JPH0587241B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an insole for a shoe that makes it possible to manufacture a product having a moisture-proof structure in hanging cloth shoes and leather shoes, and a This relates to a manufacturing method.

[Prior Art] Conventionally, this type of device is as follows.

1. Most people who wear shoes suffer from stuffy feet due to sweating, and many people have suffered from injuries and illnesses such as athlete's foot.

As a way to relieve this pain, some people put moisture-proof insoles inside their shoes, but this reduces the width of the shoes and makes the feet feel tight and uncomfortable. , toes may become deformed.

Wearing shoes that don't fit your feet can also cause other health problems.

Therefore, when considering how to wear shoes under normal conditions, it is desirable that the moisture-proofing effect be incorporated into the shoe manufacturing process and commercialized.

2. For a highly moisture-proof insole, the material is preferably a non-water-absorbing synthetic resin with a diameter of 0.5 mm to 2 mm.
The structure is preferably a net-like structure consisting of many spaces.

In addition, in order to further enhance the moisture-proofing effect, it is preferable to laminate several layers of this net-like knitted fabric to a thickness of 2 mm to 5 mm so that the entire midsole forms an air layer.

However, this insole is structurally easily deformed by external forces such as tension and compression, and is difficult to mold in the shoe manufacturing process, so it has hardly ever been commercialized.

3. Generally speaking, in cloth shoes or leather shoes in which the lace material is hung and pasted or nailed to the midsole, the midsole is hard and conforms to the shape of the bottom of the shoe last.
An important condition in the manufacturing process is that it does not deform even when it is pulled or compressed in the front, back, left, and right directions.

In other words, the human foot is a series of rounded, bulging, or concave curves.

Therefore, the same goes for shoe lasts; in the hanging-type molding process for cloth shoes and leather shoes, the material for the shoe laces is pulled strongly along the curve of the last, and is glued to the insole or nailed. Hit and fix.

At this time, if the lace material that has been stretched on the insole stretches or shrinks against the force of trying to return to its original shape, it will not be able to maintain the shape of the shoe last, making it extremely difficult to mold the shoe. .

[Problems to be Solved by the Invention] The conventional techniques described above had the following problems.

1 In particular, in the case of an insole with a mesh structure that has a high moisture-proofing effect, depending on the amount of force applied, the insole will deform significantly, causing damage to the heel, toe, inside of the stepping area, outside of the stepping area, inside of the non-stepping area, and outside of the stepping area. Even if the fin material is fixed by suspending adhesive or nailing while dispersing the tensile force, the workability is poor and it is difficult to maintain a normal midsole surface.

In particular, when hanging by a machine, the inner sole of the net-like structure bulges toward the center and cannot be formed because it is hung from the front, back, left, and right toward the center at the same time.

2 As described above, it is a necessary condition in the molding process that the insole is hard and does not deform even when some force is applied.

The present invention has been devised in view of the above-mentioned problems of the prior art, and its purpose is to provide a device that can do the following.

In order to make shoes using a net-like inner sole that has a high moisture-proofing effect, it is necessary to improve the net-like inner sole so that it does not deform when suspended, and it must not stretch even when it is pulled. .

For this reason, first, the net-like midsole is combined and integrated with a hard material that can withstand tension, thereby making the net-like midsole non-stretchable.

Next, when hanging, the heel part of the insole is made of hard and thick material such as moon-shaped material or shank material, and since there is air convection while walking and there is relatively little humidity, the heel part of the insole is moisture-proof. It should be made of a hard material that can withstand the force of lifting when removed from the structure.

[Means for Solving the Problems] In order to achieve the above object, the present invention is as follows.

The moisture-proof inner sole of the shoe of the first invention is constructed as follows.

The part of the insole from the non-stepping part to the toe part is made of a net-like material woven from non-water-absorbing fibers.
A hard material is combined and integrated with the lower surface of this part to form the toe part from the non-stepping part of the insole that has a moisture-proof structure and does not stretch, and the part from the heel part of the insole to the non-stepping part is suspended. This is a moisture-proof insole for shoes made of a hard material that can withstand the force of compression.

The method for manufacturing a moisture-proof structure insole for shoes according to the second aspect of the invention includes the first to seventh steps having the following conditions.

