Patent Description:
In warehouses and similar environments, lift trucks are typically used to pick up and deliver goods for further transport or processing. One type of lift truck comprises a load handling assembly including a mast assembly and a carriage assembly comprising a pair of laterally spaced apart forks, wherein the carriage assembly is laterally movable via a sideshift assembly. This type of lift truck also includes laterally spaced apart outriggers adjacent to the forks.

When the load handling assembly is located in a home or fully lowered and retracted position, the mast assembly, carriage assembly, and forks are located between the outriggers and the forks are vertically positioned in plane with the outriggers. However, when the carriage assembly is lifted and/or when the mast assembly or carriage assembly is moved longitudinally away from the truck frame, the load handling assembly is moved from its home position. When a reach-in function (where the mast or carriage assembly is moved longitudinally back toward the home position) or a lowering function (where the carriage assembly and the forks are lowered back toward the home position) is requested, steps must be taken once the load handling assembly reaches a predetermined threshold height to ensure that the forks and/or a load carried by the forks do not contact the outriggers.

Such steps include an operator visually inspecting the position of the forks/load and activating an override command to allow continued movement of the load handling assembly back to the home position. If the operator determines that contact will or may occur between the forks/load and the outriggers, steps must be taken by the operator, e.g., adjusting the position of the forks/load with the sideshift assembly or repositioning the load, to clear the forks/load of the outriggers before continued movement of the load handling assembly back to the home position can be carried out.

<CIT> discloses a reach-type forklift truck comprising a load handling assembly which further comprises an optical contactless sensor structure that monitors for conditions wherein movement of the carriage assembly could result in contact between the load and at least one of the outriggers; and wherein a vehicle controller receives a signal from the optical sensor structure and prevents movement of the carriage assembly in a direction toward the at least one of the outriggers if the signal from the optical sensor structure indicates that the mast is retracted between the outriggers and the forks are lowered to a predetermined height, wherein such movement could result in contact between the load and the at least one of the outriggers.

The present invention relates to lift trucks that include sensor structure for detecting potential contact between a load carried by the forks and outriggers of the truck extending longitudinally away from a truck frame.

In accordance with an aspect of the present invention, a lift truck is provided comprising a frame defining a main structural component of the lift truck; a pair of laterally spaced apart outriggers extending from the frame, each outrigger including at least one wheel; a vehicle controller for controlling at least one function of the lift truck; and a load handling assembly secured to the frame adjacent to the outriggers. The load handling assembly comprises a mast assembly positioned between the outriggers and a carriage assembly including fork structure for supporting a load on the load handling assembly. The carriage assembly is movable vertically along the mast assembly and the fork structure is also moveable laterally with respect to the mast assembly via a sideshift assembly. The lift truck further comprises an optical sensor structure that monitors for conditions wherein movement of the carriage assembly would result in contact between the load and at least one of the outriggers. The optical sensor structure comprises a pair of laterally spaced apart contactless optical sensors. Each contactless optical sensor is located adjacent to a corresponding outrigger and monitors a respective area around the corresponding outrigger for a portion of the load to enter the respective area. The vehicle controller receives a signal from the optical sensor structure and prevents movement of the carriage assembly in a direction toward the at least one of the outriggers if the signal from the optical sensor structure indicates that such movement would result in contact between the load and the at least one of the outriggers. A portion of the load entering the respective area causes the vehicle controller to prevent movement of the carriage assembly toward the at least one of the outriggers.

The fork structure may comprise a pair of laterally spaced apart forks extending longitudinally away from the frame.

The area monitored by each contactless optical sensor may extend longitudinally forward from and vertically downward from the respective contactless optical sensor. The contactless optical sensors, which may be laser sensors, may be located laterally inwardly of the corresponding outriggers, and may be affixed to the mast assembly.

The vehicle controller may be capable of operating the sideshift assembly to cause the carriage assembly to move to a position such that the load is centered with respect to the outriggers if the signal from the optical sensor structure indicates that movement of the carriage assembly toward at least one of the outriggers would result in contact between the load and the at least one of the outriggers. The vehicle controller may operate the sideshift assembly to cause the carriage assembly to move only upon authorization to do so by an operator. The controller may discontinue attempting to center the load with respect to the outriggers after the expiration of a predetermined time period.

