US20150194123A1

US20150194123A1 - Interconnecting display tiles for multi-panel displays

Info

Publication number: US20150194123A1
Application number: US13/732,654
Authority: US
Inventors: Johnny Lee; Eric Teller
Original assignee: Google LLC
Current assignee: Google LLC; X Development LLC
Priority date: 2012-04-20
Filing date: 2013-01-02
Publication date: 2015-07-09
Also published as: TWI492199B; US20130278872A1; US9053648B1; US20130279012A1; US9117383B1; US9025111B2; WO2013158244A2; US9646562B1; TWI474298B; TW201346856A; WO2013158244A3; WO2013158248A1; CN104221071A; US20170206830A1; US9146400B1; TW201346857A

Abstract

A display panel to form a multi-panel display includes a rectangular pixel region with pixels for displaying images and an electronic housing including display logic. The electronic housing includes first, second, third, and fourth interconnects coupled to facilitate power and image signals to other electronic housings of other display panels. The first, second, third, and fourth interconnects are coupled to be interconnected on a same side of the rectangular pixel region as the first, second, third, and fourth edges of the rectangular pixel region, respectively. The third edge is mechanically coupled to overhang the third interconnect by a first offset distance and the fourth edge is mechanically coupled to overhang the fourth interconnect by a second offset distance. The first interconnect extends beyond the first edge by the first offset distance and the second interconnect extends beyond the second edge by the second offset distance.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under the provisions of 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/636,458 filed on Apr. 20, 2012.

TECHNICAL FIELD

This disclosure relates generally to optics, and in particular but not exclusively, relates to displays.

BACKGROUND INFORMATION

Large displays can be prohibitively expensive as the cost to manufacture display panels rises exponentially with display area. This exponential rise in cost arises from the increased complexity of large monolithic displays, the decrease in yields associated with large displays (a greater number of components must be defect free for large displays), and increased shipping, delivery, and setup costs. Tiling smaller display panels to form larger multi-panel displays can help reduce many of the costs associated with large monolithic displays.
FIGS. 1A and 1B illustrate how tiling multiple smaller, less expensive display panels 100 together can achieve a large multi-panel display 105, which may be used as a large wall display. The individual images displayed by each display panel 100 may constitute a sub-portion of the larger overall-image collectively displayed by multi-panel display 105. While multi-panel display 105 can reduce costs, visually it has a major drawback. Each display panel 100 includes a bezel 110 around its periphery. Bezel 110 is a mechanical structure that houses pixel region 115 in which the display pixels are disposed. In recent years, manufactures have reduced the thickness of bezel 110 considerably to less than 2 mm. However, even these thin bezel trims are still very noticeable to the naked eye, distract the viewer, and otherwise detract from the overall visual experience.
Various other approaches for obtaining seamless displays include display lensing, blended projection, stackable display cubes, and LED tiles. Display lensing places a single contiguous lens in front of each display panel 100 to present a fused borderless image in a particular “sweet spot.” However, the viewing angle is relative narrow and image distortion along continuous lines still occurs. Blended projection uses software stitching and mechanical mounting of traditional projection screens. Currently, blended projection uses relatively low cost hardware and is a good option for non-planar surfaces. However, there are significant physical constraints on usage and installation and blended projection requires regular maintenance and sophisticated calibration.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

FIGS. 1A and 1B illustrate conventional display panel tiling.

FIGS. 2A-2C illustrate an example display panel for tiling an example multi-panel display formed by a plurality of the display panels, in accordance with an embodiment of the disclosure.

FIGS. 3A-3C illustrate an example display panel for tiling an example multi-panel display formed by a plurality of the display panels, in accordance with an embodiment of the disclosure.

FIG. 4 illustrates a front view of three interconnected display panels and a disconnected display panel before being connected to the three interconnected display panels, in accordance with an embodiment of the disclosure.

FIG. 5 illustrates additional details of an electronic housing layer of FIG. 4, in accordance with an embodiment of the disclosure.

FIG. 6 illustrates a multi-panel display that includes twelve display panels interconnected together, in accordance with an embodiment of the disclosure.

