Method for making product and product having ultra high molecular weight plastic parts

What is claimed is:

1. A method of joining a cap of UHMWPE to the head of a bolt having a body and a head comprising:

placing the body of the bolt in a bolt retaining opening of a mold having bottom wall and a side wall surrounding a cavity with the head of the bolt located in the cavity,

depositing particulate UHMWPE in the cavity around the head of the bolt,

compressing the particulate UHMWPE in the cavity around the head of the bolt,

heating the compressed particulate UHMWPE to a temperature of between 250 and 350 degrees F. to molecularly bond the UHMWPE to the head of the bolt,

adjusting the duration of the heating to sinter all of the UHMWPE,

cooling the UHMWPE and the bolt,

adjusting the duration of the cooling of the UHMWPE to allow all of the UHMWPE to cool to a temperature below the melting temperature of UHMWPE, and

removing the bolt with the UHMWPE cap bonded to the head of the bolt from the cavity of the mold.

2. The method of claim 1 including: spacing the head of the bolt above the bottom wall at the bottom of the cavity.

3. The method of claim 1 wherein: the particulate UHMWPE is compressed to a pressure of between 1500 and 6000 psi.

4. The method of claim 1 wherein: the compressed particulate UHMWPE is heated to a temperature between 300 to 320 degrees F.

5. The method of claim 1 wherein: the pressure on the particulate UHMWPE is maintained during the heating and cooling of the compressed UHMWPE.

6. The method of claim 1 wherein: the depositing of particulate UHMWPE in the cavity comprises placing powdered UHMWPE having an average particle size between 100 to 400 .mu.m in the cavity.

7. The method of claim 1 including: spacing the head of the bolt above the bottom wall at the bottom of the cavity, the depositing of particulate UHMWPE in the cavity comprises placing powdered UHMWPE having an average particle size between 100 to 400 .mu.m in the cavity around and above the head of the bolt, the compressing of the particulate material comprises apply a pressure of between 1500 to 6000 psi to the powdered UHMWPE in the cavity, and the heating of the compressed UHMWPE compresses heating the compressed UHMWPE to a temperature between 300 to 320 degrees F.

8. The method of claim 7 wherein: the pressure of the particulate material is maintained during the heating and cooling of the compressed UHMWPE.

9. A method of making a UHMWPE body having a reinforcing member with a mold having a cavity comprising:

depositing a first layer of particulate UHMWPE in a cavity of a mold,

placing a reinforcing member in the cavity above the first layer of particulate UHMWPE,

depositing a second layer of particulate UHMWPE to the cavity on top of the reinforcing material,

compressing the first and second layers of particulate UHMWPE and reinforcing member in the cavity,

heating the compressed particulate UHMWPE and reinforcing member to a temperature of between 250 and 350 degrees F. to molecularly bond the UHMWPE to the reinforcing member,

cooling the UHMWPE and reinforcing member, and

removing the UHMWPE and reinforcing member from the cavity of the mold.

10. The method of claim 9 wherein: the particulate UHMWPE is compressed to a pressure of between 1500 to 6000 psi.

11. The method of claim 9 wherein: the compressed particulate UHMWPE is heated to a temperature between 300 to 320 degrees F.

12. The method of claim 9 wherein: the pressure on the particulate UHMWPE is maintained during the heating and cooling of the compressed UHMWPE.

13. The method of claim 9 wherein: the depositing of the first and second layers of particulate UHMWPE in the cavity comprises placing powdered UHMWPE having an average particle size between 100 to 400 .mu.m in the cavity.

14. The method of claim 9 wherein: the placing of a reinforcing member in the cavity comprises placing a metal plate in the cavity on the first layer of particulate UHMWPE in the cavity.

15. The method of claim 9 wherein: the placing of a reinforcing member in the cavity comprises placing a layer of generally flat woven fibers in the cavity on the first layer of particulate UHMWPE in the cavity.

16. The method of claim 9 including: the depositing of the first and second layers of particulate UHMWPE in the cavity comprises placing powdered UHMWPE having an average particle size between 100 to 400 .mu.m in the cavity around the reinforcing member, the compressing of the particulate UHMWPE comprises apply a pressure of between 1500 to 6000 psi to the powdered UHMWPE in the cavity, and the heating of the compressed UHMWPE compresses heating the compressed UHMWPE to a temperature between 300 to 320 degrees F.

17. The method of claim 9 wherein: the pressure of the particulate UHMWPE is maintained during the heating and cooling of the compressed UHMWPE.

18. A method of joining a collar of UHMWPE to the head of a cap screw having a head and body, said head having a socket, comprising: placing the socket of the head on a holder in a mold having a cavity to retain the cap screw in an upright position in the cavity, placing a sleeve around the body of the screw, depositing particulate UHMWPE in the cavity around the head of the screw and sleeve, compressing the particulate UHMWPE in the cavity around the head of the cap screw, heating the compressed particulate UHMWPE in the cavity to a temperature of between 250 and 350 F., cooling the UHMWPE and cap screw, and removing the cap screw, sleeve and UHMWPE collar from the mold.

19. The method of claim 18 wherein: the particulate UHMWPE is compressed to a pressure of between 1500 to 6000 psi.

20. The method of claim 18 wherein: the compressed particulate UHMWPE is heated to a temperature between 300 to 320 degrees F.

21. The method of claim 18 wherein: the pressure on the particulate UHMWPE is maintained during the heating and cooling of the compressed UHMWPE.

22. The method of claim 18 wherein: the depositing of particulate UHMWPE in the cavity comprises placing powdered UHMWPE having an average particle size between 100 to 400 .mu.m in the cavity.

23. The method of claim 18 including: the depositing of particulate UHMWPE in the cavity comprises placing powdered UHMWPE having an average particle size between 100 to 400 .mu.m in the cavity around and above the head of the cap screw, the compressing of the particulate material comprises apply a pressure of between 1500 to 6000 psi to the powdered UHMWPE in the cavity, and the heating of the compressed UHMWPE compresses heating the compressed UHMWPE to a temperature between 300 to 320 degrees F.

24. The method of claim 23 wherein: the pressure of the particulate material is maintained during the heating and cooling of the compressed UHMWPE.

25. A method of joining a cap of UHMWPE to the head of a member having a body and a head comprising: placing the body of the member in a member retaining opening of a mold having a bottom wall and a side wall surrounding a cavity with the head of the member located in the cavity, depositing particulate UHMWPE in the cavity around the head of the member, compressing the particulate UHMWPE in the cavity around the head of the member, heating the compressed particulate UHMWPE to a temperature of between 250 and 350 degrees F. to molecularly bond the UHMWPE to the head of the member, adjusting the duration of the heating to sinter all of the UHMWPE, cooling the UHMWPE and the member, adjusting the duration of the cooling of the UHMWPE to allow all of the UHMWPE to cool to a temperature below the melting temperature of UHMWPE, and removing the member with the UHMWPE cap bonded to the head of the member from the cavity of the mold.

26. The method of claim 25 including: spacing the head of the member above the bottom wall at the bottom of the cavity.

27. The method of claim 25 wherein: the particulate UHMWPE is compressed to a pressure of between 1500 and 6000 psi.

28. The method of claim 25 wherein: the compressed particulate UHMWPE is heated to a temperature between 300 to 320 degrees F.

29. The method of claim 25 herein: the depositing of particulate UHMWPE in the cavity comprises placing powdered UHMWPE having an average particle size between 100 to 400 .mu.m in the cavity.

30. The method of claim 25 including: spacing the head of the member above the bottom wall at the bottom of the cavity, the depositing of particulate UHMWPE in the cavity comprising placing powdered UHMWPE having an average particle size between 100 to 400 .mu.m in the cavity around and above the head of the member, the compressing of the particulate material comprising applying a pressure of between 1500 to 6000 psi to the powdered UHMWPE in the cavity, and the heating of the compressed UHMWPE comprising heating the compressed UHMWPE to a temperature between 300 to 320 degrees F.

31. The method of claims 30 wherein: the pressure of the particulate material is maintained during the heating and cooling of the compressed UHMWPE.

Description Submit all comments and votes

FIELD OF THE INVENTION

The invention relates to the art of pressure molding ultra high molecular weight polyethylene (UHMWPE) to molecularly bond the UHMWPE to an article, such as a bolt, scres, plate and reinforcing member.

BACKGROUND OF THE INVENTION

Ultra high molecular weight polyethylene, herein identified as UHMWPE, is a thermoplastic having advantageous characteristics including high abrasion resistance, low coefficient of friction and exceptional toughness. UHMWPE is used in a number of applications in various industries which require abrasion resistant and low coefficient parts. The average molecular weight of UHMWPE is from 4 to 5 million. The plastic polymer is made up of long branch fee chains, and when compression molded, gives a material of impact strengths at room temperature greater than other thermoplastics. The structure of UHMWPE makes it highly resistant to repeated stress, impact and abrasion. The use of UHMWPE is limited due to difficulties in its processing. The high melt viscosity of UHMWPE limits its processing to presses and screw or ram extruders. The formed pieces are machined to desired shapes. Examples of processes for molding UHMWPE are disclosed in U.S. Pat. Nos. 2,400,094; 3,847,888; 3,975,481 and 5,453,234.

SUMMARY OF THE INVENTION

The invention comprises a method for making solid articles by and molecularly bonding to metal and other materials and the completed articles, such as a bolt having a UHMWPE cap, a socket having an UHMWPE jacket, and an UHMWPE product having a reinforcing member encapsulated within the product. The method for making UHMWPE articles uses a compression molding machine equipped with a male and female mold assembly. The female mold has at least one cavity having the size and shape of the completed UHMWPE article. The male mold has a plunger that fits into the cavity to apply substantial pressure to particulate or powdered UHMWPE located in the cavity when the female mold is moved relative to the male mold. The female cavity is open to a bolt retaining opening used to position the head of the bolt in the cavity. The particulate UHMWPE is subjected to a large compression force to purge the particulate UHMWPE of air and force UHMWPE under the head of the bolt and densified the UHMWPE around the head of the bolt. An alternative female mold has a boss on the bottom wall of the cavity for accommodating the socket of a socket head cap screw. A collar of UHMWPE is molecularly bonded to the head of the cap screw. A reinforcing member, such as a metal plate, fabric, or glass fibers, is incorporated in the UHMWPE by compressing particulate UHMWPE about the reinforcing member and molecularly bonding the UHMWPE to the reinforcing member. The compressed particulate UHMWPE is heated to a temperature of between 250 and 350 degrees F. to molecularly bond the UHMWPE to the part, such as the head of the bolt, socket, and reinforcing member located in the mold cavity. The male and female molds are heated. The heat is transferred by the mold to the compressed UHMWPE and sustained for a time to ensure that the UHMWPE is totally sintered and molecularly bonded to the article located in the mold. The pressure on the heated UHMWPE is maintained during the heating process. Upon completion of the heating process the mold and UHMWPE is allowed to cool. A cooling liquid is used to enhance the cooling rate of the UHMWPE and article. The pressure on the UHMWPE is maintained during the cooling duration. The cooled combined UHMWPE and article is removed from the female mold by releasing the pressure on the UHMWPE and retracting the cavity from the plunger of the male mold. Air under pressure may be used to separate the UHMWPE and article from the female mold.

The invention includes the combined UHMWPE and article, such as the head of a bolt, a socket, a cap screw, and a reinforcing member. The bolt has a head enclosed within a UHMWPE cap or body with the UHMWPE molecularly bonded to the top, side and bottom surfaces of the head of the bolt. The socket is a hand tool having a cylindrical body. A UHMWPE jacket is molecularly bonded to the outside of the cylindrical body. The cap screw has a head having a socket in its outer end and an outer surface. A collar of UHMWPE is molecularly bonded to the outer surface and end of the head. The reinforcing member, such as a metal plate, metal member, fabric, fiber member or a glass fibers, is located within a body of UHMWPE with the UHMWPE bonded to the reinforcing member to increase the strength of the body of UHMWPE.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an elevator bolt having a head with a UHMWPE cap;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is an end elevational view of the left or outer end thereof;

FIG. 5 is an end elevational view of the right or inner end thereof;

FIG. 6 is a sectional view taken along the line 6--6 of FIG. 2;

FIG. 7 is a perspective view of a modification of the elevator bolt of FIG. 1 having a head with a UHMWPE cap;

FIG. 8 is a side elevational view of FIG. 7;

FIG. 9 is a top plan view of FIG. 7;

FIG. 10 is an end elevational view of the left end of FIG. 7;

FIG. 11 is an end elevational view of the right end of FIG. 7;

FIG. 12 is a sectional view taken along the line 12--12 of FIG. 8;

FIG. 13 is a perspective view of UHMWPE combine skid show;

FIG. 14 is a top plan view of FIG. 13;

FIG. 15 is a side elevational view of FIG. 13;

FIG. 16 is a front elevational view of FIG. 13;

FIG. 17 is a rear elevational view of FIG. 13;

FIG. 18 is a bottom plan view of FIG. 13;

FIG. 19 is a top plan view of a portion of the whole of FIG. 13 having a head bocated in the body of UHMWPE;

FIG. 20 is a front elevational view of FIG. 19;

FIG. 21 is a sectional view taken along the line 21--21 of FIG. 19;

FIG. 22 is a sectional view taken along the line 22--22 of FIG. 21;

FIG. 23 is a perspective view of a socket tool having a jacket of ultra high molecular UHMWPE;

FIG. 24 is a side elevational view of FIG. 23;

FIG. 25 is a top plan view of FIG. 24;

FIG. 26 is a bottom plan view of FIG. 24;

FIG. 27 is an enlarged sectional view taken along line 27--27 of FIG. 25;

FIG. 28 is a perspective view of a first 27--27E member;

FIG. 29 is an enlarged cross sectional view taken along line 29--29 of FIG. 28;

FIG. 30 is a top plan view, partly sectional, of the member of FIG. 28;

FIG. 31 is a perspective view of a second UHMWPE member;

FIG. 32 is an enlarged cross sectional view taken along the line 32--32 of FIG. 31;

FIG. 33 is a top plan view, partly sectional, of the member of FIG. 31;

FIG. 34 is a front elevational view of a UHMWPE molding machine having a UHMWPE compression mold;

FIG. 35 is a sectional view of a portion of the mold shown in FIG. 34 with a bolt positioned in the mold;

FIG. 36 is a sectional view similar to FIG. 35 with particulate UHMWPE located in the mold;

FIG. 37 is a sectional view similar to FIG. 36 with UHMWPE plastic compressed about the head of the bolt;

FIG. 38 is a sectional view of a portion of a mold similar to FIG. 35 with a bolt of FIGS. 21 and 22 positioned in the mold;

FIG. 39 is a sectional view similar to FIG. 38 with particulate UHMWPE located in the mold;

FIG. 40 is a sectional view similar to FIG. 39 with particulate UHMWPE compressed about the head of the bolt;

FIG. 41 is an exploded sectional view of a mold for a socket head cap screw;

FIG. 42 is a sectional view of the mold of FIG. 41 with particulate UHMWPE plastic located in the mold;

FIG. 43 is a sectional view similar to FIG. 41 with UHMWPE plastic compressed about the head of the cap screw;

FIG. 44 is a top plan view of the cap screw with UHMWPE ring joined to the head of the cap screw;

FIG. 45 is a perspective view of a cap screw having a head with a UHMWPE cap;

FIG. 46 is a side elevational view of FIG. 45;

FIG. 47 is a top plan view of FIG. 45;

FIG. 48 is a sectional view taken along line 48--48 of FIG. 47;

FIG. 49 is a top plan view of FIG. 45;

FIG. 50 is a bottom plan view of FIG. 45;

FIG. 51 is a perspective view of a combined metal and UHMWPE plate;

FIG. 52 is a sectional view taken along line 52--52 of FIG. 51;

FIG. 53 is a transversely sectioned top plan view of FIG. 51;

FIG. 54 is a bottom plan view of the plate of FIG. 51 bent to a longitudinal channel shape; and

FIG. 55 is a sectional view taken along line 55--55 of FIG. 54.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIGS. 1 to 6, an elevator bolt 40 has a cylindrical body or stem 41 with external helical threads for accommodating a nut (not shown). Body 41 is joined a square neck 42 adapted to fit into a square hole to prevent rotation of bolt 40 when used with elevator paddles. Neck 42 is connected to a circular head 43 having a flat top surface and an outwardly tapered inner surface. A cap of UHMWPE indicated generally at 44 surrounds head 43. The plastic is a high density polyethylene having a very high molecular weight, herein identified a UHMWPE, characterized as having high abrasion resistance, low coefficient of friction and exceptional toughness. Other plastic materials, such as nylon, mylatron, acetel, and phenolis, can be used to mold cap 44 around head 43. UHMWPE is preferred for uses of bolt 40 that require high abrasion resistance properties. Cap 44 has circular top 46, a cylindrical side wall 47 and an inwardly directed annular lip 48. Top 46 has a flat outer circular surface parallel to the flat top surface of head 43 and a uniform thickness over the entire top of head 43. Side wall 47 extended around the outer peripheral edge of head 43 is joined to lip 48. Top 46, side wall 47 and lip 48 are molecularly attached to or bonded to the adjacent surfaces of head 43. The thickness of the UHMWPE can be increased to molecularly bond the UHMWPE to the neck 42 to assist in preventing rotation of the head 43 relative to cap 44.

A modification of the elevator bolt indicated generally at 49 shown in FIGS. 7 to 11, have threaded body or stem 51, a cylindrical neck 52, and a cylindrical head 53. Cap 54 has a flat top 56 joined to an annular side wall 57 that surrounds the outer peripheral edge of head 53.