Vehicle speed measurement apparatus

• US 5,554,907 A
• Filed: 06/26/1992
• Issued: 09/10/1996
• Est. Priority Date: 05/08/1992
• Status: Expired due to Fees

• Current Assignee: Mitron Systems Corporation
• Original Assignee: Mitron Systems Corporation
• Inventors: Dixon, Donald A.
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US07/904,623
• Time in Patent Office: 1,537 Days
• Field of Search: 310/330-332, 310/328, 310/338, 310/339, 310/800, 310/319, 340/933, 340/936
• US Class Current: 310/339
• CPC Class Codes: E01F 9/529 specially adapted for signalling by sound or vibrations, e.g. rumble strips; specially adapted for enforcing reduced speed, e.g. speed bumps
• CPC Class Codes: G08G 1/02 using treadles built into the road pads or other sensitive devices responsive to passage of vehicles E01F11/00
• CPC Class Codes: G08G 1/052 with provision for determining speed or overspeed speed measuring in general G01P
• CPC Class Codes: H10N 30/302 Sensors
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

A vehicle speed monitoring system has a pair of parallel piezoelectric sensors or pressure transducers carried in closely spaced relation by a common elastomeric carrier such that the distance D between the sensors is maintained constant. A time measuring circuit connected to the sensors measures the time between peak voltages induced in the piezoelectric sensor transducers which is used to calculate and display vehicle speed. A weight is secured to or embedded in the carrier to cause the carrier to hug the roadway and be immune to lifting because of air currents and turbulence.

Claims

1. In a vehicle speed sensor system for sensing wheeled vehicular traffic thereover, the improvement comprising, a flexible carrier member having an elongated flat elastomeric member, a pair of elongated piezoelectric pressure sensors embedded in closely spaced parallel relation in said flat, elastomeric member, said elastomeric member maintaining the distance between said piezoelectric pressure sensors constant, and means for measuring the time interval between peak voltages induced in said piezoelectric pressure sensors by wheeled vehicular traffic thereon, and wherein said sensors include a common strip of piezoelectric plastic and a pair of spaced electrodes are formed on said common strip to constitute said pair of piezoelectric pressure sensors.

2. The invention defined in claim 1 wherein the center-to-center spacing for said pair of spaced electrodes is less than one (1) inch.