Single-leaf spring made from composite material with a polymer matrix and manufacturing method for said leaf spring

Abstract

A single-leaf spring comprising a body and two eyes located at the ends of the body, with the body having an upper side and a lower side, that comprises at least one composite material sheet comprising a series of fiber sheets embedded in a polymer matrix to form a single-leaf spring, where the sheet is a single sheet that runs longitudinally along both sides of the body and the eyes of the leaf spring and that by having both sides folded creates the eyes of the leaf spring.

Claims

1. A single-leaf spring comprising: an elongated body, two eyes located near ends of the body, with the body having an upper side and a lower side, the body comprising: at least one composite material sheet formed by a set of fiber plies embedded in a polymer matrix to form a single-leaf spring, where the sheet is a single sheet that runs longitudinally along the upper and the lower sides of the body and eyes of the leaf spring and which, by having both sides of the sheet folded, creates the eyes of the leaf spring; and, a stitching of the at least one composite material sheet between the upper side and the lower side near the eyes of the leaf spring, wherein the polymer matrix is cured, and wherein the stitching comprises an outer surface not embedded in the cured polymer matrix.

2. The single-leaf spring, according to claim 1, further comprising at least one metal material sheet that runs longitudinally along the body of the leaf spring, with the polymer matrix injected in and around both the composite material sheet and the metal material sheet, such that the metal material sheet and the composite material sheet form a single-leaf spring.

3. The single-leaf spring, according to claim 1, further comprising at least one reinforcement sheet formed by a set of fiber plies embedded in a polymer matrix that runs longitudinally along a center of the leaf spring's body.

4. The single-leaf spring, according to claim 1, further comprising a second composite material sheet that runs longitudinally along the upper and the lower sides of the body and the eyes of the leaf spring, and that by having both sides of the second composite material sheet folded, forms the eyes of the leaf spring.

5. The single-leaf spring, according to claim 2, further comprising a second composite material sheet that runs longitudinally along the upper and the lower sides of the body and the eyes of the leaf spring, and that by having both sides of the second composite material sheet folded, forms the eyes of the leaf spring, comprising two metal material sheets, each of which are located between the first and the second composite material sheet on the upper side and lower side of the leaf spring.

6. The single-leaf spring, according to claim 2, further comprising a second composite material sheet that runs longitudinally along the upper and the lower sides of the body and the eyes of the leaf spring, and that by having both sides of the second composite material sheet folded, forms the eyes of the leaf spring, wherein the metal material sheet is located between the two sides of the sheet located farthest inside the leaf spring.

7. The single-leaf spring, according to claim 1, wherein an opening forming the eye comprises a carbon fiber braided covering.

8. The single-leaf spring, according to claim 1, wherein both ends of each ply that forms the composite material sheet are connected to each other in a staggered manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to complete the description and with the goal of providing a better understanding of the invention, some figures have been provided. These figures are an integral part of the description and they illustrate embodiments of the invention.

(2) FIG. 1 is a general side view of an embodiment of the leaf spring of the invention.

(3) FIG. 2 is a longitudinal section of the embodiment named as embodiment 1.

(4) FIG. 3 is a longitudinal section of a first embodiment of the embodiment named as embodiment 2, which contains two metal sheets.

(5) FIG. 4 is a longitudinal section of a second embodiment of the embodiment named as embodiment 2, which contains a single metal sheet.

(6) FIG. 5 is a schematic side view of the detail of the lamination of an eye from an embodiment of the leaf spring of the invention.

(7) FIGS. 6 and 7 show a lamination scheme of a first embodiment of the leaf spring from the embodiment named as embodiment 1, which contains two composite material sheets that form the upper and lower sides and the eyes of the leaf spring.

(8) FIGS. 8 and 9 show a lamination scheme of a second embodiment of the leaf spring from the embodiment named as embodiment 1, which contains a single composite material sheet that comprises the upper and lower sides and the eyes of the leaf spring.

(9) FIGS. 10 and 11 show a lamination scheme of a first embodiment of the leaf spring from the embodiment named as embodiment 2, which has two composite material sheets and two metal sheets.

