US3378175A

US3378175A - Piston for material dispensing gun cartridge

Info

Publication number: US3378175A
Application number: US524691A
Authority: US
Inventors: Frank J Krieps
Original assignee: Container Corp
Current assignee: Container Corp; Smurfit Kappa Packaging Corp
Priority date: 1966-02-03
Filing date: 1966-02-03
Publication date: 1968-04-16
Anticipated expiration: 1985-04-16

Description

F- J. KRIEPS April 16, 1968 PISTON FOR MATERIAL DISPENSING GUN CARTRIDGE Filed Feb. 3, 1966 frzuen or: Fran/ JKrzqypJ United States Patent 01 fice 3,378,175 Patented Apr. 16, 1968 3,378,175 PISTON FOR MATERIAL DISPENSING GUN CARTRIDGE Frank J. Kricps, Elmhurst, Ill., assignor to Container Corporation of America, Chicago, III., a corporation of Delaware Filed Feb. 3, 1966, Ser. No. 524,691 3 Claims. (Cl. 222-327) This invention relates to dispensing guns of the type used to dispense viscous materials such as caulking compounds and greases from expendable cartridges, and more particularly to an improved piston for an expandable cartridge.

As is known to those familiar with the art, heavy or viscous materials such as caulking compounds and greases are packed in expendable or throw-away cartridges which have a dispensing spout on one end thereof and a movable piston on the other end thereof which may be engaged by a plunger of a dispensing gun and moved forward to force the material to be dispensed through the cartridge and out of the dispensing member.

One problem frequently incurred in connection with the operation of material dispensing guns, when used to dispense relatively viscous materials, is that many of these materials have an elasticity which causes the material to continue to flow out of the dispensing spout after the movement of the plunger and piston has been stopped. This is because the material has been under compression, and, even though the movement of the piston has stopped,

the material is still under some degree of compression and tends to expand, with the result that the least resistance is offered by the dispensing spout so that material can continue to flow out for a short period of time.

In the past attempts have been made to produce dispensing gun cartridges with features designed to overcome the continued dispensing or flow of the material. Many types of so-called stop flow pistons have been produced which include a central flexible membrane or diaphragm which is supposed to flex axially forwardly and rearwardly to overcome this problem. An example of this type of arrangement can be found in US. Letters Patent No. 2,833,451 wherein the membrane of the cartridge piston is supposed to be deflected forwardly of the forward most point of the piston side walls by the plunger as the plunger is moved forward, and then is supposed to flex rearwardly when the piston is withdrawn. Although this arrangement would appear in theory to overcome the problem, in actual practice many times the diaphragm will fail to return to its relaxed or rearward-most position and will remain in the forward most position so that the desired effect is never accomplished.

It is therefore a primary object of this invention to provide, in a dispensing gun cartridge of the type described, an improved piston designed to prevent or minimize the flow of material out of the cartridge dispensing spout after the dispensing gun plunger has been released.

A more specific object of the invention is the provision, in a dispensing gun cartridge of the type described, of improved unitary piston having a cylindrical outer wall presenting internal rearwardly facing abutment surfaces, a round central section, and an annular front wall interconnecting the outer and the central section and adapted to afford a spring-like action for the central section to permit it to move forward when engaged by the plunger, but whose forward movement is limited by the engagement between the plunger and the abutment surfaces of the outer wall, so that the central section cannot move forward beyond the forward edge of the outer wall, and which can move rearwardly when pressure on plunger is released so as to suck the material rearwardly and prevent it from continuing to flow out of the cartridge spout.

These and other objects of the invention will be apparent from an examination of the following description and drawings, wherein:

FIGURE 1 is a side elevational view of a material dispensing gun and cartridge of the type to which this invention is related;

FIGURE 2 is an enlarged view of part of the structure in FIGURE 1, with portions of the structure shown in vertical cross section to illustrate the relationship of the gun plunger to a cartridge piston which embodies features of the invention. In this view the piston is shown in its relaxed position before being actuated by the gun plunger;

FIGURE 3 is a view similar to FIGURE 2 but showing the piston in the completely engaged or depressed position with the central section of the piston being shown in its forwardmost position;

FIGURE 4 is an end elevational view of the piston which is illustrated in FIGURE 2.

It will be understood that, for purposes of clarity, cer tain elements have been intentionally omitted from certain views where they are illustrated to better advantage in other views.

Referring now to the drawing for a better understanding of the invention, and more particularly to FIGURE 1, it will be seen that a material dispensing gun, indicated generally at G and provided with a movable piston P, is illustrated holding an expendable tubular cartridge, indicated generally at C, of the type used in the packaging of relatively viscous materials such as grease or caulking compound.

