Patent Application
20090156343
1. Field of the Invention
The present invention relates to a control system for use in a heating and ventilation and air conditioning (HVAC) unit.
2. Description of the Prior Art
Common devices used to manually control temperature in the HVAC unit are often comprised of pulleys connected to one another with small diameter cables. The size requirements of these pulley devices often leads to an inability to generate enough torque to easily overcome the resisting force of the HVAC unit. This creates force limitations within the HVAC unit which need to be considered during the design process. Current cable devices utilize single larger output pulleys, lever arm extensions, and complex gear boxes to achieve an increase in force with low input effort.
One such device comprises a first housing, a circular pulley having a circular pulley radius defining a circumference rotatably mounted to the first housing on a first axis, and a rotary control knob attached to the circular pulley for rotating the circular pulley to select a temperature. The device includes a second housing and a semi-circular pulley rotatably mounted to the second housing on the second axis for rotation between two stop positions. The semi-circular pulley has a base plate having a semi-circular pulley radius defining a semi-circular periphery extending about the second axis.
A cable connects the circular pulley to the semi-circular pulley to rotate the semi-circular pulley in response to the rotation of the circular pulley. A spur gear having a center and a spur gear radius defining a spur gear circumference is also rotatably mounted to the second housing. Spur gear teeth are disposed about the spur gear circumference and extend radially outwardly whereby the dimensions of the entire package must include the stacked widths of the circular pulley and the spur gear.
The invention provides such a control system wherein the semi-circular periphery of the semi-circular pulley includes a flange that extends axially from the base plate and about the periphery between two diametrically opposite flange ends on a diameter. The semi-circular pulley has pulley gear teeth disposed about the semi-circular periphery that extend radially inwardly from the flange and engage with the spur gear teeth of the spur gear to drive the spur gear.
In this disposition, the spur gear can be disposed within the periphery of the semi-circular pulley thereby providing compact packaging while also providing a mechanical advantage to increase the force with which the spur gear rotates. In other words, the dimensions of the entire package are determined by the width of the overlapping semi-circular pulley and the spur gear, i.e., the width of the semi-circular pulley alone.
Other 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:
Referring to the Figures, a control system for use in a heating, ventilation, and air conditioning (HVAC) unit is shown in
As shown in
The circular pulley 22 has a circular pulley radius Rcirc and a circumference. The circular pulley 22 defines a circular channel 36 that extends around the circumference from a connection point 38 thereby dividing the circular channel 36 circumferentially into two semi-circular sectors 40 extending in opposite directions from the connection point 38.
As shown in
The semi-circular pulley 28 includes a base plate 42 and a flange 44. The base plate 42 has a semi-circular pulley radius Rsemi defining a semi-circular periphery extending about an integral support shaft 45 on the second axis B. The flange 44 extends axially from the base plate 42 and about the periphery between two diametrically opposite flange ends 46 on a diameter D. The semi-circular pulley 28 defines a semi-circular channel 48 in the flange 44. The semi-circular channel 48 extends about the semi-circular periphery between the flange ends 46. An attachment point 50 extends axially from the base plate 42 radially inwardly from each of the flange ends 46 and on the opposite side of the diameter D from the flange 44. In other words, the base plate 42 includes two attachment points 50 adjacent the opposite flange ends 46 and adjacent the diameter D.
The cable 30 connects the circular pulley 22 to the semi-circular pulley 28 to transmit motion and rotate the semi-circular pulley 28 in response to the rotation of the circular pulley 22. The cable 30 has a midpoint 52 that is attached to the circular pulley 22 at the connection point 38. The cable 30 is entrained in the circular channel 36 about the semi-circular sectors 40 of the circular pulley 22. The cable 30 has two reaches 54 that extend from the circular pulley 22 and around opposite quadrants of the semi-circular channel 48. Each cable 30 is attached to a respective one of the attachment points 50 on the base plate 42 of the semi-circular pulley 28. In summary, as the circular pulley 22 is rotated via the rotary control knob 24, the cable 30 transmits the rotational movement from the circular pulley 22 to the semi-circular pulley 28 via rectilinear movement of the cable 30 along the reaches 54 between the pulleys 22, 28.
Each of a pair of tubes 56 is cylindrical in shape and disposed around one of the reaches 54 of the cable 30 between the circular pulley 22 and the semi-circular pulley 28. Each tube 56 guides and shields the respective reach 54 of the cable 30. The tubes 56 also prevent the respective reach 54 from kinking and/or from being damaged by the surrounding HVAC componentry.
As shown in
The center 58 of the spur gear 32 is disposed radially between the flange 44 and the second axis B of the semi-circular pulley 28. The base plate 42 defines a slot 64 that extends arcuately between slot ends 66 disposed on the diameter D. The slot 64 extends concentric with and spaced from the second axis B of the spur gear 32. The gear shaft 62 extends through the slot 64 for allowing the semi-circular pulley 28 to rotate about the second axis B as the slot 64 moves along the gear shaft 62 between the stop positions. The gear shaft 62 can engage the slot ends 66 at the stop positions, one of which is shown in
The spur gear 32 defines a cutout sector 68. The attachment points 50 are disposed within the spur gear 32 circumference and within the cutout sector 68 of the spur gear 32 in each of the stop positions. Because of the cutout sector 68, the attachment points 50 can be disposed within the circular periphery of the spur gear 32 for compact packaging while attaining maximum mechanical advantage.
The pulley gear teeth 70 extend radially inwardly from the flange 44 of the semi-circular pulley 28 and engage with the spur gear teeth 60 of the spur gear 32, whereby the semi-circular pulley 28 drives the spur gear 32.
The circular pulley radius Rcirc is equal to the spur gear radius Rspur. The semi-circular pulley radius Rsemi is greater than the circular pulley radius Rcirc (as well as the spur gear radius Rspur). As such, the semi-circular pulley 28 rotates fewer degrees than the circular pulley 22 rotates when the circular pulley 22 is rotated via the rotary control knob 24. Because of the positioning of the spur gear 32 radially inwardly of the flange 44 and the difference between the semi-circular pulley radius Rsemi and the spur gear radius Rspur, the semi-circular pulley 28 and the pulley gear teeth 70 thereof drive the spur gear 32 and rotate the spur gear 32 more degrees than the rotation of the semi-circular pulley 28. In doing so, the semi-circular pulley 28 and the spur gear 32 create a mechanical advantage. As a result, the spur gear 32 is rotated with increased force while maintaining a rotation equal to that of the circular pulley 22. In other words, the circular pulley 22 and the spur gear 32 rotate at the same rate, however, the spur gear 32 rotates with increased force due to the mechanical advantage.
In a preferred embodiment, the semi-circular pulley radius Rsemi is four thirds greater than the circular pulley radius Rcirc. As the rotary control knob 24 is rotated 270° by the passenger, the circular pulley 22 will also rotate 270°. Accordingly, the semi-circular pulley 28 would rotate two thirds of the rotation of the circular pulley 22, i.e., 180°. The spur gear 32 would then rotate three halves of the rotation of the semi-circular pulley 28, i.e., 270°, in response to the rotation of the circular pulley 22 thereby increasing the force generated by the rotation of the circular pulley 22 and maintaining the rotation of the spur gear 32, i.e., 270°, equal to the rotation of the circular pulley 22, i.e., 270°.
As shown in
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.
