Alarm system for a loading dock

ES 2 392 908 T3

DESCRIPTION

Alarm system for a loading dock

Background of the invention

Field of the invention

The subject invention relates in general to loading docks for trucks and, more particularly, to a security method for alerting workers of a dock within a building and to a security system for a building according to the preamble of claims 1 and 6 respectively.

Description of Related Art

Many buildings may have an entrance with a loading dock to facilitate the transfer of cargo between a truck and the building. A loading dock is a platform that is generally at the same height as the base of the truck or its trailer. The dock can also include a dock leveler, which is a vertically moving ramp that compensates for a height difference that may exist between the platform and the base of the truck. Dock levelers can also provide a bridge across which material handling equipment and personnel can move between the platform and the truck.

For protection against weather conditions and theft, the building entrance may include a manually or mechanically operated door. The doors for the loading docks are usually opened and closed by moving vertically so that they do not interfere with the rear of the truck or interfere with the loading and activity just inside the entrance; however, other types of doors can be used.

When there are no trucks on the dock and the weather is mild, the door can be left open to help ventilate the building with fresh air from outside. Leaving the door open, unfortunately, increases the risk of personnel or material handling equipment or other inside the building accidentally falling over the edge of the dock deck and through the open driveway entrance. In addition, leaving the door open lowers the security of the building due to the entry of unauthorized personnel or the theft of employees through the unsafe entrance.

To provide ventilation through the entrance while minimizing the risk of falls, some loading docks include a safety barrier that provides an obstruction through the entrance when no truck is present or is otherwise moving into a non-locking position as needed. Examples of such barriers are disclosed in US Patents 5,271,183 and 5,299,386.

Regardless of whether a loading dock includes a safety barrier, a lift truck that transfers a load between the truck trailer and the dock bed can present a collision risk to dock workers or others in the work area. . If a lift car is operating deep inside the truck trailer, the lift car driver and nearby pedestrians may not be aware of each other. Therefore, the lift truck can suddenly come out of the trailer and accidentally hit someone.

Document DE 100 00 131 A1 discloses a security method and system for a building including an entrance and a loading dock adapted to receive a vehicle. More specifically, the security system has a switch and control unit with buttons by which the security system is operated and which controls and coordinates the individual modules of the security device, a light indicator system that gives or denies the driver the driver's license, a warning unit that is activated if the vehicle moves, a protective device that prevents people or vehicles from falling off the ramp when it is closed, and an optoelectronic charging module with light barriers to detect the position of the vehicle.

US 2004/075046 A1 discloses a detection system for detecting a body near an entrance that includes two detectors having one or more trigger lines that overlap each other. With certain mounting arrangements, the detectors cover areas within and on both sides of the entrance. The detectors are intended to help prevent an already open door from accidentally closing on the body. The door is driven by a drive unit that ignores the detectors when the door is closed.

Summary of the invention

The object of the invention is to provide a security method and system for alerting dock workers within the building of a potential hazard at a loading dock.

ES 2 392 908 T3

According to a first aspect, the present invention provides a security method for a building that includes an entrance and a loading dock adapted to receive a vehicle, according to the content of independent claim 1. A second aspect of the invention relates to a security system, according to the content of independent claim 6. Additional aspects and embodiments of the invention are explained in the dependent claims, the following description and the drawings.

Brief description of the drawings

Figure 1 is a perspective view of a security system, in which the view is from inside a building observing a loading dock whose door and barrier are open while a truck is present at the dock.

Figure 2 is similar to Figure 1 although it shows the door closed.

Figure 3 is similar to Figure 1 but without the truck on the dock, thus the security system provides an alarm signal (eg a light).

Figure 4 is similar to Figure 3 but shows the barrier being closed.

Figure 5 is similar to Figure 4 but shows the barrier closed.

Figure 6 is similar to Figure 3 but with a person within a predetermined distance from the edge of the platform, thus the security system provides a more pronounced warning signal (eg, a buzzer).

Figure 7 is a perspective view of a security system, in which the view is taken from outside the building, and the drawing schematically shows numerous sensors installed in various locations.

Figure 8 is a ladder diagram illustrating only one of many conceivable ways to control the security system of Figure 1.

Figure 9 is a cross-sectional side view of a loading dock similar to Figure 1 but with a pivoting barrier and a vehicle restraint that engages a truck.

Figure 10 is a schematic diagram illustrating a basic concept of a loading dock alarm system.

