Sign up
Title:
OUTDOOR FURNACE MONITOR
Kind Code:
A1
Abstract:
A monitoring system that provides a display, either local or remote, of operation information regarding an outdoor furnace or boiler system. The monitor polls various sensors, including information relative to water temperature, draft fan operation, pump operation, various switch status, safety status, and emissions status. The various sensors may be operationally connected wirelessly with the monitor. The monitor displays operational status information, including indications requiring operator attention. Thus, operator maintenance is more effectively applied as needed rather than also on an information gathering basis.


Inventors:
Walborn, Warren W. (Hart, MI, US)
Application Number:
11/560514
Publication Date:
05/24/2007
Filing Date:
11/16/2006
Assignee:
PENTWATER GROUP, L.L.C. (201 N. 72nd Ave., Hart, MI, US)
Primary Class:
International Classes:
F24H9/20; F24D5/00
View Patent Images:
Related US Applications:
Attorney, Agent or Firm:
VARNUM, RIDDERING, SCHMIDT & HOWLETT LLP (333 BRIDGE STREET, NW, P.O. BOX 352, GRAND RAPIDS, MI, 49501-0352, US)
Claims:
What is claimed is:

1. An outdoor furnace arrangement comprising: a residence having a perimeter envelope and having a heat distribution device within the residence; a heat generating furnace exterior to the residence perimeter envelope and operatively connected with the heat distribution device, whereby the furnace generates heat, the heat is transferred to the heat distribution device, and the heat is distributed within the residence; a plurality of sensors disposed about the furnace; a processing unit located at one of the furnace and the residence, the processing unit being operatively connected with each of the plurality of sensors; and a display interface located within the residence, the interface being operatively connected with the processing unit.

2. The outdoor furnace arrangement of claim 1 wherein the processing unit is wirelessly connected with the sensors.

3. The outdoor furnace arrangement of claim 1 wherein the interface is wirelessly connected with the processing unit.

4. The outdoor furnace arrangement of claim 1 wherein the plurality of sensors includes at least one of a water jacket temperature sensor, a draft fan operation sensor, a circulating pump operation sensor, a water level sensor, a safety switch status sensor, a firebox temperature sensor, a chimney temperature sensor, an environmental system operation sensor, an emissions safety switch status sensor, and a filtration status sensor.

5. The outdoor furnace arrangement of claim 1 further including a closed loop liquid circulating system that is operatively connected between the furnace and the heat distribution device and that is adapted to transfer heat between the furnace and the heat distribution device.

6. The outdoor furnace arrangement of claim 1 further including a closed loop liquid circulating system that is operatively connected between the furnace and the heat distribution device and that is adapted to transfer heat between the furnace and the heat distribution device, and wherein the plurality of sensors includes at least one of a water jacket temperature sensor, a draft fan operation sensor, a circulating pump operation sensor, a water level sensor, a safety switch status sensor, a firebox temperature sensor, a chimney temperature sensor, an environmental system operation sensor, an emissions safety switch status sensor, and a filtration status sensor.

7. A method of monitoring an outdoor furnace comprising the steps of: providing a residence with a perimeter envelope; providing a heat distribution device within the perimeter envelope; providing a heat generating furnace exterior to the perimeter envelope; operatively connecting the furnace with the heat distribution device, whereby the furnace generates heat, the heat is transferred to the heat distribution device, and the heat is distributed within the residence; providing a plurality of sensors disposed about the furnace; providing a processing unit at one of the furnace and the residence, the processing unit being adapted to receive sensor signals, to process the signals, and to generate signals for a display interface; operatively connecting each of the sensors with the processing unit; providing a display interface located within the residence; operatively connecting the interface with the processing unit; and providing the processing unit with a preselected monitoring procedure program.

8. The method of claim 7 wherein the step of operatively connecting each of the sensors with the processing unit includes wireless connection of each of the sensors with the processing unit.

9. The method of claim 7 wherein the step of operatively connecting the interface with the processing unit includes wireless connection of the interface with the processing unit.

10. The method of claim 7 wherein the step of providing a plurality of sensors includes providing at least one of a water jacket temperature sensor, a draft fan operation sensor, a circulating pump operation sensor, a water level sensor, a safety switch status sensor, a firebox temperature sensor, a chimney temperature sensor, an environmental system operation sensor, an emissions safety switch status sensor, and a filtration status sensor.

