Patent Abstract:
A water or spirit level is composed of an elongated body, preferably of metal, at least one bubble mounted in the elongated body, and end caps, preferably of plastics material, at the end faces of the elongated body, wherein at least one outer surface of the elongated body constitutes a preferred measuring surface. At least one of the end caps is releasably connected to the level body such that the end cap can optionally be removed and once again replaced.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a Divisional Application of U.S. patent application Ser. No. 10/376,462, filed Feb. 28, 2003 now U.S. Pat. No. 6,988,320. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a method of using a water or spirit level composed of an elongated body, preferably of metal, at least one bubble mounted in the elongated body, and end caps, preferably of plastics material, at the end faces of the elongated body, wherein at least one outer surface of the elongated body constitutes a preferred measuring surface. 
   2. Description of the Related Art 
   Levels have been for decades manufactured all over the world in large numbers and are used regularly primarily in civil engineering. For reasons of strength and dimensional stability, the body of a level is usually composed of metal, in most cases light metal, and conventionally has a rectangular hollow cross section or a I-shaped solid cross section. In order to prevent damage to the levels in case of impacts or when dropped, the level body is provided with end caps which are composed of a relatively soft, elastic, shock-absorbing material, usually plastics material. When the level body is of a hollow section, the end caps also serve as closures. 
   A level with an end cap of plastics material is disclosed, for example, in AT 398 846 B. This level has a level body with an I-shaped cross section. The cross section of the end caps is rectangular and their dimensions are adapted to the dimensions of the level body. For fastening the end caps to the level body, the end faces of the level body are provided with two blind-end openings which have several undercuts. The end caps are provided with appropriate lugs which engage positively in the blind-end openings. In this manner, the end caps are inseparably fastened to the level body. 
   In the manufacture of levels, there is the tendency to construct the shock absorbers at the end caps larger and larger in order to achieve a better protection against damage. However, end caps which are manufactured as injection molded articles have manufacturing tolerances and also have a different coefficient of expansion than the level body. In order to prevent the end caps from projecting beyond the measuring surfaces of the level, the end caps are manufactured with smaller cross sectional dimensions than the level bodies; in addition, also for aesthetic reasons, the end caps are frequently slightly outwardly conically beveled. The smaller cross sectional dimensions result in an undesirable step in the plane of the measuring surface in the joining area between the end cap and the level body. 
   This has the result that, for example, in the corner area of two walls where a line or marking has to be transferred from one wall to the other, the line or marking cannot be continued precisely around the corner because the measuring surface of the level cannot be placed all the way into the corner because of the presence of the end cap mounted on the end face of the level body. The greater the length of the portion with no line or marking, the more effective the shock absorption of the end cap. This results in inaccuracies. 
   Many artisans solve this problem by pulling off the end cap by applying great force. However, since the end caps are not designed for such a use, they find no support when they are once again inserted into the level body; rather, the end caps remain separate and become lost. This is not satisfactory. 
   SUMMARY OF THE INVENTION 
   Therefore, it is the primary object of the present invention to provide a method of using a level which makes it possible to continue lines or markings precisely around the corner without problems, without giving up the impact protection. 
   In accordance with the present invention, the method comprises, for transferring the line or marking away from the corner onto the walls, inserting the cap in the level body, and, for continuing the line or marking in the corner, removing one of the end caps from the level body so as to expose an end face thereof, and placing the end face of the level body into the corner from each side of the corner. 
   The basic concept of the level resides in constructing the connection between an end cap and the level body so as to be releasable, so that the end cap can be optionally removed and replaced again. On the one hand, the connection between the end cap and the level body must be capable of absorbing a sufficient force in order to prevent an unintentional separation of the end cap in the case of impacts; on the other hand, it should be possible for the user to quickly and easily remove the end cap as required and, of course, to place it back onto the level body. 