The load handling assembly may only be movable to a home position if the signal from the optical sensor structure does not indicate that such movement would result in contact between the load and the outriggers.

The mast assembly may be movable in a longitudinal direction relative to the frame, and the optical sensor structure may also monitor for conditions wherein movement of the mast assembly would result in contact between the load and at least one of the outriggers. Further, the vehicle controller may also prevent movement of the mast assembly in a direction toward the at least one of the outriggers if the signal from the optical sensor structure indicates that such movement would result in contact between the load and the at least one of the outriggers.

The lift truck may further comprise a control element that is adapted to be implemented by an operator to override the prevention of movement of the carriage assembly in the direction toward the at least one of the outriggers even if the signal from the optical sensor structure indicates that such movement would result in contact between the load and the at least one of the outriggers. The operator may be able to override the prevention of movement of the carriage assembly in the direction toward the at least one of the outriggers for as long as the operator implements the control element.

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, specific preferred embodiments in which the invention may be practiced.

<FIG> illustrates a rider reach fork lift truck <NUM> according to an aspect of the present invention. The truck <NUM> includes a frame <NUM> defining a main structural component and which houses a battery <NUM> for supplying power to a traction motor (not shown) connected to a steerable wheel <NUM> and to one or more hydraulic motors (not shown), which supply power to several different systems, such as hydraulic cylinders for effecting generally vertical movement of movable mast members <NUM>, <NUM>, generally vertical movement of a carriage assembly <NUM> relative to mast member <NUM>, generally longitudinal movement of a scissors reach assembly <NUM>, and generally transverse movement of a fork carriage <NUM> relative to a carriage plate <NUM>. The traction motor and the steerable wheel <NUM> define a drive mechanism for effecting movement of the truck <NUM>. An operator's compartment <NUM> in the frame <NUM> is provided with a steering tiller (not shown) for controlling the direction of travel of the truck <NUM>, and a control handle <NUM> for controlling travel speed as well as fork height, extension, sideshift, and tilt. The speed of the truck <NUM> is measured by a tachometer, represented at <NUM>, included within the truck <NUM> in a conventional manner. A pair of outriggers <NUM>, each including at least one wheel 24A, extends longitudinally from the frame <NUM>, and an overhead guard <NUM> is placed over the operator's compartment <NUM>.

A load handling assembly <NUM> of the truck <NUM> includes, generally, a mast assembly <NUM> and the carriage assembly <NUM>, which is movable vertically along the mast assembly <NUM>. The mast assembly <NUM> is positioned between the outriggers <NUM> and includes a fixed mast member <NUM> affixed to the frame <NUM>, and nested lower and upper movable mast members <NUM>, <NUM>. As noted above, hydraulic cylinders (not shown) are provided for effecting movement of lower and upper mast members <NUM>, <NUM>, the carriage assembly <NUM>, the reach assembly <NUM> and the fork carriage <NUM>.

The carriage assembly <NUM> includes fork structure comprising a pair of forks <NUM> mounted to the fork carriage <NUM>, which is in turn mounted to the carriage plate <NUM> of the carriage assembly <NUM>. As shown in <FIG>, a load backrest <NUM> of the carriage assembly <NUM> extends generally vertically relative to the forks <NUM> and defines a surface 44A that provides a back stop for a load carried on the forks <NUM>.

As described in <CIT>, the carriage plate <NUM> is attached to the upper mast member <NUM> of the mast assembly <NUM> by the scissors reach mechanism <NUM> of the carriage assembly <NUM>. The reach mechanism <NUM> extends between the carriage plate <NUM> and a reach support <NUM>, which is mounted to the upper mast member <NUM> as shown in <FIG> for vertical movement relative to and with the upper mast member <NUM>.

An electrical proportional hydraulic valve (not shown) coupled to a vehicle controller <NUM> controls and directs hydraulic fluid to the mast assembly hydraulic cylinders. An operator controls the height of the forks <NUM> via the control handle <NUM>, which is also coupled to the controller <NUM>. In response to receiving fork elevation command signals from the handle <NUM>, the controller <NUM> generates control signals of an appropriate pulse width to the valve and further generates control signals so as to operate one or more hydraulic fluid pumps (not shown) at an appropriate speed to raise the forks <NUM>. In response to receiving fork lowering command signals from the handle <NUM>, the controller <NUM> generates control signals of an appropriate pulse width to the valve so as to lower the forks <NUM>. The control handle <NUM> is also used to control extension and retraction of the reach mechanism <NUM>, as well as sideshift functions of the carriage assembly <NUM>, which will be described in greater detail below. As shown in <FIG>, the movable mast members <NUM>, <NUM>, as well as the reach support <NUM>, are raised, and the reach mechanism <NUM> is extended. As used herein, the term "controller" is meant to encompass a single master controller or multiple dedicated controllers that control one or more functions of the truck <NUM>.

