Background Art The use of air distribution units or diffusers as part of a heating, ventilating and air conditioning (HVAC) system is relatively well known. Such systems often include an air distribution system comprising a network of air ducts, which supply heated or cooled air to various spacial areas in a building ventilated, by the HVAC system. The air is discharged from the ducts into the ventilated areas by a series of air outlets. Typically, a diffuser is provided at or near the air outlet to control the flow of air entering the ventilated areas, and to provide an even distribution of air to a desired area without undue noise or uncomfortable drafts to disturb the occupants. Many types of diffusers generally employ one or more vanes or deflectors to direct the discharged airflow in a desired orientation.

It is well known that the most effective manner of distributing air from ceiling- mounted diffusers during cooling is to direct the air in a horizontal flow across the ceiling of the room by employing what is known in the industry as the "Coanda effect." A stream of air discharged from a diffuser at an angle less than approximately 35 to 40 degrees with respect to the ceiling will tend to create a partial vacuum and cause the air stream to remain in contact with or "hug" the ceiling as a result of the Coanda effect. Cool air, therefore, can be distributed over a substantial area of the ceiling by employing the Coanda effect before the cool air begins to "sink down" into the room to cool the entire volume of the room.

In contrast, the best efficiency in connection with the distribution of heated air from ceiling-mounted diffusers is for the air to be discharged in a generally vertically oriented stream. The vertical flow component overcomes the natural buoyancy of the

heated discharged air to serve the lower strata of the room with heated air and to thereby achieve a proper mixing of the heated air with the room air. Because the discharged air flows through the occupied space before mixing is complete, drafts may be somewhat directed at the occupants. However, most people do not perceive warm drafts as uncomfortable.

In many HVAC applications, the same duct outlet may discharge both heated and cooled air. In order to achieve the most efficient and comfortable distribution of air, it is desirable to provide a diffuser with the capability of adjusting the flow pattern between a substantially horizontal orientation and a substantially vertical orientation.

For example, diffusers have been previously developed wherein a screw is rotated to adjust the orientation of diffuser elements and direct the discharged airflow in the desired orientation. Where the diffuser is located in a ceiling above the reach of the person adjusting the air flow, a special long handled tool is generally required to reach the adjusting screw.

Person, U.S. Patent No. 3,107,597 issued October 22, 1963 discloses a diffuser comprising a core of concentric truncated cones, concentrically mounted in a frustum shaped cover which is capable of directing the air flow in a relatively horizontal or vertical orientation by adjusting the vertical position of the cones with respect to the cover. Flexible hooks on the cover selectively engage individual teeth of saw toothed engagement members on the core to hold the core in discreet vertical positions relative to the cover. Upward adjustment of the core is accomplished by pushing upwardly on the core causing the teeth to ride over the hooks, thereby resenting teeth at a different level for engagement with the hooks. However, downward adjustment of the core requires that the core first be rotated to bring the teeth out of engagement with the hooks. If the diffuser is located in a high ceiling, rotation of the core requires the operator to climb a ladder or use a special tool to reach the diffuser core.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the drawings wherein: FIG. 1 is a perspective view of a ceiling diffuser arrangement according to the present invention as seen from the top;

FIG. 2 is a perspective view of the diffuser arrangement of FIG. 1 as seen from the bottom; FIG. 3 is a side elevation view of the diffuser arrangement of FIG. 1; FIG. 4 is a bottom view of the ceiling diffuser arrangement of FIG. 1; FIG. 5 is a sectional view of the ceiling diffuser arrangement taken through Section 5-5 of FIG. 4; FIG. 6 is a sectional view of the ceiling diffuser arrangement taken through Section 6-6 of FIG. 1, showing a mounting bracket for attaching a ratchet mechanism to a diffuser cover; FIG. 7 is a plan view of the mounting bracket of FIG. 6; FIG. 8 is a side view of the mounting bracket of FIG. 6; FIG. 9 is an exploded perspective view of a multi-position ratchet mechanism according to the present invention shown removed from the diffuser arrangement; FIG. 10 is a front view of the ratchet mechanism of FIG. 9 shown in its lowest position; FIG. 11 is a top view of the ratchet mechanism of FIG. 9 shown in its lowest position; FIG. 12 is a side view of the ratchet mechanism of FIG. 9 shown in its lowest position; FIG. 13 is a front view of the ratchet mechanism of FIG. 9 shown in its intermediate position; FIG. 14 is a front view of the ratchet mechanism of FIG. 9 shown in its upper position; and FIG. 15 is a front view of the ratchet mechanism of FIG. 9 shown in its release position; FIG. 16 is an exploded view of a second embodiment of a multi-position ratchet mechanism according to the invention; FIG. 17 is a front view of the ratchet mechanism of FIG. 16 shown in its lower position;

