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Description  |
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BACKGROUND OF THE INVENTION
The subject invention is directed toward the art of self-adjusting electric
tappet switches and, more particularly, to self-adjusting automotive brake
light tappet switches of the type generally including a displaceable
tappet member carrying a slider guided within a housing member for
activating one or several electrical contacts contained within the housing
to actuate an automotive brake light.
The invention is especially well suited for incorporation into automotive
brake light circuits and will be described with reference to that
application; however, as will become apparent, the invention is capable of
broader application and could be incorporated in a variety of components
or used as a separate self-adjusting electric tappet switch for many
purposes.
Self-adjusting electric tappet switches are typically used in automotive
brake light switch applications because they provide simple equalization
of tolerances between the back side of brake pedal linkages and the
vehicle metal bodies holding the brake light switch housings in place in
openings provided for accepting and fastening the switch housings to the
vehicle.
One such known self-adjusting electric tappet switch produced by the
assignee of this application includes a tappet member provided with a
plurality of circumferential first stop elements. The first stop elements
cooperate with a plurality of corresponding second stop elements provided
on a slider member comprising the known self-adjusting electric tappet
switch. The slider member is slidably received in the switch housing and
the tappet member is held in the slider member by cooperation of the first
and second plurality of stop elements. During installation of this switch
into the metal automotive vehicle bodies, the switch housing is inserted
from a face surface of the surrounding metal as viewed relative to the
brake pedal, and into an acceptance opening provided in the metal body.
The head of the elongate tappet member extending from the switch body is
thereby pressed against the upper side of the brake pedal member. In the
above-described adjustment and mounting position, the elongate tappet
member is engaged with the slider member in the housing with the tappet
member extending from the switch housing to its fullest extent.
At this stage, if the head of the tappet member is moved in the direction
of the upper side of the switch housing because of abutment against the
upper side of the brake pedal, then the tappet and slider system is first
moved into the switch housing until a specified switch position is
reached. This switch position is preferably defined by a slider stop
located in the housing. The tappet of the switch is designed with a
minimum length so that the switching position will be achieved during
installation of the switch in the acceptance opening of the metallic
vehicle body member. However, if the distance between the holding metal
and the upper side of the brake pedal is smaller than the required
displacement path of the tappet and slider system for attaining the above
switching position, then additional pressure is exerted upon the tappet
member during installation of the switch housing into the acceptance
opening through abutment of the head of the tappet member against the
upper side of the brake pedal. As a result of this additional pressure,
the threshold value force is surpassed for the arresting displacement of
the tappet relative to the slider and automatic adjustment of the tappet
takes place.
After complete installation of the switch into the acceptance opening in
the position in which the upper side of the switch housing abuts against
the underside of the holding metal, the tappet switch is fixated in the
acceptance opening by rotation of the switch body or housing through a
predetermined specified angle. To that end, the switch housing described
above includes one or more projections which project during installation
of the switch into the acceptance opening and corresponding encoding
recesses. The several projections grab behind the metal vehicle body after
rotation of the switch housing through the above-mentioned predetermined
angle around the longitudinal axis of the switch.
One disadvantage, however, with respect to switches of the general type
described above is that under certain circumstances there may be
unintentional displacement of the specified stop position between the
tappet member and the slider member. This can be caused, for example, due
to heat expansion of switch components or due to wear of the stop areas.
Manipulation of the brake pedal height or body panel or other support
structure in the area of the switch after completion of the switch
self-adjustment steps, can also lead to unintentional misadjustment of the
desired stop position. This results in an undesirable displacement of the
switching point to a point beyond the original setting so that the brake
light of the vehicle is not switched on until a given position of the
brake pedal is reached, in which significant brake effect may have already
been attained. Prior to this electric switching point, other vehicles on
the road following a vehicle experiencing the above-noted switch
disturbance, receive no indication at all with respect to the braking
process previously commenced.
German Patent Application 196 03 135.4 assigned to the assignee of the
instant application describes a self-adjusting and lockable tappet switch
which solves some of the above-noted problems. With this switch, the
tappet and slider member system can be changed from an adjustment position
to a locked position through mere rotation of the tappet member around its
longitudinal axis. In the locked position, movement of the tappet member
relative to the slider member is not possible.