DETAILED DESCRIPTION

Embodiments of display panels and multi-panel displays that include a plurality of display panels are described herein. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
FIGS. 2A-2C illustrate an example display panel 200 for tiling a multi-panel display 250 formed by a plurality of the display panels 200, in accordance with an embodiment of the disclosure. Display panel 200 is a modular display panel that is configured to be able to interconnect to other display panels 200 to form a multi-panel display that does not have seams that are easily perceived by a viewer of the multi-panel display. This modular design lends itself to easy scaling of a multi-panel display to fit a given context or space.
Display panel 200 includes pixel region 205 mechanically coupled to electronic housing 203. Pixel region 205 includes pixels and pixel circuitry. Pixel region 205 may be rectangular and the pixels may be arranged in rows and columns. Pixel region 205 could be implemented by a display panel of light-emitting-diodes (“LEDs”), an organic LED (“OLED”) panel, a liquid crystal display (“LCD”), a quantum dot array, or otherwise. Pixel region 205 may also include optical filters to optimize a given display technology, as known in the art. Pixel region 205 may be encased or enclosed in a transparent substrate such as glass or plastic. In one embodiment, a semi-flexible plastic (e.g. polyimide) is used. A thin semi-flexible material may also surround the edges of pixel region 205 to act as a gasket to protect pixel region 205 from damage when pixel region 205 is tiled with other display panels.
Electronic housing 203 includes display logic for displaying images and interconnects coupled to facilitate power and image signals. Electronics housing 203 may include device position circuitry coupled to the display logic. The device position circuitry may be coupled to the interconnects to facilitate device discovery and plug-and-play protocols. The device discovery may be performed using known techniques such as an I²C protocol, or other device discovery technique using a shared bus. By executing device discovery, the device position circuitry can determine (by querying the other connected display panels) what position in the multi-panel display that the given display panel 200 occupies. As an example, if the device position circuitry determines that the given display panel 200 is in a corner of a multi-panel display, the device position circuitry can cause the display logic to display an image (with pixel region 205) that corresponds to the corner position that the display panel occupies. By allowing each panel to detect which panel it is neighboring, the arrangement of the entire array can be reconstructed once all of the panels have been queried.
Each interconnect in electronic housing 203 may be configured to accept and transmit power and a full video signal. Beneficially, if another display panel is subsequently connected (via the interconnects), that subsequently connected display may receive its power and video signal from the interconnect. Consequently, display panel 200 would be capable of displaying a full overall image (if it is the only display panel), displaying one third of an image (if it is in multi-panel display with three total display panels), or displaying one ninth of an image (if it is in a multi-panel display with nine total display panels in a 3×3 arrangement). Therefore, the display logic in electronic housing 203 may accept a video input signal and sort the video input signal to filter or isolate the signals in the video input signal that are relevant to the display panel's position in the multi-panel display. The display logic can use the relevant video input signals to then drive pixel region 205 to display the correct portion of the overall image of the multi-panel display.
In FIG. 2A, cross sectional views of display panel 200 are presented through line A-A′ and line B-B′. The cross sectional views (combined with the top and bottom view) show that two edges of pixel region 205 overhang electronic housing 203. This feature may allow pixel regions 205 of display panels 200 to be connected closer together in a multi-panel display 250. In the cross sectional view through line A-A′, a first interconnect 221 and a third interconnect 223 are illustrated. In the cross sectional view through line B-B′, a second interconnect 222 and a fourth interconnect 224 are illustrated. The illustrated interconnects are illustrated enclosed (surrounded on 3 sides) within electronic housing 203, but the interconnects may be secured to electronic housing 203 differently from the illustration.
The cross sectional views of FIG. 2A show that electronic housing 203 includes an abutting section 227 that extends upward to abut pixel region 205 on at least portions of the first edge and the second edge of pixel region 205. Having abutting section 227 abut at least one edge of pixel region 205 can be useful for connecting driving electronics to pixel region 205. For example, in conventional LCD “glass,” a flexible circuit board often extends out from at least one edge of the pixel as a way of connecting the pixels to drive circuitry. Therefore, abutting section 227 may provide the mechanical space for the flexible circuit board to be connected to the rest of the display logic in electronic housing 203.
