Transport with rotatable load and safety bumper

A vehicle having (i) a rotatable platform for securing a load thereto, and (ii) an object detection system for detecting an object in the vehicle's path of travel. The sensitivity of the object detection system is variable so that it can be varied based on the rotated position of the load.

BACKGROUND OF THE INVENTION

The present invention is generally directed to material handling vehicles and, more particularly, to a vehicle having a rotatable platform upon which to secure a load and an adjustable safety bumper.

Automatic guided vehicles (AGVs) are used throughout the material handling industry to transport loads. The term AGV is commonly used to refer to robust vehicle designs having any of a number of available automated guidance systems. Automatic guided carts (AGCS) is a term commonly used to refer to a less robust vehicle used for similar but smaller-scale applications. Current AGC designs generally include a frame with swivel castors located at the four corners of the frame. Other features may include a drive wheel assembly and rigid castors for directional control of the cart. In one current design, two rigid castors are fixed to the frame and located approximately midway between the swivel castors on each side of the cart frame. The two pair of swivel castor axes and the rigid castor axis are generally parallel to each other. The steerable driving unit is attached to the cart frame, generally by way of a plate that is hinged and spring loaded from the cart frame to ensure that the steerable drive wheel maintains adequate traction with the support surface.

It is known in the art for an AGV to include a rotatable platform that is attached to the cart frame to which the load may be secured. The rotatable platform allows for the load to be rotated as desired and independently of the direction of travel of the AGV. This is particularly useful in a manufacturing assembly line where the load comprises a workpiece that is operated upon by a worker. It may be advantageous for the workpiece to rotate so that the worker is able to operate upon all sides of the workpiece while remaining in the approximately same position in relation to the AGV.

Various safety mechanisms are currently utilized to prevent an AGV from colliding with persons or other objects, or injuring a person or damage to an object if a collision occurs. Sonic or optical sensors may be utilized to detect an object within a predetermined distance in the AGV's path of travel and, if an object is sensed, the AGV halts movement. A mechanical bumper may also be used, in conjunction with or separate from the object detection sensors described above, to prevent injury resulting from a collision. The bumpers are commonly composed of a “soft” material, e.g., rubber, that will absorb the energy from a collision. Pressure sensors may be disposed on or within a bumper to detect a collision and halt the travel of the AGV.

Despite the presence of the individual components described above, their satisfactory combination has yet to be addressed in the art. A rotatable load that is larger than the AGV and asymmetrical, e.g., longer than it is wide, presents a number of operational difficulties with the known safety mechanisms described above.

SUMMARY OF THE INVENTION

In view of the above, a need exists for an AGV design that effectively combines the convenience of a rotatable load mounting platform with the safety and operational characteristics of object detection safety mechanisms. More particularly, a need exists for an AGV design that allows for adjusting the detection distance of the safety mechanism based on the rotated position of the load.

To meet these and other needs that will be apparent to those skilled in the art based upon this description and the appended drawings, the present invention is directed to a vehicle having a drive frame for propelling the vehicle in response to a drive control signal. The drive frame is connected with a rotatable load platform. A controller is operatively coupled to the drive frame and generates the drive control signal. An object detector is operatively coupled to the controller and communicates with the controller when it senses an object within a predetermined distance of the vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An automated guided vehicle10according to the present invention is illustrated and described with reference toFIGS. 1-6. It should be appreciated that the applications for the rotatable load with safety bumper according to the present invention may be used in a variety of applications beyond the illustrated AGV. For example, the present invention may be used with automated guided vehicles of a variety of configurations as well as other material handling vehicles, including but not limited to overhead material handling vehicles. The term vehicle as used herein is meant to be inclusive of all types of material handling apparatuses, and is not limited to an AGV as is described below in relation to a preferred embodiment.

The AGV10includes a drive frame12supported at each of its corners by swivel castors14. The drive frame12includes a drive wheel20, and a pair of rigid castors22. The drive wheel20and rigid castors22are each fixed for movement with the drive frame12. As is conventionally known, the drive wheel20is rotatable about a drive axis and a steering axis. Each of the rigid castors22are rotatable only about a single axis oriented perpendicular to the AGV's longitudinal axis. Accordingly, when the rigid castors are engaged with the cart support surface, the castors tend to maintain the directional control of the cart in its axial direction.