11. The method of claim 7 wherein the step of operatively connecting the furnace with the heat distribution device further includes providing a closed loop liquid circulating system that is operatively connected between the furnace and the heat distribution device and that is adapted to transfer heat between the furnace and the heat distribution device.

12. The method of claim 11 wherein the step of providing a plurality of sensors includes providing at least one of a water jacket temperature sensor, a draft fan operation sensor, a circulating pump operation sensor, a water level sensor, a safety switch status sensor, a firebox temperature sensor, a chimney temperature sensor, an environmental system operation sensor, an emissions safety switch status sensor, and a filtration status sensor.

13. In a residence having a perimeter envelope and having a heat distribution device within the residence, the residence being heated with a heat generating furnace that is exterior to the residence perimeter envelope and operatively connected with the heat distribution device, whereby the furnace generates heat, the heat is transferred to the heat distribution device, and the heat is distributed within the residence, the improvement of an outdoor furnace monitor comprising: a plurality of sensors disposed about the furnace; a processing unit located at one of the furnace and the residence, the processing unit being operatively connected with each of the plurality of sensors; and a display interface located within the residence, the interface being operatively connected with the processing unit.

14. The outdoor furnace monitor of claim 13 wherein the processing unit is wirelessly connected with the sensors.

15. The outdoor furnace monitor of claim 13 wherein the interface is wirelessly connected with the processing unit.

16. The outdoor furnace monitor of claim 13 wherein the plurality of sensors includes at least one of a water jacket temperature sensor, a draft fan operation sensor, a circulating pump operation sensor, a water level sensor, a safety switch status sensor, a firebox temperature sensor, a chimney temperature sensor, an environmental system operation sensor, an emissions safety switch status sensor, and a filtration status sensor.

17. The outdoor furnace monitor of claim 13 further including a closed loop liquid circulating system that is operatively connected between the furnace and the heat distribution device and that is adapted to transfer heat between the furnace and the heat distribution device.

18. The outdoor furnace monitor of claim 13 further including a closed loop liquid circulating system that is operatively connected between the furnace and the heat distribution device and that is adapted to transfer heat between the furnace and the heat distribution device, and wherein the plurality of sensors includes at least one of a water jacket temperature sensor, a draft fan operation sensor, a circulating pump operation sensor, a water level sensor, a safety switch status sensor, a firebox temperature sensor, a chimney temperature sensor, an environmental system operation sensor, an emissions safety switch status sensor, and a filtration status sensor.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuing non-provisional application of co-pending United States Provisional Patent Application Ser. No. 60/737,937, entitled Outdoor Furnace Monitor and filed on Nov. 18, 2005 by Warren W. Walborn, the disclosure of which is incorporated here by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a wireless remote monitoring station that monitors the working status of an outdoor furnace system. More specifically, a typical outdoor furnace system is fueled with wood or coal or the like, has a heating chamber and associated hardware, and has a closed loop liquid circulating system and its associated hardware. Outdoor furnace systems are commonly used to heat residential living spaces in which the heat generated by the furnace is often exchanged in a residence by a radiator device connected to a standard forced air system of ductwork to distribute the heat.

Currently, outdoor wood, coal and other types of burnable fuel furnaces are designed to heat a circulating liquid supply to between 160 and 180 degrees Fahrenheit (° F.). When the temperature drops below approximately 160° F. the draft fan is energized via a mechanical thermostat. This action provides air for the fire, which increases combustion and causes the circulating liquid to increase in temperature. The circulating liquid may be heated to a high temperature of approximately 180° F., at which point the thermostat disengages the draft fan and combustion of the fuel is reduced. The liquid cools until it reaches a low trip point of approximately 160° F. and the cycle repeats. The liquid circulating pump is always energized during the heating season and continuously circulates the liquid supply through the closed loop system, including the forced air duct system heat exchanger, or radiator.

The entire system functions properly, provided the fuel is maintained, the draft fan cycles at the proper temperatures, and the water pump continually cycles the heated water. The current state of the art is deficient in several important ways, however. First, an operator becomes aware that fuel may need to be replenished only when the operator noticed cold air blowing out of the vents, or if by physically going to and visually inspecting the firebox to see if sufficient fuel remains to burn.