One disadvantage, however, of switches of the general type described above
is that during the adjustment process, initially the slider and tappet
members must be brought into a defined position relative to each other
before displacement takes place of the tappet member relative to the
slider member for the adjustment itself to be effected. This requires a
relatively long displacement path during installation of the switch and,
furthermore, as a result of mechanical tolerances, worn locking means, or
the like, displacement of the tappet member relative to the slider member
may have previously occurred without the tappet member being in the
specified switching position. As a consequence, the desired switching
point may not be reached under certain circumstances. In that case, the
automotive brake light switch mechanism is ineffective to operate the
vehicle braking light circuit.
Another disadvantage of switches of the general type described above is
that additional work or effort is necessary to install and lock the switch
into position through the appropriate rotational motion. The installer
cannot readily simultaneously twist the tappet switch at the same time the
switch is inserted into the installation opening. Because tappet switches
known in the art become lost into the installation opening and therefore
access to the switch from the installation side becomes nearly impossible,
installers of these type of switches find it difficult to use them. In
addition, the installation and necessary self-adjustment process becomes
very difficult. In these cases, the installation by turning of these
tappet switch require additional maneuvering or an additional action and
thus increase the installation expense.
SUMMARY OF THE INVENTION
The subject invention provides an improved self-adjusting tappet switch
which practically eliminates, in a simple fashion, any defective
installation and, which evidences a high degree of operating and
installation safety while safely preventing any unintended maladjustments
of the switch system.
In accordance with a first preferred embodiment of the invention, there is
provided an improved self-adjusting tappet switch including a housing, a
slider member guided in the housing for activating one or more electrical
contacts and a tappet member displaceable relative to the slider member.
The slider member has a first engagement means and the tappet member has a
corresponding second engagement means. The slider and tappet members are
selectively arresting connectable and/or lockable with each other. At
least one of the tappet or slider members are formed in cross section in
such a manner that at least one of the two parts is retained torsion-proof
or non-rotatable during installation into an opening of an operatively
associated part. The other part is retained torsion-proof or
non-rotational within the housing. First and second means of engagement
are provided on the tappet and slider members such that the tappet and
slider members are changed from an adjustment and installation position to
a locked position by rotation of the housing while the tappet and slider
members are engaged with the opening in the installation part. The
rotation of the housing causes relative movement between the tappet and
slider members to lock the first and second engagement means together.
In accordance with the invention, there is provided an improved
self-adjusting tappet switch including a housing, an electric switch
contact carried on the housing, an elongate tappet member adapted to
engage a motor vehicle brake pedal and a slider member carried on the
elongate tappet member and adapted to engage and activate the electrical
switch contact based on movement of the tappet member relative to the
housing. The slider member is movable within the housing between a first
slider member position and a second slider member position. In the first
position, the slider member is spaced apart from the electrical switch
contact. In the second slider member position, the electrical switch
contact is activated by the slider member to in turn close an operatively
associated external motor vehicle brake light circuit. The elongate tappet
member is selectively movable within the housing between a first
installation and adjustment position and a second locked position. A one
of the slider or tappet member are provided with a plurality of
circumferential grooves and have a cross section of varied width. The
respective other one of the slider or tappet members carry engagement
parts adapted to engage the grooves. In the installation and adjustment
position, the elongate tappet member is movable relative to the slider
member to facilitate the mounting of the switch and adjustment of the
tappet member between the motor vehicle body frame and the brake pedal. In
the second locked position, an engagement portion of the tappet member
mateably connects a corresponding portion of the slider member so that the
slider member moves with the elongate tappet member in response to
movement of the brake pedal on one end of the tappet member causing the
electrical switch contact to close.
In accordance with a somewhat more limited aspect of the invention, the
tappet member is rotationally movable within the housing between the first
installation and adjustment position and the second locked position.
Further, the tappet member is adapted for longitudinal slidable movement
relative to the slider member when the tappet member is in the first
installation and adjustment position.
