This recently issued patent may allow for simpler and cheaper omnidirectional lamps. Soon we may see low-cost Chinese imports using this technique.
"LED Lighting Lamp" describes just about everything we do in this industry. Nonetheless, this is the title of a recently issued patent, issued to Yung Cheng in Macau (Portuguese China, the way Hong Kong used to be British China) -- and not assigned to any company, which is interesting. If you want to look it up, it is US #8382331. As usual, we are going to look at: A) What problem the patent is addressing, B) How the invention works, and C) Where we might expect to see LED lighting embodying this patent.
The problem
LEDs are very directional. They're not at all like an incandescent filament, which gives off light in all directions. Most of the light from an LED comes out within a cone of, say, 90 degrees -- but there's still a moderate amount coming out even up to 180 degrees. So replicating the light pattern of an incandescent light bulb has been a problem in the industry.
There have been two basic answers to date. One way to get the omni-directional light pattern is to diffuse the light, a lot. The kinds of diffusers needed to get reasonable light patterns can lose upwards of 40 percent of the light. (Remote phosphors are better, but not wildly better.)
The other way to get omnidirectionality is by aiming the various LEDs in different directions. That's what Philips did in their A19 bulb. They have three sets of LEDs, each set pointing in a different direction. Each LED set, of course, has its own PCB, and then it also has its own electrical connection to the driver, and its own heatsink. So this isn't particularly cheap. And then, Philips added in a diffuser anyway, so that they didn't get point sources of light.
The method
This patent takes the second approach. They have each LED (or set of LEDs) on a little pedestal, a "stand." "The stand is operable to raise the LED... above a top surface of the substrate," the patent says. The idea of getting the light out is best understood by looking at the drawing. The LEDs are angled outward from the axis of symmetry of the bulb, and also angled outward from the plane of the screw base of the lamp. The light thus doesn't get intercepted by the base at all, as it may when using heavy diffusion, so "the overall beam angle [may] be increased, e.g. from 140 degrees to more than 180 degrees."
The stand itself is "made from any good heat conducting material" so that the heat generated by the LED goes down through the stand to the substrate. And the stand may be hollow, allowing the connection wires to snake up through its middle of the stand, reducing clutter.
Turning to the actual claims, this patent manages to have 66 of them (really). Of these, there are four independent claims. The first independent claim describes a heatsink made of a "stand," and the stand is described as "a central longitudinal prong and two side longitudinal prongs" with the LED mounted on the end of the central prong and the two side prongs for connecting current to the LED. The second independent claim is similar, but gets rid of the two side prongs and replaces them with a hole through the middle of the stand, with the electrical connections going through the hole. The third independent claim describes a lamp built with this system, with a metal plate to hold the stand in "a desired orientation."
Likely applications
In the final independent claim, we seem to really get at the meat of the matter. A "plurality of stands being arranged in a pattern and each having a central axis, the pattern comprising an alternating two-level pattern such that adjacent stands have different inclination levels and are oriented at a different distance...from [the] axis," with the different inclinations and distances alternating from one to the next.
This last sounds like something that the inventor intends to introduce to the market. Although it sounds as expensive as the Philips construction, it might possibly actually be cheaper. It appears that individual circuit boards aren't required; and the physical assembly might be inexpensive at Chinese labor rates. What I expect is to see some of these coming out of China soon, advertised as omni-directional bulb replacements, and at a considerably lower price than the "mainstream" bulbs.
This patent, like the others we have looked at, is limited in scope, so there might be ways to design around it or to get an additional patent.
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