Lube applicator for die cast machine plunger

The present invention discloses an improved dry graphite lube applicator for die cast machines. The lube applicator comprises a hopper holding dry graphite lube, a feeding chamber in gravity communication with the hopper, a feeding turn screw disposed within the feeding chamber having a plurality of spiraling turns wherein each turn holds a predetermined amount of dry graphite, a motor connected to the feeding turn screw to rotate the feeding turn screw, a dispensing chamber in communication with the feeding chamber wherein the feeding screw deposits the predetermined amount of dry graphite, an air compressor source in pressure communication with the dispensing chamber to deliver the predetermined amount of dry graphite to an injection sleeve of the die cast machine. In further embodiments of the present invention, an additional sweeper mechanism is included.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This present invention relates to mechanized lube applicators. More
 specifically, embodiments of the present invention are directed to a lube
 applicator for applying lubrication to the plungers of die cast machines.
 2. Related Art
 Die casting is generally performed by the use of casting molds attached to
 two separate plates, a stationary plate and a movable plate. The molds are
 "cast" by bringing the movable plate against the stationary plate ("closed
 position") so that the casting molds can act as a template for the desired
 casting. While the casting molds are in the closed position, melted
 material is injected into the casting mold through an injection sleeve by
 means of a plunger in fluid communication with the casting mold on the
 stationary plate. Once the fluid cools into a solid, the movable plate
 separates from the stationary plate to release the finished casting. This
 aspect of die casting is well known.
 However, a constant problem experienced during die casting has been the
 wear and tear of the plunger during the die cast process. Early efforts to
 reduce wear and tear on the plunger was the use of grease within the
 plunger to reduce the friction experienced by the plunger as the plunger
 moved along the injection sleeve. However, grease caused numerous
 problems. Besides the messiness involved with the use of grease, grease
 was difficult to apply and was not uniformly effective throughout the
 entire injection sleeve. In addition, grease tended to adversely mix with
 the liquid casting material as the casting material passed through the
 injection sleeve.
 In the past three or four years, the use of dry graphite lubricant for the
 die cast plunger has gained popular acceptance. However, existing
 applicators for dry graphite have failed to work effectively for extended
 periods of time. A constant problem has been the hardening of the dry
 graphite at the opening of dry graphite container, otherwise known as the
 hopper. Since the dry graphite is constantly exposed to air in the prior
 art devices, the natural moisture found in the air mixes with the dry
 graphite to clog the hopper. Given that prior art devices relied on
 gravity to pass the dry graphite to the dispensing sleeve of the lube
 applicator, the lube applicator would fail to dispense dry graphite, or
 constantly dispense uneven amounts of dry graphite on each trial.
 Therefore, the lube applicator would constantly have to be disassembled
 and cleaned after only a few uses for the lube applicator to work
 effectively. The cleaning process would greatly slow down the die casting
 process resulting in loss of time and labor costs. Alternative devices
 attempted to use a vacuum feed within the dispensing sleeve to prevent the
 clogging problem, but the vacuum feeders have also failed to provide
 satisfactory results. The additional intakes and outlets in vacuum feeders
 created clogging problems at additional locations.
 An additional problem with vacuum feeders, as well as the push piston
 feeders, was that the amount of dry graphite used on each trial was not
 exact. There was no measuring means to ensure that either too little
 graphite or too much graphite was not used. Instead, whatever amount that
 fell by gravity into the dispensing sleeve of lube applicator was either
 vacuumed or pushed by the push piston into the injection sleeve.
 Another problem with existing applicators has also been the fact that there
 is no mechanism to self-clean the inside of the injection sleeve. There
 are often instances where the dry graphite will collect in the injection
 sleeve causing too much dry graphite to accumulate near the opening where
 the liquid die cast material is released into the injection sleeve.
 However, prior applicators had no mechanism to remedy this problem. The
 only means was to manually clean the inside of the injection sleeve with a
 clean rag, but again this process would entail stopping the entire process
 to clean the injection sleeve.
 SUMMARY OF THE DISCLOSURE
 It is an object of an embodiment of the present invention to provide an
 improved lube applicator for die cast machines, which obviates for
 practical purposes, the above mentioned limitations.
 According to an embodiment of the present invention, a lube applicator has
 a feeding screw to minimize direct exposure of the dry graphite to air,
 and to accurately measure the amount of dry graphite used in each trial of
 the die casting process. In addition, a sweeper means is installed which
 allows the lube applicator to self-clean the inside of the injection
 sleeve.
