U.S. patent application number 14/537879 was filed with the patent office on 2015-05-14 for skateboard / longboard truck with advanced pivot mechanism.
This patent application is currently assigned to DASHBOARDS SKIMBOARDS COMPANY, LLC. The applicant listed for this patent is DASHBOARDS SKIMBOARDS COMPANY, LLC. Invention is credited to Lloyd W. Docter, Timothy R. Mackey.
Application Number | 20150130156 14/537879 |
Document ID | / |
Family ID | 53043128 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150130156 |
Kind Code |
A1 |
Docter; Lloyd W. ; et
al. |
May 14, 2015 |
Skateboard / Longboard Truck with Advanced Pivot Mechanism
Abstract
A skateboard or longboard truck comprises a hanger that includes
a structural member that embraces an axle or pair of axles that
support two wheels. The axle or pair of axles include two bearing
standoffs that separate a bearing surface of the axle from a face
of the structural member that embraces the axle. Alternatively, the
structural member that embraces the axle or pair of axles includes
two bearing standoffs that separate a bearing surface of the face
of the structural member from a non-bearing surface of the face of
the structural member.
Inventors: |
Docter; Lloyd W.; (Tacoma,
WA) ; Mackey; Timothy R.; (Tacoma, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DASHBOARDS SKIMBOARDS COMPANY, LLC |
Fife |
WA |
US |
|
|
Assignee: |
DASHBOARDS SKIMBOARDS COMPANY,
LLC
Fife
WA
|
Family ID: |
53043128 |
Appl. No.: |
14/537879 |
Filed: |
November 10, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61903790 |
Nov 13, 2013 |
|
|
|
Current U.S.
Class: |
280/124.114 |
Current CPC
Class: |
A63C 17/015 20130101;
A63C 17/0093 20130101; A63C 17/01 20130101; B62M 1/00 20130101;
A63C 2203/42 20130101; A63C 17/0046 20130101; A63C 17/012
20130101 |
Class at
Publication: |
280/124.114 |
International
Class: |
A63C 17/00 20060101
A63C017/00 |
Claims
1. A skateboard or longboard truck comprising: a hanger including a
structural member that embraces an axle or pair of axles that
support two wheels, the hanger also having a pivot that extends out
from the structural member in a direction perpendicular to the axle
or pair of axles; and a baseplate assembly, the baseplate assembly
having a base that mounts underneath a skateboard or longboard deck
configured to receive a kingpin to secure the hanger assembly to
the baseplate assembly; wherein the axle or pair of axles include
two bearing standoffs that separate a bearing surface of the axle
from a face of the structural member that embraces the axle.
2. The skateboard or longboard truck of claim 1, wherein the
bearing standoffs are defined by axle bearing spacing steps that
are machined or formed as part of the axle or pair of axles.
3. A skateboard or longboard truck comprising: a hanger including a
structural member that embraces an axle or pair of axles that
support two wheels, the hanger also having a pivot that extends out
from the structural member in a direction perpendicular to the axle
or pair of axles; and a baseplate assembly, the baseplate assembly
having a base that mounts underneath a skateboard or longboard deck
configured to receive a kingpin to secure the hanger assembly to
the baseplate assembly; wherein the structural member that embraces
the axle or pair of axles includes two bearing standoffs that
separate a bearing surface of the face of the structural member
from a non-bearing surface of the face of the structural member
that embraces the axle.
4. A skateboard or longboard truck comprising: a hanger including a
structural member that embraces an axle or pair of axles that
support two wheels, the hanger also having a pivot that extends out
from the structural member in a direction perpendicular to the axle
or pair of axles; and a baseplate assembly, the baseplate assembly
having a base that mounts underneath a skateboard or longboard deck
configured to receive a kingpin to secure the hanger assembly to
the baseplate assembly; wherein the two bearing standoffs that
separate a bearing surface of the face of the structural member
from a non-bearing surface of the face of the structural member are
pressed onto the structural member.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of our U.S. Provisional
Application No. 61/903,790, filed Nov. 13, 2013, and entitled
"Skateboard/Longboard Truck With Active Massive Ball Pivot
Mechanism," which is herein incorporated by reference.
FIELD OF THE INVENTION
[0002] The field of the invention is skateboards and longboards,
and more particularly, trucks for skateboards and longboards.
BACKGROUND
[0003] Traditional skateboard truck assemblies accomplish the
action of turning when the rider shifts his weight on the
skateboard deck from neutral to either side of the skateboard's
longitudinal axis.
[0004] Consistent with FIG. 1 a complete skateboard assembly
consists of two skateboard trucks with four attached wheels that
are attached to a skateboard deck. Each skateboard truck comprises
a baseplate assembly, which is attached to the deck, and a hanger
assembly on which the wheels are hung.
