Abstract:
A light weight surveying pole which is of robust and highly accurate construction. The pole may include two or more pole sections which may be screwed together to make a longer pole. Fittings for use in screw-together pole sections are constructed to permit location within mating pole sections prior to application of adhesive for greater precision and maintenance of coincident axes of the pole sections when screwed together. Also, the end faces of the fittings are particularly formed to facilitate complete face-to-face contact and avoid misalignment when the pole sections are connected together.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to surveying equipment and more particularly to surveying equipment having lightweight and yet robust, precision construction. 
     Surveying equipment and particularly the support structure therefore must be able to withstand all kinds of environmental conditions while retaining its integrity and dimensional accuracy. In many instances, the dimensional accuracy is imperative in order to obtain the correct measurements in a geographic survey. For instance, prism poles and global positioning satellite (GPS) poles must be able to retain a substantially fixed position of extension as they are moved from place to place over uneven terrain and in all kinds of weather. Prism poles include two or more interfitting pole sections, and support a prism or other measurement device at the top used to sight or determine positions with laser, modulated infrared, angular and/or GPS position locators or like surveying systems. The prism reflects light back to the position locator for determining the location of the prism at different locations in a survey. The prism pole may be constructed with telescoping sections so that it may be collapsed to a reduced height (e.g., about four feet) for storage and transport, and then extended to its operating height which may be, typically, eight feet or more. In topological surveys, it is important that the pole be able to maintain its extended height as it is moved from place to place. It is therefore, critical to be able to lock the pole sections in a fixed position of extension in such a way as to have them stay. Moreover, the pole must maintain its longitudinal axis as it is extended so that its extended height is accurate every time. Similarly, the pole must be able to withstand numerous cycles of extension and retraction, and frequent rough handling while maintaining this accuracy. Still further, it is frequently desirable to completely detach the telescoping sections without substantial disassembly of the surveying pole or loss of accuracy upon reassembly. 
     The need for durability and accuracy has traditionally led to making surveying poles out of metal. However, metal poles can expand and contract significantly with changes in the temperature of the surrounding environment which is detrimental to accuracy of the survey. Metal poles are also capable of plastic deformation which can lead to inaccurate measurements. Carrying a heavy metal pole over uneven or broken terrain, as will be frequently necessary in surveying, can be very difficult and physically taxing. Using metal poles in the outdoors also presents a risk of lightening strike. It is possible to make poles out of lighter weight, non-conducting material, such as fiberglass, which are sturdy and weather-resistant. However, these poles will typically not withstand the clamping forces conventionally applied to metal poles to hold them in a fixed extension. Lower clamping forces may not adequately hold the pole sections in position. A similar problem is present when attaching something which must maintain a precise orientation, such as a level, to the pole. Non-metal materials may also be less likely to withstand impact forces associated with forcefully retracting the pole sections. 
     The surveying poles or other surveying equipment support structure may have telescoping sections, screw-together sections or a combination of the two. It is important to be able to rapidly collapse the poles for storage and transport. Also for cleaning in the field, the pole sections need to be able to be quickly and accurately disassembled and reassembled. Regardless of the material of the pole, it is often difficult to economically manufacture the pole sections so that they will maintain the same linear axis every time they are screwed together. One problem is the initial installation of screw fittings in ends of the pole sections. Care must be taken to achieve axial alignment upon installation. Another problem is the accumulation of debris on the fittings so that when screwed together, the fittings do not achieve face-to-face engagement which results in axial misalignment of the pole sections. For telescopingly interfitted pole sections, it is important to be able to easily disassociate the sections for cleaning or repair, and reassemble them while maintaining accuracy. 
     It is also not uncommon for these poles to have some accessory equipment. For instance, the bottom of a prism pole is conventionally equipped with a steel point to locate the pole on the ground. However in circumstances where the ground is soft, it is undesirable to have the point engaging the ground because the point tends to penetrate the surface of the ground. As a result, the location of the top of the pole above the ground can be inconsistent. Conventionally, the steel point has been removed and replaced with a blunt or greatly enlarged blunt end under these circumstances. The replacement involves several steps and it is necessary to carry the blunt end (or the steel point) around separately from the pole until used. The steel point can be difficult to safely carry because its point can be rather sharp. 
     SUMMARY OF THE INVENTION 
     Among the several objects and features of the present invention may be noted the provision of a lightweight surveying pole which is sturdy and weather-resistant; the provision of such a surveying pole which accurately maintains an extended height; the provision of such a surveying pole which maintains sections in a coaxial relation; the provision of such a surveying pole which can be disassembled and accurately reassembled for cleaning and repair; the provision of such a surveying pole which can be reconfigured with minimal steps; and the provision of such a surveying pole which can be efficiently manufactured with high accuracy. 
     Further among the several objects and features of the present invention may be noted the provision of a pole section for surveying equipment and a method of making such a pole section which is lightweight; the provision of such a pole section and method for making a pole section which can be repeatedly disassembled and accurately reassembled; and the provision of such a method which can be efficiently carried out with high accuracy. 
     Generally, a pole section constructed according to the principles of the present invention for use in surveying equipment is elongate and has opposite ends at least one of which is open. The pole section has an interior surface in the open end and a fitting received in the open end of the pole section. The fitting includes first and second spaced circumferential engagement surfaces in contact with the interior of the pole section for precisely locating the fitting relative to the pole section and a circumferential channel located between the engagement surfaces. The channel is spaced from the pole section, and an adhesive located in the channel and bonding the fitting to the pole section. 
