U.S. patent number RE34,142 [Application Number 07/804,440] was granted by the patent office on 1992-12-15 for pivotable screw jack drive.
This patent grant is currently assigned to Britax Rainsfords Pty. Ltd.. Invention is credited to Garry G. L. Fimeri.
United States Patent |
RE34,142 |
Fimeri |
December 15, 1992 |
Pivotable screw jack drive
Abstract
A pivotable screw jack drive for a tiltable element (11,12) such
as a rear view mirror of a motor vehicle, wherein a motor driven
worm wheel (31) also performs the function of a jacking nut (29)
which rotates about a jacking screw (35), the projecting end (41)
of the jacking screw being connected to the tiltable element
(11,12) for universal pivotal movement but being restrained against
relative rotation, the jacking nut (29) being mounted in a housing
(22) with a ball joint so that the nut and screw pivot as an
assembly.
Inventors: |
Fimeri; Garry G. L. (Morphett
Vale, AU) |
Assignee: |
Britax Rainsfords Pty. Ltd.
(Adelaide, AU)
|
Family
ID: |
25643211 |
Appl.
No.: |
07/804,440 |
Filed: |
December 10, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
130265 |
Dec 8, 1987 |
04881418 |
Nov 21, 1989 |
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Foreign Application Priority Data
Current U.S.
Class: |
74/89.14;
359/874; 359/877; 74/425; 74/479.01; 74/89.24 |
Current CPC
Class: |
B60R
1/072 (20130101); F16H 25/2009 (20130101); Y10T
74/19828 (20150115); Y10T 74/18792 (20150115); Y10T
74/18584 (20150115); Y10T 74/20207 (20150115) |
Current International
Class: |
B60R
1/072 (20060101); B60R 1/062 (20060101); F16H
25/20 (20060101); F16H 025/20 (); G02B 007/18 ();
G05G 011/00 () |
Field of
Search: |
;74/89.14,89.15,425,424.8R,479 ;359/874,877 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Herrmann; Allan D.
Attorney, Agent or Firm: Klauber & Jackson
Claims
I claim:
1. In combination with a tiltable element, a pivotable screw jack
drive for tilting control of the element, comprising:
a housing, a .Iadd.static .Iaddend.jacking nut bearing surface of
concave part-spherical shape in a wall of the housing,
a single piece jacking nut having an outer surface which is a
complementary convex part-spherical shape .[.against which said
jacking nut surface bears.]., .Iadd.the outer surface having a
center of curvature and bearing against the static surface,
.Iaddend.an inner threaded surface, and a series of gear teeth
spaced around its periphery defining a worm wheel, .Iadd.said
center of curvature lying in a plane which includes a pitch circle
of the gear teeth, .Iaddend.
a motor assembly within the housing having an output shaft, a drive
worm on the output shaft, said drive worm having threads in direct
meshing contact with the gear teeth of the worm wheel to drive the
worm wheel,
a jacking screw having a first end with a threaded male portion
which is threadably engaged in direct mating control with said
inner threaded surface of the jacking nut, and a second end which
engages said .Iadd.tiltable .Iaddend.element for relative pivotal
movement about an axis which is .[.perpendicular.]. .Iadd.angled
with respect .Iaddend.to the axis of the screw, and
restraining means for restraining the screw from rotation,
the arrangement being such that, upon motor rotation, the nut
extends or retracts the jacking screw and effects tilting of the
element.
2. A pivotable screw jack according to claim 1 wherein the envelope
shape of the worm wheel is cylindrical.
3. A pivotable screw jack according to claim 1 wherein said
restraining portion of said second end of the jacking screw
comprises a restraining spigot which so engages a complementary
surface of a slot in the .Iadd.tiltable .Iaddend.element as to
restrain the screw from rotation.
4. A pivotable screw jack according to claim 1 wherein said jacking
screw second end also comprises a part spherical surface, and said
.Iadd.tiltable .Iaddend.element contains a part spherical socket
complementary to and engaged by .[.said screw part spherical
surface.]. .Iadd.the part-spherical surface of the jacking
screw.Iaddend..
