WO2019202435A1

WO2019202435A1 - Magnetic apparatus with plurality of pole pieces and search coils for determining shape and/or contour of a work piece

Info

Publication number: WO2019202435A1
Application number: PCT/IB2019/052918
Authority: WO
Inventors: Uttam Sarda
Original assignee: Shree Magnets Private Limited
Priority date: 2018-04-16
Filing date: 2019-04-09
Publication date: 2019-10-24

Abstract

The present invention relates to a magnetic apparatus (1) with plurality of pole pieces (2) having tapered edges (3) and search coils wherein at least one of the pole pieces is divided into a plurality of segments by creation of a slot(s) (5) separating the flat and tapered surfaces and at least two search coils are provided for surrounding the designated flat, tapered or entire periphery of the pole piece(s) which enables one to determine shape/contour of the workpiece from observed variations in the flux values in the search coils. The intact pole piece surrounded by a search coil (4) and another search coil (19 or 6) may surround any other pole piece. The printed circuit boards (PCB) of the magnetic apparatus are deployed around the bases of the pole pieces in lieu of search coils for convenience of operation.

Description

COMPLETE SPECIFICATION

(See section 10 and rule 13)

1. TITLE OF THE INVENTION

“MAGNETIC APPARATUS WITH PLURALITY OF POLE PIECES AND SEARCH COILS FOR DETERMINING SHAPE AND/OR CONTOUR OF A WORK PIECE”

2. APPLICANT(S):

a) Name: SHREE MAGNETS PRIVATE LIMITED

b) Nationality: Indian

c) Address: 81, Sodepur Barasat Road, Kolkata - 700 110, West

Bengal, India.

3. PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed. 4. DESCRIPTION

Technical Field of the Invention This invention relates to a magnetic apparatus with plurality of pole pieces and search coils for effectively recording variations in flux density which are indicative of the shape and contour of a workpiece. More particularly, this invention pertains to a magnetic apparatus with plurality of search coils which effectively records variations in the flux density and employing a novel concept of segmented pole pieces with coils or flexible printed circuit boards.

Background of the Invention

Heretofore magnetic work holding devices have been employed for gripping ferromagnetic workpieces in the workshops. The same work holding device has different magnetic lifting/clamping capacity depending on the contour of the job. For assessing the magnetic flux density of the workpiece, search coil is to be provided around the periphery of the poles in the apparatus. The data generated are used to indicate whether the workpiece is within the predetermined limits, which are different for flat and round jobs and the work holding device has to be manually corrected. However, in the conventional system it is often difficult to assess whether variations in the flux values, often on the lower side, are due to unevenness of the surface of a flat job or workpiece or because of rotundity of the job. Such uncertainty results in interruptions for actual assessment and tallying of the flux values in conformity with the physical appearance of the job so that it conformed to the profile of the work piece and recorded the data accordingly.

The present invention aims at overcoming the drawbacks narrated above by providing a plurality of search coils inside and around one or each of the magnetic poles. The flux values obtained from these search coils can be used to determine the shape / contour of the job and also automatically correct the expected data of flux values.

A few prior published patent documents are known to exist which are given herein by way of reference -

EP1419034B1 discloses a magnetic clamping device having at least one magnetic holding unit comprising a switchable magnet generating a magnetic clamping force at a workpiece and a sensing means, wherein said sensing means comprises a search coil adapted to provide a detection signal indicative of a magnetic flux being applicable for at least approximately determining a clamping force exerted on the workpiece to be clamped.