FIG. 18 is a front view of the ratchet mechanism of FIG. 16 shown in its upper position; FIG. 19 is a front view of the ratchet mechanism of FIG. 16 shown in its release position.

DESCRIPTION OF THE PREFERRED EMBODIMENT The principles of the invention will now be described, by way of example, in a ratchet mechanism 20 primarily shown in FIGS. 6-15, and in a ratchet mechanism 200 primarily shown in FIGS. 16-19. For purposes of illustrating use and operation of ratchet mechanisms in accordance with the invention, the ratchet mechanism 20 will be described in part with an air diffuser apparatus 100 primarily illustrated in FIGS. 1- 5. The diffuser 100 is actually designed to utilize three of the ratchet mechanisms 20.

In general, ratchet mechanisms in accordance with the invention provide convenient means for adjustment of diffusers among discreet vertical positions by means of upwardly directed forces. No special tools are required for the adjustment, and the adjustment can be made relatively rapidly. Any elongated structure of sufficient length, such as a pole or the like, could be utilized by an operator for performing the adjustment. Although the ratchet mechanism 20 is shown and described with respect to operation with diffuser 100, ratchet mechanisms in accordance with the invention can be utilized with numerous other types of diffusers.

As best shown in FIG. 5 the cover 102 mounts a core 104 in a manner so that the core 104 is adjustable in an axially vertical direction relative to the cover 102.

The core 104 comprises upper cone 106 and lower cone 108. Preferably the upper and lower cones 106, 108 have a similar frustum shape to the cover 102, but with a relatively smaller size, so that the upper cone 106 fits concentrically below and within the cover 102, and the lower cone 108 fits concentrically below and within the upper cone 106. The upper truncated portion of the upper cone 106 is open so that air may flow through the central portion of the cone 106. The upper truncated portion of the lower cone 108 is closed by a horizontally disposed upper wall 107. Concentric cone style diffusers of the type shown are well known, and Person, U.S. Patent No.

3,107,597 issued October 22, 1963 describes such diffusers in more detail.

Air passing through the diffuser 100 passes between the cover 102 and the upper cone 106 and between the upper cone 106 and the lower cone 108 and the angled surfaces of the upper and lower cones 106 & 108 deflect the discharged air and impart horizontal velocity component thereto. The upper and lower cones 106, 108 are fixed relative to one another, but are moveable vertically relative to the cover 102.

As the upper cone 106 moves axially away (downwardly) from the cover 102, less of the air is deflected vertically by the cover 102, thus allowing a more horizontally oriented discharge flow orientation.

During cooling operations, the core 104 is lowered and positioned in a "lowered" configuration, indicated by the dotted line 112 representing the upper cone 106 when the core 104 is in the lowered configuration. In this configuration, airflow is directed substantially parallel to the plane of the ceiling 101 by the core 104, a pattern advantageous for air conditioning or other cooling operations. During heating, the core 104 is selectively positioned in an "upper" position, indicated by the dotted line 110 representing the upper cone 106 when the core 104 is in the upper configuration. In the upper configuration, airflow is directed substantially axially and downward toward the floor of the environment to be heated. An "intermediate" position shown in FIG. 5 provides both horizontal and vertical components to the airflow.

The diffuser apparatus 100 includes a plurality of ratchet mechanisms 20 interconnecting the cover 102 with the cones 106, 108. The ratchet mechanisms 20 operate in a manner so that the cones 106, 108 can be adjusted among the lower, intermediate and upper configurations solely by means of exerting axially upwardly directed forces on the core 104.