Figure 11 is a perspective view of an embodiment of a security system that responds to a potential hazard at a loading dock and also possibly a person potentially in distress in the area.

Figure 12 is a perspective view of another embodiment of a security system that responds to a potential hazard at a loading dock and also possibly a person potentially in distress in the area.

Figure 13 is a perspective view of another embodiment of a security system that responds to a potential hazard at a loading dock and also possibly a person potentially in distress in the area.

Description of the preferred embodiment

Figures 1-6 provide an interior view of a building 10 with an entrance 12 and a loading dock 14, in which the loading dock is shown in various situations. Under certain conditions, a safety system 16 provides one or more alarm signals that warn of a potential fall hazard when someone or something may possibly fall from an elevated platform 18 of the pier 14. If, for example, a gate 20 and a barrier 22 were left open while a truck 24 or other type of vehicle is not present at the dock, as shown in Figure 3, an alarm system 26 (for example, an alarm triggered by a controller) could provide an audible or visual alarm signal 28 that could alert workers on a dock in the hazard zone. In some embodiments, the system 26 may also provide a more pronounced audible or visual warning signal 30 (FIG. 6) that would signify a more imminent danger, such as a body 32 (eg, a person, a lift car, etc.). ) is dangerously close to the exposed edge of deck 18.

The security function can be achieved in numerous ways.

The response of the security system 16 (ie, the alarm system 26 plus its sensors) depends on the situation on the dock.

Figure 1, for example, shows door 20 opening while truck 24 leans against the dock. In this situation there may be no need for an alarm because the fact that truck 24 is present in the

ES 2 392 908 T3 dock minimizes or eliminates the possibility of something falling off the platform 18 and onto the roadway or falling from a conventional dock leveler 34 installed within the platform.

Figure 2 shows the closed door 20 in which a door panel 36 covers the doorway 12. With the door 20 closed, an alarm may not be necessary, unless there is still concern about something breaking through the door.

Figure 3 does not show any trucks present at the dock while door 20 is open. Since this constitutes a possible fall hazard, a controller 38 may be wired or programmed to activate an alarm 40 to produce an alarm signal 28 such as, for example, a flashing red light. Controller 38 may activate alarm 40 in response to a vehicle sensor 42 that determines that truck 24 is not within a certain distance 44 of input 12 (see Figure 9) and a barrier sensor 48 that determines that the door 20 is not closed. Sensor 48 is called a "barrier sensor" because gate 20 can itself be considered a barrier. In some embodiments, for example, barrier 22 is omitted, and door panel 36 alone (or in combination with added structure) serves as a security barrier.

Barrier sensor 48 for door 20 is schematically illustrated to represent any device for sensing a particular position of door panel 36. With further reference to Figure 7, examples of the barrier sensor 48 include, but are not limited to, an upper travel limit switch 48a, a lower travel limit switch 48b, a rotary switch (Figures 1-6 ), electromechanical switch, electromagnetic sensor, ultrasonic proximity sensor, limit switch, proximity switch, photoelectric cell, Hall effect sensor, magnetic switch, etc.

Vehicle sensor 42 is schematically illustrated to represent any device for detecting that vehicle 24 is adjacent to or within a certain distance 44 of input 12. Examples of the vehicle sensor 42 include, but are not limited to, a rotary switch, electromechanical switch, a pedal switch 42a actuated by the tire of a truck 50 (FIG. 7), a switch 42b actuated by the motion of a dock seal / shelter 52, a switch 42c actuated by movement of a vehicle restraint 54, a switch 42d actuated by movement of a bumper 56, a switch 42e actuated by the movement of a spring leveler 34, electromagnetic sensor, an ultrasonic proximity sensor 42f, limit switch, proximity switch, photoelectric cell, Hall effect sensor, magnetic switch, etc.

Controller 38 may also be connected or programmed to activate alarm 40 when vehicle sensor 42 determines that no trucks are present at the dock while barrier sensor 46 establishes that barrier 22 is in a non-locking position. Barrier sensor 46 is schematically illustrated to represent any device for sensing a particular position of barrier 22. Again with further reference to Figure 7, examples of barrier sensor 46 include, but are not limited to, a travel limit switch 46a, a rotary switch on a take-up drum (Figures 1-6), switch electromechanical, electromagnetic sensor, ultrasonic proximity sensor, proximity switch, photoelectric cell, Hall effect sensor, magnetic switch, etc. The barrier sensor 46 may be installed on a first bracket 60 that supports the barrier 22, or a barrier sensor 46b could be installed on a second bracket 64 of the barrier 22.

