U.S. patent application number 10/332719 was filed with the patent office on 2003-11-06 for track assembly.
Invention is credited to Smith, Rodger G..
Application Number | 20030206669 10/332719 |
Document ID | / |
Family ID | 29271983 |
Filed Date | 2003-11-06 |
United States Patent
Application |
20030206669 |
Kind Code |
A1 |
Smith, Rodger G. |
November 6, 2003 |
Track assembly
Abstract
A track assembly (10) comprises a seat track member (12) that in
use is secured to the base of a vehicle seat, slidably engaged with
a floor track member (14) that in use is secured to the floor of a
vehicle. At least one bearing assembly (16) is form fittingly
retained between engaging portions of the track members (12, 14) so
as to facilitate sliding movement of the seat track member (12)
along the length of the floor track member (14).The or each bearing
assembly (16) comprises an elongate spacer (52) provided with a
steel ball (54) at either of its ends. At least one plastic ball
(56) is provided in a side by side arrangement with each of the
steel balls (54) such that a steel ball (54) is located between
each plastic ball (56) and the spacer (52). In preferred
embodiments, two plastic balls (56, 58) are provided in a side by
side arrangement with each steel ball (54). The use of plastic
balls in the or each bearing assembly (16) reduces the formation of
indentations in the track members (12, 14).
Inventors: |
Smith, Rodger G.;
(Shropshire, GB) |
Correspondence
Address: |
FOLEY & LARDNER
777 EAST WISCONSIN AVENUE
SUITE 3800
MILWAUKEE
WI
53202-5308
US
|
Family ID: |
29271983 |
Appl. No.: |
10/332719 |
Filed: |
January 13, 2003 |
PCT Filed: |
July 13, 2001 |
PCT NO: |
PCT/US01/22215 |
Current U.S.
Class: |
384/47 |
Current CPC
Class: |
B60N 2/0715 20130101;
B60N 2/0818 20130101; B60N 2/0875 20130101; B60N 2/071
20130101 |
Class at
Publication: |
384/47 |
International
Class: |
A47C 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 13, 2000 |
GB |
0017111.6 |
Claims
1. A track assembly suitable for slidably mounting a seat to the
floor of a vehicle, comprising: a first track member, slidably
connected to a second track member; and at least one bearing
assembly retained between the first and second track members to
facilitate sliding movement of the first track member along the
length of the second track member; the or each bearing assembly
including first and second groups of ball bearings separated by an
elongate spacer extending in the longitudinal direction of the
tracks, each group of ball bearings including a rigid ball formed
from a rigid material and a resilient ball formed from a resilient
material, the rigid ball being located between the resilient ball,
and the respective end of the elongate spacer.
2. A track assembly suitable for slidably mounting a seat to the
floor of a vehicle, comprising: a first track member, slidably
connected to a second track member; and at least one bearing
assembly retained between the first and second track members to
facilitate sliding movement of the first track member along the
length of the second track member; the or each bearing assembly
including first and second groups of ball bearings separated by an
elongate spacer extending in the longitudinal direction of the
tracks, each group of ball bearings including at least two
different types of ball, wherein the compressibility of each of the
different types of ball is such that the ball bearings burnish the
track members and brinnelling of the track members is
prevented.
3. A track assembly, as claimed in claim 1 or claim 2, wherein the
or each bearing assembly comprises an elongate spacer and, at
either end of the spacer, two resilient balls and a rigid ball in a
side by side arrangement, the rigid ball being located between the
resilient balls and the respective end of the elongate spacer.
4. A track assembly, as claimed in any preceding claim, wherein
each of the rigid and resilient balls have the same diameter as
each other.
5. A track assembly, as claimed in any preceding claim, wherein the
resilient material is an acetal resin.
6. A track assembly as claimed in any of claims 1 to 4, wherein the
resilient material is a polyamide-amide engineering resin or a
polyamide-imide engineering resin.
7. A track assembly, as claimed in any preceding claim, wherein the
rigid material is steel.
8. A track assembly, as claimed in any preceding claim, wherein the
elongate spacer is an elongate cylindrical member having a diameter
relatively smaller than the diameter of said balls.
9. A track assembly, as claimed in any preceding claim, wherein the
elongate spacer is formed from a plastics material.
10. A track assembly, as claimed in any of claims 1 to 8, wherein
the elongate spacer is formed from metal.
11. A track assembly generally as herein described with reference
to and/or as illustrated in the accompanying drawings.
Description
[0001] The invention relates to a track assembly suitable for
slidably mounting a seat on the floor of a vehicle.
