Communications: electrical – Land vehicle alarms or indicators – External alarm or indicator of movement
Reexamination Certificate
2002-02-21
2003-12-02
Wu, Daniel J. (Department: 2632)
Communications: electrical
Land vehicle alarms or indicators
External alarm or indicator of movement
C340S469000, C340S472000, C340S431000, C340S435000, C340S384100
Reexamination Certificate
active
06657541
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a reversing alarm apparatus for a work vehicle, and more particularly, to a reversing alarm apparatus for a work vehicle, which detects reversing operation of a vehicle forward and reverse travel operating lever to transmit a vehicle reversing alarm in a vehicle forward and reverse travel operating lever device for performing speed control proportional to a magnitude of an operating stroke of the forward and reverse travel operating lever.
Conventionally, many work vehicles mount thereon a reversing alarm device for a work vehicle. Therefore, in a work vehicle, in which a traveling speed is controlled in proportion to a magnitude of an operating stroke of a forward and reverse travel operating lever, a vehicle reversing alarm is issued upon detection of reversing operation of the forward and reverse travel operating lever.
The prior art disclosed in, for example, Japanese Patent Laid-Open No. 80449/1996, s well known and a circuit diagram described in the publication is shown in
FIGS. 5
to
7
. With a first prior art of the publication, provided near a forward and reverse travel operating lever
32
for operating a direction switching valve
31
, which controls a traveling motor
30
, as shown in
FIG. 5
is a limit switch
33
for detecting the reversing operation of the forward and reverse travel operating lever
32
, so that a signal from the limit switch
33
is used to detect the reversing operation of a vehicle to issue a reversing alarm. Also, with a second prior art of the publication, a pressure switch
35
is provided in an operating pressure circuit
34
at the time of reverse traveling rotation of the traveling motor
30
as shown in
FIG. 6
, so that a signal from the pressure switch
35
is used to detect the reversing operation of a vehicle to issue a reversing alarm. Further, with a third prior art of the publication, a pressure switch
39
is provided in a reverse travel operating pilot pressure circuit
38
of a pilot valve
37
for operating a pilot direction switching valve
36
, which serves for the forward and reverse travel operation and controls the traveling motor
30
, as shown in
FIG. 7
, so that a signal from the pressure switch
39
is used to detect the reversing operation of a vehicle to issue a reversing alarm.
However, the prior art disclosed in the above-mentioned Japanese Patent Laid-Open No. 80449/1996 involves the following problems.
In the first prior art, in which the limit switch
33
detects the reversing operation of the forward and reverse travel operating lever
32
, there is a need of applying an operating force required for pushing a detection rod (a roller adapted to be pushed when contacted by a cam or the like) of the limit switch
33
at the time of reversing operation of the forward and reverse travel operating lever
32
. However, the limit switch
33
used in construction machines or the like is ordinarily strongly-built to have durability according to severe circumstances and use in work site, so that a large operating force must be applied to push the detecting rod of the limit switch
33
at the start of reversing operation, which would cause the possibility that after such pushing the detecting rod makes a stroke beyond a desired stroke position to attain an unexpected reversing speed. Also, since the limit switch
33
is not contacted in forward travel operation but rather contacted in reverse travel operation, there is caused a problem that the forward and reverse operating forces become uneven to make an operating feeling of the forward and reverse travel operating lever
32
unfavorable and, in particular, to make a minute reversing operation difficult.
In the second and third prior arts, in which the pressure switch detects the reverse travel acting pressure and the reverse travel operating pilot pressure of the traveling motor
30
, there are caused problems that a stable detecting action cannot be obtained under the influence of oil temperature and pulsation of a pressure fluid and that even after the reversing operation of the travel operating lever is stopped, a residual pressure of the pressure fluid maintains a state of detecting operation by the pressure switch to cause sounding of a reverse alarm.
BRIEF SUMMARY OF THE INVENTION
In order to improve the above-mentioned problems involved in the prior technical means, in which the reversing operation of the forward and reverse travel operating lever is indirectly grasped by a limit switch or detection of the reversing operating pilot pressure or the reversing drive pressure of a traveling drive system to sound a reversing alarm, the invention has its object to provide a reversing alarm apparatus of a work vehicle, in which reversing can be operated without application of a surplus reversing operating force at the time of reversing operation of a forward and reverse travel operating lever, and movements of the forward and reverse travel operating lever are directly detected to sound a reversing alarm.
In order to attain the above-mentioned object, the first invention provides a reversing alarm apparatus for a work vehicle provided with a forward and reverse travel operating lever device to output a forward and reverse speed command signal in accordance with an amount of an operating stroke, wherein a reversing alarm of the work vehicle is issued by a reversing operation detecting device composed of a non-contact type sensor and provided on the forward and reverse travel operating lever device.
According to the first feature of the invention, since the non-contact type sensor detects movements in the reversing operation of the forward and reverse travel operating lever and there is caused no contact between the forward and reverse travel operating lever and the sensor, no change in lever operating forces is caused at the time of reversing operation and operating forces in forward and reverse travel can be made substantially uniform not to injure the operating feeling. Also, the reversing operation is possible with small operating forces to enable improving a minute operability.
Further, since the non-contact type sensor directly detects movements in reversing operation of the forward and reverse travel-operating lever, it is possible to make sure that a reversing alarm is issued and stopped in cooperation with a lever operating action.
The second feature of the invention provides a reversing alarm apparatus for a works vehicle, in which the reversing operation detecting device of the first invention is constructed such that the non-contact type sensor is installed with a sensor detecting surface facing in a direction parallel to a forward and reverse rotation shaft of a forward and reverse travel operating lever, and the reversing operation detecting device is composed of a detected lever linkage mechanism which swings vertically in a plane perpendicular to the forward and reverse rotation shaft following rotation of the forward and reverse rotation shaft of the forward and reverse travel operating lever to intersect a sensor signal of the non-contact type sensor.
According to the second invention, since the detected lever linkage mechanism is designed to follow the reverse travel operation of the forward and reverse travel operating lever to intersect the non-contact type sensor and to follow the forward travel operation not to intersect the non-contact type sensor, the forward travel operation is not detected.
The third aspect of the invention provides a reversing alarm apparatus for a work vehicle, in which the detected lever linkage mechanism of the reversing operation detecting device of the second invention is constructed such that the detected lever linkage mechanism of the reversing operation detecting device comprises a rotation interlocking lever mounted on the forward and reverse rotation shaft of the forward and reverse travel operating lever, and a seesaw movement lever, which includes on one side thereof a lever portion having an elongated hole and on the other side thereof a detected lever por
Komatsu Ltd.
Nguyen Tai T.
Wu Daniel J.
LandOfFree
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