CA2464911A1

CA2464911A1 - Hand-held piston velocity detector

Info

Publication number: CA2464911A1
Application number: CA 2464911
Authority: CA
Inventors: Andy Wilhelmus Ketelaars
Original assignee: Eldesco Corp
Current assignee: Eldesco Corp
Priority date: 2004-04-20
Filing date: 2004-04-20
Publication date: 2005-10-20

Abstract

A piston velocity detector to determine the velocity of a magnet carrying piston in a cylinder, preferably in the form of a self-contained, hand-held, battery powered piston velocity detector including a plurality of magnet field sensors disposed in an array fixedly spaced from each other within the detector.

Description

Title Scope of the Invention [0001] This invention relates to a velocity detection device preferably to be manually held and placed near a piston carrying a magnet to determine the speed of movement of the piston.
Background of the Invention

[0002] Pneumatic cylinders are used far various purposes including automated control of machinery and robotics. The pneumatic cylinders have a piston which is linearly moveable within the cylinder. The present inventor has appreciated that the speed of movement of the piston within the cylinder is an important consideration during initial set up of operation of a machine and as well to be con sidered during maintenance or troubleshooting. However, typically there is no capability for providing an indication of piston speed.
Summary of the Invention

[0003) To at least partially overcome these disadvantages of previously known devices the present invention provides a piston velocity detector to determine the velocity of a magnet carrying piston in a cylinder, preferably in the form of a self contained, hand-held, battery powered piston velocity detector including a plurality of magnet field sensors disposed in an array fixedly spaced from each other within the detector.

[0004] An object of the present invention is to provide a velocity detector to determine the velocity of a magnet-carrying piston in the cylinder. Another object is to provide a velocity detector to determine the velocity of a malmet moving past the detector.

[0005] Another object is to provide a hand-held velocity detector particularly adapted to determine the velocity of a magnet-carrying piston in a cylinder.

[0006] Another object is to provide a method of determining the velocity of a magnet-carrying piston in a cylinder.

[0007] Another obj ect is to provide a method for set up, maintenance and/or troubleshooting of pneumatic cylinders having magnetised pistons.

[0008] In one aspect the present invention provides a self contained hand-held battery powered piston velocity detector to determine the velocity of a magnet carrying piston in a cylinder, the detector comprising:

[0009] a plurality of magnetic field sensors capable of sensing magnetic field and providing output signals corresponding to the strength of magnetic held, each of the sensors disposed in array fixedly spaced from other of the sensors,

[0010] electric circuitry which determines, from the output signals from each sensor on movement of the piston past the detector, the relative time when a magnet carried by the piston is closest to each sensor, and calculates therefrom an estimated velocity of the piston based on the relative positions of the sensors in the array, and

[0011] a display mechanism to display the estimated velocity in a human readable form.
Detailed Description of the Drawings

[0012] Further aspects and advantages of the present invention will become apparent from the following description taken together with the accompanying drawings in which:

[0013] Figure 1 is a schematic side view of a pneumatic cylinder in conjunction with a hand-held detector in accordance with the first embodimenl~ to the present invention;

[0014] Figure 2 is an exploded view of the detector of Figure 1;

[0015] Figure 3 is a schematic pictorial view showing a cylinder and a hand-held detector in accordance with a second embodiment of the present invention;

[0016] Figure 4 is an end view of the detector shown in Figure 3;

[0017] Figure 5 is a schematic side view of the detector shown in Figure 3;

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[0018] Figures 6 and 7 are respectively an end view and a side view similar to Figures 4 and 5 but showing a third embodiment of a detector in accordance with the present invention;

[0019] Figures 8 and 9 are respectively an end view and a side view similar to that in Figures 4 and 5 but of a detector in accordance with a fourth embodiment of the present invention;

[0020] Figure 10 is a schematic pictorial view of an end of a detector in accordance with a fifth embodiment of the invention;

[0021] Figure 1 I is a side view of the detector of Figure 10;

[0022] Figure 12 is a schematic pictorial view of an end of a detector in accordance with a sixth embodiment of the present invention; and

[0023] Figure 13 is a side view of the detector of Figure 12.
Detailed Description of the Drawings

[0024] Reference is made first to Figure 1 which illustrates as 10 a self contained, hand-held, battery powered piston velocity detector 10 in accordance with the present invention schematically disposed adjacent a pneumatic actuating cylinder mechanism 12 comprising an enclosed cylindrical cylinder 14 within which a piston 16 is axially slidable. The piston 16 includes a piston rod I 8 and a piston head 20. The piston head 20 includes and carnes a permanent magnet 22. The rod 18 extends out one end of the cylinder in a sealed relation as is known. Two air lines 24 an:d 26 are schematically illustrated to communicate with each closed end of the cylinder. While not shown, each of these air lines 24 and 26 are adapted, to in a controlled manner, be selectively coupled to either vent air from the cylinder or apply pressurized air to the cylinder.
In known manner, the velocity of movement of the piston 16 can be controlled as by controlling flow valves which may control the rate at which air may enter or exit the air lines to the cylinder.

