An ASABE Meeting Presentation

An ASABE Meeting Presentation

Paper Number: 10

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Novel Approaches to Passive Bin Filling for Apples

Brian Kliethermes

Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213

Alexander Leslie

Pennsylvania State University, 670 Old Harrisburg Road, Suite 204
Gettysburg, PA 17325

Russel Rohrbaugh

Pennsylvania State University, 670 Old Harrisburg Road, Suite 204
Gettysburg, PA 17325

Jacob Koan

Pennsylvania State University, 670 Old Harrisburg Road, Suite 204
Gettysburg, PA 17325

Scott Wolford

USDA-ARS Appalachian Fruit Research Station, 2217 Wiltshire Road, Appalachian Fruits RS, Kearneysville, WV, 25430-2771

Michael Glenn

USDA-ARS Appalachian Fruit Research Station, 2217 Wiltshire Road, Appalachian Fruits RS, Kearneysville, WV, 25430-2771

Karen Lewis

WSU Grant-Adams Area Extension,P.O. Box 37 – Courthouse, 35 C ST NW, Ephrata, WA 98823

Tara Baugher

Pennsylvania State University, 670 Old Harrisburg Road, Suite 204, Gettysburg, PA 17325

William Messner

Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15217.

Written for presentation at the

2010 ASABE Annual International Meeting

Sponsored by ASABE

DavidL.LawrenceConvention Center

Pittsburgh, Pennsylvania

June 20 – June 23, 2010

Mention any other presentations of this paper here, or delete this line.

Abstract.Bin filling remains among the most challenging operations of appleharvest. The current standard practice is careful release of fruit fromthe bottom of a picking bag while sweeping the across the top layer of apples already in the bin to distribute the fruit with minimal bruising. This process is time consuming and still prone to damage the fruit. In this paper we describe two new devices that show promise for increasing speed and reducing bruising in passive bin filling. The first distribution is the "energy absorbing grate for apple distribution and bin filling" in which apples are dumped through a network of elastic bands holding energy absorbing foam shapes. The vibration of the elastic bands creates a fluidized bed effect that allows apples to pass through the device while reducing their speed so that bruising is nearly eliminated. The second is the "pneumatic self-adjusting bin filler," in which alternate inflation and deflation of adjacent cylindrical bladders causes the device to climb up the rising pile of apples in the bin filler. The bladders also serve as to absorb the energy of the falling apples. We will present the design process, the results of laboratoryand field tests, lessons learned, and future plans.

Keywords. Apple harvest, bin filling, energy absorbing materials.

Introduction

Labor saving technologies such as full mechanization of harvest or less radical harvest assist technology could greatly increase the efficiency of apple harvest. One major obstacle to any technology for improving efficiency is the need to collect the fruit in a bulk container after it has been removed from the tree without causing significant damage. The standard method of fruit harvest involves having harvest employees fill a picking bag with fruit. Once the bag is full, they carefully empty their bags into a bulk bin. There is potential for substantial economic and ergonomic improvements if picking bags can be removed from the harvest process, and allow for a more continuous process.

The problem lies in the physiology of an apple. Apples are much more fragile and sensitive to bruising under fast loading (Baugher, 2006). If an apple is allowed to fall freely rather than delicately lowered into a bin, it will have a considerable amount of kinetic energy when it either hits the bottom of the bin or other apples. This kinetic energy must be absorbed by something. Without any additional materials present, this energy will be absorbed during a very short period of time in a relatively small area by either the falling apple itself, or the apples already in the bin. If materials are present during the fall that can absorb this energy before the fruit reach the bottom of the bin, bruising can be prevented.

We developed two new approaches for bin filling absorb enough energy of harvested fruit dropped onto it to prevent bruising when the apple landed on a layer of apples orthehard bottom of a bin. Either prototype would support the future development of a passive bin filling device for use in orchards. Such a device would ideally be used in combination with other harvest assist technology, primarily a harvest platform (Baugher et al., 2009). The first system is a energy absorbing grate distributor design (Fig. 1). In this system, the kinetic energy of the falling apples is absorbed by cubes (or other shapes) of energy absorbing foam or elastic cords resting on top of or suspended from a frame. The second system that was modeled is a pneumatic self-adjusting design (Fig. 7). The principle behind the design is to alternate the inflation of two or more sets of flexible cylinders so that the device continually “steps” to stay on top of apples in bin. The cylinders themselves absorb the energy of the dropping apples by keeping the air pressure in the cylinders to a minimum. With these devices, ladders and picking bags could be eliminated from the apple harvest, allowing workers to pick continuously from the beginning to the end of a row.

