Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D65/00—Parts or details
  • F16D65/38—Slack adjusters
  • F16D65/40—Slack adjusters mechanical
  • F16D65/52—Slack adjusters mechanical self-acting in one direction for adjusting excessive play
  • F16D65/56—Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut
  • F16D65/561—Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut for mounting within the confines of a drum brake
  • F16D65/562—Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut for mounting within the confines of a drum brake arranged between service brake actuator and braking member, and subjected to service brake force
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T17/00—Component parts, details, or accessories of power brake systems not covered by groups B60T8/00, B60T13/00 or B60T15/00, or presenting other characteristic features
  • B60T17/18—Safety devices; Monitoring
  • B60T17/22—Devices for monitoring or checking brake systems; Signal devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D66/00—Arrangements for monitoring working conditions, e.g. wear, temperature
  • F16D66/02—Apparatus for indicating wear
  • F16D66/021—Apparatus for indicating wear using electrical detection or indication means
  • F16D66/026—Apparatus for indicating wear using electrical detection or indication means indicating different degrees of lining wear
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D2125/00—Components of actuators
  • F16D2125/18—Mechanical mechanisms
  • F16D2125/58—Mechanical mechanisms transmitting linear movement
  • F16D2125/66—Wedges

Definitions

• This invention relates to a method for indicating wear of brake linings or brake pads at braking by means of a brake mechanism, which has two brake applying members and a synchronizing shaft rotatively connecting these two members for accomplishing synchronizing of a wear compensating ro ⁇ tation at both members. It also relates to a wear indicator for carrying out this method.
• Brake linings or brake pads are gradually worn at bra ⁇ king.
• a slack adjuster built into the brake mechanism compensates for the increasing slack or distance between the brake linings or brake pads and a brake drum or brake disc resulting from the lining or pad wear.
• the brake linings or pads have to be replaced before they are completely worn out, because otherwise the brake effect can be lost and the drum or disc be permanently damaged. It is therefore usual to provide the brake lining or brake pad with some type of wear indicator, giving a signal when the lining or pad is nearly or completely worn out .
• a synchronizing shaft of the kind referred to and uti ⁇ lized according to the invention is typically used in a so called wedge brake unit for a drum brake in heavy road ve ⁇ hicles, such as trucks and buses.
• a corresponding design may, however, equally well be used in disc brakes, and the invention is also applicable to such disc brakes.
• the synchronizing shaft is provided with gear wheels each cooperating with external helical teeth on a rotatable part of each brake applying member.
• the syn ⁇ chronizing shaft has the purpose of transmitting a slack adjusting movement from one brake applying member, where a slack adjuster is arranged, to the other.
• the invention also relates to a wear indicator for carrying out the above method, characterized in that means on the synchronizing shaft are arranged to cooperate with stationary means in the brake mechanism to provide an electric counting signal indicative for angular movement of the shaft and thus for the brake lining or brake pad wear.
• the synchronizing shaft is provided with a magnet for cooperation with a stationary electronic switch, preferably a hall switch, arranged in the vicinity thereof in the brake mechanism.
• the shaft is provided with two axially and angularly dis ⁇ placed magnets for cooperation with a hall switch each.
• the hall switches are ar ⁇ ranged on a circuit board together with a processor, a me- mory, and a back-up battery.
• the wear indicator When the wear indicator is used in a wedge brake unit with a wedge for pressing the brake applying members apart at brake application, the wedge is provided with a magnet for cooperation with a further hall switch on the circuit board in order to set the arrangement to zero.
• the drawing illustrates a brake mechanism in the form of a wedge brake unit for a drum brake, preferably for use on a heavy road vehicle, such as a truck or a bus.
• a brake unit and its use are well known in the art, and only a brief description of the brake arrangement is given without reference to any drawing.
• a wedge brake unit of the type shown in the drawing can be mounted on a fixed part at the wheel to be braked.
• the force-transmitting push rods of the unit are connected to brake shoes provided with brake linings.
• the brake shoes with its brake linings are pushed against a rotating brake drum at braking.
• a wedge brake unit as shown in the drawing has a hou- sing 1.
• a left tappet 2 and a right tappet 3 are guided for
• a wedge 4 is movable substanti ⁇ ally perpendicularly to the common axis of the two tappets 2 and 3.
• the wedge 4 is con- nected to a piston of a fluid actuated brake cylinder (not shown) .
• Force transmitting rollers 5 and 6 are arranged between mutually parallel surfaces on the wedge 4 and the respective tappets 2 and 3.