[0005] As a rider leans the skateboard deck from side to side, the
axle integral to the skateboard truck hanger assembly is forced to
stay parallel to the ground as long as the weight of the rider
forces the wheels to remain in contact with ground. Rotation of the
skateboard deck around an axis parallel to the longitudinal
centerline of the skateboard deck causes the skateboard truck
hanger assemblies to rotate--while staying parallel to the
ground--about other axes, resulting in a turning action transmitted
through the skateboard truck assemblies.
[0006] Furthermore, when the deck of a typical skateboard is
rotated, it causes the hanger assembly to rotate about an axis
between the center of the extreme end of the pivot and a point in
the center of the hanger aperture coincident with the longitudinal
centerline of the kingpin. This causes fore and aft movement of the
hanger and the wheels attached to it relative to the neutral
position of the trucks when the deck is evenly weighted and
parallel to the ground. As the rider angles the deck, the wheels
proximate to the weighted side that is angled toward the ground
move toward the middle of the skateboard deck, and the wheels on
the opposite side from the weighted edge of the deck move away from
the middle of the skateboard deck toward the ends of the skateboard
deck. The result is that the trucks allow the rider to turn the
skateboard by converting the force created by the leaning of the
skateboard deck into a controlled turning action. The turning
action is accomplished by the fore and aft movement of the wheels
attached to the skateboard trucks as they rotate on the kingpin
which is oriented at an angle less than 90 degrees to the ground
plane (FIG. 8).
SUMMARY
[0007] A skateboard or longboard truck comprises a hanger that
includes a structural member that embraces an axle or pair of axles
that support two wheels. The axle or pair of axles include two
bearing standoffs that separate the bearing surfaces of the axles
from a face of the adjoining structural member that embraces the
axle so that the outer race of an installed bearing does not
contact the structural member. Alternatively, the structural member
that embraces the axle or pair of axles includes two bearing
standoffs that are integral to the surface of the face of the
structural member that prevent the outer race of the bearing from
contacting the structural member. As a further alternative, a
bearing standoff may be fabricated as a separate component that is
attached to either the axle or the face of the structural member
that embraces the axle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The benefits, features, and advantages of the present
invention will become better understood with regard to the
following description, and accompanying drawings where:
[0009] FIG. 1 is a perspective view of a complete skateboard or
longboard assembly
[0010] FIG. 2 is a perspective view of one embodiment of a
skateboard or longboard truck according to the present
invention.
[0011] FIG. 3 is an exploded perspective view of one embodiment of
a skateboard or longboard truck according to the present
invention.
[0012] FIG. 4 is a perspective view of a hanger assembly of the
truck of FIG. 2.
[0013] FIG. 5 is a perspective view of a baseplate assembly of the
truck of FIG. 2,
[0014] FIG. 6 is a top view of the hanger assembly of the
skateboard truck assembly of FIG. 2, illustrating dimensions that
factor into the kingpin ratio, the angle of mechanical advantage,
and center of pressure.
[0015] FIG. 7 is a side section view of the truck assembly of FIG.
2, which illustrates the kingpin and baseplate angles of the truck,
dual axes of rotation, and pivot load transfer.
[0016] FIG. 8 is a bottom view of the skateboard assembly of FIG.
1, illustrating the relation between deck angle and truck turning
angle.
[0017] FIG. 9 is a perspective view of the pivot cup of FIG. 3,
[0018] FIG. 10 is top view of the pivot cup of FIG. 3, illustration
the airgap.
[0019] FIG. 11 is a perspective cut-away view of the pivot cup of
FIGS. 3 and 10, illustrating the threaded airgap and cleaning
grooves
[0020] FIG. 12 is a side view of the pivot cup of FIGS. 3, 10, and
11, showing the tolerance fin.
[0021] FIG. 13 is a perspective view of the kingpin of FIG. 3.
[0022] FIG. 14 is a top view of the kingpin of FIG. 3, illustrating
the tapered section of the shaft.
[0023] FIG. 15A is a view of the hanger assembly of FIG. 3 while
articulated, as it would characteristically be if the skateboard or
longboard deck were bearing a statically unbalanced load.
[0024] FIG. 15B is a detail view of the ball pivot and pivot cup of
FIG. 16A, showing the non-interference zone of the ball pivot and
pivot cup.
[0025] FIG. 16A is a top view of a prior art hanger while
articulated, as it would characteristically be if a skateboard or
longboard deck to which it were coupled were bearing a statically
unbalanced load.
[0026] FIG. 16B is a top detail view of the prior art pin pivot and
pivot cup of FIG. 16A, illustrating the interference zone of the
pin pivot and pivot cup.
[0027] FIG. 17 is a side view of the baseplate of FIG. 3, showing
the tapered walls and kingpin support section.
[0028] FIG. 18 is a sectional view of the hanger assembly along the
line 1-1 of FIG. 3 in the direction of the arrows, illustrating the
bushing seat.
