Abstract:
A motorized, climbing tree stand ideal for hunting has a rigid elongated, track constructed from multiple, axially aligned sections attached to a tree trunk. A carriage supporting a seat and footrest is coupled to a shuttle assembly that engages the track. The shuttle assembly mounts a battery-powered motor and a motor-driven gear that engages a toothed rack on the elongated track, moving the carriage vertically upwardly or downwardly in response to motor operation. A hand switch controls a reversing relay to control motor direction. Each track section comprises a rigid, elongated flange with an elongated, tubular sleeve terminating in a reduced diameter coupling tube that coaxially mates with the base of the sleeve in the neighboring section. Alignment rods near the upper ends of each sleeve reinforce the assembly. Adjustable, L-brackets contact the tree for bracing. Track flanges are slidably constrained between suitable rollers secured to shuttle side walls.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to elevated hunting or observation stands. More particularly, the present invention relates to hunting stands, primarily for use with trees, that transport the user to a desired elevation above ground. Known prior art stands are classified in United States Patent Class 182, Subclasses 133, 135-137, 141, and 187-188. 
     2. Description of the Related Art 
     Hunters have long recognized and appreciated the many advantages gained by hunting from elevated positions, especially with modern tree stands. Stands that have been properly designed and correctly deployed comfortably provide a safe, seated position at an elevation that is ideal for inconspicuously observing and bagging game animals. An elevated position amplifies the hunter&#39;s field of view, enlarging the potential target area. 
     Numerous diverse tree stands exist in the art. Large, relatively heavy permanent stands are well known. When properly built they can provide a sheltered hunting position well above ground offering superb visibility about a 360 degree radius. Permanent stands have several advantages. For example, they can comfortably accommodate more than one hunter, and they are spacious enough to move about. Some permanent stands have generous storage space, and they may even have electricity and various appliances. However, permanent stands are difficult and time consuming to erect, and as a practical matter, they cannot be moved between hunting locations without significant time-consuming effort. 
     On the other hand, portable tree stands are lightweight, relatively compact, and readily transportable. They can easily be carried into the woods for subsequent erection and use, and when a different hunting location is preferred, they readily disassemble for rapid deployment elsewhere. Portable stands typically comprise a seat supported upon a frame that is adapted to be semi-permanently attached to a tree. In typical “climber” designs, a compound frame has a pair of hinged members that that encircle the tree trunk. The frame elements are intermittently moved into and out of binding contact with the tree truck in response to user movement, and upward movement is enabled. As one fame element is loosened, it can be lifted vertically, while the other frame element temporarily remains in binding contact with the tree trunk. 
     Non-climbing tree stands often have seats supported above ground by one or more vertical ladder elements that elevate the frame. The seat, which may be swiveled for limited rotation so that a large ground radius may be conveniently observed, provides a comfortable and stable rest for the hunter. The frame may be anchored to the tree above ground by suitable teeth or pointed flanges that are forcibly locked into engagement with the tree truck by an encircling chain or rope that is tightened by a clamp or turnbuckle. Many portable designs are deployed at a selectable elevation established by the number and length of the ladder elements used by the stand. Once fastened in position, the seat cannot be easily moved vertically. In such designs the hunter gains access to the elevated seat by carefully ascending the ladder. 
     With climbing stands, on the other hand, the hunter may seat himself within the stand at ground level, and thereafter physically manipulate the stand to gradually climb the tree. Examples of manually-operated, climbing tree stands are provided by U.S. Pat. No. 3,727,723 issued Apr. 17, 1973, and U.S. Pat. No. 5,647,454 issued Jul. 15, 1997. 
     Other approaches to elevating tree stands exist. For example, U.S. Pat. No. 3,568,797 issued Mar. 9, 1971 discloses a stand with a collapsible seat housed within a frame moved by a hand-cranked pulley system. When the stand is attached to a tree it can be manually raised to the desired elevation with the pulley system. Similar crank-operated tree stand systems are seen in U.S. Pat. No. 3,731,762 issued May 8, 1973, U.S. Pat. No. 4,347,913 issued Sep. 7, 1982, U.S. Pat. No. 4,602,698 issued Jul. 29, 1986, U.S. Pat. No. 4,694,934 issued Sep. 22, 1987, and U.S. Pat. No. 5,009,284 issued Apr. 23, 1991. 
