India: Revocation Application/ Proceeding Summary: Improved Diffuser For An Air Conditioning System

Last Updated: 5 January 2015
Article by Ankur Sehgal

Applicant in this case is M/s Air Master Equipments India (P) Ltd and Respondents are:

  1. Mr. Ramesh Nana Mhatre, who is the inventor and Applicant of the granted patent application being discussed, and
  2. Controller of Patents who granted the patent post examination and prosecution. Title of the application is 'An improved Centre Core, Intermediate Core and an outer frame for a diffuser for use in central air conditioning system and an improved diffuser incorporating them and the method of manufacturing the same' and case number is TRA/1/2008/PT/CH. The order number of case being discussed is NO 75/2011

To brief a bit on the understanding the subject matter, in a central air conditioning system, air that is conditioned to a desired temperature at one source is distributed to various places through a network of ducts, and a diffuser is required at every outlet of the duct. Generally, these ducts are of square or rectangular cross section, most probably due to their easy self-resting and properly adjusting nature in corners of the ceiling in the buildings and vehicles, and therefore the diffuser used at the outlet of an air distribution duct is also of square or rectangular shape. The diffuser fitted at the end of the air distribution duct projects/exposes out from the ceiling of a room or any other space required to be air conditioned, and therefore plays a part in interior decoration or overall look of the room/space. Respondent, through his invention, therefore wishes to solve following drawbacks in existing diffusers:

  1. Sometimes, the side sections of each core and outer frame are welded together at corners to avoid gaps, or corner sections, after fixing into the grooved channel sections on the back of two adjacent side sections, are crimped for assembly. The cores are inter-connected through connecting strips that are welded to the collars of each core. The welding and crimping operations require extra equipment as well as these operations are very time consuming thereby increasing the cost of production.
  2. Due to the grooved channel sections at the back side of each side section and corner sections used for the assembly or cores, the weight of the diffuser is increased which also increases the cost of production.
  3. To avoid gaps at the corners of the core(s), the side sections of the cores are produced with high precision, which increases the cost.
  4. On assembly some times there remains a gap between two side sections, at the corners of the core(s), due to which diffusers are rejected, resulting into a big loss of production i.e. material and labour and which further increases the cost of production.
  5. When a diffuser is attached to a duct and conditioned air is blown through the duct, it is noticed that the air is not diffused equally to all sides at the corner sections as the grooved channel sections or ridges at the back surfaces of the cores come in the path of air and disturb the equal and proper diffusion of air in all directions. The enclosed collars of the centre core and intermediate core(s) rebounds the air, thereby reducing the flow or air through corners of the diffuser.
  6. As the diffuser is manufactured in several pieces, which are assembled, manufacturing process is cumbersome, time consuming and labour oriented and increases the cost of production.
  7. Due to the grooved channel sections and corner sections or ridges and welding spots on the back surface of the core(s), dust is accumulated therein, which is difficult to clean.
  8. Dust is also accumulated in gaps at corners on the front surfaces of the cores, which gives a dirty look to the diffuser and tarnish interior decoration look of the room/space.

A main object of this invention is therefore to obviate the above mentioned drawbacks of the existing diffusers and to provide an improved diffuser for central air conditioning system, wherein each of the central core and/or the intermediate core(s) and/or the outer frame are manufactured in a single piece and both the outer as well as inner surfaces of the cores and/or the outer frame are smooth without any extra section, projection or groove which dispenses with the requirement of extra material, and the time taken for assembly is also very much reduced and at the same time there is no obstacle in the flow path of air, which is diffused equally in all the directions. As the cores are manufactured in a single piece, there is no question of any gap at the corners thus no chance of rejection of the product and no need of any welding and crimping operations and hence the cost of production of the diffuser will obviously be very less.

Respondent No. 2 (Controller of Patents) was satisfied that the invention was patentable and accordingly the patent was granted vide No. 181821 on 18th Jan, 1995. On 25th August 2006 the Respondent No. 1 sent a legal notice to the Applicant, wherein according to this notice, the Applicant was inter alia informed of the patent in favour of the Respondent and that the Applicant was not entitled to manufacture or sell air diffusers identical to the patented product or substantially similar to it. The Applicant sent a lawyer's reply dated 13-9-2006 alleging that  the patented product was known in the market, it was neither new nor novel, and that there is concealment of material facts and that the patent was obtained by fraud. It was also alleged that the Respondent was nothing but a job-worker.