The invention, by way of example, will now be described with reference to a single ratchet mechanism 20, although the drawings illustrate the use of three ratchet mechanisms 20. As primarily shown in FIGS. 9 and 10, each ratchet mechanism 20 comprises a lower plate 22, an upper plate 24, a swing arm 26, and a locking arm 28.

The lower plate 22 attaches to the cones 106, 108 and the upper plate 24 attaches to the cover 102, as will be more fully explained hereinafter. Each upper plate 24 has a

mounting tab 25 extending outwardly radially. The cover 102 has a mount 116 for each ratchet mechanism 20, adapted to receive the mounting tab 25.

As shown in FIGS. 6-8, each mount 116 comprises a standard U-shaped suspension bracket 118 and a spring clip 120 of a type known in the art. The suspension bracket 118 has two vertical sidewalls 122 extending inwardly from the cover 102. A vertical front wall 124 connects the two sidewalls 122. The bracket 118 may be attached to the cover 102 by rivets, welding or by any other suitable means.

The front wall 124 has a square opening 126 having a mouth 128 to the lower edge of the front wall 124 and a triangular ledge 130 extending into the mouth 128. The ledge 130 has a horizontal top edge 132 and an angled bottom edge 134. The spring clip 120 is formed of a length of spring metal of approximately equal width to one of the sidewalls 122. The spring clip 120 wraps around one side wall 122, starting from inside the bracket 118, over the top edge of the side wall 122, down the outside face of the side wall 122, over the bottom edge of the sidewall 122, angling upwardly inside the bracket 118 towards the top edge of the opposite sidewall 122, and finally bends vertically downwardly to extend beneath the bracket 118. The tab 25 on a ratchet mechanism 20 is inserted into the bracket 116 by placing the tab 25 against the spring clip 120, beneath the bracket 118 and on the opposite side of the spring clip 120 from the sidewall 122 to which the spring clip 120 attaches.

The tab 25 is moved sideways to push the spring clip 120 away from the mouth 128 (to the right as shown in FIG. 6). The tab 25 may then be moved upwardly into the mouth 128, where pressure from the spring clip 120 will push the tab 25 over the ledge 130 and hold the tab 25 firmly in place atop ledge 130. In practice, multiple ratchet mechanisms 20 will be employed as described in the following paragraphs, and the tabs 25 on the ratchet mechanisms 20 will be mounted in the corresponding brackets 116 simultaneously.

As primarily shown in FIGS. 1 and 5, a central axial cylinder 136 attaches to and extends upwardly from the lower cone 108 through the center of the diffuser 100, and guides the movement of the core 104. A triangular bracket 138 surrounds and is affixed to the cylinder 136 at its connection to the lower cone 108. The bracket 138

comprises three walls 140 tangential to and affixed to the outer surface of the cylinder 136. The bracket 138 has three projections 142 extending outwardly radially from the cylinder 136 which are formed by bending the material ofthe walls 140 outwardly.

The walls 140 are of equal size so that the radial projections 142 are equally spaced about the cylinder 136. The lower plates 22 of the ratchets 20 attach to the bracket 138 at the radial projections 142, and attach to the upper cone 106, to interconnect the upper and lower cones 106, 108.

A second triangular bracket 144 surrounds the cylinder 136 at its upper end, but is not attached to the cylinder 136. The upper bracket 144 has a similar construction to the lower bracket, having three walls 146 tangential to the cylinder 136, and three radial projections 148, which are attached to the upper plates 24 of the ratchets 20 by spot welding or any other suitable method. The upper plates 24 attached to the upper bracket 144 and to the cover 102 fix the upper bracket 144 in the center of the cover 102. The upper bracket 144 guides the vertical movement of the cylinder 136, and thus the diffuser core 104.