Controller 38 may also be wired or programmed to activate alarm 40 in response to vehicle sensor 42 determining that truck 24 is not present or within a certain distance 44 of input 12 (see Figure 9) and that barrier sensor 48 determines that door 20 is not closed. Furthermore, it should be appreciated that the depicted location of the sensor 42 is for descriptive purposes only, and that other locations for the sensor 42 may be preferred such as its mounting external to the building adjacent to the dock.

Figure 4 shows barrier 22 moving from its non-locking position of Figure 3 to its locking position of Figure 5. In the locked position, barrier 22 obstructs the open entrance to help prevent something from falling through. Of the same. Although many different types of barriers would work, in this particular example barrier 22 is a tough fabric panel 58 that can be moved between locked and non-locked positions. In the non-locking position of Figure 3, the panel 58 wraps around a rotating, spring-loaded drum supported within the first bracket 60. In the locking position of Figure 5, one end 62 of the panel 58 engages on the second bracket 64 so that the panel 58 provides a taut protective fence between the brackets 60 and 64.

In Figure 5, controller 38 deactivates alarm 40 in response to barrier sensor 46 determining that barrier 58 is in its locked position in which the barrier minimizes or eliminates the risk of falling.

Figure 6 shows how the safety system 26 could be configured to respond when the risk of falling poses a more imminent danger, such as when the body 32 approaches the open doorway. To achieve this functionality, when the body 32 enters an area 66 adjacent to the entrance 12 when the door 20 is open, no truck is present, and the barrier 22 is in its unobstructed position, the

ES 2 392 908 T3 controller 38 triggers an alarm 68 to create a warning signal 30 that is audible or otherwise distinguishable from alarm signal 28. Controller 38 triggers alarm 68 in response to a remote body sensor 70 , which is schematically illustrated to represent any device for determining whether body 32 is within area 66 (ie, within a certain distance from the entrance). Examples of remote body sensor 70 include, but are not limited to, a metal detector, motion detector, a weight detector 70a associated with the dock leveler 34 (for example, attached to a lip retainer 72) to detect when the weight of a body is on the cover 74 of the dock leveler, infrared sensor, a photoelectric cell that determines if a body crosses its beam or line of sight, ultrasonic proximity sensor, electromagnetic radiation antenna, etc. Although Figures 1-6 show remote body sensor 70 installed in an elevated location, Figure 7 indicates that a remote body sensor 70b can be installed in any location that is appropriate for a particular type of sensor.

In some cases, controller 38 may include a disable switch 76 to disable alarm 68 under certain conditions such as, for example, when the door or other equipment in the area needs maintenance. If the alarm system, for example, includes both a visual signal and an audible signal, switch 76 may be configured to silence the audible signal but still allow actuation of the visual signal.

Figure 8 shows just one example of many possible control schemes that will achieve the results just described. The various elements in Figure 8 are schematic representations or symbols of what could correspond to a vehicle sensor 42, barrier sensor 48, barrier sensor 46, body sensor 70, disable switch 76, alarm 40, and alarm 68. , where 42 'corresponds to 42, 48' corresponds to 48, etc. In Figure 8, the various sensors or switches are shown in their "normal" positions when truck 24 is not present (normally sensor 42 'closed contacts are closed), door 20 is open (normally sensor closed contacts 48 'are closed), barrier 22 is in its non-blocking position (normally the closed contacts of sensor 46' are closed), body 32 is not within an area 66 (normally open contacts of sensor 70 'are open), and deactivation switch 76' is in its normally closed position. Controller 38 activates visual alarm 40 'until at least one of the following occurs: arrival of truck 24 opens vehicle sensor contacts 42', gate 20 closes to open barrier sensor contacts 48 ' , or the barrier 22 is closed to open the contacts of the barrier sensor 46 '. In cases where the barrier is provided by the gate itself, the barrier sensor 46 'is bypassed (or shorted out). If in addition to the activation of the visual alarm 40 ', the body 32 enters an area 66 to close the contacts of the remote body sensor 70', the controller 38 also activates the audible alarm 68 '. A clock 78 may be added to set a date and time stamp that identifies when alarm 68 '(and / or alarm 40') was activated, which can be useful in investigating an accident.