Second, there is no provision for remotely indicating whether the water pump is operating correctly. If the pump fails, overheating of the furnace as well as eventual freezing of the pipes may result, which likely means costly repairs to not only the furnace hardware, but also to the residence structure that the furnace is intended to heat.

Third, there is also no provision to remotely monitor proper draft fan operation. If the draft fan is not engaged at the proper time, insufficient heat will be produced. Conversely, if it remains engaged when it is supposed to turn off, overheating of the system is likely. Remote monitoring of the draft fan combined with furnace water temperature would enable the user to identify a low-fuel situation.

Thus, one may appreciate that the state of the art of outdoor furnace systems is lacking in several significant areas including safety and effectiveness.

BRIEF SUMMARY OF THE INVENTION

Accordingly, an outdoor furnace monitor arrangement of the invention includes an outdoor heat generating furnace, a residential living space with a perimeter envelope and a heat distribution device within the residence. The outdoor furnace is stationed outside the living space and operatively connected with the heat distribution device. A number of sensors are provided on the furnace, that monitor various operating aspects of the furnace; a processing unit is operatively connected with the sensors; and a display interface is provided and operatively connected with the processor.

In one aspect of the invention, the processor is wirelessly connected with one of the sensors and the interface. In another aspect of the invention, a transmitting station may be physically located near the furnace and a receiving station located remotely, including inside the residence. It is anticipated that the transmitting and the receiving units may typically be spaced up to about 300 feet. The transmitting station may include sensors that are designed to detect various operating conditions, including water jacket temperature, draft fan operation, and circulating pump operation. A micro controller may interpret the sensor data and format the data for transmission to a receiving station, including transmission over a radio frequency (RF). A remote RF receiver, for example, may convert the signal for processing and display at a receiving station. The receiving station may be located in a convenient place within the living space for ease of monitoring. The receiving station is responsible for displaying the remote furnace operating conditions and alerting the operator to proper operation or fault conditions as they occur. The following may be displayed as a minimum configuration:

    • A visual indication of the water temperature.
    • A visual indication of the operation of the draft fan.
    • A visual indication of the status of the circulating pump.
    • A visual indication of the status of the fuel.
    • An audible alarm if the circulating pump is off.
    • An audible alarm if the blower fan malfunctions.
    • An audible alarm if an overheating condition exists.
    • An audible alarm if fuel needs replenishing.

Other aspects of the invention may include a method for setting a desired refill water temperature as well as a method for silencing audible alarms.

These and other features, objectives, and benefits of the invention will be recognized by one having ordinary skill in the art and by those who practice the invention, from this disclosure, including the specification, the claims, and the drawing figures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic representation of a residential outdoor furnace monitor of the invention;

FIG. 2 is a schematic representation of the residential outdoor furnace thereof;

FIG. 3 is a schematic representation of a selected sensor collection arrangement thereof; and

FIG. 4 is a schematic representation of a basic monitor interface display thereof; and

FIG. 5 is a schematic representation of an enhanced monitor interface display of the invention; and

FIG. 6 is a table of monitor program tasks of the invention;

FIG. 7 is a modified table of monitor program tasks of the invention, showing a portion of the table of FIG. 6, namely, proper or normal operating condition indicators;

FIG. 8 is a modified table of monitor program tasks of the invention, showing a portion of the table of FIG. 6, namely, cautionary indicators; and

FIG. 9 is a modified table of monitor program tasks of the invention, showing a portion of the table of FIG. 6, namely, critical operating condition indicators; and

FIG. 10 is an schematic representation of an alternative basic monitor interface display of the invention; and

FIG. 11 is a schematic representation of an alternative enhanced monitor interface display of the invention.

DETAILED DESCRIPTION

A preferred embodiment of a residential outdoor furnace monitor according to the invention is generally shown by way of an example in the drawing figures and discussed below. A residential outdoor furnace arrangement may include a residence 100, an outdoor furnace 200, an indoor heat distribution system, and a circulating closed loop liquid supply heat transport system 300. The furnace 200 is commonly a solid fuel fired boiler that may be wood or coal fired, for example, and may further include pelletized forms of fuel. A firebox and a water jacket are configured in the furnace and facilitate heat transfer from a furnace fire as is understood by one having ordinary skill in the art. The residence 100 may include non-industrial dwellings and have a perimeter shell or envelope that defines an interior space of the residence and further defines relative general spaces of indoor and outdoor. The furnace or boiler 200 is located outdoors and may be spaced from the residence, commonly up to about three hundred feet apart.