[0029] FIG. 19A is a top view of a prior art skateboard truck
assembly with wheels mounted.
[0030] FIG. 19B is a detailed top view of a prior art skateboard
truck assembly with wheels mounted showing the need for two axle
washers to create the necessary separation between the outer
bearing race and face of the structural member.
[0031] FIG. 20A is a top view of the skateboard truck assembly with
wheels mounted.
[0032] FIG. 20B is a detailed top view of the skateboard truck
assembly with wheels mounted showing that the integral bearing
standoffs create the necessary separation between the outer bearing
race and face of the structural member.
DETAILED DESCRIPTION
[0033] The following description is presented to enable one of
ordinary skill in the art to make and use the present invention as
provided within the context of a particular application and its
requirements. Various modifications to the preferred embodiment
will, however, be apparent to one skilled in the art, and the
general principles defined herein may be applied to other
embodiments. Therefore, the present invention is not intended to be
limited to the particular embodiments shown and described herein,
but is to be accorded the widest scope consistent with the
principles and novel features herein disclosed.
[0034] The invention relates to a mechanism known in general terms
as a skateboard truck. A skateboard truck connects wheels to a
skateboard or longboard deck allowing articulation of the wheels
attached to the skateboard truck by application of the rider's
weight to one side of the deck (FIG. 8). Application of weight to
the edge of the skateboard deck allows the skateboard to be turned
as the articulation of the deck converts deck angle changes into
fore and aft movement of wheels attached to the skateboard truck.
The invention improves on prior art in multiple ways, including an
improved functional geometry, improved structural design, improved
constructability, improved maintainability, and improved durability
resulting in smoother and more responsive or immediate turning
performance.
[0035] The skateboard truck is comprised of two major assemblies,
the ball pivot hanger assembly and the baseplate assembly. The
assemblies are mechanically joined together and retained by a
kingpin washer, elastomeric bushings, and kingpin nut (FIG. 1).
[0036] The hanger assembly is comprised of the hanger body, axle,
axle washers and axle nuts. The body of the hanger incorporates a
structural member oriented along a lateral axis perpendicular to
and distal from the ball pivot. An axle made of a dissimilar
material passes through the beam section of the body parallel to
the beam. Alternatively, the axle may be made of two segments that
pass into but not through the beam. On each end of the axle or
axles there is an axle nut and axle nut washer. The ball pivot may
be an integral part of the hanger body or may be a separate
attached component. The ball pivot is formed so that it may rotate
in a similar sized pivot cup by at least about twenty degrees in
any direction without making contact with the pivot cup wall (FIG.
15). The ball pivot has a diameter that is preferably at least 13
mm in diameter. There is an aperture in the hanger assembly body
through which a kingpin passes that is located between the axle or
axles and the ball pivot. The aperture has two elastomeric bushing
seats that are concentric with the aperture and centerline of the
kingpin. The bushing seats are located above and below the aperture
(FIG. 3).
[0037] The baseplate assembly is comprised of a baseplate body,
pivot cup and a tapered kingpin (FIG. 36). The baseplate body has a
pivot cup cavity in its forward section into which a removable
friction fit pivot cup is installed. There are holes drilled into
both sides of the baseplate body that are used to provide a means
of attachment for the baseplate to the skateboard deck using
fasteners.
[0038] The pivot cup that is installed in the baseplate cavity bore
provides a load bearing surface for the hanger assembly ball pivot.
The pivot cup is designed to transmit loads from the ball pivot to
the side-walls of the baseplate pivot cup cavity. The outside
surface of cylindrical section of the pivot cup includes retention
fins or rings that provide for a friction fit allowing friction
based retention of the pivot cup in the pivot cup cavity. The
exterior bottom surface of the pivot cup is angled so that no
surface is more than fifty degrees off a line running through the
center of the pivot cup hole in the bottom of the pivot cup and the
center of the hanger-body bushing aperture. The bottom of the pivot
cup is more steeply angled than prior art to allow the cup to
compress down and toward the center of the pivot cup cavity in the
baseplate. The inside contours of the pivot cup include
self-cleaning groves that are designed to remove dirt or debris
from the ball pivot when the ball pivot rotates. In the center
bottom of the pivot cup there is a hole that provides a void for
the pivot cup to compress down and into the bottom of the baseplate
pivot cup cavity. The hole in the bottom of the pivot cup is also
is designed to collect debris as part of the pivot cup's
self-cleaning function and if threaded to provide for a means of
threaded mechanical extraction using a threaded shaft or the axle
of the hanger assembly.