Each wall 140 forming the lower triangular brackets 138 may be integrally formed of the material of one of the lower plates 22. The integral wall 140 is construct by forming an extension of the material of the lower plate 22 and bending it to the correct shape to form the wall 140. The wall 140 thus formed would have only one radial projection 142, at the opposite end from its junction with the integral lower plate 22, for connection to the adjoining ratchet mechanism 20. The walls 146 forming the upper triangular bracket 144 may similarly be formed by extending the upper plates 24. Any other suitable method may be employed for affixing the lower plates 22, to the cylinder 136 or the lower cone 108 or both. Also, any suitable method may be employed in place of the triangular bracket 144 for guiding the cylinder 136 at the juncture of the three upper plates 24.

The lower plates 22 may be attached to the upper and lower cones 106, 108 in any suitable fashion. For instance as shown in FIGS. 9 and 10, the lower plates 22 may have an angled lower edge 27, at the same angle as the upper cone 106. A tab 29 extending normal to the face of the lower plate 22 at the edge 27 attaches to the cone

106 by welding or other suitable method. A similar tab 31 extending from a lower edge 33 of the lower plate 22 can attach to the lower cone 108.

The lower plate 22 of each ratchet 20 has an L-shaped tab 30 projecting outwardly from its face. The upper plate 24 has an elongated vertical slot 32 which receives the tab 30, to interconnect the upper and lower plates 24, 22 and to direct the movement of the lower plate 22 relative to the upper plate 24. The L-shaped tab 30 comprises a stem 34 extending normal to the face of lower plate 22, and a head 36 affixed to the outer end of the stem 34 and extending parallel to the face of the lower plate 22. The tab 30 may be fabricated by forming an L-shaped tab 30, inserting the stem 34 through a hole 31 in the front face of the lower plate 22, folding over the stem 34 against the rear face of the lower plate 22, and welding the tab 30 thereto.

As shown in FIGS. 10-15, the lower plate 22 sits parallel to and behind the upper plate 24 and the L-shaped tab 30 extends through the face of the upper plate 24 at the slot 32. The tab 30 helps secure the lower plate 22 to the upper plate 24. The stem 34 of the tab 30 operates in the slot 32 in the upper plate 24. The head 36 of the tab 30 extends laterally from the stem 34 a sufficient distance to engage the upper plate 24 and hold the lower plate 22 in the slot 32. The head 36 preferably extends horizontally away from the swing arm 26, to the right as shown in FIG. 10.

Returning to FIG. 9, the swing arm 26 comprises a mounting hole 38 located in an upper horizontal section 40, a first ledge 42 and a second ledge 44 located in a vertical section 46, and a diagonal section 48 connecting vertical section 46 and horizontal section 40 at an approximately 45 degree angle thereto. The first and second ledges 42, 44 extend outwardly from the vertical section immediately below the diagonal section, and each comprises an upper straight horizontal edge 50 and a convex arcuate lower edge 52 extending from the outer most end of the edge 50 down to the vertical section 46.

The swing arm 26 mounts to the upper plate 24 by means of a tab 54. Tab 54 may comprise an attachment pad 56 parallel to and welded or otherwise affixed to upper plate 24, a stem 58 extending outwardly from, and normal to the face of upper plate 24, and a head 60 at the outer end of the stem 58, extending parallel to the upper

plate 24. The stem 58 of tab 54 is received in the mounting hole 38 on the swing arm 26. The head 60 of tab 54 extends over the horizontal section 40 of swing arm 26 to prevent swing arm 26 from dislodging from tab 54. There must be sufficient clearance between the head 60 of tab 54 and the face of upper plate 24 to allow the swing arm 26 to rotate freely about tab 54.

An additional tab 62 mounts the locking arm 28 and also limits the swing arm's 26 arc of rotation. The locking arm tab 62 has a similar construction to the swing arm mounting tab 54, having an attachment pad 64 parallel to and affixed to the face of the upper plate 24, a stem 66 extending outwardly and normal to the face of the upper bracket 24, and a head 68 at the outer end of the stem 66 extending parallel to the face of the upper bracket 24.

At the lower end of the vertical section 46 of the swing arm 26 a leg 70 extends vertically downwardly, and has an indentation 72 which engages the stem 66 of the locking arm mounting tab 62, to limit the counter-clockwise rotation of the swing arm 26. The locking arm 28 is mounted to the upper plate 24 by the tab 62.

