Claims
- 1. In a device adapted to translate a feedstock such as a thermoplastic adhesive from a solid state to a molten state, the improvement comprising
- a barrel having a charging port,
- a ram reciprocable relative to said barrel, said ram being adapted to force the feedstock toward the fore end of said barrel, and
- a heater block at least partially configured in a tapered surface located interiorly of said barrel at the fore end thereof, the axis of said tapered surface being oriented in said barrel such that the tip of said tapered surface faces said ram so as to provide initial thermal contact with the feedstock at said tip, said heater block including a base formed integral with said tapered section, said base defining a discharge bore that communicates with the interior of said barrel through at least one port in said heater block adjacent the inside periphery of said barrel,
- a discharge valve in said discharge bore for controlling the discharge of molten feedstock from said device, and
- a movable spring loaded abutment adapted continuously to bias said discharge valve closed except when said abutment is removed from abutting engagement with said valve, said abutment being retractable from abutting contact with said valve to allow said valve to open when molten feedstock discharge is desired, and said abutment being allowed to return into abutting engagement with said valve to spring bias said valve closed when molten feedstock discharge is not desired.
- 2. An improvement as set forth in claim 1 wherein said discharge valve is hydraulically unbalanced, said valve being opened at least partially due to hydraulic pressure of molten feedstock in said discharge bore after said spring loaded abutment has been removed from abutting engagement with said valve.
- 3. An improvement as set forth in claim 1 including minor spring means to assist opening of said discharge valve after said spring loaded abutment has been removed from abutting engagement with said valve, said minor spring means having a strength less than the spring loaded abutment's major spring means.
- 4. An improvement as set forth in claim 1 wherein said discharge valve includes a valve stem fixed to a valve head, said valve stem extending outwardly of said base through a valve stem port therein, and wherein said spring loaded abutment is located exteriorly of said base, and including
- a static bellows type seal fixed to one of said valve stem and said valve head at one end and to said base at the other end so as to prevent leakage of molten feedstock through said valve stem port.
- 5. An improvement as set forth in claim 4 including minor spring means to assist opening of said discharge valve after said spring loaded abutment has been removed from abutting engagement with said valve, said minor spring means having a strength less than the spring loaded abutment's major spring means, and said minor spring means being provided by placing said bellows seal under slight tension in that attitude where the discharge valve is closed.
- 6. An improvement as set forth in claim 4 including minor spring means to assist opening of said discharge valve after said spring loaded abutment has been removed from abutting engagement with said valve, said minor spring means having a strength less than the spring loaded abutment's major spring means, and said minor spring means being provided by a compression spring exteriorly of said base that is interconnected with said valve stem.
- 7. An improvement as set forth in claim 1 including
- a trigger assembly having a trigger connected to said spring loaded abutment, said spring loaded abutment being retracted from abutting contact with said valve when said trigger is actuated.
- 8. In a device adapted to translate a feedstock such as a thermoplastic adhesive from a solid state to a molten state, the improvement comprising
- a heater block disposed at the fore end of a barrel, said heater block including a nose portion that extends interiorly of the barrel in axial alignment therewith, said heater block also defining a discharge bore that communicates with the interior of said barrel,
- a hydraulically unbalanced discharge valve controlling the discharge of molten feedstock from said device, and
- a movable spring loaded abutment adapted continuously to bias said discharge valve closed except when said abutment is removed from abutting engagement with said valve, said abutment being retractable from abutting contact with said valve to allow said valve to open due to hydraulic pressure within said discharge bore when molten feedstock discharge is desired, and said abutment being allowed to return into abutting engagement with said valve to spring bias same closed against the hydraulic pressure when molten feedstock discharge is not desired.
- 9. An improvement as set forth in claim 8 wherein said hydraulically unbalanced discharge valve includes a valve stem fixed to a valve head, said valve stem extending outwardly of said base through a valve stem port therein, and wherein said spring loaded abutment is located exteriorly of said heater block.
- 10. An improvement as set forth in claim 9 including
- a static bellows type seal fixed to one of said valve stem and said valve head at one end and to said heater block at the other end so as to prevent leakage of molten feedstock through said valve stem port.
- 11. An improvement as set forth in claim 9 including
- a trigger assembly having a trigger connected to said spring loaded abutment, said spring loaded abutment being retracted from abutting contact with said valve when said trigger is actuated.
- 12. An improvement as set forth in claim 11 wherein said spring loaded abutment and valve stem are adapted to move in coaxial linear paths, and wherein said trigger is connected with said spring loaded abutment by a lost motion slot so that arcuate motion of said trigger does not violate the linear motion of said spring loaded abutment.
