Abstract:
A drive mechanism for controlling pump mechanisms for simultaneous delivery of two atomizer liquids in selectable ratio to a sprayer device comprising two pneumatically actuated piston-cylinder drive mechanisms (air motors comprising reversing valve) and two pumps driven by the piston rods of the air motors. The intake side of each of said pumps is connected to a delivery side which, in turn, is connected to the sprayer device. The piston rods of the air motors are mechanically connected to one another by an adjustable balance arm. Both air motor are respectively provided with two pilot valves that are mechanically actuatable by the motor piston to control the reversing valves of the air motors.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pump mechanism for simultaneous delivery of two atomizer liquids to a sprayer device in which the ratio between the two liquids is selectable to a greater degree than possible in the prior art. 
     2. Description of the Prior Art 
     In the pump mechanism for simultaneous delivery of two atomizer liquids to a sprayer device of the type known in the prior art, the piston rods of two paint pumps are driven by the see-saw motion of a balance arm. Two air motors in push-pull operation are utilized to impart the see-saw motion about a displaceable support. 
     The push-pull operation of the air motors requires a clocked reversing of the two air motors, each in a direction opposite to the other. Such clocked reversing of the two air motors is controlled by two pilot valves whose sensors are situated at the two dead points of the maximum piston stroke positions of one of the two air motors. When the piston of the controlling motor mechanically reaches one of the two dead points, the corresponding sensor forwards a pneumatic control signal to the two reversing valves of the two air motors. Consequently, only one of the two motors controls the pneumatic reversing event of both air motors. 
     The pump mechanisms in the prior art have means for adjusting the ratio of the atomizer liquids delivered to a sprayer device. 
     A balance arm connects the two piston rods of the air motors. A displaceable support is used as a fulcrum and placed in the region of the balance beam between the two piston rods. The ratio of the quantity of the two liquids used is controlled by moving the displaceable support in the region between the two piston rods thereby increasing the stroke length of one air motor while decreasing the stroke length of the other. However, given that the two pilot valves whose sensors are situated at the two dead points of the maximum piston stroke are located on one motor, the displacement support may only be moved in the region which increases the stroke length of the piston of the controlling motor. As such, the quantity relationship of the two liquid components can be varied to only a limited degree. The quantity of the liquid component that is conveyed by the pump driven by the controlling air motor must always amount to at least 50%. Such a result is disadvantaged in that a greater degree of flexibility in the adjustment of the ratio between the two liquids is desirable. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to improve the driven control mechanism controlling a pump mechanism of the type initially set forth such that the quantity relationship between the two liquid components can be arbitrarily modified without thereby deteriorating the precision of the clocked reversing cycle. 
     The above stated object is inventively achieved in that both air motors are provided with pilot valves having control outputs interconnected and conducted to the control inputs of the two reversing valves. Consequently, the two reversing valves are respectively driven only by the pair of pilot valves that is allocated to the air motor having the greater piston stroke. As such, the balance arm can be adjusted in both directions and any arbitrary quantity relationship of the two liquid components may be selected without thereby disturbing the reversing cycle of the two air motors. In the present invention, both a step-up ratio from 1:1 through 1:10 and a step-down ratio from 1:1 through 0.1:1 may be achieved. 
     Additionally, the present invention as set forth has an advantage in that an improvement of the definition (amount and duration) of the pneumatic reversing signals is achieved. Such an advantage is obtained by using an additional main reversing valve which directly drives the two reversing valves associated with the air motors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features, in advantages of the invention will best be understood from the following detailed description taken in conjunction with the accompanying drawing which shows a schematic diagram of the relevant parts of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As, the drive mechanism utilizes two pneumatic drive motors 10, 11 each of which is composed of a cylinder 10a, 11a, a piston 10b, 11b, and a piston rod 10c, 11c. The two pistons rods 10c, 11c are connected to one another via a balance arm 12 having a displaceable support 13. Although not shown in the schematic diagram, the two ends of the balance arm 12 are connected to the piston rods of the two paint pumps to be driven by the air motors 10, 11. 
     Each of the two motors 10, 11 has a respective pneumatic reversing valve 14, 15. Such reversing valves 14, 15 comprise a compressed air admission, two compressed air outlets, and two control admissions. The control admissions allow the compressed air to be switched from one outlet to the other outlet. The two outlets of the valves 14, 15 discharge into the interior of the allocated cylinder 10a, 11a respectively. In one cylinder the outlet is placed above the piston while in the other cylinder the output is placed below the piston. 
     Each of the air motors 10, 11 is equipped with two pilot valves 16, 17 or, respectively, 18, 19. Each pilot valve has a compressed air admission and a compressed air outlet. The passage through the valve is mechanically controlled when the sensor is mechanically pressed by the piston. The sensors of the pilot valves 16, 17, 18, 19 project from the ceiling or, respectively, from the floor of the cylinder 10a or, respectively 11a into the interior of the cylinder such that the one sensor is mechanically contacted in the one final position of the piston 10b and the other sensor is mechanically contacted in the other final position thereof. 
     The drive mechanism also utilizes a main reversing valve 20 having a structure which is similar to that of the reversing valves 14, 15 in that is has a compressed air admission and two compressed air outlets whose switching is effected by two control inputs. 
     The drive mechanism also utilizes two alternating valves 21, 22. Each of the alternator valves has two compressed air admissions and one compressed air outlet. In operation, when compressed air arrives at the one admission of the alternating valve the other admission is blocked and vise versa. 