US5432444A discloses an inspection device with an exciting coil for generating an electromagnetic field and an induction coil which are integrally connected to each other in a coaxial relation so as to induce mutual inductance in the induction coil by the electromagnetic field. The device uses electromagnetic induction for detecting an abnormality in an an object or inspecting given objects of all kinds such as, foods, medicinal tablets, synthetic resin products and various workpieces

Summary of the Invention

Present invention relates to a magnetic apparatus with plurality of search coils which effectively records variations in the flux density and employing a novel concept of segmented pole pieces with coils or flexible printed circuit boards (hereinafter referred to as PCB for the sake of brevity and convenience, unless otherwise stated) around their peripheries for recordal of variations in flux density with a degree of accuracy, which enables the user to determine the shape and/or contour of a workpiece with consequent deployment of safe working criteria. The work holding limits are defined and indicated differently for different shape, size and configuration of jobs. A flat job can be held more securely, and the flux values are expected to be significantly higher in comparison when a round job is held. The invention helps in determining the shape and contour of the workpieces on the basis of the variations in the magnetic induction in different search coils and automatically corrects the safe working limits of the device without any interruption or manual interruption.

The principal object of the invention is to provide a magnetic apparatus which can effectively record the variations in flux density with accuracy which can ascertain the shape and /or contour of a workpiece.

Another object of the invention is to provide a magnetic apparatus which can accurately record the variations in flux density which enables to determine the exact shape and configuration of a workpiece resulting in uninterrupted operations of safe work.

The other object is to provide for a process to ascertain the shape and /or contour of a workpiece or job while operating a magnetic apparatus.

The foregoing objects are achieved by the present invention disclosed herein.

According to an aspect of the present invention, a magnetic apparatus with a plurality of pole piece(s) having tapered edges and search coil, characterized in that at least one of the pole pieces is divided into a plurality of segments by creation of a slot(s), separating the flat and tapered surfaces and at least two search coils are provided for surrounding the designated flat, tapered or the entire periphery of the pole piece(s) in order to ascertain the shape or contour of the workpiece from the observed variations in the flux values in the search coils. In accordance with the aspect of the present invention, the intact pole piece is surrounded by a search coil and another search coil may surround any other pole piece. The printed circuit boards (PCB) are deployed around the bases of the pole pieces in lieu of search coils for convenience of operation.

In accordance with the aspect of the present invention, the pole pieces are divided into a plurality of rectangular flat segments, there being a small gap or channel between two adjacent segments, barring the terminal segments, the entire assembly being equipped surrounded by PCB.

In accordance with the aspect of the present invention, each segmented pole piece is equipped with a PCB, thereby affording a closer monitoring of flux values and consequent determination of shape, size and contour of the jobs or workpieces. In accordance with the aspect of the present invention, a second search coil or PCB is provided around a designated pole piece in the system which helps in determining the quantum of magnetic flux passing through a workpiece having a flat surface, whereas considerably less flux passes through the job when it has a round shape. According to another aspect of the present invention, a process to determine the shape or contour and/or size of a job or workpiece comprises of recording the magnetic flux data and analysing the observed variations of flux values while operating a magnetic apparatus, which determines the quantum of magnetic flux through a workpiece having a flat surface whereas considerably less flux passes through the job when it has a round shape. Brief description of the drawings

The invention will now be described by means of the drawings accompanying the provisional specification, each of which illustrates different embodiments of this invention.

Fig. 1 shows a conventional magnetic apparatus with search coil around the periphery of the pole pieces; Fig. 2 shows a magnetic apparatus of the present invention without any workpiece to be dealt with, e.g. lifted or shifted;

Fig. 3 shows a magnetic apparatus of the present invention with a work piece having flat surface resting on the pole pieces, simultaneously showing the direction of flow of magnetic lines of force;

Fig. 4 shows an apparatus of this invention depicting magnetic pole surface holding a workpiece with round profile and the direction of flow of magnetic lines of force; Fig. 5 shows an apparatus of this invention showing magnetic pole pieces, each of which is surrounded by search coils around the periphery of each one of the said pole pieces;

Fig. 6 is an apparatus as illustrated in Fig. 5 and carrying a job or work piece which does not cover the entire upper surface of the pole pieces;

Fig. 7 shows a PCB (printed circuit board) for acting as a search coil resting around the bottom periphery of the pole pieces; Fig. 8 shows an arrangement made in the apparatus of this invention wherein each one of the pole pieces have been subdivided into multiple segments and a PCB as shown in Fig. 7 covers the peripheral areas of the segmented pole pieces; Fig. 9 shows an apparatus of this invention with segmented pole pieces carrying a job or workpiece with a flat surface but of smaller dimensions without covering the entire upper surfaces of the segmented pole pieces, leaving some of the said pole pieces bare or unused; and Fig. 10 shows a PCB arrangement subdivided into a multiplicity of rectangular profiles covering the periphery of each one of the segmented pole pieces as in Fig. 9.

