WO2005113303A1

WO2005113303A1 - Pre-tensioner and method for preventing safety belt from unfastening

Info

Publication number: WO2005113303A1
Application number: PCT/KR2005/001136
Authority: WO
Inventors: Hyung Chan Lee
Original assignee: Samsong Industries, Ltd.
Priority date: 2004-04-20
Filing date: 2005-04-20
Publication date: 2005-12-01
Also published as: KR20050101984A; KR100590193B1

Abstract

Disclosed is a pre-tensioner for enabling a spool wound with a safety belt to make a forced reverse rotation in an emergency, which includes a gas-generating device for delivering a gas expansion force generated from gas explosion to a base cartridge upon abrupt decrease of the speed of a vehicle, a rack for protruding from the base cartridge due to the expansion force, a pinion for engaging the rack for rotation upon protrusion of the rack by a given length, a case gear with one face receiving one side of the spool and the other face receiving the pinion, and a plurality of wedges arranged between the pinion and the case gear. The pre-tensioner can quickly stop the rotation of the spool wound with the safety belt, and secure a sufficient force to stop the rotation of the spool.

Description

Description PRE-TENSIONER AND METHOD FOR PREVENTING SAFETY BELT FROM UNFASTENING Technical Field

[1] The present invention relates to a pre-tensioner for enabling a spool wound with a safety belt to make a forced reverse rotation in an emergency, which can not only minimize the spaces between the safety belt and the passenger and the back of the seat to effectively protect the passenger, but also enhance safety by preventing the safety belt from returning to the initially loosened state after tensioning. Background Art

[2] The safety belt is made of a fibrous material of high tension, and has a buckle for facilitating attachment and detachment. The spool serves to wind or unwind the safety belt as needed, attached to a sidewall of the vehicle body for enhancing the user's convenience. The spool is designed to rotate and to be returned to the initial position by the resilient force of a spring.

[3] Meanwhile, when a vehicle is stopped due to an accident such as a head-on collision, the upper part of the driver's body is hurled forward colliding against the windscreen or steering wheel, which means that the safety belt fails the protection of the driver in an actual accident. This is caused by the spaces existing between the body of the driver and the safety belt and the back of the seat. Hence, the automotive industry has needed a pre-tensioner that is a tensioning means for rotating the spool in the reverse direction and fixing it so as to eliminate the spaces in an emergency.

[4] To this end, the conventional pre-tensioner has been variously designed to rotate the spool in the reverse direction and to fix it. Typically, there have been proposed two ways, of which one is to use a wire and the other to use a rack-pinion mechanism. In addition, the pre-tensioner using a rack-pinion mechanism includes a planetary gear, roller, or pawl-ratchet.

[5] The conventional pre-tensioners will be specifically described in reference to the attached drawings.

[6] Figs. 1 and 2 show a conventional pre-tensioner using a planetary gear. Fig. 1 is an external view of the pre-tensioner in the inoperative position. Referring to Fig. 1, the fundamental structure consists of a pinion 140 engaging a rack 130. The rack 130 is inserted in a base cartridge 120. In an emergency, when a gas-generating device 110 is exploded to inject an expanded gas into the base cartridge 120, the gas pressure thrusts the rack 130 in the direction of arrow Yl to rotate the pinion 140 in the direction of arrow XI. [7] A spool (not shown) wound with a safety belt is rotatably mounted with a cylindrical support part 148 (Fig. 2) attached thereto, so that if the cylindrical support part 148 is fixed, or rotated in the reverse direction, the spool is also fixed, or rotated to wind the safety belt. Reference numeral 150 represents a gear case.

[8] Fig. 2 illustrates a planetary gear mounted inside the gear case after having worked the pre-tensioner. Referring to Fig. 2, a clutch 142 rotates along with the pinion 140 to press roller pins 141, which in turn destroys roller holder 145 holding the roller pin 141 so as to cause the roller pin 141 to contact the clutch 142, resulting in their plastic deformation.

[9] Thus, the roller pin 141 engages both the clutch 142 and cylindrical support part 148 so as to fix the cylindrical support part 148. The reference numerals not described represent respectively clutch periphery 143, pin 144, planetary gear 146, and planetary gear case 147.

