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Case Studies In TRIZ: A Quickly and Reliably Method for Opening Envelopes

Case Studies In TRIZ: A Quickly and Reliably Method for Opening Envelopes

| On 04, Aug 1999

Jia-Lin Chen\ and Ching-Huan Tseng\\
Department of Mechanical Engineering, National Chiao Tung University,
Hsinchu 30056, Taiwan, R. O. C. E-mail:
TEL:886-3-5726111 EXT. 55155 FAX:886-3-5717243


People may find that all kinds of envelopes in the stationery stores are designed in the manner like Figure 1. Different sizes of envelopes can be obtained for different sizes and formats of letters or documents. For example, large sizes of envelopes may be adopted for larger sizes of letters or documents to be sealed and open conveniently. Consumers may often consider that to open a sealed envelope with glue by tearing is a convenient and fast way. In such way, the interior documents may be tore simultaneously and the opening of the envelope is usually ragged. On the other hand, to have a reliable and sightly opening, the auxiliary instruments, such as the scissors, with the action of shaking envelopes are required. This way for opening envelopes brings extra trouble to consumers. Therefore, to design a way for opening an envelope quickly and reliably is required. However, the design requirements between tearing reliability and quickness are contradictive. The traditional method for solving problems having contractions is to compromise among these contradictions. Nevertheless, some solutions may not be generated by using such a method since the right and real problems have not been formulated.

Formulating Right Problems from Contradictions

The Altshuller’s TRIZ method offers an essential principle that contradictions are eliminated but not needed to be comprised. In other words, the core problem has to be understood so that a true and right problem can be formulated.

In the case of the envelope opening, the design trade-off may be sought for the compromise between a requirement for “large size” in order to achieve unbroken information when tearing, and for “small size” in order to waste less time in tearing envelope to access the interior information. To obtain the solution by traditional method, compromises can be made between the two requirements, such as choosing the “appropriate size” of envelopes to stuff the documents. Another method to increase the degree of safety for accessing the interior document is to “shake slowly” the envelope until the document far away the opening and use a pair of scissors to open it. However, seeking out these trade-offs is not the true behavior for solving the right or core problem, and such methods can not really solve the substantial problem in opening envelopes and will result in inconvenient use. Therefore, the right or core problems have to be formulated by considering the real contradictions not those from the traditional trade-offs. The problem should be re-analyzed and re-sated as “Using the less time to access the interior documents safely”. This statement involved the contradictions can be classified as follows in the terms of the Altshuller’s Contradiction Matrix (Altshuller, 1998):

  1. Improve the loss of time in opening, while deteriorate the reliability of

  2. Improve the reliability of tearing the envelope, while deteriorate the
    convenience of use.

  3. Improve the degree of loss of information due to tearing the folded
    document, while increase the waste of time.

The Contradiction Matrix is used to help to solve the technical traditions involving two kinds of parameters. For example, the first item shown above describes WASTE OF TIME/RELIABILITY technical contradiction, the second item is RELIABILITY/CONVENIENCE OF USE, while the third item shows LOSS OF INFORMATION/LOSS OF TIME technical contradiction. For such a WASTE OF TIME/ RELIABILITY technical contradiction, the Contradiction Matrix recommends three principles to solve the same kind conflict used by others:

  1. Prior Action

  2. Flexible Members or Thin Films

  3. Asymmetry

In these recommended principles, the principles “Prior Action” and “Flexible Members or Thin Films” are concerned. The principle “Prior Action” suggests that:

(1) Perform required changes to an object completely or partially in advance;
(2) Place objects in advance so that they can go into action immediately from the most convenient location.

While, the principle “Flexible Members or Thin Films” suggests that:

(1) Replace customary constructions with flexible membranes or thin film;
(2) Isolate an object from its outside environment with flexible membranes or thin films.

The conceptual design of tearing envelopes comes from the principle “Prior Action” is placing a tearing line or strip on the closure flap before envelopes are sealed. This device is granted a United States patent as shown in Figure 2. Similarly, for the technical contradictions of RELIABILITY/CONVENIENCE OF USE and LOSS OF INFORMATION/LOSS OF TIME, the principles “Transition into a New Dimension” and “Mediator” from the Contradiction Matrix are concerned, respectively. Of the skills suggested by the principle “Transition into a New Dimension ” are including :

(1) Utilize multi-level compositions of objects;
(2) Incline an object, or place it on its side, and
(3) Utilize the opposite side of a given surface.

While the suggestions from the principle “Mediator” are:

(1) Use an intermediary object to transfer or carry out an action, and
(2) Temporarily connect the original object to one that is easily removed.

It can be found that the common characteristic of all the suggested skills for the two contradictions in solving the problem of tearing envelope is the same as that for the first contradictive condition. In other words, the common concept is to put a mediator or object between the closure flap and the font panel before the envelopes is sealed as shown in Figure 3. Therefore, one can open the envelope easily by simply pull the end of the mediator or the object as indicated in Figure 3, and can reliably access the interior document of the envelope.


Consumers can not always tear the envelopes quickly and reliably if they always compromise the contradictions, i.e., choose an appropriate size of envelopes for putting documents. Core problems can only be solved by thoroughly understanding the technical contradictions between the technical parameters. It is proven that the Altshuller’s Contradiction Matrix and the related forty principles can provide an excellent means to establish core problem and to find the corresponding solutions.


  • Altshuller,
    Genrich, 40 Principles: TRIZ Keys to Technical Innovation, 1st edition,
    Technical Innovation Ceter, Inc., Jan. 1998.

  • United States Patent, Patent
    Number: US 5,732,877.