[0002] Vehicle seats are commonly mounted on the floor of a vehicle
by engagement between a seat track member secured to the base of
the seat and a floor track member secured to the floor of the
vehicle.
[0003] To facilitate sliding movement of the seat track member
along the length of the floor track member, it is known to provide
bearing assemblies, such as the bearing assembly 1 shown in FIG. 1,
form fittingly retained between engaging portions of the two track
members. The bearing assembly 1 effectively reduces friction
between the relevant engaging portions of the two track members,
and comprises a first steel ball 2, a spacer 3 and second and third
steel balls 4,5 in a side by side configuration, that in use
extends along the length of the two track members.
[0004] When a force is applied to a vehicle seat mounted in this
way, in order to move the seat in either direction along the length
of the floor track member, the vehicle seat transmits the force to
the bearing assemblies 1. The majority of the force is transmitted
to either the first steel balls 2, or the second and third steel
balls 4,5, depending on the direction in which the force is applied
to the seat, i.e. the desired direction of movement of the seat in
respect to the floor track member. The force causes the particular
steel balls to rotate and move in the general direction of the
force. This effectively reduces friction between the two track
members, and allows the seat track member to slide along the length
of the floor track member in the direction of movement of the
relevant steel balls.
[0005] There is a disadvantage associated with using steel balls
however. When a force is applied to the seat, it causes the seat to
tip slightly in the direction of the force. Thus the force
transmitted from the vehicle seat to the steel balls includes a
first component generally perpendicular to the length of the track
members (herein referred to as the first component), as well as a
second component generally parallel to the length of the track
members (herein referred to as the second component). The first
component of the force causes the steel balls to form indentations
in the track members. Over the lifetime of a track assembly, the
formation of such indentations, known as brinnelling, has an
adverse effect on the movement of the seat track member along the
length of the floor track member. The movement becomes bumpy and
jerky due to the indentations, and this is particularly noticeable
in vehicles in which the seats are moved frequently e.g. taxis and
police cars.
[0006] An alternative to using steel balls in the bearing assembly
is the use of balls that are made from a plastics material. Plastic
balls have a certain degree of resilience, and so when the first
component of a force is transmitted from the seat to the bearing
assembly, they are much less likely to form indentations in the
track members.
[0007] However, there are several disadvantages to using plastic
balls in such assemblies, one being plastic balls do not withstand
the same loads as steel balls.
[0008] Also, track members in such track assemblies are usually
painted. Movement of steel balls between these track members causes
burnishing of portions of the track members between which the
bearing assemblies are form fittingly retained. Such burnishing
involves removal of paint from the respective portions of the
tracks, polishing these portions and increasing the overall
clearance between the two track members. Plastic balls do not
perform this burnishing action and so tend to slide between the
track members, so forming flat edges. These flat edges eventually
prevent any rolling movement of the plastic balls, and have a
detrimental effect on the movement of a seat track member along the
length of a floor track member in a track assembly.
[0009] According to a first aspect of the invention there is
provided a track assembly suitable for slidably mounting a seat to
the floor of a vehicle, comprising:
[0010] a first track member, slidably connected to a second track
member; and
[0011] at least one bearing assembly retained between the first and
second track members to facilitate sliding movement of the first
track member along the length of the second track member;
[0012] the or each bearing assembly including first and second
groups of ball bearings separated by an elongate spacer extending
in the longitudinal direction of the tracks, each group of ball
bearings including a rigid ball formed from a rigid material and a
resilient ball formed from a resilient material, the rigid ball
being located between the resilient ball, and the respective end of
the elongate spacer.
[0013] This track assembly is advantageous because it includes both
rigid and resilient balls. The rigid balls burnish relevant
portions of the first and second track members between which the or
each, bearing assembly is retained. The provision of at least one
resilient ball in the or each bearing assembly, at a position
further away from the elongate spacer than the rigid ball, means
that a relatively larger proportion of the first component of a
force transmitted to the bearing assembly will be transmitted to
the resilient ball, or balls, than to the rigid ball. Thus
brinnelling of the track members is reduced.
[0014] According to a second aspect of the invention there is
provided a track assembly suitable for slidably mounting a seat to
the floor of a vehicle, comprising:
[0015] a first track member, slidably connected to a second track
member; and
[0016] at least one bearing assembly retained between the first and
second track members to facilitate sliding movement of the first
track member along the length of the second track member;
[0017] the or each bearing assembly including first and second
groups of ball bearings separated by an elongate spacer extending
in the longitudinal direction of the tracks, each group of ball
bearings including at least two different types of ball, wherein
the compressibility of each of the different types of ball is such
that the ball bearings burnish the track members and brinnelling of
the track members is prevented.
