Mobile drive unit with a split chassis

Abstract

Chassis assembly of a mobile drive unit for traversing a floor, the chassis assembly comprising the following: a front chassis unit (20) including a pair of drive wheel assemblies (24L;24R) and a front steering wheel (26) mounted on a front chassis base (22); a rear chassis unit (60), including a rear steering wheel (66) mounted on the rear chassis base (62), a pivot connection between the rear chassis base (62) and the front chassis base (22); wherein each of the front and rear steering rollers (26; 66) is asymmetrically offset from a center line (CL) in the direction of travel of the chassis assembly; and which allows the swiveling connection to improve the ground contact of the drive wheels (40L; 40R) and the front and rear swivel casters (26;66) when driving over uneven ground.

Description

STATE OF THE ART

[0001] The invention relates to robot devices and methods, and in particular to mobile drive units.

[0002] The movement of products in a modern warehouse environment, such as a logistics center, is a large-scale process. One method for managing order fulfillment involves storing products in freestanding racks, known as pods, and transporting these pods using mobile drive units. Some of these mobile drive units are self-powered robotic devices that move along the warehouse floor, guided by reference markers embedded in or on the floor. The mobile drive units move beneath the desired pods, lift them from the floor, and transport them to their designated locations.

[0003] One type of mobile drive unit that has been used commercially employs a one-piece chassis with a pair of motorized center wheels, a pair of front swivel casters, and a pair of rear swivel casters, all attached to the chassis by a suspension arm. For each of the front and rear swivel casters in some prior art drive units, the left and right casters are mounted on a common shaft and spaced apart such that the left and right casters span the longitudinal centerline of the mobile drive unit. EP 3 281 848 A1 discloses a chassis comprising a front chassis unit and a rear chassis unit. The front chassis unit includes a pair of drive wheels and a front swivel caster, while the rear chassis unit includes a rear swivel caster.A pivot joint connects the two chassis units and allows them to pivot relative to each other. US Patent 6,454,286 B1 relates to a propulsion device, in particular a device for easy movement on uneven ground or an inclined surface. The device has a frame that is flexible in a central section. This frame is supported by front and rear swivel casters and central drive wheels. Patent FR 1,580,897 A discloses a vehicle with an articulated chassis in which a spring mechanism exerts a preload force between the chassis parts. US Patent 2015 / 0353280 A1 discloses a mobile drive unit for use in a warehouse system.

[0004] By increasing storage density, logistics centers can increase the quantity and potentially the variety of products stored, which generally leads to an improved customer experience. The overall height of mobile drive units is a critical variable for effectively managing storage density, especially since the height of the mobile drive unit occupies vertical space that could otherwise be used by pods to hold products. Furthermore, it is common for warehouse concrete floors to have irregularities, such as expansion joints or subsidence, inherent to the construction process or caused by floor wear or damage. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view showing a swiveling chassis configuration; Fig. Figure 2 is an exploded view of the chassis made of Fig. 1; Fig. 3 is a bottom view of the chassis made of Fig. 1; Fig. Figure 4 is a perspective view of a chassis including a cover; Fig. Figure 5 is a schematic view of a cross-section of the chassis made of Fig. 1; and Fig. 6 is another view of the chassis from Fig. 5, which represents the operation of the chassis when an irregularity occurs in the ground. DETAILED DESCRIPTION OF THE DISPLAYING FORMS

[0005] The following disclosure relates to solutions to problems arising from, or at least partially relating to, achieving a short mobile propulsion unit. One exemplary mobile propulsion unit employs a one-piece chassis with a pair of motorized center wheels, a pair of front swivel casters, and a pair of rear swivel casters, all attached to the chassis by a suspension arm. The front and rear swivel casters are aligned along a longitudinal centerline of the mobile propulsion unit. Both the front and rear have two swivel casters closely connected by a common arm, which may cause instability or rocking during operation.

[0006] A mobile drive unit configured for use in existing infrastructure includes a chassis. The chassis described herein comprises a front chassis unit and a rear chassis unit, which are interlocked such that the front and / or rear chassis can pivot around a pivot point when encountering ground irregularities. The pivoting feature of the chassis allows the overall height of the mobile drive unit to be lower compared to previous generations of similar mobile drive units.

[0007] With reference to the Fig. Figures 1-3 include a chassis 10 of a mobile drive unit, comprising a first chassis assembly, such as a front chassis assembly or unit 20, and a second chassis assembly, such as a rear chassis assembly or unit 60. The front chassis assembly 20 includes a base 22, a pair of motorized wheel assemblies 24L and 24R, and a front caster 26. In the embodiment shown in the figures, the base 22 is a one-piece aluminum casting to which the wheel assemblies 24L and 24R and the front caster 26 are mounted. The base 22 includes brackets and cutouts for receiving the wheel assemblies 24L and 24R and includes a recess for mounting the front caster 26. The base 22 also includes a pair of pivot brackets 70, as explained in more detail below.

