Anti-float plunger for pneumatically actuated syringe

• US 6,334,553 B1
• Filed: 03/06/2000
• Issued: 01/01/2002
• Est. Priority Date: 03/06/2000
• Status: Expired due to Fees

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Mellos, Nick I., Bouras, Carlos E.
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): Willatt, Stephanie L.
• Application Number:
  US09/519,298
• Time in Patent Office: 666 Days
• Field of Search: 222/386, 222/386.5, 222/309, 222/389, 222/326, 222/327
• US Class Current: 222/386
• CPC Class Codes: B05C 11/10 Storage, supply or control of liquid or other fluent material; Recovery of excess liquid or other fluent material B05C1/0813, B05C5/0225, B05C17/002 and B05C19/06 take precedence
• CPC Class Codes: B05C 17/00576 characterised by the construction of a piston as pressure exerting means, or of the co-operating container
• CPC Class Codes: B05C 17/015 with pneumatically or hydraulically actuated piston or the like B05C17/00543 takes precedence

Abstract

An anti-float plunger for a pneumatically actuated syringe includes an inner cylindrical ring with two open ends held within a cylindrical cover having one open end and one closed end. The open end is at the backside of the plunger. The closed end is at the frontside, in contact with liquid to be forced through the syringe outlet. The cover includes an outer flexible wiper extending around the circumference. This wiper maintains an airtight seal with the syringe walls even when the walls bulge outwardly due to excessive backside pressure. The cover also includes a deformable membrane at the closed end, which deforms away from the outlet to alleviate residual pressure buildup on the liquid in the frontside. This structure eliminates air entrapment within the syringe, while also preventing residual pressure buildup within the syringe.

Claims

1. A plunger comprising:

a cylindrically shaped ring having two open ends;

a cylindrically shaped cover having one closed end and one open end, the ring seated within the cover to close off a first end of the ring;

a flexible wiper extending circumferentially around the cover and extending radially outwardly therefrom; and

a deformable membrane located at the closed end of the cover and spaced from the first end of the ring.

2. The plunger of claim 1 wherein the ring further comprises an intermediate shelf.

3. The plunger of claim 1 wherein the ring is plastic.

4. The plunger of claim 1 wherein the flexible wiper is located adjacent the closed end of the cover, and further comprising:

a second flexible wiper located adjacent the open end of the cover, the second wiper extending partially but not completely around the cover, due to at least one notch.

5. The plunger of claim 1 wherein the membrane is arcuately shaped when in an outermost position.

6. The plunger of claim 1 wherein the cover is made integrally out of elastomeric material.

7. The plunger of claim 6 wherein the cover is silicon rubber.

8. The plunger of claim 1 wherein the ring is made of a magnetic material, thereby to facilitate position sensing.

9. An apparatus for dispensing material comprising:

a liquid filled syringe, the syringe having an outlet;

a plunger residing within the syringe and defining a liquid-filled frontside of the syringe and a backside, whereby pressure supplied to the backside moves the plunger toward the outlet to cause liquid to flow outwardly therefrom;

a flexible wiper circumferentially surrounding the plunger and maintaining a tight circumferential seal with the syringe; and

a deformable membrane located at an end of the plunger and having an undeformed state and a deformed state, the membrane adapted to remain in the undeformed state when the plunger is moving toward the outlet under the supplied pressure and adapted to deform away from the outlet to the deformed state in response to residual pressure buildup within the frontside of the syringe when the supplied pressure is removed.

13. The apparatus of claim 9 wherein the membrane is arcuately shaped when in an outermost position.

10. An apparatus for dispensing material comprising:

a liquid filled syringe, the syringe having an outlet;

a plunger residing within the syringe and defining a liquid-filled frontside of the syringe and a backside, whereby pressure supplied to the backside moves the plunger toward the outlet to cause liquid to flow outwardly therefrom;

a flexible wiper circumferentially surrounding the plunger and maintaining a tight circumferential seal with the syringe;

a deformable membrane located at an end of the plunger and adapted to deform away from the outlet in response to residual pressure buildup within the frontside of the syringe, wherein the plunger further comprises;

a cylindrically shaped ring open at opposing ends; and

a cylindrically shaped cover open at one end and closed at another end, the closed end of the cover being the deformable membrane.

11. The apparatus of claim 10 wherein the flexible wiper is integral with the deformable membrane.

12. The apparatus of claim 10 wherein the flexible wiper is located adjacent the closed end of the cover, and further comprising:

a second flexible wiper located adjacent the open end of the cover, the second wiper extending partially but not completely around the cover, the second wiper helping to center the plunger within the syringe.

14. An apparatus for dispensing material comprising:

a liquid filled syringe, the syringe having an outlet;

a plunger residing within the syringe and defining a liquid-filled frontside of the syringe and a backside, whereby pressure supplied to the backside moves the plunger toward the outlet to cause liquid to flow outwardly therefrom;

a flexible wiper circumferentially surrounding the plunger and maintaining a tight circumferential seal with the syringe;

a deformable membrane located at an end of the plunger and adapted to deform away from the outlet in response to residual pressure buildup within the frontside of the syringe, wherein the plunger further comprises;

a cylindrically shaped ring open at opposing ends, wherein the ring is made of a magnetic material, thereby to facilitate position sensing; and

a cylindrically shaped cover open at one end and closed at another end, the closed end of the cover being the deformable membrane.

15. A method of dispensing a liquid material from a pneumatically actuated syringe, the syringe having an outlet and a plunger residing therein and defining a liquid filled frontside adjacent the outlet and also a backside, the plunger having a forward end residing in contact with the liquid material to be dispensed and having an undeformed state and a deformed state, the method comprising:

a) supplying pressurized fluid to the backside of the syringe to move the forward end of the plunger toward the outlet, thereby causing flow of the liquid material through the outlet, while maintaining the undeformed shape of the forward end of the plunger and a circumferential fluid tight seal between the plunger and the syringe; and

b) upon termination of the supplying, absorbing residual pressure in the frontside of the syringe via flexible movement of the forward end of the plunger in a direction away from the outlet to the deformed state.

16. The method of claim 15 wherein the pressurized fluid is air.

17. The method of claim 15 wherein the liquid material is selected from the following:

adhesive, sealant, encapsulant, coating, thermal grease and epoxy.

18. The method of claim 15 further comprising:

subsequently repeating said supplying and said absorbing to again cause the flow of liquid material from the outlet, the forward end of the plunger flexibly moving toward the outlet after initial resumption of the supplying.

19. The method of claim 15 wherein the plunger includes:

a flexible wiper which maintains the fluid tight seal with the syringe; and

a deformable membrane at the forward end.

20. An apparatus for dispensing liquid material comprising:

a housing having a bore therein coupled to an outlet;

a plunger disposed within the bore and mounted for movement therein;

a flexible seal circumferentially carried by the plunger and abutting the bore of the housing;

a membrane, located at an end of the plunger closest to the outlet, adapted for movement from an undeformed state to a deformed state, the membrane in the undeformed state extending away from the piston and toward the outlet of the housing and in the deformed state the membrane is retracted toward the piston and away from the outlet, the membrane remaining in the undeformed state while dispensing liquid material and whereby retraction of the membrane to the deformed state absorbs residual pressure within the housing.

21. The apparatus of claim 20 wherein the bore is coupled to a source of air pressure for moving the plunger towards the outlet.

22. The apparatus of claim 21 wherein the seal is a flexible wiper.

23. The apparatus of claim 21 wherein the membrane is arcuately shaped when in the undeformed state.