FR2579930A1 - - Google Patents

Abstract

COVER AND BINDING METHOD OF A PLURALITY OF SHEETS 15 TO ONE ANOTHER AND TO THE INSIDE SURFACE OF THE COVER 5, BY MEANS OF A LENGTH OF JUNCTION TAPE 16. THE EDGES OF THE SHEETS TO BE JOINED ARE SUCCESSIVELY OFFSET AND THE TAPE JUNCTION IS PUT IN CONTACT WITH PART OF THE REAR SURFACE OF EACH SHEET AND THE INSIDE EDGE OF EACH SHEET. PART OF THE INSIDE SURFACE OF THE COVER INCLUDES A PROTECTIVE COATING 8 AND THE COVER INCLUDES A REFERENCE LINE ALLOWING THE PLACEMENT OF TAPE 16 ON THE COVER BETWEEN THE INSIDE EDGE OF THE FIRST SHEET AND THE FOLDING LINE 7 OF THE COVER.

Description

? 9930 4 ,.

  COVER FOR BINDING SHEETS,

  BINDING PROCESS AND BOOKLET COMPRISING SHEETS THUS BOUND

  The present invention relates to an improved process for binding sheets in a new cover so as to constitute a booklet and, according to

  one aspect, it targets a perfect cover structure

  can be used to form the booklet.

  The present invention relates to an improved process for preparing a booklet, by using a pressure-sensitive adhesive tape to bind the sheets to each other and in a cover or binding.

  Adhesives have been used to connect sheets

  them on the back of covers or to fix inscriptions

  on the back of blankets or other reinforcements. We also have

  ment applied adhesives in covers, to bind the top sheet or the bottom sheet of a booklet or pamphlet to a cover, the latter

  adhesives being tapes which are applied to the

  and are placed so as to be applied against

  the top sheet and the bottom sheet of a docu-

related.

  In the first type of binding, hot melt adhesives or pressure sensitive adhesives are used and the adhesive is applied against the edge of the sheet. When bonding is done, the sheets are bound. When placing such a book or booklet so obtained, on a shelf or in a folder, the pages exert a release force on the adhesive and, over time and when there is a certain weight, the junction may yield . When using tape type sheets to hold a bound document in a cover, as described, for example, in U.S. Patents 3,749,422, 3,749,423, 3,825,963 and 3,834,739, the bound document is glued to the top and bottom covers to help retain the document

  in the cover. The adhesive used to hold the document

  the shear force is applied to the top and bottom of the covers, or the cover page and back sheet are prone to wrinkling. It is therefore considered that these patents do not relate to the present invention, or to the binding of pages to one another and to a cover by means of a single strip element, this element being an element

  flexible tape coated with pressure sensitive adhesive

  if we. The present invention provides a method for

  connect sheets to each other and in a

  in such a way that the leaves do not tend to peel off from the strip when the bound booklet is stacked, placed on a shelf or hung in a

folder.

  The types of covers used to contain the sheets so as to constitute the booklet are preferably paper covers and include a protective reinforcing coating or a strip of

  film at the marking or folding line, or covers

  polymer tures to apply the tape while allowing a determined adhesion of the tape

  cover junction. Preferred grip is com-

  taken between 200 and 700 g for 1.27 cm width of the

connecting strip.

  A cover made only of paper is not always suitable. I1 is sometimes necessary or

  desirable to detach the linked pages from the cover

  ture. This may be necessary due to a misalignment-

  pages compared to the cover when

  binding, or you may wish to make changes

  ment in linked pages and it is prudent and economical

  save the covers for reuse

  eventual tion. When the cover material is paper, the pressure sensitive adhesive on the tape

  junction adheres to the paper. When we try to remove

  worm tape, the paper may separate into layers or tear before the tape adhesive is

  detached or separated from the cover.

  The present invention relates to a method of binding sheets to one another and in a cover made of a material which may be paper or a polymer, making it possible to obtain a pleasant cover to which a junction strip adapts adequately and, after binding , the adhesive which holds the pages together and which holds the bound pages in the cover is located so as to avoid the application of a release force

with adhesive.

