---
publication_id: "OT-2026-000000010"
title: "Pallet Dispenser with Tine-and-Fork Transfer for Variable Stringers"
published_at: "2026-09-15T19:01:11.170720Z"
canonical_url: "https://opentechnical.org/p/OT-2026-000000010"
categories:
  - "material-handling/pallet-handling/pallet-dispensers"
keywords:
  - "pallet"
  - "dispenser"
  - "stringer"
  - "tine"
  - "fork"
  - "material handling"
  - "damaged"
  - "rejection"
  - "automation"
  - "stack"
---

# Pallet Dispenser with Tine-and-Fork Transfer for Variable Stringers

## Abstract

This disclosure describes a pallet dispensing system configured to handle pallets with damaged or non-standard stringer boards. The system employs a tine-and-fork transfer mechanism designed to engage with and lift individual pallets from a stack. It incorporates features for detecting stringer irregularities during engagement, allowing for selective rejection of non-conforming pallets. The system also includes provisions for accommodating stacks composed of pallets with varying overall heights, ensuring consistent dispensing operation. This arrangement mitigates jamming issues common in dispensers sensitive to precise pallet stringer geometry, enhancing operational reliability.

## 1. Technical Field

[0001] The present disclosure relates to material handling equipment, specifically to automated systems for dispensing pallets from a stacked array for subsequent processing, transport, or loading operations.

## 2. Technical Context

[0002] Pallet dispensing systems typically operate by engaging specific features of a pallet, such as the bottom deck boards or stringer boards, to separate the lowest pallet from a stack. Many existing dispensing mechanisms assume a standardized and undamaged pallet geometry, particularly regarding the dimensions and integrity of the stringer boards. Variations in stringer thickness, damage such as splits or missing sections, or non-standard stringer placement can cause these dispensers to jam. Such jams interrupt operations, require manual intervention, and can lead to damage of the pallet or the dispensing equipment. There is a need for a pallet dispensing system that can reliably separate pallets from a stack even when stringers exhibit damage or dimensional inconsistencies, and that can selectively remove non-conforming pallets from the operational flow.

## 3. System Overview

[0003] The pallet dispensing system described herein is configured to receive a stack of pallets (10) and dispense them individually onto an output conveyor (40). The core of the system is a dispensing module (20) that employs a tine-and-fork mechanism to engage the stringers of the lowest pallet. This mechanism is designed with a specific entry profile to tolerate minor stringer irregularities. The system includes sensing capabilities to detect significant damage or non-conformance of a stringer board during engagement. Upon detection of a non-conforming pallet, the system diverts that pallet to a reject path (30) rather than attempting to dispense it into the downstream process. The system also incorporates features to accommodate stacks containing pallets of varying overall heights, ensuring that the dispensing mechanism can consistently engage the lowest pallet regardless of its height relative to others in the stack. FIG. 1 illustrates the overall system flow.

## 4. Components

[0004] The system primarily comprises a pallet stack support structure, a dispensing module (20), a reject path (30), and an output conveyor (40).

[0005] The **pallet stack support structure** is typically a frame designed to hold a stack of pallets (10) vertically, allowing the lowest pallet to be accessed by the dispensing mechanism. It may incorporate guides to maintain stack alignment.

[0006] The **dispensing module (20)** is the primary mechanism for separating and dispensing pallets. It includes:

- **Dispensing tines (21)**: These are elongated members, typically two or more, designed to insert into the stringer openings of a pallet (01). Each dispensing tine (21) features a specific entry profile, such as a chamfered leading edge or a tapered tip, to facilitate entry even when stringer openings are slightly misaligned or partially obstructed. The tines (21) are mounted on a movable carriage or actuator assembly (24) that allows them to extend and retract horizontally.
- **Lifting forks (22)**: Positioned below the dispensing tines (21), these are also elongated members designed to support the pallet above the one being dispensed. They are typically slightly wider than the dispensing tines (21) and are also actuated vertically by an actuator assembly (24).
- **Actuator assembly (24)**: This assembly provides the controlled motion for both the dispensing tines (21) and the lifting forks (22). It may consist of pneumatic cylinders, hydraulic cylinders, or electric servo motors with associated linkages and guides to provide horizontal translation for the tines (21) and vertical translation for the forks (22).
- **Pallet support frame (23)**: A fixed frame component that provides a stable base for the dispensing mechanism and temporarily supports the pallet stack (10) during the dispensing cycle.
- **Stringer presence sensors (25)**: These are typically proximity sensors, such as inductive, capacitive, or optical sensors, mounted on or adjacent to the dispensing tines (21) or their path.## Technical Field

[0008] The present disclosure relates to material handling equipment, specifically to automated systems for dispensing pallets from a stacked array for subsequent processing, transport, or loading operations.