 In preferred embodiments of the present invention, a dry graphite lube
 applicator for a die cast machine comprises a hopper holding dry graphite
 lube, a feeding chamber in gravity communication with the hopper, a
 feeding turn screw disposed within the feeding chamber having a plurality
 of spiraling turns wherein each turn holds a predetermined amount of dry
 graphite, a motor connected to the feeding turn screw to rotate the
 feeding turn screw, a dispensing chamber in communication with the feeding
 chamber wherein the feeding screw deposits the predetermined amount of dry
 graphite, an air compressor source in pressure communication with the
 dispensing chamber to deliver the predetermined amount of dry graphite to
 an injection sleeve of the die cast machine. In further embodiments of the
 present invention, an additional sweeper mechanism is included.
 Other features and advantages of the invention will become apparent from
 the following detailed description, taken in conjunction with the
 accompanying drawings which illustrate, by way of example, various
 features of embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 A detailed description of the present invention will be explained with
 respect to the drawings. In FIG. 1, a dry graphite lube applicator in
 accordance with a preferred embodiment of the present invention is seen.
 Similar to prior art applicators, the lube applicator has a hopper 10
 which stores a refillable supply of dry graphite 15. The dry graphite 15
 is then gravity fed into a feeding chamber 35. However, unlike prior art
 applicators having a push piston or a vacuum feed, the present invention
 uses a feeding turn screw 30 having a plurality of spiraling turns 40 to
 move the dry graphite into a dispensing chamber 50. This is done by a
 electric gear motor 20, which is connected to one end of the feeding turn
 screw 30, which rotates the feeding turn screw 30 counterclockwise pushing
 the dry graphite 15 along the feeding turn screw 30 towards to dispensing
 chamber 50. As will be explained below, there are distinct advantages of a
 feeding turn screw 30 over prior art mechanisms.
 One of the key advantages of the feeding turn screw 30 is the ability to
 minimize direct air contact with the dry graphite 15 in the hopper 10,
 especially near the opening 12 of the hopper 10 into the feeding chamber
 35. The use of a plurality of spiraling turns 40 adapted to closely fit
 within the walls of the feeding chamber 35 in combination with the dry
 graphite caught between the spiraling turns 40 act as a buffer for the air
 to travel to the hopper. As a result, unlike prior art applicators, the
 dry graphite in combination with the natural moisture in the air does not
 clog the opening 12 of the hopper 10. Even after numerous trials, the
 present invention has yet to clog and stop functioning as in prior art
 devices.
 Another advantage of the feeding turn screw 30 is the ability to accurately
 estimate the amount of dry graphite 15 to be used on each trial of the die
 cast machine. The use of spiraling turns 40 limits the amount of dry
 graphite 15 which will be feed in the feeding chamber 35. Thus, each turn
 of the spiraling turn 40 holds a predetermined amount of dry graphite 15
 between the wall of the feeding chamber 35 and the feeding turn screw 30.
 In the preferred embodiment, the size of the feeding chamber 35 is
 approximately 127 mm long and 12.5 mm high. The length of one turn 40 is
 approximately 12 mm with the thickness of 3.8 mm. The distance between the
 feeding turn screw 30 and the wall of feeding chamber 35 is approximately
 2.5 mm. As explained in more detail below, each turn of the feeding turn
 screw 30 will deposit a predetermined amount of dry graphite 15 into the
 dispensing chamber 50. The dry graphite 15 is then "blown" by an air
 compress source 300 into the injection sleeve 130 of the die cast machine.
 Additionally, in preferred embodiments of the present invention as seen in
 FIG. 1, a sweeper mechanism is also included within the lube applicator.
 The sweeper mechanism is comprised of plunger 80 and plunger rod 82
 extending from one side of the plunger 80 with a cap 70 connected to the
 end of the plunger rod 82. The plunger 80 is housed inside a sweeper
 chamber 60, which is located opposite of the feeding chamber 35, where the
 dispensing chamber 50 located in between the feeding chamber 35 and the
 sweeper chamber 60. On the other side of the plunger 80 is a sweeper valve
 3 which controls whether compressed air from compressed air source 300 is
 released into the sweeper chamber 60 towards the plunger 80. When the
 sweeper valve 3 is opened, compressed air is released into the sweeping
 chamber 60, which then pushes the plunger 80 into a closed position where
 the cap 70 covers the entrance of the feeding chamber 35. In the preferred
 embodiment of the invention, there is a small opening in the plunger 80
 which allows the compressed air, not only to push plunger 80 towards the
 feeding chamber 35, but also for the compressed air to travel through the
 plunger 80, through the dispensing chamber 50, and to the injection sleeve
 130 to "sweep" any loose dry graphite trapped anywhere in the system. When
 the sweeper valve 3 is closed, a spring 75, located between the plunger 80
 and the spring stop 85, pushes the plunger back to an open position where
 the cap 70 now closes off the sweeper chamber 60 from the rest of the lube
 applicator. In alternative embodiments, it is possible for the feeding
 valve 4 connected to compressed air source 300 to be opened to act as
 either as an additional or alternative sweeper source.
