Cam Actuated Butterfly Valve

This invention relates to fluid valves for use in automotive heating and cooling systems.

Known water valves presently used in automotive vehicle heating and air conditioning systems include spool valves and poppet valves. A problem associated with the operation of poppet type water valves which incorporate a diaphragm seal about the poppet is that if the diaphragm fails, the coolant can quickly escape to the atmosphere resulting in immediate disabling of the vehicle cooling system.

A problem associated with known spool valves is their inherent sensitivity to any debris which might be in the cooling system working fluid. A frequent source of contamination in automotive cooling systems can be traced to small amounts of casting sand which remain on engine block surfaces even after a cleaning operation. The remaining casting sand present on the surface of the cooling system passageways in the engine block can circulate through the cooling system and become trapped around an area adjacent the valve spool or poppet and its seating face, thereby inevitably resulting in breakdown of the spool valve O-ring seals and valve leakage. In order to overcome the above mentioned shortcomings of poppet and spool type valves, butterfly type valves have found acceptance in automotive applications for controlling coolant flow in vehicle cabin heating and air conditioning systems.

However, known valves incorporating butterfly type movable valve members are inherently have heretofore been found unacceptable due to the difficulty encountered in attempting to control the valve output flow rate for a given amount of actuator displacement. Butterfly type valves are inherently sensitive and need not move through more than approximately 20 degrees of angular displacement from a closed position to achieve nearly maximum fluid flow rate. Actuation of the valve member solely by means of the widely used low-cost Bowden wire type actuator arrangement has failed to provide necessary sensitivity and positional stability, due in part to the small amount of movement required for valve actuation. Also, another difficulty encountered has been the fluid flow forces acting on the butterfly valve member tending to resist movement of the valve member. This problem is particularly severe at lower flow rate settings where the viscous forces developed across the leading or upstream edges of the butterfly valve member are highest.

The valve of the present invention incorporates a butterfly valve member mounted for rotation on a portion of a crank member which extends into the valve housing and is in sealing engagement therewith. An L-shaped end of the crank member extends through a rectangular mounting bracket which is connected to one side of the valve housing. The bracket has a pair of arcuate guide slots stamped therein which function as guide surfaces. A cam member formed of a suitable plastic or polymer material has a pair of guide tabs located on its periphery which are slidably received through the guide slots of the bracket. The tabs extend radially outwardly beyond the slot and abut the opposite side of the bracket. A locating pin and bearing surface are molded integrally into one side of the cam. The pin seats in a hole in the bracket and defines an axis of rotation for the cam while the bearing surface in cooperation with the tabs limit the axial play of the cam relative to the bracket. An input shaft is molded intregrally with the cam opposite the locating pin and provides a means for rotating the cam relative to the bracket. A series of equally spaced detent holes are formed in the bracket adjacent one of the guide slots. A projection formed on one of the guide tabs is radially aligned with the detent holes to provide graduated incremental movement of the cam. The end portion of the crank member functions as a cam follower and extends through the bracket and an arcuate slot formed in the cam. The sides of the arcuate slot define a cam profile which reacts against the cam follower end of the crank causing it to rotate in response to rotation of the cam.

The configuration of the cam slot can be varied to achieve a desired mechanical advantage and angular displacement of the crank to suit the available actuation torque applied to the cam input shaft.

The shape of the cam profile can also be varied to achieve a valve fluid flow rate directly proportional to a given amount of cam angular displacement.

FIG. 1 is a top view of the invention embodied in a flow valve assembly with portions thereof broken away;

FIG. 2 is a front view taken along line 2--2 of the embodiment of FIG. 1 with the cam removed;

FIG. 3 is a front view of the cam;

FIG. 4 is a cross-sectional view of the cam taken through section lines 4--4 of FIG. 3; and

FIG. 5 is a view of the cam of FIG. 3 showing its reverse side;

FIG. 6 is a front view similar to FIG. 1 and showing the cam rotated to a valve closed position;

FIG. 7 is a front view similar to FIG. 1 and showing the cam rotated clockwise to a valve open position.

FIG. 8 shows a graphical method for determining a desired cam profile.

Referring now to FIGS. 1 and 2, there is indicated generally by reference numeral 10 a rotary acting butterfly valve assembly, a mounting bracket 12 attached thereto, a rotary acting cam 14, a valve actuating crank 16 and an input shaft 18 extending from and molded integrally with cam 14.

Butterfly valve assembly 10 includes a housing 20 molded from a suitable plastic polymer material and which defines a fluid passageway 22 and a valve chamber 24. Valve chamber 24 is defined by an internal wall 25 which also functions as a valve seating surface.

