AIR CLEANING DEVICE AND APPARATUS

Abstract

An air cleaning device for removing aerosol particles from an air stream comprising: a particle charger comprising a housing and an electrode arrangement therein for generating air ions in the air stream, the particle charger having a particle charging zone within which, in use, aerosol particles in the air stream are electrically charged via collision with the air ions; a filter for precipitating electrically charged aerosol particles from the air stream moving through the device; and an air mover, comprising a casing, for moving the air stream through the device; wherein the particle charger and the air mover are provided upstream of the filter; and wherein the housing of the particle charger is hermetically sealed to the casing of the air mover in the direction of air flow through the device, such that the particle charger and the air mover are intimately coupled together, whereby all air entering the device has to pass through both the particle charger and the air mover.

Claims

1. An air cleaning device for removing aerosol particles from an air stream, the device comprising: (a) a particle charger comprising a housing and an electrode arrangement therein for generating air ions in the air stream, the particle charger having a particle charging zone within which, in use, aerosol particles in the air stream are electrically charged via collision with the air ions; (b) a filter for precipitating electrically charged aerosol particles from the air stream moving through the device; and (c) an air mover, comprising a casing, for moving the air stream through the device; wherein the particle charger and the air mover are provided upstream of the filter; and wherein the housing of the particle charger is hermetically sealed to the casing of the air mover in the direction of air flow through the device, such that the particle charger and the air mover are intimately coupled together, whereby all air entering the device has to pass through both the particle charger and the air mover.

2. (canceled)

3. An air cleaning apparatus for removing aerosol particles from an air stream, the apparatus comprising: (a) a housing comprising a first part of an electrode arrangement for generating air ions in the air stream; (b) a particle charger, located in the housing, and comprising a second part of the electrode arrangement for generating air ions in the air stream, wherein, together, the particle charger and the housing define a particle charging zone within which, in use, aerosol particles in the air stream are electrically charged via collision with the air ions; (c) a filter, located in the housing, for precipitating electrically charged aerosol particles from the air stream moving through the apparatus; and (d) an air mover, located in the housing, for moving the air stream through the apparatus; wherein the particle charger and the air mover are provided upstream of the filter; and wherein the housing provides a hermetic seal between the particle charger and the air mover in the direction of air flow through the apparatus, such that the particle charger and the air mover are intimately coupled together, whereby all air entering the apparatus has to pass through both the particle charger and the air mover.

4. The air cleaning device according to claim 1, wherein the particle charger and the air mover are intimately coupled as particle charger/air mover in the direction of air flow.

5. The air cleaning device according to claim 1, wherein the particle charger and the air mover are intimately coupled as air mover/particle charger in the direction of air flow.

6. The air cleaning device according to claim 1, wherein the filter is an electrostatic filter, an electrostatic precipitator, a fibrous media filter, or an electret filter.

7. The air cleaning device according to claim 1, wherein the air mover is a mechanical fan, bellows, a convective airflow device or a centrifugal fan (a blower).

8. The air cleaning device according to claim 1, wherein the electrode arrangement comprises two parts: an electrode and a counter-electrode.

9. The air cleaning device according to claim 8, wherein the particle charger comprises both the electrode and the counter-electrode.

10. (canceled)

11. The air cleaning apparatus according to claim 3, wherein the electrode arrangement comprises two parts: an electrode and a counter-electrode, and wherein the first part of the electrode arrangement comprised in the housing is the counter-electrode, and the second part of the electrode arrangement is the electrode.

12. The air cleaning device according to claim 8, wherein the electrode is in the form of a pin or elongate wire, having a tip or an end.

13. The air cleaning device according to claim 12, wherein the electrode of the particle charger is supported on a support rod.

14. The air cleaning device according to claim 13 wherein two or more pin-type electrode are supported on a common conductor rod.

15. The air cleaning device according to claim 8, wherein the counter-electrode surrounds the electrode but is separated therefrom by a clearance.

16. The air cleaning device according to claim 15, wherein the electrode is substantially concentric with the counter-electrode.

17. The air cleaning device according to claim 8, wherein the counter-electrode is comprised of a plate having an aperture therein.

18. The air cleaning device according to claim 8, wherein the counter-electrode comprises a hollow cylinder formed of conductive material or having a conductive interior surface.

