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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.
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 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. 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.
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.
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. 1a is a perspective representation of an exemplary embodiment of a
switch in accordance with the present invention;
FIG. 1b is an outline of an installation opening adapted for receiving the
switch shown in FIG. 1a;
FIG. 2 is a longitudinal section through the switch shown in FIG. 1a in an
adjustment and installation position of the tappet and slider member
system; and,
FIG. 3 is a longitudinal section through the switch shown in FIGS. 1 and 2
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 embodiment of the invention only and not for
purposes of limiting same, FIG. 1a shows a perspective view of the subject
tappet switch 100 including a housing 107 defining a shoulder 107b serving
as a stop lug or a stop surface for installing the housing 107 in an
installation opening 103 (FIG. 1b) of an operatively associated assembly
part 5.
The tappet switch 100 includes fastening members 127a, 127b which serve for
arresting or fastening the switch in the assembly part 5. The installation
opening 103 has, to that end, correspondingly formed encoding recess 103a,
103b, so that the switch can be pushed from below with the fastening
members 127a, 127b through the installation opening until the shoulder
107b abuts the underside of the assembly part 5. In this position, the
switch is lockable relative to the assembly part 5 by simply turning or
rotating the switch housing.
As shown in FIGS. 1b and 2, a rotatable separator piece 140 is provided in
the upper region of the housing 107. The separator piece 140 is rotatable
relative to the housing and includes a projection member 140a which,
likewise, essentially corresponds to the shape of the encoding recess 103a
as shown.
For inserting the switch 100 into the installation opening 103 of the
assembly part 5b, the separator piece 140 is turned or rotated relative to
the housing 107 in such a manner that the projection 140a is essentially
in alignment with the fastening means 127a. The projection 140a engages
the encoding recess 103 of the housing 107 with its shoulder 107b abutting
the underside of the assembly part 5.
The tappet member 119 extends coaxially along the axis of rotation of the
separator piece 140 opposite housing 107 in a slidable fashion via a
corresponding recess in the separator piece 140. The cross section of the
tappet member the recess in the separator piece 140 are chosen in such a
manner that the tappet member 119 is held torsion-proof in the separator
piece 140. That is, the tappet member 119 is not rotatable within the
separator piece 140. Thus, the torsion-proof fastening (non-rotatable) of
the separator piece 140 by means of the projection member 140a in the
encoding recess 103a, the tappet member is also torsion-proof
(non-rotatably) mounted to the assembly part 5. The tappet member,
however, is slidable along its longitudinal axis within the separator
piece 140. As a result, a twisting or rotating of the housing of the
switch 100 relative to the assembly part 5 is also accompanied by a
twisting and thereby realizing of a locking of the tappet and slider
member system in a manner to be subsequently described.
In order to permit locking, the tappet has, preferably on opposite
longitudinal sides, locking means 121 which, as shown in FIG. 3, are
preferably formed in a saw tooth-shaped notch arrangement. The locking
means 121 cooperate with complimentary contact means 123, which are
provided at the interior wall of the essentially annular-shaped slider
member 109. In the unlocked state of the tappet and slider member system,
a sliding displacement of the tappet member relative to the slider member
is enabled in that the locking means 121 are rendered out of contact with
the complimentary contact means 123.
For installing the tappet switch 100 in the installation opening 103, the
tappet member 119 and the separator piece 140 are brought into an
adjustment and installation position best shown in FIGS. 1a and 2. The
adjustment and installation position permits the sliding displacement of
the tappet member 119 relative to the slider member 109.
In this adjustment and installation position, the slider member is already
advantageously disposed in the desired switching position best shown in
FIGS. 2 and 3. The slider member switching position is defined by the two
extensions 140b at the underside of the separator piece 140, whereby the
slider member 109 is pressed with its upper side against the contact
surfaces 140b via a biasing spring action force. To that end, a spring
member 142 acts upon the underside of the slider member 109 and, on the
other side, upon a shoulder region 144 in the lower area of the housing
107.
In addition, a second biasing spring member 146 is provided which includes
an upper end accepted into a recess formed on the underside of the tappet
119 and which acts, with its other end, upon the bottom of the housing
107. The spring 146 is preferably held at the bottom of the housing by
means of a suitable pin 148 or other connecting device.
The switching position of the slider member 109, best represented in FIG.
2, is selected in a manner that upon elimination of the striker effect of
the extensions 140b in a manner to be subsequently described, an adequate
switch path is produced for activation of the electric contact 150. In
that regard, the electric contact 150 consists of at least two contact
elements 152, 154 which are preferably connected to the underside of the
slider member 109 by means of an electrically conducting element 156
formed on the slider member.
When inserting the switch 100 into the installation opening 103, the head
of the tappet member is initially brought into contact with the respective
side of an activation element such as a brake pedal or the like. After
that, the switch is moved in the direction toward the activation element
such as a brake pedal or the like, until the shoulder 107b rests against
the underside of the installation part 5. During this process, the tappet
member is displaced into the housing in a sliding fashion relative to the
slider member 109, whereby the slider member is held via the spring member
142 in the switching position shown in FIG. 2.