[0018] In a particularly preferred embodiment of the invention, the
or each bearing assembly comprises an elongate spacer, and at
either end of the spacer, two resilient balls and a rigid ball in a
side by side configuration, the rigid ball being located between
the resilient balls and the respective end of the spacer.
[0019] This particular configuration is advantageous over an
assembly including a single resilient ball at either end of the
bearing assembly. This is because a majority of the first component
of a force transmitted to the bearing assembly will be spread over
three balls at one end of the spacer, rather than two. Furthermore,
the largest proportion of this component of the force will be
transmitted to the resilient ball located furthest away from the
spacer. This means that the size of the proportion of the first
component of the force that is transmitted to the relevant rigid
ball will be less than the proportion that is transmitted when only
one resilient ball is provided in a side by side configuration with
the rigid ball. Thus, brinnelling of the track member is further
reduced.
[0020] The elongate spacer acts to space apart each set of
resilient and rigid balls located at either of its ends, preventing
them from grouping together. This allows the first track member to
move in either direction along the length of the second track
member. If the elongate spacer were removed, and the two sets of
balls grouped themselves together, then movement of the first track
member in one particular direction along the length of the second
track member may be prevented.
[0021] The resilient and rigid balls used in the or each bearing
assembly may have the same diameter as each other.
[0022] In other embodiments of the invention, the resilient balls
used in the or each bearing assembly may have a relatively larger
diameter than the rigid balls used in the or each bearing assembly.
The relative difference in size of the resilient and rigid balls
may compensate for compression of the resilient balls in use.
[0023] In preferred embodiments of the invention, the material from
which the resilient balls are made is sufficient to absorb downward
forces during movement of the seat, in order to avoid indentation
of the track. However, the resilient material is also rigid enough
to maintain a generally spherical shape to facilitate rolling.
[0024] In such embodiments, the resilient material may be an acetal
resin such as Dein (RTM), or a polyamide-amide resin or
polyamide-imide resin such as Torlon (RTM).
[0025] The rigid material may be steel.
[0026] The elongate spacer in the or each bearing assembly may be
an elongate cylindrical member having a diameter relatively smaller
than the diameter of each of the resilient and rigid balls. The
elongate spacer may be formed from metal or from a plastics
material.
[0027] It is particularly advantageous to use a spacer member
formed from a plastics material because sliding movement of a
plastic spacer between the relevant engaging portions of two track
members produces less noise than a metal spacer member. Car
manufacturers are particularly keen to reduce any type of noise
within their vehicles.
[0028] In preferred embodiments of the invention, the elongate
spacer member is between 12.7 cm and 15.2 cm (5 in and 6 in) in
length.
[0029] An embodiment of the invention will now be described, by way
of a non-limiting example, with reference to the accompanying
figures in which:
[0030] FIG. 1 is a plan view of a bearing assembly used in a prior
art track assembly;
[0031] FIG. 2 is a simplified representation of a track assembly in
accordance with an embodiment of the invention;
[0032] FIG. 3 is a detailed representation of the track assembly of
FIG. 2;
[0033] FIG. 4 is a plan view of the bearing assembly used in the
track assembly of FIGS. 2 and 3;
[0034] FIG. 5 is a simplified representation of the track assembly
of FIG. 2 when a force is applied to the track assembly in a first
direction parallel to the length of the track assembly; and
[0035] FIG. 6 is a simplified representation of the track assembly
of FIG. 2 when a force is applied to the track assembly in a second
direction, parallel to the length of the track assembly and
opposite in direction to the first direction.
[0036] A simplified representation of a track assembly 10 according
to an embodiment of the invention is shown in FIG. 2. The track
assembly 10 comprises a first elongate track member 12 that in use
is secured to the base of a vehicle seat (not shown) slidably
engaged with a second elongate track member 14 that in use is
secured to the floor of a vehicle (not shown).
[0037] In order to facilitate sliding movement of the first
elongate track member 12 along the length of the second elongate
track member 14, a bearing assembly 16 is form fittingly retained
between engaging portions of the two track members 12,14 along
opposing sides of the track assembly 10.
[0038] A detailed representation showing the engagement between the
first and second track members 12,14 is shown in FIG. 3.
[0039] The first track member 12 is formed from two limbs 18,20
that are secured together proximate to the seat. The free ends of
the limbs 18,20 remote from the seat, are shaped to form an
inverted U-shaped cross-sectional engaging portion 22.
