The invention relates to a heat exchanger and more particularly to a heat exchanger formed from a plurality of layered plates wherein fluid passageways are defined between alternating pairs of plates.
Heat exchangers such as evaporators can be used in heating, ventilation and air conditioning (HVAC) systems. A typical evaporator used in the HVAC modules of automotive air conditioning systems includes a core formed by pairs of embossed plates joined together to create a plurality of flow tubes for the refrigerant tubes in the interior of the core. Fins are disposed between the refrigerant flow tubes to permit ambient air to flow across the exterior of the tubes and exchange thermal energy with the refrigerant. The tubes are in fluid communication with a pair of spaced tanks formed out of the plates themselves comprising a plurality of cups punched at two ends of plates. Since the process of stacking plates and fins in the construction of the evaporator core is a laminating process, these evaporators are referred to as the laminated type of evaporators.
Generally, the evaporator core is placed in an HVAC module of the air conditioning system directly at the diffuser section of the HVAC module. Often, the incoming airflow must turn through a sharp angle in order to enter the air passages between the plate tubes of the evaporator. Associated with the sharp bending of the flow path lines is a pressure drop penalty.
The invention provides a heat exchanger having a plurality of plates stacked in alternating mirrored relation with one another. Each of the plurality of plates has a plate length extending along a plate longitudinal axis between first and second ends. Each of the plurality of plates also has a plate width extending transverse to the plate longitudinal axis. The plurality of plates cooperate to define a fluid receiving cavity extending along a receiving axis substantially perpendicular to the plate longitudinal axis. The plurality of plates also cooperate to define a fluid exiting cavity extending along an exiting axis substantially perpendicular to the plate longitudinal axis and spaced from the receiving axis. A plurality of plate cavities are defined between alternating pairs of adjacent plates and extend along the plate length. The plurality of plate cavities fluidly communicate with both of the receiving and exiting cavities. The plate width is disposed at an angle less than ninety degrees relative to both of the receiving and exiting axis.
Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
A plurality of different embodiments of the invention are shown in the Figures of the application. Similar features are shown in the various embodiments of the invention. Similar features have been numbered with a common reference numeral and have been differentiated by an alphabetic designation. Also, to enhance consistency, features in any particular drawing share the same alphabetic designation even if the feature is shown in less than all embodiments. Similar features are structured similarly, operate similarly, and/or have the same function unless otherwise indicated by the drawings or this specification. Furthermore, particular features of one embodiment can replace corresponding features in another embodiment unless otherwise indicated by the drawings or this specification.
Referring now to
The plates 12-12b cooperate to define a fluid receiving cavity 24 extending along a receiving axis 26 substantially perpendicular to the plate longitudinal axis 16.
Each of the plurality of plates 12-12b includes a substantially planar body portion 36 defining the plate length 14 and the plate width 22 and a cup portion 38 disposed at one of the first and second ends 18, 20. The cup portion 38 extends between a rim portion 40 in a first plane to a bottom portion 42 spaced from the first plane. The cup portions 38 of all of the plurality of plates 12-12b cooperate to define the fluid receiving cavity 24. A cup portion 76 is structured similarly as the cup portion 38 and the cup portions 76 of all of the plurality of plates 12-12b cooperate to define the fluid exiting cavity 28. Description of the cup portion 38 is applicable to the cup portion 76.
The plate 12 includes a lip 78 extending around the face-up surface of the planar body portion 36 and the cup portion 38 and the cup portion 76. The rim 40 is a portion of the lip 78. The lips 78 of adjacent, face-to face plates 12, 12a are engaged to one another to seal the interior defined between the outline of the lip 78. For example, the volume defined between bottom portions 42 of adjacent plates 12, 12a is a portion of the fluid receiving cavity 24. Bosses 80-80b extend from a surface 82; the surface 82 recessed from the lip 78. Boss 80 of the plate 12 is engaged with the boss 80b of the plate 12a.
