GB2141957A

GB2141957A - Process for manufacturing internally cast single threaded nut

Info

Publication number: GB2141957A
Application number: GB08411894A
Authority: GB
Inventors: Keith Thompson
Original assignee: Coats and Clark Inc
Current assignee: Coats and Clark Inc
Priority date: 1980-07-23
Filing date: 1984-05-10
Publication date: 1985-01-09
Also published as: IT8123102A0; IT1138855B; FR2487234A1; GB2141957B; GB8411894D0; GB2141650A; GB2081147B; CA1185415A; FR2487234B1; GB2081147A; GB2141650B; GB8411893D0; MX153354A; DE3128999A1

Abstract

A process (Fig. 3A) for die casting a nut having a single internal thread, employing a sequence of part ejection operations wherein the die casting cavity (31, 32) is opened by separating the die blocks (33, 34), and an ejection arrangement (33, 35, 35A, 39) thereafter removes the cast nuts from one of the die block recesses. <IMAGE>

Description

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GB2141957A

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SPECIFICATION

Process for manufacturing internally cast single threaded nut

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This invention relates to a process for making a nut having a single internal thread, and to such a nut.

A nut having a single internal thread, and 10 one process for making the same, is disclosed in U.S. Patent 4,079,475. Also there is disclosed in U.S. Design Patent No. 243063 a stamped or coined steel nut which has a particular internal thread arrangement. This 15 arrangement is merely coincidental and serves no particular purpose in this steel nut, where strength is not a problem. Nuts manufactured by casting or moulding, however, generally employ metals substantially weaker than steel, 20 so that it is important to maximize the strength of a nut to the extent possible. Therefore, the nut disclosed in U.S. Design Patent No. 243063 is not addressed to the problem of casting or moulding nuts having improved 25 mechanical strength.

According to this invention, there is provided a process for manufacturing a cast or moulded internally single threaded nut having upper and lower major surfaces and a plurality 30 of wrench-engaging surfaces extending between said major surfaces, with regions of greater and lesser material thickness normal to said thread in the radial direction thereof, comprising the steps of:

35 providing first and second contiguous opposed die blocks, each block having a recess therein, said recesses co-operating to converge along a parting line and defining a first space having the desired shape of the exterior 40 surface of said nut, said first space having portions of greater and lesser radial dimension;

disposing first and second aligned core pins within said first and second die blocks respec-45 tively, each pin having a protruding portion extending into the recess of the corresponding die block;

each said protruding portion comprising a helical ramp having an outer diameter and 50 pitch corresponding to the desired diameter and pitch of an internally threaded surface to be formed within said product, said ramp extending through a circumferential angle of less than 360°, said protruding portion includ-55 ing a vertically oriented parting line shut off surface extending between the ends of said ramp, the outer edge of said ramp having a peripheral edge groove therein, said groove extending along the edge of said ramp except 60 in the vicinity of said vertically oriented surface, said ramp having first and second shoulder portions extending between said vertically oriented surface and the ends of said groove;

the protruding portions of said core pins 65 being disposed so that the ramps thereof are in abutting relationship with the grooves of said ramps communicating with each other to form a second space defining the shape of the internal thread to be formed on said surface; 70 said core pins being oriented within said recess so that said vertically oriented parting line shutoff surface is radially aligned with a portion of said first space of greater radial dimension;

75 introducing a hardenable fluid within the spaces between said die blocks and said core pins;

causing said fluid to harden;

separating said first core pin and first die 80 block from said second core pin and second die block; and removing the hardened material from said spaces.

The invention will now be described by way 85 of example, with reference to the drawings, in which:

Figures 1A and 1B show hexagonal and coaxial type nuts respectively, of the type described in the prior art;

90 Figure 2A is a side cross sectional view of a die casting apparatus for carrying out a preferred embodiment of the process of the invention;

Figure 2B is a right side view of the appara-95 tus of Figure 2A;

Figures 3A to 3E show a die block arrangement and sequence of operation thereof, according to a second embodiment of the present invention;

100 Figures 4A to 4D show a die block arrangement and sequence of operation thereof utilized in carrying out a process according to a third embodiment of the invention;

Figures 5A to 5E show the operation of a 105 die casting arrangement according to a fourth embodiment of the invention, while Figure 5F shows the bifurcated portion of the ejection member employed in conjunction therewith;

Figures 6A to 6D show a die casting ar-110 rangement and sequence of operation thereof according to a fifth embodiment of the invention.