Energy Absorbing Grate Bin Filler

Inspiration and Design

To eliminate reduce bruising it is necessary to absorb the energy of apples falling more than one or two inches. Our first idea was dropping apples into a tank of water. However, we quickly rejected this concept because (1) apple float, and after a few apples entered the tank, apples would fall onto apples, (2) water is heavy and difficult to move around, and (3) we apples would be more prone to contamination and spoilage. We briefly considered using another liquid that was less dense than apples, such as vegetable oil, but this would still be difficult to transport, and contamination was a concern.

These two ideas led to the idea of using a dry fluid-like medium as the energy absorber. Our inspiration was the ball pits found in children’s playgrounds in which thousands of foam ball serve to cushion the movements of children as the jump and wade through the pit. If the balls are less dense than the apples, the apples would eventually move through the layers of balls, and the balls would remain on top of the pile of apples. However, some balls would undoubtedly be trapped in the pile of apples, which would be a problem at the processing plant. So, rather than dropping the apples onto a free layer of foam balls, we decided to suspend the balls from rubber bands strung on a frame (Fig. 1).The rubber bands help create a fluidized bedeffect, because they vibrate as the apples hit them. A crank or motor raises and lowers the frame.

Fig. 1. Energy absorbing grate bin filler concept.

Experiments

We tested six configurations of energy absorbing grates consisting of variations of three different materials for their ability to passively handle apples without causing damage. The experiment included four replications of six configurations. In each replication eight apples (of 2 ¾ to 3 inch size) passed through that particular configuration. Trials were conducted with Delicious, a variety with low susceptibility to bruising, and Golden Delicious, a variety with high susceptibility to bruising.

We designed an apparatus that allowed the apples to free fall in a semi-random direction onto the uppermost layer of energy absorbing material. Each type of material was arranged in a two-foot square wooden frame. Fastened to a similar frame was a padded ramp at a 15° incline. This ramp (Figure 2) was tapered with padded dividers at one end, which directed the apples in each replicate in a random direction. A rack (Figure 3) allowed the square frames to be inserted at any one of four positions with the ramp on top. The separation between the positions was 13 cm (5 in). The racks were placed every 13 cm from the bottom of the bin so that the materials could be arranged in different configurations. For each experiment, the bottommost frame was on the lowest rack and just above the bottom layer of apples, while the ramp was one rack above the uppermost material.

The three energy absorbing materials were 6.3 cm (2.5 in) diameter hard foam balls strung on elastic (rubber) bands, 7.6 cm (3 in) diameter soft foam balls strung on rubber bands, and rubber bands alone. The rubber bands were stock materials ordinarily used for training apple trees. The foam balls were purchased from toy departments.

The six configurations were as follows: one layer of 48 hard foam balls (Figure 4), one layer of 36 soft foam balls (Figure 5), one layer of each type of ball, two layers of rubber bands (Figure 6), one layer of each type of ball with one layer of rubber bands, and one layer of each type of ball with two layers of rubber bands. In the bottom of the testing apparatus was a single layer of apples onto which the test apples fell after passing through the energy absorbing materials. A control value for bruising was determined by allowing the apples to fall onto the layer of apples without any of the energy absorbing materials present.

Figure 2. Padded ramp with one replicate of apples.
Figure 3. Testing apparatus with multiple racks.

The apples were inspected for previous damage, and any bruises were circled with a permanent marker to distinguish them from bruises resulting from the experiment. The apples were left at room temperature for approximately one hour before the experiment. For each of the four replicates, eight apples were placed in the ramp and allowed to drop all at once. If any apples stopped, the frames were shaken slightly until the apples passed to the bottom. The apples then sat at room temperature overnight until they were inspected for bruising. The skin over the damaged area was peeled back and the bruise diameter was measured. The apples were then cut through the bruise and the bruise depth measured. Levels of downgrading due to bruising were determined based on USDA Grades and Standards (Table 1).

Figure 4. Hard foam balls.
Figure 5. Soft foam balls.
Figure 6. Rubber bands.

Table 2 shows the results the experiments including the percentage of downgraded fruit, mean bruise width, and mean bruise volume. All combinations showed the ability to significantly reduce bruising, but only the treatments that included rubber bands had 100% Extra Fancy grade fruit. The data suggest that the elasticity of a rubber band is capable of absorbing the energy of falling fruit. In each case, either a foam material fastened to rubber bands, or the bands themselves gripped the apples long enough for the rubber bands to stretch out around them. The rubber bands allowed the fruit to pass through one layer, and they immediately snapped back to their original positions before additional fruit fell.

