CA2549121A1 - Mechanism for infinite linear adjustment based on self-wedging principle - Google Patents

Abstract

Mechanism for infinite linear adjustment based on self-wedging principle. The internal wedging forces of that mechanism are used as counteraction forces that increase proportionally to the active external force trying to change the position of the mechanism. This mechanism has infinite linear adjustment and can hold active forces at any position of adjustment stroke.
This mechanism has a very high load characteristic, and will stay functional even when the active forces have exceeded permissible loads. Features of this mechanism allow creating, on the basis of the mechanism, very simple, durable, and reliable mechanisms for manual adjustment of a car seat.

Description

DESCRIPTION OF THE INVENTION
Mechanism For Infinite Linear Adjustment based on Self-Wedging Principle.
FIELD OF THE INVENTION
The mechanism for infinite linear adjustment based on self-wedging principle can be used in many different areas. Features of this mechanism: quality, simplicity, durability and reliability make this mechanism unique for using in automotive industry, mainly for mechanism of manual car seat adjustment.
The self-wedging mechanism for infinite linear adjustment based on the simple design (Fig.5.1) can be successfully used for creating mechanism to manually adjust back of the car seat - recliners.
The new mechanism has a much higher loading characteristic in comparison with existing recliners on the market. It will stay functional even when the active forces have exceeded the permissible load: - during an accident the active external forces can drastically exceed permissible load.
Recliners based on the new self-wedging mechanism for infinite linear adjustment will be much safer and simultaneously with new features, the new mechanism will be less expensive in production.
Heavy-duty self-wedging mechanism for infinite linear adjustment (Fig. 8.1) can be successfully used for creating a mechanism for manual linear adjustment of the car seat -slide unit. Features of this new mechanism: infinite adjustment, very high load characteristic, simplicity, durability and reliability allow to increase safety and performance of the new mechanism for manual adjustment of the car seat.

This invention is based on the following principles:
1. Mechanism for infinite linear adjustment based on self-wedging principle -using internal self-wedging forces as a counteraction force to keep position of mechanism steady under the influence of external active forces.

2. Self-wedging mechanism for infinite linear adjustment based on the principle where wedging forces increase proportionally to the active external forces trying to change position of the mechanism.

3. Self-wedging mechanism for infinite linear adjustment, which allows holding external active forces in both directions along guiding bar.

4. Self-wedging mechanism for infinite linear adjustment of the car seat that will stay functional even when the active forces have exceeded the permissible load: - during an accident the active external force can drastically exceed permissible load.

5. Heavy-duty Self-wedging mechanism for infinite linear adjustment based on self-wedging principle, however, it does not have sharp edge contact stress because of the use of special self-alignment elements.

6. Mechanism for infinite linear adjustment of the car seat, recliners or slide units, which is based on self-wedging principle and does not request any kind of alignment between left and right parts of mechanism working in the car seat.

Today on automotive market, a few different kinds of mechanisms for car seat adjustment are presented. Some of these mechanisms are used as recliners, allowing changing position of the car seat's back (Fig. 1.1; 2.1). Other mechanisms are used for linear adjustment of the car seat position -sliding unit (Fig. 6.1). Some of the cars have power seats, while other cars have seats with manual adjustment. On present market, more than 90% of the cars have manual mechanism for seat adjustment.
The mechanism of power seat adjusting usually consists of a special screw and a nut with an electrical actuator, or they consist of an electrical actuator with worm gear, rack and gear drive. The same ideas could not be successfully used to build mechanism for manual adjustment, because to adjust from one extreme position to another, the screw (or worm gear) has to make a lot of rotations.
Practically it is not possible to make so many rotations manually in a short period of time.

Mechanisms for manual adjustment can be divided into two major categories:
mechanisms with increment adjustment and mechanisms with infinite adjustment.
Mechanism with increment adjustment of the back of the car seat (recliner) is shown in Fig. 1.1.
Mechanism for adjusting the car seat in longitudinal direction (forward and back - slide unit) is shown in Fig 6.1. Mechanism with increment adjustment allows changing position of the seat stepwise. The modem mechanism with increment adjustment has the step of adjustment not less than 3 mm for the seat recliner, and not less than 10 mm for sliding unit.
This is the first disadvantage of such mechanisms. The seat cannot be held in position between steps of adjustment.
The mechanism of car seat recliners consists of two identical mechanisms on both sides of the seat.
The mechanism of car seat slide units also consists of two identical mechanisms that differ from the mechanisms of the recliner.

