The Problem
I wanted to solve a problem that had been nagging me for months. I had been in a “salad club” with my cube-mate, in which we both brought ingredients in every week to make salads for lunch. We started doing this because we were fed-up with paying high prices for small pre-packaged salads in the cafeteria. On top of being expensive, it took most of our lunch break just to go get the salads, as the cafeteria was a long walk away!
When it was my turn to bring the lettuce, I would either slice it up freehandedly on a cutting board with a knife or tear it into pieces by hand – whichever method appealed to me that week. Slicing the lettuce freehandedly on a cutting board was tricky, as I had to be careful not to cut my fingers in the process. And then there was the big mess to clean up afterwards. No matter how hard I tried, lettuce always scattered all over the countertop and floor! Tearing the leaves by hand wasn’t as messy or dangerous, but it was even more tedious. Both methods yielded a lot of pieces that were just too large to fit easily into the mouth. After being covered with salad dressing, these large pieces of lettuce were awkward and messy to eat!
In addition to lunch, I also ate salad with dinner almost every evening. So, between having enough lettuce for lunch at work and for dinner at home, I was spending a lot of time and effort slicing up lettuce. So much so that I was going to give up on cutting my own lettuce and just buy it pre-cut/pre-packaged, even though it was a very expensive alternative. What aggravated me about doing this was that it didn’t even save me much time and effort, since I washed and dried the lettuce before eating it, just to be safe! All along I kept thinking that there must be some kind of simple device that I could build to slice up a head of lettuce. My thoughts always drifted back to a multi-bladed cutting solution (like a French fry cutter) which would be hard to construct, dangerous to operate and clean, and expensive.
The Solution
I contemplated a solution for months on end, until one day it finally hit me like a bolt of lightning! I will create a slotted cylindrical enclosure to hold the lettuce in place while I slice it with a knife, using the slots to guide the knife. The slots will be arranged around the enclosure in a manner to conduct the slicing of the lettuce in a grid-like pattern. Now I would be able to cut-up lettuce as if I were using a matrix of dicing blades, like I had previously discussed. It was so obvious to me that this was the approach to take…I felt like I had finally figured this thing out!
As I was shopping during a weekly grocery run, I started thinking about my lettuce slicing idea and wondering if it would really work. I finally decided that it was time to find out! From the kitchenware section I picked out a plastic pitcher, sized “about right”, and a cheap (better yet…on clearance!) non-serrated-edged bread knife. I already had a pretty good cutting board at home so I held-off from purchasing another one. I now had everything I would need for my slicing system, including a plastic container to convert into a slicing guide cylinder.
Soon after I got home, I took the pitcher to the garage and grabbed a ruler, a black marker, and a handsaw. I set up my workspace, and examining the plastic pitcher from all vantage points, I contemplated how I was going to turn it into a Lettuce Gizmo®. It would need to have enough slots to guide a knife into cutting lettuce into approximately one inch squares. The slots would need to be tall enough to accommodate half the height of a head of lettuce, the height of the knife blade, and some space in-between the two for clearance.
First, I cut the bottom off of the pitcher and removed the handle, leaving an open-ended cylinder. Next, I marked four 5” tall slots on one side of the cylinder an inch apart, along with four 5” slots (also an inch apart) on the opposite side. I rotated the cylinder 90 degrees counterclockwise and similarly marked another four 5” slots (and then another four on the opposite side). Using the hand saw, I slowly began cutting the slots into the plastic. No matter how careful I was, though, pieces of the brittle plastic kept breaking off in every direction, and I thought I might have to start all over again with another pitcher. When I was done, I cleaned the slicing guide and looked it over. I had a pretty ragged looking prototype, but it was good enough to prove my concept.
I took the slicing guide into the kitchen and pulled a head of lettuce out of the refrigerator. I cut the lettuce head into halves and set them aside. Next, I placed the slicing guide onto the cutting board, and (shaking from the excitement of it all!) placed half of the head of lettuce into the top of the guide and downward onto the cutting board. I sliced the lettuce half from right to left through four parallel slots sets, rotated the slicing guide 90 degrees counterclockwise, and sliced through four more parallel slot sets (also from right to left). I was laughing the whole time like a mad scientist and shouting “It works!” I then brought my family into the kitchen to check it out, while I cut the other half of the lettuce.
After successfully demonstrating the principle behind the invention, it became obvious that we needed to patent the slicing guide idea, place it into production, and make it available for everyone to use… we knew we had a great idea on our hands! We had created that elusive utensil that would enable a person to easily and inexpensively slice lettuce into bite-sized pieces! No more slicing lettuce freehandedly on a cutting board with a knife, or tearing it into pieces by hand!
Building the Prototype
After building the rough prototype, I proceeded with developing a more refined version. I began by selecting a rugged plastic material to build it from. After some research, I settled on 6” PVC pipe I found at a local hardware store. The problem was, though, that I couldn’t precisely cut the (now) 5.25 inch-deep slots with any of my existing tools. This led me to purchase a “thoroughly used but cheap” beam cutting saw (with a HUGE 16 5/16” diameter circular blade!) on eBay to cut the slots. I then built a track to run it upon, suspending the saw above a pre-cut PVC cylinder setting on an adjustable table. This arrangement allowed me to cut straight across the cylinder, creating parallel slots sets (2 opposite-side slots, each set), as opposed to cutting radially across the center of the cylinder.
With this tooling I was able to make several prototypes of “4 x 4” and “5 x 5” slicing guides. I thoroughly tested these two different slot configurations, cutting dozens of heads of lettuce with both designs over several weeks’ time. I made salads for lunches and for dinners with all of this lettuce, and as we ate it we assessed which size we liked the best. We determined that the “4 x 4” configuration was the one to proceed with, as it produced pieces of lettuce that we believed to be just the right size to fit easily into the mouth and to eat (not too large, not too small). After determining how many slots the slicing guide should have, I added instructive numbering (having learned from my own experience that it was needed!) and labels to the slicing guide.