     In another aspect of the present invention, a pole section for use in surveying equipment is elongate and having opposite ends at least one of which is open. The pole section has an interior surface in the open end and a fitting received and held in the open end of the pole section. The fitting is formed with a connector element adapted for connection with a corresponding connector element of another component of the surveying equipment. The fitting includes an axially facing end surface having a surface area and facing axially outward from the pole section. The axially facing surface including a peripheral engagement portion constitutes a first smaller portion of the axially facing surface area, and an axially recessed portion constitutes a second larger portion of the surface area recessed axially from the peripheral engagement portion thereby to facilitate full face-to-face engagement of the engagement portion with said other component of the surveying equipment. 
     In a still further aspect of the invention, a method of making a pole section for surveying equipment generally comprises the steps of providing an elongate member having opposite ends at least one of which is open and an interior surface inside the open end, and a fitting having an end surface, first and second spaced circumferential engagement surfaces, a circumferential channel located between the engagement surfaces and an adhesive passage opening at one end at the end surface of the fitting and at another end in the channel. The fitting is inserted into the open end of the elongate member such that the end surface faces axially outwardly of the open end of the elongate member and the circumferential engagement surfaces engage the interior surface and align the fitting with respect to the elongate member. Adhesive is injected through the adhesive passage from the end surface of the fitting as inserted into the elongate member into the channel for bonding the fitting to the elongate member. 
     Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevation of a prism pole constructed according to the principles of the present invention; 
     FIG. 2 is an exploded perspective of the prism pole; 
     FIG. 3 is a perspective of a locking mechanism of the prism pole; 
     FIG. 4 is an exploded perspective of the locking mechanism; 
     FIG. 5 is a section taken of a front jaw of the locking mechanism in the plane including line  5 — 5  of FIG. 4; 
     FIG. 6 is a longitudinal section of an elastomeric member associated with the front jaw taken in the plane including line  6 — 6  of FIG. 4; 
     FIG. 7 is a longitudinal section of the front jaw assembled with the elastomeric member; 
     FIG. 7A is an enlarged detail of FIG. 7 illustrating the operation of the front jaw under axial forces tending to extend the surveying pole from its selected height; 
     FIG. 8 is a perspective of a base of the locking mechanism; 
     FIG. 9 is a horizontal section taken in the plane including line  9 — 9  of FIG. 3; 
     FIG. 10 a fragmentary longitudinal section of the surveying pole showing the releasable interconnection of pole sections; 
     FIG. 10A is an enlarged portion of the section of FIG. 10; 
     FIG. 11 is a front elevation of a pole plug; 
     FIG. 12 is a right side elevation of the pole plug; 
     FIG. 13 is a longitudinal section of the pole plug taken in the plane including line  13 — 13  of FIG. 11; 
     FIG. 14 is a bottom end view of a female pole end fitting including an air valve; 
     FIG. 14A is a section of the end fitting taken in the plane including line  14 A— 14 A of FIG. 14; 
     FIG. 15 is an enlarged fragmentary longitudinal section of the surveying pole showing a lower end of the pole including a male end fitting; 
     FIG. 15A is a further enlarged, fragmentary section of the surveying pole of FIG.  15  and illustrating a channel in the end fitting for glue; 
     FIG. 16 is a perspective of the male end fitting inverted from its position shown in FIG. 15; 
     FIG. 17 is a longitudinal section of the male end fitting illustrating glue passages; 
     FIG. 18 is an exploded, fragmentary perspective of two pole sections connected together by the male and female end fittings; 
     FIG. 19 is a longitudinal section of a female end fitting of another embodiment; 
     FIG. 19A is an enlarged, fragmentary portion of the section of FIG. 19; 
     FIG. 20 is a longitudinal section of a female end fitting of still another embodiment; 
     FIG. 20A is an enlarged, fragmentary portion of the section of FIG. 20; 
     FIG. 21 is a longitudinal section of a point and covering shoe of the surveying pole; 
     FIG. 22 is a perspective of the shoe; 
     FIG. 23 is an exploded perspective of a level vial holder of the surveying pole; 
     FIG. 24 is a section of the level vial holder having the shoe stowed thereon; 
     FIG. 25 is a section of the point illustrating storage of a spare tip for the point; and 
     FIG. 26 is an exploded perspective of the point and spare tip. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and in particular to FIGS. 1 and 2, a surveying pole  26  constructed according to the principles of the present invention is shown to comprise a first pole section  28  and a second pole section  30  telescopingly received in the first pole section (the reference numerals designating the subjects generally). In the preferred embodiments, the pole sections are made out of a lightweight, non-metallic composite material such as fiberglass. However, it is to be understood that the pole sections could be made of a lightweight (typically lower strength) metal or other composite material without departing from the scope of the present invention. In FIGS. 1 and 2, the second pole section  30  is retracted almost fully within the first pole section  28 . Preferably, the second pole section  30  has graduated indicia (not shown) marked thereon for indicating the height of the pole as the second section is extended from the first section  28 . A locking mechanism (indicated generally at  32 ) attached to the first pole section  28  is capable of releasably clamping the second pole section  30  in a fixed position of extension relative to the first pole section by moving a lever  34  of the locking mechanism. 