In FIG. 2B, two display panels 200 are shown before they are interconnected. In the illustrated embodiment, the fourth interconnect 224 of one display panel 200 will be connected to the second interconnect 222 of the other display panel 200. FIG. 2C shows multi-panel display 250 that includes display panels 200A, 200B, and 200C arranged is an on overlapping, fish-scale like configuration. In the illustrated embodiment, the fourth interconnect 224 of display panel 200A is connected to the second interconnect 222 of display panel 200B. Similarly, the fourth interconnect 224 of display panel 200B is connected to the second interconnect 222 of display panel 200C. The abutting section 227 of display panel 200B is disposed under the overhanging fourth edge of the pixel region 205 of display panel 200A. Similarly, the abutting section 227 of display panel 200C is disposed under the overhanging fourth edge of the pixel region 205 of display panel 200B. In other words, the pixel region 205 of the display panels can partially overlap the electronic housing 203 of adjacent display panels 200, when interconnected to do so. Because of the overlap, pixel region 205 of display panel 200B is disposed a first distance (in z-dimension 253) below pixel region 205 of display panel 200A. Similarly, pixel region 205 of display panel 200C is disposed a second distance (in z-dimension 253) below pixel region 205 of display panel 200B. Since display panels 200A, 200B, and 200C may all be substantially the same, the second distance would essentially be the same as the first distance. In the overlapping fish-scale configuration of FIG. 2C, the seams between display panels 200A, 200B, and 200C may be unperceivable to a viewer of multi-panel display 250.
Since the interconnects in display panels 200 may be configured to receive power and a video signal, a cord that includes power and a video signal may be plugged into any interconnect to supply power and video to the entire multi-panel display 250. For example, if display panel 200A receives power and video through interconnect 222, it may share the power and video signal (through any of its interconnects) with connected display panels. Therefore, display panel 200B may receive power and video signals from 200A. Similarly, display panel 200C may receive the power and video signals from display panel 200B. Hence, providing power and video signals to one interconnect of the display panels 200A, 200B, or 200C may provide power and video signals to the entire multi-panel display 250.
FIGS. 3A-3C illustrate an example display panel 300 for tiling an example multi-panel display 350 formed by a plurality of the display panels 300, in accordance with an embodiment of the disclosure. Similar to display panel 200, display panel 300 is a modular display panel that is configured to be able to interconnect to other display panels 300 to form a multi-panel display 350 that does not have seams that are easily perceived by a viewer of multi-panel display 350. Pixel region 305 and electronic housing 303 are similar to pixel region 205 and electronic housing 203, except where discussed or illustrated otherwise.
In FIG. 3A, it can be seen that electronic housing 2303 does not have abutting section 227 that extends up to abut the pixel region. Instead, that space is reserved for pixel regions 305 of other display panels 300 to occupy, when interconnected. In FIG. 3B, two display panels 300 are shown before they are interconnected. In the illustrated embodiment, the fourth interconnect 324 of one display panel 300 will be connected to the second interconnect 322 of the other display panel 300.
FIG. 3C shows multi-panel display 350 that includes display panels 300A, 300B, and 300C arranged is an on overlapping, substantially flush configuration. In the illustrated embodiment, the fourth interconnect 324 of display panel 300A is connected to the second interconnect 322 of display panel 300B. Similarly, the fourth interconnect 324 of display panel 300B is connected to the second interconnect 322 of display panel 300C. A portion of the electronic housing 303 of display panel 300B is disposed under the overhanging fourth edge of the pixel region 305 of display panel 300A. Similarly, a portion of the electronic housing 303 of display panel 300C is disposed under the overhanging fourth edge of the pixel region 305 of display panel 300B. In other words, the pixel region 305 of the display panels can partially overlap the electronic housing 303 of adjacent display panels 300, when interconnected to do so. As illustrated, the pixel regions 305 of display panels 300A, 300B, and 300C are matched closely together and are substantially flush. The close alignment of the pixel regions 305 and the substantially flush surface may make seams between display panels 300 unperceivable to a viewer of multi-panel display 350.
FIG. 4 illustrates a front view of three interconnected display panels (400A. 400B, 400C) and a disconnected display panel (400A) before being connected to the three interconnected display panels, in accordance with an embodiment of the disclosure. FIG. 4 illustrates one particular embodiment that could be implemented into display panels 200 or 300.
In FIG. 4, electronic housings 403A-D include interconnects 421, 422, 423, and 424, although interconnects 423 and 424 are not visible because they are disposed behind pixel regions 405A-D. In FIG. 4, the first interconnect 421 is coupled to be interconnected from a same side of display panel 400 as the first edge of pixel region 405. Similarly, second interconnect 422, third interconnect 423, and fourth interconnect 424 are coupled to be interconnected from a same side of display panel 400 as the second, third, and fourth edges, respectively, of pixel region 405.
