be obvious or pointed out more filly in the following detailed description of preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take physical form in certain parts and arrangements of parts, embodiments of which will be described and illustrated in the accompanying drawings which form a part hereof and wherein: 
     FIG. 1 is a side elevation view of a vehicle having a telescoping mast, shown fully extended according to the present invention mounted thereon; 
     FIG. 2 is an enlarged sectional elevation view of a portion of the mast taken along line  2 — 2  in FIG. 1; 
     FIG. 3 is a sectional elevation view similar to FIG.  2  and showing sections of the mast in a collapsed position; 
     FIG. 4 is a cross-sectional top plan view of the connection between two adjacent mast sections taken along line  4 — 4  in FIG. 2; 
     FIG. 5 is a cross-sectional bottom plan view of the same connection between two adjacent mast sections taken along line  5 — 5  in FIG. 2; 
     FIG. 6 is an exploded view of the connection components of adjacent mast sections; 
     FIG. 7 is an elevation view schematically illustrating a pneumatically actuated telescoping mast and internal power cable according to the prior art; 
     FIG. 8 is an elevation view schematically illustrating a support arrangement in a pneumatically actuated telescoping mast for an internal power cable according to the present invention; and, 
     FIG. 9 is an enlarged sectional elevation view, showing the mast fully collapsed, of the support arrangement shown in FIG.  8 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein the showings are for the purpose of illustrating preferred embodiments of the invention only and are not for the purpose of limiting same, FIG. 1 shows a pneumatically actuated telescoping mast assembly  10  according to the present invention having a base end mounted within a vehicle  12 . More particularly in this respect, mast assembly  10  includes five telescoping mast sections  16 ,  18 ,  20 ,  22 , and  24 , of which mast section  24  is a base section mounted on floor  14  of vehicle  12 . Base section  24  has a lower end  30  mounted on floor  14  by a base support  32  which, as shown in FIG. 2, includes a base plate  34 , a collar  36  welded thereto, and a mounting block  38  in collar  36  and tube end  30 . Block  38  is secured on the lower end of section  24  by one or more bolts  25 , plate  34  is attached to the underside of block  38  by bolts  31 , and plate  34  is mounted on floor  14  by bolts  33 . The other four mast sections  22 ,  20 ,  18 , and  16  extend sequentially along mast axis A from base section  24 , and satellite dish  26  is shown atop the uppermost mast section  16  together with a wiring box assembly  17  on which the light is mounted and which encloses the electrical wiring for satellite dish  26 . In FIG. 1, mast assembly  10  is shown by solid lines in its fully extended position and, immediately above the vehicle roof, is shown by phantom lines in its fully retracted position. 
     As further shown in FIG. 2, mounting block  38  and tube end  30  are provided with an air supply passageway  40  having an end  40   a  for connection to a source of air and an end  40   b  communicating with the interior of the mast. End  40   a  is adapted to be connected to a source of air such as a compressor, not shown, by an air line  42  connected to end  40   a  by a fitting  44 . Air entering passageway  40  for extending the mast sections is precluded from leaking between section  24  and mounting block  38  by an o-ring seal  52  in a radially outwardly open annular recess  54  in block  38  and which seal engages interior side  56  of mast section  24 . The air supply to the interior of mast  10  from the compressor is through well known controls, not shown, which include an up/down solenoid valve, as shown, for example, in the aforementioned U.S. Pat. No. 5,743,635 to Hulse, et al. The solenoid valve controls the extension and retraction of mast assembly  10  and the air pressure to the mast is controlled by a metering valve on the solenoid valve. 
