WO2001027425A1

WO2001027425A1 - Vehicle liftgate power operating system

Info

Publication number: WO2001027425A1
Application number: PCT/US2000/027731
Authority: WO
Inventors: David J. Chapman; Brian N. Orr; Joseph M. Johnson; Joseph D. Cranston
Original assignee: Delphi Technologies Inc
Current assignee: Delphi Technologies Inc
Priority date: 1999-10-08
Filing date: 2000-10-06
Publication date: 2001-04-19
Anticipated expiration: 2002-04-08

Abstract

A power operating system for opening and closing a vehicle liftgate (12) has a pair of drive units (22) supported on the vehicle roof and connected to the liftgate for opening and closing the liftgate. Each drive unit (22) includes a bracket (24) that is secured to the vehicle body for supporting several parts including a reversible electric motor (26), a gear unit and a track (30). The electric motor (26) drives a segmented sector (60) inside the track (30) via a pinion gear (28). The segmented sector (60) includes an elongated, arcuate toothless push link (62) that is guided by an arcuate track portion of the track and a plurality of short drive links (64) that are driven by the pinion gear (28) and stored in a storage track portion (54) when the liftgate (12) is closed. The pusher link (62) has an outboard end that is pivotally connected to the liftgate (12) to open and close the liftgate as the push link (62) is extended and retracted by the drive links (64).

Description

VEHICLE LIFTGATE POWER OPERATING SYSTEM .

5 TECHNICAL FIELD

This invention relates to a power operating system for a vehicle liftgate that is pivotally attached to a vehicle compartment for pivotal movement about a generally horizontal axis and more particularly to a power operating system that will move a liftgate from a closed position to a fully open position and from an o open position to a fully closed position.

BACKGROUND OF THE INVENTION

Utility vehicles and vans with liftgates that are hinged at the top about a generally horizontal axis are used by large numbers of people today.s Some of these liftgates are large and heavy. Their size and weight make some liftgates difficult to open and close. Some of the liftgates are also a great distance above the ground when they are fully opened. Their height above the ground makes them very difficult for some people to close. For these and other reasons many people would like to have a power operating system for opening and o closing the liftgate.

A number of different liftgate openers have been tried in recent years. Some of these liftgate openers have a single cable that opens and closes a liftgate in connection with a counterbalance system, such as gas cylinders. Liftgates with a single cable opener and closer are generally trunk lids that are 5 lightweight and have a relatively small range of movement.

Gas cylinder output varies with temperature. This complicates power liftgate systems that rely on gas cylinders to open the liftgate. The gas cylinder or cylinders must be strong enough to open the liftgate on the coldest date (-40° C). This results in gas cylinders that increase closing resistance o substantially on the hottest day (80° C). Therefore a very large electric motor must be used to close the liftgate. Liftgates that have two or more gas cylinders for a counter balance system are common. These gas cylinders generally occupy a position in which their axis is substantially parallel to the liftgate so that the gas cylinders are hidden when the liftgate is closed. In this closed position the moment arm of the 5 gas cylinders is quite small. With such systems the lift gate may move about one-third of their total travel range before the gas cylinders exert sufficient force to open a liftgate further without the application of an independent lifting force. There are even some systems in which the gas cylinders pass over center and bias a liftgate toward a closed position when the liftgate is closed. With these self-0 closing systems a liftgate may need to be more than one-third open before the gas cylinders will open the liftgate further.

The force required to hold a liftgate in a given position along its path of movement from a closed position to a fully open position varies substantially in some liftgate opening systems. A power liftgate closer must exert5 sufficient force to hold a liftgate in any given position along the path of movement, plus the force to overcome friction, and plus the force required to accelerate the liftgate during liftgate closing. If the total force exerted by the liftgate power closure varies substantially from one position between fully opened and closed to another position between fully opened and closed, it may be difficult for the control o system to detect an obstruction and stop the liftgate without incurring damage to the vehicle or to the object that obstructs the liftgate.

In our prior patent application, now U.S. Patent 6,092, 337, we disclosed an improved power operating system for a vehicle liftgate that has a pair of drive units supported on the vehicle roof for opening and closing the liftgate. Each drive unit 5 includes a bracket that is secured to the vehicle body for supporting several parts including a reversible electric motor, a gear unit and a track. The electric motor drives a segmented sector inside the track via a gear reduction unit. The segmented sector includes an arcuate push link that travels in an arcuate track portion of the track and a plurality of short sector links that are stored in a storage track portion o when the liftgate is closed. The arcuate push link has an outboard end that is pivotally connected to the liftgate to open and close the liftgate as the arcuate push link is extended and retracted by the electric motor. While this power operating system is satisfactory, further improvements are desirable.

