Tractor trailer air brakes

#The invention relates generally to the field of tractor trailer pneumatic spring brakes.

#Jack-knifing of tractor trailers is a serious problem. Jack-knifing occurs when the truck portion of a tractor trailer is forced out of alignment with the trailer, usually as a result of hard breaking. Generally speaking, jack-knifing occurs when the truck portion of the tractor trailer begins to slow down rapidly compared to the trailer portion. The momentum of the trailer portion forces the truck out of alignment with the trailer. When jack-knifing occurs, the truck operator effectively loses control of the vehicle and an accident may result. Unfortunately, jack-knifing is most likely to occur in emergency situations when the truck brakes are applied forcefully.

#Existing tractor trailer brakes are not designed to effectively prevent jack-knifing. Existing tractor trailer brakes consist of a series of pneumatically operated brakes operatively coupled to the rear wheels of the trailer. These pneumatically operated brakes are in turn operatively coupled to an air supply located in the truck via a pneumatic line. A trailer brake control valve in the truck controls the flow of air to the pneumatic brakes in the trailer, and is used to either engage or release the brakes as desired. When the operator engages the brake hand valve, pneumatic pressure travels down the pneumatic line to the pneumatic brakes causing the brakes to engage. Since the pneumatic brakes are some distance from the trailer brake control valve, there is a time delay between the activation of the trailer brake control valve and the engaging of the trailer brakes. Since the brakes in the truck portion of the tractor trailer are closer to the brake control systems than the brakes of the trailer portion are to the trailer brake control valve, the truck brakes will engage before the rear trailer brakes. In a majority of cases, this time delay is not significant; however, in emergency situations, under conditions of hard braking, this time delay may be sufficient to cause jack-knifing. Brake control systems on the market today do not address the time lag between the engaging of truck brakes and rear trailer brakes; therefore, the problem of jack-knifing tractor trailers continues.

#FIG. 1. is a cross sectional view of a typical trailer pneumatic spring brake.

#FIG. 2. is a schematic view of a pneumatic brake system made in accordance with the present invention.

#FIG. 3 is a schematic representation of the electronic control circuit of the present invention.

#Before discussing the detailed operation of the present invention, an explanation of standard brakes as used on a majority of trailers must first be discussed. A majority of trailers presently on the road have a conventional friction brake operatively coupled to each trailer wheel. The friction brake, hereafter referred to as the trailer brake, is in turn operatively coupled to a pneumatic (or air) brake. The pneumatic spring brake is a pneumatically operated device which uses a flow of high pressure air from the tractor to operate the trailer brake. The present invention utilizes a majority of the features of existing pneumatic brake systems.

#Referring to FIG. 1, a standard pneumatic brake is shown generally as item 10 and consists of a housing 12 having separate chambers 14 and 30. Chamber 14, which is commonly referred to as the service chamber, is an airtight chamber having a rigid wall 15, a flexible diaphragm 18 and port 20. Chamber 16 is generally not airtight and has spring 22 which is positioned to bias diaphragm 18 towards rigid wall 15. Spring 22 applies sufficient biasing force against diaphragm 18 to press the diaphragm against rigid wall 15 provided the air pressure in chamber 14 is not pressurized. Pressurizing service chamber 14 to beyond about 60 psi causes diaphragm 18 to move away from rigid wall 15 and towards chamber 16. Connecting rod 24 physically connects diaphragm 18 to friction break 26, such that when diaphragm 18 moves away from rigid wall 15, the rod forces the friction break 26 to engage and when diaphragm moves towards rigid wall 15, the friction break will release. Port 20 is coupled to air line 28. The air pressure in chamber 14 is controlled by air pressure supplied through air line 28.

#In addition to chambers 14 and 16, spring 22, and diaphragm 18 pneumatic spring brake 10 may have additional chamber 32, springs 34 and 36 and flexible diaphragm 38. These additional features are generally included in order to provide a parking brake feature. Not all pneumatic brakes have these parking brake features, but all pneumatic brakes will have service chamber 14, chamber 30, and flexible diaphragm 18.