  The present invention also relates to a binding cover intended for use with a band binding system for binding sheets.

  together and secure the sheets in the cover

  ture. The cover of the present invention is designed so that the tape holds the bound pages in the cover and limits their movement under the conditions

  normal use and storage.

  The present invention is aimed at covering

  binding that can be used to bind sheets together, as well as the process of binding sheets in the cover to make a new booklet. The cover is shaped so that it holds securely

  the bound sheets in place, under normal conditions

  handling and storage, without the sheets peeling from the joining strip or the strip peeling from the sheets or the cover. The binding according to the present invention comprises a sheet of cover material, generally folded

  along a center line, such as a line of mar-

  quage or a simple fold line. A line of ref-

  rence or guide is traced on the inner surface of the part of the sheet forming the top part of the cover, to indicate the position of an edge of the

  bound sheets. If the cover sheet is on

  pier and not based on polymer, it is preferable that a protective coating is applied along the fold line and that it adheres sufficiently to the strip of

  junction to fix the pages while allowing a de-

  bonding of the joint strip without causing separation

  layer ration of the covering, without breaking the strip or without transfer of adhesive to the coated region,

  when separating the joint strip from the cover.

  The desired range for this adhesion and delamination limitation is that the adhesion to the joining strip must be between 200 and 700 g for a width of 1.27 cm (ASTM D 3330-81), for a sensitive strip. pressure such as tape no C-7888, brand "Scotch", supplied by Minnesota Mining and

  Manufacturing Company, of St. Paul, Minnesota.

  The cover includes a top part and a bottom part. The protective coating extends on either side of the fold line and on the inner face of the cover part, at least over a distance of approximately 3.2 mm to 19 mm. The guide line

  is printed on the inside of the design section

  above the cover, 0.8 to 3.2 mm apart

  around the marking or folding line, to indicate

  the position of the inner edge of the first of the

  bound sheets, when placed in the cover.

  The other sheets are offset successively, with respect to the first sheet and some with respect to

  to others, in a direction opposite to the line of mar-

  on the top part of the cover. So,

  when binding the sheets in the cover

  the part of the strip element which sticks the sheets to the cover is located between the line of

  guide and fold line. As a result, when

  the booklet or that we close the cover parts of

  so as to leave the leaves flat, the strip of rush

  tion remains flat against the inside of the part

  from above the cover. It does not tend to separate

  rer of the cover and the leaves also do not tend to separate from the strip when they lie at

flat against each other.

  To assemble the booklet, place the sheets

  to be linked on top of each other, the edge of each sheet

  the which must be against the back of the booklet being

  wedged or spaced from adjacent edges of adjacent sheets

  your. An element of a pressure-sensitive adhesive strip is placed along the offset edges, and its adhesive-coated surface is pressed against the offset edges, so that it is in contact with a portion of

  rear surface and an edge portion of each sheet.

  The sheets are stacked so that the first sheet of the booklet is at the base of the sheets. The inner edge of this first sheet is aligned along the guide line, on the inside of the open cover placed under the sheets. We press

  then the edge of the joining strip against the neck

  verture, between the guide line and the marking line

  age or folding. The booklet can then be closed and re-

  turned. The opening of the first part of the cover

  discovers the first leaf and the successive leaves.

  The sheets are held together by the adhesive which is in contact with part of the back surface of each sheet and the adjacent inner edge. The present invention is described below in more detail, with reference to the accompanying drawings in which: - Figure 1 is a perspective view of an open cover made in accordance with the present invention;

  - Figure 2 is a cross section through

  large scale coverage of Figure 1,

  showing the sheets in place, aligned with the cover

  ture, as well as the strip applied to the sheets and to the cover; - Figure 3 is a large-scale schematic view illustrating the booklet according to the present invention, formed as shown in Figure 2; and - Figure 4 is a large schematic view

  scale of a booklet made so that the inside edge

  of the first sheet of the booklet is aligned with the fold line, or is on the inner surface

  of the underside of the cover.

  The present invention provides an improved binding cover usable to form a booklet or brochure for the presentation of a document.

  professional, report or other work

ge connected.

