Abstract:
The present invention provides a small, simple and easy-to-use elevation checking and measuring device that can also be used to measure points to the same level as a known point. The invention comprises a primary housing and secondary casing which contain tape measuring blades. The primary housing has opposing sidewalls each of which may include a vertical slot. The slots are designed to mate with projections extending from the secondary casing. The slots and projections provide alternative angular orientations of the housing and casing when connected together. The primary housing contains level indicators to determine when it is held level. It also includes a light source that illuminates a target at the end of the primary housing blade. Maintaining the beam on the target while using the level indicators to achieve a horizontal orientation of the primary assembly, thereby permits a user to make quick and accurate grade or height measurements with the tape measure blades.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to level and grade measuring devices and more particularly to a simple and easy-to-use level and grade measuring device employing tape measures, bubble indicators and a light beam. 
     2. Description of Related Art 
     Numerous devices have been developed to assist in the measurement and checking of site contours and elevations. The elevations of landmarks are, in the majority of cases, surveyed by means of a linear measuring instrument which requires the presence of two operators using complex and sensitive equipment. Such an operation is tedious, long and expensive. Moreover, the surveying done by two operators is conducted at the beginning of a project to determine the site topography. The survey instruments are not practical for quickly and easily checking grade levels and contours. For quick on-site use, the device should be small, self-contained, portable and easy-to-use. 
     Other devices have been developed that allow for use by a single operator. For instance, in U.S. Pat. No. 5,551,159 to Mooty, a laser level apparatus is disclosed for use by a single operator. The operator uses a grade pole having a movable laser level receiver. The receiver detects a laser signal from a mounted laser transmitter usually fixed on a tripod some distance from the device. An indicator electronically coupled to the receiver is used to provide the operator a response when the laser beam is detected. Although fairly accurate, this apparatus is complex, heavy and expensive. It requires the operator to first properly level the transmitter on the tripod, align the laser beam and then reposition the receiver to properly align the receiver to the laser beam. 
     U.S. Pat. No. 4,274,203 to Vasile also discloses a complex and bulky grade measuring device. The device is generally mounted on a tripod and uses two tape measures along with a conventional sighting device for aligning to a known point. One of the tape measures is used to measure the horizontal distance to the point and the other is used to measure the vertical height of the device above the ground. Bubble levels are mounted on the sighting mechanism to determine if it is level. The device also uses complex electronics to provide a digital display of the distance that the tape measures are extended. Again, the device is too bulky and complicated for quick and easy grade checking. 
     U.S. Pat. No. 4,459,758 to Halle also discloses a device for measuring and checking site contours and elevations. The patent discloses a rotatable table mounted on a tripod. The table holds a device which transmits a laser beam parallel to the table. The device also provides a measuring tape that can be extended parallel to the laser beam. When the table and tripod elevation is fixed, the laser beam illuminates an aimed point for the operator and the distance to the aimed point can be measured with the tape. Because of the tripod and table arrangement, this device is not capable of quick and easy measurements. In addition, the device does not provide a means for measuring the elevation of the table. 
     U.S. Pat. No. 5,784,792 to Smith discloses a hand held tool for use in checking the level or grade of ground surface at a construction area. The cylindrical device emits a laser beam from one end which is in axial alignment with the device housing. The housing contains a bubble level to ensure that the device is held level to the ground. 
     In use, the operator holds the device alongside an engineer&#39;s side stick or other measuring stick that rests on the ground. The device is aimed at a previously marked location. The user can check the level of the grade by sliding the device up or down the measuring stick. However, this device provides no means of measuring the horizontal distance from the device to the previously marked location. Also, the user must always possess a separate measuring stick to determine grade level. 
     Devices have also been developed to measure horizontal points above a reference point. U.S. Pat. No. 5,092,057 discloses a device with a bubble level to ensure that the device is horizontal. It includes a perpendicular measuring tape to determine the vertical distance to a point. The device also has slidable locator members to mark two horizontal points at a desired distance apart. However, this device provides no means to measure the horizontal distance to a point. 
     SUMMARY OF THE INVENTION 
     The present invention provides a small, simple and easy-to-use elevation checking and measuring device that can also be used to measure points to the same level as a known point. The invention comprises a primary tape measure assembly which can be used alone or in combination with a secondary tape measure assembly. Both assemblies have mounting means for effecting their engagement. The primary assembly comprises a housing with a first mounting structure and the secondary assembly comprises a casing with second and third mounting structures. Such structures may include mechanical fasteners, Velcro fasteners, clamps, magnets, clips and matching undercut parts known in the art. 
     The housing and casing both include a retractable tape measure mechanism with a blade that can be extended to a desired length. The primary assembly blade is provided with an end part having a target portion for illumination from a focused light source emitted from the primary assembly. 