To provide proper positioning of these mechanisms, both sides of the mechanisms have to work identically. A fine alignment between these mechanisms on both sides of the car seat is requested.
Nevertheless, you can always sense different clicks from left and right adjustment mechanisms on one seat when they are locking. This means that these mechanisms load differently and have different rigidity in a working position. This is the second disadvantage of such mechanisms.
Sometimes difference of alignment can be so big, that only one side of the seat is locked properly. In that case this locked mechanism has to hold twice as many forces than if both mechanisms are locked correctly. This causes the mechanism to overload. In case of an accident, this mechanism cannot sustain the active forces and can be destroyed. These kinds of mechanisms use some kind of linear rack with locking elements. If during the accident, teeth of locking elements are destroyed, the car seat starts to move in direction of the active force without any resistance. Sometimes the safety belt on the car is fastened to the top of the seat back. In case of the accident, the upper body of driver or passenger together with the back of the seat creates a very big active external force applied to recliner. If recliner cannot sustain these forces, its mechanism will be destroyed and upper body of driver or passenger together with seat belt and back of the seat will move forward. This can become a reason of serious injury.
The sliding unit of the seat has a stronger mechanism for adjustment, the rack has bigger teeth or slots, and it can sustain bigger forces. But in that case, the mechanism has to sustain much higher external forces too: total mass of the body and total mass of the seat. As time goes on, permissible loads for the mechanism will decrease because of undercut of locking teeth during working process.
Maybe after 3 - 5 years of using the car, permissible loads will be significantly low, but you will never know about it until an accident. The deterioration of the locking elements is the third disadvantage of these mechanisms.
After the accident, such mechanisms become totally destroyed and unusable. The driver or passenger(s) cannot be easily evacuated from the car because of that. This is the fourth disadvantage of such mechanism.
Another disadvantage of existing mechanism for the car seat adjustment is a bad dynamic latching. What does it mean? If the active force appears during the time when the mechanism was open for adjustment, the car seat starts to move in direction of acting force.
Even if the handle for locking was released the locking elements would be jumping from one position to another but could not lock the mechanism and movement will continue. Also the teeth of locking device can be broken very easily because of dynamic forces applying to thin parts of the teeth.

The second major group of manual mechanisms for adjustment is mechanisms with infinite adjustment (Fig 2.1). Usually such mechanisms use a force of friction as a holding locking force.
This force is "permanent" and as usual independent from the active forces.
Such mechanism does not have a high holding characteristic. Actually, the force of friction has two different values:
immovable and movable. Immovable force of friction is two times bigger than the movable force of friction. Because of that, if the active force exceeds the immovable force of friction the car seat starts to move in direction of active force with very little resistance. Even if the active force will decreases during movement, because the movable force of is friction twice less than immovable, the motion will continue. The holding characteristics of such mechanisms of adjustment are 2 - 4 times less than those of the increment adjustment mechanism. Because of that this kind of mechanism is hardly ever used for slide unit.

The presented invention: the mechanism for infinite linear adjustment based on self-wedging principle, used to create the new mechanism for manual adjustment of the car seat position does not have these disadvantages. New mechanisms have many advantages to compare with existing mechanisms. Features of the new mechanism are: infinite adjustment, high load characteristic, simplicity, durability and reliability together with very quiet working process and inexpensive in mass production.

SUMMARY OF THE INVENTION

= Mechanism for infinite linear adjustment based on self-wedging principle -using internal wedging forces as a counteraction force to keep position of mechanism steady under the influence of external active forces.
= Self-wedging mechanism for infinite linear adjustment where internal wedging forces increase proportionally to the external active forces trying to change position of the mechanism.
= Self-wedging mechanism for infinite linear adjustment that will stay functional even when the active external forces have exceeded the permissible load.
= Heavy-duty mechanism for infinite linear adjustment based on self-wedging principle and using special self-alignment elements to avoid sharp edge contact stress.