  Cover 5 according to the present invention

  is appropriate coverage and it is cons

  with a sheet 6 having for example dimensions of 46.5 cm x 28.9 cm in the case of the American market and comprising a marking line or a folding line 7 located substantially centrally and connecting the long sides of the sheet . Sheet 6 can be made of

  cover, with a starch primer, and it can

  wear an embossed finish. Sheet 6 presents a

  junction or binding area to which is applied

  that a protective coating 8. The junction zone is located on the inner surface of the top part

  of the cover, between a reference or guide line

  page 9, printed on the inside of the top part 10 of the cover sheet 6, and the line 7 for marking or folding. The position of the line of

  guidance 9 is indicated by a series of printed arrows

més sur le feuille.

  This coated area 8 of the cover provides a prepared cover which has the characteristic

  of desired release for a bonded joint strip

  pressure sensitive sive, sufficient that the bound sheets are sufficiently fixed in the covers, in order to prevent the sheets from coming off

  blankets during normal use or storage

  kage in a folder, and so that we can remove the

  cover sheets without damaging the rush strip

  without delaminating the cover material or transferring the adhesive. The ease of separation of the strip from the cover and the solidity of the joining of the sheets during storage are essential factors for the present invention. The desired range of this adhesion to the protective coating is preferably between 200 and 700 g for 1.27 cm (ASTM D 330-81), for a pressure-sensitive adhesive strip of the "Scotch" type n C-7888, supplied by Minnesota Mining and

  Manufacturing Company, of St. Paul, Mi-nnesota.

  The joining strip comprises a back or support in unified nonwoven fibrous fabric, carrying a continuous coating of a pressure-sensitive adhesive based on pure rubbery copolymer. The support is very flexible and the adhesive is applied to this support, at a thickness

  0.076 mm. The support has a barrier coating

  re to prevent migration of the adhesive through the porous support. The joining strip has a peel adhesion at 180 (ASTM D 3330-81) of 350 g for 1.27 cm of strip width. The connecting strip suitable for implementing the present invention is described in

  U.S. Patent No. 4,558,888 of December 17, 1985.

  As examples of the protective coating 8, mention may be made of a low adhesion acrylic sizing material, composed in accordance with United States patent No. 2,607,711, a low adhesion urethane sizing compound composed in accordance with United States patent. No. 2,532,011, or a low-adhesion silicone-based sizing sold under the registered trademark "Syl-Off" with the reference 294 by Dow Chemical Company, Midland, Mi; chigan. Other protective coatings 8 include a strip of polyester film placed in a hollow stamped area of the sheet 6, as shown in the drawing. The film may be a 0.025mm or 0.06mm polypropylene film, such as that supplied by Toray, Inc., Tokyo, Japan. We can also use

  a film of polystyrene or polyvinyl chloride.

  The films are described in the previous application.

  Protective coatings 8, applied in the central area of the cover and which provide

  the desired adhesion, are obtained in accordance with the examples

ples below.

EXAMPLE 1

  Embossed leather-finish base paper

  "Jersey" type% 36 kg, supplied by James Rover Corpora-

  tion, Riegel Division, Milford, New Jersey 08848, is coated with a low-glue acrylic material

  compound adhesion in accordance with US Patent No. 2,607,711.

  The base material of the cover is coated with a 5% low-adhesion acrylic sizing material, using a hand-held applicator, with a coating thickness of 0.025 mm. The sample is then air dried and tested by applying a piece of "Scotch" joint tape n C-7888, 1.27 cm wide, to the coated area and tested according to the procedures. of ASTM D 3330-80, but the joint tape being applied

  directly to the coated area. The grip force ini-

  tial is 210 g for 1.27 cm of strip and it reaches 320 g by accelerated aging for 14 days at around 50 ° C.

  Similar tests are carried out, using

  tion of a low adhesion sizing based on urethane, composed in accordance with US Pat. No. 2,532,011, and a sizing with low adhesion based on silicone but the percentage of solids must be substantially

  reduced. When the base paper is coated with the material

  re with low adhesion based on urethane, with 1% urethane in solid matter and with a wet thickness of 0.025 mm, and with the material with weak adhesion based,. of silicone with 0.5% silicone in solid matter and at a wet thickness of 0.025 mm, the initial adhesive force is 240 g for 1.27 cm of strip width in the case of the urethane material and 200 g for 1.27 cm of width tape in the case of silicone-based material. The low adhesion sizing material based on silicone is

  "Syl-Off" 194 from Dow Chemical Company, Midland, Michigan.