[10] However, the conventional pre-tensioner using the planetary gear as shown in Figs. 1 and 2 consists of at least three planetary gears 146 connected by pins 144 and planetary gear case 147, which components are difficult to manufacture as well as complicate the assembly.

[11] Further, the cylindrical roller pin 141 as the element for fixing the cylindrical support part 148 only makes point or line contact with the clutch 142 and the cylindrical support part 148, so that it is hard to provide a large supporting or fixing force through roller pin 141.

[12] Compared to this pre-tensioner using the planetary gear is a simple pre-tensioner that employs rollers inserted in a clutch provided with curved surfaces.

[13] Figs. 3 and 4 show the conventional pre-tensioner employing rollers.

[14] Fig. 3 illustrates the position of the pre-tensioner before working. Referring to Fig. 3, basically a pinion 240 engages a rack 230 inserted in a base cartridge 220. In an emergency, a gas-generating device 210 is exploded to inject an expanded gas into the base cartridge 220, which pressure thrusts the rack 230 upwards, rotating the pinion 240 clockwise.

[15] A spool (not shown) wound with a safety belt is integrated with a drive connector 261 so that if the drive connector 261 is fixed, or rotated in the reverse direction, the spool is also fixed, or rotated in the reverse direction to wind the safety belt. In order to fixedly rotate the drive connector 216 in the reverse direction, the clutch part 263 connected with the second gear 260 is designed to press the roller 262 against the drive connector 261.

[16] As the first gear 250 connected with the pinion 240 rotates clockwise, the second gear 260 rotates counterclockwise, and so the clutch part 263, so that the curved surfaces formed in the clutch part 263 cause the roller 262 to be pressed toward the drive connector 261.

[17] Fig. 4 shows the pre-tensioner after being worked. Referring to Fig. 4, the clutch part 263 presses the roller 262 against the drive connector 261, thus fixing the drive connector 261.

[18] Since the rack 230 is so designed as to keep the upward projected position without returning, the pinion 240 engaged therewith is also fixed, and so all of the first gear 250, second gear 260 and the clutch part 263, and finally so the drive connector 261.

[19] Although the conventional pre-tensioner employing the rollers as shown in Figs. 3 and 4 has an advantage over the pre-tensioner employing a planetary gear in that the number of the components is decreased to simplify manufacture, it suffers such drawback as the first and second gears 250 and 260 must be separately provided and the rollers 262 make line contact with the clutch part 263 and drive connector 261 not providing a considerable supporting or fixing force.

[20] In addition, since the roller 262 has a very small size compared to the inner space of the clutch part 263, it must travel a relatively long distance to contact the clutch part 263 and drive connector 261, and thus it takes a long time to fix the drive connector 261. Further, it occasionally occurs that the roller 262 is idled without being supported completely.

[21] Such delay impeding instant operation of the pre-tensioner of the safety belt is fatal in an emergency such as a traffic accident. Therefore, there has been needed a pre- tensioner for preventing the safety belt from loosening or unfastening and winding it in the reverse direction without a considerable delay.

[22] To overcome such delay of the pre-tensioner employing the rollers was proposed a pre-tensioner employing a pawl and ratchet.

[23] Figs. 5 and 6 illustrate the pre-tensioner employing a pawl and ratchet.

[24] Fig. 5 shows the position of the pre-tensioner before working. Referring to Fig. 5, mounted in the clutch part 310 are pawls 330 and cages 340 instead of the conventional rollers, and in addition a ratchet 320 connected with a spool (not shown) wound with a safety belt in the inside of them. The ratchet, usually called ratchet wheel, serves as a kind of break means in association with the pawl.

[25] The ratchet 320 and pawl 330 are provided with corresponding teeth in order to engage each other. If the ratchet 320 is fixed, and thus the spool (not shown), the safety belt is prevented from loosening or unfastening. The ratchet 320 stops its rotation by being engaged by the pawl 330.