The leg 70 is positioned between the locking arm 28 and the upper plate 24.

The locking arm 28 is an elongated rectangular shape having a mounting hole 74 near one end and a rectangular cutout 76 from the lower corner at the opposite end.

Middle section 66 of tab 62 is received within the mounting hole 74 in the locking arm 28. The head 68 of the tab 62 retains the locking arm 28 on the tab 62. The clearance between the head 68 and the upper plate 24 is sufficient to allow the swing arm 26 to slide freely under the locking arm 28, and to allow the locking arm 28 to pivot about the tab 62.

A catch 78 extends outwardly, horizontally from the lower end of the leg 70.

The catch 78 can be fabricated by forming the swing arm 26 so that a portion forming the catch 78 extends outwardly laterally from the bottom of the leg 70, and from the opposite side from the first and second ledges 42, 44, and then bending the catch 78 to extend normal to the face of the swing arm 26. The catch 78 limits the counter- clockwise rotation of the locking arm 28 about the tab 62.

A stop 80 extending normal to the face of the upper plate 24 limits the clockwise rotation of both the swing arm 26 and the locking arm 28. The stop 80 can be formed of an L-shaped piece of material having an attachment portion 82 parallel to and affixed as by welding to the face of the upper plate 24, and a stem 84 extending normal to the face of the upper plate 24.

The ratchet mechanism may be adjusted to three different vertical positions of the lower plate 22 relative to the upper plate 24 by purely upward forces on the lower plate 22. The lowest position is shown in FIG. 10. In this position, the L-shaped tab 30 on the lower plate 22 rests on the locking arm 28, and the stop 80 prevents clockwise rotation of the locking arm 28. To move the lower plate 22 into the intermediate position, as shown in FIG. 13, an upward force is applied to the lower plate 22 (typically by an upward force applied to the upper wall 107 of the lower cone 108). As the lower plate 22 contacts the arcuate lower edge 52 of the first ledge 42, its upward motion causes the swing arm 26 to pivot clockwise until the L-tab 30 has moved upwardly past the first ledge 42. At this point, gravity will cause the swing arm to fall back towards its original position. If the upward force on lower plate 22 is then discontinued, it will settle to rest on the upper edge 50 of the first ledge 42. To move from the intermediate position to the upper position as shown in FIG. 14, further upward force is applied to the lower plate 22 causing it to move to the upper position on the second ledge 44 in a similar fashion as the movement from the lower position to the intermediate position.

To move the lower plate 22 from the upper position to the lowest position, further upward force is applied to the lower plate 22. This upward force will cause the L-shaped tab 30 to contact the diagonal section 48 of the swing arm 26, causing a clockwise rotation of the swing arm. As the swing arm 26 rotates in a clockwise fashion, the catch 78 will move along the lower edge of the locking arm 28 until it slides into the cut-out 76. At this point, stop 80 prevents further clockwise rotation of the swing arm 26 while the catch 78 in cutout 76 prevents counter-clockwise rotation of the swing arm 26. This position is represented in FIG. 15. If the upward force is now removed from the lower plate 22, gravity will cause it to move downwardly until

it contacts the locking arm 28. When the L-shaped tab 30 contacts the locking arm 28, the force from gravity will cause a slight clockwise rotation of the locking arm 28, until the locking arm 28 contacts the stop 80. This slight rotation of the locking arm 28 is sufficient to release the catch 78 from the cutout 76, and allow the swing arm 26 to rotate counter-clockwise back to its original position. The lower plate will now be in its lowest position as shown in FIG. 10. When the ratchet mechanisms 20 are incorporated into the ceiling mounted diffuser 100 shown in FIG. 5, the upwardly directed force may be applied to the lower cone 108 with a pole or broom handle (not shown) by a user standing on the floor. A second embodiment 200 of the ratchet mechanism is shown in FIGS. 16-19. The ratchet mechanism 200 comprises a lower plate 202, an upper plate 204, a swing arm 206 and a locking arm 208.