Figures 7 and 9 show another example of a barrier 80, in which the barrier 80 includes an arm 82 that pivots between a locking position (imaginary line 84 in Figure 7) and a non-locking position (solid lines in the Figures 7 and 9). Figures 7 and 9 also show dock leveler 34 having a flange 86 whose upper edge 88 can be used as a barrier to prevent accidental fall, particularly for material handling equipment. An example of such a dock leveler is disclosed in US Patent 4,920,598. If any of these barriers were used in a security system as disclosed herein, there would be an associated sensor or detection scheme (eg, sensor 46a of Figure 7) to determine whether the barrier is or is not in a locked position.

Fig. 10 is a diagram schematically illustrating the basic concept of an alarm system 81 for a loading dock. As will be appreciated, some forms of signaling / alarm systems already exist at a loading dock. For example, most vehicle restraints include a light communication package to provide an indication to personnel within the facility as to whether or not the restraint is engaged to secure the trailer. Thus, while the general idea of ​​detecting and signaling in this context is known, the embodiments disclosed herein allow progress in the art by, for example, more specific identification and warning regarding particular hazards, or the most effective communication of risks to allow corrective or preventive action or for other reasons. In the example above, detection and signaling were provided for, among other things, the risk of an open dock, and a person in the immediate vicinity of the loading dock. Other particular risks, and / or more effective risk communication with respect to the generalized system, will be discussed. System 81 comprises stages 81a-f, where stage 81a defines a potential risk to be avoided, stage 81b determines which conditions indicate that the risk may exist, stage 81c selects the appropriate types of sensors that can detect the condition of risk, step 81d selects the appropriate locations for the sensors, step 81e selects an appropriate type of alarm, and step 81f selects the location of the alarm. There are several possible options for each of the steps 81a-f, and the resulting combinations of the options provide numerous embodiments.

For step 81a, for example, examples of potential hazards include, but are not limited to: a) the vehicle restraint 54 is unlocked and a first body 32 or a second body 108 approaches the entrance 12 or enters a vehicle 24 without security (any of the bodies 32 or 108 could be a lift car, other equipment

ES 2 392 908 T3 material handling, or a person), b) vehicle retainer 54 unlocked and body 32 or 108 is inside vehicle 24, c) body 32 or 108 moves inside vehicle 24, d ) body 32 or 108 is inside vehicle 24 but not necessarily moving, and / or e) body 108 (for example, a lift car) is inside vehicle 24 and body 32 is close (and probably cannot see the body 108 because it is inside the vehicle 24).

For step 81b, examples of conditions that indicate that one or more of the potential hazards mentioned above may exist include, but are not limited to a) the hook of the vehicle restraint 54 is retracted and the body 32 or 108 is moving close to cover 74 or inlet 12, b) vehicle restraint hook 54 is retracted and body 32 or 108 is present near cover 74 or inlet 12, c) vehicle retainer hook 54 is retracted and body 32 or 108 is moving within vehicle 24, d) vehicle retainer hook 54 is retracted and body 32 or 108 is actually within vehicle 24 but not necessarily in motion, e) body 32 or 108 moves within vehicle 24 regardless of the condition of vehicle restraint 54, f) body 32 or 108 is stationary within vehicle 24 regardless of the condition of vehicle restraint 54, g) one body is moving or stationary within vehicle 24 while a second body is moving or stationary near the deck 74 or entry 12, and h) the presence or absence of vehicle 24 at the loading dock.

For step 81c, examples of sensors that can detect one or more of the conditions mentioned above include, but are not limited to: a) an electromechanical limit switch, b) pressure switch, c) active infrared presence detector , d) passive infrared motion detector, e) photoelectric cell, f) ultrasonic proximity sensor, g) electromagnetic radiation antenna, h) metal detector, and i) weight detector.

For step 81d, examples of locations for the sensors mentioned above include, but are not limited to: a) on or near vehicle restraint 54, b) on or near deck 74, c) on an adjustable bracket or stationary adjacent to inlet 12, d) on body 32 (eg, on a person), and e) on body 108 (eg, on a lift car). One or more of these positions plus other sensor mounting locations are shown in Figures 7 and 15-17. In cases where a sensor comprises an emitter and a receiver, the emitter may be in one of the aforementioned locations. and the receiver in another. An emitter, for example, could be attached to a lift truck or a person with a corresponding receiver mounted on an adjustable bracket adjacent to input 12, or the emitter and receiver locations could be reversed.