The truck <NUM> also includes optical sensor structure <NUM>, which in the embodiment shown comprises first and second contactless optical, e.g., laser, sensors <NUM> (only one sensor <NUM> is shown in <FIG>) affixed to opposed outer sides of the fixed mast member <NUM>. The sensors <NUM> are preferably located adjacent, i.e., in close proximity to the outriggers <NUM>, although the sensors <NUM> could be located in other suitable locations, such as the alternate location marked in <FIG> as ALT. As will be described in greater detail herein, the sensors <NUM> monitor respective areas around the outriggers <NUM> for a portion of a load carried on the forks <NUM> to enter the respective area, wherein signals from the sensors <NUM> are sent to the controller <NUM>. The controller <NUM> uses the signals from the sensors <NUM> to ensure that contact between the load and the outriggers <NUM> does not occur, e.g., as a result of longitudinal, vertical, or lateral movement of the carriage assembly <NUM> toward a home position, to be described below.

<FIG> and <FIG> illustrate another type of lift truck <NUM> that the sensor structure <NUM> described above is usable with. The lift truck <NUM> shown in <FIG> and <FIG> includes a frame <NUM> defining a main structural component and which houses a battery <NUM> for supplying power to a traction motor (not shown) connected to a steerable wheel (not shown) and to one or more hydraulic motors (not shown) which supply power to several different systems, such as mast and fork hydraulic cylinders. The traction motor and the steerable wheel define a drive mechanism for effecting movement of the truck <NUM>. An operator's compartment <NUM> in the frame <NUM> is provided with a steering control <NUM> (see <FIG>) for controlling the direction of travel of the truck <NUM>, and a control handle <NUM> for controlling fork height, mast extension, sideshift, and tilt. A pair of outriggers <NUM>, each including at least one wheel 124A, extends longitudinally from the frame <NUM>. An overhead guard <NUM> is placed over the operator's compartment <NUM>.

A load handling assembly <NUM> of the truck <NUM> includes, generally, a mast assembly <NUM>, a carriage assembly <NUM> mounted to the mast assembly <NUM>, and a displacement assembly <NUM> to which the mast assembly <NUM> is mounted. The displacement assembly <NUM> is longitudinally movable relative to the frame <NUM>. The carriage assembly <NUM> is movable vertically along and with the mast assembly <NUM>. The mast assembly <NUM> is positioned between the outriggers <NUM>, and in the embodiment shown comprises lower and upper mast sections <NUM>, <NUM>, although the truck <NUM> could include additional or fewer mast sections. A mast assembly hydraulic cylinder is provided to effect movement of the upper mast section <NUM> relative to the lower mast section <NUM>. A tilt hydraulic cylinder is provided for effecting tilting movement of the mast assembly <NUM> relative to the displacement assembly <NUM>. As noted above, the mast assembly <NUM> is movable longitudinally relative to the frame <NUM>, i.e., the mast assembly <NUM> is capable of movement generally horizontally and generally parallel to level ground toward and away from the frame <NUM> via the displacement assembly <NUM> (the mast assembly <NUM> is shown in a retracted position, e.g., adjacent to the frame <NUM> in <FIG>, and an extracted position, e.g., spaced from the frame <NUM> in <FIG>). The operation of the displacement assembly <NUM> is conventional and will not be described in detail herein.

The carriage assembly <NUM> includes fork structure comprising a pair of forks <NUM> mounted to a fork carriage <NUM>. The fork carriage <NUM> is mounted to a lifting carriage <NUM> (see <FIG>), which is in turn mounted to the mast assembly <NUM> in a conventional manner. A conventional sideshift assembly <NUM> comprising a sideshift hydraulic cylinder is provided for effecting lateral or transverse movement of the fork carriage <NUM> relative to the lifting carriage <NUM>. It is noted that the fork carriage <NUM> may be tiltable relative to the lifting carriage <NUM> in lieu of the mast assembly <NUM> being tiltable relative to the displacement assembly <NUM>.