[26] In order to work the pawl 330 is rotated the clutch part 310 by a given angle, so that the cage 340 is slightly rotated about a pivot 341, thus pushing the pawl 330 from the clutch part 310 toward the ratchet 320. Reference numerals not described represent return spring 311 and first end 331 respectively. [27] Fig. 6 illustrates the position of the pre-tensioner after being worked. Referring to Fig. 6, when the clutch part 310 is rotated by a given angle to move the cage 340, the end 342 of the cage 340 supporting the pawl 330 pushes the pawl 330 to engage and to stop the ratchet 320. [28] However, the pre-tensioner employing the pawl and ratchet as shown in Figs. 5 and 6 requires a number of elements arranged in the clutch part 310. Namely, for the purpose of stopping the rotation of the ratchet 320, the cage 340 mounted by means of the pivot 341 is required in addition to the pawl 330. Besides the cage 340 must be provided with the cage end 342, and the pawl 330 also must be provided with the first end 331 and return spring 311. [29] Consequently, a plurality of components in the clutch part 310 complicate manufacture, increasing expense. Further, the complex structure diminishes reliability. Disclosure of Invention Technical Problem [30] In order to resolve the problems as described above, it is an object of the present invention to provide a pre-tensioner of a simple structure having wedges for quickly stopping a spool wound with a safety belt. [31] It is another object of the present invention to provide a pre-tensioner for applying a pressure enough to stop a spool, wherein the configuration of a clutch part and wedges is designed to make a surface contact with each other and to prevent the wedges from rotating, thereby increasing reliability. [32] It is a further object of the present invention to provide a pre-tensioner for causing wedges to quickly contact a spool so as to prevent the spool from rotation even with a slight rotation of a clutch part. Technical Solution

[33] According to the present invention, a pre-tensioner comprises a spool for winding a safety belt, a gas-generating device for delivering a gas expansion force generated by gas explosion to a base cartridge upon an abrupt decrease of the speed of a moving vehicle, a rack for protruding from the base cartridge due to the expansion force, a pinion for engaging the rack for rotation upon protrusion of the rack by a given length, a case gear with one face receiving one side of the spool and the other face receiving the pinion, and a plurality of wedges arranged between the pinion and the case gear.

[34] According to one aspect of the present invention, the rack is made of a bar provided with a plurality of teeth at one side, which teeth engage the corresponding teeth formed on the pinion. The pinion includes a clutch part provided on the opposite side of the teeth, and a wedge recess formed in the clutch part for receiving the wedges.

[35] According to another aspect of the present invention, the case gear is designed to receive the wedges inserted in the wedge recess of the pinion, the pinion being inserted in the case gear. The wedge recess has an outline shaped so as to lie between a large and a small circle concentric with the clutch part, and wedge contact portions for surrounding the wedges.

[36] According to still another aspect of the present invention, each of the wedge contact portions comprises a first catch depression having a bottom to contact the large circle, a first contact surface connecting a previous zeroth catch protrusion and the first catch depression, the catch protrusion having a top contacting the small circle, and a first catch protrusion with a top contacting the small circle for connecting the first catch depression and a subsequent second contact surface. The first contact surface is smoothly sloped in the space between the large and small circles.

[37] According to still another aspect of the present invention, each of the wedges comprises a wide end for facing the surface between the first catch depression and the first catch protrusion of the wedge contact portion, a narrow end positioned opposite to the wide end, the narrow end being smaller than the wide end, an outer contact surface so shaped as to make a surface contact with the first contact surface of the wedge contact portion, and an inner contact surface so shaped as to make a surface contact with the peripheral surface of the cylindrical support part of the spool. The inner contact surface is provided with projections.

[38] According to a further aspect of the present invention, the case gear includes a spool hole for receiving the cylindrical support part of the spool, and a plurality of collapsible wedge holders for fixedly holding the wedges, the collapsible wedge holders collapsing under a given pressure. The collapsible wedge holders are symmetrically arranged around the spool hole with a given interval between them in order to hold the wedges, the wedge holders being vertically arranged on the inner surface of the case gear so as to hold both ends of the wedges, thereby preventing the inner contact surface from contacting the cylindrical support part of the spool until the given pressure for collapsing the wedges is applied to the wedges.

[39] According to further another aspect of the present invention, the collapsible wedge holders are so shaped as to enclose the connecting portions between the inner contact surface and the wide end and between the inner contact surface and the narrow end, the wedge holders being arranged adjacent to the spool hole.

[40] According to still further another aspect of the present invention, the pinion is provided with pinion collapsing-grooves for receiving pinion collapsing-holders provided in the case gear, so that the pinion collapsing-holders cooperate with the pinion collapsing-grooves in order to prevent rotation of the pinion, the pinion collapsing-holders being collapsed under a given pressure applied to the pinion.