The bottom portion 42 includes an opening portion 46 to communicate fluid to the fluid receiving cavity 24. The opening portion 24 includes first and second apertures 48, 50. In one possible mode of operation, a fluid stream can pass through apertures 48, 50 and enter the volume defined between bottom portions 42 of adjacent plates 12, 12a. A first portion of the fluid stream can pass through apertures 48, 50 formed in the plate 12a, moving in the fluid receiving cavity 24 along the receiving axis 26. A second portion of the fluid stream can pass through gaps defined between the bosses 80-80b, moving into the plate cavity 32 along the axis 16 towards the fluid exiting cavity 28. The plate cavities 32 extend along the plate length 14 and fluidly communicate with both of the receiving and exiting cavities 24, 28. The first exemplary embodiment is a single pass heat exchanger, however alternative embodiments of the invention can be a multi-pass heat exchanger. A single pass heat exchanger involves refrigerant moving across the heat exchanger once and a multi-pass heat exchanger involves refrigerant moving across the heat exchanger more than once.
The plate width 22 is disposed at an angle 34 less than ninety degrees relative to both of the receiving and exiting axis 26, 30. The receiving and exiting axis 26, 30 are coplanar. The angle 34 can be selected in view of the operating environment of the heat exchanger 10 such that the body portions 36 are substantially incident with fluid flow external to the heat exchanger. This can be desirable to reduce external fluid flow pressure drop across the heat exchanger 10. Also, the angle 34 can be selected in view of the desired orientation of the receiving and exiting axis 26, 30.
In the first exemplary embodiment of the invention, the plate width 22 can be disposed at an angle 34 less than ninety degrees relative to both of the receiving and exiting axis 26, 30 by shifting the positions of the apertures 48, 50. The rim portion 40 is disposed in the first plane substantially parallel to the body portion 36. The bottom portion 42 extends in a second plane substantially parallel to the body portion 36. A cup longitudinal axis 44 extends between the rim portion 40 and the bottom portion 42 perpendicular to the plate longitudinal axis 16. The opening portion 46 is centered on a point spaced from the cup longitudinal axis 44. In other words, the first and second apertures 48, 50 have respective first and second centers 52, 54. One of the first and second centers 52, 54 is closer to the cup longitudinal axis 44 than the other of the first and second centers 52, 54. As result, when plates 12a, 12b are engaged in back-to-back relation, as shown in
Referring now to
The plates 12c cooperate to define a fluid receiving cavity 24a extending along a receiving axis 26a substantially perpendicular to the plate longitudinal axis 16a.
Each of the plurality of plates 12c includes a substantially planar body portion 36a defining the plate length 14a and the plate width 22a and a cup portion 38a disposed at one of the first and second ends 18a, 20a. The cup portion 38a extends between a rim portion 40a in a first plane to a bottom portion 42a spaced from the first plane. The cup portions 38a of all of the plurality of plates 12c cooperate to define the fluid receiving cavity 24a. A cup portion 76a is structured similarly as the cup portion 38a and the cup portions 76a of all of the plurality of plates 12c cooperate to define the fluid exiting cavity 28a. Description of the cup portion 38a is applicable to the cup portion 76a.
The plate 12c includes a lip 78a extending around the face-up surface of the planar body portion 36a and the cup portion 38a and the cup portion 76a. The rim 40a is a portion of the lip 78a. The lips 78a of adjacent, face-to face plates 12c are engaged to one another to seal the interior defined between the outline of the lip 78a. For example, the volume defined between bottom portions 42a of adjacent plates 12c is a portion of the fluid receiving cavity 24a. Bosses extend from a surface recessed from the lip 78a.
The bottom portion 42a includes an opening portion 46a to communicate fluid to the fluid receiving cavity 24a. The opening portion 24a includes first and second apertures 48a, 50a. In one possible mode of operation, a fluid stream can pass through apertures 48a, 50a and enter the volume defined between bottom portions 42a of adjacent plates 12c. A first portion of the fluid stream can pass through apertures 48a, 50a of a first plate 12c, the volume defined between bottom portions 42a, and further through apertures 48a, 50a formed in a second plate 12c to move in the fluid receiving cavity 24a along the receiving axis 26a. A second portion of the fluid stream can pass through gaps defined between the bosses, moving into the plate cavity 32a along the axis 16a towards the fluid exiting cavity 28a. The plate cavities 32a extend along the plate length 14a and fluidly communicate with both of the receiving and exiting cavities 24a, 28a. The second exemplary embodiment is a single pass heat exchanger, however alternative embodiments of the invention can be a multi-pass heat exchanger.