[0039] There is a kingpin support structure on the rear of the
baseplate body that contains a tapered bore-hole into which the
tapered kingpin is installed. The kingpin is a separate component
that is inserted into the baseplate's tapered kingpin bore hole as
part of the overall baseplate assembly. The kingpin has a tapered
section proximate to the end of the kingpin where the head is
designed to prevent rotation. The section in the middle of the
kingpin where elastomeric bushings are later installed is of
constant diameter that is smaller than the maximum diameter of the
kingpin proximate to the head. The end of the kingpin distal from
the head of the kingpin has threads that engage a kingpin nut. The
kingpin relies on an enlarging taper proximate to the head of the
kingpin that matches the angle of taper found in the kingpin bore
hole for its mechanical connection to the baseplate. The taper
provides for kingpin retention and load transfer to the baseplate
through the sidewalls of the tapered kingpin bore hole. Rotation of
the tapered kingpin is prevented by trapping the head of the
kingpin on the side of the kingpin bore hole that is distal from
the side of the kingpin bore hole that is adjacent to the lower
elastomeric bushing bearing surface.
[0040] The ball pivot hanger assembly is installed in the baseplate
assembly by first placing the lower elastomeric bushing on the
kingpin in contact with the adjoining baseplate bearing surface.
The second step is to concurrently insert the ball pivot on the
hanger assembly into the baseplate pivot cup while lowering the
hanger assembly over the kingpin until the lower bushing seat on
the hanger assembly has fully engaged the lower elastomeric
bushing. Next, the upper elastomeric bushing is placed over the
kingpin and seated into the upper bushing seat of the ball pivot
hanger assembly. A bushing washer is placed on top of the upper
elastomeric bushing. Finally a kingpin nut is threaded onto the
kingpin resulting in compression of the bushing washer and the
elastomeric bushings. (FIG. 1).
[0041] When fully assembled, the hanger assembly is sandwiched on
both sides of the kingpin aperture by two elastomeric bushings, a
kingpin washer and kingpin nut in a manner that allows the rider to
adjust the level of pressure on the elastomeric bushings to
increase or decrease the level of force required to angle the
skateboard deck. The functional assembly traps the ball pivot on
the hanger assembly in intimate contact with the pivot cup in the
baseplate so that the ball pivot hanger assembly can rotate without
interference and transfer loads effectively into the side wall of
the baseplate as the mechanism is rotated from side to side (FIGS.
3, 38).
[0042] The drawings, with the exception of those labeled "prior
art," illustrate an embodiment of a skateboard truck 10 comprising
a ball pivot hanger 15, a baseplate assembly 115, a pivot cup 155,
a kingpin 210, bushings 242 and 245, and various fastening members,
including washers 250, 36 and nuts 255, 37.
[0043] Geometry
[0044] The skateboard truck 10 improves upon previous skateboard
truck designs by changing the geometry and design of one or more
key elements of the skateboard truck 10. Several of these
improvements contribute to a high level of mechanical advantage 295
and improved turning function. These improvements include a larger
diameter ball pivot 65, effective transfer of ball pivot loads 142
into the side of the pivot cup cavity 140, precision bushing seats
40, the physical form of the baseplate 115 and the hanger 15, and a
tapered kingpin 210. The improvements, whether considered singly or
more preferably in combination, improve riding performance,
mechanical function, durability, constructability and
maintainability. It should be understood that the invention
encompasses not only the synergistic combination of these various
improvements, but also sub-combinations and single ones of these
improvements.
[0045] Ball Pivot Hanger
[0046] FIGS. 2-4, 6 and 20 illustrate one embodiment of a ball
pivot hanger 15. The ball pivot hanger 15 comprises a structural
member 20, an integral axle 30 (or a pair of axles 30 mounted in
the ends of the beam 20), bushing seats 40, and a ball pivot 65.
The structural member 20 has a form determined by the principles of
a wide flange I-beam. Reliefs 28 strategically reduce the mass and
weight of the hanger 15 with minimum impact on the hanger's 15
strength. The structural member 20 is oriented to span the widest
direction of the hanger 15. The integral axle 30, or axles 30 if
separate axles are utilized, optionally made of a dissimilar
material, runs from one end of the beam 20 to the other protruding
so as to provide a mounting location for skateboard wheels 325.
[0047] The ball pivot hanger 15 includes two axle bearing spacing
steps or bosses 35 (e.g., machined features at opposite distal ends
of the structural member 20). Each boss 35 creates a separation 31
between the axle bearing surface 32 and the face 33 of the
structural member 20 within which the axle 30 is contained so as to
provide a bearing standoff that eliminates the need for an axle
washer 36 known as a speedring. The boss 35 supports the central
race 34 of the bearing and prevents the outer race 39 from making
contact with the adjoining structural member 20. Alternatively, the
structural member 20 that embraces the axle 30 (or pair of axles
30) includes two bearing standoffs 35 that separate a bearing
surface 32 of the structural member 20 from a non-bearing surface
of the face 33 of the structural member 20 that embraces the axle
30. The standoff may also be an additional component that is
attached to the structural member 20 or axle 30.