[0040] The second track member 14 is generally U-shaped in
cross-section, and includes lip portions 24,26 that curve inwardly
towards the hollow interior of the second track member 14.
[0041] Rollers 28 are provided on the floor 30 of the second track
member 14 so that when the first track member 12 is slidably
engaged within the hollow interior of the second track member 14,
the engaging portion 22 rests over the rollers 28.
[0042] The side walls 32,34 of the engaging portion 22 of the first
track member 12 each include a curved portion 36 towards their free
ends.
[0043] The side walls 38,40 of the second track member 14 each
include a correspondingly curved portion 42. When the first and
second track members 12,14 are slidably engaged, the relative
positions of the curved portions 36,42 are such that they align to
define two channels 44,46 of circular cross-section extending along
opposing sides of the track assembly 10.
[0044] A bearing assembly 16 is form fittingly retained on each
opposing side of the track assembly 10, within he relevant channel
44,46.
[0045] The first track member 12 also includes two upwardly
extending retaining limbs 48,50. The retaining limbs 48,50 engage
within the curved lip portions 24,26 of the second track member 14.
This engagement prevents movement of the first track member 12,
relative to the first track member 14, in a direction perpendicular
to the length of the track assembly 10. It thus ensures that the
curved portions 36,42 remain in alignment with each other so that
the cross-sectional shape of each of the channels 44,46 does not
become distorted.
[0046] The bearing assemblies 16 are prevented from escaping from
the relevant channels 44,46 at either end of the track assembly 10,
by ball retention dimples 49 provided in the curved portion 42 of
each of the side walls 38,40 of the second track member 14.
[0047] FIG. 3 shows ball retention dimples 49 provided in the
second track member 14 at one end of the track assembly 10. The
ball retention dimples 49 are provided in a similar manner at the
other end of the second track member 14 in the track assembly
10.
[0048] The bearing assemblies 16 and the channels 44,46 may be
lubricated with grease.
[0049] The bearing assembly 16, shown generally in FIG. 2, and also
referred to in FIG. 3, is shown in more detail in FIG. 4. The
bearing assembly 16 according to this embodiment of the invention
includes an elongate spacer 52 provided at either end with a steel
ball 54. First and second resilient balls 56,58 formed from an
acetal resin such as, for example, Delrin (RTM) or a
polyamide-amide resin or a polyamide-imide resin such as, for
example, Torlon (RTM), are provided in a side by side arrangement
with the steel ball 54, at either end of the spacer 52, so that
each steel ball 54 is located between the spacer 52 and the first
and second resilient balls 56,58.
[0050] When a force F is applied to the seat to which the first
track member 12 is attached, in a direction generally parallel to
the length of the track assembly 10, as shown in FIG. 5, the
resultant turning moment causes the seat to tip slightly in the
direction of the force F. This means that a first component F.sub.1
of the force F, generally perpendicular in direction to the length
of the track assembly 10, as well as a second component F.sub.2 of
the force F, generally parallel in direction to the length of the
track assembly 10, is transmitted to the bearing assemblies 16 in
the channels 44,46.
[0051] A large proportion of the first component F.sub.1 is
transmitted to the first resilient balls 58 of the bearing
assemblies 16, each positioned furthest away from the relevant
spacer 52, in the general direction of the force F. A smaller
proportion of the first component F.sub.1 is transmitted to the
second resilient balls 56, each positioned between the relevant
first resilient ball 58 and the relevant spacer 52. An even smaller
proportion of the first component F.sub.1 is transmitted to the
steel balls 54, each positioned between the relevant second
resilient ball 56 and the relevant spacer 52.
[0052] The resilience of the first and second resilient balls 56,58
means that the proportion of the first component F.sub.1 of the
force F transmitted to these balls 56,58 does not cause
indentations to be formed in the first and second track members
12,14. The relative position of the steel balls 54 means that the
indentation effect of the proportion of the first component F.sub.1
of the force F transmitted to the steel balls 54 is greatly reduced
than if only one or two steel balls had been used in each of the
bearing assemblies 16.
[0053] The second component F.sub.2 of the force F is also
transmitted to the resilient and steel balls 54,56,58 causing them
to turn and move in a direction generally parallel to the direction
of the force F. This in turn allows the first track member 12 to
slide along the second track member 14 in the direction of the
force F.
[0054] When a force F is applied to a seat, to which the first
track member 12 is secured, in an opposite direction, as shown in
FIG. 5, then the first and second components F.sub.1,F.sub.2 of the
force F are transmitted to the steel and resilient balls 54,56,58
at the opposite end of each of the spacers 52 in a similar
manner.
* * * * *