Abstract:
A pallet insertion limit indicator includes forklift truck including prongs for engaging, raising and lowering a pallet, a surface secured to the truck and moveable with the prongs, and a laser emitter secured to the surface and able to 5 project onto the prongs a visible indicator.

Description:
[0001]    This application claims priority to and the benefit of U.S. Provisional Application No. 61/640,773, filed May 1, 2012, the full disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to a visible indicator, such as a line projected by a laser emitter, that helps prevent unintentional engagement of a pallet by the prongs of a forklift. 
         [0004]    2. Description of the Prior Art 
         [0005]    A fork truck can be used to lift and transport a shallow depth pallet or rack, whose depth is less than the length of the fork. In that procedure, sometimes called “short-forking,” the operator can insert the prongs of the fork too far into the shallow pallet causing the fork to penetrate through the other side of the shallow pallet. The outer ends of the fork can extend inadvertently into a second pallet located on the back side of the shallow pallet. 
         [0006]    When the operator attempts to lift the shallow pallet, not knowing that the fork has penetrated the second pallet behind the shallow pallet, the second pallet and other pallets stacked on it can topple over and fall onto the fork truck, possibly injuring the operator. 
         [0007]    Due to strict safety policies regarding forklift trucks, an indicator that warns about stopping forward motion of the truck when short-forking pallets cannot be attached to the forks or mast by drilling, bolting or welding, although such an indicator can be mechanically connected to the back rest. Neither a painted line nor tape can endure in service for more than a few hours. Brackets cannot be used without prohibited drilling or welding to the fork. 
       SUMMARY OF THE INVENTION 
       [0008]    A pallet insertion limit indicator includes forklift truck including prongs for engaging, raising and lowering a pallet, a surface secured to the truck and moveable with the prongs, and a laser emitter secured to the surface and able to project onto the prongs a visible indicator. 
         [0009]    The laser emitter projects a line, clearly visible to an operator seated in the forklift, onto the floor outside the lateral sides of the fork. 
         [0010]    The emitter projects clearly a line across the forks, thereby identifying a fork depth to be used with shallow depth pallets. 
         [0011]    The position of the line remains unaltered in the correct position whether the fork is raised, lowered, tilted, opened, closed, or shifted. 
         [0012]    The line can be adjusted to project a wide or narrow beam of light. Even with the fork in the up-position, the line can be seen on the inside edge of the fork. 
         [0013]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0015]      FIG. 1  is a perspective view of a forklift truck; 
           [0016]      FIG. 2  is a side view showing a forklift located in front of columns of stacked, loaded, relatively shallow pallets; 
           [0017]      FIG. 3  is a perspective top view of the floor and fork prongs showing a laser emitted line extending laterally across these surfaces; 
           [0018]      FIG. 4  is a perspective side view of a laser emitter encapsulated in a stationary mount; 
           [0019]      FIG. 5  is a front view of an adjustable laser emitter support bracket; 
           [0020]      FIG. 6  is a side view of the bracket of  FIG. 5  and showing a laser emitter mounted thereon; and 
           [0021]      FIG. 7  is a perspective view of an adjustable laser emitter support bracket. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]    As  FIG. 1  shows a forklift truck  10  includes a fork carriage  12 ; two prongs  14 ,  16  of a fork assembly  18 , which is raised, lowered and tilted by the carriage  12 ; a backrest  20 , secured to the carriage such that the backrest and carriage move as a unit; two masts  22 ,  24 , along the length of which movement of the fork assembly is directed and guided; a seat  26 , occupied by the forklift operator; an overhead support frame  28 ; a body  30 ; and tired wheels  32 ,  34  for supporting the truck on the surface  36  of a floor. 
         [0023]    As  FIG. 2  illustrates, the fork  18  can engages a pallet  40  on which is located material, equipment, product, goods or merchandise  42 . The pallet  40  is engaged by prongs  14 ,  16  of the fork assembly  18 , which moves along the depth  44  of a space  46  between the upper and lower surfaces of the pallet  40 . The pallet  40  is lifted on the fork, transported by the truck  10 , lowered by the fork into a desired position, and disengaged by the fork. 