An electrical proportional hydraulic valve (not shown) coupled to a vehicle controller <NUM> controls and directs hydraulic fluid to the mast assembly and carriage assembly hydraulic cylinders. An operator controls the height of the forks <NUM> via the control handle <NUM>, which is also coupled to the controller <NUM>. In response to receiving fork elevation command signals from the handle <NUM>, the controller <NUM> generates control signals of an appropriate pulse width to the valve and further generates control signals so as to operate one or more hydraulic fluid pumps (not shown) at an appropriate speed to raise the forks <NUM>. In response to receiving fork lowering command signals from the handle <NUM>, the controller <NUM> generates control signals of an appropriate pulse width to the valve so as to lower the forks <NUM>. The controller <NUM> is also used to control extension and retraction of the displacement assembly <NUM>, as well as sideshift functions of the carriage assembly <NUM>, which will be described in greater detail below.

The truck <NUM> also includes optical sensor structure <NUM>, which in the embodiment shown comprises first and second optical, e.g., laser, sensors <NUM> affixed to opposed outer sides of the lower mast member <NUM>. The sensors <NUM> are preferably located adjacent, i.e., in close proximity to the outriggers <NUM> and laterally inwardly of the corresponding outriggers <NUM>, although the sensors <NUM> could be located in other suitable locations. The sensors <NUM> monitor respective areas A<NUM> around the outriggers <NUM> for a portion of a load carried on the forks <NUM> to enter one or both of the respective areas A<NUM>, wherein signals from the sensors <NUM> are sent to the controller <NUM>. The controller <NUM> uses the signals from the sensors <NUM> to ensure that contact between the load and the outriggers <NUM> does not occur, e.g., as a result of vertical or lateral movement of the carriage assembly <NUM> and/or longitudinal movement of the mast assembly <NUM>. The general areas A<NUM> monitored by the sensors <NUM> can be seen in <FIG> and <FIG>. As shown, the areas A<NUM> monitored by the sensors <NUM> extend longitudinally forward from and vertically downward from each respective sensor <NUM>.

When the carriage assembly <NUM> is above a predetermined threshold height, which may be, for example, about <NUM> (about <NUM> inches), or when the mast assembly <NUM> is in a fully extended position such that the fork carriage <NUM> is located forward of the outriggers <NUM>, the truck controller <NUM> assumes that there would be no potential contact between a load <NUM> carried on the forks <NUM> and the outriggers <NUM>. In either of these situations, full operation of the load handling assembly <NUM>, including raise/lower, sideshift, reach, tilt, etc., is enabled. However, if each of these criteria is not met, the controller <NUM> may restrict one or more functions of the load handling assembly <NUM>, as will now be described.

Referring to <FIG>, the load handling assembly <NUM> of the truck <NUM> illustrated in <FIG> and <FIG> is shown in various positions. <FIG> and <FIG> illustrate the load handling assembly <NUM> in a fully retracted and lowered position, referred to herein as a "home position," and <FIG> illustrate the load handling assembly <NUM> not in fully retracted and/or lowered positions, referred to herein as "non-home positions.

As shown in <FIG> and <FIG>, the mast assembly <NUM> is in a fully retracted position, i.e., the mast assembly <NUM> is located immediately adjacent to the truck frame <NUM>, and the carriage assembly <NUM> is in a fully lowered position, below the threshold height. The load <NUM> carried on the forks <NUM> is completely located between the outriggers <NUM> in <FIG> and <FIG>, i.e., first and second lateral edges 200A, 200B of the load <NUM> are located laterally inwardly from the respective outriggers <NUM>. With the load <NUM> in the position shown in <FIG> and <FIG>, raising and lowering of the carriage assembly <NUM> is enabled by the controller <NUM>, as well as movement of the mast assembly <NUM> laterally away from the vehicle frame <NUM> and then back toward the vehicle frame <NUM>, i.e., toward the home position.