The plate width 22a is disposed at an angle 34a less than ninety degrees relative to both of the receiving and exiting axis 26a, 30a. The receiving and exiting axis 26a, 30a are coplanar. The angle 34a can be selected in view of the operating environment of the heat exchanger 10a such that the body portions 36a are substantially incident with fluid flow external to the heat exchanger. This can be desirable to reduce external fluid flow pressure drop across the heat exchanger 10a. Also, the angle 34a can be selected in view of the desired orientation of the receiving and exiting axis 26a, 30a.
In the second exemplary of the invention, the plate width 22a can be disposed at an angle 34a less than ninety degrees relative to both of the receiving and exiting axis 26a, 30a by shifting the positions of the apertures 48a, 50a. The rim portion 40a is disposed in the first plane substantially parallel to the body portion 36a. The bottom portion 42a extends in a second plane substantially parallel to the body portion 36a. A cup longitudinal axis 44a extends between the rim portion 40a and the bottom portion 42a perpendicular to the plate longitudinal axis 16a. The opening portion 46a is centered on a point spaced from the cup longitudinal axis 44a. In other words, the first and second apertures 48a, 50a have respective first and second centers 52a, 54a. One of the first and second centers 52a, 54a is closer to the cup longitudinal axis 44a than the other of the first and second centers 52a, 54a. As result, when first and second plates 12c are engaged in back-to-back relation the aperture 48a of a first plate 12c will be aligned with aperture 50a of a second plate 12c. At least one structural difference between the first and second embodiments is the shape of the cup portions 38 and 38a. The cup portion 38 is substantially symmetrical about the axis 44. The cup portion 38a extends transverse to the axis 44a and, as result, defines an outer surface 60a extending around and parallel to the axis 26a. The surface 60a can be desirable for mounting or locating the heat exchanger 10a in a fluid diffuser.
Referring now to
The plates 12d cooperate to define a fluid receiving cavity 24b extending along a receiving axis 26b substantially perpendicular to the plate longitudinal axis 16b.
Each of the plurality of plates 12d includes a substantially planar body portion 36b defining the plate length 14band the plate width 22b and a cup portion 38b disposed at one of the first and second ends 18b, 20b. The cup portion 38b extends between a rim portion 40b in a first plane to a bottom portion 42b spaced from the first plane. The cup portions 38b of all of the plurality of plates 12d cooperate to define the fluid receiving cavity 24b. A cup portion 76b is structured similarly as the cup portion 38b and the cup portions 76b of all of the plurality of plates 12d cooperate to define the fluid exiting cavity 28b. Description of the cup portion 38b is applicable to the cup portion 76b.
The plate 12d includes a lip 78b extending around the face-up surface of the planar body portion 36b and the cup portion 38b and the cup portion 76b. The rim 40b is a portion of the lip 78b. The lips 78b of adjacent, face-to face plates 12d are engaged to one another to seal the interior defined between the outline of the lip 78b. For example, the volume defined between bottom portions 42b of adjacent plates 12d is a portion of the fluid receiving cavity 24b. Bosses extend from a surface recessed from the lip 78b.
The bottom portion 42b includes an opening portion 46b to communicate fluid to the fluid receiving cavity 24b. The opening portion 24b includes first and second apertures 48b, 50b. In one possible mode of operation, a fluid stream can pass through apertures 48b, 50b and enter the volume defined between bottom portions 42b of adjacent plates 12d. A first portion of the fluid stream can pass through apertures 48b, 50b of a first plate 12d, the volume defined between bottom portions 42b, and further through apertures 48b, 50b formed in a second plate 12d to move in the fluid receiving cavity 24b along the receiving axis 26b. A second portion of the fluid stream can pass through gaps defined between the bosses, moving into the plate cavity 32b along the axis 16b towards the fluid exiting cavity 28b. The plate cavities 32b extend along the plate length 14b and fluidly communicate with both of the receiving and exiting cavities 24b, 28b. The third exemplary embodiment is a single pass heat exchanger, however alternative embodiments of the invention can be a multi-pass heat exchanger.
The plate width 22b is disposed at an angle 34b less than ninety degrees relative to both of the receiving and exiting axis 26b, 30b. The receiving and exiting axis 26b, 30b are coplanar. The angle 34b can be selected in view of the operating environment of the heat exchanger 10b such that the body portions 36b are substantially incident with fluid flow external to the heat exchanger. This can be desirable to reduce external fluid flow pressure drop across the heat exchanger 10b. Also, the angle 34b can be selected in view of the desired orientation of the receiving and exiting axis 26b, 30b.