(10) FIGS. 12 and 13 show a lamination scheme of a second embodiment of the leaf spring from the embodiment named as embodiment 2, which has two composite material sheets and one metal sheet.

(11) FIG. 14 shows a schematic view of an embodiment of the interconnection of the ends of the composite material sheet plies.

(12) FIGS. 15 and 16 show a lateral level view of an embodiment of a sheet stitching in the eye area of the leaf spring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(13) FIG. 1 shows a leaf spring as in the invention that comprises a body (1) and two eyes (2) at the ends of the body (1) and an upper side (3) and a lower side (4).

(14) FIG. 2 shows a longitudinal cross-section of the embodiment of the leaf spring named as embodiment 1, which shows that the leaf spring is comprised a sheet (20) that is in turn comprised by various fiberglass plies (25).

(15) FIG. 3 shows a longitudinal cross-section of a first embodiment of the leaf spring pertaining to the embodiment named as embodiment 2, which shows that the leaf spring is comprised by various fiberglass plies (25) and two metal material sheets (10).

(16) FIG. 4 shows a longitudinal cross-section of a second embodiment of the leaf spring pertaining to the embodiment named as embodiment 2, which shows that the leaf spring is comprised by various fiberglass plies (25) and a metal material sheet (10).

(17) FIG. 5 shows a detailed view of the eyes (2) of the leaf spring of the invention in which a single composite material sheet (20) comprising various fiberglass plies (25) surrounds the male end (5) that in turn is covered with a braiding ply (30) made from carbon fiber. The male ends (5) and the composite material sheet (20) define the eyes (2) of the leaf spring, with the composite material sheet (20) running from the lower side (4) of the leaf spring to the upper side (3) of the leaf spring.

(18) FIGS. 6 and 7 show a first embodiment of the embodiment named as embodiment 1 of the single-leaf spring. In this first embodiment of embodiment 1 there are continuous fiberglass sheets (20) comprising fiberglass plies (25) that run along both sides (3, 4) of the leaf spring and that comprise the body (1) and the eyes (2) of the leaf spring. The body (1) is comprised fiberglass plies (25) that form a sheet (20) and of a local reinforcement (21) comprising various fiberglass plies of different lengths. All of this is in accordance with the profile of the leaf spring.

(19) The manufacturing method for this embodiment comprises the following steps:

(20) 1Cutting the Plies (25)

(21) Each of the plies (25) are cut, including both the whole plies (25) and the local reinforcement plies (21), to the dimensions specified in their corresponding laminate level.

(22) After cutting, a binder may be applied to each of them, in the event that it was not applied at the factory. In addition to this and depending on the thickness of the leaf spring, an internal flow facilitation ply (40) will be cut that will be positioned at the center of the sheet to facilitate the flow of resin during injection so that the leaf spring will be impregnated correctly.

(23) 2Lamination and Generation of the Preform

(24) In order to obtain the lamination scheme shown in FIGS. 6 and 7 when the preform is generated, a process is conducted that comprises the following steps:

(25) The whole plies (25) of the most exterior sheet (20) of the leaf spring are placed on a forming tool.

(26) The reinforcement plies (21) are placed on the aforementioned sheet (20).

(27) A second set of whole plies (25) are inserted that constitute the internal sheet (20), i.e., the sheet furthest inside the leaf spring.

(28) The resin impregnation facilitation sheet (40) is inserted depending on the thickness of the leaf spring.

(29) The male ends (5) and the carbon fiber braiding (30) are inserted that form the eyes (2) in their corresponding position.

(30) The plies (25) of the sheet (20) furthest inside are folded on the male ends (5) such that the upper side (3) of the leaf spring is formed with the same sheet as the lower side (4) that also defines the eyes (2). In this stacking, the plies (25) are placed so that their ends do not end at the same transversal section, but are rather staggered to better distribute stress at the connection of the two sheet ends (20).

(31) The reinforcement sheet plies (21) are placed on the plies (25) of the lower side (4).

