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Chair

Look up chair in Wiktionary, the free dictionary.
Typical Western wooden chair

A chair is a piece of furniture for sitting, consisting of a seat, a back, and sometimes arm rests, commonly for use by one person. Chairs also often have legs to support the seat raised above the floor. Without back and arm rests it is called a stool. A chair for more than one person is a couch, sofa, settee, loveseat (two-seater without arm rest in between) or bench. A separate footrest for a chair is known as an ottoman, hassock or poof. A chair mounted in a vehicle or in a theatre is simply called a seat. Chairs as furniture are typically not attached to the floor and so can be moved.

The back often does not extend all the way to the seat to allow for ventilation. Likewise, the back and sometimes the seat are made of porous materials or have holes drilled in them for decoration and ventilation.

The back may extend above the height of the head. There may be separate headrests. Headrests for seats in vehicles are important for preventing whiplash injuries to the neck when the vehicle is involved in a rear-end collision.

See history of the chair for an extended look at chairs from antiquity to the modern day.

Design and ergonomics

This unusual rocking chair is made of rough wood to give it an old-fashioned look.

Chair design considers intended usage, ergonomics (how comfortable it is for the occupant), as well as non-ergonomic functional requirements such as size, stackability, foldability, weight, durability, stain resistance and artistic design. Intended usage determines the desired seating position. "Task chairs", or any chair intended for people to work at a desk or table, including dining chairs, can only recline very slightly; otherwise the occupant is too far away from the desk or table. Dental chairs are necessarily reclined. Easy chairs for watching television or movies are somewhere in between depending on the height of the screen.

Ergonomic designs distributes the weight of the occupant to various parts of the body. A seat that is higher results in dangling feet and increased pressure on the underside of the knees ("popliteal fold"). It may also result in no weight on the feet which means more weight elsewhere. A lower seat may shift too much weight to the "seat bones" ("ischial tuberosities").

A reclining seat and back will shift weight to the occupant's back. This may be more comfortable for some in reducing weight on the seat area, but may be problematic for others who have bad backs. In general, if the occupant is suppose to sit for a long time, weight needs to be taken off the seat area and thus "easy" chairs intended for long periods of sitting are generally at least slightly reclined. However, reclining may not be suitable for chairs intended for work or eating at table.

The back of the chair will support some of the weight of the occupant, reducing the weight on other parts of the body. In general, backrests come in three heights: Lower back backrests support only the lumbar region. Shoulder height backrests support the entire back and shoulders. Headrests support the head as well and are important in vehicles for preventing "whiplash" neck injuries in rear-end collisions where the head is jerked back suddenly. Reclining chairs typically have at least shoulder height backrests to shift weight to the shoulders instead of just the lower back.

Some chairs have foot rests. A stool or other simple chair may have a simple straight or curved bar near the bottom for the sitter to place his/her feet on.

A kneeling chair adds an additional body part, the knees, to support the weight of the body. A sit-stand chair distributes most of the weight of the occupant to the feet.

Many chairs are padded or have cushions. Padding can be on the seat of the chair only, on the seat and back, or also on any arm rests and/or foot rest the chair may have. Padding will not shift the weight to different parts of the body (unless the chair is so soft that the shape is altered). However, padding does distribute the weight by increasing the area of contact between the chair and the body. A hard wood chair feels hard because the contact point between the occupant and the chair is small. The same body weight over a smaller area means greater pressure on that area. Spreading the area reduces the pressure at any given point. In lieu of padding, flexible materials, such as wicker, may be used instead with similar effects of distributing the weight. Since most of the body weight is supported in the back of the seat, padding there should be firmer than the front of the seat which only has the weight of the legs to support. Chairs that have padding that is the same density front and back will feel soft in the back area and hard to the underside of the knees.

There may be cases where padding is not desirable. For example, in hot climates, padding with fabric or plastic covers is often uncomfortable against the skin. Where padding is not desirable, contouring may be used instead. A contoured seat pan attempts to distribute weight without padding. By matching the shape of the occupant's buttocks, weight is distributed and pressure at any given point is reduced.