= Mechanism for infmite linear adjustment based on self-wedging principle, which allows holding active forces in both directions along guiding bar.

= The new recliner for manual adjustment of the car seat based on the simple self-wedging mechanism for infinite linear adjustment.

= The new mechanism for manual linear adjustment of the car seat (slide unit) based on heavy-duty self-wedging mechanism for infinite linear adjustment.

= Mechanism for infinite linear adjustment of the car seat, recliners or slide units, which is based on self-wedging principle and does not require any kind of alignment between left and right parts of mechanism working in the car seat = Self-wedging mechanism for infinite linear adjustment that will sustain secondary impact = Self-wedging mechanism for infinite linear adjustment having a good dynamic latching LIST OF FIGURES, WHICH ARE FORMING A PART OF THIS SPECIFICATION
Fig. 1.1 - Existing mechanisms of car seat recliner with increment adjustment Fig. 1.2 - Linear rack of existing recliner with increment adjustment Fig. 1.3 - Locking elements of existing recliner with increment adjustment Fig. 2.1 - Existing mechanisms of car seat recliner with infinite adjustment Fig. 3.1 a - Self-wedging Principle inside the mechanism for infinite linear adjustment Fig. 3.2b - Self-wedging Principle inside the mechanism for infinite linear adjustment Fig. 3.2 - Two directional mechanism for infinite linear adjustment based on Self-wedging principle Fig. 4.1 - Prototype of new recliner for car seat based on simple self-wedging mechanism for infinite linear adjustment Fig. 4.2a - Guiding bar after the active forces had exceeded the permissible load Fig. 4.2b - Guiding bar after the active forces had exceeded the permissible load Fig. 5.1 - The new car seat recliner based on self-wedging mechanism for infinite linear adjustment Fig. 5.2 - The new car seat recliner (cover is removed) Fig. 5.3 - Set of details to assembly the new car seat recliner Fig. 6.1 - Existing mechanisms for manual linear adjustment of the car seat (slide unit) Fig. 6.2 - Existing slide unit - locked position Fig. 6.1 - Existing slide unit - opened position Fig. 7.1 - Principle of one-way heavy-duty self-wedging mechanism for infinite linear adjustment Fig. 7.2 - Two directional mechanism for infinite linear adjustment based on heavy-duty self-wedging principle Fig. 7.3 - Prototype of heavy-duty self-wedging mechanism for infinite linear adjustment Fig.8.1 - Scale view on self-alignment elements in wedged arms DETAILED DESCRIPTION OF THE INVENTION
NATURE OF THE INVENTION

This Invention entitled: Mechanism for Infinite Linear Adjustment based on self-wedging principle.

The first main principle of the invention is to use internal wedging forces as a counteraction force to keep position of mechanism steady under the influence of active external forces.
Explanation of a working principle is shown in the Fig. 3.1 and Fig. 3.2.
Guide bar [1] could move through guiding holes in a body [2] and wedged-hole in the arm [3]. The arm [3] has support point in the body [2] with offset from axes of guiding bar on a distance L. The spring [4] creates an internal preload force for the system. The spring [4] pushes arm [3] in such way that arm pivots around supporting point of the body [2], until two opposite points of arm's wedged-hole become in contact with guiding bar [1]. This position is a position of preloaded condition. When the active external force Fa is pushing the guiding bar [1] in the same direction as spring [4], the arm [3] is trying to move together with the guiding bar [1] because the arm [3] is seated on guiding bar [1] and in contact points between them, the friction force Ffr is presented. This causes the appearance of acting and counteracting forces between the arm [3] and body [2] - Fa,,,, and FSõP, and reaction R in contacting points between the arm [3] and guiding bar [1]. Resulting of reaction R is appearance of additional large force of friction Ffr.
The second main principle of invention is that counteraction wedging forces increase proportionally to the external active forces trying to change position of the mechanism. This means that the higher the external active force Fa, the higher the reactions R in contacting points between the arm [3] and guiding bar [1], and hence the higher the friction forces Ffr.
The system will stay immovable and steady if sum of projections of all active and counteractive forces on any direction will be equal to zero. The sum of all the momentums of forces has to be equal to zero as well.