19. The air cleaning device according to claim 18, wherein the conductive interior surface is comprised of a conductive ink or paint.

20. An air cleaning method for removing aerosol particles from an air stream and eliminating charge bypass, the method comprising: generating air ions in the air stream using a particle charger comprising a housing and an electrode arrangement therein; electrically charging aerosol particles in the air stream via their collision with air ions in a particle charging zone of the particle charger; and moving the air stream towards a filter using an air mover comprising a casing, whereby electrically charged aerosol particles in the air stream are precipitated onto the filter, wherein the housing of the particle charger is hermetically sealed to the casing of the air mover in the direction of air flow, such that the air stream is moved through an intimate couple of the particle charger and the air mover, whereby all air to be cleaned has to pass through both the particle charger and the air mover, prior to its arrival at the filter.

21. (canceled)

Description

[0090] The invention will now be further described, by way of example only, with reference to the accompanying drawings (not to scale), in which:

[0091] FIGS. 1 to 3 are schematic side cross sections of a prior art electrostatic precipitation device, discussed earlier in this specification;

[0092] FIGS. 4 and 6 are schematic perspective views of two alternative prior art electrostatic precipitation apparatus, discussed earlier in this specification;

[0093] FIGS. 5 and 7 are schematic side cross-sections of each of the two alternative prior art electrostatic precipitation apparatuses shown in FIGS. 4 and 6 respectively;

[0094] FIGS. 8 and 9 are schematic side cross sections of an embodiment of an electrostatic precipitation air cleaning device according to the present invention;

[0095] FIGS. 10, 11 and 12 are schematic side cross sections of a second embodiment of an electrostatic precipitation air cleaning device according to the present invention;

[0096] FIGS. 13 and 14 are schematic side cross sections of a third embodiment of an electrostatic precipitation air cleaning device according to the present invention;

[0097] FIGS. 15 and 16 are schematic perspective views of a fourth embodiment of an electrostatic precipitation air cleaning device according to the present invention;

[0098] FIG. 17 is a schematic perspective view of an embodiment of an electrostatic precipitation apparatus according to the invention; and

[0099] FIG. 18 is a schematic cross-section of the electrostatic precipitation apparatus shown in FIG. 17.

[0100] Referring to FIGS. 8 and 9, both of which illustrate a first embodiment of the invention, there is shown an electrostatic precipitation air cleaning device 20 for removing unwanted aerosol particles from an air stream. In a similar manner to the prior art device 10 shown in FIGS. 1 to 3, the air cleaning device 20 of FIGS. 8 and 9 comprises a particle charger 22, an air mover 25 in the form of a mechanical fan, and a filter 26 for removing charged aerosol particles from the air stream (not shown) as it flows through the device 20.

[0101] The particle charger 22 comprises a cylindrical housing 22a having an electrode arrangement therein for generating air ions in the air stream. The housing 22a is open at each of its airflow ends 22b, 22c so as to allow the air stream to pass through. The electrode arrangement comprises an electrode 23 in the form of a pin (represented by an arrow, the head of which points upstream to represent the tip of the pin) mounted centrally (lengthways) on a diametric bar 23a mounted in the housing 22a, and a counter-electrode 24 in the form of an annular conductive coating provided on the interior surface of the housing 22a, surrounding the electrode 23 in a concentric manner. A particle charging zone is the volume defined by the extent of electrical communication between the electrode 23 and counter-electrode 24 within which, in use, aerosol particles in the air stream are electrically charged via collision with the air ions.

[0102] The air mover 25 comprises a cylindrical casing 25a within which fan blades 25b are mounted (only two of which are shown for clarity). The cylindrical casing 25a of the fan 25 and the cylindrical housing 22a of the particle charger 22 are both made of a material that can be machined, injection-moulded or otherwise formed to a high dimensional precision, e.g. a plastics material such as PVC or a die-cast metal. The cylindrical casing 25a of the fan 25 is hermetically sealed to the cylindrical housing 22a of the particle charger 22 in the direction of air flow, whereby all air entering the device 20 has to pass through both the particle charger 22 and the air mover 25, such that charge bypass is eliminated.