In the third exemplary of the invention, the plate width 22b can be disposed at an angle 34b less than ninety degrees relative to both of the receiving and exiting axis 26b, 30b by disposing the apertures 48b and 50b in one or more planes transverse to the body portion 36b. The body portion 36b and the rim portion 40b, disposed in the first plane, are substantially parallel to one another. The bottom portion 42b extends in second and third planes parallel and spaced from one another. The aperture 48b is defined in the second plane and the aperture 50b is disposed in the third plane. Both of the second and third planes are transverse to body portion 36b, as best shown in
The surfaces 58b, 60b are indicated with respect to the cup portion 76b based on the selected cross-section shown in
Referring now to
The plates 12e cooperate to define a fluid receiving cavity 24c extending along a receiving axis 26c substantially perpendicular to the plate longitudinal axis 16c.
Each of the plurality of plates 12e includes a substantially planar body portion 36c defining the plate length 14c and the plate width 22c and a cup portion 38c disposed at one of the first and second ends 18c, 20c. The cup portion 38c extends between a rim portion 40c in a first plane to a bottom portion 42c spaced from the first plane. The cup portions 38c of all of the plurality of plates 12e cooperate to define the fluid receiving cavity 24c. A cup portion 76c is structured similarly as the cup portion 38c and the cup portions 76c of all of the plurality of plates 12e cooperate to define the fluid exiting cavity 28c. Description of the cup portion 38c is applicable to the cup portion 76c.
The plate 12e includes a lip 78c extending around the face-up surface of the planar body portion 36c and the cup portion 38c and the cup portion 76c. The rim 40c is a portion of the lip 78c. The lips 78c of adjacent, face-to face plates 12e are engaged to one another to seal the interior defined between the outline of the lip 78c. For example, the volume defined between bottom portions 42c of adjacent plates 12e is a portion of the fluid receiving cavity 24c. Bosses extend from a surface recessed from the lip 78c.
The bottom portion 42c includes an opening portion 46c to communicate fluid to the fluid receiving cavity 24c. The opening portion 24c includes first and second apertures 48c, 50c. In one possible mode of operation, a fluid stream can pass through apertures 48c, 50c and enter the volume defined between bottom portions 42c of adjacent plates 12e. A first portion of the fluid stream can pass through apertures 48c, 50c of a first plate 12e, the volume defined between bottom portions 42c, and further through apertures 48c, 50c formed in a second plate 12e to move in the fluid receiving cavity 24c along the receiving axis 26c. A second portion of the fluid stream can pass through gaps defined between the bosses, moving into the plate cavity 32c along the axis 16c towards the fluid exiting cavity 28c. The plate cavities 32c extend along the plate length 14c and fluidly communicate with both of the receiving and exiting cavities 24c, 28c. The fourth exemplary embodiment is a single pass heat exchanger, however alternative embodiments of the invention can be a multi-pass heat exchanger.
The plate width 22c is disposed at an angle 34c less than ninety degrees relative to both of the receiving and exiting axis 26c, 30c. The receiving and exiting axis 26c, 30c are coplanar. The angle 34c can be selected in view of the operating environment of the heat exchanger 10c such that the body portions 36c are substantially incident with fluid flow external to the heat exchanger. This can be desirable to reduce external fluid flow pressure drop across the heat exchanger 10c. Also, the angle 34c can be selected in view of the desired orientation of the receiving and exiting axis 26c, 30c.
In the fourth exemplary of the invention, the plate width 22c can be disposed at an angle 34c less than ninety degrees relative to both of the receiving and exiting axis 26c, 30c by twisting, or rotating, the body portion 36c and the cup portion 38c relative to one another. The body portion 36c and the rim portion 40c, disposed in the first plane, are transverse to one another. The bottom portion 42c extends in a second plane substantially parallel to the first plane. The opening portion 46c, with apertures 48c, 50c is centered in the cup portion 38c. Where first and second plates 12e are engaged back-to back, the aperture 48c of a first plate 12e will engage the aperture 50c of the second plate 12e. The bottom portion 42c includes a first outer surface 58c extending perpendicular to the receiving axis 26c and a second outer surface 60c adjacent to the first outer surface 58c and extending parallel to the receiving axis 26c. The surfaces 58c, 60c can be desirable for mounting or locating the heat exchanger 10c in a fluid diffuser.