Actual chair dimensions are determined by measurements of the human body or anthropometric measurements. Individuals may be measured for a custom chair. Anthropometric statistics may be gathered for mass produced chairs. The two most relevant anthropometric measurement for chair design is the popliteal height and buttock popliteal length.

For someone seated, the popliteal height is the distance from the underside of the foot to the underside of the thigh at the knees. It is sometimes called the "stool height". (The term "sitting height" is reserved for the height to the top of the head when seated.) For American men, the median popliteal height is 16.3 inches and for American women it is 15.0 inches[1]. The popliteal height, after adjusting for heels, clothing and other issues is used to determine the height of the chair seat. Mass produced chairs are typically 17 inches high.

For someone seated, the buttock popliteal length is the horizontal distance from the back most part of the buttocks to the back of the lower leg. This anthropometric measurement is used to determine the seat depth. Mass produced chairs are typically 38-43 cm deep.

Additional anthropometric measurements may be relevant to designing a chair. Hip breadth is used for chair width and armrest width. Elbow rest height is used to determine the height of the armrests. The buttock-knee length is used to determine "leg room" between rows of chairs. "Seat pitch" is the distance between rows of seats. In some airplanes and stadiums the seat pitch is so small that there is sometimes there is no leg room for the average person.

For adjustable chairs, the aforementioned principles are applied in adjusting the chair to the individual occupant.

Arm rests

Traditional Japanese chair with zabuton and separate armrest Bus shelter with seats with arm rests in between

A chair may or may not have armrests. If so, armrests will support part of the body weight through the arms if the arms are resting on the armrests. Armrests further have the function of making entry and exit from the chair easier (but from the side it becomes more difficult). Armrests should support the forearm and not the sensitive elbow area. Hence in some chair designs, the armrest is not continuous to the chair back, but is missing in the elbow area.

A couch, bench, or other arrangement of seats next to each other may have arm rest at the sides and/or arm rests in between. The latter may be provided for comfort, but also for privacy e.g. in public transport and other public places, and to prevent lying on the bench or coach. Arm rests prevent or complicate both desired and undesired proximity. A loveseat in particular, has no arm rest in between.

See also seats in movie theaters, and pictures of benches with and without arm rests.

Chair seats

A bench is long enough for several people to sit on

Chair seats vary widely in construction and may or may not match construction of the chair's back. Some systems include: Solid center seats where a solid material forms the chair seat.

  • Solid wood, may or may not be shaped to human contours.
  • Wood slats, often seen on outdoor chairs
  • Padded leather, generally a flat wood base covered in padding and contained in soft leather
  • Stuffed fabric, similar to padded leather
  • Metal seats of solid or open design
  • Molded plastic
  • Stone, often marble

Open center seats where a soft material is attached to the tops of chair legs or between stretchers to form the seat.

  • Wicker, woven to provide a surface with give to it
  • Leather, may be tooled with a design
  • Fabric, simple covering without support
  • Tape, wide fabric tape woven into seat, seen in lawn chairs and some old chairs
  • Caning, woven from rush, reed, rawhide, heavy paper, strong grasses, cattails to form the seat, often in elaborate patterns
  • Splint, ash, oak or hickory strips are woven
  • Metal, Metal mesh or wire woven to form seat

Standards and specifications

Design considerations for chairs have been codified into standards. ISO 9241-5:1988[2], "Ergonomic requirements for office work with visual display terminals (VDTs) -- Part 5: Workstation layout and postural requirements " is the most common one for modern chair design.

There are multiple specific standards for different types of chairs. Dental chairs are specified by ISO 6875. Bean bag chairs are specified by ANSI standard ASTM F1912-98[3]. ISO 7174 specifies stability of rocking and tilting chairs. ASTM F1858-98 specifies lawn chairs. ASTM E1822-02b defines the combustibility of chairs when they are stacked.