With reference to <FIG>, the load <NUM> is not completely located between the outriggers <NUM> in each of these figures. Specifically, in <FIG>, the load <NUM> extends laterally over each of the outriggers <NUM>, the carriage assembly <NUM> is below the threshold height, and the mast assembly <NUM> is not in a fully extended position; in <FIG> and <FIG>, the load <NUM> is offset on the forks <NUM> and extends laterally over the outrigger <NUM> depicted on the right in <FIG> and <FIG> (hereinafter "right outrigger <NUM>"), the carriage assembly <NUM> is below the threshold height, and the mast assembly <NUM> is not in a fully extended position; and in <FIG>, the load <NUM> is positioned in front of the right outrigger <NUM>, the carriage assembly <NUM> is below the threshold height, and the mast assembly <NUM> is in a fully extended position.

Function of the sensors <NUM> and the controller <NUM> with respect to each of <FIG> will now be described.

With the load <NUM> in the position shown in <FIG>, each sensor <NUM> detects that a corresponding one of the first and second lateral edges 200A, 200B of the load <NUM> is positioned in the sensor's monitored area A<NUM> over a respective outrigger <NUM>. The signals from the sensors <NUM> are sent to the vehicle controller <NUM>, which prevents movement of the carriage assembly <NUM> back to the home position, i.e., in a downward direction toward the outriggers <NUM> as shown in <FIG>, as such movement would result in undesirable contact between the load <NUM> and each of the outriggers <NUM>. However, upward movement of the carriage assembly <NUM>, lateral movement of the carriage assembly <NUM>, i.e., using the sideshift assembly <NUM>, and longitudinal movement of the mast assembly <NUM> in a direction away from the truck frame <NUM> may still be enabled by the controller <NUM> with the load <NUM> in the position shown in <FIG>.

Referring now to <FIG> and <FIG>, with the load <NUM> positioned as shown, the sensor <NUM> depicted on the right in <FIG> and <FIG> (hereinafter "right sensor <NUM>") detects that the first lateral edge 200A of the load <NUM> is positioned in the monitored area A<NUM> over the right outrigger <NUM>. The signals from the right sensor <NUM> corresponding to detection of an objection in its corresponding monitored area A<NUM> are sent to the vehicle controller <NUM>, which prevents movement of the carriage assembly <NUM> back to the home position, i.e., in a downward direction toward the outriggers <NUM> as shown in <FIG> and <FIG>, as such movement would result in undesirable contact between the load <NUM> and the right outrigger <NUM>. However, upward movement of the carriage assembly <NUM>, lateral movement of the carriage assembly <NUM>, and longitudinal movement of the mast assembly <NUM> in a direction away from the truck frame <NUM> may still be enabled by the controller <NUM> with the load <NUM> in the position shown in <FIG> and <FIG>.

With the load <NUM> in the position shown in <FIG>, the right sensor <NUM> detects that the first lateral edge 200A of the load <NUM> is positioned in the monitored area A<NUM> in front of the right outrigger <NUM>. The signals from the right sensor <NUM> are sent to the vehicle controller <NUM>, which prevents movement of the mast assembly <NUM> back to the home position, i.e., in a direction toward the truck frame <NUM> and toward the outriggers <NUM> as shown in <FIG>, as such movement would result in undesirable contact between the load <NUM> and the right outrigger <NUM>. However, upward movement of the carriage assembly <NUM>, lateral movement of the carriage assembly <NUM>, and longitudinal movement of the mast assembly <NUM> in a direction away from the truck frame <NUM> may still be enabled by the controller <NUM> with the load <NUM> in the position shown in <FIG>.

In accordance with an aspect of the present invention, the signals from the sensors <NUM> may be usable by the controller <NUM> to perform an optional load centering function. For example, if the signal from one of the sensors <NUM> indicates potential contact between the load <NUM> and the corresponding outrigger <NUM>, the controller <NUM> may prompt a vehicle operator with a request for the operator to command the controller <NUM> to perform a load centering function. The prompt may be presented on a conventional user display <NUM> (See <FIG>), e.g., a touch screen, located in the operator's compartment <NUM>. If the operator accepts the prompt, the controller <NUM> operates the sideshift assembly <NUM> to move the fork carriage <NUM> of the carriage assembly <NUM> laterally until the signals from the sensors <NUM> indicate that the load <NUM> is centered with respect to the outriggers <NUM>.

