IN MOLD ASSEMBLY OF TWO HINGES

Abstract

The present invention is directed to a 4-bar kinematic link component and method for forming the 4-bar kinematic link using a single rotary molding tool. The invention eliminates the need to form individual components of the bracket from several different tools, which will then requires additional assembly steps. The 4-bar kinematic link is formed from two different materials each having a different in mold shrinkage value. This allows for hinge pins to be formed through a base component in a way that will prevent sticking of the components together thereby allowing the parts to have it relative to one another using the hinge pin. The final component is a 4-bar kinematic link that can be used as a 4 bar link mechanism for providing motion.

Claims

1. A 4-bar kinematic link comprising: a base member formed of composite material, having at least two sets of a plurality of apertures formed on the surface of the base member; an upper arm formed of composite material, the upper arm having a body with two tabs extending from the body and a hinge pin extending between the two tabs, the hinge pin extends rotatably through one of the at least two sets of the plurality of apertures of the base member, wherein the body, hinge pin and two tabs are integrally formed together as one piece and the hinge pin is formed through the one of the at least two sets of the plurality of apertures of the base member; and a lower arm formed of composite material, the lower arm having a body with two tabs extending from the body and a hinge pin extending between the two tabs, the hinge pin extends rotatably through another one of the at least two sets for the plurality of apertures of the base member, wherein the body, hinge pin and two tabs are integrally formed together as one piece and the hinge pin is formed through the another one of the at least two sets of the plurality of apertures of the base member.

2. The 4-bar kinematic link of claim 1 wherein each one set of the at least two sets of a plurality of pivot apertures includes a left side aperture, a right side aperture and a middle aperture all formed in the base member.

3. The 4-bar kinematic link of claim 1 wherein the base member further includes a plurality of mounting apertures for connecting the base member to a composite air deflector.

4. The 4-bar kinematic link of claim 1 wherein the base member is formed of polyamide material having a mold shrinkage value of about 0.5% and the upper arm and lower arm are formed of polybutylene terephthalate material having a mold shrinkage value of greater than about 0.5%.

5. The 4-bar kinematic link of claim 4 wherein the polyamide material has about 33% glass fiber filler by weight of the polyamide composite material with the glass fiber filler and the polybutylene terephthalate material has about 20% glass fiber filler by weight of the polybutylene terephthalate with a glass filler.

6. The 4-bar kinematic link of claim 1 wherein the base member is formed of polyamide material having a mold shrinkage value of about 0.003 at bar, in/in and the upper arm and lower arm are formed of polybutylene terephthalate material having a mold shrinkage value of greater than about 0.004 at bar, in/in.

7. The 4-bar kinematic link of claim 6 wherein the polyamide material has about 33% glass fiber filler by weight of the polyamide material with the glass fiber filler and the polybutylene terephthalate material has about 20% glass fiber filler by weight of the polybutylene terephthalate material with a glass filler.

8. The 4-bar kinematic link of claim 1 wherein the body of the lower arm has a mounting aperture and the body of the upper arm has a mounting aperture.