The Business and Institutional Furniture Manufacturer's Association (BIFMA) defines BIFMA X5.1 for testing of commercial-grade chairs. It specifies things like[4]:

  • chair backstrength of 150 pounds (68 kg)
  • chair stability if weight is transferred completely to the front or back legs
  • leg strength of 75 pounds (34 kg) applied one inch (25 mm) from the bottom of the leg
  • seat strength of 225 pounds (102 kg) dropped from six inches (150 mm) above the seat
  • seat cycle strength of 100,000 repetitions of 125 pounds (57 kg) dropped from 2 inches (50 mm) above the seat

The specification further defines heavier "proof" loads that chairs must withstand. Under these higher loads, the chair may be damaged, but it must not fail catastrophically.

Large institutions that make bulk purchases will reference these standards within their own even more detailed criteria for purchase [5]. Governments will often issue standards for purchases by government agencies (e.g. Canada's Canadian General Standards Board CAN/CGSB 44.15M [6] on "Straight Stacking Chair, Steel").

Accessories

In place of a built-in footrest, some chairs come with a matching ottoman. An ottoman is a short stool to be used as a footrest but can sometimes be used as a stool. If matched to a glider, the ottoman may be mounted on swing arms so that the ottoman rocks back and forth with the main glider.

A chair cover is a temporary fabric cover for a side chair. They are typically rented for formal events such as wedding receptions to increase the attractiveness of the chairs and decor. The chair covers may come with decorative chair ties, a ribbon to be tied as a bow behind the chair. Covers for sofas and couches are also available for homes with small children and pets. In the second half of 20th century, some people used custom clear plastic covers for expensive sofas and chairs to protect them.

Chair pads are cushions for chairs. Some are decorative. In cars, they may be used to increase the height of the driver. Orthopedic backrests provide support for the back. Obus Forme is a major brand in this category and helped develop this market niche. Car seats sometimes have built-in and adjustable lumbar supports.

Chair mats are plastic mats meant to cover carpet. This allows chairs on wheels to roll easily over the carpet and it protects the carpet. They come in various shapes, some specifically sized to fit partially under a desk.

Remote control bags can be draped over the arm of easy chairs or sofas and used to hold remote controls. They are counter-weighted so as to not slide off the arms under the weight of the remote control.

English phrases relating to chairs

A movie or a story is said to keep you on the edge of your chair, if it is suspenseful and engaging.

If you nearly fell off your chair, it was because you were very surprised.

Activities that are likely to be made insignificant or undone by some future event are said to be like rearranging the deckchairs on the Titanic.

When English-speaking philosophers talk about the material world as opposed to ideas, their phrase is tables and chairs.


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When English-speaking philosophers talk about the material world as opposed to ideas, their phrase is tables and chairs. See also Don't ask, don't tell. Activities that are likely to be made insignificant or undone by some future event are said to be like rearranging the deckchairs on the Titanic. Also the other may insist that one answers the question. If you nearly fell off your chair, it was because you were very surprised. The alternative, when asked about something, declining to answer, may suggest the answer and may therefore not always be suitable to keep the secret. A movie or a story is said to keep you on the edge of your chair, if it is suspenseful and engaging. One may have to lie in order to hold a secret, which might lead to psychological repercussions.

They are counter-weighted so as to not slide off the arms under the weight of the remote control. Excessive secrecy is often cited as a source of much human conflict. Remote control bags can be draped over the arm of easy chairs or sofas and used to hold remote controls. It is considered easier to verify software reliability if one can be sure that different parts of the program only have access to certain information. They come in various shapes, some specifically sized to fit partially under a desk. Information hiding is a design principle in much software engineering. This allows chairs on wheels to roll easily over the carpet and it protects the carpet. See Full disclosure, Kerckhoffs' law, Security through obscurity.

Chair mats are plastic mats meant to cover carpet. Many believe that security technology can be more effective if it itself is not kept secret. Car seats sometimes have built-in and adjustable lumbar supports. The latter depends on the secrecy of cryptographic keys. Obus Forme is a major brand in this category and helped develop this market niche. Techniques used include physical security and cryptography. Orthopedic backrests provide support for the back. Preservation of secrets is one of the goals of information security.