Referring now to
The plates 12f cooperate to define a fluid receiving cavity 24d extending along a receiving axis 26d substantially perpendicular to the plate longitudinal axis 16d.
Each of the plurality of plates 12f includes a substantially planar body portion 36d defining the plate length 14d and the plate width 22d and a cup portion 38d disposed at one of the first and second ends 18d, 20d. The cup portion 38d extends between a rim portion 40d in a first plane to a bottom portion 42d spaced from the first plane. The cup portions 38d of all of the plurality of plates 12f cooperate to define the fluid receiving cavity 24d. A cup portion 76d is structured similarly as the cup portion 38d and the cup portions 76d of all of the plurality of plates 12f cooperate to define the fluid exiting cavity 28d. Description of the cup portion 38d is applicable to the cup portion 76d.
The plate 12f includes a lip 78d extending around the face-up surface of the planar body portion 36d and the cup portion 38d and the cup portion 76d. The rim 40d is a portion of the lip 78d. The lips 78d of adjacent, face-to face plates 12f are engaged to one another to seal the interior defined between the outline of the lip 78d. For example, the volume defined between bottom portions 42d of adjacent plates 12f is a portion of the fluid receiving cavity 24d. Bosses extend from a surface recessed from the lip 78d.
The bottom portion 42d includes an opening portion 46d to communicate fluid to the fluid receiving cavity 24d. The opening portion 24d includes first and second apertures 48d, 50d. In one possible mode of operation, a fluid stream can pass through apertures 48d, 50d and enter the volume defined between bottom portions 42d of adjacent plates 12f. A first portion of the fluid stream can pass through apertures 48d, 50d of a first plate 12f, the volume defined between bottom portions 42d, and further through apertures 48d, 50d formed in a second plate 12f to move in the fluid receiving cavity 24d along the receiving axis 26d. A second portion of the fluid stream can pass through gaps defined between the bosses, moving into the plate cavity 32d along the axis 16d towards the fluid exiting cavity 28d. The plate cavities 32d extend along the plate length 14d and fluidly communicate with both of the receiving and exiting cavities 24d, 28d. The fifth exemplary embodiment is a single pass heat exchanger, however alternative embodiments of the invention can be a multi-pass heat exchanger.
The plate width 22d is disposed at an angle 34d less than ninety degrees relative to both of the receiving and exiting axis 26d, 30d. The receiving and exiting axis 26d, 30d are coplanar. The angle 34d can be selected in view of the operating environment of the heat exchanger 10d such that the body portions 36d are substantially incident with fluid flow external to the heat exchanger. This can be desirable to reduce external fluid flow pressure drop across the heat exchanger 10d. Also, the angle 34d can be selected in view of the desired orientation of the receiving and exiting axis 26d, 30d.
In the fifth exemplary of the invention, the plate width 22d can be disposed at an angle 34d less than ninety degrees relative to both of the receiving and exiting axis 26d, 30d by disposing the apertures 48d and 50d in one or more planes transverse to the body portion 36d. The body portion 36d and the rim portion 40d, disposed in the first plane, are substantially parallel to one another. The bottom portion 42b extends in a second plane transverse to the first plane and to the body portion 36d. The apertures 48d, 50d are centered with respect to the axis 16d. Where first and second plates 12f are engaged back-to back, the aperture 48d of a first plate 12f will engage the aperture 50d of the second plate 12f. The bottom portion 42d includes a first outer surface 58d extending perpendicular to the receiving axis 26d. A second outer surface 60d is adjacent to the first outer surface 58d and extends transverse to the receiving axis 26b. In alternative embodiments of the invention, the second outer surface 60d could extend parallel to the receiving axis 26b. The surfaces 58d, 60d can be desirable for mounting or locating the heat exchanger 10d in a fluid diffuser.
Referring now to
The plates 12g cooperate to define a fluid receiving cavity 24e extending along a receiving axis 26e substantially perpendicular to the plate longitudinal axis 16e.
Each of the plurality of plates 12g includes a substantially planar body portion 36e defining the plate length 14e and the plate width 22e and a cup portion 38e disposed at one of the first and second ends 18e, 20e. The cup portion 38e extends between a rim portion 40e in a first plane to a bottom portion 42e spaced from the first plane. The cup portions 38e of all of the plurality of plates 12g cooperate to define the fluid receiving cavity 24e. A cup portion 76e is structured similarly as the cup portion 38e and the cup portions 76e of all of the plurality of plates 12g cooperate to define the fluid exiting cavity 28e. Description of the cup portion 38e is applicable to the cup portion 76e.