[0025] In use, the outer end 28 of the piston I8 may be connected to one element and a far end 30 of the cylinder I4 may be connected to another element such that the movement of the piston 18 in the cylinder 14 provides relative movement between the elements.

[0026] The piston 18 is coaxially slidable within the cylinder 14 about a cylinder axis 32.

[0027] Figure 1 schematically shows the detector 10. The detector 10 as best seen in a schematic pictorial exploded view in Figure 2 preferably has upper and lower outer casing 34 and 36 carrying a circuit board 38 there between. The circuit board 38 carries a pair of batteries 40 to provide power for electronic circuitry including a central processing unit 42, two manual switches 44 and 46, an array of magnetic field sensors 50 and a liquid crystal display 48. The detector 10 is preferably sized so as to be hand-held and preferably is in the size of a normal writing instrument such as a pen or pencil having for example a length in the range of 8 to 20 centimetres and a width in the range of preferably about 1 to 2 centimetres.

[0028] In the preferred embodiments, the magnetic field sensors 50 are preferably Hall effect sensors. Hall effect sensors are well known and for example are used to provide a voltage signal proportional preferably directly, proportional to the strength of the magnetic field sensed by the Hall effect sensors. Such sensors are well known and for example sensors of this type are described in U.S. Patent No. 5,581,179 to Engela et al.

[0029] A preferred manner of use of the Hall effect sensors in accordance with the present invention is to provide at least two sensors at different axial positions relative to the axis of the cylinder 14 such that, on the piston head 20 moving past the sensors 50, to determine the time when the piston head 20 is closest to each sensor 50. The magnet 22 and the piston head 20 will be closest to each sensor 50 at a time when the voltage signal from that sensor is at its peak or maximum. From the different relative times that the magnet 22 carries by the piston is determined to be closest to each sensor 50, it is possible to calculate the estimated velocity of the piston 16 based on the relative positions of the sensors. The input from the sensors are provided to the central processing unit 42 where calculations are carried out and output is displayed on the LCD display providing an estimated velocity in suitable units such as meters per second.
The LCD
display 48 of course provides the display in human readable form. If desired, the LCD 48 may also display frequency.

[0030] In the context of Figure l, the hand-held detector 10 is manually held proximate to the cylinder 14 with the two sensors 50 spaced apart a fixed distance indicated D. In this embodiment utilizing two sensors, the hand-held unit 10 needs to be held stationary adjacent the cylinder with the sensors 50 spaced from each other in a direction parallel to the cylinder axis 32.

(0031] In this regard in accordance with the present invention, the two Hall effect sensors 50 are spaced side by side in a symmetrical arrangement on either side of a plane of symmetry indicated as 52 which extends out of the plane of Figure 1 normal to the axis

32. The planar face of the LCD display 48 is illustrated as being disposed in a plane normal to the plane of symmetry 52.
[0032] For proper reading with the two sensors 50 arranged as illustrated in Figure l, the detector 10 is to be arranged with its plane of symmetry 52 perpendicular to the axis 32. To state this another way, the detector 10 should be directed such that it extends perpendicularly away from the axis of the cylinder 14 and with the planar face of the LCD display 48 disposed in a plane which is parallel to the axis 32. The longitudinal configuration of the detector 10 and the planar face of the LCD display 48 as well as for example the relative orientation of the sides 54 and top 56 of the casing of the detector 10 provide visual indicators to a user as to a proper manner in to which to orient the detector relative to any cylinder 14 to obtain an appropriate reading.

(0033] The detector 10 preferably has manual controls for use by a user. The preferred embodiment of Figures 1 and 2 has merely two controls one comprising a reset button 74 and the other comprising a hold button 76. The detector 10 is preferably arranged such that after any use the electrical circuitry will turn itself off following a period of time, for example thirty seconds. The reset button 74 effectively serves as firstly an on button to turn the device on and secondly as a button to cancel the previous display on the LCD display 48 readying the detector for an additional measurement. The detector is preferably provided with circuitry such that merely one velocity measurement is made at a time and the LCD display will display the reading from that one measurement fox a stated period of time for example thirty seconds. If the measurement is desired to be held for a longer period of time as for example three minutes then the hold button 76 is pushed for continued longer display.

