Lifting assistance system for vehicle tailgate

Abstract

The vehicle tailgate lift assist system has a vehicle tailgate adapted to open and close by rotating about a tailgate pivot axis relative to the vehicle body, a coupling means for releasably connecting the vehicle tailgate and the vehicle body, an energy storage device adapted to be located within the vehicle body and pivotally fixed to the vehicle body at one end, a crank arm pivotally attached to the energy storage device at a second end of the energy storage device and rigidly attached to an actuation shaft coaxially aligned with the tailgate pivot axis, and a pivot bracket assembly having a mounting bracket fixed to the vehicle body and carrying a pivot bearing arrangement to facilitate a robust rotational joint about the tailgate pivot axis. The pivot bearing arrangement has an integral component that fits over a pivot sleeve and acts as a bushing between the actuation shaft and the pivot sleeve such that relative rotational movement of the tailgate and the vehicle body results in linear movement of the energy storage device and maximum energy storage in the tailgate fully open position.

Description

[Technical field]

[0001] FIELD OF THEINVENTION FIELD OF THEINVENTION The present invention is in the field of vehicle tailgates and means for opening, holding open and closing same. [Background technology]

[0002] background Vehicle tailgates, particularly those for pickup trucks, must be easily openable and closable, and preferably also removable from the vehicle body. It is also desirable to provide a lift-assist feature to provide damping to resist the force of gravity acting on the opening tailgate, while also assisting in closing the tailgate by storing energy and subsequently dissipating such stored energy to significantly overcome the force of gravity acting on the tailgate. U.S. Patent No. 6,773,047 to Gruber describes a very useful means for achieving both the objectives of tailgate removability and lift-assistance.

[0003] Tailgate hinge joints on work pickup trucks are typically exposed to relatively hostile environments. Dirt, dust, salt, mud and other debris from road or off-road surfaces and work sites tend to deteriorate the operation of tailgate hinge joints. Loading and unloading cargo from the truck bed can also cause debris to come into contact with such joints. Such debris can cause unwanted friction between parts at the joints, which can interfere with smooth opening and closing of the tailgate and can cause wear and tear on the parts themselves. Weather, including precipitation and exposure of the system to moisture and electrolytes, can also contribute to deterioration of the performance of the tailgate opening and closing system.

[0004] Additionally, the tailgate will be subject to significant vibration and inertial loads as the vehicle negotiates uneven road surfaces or other terrain. A removable tailgate also necessarily has relatively loose attachments to permit removal and reinstallation of the tailgate without undue effort or damage to the tailgate or vehicle body. A combination of environmental, vibration and inertial effects, ingress of dirt into loose hinge joints, and other such factors can result in wear and instability over time.

[0005] It would therefore be advantageous to provide a removable vehicle tailgate system that reduces exposure of the joint system mechanisms to debris, weather and other external factors. It would also be advantageous to provide a removable vehicle tailgate system that reduces the effects of vibration and inertial loads. Additionally, it would be advantageous to provide a removable vehicle tailgate system that is robust and reduces wear and instability. Additionally, it would be beneficial to provide these benefits with a reduced number of parts. Summary of the Invention

[0006] overview U.S. Patent No. 6,773,047 shows a mechanism for allowing attachment and removal of a tailgate from a vehicle body. Among the vehicle body side components of the mechanism are two bushings that allow the actuation shaft to rotate within a sleeve structure while remaining aligned with the pivot bracket axis (about which the tailgate pivots). A male slot drive feature is coaxially attached to the actuation shaft via a screw. The screw also holds the actuation shaft and the entire pivotable assembly in the rigid body pivot bracket while allowing rotational movement. Additionally, an exterior bearing surface feature of the tailgate pivot bracket interfaces with an interior bearing surface feature of the tailgate pivot bracket to create a rotational joint.

[0007] We have found that by consolidating the functions of the two actuation shaft bushings into a one-piece bushing component that is overlaid on the actuation shaft, and by eliminating the male slot drive features and screws, a simpler and more robust structure is achieved that reduces environmental, vibrational and inertial effects. Additionally, the provision of annular ribs on both ends of the overlaid bushing, which are compressed when the mechanism is assembled, provides an excellent sealed fit with the rotating actuation shaft assembly and prevents the ingress of debris and foreign matter into the joint.

[0008] The pivot bracket assembly mounted to the body of the vehicle has a number of components. At the center of the pivot bracket assembly is an actuation shaft or drive shaft. The drive shaft preferably has an overhanging drive head that is adapted to releasably engage a corresponding drive cup mounted to the tailgate. This releasability feature allows the tailgate to be removed from the vehicle when desired. A crank arm is rigidly mounted to the opposite end of the drive shaft. Typically, an opening or orifice in the crank arm slides over the end of the drive shaft and is held in place by swaging the end of the drive shaft against the crank arm. Of course, other conventional means for holding the crank arm to the drive shaft are possible, such as welding, crimping, using a threaded connector such as a nut on the threaded end section of the drive shaft, etc. However, swaging allows the lift assist mechanism to be rigidly connected at minimal cost and without additional fasteners or fasteners.