A load platform30is secured to the drive frame12by means of a swivel mechanism32. The load platform30is specially designed in order to receive and secure the load40. InFIG. 3, a load platform30with frame mounts36designed to receive an automobile frame as the load40is illustrated. The frame mounts36are arranged such that they mate with the load40at specified securing points42. In this way, the load40is restricted from moving independently of the load platform30. Various other means of securing the load40to the load platform30, for example using lag bolts and nuts, are well known in the art and could be used.

The swivel mechanism32, illustrated inFIG. 5, allows the load platform30to rotate in relation to the drive frame12. The swivel mechanism32is preferably composed of a ball bearing swivel. The swivel mechanism32may have memory positions, which provide for specific rotated stop positions. These memory positions may comprise physical detents that provide positive stops or, in the case of automatic rotation of the swivel mechanism32, electric memory stops, or both. In this way, the load40may be rotated to determined positions with high accuracy. Additionally, the swivel mechanism32preferably includes a locking mechanism34that, when engaged, locks the load40in any rotated position. The locking mechanism34may take the form of any of the well known locking mechanisms in the art, for example using locking gears, a magnetic stop, or the use of a cam-bar or a locking pin connected to one portion of the swivel mechanism32to engage a recess in the other portion of the swivel mechanism32. In a preferred embodiment illustrated inFIG. 5, the locking mechanism34comprises a locking pin35coupled to the swivel mechanism32and including a spring37. The spring37is arranged such that the locking pin35is biased to remain engaged with recess39in the locked position. In this embodiment, a force must be applied to the locking pin35to compress the spring37and disengage the locking mechanism34. Alternatively, the force may be applied directly to the spring37itself. In either case, once this force is removed, the spring37expands and directs the locking pin35to engage the recess39in the locked position.

The swivel mechanism32preferably may be operated both manually and automatically. In manual operation, a worker first disengages the locking mechanism34and then applies a rotational force to the load platform30. This rotational force may also be applied to the load40, however the load40should be rigidly secured to the load platform30to prevent load disengagement and risk of injury. The worker then may rotate the load platform30to the desired position, and engage the locking mechanism34to prevent further rotation. The rotational force may also be generated by an electric motor or hydraulic system in response to a signal from the worker, e.g., by remote control.

In automatic operation, the load platform30will rotate as the AGV travels along its path. The rotational positions may be programmed into a controller16on the AGV. Alternatively, the controller16may receive rotation instructions as the AGV moves along its path of travel, as is known in the art. It should be appreciated that the controller16may be a microcontroller, a servo mechanism communicating with a remote controller, or any other means for controlling, including but not limited to a receiver in communication with the motor or motors used to propel the AGV10, rotate the load platform30, etc. Once the controller16determines that the load platform30should be rotated, the locking mechanism34is first disengaged in response to an instruction from a controller16. The controller16then sends a signal to a rotation mechanism, preferably an electric motor, which generates a rotational force to be applied to the swivel mechanism32. The magnitude, direction, and duration of this rotational force is determined by the controller16to ensure that the load platform30is rotated to the proper rotated position. Once the load platform30has reached the proper rotated position, the controller16then instructs the locking mechanism34to engage, thereby inhibiting further rotation.

The AGV further includes an object detection system50. The object detection system50is designed to alter the travel of the AGV when an object is detected in the AGV's path of travel. In a preferred embodiment, the AGV stops when an object is detected. The object detection system50includes at least one sensor52and is in communication with the drive frame12through the controller16. The sensor52is disposed on one end of the AGV, preferably the front end, and operates to detect physical objects within its range of detection in the path of travel of the AGV10when it is moving forward. Additional sensors52may be disposed on other ends of the AGV10, to detect objects in the path of travel of the AGV10when it is moving in a direction other than forwards, for example, a sensor52disposed on the rear of the AGV10to detect objects when it is moving backwards. The sensor52preferably has variable sensitivity, so that its range of detection may be adjusted. The range of detection of the sensor is preferably adjusted automatically by the controller16, based upon certain conditions. One of the conditions is the speed of the AGV. It is preferred to have a longer range of detection as the speed of the AGV increases. Additionally, the range of detection is preferably adjusted based on the rotated position of the load platform30, as described below.