Referring to Figure 1A, the die cast nut 10A has a hexagonal periphery, and planar 115 opposing major surfaces with an internal hole adjacent the thread 11 A. The thread 11A has a helical configuration, and extends through a circumferential angle of less than 360°, with an angular space 5 on the order of 5 to 15°. 120 The ends of the thread 11A are separated in a direction extending between the major surfaces of the nut 10A, by a distance equal to the desired thread pitch, and the diameter of thread 11A corresponds to the diameter of the 125 shaft with which said thread is to be compatible.

The ends of the thread 11A are disposed adjacent one of the "corners" of the nut 10A, i.e. a region where the nut has greater rather 130 than lesser radial width, for the purpose of

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improving the strength of the nut. In the manufacturing process disclosed in U.S. 4,079,475, this positioning of the ends of the thread 11A is accomplished by disposing the 5 vertically oriented parting line shut off surface 20 which defines said ends, in radial alignment with one of the "corners" of the recesses 29 (see Figs. 4 to 6 of said patent). The term "vertically oriented parting line shut 10 off surface" has the same meaning in the instant application as in said patent.

Fig. 1b shows a "coaxial" type nut having 6 radial protuberances which may be engaged by a tool to rotate the nut. The ends 15b and 15 1 7b of the thread 11b are radially aligned with one of the protuberances 14b, i.e., a portion of the nut 10b having greater rather than lesser radial width (as opposed to aligning the thread ends with a region 13b of 20 lesser radial width).

Rather than manufacturing the nuts 10a and 10b utilizing the die casting arrangement shown in Figs. 6 and 7 of U.S. Patent 4,079,475, said nuts may alternatively be 25 manufactured utilizing the die casting arrangement shown in Figs. 2a and 2b, wherein the elements 23 and 24 are first and second opposed die blocks having an interfface at the parting line 210. The die blocks cooperate to 30 define spaces 21 and 22 adjacent the parting line, each of said spaces having a configuration conforming to that of the desired nut to be cast. In each case the vertical parting line shut off surface is aligned with a portion of 35 the nut having relatively great radial width.

The parting line 210 is asymmetrically disposed with respect to the blocks 23 and 24, so that a major portion of the nut is formed in the recess of the block 23, and a minor 40 portion is formed in the communicating recess of the block 24. Therefore, when the blocks are separated after the molten zinc or other casting material injected into the cavities 21 and 22 (through the runner recess and gates 45 211) has hardened, the nuts initially remain in the cavities of the die block 23.

Disposed to the left of the die block 23 is a backing plate 28, to which are affixed a plurality (i.e., two or more) of ejector pins 25 50 to 27. These ejector pins extend through holes in the die block 23 to abut portions of the die casting.

Laterally disposed ejector stops 29 and 29A engage corresponding slots in,the backing 55 plate 28 to permit limited movement of the backing plate away from the parting line 210; and to permit slightly greater movement of the die block 23 away from said parting line.

After the nuts have been formed in the 60 cavities 21 and 22, the die blocks 23 and 24 are moved away from each other and away from the parting line 210. Initially, the backing plate 28 moves with the die block 23.

This movement of the backing plate 28 with 65 the die block 23 is provided primarily by ejector pins 25 to 27, which are initially restricted from movement with respect to die block 23 by shrinkage which holds the molded nuts 21 and 22 onto the root diameter of said die block. That is, it is essentially the required ejection force for the nuts 21 and 22 which urges the backing plate 28 toward the ejector stops 29 and 29A. The movement of the die block 28 is halted after it travels a predetermined distance by engagement with the ejector stops 29 and 2 9A,

while the die block 23 continues to move a small additional distance a, causing the initial separation b between the backing plate 28 and die block 23 to contract until the adjacent surfaces thereof come in contact with each other, thus causing the ejector pins 25 to 27 to force the molded nuts out of their recesses in the die block 23.