     A variation of the cable-driven theme is seen in U.S. Pat. No. 6,079,517 issued Jun. 27, 2000, showing a power driven tree stand that combines a winch with wheels that contact the tree truck. 
     A similar cable-elevated, wheeled carriage is seen in the powered deer stand depicted in U.S. Pat. Application No. 2003/0178251 published Sep. 25, 2003. 
     Motorized or power-driven tree stands are also known in the art. Since many hunters are elderly or physically handicapped or otherwise physically incapacitated, powered deer stands have recognized advantages. For example, U.S. Pat. No. 4,811,803 issued Mar. 14, 1989 illustrates a self-propelled deer stand that elevates hunters above the ground. A pivoted chassis rotates to a vertical position when the structure is raised off the ground. The deer stand uses a motor-powered winch and a cable assembly that elevates it. 
     However, there is a need or a power-driven hunting stand that avoids the use of cables or overhead chains or hoists. Such designs are cumbersome and difficult to deploy, especially for handicapped or elderly hunters. When installed carelessly or inadequately, they tend to be unstable. Often cable-driven designs require deployment, at least in part, upon an overhead branch, which can be difficult to reach, particularly when mounting the tree stand on pine trees. Further, cable-driven power stands do not adequately brace themselves against the tree trunk, increasing the risk of falling or slipping. Known systems involving wheels that contact the tree trunk are unstable and they tend to slip. Insufficient traction is developed by the wheels that rub against the external tree trunk. 
     Furthermore, there is a need for a power driven deer stand that is essentially portable. 
     While some portable designs are quite rugged despite their light weight, one common problem with so-called portable stands is that they can be relatively flimsy and unstable. On the other hand, ruggedized, heavy duty designs made of bulky metal parts tend to be heavy and cumbersome. However, it is important to realize that the disadvantages associated with heavier tree stands are outweighed by their dexterity. In the past, for example, hunters often preferred lightweight deer stands that could be easily carried in a backpack and quickly deployed after a single trip into the woods. Thus lightweight climbing stands have been popular. However, while a deer stand that can be carried into the woods in a single trip has obvious advantages, many hunters no longer demand such simplicity. Larger, heavier “portable” stands that can be carried by one or more hunters, or by a single hunter who makes separate trips, have significant advantages. What is important with heavier “portable” designs is that the parts, once transported, fit together easily on the job site for quick erection, and that the assembled unit operates safely and reliably. In this regard, it should be appreciated that a heavy-duty “portable” stand may be as stable a hunting platform as the typical elevated “permanent” stand. 
     The number of parts required to assemble the stand, or the number of trips into the woods carrying parts, is not critical to many users. It is not uncommon these days that heavier “portable” tree stands be delivered to the hunting site in an all-terrain vehicle or pickup truck, avoiding the necessity for time consuming trips where the hunter manually carries the stand&#39;s parts. Usually such stands are deployed by a group of hunters several days before the hunting season, so portability, light weight and speed of erection are features that are gradually diminishing in importance. 
     What is important to many hunters is that the stand be easy to climb. Thus a powered stand that transports the hunter to the desired elevated hunting position is desirable. Typical climbing stands that are operated manually are of no value to handicapped or elderly hunters. If a heavy duty “portable” stand that is rugged and powered can elevate the hunter automatically to an elevated position, the disadvantages associated with increased weight will be forgotten and excused. Further, such a system must offer a stable and safe support once deployed, and ease of both ingress and egress must be facilitated. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention provides a motorized, elevating device that safely and reliably elevates a user to a desired vertical elevation along an elongated, cylindrical object such as a pole. Preferably the device functions as a deer stand, and it is deployed within the woods against a selected tree. My invention provides a power means to elevate the hunter to a desired position vertically above ground. 
     The motorized, climbing stand is ideal for hunting. An elongated, track constructed in the field from multiple, axially aligned sections, is attached to a tree trunk by suitable clamps or bands. A carriage with a comfortable seat is coupled to a shuttle assembly that engages the track. The shuttle assembly mounts a motor and a driven gear that engages the track, enabling the carriage to move vertically upwardly or downwardly in response to motor operation. 