The plate 12g includes a lip 78e extending around the face-up surface of the planar body portion 36e and the cup portion 38e and the cup portion 76e. The rim 40e is a portion of the lip 78e. The lips 78e of adjacent, face-to face plates 12g are engaged to one another to seal the interior defined between the outline of the lip 78e. For example, the volume defined between bottom portions 42e of adjacent plates 12g is a portion of the fluid receiving cavity 24e. Bosses extend from a surface recessed from the lip 78e.
The bottom portion 42e includes an opening portion 46e to communicate fluid to the fluid receiving cavity 24e. The opening portion 24e includes first and second apertures 48e, 50e. In one possible mode of operation, a fluid stream can pass through apertures 48e, 50e and enter the volume defined between bottom portions 42e of adjacent plates 12g. A first portion of the fluid stream can pass through apertures 48e, 50e of a first plate 12g, the volume defined between bottom portions 42e, and further through apertures 48e, 50e formed in a second plate 12g to move in the fluid receiving cavity 24e along the receiving axis 26e. A second portion of the fluid stream can pass through gaps defined between the bosses, moving into the plate cavity 32e along the axis 16e towards the fluid exiting cavity 28e. The plate cavities 32e extend along the plate length 14e and fluidly communicate with both of the receiving and exiting cavities 24e, 28e. The sixth exemplary embodiment is a single pass heat exchanger, however alternative embodiments of the invention can be a multi-pass heat exchanger.
The plate width 22e is disposed at an angle 34e less than ninety degrees relative to both of the receiving and exiting axis 26e, 30e. The receiving and exiting axis 26e, 30e are coplanar. The angle 34e can be selected in view of the operating environment of the heat exchanger 10e such that the body portions 36e are substantially incident with fluid flow external to the heat exchanger. This can be desirable to reduce external fluid flow pressure drop across the heat exchanger 10e. Also, the angle 34e can be selected in view of the desired orientation of the receiving and exiting axis 26e, 30e.
In the sixth exemplary of the invention, the plate width 22e can be disposed at an angle 34e less than perpendicular relative to both of the receiving and exiting axis 26e, 30e by disposing the apertures 48e and 50e in one or more planes transverse to the body portion 36e. The body portion 36e and the rim portion 40e, disposed in the first plane, are substantially parallel to one another. The bottom portion 42e extends in second and third planes parallel and spaced from one another. The aperture 48e is defined in the second plane and the aperture 50e is disposed in the third plane. Both of the second and third planes are transverse to body portion 36e, as best shown in
The structural features of the six embodiments can vary based on three considerations—manufacturability, achievable angle of attack of the incoming air into the HVAC module and the ability to seal the HVAC module after placement of the evaporator core within the HVAC module. The choice of a particular embodiment in an HVAC module may be dictated by any one or combination of these three considerations. The manufacturability may be an important consideration from the standpoint of cost savings. The angle of attack is often responsive to the constraints imposed by the particular design of the air conditioning system. Sealing of the HVAC module is a consideration to reduce the likelihood of noise free operation of the air conditioning system without loss of its cooling capacity. A perceived advantage of the first embodiment is that it is probably the easiest to manufacture with the cup side wall perpendicular to the plate plane. A possible drawback of this embodiment is the relatively shallow angle of attack of the incoming air. The perceived advantage of the second embodiment, with non-perpendicular cup side wall with reference to the plate plane, is that it affords ease of assembly into the HVAC module and as such desirable sealing of the HVAC module. It may improve the angle of attack of the incoming over the first embodiment, but not appreciably. A perceived advantage of the third embodiment, with dual-step cup construction, is that it affords flexibility of a large angle of attack of the incoming air stream facilitated by the large slant of the cup wall. The fourth embodiment, with twisted plates, offers the same advantage as the third embodiment with respect to the angle of attack of the incoming air stream, the difference being the method of forming the cups. The fifth embodiment, with triangular cup construction, offers the same advantage as the third and fourth embodiments as regarded the angle of attack of the incoming air, the difference being in the fifth embodiment the angle of attack is achieved simply by the stamping operation during the course of the plate fabrication. The sixth embodiment, with two-step cup, offers the same advantage as the fifth embodiment with the added advantage that it further increases the angle of attack range.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.