1st step: Cutting a net-like knitted fabric made of non-water-absorbent synthetic fibers with a diameter of 0.5 mm to 2 mm using an insole tread-on part cutting die to obtain the tread-on part 1 of the non-water-absorbent net-structure knitted fabric. .

2nd process: A semi-rigid, non-water-absorbent sheet of a specified thickness that does not deform when the material is suspended is cut using a sheet cutting die for the insole treading part, and the part that will not be stepped on is cut off to form a bottom hem. To obtain a treading part 2 of a hard sheet.

Third step: Cutting the unvulcanized sheet of predetermined thickness with a treading part cutting die to obtain the treading part 3 of the unvulcanized rubber sheet.

4th process A hard, non-water-absorbent sheet of a specified thickness that does not deform when the heel material is suspended is cut using a mid-sole heel cutting die, and the part that is not stepped on is cut off into a bevel at the top. To obtain the heel portion 4 of the seat.

Fifth step: The stepping part 2 of the non-water-absorbing semi-rigid sheet, the stepping part 3 of the unvulcanized rubber sheet, and the heel part 4 of the non-water-absorbing hard sheet are attached to the mold body 6 for creating a moisture-proof structure insole. Heel part 4 of hard sheet, stepping part 2 of non-water-absorbing semi-rigid sheet, stepping part 3 of unvulcanized rubber sheet
Set in this order, close the upper lid 5 of the mold for creating a designed moisture-proof inner sole, and vulcanize by applying pressure and heating with a vulcanizing press.

Sixth step: After the vulcanization time has elapsed, take out the mold for creating a moisture-proof inner sole from the vulcanizing press, open the mold top lid 5, and take out the semi-finished product 7 for the moisture-proof inner sole.

7th step Next, on the semi-finished product 7 for the moisture-proof structure insole, the treading part 1 of the non-water-absorbing network structure knitted fabric is stacked and fixed so as not to shift from front to back and left and right to obtain the moisture-proof structure insole A. thing.

The method for manufacturing a moisture-proof structure insole for shoes according to the third aspect of the invention includes first to fourth steps having the following conditions.

First step: Roll hard thermoplastic vinyl chloride at a predetermined temperature using a rolling press plate with a design or a roll dispenser, and cool it to obtain a vinyl chloride sheet 8 for a moisture-proof inner sole.

2nd step: Layering the heat-melting network-structure knitted fabric 8A made of vinyl chloride fibers on the design forming part, which is the treading part, of the vinyl chloride sheet 8 for the moisture-proof inner sole.

Third step: Attach a cutting die for the inner sole to a high-frequency heat fusion machine, set the vinyl chloride sheet and net-like structure knitted fabric obtained in the second step, and cut out by applying electricity.

4th step After cutting out, take out the moisture-proof structure inner sole B cut into the inner sole shape from a high frequency heat fusion machine.

The method for manufacturing a moisture-proof structure insole for shoes according to the fourth aspect of the invention includes first to third steps having the following conditions.

1st Step: Creating an insole with a designed moisture-proof structure. Putting an appropriate amount of hard unvulcanized rubber mixed with a vulcanizing agent into the mold volume and vulcanizing it.

2nd step: After vulcanization, open the upper mold lid 5 and take out the semi-finished product 9 for the moisture-proof inner sole.

Third step: A moisture-proof structure insole C is obtained by stacking and fixing a treading part 1 of a non-water-absorbing network structure knitted fabric on a semi-finished product 9 for a moisture-proof structure insole so as not to shift from front to back and from side to side.

[Function] Moisture that sweats during wearing does not accumulate on the soles of the feet, but passes through the socks and the net-like structure, reaching the rubber sheet (vinyl chloride sheet in manufacturing method 2) underneath, and reaching the upper surface of the sheet. depth configured in
Rectangular recesses of 1.5mm to 2mm, height 2mm to 3mm, width 10mm to 20mm, depth 1.5mm to 2mm, diameter 3mm to 5mm
Water droplets with a diameter of approximately 1 mm accumulate in the circular recesses of the foot, and the soles of the feet remain dry with very little moisture, leaving them feeling refreshed without feeling stuffy.

In addition, when the net-like structure part and the recessed part are combined, an air layer with a width of 3 mm to 7 mm is formed in the insole. , shoes with this moisture-proof structure insole have extremely high cold protection effects (moisture-proof,
It has a cold-proof structure).