[41] The present invention also provides a method of rotating a spool wound with a safety belt in the reverse direction by means of a rack and pinion, which comprises the steps of enabling a gas expansion due to explosion of a gas-generating device to push up the lower end of the rack mounted in a base cartridge, making the rack rise to a given distance so as to rotate the pinion engaging the rack by a given angle, transmitting the rotational force of the pinion to a clutch part formed therein to collapse pinion collapsing-holders of a case gear, making the clutch part keep on rotating so that the contact surfaces of wedge contact portions contact the outer contact surfaces of wedges mounted in a case gear to apply a pressure thereto, collapsing collapsible wedge holders of the case gear by transmitting the pressure applied to the outer contact surfaces of the wedges to inner contact surfaces, making the inner contact surfaces move to the peripheral surface of a cylindrical support part of the spool through displacement of the wedges from the initial positions after collapsing of the collapsible wedge holders so that the inner contact surfaces are pressed against the cylindrical support part so as to be integrated therewith, thus enabling the motion of the spool to follow that of the pinion, and further rotating the pinion through an additional rise of the rack by a given length so as to rotate the spool connected to the cylindrical support part by a given angle. Advantageous Effects

[42] The inventive pre-tensioner achieves the reverse turn of the safety belt by means of a simple structure, which reduces the number of components so as to facilitate manufacture and simplify assembly.

[43] In addition, the present invention causes the wedges to contact the clutch part directly without rotation of the wedges, making a quick reverse turn of the safety belt.

[44] Further, the present invention causes the wedges to make a surface contact, producing a more secure and stable contact pressure than a line contact. Brief Description of the Drawings

[45] Fig. 1 is a schematic view of a conventional pre-tensioner employing a planetary gear;

[46] Fig. 2 is an inner view for showing the operational structure of a conventional pre- tensioner employing a planetary gear;

[47] Fig. 3 is a structural view for showing the inoperative position of a conventional pre-tensioner employing rollers;

[48] Fig. 4 is a structural view for showing the operative position of a conventional pre- tensioner employing rollers;

[49] Fig. 5 is a structural view for showing the inoperative position of a conventional pre-tensioner employing pawl and ratchet;

[50] Fig. 6 is a structural view for showing the operative position of a conventional pre- tensioner employing pawl and ratchet;

[51] Fig. 7 is an exploded view of the inventive pre-tensioner for showing the parts separated;

[52] Fig. 8 is a structural view for showing the inoperative position of the inventive pre- tensioner;

[53] Fig. 9 is a structural view for showing the operative position of the inventive pre- tensioner;

[54] Fig. 10 is a view for illustrating the configuration of a pinion according to the present invention;

[55] Fig. 11 is a view for showing the shape of the clutch part of a pinion according to the present invention;

[56] Fig. 12 is an enlarged partial view of the shape of the clutch part of a pinion according to the present invention;

[57] Fig. 13 is a perspective view for showing the shape of a wedge according to the present invention;

[58] Fig. 14 is a structural view for illustrating a case gear mounted with wedges according to the present invention;

[59] Fig. 15 is a cross sectional view for illustrating a pinion inserted in a case gear mounted with wedges according to the present invention;

[60] Fig. 16 is a view for illustrating the inventive pre-tensioner beginning to operate; and

[61] Fig. 17 is a view for illustrating a chief operative position of the inventive pre- tensioner. Best Mode for Carrying Out the Invention

[62] Fig. 7 illustrates the inventive pre-tensioner disassembled to display essential parts. Referring to Fig. 7, a pre-tensioner according to the present invention includes a gas- generating device 10 for generating a gas upon an abrupt decrease of the speed of a moving vehicle, a rack 30 provided with a plurality of teeth on one side, a base cartridge 20 for receiving the expanded gas to push the rack 30 upward, a pinion 40 provided with a plurality of teeth for engaging the rack 30 for rotation, and a case gear 60 for sequentially mounting a plurality of wedges 50 of a given form and the pinion 40 over them.

[63] Besides, a spool 70 is provided with a cylindrical support part 72 inserted in the case gear 60 and a shaft 74 penetrating the pinion 40. All these component parts are mounted on a frame 80.

[64] A safety belt is wound around the spool 70, which can be freely rotated to wind the safety belt normally without contacting the wedges 50. The cylindrical support part 72 is integrally formed with one end of the spool 70, inserted in the case gear 60. Hence, if the cylindrical support part 72 is fixedly supported by the wedges 50, the spool 70 is prevented from rotating, and thus the safety belt from loosening.

[65] The wedges 50 are mounted in the case gear 60, covered by the pinion 40. If the pinion 40 is rotated, the wedges 50 moves to contact the cylindrical support part 72 in the case gear 60. The number of wedges is at least two, and preferably three or four, of the same size and shape.

[66] Fig. 8 illustrates the essential elements of the inventive pre-tensioner associated with each other.

[67] Referring to Fig. 8, Fig. 8(a) is a perspective view for illustrating the cooperation of the elements, Fig. 8(b) a front view, and Fig. 8(c) a cross sectional view taken along line A-A of Fig. 8(b).

[68] The cylindrical support part 72 of the spool 70 is inserted in the case gear 60, while the wedges 50 are mounted in the case gear 60, associated with the pinion 40. The shaft 74 of the spool 70 is protruded through the pinion 40.

[69] The rack 30 is inserted in the base cartridge 20. The gas-generating device 10 is connected with the base cartridge 20, so as to push the rack 30 upward. The teeth of the rack 30 engage those of the pinion 40, and thus the pinion 40 is not rotated normally without moving the rack 30.

[70] Referring to the cross sectional view of Fig. 8(c), mounted around the cylindrical support part 72 are the wedges 50, which are surrounded by the pinion 40. The spool 70 is integrally formed with the cylindrical support part 72 and the shaft 74.

[71] Fig. 9 is an enlarged perspective view for illustrating the cooperation of the essential components according to the present invention.

[72] Referring to Fig. 9, the teeth 32 of the rack 30 engage the teeth 41 of the pinion 40, so that the upward movement of the rack 30 can rotate the pinion 40. The pinion 40 contains the wedges 50 mounted in the case gear 60. The shaft 74 of the spool 70 is inserted in the shaft hole 42 (shown in Fig. 10) formed through the pinion 40.

[73] Fig. 10 gives enlarged views for illustrating the pinion.

[74] Referring to Fig. 10, Fig. 10(a) is a perspective view of the pinion, and Figs. 10(b) and 10(c) show the pinion separated into the upper and lower parts. Fig. 10(b) shows the shape of the clutch part 43 of the pinion 40, and Fig. 10(c) the shape of the upper part of the pinion 40.

[75] The periphery of the pinion 40 is provided with a pair of pinion collapsing-grooves 44 symmetrically arranged. The pinion collapsing-grooves 44 receive respective pinion collapsing-holders 64 (shown in Fig. 14) provided in the case gear 60, fixing the pinion 40 in the case gear 60. The upper part of the pinion 40 is provided with teeth 41 and a central shaft hole 42. [76] The lower part of the pinion 40 is provided with the clutch part 43 to contact the wedges 50. A wedge recess 45 is formed in the clutch part 43 to engage the wedges 50.

[77] Figs. 11 and 12 are enlarged views of the clutch part in the lower part of the pinion. Fig. 11 is an enlarged view of the clutch part, and Fig. 12 an enlarged view of a part of the clutch part.

[78] As shown in Fig. 11, the wedge recess 45 of the clutch part 43 is shaped like the vanes of a screw. The outline 45a of the wedge recess is formed by repetitions of the same shape so as to fit a plurality of the wedges 50. The outline 45a must be in the region of a given range.

[79] The outline 45a of the wedge recess is made into a given form between a large circle A and a small circle B concentric with the circular pinion 40. The large and small circles A and B are imaginary circles for illustrating the position and shape of the outline 45a of the wedge recess.

[80] The outline 45a of the wedge recess is formed with catch protrusions 48, 48a (shown in Fig. 12) having a top to contact the small circle and with catch depressions having a bottom to contact the large circle. The diameters of the small and large circles A and B may be properly chosen according to the shape of the wedge 50.

[81] The outline 45a of the wedge recess is formed by repetitions of a shape similar to an inverted U-shape slanting toward one side by a given angle. It is preferable that the sides of the shape are formed into curved shape rather than planar shape and to accommodate three to four wedges 50.