9. A method of forming a 4-bar kinematic link comprising the steps of: providing a rotary tool having a rotary platen rotatable at least one hundred eighty degrees and at least one linearly moveable platen capable of moving between an open position and a closed position relative to the rotary platen; providing on the rotary platen a first forming region having a rotary base member forming surface, an rotary upper arm forming surface and a rotary lower arm forming surface, a second forming region having a rotary base member forming surface, a rotary upper arm forming surface and a rotary lower arm forming surface; providing on the at least one linearly moveable platen having a first forming region having a linear base member forming surface, a linear upper arm filler surface, a linear lower arm filler surface, the at least one linearly moveable platen including a second forming region having a linear base member forming surface, a linear upper arm forming surface and a linear lower arm forming surface; providing at least one first shot injection port connected to the first forming region of the at least one linearly moveable platen and at least one second shot injection port connected to the second forming region of the at least one linearly moveable platen; providing a first shot of molten material and a second shot or molten material; moving the at least one linearly moveable platen toward the at least one rotary platen and creating a first base member molding cavity which is a closed cavity defined by the first forming region of the rotary platen and the first forming region of the at least one linearly moveable platen and creating a first arm member molding cavity which is a closed cavity defined by the second forming region of the rotary platen and the second forming region of the at least one linearly moveable platen; injecting the first shot of molten material through the at least one first shot injection port into the first base member molding cavity and forming a base member from the first shot of molten material; opening the first base member molding cavity and the first arm molding cavity by moving the at least one linear moveable platen away from the at least one rotary platen, wherein the formed base member stays on the surface of the rotary base member forming surface of the first forming region of the rotary platen; rotating the at least one rotary platen about an axis so that first forming region and the formed base member become aligned with the second forming region of the at least one liner moveable platen; moving the at least one linearly moveable platen toward the at least one rotary platen and creating a second base member molding cavity which is a closed cavity defined by the second forming region of the rotary platen and the first forming region of the at least one linearly moveable platen and creating a second arm member molding cavity which is a closed cavity defined by the first forming region of the rotary platen and the second forming region of the at least one linearly moveable platen, wherein the formed base member is contained within the second arm member molding cavity; injecting the second shot of molten material through the at least one second shot injection port into the second arm member molding cavity to form an upper arm member and lower arm member, wherein the second shot of molten material flows into contact with and between the rotary upper arm forming surface and the linear upper arm forming surface and the second shot of molten material flows through an upper set of apertures in the base member to form a hinge pin portion of the upper arm, wherein the second shot of molten material flows into contact with and between the rotary lower arm forming surface and the linear lower arm forming surface and the second shot of molten material flows through a lower set of apertures in the base member to form a hinge pin portion of the lower arm; curing the second shot of molten material in the second arm member molding cavity for form the 4-bar kinematic link, wherein the molten material of the second shot shrinks thereby creating a clearance between the hinge pin of the upper arm and the upper set of apertures in the base member to allow the hinge pin of the upper arm to rotate freely in the upper set of apertures in the base member and creating a clearance between the hinge pin of the lower arm and the lower set of apertures in the base member to allow the hinge pin of the lower arm to rotate freely in the lower set of apertures in the base member; and moving the at least one linearly moveable platen away from the at least one rotary platen and removing the 4-bar kinematic link.

10. The method of claim 9 wherein the first shot of molten material is a polyamide material having a mold shrinkage value of about 0.5% and the second shot of molten material is a polybutylene terephthalate material having a mold shrinkage value of greater than about 0.5%.

11. The method of claim 10 wherein the polyamide material has about 33% glass fiber filler by weight of the polyamide material with the glass fiber filler and the polybutylene terephthalate material has about 20% glass fiber filler by weight of the polybutylene terephthalate material with a glass filler.

12. The method of claim 9 wherein the base member is formed of polyamide material having a mold shrinkage value of about 0.003 at bar, in/in and the upper arm and lower arm are formed of polybutylene terephthalate material having a mold shrinkage value of greater than about 0.004 at bar, in/in.

13. The method of claim 12 wherein the polyamide material has about 33% glass fiber filler by weight of the polyamide material with the glass fiber filler and the polybutylene terephthalate material has about 20% glass fiber filler by weight of the polybutylene terephthalate material with a glass filler.

14. The method of claim 9 further comprising the steps of: injecting the first shot of molten material through the at least one first shot injection port into the second base member molding cavity and forming a second base member from the first shot of molten material.

