Title of Invention

"AN IMPROVED COLLAPSIBLE STEERING COLUMN ASSEMBLY FOR AUTOMOBILE"

Abstract

An improved collapsible steering column assembly for automobiles comprising- column jacket assembly, mounted on the vehicle, steering shaft assembly being housed in said column jacket assembly for steering the vehicle, an intermediate shaft assembly, one end of which being connected to said steering shaft assembly and another to the steering gear assembly, characterized in that an energy-absorbing bracket (EA Bracket) is mounted on the outer pipe of column jacket assembly, split type capsule consisting of plastic retainer & capsule insert mounted on the upper bracket of said column jacket assembly for absorbing the impact load, shaft and tube of said steering shaft assembly and intermediate shaft assembly being provided with splines and crimped at least at one place, the arrangement being such that when the driver hits the steering wheel at the time of collision, the split-type capsule breaks and the crimping in steering shaft assembly and the intermediate shaft assembly breaks simultaneously and thereafter said EA bracket bends and absorbs the impact energy, thereby the steering column assembly collapses when the impact is from the opposite vehicle, the crimping between the tube and the shaft after the universal joint breaks.

Full Text

AN IMPROVED COLLAPSIBLE STEERING COLUMN ASSEMBLY FOR AUTOMOBILES This invention relates to An improved collapsible steering column assembly for automobiles. BACKGROUND OF THE INVENTION: Conventionally the collapsible column consists of Column Jacket assembly (Cl), Steering shaft assembly (C2) and Intermediate shaft assembly (C3), as shown in Fig 1-b. of the accompanying drawings. The conventional column Jacket assembly (Cl) is the outer part of the collapsible column which provides support to the steering shaft assembly (C2) and on which steering lock and ignition switch are mounted (not shown). The conventional column jacket assembly comprises an outer pipe (2), upper bracket (7), inner pipe (8), lower bracket (9), steel balls retained in a plastic retainer called ball retainer (6), and are press fitted between the inner pipe (8) and outer pipe (2) so as to ensure the desired sliding load. Size of the balls decides the interference load between said outer and inner pipes and thereby determines the collapsing load of the Column jacket assembly. During collision, the impact load is transferred to said outer pipe (2) from the steering wheel (SW), which starts sliding over said inner pipe (8). During this process the steel balls roll over the contact surface of said inner and outer pipe and thereby absorbing the impact energy. The capsule (5) is a part fitted on the upper bracket (7) of Column jacket assembly (Cl) and is in contact with the vehicle body after the column is mounted with the help of bolts (B). Normally, two Capsules (5) made of aluminum are used in one steering column assembly. Each capsule has 4 small holes (hl,h2,h3,h4) and similar matching holes (hl,h2,h3,h4)pnme are there on the bracket (7). Plastic resin is injected into said holes (hi, h2, h3, h4) putting capsules (5) and bracket (7) together. This forms total eight nos of plastic shear pins (pl,p2,...p8), which shear off at a particular load (usually 100-200 Kgf). When the driver hits the steering wheel these shear pins break off along with the shear pins of shaft assembly and the column jacket assembly slides down away from the driver leaving the capsules alone mounted on the vehicle body (see Fig- 4). The disadvantages of this column jacket assembly and capsule are as follows: the design is expensive; as it has imported parts like ball retainer, steel balls, two pipes and other special assembly process difficulty in manufacturing- High rejection rate since the no. of parts are more, the inventory carrying cost is also high production cycle time is more high cost of capsule difficulties in manufacturing as various parameters are to be controlled for ensuring the required shear force of capsule capsule not replaceable The steering shaft assembly (C2) is connected to the steering wheel (SW) and steering gear (SG). The conventional steering shaft assembly (C2) comprises upper shaft (1), tube (3) and shaft (10). The tube (3) has four holes (H1,H2...) and the shaft (10) has grooves (Gl, G2). A particular plastic resin is injected in the holes of tube (3) and grooves of shaft (10) when both are aligned. This leads to formation of four plastic shear pins (PI, P2, P3, P4). At the time of collision, these shear pins break at certain load, usually 150 ~ 250 Kgf and the shaft (10) slides into tube (3) thereby protecting the driver (see Fig-3). The disadvantages of steering shaft assembly are as follows: high production cycle time. difficulties in manufacturing as various parameters are to be controlled for ensuring the required shear force. deterioration in the performance in the field due to loosening of injected plastic resulting to increase in warranty problems (Noise or rough roads). The intermediate shaft assembly (C3) consists of sub-shaft (13), lower tube (14) and universal joint (15). The lower tube (14) has four holes (H1,H2...) and the sub-shaft (13) has grooves (gl, g2). Plastic resin is injected in the holes of lower tube (14) and grooves of sub-shaft (13) when both are aligned. This leads to formation of four plastic shear pins. At the time of collision, these shear pins break at certain load, normally 200 -300 Kgf and the sub-shaft (13) slides into lower tube (14). The disadvantages of Intermediate shaft