Soon I realized that although machining Lettuce Gizmo® with the beam-cutting saw and track yielded a fine product, this was NOT the way to produce large quantities of the slicing guides! The machining approach required just too much hands-on labor to very affordably produce the slicing guides. It also required a lot of costly shipments of pipe to the production site to feed the production line. Last of all, the machining process yielded a large volume of plastic cuttings that would need to be gathered and hauled away for disposal – another added expense (and these statically charged cuttings stuck to everything, creating a hard to clean mess!).
I decided that these slicing guides would have to be produced through the plastic injection molding process to make them more affordable. I began consulting with local plastics companies to find out the costs to design and build an injection mold and to produce the slicing guides. We determined that it was feasible to build an injection mold to produce the basic part, needing only to add a slight taper to the inside of the slicing guide to aid in ejecting it from the mold. We would have to look at the other specific details of the part individually, though, to determine which of these we could actually incorporate into the mold.
We first investigated the placement of labeling and slot-indexing numbering around the upper areas of the slicing guide, deciding that the best approach was to mold them into the part. This replaced the original approach of performing secondary ink-stamping operations to place the labels and numbers onto the part. Ink stamping would add significant cost to the product, as it would require additional equipment, materials, labor, and time.
We next investigated how we could eject the slicing guide from the mold in a manner that would not disfigure the labeling. Per the new design, the part’s labeling would be scraped off by the outer mold’s surfaces during ejection of the part. This problem was coupled with the problem of how we would add radii to all of the (sharp) edges of the slots to dull them so that they would not cut the user’s fingers while handling the slicing guide. We determined that the addition of the radii to the part would need to be accomplished through the mold design itself, too. Otherwise, costly secondary hand-deburring operations to remove the sharp edges would have to be performed on every slicing guide.
To accomplish the ejecting and radiusing capabilities through the design of the mold itself, we decided to divide the mold surrounding the outside of the slicing guide cavity into four sections, with four retractable slides. These slides would contain the labeling dies for the outside of the part and the splines for the slots. After the plastic had been injected into the mold cavity and cooled (forming the slicing guide), these slides would move outward and away from the part, and then the slicing guide would be ejected. This would enable unobstructed separation of the slicing guide from the mold upon ejection.
Now that we could incorporate the labeling and numbering into the molding of the part, I redesigned the slicing guide’s front and side labels to 0.025” raised 3-dimensional characters. I similarly reconfigured the slot-guiding numbers to raised 0.025” 3-dimensional numbers. Although these numbers had initially been placed just above the slots, I found that they were easier to see and follow from the top, so I repositioned them to the top (with no impact to the mold). As redesigned, all of the labeling and numbering would now clear the mold (undamaged) during the ejection process.
The commercial off-the-shelf cutting board I used during prototype development worked well, and it was a perfect match for the slicing guide. I therefore decided that the Lettuce Gizmo® Slicing System would use these cutting boards, as-is. I contacted the (local) manufacturer, obtained acceptable quotes for these boards in bulk quantities, and selected that manufacturer to be my supplier. This ended up, at the time, being the only part of the slicing system that I did not design myself!
I had initially used a commercially-available knife with my prototype slicing system that was perfect for the task at hand (both low-cost and didn’t cut the walls of the slicing guide), but I couldn’t include it in my final slicing system as the knife distributor was unwilling to sell the knife to me in bulk. This led me to purchase and test a multitude of different low-cost kitchen knives with the slicing guide, but they were all found to cut into the plastic walls of the guide’s slots and were therefore unfit for use. These knives all had serrated edges, and what I needed was a low-cost double-bevel-edge-ground knife, of which I could not find. So, I decided that I would need to create my own knife from scratch. Using CAD software, I began analyzing the information I had accumulated from my knife research to develop an optimal design that would NOT cut into the walls of the slots.
I went through several design iterations of the knife, building multiple samples by hand until achieving a design that both prevented the blade’s sharp edge from touching and cutting into the walls of the slicing guide’s slots and would be long enough to stay within the slots while slicing the lettuce. Having settled upon a final overall design, I made production-representative knife samples from blanks I cut from cutlery-grade stainless steel, which I sharpened and then molded handles onto. I then worked with a wholesaler to locate a manufacturer for my design, supplying him with engineering drawings and production-representative samples of the knife which he forwarded to his prospective manufacturers for production and shipping quotes.
My custom knife ended-up being about 1/2” taller than the commercially-available knife that I had started with. In order for the slicing guide to accommodate the height of the new knife plus the height of the lettuce, I then increased the slot height by 1/2″ AND the overall height by 1/2”.
Note that through further research a few years later, a suitable, affordable, commercially available double-bevel-edge-ground knife was located and is now the knife being utilized in this slicing system.
The Final Product
In summary, through more than two years of development, the slicing system had gone from a rough slicing guide prototype carved from a plastic pitcher, utilizing a commercial cutting board and a commercial knife, to a machined PVC pipe slicing guide, utilizing a commercial cutting board and a custom-designed knife (and then, finally, a commercial knife).
Note that once the demand for the slicing systems justifies building a slicing guide injection mold to enable a high production rate, the CAD-designed slicing guide will be manufactured (through the injection molding process) and will replace the machined PVC pipe configuration.
The pictures and drawings documenting the stages of development of the Lettuce Gizmo® Slicing System have been included on the PROTOYPE page to illustrate the effort that went into developing this innovative new product.