[0103] Unlike the device 10 shown in FIGS. 1 to 3, the order of the components and the relative spatial orientation of the components in the device 20 shown in FIGS. 8 and 9 is quite different: the particle charger 22 and the fan 25 are joined together in an airtight manner as an intimate couple 29, with the particle charger 22 being upstream of the fan 25. The air stream flows via an inlet 27 at the entrance to the particle charger 22, in the direction of arrow A, through the intimate couple 29 of particle charger 22 and fan 25, to the filter 26 via a gap, G, (illustrated by the dotted lines) therebetween and on to an outlet 28. In practice, this gap, G, would be contained by tapered cowling 21 or other such suitable ducting, as shown in FIG. 9.

[0104] In the device 20 in FIGS. 8 and 9, the particle charger 22 comprises a pin (corona) electrode 23, which is mounted centrally relative to a surrounding counter-electrode 24 so as to enable corona discharge from the tip of the pin and the generation of air ions for charging aerosol particles in the air stream in the manner discussed earlier in this specification.

[0105] As shown clearly in FIGS. 8 and 9, the particle charger 22 and the fan 25 are joined together in an airtight manner (a hermetic seal is formed) forming the intimate couple 29 upstream of the filter 26; there is no gap between the particle charger 22 and the fan 25, and although a gap, G, is shown as being present between the intimate couple 29 and the filter 26, it is under positive pressure with respect to ambient air and thus any bypass or leakage into the gap, G, (as a result of any imperfection in the cowling 21) of uncharged aerosol particles to the filter 26 is minimised, if not also completely eliminated.

[0106] In other words, unlike the prior art device 10 shown in FIGS. 1 to 3, the air stream passageway in the device 20 in FIGS. 8 and 9 undergoes only a single change in cross-sectional area (perpendicular to the direction of air flow) from the inlet 27 to the outlet 28. The passageway is relatively narrow (i.e. has a small cross-sectional area) at the inlet 27 of the device 20 to ensure that substantially all of the aerosol particles in the air flowing therethrough encounter air ions for charge transfer. Downstream of the particle charger 22 is provided the fan 25, and the passageway remains substantially constant in cross-section from the particle charger 22 to the fan 25, assisting formation of the intimate couple 29. Downstream of the fan 25, the passageway undergoes an expansion in cross-sectional area to accommodate the relatively large filter 26.

[0107] As there is only a single change in cross-sectional area of the air stream passageway, air passing through the device 20 in FIGS. 8 and 9 encounters less turbulence, air resistance, requires less energy and produces less noise; and the need for relatively costly cowling/ducting required to match the different cross sections as compared with the prior art device 1 in FIGS. 1 to 3 (which comprises two changes in cross sectional area of the gas passageway) is reduced.

[0108] The intimate couple of the particle charger 22 and the fan 25 is coupled to the filter 26 by means of cowling 21, which extends from an outlet of the fan casing 25a to the filter 26. Further external structure of the device 20, which is unimportant to the functioning components described above, is indicated schematically by the dotted lines shown in FIG. 9.

[0109] Referring now to FIGS. 10, 11 and 12, there is shown therein a second embodiment of an electrostatic precipitation air cleaning device 30 in accordance with the present invention for removing aerosol particles from an air stream. The device 30 of the second embodiment is similar to the first embodiment shown in FIGS. 8 and 9, and only the differences between the devices 20, 30 will be described in detail below. In FIGS. 10, 11 and 12, the components corresponding to those described above in relation to FIGS. 8 and 9 take the reference numbers used in FIGS. 8 and 9 but raised by 10.

[0110] Unlike the device 20 in FIGS. 8 and 9, because the filter 36 is sized such that its cross-section is the same as the cross-sectional area of the intimate couple 39 (formed by joining in an airtight manner of the particle charger 32 and the air mover in the form of a fan 35, such that the housing of the former is hermetically sealed to the casing of the latter), the air stream passageway in the device 30 in FIGS. 10, 11 and 12 undergoes no change in cross-sectional area from the inlet 37 to the outlet 38. As there is no change in cross-sectional area, air flowing through the device in FIGS. 10, 11 and 12 encounters less turbulence, air resistance, requires less energy and produces less noise; and there is no need for any relatively costly cowling/ducting to match different cross-sections as compared with the prior art device 10 shown in FIGS. 1 to 3 and with the device 20 according to the invention shown in FIGS. 8 and 9. Charge bypass is eliminated, filtration bypass and/or leakage is also reduced and particle charging efficiency and therefore capture is increased over and above that already achieved with the embodiment of the invention shown in FIGS. 8 and 9.