assembly are as follows: difficulties in manufacturing as various parameters are to be controlled for ensuring the required shear force. deterioration in the performance in the field due to loosening of injected plastic resulting to increase in warranty problems (Noise on rough roads). The object and summary of the invention The object of the instant invention is to obviate the above disadvantages and to provide the collapsible column at low cost, lightweight and easy to manufacture with replaceable capsule during servicing. To achieve the said objectives this invention provides an improved collapsible steering column assembly for automobiles comprising- column jacket assembly, mounted on the vehicle, steering shaft assembly being housed in said column jacket assembly for steering the vehicle, an intermediate shaft assembly, one end of which being connected to said steering shaft assembly and another to the steering gear assembly, characterized in that an energy-absorbing bracket (EA Bracket) is mounted on the outer pipe of column jacket assembly, split type capsule consisting of plastic retainer & capsule insert mounted on the upper bracket of said column jacket assembly for absorbing the impact load, shaft and tube of said steering shaft assembly and intermediate shaft assembly being provided with splines and crimped at least at one place, the arrangement being such that when the driver hits the steering wheel at the time of collision, the split-type capsule breaks and the crimping in steering shaft assembly and the intermediate shaft assembly breaks simultaneously and thereafter said EA bracket bends and absorbs the impact energy, thereby the steering column assembly collapses when the impact is from the opposite vehicle, the crimping between the tube and the shaft after the universal joint breaks. The said energy absorbing bracket comprising of sheet metal as the base material, having at least two slots for mounting on the vehicle and a hole for fitment of the column pipe, at least two bends are provided on the vertical surface of said bracket depending upon the diameter of said column pipe and the position of the mounting surface of said bracket. The split type capsule comprising of at least one retainer and one capsule insert having at least two shear pins, which break off when subjected to impact load ranging from 100 - 200 kgf. The said retainer and capsule insert having at least two shear pins are mad of plastic resin. The said retainer is made of nylon and said capsule insert having at least two shear pins is made of polyacetal resin. The said steering shaft assembly comprises at least one shaft and tube each having serrations the Shaft is held inside the tube, and is crimped at least at one place to create adequate resistance between shaft and tube. Brief Description of the Drawings: The invention will now be described with reference to the accompanying drawings Figures la shows the conventional steering column fitted in a passenger vehicle. Figure Ib shows the conventional collapsible steering column assembly. Figure 2 shows the conventional column jacket assembly Figure 3 shows the conventional steering shaft assembly. Figure 4 shows the conventional capsule in column jacket assembly. Figure 5 shows column jacket assembly with EA bracket, according to this invention. Figure 6 shows the working principle of energy absorbing (EA) bracket Figure 7 shows the different views of the energy-absorbing (EA) bracket. Figure 8 shows the crimping of steering shaft assembly. Figure 9 shows the column and jacket assembly with retainer and capsule insert, according to this invention Figure 10 shows exploded view of retainer and capsule insert in column jacket assembly. Figure 11 shows the different views of retainer and capsule insert. Figure 12 shows the improved collapsible steering column, according to this invention. Detailed Description Figure la & 1 b, figure 2, 3 & 4 have been described under the heading 'background' along with their disadvantages. Figure 5 shows the column jacket assembly according to this invention. It may be seen that an energy-absorbing (EA) bracket (la) is mounted on the column pipe (2a) along with the upper bracket (7), which eliminates the use of steel balls, ball retainer and lower pipe which was used in the conventional column jacket assembly. The working principle of EA bracket is shown in figure 6. In this figure, how the EA bracket bends and absorbs the impact load before the impact and after the impact is shown. This bracket eliminates the use of ball retainer, steel balls, and additional pipe, making the product economical. In figure 7, different views of the bracket are shown. The EA bracket (la) consists of two slots SI, S2, top surface (Ts) and hole (H). The unique features of the bracket are bends Bl, B2 and hole (H). The column pipe (2a) fits in hole (H) and the bends (Bl & B2) helps in absorbing the impact energy. Figure 8 shows the energy absorption in steering shaft assembly (C2), which does not use conventional plastic injection molded shear pins for energy absorption. In the instant invention shaft (3a) and tube (4a) of steering shaft assembly both having matching external and internal splines respectively. The desired collapse load is achieved by crimping the tube (4a) at predetermined place(s) using a special jig and then pressing the shaft (3a) inside the tube (4a) at a predetermined distance. This crimping of the tube is easy to manufacture at low cost and has better process capability. hi figure 9, two-piece plastic capsule using a retainer and capsule insert