1.  Field of the Invention
The present invention relates in general to a bumper device for an automated guided vehicle (AGV). 
2.  Description of the Related Art
An AGV is an apparatus for a factory automation system, for conveying goods, articles, etc.  without manipulation by hand in a factory. 
The AGV automatically travels along a predetermined path by a controller (not shown) installed therein, and thus the AGV is equipped with a bumper device protecting a vehicle body in preparation for a possible impact on running. 
A conventional bumper device 201 for an AGV 205, as shown in FIG.  9, comprises a bumper member 280 installed at a circumference of a vehicle body 207, and an impact sensor 290 installed inside the bumper member 280. 
The bumper member 280 is made of an elastic material such as rubber, plastics, etc.  in order to absorb a shock generated when the AGV 205 impacts on other objects.  Further, the impact sensor 290 is of a shape corresponding to the bumper member 280 so as to sense an impact given on the bumper member 280.  The impact sensor 290 is installed inside the bumper member 280 by way of an insert molding.  Further, the impact sensor 290 is electrically connected to the controller of the AGV 205. 
With this configuration, in the conventional bumper device 201, if the AGV 205 impacts on other objects, the bumper member 280 absorbs the impact, and the impact sensor 290 senses the impact transmitted from the bumper member 280 and transmits it to the controller (not shown) of the AGV 205.  Then, the controller stops the AGV 205. 
However, in the conventional bumper device, because the impact sensor is insert-molded in the bumper member, it is impossible to sense an impact generated beyond a sensing area.  That is, there is a problem that the sensing area is limited with respect to regions and direction in which impacts are generated. 
In addition, because the impact sensor is insert-molded inside the bumper member, a distance between an impact position and the impact sensor may be not uniform due to a molding tolerance, a dimensional tolerance, or etc.,  during a manufacturing process thereof.  Thus, a sensitivity of the impact sensor may be different according to an impact region of the bumper device. 
Moreover, because the bumper member is fixed on the AGV and absorbs an impact with elasticity of the bumper member itself, the bumper device has limitations in an absorbing capability. 
Accordingly, the present invention has been made keeping in mind the above-described shortcoming and user""s need, and an object of the present invention is to provide a bumper device for an AGV, which can promptly sense and effectively absorb an impact given from every region and every direction. 
This and other objects of the present invention may be accomplished by the provision of a bumper device for an AGV comprising a bumper which absorbs a shock generated in a backward direction of a bumper supporting member combined with a vehicle body of the AGV.  The bumper is supported on the bumper supporting member.  The bumper device includes a movement supporting means installed at the bumper supporting member to movably support the bumper, and a movement sensor to sense a movement of the bumper. 
Preferably, the movement supporting means includes a backward and forward shock absorber. 
Effectively, the backward and forward shock absorber is comprised of a guide provided on the bumper supporting member along a backward and forward direction; a supporting slider coupled to the guide so as to slide backward and forward, and supporting the bumper; a backward and forward shock absorbent member installed at the bumper supporting member at the rear of the supporting slider and elastically diminishing a backward movement of the supporting slider. 
Preferably, the backward and forward shock absorbent member is comprised of a spring supporter installed at the rear of the guiding slider, and a backward and forward shock absorbent spring held between the spring supporter and the supporting slider. 
Effectively, at the spring supporter is installed a spring holding shaft supporting the backward and forward shock absorbent spring; and on the supporting slider is formed a shaft hole through which the spring holding shaft passes. 
Preferably, the movement supporting means includes a multi-directional shock absorber installed in front of the supporting slider and absorbing multi-directional shock of the bumper. 
Effectively, the multi-directional shock absorber is comprised of a slider connector combined to the supporting slider; a bumper connector combined to the bumper; and a universal joint movably combining the slider connector with the bumper. 
Preferably, one end of the bumper connector directly toward the bumper is combined with a rotary shaft perpendicular to a sliding direction of the supporting slider; and on the bumper is provided a rotary shaft accommodating part rotatably combined to the rotary shaft. 
Effectively, the bumper is comprised of a bumper plate perpendicular to the guide, and an elastic absorbent member combined on the front of the bumper plate; and the rotary shaft accommodating part is provided on the rear of the bumper plate. 
Preferably, the bumper device further comprises a multi-directional shock absorbent spring surrounding the multi-directional shock absorber between the supporting slider and the bumper and absorbing the shock of impact on the bumper. 
Effectively, the movement sensor includes a sensor plate combined to the bumper and having a sensing hole thereon; a light element emitting light passing through the sensing hole; and a light receiving element sensing the light passed through the sensing hole from the light element. 
Preferably, the bumper device further comprises a droop preventive unit having one end combined to the bumper supporting member and the other end contacting with a rear lower part of the bumper, in order to prevent the bumper from drooping. 
Effectively, the droop preventive unit is comprised of a hollow plunger-accommodating member combined to the bumper supporting member; a plunger spring accommodated in the plunger-accommodating member; and a plunger accommodated in the plunger-accommodating member and contacting with a rear lower part of the bumper by elasticity of the plunger spring. 
Preferably, the movement supporting means is provided in pairs at opposite sides of the bumper plate.