TV Tray Table. Cherry. Refinement in Details.

Cherry.  5i

This is my 3rd TV Tray Table prototype.  Made from Cherry wood.  It demonstrates different details used with the same dual position geometry that the first two have.  Those two are here:

Ash Version

Red Oak Version

Ash, Cherry, Red Oak

The first two use threaded bolts into embedded nuts or barrel nuts to hold the outer legs to the top and the inner leg frame. They could come unscrewed in use as the frame is folded and unfolded. This Cherry wood version addresses that flaw and uses a new detail.  The bolt heads look the same but won't come unscrewed in use.

Pivot Bolts

The bolts pictured above are the pivot bolts for the outer leg connection to the top and inner leg frame. They slip through a hole in the outer leg and into the top's rear corners, or the inner leg frame sides. They are held there by an intersecting binding screw shaft. They can spin in place but won't unscrew themselves as the table folds or unfolds.  I was unable to find such a thing looking online, so I cut these from longer bolts using the rotary axis on my CNC. 

Binding Bolts.  18mm Shafts

I've used different strategies to tension the frame so it won't collapse.  Wire cable on the Ash version, and straps at the top in the Oak version are both complicated to make/install.  This Cherry wood version uses short 3/4" wide straps between the front and back legs. They are 5" below the pivot point to keep the legs from splitting apart.  The unique use and path of the straps adapts to both slanted and inside-out horizontal top positions. The strap location is just below where the top rests when the stand is folded up flat. A little serendipity in what was an arbitrary location choice. 

Folded Flat

The outer legs of this Cherry wood version run straight, with only a small bump over to the offset hole at the top.  A simple detail that might draw some attention.  The bump is neatly in plane with the slanted top.  

Slanted top

It is an interesting bump above the top when horizontal. 

Horizontal top.

This Cherry version uses a simple short strap with a grommet in both ends to handle the tension when the legs want to split apart. 

Grommet in strap end.

A binding bolt passes through the grommet inside each leg to retain the straps but lets the strap rotate to accommodate the angle it approach each leg. The straps slip into 1/8" wide slots. One edge of the slot is rounded over so the edge won't wear on the strap as it exits and wraps around the leg to head toward the other leg. 

Straps held by binding bolts

This Cherry table is so far my favorite of the three. Beautiful wood. Complimentary green straps. A pleasant presence. 

This design is patented. The details can vary, but the geometry that lets the table stand flat or turn inside out to be slanted down is the unique property.

 

For information on licensing the design please contact:

Sarah Nolting
Licensing Associate
Kansas State University Innovation Partners
(785) 532-3910
snolting@ksu.edu
www.k-state.edu/innovation-partners

Questions and comments are welcomed!

4D

 

Tension Straps vs Tension Cable

Iteration is the secret to finding the best solution. 

One solution to locking the geometry of my TV Tray Table in both positions is a tension cable between the legs below the pivot bolt.  This cable is not ideal, being unorthodox and fussy to install in the design.  Using straps at the top as shown in the oak variation works well, and the straps are easy to make and install. This post is about the potential of using straps below the pivot bolt as an alternative to cable down there. 

I could visualize how straps might be used down there, but only a mock-up would prove or disprove that the idea works. 

Tension Strap in slots

Works in both positions of the table.

There are grommets in the ends of the strap.  They slide into slots and are then pinned in place by intersecting binding bolts. The slot is wider than the strap to allow for the approach angle into the legs. The binding pin acts as a pivot point for the strap so it can adjust/rotate as the legs invert then splay out. 

Straps are easy to install or remove.  Webbing is inexpensive and available in different colors. The heads of the binding pins can be black or bronze or chrome or brass or gold or likely found in different colors. Imagine if these were available at Target. The straps could be Target red, The bolt heads could be white. A version sold at Home Depot could have orange  straps and grey bolt heads. Change to blue and white for those sold at Lowes. 

The unique TV tray table design this detail could be used with is shown here:  Ash Version

A Version of the table with straps at the top is shown here: Oak Variation.

The design is patented. Contact info on licensing the design can be found at the bottom of both the above links. 

Question or comments are encouraged!

4D

Variations of a TV Tray Table

Iteration is the secret to the best solutions. A patent was granted for my folding tray table design. It was about the geometry that allows it to be horizontal in one position or slanted down in another.  This is a variation using the same geometry but with different details.

The top on this version has front rounded corners.  

Red Oak.  Slanted top.

The side legs have a slight curve rather than a jog in them to reach the offset bolt connection required so the design folds flat.

Flipped over. Top flat.