[0048] Concentric top and bottom bushing seats 40 extend outwardly
from a midsection of the structural member 20 and provide a zero
tolerance fit for elastomeric bushings 242, 245. An aperture 45
formed through the centers of the bushing seats 40 receives a
kingpin 210 to mount the hanger 15, sandwiched between the two
elastomeric bushings 242, 245 to the baseplate 115. An aperture 45
in the hanger 15 between the ball pivot 65 and the axle 30 allows a
kingpin 210 to pass through the hanger 15 to assemble the hanger 15
to the baseplate 115.
[0049] Ball pivot
[0050] FIG. 15 illustrates one embodiment of a ball pivot 65
incorporated into a hanger 15. The ball pivot 65 extends
perpendicularly out from the midsection of the structural member 20
and axle 30 and is, in one embodiment, preferably cast, forged, or
machined as an integral part of the hanger 15 (FIG. 6). The ball
pivot 65 located on the hanger 15 differs from other traditional
pin pivot or ball designs due to its much larger diameter 75,
preferably at least 13 mm, and resulting larger bearing surface.
The ball pivot's 65 larger surface area combined with the pivot cup
155 and baseplate 115 design allow for pivot loads 142 to be
transferred into the side wall 147 and tapered cavity walls 145 of
the baseplate pivot cup cavity 140 instead of the bottom of the
pivot cavity 140 as is typical with prior art (FIG. 16). The design
of the ball pivot 65 transfers turning load from the ball pivot 65
to the side wall 160 of the pivot cup 155 at a point much closer to
the kingpin 210 compared to the small diameter ball or pin pivots
85 of many other designs, that transfer load from the pivot 85 to
or near the bottom 102 of the pivot cup 103 through the end 95 of
the pivot 85 distal to the axle. The large diameter ball pivot
hanger 15, pivot cup design 155, tapered kingpin 210 and baseplate
115 design act synergistically to achieve improved turning
performance.
[0051] The ball pivot 65 provides unrestricted movement when
compared to prior art pin pivots 85 that are not designed to
accommodate significant unrestricted rotation on two planes as the
skateboard truck 320 is articulated. The ball pivot 65 provides
unrestricted turning action within at least about ten degrees from
a neutral center line 300 that passes through the center of
rotation 70 and a point 60 coincident with the center of the
kingpin aperture 45 and the longitudinal center 212 of the kingpin
210 (FIGS. 7, 13-14). Unrestricted turning action within the
non-interference area 80 (FIG. 15) is achieved due to an absence of
mechanical interference with the pivot cup side wall 160 or
progressive resistance from the compression of an elastomeric pivot
cup 100 as is common with prior art designs (FIG. 16). This
improvement also eliminates the stress and mechanical wear that
takes place with many conventional pin pivot 85 designs when they
make physical contact with the wall of the pivot cup or pivot cup
cavity. The ball pivot 65 on the hanger 15 in conjunction with the
pivot cup 155 is configured to provide constant low-friction
intimate contact between the pivot cup 155 and the ball pivot 65
allowing the ball pivot 65 to pass its loads through the sidewalls
160 of the pivot cup 155 and then directly into the side wall 160
of the baseplate pivot cup cavity 140.
[0052] Pivot Cup
[0053] FIGS. 9-12 illustrate one embodiment of a pivot cup 155. The
pivot cup 155 is installed in the baseplate pivot cup cavity 140.
The pivot cup 155 comprises an internal pivot-bearing surface area
165 defined by curved cylindrical interior sidewalls 160, a
cylindrical outer top surface 162, a ramped outer bottom surface
170, cleaning grooves or channels 180, retention fins or rings 195,
200, and a ramping tolerance fin 205. The pivot cup 155 is formed
with a bottom center hole or pocket 185 that is configured to avoid
contact with a bottom surface area portion 165 of the ball pivot 65
of at least approximately 0.6 steradians. This causes pivot loads
177 to be transferred into the side wall 147 of the baseplate pivot
cup cavity 140 instead of the bottom of the pivot cavity as is
typical with prior art (FIG. 16).
[0054] The pivot cup 155 provides a load bearing low friction
constant contact transfer surface between the ball pivot 65 and the
baseplate pivot cup cavity side wall 147. The pivot cup 115 may be
composed of nylon, POM (acetyl), PU (Polyurethane) or other
suitable low friction, bearing surface materials. The cylindrical
outer top surface 162 of the pivot cup 155 contains fins or rings
195, 200, 205 designed to compensate for dimensional tolerance
variations between the pivot cup 155 and the pivot cup cavity 140.