FIG. 5 illustrates additional details of electronic housings 403A-D, that may have been covered by pixel regions 405A-D in FIG. 4, in accordance with an embodiment of the disclosure. In addition, FIG. 5 also shows example mechanical mounting structures (“MMSs”) that are positioned to mechanically couple display panels 400 together. Taking FIGS. 4 and 5 in combination, it is apparent that the third edge of pixel regions 405 are mechanically coupled to overhang third interconnect 423 by a first offset distance 411 and that the fourth edge of pixel regions 405 are mechanically coupled to overhang fourth interconnect 424 by second offset distance 412. Also apparent is that first interconnect 421 extends beyond the first edge of pixel regions 405 by first offset distance 411 and that the second interconnect 422 extends beyond the second edge by second offset distance 412.
When display panels 400 are interconnected, first interconnects 421 of one display panel 400 are connected to third interconnects 423 of another display panel 400. Similarly, second interconnects 422 are connected with fourth interconnects 424. Therefore, offset distances 411 and 412 that are common to all the display panels 400 create predictable, fixed positions for the interconnects to connect that also facilitates tiled alignment of the pixel regions 405 of the different display panels 400. It is appreciated that the shape of electronic housing 404 may be different than what is illustrated in FIGS. 4 and 5, as long as the shape does not mechanically interfere with connecting the interconnects of different display panels 400.
FIG. 5 illustrates MMSs 561, 562, 563, and 564 that are configured to mechanically couple display panels 400 together. In FIG. 5, the first MMS 561 is disposed to be mechanically interconnected (with another MMS) from a same side of display panel 400 as the first edge of pixel region 405. Similarly, second MMS 562, third MMS 563, and fourth MMS 564 are disposed to be mechanically interconnected from a same side of display panel 400 as the second, third, and fourth edges, respectively, of pixel region 405. First MMS 561 is configured to be connected to a third MMS 563 of another electronic housing 403 and second MMS 562 is configured to be connected to a fourth MMS 564 of another electronic housing 403. The illustrated positions of MMSs 561, 562, 563, and 564 are for illustration purposes and may be altered in other configurations. Example MMSs may include snap connectors, mechanical connectors secured by screws, or otherwise. In one embodiment, interconnects 421, 422, 423, and 424 include mechanical mounting structures integrated within the interconnect that are sufficient to mechanically support display panels 400 being mechanically tiled together.
Taking FIGS. 4 and 5 in combination, it is apparent that the third edge of pixel regions 405 is mechanically coupled to overhang third MMS 563 by first offset distance 411 and that the fourth edge of pixel regions 405 is mechanically coupled to overhang fourth MMS 564 by second offset distance 412. Also apparent is that first MMS 561 extends beyond the first edge of pixel regions 405 by first offset distance 411 and that the second MMS 562 extends beyond the second edge by second offset distance 412.
FIG. 6 illustrates a multi-panel display 650 that includes twelve display panels 600 interconnected together in a 3×4 display panel array, in accordance with an embodiment of the disclosure. Display panels 600 could include display panel features shown in connection with the discussions of FIGS. 2, 3, 4, and 5. Given the close proximity that the pixel regions 605 are able to achieve because of the mechanical configurations of display panels 600, the seams between display panels 600 may be unperceivable by a viewer of multi-panel 650. If display panels 600 include the features of display panel 300, pixel regions 605 will be substantially flush.
If display panel 600 includes the features of display panel 200, multi-panel display 650 could be configured in fish-scale configuration. In one example, a corner display panel 600A is adjacent to display panel 600B and adjacent to 600E and pixel regions 605B and 605E are disposed one level below 605A as display panel 600A overlaps display panels 600B and 600E in a fish-scale configuration, as discussed in FIG. 2. In that case, pixel regions 605I, 605F, and 605C may be disposed two levels below pixel region 605A, but only one level below pixel regions 605E and 605B. Similarly, pixel regions 605J, 605G, and 605D may be disposed three levels below pixel region 605A as the overlapping fish-scale configuration moves diagonally through multi-panel display 650. Pixel regions 605K and 605H may be disposed four levels below pixel region 605A and pixel region 605L may be disposed five levels below pixel region 605A.
Because of the modularity of display panels, multi-panel display 650 can be easily expanded or contracted. If a smaller multi-panel display 650 is desired, a user can simply disconnect display panels 600D, 600H, and 600L (as an example) to form a 3×3 multi-panel display. If a larger multi-panel display 650 is desired, a user can easily connect additional display panels 600. For example, to expand multi-panel display 650, a user could interconnect eight more display panels 600 to form a 4×5 multi-panel display. As discussed earlier, device position circuitry may do device discovery and adjust the images for the rest of the display panels 600, based on a subtraction or addition of display panels 600.
The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.
These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.