EXAMPLE 2

  A strip of 0.05 mm thick polyester film (Minnesota Mining and Manufacturing Company, 3M OR 870 197) is applied to a paper cover.

  embossed leather finish like "Jersey" at 36 kg four-

  nor by James River Corporation, along the fold line of the cover. The film is coated with a material

  5% D low adhesion acrylic glue

  O10 te in solid matter, by means of a hand device with opening of 0,025 mm. The polyester film strip is air dried and then tested with the 1.27 cm "Scotch" type joint strip N C-7888. The initial peel strength is 165 g for a bandwidth

  1.27 cm, with resistance after accelerated aging

  245 g léré for 1.27 cm band width.

  The use of acrylic material with low adhesion at 5% solids on the polyester does not make it possible to obtain a usable protective coating.

  for the paper cover. It would be inadequate

  Brick a cover for the binding of sheets if the sheets were detached from the cover in use

  normal a few minutes or a few days after re-reading

re leaves.

EXAMPLE 3

  A 0.025 mm thick polyester film, manufactured by Minnesota Mining and Manufacturing Company under the reference No. 860140, is applied to a 36 kg embossed Jersey paper cover from James River. the "Scotch" junction tape n C-7888. Initial peel strength of the junction

  is 400 g and the resistance after aging accelerates

  léré, as described above in Example 1, exceeds

  1040 g for 1.27 cm band width.

  The polyester film which is not coated and

  which is stuck in a blanket can provide a rush

  appropriate but it does not have the characteristic

  than reuse for a certain period. The initial bond strength is such that the coverage would

  reusable to correct the position of the sheets

  linked in the cover but would not be reusable after a certain time when we would like to remove the

  bound documents in the cover.

li

EXAMPLE 4

  A polypro- film is supported on a surface

  0.06 mm thick pylene, supplied by Toray, Inc. Tokyo, Japan, for peel adhesion testing. No treatment is carried out and no coating is

  applied to the exposed surface of the film. The strength of adhesion

  The initial rence is 320 g for a "Scotch" junction strip 1.27 cm wide. The test results after

  accelerated aging are 440 g.

  Polypropylene supplied by Toray, Inc. is very suitable as a protective coating for the base cover and allows the application and removal of the

  joining strip, without transfer of the adhesive from the

  of junction to the film, without deterioration of the paper

  cover or without breakage of the joint strip.

EXAMPLE 5

  We apply a poly-

  0.003 cm thick propylene, supplied by Minnesota Mining and Manufacturing Company. The film is passed under a corona bar. The peel adhesion test gives an initial adhesion strength of 450 g for one test and 430 g for the second test. The test after aging for 14 days at approximately 50 ° C., to simulate a year, gives a peel strength of 560 g and 590 g for 1.27 cm of strip width, in two tests

of aging.

  This prolypropylene film also provides a

  satisfactory protective coating.

  Another untreated film which passes the test correctly is a cellophane film supplied by E.I. du Pont de Nemours & Co., Wilmington, Delaware, with a thickness of 0.036 mm. This material has an initial adhesion strength of 330 g for 1.27 cm of strip width and

  an adhesion of 570 g after accelerated aging.

  An untreated polystyrene film, supplied by Dow Chemical Company, has an initial peel strength of 420 g and a strength of 530 g per 1.27 cm

  bandwidth after accelerated aging.

  Untreated polyvinyl chloride films have an initial peel strength of 400 g for 1.27 cm of strip width, but the strip sticks to the surface and

  cannot be removed after accelerated aging.

  An untreated cellulose acetate film has

  with an initial adhesion strength of 440 g for 1.27 cm of strip width and an adhesion of 960 g after

accelerated aging.

  An unplasticized polyvinyl chloride film has an initial peel strength of 320 g per 1.27 cm of strip width but, after accelerated aging, the strip sticks to the surface of the film and does not

cannot be removed.