It may be advantageous to adjust the range of detection based upon the rotated position of the load40. This is particularly true in the event that the load40is asymmetrical and larger than the AGV10. An example of this situation is illustrated inFIGS. 1 and 2. InFIG. 1, a load40is shown that is rotated perpendicular to the drive frame12. InFIG. 2, the load40is aligned to the drive frame12and, in the shadow lines, aligned at an angle to the drive frame12. As is plainly shown, the front of the loaded AGV varies in distance from the object detection system50depending on the rotated position of the load40. InFIG. 1, the frontmost portion of the loaded AGV10is the object detection system50itself. Therefore, the range of detection can be relatively short. InFIG. 2, however, the frontmost portion of the loaded AGV10is the front44of the load40. Therefore, the range of detection should be relatively long in this instance.

In a preferred embodiment, the controller16is programmed to include predetermined ranges of detection for every given rotated position, for example, in a look up table. The controller16is in communication with a rotation sensor18that is capable of determining the rotated position of the load platform30. Based on the rotated position provided by the rotation sensor18, the controller16adjusts the range of detection of the sensor52. One alternative embodiment of the invention includes a distance sensor in the object detection system50, whereby the distance sensor determines the distance to the frontmost portion of the AGV, and the range of detection is adjusted based on this distance, preferably by adding to it a buffer distance. Another alternative embodiment includes eliminating the rotation sensor18and only allowing automatic rotation of the load platform30. In this embodiment, the controller16may be preprogrammed with the ranges of detection for the planned rotated positions and, when the controller16instructs the rotation mechanism to move to each rotated position, the controller16adjusts the range of detection based on that preprogrammed for that rotated position.

In a preferred embodiment, the bank length60of the AGV10is also adjusted based on the rotated position of the load platform30. As two AGV's move into proximity of each other in the direction of travel, it is desirable to control the distance between them such that they do not collide with each other. One method of controlling this distance is to choose a minimum distance, i.e., a bank length60, to be maintained between AGV's at all times. If an AGV10senses another AGV at a distance equal to or less than its bank length60, the controller16will instruct the drive train12to cease movement toward the other AGV.

In a preferred embodiment, illustrated inFIG. 6, the bank length60comprises the distance between the centerpoints of two AGV's. It is desirable to choose a bank length60that is as short as practical such that the amount of space occupied by a given number of AGV's is minimized. In order to accomplish this, the bank length60is variable based on the length of the load40in the direction of travel of the AGV10. As described above, this length is dependent on the rotated position of the load platform30.

FIG. 6shows a plurality of AGV's10a-daccording to the present invention, each of which include an object detection system50and are traveling along the dotted path70in the direction of arrow72. As stated above and illustrated in this figure, the bank length60for a given AGV10can be minimized as the length of the load40in the direction of travel of the AGV10decreases. Therefore, the bank length60for AGV's10cand10dcan be chosen to be shorter than the bank length60for AGV's10aand10b. InFIG. 6, AGV's10band10cwill be precluded from moving in the direction of arrow72because of the position of AGV's10cand10d, respectively, while AGV's10aand10dare free to move in the direction of arrow72.

The controller16may be programmed to include predetermined bank lengths for every given rotated position, for example, in a look up table. The controller16is in communication with a rotation sensor18that is capable of determining the rotated position of the load platform30. Based on the rotated position provided by the rotation sensor18, the controller16determines the appropriate bank length60, which is then communicated to the drive frame12. Similar to that described above in relation to the range of detection, another alternative embodiment includes eliminating the rotation sensor18and only allowing automatic rotation of the load platform30. In this embodiment, the controller16may be preprogrammed with the bank lengths for the planned rotated positions and, when the controller16instructs the rotation mechanism to move to each rotated position, the controller16selects the bank length that was preprogrammed for that rotated position.

The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.