SUMMARY OF THE INVENTION 5 The object of the invention is to provide a still further improved vehicle liftgate power operating system.

A feature of the vehicle liftgate power operating system of the invention is that the arcuate push link that is pivotally connected to the liftgate does not engage the pinion gear which improves gear fit because the tooth0 engagement of the short sector links with the pinion gear is not influenced by the manufacturing tolerances for location of the liftgate.

Another feature of the invention is that the liftgate power operating system allows greater design freedom because the short sector links need not have the same radius of curvature as the arcuate push link. s Still another feature of the liftgate power operating system of the invention is that tooth engagement of the short sector links with the pinion gear depends solely on the manufacture of the drive unit and not on installation of drive unit in the vehicle.

Yet another feature of the invention is that the push link can be o toothless to reduce manufacturing cost.

An optional feature of the invention is that the liftgate power operating system has a pinion gear that can be engaged solely by short sector links that are identical to reduce manufacturing cost.

Another optional feature of the liftgate power operating system of 5 the invention is that tooth profile of the short sector links can be modified to accommodate misalignment due to a loose track or loose pivot pin.

These and other objects, features and advantages of the invention will become more apparent from the following description of a preferred embodiment taken in conjunction with the accompanying drawing. BRIEF DESCRIPTION OF THE DRAWINGS

The presently preferred embodiment of the invention is disclosed in the following description and in the accompanying drawings, wherein: 5 Figure 1 is a perspective view of the rear portion of a vehicle equipped with a liftgate power operating system of the invention showing the liftgate in an open position;

Figure 2 is an enlarged perspective view of the right hand drive unit of the power operating system of figure 1 showing the drive unit when the liftgate iso closed;

Figure 3 is an enlarged side view of the right hand drive unit shown in figure 2 with parts removed to show internal detail;

Figure 4 is an enlarged side view of the right hand drive unit shown in figure 2 with parts removed to show internal detail when the liftgate is in the5 open position; and

Figure 5 is a section taken substantially along the line 5-5 of Figure 4 looking in the direction of the arrows;

Figure 6 is a section taken substantially along the line 6-6 of Figure 4 looking in the direction of the arrows; o Figure 7 is a section taken substantially along the line 7-7 of Figure

4 looking in the direction of the arrows;

Figure 8 is an enlarged exploded perspective view of the right hand drive unit shown in figure 2 with parts removed to show internal detail;

Figure 9 is a side view of a modified sector link for the drive unit 5 shown in figures 2-8;

Figure 10 is a perspective view of part of a segmented sector for the drive unit shown in figures 2-8 having modified sector links shown in figure 9;

Figure 11 is a side view showing the fit of a drive pinion with the overlapping ends of two adjacent modified sector links under conditions of perfect o alignment; Figure 12 is a side view showing the fit of a drive pinion with the overlapping ends of two adjacent modified sector links under loose track conditions;

Figure 13 is a side view showing the fit of a drive pinion with the 5 overlapping ends of two adjacent modified sector links under loose pivot pin conditions;

Figure 14 is a perspective view of part of an alternative segmented sector for the drive unit shown in figures 1-8; and

Figure 15 is a perspective view of part of another alternative0 segmented sector for the drive unit shown in figures 1-8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to figure 1, vehicle 10 has a liftgate 12 that is5 attached to the aft end of the vehicle roof by two hinge assemblies. The typical right hand hinge assembly 14 is shown in figures 2, 3 and 4.

Hinge assemblies 14 have hinge portions 16 that are secured to a roof channel of the vehicle 10 and hinge portions 18 that are secured to a top channel of the liftgate 12. Hinge portions 18 are attached to hinge portions 16 by 0 pivot pins 20 so that liftgate 12 pivots about a pivot axis indicated at 21 in figures 2, 3 and 4 from a closed position shown in figures 2 and 3 to a raised open position shown in figures 1 and 4. Pivot axis 21 is generally substantially horizontal and liftgate 12 is generally permitted to pivot about 90° about pivot axis 21. However, the range of movement can be varied substantially from one model of vehicle to 5 another.