     A compressed air source 30 supplies compressed air to the inputs of the reversing valves 14, 15, 20 and to the pilot valves 16, 17, 18, 19 via a pressure regulator 31 and a main compressed air line 32. The output lines 16a, 17a, 18a, 19a of the four pilot valves 16, 17, 18, 19 are crossed at the inputs of the two alternating valves 21, 22 such that the output line 16a of the upper pilot valve 16 of the air motor 10 and the outpput line 19a of the lower pilot valve 19 of the air motor 11 are connected to the inputs of the alternating valve 21. Similarly, the output line 17a of the lower pilot valve 17 of the air motor 10 and the output line 18a of the upper pilot valve 18 of the air motor 11 are connected to the inputs of the alternating valve 22. 
     The output lines 21a, 22a of the two alternating valves 21, 22 are connected to the two control inputs of the main reversing valve 20. The two outputs of the main reversing valve 20 are connected to the control inputs of the two reversing valves 14, 15 such that the one output line 20a branches into lines 20a&#39; and 20a&#34;. Line 20a&#39; connects to the upper control admission of the reversing valve 14 and line 20a&#34; connects to the lower control admission of the reversing valve 15. 
     In contrast thereto, the second admission 20b of the main reversing valve 20 splits into two lines 20 b&#39;   and 20 b&#34; . Line 20 b&#39;   leads to the lower control admission of the reversing valve 14 and line 20 b&#34;   leads to the upper control admission of the reversing valve 15. 
     In operation, the reversing valves 14, 15 respectively allocated to the air motors 10, 11 alternately allow compressed air into the cylinder space above the piston 10b, or respectively, below the piston 11b. The two reversing valves 14, 15 are supplied by the same control line and operate the motors in a push-pull fashion. 
     Assuming that the displaceable support 13 of the balance arm 12 is displaced towards the left, the balance arm section 12a will become shorter than the balance arm section 12b. As a result, the stroke of the piston 10b is shorter then the stroke of the piston 11 b . Consequently, given an upward motion of the piston 11b and downward motion of the piston 10 b , piston 11b  reaches the sensor of its upper pilot valve 18 at a point in time at which the piston 10a is still some distance from the sensor of its lower pilot valve 17. When the piston 11b mechanically contacts the sensor of the pilot valve 18, the valve is enabled. As such, compressed air flows through the output line 18a to the one admission of the alternating valve 22. Given the operation of the alternating valves previously set forth, the other admission of the alternating valve 22 connected to line 17a is blocked. Consequently, the compressed air flows from the outlet line 22a of the alternating valve 22 to the lower control admission of the main reversing valve 20. 
     When the compressed air enters the lower control admission of the main reversing valve 20, the output of the main reversing valve 20 is switched from its one outlet 20a to its other outlet 20b thereby applying compressed air to the control lines of the two reversing valves 14, 15 via the lines 20b&#39; and 20b&#34;. As a result thereof, the compressed air proceeds into the cylinders 11a or, respectively, 10 a  above the piston 10 b  or below the piston 11 b  thereby reversing the piston motion. 
     During the course of its downward motion, the piston 11 b  again reaches the sensor of its lower pilot valve 19 before the piston 10b is capable of reaching the sensor of its upper pilot valve 16. Consequently, the same switching function as set forth above is triggered by the pilot valve 19 via the main reversing valve 20. However, the switching action reverses the direction of the previous cycle. 
     As illustrated by the discussion set forth above, the switching is exclusively initiated by the two pilot valves 18, 19 with a displaceable support 13 on the balance beam 12 is displaced to the left. In such operation, the pilot valves 16, 17 are disconnected for the control circulation by the alternating valves 21, 22. 
     Alternatively, when the displaceable support 13 of the balance arm 12 is displaced toward the right, the arm section 12a becomes greater then the arm section 12b. Consequently, piston 10b mechanically contacts the sensors of the pilot valves 16, 17 before piston 11b contacts the sensors of the pilot valves 18, 19. As such, the compressed air of the pilot valves 16, 17 reaches the alternating valves 21, 22 first so that the lines 18a and 19a are effectively disconnected thereby transferring the control of the main reversing valve 20 and, as a result, of the reversing valves 14, 15, to the pilot valves 16, 17. 
     As illustrated, the displaceable support 13 can be arbitrarily displaced toward the right or left. The motor having the respectively greater piston stroke automatically assumes control of the reversing mechanisms thereby removing the limitations which result when the displaceable support has a limited direction of mobility. 
     In utilizing a main reversing valve 20 and alternating valves 21, 22, exactly defined pneumatic control signals that assure the precision of the pneumatic control are guaranteed. Such precision is of great significance since the two air motors 14, 15 are mechanically connected to one another via the balance arm 12. 
     Numerous modifications to the preferred embodiment set forth are possible. For example, the alternating valves may be omitted upon condition that the pilot valves are provided with check means which automatically prevent the penetration of compressed air at the output side. Furthermore, the main reversing valve may be omitted and the outputs of the two alternating valves could be conducted directly to control inputs of the two reversing valves. However, such a modification may degrade the integrity of the pneumatic control signals arriving at the reversing valves. 
     Although modifications and changes may be suggested by those skilled in the art, it is the intension of the inventor to embody within the patent warranted hereon and changes and modifications as reasonably and properly come within the scope of this contribution to the art.