Cartridge C, as best seen in FIGURES 1 and 2, is of cylindrical shape having a cylindrical. outer wall 16, defining a tube for holding the material M, and which has its forward end closed by a conventional dispensing spout number 12 and its rearward end closed by a piston member, indicated generally at 14, embodying features of the invention.

In actual practice the tube is formed with dispensing spout member 12 affixed to the forward end thereof, and then, after the tube has been filled with the material to be packaged, piston member 14 is inserted in the opposite end of the tube to close the tube. In operation, after the cartridge has been placed within a caulking gun in the position shown in FIGURE 1, as the trigger of the gun is depressed the plunger is urged forward into an engagement with the piston member 14. As piston member 14 is moved forward by the plunger it compresses the material in the tube and drives it forward in the tube and out through dispensing spout member 12.

Turning now to FIGURE 2 of the drawing; it Will be seen that piston member 14 is a one-piece 0r unitary article which is preferably molded from a relatively stiff, though resilient, plastic material such a polypropylene. Piston member 14 includes a generally cylindrical outer wall 16 and a preferably round central section 20 which are interconnected by an annular front wall 18.

Central section 20 includes a preferably cylindrical inner wall 22 which is disposed concentrically within outer Wall 16, but is of appreciably less length than outer wall 16, so that when the piston is in the non-engaged or relaxed condition the front and rear edges of the piston outer wall extend forwardly and rearwardly, respectively of central section inner wall 22. The area defined by inner wall 22 is closed by a dome-like center wall 24 which, at its outer periphery, is formed integrally with the rear edge of inner wall 22. Center wall 24 is bowed forwardly so as to prevent a convex surface on its front side and a concave surface on its rear side.

Still referring to FIGURE 2, it will be seen that front wall 18 is integrally formed at its outer edge with the front edge of outer wall 16 and is integrally formed at its inner edge with the front edge of inner wall 22. Front wall 18 slopes radially inwardly and axially rearwardly from the front edge of outer wall 16, as best seen in FIGURE 2, when the piston member is in its relaxed condition, so that central section 20 of the piston is disposed rearwardly of the forward extremity of the piston outer wall 16.

As best seen in FIGURES 2 and 4, outer wall 16 is provided on its inside with a plurality of integrally formed, circumferentially spaced, longitudinally extending, internal ribs which present rearwardly facing abutment surfaces 32 disposed in common plane extending in a direction normal to the axis of the piston and lying between the rearward extremity of the central section, when the piston is in relaxed condition, and the forward extremity of the outer wall 16.

The purpose of the ribs and abutment surfaces is to take the ultimate or basic force from the thrust of the plunger and transmit it to the piston outer wall 16 after the central section of the piston has been initially engaged by the piston in its forward movement. When the plunger of the gun moves forward to engage the piston member it first contacts the rearward edges of central section inner wall 22 and moves the central section forward, or to the left as seen in FIGURE 2. Because of the snug frictional engagement between the piston outer wall and the side wall of the cartridge, the piston member itself does not move forward until the plunger has deflected the central section forwardly a sufficient distance to cause the outer edges of the plunger to engage the abutment surfaces of the piston member ribs as shown in FIGURE 3.

At this point the full thrust of the plunger force is transmitted to the piston member outer wall through the rib surfaces, and the piston member is thereafter driven forward in the cartridge thereby forcing the material fort wardly and out of the spout or dispensing member 12 of the cartridge.

Because of the angle of the rearwardly sloping front wall 18 a great resiliency is imparted to the central section of the piston member, so that when the pressure on the plunger of the gun is released the outer wall urges the central section to spring rearwardly. This takes the pressure off of the compressed material in the tube and allows a portion of it to move rearwardly and occupy the space in the area of the central section, so that it will not be under such pressure as to cause it to flow out of the dispensing spout of the cartridge.

The essence of the invention resides in the provision of the abutment surfaces on the outer wall ribs which carry the load of the plunger force, so that the force does not have to be borne entirely by the central portion of the piston member. It has been found in arrangements where the central section of the piston member bears the entire load it pops forward of the front edges of the outer wall and does not have the force or strength or resiliency to return to its original position to accomplish the function intended, namely the preventing of flow of material out of the spout member after the plunger has been withdrawn.

In order to facilitate insertion of the piston member into the cartridge at the time the cartridge is filled and closed, the forward edge of outer wall 16 may be recessed slightly, as shown at 34. This not only facilitates insertion of the piston member but it also facilitates the forward distention of the central section and front wall as it is engaged by the gun plunger.