15. A 4-bar kinematic link comprising: a base member formed of composite plastic, having two upper hinge pins extending from the surface of the base member and two lower hinge pins extending from the surface of the base member, wherein the base member, two upper hinge pins and two lower hinge pins are integrally formed together as one piece; an upper arm formed of a composite material, the upper arm having a body with two tabs extending from the body and a pivot aperture extending through each of the two tabs, wherein each pivot aperture receives one of the two upper hinge pins of the base member, wherein the body and two tabs are integrally formed together as one piece such that the apertures of the upper arm are formed about the respective one of the two upper hinge pins of the base member; a lower arm formed of a composite material, the lower arm having a body with two tabs extending from the body and a pivot aperture extending through each of the two tabs, wherein each pivot aperture receives one of the two lower hinge pins of the base member wherein the body and two tabs are integrally formed together as one piece such that the apertures of the lower arm are formed about the respective one of the two lower hinge pins of the base member.

16. The 4-bar kinematic link of claim 15 wherein the base member further includes a plurality of mounting apertures for connecting the base member to a composite air deflector.

17. The 4-bar kinematic link of claim 15 wherein the base member is formed of polyamide composite material having a mold shrinkage value of about 0.5% and the upper arm and lower arm are formed of polybutylene terephthalate having a mold shrinkage value of greater than about 0.5%.

18. The 4-bar kinematic link of claim 17 wherein the polyamide composite material has about 33% glass fiber filler by weight of the polyamide composite material with the glass fiber filler and the polybutylene terephthalate has about 20% glass fiber filler by weight of the polybutylene terephthalate with a glass filler.

19. The 4-bar kinematic link of claim 15 wherein the base member is formed of polyamide composite material having a mold shrinkage value of about 0.003 at bar, in/in and the upper arm and lower arm are formed of polybutylene terephthalate having a mold shrinkage value of greater than about 0.004 at bar, in/in.

20. The 4-bar kinematic link of claim 19 wherein the polyamide composite material has about 33% glass fiber filler by weight of the polyamide composite material with the glass fiber filler and the polybutylene terephthalate has about 20% glass fiber filler by weight of the polybutylene terephthalate with a glass filler.

21. The 4-bar kinematic link of claim 15 wherein the body of the lower arm has a mounting aperture and the body of the upper arm has a mounting aperture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0011] FIG. 1A is a schematic view of the 4-bar kinematic link and an overview of the method for forming the 4-bar kinematic link in accordance with a first embodiment of the present invention.

[0012] FIG. 1B is a schematic view of the 4-bar kinematic link and an overview of the method for forming the 4-bar kinematic link in accordance with a second embodiment of the present invention.

[0013] FIG. 2 is a schematic view of a prior art bracket and components.

[0014] FIG. 3A is a rear isometric view of the 4-bar kinematic link according to the first embodiment of the present invention.

[0015] FIG. 3B is a side isometric view of the 4-bar kinematic link according to the first embodiment of the present invention.

[0016] FIG. 3C is a rear perspective view of the 4-bar kinematic link according to the first embodiment of the present invention.

[0017] FIG. 4 is a rear perspective view of the components of the 4-bar kinematic link according to the second embodiment of the invention.

[0018] FIG. 5A is a side plan schematic view of a rotary tool for producing the 4-bar kinematic link using a method according to a third embodiment of the present invention.

[0019] FIG. 5B is a top plan schematic view of the linearly moveable platen.

[0020] FIG. 5C is a top plan schematic view of the rotary platen.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0022] Referring now to FIG. 1A a schematic view of a 4-bar kinematic link 10 and an overview of the method for forming the 4-bar kinematic link in accordance with a first embodiment of the present invention is shown. Additionally FIGS. 3A, 3B and 3C show the 4-bar kinematic link 10 and components in greater detail. The 4-bar kinematic link 10 includes a base member 12 formed of composite material, having at least two sets of a plurality of apertures, where each one set includes a left side aperture 14, 14 formed through a left sidewall of the base member 12, a right side aperture 16, 16 formed through a right sidewall of the base member 12 and a middle aperture 18, 18 formed through a middle rib of the base member 12. In each one set the left side aperture 14, 14, right side aperture 16, 16 and middle aperture 18, 18 are all aligned for the purpose of allowing a hinge pin (described below) to be rotatably formed through each set of the at least two sets of a plurality of apertures. Also while three apertures (i.e., left, right and middle) are described it is within the scope of this invention for a greater or lesser number of apertures to be used in each set depending on the size of the base member 12 or design criteria of a particular application.