[0009] At the end of the crank arm distal to the drive shaft, the crank arm is rotationally connected to the end of an energy storage device (typically a pneumatic cylinder or gas strut). The distal end of the gas strut is rotationally connected to the vehicle body. Thus, as the tailgate opens, the connected drive cup and drive head cause rotation of the drive shaft (which rotates the crank arm and extends the gas strut), thus simultaneously controlling the opening of the tailgate and storing energy in the gas strut to assist in the final closing of the tailgate.

[0010] The pivot bracket assembly further has a pivot sleeve connected to a mounting bracket which is in turn mounted to the vehicle body, typically at the D-pillar in the cargo section of a pick-up truck. The pivot sleeve is adapted to rotate about the drive shaft as the drive shaft rotates. To facilitate this relative rotation, there is a pivot bushing between the pivot sleeve and the drive shaft. Preferably, the pivot bushing has an integral component that is overlaid on the pivot sleeve. The pivot bushing may be made of plastic or a similar synthetic material.

[0011] One or more ribs are provided on the ends of the pivot bushing to seal the pivot bracket assembly from elements and debris, among other foreign objects. The ribs, preferably circular or annular, may be compressed onto a drive head located at a first end of the drive shaft and onto a crank arm mounted on an opposite second end of the drive shaft during assembly of the system. Riveting the second end of the drive shaft by swaging or a similar technique to secure the crank arm provides sufficient force to compress the ribs on either end of the overlaid bushing onto each of the crank arms and drive head. The drive head provides an external bearing surface that reversibly fits into a drive cup mounted on the tailgate. The drive head may be made of plastic or similar synthetic material that is overlaid on one end of the drive shaft. This provides a reduced friction external bearing surface that helps absorb vibrations. Alternatively, a steel or other metal drive head fixed to or integral with the drive shaft may be used. If desired, other materials such as hardened plastic or other synthetic materials may form the drive shaft.

[0012] In a principal aspect of the invention, a vehicle tailgate lift assist system has a vehicle tailgate adapted to open and close by rotating about a tailgate pivot axis relative to the vehicle body, a coupling means for releasably connecting the vehicle tailgate and the vehicle body, an energy storage device adapted to be located within the vehicle body and pivotally fixed to the vehicle body at a first end, a crank arm pivotally attached to a second end of the energy storage device and rigidly attached to an actuation shaft coaxially aligned with the tailgate pivot axis, a pivot bracket assembly having a mounting bracket fixed to the vehicle body and carrying a pivot bearing arrangement to promote a robust rotational joint about the tailgate pivot axis, the pivot bearing arrangement having an integral component that overlies a pivot sleeve and acts as a bushing between the actuation shaft and the pivot sleeve, such that relative rotational movement of the tailgate and the vehicle body results in linear extension of the energy storage device and maximum energy storage in the tailgate fully open position.

[0013] In a further aspect, both ends of the over-hanging bushing are provided with circular sealing ribs.

[0014] In a further aspect, the sealing rib is compressed against the crank arm at one end of the over-mounted bushing and against the drive head at the other end of the over-mounted bushing.

[0015] In a further aspect, the sealing rib is compressed when the second end of the drive shaft adjacent the crank arm is swaged onto the crank arm.

[0016] In a further aspect, the bushing is made from plastic or a similar synthetic material.

[0017] In a further aspect, the energy storage device comprises gas struts.

[0018] In a further aspect, the coupling means includes a drive head on a first end of the drive shaft and a drive cup connected to the vehicle tailgate.

[0019] In a further aspect, the drive head is fitted over the drive shaft.

[0020] In a further aspect, the drive head is made from plastic or similar synthetic material.

[0021] In a further aspect, the pivot axis runs through the drive head and drive cup when they are engaged.

[0022] Further aspects of the lift assist system for a vehicle tailgate will be apparent from the following description and explanations. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a perspective view of elements of a lift-assist system for a vehicle tailgate and a vehicle tailgate. [Diagram 2] FIG. 2 is an elevational cross-sectional view of a lift assist system for a vehicle tailgate, showing its attachment to the vehicle body and its engagement with the vehicle tailgate. [Diagram 3] FIG. 3 is an elevational cross-sectional view of a lift assist system for a vehicle tailgate, showing the system attached to the vehicle body and disengaged from the vehicle tailgate. [Figure 4] FIG. 4 is an elevational cross-sectional view of a portion of a lift assist system for a vehicle tailgate. [Diagram 5] FIG. 5 is an elevational cross-sectional view of a portion of a lift assist system for a vehicle tailgate showing the pivot bushing sealing to the crank arm via a rib and the drive shaft riveted to the crank arm. [Figure 6]FIG. 6 is an elevational cross-sectional view of a portion of a lift assist system for a vehicle tailgate showing the sealing of the pivot bushing to the drive head via a rib. [Figure 7] FIG. 7 is a perspective cross-sectional view of a pivot sleeve having an overlaid pivot bushing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Detailed Description Referring to FIG. 1, the vehicle tailgate lift assist mechanism 1 releasably connects a vehicle body 7 and a tailgate 3. The tailgate 3 rotates about a tailgate pivot axis X. The lift assist mechanism 1 is mounted to the vehicle body 7 as described herein. An actuation shaft or drive shaft 15 is rigidly connected to a crank arm 13 at a second end. The opposite first end of the drive shaft 15 has a drive head 29. The drive head 29 may have the material of the drive shaft (typically metal), but is preferably overlaid on the drive shaft 15 and is made of plastic or other synthetic material. The drive head 29 engages with a drive cup 31 mounted on the tailgate 3. The drive head and drive cup together comprise a coupling means 27. When the drive head 29 engages with the drive cup 31, the tailgate 3 may rotate about the pivot axis X.