Subsequent to the above steps, the housing 107 of the switch is next
rotated in a manner described above by a specified predetermined angular
increment, for example 90.degree. thereby locking the tappet and slider
member system. The locked position is best shown in FIG. 3. As is apparent
from the above and as shown in the drawings, the rotating of the housing
concurrently rotates the slider member 109 relative to the separator piece
140. In that way, the movement of the housing 107 concurrently achieves a
modification in the relationship between the extensions 140b in a manner
that the extensions lose their effectiveness as stop lugs against the
slider member since they, as best shown in FIG. 3, thereafter face
corresponding recesses 158 formed in the upper side of the slider member
109. In this-manner, with movement of the activation element such as a
brake pedal or the like away from the installation part 5, a switching
path of the slider member in the same direction (away from the
installation part) is enabled. Upon displacement or movement of the slider
member 109 or of the tappet and slider member system, the extensions 140b
engage the recesses 158. After traversing a given displacement path, the
contact elements 152, 154 are thereby electrically connected via the
conductive element 158 formed on the slider member thereby establishing an
electrical closed contact path.
The switch construction of the preferred embodiment prevents, in a very
simple fashion, that any damage or destruction of the switch will occur
upon a movement of the activation element in a direction opposite from the
activation direction proper of the switch. To that end, the switch
construction assures that the slider or the tappet and slider member
system, starting in the switching position shown in FIGS. 2 and 3, has
available an adequate displacement path in the respective activation
direction (the downward direction in FIGS. 2 and 3). With this type of
switch construction, it is not necessary to realize the trailing effect,
stop lugs or the like implemented by means of a corresponding additional
interlocking mechanism in the tappet member or the housing member. In
addition, the preferred switch construction does not require any
additional springs or biasing members or the like.
Turning now to FIG. 3, the saw tooth-shaped locking arrangement 121 is
constructed in a manner that each tooth has an essentially horizontally
extending upper and an obliquely extending lower area. The complimentary
engagement means 123 of the slider member 109 are designed to intermate
with the locking arrangement 121. The areas of each of the two engagement
tooth arrangements 121 and/or of the contact means 123 cooperate during a
first contact making engagement during the rotation of the slider member
109 with the housing 107 in order to lock the tappet and slider member
system together. The engagement areas 121, 123 are preferably formed in a
manner that no frontal surfaces abut each other at obtuse angles thereby
blocking and/or locking rotational movement between the tappet and slider
member. For that purpose, the leading or initial frontal surfaces or areas
of the engagement portions 121, 123 may alternatively be formed to include
an azimuthally extending pitch so that the lead areas of the frontal
surfaces are reduced to form a first cutting edge on each tooth. The pitch
extending in the azimuthal direction is constructed in such a manner that
upon contact making of the initial areas of the locking teeth arrangements
121 and the contact means 123, with slightly staggered tooth systems, the
tappet member with fixed slider is moved as far as is needed into the
switch housing 107 until the tooth systems are in correct complimentary
contact position. To that end, for example, the underside of each saw
tooth of the contact means 123 may be formed to have in its initial area
an azimuthally directed extending pitch extending from the superimposed
oblique surface obliquely in the direction of the horizontally extending
underside. Concurrently, the extremely small frontal surface or frontal
cutting edge of each initial or lead area no longer extends in the radial
direction but at such a pitch that with engagement of the initial areas of
the tappet member and slider member tooth systems, the radially exterior
areas first cooperate and only after certain overlapping of the tooth
systems do the individual teeth interact fully in the sense of complete
engagement.
As an alternative embodiment, instead of forming the azimuthal pitch on the
undersides of the teeth of the slider member, the upper sides of the
tappet member teeth can also be provided with corresponding complimentary
slopes.
In contrast to the prior art known switches described above, the
self-adjusting tappet switch according to the present invention greatly
improves the installation and operating safety of the switch. In addition,
although the preferred locking of the tappet and slider members take place
by movement of the parts relative to each other, any other chosen manner
of locking engagement may be used. As an example, the slider member may be
displaceable in a plane extending vertically to the tappet member axis in
order to bring corresponding engagement means to engagement, or in order
to connect, after adjustment of the tappet member, with the slider member
via insertion of a connection piece for example through a housing opening.
Also, the locking of the tappet and slider member system and the
simultaneous release of the switching path block can be accomplished by
one or more separate actions. As an example, the locking can be
accomplished by means of the described rotation of the tappet member
relative to the slider member and the elimination of the stop lug effect
can be effected through separate rotation or translatory movement of a
stop lug element.
Instead of a stop lug for fastening the slider member in the specified
switching position, the slider member can also be held in the desired
position by one or more spring members and can, if needed, be deflected on
either side from the thereby defined resting position in order to bring
about the respective switching movement.
The invention has been described with reference to the preferred
embodiment. Obviously, modifications and alterations will occur to others
upon a reading and understanding of this specification. It is intended to
include all such modifications and alterations insofar as they come within
the scope of the appended claims or the equivalents thereof.
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