   In accordance with a preferred feature of the level, a locking device in the form of a resiliently mounted locking knob is provided on the shaft of the end cap with which the end cap is connected to the end face of the level body, wherein the locking knob extends into or through an indentation or opening provided at the appropriate location in the wall of the level body. Since the locking knob is resiliently fastened to the shaft, the locking knob can be resiliently inserted by applying a compressive force. 
   The locking knob is inserted when the end cap is mounted on the level body, however, when the indentation or opening in the wall of the level body is reached, the locking knob jumps out and ensures with its outer surface a locking action relative to the wall of the indentation or opening. By pressing in the locking knob, which advantageously is arranged on two oppositely located sides of the level body, the locking action can be released, so that the end cap can be pulled off. 
   While the use of the locking knob is the preferred solution, which has the advantage that no tool is required for its actuation, there are other embodiments of locking means, for example, by clamping screws or also locking means which act like bayonet closures, or also magnetic locking means. 
   The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawing: 
       FIG. 1  is a side view of a first embodiment of the level according to the present invention, shown with a portion of the wall of the level body broken away; 
       FIG. 2  is a side view of an end cap to be mounted on the level of  FIG. 1 ; 
       FIG. 3  is a sectional view taken along sectional line III—III of  FIG. 1 ; 
       FIG. 4  is a perspective view of the end cap; 
       FIG. 5  is a side view of a second embodiment of the level according to the present invention; 
       FIG. 6  is a side view of an end cap to be mounted on the level of  FIG. 5 ; 
       FIG. 7  is a sectional view taken along sectional line VII—VII of  FIG. 5 ; 
       FIG. 8  is a sectional view taken along sectional line VIII—VIII of  FIG. 5 ; 
       FIG. 9  is a side view of a third embodiment of the level according to the present invention; 
       FIG. 10  is a side view of an end cap to be mounted on the level of  FIG. 9 ; and 
       FIG. 11  is a sectional view taken along sectional line XI—XI of  FIG. 9 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a side view of a first level  1 . The level  1  has an elongated body  2  which is constructed as a hollow profile of metal, particularly light metal, and is provided in the known manner with recesses or openings  3  and  4  for the insertion of bubbles which extend perpendicularly of each other. Of the end caps  7  arranged on the ends  5 ,  6  at the end faces of the level body  1 , the end cap  7  on the left end  5  is shown inserted and partially in section, while the end cap  7  on the right end  6  is shown as  FIG. 2  still outside of the body  2  shortly before being inserted. 
   The end cap  7 , shown in a side view in  FIG. 2  and in a perspective view in  FIG. 4 , is composed of an end plate  8  whose circumference corresponds approximately to the cross section of the body  2  and which with its thickness projects beyond the body  2 , and of a hollow shaft  9  connected to the end plate  8 . Together with the inner portion  10  of the end plate  8 , the hollow shaft  9  is composed of a harder plastics material of higher strength because it must ensure the connection between the end cap  7  and the body  2 , and an outer part  11  of the end plate  8  which is of a softer plastics material and serves for shock absorption. The end cap  7  can be manufactured in the known manner in a two-component injection molding process in order to ensure a permanent connection of the parts  10 ,  11 . 
   The outer dimensions of the hollow shaft  9  are slightly smaller than the inner dimensions of the body  2 , so that the end cap  7  can be pushed in the direction of arrow  12  into the hollow space of the body  2 , as seen in  FIG. 1 . In order to be able to compensate for any tolerances, ribs  13 ,  14  are provided on the outer surfaces of the walls of the shaft  9 , wherein the excess dimensions of the ribs are cut off when the end cap is pushed in for the first time, so that a secure frictional engagement is ensured. Further details of the end cap  7  can be seen in  FIG. 4 . 