     Each track section comprises a rigid, elongated flange is flat. The front of each flange has a section of toothed rack with teeth adapted to be engaged by motor-driven gear. The rack section is coextensive with the flange. The inner side of the flange of each section has an elongated, tubular sleeve coextensive with the flange. A reduced diameter coupling tube projects outwardly from the upper sleeve end, for coaxial mating with the base of the sleeve in the next section. Alignment rods near the upper ends of each sleeve project outwardly with the coupling tubes for reinforcement. Adjustable, two-piece L-brackets welded to the sleeves Contact the tree or column to brace the rack. When the shuttle is penetrated by aligned track sections, the track flanges are slidably constrained between suitable rollers secured to shuttle side walls. 
     The carriage provides a comfortable seat and a foldable footrest. Suitable orifices defined in frame crosspieces enable coupling to the shuttle. A pair of spaced-apart wings defined on the shuttle releasably engage the carriage frame crosspieces to support the carriage during movement. Preferably a safety lock and a hand crank are provided in case of motor or drive train failure. 
     Thus, one important and basic object of my invention is to provide a motorized or powered lift for elevating users vertically against a cylindrical object such as a pole or tower or tree. 
     Another fundamental object is to provide a motorized hunting or deer stand that powers the hunter to the desired elevation. 
     A related object is to provide a climbing hunter&#39;s stand that has a motor-driven seat. 
     It is also an object to replace manually operated climbing stands. 
     Another important object of the present invention is to provide a motorized tree stand that is simple to operate and easy to deploy. 
     Still another object of the present invention is to provide a deer stand of the character described that can be relatively easily disassembled and then transported. 
     Another important object is to provide a deer stand of the character described that uses a reliable drive propulsion system that does not frictionally rotate against the tree trunk surface. 
     A general object is to provide a motorized lift of the character described that is adapted for use with a variety of cylindrical objects including poles and trees of different diameters, lengths, and configurations. 
     Another object is to provide a tree stand that inherently adapts itself for use with trees of different circumferences. 
     It is another object of the present invention to provide a motorized tree stand of the character described that may be easily and efficiently assembled and deployed. 
     Another object of the present invention is to provide a motorized tree stand of the character described that enables a hunter to rapidly climb or descend a tree. 
     These and other objects and advantages of the present invention, along with features of novelty appurtenant thereto, will appear or become apparent in the course of the following descriptive sections. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the following drawings, which form a part of the specification and which are to be construed in conjunction therewith, and in which like reference numerals have been employed throughout wherever possible to indicate like parts in the various views: 
         FIG. 1  is a fragmentary isometric view of the tree stand shown in a lowered, user-accessible position proximate a cylindrical object, preferably a tree; 
         FIG. 2  is a front plan view of the stand; 
         FIG. 3  is an enlarged, fragmentary, outer isometric view of the preferred track showing the geared rack; 
         FIG. 4  is an enlarged, fragmentary isometric view of the inner side of the preferred track showing the ends of typical track sections that are to be axially fitted together; 
         FIG. 5  is an enlarged, frontal isometric view of the preferred shuttle; 
         FIG. 6  is an enlarged, fragmentary sectional view showing how the shuttle surmounts the track, taken generally along line  6 - 6  in  FIG. 5 , 
         FIG. 7  is an enlarged, frontal isometric view of the preferred carriage; 
         FIG. 8  is an enlarged, rear isometric view of the preferred carriage; 
         FIG. 9  is an isometric view of the preferred carriage similar to  FIG. 8 , but showing the auxiliary hand crank; 
         FIG. 10  is an enlarged, fragmentary isometric view derived from circled region “ 10 ” in  FIG. 9 ; 
         FIG. 11  is an enlarged, fragmentary, exploded isometric view of the preferred coupling assembly that interconnects the carriage with the shuttle with portions thereof omitted for clarity; 
         FIG. 12  is an exploded, fragmentary isometric view similar to  FIG. 11  showing additional details including the motor, the motor housing and the gear drive assembly; 
         FIG. 13  is an enlarged, fragmentary view taken generally along line  13 - 13  of  FIG. 12 , with portions thereof broken away or shown in section for clarity; 
         FIG. 14  is a fragmentary isometric view of an alternate, carriage preferably used for pole climbing instead of hunting; and, 
         FIG. 15  is a block diagram of the preferred electrical wiring. 