[82] As shown in Fig. 12, there are provided wedge contact portions 46 for receiving the wedges 50, which include a first catch protrusion 48 having a top to contact the small circle B, a first contact surface 49 smoothly forming a curved slanting surface from a previous zeroth catch protrusion 48a to the large circle A, and a first catch depression 47 formed between the first contact surface 49 and the first catch protrusion 48 by abruptly turning the end of the first contact surface 49 abutting the large circle A toward the small circle B. Namely, the wedge contact portion is the space surrounded by the contact surface, catch depression, and catch protrusion.

[83] The wedge contact portions are all of the same shape, and for convenience s sake, the catch protrusion connected to the first contact surface 49 counterclockwise is called the zeroth catch protrusion 48a, and the contact surface connecting the first catch depression and the first catch protrusion a second contact surface 49a.

[84] The first contact surface 49 is preferably curved, serving to press the wedge 50 toward the cylindrical support part 72 of the spool 70 upon movement of the clutch part 43. The first contact surface 49 is sloped through a small angle between the large and small circles A and B.

[85] If the first contact surface 49 is formed so as to abruptly connect the large and small circles A and B, a slight rotation of the clutch part can push the wedge 50 deeply toward the inside, or otherwise it being formed so as to smoothly connect the large and small circles A and B, a relatively long rotation of the clutch part is needed to push the wedge deeply.

[86] The slope and curvature of the first contact surface 49 may be properly changed, and it is preferable to determine the shape and position of the first contact surface 49 so that the wedge 50 can tightly hold the cylindrical support part 72 of the spool by 9 rotation of the clutch part 43.

[87] Fig. 13 is an enlarged view of the wedge according to the present invention.

[88] Referring to Fig. 13, the wedge 50 is provided with an outer contact surface 56 so shaped as to make a surface contact with the first contact surface 49 of the clutch part 43. The shapes of the first contact surface 49 and the outer contact surface 49 correspond with each other, making a surface contact.

[89] Respectively provided on both sides of the outer contact surface 56 are a wide end 52 for facing the surface between the first catch depression 47 and the first catch protrusion 48 and a narrow end 54 positioned toward the zeroth catch protrusion 48a. The wide and narrow ends 52 and 54 are preferably connected with the outer and inner contact surfaces 56 and 58 through curved surfaces, and they have no special functions, for the force of the clutch part 43 is delivered mostly through the first contact surface 49 and outer contact surface 56.

[90] The inner contact surface 58 is opposed to the outer contact surface 56. The inner contact surface 58 is normally separated from the cylindrical support part 72 of the spool by a given gap without contacting it. This gap is maintained by collapsible wedge holders 66 (shown in Fig. 14) of the case gear 60.

[91] The inner contact surface 58 engages the cylindrical support part 72 of the spool 70 under the pressure applied to the outer contact surface 56, plastically deformed to prevent rotation of the spool. The inner contact surface 58 is preferably shaped to correspond with the peripheral surface of the cylindrical support part 72, thus making a surface contact with it.

[92] The inner contact surface 58 may be provided with a plurality of projections 58a, which penetrate the cylindrical support part 72 of the spool 70 after contacting it, plastically deformed to more securely bind the wedge 50 and spool 70.

[93] Fig. 14 illustrates the wedges mounted in the case gear.

[94] As shown in Fig. 14, the case gear 60 has a central portion provided with a spool hole 62 for receiving the cylindrical support part 72 of the spool 70. Mounted around the spool hole 62 are the wedges 50. A plurality of collapsible wedge holders 66 are also formed around the spool hole 62 so as to maintain the gaps between the wedges 50 and the cylindrical support part 72, thus normally preventing the wedges 50 from contacting the cylindrical support part 72.

[95] It is preferable that the collapsible wedge holders 66 are vertically arranged on the inner surface of the case gear 60 so as to hold both ends of the wedges 50. If the collapsible wedge holders 66 are arranged too far from the spool hole 62, and thus the gap between the wedge 50 and the cylindrical support part 72, it will take a long time for the wedge 50 to contact the cylindrical support part 72 in an emergency.