Lift gate 12 is opened and closed by a power operating system that includes two identical drive units 22 that are installed in the aft end of the vehicle roof. Drive units 22 are laterally spaced from each other and near the respective vertical body pillars at the aft end of vehicle 10 that define the rear opening that is o closed by lift gate 12. The typical drive unit 22 is shown in figures 2, 3 and 4 with the interior trim cover 23 removed to show detail of the drive unit. Each drive unit 22 comprises a bracket 24 that is secured to the vehicle body in a fixed position for supporting several parts including a reversible electric motor 26, a conventional two-stage speed reducing, torque multiplying, planetary gear set inside the electric motor casing that drives an output pinion gear 5 28, a multi-piece track 30 comprising a track base 31 , a track cover 32 and an anti- rattle member 33 as best shown in figure 8. Drive unit 22 also includes an optional position sensor 40 located in a housing 42 that is an integral part of track cover 32. Position sensor 40 includes a gear wheel 44 that rotates with output gear 28, an optical wheel 46 driven by output gear 28, a sensor element 48 and a cover 50. The0 position sensor 40 operates in a well known manner to control electric motor 26 through a suitable motor control (not shown) so that the motor either drives enough in one direction to open the liftgate and then stops or drives enough in the opposite direction to close the liftgate and then stops.

The multi-piece track 30 includes a rearward track portion 52 and a5 contiguous forward track portion 54 that are secured to the vehicle body in a fixed position as best shown in figure 2. Bracket 24 attaches the forward track portion 54 while the two -piece hanger 56 attaches the aft end of track 30 to vehicle 10. Rearward track portion 52 is preferably arcuately shaped to hug the aft end of the vehicle roof, particularly the box beam that carries the hinge portions 16 shown in o figures 3 and 4 in order to maximize unobstructed load height at the liftgate opening. Track portion 52 is also preferably arcuately shaped with a radius of curvature that is centered on the hinge axis 21 of lift gate 12. Forward track portion 54 preferably is above the arcuate rearward tract portion 52 and turns in an opposite direction resulting in a wave like configuration for track 30 that follows the interior 5 contour of the vehicle roof closely. This wave like configuration and close following reduces space requirements and minimizes intrusion into the cargo compartment particularly in the vertical direction. Drive unit 22 preferably has the electric motor 26 and housing 42 located beneath the reverse curve of the higher forward track portion 54 so that the protrusion into the cargo compartment is o reduced as much as possible. A segmented sector 60 is disposed in track 30. Segmented sector 60 comprises an elongated push link 62 and a plurality of short sector links that are pivotally connected end-to-end in chain-like fashion. Elongated push link 64 is also preferably arcuately shaped with a curvature that matches that of track portion 5 50 so that the elongated push link 62 translates back and forth in track portion 50 pivoting about the hinge axis 21 shown in figures 3 and 4 between the retracted position shown in figures 2 and 4 and the extended position that is shown in figures 1 and 4. This concentric path of movement eliminates pivotal movement of the elongated push link 62 with respect to liftgate 12 and consequently link 62 can be

10 sealed at the vehicle body exit easily. The body exit for link 62 can even be placed in the vertical body pillar outside the liftgate perimeter seal (not shown).

The short sector links 64 are stored in forward track portion 54 when liftgate 12 is closed as shown in figures 2 and 4 and then travel into the rearward arcuate portion 52 when liftgate 12 is opened. Consequently, sector links

15 64 are preferably made as short curved links to facilitate travel in the wave like track 30. Anti rattle member 33 is disposed in the forward linear end of forward track portion 31 and acts as a resilient blade to push rollers 66 down against the bottom of the track. Rollers 66 are provided at the pivot pins joining adjacent sector links 64 as explained below.

2 o The outboard end of elongated, arcuate push link 62 is pivotally connected to liftgate 12 by means of hinge bracket 78. The inboard end of elongated, arcuate push link 62 is pivotally connected to the outboard end of a first pair of laterally spaced, short sector links 64. The inboard end of arcuate push link 62 carries two rollers 66 at the pivotal connection with the first pair of short sector 5 links 64 to facilitate movement in track 30. The inboard ends of the first pair of sector links 64 and the remaining sector links 64 also preferably carry rollers 66 at their respective pivotal connections to facilitate movement in track 30. Track 30 also preferably flares slightly at the rearward end to accommodate manufacturing tolerances with respect to the location of liftgate 12 and hinge axis 21. o Figure 9 shows a typical sector link 64. Each sector link 64 is arcuately shaped with a large radius of curvature and has a series of teeth 68 on the concave side which faces down when link 64 is in track 30. Teeth 68 are preferably involute. The curvature of sector links 64 is opposite the curvature of push link 62 which is possible because push link 62 does not engage drive pinion gear 28. The opposite curvature of sector links 64 allows a more forward location of electric 5 motor 26 and drive pinion gear 28 which reduces intrusion of drive unit 22 into the cargo compartment.