5. A pivotable screw jack according to claim 1 wherein said jacking
screw first end is bifurcate, .[.having.]. .Iadd.has .Iaddend.two
limbs each with outer curved .[.thread.]. .Iadd.threaded
.Iaddend.surfaces which threadably engage said inner threaded
surface of the jacking nut, and a "U"-shaped spring between said
limbs urging their threaded surfaces into that engagement.
6. A pivotable screw jack according to claim 1 wherein said
tiltable element comprises a backing plate of a rear vision mirror
for a motor vehicle.
7. In combination with a tiltable element, a pivotable screw jack
drive for tilting control of the element, comprising:
a housing, a .Iadd.static housing, a .Iaddend.jacking nut bearing
surface of concave part-spherical shape in a wall of the
housing,
a .Iadd.single piece .Iaddend.jacking nut having an outer surface
which is a complementary convex part-spherical shape .[.against
which said jacking nut surface bears.]., .Iadd.the outer surface
having a center of curvature and bearing against said static
bearing surface, .Iaddend.an inner threaded surface, and a series
of gear teeth spaced around its periphery.Iadd., said gear teeth
.Iaddend.defining a worm wheel,
a motor assembly within the housing having an output shaft, a drive
worm on the output shaft in driving engagement with the worm wheel
.Iadd.teeth.Iaddend.,
a jacking screw having a first end with a threaded male portion
which threadably engages said inner threaded surface of the jacking
nut, and a second end which engages said .Iadd.tiltable
.Iaddend.element for relative pivotal movement about an axis which
is perpendicular to the axis of the screw, .[.and.].
restraining means for restraining the screw from rotation,
a mounting plate,
means joining the housing to the mounting plate, and
a spring engaging said .Iadd.convex .Iaddend.part-spherical surface
of said jacking nut, the spring having projecting limbs which react
against a surface of the mounting plate, thereby retaining said
jacking nut outer surface in contact with said jacking nut bearing
surface,
the arrangement being such that, upon motor rotation, the nut
extends or retracts the jacking screw and effects tilting of the
element .Iadd.and movement of the gear teeth across the drive
worm.Iaddend..
8. A pivotable screw jack according to claim 7 further comprising a
soft gasket contiguous with a surface of said mounting plate and
between said mounting plate and spring limbs.
9. A rear vision mirror assembly for a motor vehicle
comprising:
a backing plate, a part-spherical surface of the backing plate
which defines a first element of a first ball and socket joint,
a mounting plate, a second element of the first ball and socket
joint on the mounting plate engaging the first element thereof for
relative pivotal and rotational movement of the backing plate with
respect to the mounting plate,
two further part-spherical surfaces of the backing plate being
concave and defining respectively first elements of second and
third ball and socket joints in the backing plate, which subtend an
angle of 90.degree. with the .Iadd.first element of the
.Iaddend.first said ball and socket.Iadd., .Iaddend.
two pivotable screw jack drives, each including:
a housing, a .[.jacking nut.]. .Iadd.static .Iaddend.bearing
surface of concave part-spherical shape in a wall of the
housing,
a jacking nut having an outer surface which is a complementary
convex part-spherical shape .[.against which said jacking nut
surface bears.]. .Iadd.the outer surface having a center of
curvature and bearing against said static bearing surface.Iaddend.,
an inner threaded surface, and a series of gear teeth spaced around
its periphery defining a worm wheel, .Iadd.said center of curvature
lying in a plane which includes a pitch circle of the gear teeth,
.Iaddend.
a motor assembly within the housing having an output shaft, a drive
worm on the output shaft in driving engagement with the worm
wheel,
a jacking screw having a first end with a threaded male portions
which threadably engages said inner threaded surface of the jacking
nut, and a second end which engages said .Iadd.tiltable
.Iaddend.element for relative pivotal movement about an axis which
is perpendicular to the axis of the screw, and
restraining means for restraining the screw from rotation,
the arrangement being such that, upon motor rotation, the nut
extends or retracts the jacking screw and effects tilting of the
.Iadd.tiltable .Iaddend.element,
respective springs co-acting between the mounting plate and the
jacking nut part-spherical surfaces retaining said screw jack
drives between the mounting plate and the housing,
said second ends of said jacking screws comprising the second
elements of said second and third ball and socket joints, and
pivotally engaging respective said further backing plate
surfaces.