I claim:

1. In an expendable tubular cartridge for a material dispensing gun with a movable plunger, which cartridge includes a cylindrical side wall forming a tube open at opposite ends and a dispensing spout member fixedly associated with the front end of the tube remote from the gun plunger for closing said front tube end, a unitary piston member slidably positioned within said tube at the rear end thereof adjacent said plunger for closing said rear tube end and for urging said material through said tube toward said dispensing spout member when actuated by said gun plunger, said piston member being formed from a relative stiff though resilient plastic material such as polypropylene and comprising in combination:

(a) a cylindrical outer wall disposed in snug frictional engagement with the inner surface of said cartridge side wall for slidable movement longitudinally of the cartridge only when actuated by said plunger;

(b) a circular central section, including:

(i) a cylindrical inner wall concentrically disposed within the outer wall and being of lesser length than said outer wall;

(ii) a round center wall formed integrally with the rear edge of said inner wall to close the center of the piston member and being bowed forwardly to present a convex surface on its front side and a concave surface on its rear side;

(c) a flexible, annular, transverse, front wall having its outer edge formed integrally with the front edge of said outer wall and extending radially inwardly and rearwardly and having its inner edge formed integrally with the front edge of said inner wall;

(d) a plurality of internal, circumferentially spaced, longitudinally extending ribs presenting coplanar, rearwardly facing, abutment surfaces the location of which relative to said central section, is such that upon initial contact between the plunger and pistonmember the plunger will first engage the central section and move it forward relative to the outer wall, against the resilient pressure of said front wall and the material in said tube, until the plunger engages said rib abutment surfaces to thereby prevent further forward movement of said central section beyond the front edge of said outer wall and further transmit the driving force of the plunger through said ribs to said outer wall to cause said piston member to move forward in said tube;

(e) said front wall afiording a spring-like action for said central section to permit it to move forward when engaged by the plunger and to move it rearwardly when pressure on the plunger is released to suck the material rearward and thereby prevent it from continuing to flow out of the cartridge through said spout member.

2. In an expendable tubular cartridge for a material dispensing gun with a movable plunger, which cartridge includes a cylindrical side wall forming a tube open at opposite ends and a dispensing spout member fixedly associated with the front end of the tube remote from the gun plunger for closing said front tube end, a unitary piston member slidably positioned within said tube at the rear end thereof adjacent said plunger for closing said rear tube end and for urging said material through said tube toward said dispensing spout member when actuated by said gun plunger, said piston member comprising in combination:

(b) a circular central section, including:

(d) said outer wall presenting at least one internal, rearwardly facing, abutment surface the location of which relative to said central section, is such that upon initial contact between the plunger and pistonmember the plunger will first engage the central section and move it forward relative to the outer wall, against the resilient pressure of said front wall and the material in said tube, until the plunger engages said abutment surface to thereby prevent further forward movement of said central section beyond the front edge of said outer wall and further to transmit the driving force of the plunger to said outer wall to cause said piston member to move forward in said tube;

(e) said front wall affording a spring-like action for said central section to permit it to move forward when engaged by the plunger and to move it rearwardly when pressure on the plunger is released to suck the material rearward and thereby prevent it from continuing to flow out of the cartridge through said spout member.

3. In an expendable tubular cartridge for a material dispensing gun with a movable plunger, which cartridge includes a cylindrical side wall forming a tube open at opposite ends and a dispensing spout member fixedly associated with the front end of the tube remote from the gun plunger for closing said front tube end, a unitary piston member slidably positioned within said tube at the rear end thereof adjacent said plunger for closing said rear tube end and for urging said material through said tube toward said dispensing spout member when actuated by said gun plunger, said piston member comprising in combination:

(a) a cylindrical outer wall disposed in snug frictional engagement with the inner surface of said cartridge only when actuated by said plunger;

(b) a central section disposed within the outer wall;

(d) said outer wall presenting at least one internal, rearwardly facing, abutment surface the location of which relative to said central section, is such that upon initial contact between the plunger and pistonmember the plunger will first engage the central section and move it forward relative to the outer wall, against the resilient pressure of said front wall and the material in said tube, until the plunger engages said abutment surface to thereby prevent further for- Ward movement of said central section beyond the front edge of said outer wall and further to transmit the driving force of the plunger to said outer wall to cause said piston member to move forward in said tube;

(c) said front wall affording a spring-like action for said central section to permit it to move forward when engaged by the plunger and to move it rearwardly when pressure on the plunger is released to suck the material rearward and thereby prevent it from continuing to flow out of the cartridge through said spout member.