= Fa - external active force trying to change position of guide bar [1]
= Fsõp & Fam - opposite forces (active and counteractive) between supporting point of the body [2] and arm [3]

= R - forces of reaction in contact spots between arm [3] and guiding bar [1]

= Ff, - forces of friction that appear because of force of reaction R and forces of friction always acting against the external active force Fa, which is trying to change position of mechanism.

The equations for static condition of the mechanism is:
= EF = 0, - the sum of all forces applied to any part of mechanism equals zero = EM = 0, - the sum of all momentum of forces applied to any part of mechanism equals zero Forces applied to the arm [3] are forces FSõp and forces of reactions R. The sum of momentum of forces relatively to the center of wedged-hole will be:

=FSõp=L-2R=e=0.
=R=FSõp=L/2e=Fsõp=L/h (1) The sum of all forces applied to the bar [2], in projection to its axes equals zero = Fa - 2Ffr = 0 = Fa = 2 Fft (2) The force of friction equals value of normal reaction R multiplied by coefficient of friction = Ffr = k- R (where "k" is coefficient of friction) (3) = Fa = Fsup active force has to be equal to supporting force (4) = Fsup = 2 Ff, (5) Solving equations (1); (2); (3); (4) and (5) we will get condition of immobility =h=2k=L (6) Equalizing: Formula (6) is the condition of immobility of the guide bar under any active forces applied to it in direction of wedging. To provide this condition, the system has to be designed using proper geometrical ratios for a certain coefficient of friction. Formula (6) can be transformed into h<2kL(L>h/2k) Usually for dry condition, the coefficient of friction for two parts from steel has to be counted around 0.2. Because we cannot be absolutely sure about dry condition of friction, for practical calculation it is better to use coefficient of friction "k" between values 0.1 - 0.12 for parts from steel. That means: - if the distance "h" is less than 0.2 = L - the mechanism always will have self-wedging condition and will stay immovable against external active force.
To open this mechanism and allow guide bar to move through the body, to adjust position, the arm [3] has to be pushed against spring for preloading [4] and straightened.
In that case clearance appears between surface of guiding bar [1] and hole inside the arm [3], and the guiding bar could move free without any resistance.

The third main principle of invention is the possibility to hold active forces equally in both directions along guiding bar. Two directional mechanism for infinite linear adjustment based on self-wedging principle is shown in Fig. 3.3. This is simply a double mechanism, symmetrically acting to opposite direction. When arms [3L] and [3R] straightening and clearance between wedged-holes of arm and guiding bar are present - the guiding bar can move through the body without resistance. When arms [3L] and [3R] are released (working position) the guiding bar is wedged and could not change its position under the external acting force from both directions. In one direction, the active force will be held by arm [3L], in another direction the force will be held by arm [3R].
The prototype of two directional Self-Wedging Mechanism for Infinite Linear Adjustment is shown in Fig. 4.1. This mechanism is very simple and very reliable. In comparison with existing recliner with increment adjustment shown in the Fig.1.1, this self-wedging mechanism for infinite linear adjustment, with the same dimension as existing mechanism with increment adjustment, could hold two times more active forces.