[0023] The base member 12 also includes a plurality of mounting apertures 20 for connecting the base member 12 to an air deflector 22 schematically shown in FIG. 3B. The connection can be made with a suitable mechanical fastener, welding, adhesives or other connection. While an air deflector 22 is depicted, it is within the scope of this invention for the air deflector 22 to be some other structure moveable by the 4-bar kinematic link 10. For example the air deflector 22 can be a vehicle bumper, active grill system components, spoiler, running board, wheel well dam, lift gate, vehicle door, trunk lid, engine hood, window regulator or any other type of automotive structure that would benefit from four bar linkage movement.

[0024] The 4-bar kinematic link 10 also includes an upper arm 24 formed of composite material. The upper arm 24 has a body 26 portion with two tabs 28, 28 extending from the body 26 and a hinge pin 30 extending between the two tabs 28, 28. The hinge pin 30 extends rotatably through one of the at least two sets of the plurality of apertures of the base member 12. The body 26, hinge pin 30 and two tabs 28, 28 are integrally formed together as one piece and the hinge pin 30 is formed through the one of the at least two sets of the plurality of apertures of the base member 12. The body 26 of the upper arm 24 also has a mounting aperture 32 or channel that extends through the body 26. The mounting aperture is used to connect the upper arm 24 to another object in a fixed or rotational manner.

[0025] The 4-bar kinematic link 10 also includes a lower arm 34 formed of composite material. The lower arm 34 has a body 36 with two tabs 38, 38 extending from the body 36 and a hinge pin 40 extending between the two tabs 38, 38. The hinge pin 40 extends rotatably through another one of the at least two sets for the plurality of apertures of the base member 12. The body 36, hinge pin 40 and two tabs 38, 38 are integrally formed together as one piece and the hinge pin 40 is formed through the one of the at least two sets of the plurality of apertures of the base member 12. The body 36 of the lower arm 34 also has a mounting aperture 42 or channel that extends through the body 36. The mounting aperture 42 is used to connect the lower arm 34 to another object in a fixed or rotational manner.

[0026] As will be described in greater detail below, the 4-bar kinematic link 10 is formed in a molding tool, without the need for manual assembly of the components. This provides a significant savings in the cost of producing the 4-bar kinematic link 10 when compared to the prior art assemblies. However, in order to form the 4-bar kinematic link 10 in a mold tool, the upper arm 24 and lower arm 34 must be connected to the base member 12 in a way that will allow the upper arm 24 and lower arm 34 to be pivotally connected to the base member 12. This is accomplished during the molding process by using two different shots of molten material having different shrinkage rates. With respect to the upper arm 24, this allows a clearance or gap 31 between the hinge pin 30 and the left side aperture 14, right side aperture 16 and middle aperture 18 of the base member 12 to be formed so that the hinge pin 30 can freely rotate. With respect to the lower arm 34, the shrinkage rates allow a clearance or gap 41 between the hinge pin 40 and the left side aperture 14, right side aperture 16 and middle aperture 18 of the base member 12 to be formed so that the hinge pin 40 can freely rotate.

[0027] Referring now to FIG. 1B a schematic view of a 4-bar kinematic link 100 and an overview of the method for forming the 4-bar kinematic link in accordance with a second embodiment of the present invention is shown. Additionally FIG. 4 shows the 4-bar kinematic link 100 and components in greater detail. The 4-bar kinematic link 100 is a variation with the 4-bar kinematic link 10 shown in FIGS. 1A, 3A, 3B and 3C, therefore similar structures are shown with reference numbers differing by 100. The 4-bar kinematic link 100 includes a base 112 member formed of composite plastic. The base member 112 has two upper hinge pins 144, 144 extending from the surface of the base member 112 and two lower hinge pins 146, 146 extending from the surface of the base member 112. The base member 112, two upper hinge pins 144 and two lower hinge pins 146 are integrally formed together as one piece.

