GB2192124A

GB2192124A - Safety belt retractor with belt retightener

Info

Publication number: GB2192124A
Application number: GB08712204A
Authority: GB
Inventors: Artur Fohl
Original assignee: TRW Occupant Restraint Systems GmbH
Current assignee: TRW Occupant Restraint Systems GmbH
Priority date: 1986-07-03
Filing date: 1987-05-22
Publication date: 1988-01-06
Also published as: IT1228250B; ES2006195A6; AU579521B2; SE8702675D0; FR2600955A1; GB8712204D0; JPS6325156A; DE3622411A1; SE8702675L; AU7520587A; BR8703334A; IT8721146A0

Abstract

A safety belt retractor includes a coupling means for drivingly coupling the belt reel with a pulling cable (14) one end of which is connected to the piston (16) of a piston/cylinder drive means (18) and an intermediate section (14A) of which is wrapped round the outer periphery of a roller (10) connected for joint rotation to the belt reel of the retractor. The free end of the pulling cable is led through a restraining means (22). To ensure that, after completion of a belt tightening operation,the roller (10) is rotatable without inhibition by the pulling cable (14), the working stroke of the piston/cylinder drive means (18) and the length of the pulling cable (14) are adapted to each other in such a manner that, after execution of the working stroke, the free end of the pulling cable has passed completely through the restraining means (22). <IMAGE>

Description

SPECIFICATION Safety belt retractor with belt retightener The invention relates to an improved safety belt re tractor provided with a belt retightener.

The belt retig htener of known retractors includes an elasticallyflexible pulling cable or rope which is wrapped several times with radial clearance round a pulley or roller connected to the reel of the retractor.

One end of the cable is connected to the piston of a piston/cylinder drive means. The other, free end of the cable is led through a restraining means restrain ing the movement ofthe cable. In the inoperative state ofthe retightenerthe cable is maintained as spaced from the roller or pulley by its own rigidity in the region ofthewrap portion in a housing surround ing the roller.

When in an emergency to execute a tightening operation the drive means is activated the wrap portion ofthe pulling cable is contracted and coupled by wrap friction to the roller. The tension exerted bythe piston ofthe piston/cylinder drive means on the cable effects a rotation ofthe roller and the reel connected non-rotatablythereto in the direction of rotation necessary for belttightening to remove any slack in the belt system. At the end of a working stroke of the piston/cylinder drive means the frictional engagement between the wrap portion ofthe cable and the roller is maintained due to continued tensioning ofthecablesothatthe rotation ofthis roller and consequently of the takeup shaft is blocked.

The present invention provides a safety belt retractorwherein after execution of a belt tightening operation the pulley or roller, and consequently the reel of the safety belt retractor, is free to rotate without inhibition by the cable.

According to the present invention, this is achieved bytheworking strokeofthe drive means and the length of the pulling means being adapted to each other in such a manner that after execution of the working stroke of the drive means the free end of the pulling means has passed completelythrough the restraining means. When the pulling means has been pulled completely through the restraining means firstly its longitudinal tension is eliminated and thus also the frictional engagement of the wrap portion with the outer surface of the pulley because the pulling means due to its inherent stiffness springs backagainstthe innerwall of the housing surrounding the pulley. The rotation ofthe pulley is then no longer hindered by the pulling means.This givesthe advantage that after completion of a tightening operation the locking ofthe safety belt retractor can easily be disabled by rotating the reel a few angular degrees sufficient to disengage the pawl of the emergency locking mechanism associated with the reel of the retractor. This makes it easiertofree the vehicle occupant secured by the safety belt from the tensioned belt.

The invention utilizestheknowledgethattwofactors are responsible for the blocking ofthe pulley remaining after execution of a tightening operation.

Firstly, after execution of the working stroke of the piston and cylinder drive meansthe piston is usually firmly held in the cylinder and secondly the free end of the pulling means is held towards the end ofthe working stroke also by the restraining means so that the tension of the pulling means is maintained.Since the piston of the piston and cylinder drive means for better utilization of the drive power available is re ceivedwith narrow fit in the cylinder and moreover expediently the end of the cylinder corresponding to the working stroke end is tapered to stop the piston and thus prevent the latter flying out of the cylinder, and consequently a jamming ofthe piston in the cylinder on completion of a tightening operation is hardly to be avoided, the invention proposes making the length of the pulling means adequately short so that at least after execution of a complete working stroke the free end of the pulling means has passed through the restraining means.

Similar conditions are encountered if instead of a piston/cylinder drive means an inertial mass is used which is displaceable relatively to the vehicle frame and to which the pulling means is connected. Said mass cannot as a rule be moved back after execution ofthetightening operation. The invention can also be applied when using drive sources ofthis type or similar drive sources.

Further advantages, features and further developments ofthe invention will be apparent from the subsidiary claims, the following description and the drawings, to which reference is made and wherein: Figure lisa schematic sectional view of a piston/ cylinder drive means and a coupling meansforthe belt reel of a safety belt retractorwith a belt retightener in the inoperative condition; Figure la is a particular embodiment of a restraining means also in inoperative position of the belt retightener; Figure2 is a sectional view analogous to Figure 1 but in the condition after execution of a retightening operation; and Figure 2a shows the restraining means according to Figure 1 a also after execution of a retightening operation.

