Tension Limiting Ratchet Mechanism

Abstract

The present disclosure provides a new method and apparatus for a ratchet tensioning mechanism. The apparatus uses a spring release mechanism to limit the torque applied via the tensioning device to a predetermined level. In an alternative configuration the limit of the tension could be adjusted by the user.

Claims

1. In a strap ratchet mechanism having a handle that winds a strap around a transverse spool connected to a ratchet wheel having a plurality of anti-reverse pawls, the improvement comprising: a handle having a first portion and a releasably engaged second portion that will disengage upon reaching a preselected tension level in said strap, whereby the handle comprises: a. an inner handle portion mounted so it pivots around a transversely mounted ratchet wheel and engages a ratchet pawl release, said inner handle portion further comprising (i) a transversely mounted pivot pin at a distal position from the ratchet wheel and (ii) at least one spring-biased plunger oriented parallel to said pivot pin, each plunger having a terminal detent; b. an outer handle portion that pivots about said pivot pin that is incorporated into the inner portion and that spans across the inner handle portion at said pivot pin, wherein said outer handle portion includes first and second side plates on either side of said pivot pin and a transverse operator handle spanning a distance between the side plates opposite said pivot pin, wherein each said side plate has a hole that aligns with a detent of a spring plunger when said outer handle portion is in a locked position relative to said inner handle portion, wherein at least one detent from the inner handle portion disengages from its corresponding hole on said outer handle portion upon reaching a preset torque applied to said outer handle portion that is related to a preselected strap tension.

2. A ratchet mechanism according to claim 1 wherein said handle comprises two spring-biased plungers that share a common spring inside the plunger.

3. A ratchet mechanism according to claim 1 wherein said handle comprises two spring-biased plungers, each having a spring inside each plunger.

4. A ratchet mechanism according to claim 1 wherein the biasing force on each detent is adjustable in biasing force.

5. A ratchet mechanism according to claim 1 wherein the biasing force on each detent is not adjustable in biasing force.

6. A support seat retention kit comprising a juvenile support seat, a length of strap, and the ratchet mechanism of claim 1.

7. A process for securing a juvenile support seat in a motor vehicle with a tension-limiting ratchet having (i) a length of strap extending from a fixed strap end and (ii) a free strap end allowing access to a winding spool driven by a handle, the process comprising: a. attaching a terminal end of said fixed end strap to a first connection point in a vehicle; b. connecting a terminal end of a connection strap to a second connection point in said vehicle and feeding said connection strap into said winding spool; c. winding said connection strap onto said winding spool by repeatedly advancing and withdrawing the handle to selectively rotate said spool by engaging and disengaging pawls driving said winding spool; d. winding the connection strap onto said spool until the tension-limiting handle of said ratchet disengages upon reaching a preselected tension level in said connection strap.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0020] FIG. 1 shows a cross section view of a ratchet and adjustable tension handle according to the invention.

[0021] FIG. 2 illustrates a tension-limiting ratchet from the ratchet free end view.

[0022] FIG. 3 illustrates a tension-limiting ratchet from the top view.

[0023] FIG. 4 depicts the assembly when installed in a vehicle to restrain a car seat between adjacent anchor positions in a vehicle.

[0024] FIG. 5 is a press-fit, spring-biased plunger of a fixed biasing force and terminal detent.

[0025] FIG. 6 shows an adjustable, spring-biased plunger and terminal detent.

[0026] FIG. 7 illustrates a different type of adjustable, spring-biased plunger and terminal detent.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The tension-limiting ratchet described herein is created by dividing a conventional ratchet tensioning handle into two sections that are pivotably connected with a spring-biased, adjustable, release detent. The adjustable release is threaded to move from a first handle section towards or away from a recess in the second handle section. The position of the release detent thus controls the amount of force allowed when tightening the ratchet while winding a strap onto the rotated reel. When properly set, the release detent prevents too much or too little tension to be applied to the strap that holds in the car seat and thereby produces a more consistent and reliable installation.

[0028] The first section of the ratchet is the lower part of the handle that is positioned inside an upper part of the handle. This lower, inner handle portion carries the pawl mechanism that interacts with notches associated with the spool to wind strapping onto the central spool about a winding axis. This section operates like a conventional ratchet.

[0029] The second section is attached to the first section in a manner that allows the second section to pivot about a pivot located near the end of the first section. A spring release mechanism is used to tie the motion of the two sections together until a predetermined amount of force (torque) is applied to the second section of the handle.