Each end tooth 70 of each sector link 64 is preferably modified by relieving the side faces of the tooth tip 72 so that the side faces of tip 72 taper inwardly in the radial direction more than a conventional tooth, such as an involute0 tooth, as best shown in figure 11. The purpose of the modification is described below. Each sector link 64 has pivot holes 74 at each end that are aligned with the penultimate tooth 68 at each end. The penultimate tooth 68 is a conventional involute tooth whereas the end tooth 70 preferably has a tip 72 that is modified as described above. 5 Figure 10 is a perspective view of part of the segmented sector 60 that is preferably used in the drive unit 22. Here, the short sector links 64 are arranged in side-by-side pairs with the overlapping ends of adjacent pairs interdigitated and fastened together by a pivot pin 76. Pivot pin 76 extends through pivot holes 74 in four sector links 64 to support two rollers 66 outwardly of the o overlapped link ends. Sector links 64 are preferably shaped in plan view as shown in figure 9 and include modified end teeth 70 as described above. The elongated, arcuate push link 62 is also preferably a pair of side-by-side links when pairs of sector links 64 are used as best shown in figure 8. The two side-by-side push links 62 are spaced apart by hinge bracket 78 and spacers 80 so that the inboard ends of 5 the two side-by-side push links 62 interdigitate with the first pair of short sector links 64.

Referring now to figure 9 and as indicated above, the penultimate teeth 68 that are aligned with the pivot holes 74 in the radial direction are conventionally shaped, for instance as involute teeth, while the end teeth 70 are o modified by relieving the side faces of the tooth tips 72 so that the side faces taper inwardly in the radial direction more than a conventional involute tooth. Figure 11 is a side view showing the fit of the drive pinion 28 with the overlapping ends of two adjacent sector links 68 under conditions of perfect alignment. The modified end tooth 70 of each link is aligned with the tooth 68 that is the third from the overlapped end of the adjacent sector link 68. The penultimate tooth 68 of the 5 overlapped ends of each link is conventional. Under these conditions, the teeth 29 of the output gear or drive pinion 28 of the gear reduction unit always engage and push conventional teeth 68 of the links 64 in one direction or the other and in some instances the unmodified portions of end teeth 70.

Figure 12 is a side view showing the fit of the drive pinion 28 with0 the overlapping ends of two adjacent sector links 66 under loose track conditions. Under these conditions, a tooth 29 of the drive pinion 28 engages both the tip of the third- from-the-end conventional tooth 68 of the right hand driven link 64 and the modified tip 72 of end tooth 70 of the left hand following link 64. As drive pinion 28 rotates clockwise as viewed in figure 12, tooth 29 engages the teeth 68, 70s deeper and deeper to align the teeth 68 and 70 so that there is a smooth transition to the engagement of the following drive pinion tooth 29 with the penultimate teeth 68 of the two links which teeth are both conventionally shaped and aligned by the time that these teeth are engaged by the following drive pinion tooth 29.

Figure 13 is a side view showing the fit of the drive pinion 28 with o the overlapping ends of two adjacent sector links 64 under loose pin conditions.

Under these conditions, a tooth 29 of the drive pinion 28 also engages both the tip of the third- from-the-end conventional tooth 68 of the right hand driven link 64 and the modified tip 72 of end tooth 70 of the left hand following link 64. As drive pinion 28 rotates clockwise as viewed in figure 13, tooth 29 engages the teeth5 deeper and deeper to align the teeth 68 and 70 so that there is a smooth transition to the engagement of the following drive pinion tooth 29 with the penultimate teeth 68 of the two links which teeth are both conventionally shaped and aligned by the time that these teeth are engaged by the following drive pinion tooth 29.