     Each of the mast sections  16 ,  18 ,  20 ,  22 ,  24  includes a corresponding mast tube designated, sequentially,  16   a ,  18   a ,  20   a ,  22   a ,  24   a , and each of the tubes has an upper end and a lower end with respect to the vertical orientation of the mast assembly in FIG.  1 . As will be more fully described hereinafter, axially adjacent ones of the mast sections include interengaging guide and stop components on the mast tubes and which are structurally and functionally identical and vary only in diametrical dimensions which are dictated by the diameter of the corresponding mast tube. FIGS. 2 and 3 show adjacent mast sections  20  and  22 , and it will be appreciated that the following description with respect to the guide and stop components on the tubes  20   a  and  22   a  thereof are applicable to the other mast sections of mast assembly  10 . FIGS. 4-6 further show relationships between certain of the components interconnecting adjacent mast tubes. The connecting components basically comprise a stop collar  64 , stop collar insert  66  and snap ring  68  at the upper end of each tube, a double wrap snap ring  70  intermediate the upper and lower ends of each tube as shown with respect to tube  20   a  in FIGS. 2,  3  and  6 , and a guide collar  72  and sealing gasket  74  at the lower end of each tube. More specifically, stop collar  64  surrounds the upper end of each tube and receives a corresponding stop collar insert  66  under an inner circumferential lip  76  of the stop collar. Insert  66  is secured to collar  64  by four connecting pins  78  to prevent rotation of insert  66  relative to collar  64 . Pins  78  extend through holes  80  through lip  76  of collar  64  and holes  92  through stop collar insert  66 . Stop collar insert  66  includes diametrically opposing notches or keyways  96  and  98  on the inner side thereof for respectively receiving longitudinal protrusions or keys  102  and  104  which extend along diametrically opposite sides of tubes  20   a  and  22   a  to prevent rotation of the stop rings and inserts relative to the mast tubes. 
     Collar  64  includes diametrically opposing key pockets  106  and  108  on the lower inner side thereof for respectively receiving the upper end of longitudinal keys  102  and  104  preventing rotation of collar  64 . The keys  102 ,  104 , keyways  96 ,  98 , and key pockets  106 ,  108  lock mast to fixed mast section  24  preventing rotation thereof. 
     Collars  64  and inserts  66  are mounted on upper ends  114  of tubes  18   a ,  20   a ,  22   a , and  24   a  by a corresponding snap ring  68  which is received in an inwardly open circumferential groove  110  on the inner side of collar  64  and an outwardly open circumferential groove  112  in the corresponding mast tube axially inwardly of top end  114  thereof. Snap ring  68  has opposite ends  67  providing an open sector  69  in its free state to allow for radially constricting the ring, and circumferential groove  110  includes an axially downwardly open space  116  which allows for access to ends  67  for spreading snap ring  68  relative to its free state. In assembly, snap ring  68  is first slightly compressed circumferentially by urging the ends  67  toward each other allowing the snap ring to be received within stop collar  64  to a point of engagement with circumferential groove  110 . At such time, ring  68  expands and snaps into groove  110  and remains therein. The radial depth (largest diameter) of groove  110  is greater than the outer diameter of ring  68  in the free state thereof, thus providing a space  117  for expanding the ring from its free state. By accessing ring ends  67  through opening  116 , ring  68  can be circumferentially expanded so that the upper end of the corresponding mast tube is able to pass through the ring, and stop collar  64  is then moved axially onto the tube. When grooves  110  and  112  are aligned, the memory of ring  68  causes it to contract into groove  112  thereby axially retaining stop collar  64  and insert  66  on the tube end. 
     Tubes  16   a ,  18   a ,  20   a  and  22   a  of mast sections  16 ,  18 ,  20  and  22  include a double wrap snap ring  70  which, as will be appreciated from tube  20   a  in FIG. 3, is received in an outer circumferential groove  124  extending circumferentially around the mast tube at a location close to the lower end thereof. In assembly, snap ring  70  is circumferentially expanded and then slid axially over the outer side of the mast tube until received in groove  124 . During mast extension, snap ring  70  stops vertical movement between adjacent mast tubes when the snap ring abuts bottom side  130  of the stop collar insert  66  on the adjacent mast tube. During retraction of the mast sections, relative displacement stops when the lower end  150  of the stop collar engages the upper end of the stop collar on the outwardly adjacent tube. Collar  64  may be provided with bumpers or seals engaging lower end  150  thereof. 