After this exchange of correspondence, the Applicant filed O.P. 704 of 2006 before the Hon'ble Madras High Court for revocation of the patent. This was transferred to IPAB. Counter statement was filed and both sides also filed the evidence to support their case.  Applicant submitted that there was no novelty in the invention and it was obvious and also submitted that the main feature of the invention even according to the Respondent was that it was a single piece centre core to facilitate clean flow of air. He submitted that diffusers have been known for long and there was evidence to show that there was prior art where the single piece units were known. He referred to Series 5700 louvre face ceiling diffusers. From the paper book, he pointed out that there is specific reference to one piece stamped steel construction and that this prior art was also meant to provide an economic solution to air distribution problems requiring equal throw in all directions. According to him, this anticipated the patented product. Further, he submitted that if the only difference is the manner in which the inner assembly can be removed, that hardly qualifies for the grant of a patent.  He then referred to another prior art.  Series 5800 and 5800A louver face Directional Diffusers. He submitted that this too indicated provision of equal throw, quick release of inner assembly for immediate access and ease of installation. According to him, the fact that the prior art was used for ceiling air–conditioners while the patent product was for central air-conditioner will not make it non-obvious.  He also referred to Titus and Trox catalogues, without bearing any dates. On being asked to provide the dates of these documents, he was unable to give any acceptable evidence. Therefore, only two prior arts were provided by the applicant.

Respondent (Patentee) on the other hand submitted that till 1995 there was no prior art that anticipated the claimed subject matter. All the single piece units were extruded aluminium, which meant that metal sheets were cut and joined. The patented product was, on the other hand, made as a single unit from a special die in a metal press.

Respondent also produced, before the IPAB board, samples of the prior art and the patented product and submitted that it was wrong to call the Respondent a job worker and that he had won many awards and recognition of his expertise. He submitted that the patented product was supplied by the Respondent to persons in the same business not only in India but abroad too. He submitted that while the prior art shows joints, corners and gaps, the patented product is one smooth surface with no gaps or joints. Also, in the prior art, the assembly is detached by turning clockwise, whereas in the patent product, it is held by spring and is removed by applying pressure. He also submitted that in the prior art, there is a buttoned hole in the centre cone, while the patented product has an outwardly and downwardly directed slanting surface with neither a button nor hole. He submitted that the prior art has uneven surface and crimping and that the air is distributed by rebound, whereas in the patented product, there are no hindrances to the flow of air. The patented product has clear slots while the prior art does not. He further submitted that the prior art is limited to 2 or 3 cone inner assembly, whereas the patented product can have multiple cores depending on the requirement. The Respondent further pointed out to the tabular column in the Respondent's counter statement where each and every distinguishing feature of the patented product is explained and submitted that the prior art does not teach the invention and that the patented produce is new and non-obvious.  He also submitted that, in addition to the counter statement, the Respondent has marked in evidence the affidavit of one Mr. Pankaj Dharker of impeccable credentials who has affirmed that the product is an invention. He submitted that there is no proof of wrongful use or suppression of information and therefore the Applicant can not raise these grounds without proof. As regards prior publication, the Respondent submitted that there should be material to show that it was published. Respondent further submitted that as regards the ETL report, no reliance can be placed on it without an affidavit to file it as evidence, and in any event, it only refers to diffusers constructed of extruded aluminium, which can not be prior art as far as this product is concerned.