Thereafter the die blocks 23 and 24 are again brought into mutual engagement, and the die casting process is repeated.

In the alternative arrangement shown in Figs. 3a to 3e, die blocks 33 and 34 are employed, having separate rather than integral core pins 35/35A and 36/36A respectively; i.e., a construction generally corresponding with that shown in the corresponding portion of Fig. 6 of U.S. Patent 4,079,475.

In this case, however, the core pins are slidably movable within their corresponding die blocks.

The die casting liquid is introduced to the cavities 31 and 32 through the runner recess and gates 310.

After the liquid has solidified to form the die cast nuts, the core pin mounting block 37A is moved to the right thereby pulling the core pins 36 and 36A away from the parting line 38, as shown in Fig. 3b.

Then the right hand die block 34 is moved away from the parting line 38, as shown in Fig. 3c.

The next step in the ejection sequence is movement of the core pin mounting block 37 to the left, to pull the core pins 35 and 35A away from the parting line 38, as shown in Fig. 3d.

The final step involves transverse movement of the ejection finger 39 along the parting line 38 adjacent the mating surface of the die block 33, to eject the corresponding nut 320 from the recess of the die block 33. Only the lower half section of the arrangement shown in Fig. 3a is shown in Figs. 3b to 3e, in order to reduce the drawing complexity.

Thereafter the ejection finger 39 is retracted, and the die blocks and core pins are again brought into mutual engagement so that the cycle can be repeated.

Another arrangement is shown in Figs. 4a to 4d, wherein instead of the ejection pins 25 to 27 of Fig. 2a, ejection sleeves 49 and 49A are provided, the sleeves being slidably mov70

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able within the die block 43 and surrounding the respective elongated core pins 46 and 46A. Only the lower half section of the arrangement shown in Fig. 4a is shown in Figs.

5 4b to 4d, in order to reduce the drawing complexity.

After the nut 420 is formed, the right hand die blook 44 and its associated core pin 45 are moved away from the parting line 411, as 10 shown in Fig. 4b. Thereafter the left hand die block 43 and its associated elongated core pins 46 and 46A and ejection sleeve 49 (which is affixed to the ejection sleeve mounting block 48) are moved away from the 1 5 parting line 411, until rearward movement of hte mounting block 48 is halted by the ejection stop 47. At this time the die block 43 and core pin 46 continue to move rearward until the die block 43 has closed the gap c, 20 while the ejection sleeve 49 remains stationary, causing the ejection sleeve 49 to eject the nut 420 from the recess of the die block 43 and off the elongated core pin 46.

Figs. 5a to 5f illustrate still another embodi-25 ment of the invention, employing a die block construction in which the core pins are both separately movable with respect to their respective die blocks.

As in the arrangement illustrated in Figs. 3a 30 to 3e, an ejection member is transversely movable along the parting line, and acts to separate the formed nut 513 from the core pin 510 to which it initally adheres by virtue of the fact that the die cavity 52 is asymmetri-35 cal with respect to the parting line 511,

having greater depth in the die block 53 adjacent the core pin 510.

As shown in Fig. 5a, the die block and core pins are disposed adjacent the parting line 40 511, and molten zinc or other hardenable fluid material is injected into the die cavity along the parting line 511, through conventional means to cool and thereby form the desired nut.

45 Thereafter as shown in Fig. 5b, the die backup block 55 is drawn in a direction away from the parting line, to thereby move the elongated core pin 56 affixed thereto away from the parting line 511, as far as the 50 shoulder screw 58 will allow. Space d is now eliminated.

Then, as shown in Fig. 5c, continued movement of the die backup block 55 causes the shoulder screw 58 to move the die block 54 55 away from the parting line 511.

The next step as shown in Fig. 5d, involves movement of the die block 53 away from the parting line, while the core pin 510 remains in its initial position, creating a clearance 60 space between the formed nut 513 and the adjacent surface of the die block 53.