  Films can be bonded to the inside of the covers by a pressure-sensitive adhesive transfer tape, such as the adhesive transfer tape

  "Scotch" n 465 supplied by Minnesota Mining and Manufac-

turing Company, St. Paul, Minnesota.

  A cover suitable for use in the binding of sheets by means of a strip must have a peel resistance of the order of 200 g for 1.27 cm of width of joint strip and not more than 700 g for 1 , 27 cm wide joint strip. In this

  range, bound sheets can be removed from the

  cument without breaking the junction tape and the foils

  are sufficiently fixed in the covers to prevent the sheets, at least 25 pages bound in 9 kg paper for 120 m2 of ream size, from coming off the covers during storage in a folder. Ease of leaf removal and solid binding

  leaves during storage are factors

  mercifully important for the covers.

  It is important to apply a protective coating to a paper cover to prevent

  base paper to split into layers when removed

  ve the joining strip of the cover.

  The surface treatment of the paper or the special film applied to the paper must conform to the surface of the paper and the marking lines. They must not significantly modify the opening or closing characteristics of the cover during binding of the sheets or during handling or

  normal storage. A coating causing brittleness

  This results in reduced flexibility of

  the cover during binding, then during handling

  pulation and storage. The use of films or

  coatings over 0.076 mm thick for additional

  very protective coatings tend to reduce the flexi-

  bility and conformability of the covers during binding, then manipulation for the constitution of files. The use of polymer films or - coating treatment exceeding 0.076 mm in gauge on the interior surfaces of the top cover

  and from below, near the fold line increases sen-

  the thickness of the bound document and therefore reduces its commercial interest. The area treated inside the cover depends on the width of the junction strip used, the number of pages bound in the

  cover and binding of several bundles of paper

piers in one cover.

  The method of forming a booklet in accordance with the present invention comprises superimposing the

  sheets 15 to be bound, in correct order one to the other

  above others. You can place the sheets 15 in

  a pile, the first sheet being placed at the base.

  We then shift the sheets one by one

  to the others, so that the edges of the leaves which

  be linked against the back of the booklet are offset

  or spaced substantially uniformly from the first

  my leaf. The shift can be carried out by means of an apparatus, for example an apparatus for binding sheets as described in US Pat. No. 4,581,296 issued to the same applicant. In this patent, the sheets are aligned along the inner edge of each sheet. The sheets of the stack are then clamped together, at their opposite edges. The lower edges are then moved in an arc and brought over the tight edges, so as to rest on a tray. The curvature of the leaves in the arc brings the inner edges to a situation of offset which preferably uncovers part of the surface

  back of each sheet and edge.

  The inner edges of the sheets 15 being offset, a member 16 of junction tape is placed along the length of the edges. The adhesive coated surface of the joint strip is pressed into contact with a portion of each surface and with the edge of each sheet. A border of the strip extends beyond the edge of the bottom sheet. Place a blanket 5 under the sheets. Reference line 9 of the cover

  is aligned with the edge of the bottom sheet 15.

  The adhesive-coated edge of the joint strip 16 is then pressed against the inner surface of the top part of the cover, between the reference line 9 and the fold line 7 and, if the width of the strip junction allows, we stick the rest of

  the border at the cover beyond the fold line

  age 7 and on the inside of the rear part of

  the cover, as shown in Figures 2 and 3.

  The illustrated reference line 9 is printed on the inner surface of the front part of the cover, at a distance of about 0.8 to 3.2 mm from the fold line 7, or it can be printed on the film

  8 constituting the protective coating and super

  - place the film in agreement so as to place the printed reference line in the desired position, on

  the front part of the cover sheet 6.

  This method of joining sheets 15 and

  bonding sheets to a blanket provides

  vret which can withstand normal use and storage, for example stacking on a shelf, or as books placed on edge on a shelf, or in a folder, without the sheets separating from

  the joining strip or that the strip comes off from the

  protective cover clothing.