Regulation of a solid fuel furnace fire, that is to say its heat output, substantially relates to controlling fuel combustion by controlling draft air supply, assuming fuel is available. The more draft air that is available, the hotter the furnace burns. Conversely, the less draft air that is available, the cooler the furnace burns, even to the point of the fire becoming extinguished. Draft air flow is preferably controlled with a draft air blower 202. Draft air is limited when the fan is not operating, and draft air is forced into the fire when the fan is powered. The powering of the draft air fan may be regulated with a thermostat. The thermostat may directly read fire temperature or firebox temperature, may read exhaust flu temperature, and commonly reads water jacket temperature in a residential outdoor furnace. Water jacket temperature operating set points for a draft fan thermostat may include a low or fan on temperature of about 160° F. (degrees Fahrenheit) and a high or fan off temperature of about 180° F.

While a draft air blower 202 is expressly shown and discussed with regard to combustion or draft air supply in an exemplary outdoor furnace or boiler 200 relative to a preferred embodiment of a residential outdoor furnace monitor according to the invention, one having ordinary skill in the art understands that the present invention is not limited by this example. Rather, one having ordinary skill in the art knows that some outdoor wood furnaces 200 may alternatively have a “Natural Draft” system in which a flu door, which is typically relatively small, is actuated between an open position, in which air is allowed to enter the firebox and feed the fire, and a closed position, in which combustion air is restricted from flowing to the fire. The one also understands that the invention and concepts of the invention are useful and apply equally well to “Natural Draft” system furnaces or boilers. Further, the small flu door may include a commonly known butterfly valve or damper. Use of an outdoor furnace monitor according to the invention with a “Natural Draft” combustion air system may include a sensor and display combination that reports the relative position of the door. A more involved application of the invention to a “Natural Draft” system may include providing a powered actuator that is operatively connected with the door and provides a feedback loop whereby the actuator moves the door between the open and the closed positions in response to preselected combinations of sensor values.

The heat distribution system may commonly be provided in the form of at least a radiator that is located inside the residence, namely, indoors. The heat distribution system is typically more extensive than merely a radiator, however, and may include a ducted forced air distribution system in which the radiator is defined as a water to air heat exchanger that is located in a fan forced air plenum or the like. The outdoor furnace and the indoor heat distribution system are interconnected with a heat transport in the form of the closed loop liquid circulating supply system.

While air or other media may be used to transfer heat from the furnace outside the home to the radiator or distribution system inside the home, water or a water solution is preferably used to collect heat from the furnace and transport the heat to the home. Water has a good specific heat value, is generally safe to handle, and is otherwise convenient and economical to use. The primary shortfall of water is its tendency to freeze when cooled sufficiently. One having ordinary skill in the art of hydronic heating understands that the liquid supply may include various additives in solution to obtain various desirably characteristics and which may also result in undesirable considerations. For example, an antifreeze may be added to the liquid supply, but environmental impact considerations, indoor or outdoor, may arise.

The liquid supply circulating system 300 is preferably kept from freezing conditions, including maintaining water temperature and circulation. Thus, the liquid heat transport system has a continuously operating circulating pump. Keeping the liquid heat transport continuously flowing helps resist freezing if the furnace fire should become extinguished and also helps cool the furnace should the furnace, conversely, become over fired.

As may be noted from the above disclosure, solid fuel fired boilers or furnaces and the like require periodic attendance to assure safe operation and to stoke the fire as needed. Convenient operation according to the invention is provided with the addition of operation status sensors (FIG. 3), of a sensor signal processing unit (FIGS. 4 and 5), and of a sensor information display. The sensors may, as a base or minimum preferred arrangement, include water jacket temperature 312, draft fan operation 314, and liquid circulating system pump operation sensors 316, with a corresponding display interface 400 (FIG. 4). Thus, the exemplary basic display interface 400 may include a water jacket temperature readout 402, a draft fan on/off indication 404, an operator input 406 to set a fuel refill criteria, an indicator 408 that the fuel refill criteria is met, an over heated furnace alarm 410, a liquid circulation system pump on/off indication 412, and an audible alarm override 414.