     
    
    
     DETAILED DESCRIPTION 
     With initial reference directed now to  FIGS. 1 and 2  of the appended drawings, a motorized, climbing device, constructed generally in accordance with the best mode of the invention, has been generally designated by the reference numeral  10 . Preferably device  10  is in the form of a hunter&#39;s tree-climbing stand. However, the device may be used to climb any elongate, vertical column or pole that is generally cylindrical and which has a smooth lower circumference. 
     The tree stand embodiment is preferred. The stand  10  is illustrated in a lowered position in  FIG. 1 , providing access for a hunter or other passenger or user to be seated within a carriage  12  that engages a track  14 . Preferably the hunting stand  10  is used by sportsmen or outdoorsmen that desire an elevated observation position for hunting, as is common practice with deer hunters. Of course the stand  10  presents numerous advantages and features that are useful to others besides hunters such as those that service telephone or power lines. 
     It is preferred that the elongated, sectioned track  14  be secured to the external surface of the vertically upright tree (or column or pole). Preferably the hunting stand is deployed upon a pine tree whose smooth lower regions are free of branches  9  or other obstructions or protrusions that would interfere with vertical travel during normal operation. Although rigid and robust, the various components are relatively lightweight and they may be easily transported into the woods. Once unloaded from the vehicle (i.e., an ATV or pickup truck) at the hunting or job site, they may be securely installed and assembled as hereinafter described. Once the stand  10  is installed, a seated hunter can simply operate toggle switch  252  ( FIG. 12 ) to elevate himself upon carriage  12  several feet above ground  15  to have a commanding view of the desired hunting area proximate tree or column  16 . When the alternative carriage of  FIG. 14  is deployed, the device  10  functions as an elevator and may be used to service vertically elevated objects such as power lines, telephone lines and the like. 
     The elongated track  14  preferably comprises several similar, interfitting sections that are axially coupled together at the hunting site. The track is attached to the tree (or column)  16  along an exposed, smooth portion of the tree trunk that is free of obstructions or significant surface irregularities. Alternate, aligned track sections  17 ,  18 , and  19  (i.e.,  FIGS. 2 ,  3 ) for example, are axially fitted together as explained hereinafter and then affixed to the tree trunk by encircling band clamps  21  of conventional construction. Each band clamp comprises an encircling loop  22  (i.e.,  FIG. 4 ) whose ends are provided with suitable hooks  23  and turnbuckles that engage rigid L-brackets  24  that are affixed at regular spaced-apart intervals to the rear of each track section (i.e.,  FIG. 3 ). A variety of conventional, encircling clams or cables known in the art may be used. 
     The assembled track  14  (i.e.,  FIG. 1 ) is surmounted by a vertically displaceable shuttle  26  ( FIG. 5 ) through which the track extends. The shuttle  26  supports and is interconnected with a coupling assembly described later (i.e.,  FIGS. 6 ,  9 - 11 ). A preferably electric drive motor  103  and a rotatable drive gear  108  described later (i.e.,  FIG. 6 ,  11 - 12 ) engages the track  30 . Carriage  12  is removably fitted to and supported by the coupling hardware (i.e.,  FIG. 11 ), so it travels vertically upwardly or downwardly relative to the track  30  with the shuttle  26  in response to motor operation. Shuttle  26  is prevented from being accidentally driven off of top track  19  by stops  20  ( FIG. 2 ) on track section  19 . 
     With joint reference directed now to  FIGS. 3 and 4 , the track  14  comprises a plurality of similar track sections  17 - 19  that are to be fitted together axially and then secured to the tree  16  substantially perpendicular to the ground  15 . Each track section comprises an elongated, rigid flange  28  that is generally rectangular. The front or outer side of each flange  28  supports a section of toothed rack  30  whose rigid teeth  31  are ultimately engaged by the motor-driven gear described later. The rack  30  is secured at the middle of the flange  28  by welding, and it extends along the entire length of the flange in parallel relation thereto. The rear or inner side of each flange supports a rigid, elongated sleeve  33  ( FIGS. 4 ,  6 ) that is welded at the center of the flange rear. The rigid, tubular sleeve  33  is substantially coextensive with the flange  28  of each track section  17 - 19  and is parallel with the flange. The upper end of each sleeve  33  (i.e.,  FIG. 4 ) coaxially supports a smaller diameter coupling tube  36  that projects approximately six inches away from it. The reduced diameter of coupling tubes  36  enables it to fit within the interior diameter of the sleeve  33 . In assembly each coupling tube  36  is coaxially fitted to a bottom sleeve end  38  of an adjacent track section to unite the track assembly. When properly assembled, aligned segments of the rack  30  abut gently and present a continuous rack with uniformly spaced apart teeth  31 . 