(32) The plies (25) of the most outlying sheet (20) are folded on the male ends (5) of the eyes (2) in order to create both the eyes (2) and the upper side (3) of the leaf spring. As with the inner sheet (20), the ends of the plies (25) are staggered. This staggering (see FIG. 14) should be done in the flat area (50) of the leaf spring, which is in the same area where the bushing is located. This ensures that the plies (25) are not lying in the same transversal position, therefore, correctly distributing stresses.

(33) 3Filling of the Hollow

(34) The hollow area around the male end (5) left after the folding of the fiberglass plies (25) to create the eye (2) should be filled to prevent excess resin that would result in a weak area where delamination might originate in the central area of the leaf spring. To do this, a fiberglass part (6) with binder is used called roving with the proper shape (see FIG. 5). The shape of the roving is created using pressure and temperature until the required form is obtained.

(35) 4Shaping

(36) Once the sheet is completed on the tool and with the roving placed in its correct position, the tool is closed and heated for the proper time and the right temperature for the binder to meld. This way the preform is created.

(37) 5Stitching (23)

(38) Owing to the low resistance of the composite material sheet (20) to loads transmitted in the normal direction to it (whether normal loads or shear loads), it needs to be reinforced in the area around the eyes (2) so that it can withstand the forces that will arise when the truck brakes. In order to achieve this, a stitching technique (23) is used whereby the upper side (3) and the lower side (4) of the fiberglass sheet (20) are stitched around the eye (2) of the leaf spring using reinforced string such that resistance is added to the sheet (20) in its normal direction, therefore, preventing the two sides (3, 4) from separating from each other. The stitching (23) is done in the area of the eye (2) as shown in the scheme of FIGS. 15 and 16. The distance between the stitches is not based on the size of the leaf. The number of stitches (23) comprising the leaf depends on the leaf's size. In both cases, it has been calculated using finite elements, therefore, ensuring the integrity of the sheet and guaranteeing the desired dynamism.

(39) The stitching (23) is performed once it has been removed from the tool with the preform hardened. This process is conducted using a stitching robot that ensures the automation of the process. The stitch number and distance parameters will be followed that can be seen in FIGS. 15 and 16.

(40) The distance between stitches and the number of rows also depends on the type of leaf spring and the type of string being used.

(41) 6Injection

(42) The preform is placed in the mold again and it is then injected following the parameters for the required number of cycles, for the resin/hardener mixture and for the pressure using any of the RTM techniques.

(43) FIGS. 8 and 9 show a second embodiment of the embodiment named as embodiment 1. In this second embodiment there are continuous fiberglass plies (25) that form a single sheet (20) that runs along both sides (3, 4) of the leaf spring and that form the body (1) and the eyes (2) of the leaf spring. The body (1) is comprised of fiberglass plies (25) that form a sheet (20) and also of an internal reinforcement (21) formed by various fiberglass plies (25) of different lengths. All of this forms the profile of the leaf spring.

(44) The manufacturing method for this second embodiment comprises the following steps:

(45) 1Cutting the plies (25)

(46) Each of the plies (25) is cut, including both the whole plies (25) and the local reinforcement plies (21), to the dimensions specified in their corresponding laminate level.

(47) After cutting, a binder may be applied to each of them, in the event that it was not applied at the factory. In addition to this and depending on the thickness of the leaf spring, an internal flow facilitation ply (40) will be cut that will be positioned at the center of the sheet to facilitate the flow of resin during injection so that the leaf spring will be impregnated correctly.

(48) 2Lamination and Generation of the Preform

(49) In order to obtain the lamination scheme shown in FIGS. 8 and 9 when the preform is generated, a process is conducted that comprises the following steps:

(50) The whole plies (25) of the sheet (20) of the leaf spring are placed on a forming tool.

(51) The reinforcement plies (21) are placed on the aforementioned sheet (20).

(52) The resin impregnation facilitation ply (40) may optionally be inserted depending on the thickness of the leaf spring.