[0028] The 4-bar kinematic link 100 further includes an upper arm 124 formed of a composite material, the upper arm 124 having a body 126 with two tabs 128, 128 extending from the body 126 and a pivot aperture 148, 148 extending through each of the two tabs 128, 128. Each pivot aperture 148, 148 receives one of the two upper hinge pins 144, 144 of the base member 112. The body 126 and two tabs 128, 128 are integrally formed together as one piece such that the apertures 148, 148 of the upper arm 124 are formed about the respective one of the two upper hinge pins 144, 144 of the base member 112.

[0029] The 4-bar kinematic link 100 further includes a lower arm 134 formed of a composite material, the lower arm 134 having a body 136 with two tabs 138, 138 extending from the body 136 and a pivot aperture 150,150 extending through each of the two tabs 138, 138. Each pivot aperture 150, 150 receives one of the two lower hinge pins 146, 146 of the base member 112. The body 136 and two tabs 138, 138 are integrally formed together as one piece such that the apertures 150, 150 of the lower arm 134 are formed about the respective one of the two lower hinge pins 150, 150 of the base member 112.

[0030] Regarding the molten materials used to form the 4-bar kinematic link 10, 100 in both embodiments described above, the base member 12, 112 is formed using a first shot of molten material, while the upper arm 24, 124 and lower arm 34, 134 are formed using a second shot of molten material. In one embodiment of the invention the first shot of molten material is polyamide material having a mold shrinkage value of about 0.5% and the second shot of molten material is a polybutylene terephthalate material having a mold shrinkage value of greater than about 0.5%. The term mold shrinkage value is a rate percentage of the volume contraction of the polymers during the cooling step of the processing of the polymers. In one exemplary embodiment of the invention the polyamide material has about 33% glass fiber filler by weight of the polyamide composite material with the glass fiber filler and the polybutylene terephthalate material has about 20% glass fiber filler by weight of the polybutylene terephthalate with a glass filler. In another embodiment of the invention the first shot of molten material is formed of polyamide material having a mold shrinkage value of about 0.003 at bar, in/in and the second shot of molten material is polybutylene terephthalate material having a mold shrinkage value of greater than about 0.004 at bar, in/in. In this embodiment the polyamide material has about 33% glass fiber filler by weight of the polyamide material with the glass fiber filler and the polybutylene terephthalate material has about 20% glass fiber filler by weight of the polybutylene terephthalate material with a glass filler. An example of a suitable polyamide material is Ultramid 8233G HS BK-102 Polyamide 6 produced by BASF Corporation 1609 Biddle Avenue, Wyandotte, Mich. 48192. An example of a suitable polybutylene terephthalate material is Ultradur B 4300 G4 PBT (Polybutylene Terephthalate) produced by BASF Corporation 1609 Biddle Avenue, Wyandotte, Mich. 48192. However, it is within the scope of this invention to us other suitable polyamide and polybutylene terephthalate materials.

[0031] FIG. 5A is a side plan schematic view of a rotary tool 200 for producing in mold the 4-bar kinematic link 10, 100 according to either of the embodiments above. The rotary tool 200 is used as part of a method of forming a 4-bar kinematic link 10, 100 and includes several steps that allow for the 4-bar kinematic link 10, 100 to be formed in the rotary tool 200 without the need for additional assembly outside of the rotary tool 200.

[0032] The rotary tool 200 has provided a rotary platen 202 rotatable at least one hundred eighty degrees, but can also rotate three hundred sixty degrees. The rotary tool 200 also includes least one linearly moveable platen 204, 206 capable of moving between an open position and a closed position relative to the rotary platen 202. The at least one linearly moveable platen 204, 206 is depicted as having two platens that can move independently of each other and provide different mold surface variations. It is within the scope of this invention for a greater or lesser number of platens to be used.