## 5. Technical Context

[0009] Pallet dispensing systems typically operate by engaging specific features of a pallet, such as the bottom deck boards or stringer boards, to separate the lowest pallet from a stack. Many existing dispensing mechanisms assume a standardized and undamaged pallet geometry, particularly regarding the dimensions and integrity of the stringer boards. Variations in stringer thickness, damage such as splits or missing sections, or non-standard stringer placement can cause these dispensers to jam. Such jams interrupt operations, require manual intervention, and can lead to damage of the pallet or the dispensing equipment. There is a need for a pallet dispensing system that can reliably separate pallets from a stack even when stringers exhibit damage or dimensional inconsistencies, and that can selectively remove non-conforming pallets from the operational flow.

## 6. System Overview

[0010] The pallet dispensing system described herein is configured to receive a stack of pallets (10) and dispense them individually onto an output conveyor (40). The core of the system is a dispensing module (20) that employs a tine-and-fork mechanism to engage the stringers of the lowest pallet. This mechanism is designed with a specific entry profile to tolerate minor stringer irregularities. The system includes sensing capabilities to detect significant damage or non-conformance of a stringer board during engagement. Upon detection of a non-conforming pallet, the system diverts that pallet to a reject path (30) rather than attempting to dispense it into the downstream process. The system also incorporates features to accommodate stacks containing pallets of varying overall heights, ensuring that the dispensing mechanism can consistently engage the lowest pallet regardless of its height relative to others in the stack. FIG. 1 illustrates the overall system flow.

## 7. Components

[0011] The system primarily comprises a pallet stack support structure, a dispensing module (20), a reject path (30), and an output conveyor (40).

[0012] The **pallet stack support structure** is typically a frame designed to hold a stack of pallets (10) vertically, allowing the lowest pallet to be accessed by the dispensing mechanism. It may incorporate guides to maintain stack alignment.

[0013] The **dispensing module (20)** is the primary mechanism for separating and dispensing pallets. It includes:

- **Dispensing tines (21)**: These are elongated members, typically two or more, designed to insert into the stringer openings of a pallet (01). Each dispensing tine (21) features a specific entry profile, such as a chamfered leading edge or a tapered tip, to facilitate entry even when stringer openings are slightly misaligned or partially obstructed. The tines (21) are mounted on a movable carriage or actuator assembly (24) that allows them to extend and retract horizontally.
- **Lifting forks (22)**: Positioned below the dispensing tines (21), these are also elongated members designed to support the pallet above the one being dispensed. They are typically slightly wider than the dispensing tines (21) and are also actuated vertically by an actuator assembly (24).
- **Actuator assembly (24)**: This assembly provides the controlled motion for both the dispensing tines (21) and the lifting forks (22). It may consist of pneumatic cylinders, hydraulic cylinders, or electric servo motors with associated linkages and guides to provide horizontal translation for the tines (21) and vertical translation for the forks (22).
- **Pallet support frame (23)**: A fixed frame component that provides a stable base for the dispensing mechanism and temporarily supports the pallet stack (10) during the dispensing cycle.
- **Stringer presence sensors (25)**: These are typically proximity sensors, such as inductive, capacitive, or optical sensors, mounted on or adjacent to the dispensing tines (21) or their path. These sensors detect the presence of a stringer board (02) as the tines (21) attempt to enter the pallet opening. FIG. 2 shows sensor (25) placement.
- **Load cells (26)**: Optionally integrated into the tine (21) mounting or actuator (24) linkage, these measure resistance encountered during tine insertion.

[0015] The **reject path (30)** is an auxiliary conveying or handling system positioned to receive pallets determined to be non-conforming. It may include:

- **Reject conveyor (31)**: A conveyor belt or chain conveyor configured to move rejected pallets away from the main flow.
- **Divert arm (32)**: A pneumatically or electrically actuated arm that pushes a non-conforming pallet off the normal dispensing path onto the reject conveyor (31).
- **Reject chute (33)**: A gravity-fed chute for collecting rejected pallets in a designated area.

[0017] The **output conveyor (40)** is a standard conveying system, such as a roller conveyor or chain conveyor, that receives the successfully dispensed pallets (01) for further processing.