As is also shown in Fig. 5d, a bifurcated ejection member 512 is then caused to move transversely into the clearance space, so that 65 its bifurcated or forked ends 520 are disposed between the flanges of the nut 513 and the adjacent surface of the die block 53.

The last step as illustrated in Fig. 5e, involves continued movement of the die block 53 and ccre pin 510 together, away from the parting line, so that the nut 513 engages the bifurcations 520 of the ejection member 512, and is thereby separated from the end of the core pin 510.

The ejector stops 57 and 59 form the limitation of movement functions which are obvious from the drawing, in similar fashion to the ejector stops utilized in the previously described embodiments of the invention.

A variation of the arrangement described with reference to Figs. 3a to 3e is shown in Figs. 6a to 6d.

As illustrated in Fig. 6a, nuts 62 and 62a are die cast in the cavity formed by die blocks

63 and 64 and core pins 67, 67A, 68 and 68A. Then, as illustrated in Fig. 6b, the core pin 68 is moved away from the parting line

614.

The spring 610 is situated within the block 616, and urges said block away from backup block 66. Due to the connection between blocks 616 and die block 64 via shoulder screws 612 and 612A, the spring 610 acts to urge the blocks 64 and 66 away from each other.

When the core pin 68 is moved away from the parting line 614, the spring 610 continues to urge the die block 64 toward the parting line, until the distance between die block 64 and backup block 66 becomes sufficiently great so that block 66 engages block 616, i.e., the shoulder screws 612 and 612A reach their stop limits. Further movement of the core pin 68 away from the parting line (see Fig. 6c) causes movement of die block

64 away from the parting line, with the nut 62 being retained in the surface recess of die block 63.

Next, as illustrated in Fig. 6d, the core pin 67 and die block 63 are simultaneously moved away from the parting line 614, with the movement of the die backup block 65 continuing to move the core pin 67 away from the die block 63, to reach the final position thereof shown in Fig. 6d, wherein the face of the die block 63 adjacent the die cavity is positioned in line with the transversely movable ejection finger or wiper

615.

The wiper 615 is moved transversely to separate the formed nut 62 from the die block 63.

Thereafter the finger 615 retracts, the die block 63 and 64 and their associated core pins move together at the parting line and the cycle is repeated.

Claims

A process for manufacturing a cast or moulded internally single threaded nut having

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upper and lower major surfaces and a plurality of wrench-engaging surfaces extending between said major surfaces, with regions of greater and lesser material thickness normal to 5 said thread in the radial direction thereof, comprising the steps of:

providing first and second contiguous opposed die blocks, each block having a recess therein, said recesses co-operating to con-10 verge along a parting line and defining a first space having the desired shape of the exterior surface of said nut, said first space having portions of greater and lesser radial dimension;

15 disposing first and second aligned core pins within said first and second die blocks respectively, each pin having a protruding portion extending into the recess of the corresponding die block;

20 each said protruding portion comprising a helical ramp having an outer diameter and pitch corresponding to the desired diameter and pitch of an internally threaded surface to be formed within said product, said ramp 25 extending through a circumferential angle of less than 360°, said protruding portion including a vertically oriented parting line shut off surface extending between the ends of said ramp, the outer edge of said ramp having a 30 peripheral edge groove therein, said groove extending along the edge of said ramp except in the vicinity of said vertically oriented surface, said ramp having first and second shoulder portions extending between said vertically 35 oriented surface and the ends of said groove; the protruding portions of said core pins being disposed so that the ramps thereof are in abutting relationship with the grooves of said ramps communicating with each other to 40 form a second space defining the shape of the internal thread to be formed on said surface;

said core pins being oriented within said recess so that said vertically oriented parting line shutoff surface is radially aligned with a 45 portion of said first space of greater radial dimension;

introducing a hardenable fluid within the spaces between said die blocks and said core pins;

50 causing said fluid to harder-

separating said first core pin and first die block from said second core pin and second die block; and removing the hardened material from said 55 spaces.

Printed in the United Kingdom for

Her Majesty's Stationery Office, Dd 8818935, 1985, 4235. Published at The Patent Office. 25 Southampton Buildings,

London, WC2A 1AY, from which copies may be obtained.