10. A rear vision mirror assembly according to claim 9 wherein each
ball and socket joint first element is a socket and second element
its complementary ball, and further comprising slot surfaces in
said backing plate defining two slots opening into said second and
third sockets and directed therefrom towards the first said ball
and socket joint,
and respective spigots projecting from the balls of said second and
third ball and socket joints engaging walls of said slots and
restraining those balls against rotation.
Description
.Iadd.CROSS REFERENCE TO RELATED APPLICATION
This is a reissue of U.S. Pat. No. 4,881,418, issued on Nov. 21,
1989. .Iaddend.
This invention relates to a pivotable screw jack drive when in
combination with a tilting element, for use in tilting control of
position of that element, for example, of a rear vision mirror. The
invention extends to a rear vision mirror assembly which embodies
such a screw jack drive for tilting control.
BACKGROUND OF THE INVENTION
.Iadd.FIELD OF THE INVENTION .Iaddend.
The positioning of a tiltable element relates to rotation of that
element about the two principal axes, which, in most instances, are
contained within a single plane. Such rotation can either be
achieved by applying a lifting or lowering force at three or more
points, or by supporting the tiltable element on a pivot point and
providing two lifting or lowering forces at spaced positions which
most desirably form an angle of 90.degree. with respect to the
pivot point. The invention is particularly useful with the latter
arrangement.
An example of a tiltable element that would be adjusted in the
above manner is a rear view mirror of a motor vehicle, and the
invention is particularly applicable thereto. Rear view mirrors
require adjustment to suit different drivers or different driving
positions. Frequently, adjustment of external rear view mirrors for
the required accuracy is difficult due to at least one of the
mirrors being distant from the driving position. Therefore, some
means for remotely adjusting the tilt of a mirror is desirable.
PRIOR ART
This problem has been recognised, and screw jacks have been
proposed heretofore. By far the most relevant prior art known is
disclosed in the U.S. Pat. No. 4,482,211 in the name of Fisher,
which also related to a pair of screw jacks which, with a rear
vision mirror ball mounting, subtended an angle of 90.degree. to
each other.[...]..Iadd.; U.S. Pat. No. 4,598,605 Manzoni, wherein a
pinion gear member is pivotable in a ball joint which has a center
of curvature some distance below any pitch circle of the gear teeth
of the worm wheel; and U.S. Pat. No. 3,069,924 wherein the nut
thread and pinion teeth are on separate components. .Iaddend.
The use of a screw jack to adjust a tiltable element of a mirror
requires pivotal movement of the screw jack in relation to the
mirror, and such tilting movement must be universal. Therefore, one
end of the screw jack must not only be pivotally attached with
respect to the mirror backing, but the opposite end of the screw
jack must also be able to pivot.
In the past, as in aforesaid U.S. Pat. No. 4,482,211 providing
pivots at both ends of the screw jack together with a drive means
for extension and retraction of the screw jack has resulted in a
complicated design and a large number of components being used. For
example, in the aforesaid Patent, the jacking member of the screw
jack was provided with an external thread which was indirectly
engaged by a ring gear, which itself was driven by an electric
motor via a worm gear. The jacking member was coupled to the ring
gear through a ball-shaped member contained within an annulus in
the ring gear, and which was pivotal within the ring gear but not
rotatable with respect thereto about the gear's axis of rotation.
Although this provided an excellent mechanical arrangement, there
was an excessive number of components, all requiring close
tolerances of fit and time consuming assembly, and as a consequence
some of the components were very small and lacked the robustness
which this invention seeks to achieve.
It is an object of this invention to provide a screw jack drive
which overcomes the abovementioned problems and results in a drive
system that has a smaller number of components, which is easier to
assemble, and which has improved reliability of operation.
BRIEF SUMMARY OF THE INVENTION
In its broadest form, the invention comprises a pivotable screw
jack drive for a tiltable element such as a rear view mirror of a
motor vehicle, wherein a motor driven worm wheel also performs the
function of a jacking nut which rotates about a jacking screw, the
projecting end of the jacking screw being connected to the tiltable
element for universal pivotal movement but being restrained against
relative rotation, the jacking nut being mounted in a housing with
a ball joint so that the nut and screw pivot as an assembly. The
nut has around its periphery gear teeth which define the worm
wheel, for example, of cylindrical shape, .Iadd.the pitch circle of
the gear teeth being in the same place as the ball joint center of
curvature, .Iaddend.and a motor has a worm which engages the gear
teeth to effect rotation of the nut and consequent tilting of the
tiltable element, and consequential pivoting of the nut and screw
is accommodated by movement of the gear teeth across the drive
worm.