Submissions were heard and the matter was examined by Hon'ble Justice Prabha Sridevan, wherein it was concluded that the Respondent was most certainly not a job worker and that the evidence filed by the Respondent shows the number of awards and recognition of his merit that he has received from various people including the Government. It was further held that the Applicant also did not seriously urge that stand and that the applicant had not filed any evidence apart from the two prior arts to support its case. It was further stated that the Respondent, on the other hand, had filed a very important piece of evidence that was the affidavit of the expert in the field and spoke of the disadvantages that existed in the diffusers prior to 1995. Evidence of Pankaj Dharker showed that in the existing art, because of the corner sections and the grooved channels, flow of the air was obstructed and that there was a reduction of airflow because in the prior art air rebounded. It was also appreciated that the assembly of various parts was a costly process and that the prior art required joining of the various parts and if this was not done with a high degree of accuracy, there was likely to be higher rate of rejection. Furthermore, it was noted that the prior art designs were aesthetically inferior and that the accumulation of dust was high. His affidavit showed the prior art and the patented product in comparison, both with photographs and with explanatory notes. From the affidavit of the respondent and the supporting evidence, it was concluded that the prior art series 5700 and 5800 did not teach the patented product, and that the claimed subject matter was a new invention that served the object of the invention and also avoided the existing drawbacks of the prior art. 5700 and 5800 are the same except for the fact that 5700 has a 2 cone assembly, while 5800 has a 3 cone assembly. The TROX and the Titus catalogues were not considered since there was no date and It was not know if they are prior to the patented product, but the expert dealt with even those products and has given the opinion that they do not teach this invention. A test for obviousness was applied and it was concluded that the invention was non-obvious. In view of the reasons stated above, it was confirmed that the invention was novel and non-obvious and the revocation application was dismissed.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

To print this article, all you need is to be registered on

Click to Login as an existing user or Register so you can print this article.

In association with
Up-coming Events Search
Font Size:
Mondaq on Twitter
Register for Access and our Free Biweekly Alert for
This service is completely free. Access 250,000 archived articles from 100+ countries and get a personalised email twice a week covering developments (and yes, our lawyers like to think you’ve read our Disclaimer).
Email Address
Company Name
Confirm Password
Mondaq Topics -- Select your Interests
 Law Performance
 Law Practice
 Media & IT
 Real Estate
 Wealth Mgt
Asia Pacific
European Union
Latin America
Middle East
United States
Worldwide Updates
Check to state you have read and
agree to our Terms and Conditions

Terms & Conditions and Privacy Statement (the Website) is owned and managed by Mondaq Ltd and as a user you are granted a non-exclusive, revocable license to access the Website under its terms and conditions of use. Your use of the Website constitutes your agreement to the following terms and conditions of use. Mondaq Ltd may terminate your use of the Website if you are in breach of these terms and conditions or if Mondaq Ltd decides to terminate your license of use for whatever reason.

Use of

You may use the Website but are required to register as a user if you wish to read the full text of the content and articles available (the Content). You may not modify, publish, transmit, transfer or sell, reproduce, create derivative works from, distribute, perform, link, display, or in any way exploit any of the Content, in whole or in part, except as expressly permitted in these terms & conditions or with the prior written consent of Mondaq Ltd. You may not use electronic or other means to extract details or information about’s content, users or contributors in order to offer them any services or products which compete directly or indirectly with Mondaq Ltd’s services and products.


Mondaq Ltd and/or its respective suppliers make no representations about the suitability of the information contained in the documents and related graphics published on this server for any purpose. All such documents and related graphics are provided "as is" without warranty of any kind. Mondaq Ltd and/or its respective suppliers hereby disclaim all warranties and conditions with regard to this information, including all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement. In no event shall Mondaq Ltd and/or its respective suppliers be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of information available from this server.

The documents and related graphics published on this server could include technical inaccuracies or typographical errors. Changes are periodically added to the information herein. Mondaq Ltd and/or its respective suppliers may make improvements and/or changes in the product(s) and/or the program(s) described herein at any time.


Mondaq Ltd requires you to register and provide information that personally identifies you, including what sort of information you are interested in, for three primary purposes:

  • To allow you to personalize the Mondaq websites you are visiting.
  • To enable features such as password reminder, newsletter alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
  • To produce demographic feedback for our information providers who provide information free for your use.

Mondaq (and its affiliate sites) do not sell or provide your details to third parties other than information providers. The reason we provide our information providers with this information is so that they can measure the response their articles are receiving and provide you with information about their products and services.

If you do not want us to provide your name and email address you may opt out by clicking here .

If you do not wish to receive any future announcements of products and services offered by Mondaq by clicking here .