## 8. Operation

[0018] The dispensing cycle initiates with a stack of pallets (10) positioned on the pallet support frame (23).

[0019] **Start-up and Stack Engagement:**

- The entire stack of pallets (10) rests on the lifting forks (22), which are initially in a raised position.
- The dispensing tines (21) are retracted.
- The lifting forks (22) lower the entire stack until the lowest pallet (01) rests on fixed ledges or the output conveyor (40) if it is of sufficient height and strength to support the stack.
- The lifting forks (22) then retract slightly, creating a gap (G) between the top surface of the lifting forks (22) and the bottom surface of the stringers (02) of the second-lowest pallet. This gap is sized to permit the dispensing tines (21) to enter the lowest pallet (01).

[0021] **Tine Entry and Damage Detection:**

- The dispensing tines (21) extend horizontally into the stringer openings of the lowest pallet (01).
- As each tine (21) advances, its stringer presence sensor (25) monitors for the presence of the stringer board (02). A healthy stringer allows the tine (21) to pass into the pallet opening, and the sensor (25) either registers no obstruction or registers the stringer passing by in a specific sequence.
- If a stringer board (02) is damaged (e.g., splintered, missing a section, or inwardly deformed), the tine (21) may encounter resistance or fail to fully enter the pallet opening within a predetermined time or distance.
- **Detection by sensor (25)**: If a sensor (25) fails to detect a stringer where one is expected, or detects an obstruction prematurely, it indicates a stringer irregularity. For example, if the tine (21) extends beyond a nominal stringer position without its sensor (25) detecting the stringer's far side, a missing stringer section is indicated. Conversely, if a sensor (25) detects an object very early in the insertion stroke, it may indicate a collapsed or severely deformed stringer.
- **Detection by load cells (26)**: If load cells (26) are present, an excessive force reading during tine (21) insertion beyond a calibrated threshold indicates physical obstruction from a damaged stringer (02) or other debris.
- If stringer damage or non-conformance is detected, the system enters a fault recovery sequence.

[0023] **Pallet Dispensing or Rejection:**

- **Normal Dispense (No Damage Detected):**
- Once the dispensing tines (21) are fully inserted into the lowest pallet (01), the lifting forks (22) retract further downwards, allowing the second-lowest pallet and the remainder of the stack to rest on the fully inserted dispensing tines (21).
- The lowest pallet (01), now unsupported by the stack above, is then free to be transported away, typically by the output conveyor (40), which actuates to move the pallet clear.
- After the pallet clears, the dispensing tines (21) retract. The lifting forks (22) then raise to support the stack from below, and the cycle repeats.
- **Reject Path Activation (Damage Detected):**
- If damage is detected during tine (21) entry, the system halts the normal dispensing sequence.
- The dispensing tines (21) may retract slightly to disengage if partially inserted, or remain partially inserted depending on the fault.
- The lowest pallet (01) is then diverted. This may involve the output conveyor (40) moving the pallet to a position where a divert arm (32) pushes it onto the reject conveyor (31), or the entire dispensing module (20) may reconfigure to drop the pallet directly onto a reject chute (33).
- Once the rejected pallet (01) is clear, the dispensing tines (21) retract, and the lifting forks (22) raise to support the stack. The system may then attempt to dispense the next pallet or wait for operator intervention.

[0025] **Steady Running:** The system continuously cycles through the sequence of lowering the stack, inserting tines, detecting stringer integrity, dispensing good pallets, or rejecting non-conforming pallets.

[0026] **Fault or Interruption:** In addition to stringer damage, other faults such as stack misalignment, sensor failure, or actuator malfunction will cause the system to halt operation. Error codes are typically generated for diagnostic purposes. E-stop events immediately cease all motion.

## 9. Example Embodiments

[0027] **Embodiment 1** In this configuration, the dispensing tines (21) are designed with a leading edge chamfered at an angle of 30 degrees for a length of 50 mm. This profile aids in guiding the tine (21) past minor obstructions or misalignments in the stringer opening. The stringer presence sensors (25) are optical through-beam sensors, with one emitter and one receiver pair mounted on each tine (21), positioned 20 mm from the tip. A successful insertion is registered when the beam is momentarily broken by the leading edge of the stringer, and then remains unbroken for the remainder of the insertion stroke, indicating clear passage. If the beam remains broken, it indicates an obstruction. If the beam is never broken after a full insertion stroke, it indicates a missing stringer. Rejected pallets are pushed laterally by a pneumatic divert arm (32) onto a separate reject conveyor (31) running parallel to the output conveyor (40).