(53) The reinforcement plies (21) are placed on the impregnation facilitation sheet (40),

(54) The male ends (5) and the carbon fiber braiding (30) are located in their corresponding position forming the eyes (2).

(55) The plies (25) of the fiberglass sheet (20) are folded on the male ends (5) of the eyes (2) in order to create both the eyes (2) and the upper side (3) of the leaf spring. The ends of the plies (25) are staggered. This staggering should be done in the flat area of the leaf spring which is in the same area where the bushing is located. This ensures that the plies (25) are not lying in the same position, therefore, correctly distributing stresses.

(56) 3Filling of the Hollow

(57) The hollow area around the male end (5) left after the folding of the fiberglass plies (25) to create the eye (2) should be filled to prevent excess resin that would result in a weak area where delamination might originate in the central area of the leaf spring. To do this a fiberglass part (6) with binder with the proper shape is used, called roving. The shape of the roving binder is created using pressure and temperature until the required form is obtained.

(58) 4Shaping

(59) Once the sheet is completed on the tool and with the roving placed in its correct position, the tool is closed and heated for the proper time and the right temperature for the binder to meld. This way the preform is created.

(60) 5Stitching (23)

(61) Owing to the low resistance of the composite material sheet (20) to loads transmitted in the normal direction to it (whether normal loads or shear loads), it needs to be reinforced in the area around the eyes (2) so that it can withstand the forces that will arise when the truck brakes. In order to achieve this, a stitching technique (23) is used whereby the upper side (3) and the lower side (4) of the fiberglass sheet (20) are stitched around the eye (2) of the leaf spring using reinforced string such that resistance is added to the sheet (20) in its normal direction, therefore, preventing the two sides (3, 4) from separating from each other. The stitching (23) is done in the area of the eye (2) as shown in the scheme of FIGS. 15 and 16. The distance between the stitches is not based on the size of the leaf. The number of stitches (23) comprising the leaf depends on the leaf's size. In both cases, it has been calculated using finite elements, therefore, ensuring the integrity of the sheet and guaranteeing the desired dynamism.

(62) The stitching (23) is performed once it has been removed from the tool with the preform hardened. This process is conducted using a stitching robot that ensures the automation of the process. The stitch number and distance parameters will be followed that can be seen in FIGS. 15 and 16.

(63) The distance between stitches and the number of rows also depends on the type of leaf spring and the type of string being used.

(64) 6Injection

(65) The preform is placed in the mold again and it is then injected following the parameters for the required number of cycles, for the resin/hardener mixture and for the pressure using any of the RTM techniques.

(66) FIGS. 10 and 11 show a first embodiment of the embodiment named as embodiment 2 of the single-leaf spring. In this first embodiment of embodiment 2, there are fiberglass plies (25) that form two composite sheets (20) and two steel sheets (10) located between the two sides of the sheet furthest inside (20) and the local reinforcement (21). All of these elements form the profile of the leaf spring.

(67) The manufacturing method for this first embodiment of the second version of the leaf spring object of the invention comprises the following steps:

(68) 1Cutting the Plies (25).

(69) Each of the plies (25) are cut, including both the whole plies (25) and the local reinforcement plies (21), to the dimensions specified in their corresponding laminate level.

(70) After cutting, a binder may be applied to each of them, in the event that it was not applied at the factory. In addition to this and depending on the thickness of the leaf spring, an internal flow facilitation ply (40) will be cut that will be positioned at the center of the sheet to facilitate the flow of resin during injection so that the leaf spring will be impregnated correctly.

(71) 2Cutting the Steel Sheets.

(72) Cutting of metal material sheets (10), for example steel that is 1.5 mm thick and 60 mm wide. The length of the sheet (10) runs from one parabolic area of the leaf spring to the other. The dimensions of the steel sheet have been calculated using finite elements in order to ensure the dimensions of the sheets will be optimal and to give the sheet the desired dynamic behavior.