Table 1. Classification of bruise damage, based on USDA Grades and Standards.

Class / USDA fresh market standard / Bruise specifications
1 / “Extra Fancy” / No bruising
2 / “Extra Fancy” / Bruise diameter ≤ 3.2 mm (1/8 in)
3 / “Extra Fancy” / Bruise diameter 3.2 mm (1/8 in) to 6.4 mm (¼ in)
4 / “Extra Fancy” / Bruise diameter 6.4mm (¼ in) to 12.7 mm (½ in) or area of several bruises ≤ 127 mm2
5 / “Fancy” / Bruise diameter 12.7 mm (½ in)to 19 mm (3/4 in)
6 / Downgraded / Bruises larger than the tolerances in “Fancy”
7 / Downgraded / Cuts or punctures of any size

Table 2. Effects of energy absorbing grates on apple bruising and USDA fresh market grade (percentages based on % of total apples tested).

Treatment / Downgraded to Fancy Grade
(%) / Downgraded to No. 1 or Utility Grade
(%) / Bruise width
(mm) / Bruise volume
(mm3)
Hard foam balls / 3 / 0 / 1.1 bz / 10.7 b
Soft foam balls / 3 / 0 / 2.1 b / 12.4 b
1 layer each ball type / 3 / 0 / 1.0 b / 19.2 b
2 layers rubber bands / 0 / 0 / 1.3 b / 8.2 b
2 layers balls + 1 layer bands / 0 / 0 / 0.6 b / 3.6 b
2 layers balls + 2 layers bands / 0 / 0 / 1.6 b / 43.9 b
Control / 28 / 3 / 7.1 a / 195.1 a

z Means, within columns, followed by dissimilar letters are significantly different according to Fisher’s protected least significant difference, P ≤ 0.05.

Pneumatic Self-Adjusting Bin Filler

A disadvantage of the energy absorbing grate is that manual intervention is required to keep it at the proper height above the apples already in the bin or the bottom of the bin itself. Inspired by the idea of “stepping” over layers apples in the bin, we conceived pneumatic “feet” consisting of bladders that alternate inflate and deflate (Fig. 7). The bladder material and the pressurize air absorb the energy of the falling apples.

Fig. 7 pneumatic self-adjusting apple distributor

Experiments with Full Scale Bin Filler Prototypes

We constructed one full scale prototype of each bin filler. The energy absorbing grate (Figure 8) used nylon bungee cords with a foam base pad. The energy absorbing grate bin filler contained two layers of nylon bungee cords 9 mm (0.36 in) in diameter configured approximately at a spacing of 3.75 cm (1.5 in). The drop height between the two layers of bungee cords was 7.5 cm (3 in) and the drop height to the foam mat was 9 cm (3.5 in).

Fig. 8.Full scale prototype of energy absorbing grate with test ramp.

The pneumatic self-adjusting bin filler contained two layers of 10 cm (4 in) plastic inflated bladders (Fig. 9). The pressure in the upper bladder layer was slightly lower than the pressure in the bottom bladder layer. This enabled the system to absorb the largest amount of energy without causing apples to bounce upon impact.

Fig. 9.Pneumatic self-adjusting bin filler with test ramp.

The study included four replications of three drop height configurations—2.5, 5, and 10 cm (1, 2, and 4 in), respectively. In each replication eight apples (of 2 ¾ to 3 inch size) passed through each particular bin filler configuration. Trials were conducted with Golden Delicious, a variety with high susceptibility to bruising. The testing apparatus was designed to allow the apples to free fall in a semi-random direction onto the uppermost layer of energy absorbing material. Additionally, one incomplete layer of red apples was placed on the bottom of the bin allowing room for the test apples to distribute. The test apples were placed on a padded ramp at a 15° incline with padded dividers to prevent bruising prior to departure from the ramp.

A control value for bruising was determined by allowing the apples to fall onto the incomplete layer of apples without any of the energy absorbing materials present. For the singulation trials, each apple was released individually from the ramp to completely isolate any initial bruising from apple collisions between the end of the ramp and the bin filler.

The apples were inspected for previous damage, and any bruises were circled with a permanent marker to distinguish them from bruises resulting from the experiment. The apples were left at room temperature for approximately one hour before the experiment. For each of the four replicates, eight apples were placed in the ramp and allowed to drop all at once. The apples remained at room temperature overnight until they were inspected for bruising. The skin over the damaged area was peeled back and the bruise diameter was measured. Then the apples were cut through the bruise to measure the bruise depth. Levels of downgrading due to bruising were determined based on USDA Grades and Standards (Table 1).