In cars, they may be used to increase the height of the driver. even has a special law protecting records of video tape rentals and sales (18 USC 2710), apparently passed when members of Congress realized their video viewing habits could be politically embarrassing. Some are decorative. The U.S. Chair pads are cushions for chairs. Europe has particularly strict laws about database privacy. In the second half of 20th century, some people used custom clear plastic covers for expensive sofas and chairs to protect them. Other laws require organizations to keep certain information secret, such as medical records (HIPAA in the U.S.), or financial reports that are under preparation (to limit insider trading).

Covers for sofas and couches are also available for homes with small children and pets. Secrecy is central to organized crime. The chair covers may come with decorative chair ties, a ribbon to be tied as a bow behind the chair. Secret societies use secrecy as a way to attract members by creating a sense of importance. They are typically rented for formal events such as wedding receptions to increase the attractiveness of the chairs and decor. Keeping one's strategy secret is important in many aspects of game theory. A chair cover is a temporary fabric cover for a side chair. The patent system encourages inventors to publish information in exchange for a limited time monopoly on its use, though patent applications are initally secret.

If matched to a glider, the ottoman may be mounted on swing arms so that the ottoman rocks back and forth with the main glider. New products under development, unique manufacturing techniques, or simply lists of customers are types of information protected by trade secret laws. An ottoman is a short stool to be used as a footrest but can sometimes be used as a stool. Organizations, ranging from multi-national for profit corporations to nonprofit charities, keep secrets for competitive advantage, to meet legal requirements, or, in some cases, to conceal nefarious behavior. In place of a built-in footrest, some chairs come with a matching ottoman. (For a current (2005) example, see Plame affair.). Canada's Canadian General Standards Board CAN/CGSB 44.15M [6] on "Straight Stacking Chair, Steel"). Government officials sometimes leak information they are supposed to keep secret.

Governments will often issue standards for purchases by government agencies (e.g. Freedom of Information Act and sunshine laws. Large institutions that make bulk purchases will reference these standards within their own even more detailed criteria for purchase [5]. Many countries have laws that attempt to limit government secrecy, such as the U.S. Under these higher loads, the chair may be damaged, but it must not fail catastrophically. Few people dispute the desirability of keeping Critical Nuclear Weapon Design Information secret, but many believe government secrecy to be excessive and too often employed for political purposes. The specification further defines heavier "proof" loads that chairs must withstand. An individual needs a security clearance for access and other protection methods, such as keeping documents in a safe, are stipulated.

It specifies things like[4]:. Most nations have some form of Official Secrets Act (the Espionage Act in the U.S.) and classify material according to the level of protection needed (hence the term "classified information"). The Business and Institutional Furniture Manufacturer's Association (BIFMA) defines BIFMA X5.1 for testing of commercial-grade chairs. These state secrets can include weapon designs, military plans, diplomatic negotiation tactics, and secrets obtained illicitly from others ("intelligence"). ASTM E1822-02b defines the combustibility of chairs when they are stacked. Governments often attempt to conceal information from other governments or the public. ASTM F1858-98 specifies lawn chairs. On occasion, the information may be something innocent such as a recipe.

ISO 7174 specifies stability of rocking and tilting chairs. Agreement to maintain the secret is often coerced through the use of such tactics as "shaming" and reference to family honour. Bean bag chairs are specified by ANSI standard ASTM F1912-98[3]. Families sometimes maintain "family secrets", using a mutually agreed-upon construct (an official family story) to never discuss disagreeable issues concerning the family, either within the family or with those outside the family. Dental chairs are specified by ISO 6875. On a deeper level, humans attempt to conceal aspects of their own self which they are not capable of incorporating psychologically into their conscious being. There are multiple specific standards for different types of chairs. ) Humans attempt to consciously conceal aspects of themselves from others, due to, for example, shame or fear of rejection, loss of acceptance, loss of employment, or other negative repercussions.