[0033] FIG. 5C is a plan view showing the details of the rotary platen 202 includes a first forming region 208 having a rotary base member forming surface 210, a rotary upper arm forming surface 212 and a rotary lower arm forming surface 214, a second forming region 216 having a rotary base member forming surface 218, a rotary upper arm forming surface 220 and a rotary lower arm forming surface 222.

[0034] In order to form the left side apertures 14, 14, right side apertures 16, 16 and middle apertures 18, 18 in the base member 12 shown in FIG. 1A, the first forming region 208 and second forming region 216 include base member pins 224, 224 that are pins capable of moving between an extended and retraced position across the rotary base member forming surface 210, 216 of the two forming regions. When molten resin is injected at the base member 12, 112 will form around the base member pins 224, 224 to create the apertures in the base member 12, 112.

[0035] In order to form the mounting aperture 32 of the upper arm 24 and the mounting aperture 42 of the lower arm 34 shown in FIG. 1A, the first forming region 208 and second forming region 216 include upper mounting aperture pins 226, 226 and lower mounting aperture pins 228, 228. The upper mounting aperture pins 226, 226 move between extended and retracted positions across the rotary upper arm forming surface 212, 220. The lower mounting aperture pins 228, 228 move between extended and retracted positions across the rotary lower arm forming surface 214, 222. When molten resin is injected each mounting aperture 32, 42 will form around the respective upper mounting aperture pins 226, 226 or lower mounding aperture pins 228, 228.

[0036] FIG. 5B depicts a plan view of the at least one linearly moveable platen 204, 206 which has a first forming region 232 having a linear base member forming surface 234, a linear upper arm filler surface 236 and a linear lower arm filler surface 238. The at least one linearly moveable platen 204, 206 includes a second forming region 240 having a linear base member forming surface 242, a linear upper arm forming surface 244 and a linear lower arm forming surface 246.

[0037] Referring back to FIG. 5A the at least one linearly movable platen 204, 206 includes at least one first shot injection port 248 for injecting a first shot of molten material into the first forming region 232 of the at least one linearly moveable platen 204, 206. There is also at least one second shot injection port 250 for injecting a second shot of molten material into the second forming region 240 of the at least one linearly moveable platen 204, 206. The type of molten material used is described above.

[0038] Referring now to FIGS. 5A, 5B and 5C the steps of forming of the 4-bar kinematic link 10, 100 using the rotary tool 200 are described. During a first step the at least one linearly moveable platen 204, 206 is moved toward the at least one rotary platen 202 so that the two meet creating a first base member molding cavity 252, which is a closed cavity defined by the first forming region 208 of the rotary platen 202 and the first forming region 232 of the at least one linearly moveable platen 204, 206. Also this step of moving includes creating a first arm member molding cavity 254 which is a closed cavity defined by the second forming region 216 of the rotary platen 202 and the second forming region 240 of the at least one linearly moveable platen 204, 206.

[0039] Next the method includes injecting a first shot of molten material 256 through the at least one first shot injection port 248 into the first base member molding cavity 252 and forming a base member 12, 112 from the first shot of molten material 252. The first shot of molten material 256 is restricted to flowing into only into the rotary base member forming surface 210 of the first forming region 208 and linear base member forming surface 234 of the first forming region 232 because the rotary upper arm forming surface 212 and rotary lower arm forming surface 214, both of the first forming region 208, are blocked or filled by the respective linear upper arm filler surface 236 and linear lower arm filler surface 238, both of the first forming region 232. The linear upper arm filler surface 236 and linear lower arm filler surface 238 both are filler pieces that are configured to fill or block the flow of the first shot of molten material 256 and confine the first shot of molten material 256 to the rotary base member forming surface 210 of the first forming region 208 and the linear base member forming surface 234 of the first forming region 232. The first shot of molten material 256 is then cured creating the base member 12, 112.