More specifically, the invention consists of a combination of a
tiltable element and a pivotable screw jack drive which controls
tilting of the element, and which comprises a housing, a jacking
nut bearing surface in a wall of the housing, a jacking nut having
an outer surface which is also a bearing surface, an inner threaded
surface, and a series of gear teeth spaced around its periphery
defining a worm wheel, at least one of the bearing surfaces being
of part spherical shape, .Iadd.the center of curvature of which
lies in a plane containing a pitch circle of the teeth, .Iaddend.a
motor assembly within the housing having an output shaft, a drive
worm on the output shaft in driving engagement with the worm wheel,
a jacking screw having a first end with a threaded male portion
which threadably engages said inner threaded surface of the jacking
nut, and a second end which engages said element for relative
pivotal movement about an axis which is perpendicular to the axis
of the screw, and restraining means for restraining the screw from
rotation, the arrangement being such that, upon motor rotation, the
nut extends or retracts the jacking screw and effects tilting of
the element.
.Iadd.BRIEF DESCRIPTION OF THE DRAWING .Iaddend.
An embodiment of the invention is described hereunder in some
detail with reference to, and is illustrated in, the accompanying
drawings, in which:
FIG. 1 is a rear elevation of a rear view mirror (that is, viewed
in a rearward direction) with respect to a motor vehicle on which
it is mounted;
FIG. 2 is a cross-section taken on line 2--2 of FIG. 1, but
omitting the motor and worm wheel assemblies;
FIG. 3 is a front elevation of the motor housing assembly, FIG. 3
also identifying the cross-section plane 2--2;
FIG. 4 is an "exploded" view of the motor housing assembly, with
one screw jack and its drive motor removed;
FIG. 5 is a cross-section through a screw jack assembly, which best
illustrates the invention herein claimed; and
FIG. 6 is a geometric representation of the movement of the gear
teeth across the drive worm, which takes place upon pivotal
movement of the nut and screw assembly.
.Iadd.DESCRIPTION OF THE PREFERRED EMBODIMENT .Iaddend.
In this embodiment, the tiltable element of the invention is the
rear vision mirror which is contained within an outer shroud 10
which is hinged in known manner to a mounting (not shown) secured
to the outer surface of a motor vehicle in such a way that the
shroud 10 will be displaced upon striking an obstruction. The
invention however is not limited to such use and can be applied to
other tiltable elements, or to rear vision mirrors which do not
have this provision.
The rear vision mirror 11 is carried on a mirror backing plate 12
(not shown in FIG. 3), the backing plate 12 being provided with a
first ball socket 13 about which it can both universally pivot and
rotate, the ball socket 13 engaging a ball 14 carried on a mounting
plate 15 secured by screws 16 to the outer shroud 10. The
requirement is to pivot the rear vision mirror 11 and its backing
plate 12 with respect to the shroud, for rotation (in this
embodiment) about both vertical and horizontal axes of the ball
14.
The mounting plate 15 is provided with female lugs 20 (FIG. 3)
which are engaged by protruding lugs 21 (FIG. 4) of a housing 22.
The housing 22 contains two pivotal screw jack drives generally
designated 23, and each being as shown in a larger scale in FIG.
5.
Each screw jack drive 23 comprises an electric motor assembly 24 of
the reversible type, the output shaft of which carries on it a
drive worm 25.
The housing 22 contains two part spherical hollow jacking nut
bearing surfaces 27 (FIG. 4), and these .Iadd.static surfaces
.Iaddend.are engaged by complementary part spherical bearing
surfaces 28 of respective jacking nuts 29, each jacking nut 29
having an inner threaded surface 30, and a series of gear teeth 31
(which are either spur gear teeth or slightly helical to match the
helix angle of the worm), the gear teeth 31 being spaced around the
periphery of the jacking nut 29 to constitute a worm wheel which
has a cylindrical envelope shape (that is, they are not concave
teeth as with the ordinary worm wheel). .Iadd.The plane P-P (FIG.
5) is a plane which is in the axial center of the teeth, and
contains a pitch circle of the teeth. This plane also includes the
center `C` of curvature of the part-spherical bearing surfaces 28.
.Iaddend.
A jacking screw 35 is bifurcate and has two limbs 36 (FIG. 4) which
are splayed out by a resilient "U"shaped spring 37, the inner ends
of the limbs 36 having male threads 38 thereon which threadably
engage the inner threaded surface 30 of the jacking nut 29 as best
seen in FIG. 5. The projecting end of each jacking screw 35 passes
through a soft elastomeric gasket 40 located between the housing 22
and the mounting plate 15, and terminates at its upper end in a
ball head 41, the ball head 41 having a projecting spigot 42 which
constitutes a restraining portion, rotation of the jacking screw
being restrained by spigot 42 engaging a complementary surface of a
slot 43 (FIG. 2), there being second and third ball sockets 44 each
having a slot 43 opening into it, on the underside of the backing
plate 12 of the mirror 11. The slots are directed towards the first
socket 13. However the ball head 41 is otherwise movable within the
part spherical socket 44 for the required pivotal movement in the
two directions for vertical and horizontal adjustment of the
position of the mirror 11. The arrangement therefore is such that,
upon motor rotation, the worm 25 causes rotation of the jacking nut
29 to drive the jacking screw 35 outwardly or withdraw it back into
the nut. In the event of there being excessive drive, the bifurcate
limbs 36 merely spring together as the threads ride over one
another, and this constitutes an in-built overload protection
device. By driving the jacking screw 35 outwardly or withdrawing it
inwardly, the backing plate 12 is tilted about the ball socket 13
in either one of the two planes, and since the ball heads 41 of the
jacking screws 35 subtend an angle of 90.degree. with each other
with respect to the bolt ball socket 13, the adjustment takes place
in either one of the two planes.
However, tilting of the mirror 11 necessarily means that there is
some tilting of the assembly of the jacking nut 29 and jacking
screw 35, and.Iadd., since the plane P-P contains both the center
of curvature `C` of the bearing surface 28 and also a pitch circle
of the gear teeth 31, tilting of the jacking nut 29 .Iaddend.
.[.this.]. causes the gear teeth 31 to move across the thread of
the worm 25 by a small degree only. FIG. 6 illustrates the geometry
of this movement, and the displacement angle A from central
position is very small (a small adjustment only being required for
the mirror) and this corresponds to a distance D. The difference in
engagement between the teeth and the threads of the worm is
therefore extremely small, being trigonomically identified by (1-R
cos A), wherein R is the radius of tilt, this being so small as to
be negligible in the application described herein. It is
recognition of this factor which enables the entire arrangement to
work very satisfactorily under a wide range of conditions, with
parts which are not so small as with previously proposed similar
arrangements, since there is no articulation required between the
jacking screw 35 and the jacking nut 29. Parts therefore are lower
in cost, fewer in number and much more rugged.
As seen in FIG. 1, there are two ball heads 41 which engage in
complementary ball sockets 44 on the backing plate 12, and these
subtend an angle of 90.degree. with the center of the ball and
socket joint 13/14, so that pivotal movement effected by one screw
jack drive 23 in, say, an X-Y plane does not affect adjustment in
the Y-Z plane, and vice versa.
As the pivotal movement of the assembly of jacking screw and
jacking nut takes place, there must be some lateral displacement
intermediate the ends and this is accommodated by means of a three
limb spring 48 which engages the upper surface of the jacking nut
29, and the limbs 49 thereof bear upwardly against the underside of
the soft gasket 40 and reacts, through gasket 40, against the
mounting plate 15 which performs the dual function of providing a
moisture barrier for the inner space within the housing 22 and also
facilitating the very small amount of lateral movement required
between the limbs 49 and the mounting plate 15.
A consideration of the geometry as best seen in FIG. 5 will
indicate that the lateral movement of the assembly of jacking nut
29 and jacking screw 35 is extremely limited in the plane which
includes the central axis of the worm 25 because the center of
rotation of the bearing surface 28 is coplanar with the axis of the
drive worm 25 when the longitudinal central axis of the assembly is
in its medial position.
* * * * *