     Each mast tube further includes a guide collar  72  on lower end  115  thereof which includes a cylindrical skirt  73  having a radially inwardly extending circumferential rib  75  received in an outwardly open circumferential groove  132  proximal to bottom end  115  of the tube. Guide collar  72  further includes a radially inwardly extending circumferential channel portion  77  underlying end  115  and providing a radially outwardly open circumferential recess  142  which receives a gasket  74  having a flexible lip  74   a  for sealing engagement with the inner side of the outwardly adjacent mast tube. Gasket  74  ensures an airtight seal between the adjacent mast tubes. 
     In the preferred embodiment of the invention, stop collar  64  is of aluminum and insert  66  is of a suitable plastic such as DELRIN. Guide collar  72  is of aluminum with a suitable plastic inner lining such as DELRIN, and gasket  74  is of a suitable resilient sealing material. Snap ring  68  and double wrap snap ring  70  are of a spring-type material such that the rings are flexible, expandable and corrosion resistant, and return to the normal or unstressed position thereof after having been deformed and released. 
     Satellite dish  26  at the upper end of the mast assembly requires a power source  174 , and FIGS. 8 and 9 show an arrangement for supplying power to upper end  11  of the mast assembly in accordance with the present invention. FIG. 7 shows a prior art arrangement for supplying power through a wire coil  156  within the interior  154  of a mast as described herein having sections  16 ,  18 ,  20 ,  22 ,  24 . The prior art coil has convolutions  156   a  starting at a bottom end  157  and extending upward to the top end  158  of the mast. Initially, the convolutions of coil  156  are helical, and the coil is capable of extending and retracting within the mast assembly. As shown in FIG. 7, however, when the mast is fully extended, the weight of the coil convolutions tends to concentrate the latter at the bottom of the mast assembly and the coils at the upper end of the mast tend to straighten out. Concentration of the coils at the bottom can cause tangling, snagging, and interference of the convolutions with one another when the mast assembly is extended and retracted. Additionally, when the mast is fully extended, the stress on upper termination  162  of the coil resulting from the weight of the coil can cause the cable to break at the upper end thereof. 
     FIGS. 8 and 9 show a feature of the invention by which the disadvantages of the arrangement shown in FIG. 7 are overcome. More particularly in this respect, a sleeve or tube  166  is connected to the lower end of the tube of one of the intermediate mast sections, such as tube  20   a  of mast section  20 , and extends axially upwardly thereinto to a point about midway between the tube ends. A support collar  167  is attached to the upper end of sleeve  166 , and coil  156  extends through the sleeve and mast tubes  16   a ,  18   a ,  20   a ,  22   a ,  24   a  and is interengaged with the coil collar  167  about midway between the opposite ends thereof. More particularly in this respect, support collar  167  is interposed between adjacent coil convolutions  156   a  at the midpoint of the coil whereby, when the mast sections are extended as shown in FIG. 8, support collar  167  lifts the coil convolutions therebeneath and supports the lower one of the convolutions of the portion of the coil thereabove. Accordingly, the coil convolutions are generally uniformly spaced apart between the bottom and top ends of the extended mast, as shown in FIG.  8 . As will be appreciated, support collar  167  includes an opening  168  therethrough which allows air to pass across the support collar, thereby facilitating mast extension by the pneumatic drive system. As will be appreciated from FIG. 9, the guide collar  172  on the lower end of mast tube  20   a  is modified to accommodate the mounting of tube  166  and support collar  167  thereon. In this respect, channel portion  77   a  thereof is extended radially inwardly to underlie the lower ends of tubes  16   a  and  18   a  and extends downwardly to position tube  20   a  relative to mounting block  38  when the mast sections are fully retracted, whereby the mounting block supports the upper and lower coil sections in the collapsed positions thereof. It will be appreciated that one or more additional tubes and collars similar to tube  166  and support collar  167  can be attached to others of the mast tubes or to the tubes of additional mast sections for further supporting coil  156  as the mast sections are extended and retracted. 
     While considerable emphasis has been placed herein on the preferred embodiments of the invention, it will be appreciated that other embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the invention. Accordingly, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.