A metallic housing extension 26 is crimped over a flanged portion 27 of housing 20 and sealed thereto by an annular seal ring 28 mounted in a groove 30 molded into the face of flanged portion 27. A boss 32 projects from one side of housing 20 and provides a flat mounting surface 34 for bracket 12 which is secured thereto by screws 36 and 38. Crank 16 includes a first section 40 extending through valve chamber 24. The lower end of section 40 is seated in a blind hole 42 in housing 20. A seal ring 44 is mounted in a counterbore 46 molded in boss 32 and prevents fluid leakage from the valve chamber. Seal ring 44 is retained in counterbore 46 by a crimped portion 48 in bracket 12.

A valve member 50 formed of rubber or any other suitable material compatible with high temperature cooling fluids is provided and has a peripheral valve surface 52 preferably molded around a metallic plate, not shown, rigidly attached to section 40 of the crank.

The crank 16 includes a second section 54 which extends exteriorly of housing 20 and terminates in a cam follower portion 55.

Referring now to FIG. 2, arcuate guide slots 56 and 58 are concentrically formed in bracket 12 oppositely spaced about a mounting hole 60 provided in bracket 12. Hole 60 defines an axis of rotation for cam 14 as will hereinafter be described in greater detail. A plurality of arcuately disposed equally spaced detent holes 62 are formed in bracket 12 adjacent the upper edge of slot 56. The left end portion 64 of slot 56 and the right end portion 66 of slot 58 function as stop surfaces for cam 14.

Referring now to FIGS. 3-5, guide tabs 68 and 70 are formed and molded integrally around the periphery of cam 14 and are spaced apart 180 degrees. An arcuate slot 72 is formed in cam 14 and defines a cam profile which is engageable with a cam follower portion 74 (FIG. 1) defined by the outer end of crank 16. Referring to FIG. 4, projections 76 and 78 are formed on guide tabs 68 and 70 respectively and define bearing surfaces which engage with the butterfly valve side of bracket 12 as shown by FIG. 1. As shown by FIG. 4, a boss 80 is formed on the bracket side of cam 14 and has formed on the end face thereof projections 82 which are engageable with the front side of bracket 12 as shown by FIG. 1. A cylindrical projection 84 coaxial with cam input shaft 18 extends outwardly from the end face of boss 8000 and is received in bracket hole 60 (FIG. 2).

Cam 14 is assembled to bracket 12 by first aligning cam follower 74 over slot 72 and then aligning guide tabs 68 and 70 with key-slot portion 86 and 88 of slots 56 and 58 respectively (FIG. 2), and aligning cylindrical projection 84 over hole 60. Cam 14 is then pressed against bracket 12 and rotated counterclockwise as viewed in FIGS. 6 and 7 until projection 76 seats over one of the detent holes 62.

In operation, butterfly valve 10 is actuated to a closed position by rotating cam input shaft 18 counterclockwise to the position as shown by FIG. 6 until tabs 68 and 70 abut stop surfaces 64 and 66, respectively (FIG. 2 ). The valve is actuated to its fully open position by rotating cam 14 clockwise as viewed in FIGS. 6 and 7 until projection 76 is seated in detent hole 62 closest to key portion 86. Further clockwise movement of cam 14 is limited by the driving means connected to input shaft 18, not shown.

In the presently preferred practice, slot 72 is configured to provide an increase in flow rate through valve 12 directly proportional to the incremental increase in angular displacement of cam 14. However, other slot configurations may be employed where a direct proportional relationship is not desired.

A graphical method for determining a desired cam profile is shown by FIG. 8. To determine a cam profile for achieving a flow rate directly proportional to cam angular displacement, it is first necessary to determine valve fluid flow rates for given angular displacements of the butterfly valve member from a valve closed to a valve open position. These values are then plotted graphically as a function of crank displacement and cam follower position and in the FIG. 8 example are shown by reference numerals 55A through 55F. The center of rotation of the cam, represented by point X, is then located relative to the center of rotation of the crank member, represented by point Y. The maximum input actuation angle desired is then laid out graphically by radial lines A and F. Radial lines B through E are then equally spaced between lines A and F where the number of segments is dependent upon the number of angular positions given for cam follower 55. A series of lines G, H, J, K, L, and M concentric about center of cam rotation X are drawn through points 55A through 55F until each intersects with radial lines F through A, respectively. The point of intersection of each concentric line with its corresponding radial line, indicated by positions 55A, 55B', 55C', 55D', 55E', and 55F', defines a point on the required cam profile. Construction of the cam profile is completed by drawing a continuous arcuate line indicated by reference numeral 90, around points 55A and 55B' through 55F'.

It will be understood to those having ordinary skill in the art that modifications and variations of the invention may be made without departing from the scope of the invention which is described in the following claims.