The fourth main principle of invention is that mechanism can stay operable (to a certain degree) even when the active forces have exceeded the permissible load and mechanism was damaged. This quality is especially important in automotive industry, when this mechanism would be used as mechanism for adjustment of the car seat. During an accident, the external active forces can drastically exceed permissible load. It is very important that even after being damaged during an accident, the mechanism for car seat adjustment can remain operable.
Comparing the invention with existing slide-unit with increment adjustment where some kind of linear rack with locking elements is used. If during an accident, teeth of locking elements are destroyed, the car seat starts to move in direction of active inertia force without any resistance. The presented invention does not have locking teeth in locking mechanism that could be broken. The counteracting force is a force of friction, which appears as result of reactions R in contacting points between the arm [3] and guiding bar [1]. The higher the active force Fa, the higher reactions R and hence the higher the friction forces Ffr. When the active force will exceed permissible loads, the contact forces inside mechanism will exceed legitimate value. In that case nothing will be destroyed.
The material of guiding bar and wedged arms starts to deform and contact surface starts to increase, hence contact stress will decrease. If value of active force overloads the permissible load by 1.5 - 2 times, the guiding bar will get scratches as shown in Fig. 4.2a. When active force will overload permissible force by 2 - 4 times the guiding bar will get bite from reaction forces R shown in Fig.
4.2b. However, the new mechanism will stay functional and will sustain the active force. This is a very big advantage of the new mechanism. It makes the safety of this system much higher.
Very important feature of the new mechanism used for adjustment of the car seat is possibility to sustain secondary impact. For example: two cars are staying at a red light one after another. A third car fails to stop and hits the second car from the back. In that case everything inside the second car gets big inertial forces in the reverse direction. The second car is pushed forward and it hits the first car staying in front of it. At this time inertial forces will be directed forward. This example shows how in a short period of time, mechanisms of the car seat adjustment could be under the influence of two significant inertial forces acting one after another in different directions. If existing mechanism of the car seat adjustment failed during the first impact, the teeth of locking device broke, it could not sustain secondary impact at all, and car seat will move in direction of second impact without any resistance. The new mechanism would not fail in the same scenario. During the first impact in one direction, one of the arms was wedged and sustains the active force. Even if the active force exceeds permissible load and guiding bar was damaged, the secondary impact in opposite direction will load another wedging arm that will work with surface of guiding bar that was not damaged during the first impact. This is a very big advantage of the new mechanism. It makes the safety of this system much higher.
One of the disadvantages of existing mechanism for the car seat adjustment is a bad dynamic latching. The new self-wedged mechanism for infinite linear adjustment has a very good characteristic of the dynamic latching because it does not have locking teeth.
The wedged force can be applied to any part of guiding bar, so dynamic latching will appear as soon as the handle for adjustment is released. This is other big advantage of the new mechanism that makes it safer.

The profile of guiding bar for such system can be different: round, square, rectangular or something else. To provide proper work of the mechanism, the hole in the arm has to correspond with profile of guiding bar. The guiding bar can have a rectangular profile, and the wedging arm can have not a hole, but just a side slot. The mechanism can work in both ways:
the guiding bar can be moved when the body is fixed in place, or guiding bar can be fixed in place and the body can be moved.
This simple mechanism for infinite linear adjustment based on self-wedging principle can be successfully used for mechanism where maximum loads will not exceed 4000 -8000 Newtons. It will be perfect for creating the new mechanism of the car seats recliners. One of possible designs of the new car seat recliner based on Self-wedging mechanism with infinite linear adjustment is shown in Figures 5.1; 5.2 and 5.3. This recliner has the similar dimension with existing mechanism, and it can hold two times more load forces than existing recliner with increment adjustment shown in Fig.
1.1, and five times more than existing mechanism with infinite adjustment shown in Fig. 2.1.

In Fig. 6.1; 6.2; 6.3 is shown mechanism for increment linear adjustment of the position of the car seat - sliding unit. This mechanism has to hold active forces much greater than recliner. This mechanism has to sustain against active inertial force of total mass of the body plus total mass of the car seat. This force can be significant. Because of that, presently, for linear adjustment of the car seat position, manual mechanism with infinite linear adjustment is not used.
One of existing mechanisms for increment linear adjustment of the car seat is shown in Fig.
6.1. To hold a great active force, teeth and rack of this mechanism are large, hence the steps of adjustment are large too, not less than 10 mm. This is the major disadvantage of such system. The car seat can be adjusted lengthwise only by increments and these increments are sufficiently big.
Another disadvantage of such mechanism is the required alignment between left and right slide of the car seat.

The new Heavy-duty mechanism for infinite linear adjustment based on self-wedging principle can hold a very large active force. This mechanism can hold active force multiple times greater than simple mechanism. The principle of heavy-duty mechanism for infinite linear adjustment based on self-wedging principle is shown in Fig. 7.1 and Fig. 7.2. The main idea of this mechanism is to avoid the high contact stress at sharp edges. This has become possible if special self-alightment elements will be used. Avoiding the high contact stress at sharp edges is the fifth main principle of invention.