The lower plate 202 attaches to the cones 106, 108 and the upper plate 204 attaches to the cover 102 as in the first embodiment, and these attachments are not further illustrated. The lower plate 202 is flat, and preferably formed of low carbon steel. The lower plate 202 has a front face 210, a rear face 212, an inside vertical edge 214, and an essentially parallel outside vertical edge 216 and an upper horizontal edge 218. An upper angled edge 220 angles between the upper horizontal edge 218 and the inside vertical edge 214. A lower bracket mounting projection 222 extends outwardly from the lower inside vertical edge 214 and provides an attachment for mounting the lower bracket 138 as in the first embodiment. A lower cone mount 224 extends normal to the rear face 212 of the lower plate 202, and is angled relative to the inside vertical edge 214 at the proper angle to engage the lower cone 108 (not shown in FIGS. 16-19). The lower cone-mounting tab 224 can be formed by bending a portion of the material of the lower plate 202 normal to the rear face 212. The lower cone mounting tab 224 is preferably located at the lower most portion of the lower plate 202 on the lower bracket mounting tab 222. An upper cone-mounting tab 226 also extends normal to the rear face 212 of the lower plate 202, and is formed in a similar fashion to the lower cone-mounting tab 224. The upper cone-mounting tab 226 is preferably located at the lowermost end of the outside vertical edge 216. A lower angled edge 228 extends between the lower cone-mounting tab 224 and the upper

cone-mounting tab 226. An L-shaped tab 230 extends normal to the front face 210 at the junction between the upper horizontal edge 218 and the upper angled edge 220.

The L-shaped tab 230 comprises a stem portion 232 extending outwardly from the front face 210 and a head portion 234 extending horizontally from the end of the stem portion 232.

The upper plate 204 is a flat plate preferably formed of low carbon steel. The upper plate 204 has a vertical inside edge 236, a vertical outside edge 238, a horizontal upper edge 240, a horizontal bottom edge 242, a front face 235 and a rear face 237. The upper plate 204 has a rectangular inside cutout 246 at the intersection of the inside edge 236 and the bottom edge 242, and a second, somewhat larger rectangular outside cutout 248 at the intersection of the outside edge 238 and the bottom edge 242. A mounting tab 250 extends outwardly horizontally from the lowermost outside edge 238. The mounting tab 250 has a generally horizontal upper edge 252 and a lower edge 254 which angled slightly upwards as it extends outwardly from the outside edge 238. A rounded corner 256 is provided at the outside end of the upper edge 254 of the mounting tab 250. A swing arm stop, or tab 258 extends normal to the front face 235 of the upper plate 204. The swing arm stop 258 is located along the inside edge 236, and can be formed by making two notches 260 inwardly from the inside edge 236 to form a tab 258 which may be bent so that it extends normal to the front face 235. The material forming the tab 258 may also be formed by extending a portion of the upper plate 204 outwardly from the inside edge 236 and bending that material to extend outwardly and normal to the front face 235 to form the swing arm stop 258. The upper plate 204 is provided with an elongated vertically oriented slot 260. The upper plate 204 is also provided with a hole 262 located in the upper outermost corner for mounting the swing arm 206, and a separate hole 264 located beneath the slot 260 for mounting the locking arm 208.

The swing arm 206 comprises a mounting hole 266 located in an upper horizontal section 268, a vertical section 270 and an angled edge 272 defining the lower edge of the horizontal section 268. A ledge 274 extends from the vertical section 270 and is located underneath the angled edge 272. The ledge 274 is

triangular in shape and comprises an upper edge 276 which extends outwardly and horizontally from the vertical section 270, and a lower edge 278 which angles outwardly as it extends upwardly from the vertical section 270 to meet the upper edge 276 of the ledge 274. A locking arm catch 280 is located at the bottom of the vertical section 270. The locking arm catch 280 comprises a tab 25 of material extending outwardly from the vertical section 270 from the opposite side as the ledge 274, and which is bent into a U-shape.

The locking arm 208 comprises an inside vertical arm 282 and an outside vertical arm 284 connected by a base portion 286. The inside (left, as seen in FIGS.