In addition, the recess provided in the above sheet has a diameter of approximately 1 mm.
Although the water droplets are in the form of particles, each recess is formed independently, which has the effect of preventing the water droplets from flowing and gathering in one place and wetting the soles of the feet.

In addition, these water droplets can be allowed to evaporate at room temperature until the next morning after being worn.

[Embodiments of the invention] Examples will be described with reference to the drawings.

A, B, and C are the moisture-proof inner soles of the shoes of the present invention, and the portion of the inner sole from the non-stepping part to the toe part is made of a net-like material knitted with non-water-absorbing fibers. Hard materials are combined and integrated on the lower surface to form a toe part from the non-stepping part of the insole that has a moisture-proof structure and does not stretch, and the part from the heel part of the insole to the non-stepping part is a hanging part. Constructed as a hard material that can withstand the forces of time.

Manufacturing method 1 1st step A knitted fabric with a net-like structure made of non-water-absorbent synthetic fibers with a diameter of 0.5 mm to 2 mm is cut using a cutting die for the insole tread-on part to obtain the tread-on part 1 of the non-water-absorbent network-structure knitted fabric. (see Figure 1).

Note that the knitted fabric with a net-like structure has a thickness of 2 mm to 5 mm depending on the degree of moisture-proofing effect, design preference, difficulty of work, etc.
They may be used by laminating them to an arbitrary thickness of mm.

2nd process Cut a semi-rigid, non-water-absorbing sheet with a thickness of 0.5 mm to 3 mm that does not deform when hanging the shank material with a sheet cutting die for the midsole treading part, and cut off the part that will not be treaded on to form the bottom hem. , non-water-absorbing semi-rigid sheet treading section 2
get.

Next, rubber glue (adhesive) is applied to the entire upper surface 2A of this treading part 2 and the beveled part 2B (see FIG. 3).

The material refers to a synthetic resin sheet or a compressed board sheet impregnated with synthetic resin or glue.

Third step: An unvulcanized rubber sheet having a thickness of 1 mm to 3 mm is cut using a treading part cutting die to obtain a treading part 3 of the unvulcanized rubber sheet (see FIG. 5).

4th process A hard, non-water-absorbent sheet with a thickness of 4 mm to 8 mm that does not deform when the heel material is suspended is cut using a mid-sole heel cutting die, and the part that will not be stepped on is cut off into a slit at the top. A heel portion 4 made of a hard sheet is obtained.

Next, apply rubber glue to the slotted part 4A (No. 7
(see figure).

A sheet is a foamed rubber that does not deform or deteriorate during vulcanization.
Refers to foamed synthetic resin or compressed board impregnated with synthetic resin or glue.

5th step Creating a moisture-proof inner sole In the mold body 6, set the heel part 4 of the non-water-absorbing hard sheet, the stepping part 2 of the non-water-absorbing hard sheet, and the stepping part 3 of the unvulcanized rubber sheet in this order ( (see FIG. 13), the upper lid 5 of the mold for creating the moisture-proof inner sole is closed, and the mold is pressurized and heated using a vulcanizing press to vulcanize.

Moisture-proof structure inner sole creation mold upper lid 5 has a depth of 1.5 mm to 2
It is carved and designed so that a large number of rectangular recesses 5A measuring 2 mm to 3 mm in length and 10 mm to 20 mm in width and circular recesses 5A with a depth of 1.5 mm to 2 mm and a diameter of 3 mm to 5 mm are formed.

6th step After the vulcanization time has elapsed, take out the mold body for creating a moisture-proof inner sole from the vulcanization press machine together with the upper lid 5 of the mold for creating a moisture-proof inner sole, open the upper lid 5 of the mold for creating a moisture-proof inner sole, and open the mold upper lid 5 for creating a moisture-proof inner sole. The semi-finished product 7 for the structural midsole is taken out.

The structure of the semi-finished product 7 for the moisture-proof inner sole is as follows.

The stepping part 2 is made of a non-water absorbent semi-rigid sheet, the stepping part 3 is made of an unvulcanized rubber sheet, and the heel part 4 is made of a non-water absorbing hard sheet.
The molded upper lid 5 forms a number of recesses 3A on the upper surface of the stepping portion 3 (see FIG. 14).