As can be appreciated, a primary object of the present invention is the
provision of a new and improved self-adjusting tappet switch which
substantially eliminates, in a simple fashion, any defective installation
of the switch in a motor vehicle while maintaining a high degree of
operating and installation safety.
It is an advantage of the invention that the slider member is positioned in
the desired switching position within the housing during installation and
adjustment of the switch in a motor vehicle. Inasmuch as during the actual
adjustment process, the slider need not be moved, greater installation and
operating safety directly results. After the adjustment process, the
tappet member and switch are joinable via the electric contact means, so
that only then a displacement of the slider is possible and necessary in
order to produce electric switching movements.
It is another advantage of the present invention that the cross section of
the tappet or slider members are formed to engage corresponding
constructions on the target installation opening so that either the tappet
member or the slider member is held non-rotatably in the acceptance
opening and the respective other part is held non-rotationally in the
housing. Thus, by means of a simple rotation of the switch housing around
a specific angle, the tappet and slider members are thereby locked within
the housing effecting switch adjustment. This is particularly beneficial
with respect to lowering the expense of installing the switch. In the
first preferred embodiment of the invention described below, the first
attachment means provided on the housing are adapted to engage a
corresponding attachment means provided on the installation part whereby
rotation of the housing produces both a locking of the tappet and slider
member system as well as a simultaneous connecting of the switch housing
into the acceptance opening of the installation part.
It is a benefit of another preferred embodiment of the invention that the
tappet and slider members have first and second attachment means which
allow a notched displacement of one of the two elements relative to the
other in an angular position defining the installation and adjustment
position.
When employed as a motor vehicle brake light switch, the switching movement
of the subject invention is produced through activation of the motor
vehicle brake pedal. It is to be noted, however, that switches of this
type are arranged adjacent brake pedal linkage which, upon activation of
the brake pedal, move in a direction having a tendency to increase the
distance between the switch and the respective upper or underside of the
brake pedal. In other words, when the brake pedal is activated, the tappet
member, together with the slider member, is moved in a direction out of
the switch housing due to tensioning by a resilient spring element within
the housing. It is an advantage of the present invention that the subject
self-adjusting tappet switch is usable in the opposite orientation or
direction where the tappet member and slider member are moved together
into the switch housing for activation of the electric contacts therein.
Another advantage of the preferred embodiment of the invention is that the
slider member is acted on by a resilient spring element and held in a
predetermined switching position spaced apart from the electric contacts
while the tappet and slider members are disposed in the mounting and
adjustment position. To facilitate switch adjustment, the connection force
between the tappet member and the slider member while in the mounting and
adjustment position is matched to the triggering force of the resilient
spring element in such a manner that displacement of the tappet member
relative to the slider member takes place in the mounting and adjustment
position without a deflection of the slider member from the predetermined
switching position. For that purpose, the tappet and slider members are
preferably designed in such a manner that in the mounted and adjustment
position, the tappet and slider members are slidably displaceable in the
housing.
Still yet another advantage of the present invention is that while in the
mounting and adjustment position, the tappet member is acted upon by a
second resilient spring element so that the tappet member may be moved
against a stop element on the housing limiting the tappet member movement
in a direction away from the housing.
One benefit of the present invention is that the switching position of the
slider member is defined by a stop element disposed in the housing. The
stop element is only effective for maintaining the switching position of
the slider member while the slider and tappet members are in the mounting
and adjustment position. After changing over the tappet and slider members
into the locked position, the stop elements are simultaneously moved out
of the way enabling the slider member to move in a direction toward the
electric contacts in the housing for activating the electric contacts. The
stop lug member is formed by a separator piece in a recess of an
operatively associated installation part on the motor vehicle body. The
tappet member is coaxially guidable through the stop lug and recess.
The slider member and separator piece preferably have projections and/or
recesses which cooperate in a manner that in the adjustment and
installation position, the slider member is held in the switching position
and, in the locked position, the projections and/or recesses engage each
other and release movement of the slider member from the switching
position in order to activate or deactivate the electric contacts in the
housing.