This table was my initial crude prototype, and suffered through 3 iterations before appearing here in its best form. Ball chain was what I initially used as the tension member that went between the front and back legs. Ball chain proved to be unpredictable in strength and prone to breaking apart.  One inch wide strapping at the top is my second approach.  First try with the straps found that due to the unique geometry they needed a unique path. The path they took needed to leave the legs the same distance apart in both positions. A new path was found that works. A replacement top stretcher was made. Two straps run between the center of the back edge and the middle of the top stretcher. Binding pins through grommets in the ends of the straps lock them into slots. 

Straps into back edge

The table transposes with the leg frame pulled through and the top flipped over. In the image below you can see the straps running over then into the top stretcher.  When in the flat position the straps run directly into the stretcher.  

Over and into the stretcher side.

Straight into the stretcher side.

The same unique geometry is expressed in this version with different materials, different details, and different tensioning strategies. Iteration.

This version is mostly red oak. My alternative version is here:  Made from Ash wood

This design is patented. For information about licensing the design please contact:

Sarah Nolting
Licensing Associate
Kansas State University Innovation Partners
(785) 532-3910
snolting@ksu.edu
www.k-state.edu/innovation-partners
   

An Ancient Light Wedge for Back Lighting Slides

Before digital photos arrived, film was used to capture images. There were two basic options for the type of film used including negatives for producing printed photos, and positives for mounting in a frame and projecting with a slide projector. For preparing a slide show to present to a class or audience reviewing the slides it took some creativity. To quickly view and choose the slides you wanted to use, a backlit light table was one option. They weren't portable or that common.  Handheld gadgets you could place a slide on/in to backlight the slide and sometime magnify the captured image to view were also an option. 

When I was in college I kept my slides in plastic notebook sheets designed for that purpose.  To quickly view a page at a time I made this light wedge.  Wedged so it could slip between sheets while still in the notebook.  A single incandescent light tube provided the backlight.

Slid Open

The bulb put off heat though. Although there were vent holes for the heat to escape through I found I couldn't use the wedge for more than 10 minutes or so before turning it off to cool down. Longer than that and the built up heat would warp the frosted plastic cover. 

The frosted plastic cover did a better job of spreading the light than it seems in the first image above shot.

I still have a couple notebooks full of slides I took. Somewhere. They include some black and white photo negatives I mounted in slide frames. I used negatives to project onto 50% gray poster board to then sketch over to make pseudo-realistic posters. I'd color over the dark areas with a white pencil, and color over the light areas with a black pencil.  That was my secret for the posters I would submit with my furniture designs when sent to competitions. I would make an updated version of this light wedge using cooler LED strips, but there are thin LED light panels already available that could be used. This wedge light is destined for a yard sale. 

Switch and Handle

Somewhere I have an ancient slide projector.  If I can find it a trip down memory lane is inevitable. Hopefully my slides are in the same box as the slide projector, buried somewhere in my house or garage.   

4D

An Improved TV Tray Table Design!

There is a dated X frame wood TV tray table design out there, available many places.  I have one, bought from my local Target store. Trying it out I was appalled at how poor the ergonomics of it are.  This disappointment spurred my creative genes to design a simple version that solves every complaint I have with the original. In my iterative sketching process I stumbled upon a geometry that allows the design to be turned inside out to serve in two useful positions.

Slanted Top

My design is patented.

In one position the top is slanted with a stop lip on the front edge. Musician?  A place for your manuscript paper when jotting down a tune. Have a tablet?  A better eyeline to see it when using it. A good place for note or sketch pad, and your pen/pencil can park on the protruding ledge.  

Turn the table inside out (flip the top and pull the leg frame through) and the top ends up horizontal for your lunch tray or laptop or solitaire card game.  

Horizontal Top

You'll appreciate the ergonomics of my design in either position. The bottom stretcher on the original is too low to slip my feet under. My design moves the bottom stretcher up.  It also beefs up the size of the stretchers for a more rigid frame.  The legs on mine are spread out to the edges of the top for more leg space between them. 

Side by Side

The asymmetric X of my design allows swing space for knees, and easier access and egress from being seated at this table. It also allows pulling the table closer to you when seated in a chair. 

Knee Space

My design uses a simple tension cable uniquely routed to lock the geometry in both positions. This option is between the front and back legs. A tension strap could instead be attached to the back edge of the top and the top stretcher. Shown here in another prototype of mine: 

One inch straps

This red oak version can be found here:  Red oak table

My design folds up flat for efficient packaging or storage.  A simple rack to hold 4 or 6 or 8  tables would be easy to make and have a small footprint. 

Two Inches Thick

This table is a simple example of 4th dimension design. It can serve the owner in slanted or horizontal configurations, or be flat for storage or packing at different times. Time being the 4th dimension. 

You can pick up the table to move it by simply reaching under the center of the sides and holding the legs against the top as you pick it up.  Or by picking it up from the center of the top stretcher.  

The wood top could have an added value inlay to appeal to specific audiences. Team logos, family crests, sports icons, company brands/logos, etc.. Something unique on each side perhaps. Customize it for each client for an added fee.  