is shown, according to this invention in place of conventional aluminum capsule. Retainer (5 a) is the base part made of high strength plastic material, which provides necessary mounting support to the steering column. The retainer has holes to house the shear pins formed in the capsule insert (6a). Capsule insert (6a) is the part having minimum two shear pins (p1, p2) made of plastic resin. The shear pins break off during impact. In figure 10, two pairs of Retainer and Capsule inserts have been used. The retainer comes at the bottom of the bracket (la). On the top of the bracket there comes the capsule insert (6a). The shear pins of the capsule insert (6a) are pressed in to the holes of retainer (5a) passing through the holes provided in the bracket (la). When there is an impact on the steering column from steering wheel side, the shear pins (pi, p2) break off. In figure 11, retainer (5 a) and capsule insert (6a) are shown in top view, front view and perspective view. This constitutes a new capsule according to this invention. Figure 12 shows an improved collapsible steering column assembly, according to this invention. (SW) shows the steering wheel, (3a) shows the shaft, (2a) is the column pipe fitted in (7a) having capsule consisting of retainer (5a) and capsule insert (6a). The said column pipe (2a) is then fitted in EA bracket (la) having slots SI & S2 and top surface (Ts) through the hole (H). The shaft (3a) and tube (4a) are crimped together inside the pipe column (2a). The said tube (4a) is connected to the universal joint (11). On the other side of this universal joint (11), sub-shaft (13a) is provided, which goes inside tube (14a) and is crimped. At the end of the tube (14a), a universal joint (15) is connected. The parts before the universal joint (11) functions when the driver falls on the steering wheel during collision and the parts after the universal joint (11) functions when the other vehicle hits the vehicle in front. When the driver falls on the steering wheel (SW), the crimping between (3a) and (4a) and the shear pins of capsule insert (6a) breaks simultaneously. Thereafter, the EA bracket (la) bends to absorb the impact energy. If there is an impact from the opposite vehicle, the crimping between the tube (14a) and the shaft (13a) breaks. Advantages of the instant invention: Low cost Ease of manufacturing Lightweight Ease of assembling New Capsules are possible to be replaced in servicing We claim: 1. An improved collapsible steering column assembly for automobiles comprising- column jacket assembly, mounted on the vehicle, steering shaft assembly being housed in said column jacket assembly for steering the vehicle, an intermediate shaft assembly, one end of which being connected to said steering shaft assembly and another to the steering gear assembly, characterized in that an energy-absorbing bracket (EA Bracket) is mounted on the outer pipe of column jacket assembly, split type capsule consisting of plastic retainer & capsule insert mounted on the upper bracket of said column jacket assembly for absorbing the impact load, shaft and tube of said steering shaft assembly and intermediate shaft assembly being provided with splines and crimped at least at one place, the arrangement being such that when the driver hits the steering wheel at the time of collision, the split-type capsule breaks and the crimping in steering shaft assembly and the intermediate shaft assembly breaks simultaneously and thereafter said EA bracket bends and absorbs the impact energy, thereby the steering column assembly collapses when the impact is from the opposite vehicle, the crimping between the tube and the shaft after the universal joint breaks. 2. An improved collapsible steering column assembly as claimed in claim 1, wherein said energy absorbing bracket comprising of sheet metal as the base material, having at least two slots for mounting on the vehicle and a hole for fitment of the column pipe, at least two bends are provided on the vertical surface of said bracket depending upon the diameter of said column pipe and the position of the mounting surface of said bracket. 3. An improved collapsible steering column assembly as claimed in claim 1, wherein split type capsule comprising of at least one retainer and one capsule insert having at least two shear pins which break off when subjected to impact load ranging from 100 - 200 kgf. 4. An improved collapsible steering column assembly as claimed in claim 3, wherein said retainer and capsule insert having at least two shear pins are mad of plastic resin. 5. An improved collapsible steering column assembly as claimed in claim 3, wherein said retainer is made of nylon and said capsule insert having at least two shear pins is made of polyacetal resin. 6. An improved collapsible steering column assembly as claimed in claim 1, wherein said steering shaft assembly comprises at least one shaft and tube each having serrations the Shaft is held inside the tube, and is crimped at least at one place to create adequate resistance between shaft and tube. 7. An improved collapsible steering column assembly for automobiles substantially as herein described with reference to figures 5 to 12 of the accompanying drawings.

Documents:

1013-del-2002-abstract.pdf

1013-del-2002-claims.pdf

1013-del-2002-correspondence-others.pdf

1013-del-2002-correspondence-po.pdf

1013-del-2002-description (complete).pdf

1013-del-2002-drawings.pdf

1013-del-2002-form-1.pdf

1013-del-2002-form-19.pdf

1013-del-2002-form-2.pdf

1013-del-2002-form-3.pdf

1013-del-2002-gpa.pdf

1013-del-2002-pa.pdf