[96] Hence, it is desired that the collapsible wedge holders 66 be arranged most adjacent to the spool hole 62 without obstructing the insertion of the cylindrical support part 72 into the spool hole 62. Referring to a partially enlarged view as shown on the right of Fig. 14, the collapsible wedge holders 66 are shown to hold the wedges 50, preventing the projections 58a of the wedges 50 from contacting the cylindrical support part 72.

[97] In addition, the collapsible wedge holders 66 are designed to collapse under a given pressure, so that the wedges 50 may engage the cylindrical support part 72 in an emergency. Namely, when an abrupt break of a moving vehicle in a traffic accident causes the rack 30 to rise to rotate the pinion 40, the collapsible wedge holders 66 immediately collapse.

[98] Meanwhile, the case gear 60 preferably includes pinion collapsing-holders 64 for fixing the pinion 40 at an upper and a lower surface portion. In addition, the pinion 40 is provided with corresponding pinion collapsing-grooves 44, so that the pinion 40 can be properly mounted in the case gear 60 only by fitting the pinion collapsing-holders 64 into the corresponding pinion collapsing-grooves 44 without attending the position of the wedges 50, thereby facilitating the assembly.

[99] The pinion collapsing holders 64 inserted in the pinion collapsing-grooves 44 of the pinion 40 immediately collapse under a given pressure, allowing the pinion 40 to rotate.

[100] Fig. 15 is cross sectional views for illustrating the association of the wedges mounted in the case gear and the pinion.

[101] As shown in Fig. 15, the pinion collapsing-holders 64 are inserted in the pinion collapsing-grooves 44, and the wedges 50 are arranged with the outer contact surfaces 56 contacting respectively the first contact surfaces 49.

[102] Hereinafter, the operation of the inventive pre-tensioner is described specifically with reference to Figs. 16 and 17.

[103] Fig. 16 is a view for illustrating the gas generating-device just after gas explosion.

[104] Referring to Fig. 16, the rack 30 rises in the direction of arrow A to rotate the pinion 40 in the clockwise direction B. At this time the pinion collapsing-holders 64 collapse to allow the pinion 40 to rotate. In addition, as the rotating clutch part 43 presses the wedges, the collapsible wedge holders 66 inside the wedges 50 also collapse.

[105] The rotation of the pinion 40 causes the clutch part 43 to press the wedges 50 in the direction of arrow C against the cylindrical support part 72, as shown in Fig. 16(c). At this time the clutch 43 makes a surface contact with the wedges 50 through the first contact surface 49 and outer contact surface 56. [106] Fig. 17 is a view for illustrating the rack having risen to a given length.

[107] Referring to Fig. 17, as the rack 30 rises, the pinion 40 keeps on rotating in the clockwise direction B, thus causing the clutch part 43 to further press the wedges 50. In this case, as shown in Fig. 17(d), the projections 58a of the wedges 50 penetrate the cylindrical support part 72, undergoing plastic deformation so as to be fixed thereto. [108] The cylindrical support part 72 rotates along with the clutch part 43 in the clockwise direction B, causing the spool 70 to wind the safety belt. Because the first contact surface 49 is sloped inwardly from the first catch depression 47 to the zeroth catch depression 48a contacting the small circle, the wedges 50 continue to be more strongly pressed in the inward direction of arrow D. [109] Thus, as the rack 30 continues to rise, the spool 70 keeps on rotating in the reverse direction of arrow B, thereby more and more tensioning the safety belt to hold the wearer from being hurled forward. Industrial Applicability [110] The present invention provides a pre-tensioner of simple structure that employs wedges to quickly stop the rotation of the spool. [Ill] Moreover, the present invention provides a reliable pre-tensioner having a clutch part that is designed to have a configuration both making a surface contact with the wedges and obstructing their rotation, thereby securing a sufficient force to stop the rotation of the spool. [112] Besides, the present invention provides a reliable pre-tensioner that causes the wedges to make a quick contact to stop the rotation of the spool by means of a slight rotation of a clutch part.

Claims

[1] A pre-tensioner for preventing loosening of a safety belt upon an abrupt decrease of the speed of a moving vehicle, comprising: a spool for winding said belt; a gas-generating device for delivering a gas expansion force generated by gas explosion to a base cartridge upon an abrupt decrease of said speed; a rack provided with a plurality of teeth on one side for protruding from said base cartridge by means of said expansion force; a pinion provided with a plurality of teeth for engaging said rack for rotation upon protrusion of said rack by a given length; a case gear provided with one face receiving one side of said spool and the other face receiving said pinion; and a plurality of wedges arranged between said pinion and said case gear.