The fins 195 retain the pivot cup 155 in the pivot cup cavity 140
and prevent pivot cup 140 rotation. The pivot cup's outer bottom
surface 170 is angled to match the bottom portion 145 of the
baseplate pivot cup cavity 140 (FIG. 7). This angle provides a
ramping force toward the center of the pivot cup cavity 140 when
the pivot cup 155 is pressed into the cavity 140. The ramping force
is present when the truck 10 is in use and loads are applied via
the rider's weight through the ball pivot 65 on the hanger 15. The
ramping action is designed to center and compress the pivot cup 155
in the baseplate pivot cup cavity 140.
[0055] The interior sidewalls 160 of the pivot cup 155 contain
grooves or channels 180 designed to provide a self-cleaning action
relative to the surface of the ball pivot 65 as it rotates in the
pivot cup 155 (FIG. 10, 11). The pivot cup 155 contains a hole 185
in its center so that as the pivot cup 155 is driven into the pivot
cup cavity 140 by the ramping action it can compress without
interference inward toward the center of the pivot cup cavity 140,
ensuring intimate contact between the internal pivot-bearing
surface area 165 of the pivot cup 155 and the ball pivot 65. The
center hole 185 in the bottom of the pivot cup 155 also serves to
provide self-cleaning, debris retention and threaded mechanical
extraction functions. The pivot cup's center hole 185 may be
threaded, allowing mechanical extraction of the pivot cup 165 from
the pivot cup cavity 140 using a threaded rod or hanger axle 30
(FIG. 4). Prior art pivot cups are made of soft elastomeric
material and do not incorporate self-cleaning, self-centering,
tolerance absorbing components, a provision for mechanical removal
using threaded tools, or steep ramping surfaces
[0056] Baseplate
[0057] FIGS. 5, 7 and 17 illustrate one embodiment of a baseplate
115. The baseplate 115 comprises a flanged base 116, a kingpin
support structure 224, and a pivot cup cavity bore 140. The pivot
cup cavity bore 140, located at a forward section of the baseplate
115, is drilled at angle parallel to the primary or first axis 300
of rotation of the hanger 15. The top portion 147 of the pivot cup
bore 140 is defined by cylindrically shaped walls. The bottom
portion 145 of the pivot cup bore 140 is defined by conically
shaped tapered cavity walls angled no more than fifty degrees off
of the primary rotational axis 300. Accordingly, the opening angle
149 formed by the tapered cavity walls is no greater than one
hundred degrees. The steep tapering of the cavity walls use the
force from the rider's weight that is applied via the ball pivot 65
to drive the pivot cup 155 into the angled bottom portion 145 of
the pivot cup cavity bore 140. The ramped outer bottom surface 170
of the pivot cup 140 is configured with angles that match the angle
of the bottom portion 145 of the pivot cavity bore 140 and allows
for pivot cup compression into the pivot cup cavity bore 140.
Compression of the pivot cup 155 aids in preserving the constant
center of rotation 70 allowed for by the ball pivot 65.
[0058] Also unlike prior art, on the rear section of the baseplate
115 there is a section of the body through which a tapered borehole
211 provides a support structure for the tapered kingpin 210. The
diameter 214 of the kingpin bore 211 hole proximate to the bolt
head 215 is larger than the bore diameter 213 distal to the bolt
head 215 (FIG. 17). The lower section 222 of the kingpin support
structure 224 includes a channel 218 that is used to prevent
rotation of the kingpin's head 215 when the kingpin nut 255 is
tightened to adjust bushing 242, 245 tension. The upper section 223
of the kingpin bore hole 211 is designed to function as a seat for
the lower elastomeric bushing 242. The flanges 116 of the base
extend along both sides of the baseplate 115. The flanges 116
contain holes 117 that provide a means to use fasteners to attach
the baseplate 115 to the skateboard deck 330 (FIG. 5, 7, 17).
[0059] Kingpin
[0060] FIGS. 3, 7, and 13-14 illustrate one embodiment of a tapered
kingpin assembly 207. The tapered kingpin assembly 207 comprises a
tapered kingpin 210, a kingpin bushing washer 250, two elastic
bushings 242, 245, and a nut 255. The tapered kingpin 210, which
comprises a head 215 connected to a shaft 220, is used to connect
the hanger 15 to the baseplate 115. The tapered kingpin 210 is
removable with no damage to the baseplate assembly 115 and achieves
a zero clearance fit when tightened into a matching tapered
baseplate kingpin borehole 211. When tightened by the compression
of the kingpin nut 255 against the kingpin bushing washer 250 and
two elastomeric bushings 242, 245, the kingpin 210 acts as a rigid
and integral component of the baseplate 115. This increased
rigidity of the baseplate 115 and kingpin assembly 207 results in
improved turning performance by eliminating rocking or working of
the kingpin 210 back and forth in a traditional kingpin
borehole.