[0111] FIG. 12 shows a particular effect achievable with the present invention when charge bypass is eliminated, even though there may still be an amount of filtration bypass (because air filters must be designed to be removed from an air cleaner for replacement or cleaning and therefore the fit between the filter frame and the surrounding housing or ductwork is necessarily a sliding fit with inevitable bypass). Air is drawn through the particle charging zone such that charging of aerosol particles therein occurs. After passing through the fan 35, the air is in a positive pressure region and is blown through the filter 36 (and outlet grille, not shown) to produce a smooth laminar flow of air, represented by arrow L, which is of particular use when it can be directed toward the face of the user. The effect is particularly pronounced when the filter 36 is an electrostatic filter, such as is described in International patent publication WO00/61293. All of the charged particles passing through the filter are filtered out, and if there is any small leakage of bypass air (shown by arrows B) around the sides of the filter 36, this is not mixed with, and does not impact the laminar flow of, air exiting the filter 36. The user is subject to the full benefits of the particle-free air issuing from the filter 36. Such an effect is in direct contrast to most prior art portable air cleaners, such as is exemplified in FIGS. 1 to 3, which are designed with the fan downstream of the filtration means (whether that be an ion charger and filter combination or solely a filter). This results in the filtration means being under negative pressure with respect to the ambient air, which means that uncharged, unfiltered air (bypass air) is drawn through gaps or joints into the air cleaner at any or all of the coupling points. Bypass air (for example originating from around the removable filter) is drawn into the turbulent (negative pressure) region downstream of the fan where it is mixed with the clean air being drawn through the filter. Air blown out by the fan, in this common design of prior art air cleaner, is often at high velocity, is non laminar, is uncomfortable when blown at a personal user and is contaminated by this unfiltered air. Overall particle removal efficiency as measured between air into the air cleaner and out of the fan is often significantly reduced. The embodiment of the invention shown in FIGS. 10, 11 and 12 overcomes these prior art disadvantages.

[0112] Referring now to FIGS. 13 and 14, there is shown therein a further electrostatic precipitation air cleaning device 40 in accordance with the present invention for removing aerosol particles from an air stream. The device 40 of the third embodiment is effectively a stack of three of the devices 30 shown in FIGS. 10, 11 and 12, and as such the same reference numbers as those used to describe FIGS. 10, 11 and 12 will be used in FIGS. 13 and 14.

[0113] Three particle chargers 32, each having a pin electrode 33, and three air movers in the form of mechanical fans 35 are provided upstream of a single filter 36 in the device in FIGS. 13 and 14 (cf one of each respective component in the devices 20, 30 in FIGS. 8 and 9, and FIGS. 10, 11 and 12), i.e. three intimate couples 39 are provided upstream of the single filter 36. The presence of a single filter, spanning the three intimate couples 39, rather than three separate filters (one per couple) is the only modification made as compared to an exact stack of three of the devices 30 shown in FIGS. 10, 11 and 12. Of course, the embodiment shown in FIGS. 13 and 14 could be so modified such that the filter 36 spanned just two of the intimate couples 39 (with the third couple being provided with its own filter), or such that each intimate couple is provided with its own filter. All of these combinations are within the scope of the present invention.

[0114] The three particle chargers 32 are provided in the air stream passageway in a side-by-side arrangement (in this case, stacked one on top of the other), such that air flowing through the device encounters one or the other two particle chargers 32. Similarly, the three fans 35 are also provided in a side-by-side arrangement (again stacked one on top of the other and each being substantially co-axial with a respective particle charger 32), such that air flowing through the device 40 is drawn through one or the other two fans 35.

[0115] In use, some air flowing through the air stream passageway flows through the uppermost particle charger 32 and uppermost fan 35 to the common filter 36, some through the middle particle charger 32 and middle fan to the common filter 36, and some through the lowermost particle charger 32 and the lowermost fan 35 to the common filter 36.

[0116] Each of the three particle chargers 32 has a similar cross-sectional area to each of the three fans 35, and so the total air stream passageway therebetween remains substantially constant in cross-sectional area. The collective cross-sectional area of the three particle chargers 32 and three fans 35 is similar to that of the single filter 36, (i.e. the filter 36 has a cross-sectional area approximately three times that of each intimate couple 39). Because of the similarity in cross-sectional area, the air stream passageway between the fans 35 and the filter 36 remains substantially constant in cross-section.