Thus it can be seen that the end teeth 70 with the modified tips 72 o that overlap the third- from-the-end conventional tooth 68 of the adjacent link provide for a quiet and smooth operation of the mechanism even when misalignments due to a loose track or a loose pivot pin occur.

The power operating system of the invention further includes a conventional power source such as the vehicle battery (not shown) and a suitable 5 motor control for energizing and shutting off the reversible electric motor 26. Motor controls are well known to those skilled in the art and thus need not be described in detail.

The power operating system operates as follows. Assuming that the liftgate 12 is closed as shown in figures 2 and 3, electric motor 26 is energized too open liftgate 12. When energized, electric motor 26 rotates pinion gear 28 clockwise driving the side-by-side pairs of sector links 64 rearward in succession until arcuate push link 62 is driven from the retracted position shown in figures 2 and 3 to the extended position shown in figures 1 and 4. This raises liftgate 12 from the closed position shown in figures 2 and 3 to the raised open position showns in figures 1 and 4. When the liftgate 12 is fully opened, a limit switch or the like is actuated to shut off electric motor 26. Liftgate 12 is closed by reversing electric motor 26 so that pinion gear 28 drives segmented sector 60 back to the retracted position shown in figures 2 and 3.

In some designs, the pinion gear 28 may not drive the first and o possibly the second rearward pairs of sector links 64 due to the forward placement of the electric motor 26 as shown in figure 3. In these circumstances, the rearward pairs of sector links 64 act as short spacer links and may be replaced with toothless links of the same shape. However, it is usually more economical to use identical links. 5 In any event, the pinion gear 28 preferably does not drive the elongated arcuate push link 62 under any circumstances. Consequently, push link 62 is preferably toothless to save manufacturing cost. Moreover, this arrangement provides considerable freedom in locating the electric motor 26, as well as shaping the sector links 64, the tooth profile and the storage portion 54 of the track 30. o With a proper motor control circuit, electric motor 26 can be de- energized at any time in which case liftgate 12 can be stopped at any intermediate position and held in the intermediate position by the friction in the gear train without any need for a brake, detent or the like. The liftgate 12 can then be moved by energizing electric motor 26 or the liftgate 12 can then be moved manually because the gear train can be designed with sufficient efficiency to permit back 5 drive to electric motor 26.

The power operating system can be designed to work alone or in conjunction with gas cylinders which are well known in the art with the primary adjustment being the size of the electric motor 26.

The power operating system described above preferably includeso two identical drive units 22 for balanced operation and reduced manufacturing costs. However, the drive units need not be identical and in some instances, a single drive unit may be sufficient.

It is also possible to use two drive units with a single reversible electric motor driving both pinion gears 28. In such an arrangement the axis of the5 electric motor is parallel to the axis of the pinion gears as shown.

Figure 14 shows part of an alternative segmented sector 160 for drive unit 22. Here two thinner short sector links 164 are laterally spaced in a side- by-side pair that is connected to a thicker short sector link 165 that has an end that is inserted between the ends of the side-by-side pair. The overlapping ends are o connected by pivot pin 176 that supports rollers 166 outwardly of the thinner sector links 164. The opposite end of the thicker sector link 165 is inserted between the ends of another laterally spaced side-by-side pair of thinner sector links 164 and the overlapping ends are connected together by another pivot pin 176 that supports two more rollers 166 adjacent the outer sides of the two pair of thinner sector links 166. 5 The pattern is repeated until segmented sector 160 is long enough. Sector links 164 and 165 are shaped in plan view as shown in figure 9 and preferably also include modified end teeth as described above. In this instance, the segmented sector 160 would include either a single elongated, arcuate push link (not shown) connected to the liftgate (not shown) that is as thick as sector link 165 or two thin elongated, o arcuate push links (not shown) that are spaced apart to accommodate a thick sector link 165. Figure 15 is a perspective view of part of another alternative segmented sector 260 for drive unit 22. Here each sector link 264 is Z-shaped with the overlapping ends providing a constant thickness for spacing the rollers 266 that are supported by the pivot pin 276 that connects the adjacent sector links 264. Sector links 264 are also shaped in plan view as shown in figure 7 and also preferably include modified end teeth as described above. In this instance, a single, thick, arcuate, elongated push link (not shown) is pivotally connected to the liftgate (not shown). The inboard end of such a push link would be shaped to mate with the end of the first short sector link 264. Obviously, many modifications and variations of the present invention in light of the above teachings may be made. It is, therefore, to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims

We claim:

1. A power operating system for opening and closing a vehicle liftgate (12) that is pivotally attached to an aft end of a vehicle roof for pivotal movement about a generally horizontal hinge axis (21) between an open position and a closed position comprising: at least one drive unit (22) that includes a reversible electric motor (26), a segmented sector (60) driven by the electric motor (26) and a track (30), the segmented sector (60) having a plurality of links (62, 64) including a push link (62) that is guided by the track, the push link being pivotally attached to the liftgate (12)at one end and to another link (64) of the segmented sector at the other end.