[0025] The end of the crank arm 13 that is not connected to the drive shaft 15 is rotatably connected to an energy storage device (typically a gas strut 9). The gas strut 9 is pivotally connected to the vehicle body 7 (e.g., by a pivot axis anchor 11). As the tailgate 3 opens when the drive head 29 and drive cup 31 engage, the drive shaft 15 rotates the crank arm 13 and extends the gas strut 9 to store energy. The resistance of the gas strut 9 allows the tailgate to open in a controlled manner. The energy stored in the gas strut 9 while the tailgate is opening helps overcome the weight of the tailgate 3 when it is closing. The drive shaft 15 rotates in a pivot sleeve 17 that is held in place by a mounting bracket 21. This assembly has a pivot bracket assembly 19.

[0026] The pivot bracket assembly 19 has a pivot bearing arrangement 23 which allows rotation of the drive shaft 15 within the pivot sleeve 17. The pivot bearing arrangement further includes an integral component 25 which fits over the pivot sleeve 17 and functions as a pivot bushing. Each end of the pivot bushing 25 includes a circular or annular rib 33 which is each compressed against the drive head 29 and crank arm 13 when the pivot bracket assembly 19 is assembled. This compression of the annular rib 33 against the drive head 29 and crank arm 13 seals the unit against debris, moisture or other undesirable external influences. Typically, this compression is performed by compressing the second end 15 of the drive shaft 15 against the drive head 29 and crank arm 13. b This occurs when the crank arm 13 is swaged or riveted onto the crank arm 13.

[0027] A mounting bracket 21 mounted to the body 7 holds the pivot sleeve 17 from rotating relative to the drive shaft 15. The mounting bracket may be secured to the body 7 (typically a D-pillar of a truck bed) by bolting, welding or other conventional methods.

Claims

1. 1. A tailgate lift assist system for a vehicle, the tailgate lift assist system comprising: a) a tailgate for a vehicle, the tailgate adapted to be opened and closed by rotating about a tailgate pivot axis relative to a vehicle body; b) having a coupling means for releasably connecting said vehicle tailgate and said vehicle body; c) having an energy storage device, the energy storage device adapted to be located within the vehicle body and pivotally secured to the vehicle body at a first end; d) a crank arm pivotally attached to a second end of the energy storage device and rigidly attached to an actuation shaft coaxially aligned with the tailgate pivot axis; e) a pivot bracket assembly having a mounting bracket secured to the vehicle body and carrying a pivot bearing arrangement to facilitate rotational engagement about the tailgate pivot axis; f) said pivot bearing arrangement having an integral component which fits over a pivot sleeve to act as a bushing between said actuation shaft and said pivot sleeve, said bushing sealably fitting to said crank arm at one end of said bushing and to a drive head of said actuation shaft at an opposite end of said bushing; g) the coupling means includes a drive head adapted to rotate with the actuation shaft and to releasably engage a drive cup connected to the vehicle tailgate; the relative rotational movement of the tailgate and the vehicle body is such that it results in linear extension of the energy storage device and maximum energy storage in the tailgate fully open position; The vehicle tailgate lifting assistance system.

2. 2. The vehicle tailgate lift assist system of claim 1, wherein both ends of said over-covered bushing are provided with circular sealing ribs.

3. 3. The vehicle tailgate lift assist system of claim 2, wherein said sealing rib is compressed against said crank arm at said one end of said over-covered bushing and against said drive head at said opposite end of said over-covered bushing.

4. 4. The vehicle tailgate lift assist system of claim 3, wherein the sealing rib is compressed when the second end of the actuating shaft adjacent the crank arm is swaged onto the crank arm.

5. 2. The vehicle tailgate lift assist system of claim 1, wherein said bushing is made of plastic.

6. 10. The vehicle tailgate lift assist system of claim 1, wherein the energy storage device comprises a gas strut.

7. 2. The vehicle tailgate lift assist system of claim 1, wherein the drive head is fitted over the actuation shaft.

8. 8. The vehicle tailgate lift assist system of claim 7, wherein the drive head is made of plastic.

9. 2. The vehicle tailgate lift assist system of claim 1, wherein said pivot shaft runs through said drive head and said drive cup when engaged.

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