Information Collection and Use

We require site users to register with Mondaq (and its affiliate sites) to view the free information on the site. We also collect information from our users at several different points on the websites: this is so that we can customise the sites according to individual usage, provide 'session-aware' functionality, and ensure that content is acquired and developed appropriately. This gives us an overall picture of our user profiles, which in turn shows to our Editorial Contributors the type of person they are reaching by posting articles on Mondaq (and its affiliate sites) – meaning more free content for registered users.

We are only able to provide the material on the Mondaq (and its affiliate sites) site free to site visitors because we can pass on information about the pages that users are viewing and the personal information users provide to us (e.g. email addresses) to reputable contributing firms such as law firms who author those pages. We do not sell or rent information to anyone else other than the authors of those pages, who may change from time to time. Should you wish us not to disclose your details to any of these parties, please tick the box above or tick the box marked "Opt out of Registration Information Disclosure" on the Your Profile page. We and our author organisations may only contact you via email or other means if you allow us to do so. Users can opt out of contact when they register on the site, or send an email to with “no disclosure” in the subject heading

Mondaq News Alerts

In order to receive Mondaq News Alerts, users have to complete a separate registration form. This is a personalised service where users choose regions and topics of interest and we send it only to those users who have requested it. Users can stop receiving these Alerts by going to the Mondaq News Alerts page and deselecting all interest areas. In the same way users can amend their personal preferences to add or remove subject areas.


A cookie is a small text file written to a user’s hard drive that contains an identifying user number. The cookies do not contain any personal information about users. We use the cookie so users do not have to log in every time they use the service and the cookie will automatically expire if you do not visit the Mondaq website (or its affiliate sites) for 12 months. We also use the cookie to personalise a user's experience of the site (for example to show information specific to a user's region). As the Mondaq sites are fully personalised and cookies are essential to its core technology the site will function unpredictably with browsers that do not support cookies - or where cookies are disabled (in these circumstances we advise you to attempt to locate the information you require elsewhere on the web). However if you are concerned about the presence of a Mondaq cookie on your machine you can also choose to expire the cookie immediately (remove it) by selecting the 'Log Off' menu option as the last thing you do when you use the site.

Some of our business partners may use cookies on our site (for example, advertisers). However, we have no access to or control over these cookies and we are not aware of any at present that do so.

Log Files

We use IP addresses to analyse trends, administer the site, track movement, and gather broad demographic information for aggregate use. IP addresses are not linked to personally identifiable information.


This web site contains links to other sites. Please be aware that Mondaq (or its affiliate sites) are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of these third party sites. This privacy statement applies solely to information collected by this Web site.

Surveys & Contests

From time-to-time our site requests information from users via surveys or contests. Participation in these surveys or contests is completely voluntary and the user therefore has a choice whether or not to disclose any information requested. Information requested may include contact information (such as name and delivery address), and demographic information (such as postcode, age level). Contact information will be used to notify the winners and award prizes. Survey information will be used for purposes of monitoring or improving the functionality of the site.


If a user elects to use our referral service for informing a friend about our site, we ask them for the friend’s name and email address. Mondaq stores this information and may contact the friend to invite them to register with Mondaq, but they will not be contacted more than once. The friend may contact Mondaq to request the removal of this information from our database.


This website takes every reasonable precaution to protect our users’ information. When users submit sensitive information via the website, your information is protected using firewalls and other security technology. If you have any questions about the security at our website, you can send an email to

Correcting/Updating Personal Information

If a user’s personally identifiable information changes (such as postcode), or if a user no longer desires our service, we will endeavour to provide a way to correct, update or remove that user’s personal data provided to us. This can usually be done at the “Your Profile” page or by sending an email to

Notification of Changes

If we decide to change our Terms & Conditions or Privacy Policy, we will post those changes on our site so our users are always aware of what information we collect, how we use it, and under what circumstances, if any, we disclose it. If at any point we decide to use personally identifiable information in a manner different from that stated at the time it was collected, we will notify users by way of an email. Users will have a choice as to whether or not we use their information in this different manner. We will use information in accordance with the privacy policy under which the information was collected.

How to contact Mondaq

You can contact us with comments or queries at

If for some reason you believe Mondaq Ltd. has not adhered to these principles, please notify us by e-mail at and we will use commercially reasonable efforts to determine and correct the problem promptly.