         [0024]    The pallet  40  that is engaged by the fork  18  may have another pallet  48  or group of ballets stacked on the engaged pallet  40 , in which case pallet  48  is also loaded with additional material, equipment, product, goods or merchandise  50 . 
         [0025]    Because the length of the prongs  14 ,  16  is greater than the depth  44  of pallet  40 , the fork can extend into and engage, at least along a portion of the fork length, also a pallet  52 , located behind pallet  40  and such other pallets  54  that are stacked on pallet  52 . Then when the fork  18  is lifted to transport pallet  40 , pallets  52 ,  54  and the goods  56 ,  58  loaded on those pallets are lifted inadvertently without knowledge of the operator. 
         [0026]    To avoid this error, a bracket  60  for supporting a laser emitter  62  is secured preferably to one of the vertical rails  64  of the backrest  20 , preferably at the center of the backrest  20  between its lateral extremities and aligned with the longitudinal centerline of the truck  10 . Bracket  60  may be secured to the backrest  20  mechanically or with a chemical bonding agent, preferably epoxy. 
         [0027]    Alternatively bracket  60  and the laser emitter  62  are secured to the fork carriage  12 , preferably at a laterally centered location, the beam produced by the emitter being projected onto the surfaces of the prongs  14 ,  16  and the floor surface  36 . 
         [0028]    Bracket  60  may support the laser emitter  62  in a stationary position or in an adjustable position, which permits the location of line  64  to vary along the length of the prongs  14 ,  16  in accordance with the depth  44  of the pallet  40  that is to be transported. 
         [0029]    A laser emitter  62  supported on bracket  60  is directed downward and forward onto the upper surface of prongs  14 ,  16  and onto the floor surface  36 . The laser emitter  62  produces a lateral laser line  66  directed laterally, as shown in  FIG. 3 . Because the upper surfaces of prongs  14 ,  16  are at a higher elevation than that of the floor surface  36 , line  66  is also at a higher elevation on the prongs that it is on the floor surface  36 . Line  66  extends laterally onto the floor outboard past the lateral sides of the prongs  14 ,  16  and between the prongs, so that the operator can see the line clearly while seated in the truck  10 . 
         [0030]    Preferably the laser emitter  62  projects a bright laser line  66  across the forks prongs  14 ,  16  several inches deeper than the depth of the shallowest pallet  40 . The emitter can be adjusted such that it projects a wide or narrow beam of light. The laser emitters project light in various colors including red and bright green, according the ambient visibility requirements and the operator&#39;s vision acuity and limitations. 
         [0031]      FIGS. 5 and 6  show an adjustable support bracket  68 , which can be used to support a laser emitter  70  and to adjust the angular position of the laser emitter  70  as it pivots about axis  72  and projects line  66  onto the prongs  14 ,  16  and floor surface  36 . Bolts  74 ,  75  maintain the angular position of emitter  70  in bracket  68 . 
         [0032]      FIG. 7  shows a support bracket  76 , which provides for the position of a laser emitter  70  to be adjusted angularly about two axes  78 ,  80 , such that the emitter projects line  66  onto the prongs  14 ,  16  and floor surface  36 . 
         [0033]    The laser emitter  62 ,  70  may by powered by a battery pack or it may be supplied from the power supply of the forklift truck  10 . If the laser emitter  62 ,  70  is supplied with electric power directly from the battery of a forklift truck  10 , a voltage regulator may be required to reduce the voltage from that of the battery, which may be 48 volts or 36 volts, to the voltage of the laser emitter, which may be 5 volts. The laser emitter  62 ,  70  may be hard-wired to the electrical system of the truck  10  such that it turns on and off automatically when the truck motor is started and stopped. Laser emitters compatible with 12 volt power supply are readily available commercially and would require no voltage reduction when connected to a 12 volt power source. 
         [0034]    The visible insertion limit indicator can be used in other applications than a forklift truck to limit the extend to which a projection, of any kind, secured to a transporting device, such as a vehicle, can be inserted into any passageway such as a pipe, fluid or electric conduit, sewer line, etc. 
         [0035]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.