ISO 9241-5:1988[2], "Ergonomic requirements for office work with visual display terminals (VDTs) -- Part 5: Workstation layout and postural requirements " is the most common one for modern chair design. (In practice, finding a human is often not difficult, especially with the aid of telephone directories, private eyes, etc. Design considerations for chairs have been codified into standards. Animals, including humans (in some cases), generally endeavor to conceal the location of their den or nest from predators. Open center seats where a soft material is attached to the tops of chair legs or between stretchers to form the seat. One reason for sexual reproduction and speciation may be to allow members of a species to share genetic improvements without their becoming available to competitors. Some systems include: Solid center seats where a solid material forms the chair seat. Secrecy is built into biology.

Chair seats vary widely in construction and may or may not match construction of the chair's back. . See also seats in movie theaters, and pictures of benches with and without arm rests. Closely allied—perhaps synonymous—notions of confidentiality and privacy are often considered virtues (One should keep confidences and respect privacy.). A loveseat in particular, has no arm rest in between. Many people claim that, at least in some situations, it is better for everyone if everyone knows all the facts—there should be no secrets. Arm rests prevent or complicate both desired and undesired proximity. Secrecy is often controversial.

in public transport and other public places, and to prevent lying on the bench or coach. That which is kept hidden is known as the secret. The latter may be provided for comfort, but also for privacy e.g. Secrecy is the practice of hiding information from others. A couch, bench, or other arrangement of seats next to each other may have arm rest at the sides and/or arm rests in between. Hence in some chair designs, the armrest is not continuous to the chair back, but is missing in the elbow area.

Armrests should support the forearm and not the sensitive elbow area. Armrests further have the function of making entry and exit from the chair easier (but from the side it becomes more difficult). If so, armrests will support part of the body weight through the arms if the arms are resting on the armrests. A chair may or may not have armrests.

For adjustable chairs, the aforementioned principles are applied in adjusting the chair to the individual occupant. In some airplanes and stadiums the seat pitch is so small that there is sometimes there is no leg room for the average person. "Seat pitch" is the distance between rows of seats. The buttock-knee length is used to determine "leg room" between rows of chairs.

Elbow rest height is used to determine the height of the armrests. Hip breadth is used for chair width and armrest width. Additional anthropometric measurements may be relevant to designing a chair. Mass produced chairs are typically 38-43 cm deep.

This anthropometric measurement is used to determine the seat depth. For someone seated, the buttock popliteal length is the horizontal distance from the back most part of the buttocks to the back of the lower leg. Mass produced chairs are typically 17 inches high. The popliteal height, after adjusting for heels, clothing and other issues is used to determine the height of the chair seat.

(The term "sitting height" is reserved for the height to the top of the head when seated.) For American men, the median popliteal height is 16.3 inches and for American women it is 15.0 inches[1]. It is sometimes called the "stool height". For someone seated, the popliteal height is the distance from the underside of the foot to the underside of the thigh at the knees. The two most relevant anthropometric measurement for chair design is the popliteal height and buttock popliteal length.

Anthropometric statistics may be gathered for mass produced chairs. Individuals may be measured for a custom chair. Actual chair dimensions are determined by measurements of the human body or anthropometric measurements. By matching the shape of the occupant's buttocks, weight is distributed and pressure at any given point is reduced.

A contoured seat pan attempts to distribute weight without padding. Where padding is not desirable, contouring may be used instead. For example, in hot climates, padding with fabric or plastic covers is often uncomfortable against the skin. There may be cases where padding is not desirable.

Chairs that have padding that is the same density front and back will feel soft in the back area and hard to the underside of the knees. Since most of the body weight is supported in the back of the seat, padding there should be firmer than the front of the seat which only has the weight of the legs to support. In lieu of padding, flexible materials, such as wicker, may be used instead with similar effects of distributing the weight. Spreading the area reduces the pressure at any given point.

The same body weight over a smaller area means greater pressure on that area. A hard wood chair feels hard because the contact point between the occupant and the chair is small. However, padding does distribute the weight by increasing the area of contact between the chair and the body. Padding will not shift the weight to different parts of the body (unless the chair is so soft that the shape is altered).