16-19) lower corner 288 of the base portion 286 may be chamfered to reduce the free area needed for swinging the locking arm 208. A triangular shaped locking ledge 290 extends outwardly from the inside vertical arm 282, and comprises a horizontal upper edge 292 and a lower edge 294 which angles upwardly as it extends outwardly to meet the upper edge 292. A distal portion 296 of the inside vertical arm 282, distal to the locking ledge 290, can be narrower than the rest of the inside vertical arm 282. At the distal end of the outside vertical arm 284, there is a landing pad 298. The landing pad 298 extends normal to the face of the locking arm 208 and at an approximately 45" angle to the outside vertical arm 284. The landing pad can be formed by bending a portion of the outside vertical arm 284 to extend normal to the face of the locking arm 208. Preferably, the landing pad extends outwardly beyond the width of the outside vertical arm 284. A hole 300 is provided in the base portion 286 for mounting the locking arm to the upper plate 204.

In the assembled ratchet mechanism 200, the swing arm 206 is rotatably mounted to the front face 235 of the upper plate 204 by means of a rivet 302 through the hole 266 in the swing arm 206 and the hole 262 in the upper plate 204. The locking arm 208 overlies the swing arm 206 and is rotatably mounted to the upper plate 204 by means of a rivet 304 through the hole 300 in the locking arm 208 and the hole 264 in the upper plate 204. The lower plate 202 attaches to the upper plate 204 by means of the L-shaped tab 230. The tab 230 is inserted from the rear through the slot 260 in the upper plate 204 so that the stem 232 of the tab 230 engages the slot 260

and the head 234 of the tab 230 overlies the front face 235 of the upper plate 204 and prevents the tab 230 from disengaging the slot 260.

The second embodiment of the ratchet 200, functions similarly to the first embodiment of the ratchet 20, except it has only two positions. To move the ratchet 200 from the lowered position (FIG. 17) to the upper position (FIG. 18), an upwardly directed force is applied to the lower plate 202 causing the tab 230 to move upwardly in the slot 260. As the tab 230 moves upwardly, it will engage the lower angled edge 278 of the ledge 274, causing the swing arm 206 to move slightly clockwise, thus allowing the tab 230 to move upwardly past the ledge 274. After the tab 230 clears the ledge 274, the swing arm will fall back to its original position by the force of gravity. If the upwardly directed force is then removed, the tab 230 will settle onto the upper edge 276 of the ledge 274. The ratchet 200 is then in the upper position.

To move the ratchet 200 back to the lowered position, additional upwardly directed force is applied to the lower plate 202, causing the tab 230 to move upwardly and contact the angled edge 272 of the swing arm 206. The upwardly directed force acting against the angled edge 272 will cause the swing arm 206 to rotate clockwise until it touches the swing arm stop 258. While the swing arm 206 is rotating, gravity is acting on the locking arm 208. Because it is mounted off center about its mounting hole 300, gravity tends to pull the locking arm 208 to rotate in the counter-clockwise direction, so that as the swing arm 206 rotates, the locking arm catch 280 on the swing arm 206 will move over the ledge 290 on the locking arm 208. When the upwardly directed force on the lower plate 202 is released, the locking arm catch 280 engages the ledge 290 and prevents the swing arm 206 from falling back to its original position by gravity. With the swing arm 206 and its ledge 274 out of the path of the tab 230, it can settle back to the lower position by the force of gravity. As the tab 230 reaches the lower position, it contacts the landing pad 298, imparting a clockwise rotation to the locking arm 208, and releasing the swing arm 206 from the locking arm catch 280.

The ratchet mechanism 200 thus settles back to the position shown in FIG. 17.

Typically with the ratchet mechanisms 200 installed in a diffuser 100 similarly to the ratchet mechanisms 200 as shown in FIG. 5, the upwardly directed force will be applied to the lower cone 108, which is connected to the lower plate 202.

While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particular in light of the foregoing teachings.

Reasonable variation and modification are possible within the foregoing disclosure of the invention without departing from the scope of the invention.