[0040] Next the method includes opening the first base member molding cavity 252 and the first arm molding cavity 254 by moving the at least one linear moveable platen 204, 206 away from the at least one rotary platen 202. The formed base member 12, 112 stays on the surface of the rotary base member forming surface 210 of the first forming region 208 of the rotary platen 202.

[0041] Next the method includes rotating the at least one rotary platen 202 about an axis A so that first forming region 208 and the formed base member 12, 112 become aligned with the second forming region 240 of the at least one liner moveable platen 204, 206. Next the method includes moving the at least one linearly moveable platen 204, 206 toward the at least one rotary platen 202 and creating a second base member molding cavity 260 which is a closed cavity defined by the second forming region 216 of the rotary platen 202 and the first forming region 232 of the at least one linearly moveable platen 204, 206 and creating a second arm member molding cavity 262 which is a closed cavity defined by the first forming region 208 of the rotary platen 202 and the second forming region 216 of the at least one linearly moveable platen 204, 206, wherein the formed base member 12, 112 is contained within the second arm member molding cavity 262.

[0042] Next the method includes injecting a second shot of molten material 258 through the at least one second shot injection port 250 into the second arm member molding cavity 262 to form an upper arm member 24, 124 and lower arm member 34, 134.

[0043] When forming the base member 12 the second shot of molten material 258 flows into contact with and between the rotary upper arm forming surface 212 and the linear upper arm forming surface 244 and the second shot of molten material 258 flows through an upper set of apertures, that is the left side aperture 14, right side aperture 16 and middle aperture 18, in the base member 10 to form the 30 hinge pin portion of the upper arm 24. The second shot of molten material 258 will also flow into contact with and between the rotary lower arm forming surface 214 and the linear lower arm forming surface 246 and the second shot of molten material 250 flows through a lower set of apertures in the base member 10, that is the left side aperture 14, right side aperture 16 and middle aperture 18, in the base member 10 to form the hinge pin 40 portion of the lower arm 34.

[0044] When forming the base member 112 the hinge pins are already formed as part of the base member 112, therefore the second shot of molten material 250 will just flow around the surface of the upper hinge pins 144, 144 and lower hinge pins 146, 146 shown in FIG. 1B.

[0045] Next the method includes curing the second shot of molten material 250 in the second arm member molding cavity 262 for form the 4-bar kinematic link 10. During this step the second shot of molten material 250 shrinks thereby creating a clearance (described above in and shown in FIG. 3B) between the hinge pin 30 of the upper arm 24 and the upper set of apertures in the base member 12 to allow the hinge pin 30 of the upper arm 24 to rotate freely about the upper set of apertures in the base member 12. Also created is a clearance (described above in and shown in FIG. 3B) between the hinge pin 40 of the lower arm 34 and the lower set of apertures in the base member 12 to allow the hinge pin 40 of the lower arm 34 to rotate freely in the lower set of apertures in the base member 12.

[0046] When forming the base member 112 the hinge pins are already formed as part of the base member 112, therefore the second shot of molten material 250 will just flow around the surface of the upper hinge pins 144, 144 and lower hinge pins 146, 146 shown in FIG. 1B.

[0047] Next the method includes injecting a first shot of molten material 256 through the at least one first shot injection port 248 into the second base member molding cavity 260 and forming a second base member from the first shot of molten material 256. This step allows for the simultaneous formation of a second bases member while the second shot of molten material 258 is being injected into the second arm member forming cavity 262.

[0048] A final step of the method includes moving the at least one linearly moveable platen 204, 206 away from the at least one rotary platen 202 and removing the finished 4-bar kinematic link 10, 100. After this step the rotary platen 202 can rotate again to move the formed second base member into alignment to reform the first arm member molding cavity 254, which will have the second base member ready for receiving a second shot of molten material according to the steps described above.

[0049] Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited, since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and following claims.