     For illustrative purposes, the first mounting structure is shown in the drawings as a vertical slot on at least one housing sidewall. The slot is designed to mate with a second or third corresponding mounting structure shown as a projection extending from the casing of the secondary tape measure assembly. This construction permits releasable engagement of the assemblies in multiple orthogonal orientations. 
     In one preferred orientation of the combined assemblies, the secondary blade, when extended from the secondary assembly casing, will be perpendicular to the primary blade when it is extended from the primary assembly housing. As so disposed, the primary blade can be used to measure horizontal distance to a point, while the secondary blade can be used to measure vertical distance. 
     In another preferred orientation, the extended blades are perpendicular to each other, but the secondary blade from the casing will be in a horizontal plane that is parallel to the primary blade. As so disposed, the primary blade will measure the distance to a known point and the secondary blade can measure the distance to a point in a related horizontal plane which is perpendicular to the primary blade. 
     The primary housing may have one or more level indicating means to show whether the primary housing is horizontal and not angularly canted. The primary housing also has a light source that projects a light beam adjacent to and longitudinally aligned with the primary measuring blade. When the primary blade is extended and the primary housing is horizontal, the light beam will illuminate the blade end part target portion. The primary housing includes a light actuation switch, electronic componentry and internal batteries to power the light source. 
     The invention provides a simple, quick and easy to use device to coordinate height and elevation measurements and to check the grade on a construction site. A single operator can use the device which is small enough to be stowed in a tool box or on a tool belt. The device can also be used to determine horizontal points on a wall from a known point. This is particularly useful in hanging pictures and wall decorations. 
    
    
     These and other further features and advantages of the invention will be apparent to those skilled in the art from the following detailed description, taken together with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a primary tape measure assembly constructed in accordance with the present invention. 
     FIG. 2 is a front end elevational view taken along lines  2 — 2  of FIG.  1 . 
     FIG. 3 is a top plan view taken along lines  3 — 3  of FIG.  1 . 
     FIG. 4 is a cross-sectional view taken along lines  4 — 4  of FIG.  2 . 
     FIG. 5 is a back end elevational view of a secondary tape measure assembly constructed in accordance with the present invention. 
     FIG. 6 is a left side elevational view of the secondary tape measure assembly shown in FIG. 5, the right side being identical thereto. 
     FIG. 7 is a front end elevational view of the secondary tape measure assembly shown in FIG.  5 . 
     FIG. 8 is an isometric view of the bottom and left side panel of the secondary tape measure assembly shown in FIG. 5 with the secondary measuring tape blade partially extended. 
     FIG. 9 is also an isometric view of the back end and left side panel of the secondary tape measure assembly shown in FIG.  8 . 
     FIG. 10 is an enlarged isometric view of the secondary tape measure assembly being engaged with the primary tape measure assembly in an orientation whereby the secondary blade extends vertically down and perpendicular to the primary blade. 
     FIG. 11 is an isometric reduced scale view of the combined assemblies oriented as in FIG. 10 being used to check a grade level. 
     FIG. 12 is an enlarged isometric view of the secondary tape measure assembly combined with the primary tape measure assembly in an alternative orientation whereby the respective extended blades are perpendicular to each other and in parallel planes. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the drawings, FIGS. 1-4 illustrate the construction of primary tape measure assembly  10 . The primary tape measure assembly comprises a hollow housing  12  defining an interior for enclosing a coiled tape measure mechanism  22  depicted in phantom. The mechanism comprises a measuring blade that is coiled about a shaft  26  and is spring biased in a retracted position. 
     A variety of tape measure mechanisms known in the art may be used with the invention. As referenced herein, the term “blade” shall encompass strips of metal or fabric, marked wires, cords and any other measuring lines that are coilable within a small housing or casing. 
     The housing is defined by opposing mirror image sidewalls comprising first sidewall  14  and second sidewall  16 . The sidewalls are interiorally supported by lateral housing posts  23  extending across selected areas of the housing interior. If the housing comprises bilateral housing parts, mechanical fasteners, such as rivets or screws, will be used to engage the posts for securing the parts together. 
     The housing is further characterized by an arcuate top wall  13  which tapers rearwardly into a back wall  15 . The back wall merges into a curved end  60  from which extends an undercut wall  63 . The undercut wall terminates at bottom wall  17  which defines a lowermost portion of the housing  12 . The bottom wall extends to a front wall  19  which defines the front of the housing. 
