Abstract:
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.

Description:
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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A detailed description of embodiments of the invention will be made with reference to the accompanying drawings, wherein like numerals designate corresponding parts in the several figures. 
     FIG. 1 is a cross-sectional view of the preferred embodiment of the lube applicator; 
     FIG. 2 is a schematic view of the preferred embodiment of the lube applicator; 
     FIG. 3 is a flow chart showing the steps of applying the lube applicator in accordance with the preferred embodiment of the present invention; and 
     FIG. 4 is a cross-sectional view of an alternative embodiment of the lube applicator. 
    
    
     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.