Additionally, the controller <NUM> may automatically perform a load centering function, i.e., without prompting the operator, if the signal from one of the sensors <NUM> indicates potential contact between the load <NUM> and the corresponding outrigger <NUM> and the operator requests a command that would potentially cause such contact, e.g., a reach in command, wherein the mast assembly <NUM> is retracted back toward the truck frame <NUM>, or a lowering command, wherein the carriage assembly <NUM> is lowered toward the ground. If the controller <NUM> automatically performs a load centering function, the operator can control the speed of the sideshift assembly <NUM> using the control handle <NUM>, wherein the speed of the sideshift assembly <NUM> corresponds to the amplitude of the command being requested by the operator, i.e., reach in or lower command. If the operator were to release the control handle <NUM>, the amplitude of the requested command would go to zero (<NUM>), therefore stopping the sideshift assembly <NUM> and halting the automatic load centering function.

If the load centering function results in the load <NUM> being completely located between the outriggers <NUM>, i.e., wherein the first and second lateral edges 200A, 200B are located laterally inwardly from the respective outriggers <NUM>, the controller <NUM> enables movement of the load handling assembly <NUM> back to the home position until/unless the signal from one or both of the sensors <NUM> indicates potential contact between the load <NUM> and one or both of the outriggers <NUM>.

In one example of this aspect of the invention, with reference to <FIG>, the right sensor <NUM> detects that the first lateral edge 200A of the load <NUM> is positioned in front of the right outrigger <NUM>, and the signals from the right sensor <NUM> are sent to the vehicle controller <NUM>, as discussed above. In the case of the load being positioned as shown in <FIG>, if the operator accepts the load centering prompt by the controller <NUM> (assuming that an operator prompt is utilized in this example), the controller <NUM> utilizes the sideshift assembly <NUM> to move the carriage assembly <NUM> and the load to the left as shown in <FIG>. Once the load <NUM> is centered between the outriggers <NUM>, which is determined by the controller <NUM> using the signals from the sensors <NUM>, if the load <NUM> is completely located between the outriggers <NUM>, the controller <NUM> permits movement of the load handling assembly <NUM> back to the home position, i.e., by moving the mast assembly <NUM> in a direction toward the truck frame <NUM> in the configuration shown in <FIG>.

The load centering function works similarly in the configurations where the load <NUM> is located directly above the left and/or right outriggers <NUM> (rather than in front of the outriggers <NUM> as shown in <FIG>).

It is noted that in the configurations shown in <FIG>, while the loads <NUM> depicted could be centered with respect to the outriggers <NUM> in each of these figures, the load <NUM> could not be positioned completely between the outriggers <NUM> without setting the load <NUM> down and rotating the load <NUM> or picking it up from a different direction, as the loads <NUM> depicted in these figures are wider than a width between the outriggers <NUM>.

In accordance with an aspect of the present invention, a timeout algorithm may optionally be implemented to avoid a perpetual lateral oscillation of the fork carriage <NUM> between the left and right sensors <NUM> if the controller <NUM> is unable to successfully center a load <NUM> with respect to the outriggers <NUM> within a predetermined time period after commencement of the load centering function, i.e., the controller <NUM> may be programmed to discontinue the load centering function after the predetermined time period has lapsed. Upon expiration of the predetermined time period after commencement of the load centering function where the controller <NUM> is unable to successfully center the load <NUM> with respect to the outriggers <NUM>, the controller <NUM> may prevent the implementation of lowering and reach in commands until a lifting or reach out command is implemented or the operator manually adjusts the position of the load <NUM> to a centered position between the outriggers <NUM>.

It is also noted that conventional carriage assembly centering technology, wherein the carriage assembly <NUM> is centered between the outriggers <NUM> using one or more sensors and the sideshift assembly <NUM>, could be used in the trucks <NUM>, <NUM> described herein.

It is further noted that the present invention can be implemented without modification of the load <NUM>, e.g., a pallet, carried by the trucks <NUM>, <NUM>, since the sensors <NUM> are capable of detecting potential contact between the truck outriggers <NUM>, <NUM> and any object supported on the forks <NUM> that enters the monitored areas A<NUM>.

