Abstract:
An alarm system for use with unloading tractor-trailers includes an alarm that is physically located within the tractor-trailer and connected to a fixed structure located outside the tractor-trailer. If the tractor-trailer inadvertently pulls away from the loading dock while a forklift driver is in the trailer, the alarm will go off inside the trailer making the forklift driver aware of the movement of the trailer.

Description:
BACKGROUND OF THE INVENTION 
   Cargo in tractor-trailers is frequently unloaded by backing the trailer up against a loading dock. A forklift is then used to transport the product from inside the trailer to the loading dock and storage area. This requires the forklift to enter the trailer repeatedly. It is possible, for various reasons, for the trailer to move away from the loading dock while the forklift and forklift driver are in the trailer. Due to noise and vibration caused by the forklift, this may not be apparent. If the forklift driver than backs out of the trailer, which has moved away from the loading dock, the forklift will fall several feet, which can cause severe injury or death. 
   There are various alarm systems that can be used to warn individuals if a trailer is inadvertently pulled away from a loading dock. Such systems generally employ an alarm that is located on the loading dock. Such systems are problematic because they require that the system be properly attached to the truck. A forklift driver, once inside the trailer, has no way of knowing or verifying that the alarm system has been properly attached to the trailer. Further, even if the device is properly attached, an alarm outside the trailer may not be heard by the forklift operator. The inside of the trailer reverberates with the sound of the forklift, and, thus, can drown out the sound of an alarm that is located outside the trailer. 
   SUMMARY OF THE INVENTION 
   The present invention is premised on the realization that an alarm system that incorporates an alarm physically located within the trailer will provide a level of safety not provided by prior art alarms. Such a device, when located inside the trailer and attached to, for example, the loading dock by a cord or the like, will provide an alarm inside the trailer, which the forklift driver must hear. This can also be associated with a light signal, so that the forklift driver also sees a warning. The device of the present invention is beneficial in that the forklift driver can see that the device is in the truck and, thus, properly activated at all times, thereby providing an added level of security for the forklift driver. A test button can also be provided that will allow the fork lift driver to test the alarm to make sure that it is properly functioning. 
   The objects and advantages of the present invention will be further appreciated in light of the following detailed description and drawings in which: 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view partially broken away of the alarm system of the present invention located within a trailer; 
       FIG. 2  is an elevation view partially broken away of the alarm for use in the present invention; 
       FIG. 3  is an elevation view partially broken away similar to  FIG. 2 ; 
       FIG. 4  is a diagrammatic depiction of the electrical wiring of the alarm for use in the present invention; and 
       FIG. 5  is a cross sectional view taken of lines  5 - 5  of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   As shown in  FIG. 1 , the alarm system of the present invention includes an alarm  10  which is located on the bed of a trailer  12  which is located at a loading dock structure  14 . A cord  16  connects a magnetic switch  18  on the alarm  10  to a fixed structure, preferably a structure on the loading dock  14 . Thus, in operation, when the trailer  12  moves away from the loading dock, the cord  16  will be stretched out and pull the magnetic switch  18 , causing the alarm  10  to go off. 
   More particularly, the alarm  10  includes an enlarged base  22  having an upwardly extending cylindrical stem  24  extending to a handle  26 . The base  22  includes a lower most weighted portion  30 , which is generally a series of iron weights, or the like, and a bottom  32 , which is a permanent magnet. 
   Located inside the base  22  is a battery compartment  36  housing a battery  38 . Located at the top of stem  24  is a signal generator  42 , shown in phantom, which, as shown, is a noise-generating device. As shown in  FIG. 3 , connecting the battery  38  to the signal generator are first, second and third switches  44 ,  46  and  47 . 
   These switches, as described below, will normally be in an open position. When any of these switches is closed, current will be directed to the signal generator  42  causing the audible or visual signal. 