[0117] In light of the above, as with the device in FIGS. 10, 11 and 12, the air stream passageway in the device in FIGS. 13 and 14 undergoes substantially no change in cross-sectional area from its inlets 37 to its outlets 38. As there is substantially no change in cross-sectional area, air passing through the device 40 in FIGS. 13 and 14 encounters less turbulence, air resistance, requires less energy and produces less noise; there is no need for relatively costly connecting tubes required to match the different cross sections as compared with the devices 20, 30 in FIGS. 8 and 9, and 10, 11 and 12. As shown, the common filter 36 is fitted to the downstream end of the three intimate couples 39 by means of a straightforward housing (not shown). Thus charge by[pass is eliminated, filtration bypass and/or leakage is also reduced and particle charging efficiency and therefore capture is increased over and above that already achieved with the embodiment of the invention shown in FIGS. 8 and 9.

[0118] Referring now to FIGS. 15 and 16, there is shown therein a further electrostatic precipitation air cleaning device 50 in accordance with the invention for removing aerosol particles from an air stream. The device 50 comprises a particle charger 52, an air mover 55 in the form of a blower, and a filter, which although not explicitly shown here, would be positioned downstream of the air flow exiting the blower 55, which air flow is labelled with arrow F.

[0119] The particle charger 52 and the blower 55 are joined together (hermetically sealed together) in an airtight manner as an intimate couple 59, with the particle charger 52 being upstream of the blower 55. The air stream flows via an inlet 57 at the entrance to the particle charger 52, through the intimate couple 59 of particle charger 52 and blower 55, to the filter (somewhere downstream of air flow shown by arrow F) and on to an outlet (not shown). In practice, cowling or other such suitable ducting would be provided to position the filter externally of the blower 55.

[0120] More specifically in FIGS. 15 and 16, the particle charger 52 comprises a pin (corona) electrode 53 mounted centrally on a diametric rod 53a which is mounted in an intake (air inlet section) 51 of the blower 55. The intake 51 is conductive and earthed, and as a result the intake 51 behaves as a counter-electrode (also referenced as 54 hereinafter) for the pin electrode 53, thereby improving particle charging effectiveness. The intake 51 is shown as a protruding member in FIG. 5, however it could easily be in the form of an opening in the otherwise flat outer surface of the side of the blower 55. The intake 51, whether in the form of a protrusion (as shown) or a flush opening (as an alternative) can itself be conductive (as described above) or, if formed of a non-conductive material, e.g. a plastics material, be provided with a conductive interior surface, e.g. an area, preferably a ring, of conductive ink or paint to form the counter-electrode. The intake 51 of the blower 55 is substantially cylindrical, meaning that the counter-electrode 54 is similarly cylindrical, whereas the tip of the pin electrode 53 is substantially a point. The cylindrical counter-electrode 54 and tip of the pin electrode 53 are, therefore, symmetrically arranged, which means, in combination with the pin electrode 53 and the counter-electrode 54 being concentric, that the distance from the pin tip to the inner surface of the surrounding electrode is approximately constant. This means that the air ion flux between the pin electrode 53 and the surrounding counter-electrode 54 is radial, thereby increasing the likelihood of air ion-aerosol particle collisions, which further improves particle charging effectiveness by the corona electrode 53 and eliminates charge bypass.

Test Data

[0121] An electrostatic air precipitation device, of the type schematically shown in FIGS. 10, 11 and 12 of the accompanying drawings, was tested for its aerosol particle capture efficiency by varying the current supplied to the pin emission electrode of the particle charger as a function of captured particle size. Air flow to the device was controlled at 1.2 metres per second filter face velocity for all tests. The filter used was an electrostatic, fluted ifD filter of 3 inches (76.2 mm) depth supplied by Darwin Technology International Limited (www.tfdair.com); the ifD filter was operated at 10 kV between adjacent electrodes. The number of particles was measured using a laser particle counter (Lighthouse Handheld Model No. 3016) which was operated consistently so that a % particle capture efficiency could be calculated. The results are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Current Supplied Captured Particle Size (m) (A) 0.3 0.5 0.7 1.0 2.0 5.0 1.0 99.35 99.46 99.26 99.59 99.03 100.00 2.0 99.88 99.92 99.94 99.88 100.00 100.00 3.0 99.95 100.00 100.00 100.00 100.00 100.00 4.0 99.99 100.00 100.00 100.00 100.00 100.00 5.0 100.00 100.00 100.00 100.00 100.00 100.00