   A locking knob  15  each is provided on opposite sides of the wall  23  of the shaft  9 . The locking knobs  15  each have a circular circumference and form a cylindrical portion  16  which protrudes beyond the surface of the respective shaft wall. Each locking knob  15  is located in an opening  17  of the wall  23  of the shaft  9  and is connected to the wall  23  only through two narrow webs  18 . The webs  18  are constructed so as to be resilient and twistable, so that the locking knob  15  can be pushed down by applying a pressure onto its surface, wherein the locking knob  15  returns into its original position after the pressure is no longer applied. 
   Corresponding to the locking knobs  15 , openings  19  are provided in the outer wall  21  of the level body  2 , wherein, in the inserted state of the end cap  7  shown in  FIG. 3 , the oppositely located locking knobs  15  extend into and fill out the openings  19 . The cylindrical outer surface  16  of each locking knob  15  then is in contact with the circumference of the holes  19 , so that the end cap  7  is prevented from being separated from the connection with the body  2  of the level. By exerting a compressive force in the direction of arrows  20 , which can be easily accomplished by the thumb and index finger of a hand, the locking knobs  15  can be pushed down to such an extent that the end cap  7  can be pulled off the body  2  of the level  1  without being damaged in the direction of arrow  22  seen in  FIG. 3 . The reinsertion of the end cap  7  takes place in the reverse sequence. 
     FIG. 5  is a side view of a second embodiment of the level  31 . The level  31  has an elongated body  32  which is constructed as an I-section of metal, particularly light metal, and which is provided in the known manner with recesses or openings  33 ,  34  for inserting bubbles which extend perpendicularly of each other. Of the end caps  37  arranged at the ends  35 ,  36  of the level body  32 , the end cap  37  at the end  35  is already placed on the level body, while the end cap  37  at the right end  36  is illustrated as  FIG. 6  shortly before being placed on the body  32 . 
   The end cap  37  illustrated in  FIG. 6  in a side view is composed of an end plate  38  whose circumference corresponds approximately to the cross section of the body  32 , and of a shaft  37  connected to the end plate  38 . 
   The shaft  39  is composed of two pairs of parallel, oppositely arranged tongues  42 ,  44 . The distance between the pairs of tongues  42 ,  44  is adjusted as exactly as possible to the thickness of the wall  41  of the level body  32 . Arranged between the pairs of tongues  42 ,  44  is on the side of the pair of tongues  42  a resilient surface  43  which supports the resiliently lowerable projection  45 . Further details of the connections can be seen in  FIGS. 7 and 8  which show sectional views along lines VII—VII and VIII—VIII in  FIG. 5 . 
   For locking the end caps  37  to the level body  32 , the level body  32  has openings  49  into which the projections  45  engage. For releasing the end caps  37 , the artisan presses with a finger on the projection  45  and is able to pull off the end cap  37 . 
     FIG. 9  is a side view of a third level  51 . The level  51  has an elongated body  32  constructed as an I-section of metal, particularly light metal, and provided with recesses or openings  33 ,  34  for inserting bubbles which extend perpendicularly of each other. Of the end cap  57  arranged on the ends  35 ,  36  of the level body  32 , the end cap  57  on the left end  35  is placed on the level body  32 , while the end cap  57  shown in  FIG. 10  on the right end  36  is still outside of the body  32 . 
   The end cap  57  illustrated in  FIG. 10  in a side view is composed of an end plate  58  whose circumference approximately corresponds to the cross section of the body  32  and which with its thickness protrudes beyond the body  32 , and of a shaft  59  connected to the end plate  58 . 
   The shaft  59  is composed of two parallel, resilient surfaces  63 , wherein the distances between the surfaces  63  is adjusted to the thickness of the wall  41  of the level body  32 . A projection  65  is integrally formed on each resilient surface  63 . Both projections  65  engage in the openings  49  in the wall  41  of the level body  32 , as can be seen in  FIG. 11 . 
   To be able to separate the end cap  57  from the level body  32 , the ends  64  of the resilient surfaces  63  are constructed as actuating surfaces, as illustrated in  FIG. 11 . 
   While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

Technology Classification (CPC): 6