[0034] Reference is made to Figures 3, 4 and 5 which illustrate a second embodiment of a detector 10 in accordance with the present invention which is substantially identical to that shown in the first embodiment but utilizes a detector having a different casing.
The detector IO illustrated in Figures 3 to 5 has a cylindrical. body 58 which carries at one end a locating arm 60. The locating arm 60 comprises an elongate rod with a flat surface 62 adapted to be placed in engagement with the outer surface of the cylinder 14. The locating arm 60 is elongate and adapted such that the arm extends longitudinally parallel to the axis 32 of the cylinder when the detector 10 is in a desired position.
The arm 60 is secured to the detector body 58 in a manner that with the arm 60 engaging the surface of the cylinder the main body 58 of the detector 10 extends perpendicular to the surface of the cylinder.

[0035] The detector illustrated in Figures 3 to 5 like the detector illustrated in Figures 1 and 2 includes two Hall effect sensors 50 which sensors as best seen in the end view of Figure 3 and the side view of Figure 4 are located in an array spaced a fixed distance from each other a constant distance from the surface 62 of the arm 60 and longitudinally relative to the arm 60.

[0036] The arm 60 in combination with the detector body 58 thus provides a visual indicator to a user as to how to orient the detector 10 by location engaging or adjacent a cylinder to provide for an accurate measurement of the velocity.

[0037] In accordance with the embodiment illustrated in Figures 3 to 5, the locating arm 60 may be a separate removable element which can be removed to facilitate carrying of the sensor in a pocket or may be removable to be received in a recess provided in the main detector for easy carrying. The locating arm 60 may also be hinged or foldable so as to be folded to extend along the sides of the main body 58 of the detector in use.

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[0038] For convenience the sensors in Figures 3 to 5 and 6 to 13 are shown in solid lines even though they are not visible from outside the detector 10 and would normally be shown in dashed lines. For convenience also Figures 3 to 5 and 6 to 13 the equivalent of the LCD display and switches are not shown.

[0039] Reference is now made to Figures 6 to 13 which illustrate third to sixth embodiments of detectors in accordance with the present invention adopting different configurations of fixed arrays for sensors to be used with detectors in accordance with the present invention.

[0040] Refernng to Figures 6 and 7, three sensors 50 are shown as provided in a triangular array. The three sensors 50 are all disposed in a common flat plane 64 and this plane 64 is preferably normal to a longitudinal centre axis 66 centrally through the detector body 58. In accordance with the embodiment illustrated in Figures 6 and 7, preferably the forward end of the detector 10 provides a flat planar surface 70 parallel to the plane 64 in which the three sensors 50 lie. Preferably the flat forward surface 70 of the detector is engaged adjacent the outer surface of the cylinder 14 to extend tangently thereto in which case the longitudinal centre axis 66 through the main body of the detector 10 would be normal to the axis 32 of the cylinder. W accordance with the embodiment in Figure 6, accurate velocity measurement may be detected in every rotational position the detector may assume as rotated about its longitudinal centre axis 66.

[0041] Figures 8 and 9 illustrate an embodiment substantially identical to that in Figures 6 and 7 however having four sensors 50 arranged in a plane 64 equally distanced from the flat front end surface 70 of the detector 10 as in a square.
Operation and use of the embodiment of Figures 8 and 9 are substantially the same as with Figures 6 and 7.

[0042] Reference is made to Figures IO and I I which illustrate the use of four sensors 50 however disposed in a pyramid as shown with three of the sensors disposed in a triangle in a plane 64 parallel to the flat front surface 70 of the detector I O and the fourth disposed spaced from this plane 64. With the embodiment illustrated in Figures IO
and 1 l, the detector I O may be used by merely placing the end of the detector I O adjacent the cylinder and accurate readings can be obtain irrespective of the angular orientation of the detector's central axis 66 relative to the cylinder.

[0043] Figures 12 and 13 illustrate a three dimensional array incorporating six sensors 50 each disposed at the corner of a cube. As is the case with the array in Figures and 1 l, a detector 10 incorporating the sensors in the three dimensional array of Figure 12 can provide for accurate sensing irrespective of the relative orientation of the array relative to the cylinder.