[0061] Prior art includes two primary styles of kingpins. Kingpins
that were intended to be removable were based on a simple bolt
design with dimensional tolerances that resulted in movement of the
kingpin from side to side in the kingpin baseplate bore hole as the
truck was subjected to turning actions. Alternatively kingpins used
in some prior art skateboard trucks incorporated barbed or splined
driven bolts that were driven into the kingpin borehole. The
splined or barbed bolt design was not easily removable and the
process of removal and reinstallation would frequently result in
damage to the kingpin bore hole that would further allow the
kingpin to work back and forth as the deck angle was changed. Both
the traditional bolt and barbed or splined prior art kingpin
designs resulted in degraded truck performance, constructability
and or maintainability.
[0062] The kingpin shaft 220 includes a middle tapered section 225.
The remaining one or more sections of the shaft including the
threaded end 240 and the constant diameter, are untapered. The
tapered portion 225 of the kingpin 210 is located along a portion
of the shaft that, when assembled, makes contact with the tapered
baseplate borehole 211. The tapered portion 225 of the kingpin 210
is distal from the threaded end 240 of the kingpin 210 and
proximate to the polygonal head 215. The diameter 230 of the
kingpin 210 gets progressively smaller as one travels the length of
the tapered section 225 of the shaft 220 from the top end of the
tapered section 225, proximate to the polygonal head 215, toward
the bottom end of the tapered section 225, relatively more
proximate to the bolt threads 240. The diameter 227 of the kingpin
210 is constant in the un-tapered sections 227 of the shaft 220
which are not designed to engage the baseplate tapered borehole
211, including locations where the kingpin 210 passes through the
elastomeric bushings 242, 245 (FIG. 7, 13, 14).
[0063] The tapered kingpin 210 can be inserted into the tapered
baseplate bore hole 211 until the increasing diameter of tapered
kingpin 210 exceeds the matching maximum tapered borehole diameter
213, 214. The kingpin 210 seats in the tapered borehole 211 with an
intimate, zero clearance fit because the kingpin 210 always tapers
to a diameter 230 larger than the largest tapered kingpin bore
diameter 213 in the baseplate 115. The tapered shaft 225 of the
kingpin 210 is designed retain the kingpin 210 with the head 215 of
the kingpin 210 slightly out of contact with the side of the
tapered baseplate borehole 130 that is opposite from the side 241
where the elastomeric bushings 242, 245 seat (FIG. 7, 17, 13,
14).
[0064] The tapered kingpin 210 and tapered kingpin bore hole 211
provide a precision zero clearance kingpin fit in the baseplate
kingpin tapered bore hole 211 while allowing for easy removal
without damage to the kingpin 210 or kingpin borehole 211. Because
the kingpin 210 is in intimate contact with the tapered sidewalls
226 of the baseplate 115, the baseplate 115 and kingpin 210 act as
one unit transmitting forces precisely and immediately from the
changing deck angle 318 into the truck assembly 10 (FIG. 7, 17, 13,
14).
[0065] Center of Rotation
[0066] The location of the center of rotation 70 of the ball pivot
65 (FIG. 6) is different from prior art. The center of rotation 70
of the ball pivot 65 (FIG. 6), and the center of rotation 95 of a
conventional prior art pin pivot 85, are both herein defined as a
point within or upon the surface of the pivot 65, 80 that
translates the least, with respect to the baseplate, as the pivot
65, 80 rotates within a similarly sized pivot cup 155. The larger
diameter ball pivot 65 combined with the pivot cup 155 and
baseplate 115 designs move the center of rotation 70 closer to the
center of the kingpin aperture than is found in prior art designs.
The center of rotation 70 is in the geometric center of the ball
pivot 65. Prior art designs have pin or ball pivots that are
typically less than 13 mm in diameter. The center of rotation 95
for prior art pin or ball pivots is the center of the pivot radius
proximate to the end of the pivot. Due to the small pivot diameter
and the use flexible low-durometer pivot cups (e.g., below 95a
durometer), these prior art designs transfer load thru the end of
the pivot by bearing on the bottom of pivot cup. In most cases the
use of a small diameter pivot and an elastomeric pivot cup does not
provide for a constant center rotation (FIG. 6, 15, 16).
[0067] Center of Pressure
[0068] The center of pressure 83 (FIG. 6) for the ball pivot 65 is
the location on the ball pivot's face central to where the greatest
load is transmitted through the walls of the pivot cup 155. As a
result of moving the center of rotation 70 of the ball pivot 65
back to a point equidistant from all sides of the ball pivot's 65
rotating sphere, the center of pressure 83 also moves back and to
the side of the ball pivot 65 relative to traditional pin pivot or
ball pivot designs 65. When turning the truck 10, the center of
pressure 83 is applied against the side 147 of the pivot cup cavity
140 at a point that is significantly distal from the bottom of the
pivot cup cavity 140. The center of pressure for prior art pin or
ball pivots, by contrast, is concentrated proximate to the bottom
of the pivot cup cavity.