     The lowermost portion of the front wall is provided with a tape opening  25  through which primary blade  24  of the tape measure mechanism passes. Proximate the forward area of first sidewall  14  is an elongated first slot  18 . The slot extends from top wall  13  downwardly, in a direction parallel to a vertical axis, a terminal end  38  that is spaced above the bottom wall  17  and tape opening  25 . Similarly, second sidewall  16  is provided with a corresponding second slot  20 . The second slot extends downwardly along the second sidewall in a manner identical to the first slot  18 . Both slots have a narrow sidewall entrance which expands into a circular passageway for a purpose to be hereinafter described. 
     The forward portion of the top wall  13  proximate the area between the first and second slots includes a primary blade brake switch. The brake switch rotates about a pivot shaft  35 . One end of the switch is secured to a brake arm  36  having a terminal end. The terminal end directly or indirectly frictionally engages primary blade  24  to constrain movement of the blade in a manner known in the art. 
     Instead of a normal hook-end at the free end of the blade, the present invention provides for a unique end part  28 . The end part comprises a plate-like member having an upper target portion  30  and a lower connector tab  32 . The connector tab functions in the same manner as a conventional tape measure hook. The target portion may be provided with a target spot  31  for a purpose to be hereinafter described. 
     Adjacent to the brake switch  34  is a light switch  48 . The light switch is part of the housing light means and functions in a conventional manner by electrically connecting a light source  42  with electronic componentry  49  and a power source shown as battery  50 . This is accomplished by extending an electrical conductor, shown as wire  46 , to the power source and to a light source receptacle  44 . The receptacle may contain a conventional bulb and lens system or a laser illumination device. The laser device is preferred because it can focus a narrow light beam  52  over a greater distance. 
     The light source projects light through an opening  21  in the lower portion of front wall  19 . Preferably, the beam of light  52  extends outwardly in a manner parallel to the center longitudinal axis of blade  24  when it is withdrawn from the housing. The light source will have sufficient power and be sufficiently focused to noticeably illuminate the target spot  31  when the spot is several feet away from the source. To facilitate illumination, the target spot may have luminous or reflective characteristics. 
     The end part target portion  30  may include a hinge  33  at its junction with the connector tab. This will allow it to be moved out of the beam of light emanating from opening  21 . In this way, the housing may be used as a light pointer. 
     Located at the uppermost portion of top wall  13  is a first recess  54  and a second recess  56 . Each recess extends parallel to a respective first and second sidewall and provides a protected area for placement of level indicator means shown as respective bubble levels  55 , 57 . The axial alignment of each of the bubble levels define a plane that is parallel to the orthogonal X axis and the longitudinal axis of light beam  52 . 
     At the curved end  60  of primary housing back wall  15 , is a lateral recess  62 . This recess extends at least across a portion of the back wall width. Secured within the recess is a third indicator means shown as lateral bubble level  64 . The longitudinal axis of the lateral bubble level extends along the orthogonal Z axis which is perpendicular to the axis of the first and second bubble levels. It is also perpendicular to light beam  52  and the longitudinal axis of tape measure blade  24 . 
     From the above positions of the level indicators, the primary housing  12  can be rotated about the Z axis so that the primary blade  24  will be horizontal to the ground. The housing can also be leveled laterally by rotation of the housing about the X axis. 
     With reference now to FIGS. 5-9, the secondary tape measure assembly is shown generally by reference  70 . This assembly comprises a casing  72  having an interior within which is enclosed a coiled spring-biased tape measure mechanism constructed in a manner known in the art. The assembly includes a secondary blade  92  having an end hook  94  for releasable attachment to items from which measurements are to be taken. 
     The casing  72  includes opposing mirror image side panels comprising a first side panel  74  and a second side panel  76 . The panels are enclosed with a top wall  78  which merges into a rounded upper corner portion  80 . The upper corner portion merges into a rear wall  82  which terminates at lower wall  84 . The lower wall extends to a forward wall  86  which is provided with a lower wall opening through which secondary blade  92  extends. 
     The rounded upper corner of the casing includes a blade lock switch  81 . The lock switch functions to temporarily secure the blade at selected extended positions in a manner known in the art. 
     Extending along the midline of at least a portion of the lower wall  84 , is a downwardly extending flange  89 . The outer end of the flange is provided with a slot engagement means shown as an enlarged lower projection  88 . The lower projection has a circular cross-sectional shape that corresponds to the cross-sectional outline of first and second slots  18 , 20  of the primary housing  12 . 
     As best shown in FIG. 6, it is preferred that the flange and lower projection not extend the full length of lower wall  82 . Instead it extends from rear wall  82  forward toward front wall  86  a distance sufficient to leave a spacing apart from end hook  94  to permit convenient manual access to the end hook. The width of the flange  89  need only be sufficient to set apart the lower wall  84  and blade  92  from second sidewall  16  of the primary housing  12 . The purpose of this spacing is to permit free movement of blade  92  and end hook  94  when the primary and secondary housings are engaged in the Y,X orthogonal orientation depicted in FIG.  10 . 