 FIG. 2 describes the control connections of the preferred embodiment of
 present invention according to FIG. 1. A control circuit 150 is connected
 to a timer 200. According to the preset values set in timer 200, the
 control circuit 150 delivers a signal to sweeper solenoid 1 (sol 1) to
 either open or close the sweeper valve 3 to allow compress air to reach
 the sweeper chamber 60. Typically, the sweeper valve 3 delivers
 approximately 80 to 100 psi of compressed air from compressed air source
 300 for approximately 3 to 6 seconds according to the value stored in
 timer 200. The control circuit 150 also delivers a signal to turn on and
 off electric gear motor 20 according to timer 200. The electric gear motor
 20 is connected to the feeding turn screw 30 by gear joint 22 where the
 motor 20 turns feeding turn screw 30 in a counterclockwise direction. In
 addition, the control circuit 150 also delivers a signal to feeder
 solenoid 2 (sol 2) to either open or close feeding valve 4 to allow
 compress air to reach dispensing chamber 50. Typically, the feeding valve
 4 delivers approximately 30 psi of compressed air from compressed air
 source 300 for approximately 0.5 to 1.5 seconds according to the value
 stored in timer 200.
 FIG. 3 illustrates in flow chart form the basic steps in the function of
 the preferred embodiment of the present invention. In step 301, the
 control circuit 150 activates sweeper solenoid 1 (sol 1) to open sweeper
 valve 3. Once the sweeper valve 3 is open, compressed air from compressed
 air source 300 pushes plunger 80 to press cap 70 to cover the entrance of
 feeding chamber 35. In this closed position, the plunger 80 presses spring
 75 against spring stop 85. The compressed air then "sweeps" the dispensing
 chamber 50 through to the injection sleeve 130 clearing the passageways of
 the lube applicator of any stray dry graphite 15. In step 302, the control
 circuit 150 deactivates sweeper solenoid 1 (sol 1), which closes sweeper
 valve 3 and shutting off the compressed air from reaching sweeper chamber
 60. The removal of the compressed air from the sweeper chamber 60 allows
 spring 75 to push plunger 80 back to the open position, removing the cap
 70 from the feeding chamber 35 and then closing the entrance of the
 sweeper chamber 60.
 Step 303 follows the sweeper steps. Control circuit 150 activates the motor
 20 to turn the feeding turn screw 30 for one turn, releasing dry graphite
 15 into dispensing chamber 50. In addition, as the feeding turn screw 30
 is turned, additional dry graphite 15 from the hopper 10 is gravity feed
 into feeding chamber 35 as additional room opens up in the feeding chamber
 between spiraling turns 40. In step 304, according to timer 200, control
 circuit 150 turns off the motor 20. In step 305, control circuit 150
 activates feeder solenoid 2 (sol 2) to open feeding valve 4. Once the
 feeding valve 4 is open, compressed air from compressed air source 300
 injects the dry graphite 15 in dispensing chamber 50 (dispensed by the
 feeding turn screw 30) into injection sleeve 130. Inside the injection
 sleeve 130, the dry graphite 15 can acts as lubricant for plunger piston
 tip 120. In step 306, according to timer 200, control circuit 150
 deactivates feeder solenoid 2 (sol 2), which closes feeder valve 4 and
 shutting off the compressed air from reaching dispensing chamber 50.
 While the description above refers to particular embodiments of the present
 invention, it should be understood that many modifications may be made
 without departing from the spirit thereof. For example, as seen in FIG. 4,
 the sweeper chamber 60 can be located in a diagonal relationship with
 respect to the feeding chamber 35. In this cap 70 is connected to plunger
 rod 82 by a hinge 83 to allow the cap 70 to cover the feeding chamber 35
 in the closed position and still cover the sweeper chamber 60 in the open
 position. In addition, plunger 80 can be moved in the open and closed
 position by a push piston rather than by the compressed air source. In
 this case, feeding valve 4 can act as the sweeper. Thus, the accompanying
 claims are intended to cover these and other modifications as would fall
 within the true scope and spirit of the present invention.
 The presently disclosed embodiments are therefore to be considered in all
 respects as illustrative and not restrictive. The scope of the invention
 is therefore indicated by the appended claims, rather than the foregoing
 description, and all changes which come within the meaning and range of
 equivalency of the claims are therefore intended to be embraced therein.