Claims

1. A multi-panel display comprising:

a plurality of display panels mechanically coupled together, each of the display panels comprising:

a rectangular pixel region having first, second, third, and fourth edges, the rectangular pixel region having pixels to display images, wherein the first edge and the third edge of the rectangular pixel region are opposite each other; and

an electronic housing including display logic for displaying the images and first, second, third, and fourth interconnects coupled to facilitate power and image signals, wherein the first, second, third, and fourth interconnects are coupled to be interconnected on a same side of the rectangular pixel region as the first, second, third, and fourth edges, respectively, and wherein the third edge is mechanically coupled to overhang the third interconnect by a first offset distance and the fourth edge is mechanically coupled to overhang the fourth interconnect by a second offset distance, the first interconnect extending beyond the first edge by the first offset distance and the second interconnect extending beyond the second edge by the second offset distance, each of the display panels coupled together by at least one of the first, second, third, and fourth interconnects,

wherein an abutting section of the electronic housing of a given display panel extends upward to abut portions of the first edge and the second edge of the rectangular pixel region of the given display panel such that the electronic housing is deeper along the first edge and the second edge than directly underneath the rectangular pixel region, and wherein a first display panel and a second display panel among the plurality of display panels are adjacent, and further wherein the rectangular pixel region of the first display panel partially overlaps the electronic housing of the second display panel, the rectangular pixel region of the second display panel being disposed a first distance below the rectangular pixel region of the first display panel.

2. The multi-panel display of claim 1, wherein if the first interconnect of a given display panel is connected to another display panel in the plurality of display panels, then the first interconnect is connected to the third interconnect of the another display panel, and wherein if the second interconnect of a given display panel is connected to another display panel in the plurality of display panels, then the second interconnect is connected to the fourth interconnect of the another display panel.

3. (canceled)

4. The multi-panel display of claim 1, wherein the first display panel is on a corner of the multi-panel display and a third display panel among the plurality of display panels is also adjacent to the first display panel, wherein the rectangular pixel region of the third display is also disposed the first distance below the rectangular pixel region of the first display panel.

5. The multi-panel display of claim 1, wherein the rectangular pixel region of the second display panel overlaps the electronic housing of a third display panel among the plurality of display panels and the rectangular pixel region of the third display panel is disposed a second distance below the rectangular pixel region of the second display panel, the first distance being substantially the same as the second distance.