References Cited UNITED STATES PATENTS 2,833,451 5/1958 Sherbondy 222-327 3,029,985 4/1962 Krueger et a1 222--327 3,250,443 5/1966 Abbott 222327 ROBERT B. REEVES, Primary Examiner.

Claims

1. IN AN EXPENDABLE TUBULAR CARTRIDGE FOR A MATERIAL DISPENSING GUN WITH A MOVABLE PLUNGER, WHICH CARTRIDGE INCLUDES A CYLINDRICAL SIDE WALL FORMING A TUBE OPEN AT OPPOSITE ENDS AND A DISPENSING SPOUT MEMBER FIXEDLY ASSOCIATED WITH THE FRONT END OF THE TUBE REMOTE FROM THE GUN PLUNGER FOR CLOSING SAID FRONT TUBE END, A UNITARY PISTON MEMBER SLIDABLY POSITIONED WITHIN SAID TUBE AT THE REAR END THEREOF ADJACENT SAID PLUNGER FOR CLOSING SAID REAR TUBE END AND FOR URGING SAID MATERIAL THROUGH SAID TUBE TOWARD SAID DISPENSING SPOUT MEMBER WHEN ACTUATED BY SAID GUN PLUNGER, SAID PISTON MEMBER BEING FORMED FROM A RELATIVE STIFF THOUGH RESILIENT PLASTIC MATERIAL SUCH AS POLYPROPYLENE AND COMPRISING IN COMBINATON: (A) A CYLINDRICAL OUTER WALL DISPOSED IN SNUG FRICTIONAL ENGAGEMENT WITH THE INNER SURFACE OF SAID CARTRIDGE SIDE WALL FOR SLIDABLE MOVEMENT LONGITUDINALLY OF THE CARTRIDGE ONLY WHEN ACTUATED BY SAID PLUNGER; (B) A CIRCULAR CENTRAL SECTION, INCLUDING: (I) A CYLINDRICAL INNER WALL CONCENTRICALLY DISPOSED WITHIN THE OUTER WALL AND BEING OF LESSER LENGTH THAN SAID OUTER WALL; (II) A ROUND CENTER WALL FORMED INTEGRALLY WITH THE REAR EDGE OF SAID INNER WALL TO CLOSE THE CENTER OF THE PISTON MEMBER AND BEING BOWED FORWARDLY TO PRESENT A CONVEX SURFACE ON ITS FRONT SIDE AND A CONCAVE SURFACE ON ITS REAR SIDE; (C) A FLEXIBLE, ANNULAR, TRANSVERSE, FRONT WALL HAVING ITS OUTER EDGE FORMED INTEGRALLY WITH THE FRONT EDGE OF SAID OUTER WALL AND EXTENDING RADIALLY INWARDLY AND REARWARDLY AND HAVING ITS INNER EDGE FORMED INTEGRALLY WITH THE FRONT EDGE OF SAID INNER WALL; (D) A PLURALITY OF INTERNAL, CIRCUMFERENTIALLY SPACED, LONGITUDINALLY EXTENDING RIBS PRESENTING COPLANAR, REARWARDLY FACING, ABUTMENT SURFACES THE LOCATION OF WHICH RELATIVE TO SAID CENTRAL SECTION, IS SUCH THAT UPON INITIAL CONTACT BETWEEN THE PLUNGER AND PISTONMEMBER THE PLUNGER WILL FIRST ENGAGE THE CENTRAL SECTION AND MOVE IT FORWARD RELATIVE TO THE OUTER WALL, AGAINST THE RESILIENT PRESSURE OF SAID FRONT WALL AND THE MATERIAL IN SAID TUBE, UNTIL THE PLUNGER ENGAGES SAID RIB ABUTMENT SURFACES TO THEREBY PREVENT FURTHER FORWARD MOVEMENT OF SAID CENTRAL SECTION BEYOND THE FRONT EDGE OF SAID OUTER WALL AND FURTHER TRANSMIT THE DRIVING FORCE OF THE PLUNGER THROUGH SAID RIBS TO SAID OUTER WALL TO CAUSE SAID PISTON MEMBER TO MOVE FORWARD IN SAID TUBE; (E) SAID FRONT WALL AFFORDING A SPRING-LIKE ACTION FOR SAID CENTRAL SECTION TO PERMIT IT TO MOVE FORWARD WHEN ENGAGED BY THE PLUNGER AND TO MOVE IT REARWARDLY WHEN PRESSURE ON THE PLUNGER IS RELEASED TO SUCK THE MATERIAL REARWARD AND THEREBY PREVENT IT FROM CONTINUING TO FLOW OUT OF THJE CARTRIDGE THROUGH SAID SPOUT MEMBER.