(73) 3Lamination and Generation of the Preform

(74) In order to obtain the lamination scheme shown in FIGS. 10 and 11 when the preform is generated, a process is conducted that comprises the following steps:

(75) The whole plies (25) of the most exterior sheet (20) of the leaf spring are placed on the tool.

(76) The reinforcement plies (21) are placed on the aforementioned sheet (20).

(77) The first sheet of metal material (10) is placed, which may be a tempered, hardened steel sheet.

(78) The second whole sheet (20) is placed, i.e., the sheet furthest inside the leaf spring.

(79) The resin impregnation facilitation ply (40) is placed.

(80) The male ends (5) that comprise the eyes (2) are placed in their corresponding position.

(81) The plies (25) of the sheet (20) furthest inside are folded on the male ends (5) such that the upper side (3) of the leaf spring is formed with the same sheet as the upper side (4) that also defines the eyes (2). In this stacking the plies (25) are placed so that their ends do not end at the same transversal section, but are rather staggered to better distribute stress at the connection of the two ends of the whole sheet (20).

(82) The second sheet of metal material (10) is placed on the upper side (3) of the internal sheet (20).

(83) The reinforcement sheet plies (21) of the upper side (3) are placed on the metal sheet (10) of the upper side (3).

(84) The plies (25) of the most outlying sheet (20) are folded on the male ends (5) of the eyes (2) in order to create both the eyes (2) and the upper side (3) of the leaf spring. As with the inner sheet (20), the ends of the plies (25) are staggered. This staggering (see FIG. 14) should be done in the flat area (50) of the leaf spring that is in the same area where the bushing is located. This ensures that the plies (25) are not lying in the same position, therefore, correctly distributing stresses.

(85) 4Filling of the Hollow.

(86) The hollow area around the male end (5) left after the folding of the fiberglass sheet (20) to create the eye (2) should be filled to prevent excess resin that would result in a weak area where delamination might originate in the central area of the leaf spring. To do this a fiberglass part (6) with binder with the proper shape is used, called roving. The shape of the roving is created using pressure and temperature until the required form is obtained.

(87) 5Shaping

(88) Once the sheet is completed on the tool and with the roving placed in its correct position, the tool is closed and heated for the proper time and the right temperature for the binder to meld. This way the preform is created.

(89) 6Stitching (23)

(90) Owing to the low resistance of the composite material sheet (20) to loads transmitted in the normal direction to it (whether normal loads or shear loads), it needs to be reinforced in the area around the eyes (2) so that it can withstand the forces that will arise when the truck brakes. In order to achieve this, a stitching technique (23) is used whereby the upper side (3) and the lower side (4) of the fiberglass sheet (20) are stitched around the eye (2) of the leaf spring using reinforced string such that resistance is added to the sheet (20) in its normal direction, therefore, preventing the two sides (3, 4) from separating from each other. The stitching (23) is done in the area of the eye (2) as shown in the scheme of FIGS. 15 and 16. The distance between the stitches is not based on the size of the leaf. The number of stitches (23) comprising the leaf depends on the leaf's size. In both cases, it has been calculated using finite elements, therefore, ensuring the integrity of the sheet and guaranteeing the desired dynamism.

(91) The stitching (23) is performed once it has been removed from the tool with the preform hardened. This process is conducted using a stitching robot that ensures the automation of the process. The stitch number and distance parameters will be followed that can be seen in FIGS. 15 and 16.

(92) The distance between stitches and the number of rows also depends on the type of leaf spring and the type of string being used.

(93) 7Injection

(94) The preform is placed in the mold again and it is then injected following the parameters for the required number of cycles, the resin/hardener mixture and the pressure using any of the RTM techniques.

(95) FIGS. 12 and 13 show a second embodiment of the single-leaf spring corresponding to the embodiment named as embodiment 2.

(96) In this second embodiment of embodiment 2, there are fiberglass plies (25) that form the composite material sheet (20) that extends across both sides (3, 4) of the leaf spring and that form the body (1) and the eyes (2) of the leaf spring and a metal sheet (10) located between the two sides of the continuous sheet (20) and the internal reinforcement (21). All of these elements form the profile of the leaf spring.