For step 81e, examples of suitable types of alarms include, but are not limited to: a) lights of different colors to indicate different conditions, b) flashing light, c) illuminated signs or icons representing various hazards or conditions, d ) a conventional audio signal (eg siren, buzzer, horn, etc.), and e) directed audio or directional sound focused on a certain area or individual. In some cases, a person may wear some form of personalized identification such as an RFID tag that allows an alarm system to provide a personalized message to that particular individual. The alarm, for example, can deliver a verbal message that mentions the individual's name or uses language particularly suitable for the individual.

For step 81f, examples of possible alarm locations include, but are not limited to: a) along a vertical edge of the inlet 12, b) along an upper horizontal edge of the inlet 12, c) along a continuous length extending from one side to the horizontal edge of the inlet 12, d) along an intermittent length extending from one side to the horizontal edge of the inlet 12, e) over an adjustable or fixed bracket that rises or distance from an upper edge of the inlet 12 (for example, light 85 in figure 15), f) adjacent to a peripheral edge of the cover 74 (for example, light 83 in Figure 15), g) a location where the alarm emits sound or light into the vehicle 24, h) a location where the alarm emits sound or light in front of the entrance 12 in the proximity of the dock leveler 34, and i) carried on or with a pedestrian who is alerted.

Various combinations of options in steps 81a-f provide numerous possible embodiments. An example, for example, may include activating a visible red light in the loading dock area outside the vehicle 24 when the body 32 or 108 moves adjacent to or inside the vehicle 24 or when it is simply present in the vehicle, and activating a green light when no movement and / or presence is detected. Another example may include selectively projecting lights of various colors (e.g. red, amber green) into the vehicle 24 (where it can be seen by the forklift operator) and / or into the loading dock area to indicate the situation in relation to vehicle restraint 54 (eg, whether it is engaged or not) and the presence or movement of body 32 or 108 within or adjacent to vehicle 24. Light 83 projects light both inside and outside of vehicle 24. In this regard, being able to detect the presence of a vehicle or pedestrian in vehicle 24 could be related to light or other communication outside the building so that, for example, it can be seen by the driver of the vehicle 24. The vehicle retainers mentioned herein are provided to prevent a vehicle 24 from leaving the loading dock. Clearly, the retention cannot perform this function if it is not latched. In addition, when it is not engaged, the driver is normally presented with a green light, indicating that it is unlocked and can exit. Therefore, it would be beneficial to indicate to the driver not to

ES 2 392 908 T3 exits whenever a person or forklift is in the vehicle 24. The sensors disclosed herein could be used as a trigger signal to illuminate an exterior red light (seen by the driver of vehicle 24) at all times that a body is present on the trailer, regardless of whether the vehicle restraint is engaged or not.

As mentioned earlier in the description of FIG. 3, it was noted that in some embodiments, barrier 22 is omitted and door panel 36 can only serve as a security barrier. Figure 11, for example, shows a loading dock 106 without a barrier 22. In this case, the door panel 36 is open and the vehicle 24 is properly parked adjacent to the entrance 12. However, a body 108 (for example, a lift truck or other type of material handling equipment) loading and unloading a load from inside the vehicle 24 can create a potentially hazardous situation for another body 32 (for example, a person , another lift car, etc.) that is within zone 66 adjacent to entrance 12.

To avoid a collision between bodies 32 and 108, a safety system 110 alerts the body 32 and / or 108 of the risk. In some embodiments, security system 110 includes one or more remote body sensors 112 mounted outside of vehicle 24 and preferably within the building. Each of the sensors 112 transmits a detection signal 114 through an interior 116 of the vehicle 24, wherein the detection signal 114 detects whether the body 108 is within the vehicle 24. Sensor 112 can be any suitable device including, but not limited to, a powerful passive infrared motion sensor that responds to body movement 108, or a photoelectric beam installed in an appropriate location where the beam can be interrupted. when body 108 enters or leaves vehicle 24.

To alert body 32 and / or body 108 of the potential hazard, an alarm system 118 in effective communication with sensors 112 provides a visual or audible alarm signal. Examples of the alarm system 118 include, but are not limited to, a single light 40 that emits a light signal 28, a stop / go light 120 that emits a red or green signal 122 that is visible to the body 108 within of the vehicle 24, or one or more elongated luminaires 124 that may be mounted along the perimeter of the entrance 12, preferably parallel to the vertical or horizontal edges of the entrance. Obviously, countless other light and screen arrangements are also within the scope of the invention.