In addition, the present specification also refers to the sole figure accompanying this specification which illustrates another embodiment of the present invention.

Detailed Description of the Invention

According to the invention there is provided a magnetic apparatus with plurality of pole pieces having tapered edges and search coil, characterized in that at least one of the pole pieces is divided into a plurality of segments by creation of a slot, separating the flat and tapered surfaces and at least two search coils are provided for surrounding the designated flat, tapered or the entire periphery of the pole piece in order to ascertain the shape or contour of the workpiece from the observed variations in the flux values in the search coils.

In accordance with another embodiment of the invention, the intact pole piece is surrounded by a search coil and another search coil surrounds the flat or tapered area of the other pole piece. In a further embodiment of the invention the segmented pole pieces carry search coils around all of them by employing PCB for ease of operation and also to handle round job. In a still further embodiment of the invention each one of the pole pieces are divided into a multiplicity of parts or segments and around each one of such segmented pole parts there is deployed PCB suitably secured for ease of connection and recordal of data.

The invention also encompasses a process to determine the shape/size /contour of a job or workpiece by recording the variations of magnetic flux data while operating the invented magnetic apparatus.

The invention will now be further amplified with reference to the aforesaid drawings accompanying the provisional specification and also this specification thereafter.

In Fig. 1, (1) stands for the magnetic apparatus, (2) shows the magnetic pole, (3) shows the chamfered edge of the magnetic pole to accommodate work pieces with round and or flat profile and (4) depicts search coil. Referring to Fig. 2 illustrating the magnetic apparatus of the present invention wherein numerals (1), (2), (3) and (4) have the same significance as above, (5) shows the slot and (6) denotes the search coil specifically designated for sensing flux generated in flat workpieces. Fig. 3 of the drawings shows a flat workpiece, (7) and (8) gives the direction of lines of force flowing through the workpiece having no surface undulations or irregularities. In Fig. 4 of the drawings there is shown a round object (9) resting on the chamfered edges of the magnetic poles and having search coils as shown in Fig. 2 of the drawing and (10) shows the flow path of the magnetic lines of force. Fig. 5 shows a duality of pole pieces (11) each one of which carries a search coil (12) at the bottom periphery, which could be done manually, or two separate segmented PCB may be deployed for convenience of operation.

Fig. 6 shows an arrangement with two separate pole pieces carrying a job (13) which has a flat, quadrilateral profile not covering the entire upper surface area of the pole pieces.

Fig. 7 shows a PCB with two rectangular halves capable of covering the peripheral regions of the pole pieces.

Fig. 8 shows an arrangement in accordance with a particular embodiment of this invention in which each pole piece is divided into a multiplicity of segments, there being a small gap or separation (14) between two adjacent segments, barring the terminal ones, and equipped with a PCB (15) as illustrated in Fig. 7.

Fig. 9 shows an arrangement with segmented pole pieces as in Fig. 8 and carrying a job or workpiece (16) which is of smaller dimension in comparison to the available total surface area of the pole pieces. In this instance the workpiece is firmly held due to the ingress of magnetic flux through the job which necessitates extra effort to dislodge it form the chuck head. However, the variation in the flux density gives an indication of the profile and dimension of the workpiece subjected to machining.

Fig. 10 shows yet another embodiment of this invention wherein PCB has been designed in such a manner that it covers the periphery of each segmented pole pieces affording a closer monitoring of flux values and determination of shape, size and contour of the jobs or workpieces taken up on the working table or chuck for machining.