It can also vary in finished detail. One may have bullnosed front and back edges like the example above.  Another might have the front corners radiused with a squared edge wrapping from side to front to other side.  The back edge still rounded over as shown below.

Red Oak Top Alternative

Rear Corner Detail

The stop ledge can be made from a matching wood or contrasting wood to emphasize it's presence.  It could even be a strip of aluminum or brass or something more exotic.  Bronze or black oxide or chrome or powder coated bolts in just about any color are options to consider. There are also hardware options out there for how to connect the legs and table top. 

This design is patented. For information about licensing the design please contact:

Sarah Nolting
Licensing Associate
Kansas State University Innovation Partners
(785) 532-3910
snolting@ksu.edu
www.k-state.edu/innovation-partners

Comments and questions I encourage and appreciate.  

4D

Using Square Nuts for Connections in Knock-Down Projects

Barrel Nuts vs Square Nuts?

A classic solution to bolt wood parts together is to use a barrel nut (aka cross dowel) to insert threads for bolts to thread into.  Using a drill press you can make a perfect hole for the barrel  nut.  Barrel nuts are relatively pricey compared to standard hex or square nuts.   If you have a CNC though it is possible to embed square nuts for threads rather than barrel nuts.  The pocket for a square nut can be made with a 1/8" spiral upcut router bit.  An optimum shape for such a pocket can be found using these drafting steps:

Making a pocket for a square nut.

From left to right in the image above:

1. Know the dimensions of your nut.  A digital caliper is a handy tool to keep near your CNC.

2. The critical shape to use is the top rectangular view of the nut. 

3. In each corner draw a circle the diameter of the bit you'll be using.  I usually use a 1/8"d spiral upcut bit.

4. Draw in the diagonal lines from corner to opposing corner. 

5. Where the diagonal lines cross the initial circles, center another 1/8" circle. 

6. You can delete the diagonal lines and initial corner circles.

7. Trim away the inner sections of each circle, and the corner of the rectangle where they cross the circle line. 

Make sure all the vectors are joined, and you've got a vector shape you can pocket out  to sink that square nut into.  Although my software (Aspire from Vectric.com) has a dogbone tool it doesn't make corners optimized to leave the most flat surface for the nut.  These steps do. 

I buy square nuts from McMaster Carr.  I prefer using stainless steel nuts as they won't rust if the wood has a high moisture content.

To cover the square nut a simpler rounded rectangle shape pocket above the nut can be filled with a CNC cut plug.  One example of an inserted square nut:

Embedded Square Nut

I've seen many CNC cut slots made to access hex nuts in plywood or other sheet goods. In most there is a little room around the nut for the tips of needle nosed plyers to keep the nut from spinning while tightening or loosening the connection.  Using a square nut and a snug fitting CNC cut pocket the nut won't spin. A side benefit is that you won't have to worry about the orientation of the nut.  Using barrel nuts you do. 

4D

Fast Food Mishap Solutions

Not often, but I do occasionally pick up a burger and fries for lunch or dinner from any of the assorted establishments in my town.  I always set the sack of food on the passenger seat, and usually remember to hold it there when I'm braking or turning.  Last trip I was distracted with snowy street conditions and forgot to hold the sack when I braked at a corner. 

Thanks to Newton's first law the fries found a new home on the passenger side floor. 

Vowing never to have to worry about this again I've come up with two potential solutions.  The first is a simple cardboard box to place the food sack into.  Fast food sacks are usually 5" x 7" or 3.5" x 5".  This box is sized for the larger sack, but has a removable divider to partition it for smaller sacks. It also has a flap that tucks between seat and back which keeps the box in place and contents upright. 

 Another bug is that sacks often open up.  On cold days they will lose heat quicker if open.   This solution keeps the sack closed and hangs on for cornering and braking.  A 2" strap and a chip clip.  Held between seat back and head rest with a 1" dowel the strap wraps around.  I can adjust the strap length if needed. 

The best solution may be a combination of both ideas.  A smaller chip clip could be left in the box to use with each acquired meal. Pinch the top of the sack closed to retain any heat while also keeping the sack from tipping over or sliding off the seat. 

I noticed among my camera gear an old but fancy camera strap.  It has pivoting clips on both ends.  It wouldn't be hard to clip one end to a chip clip, and the built-in length adjustability would be useful.   I ordered a couple nice straps, and have another chip clip I can use.  The old tan strapping needs replacing and the new straps will class up the prototypes. 

 

I can confirm that the cardboard box idea works as intended.  Simply drop the sack of food into the box and it'll stay in place and upright.  I suggest making it 1/4" larger though. I can also confirm that the chip clip strap works.   A tiny bit fussy to get the sack of food clipped shut and hanging though. 

4D