Outlet valve arrangements for enhanced pump efficiency

1. A dispenser comprising:

a housing;

an container disposed in the housing for holding a liquid;

the container having a liquid outlet located proximate the bottom of the container;

an outlet nozzle; and

a pump disposed between the container and the outlet nozzle,

wherein the pump is a sequentially activated multi-diaphragm pump having a plurality of pump chambers;

the pump having:

a pump inlet in fluid communication with the liquid outlet of the container;

a pump outlet in fluid communication with the outlet nozzle;

at least one of the plurality of pump chambers in fluid communication with the pump inlet and the pump outlet, wherein the at least one of the plurality of pump chambers is movable between an expanded position and a compressed position;

a first check valve disposed between the pump and the outlet nozzle, wherein the first check valve has a first cracking pressure; and

a second check valve disposed between the first check valve and the outlet nozzle, wherein the second check valve has a second cracking pressure;

wherein the second cracking pressure of the second check valve is greater than the first cracking pressure of the first check valve.

2. The dispenser of claim 1 , wherein movement of the pump chamber from the expanded position to the compressed position causes the first check valve to move to an open position such that a fluid flows from the pump chamber, past the first check valve, past the second check valve, and out of the outlet nozzle.

3. The dispenser of claim 1 , wherein the first check valve is a normally-closed valve.

4. The dispenser of claim 1 , wherein the second check valve is a normally-closed valve.

5. The dispenser of claim 1 , wherein the second check valve comprises a biasing member to urge a valve member against a valve seat.

6. The dispenser of claim 1 , further comprising a third check valve disposed between the pump and the second check valve;

wherein movement of a first pump chamber causes the first check valve to move to an open position such that fluid flows from the first pump chamber, past the first check valve, past the second check valve, and out of the outlet nozzle; and

wherein movement of a second pump chamber causes the third check valve to move to an open position such that fluid flows from the second pump chamber, past the third check valve, past the second check valve, and out of the outlet nozzle.

7. The dispenser of claim 1 , wherein the first cracking pressure of the first check valve is between about 0 psi and about 2 psi.

8. The dispenser of claim 1 , wherein the second cracking pressure of the second check valve is between about 0.5 psi and about 3 psi.

9. The dispenser of claim 1 , wherein a ratio of the second cracking pressure to the first cracking pressure is between about 2 to 1 and about 4 to 1.

10. A dispenser for dispensing soap, sanitizer or lotion comprising:

a housing;

an container having a liquid outlet located proximate the bottom of the container disposed in the housing holding a soap, a sanitizer or a lotion;

an outlet nozzle; and

a diaphragm pump disposed between the container and the outlet nozzle, the diaphragm pump having:

a pump inlet in fluid communication with the container;

a pump outlet in fluid communication with the outlet nozzle;

a pump chamber in fluid communication with the pump inlet and the pump outlet, wherein the pump chamber is movable between an expanded position and a compressed position;

a first check valve disposed between the pump outlet and the outlet nozzle, the first check valve having a cracking pressure that is less than about 0.5 psi;

a second check valve disposed between the first check valve and the outlet nozzle, the second check valve having a cracking pressure that is greater than about 0.5 psi.

11. The dispenser of claim 10 , wherein the first check valve is a normally-closed valve.

12. The dispenser of claim 10 , wherein the second check valve comprises a sealing member and a biasing member.

13. The dispenser of claim 10 , wherein the pump is a sequentially activated multi-diaphragm pump having a plurality of pump chambers.

14. The dispenser of claim 13 , further comprising a third check valve disposed between the pump and the second check valve;

wherein movement of a first pump chamber causes the first check valve to open and close; and

wherein movement of a second pump chamber causes the third check valve to open and close;

and wherein fluid that flows past the first check valve and the third check valve, causes the second check valve to open to allow the fluid to flow past.

15. The dispenser of claim 14 , wherein each pump chamber has a volume of between about 0.2 cc and about 0.5 cc when the pump chamber is in the expanded position.

16. The dispenser of claim 10 , wherein the pump chamber has a volume of between about 0.2 cc and about 0.5 cc when the pump chamber is in the expanded position.

17. The dispenser of claim 10 , wherein a ratio of the second cracking pressure to the first cracking pressure is between about 2 to 1 and about 4 to 1.

18. A dispenser comprising:

a housing;

an actuator located within the housing;

a container located within the housing;

the container carrying a fluid that includes a soap, a lotion, or a sanitizer;

a sequentially activated multi-diaphragm pump;

the sequentially activated multi-diaphragm pump having an inlet;

at least two pump chambers; and

an outlet;

at least one fast acting outlet valve located downstream of the pump outlet;

a slow acting outlet valve located downstream of the at least one fast acting outlet valve; and

an outlet nozzle;

wherein, during a selected dispensing time, the fast acting outlet valve cycles open and closed at least two times for every time the slow acting outlet valve cycles open and closed.