To avoid sending unnecessary warnings when no body 32 is present while body 108 is loading or unloading vehicle 24, in some embodiments, security system 110 includes a body sensor 70 to detect the presence of body 32 that is within the vehicle. area 66 adjacent to entrance 12. In this case, alarm system 110 provides a visual or audible alarm signal only if both bodies 32 and 108 are present. Thus, an alarm is only activated in response to the combination of a potentially hazardous situation on loading dock 106 plus the presence of a body (eg, body 32) that could be adversely affected by the hazard.

Sensor 112 is best mounted in a location where it can detect the presence of body 108 deep within vehicle 24, yet sensor 112 is preferably located where it is unlikely to be struck by body 108 entering or leaving. the vehicle 24. It may be desirable to have two sensors 112 at the top two corners of the inlet 12 or to have a single sensor 112 located centrally above the inlet. If sensor 112 is located in a location where body 108 could strike it, sensor 112 is preferably mounted on a movable bracket 126 that can yield in response to shock against a sensor 112. Brace 126, for example, may include a pivoting or elastic arm 128 that can bend or rotate outward upon collision with it and then automatically return to its original position. The clamp 126 may be designed to hold a single sensor or a series of sensors.

As an alternative to mounting the sensor 112 outside of the vehicle 24 and "facing inward", Figure 12 shows a security system 130 in which a body sensor 132 comprises an infrared transmitter 134 mounted on the body 108 and a receiver. corresponding 134 installed inside the building. The presence of body 108 within vehicle 24 is detected when transmitter 134 transmits an infrared detection signal 136 through interior 116 of vehicle 24 to receiver 134. Transmitter 134 is preferably mounted to the rear of body 108, with receiver 134 mounted to "orient" into vehicle 24, such that body 108 is only detected when it has fully penetrated vehicle 24. Connecting the alarm system 11 in effective communication with the receiver 134 allows the security system 130 to function in a manner similar to that of the system 110. It will be appreciated that mounting the transmitters 134 on individuals would allow them to be detected within the vehicle as well.

Figure 13 shows another security system 138 that is similar to system 110; however, a mirror 140 reflects a detection signal 142 from a sensor 70 to detect the presence of the body 108 within the vehicle 24. The mirror 140 allows the sensor 70 to be mounted in a location where the sensor 70 is less likely to be hit by the body 108. To protect mirror 140 from damaging impact, mirror 140 may be supported by an elastically bendable bracket 144.

ES 2 392 908 T3

In some embodiments, a building loading dock security system alerts workers on a dock within the building when there is a risk of falling due to the gate or barrier being open while no truck is present in the building. dock.

In some embodiments, the dock includes a barrier in addition to a gate, and in other embodiments, the gate itself serves as a barrier and the additional barrier is omitted.

In some embodiments, the barrier is attached to the door, and in other embodiments, the barrier is mounted separate from the door.

In some embodiments, a sensor determines whether a truck or other type of vehicle is within a certain distance from the entrance, where the certain distance is sufficient for the lip of a dock leveler to rest on the base of the truck.

In some embodiments, a sensor determines whether a truck or other type of vehicle is within a certain distance from the entrance, where the certain distance is sufficient for a vehicle retainer to engage the ICC bar of a truck (crash protection rear).

In some embodiments, a sensor determines whether a body crosses a line of sight to enter an area or approach within a certain distance from the entrance.

In some embodiments, a remote body sensor in the form of a strain gauge or scale associated with a dock leveler determines when the weight of a person or object is on the dock leveler cover, whereby the sensor can determine if the body is near the entrance.

In some embodiments, the security system does not respond to a remote body sensor when the door is closed.

In some embodiments, the security system uses both visual and audible alarms to indicate different levels of possible danger.

In some embodiments, the security system provides a date and time stamp that identifies when a risky situation may have occurred.

In some embodiments, the security system "faces" into a trailer to determine if a lift truck or other material handling equipment is present.

In some embodiments, a security system sends a lift car detection signal into a trailer, and in other embodiments, the signal originates from the lift car and is transmitted out through the trailer. In either case, the signal is used to determine if the lift truck (or other type of material handling equipment) is operating inside the trailer.

In some embodiments, the security system only generates an alarm when the combination of both a potential hazard and a potentially endangered person is at a loading dock.

In some embodiments, an elongated light illuminates the perimeter of a loading dock entrance to indicate that a hazard, such as a lift truck operating inside a trailer, may be near the entrance.

It should be appreciated by those of ordinary skill in the art that various modifications are within the scope of the invention determined by reference to the appended claims.