Seventh step Next, on the semi-finished product 7 for the moisture-proof inner sole (above the concave shape), the treading part 1 of the non-water-absorbing network structure knitted fabric is placed.
Stack them and fix them so that they do not shift from front to back and left to right.

Fixing methods include dotting in several places with adhesive, sewing around the center and periphery using a sewing machine, and punching, which is secured with caulking, etc., but the method is selected based on preference, workability, cost, etc. do it. With the above steps, the moisture-proof structure insole A according to manufacturing method 1 is completed.

Manufacturing method 2 1st step Hard thermoplastic vinyl chloride is rolled at 80℃ using a rolling press plate with a design or a roll dispensing machine.
Roll at a temperature of 120℃ and cool.

As a result, a vinyl chloride sheet 8 for a moisture-proof inner sole shown in FIG. 17 is obtained.

The press board is engraved so that the same thickness and the same design as the semi-finished product 7 for the moisture-proof inner sole created in the 6th step of manufacturing method 1 is formed on the vinyl chloride sheet. Both have a long length (sheet width) of approximately 35 cm.

Also, in the case of roll dispensing, the roll is engraved so that sheets similar to those described above can be dispensed.

In the case of press plates, the length (vertical) of one sheet is
A length of 0.5m to 1m provides good workability (see Figure 17), but in the case of roll dispensing, a length of 2m to 3m results in less loss and higher yield.

2nd step Heat meltable network structure knitted fabric 8A made of vinyl chloride fibers is overlaid on the design forming part which is the stepping part of the vinyl chloride sheet 8 for the moisture-proof structure insole (first
(See Figure 9).

In this case, they may be laminated to any desired thickness.

Third step: A cutting die for the inner sole is attached to a high-frequency heat fusion machine, the vinyl chloride sheet obtained in the second step and the net-like structure knitted fabric are set, and electricity is applied to cut them out.

At this time, place the inner sole cutting die 1mm higher than the height of the cutting die blade.
By placing several metal rods that are ~2 mm shorter, 2 mm to 3 mm in diameter, and made of the same material as the insole cutting die inside the insole cutting die, the surrounding area is cut by thermal melting in several places on the treading part. is fixed by heat fusion (see FIGS. 21 and 20).

In the figure, 8B is a groove-shaped portion carved with a metal rod.

4th step After cutting out, take out the moisture-proof structure insole cut into the shape of the insole from a high frequency heat fusion machine.

The high-frequency heat fusion machine adjusts the amount of electricity, time, and pressure.
Also, depending on the shape of the presser die, it has functions such as fusion bonding and melt cutting.

With the above steps, the moisture-proof structure inner sole B according to manufacturing method 2 is completed.

Manufacturing method 3 1st step Creating a designed moisture-proof inner sole Into the mold body 6, an appropriate amount of hard unvulcanized rubber mixed with a vulcanizing agent is placed in the mold volume and vulcanized.

2nd Step After vulcanization, open the upper mold lid 5 and take out the semi-finished product 9 for the moisture-proof inner sole (see FIG. 22).

The shape of the semi-finished product 9 for the moisture-proof structure insole is the same as that created in the sixth step of manufacturing method 1,
The material is one piece made of hard vulcanized rubber.

Third step: Next, on top of the semi-finished product 9 for the moisture-proof structure insole (above the concave shape), the treading part 1 of the non-water-absorbing network structure knitted fabric is stacked and fixed so as not to shift from front to back and from side to side. (See Figure 24).

Fixing methods include dotting in several places with adhesive, sewing around the center and periphery using a sewing machine, and punching and sewing machines that use crimps to secure the fixing, but these methods should be considered based on preference, workability, cost, etc. Just choose.

With the above steps, the moisture-proof structure inner sole C is completed.

From then on, cloth shoes and leather shoes will be manufactured using normal shoemaking methods.

In manufacturing methods 1 and 3, a moisture-proof insole is created by fixing a knitted fabric in a tread-in shape to an integrated product (semi-finished product) of a heel in an insole shape and a tread-in part.

In manufacturing method 2, the shape of the insole is obtained for the first time in the fourth step, and until then, the vinyl chloride sheet and the knitted fabric are just materials.