An alternative basic monitor interface 600 may include a multifunction display 602 and display sensitive multifunction control buttons 604 (FIG. 10). In this configuration, a light 606 may blink and a chirp sound intermittently in the event of an information message. A mute button 608 may reset an alarm, mute sound, and extinguish the light. The alarm conditions may also automatically reset when a condition that initiates an alarm is corrected. The mute button may also cycle a menu, including a “Fuel Refill Temperature Set Point” screen on the multifunction display. The Fuel Refill Temperature Set Point is a user selected temperature at which the monitor interface may be set to advise the user of a low fuel level status. The control buttons may be two buttons to the right of the mute button and provide display sensitive multifunction control. The mute button may reset or scroll the readout to other menu selections. The display may also reset to a root or standard form screen by inactivity of the controls.

Again, the “Natural Draft” system discussed above is noted as an alternative to the draft air blower 202. As adapted to a “Natural Draft” system, the indicator 404 may be relabeled to indicate combustion air open/closed, or the like. Further, the indicator 404 may be generically labeled to include a report or indication relative to any control of draft or combustion air.

The inventor has found that known inductive current draw sensors are effective for both circulation pump and draft fan operation indication and are useful in both original equipment manufacture and in pre-existing equipment installation situations. Also, a known surface mount water jacket temperature sensor is conveniently applied in both original equipment manufacture and in pre-existing equipment retrofit situations. Although, one having ordinary skill in the art understands that various types of sensors may be utilized to provide various desired operating condition information and to meet particular manufacturing or user preferences with equivalent utility.

An exemplary enhanced sensor arrangement may, in addition to those discussed above, include water level 326, safety switch status 328, firebox temperature 330, chimney temperature 332, environmental system operation 334, emissions safety switch status 336, filtration status 338, water purity 342, fuel storage level 244, and fuel feed status 246 with a corresponding enhanced display interface 500 (FIG. 5). Water purity may include pH and mineral or hardness monitoring. As with the exemplary basic display interface 400, the enhanced display may include a water jacket temperature readout 502, a draft fan on/off indication 504, an operator input 506 to set a fuel refill criteria, an indicator 508 that the fuel refill criteria is met, an over heated furnace alarm 510, a liquid circulation system pump on/off indication 512, and an audible alarm override 514. Further features of the enhanced display may include a water refill indicator 516; a safety switch status indicator 518; firebox and chimney temperature readouts 520 and 522, respectively; and environmental, emissions, and filtration status indicators, 524, 526, and 528, respectively. The “Natural Draft” system discussed in more detail above is again noted relative to indicator 504.

A further enhancement may, in addition or alternatively, include sensing and indication relative to an automated fuel feed arrangement in which providing fuel to the furnace fire is automated. Various automated fuel feed arrangements are commercially available and known to one having ordinary skill in the art. Thus, sensing and reporting of a stored fuel quantity may be included as an option in the invention. An arrangement of sensing and reporting relative to a feed system that transports or feeds fuel from the stored fuel to the furnace fire may also optionally be included in the monitor of the invention. For example, an inductive current draw sensor may indicate a feed system motor operation.

As with the alternative basic monitor, an alternative enhanced monitor interface 700 may include a multifunction display 702 and display sensitive multifunction control buttons 704 (FIG. 11). In this configuration, a light 706 may blink and a chirp sound intermittently in the event of an information message. A mute button 708 may reset an alarm, mute sound, and extinguish the light. The alarm conditions may also automatically reset when a condition that initiates an alarm is corrected. The mute button may also cycle a menu, including a “Fuel Refill Temperature Set Point” screen on the multifunction display. The Fuel Refill Temperature Set Point is a user selected temperature at which the monitor interface may be set to advise the user of a low fuel level status. The control buttons may be two buttons to the right of the mute button and provide display sensitive multifunction control. The mute button may reset or scroll the readout to other menu selections. The display may also reset to a root or standard form screen by inactivity of the controls.

The various selected sensors may be hard wired with the sensor signal processing unit. Alternatively, and more preferred, the sensors are connected with a wireless signal transmitter 550 (FIG. 3) and the sensors' signals are communicated wirelessly with the sensor signal processing unit. Thus, the sensor signal processing unit may include a cooperating wireless receiver.