From an operational point of view, only one search coil (4) in and/or around periphery as in the conventional equipment is meant to detect for both flat and round workpieces.

For round jobs, the flux values could also be lower due to presence of large air gaps and undulations while handling even flat workpieces and this constituted a drawback for the conventional equipment. On the contrary, according to the subject invention the second search coil (6) provided around the flat area of the second pole piece in the set up detects magnetic flux passing through it only when the workpiece has a flat surface. However, less flux would pass through it when the job has a round shape. The observed variations in the values of flux are indicative of the profile of the workpiece, i.e. whether the job is flat or round. Similar flux values observed infer that the job has a flat surface. On the other hand, when the value(s) obtained from (6) is significantly lower than the value(s) obtained from (19), then such variations denote that the job is round and such a ready reckoning of the job profile is indeed a distinct advantage of the present invention which substantially eliminates all elements of uncertainty.

The invention will be further explained by means of an additional embodiment of the invention with Fig. 11 accompanying this specification in which numerals 1 to 6 have the same significance as defined hereinabove in connection with Figs. 1 and 2 of the drawings accompanying this specification. Numeral (19) indicates a search coil around tapered peripheral area the pole piece, and the difference in the generated flux values in the different search coils indicates the shape of work piece and the expected magnetic force generated. It has been observed that for work pieces having flat surfaces but of smaller dimensions the arrangement shown in Fig. 9 affords a greater degree of accuracy in recording measurements of flux density in comparison to the arrangement shown in Fig. 6 as the segmented pole pieces which are not brought into play are effectively traced while recording the variations in flux density. This constitutes a notable improvement not hitherto achieved.

The subject invention enables an operator to determine automatically the exterior contour of a workpiece by merely noting/comparing the different values of the magnetic flux and resulting variations in parameters like voltage in different search coils.

Having described the invention in detail with particular reference to the illustrative drawings accompanying this specification, it will now be more specifically defined by means of claims appended hereafter.

Although the preferred embodiment of the subject invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing or deviating from the scope and spirit of the invention.

Having described the invention in detail with particular reference to the illustrative drawings and relevant description given above, it will now be more specifically defined by means of claims appended hereafter.

Claims

5. CLAIMS I/We Claim

1. A magnetic apparatus (1) with plurality of pole piece(s) (2) having tapered edges and search coil, characterized in that at least one of the pole pieces is divided into a plurality of segments by creation of a slot (s) (5), separating the flat and tapered surfaces and at least two search coils are provided for surrounding the designated flat, tapered or the entire periphery of the pole piece(s) in order to ascertain the shape or contour of the workpiece from the observed variations in the flux values in the search coils.

2. A magnetic apparatus as claimed in Claim 1, wherein the intact pole piece is surrounded by a search coil (4) and another search coil (19 or 6) may surround any other pole piece.

3. A magnetic apparatus as claimed in Claim 1, wherein printed circuit boards

(PCB) are deployed around the bases of the pole pieces in lieu of search coils for convenience of operation.

4. A magnetic apparatus as claimed in Claims 1 to 3, wherein the pole pieces are divided into a plurality of rectangular flat segments, there being a small gap or channel between two adjacent segments (14), barring the terminal segments, the entire assembly being equipped surrounded by PCB (15).

5. A magnetic apparatus as claimed in Claims 1 to 4, wherein each segmented pole piece is equipped with a PCB, thereby affording a closer monitoring of flux values and consequent determination of shape, size and contour of the jobs or workpieces.

6. A magnetic apparatus as claimed in any of the preceding claims, wherein a second search coil or PCB (6) is provided around a designated pole piece in the system which helps in determining the quantum of magnetic flux passing through a workpiece having a flat surface, whereas considerably less flux passes through the job when it has a round shape.

7. A process to determine the shape/contour/size of a job or workpiece comprising recording the magnetic flux data and analysing the observed variations of flux values while operating a magnetic apparatus of claim 1 to 6, which determines the quantum of magnetic flux through a workpiece having a flat surface whereas considerably less flux passes through the job when it has a round shape.