In accordance with another aspect of the present invention, the vehicle controller <NUM> may be programmed to deactivate/override the restriction of vehicle functions, such as those based on the position of the load <NUM> as described herein. For example, a control element <NUM>, illustrated in <FIG> as an icon on the user display <NUM> (although the control element could also be, for example, a knob, button, or switch provided in the operator's compartment <NUM>), may be implemented by the operator, e.g., by the operator continuously implementing the control element, during which time the operator is able to freely control all mast and carriage assembly <NUM>, <NUM> functions, including reach in, reach out, raise, lower, sideshift, etc. Upon the operator releasing the control element, the controller <NUM> may be programmed to reinstate the restriction of the vehicle functions based on the position of the load <NUM> as described herein.

While the function of the sensors <NUM> and the controller <NUM> have been discussed herein with reference to the truck <NUM> of <FIG> and <FIG>, the sensors <NUM> and controller <NUM> of the truck <NUM> described above for <FIG> function in a similar manner, with an exception that the carriage assembly <NUM> of <FIG> moves longitudinally from the mast assembly <NUM>, i.e., via the reach mechanism <NUM>, whereas the mast assembly <NUM> in the truck <NUM> of <FIG> and <FIG> moves longitudinally relative to the truck frame <NUM>. In the truck <NUM> of <FIG>, if a portion of a load is positioned immediately in front of one of the outriggers <NUM> while the carriage assembly <NUM> is in a lowered position, i.e., below a predetermined threshold height, movement of the carriage assembly <NUM> in a direction toward the mast assembly <NUM> is prevented by the controller <NUM> until the load is completely located between the outriggers <NUM>. The use of the sensors <NUM> and the controller <NUM> of <FIG> for carriage assembly lowering is the same as described above for the truck <NUM>.

Finally, as an optional feature, the lowering speed of the carriage assembly <NUM>, <NUM> may be limited depending on fork height, e.g., to soften the placement of the load <NUM> on the ground.

Claim 1:
A lift truck (<NUM>, <NUM>) comprising:
a frame (<NUM>, <NUM>) defining a main structural component of the lift truck;
a pair of laterally spaced apart outriggers (<NUM>, <NUM>) extending from the frame (<NUM>, <NUM>), each outrigger including at least one wheel;
a vehicle controller (<NUM>, <NUM>) for controlling at least one function of the lift truck (<NUM>, <NUM>;
a load handling assembly (<NUM>, <NUM>) secured to the frame (<NUM>, <NUM>) adjacent to the outriggers (<NUM>, <NUM>), the load handling assembly (<NUM>, <NUM>) comprising:
a mast assembly (<NUM>, <NUM>) positioned between the outriggers (<NUM>, <NUM>); and
a carriage assembly (<NUM>, <NUM>) including fork structure for supporting a load (<NUM>) on the load handling assembly (<NUM>, <NUM>), the carriage assembly (<NUM>, <NUM>) being movable vertically along the mast assembly (<NUM>, <NUM>) and the fork structure being moveable laterally with respect to the mast assembly (<NUM>, <NUM>) via a sideshift assembly (<NUM>);
wherein the load handling assembly (<NUM>, <NUM>) further comprises an optical sensor structure (<NUM>) that monitors for conditions wherein movement of the carriage assembly (<NUM>, <NUM>) would result in contact between the load (<NUM>) and at least one of the outriggers (<NUM>, <NUM>); wherein the optical sensor structure (<NUM>) comprises a pair of laterally spaced apart contactless optical sensors (<NUM>), each contactless optical sensor (<NUM>) being located adjacent to a corresponding outrigger (<NUM>, <NUM>) and monitoring a respective area (A<NUM>) around the corresponding outrigger (<NUM>, <NUM>) for a portion of the load (<NUM>) to enter the respective area; and
wherein the vehicle controller (<NUM>, <NUM>) receives a signal from the optical sensor structure (<NUM>) and prevents movement of the carriage assembly (<NUM>, <NUM>) in a direction toward the at least one of the outriggers (<NUM>, <NUM>) if the signal from the optical sensor structure (<NUM>) indicates that such movement would result in contact between the load (<NUM>) and the at least one of the outriggers (<NUM>, <NUM>), and wherein a portion of the load (<NUM>) entering the respective area causes the vehicle controller (<NUM>, <NUM>) to prevent movement of the carriage assembly (<NUM>, <NUM>) toward the at least one of the outriggers (<NUM>, <NUM>).