     A female end fitting, generally indicated at  36 , is located at the top of the second pole section  30  and receives a mount  37  for mounting a prism  38  (FIG. 2) or other surveying device (e.g., a GPS antenna) at the top of the pole  26 . The references to “top”, “bottom”, “lower” and “upper” are used for convenience in describing relative position of parts, and apply when the surveying pole  26  is in ordinary use as shown in FIG.  1 . However, these and other positional terms do not require the surveying pole  26  to maintain any particular orientation to fall within the scope of the invention. The prism  38  reflects back infrared or laser light from a position locator for establishing the position and/or elevation of the location where the surveying pole  26  is placed. A level vial  40  in a level vial holder, generally indicated at  42  and affixed to the first pole section  28 , is used to maintain the surveying pole  26  is a vertical position while measurements are being taken. The lower end of the surveying pole  26  has a metal point (generally indicated at  44  in FIG. 2) screwed into the first pole section  28  for engaging the ground. The metal point  44  can be covered by a shoe  46 , as is shown in FIG. 1 for use in conditions described hereinafter. 
     Referring now to FIGS. 3-9, the locking mechanism  32  includes a base indicated generally at  48  comprising a first base member  50  and a second base member  52 . In the preferred embodiments, the first and second members of the base are primarily made of a substantially rigid plastic (e.g., an acetyl plastic). The first base member  50  is sized and shaped to fit over the top end of the first pole section  28  such that a collar  54  rests generally on the top end of the first pole section and a depending, semi-cylindrical skirt  56  engages one side of the first pole section adjacent thereto. A central opening of the collar  54  is sized to permit the second pole section  30  to pass freely through the first base member  50 . Metal thread elements  58  are force fitted into openings (not shown) in the skirt  56 . The semi-cylindrical second base member  52  engages the opposite side of the first pole section  28  just below the top end and is attached to the skirt  56  of by bolts  62  which pass through the second base member and into the thread elements  58  in the skirt. Thus, the base  48  is held on the top end of the first pole section  28  by engagement of the collar  54  with the end of the first pole section and by the clamping action of the opposed skirt  56  and second base member  52  through their interconnection by the bolts  62 . The concave opposing surfaces of the skirt  56  and the second base member are overmolded with a softer elastomeric material  64  which grippingly engages the first pole section  28  to further assist holding the base in a fixed longitudinal position on the first pole section. Only the concave surface and elastomeric material  64  of the second base member  52  can be seen in the drawings (FIG.  4 ), the shape and arrangement of the concave surface and elastomeric material of the skirt being substantially identical thereto. The elastomeric material  64  is preferably injection molded onto the skirt  56  and second base member  52 , previously also formed by injection molding. The skirt and clamp each are formed with cavities and passages (not shown) into which the elastomeric material flows, thereby connecting the elastomeric material to the skirt and clamp. 
     The first base member  50  further includes a pair of diametrically opposite supports  66  projecting axially upward from the collar  54  of the first base member for supporting an upper clamping assembly operable to clamp the second pole section  30  in a fixed position of extension relative to the first pole section  28 . The upper clamping assembly comprises a front clamping jaw  68  and a rear clamping jaw  70  formed of the same rigid plastic as the first and second base members  50 ,  52 . The rear clamping jaw  70  is generally semi-cylindrical in shape and includes a pair of spaced apart ears  72  projecting outward from the rear clamping jaw. The ears  72  are each formed with an elongated opening  72 A which receives a pivot pin  74  mounting the lever  34  on the rear clamping jaw  70 . The front clamping jaw  68  is attached to the rear clamping jaw  70  by a pair of bolts  76  which pass through the front clamping jaw and respective middle openings  66 A in the supports  66  of the base  48  and into the rear clamping jaw. The bolts  76  each pass through the semi-cylindrical portion of the rear clamping jaw  70  and into a respective one of the elongate openings  72 A in the ears  72 . The middle portion of each bolt  76  is smooth to permit the front and rear jaws  68 ,  70  to slide on the bolt. Four coil springs  78 , each extending through a respective spring hole  66 B in the supports  66  of the base  48 , are interposed between the front and rear clamping jaws  68 ,  70 , biasing the jaws apart from each other and away from the second pole section  30  to an unlocked position. 
