AKTIEBOLAGET SKF (Gothenburg, SE) has been issued patent number 9127718, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.
The patent's inventors are Barcat, Florian (Tours, FR); Chaussat, Sylvain (Tours, FR); Maze, Pierrick (Tours, FR).
This patent was filed on December 17, 2010 and was published online on September 8, 2015.
From the background information supplied by the inventors, news correspondents obtained the following quote: "Generally speaking, a bearing comprises an inner ring and an outer ring adapted to rotate around a rotation axis, one with respect to the other. In a plain bearing, the two rings are in sliding contact. In a rolling bearing, several rolling bodies are installed between the two rings. These rolling bodies can be balls, rollers or needles. Thus, a rolling bearing can be, for instance, a ball bearing, a roller bearing or needle bearing.
"In the field of bearings, it is known to use a tachometer in order to determine the rotation speed of a member supported by a bearing. As explained in EP-A-1 933 155, one can use an encoder washer with magnetic poles fast in rotation with a rotating ring of a bearing, and one or several sensors distributed around the encoder washer or located in front of it. An air gap is provided between the encoder washer and the or each sensor and detection of the rotation parameter occurs through this air gap, thanks to the variation of a magnetic field generated by the encoder washer.
"Such a detection device can be used in a magnetically perturbed environment such as in the neighbourhood of an electric motor where high magnetic fields are generated between the stator and the rotor. Under such circumstances, the accuracy of the measure performed by the sensor or sensors can be affected by a surrounding perturbing magnetic field, in particular because of electromagnetic interference or EMI.
"U.S. Pat. No. B-6,741,073 discloses several complicated devices meant to build a magnetic bypass in order to avoid influencing a magnetic sensor. This does not protect the sensor from a surrounding perturbing magnetic field.
"U.S. Pat. No. B-7,249,891 teaches the use of a conductive member having an electromagnetic shielding effect on one side only of a sensor holder, which does not efficiently protect a sensor from a surrounding perturbing magnetic field."
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "This invention aims at solving these problems with a new rotation detection set which is efficient even if it works in a magnetically perturbed environment.
"To this end, the invention concerns a rotation detection set comprising an encoder washer rotatable around a rotation axis, at least one sensor adapted to detect a rotation parameter of the encoder washer through an air gap, a support member for holding the sensor with respect to the rotation axis and a mounting member for immobilizing the support member with respect to a fixed structure. According to the invention, the mounting member is made of one piece of magnetic material and has a first wall located on the same side of the air gap as the encoder washer and a second wall located on the same side of the air gap as the sensor, whereas a magnetic body of the encoder washer, the air gap and the sensor are located in a volume defined by this mounting member between these two walls.
"Thanks to the invention, the mounting member works as a magnetic shielding cover which protects the air gap, and thus the variable magnetic field produced by the encoder washer magnetic body, from perturbations coming from either sides of the air gap. The fact that the mounting member is made of one piece makes it economic and reliable.
"In the present description, unless otherwise specified, the words 'axial', 'radial', 'axially' and 'radially' relate to the rotation axis of the encoder washer. A direction is 'axial' when it is parallel to such an axis and a direction or an axis is 'radial' when it is perpendicular to and secant with such an axis.
"According to further aspects of the invention which are advantageous but not compulsory, the rotation detection set might incorporate one or several of the following features, taken in any technically admissible combination: A third wall of the mounting member connects its first and second walls and it is perpendicular to the first and second walls. The third wall is provided with a hole for the connection of the sensor to an electronic device. The support member has an extension engaged within the hole of the mounting member and this extension defines a housing where the sensor is accommodated. The rotation detection device includes several sensors and all these sensors are accommodated in the housing of the extension. The first and second walls are parallel to the rotation axis of the encoder washer. The mounting member is ferromagnetic, in particular made of iron or an iron-based alloy.
"The invention also concerns a bearing assembly comprising a bearing, with a fixed ring and a rotatable ring, and a rotation detection set as mentioned here-above, the encoder washer of the rotation detection set being fast in rotation with the rotatable ring and the support member being immobilized by the mounting member with respect to the fixed ring.
"Advantageously, the mounting member is affixed onto the fixed ring of the bearing by elastic deformation of the mounting member."
For the URL and additional information on this patent, see: Barcat, Florian; Chaussat, Sylvain; Maze, Pierrick. Rotation Detection Set and Bearing Assembly Comprising Such a Detection Set. U.S. Patent Number 9127718, filed December 17, 2010, and published online on September 8, 2015. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsr