Source: http://www.google.com/patents/US4501301?dq=6,373,753
Timestamp: 2014-09-16 10:41:30
Document Index: 528650291

Matched Legal Cases: ['art 33', 'art 36', 'art 35', 'art 35', 'art 33', 'art 36', 'art 35', 'art 36', 'art 36']

Patent US4501301 - Pipe thread protector - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsA cup shaped or cylindrical thread protector, having circumferentially spaced, internally projecting lugs, is formed by injection molding of a thermoplastic resin into a female mold cavity having a smooth cylindrical interior and having a male mold member fitting therein and cooperable therewith to define...http://www.google.com/patents/US4501301?utm_source=gb-gplus-sharePatent US4501301 - Pipe thread protectorAdvanced Patent SearchPublication numberUS4501301 APublication typeGrantApplication numberUS 06/512,689Publication dateFeb 26, 1985Filing dateJul 11, 1983Priority dateJul 20, 1981Fee statusLapsedPublication number06512689, 512689, US 4501301 A, US 4501301A, US-A-4501301, US4501301 A, US4501301AInventorsRoger L. Snow, Sr., Thomas J. AtkinsonOriginal AssigneeSnow Sr Roger L, Atkinson Thomas JExport CitationBiBTeX, EndNote, RefManPatent Citations (10), Referenced by (10), Classifications (4), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetPipe thread protectorUS 4501301 AAbstract A cup shaped or cylindrical thread protector, having circumferentially spaced, internally projecting lugs, is formed by injection molding of a thermoplastic resin into a female mold cavity having a smooth cylindrical interior and having a male mold member fitting therein and cooperable therewith to define a cup shaped or cylindrical cavity. The male mold member has a plurality of recesses of a size and shape operable to produce said lugs in the molded thread protector produced therein. When the thread protector is molded, the male mold member is rotated about its axis sufficiently to compress said lugs into the cup wall thereof at a time after the thermoplastic has solidified but before it has cooled and is then pulled from within the cup shaped member.
We claim: 1. A thread protector for threaded pipe or the like, formed in a mold, comprisinga cup shaped or hollow cylindrical member of soft, elastic thermoplastic material having a rear end or closed end wall, a cylindrical side wall with a smooth cylindrical exterior surface free from longitudinal mold part lines and an open forward end, a plurality of circumferentially oriented lugs spaced circumferentially from each other on and extending from the inner surface of said side wall and integral therewith and of a size and shape permitting the same to be forced over the threaded end of a pipe and to fit into and engage the threads thereof to prevent easy and accidental removal therefrom, each of said lugs having a rear face toward the rear end of said hollow member extending substantially normal to the axis thereof and a forward face in the form of an inclined surface forming an acute dihedral angle therewith sloping toward said open end, each of said lugs having side walls on each side thereof tapering outward from said rear face and said forward face, and each of said lugs being sufficiently thin to permit the same to be compressed completely into the wall of said hollow member during formation and removal from said mold and having tapered edges on each side of the lug facilitating the removal of said hollow member from said mold without shearing the same from the wall. 2. A thread protector according to claim 1 in whichsaid rear faces of said lugs lie substantially in a single plane. 3. A thread protector according to claim 1 in whichsaid rear faces of said lugs lie in a plurality of substantially parallel planes spaced longitudinally of the axis of said cup shaped member. 4. A thread protector according to claim 3 in whicha plurality of said lugs have the rear faces thereof lying substantially in one plane and another plurality of said lugs have the rear faces thereof lying substantially in a different plane. 5. A thread protector according to claim 2 in whichthere are from two to twelve lugs equally spaced on the inner surface of said cup shaped member. 6. A thread protector according to claim 4 in whichthere are from two to twelve lugs in each of said planes equally spaced on the inner surface of said cup shaped member. 7. A thread protector comprising a cup shaped or hollow cylindrical member of soft, elastic thermoplastic material, free from longitudinal part lines, produced by the steps ofproviding injection molding apparatus comprising a first mold member having a cylindrical female mold cavity and a second mold member comprising a male mold member having recesses in the surface thereof forming a negative image of lugs on a cup shaped or hollow cylindrical member to be molded therein, said recesses having a rear face toward the rear end of said hollow member extending substantially normal to the axis thereof and a forward face in the form of an inclined surface forming an acute dihedral angle therewith sloping toward said open end, of a depth sufficiently shallow to permit the material molded therein to be compressed completely into the wall of said hollow member during formation and removal from the mold and having tapered side walls, tapering outward edgewise from said rear face and said forward face, on each side facilitating the removal of said hollow member from the mold without shearing the lugs from the wall, placing said second mold member inside said first mold member to define a cup shaped or hollow cylindrical mold cavity, injecting hot, fluid, thermoplastic resin into said cup shaped or hollow cylindrical mold cavity to fill the same, allowing said resin to cool and solidify in said cup shaped mold cavity to produce said cup shaped or hollow cylindrical member, twisting said second mold member a fraction of a turn, sufficient to compress the lugs on said cup shaped or hollow cylindrical member into the cylindrical wall thereof, after said resin has solidified but before the same has cooled substantially, withdrawing said second mold member from said cup shaped member and from said first mold member, and separating said cup shaped or hollow cylindrical member from said first mold member and allowing said lugs to recover from compression into said cylindrical wall into an inwardly extending position and to cool in such position. 8. A thread protector according to claim 7 in whichsaid second mold member is first withdrawn from said injection molded cup shaped or hollow cylindrical member and said member subsequently removed from said female mold cavity. 9. A thread protector according to claim 7 in whichsaid second mold member and said injection molded cup shaped or hollow cylindrical member are removed together from said female mold cavity, and said member subsequently removed from said second mold member. Description
CROSS REFERENCE TO RELATED APPLICATION This application is a division of copending application Ser. No. 284,690, filed July 20, 1981, now U.S. Pat. No. 4,399,092.
This invention relates to new and useful improvements in molded thermoplastic thread protectors for the threaded ends of pipe or casing.
Armour U.S. Pat. No. 3,013,308 discloses a method and apparatus for manufacture of threaded plastic parts. The internal portion of the mold is threaded and the part must be unscrewed from the threaded portion of the mold.
SUMMARY OF THE INVENTION One of the objects of this invention is to provide a new and improved, injection molded, thermoplastic thread protector for threaded pipes and casing and the like which can be driven onto the threaded pide ends by pounding or hammering rather than by a screwing or threading operation.
Still another object of this invention is to provide a new and improved process or method for injection molding of cup shaped or hollow cylindrical thermoplastic thread protectors having internally extending lugs which does not require the use of a collapsible mold portion.
The above noted objects and other objects of the invention are accomplished by a molded thermoplastic thread protector for the threaded ends of pipe or casing which consists of a hollow cylindrical or cup shaped member only slightly larger than the threaded pipe end and adapted to fit thereover. The interior surface of said cup shaped or cylindrical member has a plurality of separate, circumferentially spaced, internally projecting lugs, each having a rear face toward the closed end wall or rear end of said cup shaped or cylindrical member extending substantially normal to the longitudinal axis thereof and having a forward face or wall portion in the form of an inclined surface extending toward the open end of said cup shaped or cylindrical member. Said lugs are of a size and shape to be forced over the threaded end of a pipe and to engage the threads thereof to prevent easy and accidental removal. The cup shaped or cylindrical thread protector is formed by injection molding of a thermoplastic resin into a female mold cavity having a smooth cylindrical interior and having a male mold member fitting therein and cooperable therewith to define a cup shaped or hollow cylindrical cavity. The male mold member has a plurality of recesses of a size and shape operable to produce said lugs in the molded thread protector produced therein. When the thread protector is molded, the male mold member is rotated about its axis sufficiently to compress said lugs into the cup wall thereof at a time after the thermoplastic has solidified but before it has cooled and is then pulled from within the cup shaped member.
DESCRIPTION OF THE PREFERRED EMBODIMENTS THE THREAD PROTECTOR In FIG. 1, there is shown a pipe or casing or conduit 10 having a threaded end portion 11 and a prior art type of thread protector 12 therefor. Thread protector 12 is formed of a thermoplastic resin and has a closed end wall 13, cylindrical side wall 14 and open end 15. The inner surface of the cylindrical side wall 14 is threaded as indicated at 16 with threads that match the threaded end 11 of pipe or conduit or casing 10. This prior art type of thread protector 12 is screwed manually onto threaded end 11 to provide protection for the threads during shipment or handling. This prior art type of thread protector 12 has required a considerable amount of manual work and lost time in placing the protector in position on the threaded end 11 of pipe 10. As a result, there has been a substantial need for thread protectors that can be easily installed, securely in position without resorting to a manual threading of the protector on the end of the pipe.