   The first switch  44  is located in the base  50  of stem  24 . The base  50  of stem  24  is surrounded by a square metal collar  52 . First switch  44  is located inside stem  24  immediately above the metal collar  52 . A U-shaped switch member  54  is fixed to the metal collar  52  held in place by a first magnet  56  with a portion  57  of the U-shaped member engaging the sides of collar  52 . An upper portion  59  of the U-shaped member  54  extends above the collar  52  and aligns with the first switch  44 . Attached to the upper portion  59  is an upper magnet  58 . Switch  44  is biased in a closed position. Upper magnet  58  is designed to maintain the first switch in an open position, as shown in  FIG. 2 . Absent magnet  58 , the first switch  44  would close, as shown in  FIG. 3 , allowing current to flow. Cord  16  is attached via a connector  60  to the upper portion  59  of U-shaped member  54 . 
   As indicated previously, the handle  26  is attached to an upper portion  61  of stem  24 . The base  62  of handle  26  includes a screened opening  64  aligned immediately above the signal generator or noise generator  42 . 
   The alarm  10  includes a spring-biased button  70  for activating second switch  46 , which permits an individual to determine if the alarm is operating properly. Also located in stem  24  is a tilt switch  47 . 
   As shown in  FIG. 4 , the signal generator or alarm  42  is operated by direct current having a first wire  80  connected to a first pole  82  of battery  38 . Battery  38  can be a 9-volt battery or any battery effective to activate the alarm  42 . A second wire  84  of alarm  42  connects to the three normally open switches  46 ,  44 , and  47 . As indicated below, closing any of these switches will complete the circuit to pole  86  of battery  38  causing the alarm  42  to sound. A low battery indicator or alarm can also be employed if desired. 
   To use the alarm of the present invention, the alarm  10  is positioned inside the trailer  12  of a truck or a truck bed that is adjacent, for example, a loading dock  14 . If the truck bed is ferromagnetic, the magnet  32  will hold the alarm  10  in position. If the bed is wood or aluminum, or other non-ferromagnetic material, the mass of weights  30  are designed to provide sufficient resistance to hold the alarm  10  in position. The U-shaped switch member  54  is located over the square collar  52  so that upper magnet  58  is aligned with first switch  44 , maintaining it in an open position, as shown in  FIG. 2 . Likewise, second, or test, switch  46  is in an open position. The cord  16 , which is attached to the U-shaped switch member  54  at one end, is then tied at the opposite end to a fixed structure outside the trailer  12 . This can be a portion of the loading dock, or the wall, or other structure, as desired. The cord  16  should be relatively taut, and, certainly, should not have enough slack to allow the trailer to move away from the loading dock without setting off the alarm. 
   When placing the alarm  10  in the trailer, the operator can press test switch  46  and set off the alarm to determine if the alarm is working. The trailer  12  can then be unloaded by the forklift operator. In the event the trailer moves away while the forklift is in the trailer, the cord  16  will pull the U-shaped switch member  54  separating it from the collar  52 , as shown in  FIG. 3 , pulling the second magnet  58  away from switch  44  causing the switch to close. This will, in turn, activate the signal device  42 , which will inform the forklift driver that the trailer  12  has moved away from the loading dock  14 . After the trailer  12  is safely unloaded, the alarm  10  is removed from the trailer. If the alarm  10  is knocked over for any reason, tilt switch  47  will close, also activating the alarm. 
   If desired, the alarm  42  can also comprise a flashing light. Any alarm device that would affectively alert a forklift driver can be used in the present invention. Further, other types of switches can be employed in place of magnetic switch  44  as long as the switch closes in response to cord  16  being pulled. 
   Using the alarm  10  provides several advantages. Most importantly, it creates the alarm inside the trailer where it is most easily noticed by the forklift operator. Further, the forklift operator will appreciate that the alarm is in position because he can see the alarm in position. Finally, if necessary, he can test it to make certain that the battery is operating. This provides not only a sense of security, but added security for the forklift operator. 
   This has been a description of the present invention along with the preferred method of practicing the present invention. However, the invention itself should only be defined by the appended claims,