* As shown in Figure 4, if the first

  first page is bound in the booklet so that the inside edge of the front sheet 20 bound in the cover 21 is aligned with the fold line 24 or

  parallel to the fold line and on the inside of the back or bottom 22 of the cover

  ture 21, closing the cover around the fold line 24 causes the junction strip 25 to come off relative to the surface of the back of the

  blanket. The size of the detachment depends on the name-

  bre and the thickness of the leaves, but the closure generates a detachment force. Similarly, when stacking the booklets constructed as shown in the

  Figure 4, the inner edge of the front sheet is

  tape adhesive tape 25. When opening in-

  following the booklet, we find the first detailed sheet

  free or partially detached from the adhesive junction.

  In FIG. 4, if the strip were held very tightly on the inside face of the back of the cover, the inside edges of the paper would be wavy or curved. The

  paper stiffness and storage conditions

  drent peel force over a period of time, so that the inner edge of the first sheet is detached from the strip. In the case of thick booklets,

other leaves come off.

  The booklet represented in FIG. 3, formed in accordance with the present invention, is not subjected to a bending, curving or detachment force

  on the strip 16 or the sheets 15. The coating adheres

  band sif 16 is subjected to shear forces-

  when placing the booklet on a shelf or

  upside down in a folder, the fold line of the cou-

  the booklet is located at the top. In a pile, the leaves are flat. The strip 16 is flat between the first sheet 15 and the fold line 7 of the

  cover 5. The adhesive of the strip 16 may be in

  pressure. In any case, no peel force

exercises. - -

  The shear strength of the joint strip 16, compared to its peel strength on the protective coating, is much greater. The

  table below shows the difference between the resistance

  this in shearing on different coating materials-

  protective, compared to peel strength,

  by means of a joining strip 16 described in the patent

  vet supra No. 4,558,888 and sold by Minnesota Mining and Manufacturing Company, St-Paul, Minnesota under the name of joint strip na C-7888. The test is carried out

  by suspending a mass of 200 g from a banister element

  of having a surface of 1.27 cm x 1.27 cm, glued to the

  coating material, and time recording required

  so that the strip separates completely from the material. Material Coat (Mn) Shear (min) Polypropylene samples 2.86 (average) 935.8 (average) Polyester 5 samples 6.9 (average) 1764.7 (average) Paper, "Jersey" cover area samples 19.16 (average) 1600, 2 (average) Paper ("Jersey" cover) with a wet coating thickness of 0.0025 cm

acrylic material

low adhesion bonding

rate at 1%.

  3 samples 3.0 (average) 1233.3 (average) Polyethylene 5 samples 0.1 (average) 237.3 (average) Unplasticized polyvinyl chloride samples 143.96 (average) 208.7 (average) "Jersey" is a registered trademark of James River Corporation,

Milford, New Jersey 08848.

  To carry out the above test, procedure A of test standard ASTM D -3654-82 is used, except that the material to be tested is applied to the surface of the panel. To carry out the above peel test, the ASTMD-3330-83 method for the preparation of the sample is followed and it is peeled off to the point where the remaining bonded area is 1.27 cm × 1.27 cm. The sample is peeled, as in ASTM D-3654-82,

  using a mass of 200 g. We note the times required

  to completely separate the strip from the test surface.

  In another embodiment, the cover

  ture of top 10 or front face of the binding 5 can consist of a transparent film which is superimposed on a paper cover. The transparent cover avoids having to apply a title or a label on the outside of the cover, since you can easily see the title page of the bound document, through

  the transparent cover part of the binding.

  Binding 5 can consist of a film

  of polymer and it does not require a pro coating

  cover if the binding is a polymer having an adhesion

  relative to the junction strip which is compri-

  between 200 and 700 g for 1.27 cm of joint strip width, in a standardized peel resistance test at 180 for pressure-sensitive adhesive strips. An example of a suitable polymer film is polypropylene, in a sheet having a line

  marking 7 which opens and closes the cover

flat green.