- 13. An improvment as set forth in claim 8 wherein said hydraulically unbalanced discharge valve is provided with a minor spring assist, said minor spring assist adapted to oppose the spring loaded abutment's major spring to aid in opening said discharge valve when said spring loaded abutment is removed from abutting engagement with said valve.
- 14. An improvement as set forth in claim 13 wherein said hydraulically unbalanced discharge valve includes
- a valve stem fixed to a valve head, said valve stem extending outwardly of said base through a valve stem port therein and
- a static bellows type seal fixed to one of said valve stem and said valve head at one end and to said heater block at the other end so as to prevent leakage of molten feedstock through said valve stem port, and
- wherein said spring loaded abutment is located exteriorly of said heater block, and
- wherein said minor spring is in the nature of a compression spring located exteriorly of said heater block and interconnected with said valve stem.
- 15. An improvement as set forth in claim 13 wherein said hydraulically unbalanced discharge valve includes
- a valve stem fixed to a valve head, said valve stem extending outwardly of said base through a valve stem port therein, and
- a static bellows type seal fixed to one of said valve stem and said valve head at one end and to said heater block at the other end so as to prevent leakage of molten feedstock through said valve stem port, and
- wherein said spring loaded abutment is located exteriorly of said heater block, and
- wherein said minor spring assist is provided by placing said bellows type seal in tension when said discharge valve is closed.
- 16. In a device adapted to translate a feedstock such as a thermoplastic adhesive from a solid state to a molten state, the improvement comprising
- a barrel, and a heater block located at the fore end of said barrel, and
- a cooling means including coolant distribution chamber disposed about the outer periphery of said barrel aft of said heater block and operable to direct a coolant flow of air from said chamber to the atmosphere in an axial direction over the outer peripheral surface of said barrel, said coolant means being operable to establish air flow level sufficient to maintain a substantial axial thermal gradient along the length in said barrel so as to maintain a solid-melt interface inside the barrel adjacent to said heater block.
- 17. An improvement as set forth in claim 16 wherein said cooling chamber is in the nature of an annular chamber, same being provided coolant air from a fluid source.
- 18. An improvement as set forth in claim 17 wherein the fore wall of said cooling chamber is sized to create an annular gap at said barrel's outer periphery, thereby providing an annular port through which the coolant air can escape around the forward end of said barrel.
- 19. An improvement as set forth in claim 17 wherein said fluid source is a single inlet air line, and including
- a ram at least partially located in said barrel and driven by a pneumatic motor, said single inlet air line also serving to power said pneumatic motor for the gun's ram.
- 20. A thermoplastic material dispensing apparatus adapted to convert solid thermoplastic feedstock material from a solid state to a molten state and subsequently dispense said molten material, said apparatus including
- a barrel having a charging port,
- a ram reciprocable relative to said barrel, said ram being adapted to force the feedstock toward the fore end of said barrel, and
- a heater block generally shaped as a truncated cone located interiorly of said barrel at the fore end thereof, said cone being foreshortened from its vanishing point to create a blunt end tip, the axis of said truncated cone being aligned generally parallel to the axis of said barrel and being oriented in said barrel such that said blunt tip of said truncated cone faces said ram so as to provide initial thermal contact with the feedstock at said tip,
- said truncated cone being truncated from its vanishing point to an extent sufficient to enable a consistent thermal gradient to be maintained along the axis of said heater block, and to enable the temperature of the truncated blunt end tip to be maintained at least at the melt point of the feedstock without substantially exceeding the melt point temperature of the feedstock at any point on the surface of the truncated cone so that melt rate of the feedstock is maximized without subjecting the feedstock to excessive temperature.
- 21. A thermoplastic material dispensing apparatus adapted to convert a thermoplastic feedstock material from a solid state to a molten state and subsequently dispense said molten material, said apparatus including,
- a main frame,
- a barrel with a charging port supported by said frame,
- means including a coolant flow distribution chamber surrounding said barrel, first porting means for connecting said coolant flow distribution chamber to a source of cooling fluid,
- a heater and nozzle mounted at the fore end of said barrel,
- a ram reciprocable relative to said barrel, said ram being adapted to force the feedstock toward the fore end of said barrel, and said ram having a piston head located within a motor housing, said piston head being reciprocable in said motor housing, second porting means for connecting said source of cooling fluid to said motor housing, and
- valve means disposed in said motor housing, said valve means being operable to control the flow of motive cooling fluid to and from said motor housing, said motive fluid being operable to positively drive and cool said piston and ram within said motor housing in both fore or aft directions of reciprocation.