[0044] In accordance with the present invention there is provided a method for set up, maintenance and troubleshooting of cylinders. In accordance with this method, a user takes a measurement of the velocity of the piston in the cylinder at a specific location along the cylinder. Preferably this position is marked as for example by placing a label or ink marking or scratches, small drill hole notch or engraving mark on the outside surface of the cylinder and recording the velocity at this point.
Subsequently, in the event of maintenance and/or troubleshooting, further measurements may be made at the same location to determine consistency of use. Such a marking is iindicated in Figure 2 by a line 78.

[0045) In respect of calculations required in respect of the two sensor detectors illustrated in Figures 1 to 5, with the sensors correctly oriented parallel to the axis 32, and knowing the distance between the two sensors, the velocity of the piston head can be determined merely by calculating the time between the maximum sensed by each of the two sensors and dividing the distance between the two sensors by this time.

[0046] In the context of the sensor illustrated in Figures 6 and 7, the relative times of maximum signal for each of the three sensors 50 will provide: a trigonometric function to calculate the velocity having regard to the spacing of the sensors within their common plane 64 and the time of maximum signal at each sensor. As a simple example, if the three sensors are arranged in a right triangle and two of the sensors on a first side of the right triangle have a maximum at the identical time then the velocity can be calculated by dividing the distance between the two sensors on the other, second right side of the triangle with the difference in time between those two sensors. Similar arrangements can be made with triangles of other known shapes. Similarly, insofar as in accordance with the embodiments of Figures 8 and 9 there are more than three sensors in the same plane then similar geometric calculations can be made with the additional sensors providing for increased accuracy.

[0047] All of the calculations of course in accordance with the embodiments of Figures 1 to 8 assume that the detector 10 is held fixed in the desired orientation for its array relative to the cylinder. The velocity is calculated indicative of the average speed and does not provide an indication of acceleration or deceleration.

[0048] In respect of the embodiments illustrated in Figures 10 and 13 which provide a three dimensional array of sensors, the sensors preferably are calibrated to provide for comparable signals with distance from the magnet as for example by each of the sensors being identical. With knowledge of the distance of each sensor from the magnet, in a similar manner that two dimensional trigonometric arrangements were developed in respect of the embodiments of Figures 6 to 9, three dimensional trigonometric calculations can be preformed and thus provide an estimate of the piston speed without the need for the detector array to be located in any particular three dimensional orientation relative to the cylinder or its axis.

[0049] In respect of the detectors having three or more sensors in an array and where not all such sensors are disposed on the same linear line then. is it preferred to have each sensor provided, preferably to be identical, such that the signal produced by the magnet passing the sensor can also provide an indication as to the distance of each sensor from the piston head. Information regarding the distance of each sensor from the piston head can be used towards calculating the relative direction of movement of the piston, that is, the orientation of the axis 32 of the cylinder relative to the orientation of the sensors in the array.

[0050] While the invention has been described with reference to preferred embodiments many modifications and variations will occur to persons skilled in the art.
For a definition of the invention reference is made to the following claims.

Claims

WE CLAIM:

1. A self contained hand-held battery powered piston velocity detector to determine the velocity of a magnet carrying piston in a cylinder, the detector comprising:
a plurality of magnetic field sensors capable of sensing magnetic field and providing output signals corresponding to the strength of magnetic field, each of the sensors disposed in array fixedly spaced from other of the sensors, electric circuitry which determines, from the output signals from each sensor on movement of the piston past the detector, the relative time when a magnet carried by the piston is closest to each sensor, and calculates therefrom an estimated velocity of the piston based on the relative positions of the sensors in the array, a display mechanism to display the estimated velocity in a human readable form.

2. A detector as claimed in claim 1 wherein the electronic circuitry determines at the time when the piston is closest to any one sensor the relative strength of the magnetic field at that sensor.

3. A detector as claimed in claim 2 wherein the plurality of sensors includes at least three sensors, and calculates the estimated velocity having regard to a calculated annular juxtaposition of the sensors relative to direction of movement of the piston.

4. A detector as claimed in claim 1 wherein the detector having external features visually apparent to a user in guiding the user in relative location of the detector to have the array of sensors in desired juxtaposition relative a piston carrying cylinder.

5. A detector as claimed in claim 4 wherein the detector having two sensors, the external feature guiding location of the detector with the two sensors spaced in a direction parallel an axis of the cylinder.

6. A detector as claimed in claim 4 wherein the detector having three sensors arranged in a triangle in a plane;
the external feature guiding location of the detector with the plane normal to a radius of an axis of the cylinder.

7. A detector as claimed in claim 2 having at least four detectors three arranged in a triangle in a plane and a fourth spaced from the plane.