It is an advantage of the first preferred embodiment of the invention that
a twisting a rotational movement of the switch housing is possible only
when the tappet and slider system is physically moved far enough into the
switch housing until the torsion-proof connection of an attachment part on
the housing is disengaged from the installation part. The part which is
torsion-proof connected with the housing (tappet or slider member) is
preferably designed that the twisting of the switch housing is possible
only when the slider is in the switching position which it is to occupy
after the installation of the switch in the vehicle body panel. For that
purpose, the slider member preferably includes a circumferential
projection formed in a longitudinal direction which engages a
corresponding encoding recess in the installation opening whereby the
upper edge of the projection is arranged in such a manner that rotation of
the switch housing, and thus rotation of the slider which is torsion-proof
connected with the switch housing, is released only when the slider member
is at least approximately in the desired switching position.
In another specific embodiment of the invention, the slider and tappet
system is biased with a resilient spring element while in the installation
and adjustment position and held in a predetermined switching position.
The connection between the tappet and slider member in the installation
and adjustment position is preferably attuned to the tensioning force of
the resilient element such that displacement of the tappet member toward
the slider member in the installation and adjustment position occurs
without deflection of the slider member from the switching position. For
that purpose, the slider and tappet member are preferably designed such
that in the installation and adjustment position, slidable displacement
between the tappet and slider member is made possible.
It is another advantage of the invention that the desired switching
position of the slider member is defined by a stop lug which is effective
only in the installation and adjustment position and permits, following
rotation of the switch housing and locking of the tappet switch system
together, that the slider member moves out of the switching position in
order to activate and deactivate the electrical contacts. The stop lug,
however, limits the movement of the slider in the opposite direction,
i.e., in the direction in which the tappet is moved out of the switch. The
stop lug is preferably formed in one specific embodiment of the invention
by means of a separation piece, held torsion-proof in the installation
part in a recess thereof through which the tappet member is coaxially
guided. The separation piece and the slider member preferably include
projections and/or recesses which cooperate in such a manner that the
slider member is held in the switching position while in the adjustment
and installation position. In the locked position, the projections and/or
recesses engage each other and release the movement of the slider member
from the switching position in order to activate and deactivate the
electric contacts.
It is another advantage of one preferred embodiment of the invention that
the tappet member is stressed or biased by a resilient spring element in
such a manner that it is moved in the direction out of the switching
housing whereby the tappet member preferably includes a stop to limit the
movement.
The above specific preferred embodiments of the invention have the overall
advantage that the destruction of or damage to the switch can be prevented
in a simple fashion because the housing is advantageously formed to
accommodate gross movements of the tappet member into the housing due to
faulty operation or unexpected use of the switch. In that regard, an
adequate displacement path for tappet and slider member movement is
provided for in the housing. A benefit of this construction is that
additional stop lug members or similar tabs or stops or the like are not
necessary for blocking movement of the tappet or slider members into the
housing to prevent destruction thereof.
Still other advantages and benefits of the invention will become apparent
to those skilled in the art upon a reading and understanding of the
following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may take physical form in certain parts and arrangements of
parts, a preferred embodiment of which will be described in detail in this
specification and illustrated in the accompanying drawings which form a
part hereof, and wherein:
FIG. 1 is a longitudinal section through a first preferred embodiment of a
switch in accordance with the present invention taken along line 1--1 of
FIG. 2;
FIG. 2 is a top view of the switch shown in FIG. 1;
FIG. 3 is a longitudinal section taken along line 3--3 of FIG. 2;
FIG. 4a is a perspective representation of an exemplary embodiment of a
switch in accordance with the present invention;
FIG. 4b is an outline of an installation opening adapted for receiving the
switch shown in FIG. 4a;
FIG. 5 is a longitudinal section through the switch shown in FIG. 4a in an
adjustment and installation position of the tappet and slider member
system; and,
FIG. 6 is a longitudinal section through the switch shown in FIGS. 4 and 5
in a mounted or tappet and slider member locked position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings wherein the showings are for the purposes of
illustrating the preferred embodiments of the invention only and not for
purposes of limiting same, FIGS. 1-3 show the first embodiment of the
self-adjusting tappet switch 1 according to the present invention. The
tappet switch 1 is mounted in an installation opening 3 of an installation
part 5, for example the retaining sheet metal of a motor vehicle. The
tappet switch 1 includes a housing 7 which is formed to define an
extension 7a at the upper side of the housing, the extension being adapted
to engage the installation opening 3, whereby the extension 7a or the
installation opening 3 are designed in such a manner that after insertion
of the tappet switch 1 or the housing 7 into the installation opening 3,
rotation of the switch housing 7 around the longitudinal axis of the
tappet switch 1 is enable.