[0008] The rear chassis assembly 60 comprises a base 62 and a rear wheel 66. The base 62 is preferably a one-piece aluminum casting having a recess for mounting the rear caster 66 and an underside recess (from above as reference number 74 in Fig. (2 shown) for mounting a ballast 94. The base 62 can also contain a holder 58 for batteries. Fig. Section 3 presents aspects of the split chassis and the relationship of the steering wheels, omitting other features such as the ballast 94.

[0009] The rear chassis assembly 60 includes a pair of forward-extending arms 68 that engage in the pivot mounts 70 of the front base 22. A pair of pins 71 ( Fig. 2) connects the arms 68 to the brackets 70 to allow the front base 22 and the rear base 62 to pivot relative to each other. The pins 71 define a chassis pivot axis PA ( Fig. 1), around which bases 22 and 62 pivot or rotate as needed. The PA axis is horizontal and transverse. The PA axis is also perpendicular to a forward direction of movement that is in Fig. 1 is represented by the line CL, since the forward direction of movement in the illustrated embodiment is parallel to the center line CL of the MDU. The center line CL bisects bases 22 and 62 and is equidistant between the drive wheel assemblies 24L and 24R.

[0010] The casters 26 and 66 are mounted on the base 22 and 62, respectively. The caster shafts extend through the base and are secured with screws. Preferably, the casters 26 and 66 are conventional and may include double wheels. The casters 26 and 66 pivot freely about the vertical axis through the shafts and are not driven. The casters 26 and 66 are asymmetrical and offset laterally from the center line CL. In the embodiment shown in the figures, the front caster 26 is spaced to the left of the center line CL, and the rear caster 66 is spaced to the right of the center line CL. This offset allows the drive unit to travel over a reference mark, such as a barcode or a 3D code, in the floor without either wheel touching the mark. Thus, the center line CL of the MDU passes directly over a reference mark when the drive unit travels forward.

[0011] Each motor assembly 24L and 24R contains a conventional motor 42L and 42R (as understood by those familiar with mobile drive unit technology) and a drive wheel 40L and 40R, respectively. The wheels 40L and 40R are located approximately in the center (front and rear) of the mobile drive unit. Each wheel 40L and 40R can be driven according to control signals to move the drive unit forward, or the direction of one of the wheels can be reversed so that the drive unit can rotate in place.

[0012] A pair of spring assemblies 80 has the function of transmitting a downward force to each of the front caster 26 and the rear caster 66, thus reducing the downward force on the drive wheels 40L and 40R. Each spring assembly 80 includes a support arm 82 that is attached to a rear section of the front chassis base 22 and extends rearward to a front section of the rear chassis base 62. The spring assembly 80 includes a compression spring 84 located in a pocket 76 formed in the rear base 62. The compression spring 84 includes an adjusting screw that allows the spring 84 to set a preload force.

[0013] Referring to Fig. 4. The mobile drive unit can include a front cover 28, which is attached to the front base 22, and a rear cover 69, which is attached to the rear base 62. Each cover 28 and 69 has a cutout section which, together with the corresponding cutouts in the bases 22 and 62, forms a wheel cutout through which the wheels 40L / 40R extend. In this respect, the wheels 40L and 40R can extend laterally to the wheel-side sides of the mobile drive unit.

[0014] Each of the front bases 22 and the rear base 62 contains a support structure or brackets 99 for mounting a support structure 98, as explained below and in the Fig. 5 and Fig. Figure 6 shows schematically. The supports 99 can have any configuration and supports connected to the supports 99 can assume any configuration, since the supports 99 (without restriction) include pivot points and a fixed structure.

[0015] Fig. Figure 5 schematically represents the front chassis unit 20 and the rear chassis unit 60, which carry a load W on an upper structure 96. The upper structure 96 can be any structure, such as one in Fig. The 4 shown turntable, or any other structure without restriction. Accordingly, the upper structure supports 98 can be any configuration and are shown only for illustration purposes, as is understood, and can be implemented by persons familiar with the technology of the mobile drive unit, depending on the specific parameters of the application.

[0016] A component, such as a battery pack 59, is mounted on the rear base 62 to represent the operation of the mobile drive unit ( Fig. 5 and Fig. 6) In this respect, the component / battery 59 is used to represent the gap between the components mounted on the rear chassis base 62 of the mobile drive unit and the upper structure 96, this gap being necessary to prevent damage to the components. Thus, Fig. 5 the drive unit on a flat surface such that the upper structure 96 is spaced away from the component 59 to form a gap G.

[0017] Upon receiving a drive signal from the controllers to move forward, motors 42L and 42R provide torque to wheels 40L and 40R. If an irregularity occurs, such as a bump (I), as described in... Fig. As shown in Figure 6, the rear chassis unit 60 follows the front chassis unit 20 over the irregularity I such that the rear chassis unit 60 pivots relative to the front chassis unit 20. The gap G is maintained.

[0018] The pivoting relationship differs from previous mobile drive units, in which component 59 (or the highest vertical component on the rear unit) was attached to an extension of the front chassis, in such a way that the occurrence of the in Fig.The irregularity shown in Figure 6 eliminated the gap G, allowing the upper structure to touch the components. To prevent contact between the upper structure and the components, prior art mobile drive units were configured with a larger gap and therefore a greater overall height compared to the mobile drive unit. In this respect, in the embodiment shown, both the highest mounted vertical component and the support structure 98 for the upper structure are located on the base 62 of the rear chassis unit.