     Actuation of the locking mechanism  32  to move the front and rear clamping jaws  68 ,  70  between the locked and unlocked positions is accomplished by the lever  34 , mounted for pivoting about a horizontal axis by the pivot pin  74 . The ends of the pivot pin are received in the elongate openings  72 A of the ears  72  of the rear clamping jaw  70 , and are capable of relative movement lengthwise of the elongate openings. The bolts  76  interconnecting the front and rear clamping jaws  68 ,  70  pass through and are threadably engaged with the pivot pin  74  within the elongate openings  72 A of the ears. The threaded engagement of the bolts  76  in the pivot pin  74  fixes the distance between heads  76 A of the bolts and the pivot pin, and consequently the distance between the axis of rotation of the lever  34  and the bolt heads. This distance can be adjusted in manufacture of the surveying pole  26  to select the initial clamping force applied by the jaws  68 ,  70  to the second pole section. In this way, the locking mechanism  32  can be adapted for use with poles (or rods) of different materials and for different applications where more or less clamping force is appropriate. Camming action of the lever  34  produces movement of the front and rear clamping jaws  68 ,  70  between the locked and unlocked positions. The lever  34  includes an attachment end having a passage through which the pivot pin  74  is received. The attachment end is asymmetrical with respect to the passage, having a greater thickness of material (relative to the passage) on a rounded locking surface  80  than on a flat unlocking surface  82 . In the unlocked position, the lever  34  extends laterally outward from the locking mechanism  32  and the flat unlocking surface  82  engages the rear clamping jaw  70 , allowing the maximum space between the heads  76 A of the bolts and the pivot pin  74 . Thus, the front and rear clamping jaws  68 ,  70  are able to move under the bias of the coil springs  78  away from each other and out of engagement with the second pole section  30 . When the lever  34  is pivoted down on the pivot pin  74  the rounded locking surface  82  engages the rear clamping jaw  70 , simultaneously pushing the rear clamping jaw forward and pulling (by operation of the bolt heads  76 A) the front clamping jaw  68  rearward to clamp against the second pole section  30 . 
     The front and rear clamping jaws  68 ,  70  are each attached to the collar  54  of the base  48  in such a way as to insure that the jaws will both move away from the second pole section  30  when the lever  34  is moved from the locked position to the unlocked position. The front and rear clamping jaws  68 ,  70  each have tabs (designated  68 A and  70 A, respectively in FIG. 9) projecting down into respective slots  84  in the collar  54  which open into the central opening of the collar. As the front and rear clamping jaws  68 ,  70  move together and apart under actuation by the lever  34 , the tabs  68 A,  70 A move in the slots  84 . It will be understood that as soon as the tabs  68 A,  70 A of each jaw reach the outer end of the slot  84 , further motion away from the second pole section  30  is prohibited. Thus, the slots  84  do not allow all of the movement front and rear clamping jaws  68 ,  70  which is permitted in the unlocked position to be taken up by only one of the jaws. If one of the jaws  68 ,  70  reaches the end of its corresponding slots  84  first, it will stop and the biasing force of the coil springs  78  will be applied solely to the other jaw to force it outward. Thus, the locking mechanism  32  is inhibited from sticking when the lever  34  is moved to the unlocked position so there is no interference with the easy extension or retraction of the second pole section  30  relative to the first pole section  28  in the unlocked position. 
     The locking mechanism  32  is constructed to tightly grip the second pole section  30  in the locked position without high clamping forces being applied to the second pole section which could crush the second pole section. In that regard the upper clamping assembly further includes elastomeric pads  86  (FIG. 4) which are overmolded onto the hard plastic of the front and rear clamping jaws  68 ,  70 , respectively. The clamping jaws  68 ,  70  are formed with internal cavities and passages into which the elastomeric pad material flows, joining the elastomeric pad  86  to the jaw. The elastomeric pads  86  avoid point contact of the jaws  68 ,  70  with the second pole section  30  to more evenly distribute the clamping force. In that regard, the elastomeric pads  86  have a radius of curvature which is equal to the radius of the second pole section  30 . The pads  86  conform to the available volume as they are clamped against the second pole section  30  which facilitates full contact between the pads and the second pole section, and more even application of pressure. The elastomeric pads  86  should be made of a material which is sufficiently resilient and has a high coefficient of friction. In the preferred embodiment, the elastomeric pads are made of a suitable rubber like substance, and preferably a substance having a durometer of 25-45 Shore A and a compression set of less than 30%. The front and rear clamping jaws  68 ,  70  and elastomeric pads  86  are constructed and arranged relative to each other to enhance the gripping action of the elastomeric pad when the second pole section  30  is subjected to forces tending to cause axial movement of the second pole section. The pertinent construction of the front and rear clamping jaws  68 ,  70  and elastomeric pads is identical. Therefore, explanation will be made with reference to FIGS. 5-7 showing only the front jaw  68 . 
     FIG. 5 is a longitudinal section of the front clamping jaw  68  with the elastomeric pad  86  removed. A center section of a concave interior face of the jaw  68  is made to have generally wedge-shaped formations  88  having a longer leg  88 A and a shorter leg  88 B. The elastomeric pad  86 , shown in longitudinal section in FIG. 6, has symmetrical ridges  90  on its interior face for engaging the second pole section  30 , and wedge-shaped formations  92  on its exterior face. The peaks of the ridges  90  and the wedge-shaped formations  92  of the elastomeric pads  86  are nearly directly opposed from each other so that the elastomeric pad is thickest at these peaks. The wedge-shaped formations  92  of the elastomeric pad have a shape which is complementary to (i.e., having long and short legs  92 A,  92 B) and are interfitted with the wedge-shaped formations  88  of the front clamping jaw  68 , as may be seen in FIG.  7 . The interfitted wedge-shaped formations  88 ,  92  provide additional gripping force when the second pole section  30  is subjected to forces tending to move the second pole section axially in extension or retraction relative to the first. The configuration and arrangement of the wedge-shaped formations  88 ,  92  are particularly selected to resist the more common axial forces tending to cause the second pole section  30  to retract into the first pole section  28 . Forces tending to induce axial movement of the second pole section  30  are experienced by the elastomeric pad  86  as shearing forces. The mating of the wedge-shaped formations  88 ,  92  places legs  88 A,  88 B of each formation of the front clamping jaw  68  in a partially axially opposed relation with the legs  92 A,  92 B of the wedge-shaped formations of the elastomeric pad  86 , and thereby inhibits relative movement of the elastomeric pad relative to the front clamping jaw in an axial direction. Any small movement which may occur results in the peaks of the wedge-shaped formations  92  of the elastomeric pad riding up toward the peaks of the wedge-shaped formations  88  of the front clamping jaw  68 . This squeezes the elastomeric pad  86  as indicated by the double arrows in the enlarged, fragmentary section shown in FIG.  7 A. The resiliency of the elastomeric pad  86  causes it to apply more pressure as it is compressed, and greater holding force against the second pole section  30 , preventing its permanent movement relative to the first pole section  28  when the locking mechanism  32  is locked. Thus, the locking mechanism  32  of the present invention is capable of applying a substantial holding force without a large initial clamping force so that the non-metallic material of the second pole section  30  is guarded from damage by the locking mechanism. Moreover, the amount of the gripping force increases as the force tending to move the pole sections axially relative to one another increases. 