[0030] A preferred embodiment of the spring release mechanism has two plungers located within the lower, first section of the handle and extends between left and right plates on the upper, second handle section. It will be understood that a single, double-ended detent can replace the use of two, single detent plungers. Each plunger has one spring-biased, rounded end that presses outwardly towards the side plates on the upper, outer, second section of the handle.

[0031] The second section of the handle is positioned outside of the lower, inner handle portion and contains holes that line up with the plungers when the first and second sections are in an operating position to wind up a strap on a reel in the lower, first section. The plungers are forced outward against the outer plates of the upper second section of the handle by springs within plungers. The amount of force applied by the springs to the plungers can be either fixed or adjustable.

[0032] If desired, the openings that engage the spring-biased detents may be reinforced to resist wear or premature failure. For example, a hardened steel insert on the inside of the handle side plates may be used around the recess openings. Alternatively, some portion or all of the disengageable handle might be heat treated to a hardness at least as high as that of the detent and thereby help to resist wear from repeated use.

[0033] Those skilled in this art will appreciate that the relative positions of the upper and lower handle sections may be reversed such that the lower handle portion has recesses for the detents and is positioned outside the upper handle portion that carries the spring-biased plunger.

[0034] One method of adjusting the spring force within the detent would be to use a jack-screw type of mechanism pushing on the rear of the springs. A second method would be a self-contained spring plunger that threads into a tube with a female thread. The detent would then be advanced or retracted using the external threads to adjust the spring force by its proximity to the associated recess or hole in the second section.

[0035] The plungers used in the present invention can be externally threaded or press fit. The use of external threads allows for adjustment, while the press fit plunger provides a manufacturer with the ability to set the desired break release torque.

[0036] Tabs on the second, outside section of the handle limit the amount that the section can rotate once it has been released by the spring mechanism. Once these tabs reach the first, inner section of the handle the ratchet can be rotated enough to release the retaining, or counter-rotation mechanism.

[0037] As shown in the figures, the child seat retention system is created by attaching two standard child seat clips 19 to the fixed and free ends 1, 2 of the tension limiting ratchet strap assembly 3. The ratchet portion 4 is operated to wind excess strap 5 onto the spool 6 until sufficient tension has been applied that the tension force exceeds the retaining forces of the spring-biased plunger detents 7 releasably associated with the upper portion 81 of ratchet handle 8. When that tension is exceeded, the plunger detents 7 will slip free from the recesses 9 in the outer handle plates 10 and prevent the application of additional force on the strap 5.

[0038] FIGS. 3 and 5-7 show additional details of the spring-biased plunger assembly 11. As shown in FIGS. 3, 6, and 7 assembly 11 can exhibit external threads 12 in plunger body 13. Alternatively, press-fit plunger 16 can be inserted into either end of a plunger assembly and used with fixed spring 17 of a specified bias force. Such an embodiment would not be adjustable and would allow the manufacturer to specify the minimum amount of torque needed for securing a car seat 18 to structural seat engaging points 19 within a vehicle.

[0039] Internal springs 14 press against fixed stops 15 or adjustable stop 16 and urge detents 7 outwardly into engagement with recesses 9 in the left and right lateral plates 10 of handle 8. At an adjustable level of shear based on the bias force of springs 14, 17 detents 7 slip out of recesses 9 and allow handle portion 81 to rotate without further turning spool 6. The precise level of this breakaway shear depends on the compressive strength of springs 14, 17.

[0040] The present invention is particularly useful for securing a child's car seat 18 in a vehicle with a specified amount of tension on the restraining straps. As shown in FIG. 4, the strap free end 2 is threaded from the right side of seat 18 through opening 20 and secured on the opposite side to the seat belt connection or suitable structural attachment point (not shown). The strap fixed end is secured to a seat belt connector or standard seat clip 19 that is secured to a suitable structural attachment point (not shown) behind the seat cushion. Upper ratchet handle portion 81 moves with lower ratchet handle portion 82 through the engagement of detents 7 with recesses 9 in lateral plates 10 as the strap is wound onto spool 6. When the amount of torque applied to upper handle portion 81 exceeds the biasing force against the lateral plates of the upper handle portion, the detents slip from the recesses and release the upper handle portion from engagement with the lower handle portion. By this mechanism, a consistent level of torque can be assured if the installer consistently tightens the ratchet to its breakaway tension.