The guide bar [1] passes through the body [2]. The wedged arm [3] contacts with the guiding bar, not directly, but through self-alightment elements [4]. The contact surface, in that case can be very big, and squeezing force of reaction "R" will be divided between all contact surfaces. The contact stress in that case will not be high. The spring [5] is needed only for creating preloading condition. The axis [6] is used as a base for pivoting of arm [3]. When the arm [3] is pushing against spring [5], the arm pivots around axis [6], and small clearance appears between self-alightment elements and the guiding bar [1]. In that case, guiding bar can move through body [2] practically without resistance. When the spring [5] preloads the mechanism, the clearance between elements of self-alignment [4], wedged arms [3], and guiding bar [1] is not presented.
When the active force is trying to move guiding bar [1] in wedging direction, the arm [3] is distorted and wedging forces squeeze the guiding bar [1] and it becomes locked from movement. The one-way heavy-duty mechanism for infinite linear adjustment based on self-wedging principle is shown in Fig. 7.1.
The two-way heavy-duty mechanism for infinite linear adjustrnent based on self-wedging principle is shown in Fig. 7.2. It is the same one-way mechanism but doubled symmetrically.
The prototype of two-way heavy-duty mechanism for infinite linear adjustment based on self-wedging principle is shown in Fig. 7.3. This mechanism was tested at active force of 20,000 Newtons. No signs of contact stress were found on the guiding bar 3/8"
diameter. The profile of guiding bar for heavy-duty mechanism for infinite linear adjustment based on self-wedging principle can be different as well: round, square, rectangular, and so on.
The theory of force calculation for this mechanism is identical to force calculation of simple mechanism for infinite linear adjustment based on self-wedging principle. For heavy-duty mechanism, contact surface is so big, that contact strength is not critical any more. For this kind of mechanism, the tension strength as usual is critical. The mechanism can hold an active force as big as the active force that be held by the guiding bar for stretching. That means that mechanism with a guiding bar of 12 mm diameter can hold a force of 30,000 Newtons, the same as guiding bar.
Simplicity, durability and reliability of this mechanism make it very useful for any kind of mechanism for infinite linear adjustment. This kind of mechanism can be used successfully to build sliding unit for the car seat with infinite adjustment.
One of possible designs for manual mechanism for infinite linear adjustment of the car seat -slide unit is shown in Fig. 8.1 and 8.2. Self-alignment elements have a very big contact surface with wedging arms and with surface of base profile. This mechanism will sustain very high loads and simultaneously with that it has infinite linear adjustment. The car seat with such mechanism can be locked at any position from one extreme position to another. The manual mechanism of car seat adjustment based on this design does not request alignment between left and right slide of the one car seat. Using such kind of mechanism for liner adjustment of the car seat allows to drastically improve quality of manual mechanism for linear car seat adjustment!

Claims (12)

1. Using internal self-wedging forces as a counteraction force that will sustain external active force to keep position of mechanism steady and immovable.

2. Using internal self-wedging forces, which will increase proportionally to the active forces trying to change position of the mechanism.

3. Mechanism for infinite linear adjustment based on self-wedging principle -using internal wedging forces as a counteraction force to keep position of mechanism steady under the influence of external active forces.

4. Mechanism for infinite linear adjustment based on self-wedging principle where wedging forces increase proportionally to the active forces trying to change position of the mechanism.

5. Self-wedging mechanism for infinite linear adjustment that will stay functional even after it has been damaged due to the active external forces exceeding the permissible load.

6. Two-way action mechanism for infinite linear adjustment based on self-wedging principle, which allows holding active external forces from both directions along guiding bar.

7. Self-wedging mechanism for infinite linear adjustment that will sustain secondary impact.

8. The new Self-wedging mechanism for infinite linear adjustment having a good dynamic latching.

9. Heavy-duty mechanism for infinite linear adjustment based on self-wedging principle and using special self-alignment elements to avoid high contact stress of sharp edge.

10. Mechanism for infinite linear adjustment based on self-wedging principle that does not request any kind of alignment between two mechanisms working in the car seat.

11. Based on claims 1; 2; 3; 4; 5; 6; 7; 8 and 10 the new recliner for the car seat with infinite adjustment.

12. The new mechanism for lengthwise infinite adjustment of the car seat based on claims 1 through 10.