     Although it is important to keep the second pole section  30  from moving relative to the first pole section  28  when the surveying pole  26  is in use, there are occasions where it is desirable to completely remove the second pole section from the first section, such as for cleaning or repair. It is desirable to be able to remove the second pole section  30  from the first section  28  with a minimum of disassembly and reassembly work. However, the second pole section  30  must be able to remain connected to the first pole section  28  in any orientation when the pole sections are interconnected. The second pole section  30  of the present invention can be removed when the locking mechanism  32  is in its unlocked position, by application of sufficient axial force in the direction of extension. 
     Referring now to FIGS. 10-13, a resilient plastic pole plug (generally indicated at  94 ) is fitted into the lower end of the second pole section  30  (see FIG.  10 ). The pole plug  94  is generally tubular in shape, and has a smaller, upper portion  95  received in the second pole section  30  and an enlarged lower end  96  extending below the lower end of the second pole section which serves to hold the second section in the first pole section  28  as will be described. The upper portion  95  is formed with snap connection nubs  98  projecting radially outward from the upper portion (FIG.  11 ). The nubs  98  fit into respective holes  170  near the lower end of the second pole section  30  to affix the pole plug  94  in the second pole section. The nubs  98  have a sloped upper surface  98 A which facilitates insertion of the plug  94  into the open lower end of the second pole section  30  until the nubs snap into the holes  170 . To further facilitate deformation of the plug  94  necessary to insert it into the lower end of the second pole section  30 , longitudinal slits  97  are formed in the plug on both sides of each nub  98 . The slits  97  strategically weaken the side walls of the plug  94  for inward flexing between the slits when the plug is inserted into the lower end of the second pole section  30  and the nubs engage the inner surface of the second pole section. As shown in FIG. 13, there are ribs  99  on the interior of the plug  94  inside of each slit  97 . The ribs  99  reinforce the side wall of the plug  94  to facilitate return to its original diameter when the nubs  98  come into registration with the holes  170  in the second pole section  30  for snapping the nubs into the holes. A lower axial surface  98 B is substantially horizontal so as to prevent the plug  94  from being removed from the holes  170  in the second pole section  30  once inserted. 
     The first pole section  28  is formed with two different interior diameters near its upper end. The portion immediately adjacent to the upper end has a smaller interior diameter than portions of the first pole section  28  below that portion. Thus, an axially downwardly facing shoulder  100  (see FIG. 10A) is defined in the first pole section  28 . The enlarged lower end  96  of the pole plug  94  projects radially outwardly from the exterior surface of the second pole section  30  defining an axially upwardly facing shoulder  96 A (see FIGS.  10 A and  13 ). When the first and second pole sections  28 ,  30  are assembled together, these shoulders  96 A,  100  are in axially opposed relationship and will engage, if the second pole section  30  is extended from the first pole section  28  a sufficient distance, to prevent the withdrawal of the second pole section from the first pole section. However, the enlarged lower end  96  of the pole plug  94  is configured to flex radially inwardly upon application of sufficient axial force so as to allow the enlarged lower end to pass the shoulder  100  of the first pole section  28  so that the second pole section  30  can be pulled completely out of the first pole section. In that regard, the enlarged lower end  96  has diametrically opposed, axially directed slits  102  opening outwardly from the lower end of the pole plug  94  (FIGS.  12  and  13 ). These slits  102  strategically weaken the pole plug  94  and provide space to facilitate inward flexing of the halves of the enlarged lower end  96  on opposite sides of the slits. The second pole section  30  can be reinserted into the first pole section  28 . The enlarged lower end  96  is radially deflected as the second pole section  30  is first inserted, and a chamfer  104  at the bottom of the enlarged lower end facilitates this deflection. Once the enlarged lower end  96  of the pole plug  94  passes the shoulder  100  of the first pole section  28 , the lower end snaps out into position (i.e., with shoulder  96 A of the enlarged lower end opposing the shoulder  100 ) to inhibit unintentional withdrawal of the second pole section  30  from the first pole section. 