2. The power operating system as defined in claim 1 wherein the segment sector (60) is driven by the electric motor (26) via a pinion gear (28) that engages selected ones of the plurality of links (64) but not the push link (62).

3. The power operating system as defined in claim 2 wherein the push link (62) is toothless.

4. The power operating system as defined in claim 2 wherein the track (30) has an rearward portion (52) that is arcuately shaped with a radius of curvature that is centered on the hinge axis (21) and the push link (62) is also arcuately shaped with a curvature that matches that of the track, the push link being guided by the rearward portion of the track so that the push link pivots about the hinge axis.

5. The power operating system as defined in claim 2 wherein the track (30) is wave shaped and has a forward portion (54) for storing at least a portion of the segmented sector (60) when the liftgate is in the closed position.

6. The power operating system as defined in claim 2 wherein the segmented sector (60) has a plurality of short sector links (64) that are pivotally connected end to end in chain like fashion.

7. The power operating system as defined in claim 6 wherein the plurality of short sector links (64) include drive links (64) that have teeth.

8. The power operating system as defined in claim 7 wherein the drive links (64) that have teeth are curved with a concave side and a convex side and the teeth (68, 70) are on the concave side.

9. The power operating system as defined in claim 7 wherein the drive links (64) that have teeth have a plurality of teeth (68, 70) on one side and a pivot hole (74) adjacent each end, the plurality of teeth including modified teeth (70) at each end of the link and a number of conventional teeth (68) between the modified end teeth, the modified teeth (70) having tips (72) that taper inwardly in the radial direction more than the conventional teeth (68).

10. The power operating system as defined in claim 9 wherein the pivot hole (74) adjacent each end is aligned with the penultimate tooth (68) adjacent each respective end.

11. The power operating system as defined in claim 7 wherein the drive links (64) that have teeth are arranged in laterally spaced pairs.

12. The power operating system as defined in claim 7 wherein the drive links (164, 165) that have teeth are arranged in laterally spaced pairs of drive links (164) that are alternated with a single thicker drive link (165).

13. The power operating system as defined in claim 7 wherein the drive links (214) that have teeth are z-shaped. 14

14. A power operating system for opening and closing a vehicle liftgate (12) that is pivotally attached to an aft end of a vehicle roof for pivotal movement about a generally horizontal hinge axis (21) between an open position and a closed position comprising: at least one drive unit (22) that includes a reversible electric motor (26), a segmented sector (60) driven by the electric motor (26) and a track (30), the segmented sector (60) including an elongated, arcuate push link (62) and a plurality of short segment links (64) that are pivotally connected end to end in chain like fashion, the push link (62) being pivotally attached to the liftgate (12) at one end and guided by the track (30) at the other end, and the short segment links (64) including drive links (64) having teeth.

15. The power operating system as defined in claim 14 wherein the drive links (64) that have teeth have a plurality of teeth (68, 70) on one side and a pivot hole (74) adjacent each end, the plurality of teeth including modified teeth (70) at each end of the link and a number of conventional teeth (68) between the modified end teeth, the modified teeth (70) having tips (72) that taper inwardly in the radial direction more than the conventional teeth (68).

16. The power operating system as defined in claim 16 wherein the pivot hole (74) adjacent each end is aligned with the penultimate tooth (68) adjacent each respective end.

17. The power operating system as defined in claim 14 wherein the push link (62) is toothless and the track (30) has an rearward portion (52) that is arcuately shaped with a radius of curvature that is centered on the hinge axis (21) and the pusher link (62) is also arcuately shaped with a curvature that matches that of the track so that the pusher link (62) pivots about the hinge axis (21) guided by the rearward portion (52) of the track (30). 15

18. The power operating system as defined in claim 15 wherein the drive links (64) that have teeth are curved with a concave side and a convex side and the teeth (68, 70) are on the concave side.