[2] A pre-tensioner as defined in Claim 1, wherein said pinion includes a clutch part provided on the opposite side of said teeth, and a wedge recess formed in said clutch part for receiving said wedges.

[3] A pre-tensioner as defined in Claim 2, wherein said case gear is designed to receive said wedges inserted in said wedge recess of said pinion, said pinion being inserted in said case gear.

[4] A pre-tensioner as defined in Claim 3, wherein said wedge recess has an outline shaped so as to lie between a large and a small circle concentric with said clutch part, and wedge contact portions for surrounding said wedges.

[5] A pre-tensioner as defined in Claim 4, wherein each of said wedge contact portions comprises: a first catch depression having a bottom to contact said large circle; a first contact surface connecting a previous zeroth catch protrusion having a top to contact said small circle with said first catch depression; and a first catch protrusion having a top to contact said small circle for connecting said first catch depression and a subsequent second contact surface.

[6] A pre-tensioner as defined in Claim 5, wherein said first contact surface is smoothly sloped in the space between said large and small circles.

[7] A pretensioner as defined in Claim 5, wherein each of said wedges comprises: a wide end for facing the surface between the first catch depression and the first catch protrusion of said wedge contact portion; a narrow end positioned opposite to said wide end, said narrow end being smaller than said wide end; an outer contact surface so shaped as to make a surface contact with said first contact surface of said wedge contact portion; and an inner contact surface so shaped as to make a surface contact with the peripheral surface of the cylindrical support part of said spool.

[8] A pre-tensioner as defined in Claim 7, wherein said inner contact surface is provided with projections.

[9] A pre-tensioner as defined in Claim 3, wherein said case gear includes: a spool hole for receiving the cylindrical support part of said spool; and a plurality of collapsible wedge holders for fixedly holding said wedges, said collapsible wedge holders collapsing under a given pressure.

[10] A pre-tensioner as defined in Claim 9, wherein said collapsible wedge holders are symmetrically arranged around said spool hole with a given interval between them in order to hold said wedges, said wedge holders being vertically arranged on the inner surface of said case gear so as to hold both ends of said wedges, thereby preventing said inner contact surface from contacting the cylindrical support part of said spool until said given pressure for collapsing said wedges is applied to said wedges.

[11] A pre-tensioner as defined in Claim 10, wherein said collapsible wedge holders are so shaped as to enclose the connecting portions between said inner contact surface and said wide end and between said inner contact surface and said narrow end, said wedge holders being arranged adjacent to said spool hole.

[12] A pre-tensioner as defined in any of Claims 2-11, wherein said pinion is provided with pinion collapsing-grooves for receiving pinion collapsing-holders provided in said case gear, so that said pinion collapsing-holders cooperate with said pinion collapsing-grooves in order to prevent rotation of said pinion, said pinion collapsing-holders collapsing under a given pressure applied to said pinion.

[13] A method of preventing loosening of a safety belt by enabling a spool wound with said safety belt to rotate in the reverse direction by means of a rack and pinion when the speed of a moving vehicle is abruptly decreased due to collision of the vehicle, comprising the steps of: enabling a gas expansion due to explosion of a gas-generating device to push up the lower end of said rack mounted in a base cartridge; making said rack rise to a given distance so as to rotate said pinion engaging said rack by a given angle; transmitting the rotational force of said pinion to a clutch part formed therein to collapse pinion collapsing-holders of a case gear; making said clutch part keep on rotating so that the contact surfaces of wedge contact portions contact the outer contact surfaces of wedges mounted in a case gear to apply a pressure thereto; collapsing collapsible wedge holders of said case gear by transmitting the pressure applied to the outer contact surfaces of said wedges to inner contact surfaces; making said inner contact surfaces move to the peripheral surface of a cylindrical support part of said spool through displacement of said wedges from the initial positions after collapsing of said collapsible wedge holders so that said inner contact surfaces are pressed against said cylindrical support part so as to be integrated therewith, thus enabling the motion of said spool to follow that of said pinion; and further rotating said pinion through an additional rise of said rack by a given length so as to rotate said spool connected to said cylindrical support part by a given angle.