(97) The production process for this third embodiment comprises the following steps:

(98) 1Cutting the Plies (25)

(99) Each of the plies (25) is cut, including both the whole plies (25) and the local reinforcement plies (21), to the dimensions specified in their corresponding laminate level.

(100) After cutting, a binder may be applied to each of them, in the event that it was not applied at the factory. In addition to this and depending on the thickness of the leaf spring, an internal flow facilitation ply (40) will be cut that will be positioned at the center of the sheet to facilitate the flow of resin during injection so that the leaf spring will be impregnated correctly.

(101) 2Cutting of the Steel Sheets (10)

(102) Cutting, for example, a steel sheet that is 1.5 mm thick and 60 mm wide. The length of the metal sheet (10) runs from one parabolic area of the leaf spring to the other. The dimensions of the steel sheet have been calculated using finite elements in order to ensure the dimensions of the sheets will be optimal and to give the sheet the desired dynamic behavior.

(103) 3Lamination and Generation of the Preform

(104) In order to obtain the lamination scheme shown in FIGS. 12 and 13 when the preform is generated, a process is conducted that comprises the following steps:

(105) The whole plies (25) of the most exterior sheet (20) of the leaf spring are placed on a mold.

(106) The reinforcement plies (21) are placed on the aforementioned sheet (20).

(107) The metal material sheet (10) is placed, which may be a tempered, hardened steel sheet.

(108) The reinforcement sheet plies (21) of the upper side (3) are placed on the metal sheet (10) of the upper side (3).

(109) The male ends (5) that form the eyes (2) are placed in their corresponding position.

(110) The plies (25) of the most outlying sheet (20) are folded on the male ends (5) of the eyes (2) in order to create both the eyes (2) and the upper side (3) of the leaf spring. As with the inner sheet (20), the ends of the plies (25) are staggered. This staggering (see FIG. 14) should be done in the flat area (50) of the leaf spring that is in the same area where the bushing is located. This ensures that the plies are not lying in the same position, therefore, correctly distributing stresses

(111) 4Filling of the Hollow

(112) The hollow area around the male end (5) left after the folding of the fiberglass plies (25) to create the eye (2) should be filled to prevent excess resin that would result in a weak area where delamination might originate in the central area of the leaf spring. To do this a fiberglass part (6) is used with a roving with the proper shape. The shape of the roving is created using pressure and temperature until the required form is obtained.

(113) 5Shaping

(114) Once the sheet is completed on the tool and with the roving placed in its correct position, the mold is closed and heated for the proper time and the right temperature for the binder to meld. This way the preform is created.

(115) 5Stitching (23)

(116) Owing to the low resistance of the composite material sheet (20) to loads transmitted in the normal direction to it (whether normal loads or shear loads), it needs to be reinforced in the area around the eyes (2) so that it can withstand the forces that will arise when the truck brakes. In order to achieve this, a stitching technique (23) is used whereby the upper side (3) and the lower side (4) of the fiberglass sheet (20) are stitched around the eye (2) of the leaf spring using reinforced string such that resistance is added to the sheet (20) in its normal direction, therefore, preventing the two sides (3, 4) from separating from each other. The stitching (23) is done in the area of the eye (2) as shown in the scheme of FIGS. 15 and 16. The distance between the stitches is not based on the size of the leaf. The number of stitches (23) comprising the leaf depends on the leaf's size. In both cases, it has been calculated using finite elements, therefore, ensuring the integrity of the sheet and guaranteeing the desired dynamism.

(117) The stitching (23) is performed once it has been removed from the mold with the preform hardened. This process is conducted using a stitching robot that ensures the automation of the process. The stitch number and distance parameters will be followed that can be seen in FIGS. 15 and 16.

(118) The distance between stitches and the number of rows also depends on the type of leaf spring and the type of string being used.

(119) 6Injection.

(120) The preform is placed in the mold again and it is then injected following the parameters for the required number of cycles, the resin/hardener mixture and the pressure using any of the RTM techniques.

(121) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.