In manufacturing methods 1 and 3, the insole is made one pair at a time, but in manufacturing method 2, the insole is in the form of a large sheet until it is punched out with a cutting die (electrically heated).

In addition, in manufacturing method 2, the vinyl and knitted fabric are fixed (become an integral part) at the same time as they are punched out, creating an insole.

Referring to FIG. 18, 10 is a shoe manufactured using the moisture-proof insole obtained by manufacturing method 1.

In the figure, 10A is the core sole, 10B is the outer sole,
10C is toe reinforcement material, 10D is moon-shaped material, 10
E is the shank material.

[Effects of the Invention] Since the present invention is configured as described above, it produces the following effects.

When manufacturing cloth shoes or leather shoes using normal shoe manufacturing methods, this moisture-proof insole will not deform even if it is strongly pulled by the lace material during hanging, and the molding process can be carried out easily and accurately. This has made it possible to manufacture non-vulcanized cloth shoes and leather shoes with a moisture-proof structure in the midsole using the hanging method.

The moisture-proof structure insole obtained according to the present invention is made of non-water-absorbing synthetic fibers from the non-stepping part to the toe part, and is made of single fibers of a predetermined diameter woven into a net-like structure to have a predetermined thickness.

For this reason, the moisture that sweats while wearing the socks does not accumulate on the soles of the feet, but passes through the socks and the mesh structure.
Water reaches the rubber sheet below (PVC sheet in manufacturing method 2) and collects in rectangular or circular recesses formed on the upper surface of the sheet in the form of droplets of a predetermined diameter, leaving the soles of the feet extremely humid. It maintains a dry condition with little moisture, and is refreshing without feeling stuffy.

In addition, when the net-like structure part and the recessed part are combined, an air layer of a predetermined width is formed in the insole.This air layer not only increases the moisture-proofing effect of the sole of the foot, but also has a high insulation effect. Shoes using this moisture-proof inner sole can also have extremely high cold-proofing effects (they have a moisture-proof and cold-proof structure).

In addition, water droplets of a predetermined diameter form in the recesses provided in the sheet, but each recess is formed independently, which has the effect of preventing the water droplets from flowing and gathering in one place and wetting the soles of the feet. There is.

Moreover, these water droplets can be evaporated at room temperature by the next morning after wearing the shoes.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the treading part of the non-water-absorbing network structure knitted fabric, Fig. 2 is a side view of the same as above, Fig. 3 is a plan view of the treading part of the non-water-absorbing semi-rigid sheet, and Fig. 4 is A side view of the same as above, FIG. 5 is a plan view of the stepping part of the unvulcanized rubber sheet, FIG. 6 is a side view of the same as above, FIG. 7 is a plan view of the heel part of the non-water-absorbing hard sheet, and FIG. 8 is a side view of the same as above, FIG. 9 is a bottom view of the upper lid of the mold for creating a moisture-proof structure inner sole, FIG. 10 is a cross-sectional view taken along the line A-A, and FIG.
Figure 2 is a sectional view taken along line B-B, Figure 13 is a longitudinal sectional view of each material set inside the mold body, and Figure 14 is a longitudinal sectional view of the mold body.
The figure is a side view of a semi-finished product for a moisture-proof inner sole, and Figure 15 is a plan view of a moisture-proof inner sole obtained by manufacturing method 1.
Figure 6 is a side view of the same as above, Figure 17 is a perspective view of the vinyl chloride sheet used in manufacturing method 2, Figure 18 is a cross-sectional view of shoes manufactured using the moisture-proof inner sole obtained in manufacturing method 1, and Figure 17 is a perspective view of the vinyl chloride sheet used in manufacturing method 2. Figure 19 is a partially cutaway perspective view of the hard vinyl obtained in the first step of manufacturing method 2 overlaid with a net-like knitted fabric, and Figure 20 is a partially cutaway view of the hard vinyl obtained in the first step of manufacturing method 2.
21 is a side view of the moisture-proof inner sole obtained by manufacturing method 2, and FIG. 22 is a plan view of the semi-finished product for the moisture-proof inner sole obtained by manufacturing method 3. , FIG. 23 is a side view of the same as above, and FIG. 24 is a side view of the moisture-proof inner sole obtained by manufacturing method 3. 1...Treading part of non-water-absorbent network structure knitted fabric, 2...
...Treading part made of non-water-absorbing semi-rigid sheet, 3...Treading part made of unvulcanized rubber sheet, 4...Heel part made of non-water-absorbing hard sheet, 5...Mold top lid, 6...Moisture-proof inner sole Creation mold body, 7...Semi-finished product for moisture-proof structure insole, 8...Pinyl chloride sheet for moisture-proof structure insole, 9...Semi-finished product for moisture-proof structure insole.