- 22. The apparatus as set forth in claim 21 wherein said main frame comprises
- a fluid manifold, and
- passageways formed in said manifold for simultaneously conducting motive cooling fluid to said motor housing and cooling fluid to the fore end of said barrel.
- 23. The apparatus set forth in claim 21 wherein said ram has a hardened element secured to its forward end, said hardened element cooperating with said charging port in said barrel to form a shear, said shear being adapted to cut off any excess feedstock material tending to block said charging port during forward movement of said ram.
- 24. The apparatus set forth in claim 21 wherein said piston head has a cross-sectional area which is at least three times greater than the cross-sectional area of said ram.
- 25. Thermoplastic feedstock melting means comprising a heating surface disposed within a feedstock transfer barrel, said heating surface configured to simultaneously melt solid advancing feedstock and radially outwardly displace said solid advancing feedstock into intimate contact with the interior surface of said feedstock transfer barrel, and means including an air coolant distribution channel surrounding said barrel for directing coolant fluid from said channel into the atmosphere in an axial direction over the outer peripheral surface of said barrel to cool said barrel and establish a substantial axial thermal gradient with decreasing barrel temperature upstream of said heating surface.
- 26. A device adapted to translate a feedstock such as a solid thermoplastic adhesive from a solid state to a molten state, comprising
- a barrel having a charging port,
- a ram reciprocable relative to said barrel, said ram being adapted to force the feedstock toward the fore end of said barrel, and
- a heater block at least partially configured in a tapered surface located interiorly of said barrel at the fore end thereof, said tapered surface being oriented in said barrel such that an end tip of said tapered surface faces said ram so as to provide initial thermal contact with the feedstock at said tip,
- said tapered surface of said heater block and the interior surface of said barrel defining therebetween a converging channel through which the feedstock is forced during passage toward said fore end of said barrel,
- said feedstock having a transition region in which it converts from the solid to the molten state, and the improvement which comprises
- means for maintaining the said transition region at the point at which it contacts said barrel confined within said converging channel such that said barrel contacting portion of said transition region is subject to a force normal to said interior surface of said barrel and acts as a physical dam to prevent backflow of molten material along the inside surface of said barrel,
- said transition region confining means including an air flow channel surrounding said barrel aft of said heater block, and means for transmitting air from said air flow channel over the outer surface of said barrel so as to radially carry heat away from said barrel via said air.
- 27. The device of claim 26 in which said transition region confining means includes means for maintaining a large thermal temperature gradient along the axial extent of said barrel in the region of said heater block.
- 28. The device of claim 26 in which said tapered surface heater block is generally conical from base to tip, said tapered surface being shortened from its apex to define a blunt tip the surface area of which is determined by the combination of surface heat flux and thermal conductivity of said heater block so that the tip temperature of said heater block is maintained at or above the feedstock softening point and the temperature of said tapered surface has a minimum thermal gradient.
- 29. A device adapted to translate a feedstock such as a solid thermoplastic adhesive from a solid state to a molten state, comprising
- a barrel having a charging port,
- a ram reciprocable relative to said barrel, said ram being adapted to force the feedstock toward the fore end of said barrel, and
- a heater block at least partially configured in a tapered surface located interiorly of said barrel at the fore end thereof, said tapered surface being oriented in said barrel such that an end tip of said tapered surface faces said ram so as to provide initial thermal contact with the feedstock at said tip,
- said tapered surface of said heater block and the interior surface of said barrel defining therebetween a converging channel through which the feedstock is forced during passage toward said fore end of said barrel,
- said feedstock having a transition region in which it converts from the solid to the molten state, and the improvement which comprises
- means for maintaining the said transition region at the point at which it contacts said barrel confined within said converging channel such that said barrel contacting portion of said transition region is subject to a force normal to said interior surface of said barrel and acts as a physical dam to prevent backflow of molten material along the inside surface of said barrel.
- 30. The device of claim 29 in which said transition region confining means includes an air coolant distribution chamber surrounding said barrel for receiving coolant fluid and directing it into the atmosphere.
Parent Case Info
This application is a continuation of application Ser. No. 500,751, filed Aug. 26, 1974, which application is in turn a continuation of application Ser. No. 307,020, filed Nov. 16, 1972, both now abandoned.
US Referenced Citations (6)
Continuations (2)
|
Number |
Date |
Country |
Parent |
500751 |
Aug 1974 |
|
Parent |
307020 |
Nov 1972 |
|