[0069] Angle of Mechanical Advantage
[0070] Various aspects of the invention contribute to the truck's
high and consistent mechanical advantage 295 in translating and
amplifying the force a rider exerts on the deck into a force that
turns the truck (FIG. 6). One influential contribution to the
truck's mechanical advantage is the angle 295 between two lines,
referred to herein as the "angle of mechanical advantage." The
first line is the primary rotational axis 300 that runs between the
center 60 of the kingpin aperture 45 and the ball pivot's constant
center of rotation 70 (FIG. 7). The second line 297 runs between an
outermost contact point 298 of the ball pivot 65 with the pivot cup
155 and the opposing outermost bearing surface 299 of the bushing
seat 40 that retains the elastomeric bushing 242, 245 laterally in
the hanger 15. Stated another way, the angle of mechanical
advantage 295 is approximately equal to an inverse tangent of the
sum of the ball pivot radius and the kingpin bushing radius divided
by the ball-pivot-center-to-kingpin-center distance. A higher angle
of mechanical advantage 295, one that is, for example, at least
twenty and preferably at least twenty-five degrees, significantly
improves the rider's ability to compress the elastomeric bushings
242, 245 and magnifies the turning action of the truck 10 when
compared with prior art designs. Additionally, the higher level of
mechanical advantage 295 allows the truck 10 to rotate on two
planes concurrently.
[0071] The proximity between the center of rotation 70 of the ball
pivot 65 and the center 60 of the kingpin aperture 45, the diameter
75 of the ball pivot 65, the diameter 41 of the bushing seat 40,
and the lack of movement achieved by the tapered kingpin 210 all
combine to influence the angle of mechanical advantage 295 and the
overall effective leverage the rider achieves against the
elastomeric bushings 242, 245. A high mechanical advantage 295
without pivot cup 155 restriction also facilitates a more dynamic
turning response characteristic.
[0072] King Pin Ratio
[0073] Another contribution to the truck's mechanical advantage is
the kingpin ratio (FIG. 6). The kingpin ratio 290 is defined by the
distance 291 between the kingpin aperture center 60 and
longitudinal axle centerline 270 divided by the distance 292
between the ball pivot center 70, or the constant center of
rotation 70 and the kingpin aperture center 60. The hanger 15 has a
kingpin ratio 291, expressed as a percentage, of fifty-two percent
or more. A higher percentage kingpin ratio, in addition to a high
angle of mechanical advantage, contributes to the truck's greater
mechanical advantage relative to prior art designs.
[0074] Concurrent Rotation on Two Axis
[0075] The ball pivot hanger 15 rotates concurrently around two
axes 300, 305 (FIG. 7). The first axis 300 is between the constant
center of rotation 70 of the ball pivot 65 and the kingpin aperture
center 60. The second axis 305 is parallel to the longitudinal
centerline 212 of the kingpin 210 and runs thru the constant center
of rotation 70 of the ball pivot 65. This second axis 305 allows
the hanger 15 to shift from side to side relative to the kingpin
210 while concurrently rotating relative to the first axis 300 with
no pivot cup 155 or pivot cup cavity interference 140. To rotate
around the second axis 305, the bushings 242, 245 must be
compressed parallel to the kingpin bore hole 211 and the hanger
bushing seat retention wall 43. Any change in deck angle results in
both a vertical compression and horizontal compression of the
bushings relative to the kingpin (FIG. 7).
[0076] Riding benefit of Design
[0077] All of the forces that compress the bushings 242, 245 and
result in the articulation of the hanger 15 are from the rider's
weight. All of the rider's weight is supported by the four wheels
325 mounted on the two axles 30. A larger distance 291 between the
axle 30 and kingpin aperture center 210 in relation to the distance
292 from the kingpin aperture center 210 to the constant center of
rotation 70 results in greater mechanical advantage. A greater
mechanical advantage results in more leverage acting on the
bushings 242, 245. With more leverage on the bushings 242, 245, the
rider is able to more effectively rotate the hanger 15 around the
first 300 and the second axes 305. Because of this increased
mechanical advantage 295, the lack of pivot interference with the
pivot cup 155 or baseplate pivot cup cavity 140, and the ability to
rotate the hanger 15 concurrently around two axes 300, 305,
immediate articulation is achieved resulting in improved turning
performance.
[0078] Although the present invention has been described in
considerable detail with reference to certain preferred versions
thereof, other versions and variations are possible and
contemplated. Those skilled in the art should appreciate that they
can readily use the disclosed conception and specific embodiments
as a basis for designing or modifying other structures for carrying
out the same purposes of the present invention without departing
from the spirit and scope of the invention as defined by the
appended claims.
* * * * *