A slider member 9 is provided within the housing 7. The slider member is
displaceably guided in the longitudinal axis of the tappet switch 1. To
that end, as shown in FIG. 1 and 2, the slider member 9 includes a base
9a, which is guided laterally through the inner walls of the housing 7. In
addition, the base 9a defines a recess opening 9d which is adapted for
receiving a pin 11, extending in the direction of the overall longitudinal
axis of the switch. The pin and recess opening 9d facilitate additional
longitudinal guidance for the slider member 9.
The base 9a has, at its bottom end, a recess 13, which serves for receiving
an upper area of a coil spring 15. The coil spring supports itself with
its upper end against the upper inner wall of the recess 13 and with its
lower end against the bottom of housing 7. A hollow cylindrical projection
17 is formed at the bottom of the housing 7 for providing fastening and
guidance of the coil spring. The projection 17 is sized to engage the
interior surface of the coils of coil spring 15.
The coil spring 15 acts upon the slider member 9 in such a manner that the
slider member is pressed against the inner wall of the cover area of the
housing by means of a projection 9c provided at the upper end of the
slider, which, in its preferred form, is shaped in the form of a ring. The
ring or annular-shaped projection 9c thus serves as a stop lug for
limiting the longitudinal displacement of the slider in an upward
direction as viewed in FIGS. 1 and 3.
To effect electrical switching in the subject embodiment, the slider member
9 carries one or more contact elements (not shown) having one or more
electrical contacts therein. The one or more contact elements are
preferably arranged in the lower portion 9a of the slider in a well known
manner and are arranged to function in cooperation with one or more
electrically conductive elements (not shown) carried on the housing such
as illustrated in FIGS. 5 and 6 and described below.
The slider member 9 is preferably formed in the shape of a hollow cylinder
as shown, whereby a tappet member 19 engages, from above, with the slider
member. Tappet member 19 has in the area which engages with the slider
member 9, an arresting means 21, which, as shown in FIGS. 1 and 3, are
preferably formed as a plurality of longitudinally spaced apart
circumferential serrations. The plurality of spaced apart serrations 21
cooperate with a resilient engagement member 23, arranged at least in part
inside the slider member 9 as shown. In the preferred embodiment
illustrated, the engagement member 23 is a spring with a pair of opposing
resilient arms 23a, 23b as shown in FIG. 3.
As further shown in the FIGURES, the cross-section of the subject tappet
switch 1 in the area of the arresting means 21 is formed in a manner that
the resilient arms 23a, 23b of the engagement member 23 in a first angular
position of the tappet member 19 extend radially inwardly to engage the
outer surface of the arresting means 21. However, there is provided
sufficient annular space between the exterior side of the arresting means
21 and the interior wall of the slider member 9 in order to facilitate an
arresting longitudinal displacement of the tappet member 19 relative to
the slider member 9. In other words, the annular space in the first
angular position of the tappet member 19 is large enough in order to
facilitate a radial movement of the resilient arms 25a, 23b toward the
outside so that the resilient arms 23a, 23b are movable via the stop teeth
of the arresting means 21. The first angular position of the tappet member
relative to the slider member defines the adjustment and installation
position of the subject tappet switch 1 of the tappet-slider system as
best shown in FIGS. 1 and 3.
Rotation of the tappet member 19 around its longitudinal axis by a
specified angular degree increment results in a greater cross section
diameter of the tappet disposed between the pair of resilient arms 23a,
23b. The tappet member 9 in the area of the arresting means 21 is
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