     Each section of track  17 - 19  has a pair of alignment rods  40  proximate the upper end of its sleeve  33  that project outwardly, spaced-apart from and parallel with coupling tube  36 . Rods  40  are welded at the sides of the sleeve  33 , at the region where the sleeve borders the flange  28 . As appreciated from  FIGS. 4 and 6 , for example, when two track sections are fitted together, rods  40  project forwardly to the next track section, aligning them proximate the lower sleeve end  38  in sliding contact with the flange  28  of the adjacent track section. Rods  40  thus prevent twisting as contact with the adjacent flange minimizes torsional displacements. The bottom of the bottom track section  71  has a pair of similar rods  41  that are non-parallel, and which anchor themselves within the ground. 
     As best seen in  FIG. 4 , the preferably two-piece brackets  24  have a preferably L-shaped cross section. Each bracket  44  comprises a flat base  42  welded to sleeve  33  that is parallel with and spaced-apart from flange  28 . A perpendicular bracket section  44  is welded to base  42  and projects vertically away from the base. Perpendicular section  44  has a pair of slots  46  ( FIG. 4 ) enabling it to mate with a similarly slotted plate  81  whose projecting, pointed sides on either aside of central notch  80  engage the tree. Plate  81  is adjustably, slidably secured to bracket section  44 . Bolts  82  extend through the aligned slots  46  and wing nuts  83  are tightened to secure the plate  81  in a desired position. Slots  48  are defined in the base sections  42  of brackets  24  to receive ends of the encircling loops described earlier. As seen in  FIG. 4 , the end of loop  22  has a hook  23  that engages a slot  48  to mount the stand. The opposite end of the loop  22  may comprise an over-center clamp, or a turnbuckle, coupled to a similar hook engaging another bracket slot  48 . During installation, adjustments to plate  81  enable the L-brackets  24  to adapt for minor irregularities in the outer surface of tree  16 . 
     Referring now to  FIGS. 5 and 6 , the elongated shuttle  26  is of generally C-shaped cross section. The front panel  48  provides a mounting surface for the coupling hardware described hereinafter. An elongated access orifice  49  clears the drive gear described later, which engages the rack  30  positioned below it in assembly. Panel  48  is integral with a pair of parallel, spaced-apart sides  51  and  52  which are positioned, in assembly opposite the edges of the rack flanges  28  ( FIG. 6 ). There are a plurality of pairs of spaced apart guide rollers  54  projecting inwardly of the shuttle from each side  51 ,  52 , secured by fasteners  53 . As seen in  FIG. 6 , for example, the track flanges  28  are positioned between and constrained by rollers  54  in use. A plurality of spaced-apart pairs of similar guide rollers  56  project inwardly from shuttle panel  48  and slidably adjoin opposite sides of the track  30 , as best seen in  FIG. 6 . 
     The preferred carriage  12  is detailed in  FIGS. 7-10 . A rigid, generally cubicle frame  60  ( FIG. 8 ) comprises parallel vertical legs  62  (i.e.,  FIG. 9) and 63  ( FIG. 8 ) at the carriage rear and a pair of lateral supports  64  and  65  extending horizontally between them. Supports  64  and  65  comprise numerous spaced apart orifices  61 ,  66  respectively that are engaged when the carriage is user-fitted to the shuttle coupling means as described hereinafter. Spaced apart side rails  67  and  68  extend horizontally at the bottom of the carriage between the front and rear; upper frame rails  69  and  70  are spaced above lower support rails  68  and  67  respectively. Vertical supports  72  and  73  extend between the upper and lower frame rails for strength. In the best mode a seat  75  is preferably disposed atop the carriage frame. Hand rails  76  and  77  are mounted on each side of the seat  75  adjacent a comfortable cushion  78 . Rails  79  support a back-supporting cushion  80 . A generally rectangular footrest  82  has a pair of side rails  84  pivoted to the carriage frame by hinges  85 . The footrest  82  is maintained in a substantially horizontal position during use by suitable cables  86  extending between clevis&#39;s  87  ( FIG. 8) and 88  ( FIG. 7 ). 