6-8. (canceled)

9. The multi-panel display of claim 1, wherein the electronic housing of each display panel includes first, second, third, and fourth mechanical mounting structures (“MMSs”) for structurally supporting the multi-panel display, the first, second, third, and fourth MMSs coupled to be interconnected on a same side of the rectangular pixel region as the first, second, third, and fourth edges, respectively, the respective MMSs mechanically interconnecting the plurality of the display panels.

10. The multi-panel display of claim 9, wherein the first, second, third, and fourth interconnects are integrated with the first, second, third, and fourth MMSs.

11. The multi-panel display of claim 9, wherein the third edge is mechanically coupled to overhang the third MMS by the first offset distance, the fourth edge is mechanically coupled to overhang the second MMS by the second offset distance, and wherein the first MMS extends beyond the first edge by the first offset distance and the second MMS extends beyond the second edge by the second offset distance.

12. The multi-panel display of claim 1, wherein the image displayed by each display panel is a portion of an overall image displayed by the multi-panel display.

13. The multi-panel display of claim 1, wherein each of the rectangular pixel regions include a semi-flexible material disposed along the first, second, third, and fourth edges.

14. The multi-panel display of claim 1, wherein the electronic housing includes device position circuitry coupled to the display logic and coupled to the first, second, third, and fourth interconnects which are further configured to facilitate device discovery, and wherein the device position circuitry is configured to determine a position that a given display panel occupies in the multi-panel display and cause the display logic to display an image on the rectangular pixel region corresponding with the position that the given display panel occupies.

15. A display panel for connecting to other display panels to form a multi-panel display, the display panel comprising:

an electronic housing including display logic for displaying the images and first, second, third, and fourth interconnects coupled to facilitate power and image signals to other electronic housings of the other display panels to be connected to the display panel, wherein the first, second, third, and fourth interconnects are coupled to be interconnected on a same side of the rectangular pixel region as the first, second, third, and fourth edges, respectively, and wherein the third edge is mechanically coupled to overhang the third interconnect by a first offset distance and the fourth edge is mechanically coupled to overhang the fourth interconnect by a second offset distance, the first interconnect extending beyond the first edge by the first offset distance and the second interconnect extending beyond the second edge by the second offset distance, and further wherein an abutting section of the electronic housing extends upward to abut portions of the first edge and the second edge of the rectangular pixel region such that the electronic housing is deeper along the first edge and the second edge than directly underneath the rectangular pixel region.

16. (canceled)

17. The display panel of claim 15, wherein the rectangular pixel region is surrounded by a semi-flexible material.

18. The display panel of claim 15, wherein the electronic housing includes device position circuitry coupled to the display logic and coupled to the first, second, third, and fourth interconnects configured to facilitate device discovery, and wherein the device position circuitry is configured to determine a position that a given display panel occupies in the multi-panel display and cause the display logic to display an image on the rectangular pixel region corresponding with the position that the given display panel occupies.

19. The display panel of claim 15, wherein the electronic housing of each display panel includes first, second, third, and fourth mechanical mounting structures (“MMSs”) for structurally supporting the multi-panel display, the first, second, third, and fourth MMSs coupled to be interconnected on a same side of the rectangular pixel region as the first, second, third, and fourth edges, respectively.

20. The display panel of claim 19, wherein the first,

second, third, and fourth interconnects are integrated with the first, second, third, and fourth MMSs.

21. A multi-panel display comprising:

wherein the electronic housing of each display panel includes first, second, third, and fourth mechanical mounting structures (“MMSs”) for structurally supporting the multi-panel display, the first, second, third, and fourth MMSs coupled to be interconnected on a same side of the rectangular pixel region as the first, second, third, and fourth edges, respectively, the respective MMSs mechanically interconnecting the plurality of the display panels, and wherein the third edge is mechanically coupled to overhang the third MMS by the first offset distance, the fourth edge is mechanically coupled to overhang the second MMS by the second offset distance, and further wherein the first MMS extends beyond the first edge by the first offset distance and the second MMS extends beyond the second edge by the second offset distance.