     Surveying poles of the type to which the present invention generally relates are used outside in different environmental conditions and also tend to be handled roughly. Poles made of non-metallic material or a low strength metal may need additional protection to avoid damage when handled. For instance, the surveying pole  26  may become damaged if the second pole section  30  is violently retracted into the first pole section  28  after the pole has been used. It is known to provide dampening systems to reduce the shock experienced by the pole sections under these circumstances. However, these tend to be complex and require additional parts. The first and second pole sections  28 ,  30  of the present invention are sized so that the second pole section fits snugly within the first pole section. The contact between the pole sections is such that the seal is nearly airtight. Thus when the second pole section  30  is extended from the first the total internal volume of the surveying pole  26  is increased, initially drawing a slight vacuum within the surveying pole. Similarly, when the second pole section  30  is retracted within the first, there is an air pressure increase over atmospheric in the first pole section  28  as the internal volume of the surveying pole  26  is reduced. 
     The female fitting  36  in the upper end of the second pole section  30  is made out of machined aluminum. As shown in FIG. 14A, the female fitting  36  is tubular and has an upper annular lip  106  which rests against the end of the second pole section  30 . A reduced inner diameter portion  108  of the fitting  36  has threads. In the embodiment illustrated in FIGS. 1 and 2, the reduced diameter portion receives the prism mount  37  for connecting the mount to the surveying pole  26 . An air hole  110  in the fitting  36  extends from the top end of the fitting down into a larger inner diameter portion  112  of the fitting. The air hole  110  is formed in a annular region outside the threaded reduced diameter portion  108 . The air hole  110  is sized to permit air to pass through the fitting  36  out of or in to the interior of the surveying pole  26  defined by the first and second pole sections  28 ,  30  at a controlled rate. In the most preferred embodiment, a valve generally indicated at  114  is provided, but the air hole  110  could be used without the valve and remain in the scope of the present invention. Moreover, additional air holes (not shown) can be provided for additional control of the rate of air passage through the fitting  36  out of the surveying pole  26 . 
     The valve  114  functions as a check valve to permit air flow into the surveying pole  26  through the air hole  110  as the second pole section  30  is extended from the first pole section  28 , and to prevent flow through the air hole when the second pole section is retracted. The valve  114  comprises an arcuate flap  114 A mounted by a pin  114 B on the interior of the female fitting  36  at the junction of the reduced and larger diameter portions  108 ,  112 . In addition to the pin  114 B a shorter arcuate piece  114 C rests on top of one end of the flap  114 A for strength (see FIG.  14 ). The flap  114 A is made of a resilient, flexible material so that when the second pole section  30  is extended from the first pole section  28 , the flap flexes down, uncovering the air hole  110  as air rushes into the surveying pole  26 . However, when the second pole section  30  is retracted into the first pole section  28 , air rushing to escape from the volume in the first pole section pushes the flap  114 A over the air hole  110 , blocking it from access by the air. The closure of the air hole  110  does not entirely prohibit air from escaping, but makes it seek out smaller openings (e.g., by passing through the threaded opening  108  around the mount  37 ). Thus the air resists retraction, acting as a cushion limiting the rate at which the second section  30  can be retracted into the first section  28  and softening the impact of the second pole section against the first as it reaches a fully retracted position. It will be understood that additional air holes (not shown) without a valve could be used in combination with the air hole  110  and valve  114  for more controlled air escape without departing from the scope of the present invention. Control may be achieved by sizing the air holes. 
     Referring to FIGS. 15-17, the first pole section  28  has an aluminum male fitting (generally indicated at  116 ) at its lower end which is similar in construction to the female fitting  36  of the second pole section  30 , but has a threaded male end  118  projecting axially outward from the lower end of the fitting. The threaded end  118  mounts the point  44  of the surveying pole  26  onto the first pole section  28 . The male fitting  116  is generally tubular in shape and includes a lip  120  which engages the lower end of the first pole section  28  fixing the axial position of the male fitting. Both the female and male fittings  36 ,  116  are constructed to achieve precise location in their respective pole sections  30 ,  28 . In particular, they are constructed to permit affixation after insertion into the end of the pole section. This construction is identical for both the female fitting  36  and the male fitting  116 , and will be described only in regard to the male fitting. The male fitting  116  has a shallow circumferential channel  122  extending completely about the fitting intermediate the ends of the fitting (see FIGS.  15  and  15 A). In addition, two diametrically opposite adhesive passages (designated  124 A and  124 B, respectively) are formed in the fitting  116  which open at the lower end of the fitting and into the channel  122 , as best seen in FIGS. 16 and 17. The precise number of passages may be other than described without departing from the scope of the present invention. 
     A flowable, thermosetting adhesive may be injected through one of these passages (e.g., passage  124 A) into the channel  122 . The adhesive has not been illustrated in FIG. 15A so that the channel  122  can be clearly seen, but would be filled with adhesive in a completed surveying pole section  28 . Thus, the fitting  116  can be press fitted into the end of the first pole section  28  without application of any adhesive, and positively located by the engagement of the lip  120  with the end of the first pole section. The lip  120  and other portions  125  of the fitting  116  engaging the first pole section  28  are formed very precisely so that close axial alignment is achieved. After insertion of the fitting  116 , adhesive is injected through one of the passages  124 A into the channel  122 . The adhesive flows in both directions around the channel  122  and fills the channel. When the channel  122  is filled, adhesive passes into the other passage  124 B and out of the fitting  116  so that the person injecting the adhesive has visual confirmation from outside the first pole section  28  that the channel is completely filled. The interior surface of the first pole section  28  opposite the channel  122  is preferably roughened to promote bonding. The channel  122  and interior surface of the first pole section  28  when the fitting  116  is inserted into the pole section define a fixed volume of adhesive within the pole section. By selecting the size, and particularly the depth of the channel  122  an optimal amount of adhesive may be placed in each and every fitting that is attached to a pole section, with no requirement for skill on part of the person doing the assembly. The selection of the axial dimension of the channel  122  controls the spread of the adhesive layer, and the depth of the channel controls the bondline thickness. Particular adhesives will have optimum ranges for both spread and bondline which can be precisely accommodated by the channel. It is also envisioned that the channel could be formed in the pole section rather than in the fitting  116 . 