     With joint reference directed now to  FIGS. 9-12 , the coupling assembly  90  ( FIGS. 11-12 ) interconnects the carriage  12  with the shuttle  26  and track  14 . The shuttle  26  is fitted with upper and lower, spaced apart wings  94  and  95  respectively that have upwardly projecting pins  96 ,  97  respectively. The carriage  12  is disposed upon the shuttle wings  94 ,  95 . It is user-fitted to the shuttle by fitting pins  96  emanating from wing  94  ( FIG. 11 ) into orifices  66  in cross piece  65  ( FIG. 8 ). Similarly, pins  97  in wing  95  penetrate orifices  61  in carriage frame cross piece  64 . The other coupling hardware seen in  FIG. 11 , for example, will be positioned beneath the seat  75  between the previously described frame members  62 ,  53 ,  65  etc. 
     Housing  92  is attached to sides  51  and  52  of carriage  26  by screws  87  shown in ( FIG. 12 ). Cover  113  may be removed by removing similar screws. A support bracket  100  is fitted within housing  92 . Bracket  100  has a horizontal support plate  102  ( FIG. 11 ) upon which a drive motor  103  ( FIG. 12 ) is secured. Similarly, bracket  100  has a vertically oriented support plate  105  that secures the drive gear assembly  106 . A toothed drive gear  108  driven by preferably DC motor  103  is positioned so that it penetrates shuttle slot  49  (i.e.,  FIG. 5 ) and engages the rack  30  to propel the carriage. In assembly the motor  103 , the gear drive assembly and related components are protected within housing  92 . A preferably twenty-four volt battery  86  ( FIG. 12 ) is disposed within battery holder  116  which is mounted to surface  111  of housing  92 . 
     A safety lock is provided. Referencing  FIG. 11 , the front panel  110  of the housing  92  has a port through which an elongated lock actuator  115  extends. The lock handle  112  and actuator  115  must be deflected to operate the stand. A follower  119  coaxially engages a spring  120  and it secures a ratchet  122  attached by a nut  123 . Ratchet  122  is yieldably biased towards the rack  30  (i.e., teeth  31 ) to lock the carriage in place when a desired elevation is attained, independently of the motor or driving system. 
     Referring to  FIG. 10 , the shuttle  26  supports a manual cranking system  130  that can be used when and if the motor fails. A hand crank  133  drives motor shaft  85  which extends through drive gear assembly  106  within enclosure  134  and out to hand crank  133 . 
     The alternate embodiment of a carriage  200  can be used by lineman to service power and telephone lines and is shown and described in ( FIG. 14 ). Like carriage  12 , carriage  200  uses spaced apart orifices  61  and  66  respectively that are engaged when the carriage is user-fitted to the shuttle  26  in the same manner as shown an described for carriage  12 . Carriage  200  has a generally cube shaped frame with a foot platform  201  comprising several spaced apart, parallel angle bars  202  welded to perpendicular angle bars  203  and  204 . Square bars  205  and  206  and  217  are welded to vertical supports  207 ,  208 ,  209 , and  210 . Hand rails  211  and  212  are mounted on each side of carriage. Square bar  213  is welded to bars  207  and  210  for rigid support. Vertical supports  215  extend between the upper cross bars  216  and lower bars  203  and  204 . A safety bar  214  swings open when access or egress to the platform is desired. Gussets  218  are welded at the four bottom corners of the frame for support. 
       FIG. 15  illustrates the generalized electrical wiring scheme. A terminal block circuit  251  interconnects with a 24-volt DC battery pack. Power delivered across couplings  255 ,  256  delivers current to a high current relay switch  252  that includes a reversing function for changing current polarity. Current outputted from the relay stage  252  passes through circuits  253  and  254  tot energize the motor through coupling  250 . 
     From the foregoing, it will be seen that this invention is one well adapted to obtain all the ends and objects herein set forth, together with other advantages which are inherent to the structure. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
     As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.