A processor monitoring procedure program task table that is suitable for a sensor signal processing unit that is configured for and may be associated with the basic sensor arrangement of FIG. 4, is shown in FIGS. 6-9. One having ordinary skill in the art understands that commonly available components may be assembled in various configurations according to an assembler's preferences to yield a processing unit that may be programmed with a variety of code according to a programmer's predispositions in a context of the assembled hardware to provide the sensor signal processing tasks of an outdoor furnace monitor system of the invention. Alternatively, one may develop a lower technology processor with an arrangement of relays in various parallel and series connections, whereby the electrical configuration of relays hard codes the process.

As a starting point of discussion, the closed loop liquid circulating system is preferably constantly in circulation as discussed above, and the liquid circulation system pump is, therefore, preferably continuously on. Thus, a normal condition for the pump is an “on” status and an “off” status requires operator attention. This requirement may be taken as a monitor rule in the monitor procedure program, so that the processor unit will generate an alarm whenever the pump current draw inductive sensor generates a signal that no current is drawn or fails to generate a signal that current is being drawn, for example, depending upon the preference of one who uses the invention as one having ordinary skill in the art understands. This rule is demonstrated in the table by comparison of the third table column of Water Pump Condition with the last table column of Audible Alarm. The alarm is indicated as sounding whenever the pump is off.

Another critical outdoor furnace condition that is mapped in the sensor signal processing unit monitoring procedure program task table is an “over fired” condition in which the furnace fire is or is approaching a dangerously hot condition. This requirement may also be taken as a monitor rule in the monitor procedure program, so that the processor unit will generate an alarm when an excessively high temperature is sensed. A critically high, or alarmingly high, water jacket temperature is demonstrated in the tables of FIGS. 6 and 9 as the overheat LED. Thus, the alarm is sounded when the water jacket temperature meets a preset criteria, about 190° F. in this example.

An indication of a trend of increasing water jacket temperature is also accommodated when the water jacket temperature is in an elevated range of about 180-190° F., for example. This situation presents a more involved rule requirement for the sensor signal processor unit monitoring procedure program by adding a second factor or sensor input into the rule. Here, the water jacket temperature and the draft fan status are combined and present operation trends as well as critical or alarm conditions. More specifically, an elevated water jacket temperature in combination with the draft fan being off is not a critical situation and the indicator lights and the water jacket temperature indicators display the elevated temperature trend. An elevated water jacket temperature in combination with the draft fan being on, however, may present a critical situation. Thus, not only the indicator lights and the water jacket temperature indicators display the critical temperature condition, the alarm also sounds.

Conversely, a low water jacket temperature may indicate a low fire concern. When the water jacket temperature is low and the draft fan is off, a freezing threat may be developing and the alarm is sounded. When the water jacket temperature is low and the draft fan is on, however, the fire should be building and raising the water jacket temperature. Thus, the indicator lights and the water jacket temperature indicators display a low temperature trend. The tables show this with various exemplary temperature conditions. A normal operating temperature range of the water jacket in this example is about 160-180° F.; with a low operating temperature ranging about 150-160° F.; and an alarmingly low temperature may be set at below 150° F. The display interface indications for each of the temperature zone conditions includes consideration of the draft fan condition. The actual indications displayed will then be in a range from a normal indication preferably with a green light indicator, through an indication that attention is required preferably with a yellow light indicator, to an alarm indication that attention is critical preferably with a red light indicator and audible alarm, as appropriate to the various combinations of sensor conditions presented. One having ordinary skill in the art understands that the low temperature trend identified in this example may result from various causes, including a low fuel condition and blocked air flow passage, perhaps by little critters

Thus, as one having ordinary skill in the art will see, an exemplary processor unit monitoring procedure program may include a selected set of various program rules as demonstrated by the tables of FIGS. 6-9, that include considerations for indicating operating condition trends as well as indicating critical operating conditions. Further, one having ordinary skill in the art and those who practice the invention will understand from this disclosure that various modifications and improvements may be made without departing from the spirit of the disclosed inventive concept. One will also understand that various relational terms, including left, right, front, back, top, and bottom, for example, are used in the detailed description of the invention and in the claims only to convey relative positioning of various elements of the claimed invention.