[0019] The structure described herein allows for a lower overall height. Previous mobile drive units had an overall height of 10 inches or more. The mobile drive unit has an overall height of 7.785 inches.

[0020] The mobile drive unit includes control devices, cameras and other sensors, a docking connector, a turntable, motors for raising and rotating the turntable, and other components. A person familiar with the technology of the mobile drive unit understands how the additional components are mounted and used on the front and rear chassis units disclosed herein, in accordance with the specific objectives and design of the application of the mobile drive unit.

[0021] The present invention has been described by using a particular embodiment to illustrate certain features. For a non-limiting example only, components are referred to as front and rear to illustrate the structure and function; however, the invention is not limited to these particular front and rear orientations unless expressly stated in the claims. Furthermore, the present invention is not limited to any structure or function, nor is it limited to any solution to a problem described herein unless expressly stated in the claims. Likewise, the invention is in no way limited to embodying any advantage unless expressly stated in the claims. Rather, the structure and function described herein are merely a representation, and the claims are intended to encompass their full scope.

Claims

[1] Chassis assembly of a mobile drive unit for traversing a floor, the chassis assembly comprising: a front chassis unit (20) including a pair of drive wheel assemblies (24L;24R) and a front steering wheel (26) mounted on a front chassis base (22); a rear chassis unit (60), including a rear steering wheel (66) mounted on the rear chassis base (62), a pivot connection between the rear chassis base (62) and the front chassis base (22); wherein each of the front and rear steering rollers (26; 66) is asymmetrically offset from a center line (CL) in the direction of travel of the chassis assembly; and which allows the swiveling connection to improve the ground contact of the drive wheels (40L; 40R) and the front and rear swivel casters (26;66) when driving over uneven ground. [2] Chassis assembly according to claim 1, wherein the front and rear steering wheels (26;66) are configured such that the front and rear steering wheels (26;66) are spaced apart from a floor reference marking when the mobile drive unit travels in a straight line over the floor reference marking. [3] Chassis assembly according to claim 2, wherein the mobile drive unit is configured to carry a pod. [4] Chassis assembly according to claim 3, further comprising a spring assembly (80) with a preload force exerting a downward force on each of the front and rear steering wheel (26, 66); wherein the spring assembly (80) includes a support arm (82) attached to the front chassis unit (20) or the rear chassis unit (60) and a spring exerting a spring force on each of the front steering wheel unit and the rear steering wheel unit. [5] Chassis assembly according to claim 3, further comprising a battery (59) which (i) is electrically connected to the drive wheels (40L;40R) to supply power to the drive wheels (40L;40R), and (ii) is mounted on the rear chassis unit (60), wherein the battery (59) extends upwards from the rear chassis unit (60) and defines a vertical extension on the rear chassis unit (60). [6] Chassis assembly according to claim 5, further comprising an upper structure (96) extending over at least sections of the front chassis and the rear chassis, a vertical dimension between the upper structure (96) and a component (59) defining a gap G, wherein the pivotable connection enables the rear chassis unit (60) to pivot relative to the front chassis unit in order to at least partially maintain the gap G. [7] Chassis assembly according to claim 6, wherein the front chassis includes a front support and the rear chassis includes a rear support; wherein a load (W) is supported by the upper structure, which is transferred from the upper structure (96) to the front and rear supports by a support structure (98); and wherein the front chassis unit (20) has a one-piece base which is a casting, and the rear chassis unit (60) has a one-piece base which is a casting, and the rear chassis unit (60) includes a ballast coupled to a rear end thereof. [8] Chassis assembly according to claim 3, comprising a cover (28; 69), wherein the cover (28; 69) comprises a front cover unit attached to the front chassis unit (20) and a rear cover unit attached to the rear chassis unit (60), wherein the front cover unit and the rear cover unit are spaced apart from each other by a gap which allows the front chassis unit (20) to pivot relative to the rear chassis unit (60). [9] Method for transporting a load by means of a mobile drive unit, comprising a chassis assembly of a mobile drive unit according to claim 1, comprising the following steps: (a) Receiving a drive signal by the mobile drive unit; (b) in response to the receiving step (a) driving the pair of drive wheels to propel the mobile drive unit in a forward direction over a ground reference marker, each of the front and rear steering wheels (26; 66) being asymmetrically offset relative to the ground marker; and; (c) upon the occurrence of a ground irregularity, pivoting of the front chassis unit (20) of the mobile drive unit relative to the rear chassis unit (60) of the mobile drive unit. [10] Method according to claim 9, further comprising the step of pre-tensioning the front chassis unit (20) relative to the rear chassis unit (60) in order to exert a force on the front steering wheel (26) and the rear steering wheel (66) respectively via a spring assembly. [11] Method according to claim 9, further comprising the step of loading the mobile drive unit with a pod holding products. [12] Method according to claim 9, wherein step (c) comprises pivoting a front cover unit of the front chassis unit (20) relative to a rear cover unit of the rear chassis unit (60).

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