Claims (1)

[Scope of Claims] 1. The part of the insole from the non-stepping part to the toe part is made of a net-like material woven from non-water-absorbing fibers, and a hard material is combined with the lower surface of this part to form an integral part. The toe part is formed from the non-stepping part of the insole that has a moisture-proof structure and does not stretch, and the part of the insole from the heel part to the non-stepping part is made of a hard material that can withstand the force when hanging. Features a moisture-proof insole for shoes. 2. A method for manufacturing a moisture-proof insole for shoes, characterized by comprising the first to seventh steps having the following conditions. 1st step: Cutting a net-like knitted fabric made of non-water-absorbent synthetic fibers with a diameter of 0.5 mm to 2 mm using an insole tread-on part cutting die to obtain the tread-on part 1 of the non-water-absorbent net-structure knitted fabric. . 2nd process: A semi-rigid, non-water-absorbent sheet of a specified thickness that does not deform when the material is suspended is cut using a sheet cutting die for the insole treading part, and the part that will not be stepped on is cut off to form a bottom hem. To obtain a treading part 2 of a hard sheet. Third step: Cutting an unvulcanized rubber sheet of a predetermined thickness with a treading part cutting die to obtain a treading part 3 of the unvulcanized rubber sheet. 4th process A hard, non-water-absorbent sheet of a specified thickness that does not deform when the heel material is suspended is cut using a mid-sole heel cutting die, and the part that is not stepped on is cut off into a bevel at the top. To obtain the heel portion 4 of the seat. 5th step Creating a moisture-proof structure insole A heel part 4 of a non-water-absorbing hard sheet, a stepping part 2 of a non-water-absorbing hard sheet, and a stepping part 3 of an unvulcanized rubber sheet are set in the mold body 6 in this order, The upper lid 5 of the mold for creating a designed moisture-proof structure inner sole is closed, and vulcanization is performed by pressurizing and heating with a vulcanizing press. Sixth step: After the vulcanization time has elapsed, take out the mold for creating a moisture-proof inner sole from the vulcanizing press, open the mold top lid 5, and take out the semi-finished product 7 for the moisture-proof inner sole. Seventh step: To obtain a moisture-proof inner sole A by stacking and fixing a treading part 1 of a non-water-absorbing network structure knitted fabric on a semi-finished product 7 for a moisture-proof inner sole so as not to shift from front to back and from side to side. 3. A method for manufacturing a moisture-proof insole for shoes, comprising the first to fourth steps having the following conditions. First step: Roll hard thermoplastic vinyl chloride at a predetermined temperature using a rolling press plate with a design or a roll dispenser, and cool it to obtain a vinyl chloride sheet 8 for a moisture-proof inner sole. 2nd step: Layering the heat-melting network-structure knitted fabric 8A made of vinyl chloride fibers on the design forming part, which is the treading part, of the vinyl chloride sheet 8 for the moisture-proof inner sole. Third step: Attach a cutting die for the inner sole to a high-frequency heat fusion machine, set the vinyl chloride sheet and net-like structure knitted fabric obtained in the second step, and cut out by applying electricity. 4th step After cutting out, take out the moisture-proof structure inner sole B cut into the inner sole shape from a high frequency heat fusion machine. 4. A method for manufacturing a moisture-proof insole for shoes, comprising the first to third steps having the following conditions. 1st Step: Creating an insole with a designed moisture-proof structure. Putting an appropriate amount of hard unvulcanized rubber mixed with a vulcanizing agent into the mold volume and vulcanizing it. 2nd step: After vulcanization, open the upper mold lid 5 and take out the semi-finished product 9 for the moisture-proof inner sole. Third step: A moisture-proof structure insole C is obtained by stacking and fixing the stepping part 1 of the non-water-absorbing network structure knitted fabric on the semi-finished product 9 for the moisture-proof structure insole so as not to shift from front to back and from side to side.