     Forward wall  86  of the casing  72  is also provided with a slot engagement means shown by forward projection  90 . As shown, the forward projection extends from a position adjacent top wall  78  downwardly to a terminal end that is spaced above blade  92 . This disposition permits better access to manually engage end hook  94  and prevents interference of the forward projection with operation of the tape. 
     The forward projection  90  does not include a significant flange portion to extend the projection outwardly from wall  86 . This permits a closer engagement of the casing with primary housing  12  as depicted in FIG. 12. A tight fit is important to avoid unwanted deviation in the orthogonal alignment of the combined assemblies. 
     To facilitate sliding engagement, the forward projection will have a cross-sectional shape that corresponds to the cross-sectional outline of the opening of first slot  18 . Additionally, the forward projection extends along the center midline of forward wall  86  and the center axis of the lower projection  88  and forward projection  90  along with the center axis of blade  92 , define an imaginary plane extending along the Y,Z axis. Also, the lower and forward projections and the first and second slot openings all have the same cross-sectional configuration. This allows either one of the lower or forward projections to be engaged with either one of the first and second primary housing slots. 
     In operation, the primary tape measure assembly  10  can be used alone to determine the same elevation from the elevation of a known point. This is accomplished by anchoring connector tab  32  to the known point and moving the primary assembly away. The primary blade will be drawn out as the assembly is moved away. Once the location is reached for which an elevation is to be ascertained, the level indicators are observed to ensure the assembly is horizontal and not canted. Light switch  48  is actuated to illuminate light source  42  and emit a light beam  52 . While maintaining the assembly level, the light beam is focused upon target spot  31  of the target portion  30 . When the spot is illuminated, the primary assembly will be at the same horizontal level as the known point. This procedure is useful in many applications including the attachment of wall decorations and related items to vertical surfaces. 
     A series of steps similar to the above may be followed when the secondary tape measure assembly  70  is engaged with second slot opening  20 . This engagement is shown by arrow A in FIG. 10 indicating movement of lower projection  88  downwardly into second slot  20 . In this orientation, blade  92  will extend along the Y axis and blade  24  will extend along the X axis. 
     The above orientation is particularly useful for checking and measuring the grade on a construction site. This application is depicted in FIG. 11 wherein the primary blade  24  will measure the distance from grade stake  97  while the grade drop-off can be measured with the downwardly extending secondary blade  92 . 
     For example, if the grade stake reads that the design elevation is 10 feet offset (10′ o/s) and 1.5 feet below top of survey hub (“CUT 1.5”), the grade drop-off should be 1.5 feet at a distance of 10 feet. The connector tab  32  is anchored to the survey stake and the combined assemblies, in the X,Y orientation depicted in FIG. 10, is moved away from the stake in the desired direction, to a length of 10 feet. The level indicator bubbles are observed to ensure that the primary assembly is held horizontal and level. Light switch  48  is pressed to activate light beam  52  and, while holding the tape assemblies horizontal and level, the assembly combination is moved until target spot  31  becomes illuminated by the light beam. Upon illumination, secondary blade  24  is extended to measure the distance to the ground, in this case to check that the distance is 1.5 feet. Using the assembly combination in this manner allows for quick and simple grade measuring and checking. 
     FIG. 12 shows another preferred embodiment of the invention wherein forward projection  90  is mated with first slot  18  of the primary assembly. This may be referenced as an X,Z orientation wherein secondary blade  92  is slightly below and perpendicular to blade  24 . Both blades will extend in offset but parallel planes defined by the X,Z axes. Note that the forward projection  90  could also be mated with second slot  20 . In this case, blade  92  would extend along the Z axis in an opposite direction. 
     The above embodiment is useful to conduct relative horizontal measurements from a known point. For example, the combined assemblies can be rested against a vertical wall structure with bottom wall  17  against the wall structure. Connector tab  32  is then fixed to a known point. The tape combination is moved horizontally away from the known point while extending primary blade  24 . Upon reaching the desired measured distance for a new point, the light switch  48  is pressed activating the light source  42 . The combined tapes are then moved up and down until light beam  52  illuminates target spot  31 . While the spot remains illuminated, the tapes are further moved while watching the level indicator. When a horizontal level is achieved, the measured new point can be marked. It will be at the same level as the known anchor point. 
     At desired intervals, the wall could be marked to show points on the same level as the known point. Alternatively, at desired intervals, secondary blade  92  can be extended to a desired length for marking points perpendicularly below or above a selected level, depending on whether the secondary assembly is connected to the first or second slot of the primary assembly. 
     Although the present invention has been described in considerable detail with reference to certain exemplary configurations thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the specific versions contained herein.