[0028] **Embodiment 2** This embodiment utilizes dispensing tines (21) with a tapered tip over the first 75 mm, reducing the tine height by 5 mm. Load cells (26) are integrated into the mounting block of each dispensing tine (21). During insertion, the force exerted on each tine (21) is monitored. A force exceeding 150 N for more than 100 ms during insertion triggers a detection of a damaged stringer. Pallets detected as damaged are not fully engaged by the tines (21). Instead, the lifting forks (22) lower the entire stack slightly, allowing the lowest pallet (01) to rest on a set of retracting support arms (34) that are part of the reject path (30). These support arms (34) then retract, dropping the pallet onto a gravity reject chute (33) below. The stack is then re-engaged by the lifting forks (22) for subsequent dispensing attempts.

[0029] **Embodiment 3** This configuration addresses mixed pallet heights within the stack. The pallet stack support structure includes a variable-height platform (11) actuated by a scissor lift mechanism. Before each dispensing cycle, a laser distance sensor (13) measures the height of the top of the pallet stack (10). A controller then adjusts the platform (11) height to ensure that the lowest pallet (01) in the stack is always presented at a consistent vertical datum relative to the dispensing tines (21) and lifting forks (22). The dispensing tines (21) themselves have a chamfered profile as in Embodiment 1. Stringer integrity is checked by monitoring the current draw of the electric servo motor actuating the tines (21); an increase above a predetermined threshold during insertion signifies an obstruction. Rejected pallets are retained by the dispensing tines (21) and then lowered onto a dedicated reject cart positioned directly below the dispensing module (20).

## 10. Alternative Configurations

[0030] The dispensing tines (21) could be designed as rollers rather than fixed bars, allowing them to rotate if they encounter resistance, potentially reducing jamming. The lifting forks (22) could be independently actuated from the dispensing tines (21) to provide more versatile control over stack manipulation. The stringer presence sensors (25) could be ultrasound-based, providing a non-contact method for assessing the integrity or presence of stringer material. Instead of fixed tines, the system could employ a single, wider blade with multiple embedded sensors to scan the entire stringer width. The reject path (30) could incorporate a visual inspection system to categorize the type of damage on rejected pallets.

## 11. Parameter Variations

| Parameter | Range | Effect of Increasing Value | Effect of Decreasing Value |
| --- | --- | --- | --- |
| Tine (21) Insertion Speed | 0.1 to 0.5 m/s | Faster throughput, increased impact forces on stringers. | Slower throughput, reduced impact forces, more precise sensing. |
| Chamfer Angle of Tine (21) Tip | 15 to 45 degrees | More aggressive guidance, less material at tip. | Less aggressive guidance, stronger tip, more prone to snagging. |
| Stringer Damage Force Threshold | 100 to 300 N | Fewer pallets rejected (higher tolerance for damage). | More pallets rejected (lower tolerance for damage). |
| Sensor (25) Trigger Distance | 5 to 20 mm from tine (21) tip | Earlier detection of stringer presence or obstruction. | Later detection, allows more tine (21) penetration. |
| Pallet Stack (10) Height | 5 to 20 pallets | Increased load on lifting forks (22). | Reduced load, potentially faster cycle if stack replenishment is quick. |
| Gap (G) Between Pallets | 10 to 25 mm | Easier tine (21) entry, less support for upper stack. | Tighter fit for tines (21), better stack support. |

## 12. Additional Implementations

[0032] The system could be integrated with an upstream pallet inspection station that pre-screens pallets for obvious damage, preventing severely damaged pallets from even entering the stack. Downstream, the system could communicate with a robotic depalletizing cell, signaling when a pallet is ready for processing or indicating that a rejected pallet has been diverted. The dispensing module (20) could be mounted on a movable gantry to service multiple pallet stack locations. For applications requiring specific pallet orientation, the output conveyor (40) could include a turntable or a pallet rotator to adjust the pallet's alignment before it proceeds to the next stage. The system could also incorporate a pallet counting mechanism to track dispensed and rejected pallets, providing operational statistics.

## 13. Figures

![FIG. 1](figures/fig-001.svg) A block diagram illustrating the major functional units of the pallet dispensing system.

![FIG. 2](figures/fig-002.svg) An elevation view detailing the interaction of the dispensing tines and lifting forks with a pallet stringer.