In Figures 1 and 2 for simplicity of a safety belt retractor all that is shown is a pulley or roller 10 which forms a lateral extension of the takeup shaft of the safety belttakeup means on which the webbing is coiled. With regard to details ofthe construction of the safety belttakeup retractor and the coupling meansforthe belttakeup reel thereof, reference is made to German published patentapplication 3,328,874 incorporated by reference. The roller 10 is surrounded by a cage-like housing member 12. The outer surface of the roller 10its encircled by a pulling cable 1 4whose wrap portion is designated by 1 4A.

The elastically flexible pulling cable 14 encircles in several convolutions the roller 10. The radial spacing between the outer surface of the roller 10 and the inner surface ofthe housing member 12 is appreci ably greaterthan the diameterofthe pulling cable 14.

The one end ofthe pulling cable 14 is connected to the piston 16 of a piston/cylinder drive means. The piston 16 is received with close fit in the cylinder 20 ofthe piston/cylinderdrive means 18. Not illustrated in the drawings for simplification is a power source for acting on the piston 16 within the cylinder 18. This energy source is conveniently a pyrotechnical gas generator of conventional type. At its end remote from the piston 16 in Figure 1, corresponding to the end of the working stroke of the piston/cylinder drive means 18, the cylinder 20 has a tapered portion 20A.

On the side of the wrap portion 1 4A opposite the piston/cylinderdrive means 18 the pulling cable 14 has a free end and is led through a restraining means 22 which is formed by three closely spaced guide pins 22A, 22B and 22C. Between said guide pins 22A, 22B and 22Cthe pulling cable 14is led, being elastically deformed. Another embodiment of the restraining means 22 is shown in Figure la. It consists of a chicane-like guide.

In the initial state shown in Figure 1 the wrap portion 14Aofthe pulling cable 14 loosely engagesthe outer surface of the roller 10. If a tightening operation is now activated the piston 16 in the cylinder 18 is driven forwards so that is exerts a tension on the pulling cable 14 and asa resultthewrap portion 14A is tightened on the surface of the roller 10 because the free end ofthe pulling cable 14 is restrained by the restraining means 22.By the frictional engagement now established between the wrap portion 1 4A ofthe pulling cable 14 and the outer surface ofthe roller 10 the drive coupling is established between the piston 16 and the roller 10 so thatthe linear movement of the piston 16 causes a rotational movement of the roller 10 which is transmitted to the belt reel fortightening the safety belt.

Now, shortly before the piston 16 has reached the end ofitsworking strokethefree end of the pulling cable 14 has already been pulled completely through between the guide pins 22A, 22B, 22C. Since no braking action is now exerted on the free end of the pulling cable the latter detaches itself from the per iphery of the roller 10 and jumps elastically back against the innerwall ofthe housing member 12.

This condition is shown in Figure 2. The roller 10 can now be rotated without inhibition by the pulling cable 14. The tapered portion 20A stops thefurther movement ofthe piston 16 6 in the cylinder 18 so that the piston 16 cannotfly out ofthe cylinder 18.

Figure 2a shows the restraining means according to Figure 1 a in the same state as in Figure 2, i.e. after completion ofthetightening operation.

Claims

1. Asafety beltretractorfor motor vehicles, having a takeup reel forthe belt webbing and a belt retightener comprising a pulley connected to said takeup reel forjoint rotation and an elasticallyflexible pulling means which is wrapped with radial clearance several times round said pulley and has one end connected to a linear drive means having a working stroke, and another, free end led through a restraining means restraining its movement, the pulling means in the inoperative state ofthe retightener being accommodated in a housing surrounding the pulley activation of the linear drive means causing the pulling means to be contracted and drivingly coupled to the pulley by friction, the working stroke ofthe drive means and the length of the pulling means being adapted to each other in such a manner that after execution of the working stroke ofthe drive means the free end of the pulling means has passed completelythrough the restraining means.

2. Theretractorofclaim 1, wherein the length of the pulling means is dimensioned such that before completion oftheworking stroke of the drive means the free end of the pulling means has passed com pletelythroughthe restraining means.

3. The retractor of claim 1, wherein the restraining means include guiding means by which the pulling means is elastically deformed.

4. The retractor of claim 1, wherein the linear drive means is a piston/cylinder drive to the piston of which said one end of the pulling means is connected.

5. The retractor of claim 4, wherein the cylinder of the piston/cylinder drive means has an end corresponding to the end of the working stroke and which is tapered for stopping the piston at the end of its working stroke.

6. The retractor of claim 1, wherein the linear drive means comprises an inertial mass which is displaceable relatively to the body of the motorvehicle and to which the pulling means is connected.

7. A safety belt retractor substantially as herein described with reference to Figures 1 and 2, or Figures 1 and 2 as modified by Figures 1 a and 2a, ofthe accompanying drawings.