Padding can be on the seat of the chair only, on the seat and back, or also on any arm rests and/or foot rest the chair may have. Many chairs are padded or have cushions. A sit-stand chair distributes most of the weight of the occupant to the feet. A kneeling chair adds an additional body part, the knees, to support the weight of the body.

A stool or other simple chair may have a simple straight or curved bar near the bottom for the sitter to place his/her feet on. Some chairs have foot rests. Reclining chairs typically have at least shoulder height backrests to shift weight to the shoulders instead of just the lower back. Headrests support the head as well and are important in vehicles for preventing "whiplash" neck injuries in rear-end collisions where the head is jerked back suddenly.

Shoulder height backrests support the entire back and shoulders. In general, backrests come in three heights: Lower back backrests support only the lumbar region. The back of the chair will support some of the weight of the occupant, reducing the weight on other parts of the body. However, reclining may not be suitable for chairs intended for work or eating at table.

In general, if the occupant is suppose to sit for a long time, weight needs to be taken off the seat area and thus "easy" chairs intended for long periods of sitting are generally at least slightly reclined. This may be more comfortable for some in reducing weight on the seat area, but may be problematic for others who have bad backs. A reclining seat and back will shift weight to the occupant's back. A lower seat may shift too much weight to the "seat bones" ("ischial tuberosities").

It may also result in no weight on the feet which means more weight elsewhere. A seat that is higher results in dangling feet and increased pressure on the underside of the knees ("popliteal fold"). Ergonomic designs distributes the weight of the occupant to various parts of the body. Easy chairs for watching television or movies are somewhere in between depending on the height of the screen.

Dental chairs are necessarily reclined. "Task chairs", or any chair intended for people to work at a desk or table, including dining chairs, can only recline very slightly; otherwise the occupant is too far away from the desk or table. Intended usage determines the desired seating position. Chair design considers intended usage, ergonomics (how comfortable it is for the occupant), as well as non-ergonomic functional requirements such as size, stackability, foldability, weight, durability, stain resistance and artistic design.

. See history of the chair for an extended look at chairs from antiquity to the modern day. Headrests for seats in vehicles are important for preventing whiplash injuries to the neck when the vehicle is involved in a rear-end collision. There may be separate headrests.

The back may extend above the height of the head. Likewise, the back and sometimes the seat are made of porous materials or have holes drilled in them for decoration and ventilation. The back often does not extend all the way to the seat to allow for ventilation. Chairs as furniture are typically not attached to the floor and so can be moved.

A chair mounted in a vehicle or in a theatre is simply called a seat. A separate footrest for a chair is known as an ottoman, hassock or poof. A chair for more than one person is a couch, sofa, settee, loveseat (two-seater without arm rest in between) or bench. Without back and arm rests it is called a stool.

Chairs also often have legs to support the seat raised above the floor. A chair is a piece of furniture for sitting, consisting of a seat, a back, and sometimes arm rests, commonly for use by one person. seat cycle strength of 100,000 repetitions of 125 pounds (57 kg) dropped from 2 inches (50 mm) above the seat. seat strength of 225 pounds (102 kg) dropped from six inches (150 mm) above the seat.

leg strength of 75 pounds (34 kg) applied one inch (25 mm) from the bottom of the leg. chair stability if weight is transferred completely to the front or back legs. chair backstrength of 150 pounds (68 kg). Metal, Metal mesh or wire woven to form seat.

Splint, ash, oak or hickory strips are woven. Caning, woven from rush, reed, rawhide, heavy paper, strong grasses, cattails to form the seat, often in elaborate patterns. Tape, wide fabric tape woven into seat, seen in lawn chairs and some old chairs. Fabric, simple covering without support.

Leather, may be tooled with a design. Wicker, woven to provide a surface with give to it. Stone, often marble. Molded plastic.

Metal seats of solid or open design. Stuffed fabric, similar to padded leather. Padded leather, generally a flat wood base covered in padding and contained in soft leather. Wood slats, often seen on outdoor chairs.

Solid wood, may or may not be shaped to human contours.

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