     In some instances, the female and male fittings are used together to screw together pole sections, as is illustrated in FIG.  18 . The surveying pole  26  of FIG. 1 has but two pole sections  28 ,  30 , which are arranged in telescoping fashion. However for taller poles, there may be more than two telescoping sections. In other instances, the poles may consist solely of sections which screw together and do not telescope relative to each other. In addition, the fittings may be used in other than surveying poles. A specifically contemplated use is for collapsible legs of a tripod. Although the pole sections are shown herein as being round, fittings of the type described could be used with pole sections of other non-circular cross sections. In that event, the fitting would have a matching cross section. As illustrated in FIG. 18, the female and male fittings  36 ′,  116 ′ are shown as exploded from third and fourth pole sections  128 ,  130 , which are not a part of the FIG. 1 embodiment. The female and male fittings  36 ′,  116 ′ are of the same construction as the fittings  36  and  116  described above and bear the same reference numerals distinguished by the addition of a prime. In the joint illustrated, an O-ring  132  provides for sealing between the two pole sections  128 ,  130 . Of course, the female and male fittings  36 ′,  116 ′ would first be independently adhered in the open ends of the third and fourth pole sections  128 ,  130 , respectively. The O-ring  132  is preferably mounted on the threaded end  118 ′ of the male fitting  116 ′. 
     The female and male fittings  36 ′,  116 ′ are particularly constructed to permit accurate axial alignment of the third and fourth pole sections  128 ,  130  when they are screwed together. A common difficulty for conventional screw-together sections is that debris between the fittings can cause one fitting (and hence one pole section) to be tilted slightly relative to the other. Even a relatively small bit of debris can significantly affect the alignment of the pole sections. Thus, the female and male fittings  36 ′,  116 ′ of the present invention are formed so that the area of contact of the fittings when screwed together is limited to a thin annular contact surface  134 . The pertinent construction of the female and male fittings  36 ′,  116 ′ to form the annular contact surface  134  is the same, so only the construction of the female fitting  36 ′ is shown (FIGS. 19 and 19A) and described hereinafter. The thin annular contact surface  134  is formed by machining a recessed area  136  everywhere on the end face of the female fitting except at the annular contact surface. Debris in opposed recessed areas  136  of the female and male fittings  36 ′,  116 ′ will generally not engage both fittings when the two are mated, and thus will not interfere with the axial alignment of the fittings. For smaller fittings, where it is difficult to machine a contact surface which is wide enough, an end face  138  of a female fitting  36 ″ is beveled as shown in FIGS. 20 and 20A. The end face  138  of the fitting slopes axially inwardly from the peripheral edge of the end face to the central, threaded opening  108 ″. The slope of the end face  138  is very small, but may be seen in the greatly enlarged fragmentary view of FIG.  20 A. The male fitting (not shown) has the same construction except that the bevel terminates at the projecting threaded end. 
     Referring now to FIG. 21, the metal point  44  as covered by the shoe  46  in FIG. 1 is shown separated from the surveying pole  26 . The metal point  44  includes a body  140  made of a lesser density material (e.g., aluminum) and a tip  142  made of a more dense material (e.g., steel). The body  140  has a central pole mounting bore  140 A opening at the upper end of the body and extending into the body. The pole mounting bore  140 A has threads at its upper end for threadably engaging the threaded end  118  of the male fitting  116  to attach the point  44  to the first pole section  28 . The attachment of the point  44  to the surveying pole  26  is releasable, permitting the point to be removed if desired. The body  140  has an axially extending tip mounting bore  140 B opening at the bottom of the body. The tip mounting bore  140 B has internal threads engageable with corresponding threads on a male portion  142 A of the tip  142 . The dual construction of the point  44  reduces its overall weight. The tip  142  is smaller and less expensive than larger unitary points containing more material. If the tip  142  is broken, as is known to occur in the field, it is less expensive to replace. 
     As shown in FIGS. 25 and 26, the point is constructed to hold a spare tip  143 . The interior of the body  140  of the point  44  is bored and counterbored to three different diameters. The lower bore is the tip mounting bore  140 B. The upper two counterbores are sized to substantially receive the spare tip  143  held in the body  140  in an elastic, foam tube  145 . The spare tip  143  preferably has a slightly larger maximum diameter than the opening of the tube  145  so that the tube bears against and holds onto the spare tip. The lower end of the tube  145  is beveled to facilitate location of the foam tube in the lower end of the upper counterbore to hold the tube and spare tip  143  in place in the body  140 . As may be seen in FIG. 25, the spare tip  143  extends entirely through the tube  143  and the middle counterbore when stowed in the body  140 . Should the tip  142  break or become worn, the point  44  can be removed from the surveying pole  26  by unscrewing the body  140  from the male fitting  116  at the lower end of the first pole section  28 . The damaged tip  142  can be unscrewed from the body  140  and the spare tip  143  removed from the body and taken out of the tube  145 . The spare tip  143  is screwed into the tip mounting bore  140 B of the body  140 , and the point  44  is reconnected to the surveying pole  26 . If desired, the damaged tip  142  can be stowed in the body  140  in the same fashion as the spare tip  143 . 