[0122] The percentage particle capture efficiencies noted in Table 2 above clearly show a general trend of increasing efficiency with increased current supplied, for each of the particle sizes captured, and increasing efficiency with which increasingly large particles are captured for a given current supplied (subject to experimental error).

[0123] Larger aerosol particles are generally easier to capture than smaller particles (due in part to there being a greater likelihood of collision of larger particles with air ions and thus more charged particles to capture). However, even with aerosol particle sizes as small as 0.3 m, with only 1.0 pA of current supplied to the pin-type electrode, greater than 99% (99.35%) efficiency is achieved, this rising to 99.99% with 4.0 pA of current supplied.

[0124] It should of course be noted that all of the efficiencies quoted are subject to the operational measurement limitations of the particle counter.

[0125] Referring now to FIGS. 17 and 18, there is shown an embodiment of an air cleaning apparatus according to the invention, which may form part of an HVAC system.

[0126] Electrostatic precipitation apparatus 60 is designed to remove unwanted aerosol particles from an air stream with high efficiency (typically 99.99%) and comprises an air mover 65 in the form of a mechanical fan, a particle charger 62, and a filter 66 for removing charged aerosol particles from the air stream (dirty air) (not shown) as it flows through the apparatus 60 in the volume defined by ductwork 69, in the direction of arrow A, through the filter 66, to an outlet (not shown) downstream of the filter 66. Each of the particle charger 62, the fan 65 and the filter 66 is provided within the ductwork 69, i.e. a housing to accommodate said components.

[0127] The particle charger 62 comprises an electrode in the form of a single pin 63 mounted centrally along the length of a rod 63a that is electrically coupled to a surrounding counter-electrode 63b formed on the interior surface of a portion of the ductwork 69 in the region of the pin 63 so as to enable corona discharge from the tip of the pin 63 and the generation of air ions for charging aerosol particles in the air stream in the manner discussed earlier in this specification. The pin 63 is illustrated in as an arrow which the arrowhead representing the tip of the pin. The counter-electrode 63b is shown in dotted outline and is formed from conductive ink or paint applied directly to the interior surface of the ductwork 69. Alternatively, the ductwork 69 itself may be made of a suitably conductive material. The rod 63a on which the pin 63 is mounted is fitted into the ductwork 69 by any conventional fixing means, including, for example, gluing, soldering, welding, etc.

[0128] As shown clearly in FIGS. 17 and 18, the particle charger 62 and the fan 65 are provided upstream of the filter 66. Because the particle charger 62 and the ductwork 69 together form the particle charging zone (having air ion flow lines shown by the dotted arrows in FIG. 18) within which aerosol particles will be electrically charged, and because the ductwork 69 provides a hermetic seal between the particle charger 62 and the fan 65 in the direction of air flow, all air entering the apparatus 60 via the ductwork 69, has to pass through both the particle charger 62 and the fan 65, such that charge bypass is eliminated.

[0129] Of course, the order of the components shown could be altered, in that the relative positions of the particle charger 62 and fan 65 could be exchanged so that the fan 65 is downstream of the particle charger 62 (but still upstream of the filter 66). The position of the counter-electrode 63b would also need to be moved to match the position of the particle charger 62, unless a greater proportion of the interior surface of the ductwork 69 were to be made conductive, or if the ductwork 69 per se was conductive. The effect of elimination of charge bypass would nonetheless be the same.

[0130] It will be appreciated that certain features of the invention, which are for clarity described separately, particularly those in the context of alternative embodiments, may also be provided in combination in a single embodiment.

[0131] Conversely, various features of the invention which are described in combination, in the context of a single embodiment, may also be provided separately, or in any suitable combination.

[0132] It will also be appreciated that various modification, alterations and/or additions to the described embodiments may be introduced without departing from the scope of the present invention, as defined in the following claims. Many other possible modifications would be appreciated by one of skill in the art following the teaching in this description.