In FIGS. 2 and 3, there is shown a preferred embodiment of an improved pipe thread protector 17 which can be installed by application of an end-wise force, as by pounding or hammering. Thread protector 17 is of a thermoplastic material and is of injection molded construction. The thermoplastic material is a relatively soft thermoplastic material, as distinguished from hard plastic materials that are formed by thermosetting resins.
Lugs 21 and 22 have forward wall portion 26 and 27 which are inclined or tapered toward the open end 19 of the cup shaped thread protector 17. Lugs 21 each have tapered side walls 28 and 29 which taper outwardly from the flat rear wall portions 25 and tapered forward wall portions 27. Lugs 22 similarly have tapered side wall portions 30 and 31. If desired, the inclined walls and tapered side walls of the lugs may be combined into a single continuous wall which is inclined toward the open or forward end and tapered from side to side. The tapering forward walls 26 and 27 of lugs 21 and 22 are capable sliding over the threads on the threaded end 11 of pipe 10 when thread protector 17 is driven onto the end to protect threads thereof.
The flat rear faces 24 and 25 of lugs 21 and 22 are retaining faces which engage in the threads 11 of pipe 10 to hold thread protector 17 against being dislodged therefrom. The tapered side walls 28 and 29 of lugs 21 and tapered side walls 30 and 31 of lugs 22 facilitate the molding of the thread protector 17 by an injection molding procedure which will be subsequently described.
In FIG. 4, there is shown a two part mold 32 consisting of a mold part 33 having a hollow cylindrical female mold cavity 34. A second mold member 35 has a projecting male part 36 which fits into female mold cavity 34 and is spaced from the walls thereof to define a mold cavity corresponding in shape to molded thread protector 17. A small opening 37 is provided which opens into mold cavity 38 for introduction of hot molten or fluid thermoplastic resin. The projecting male portion 36 of mold part 35 has a plurality of cavities 39 and 40 which correspond to lugs 21 and 22 in thread protector 17.
Cavities 39 and 40 have flat end walls 41 and 42 which lie substantially on a plane normal to the longitudinal axis of the mold cavity. Cavities 39 and 40 have inclined walls 43 and 44 which correspond to the inclined walls 26 and 27 of lugs 21 and 22. Side walls 45 and 46 of cavities 39 and 40 are tapered as seen in FIG. 5. This taper corresponds to the side taper of 28 and 29 as seen in FIG. 3 looking into the end of cup shaped thread protector 17. If the thread protector is made with a curved forwardly inclined surface which tapers from side to side, the recesses in the male mold portion are similarly constructed.
In the manufacture of thread protector 17 by the method of this invention, mold part 35 is positioned with projecting male portion 36 in cavity 34 of the female mold part 33. This defines a mold cavity 38 having the same shape as thread protectors 17 including the internal lugs 21 and 22 thereof. A hot, molten or fluid, thermoplastic resin (preferably a high impact nylon or a high impact polyethylene resin) is injected into mold cavity 38 by suitable injection molding equipment through inlet passage 37.
The tapered side walls 45 and 46 of mold cavities 39 and 40 allow for the rotation of mold member 35 and the projecting part 36 without shearing off the lugs. When the mold member 35 has been twisted or turned a partial turn in this manner, it is removed from the interior of the injection molded plastic thread protector 17, and thread protector 17 is removed from the female mold cavity 34. Alternatively, the injection molded thread protector 17 may be removed along with mold part 35 (after the partial turn, described above) and the molded thread protector 17 stripped from the projecting mold part 36. The product produced in each of the foregoing procedures is smooth and cylindrical and free from longitudinal part lines as a result of the shape of the mold cavity as described above.
After injection molded thread protector 17 is removed from the mold cavity and from projecting mold part 36, the lugs 21 and 22 which were compressed into cylindrical side wall 20 recover from the compressed condition until they protrude to the normally extended distance inward as shown in FIGS. 2 and 3. This recovery results from the so called "memory" of the plastic which allows it to be deformed under conditions other than conditions of plastic flow and recover from the deformed condition to its original state.
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