• the wedge 4 is additionally guided by a guide roller 7 arranged between mutually parallel surfaces, which are perpendicular to the common axis of the tappets 2 and 3, on the wedge 4 and in the housing 1, respectively.
• a tappet nut 8 and 9, respectively, is arranged on each of the non-rotatable tappets 2 and 3.
• Each tappet nut 8 and 9 is rotatably arranged on its respective tappet 2 and 3.
• Tappet screws 10 and 11 with external threads engage internal threads in the respective tappet nuts 8 and 9.
• the thread directions of the threads at the left hand side (tappet nut 8 and tappet screw 10) are opposite to those at the right hand side (tappet nut 9 and tappet screw 11) for reasons described below.
• the same is true also for the directions of helical teeth provided on the periphery of the tappet nuts 8 and 9.
• Each tappet screw 10 and 11 is provided with means at its free end for non-rotatable connection with a brake shoe (not shown) ; the tappet screws are arranged to press the brake shoes apart for braking engagement with a brake drum.
• the non-rotatable arrangement of the tappet screws 10 and 11 means that they will move axially, when the correspon- ding tappet nuts 8 and 9 are rotated.
• the tappet 2 or 3 , the tappet nut 8 or 9, and the tappet screw 10 or 11 forms a unit, which may be referred to as a brake applying member.
• a slack adjuster - to be briefly described only - is arranged in the housing 1 for cooperation with the right
• the slack adjuster includes the following co ⁇ axial elements: a toothed clutch 12, a powerful clutch spring 13, a worm gear 14 engaging the helical teeth of the right tappet nut 9, and a spring 15.
• the function of a slack adjuster of this general type is known in the art and will not be described here, as it is not essential for a proper understanding of the invention.
• a synchronizing shaft 17, rotatably journalled in the housing 1, is at its respective ends provided with helical gear wheels 18 and 19 engaging the tappet nuts 8 and 9.
• the function of this synchronizing shaft - hereinafter collec ⁇ tively numbered 17-19 - is to transmit the rotational move ⁇ ments of the right tappet nut 9 to the left tappet nut 8 and thus to accomplish the same slack adjusting at the brake shoe connected to the left tappet screw 10 as at the one connected to the right tappet screw 11.
• the synchroni ⁇ zing shaft 17-19 will also rotate back and forth at each brake application and brake release without any slack ad ⁇ justing, when the tappet nuts 8 and 9 only move axially due to the permanent engagement between the tappet nuts 8 and 9 and the gear wheels 18 and 19.
• the circuit board 20 On its side facing the shaft 17-19 the circuit board 20 is provided with two hall switches 22, whereas the shaft 17-19 is equipped with two corresponding, angularly displaced magnets 23.
• the sensor type may be different: A coil may be used instead of the hall switch and may possi ⁇ bly cooperate with a cog wheel instead of the magnets. Also sensors of capacitive or resistive type may be used.
• a pulse will be communicated to a processor 24, which counts the pulses and converts the signal to a desi ⁇ red form, analogous or digital. Also arranged on the cir ⁇ cuit board 20 is a memory 25, which stores the counting.
• batteries 26 for current supply at failure of the ordinary current supply may be provided.
• the arrangement can be set to zero by means of a device, which actuates the hall switch 28 mechanically, or another switch, that provides a signal to the processor 24.
• a still further magnet 29 may be provided on the upper part of the wedge 4 for the purpose of warning for an excessive stroke of the wedge.
• the synchronizing shaft 17-19 is imparted a rotational movement from two sources, namely on one hand the rotation stemming from the slack adjuster 12-15 for compensating for the brake lining wear, on the other hand the rotation back and forth at each brake application and release. Due to the provision of the two angularly displaced magnets 22 on the shaft 17-19, the arrangement is able to neutralize the influence of the latter source.
• the arrangement is primarily used for supplying sig- nals indicative for the wear rates at the different wheels to a central vehicle computer, which modifies the wheel brake pressures for equalizing the wear at the different wheels.
• a secondary use may be to supply an indication of the wear to the vehicle driver.
• SUBSTITUTE SHEET focussed on a so called wedge brake unit for a drum brake, it should be noted that the idea can equally well be utili ⁇ zed at other brake arrangements. Especially, it may be uti ⁇ lized at a disc brake arrangement provided with a synchro ⁇ nizing shaft.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Transportation (AREA)
• Braking Arrangements (AREA)

Priority Applications (1)

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Publications (1)

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Family Applications (1)

Country Status (3)

Cited By (5)

Families Citing this family (1)

Citations (3)

• 1993
  • 1993-11-02 SE SE9303597A patent/SE9303597L/sv not_active Application Discontinuation
• 1994
  • 1994-10-24 WO PCT/SE1994/000997 patent/WO1995012769A1/en active Application Filing
  • 1994-10-24 AU AU81189/94A patent/AU8118994A/en not_active Withdrawn

Patent Citations (3)

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