     The body  140  further includes external threads  140 C located just below a larger, knurled head  140 D of the body which contacts the end face of the male fitting  116  when the point  44  is attached to the surveying pole  26 . These threads  140 C mount the shoe  46  directly on the point  44  so that the shoe can be used without removing the point. Other types of connection, such as a bayonet type connection (not shown), may be used to attach the shoe without departing from the scope of the present invention. It is unnecessary to remove the point  44  when it is not needed, as it can simply be covered up by the shoe  46 . In the illustrated embodiment, the shoe  46  is made of plastic (e.g., a polycarbonate plastic), but may be made of metal or other suitable material without departing from the scope of the present invention. The shoe  46  is tubular in shape and closed at its lower end. Its upper end margin  46 A is flared outwardly to match the shape of the body  140 , and has internal threads  46 B which engage the external threads  140 C of the body when the shoe is mounted on the point  44 . 
     The shoe  46  is used is softer terrain to support the surveying pole  26  above the ground and prevent the pole from sinking into the ground. A flat bottom  46 C of the shoe  46  has a surface area which is selected to distribute the weight of the surveying pole  26  sufficiently to prevent the pole from sinking into the ground. Although the surface area of the flat bottom  46 C is shown as being equal to the cross sectional area of the lower portion of the shoe  46 , the flat bottom can be made to extend radially outwardly from the lower portion (and upper end margin  46 A) of the shoe to increase the weight distribution of the surveying pole  26 . A larger flat bottom would permit the surveying pole to be used on softer ground. The shoe  46  can also sheath the point  44  during transport which protects the tip  142  and personnel. When not in use, the shoe  46  can be conveniently stowed on the surveying pole  26  as will be described. 
     The level vial holder  42  shown in exploded view in FIG. 23 is constructed to be clamped to the first pole section  28 . The level vial holder  42  includes a first holder member  144  and a second holder member  146 , each having an engagement surface (designated  144 A,  146 A, respectively) shaped in close correspondence to the circumferential shape of the first pole section  28 . The first holder member  144  is made of a rigid plastic material (e.g., acetyl plastic) and is free of other material on its engagement surface  144 A so that when attached to the first pole section  28  the engagement surface engages and precisely locates the level vial holder  42  relative to the first pole section. In particular, the center axis of a round vial container portion  148  of the first holder member  144  is made parallel with the longitudinal axis of the surveying pole  26 , as is required for the level vial  40  (see FIG. 2) to accurately indicate when the surveying pole is in a vertical orientation. The second holder member  146  has an elastomeric pad  150  overmolded onto its engagement surface  146 A so that the high friction elastomeric pad engages the first pole section  28  to provide gripping action to hold the level vial  40  in position. The second holder member  146  is attached to the first member  144  by four bolts  152  which pass through corresponding openings in the second holder member into openings of the first holder member. The openings of the first holder member have previously received thread inserts  154  for engaging the threads of the bolts  152 . It will be understood that in assembly, the first holder member  144  is placed on one side of the first pole section  28  and the second holder member  146  is placed on the other side of the first pole section diametrically opposite the first member. The bolts  152  are passed through the second holder member  146  and into the first holder member  144  and tightened down to clamp the holder members onto the first pole section  28  so that the level vial  40  is held in fixed position on the first pole section. 
     The level vial  40  (shown in FIG. 2) is received in the round portion  148  of the first holder member  144  and rests on an elastomeric support  156  therein. A cover  158  closes the level vial  40  in the round portion  148 . The cover  158  is secured to the first holder member  144  by three bolts  160  which extend through the underside of the round portion  148  up into threaded holes  158 A in the cover (see FIG.  24 ). The orientation of the level vial  40  can be adjusted by the bolts  160 . The elastomeric support  156  permits pivoting movement of the level vial  40  within the level vial holder  42  to achieve the proper alignment with the surveying pole axis. The level vial  40  has been shown in full lines and not in cross section in FIG. 24 to simplify and increase the clarity of the illustration. 
     The round portion  148  of the first holder member  144  is formed to stow the shoe  46  on the surveying pole  26  when not in use. In this way, it is unnecessary to keep track of the shoe  46  when not in use. It is immediately available when needed. More specifically, the first holder member  144  has a depending portion  162  which is formed with external threads. The depending portion  162  is sized the same as the upper part of the body  140  which mounts the shoe  46  on the point  44 . Thus, the internal threads  46 B of the shoe  46  can engage the threads of the depending portion  162  to temporarily attach the shoe to the level vial holder  42  for stowing the shoe, as shown in FIG.  24 . The shoe  46  may be connected to other parts of the surveying pole and/or by other types of connectors (not shown) without departing from the scope of the present invention. 
     When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.