Claims (15)

  1. Cover (5) for covering and holding sheets (15) of paper bound in a booklet or brochure,   comprising a sheet (6) of dipping material   predetermined dimension so as to cover the connected sheets when folded along a fold line (7), characterized in that said sheet (6) has a surface, adjacent to the fold line, which is protected by a coating (8) having sufficient adhesion to a pressure sensitive adhesive joint strip (16)   for connecting the sheets (15) to said sheet (6)   groove while allowing the separation of the joining strip under peeling forces of between 200 and 700 g per 1.27 cm width of said pressure-sensitive adhesive joining strip without damaging the sheet   cover or junction tape.   2. Cover according to claim 1, charac-   terized in that the protective coating (8) is applied   to the cover on both sides of the fold line (7).   3. Cover according to claim 1 or 2,   characterized in that the protective coating is a re-   sizing garment with low adhesion applied to a cover sheet of paper, and in that this coating has an adhesive force on the joint strip of 200 to 700 g for 1.27 cm of width of joint strip, in a standardized peel strength test for a   pressure-sensitive adhesive tape.   4. Cover according to one of the claims   1 or 2, characterized in that the cover sheet (6) is made of paper and the protective covering (8) consists of a length of polymer film applied along the fold line and whose adhesion to the strip junction is 200 to 700 g for 1.27 cm of strip width, in a standardized peel strength test for a strip pressure sensitive.   5. Cover according to claim 4, charac-   terized in that said film is a polypropylene film, polystyrene or cellophane.   6. Cover according to claim 3, charac-   terized in that the low adhesion sizing contains% of acrylate in solids with a thickness of 0.025 mm wet coating.   7. Cover according to claim 3, charac-   terized in that said low adhesion sizing contains I% urethane in solid matter, with a thickness of 0.025 mm wet coating.   8. Cover according to claim 3, charac-   terized in that the low adhesion sizing contains 0.5 t of silicone in solid materials, with a thickness 0.025 mm wet coating.   9. Cover according to any one of the res-   dications previous, characterized in that a reference line (9) is provided on the inner surface of the cover sheet (6); parallel to the fold line (7), to indicate the position of an edge of the sheets connected (15).   10. Cover according to claim 9, charac-   terized in that the reference line is placed at a   distance from 0.8 to 3.2 mm from the fold line, for   the longitudinal edge of the upper sheet desdi- your bound sheets.   11. A method of binding sheets to each other to constitute a booklet, which consists of stacking the sheets to be bound, these sheets being in order; shifting the inner edge of each sheet relative to the adjacent sheet, the edge of the first sheet of the booklet being placed at the base, so as to uncover a narrow part of the rear surface of each sheet and the edge; applying a length of joint strip, comprising a coating of pressure-sensitive adhesive on a surface, along the offset edges of the sheets,   the adhesive being in contact with the narrow part of the surface   this back of each leaf and with part of the edge; and placing a cover under the edges of the sheets, this cover comprising a front part and a rear part connected to each other along a line of   folding, said method being characterized in that it consists   further te aligning the inner edge of the first sheet with a reference line provided on the inner surface of the front part of the cover, this reference line being spaced from the fold line and parallel to it; and pressing an edge of the joining strip, adjacent and parallel to the edge of the first sheet, on the inner surface of the front part of the cover, between the edge of the first sheet and fold line.   12. Method according to claim 1, characterized in that   that it also includes the printing operation of the line of   ference at a distance of approximately 0.8 to 3.2 mm from the line folding.   13. The method of claim 11, character-   laughed in that the shifting operation involves stacking the sheets in order, so that the first sheet is at the top of the stack and all the edges of the   sheets are aligned; tightening the free outside edges   laughing leaves to prevent movement; and moving the inner edges of the sheets to be bound, over the stopped outer edges, until the sheets form a loop and the inner edges of   all the sheets are in offset relation.   14. Booklet comprising a cover for sheets (15), comprising a front cover part   (10) and a rear cover part connected to the   right of a fold line (9) so as to close towards each other and to have an inner surface and an outer surface; and a plurality of sheets   (15) arranged in the cover between the interior surface   re of the front part of the cover and the surface   inside of the rear part of the cover,   characterized in that the first sheet of said plu-   sheet reality has an inner edge adjacent to the inner surface of the front part of the cover and spaced from the fold line (9), the other sheets being spaced apart by a progressively increasing distance from the fold line and to the first sheet, and in that a length of joint strip (16) having an adhesive-coated surface is glued to the edges of said plurality of sheets   and to a narrow part of the rear surface of each   ne of these sheets, an edge of the joining strip being glued to the inner surface of the front part   of the cover, between the inside edge of the first re sheet and fold line.