In an electrical distribution cabinet a mechanism providing quick, reliable, passive arc blast control has a flue chamber surrounding the likely arc site such as an electrical connection point. The flue chamber provides a flue channel which lengthens the arc and attenuates the current and temperature until the arc is extinguished. Preferably, the flue chamber and channel are formed of opposable open-faced polyhedral structures, one fitting inside the other. The mechanism is particularly suited for draw-out circuit breaker connections in a switch gear cabinet.

A driver for a switch in a GIS (Gas Insulation Switchgear) includes a motor, a shaft connected with a moving contact of the switch, a gear connected with one terminal of the shaft and configured to transfer power of the motor to cause the shaft to reciprocate the moving contact through the shaft, a cam spline combined with the shaft and spaced apart from the gear, and a micro-switch connected with the cam spline and configured to control an operation of the motor.

The present disclosure relates to a vacuum interrupter capable of easily installing a central arc shielding plate in alignment without biasing in a radial direction. The vacuum interrupter includes a protruding guide unit protruding from a stationary electrode seal cup in a perpendicular direction to guide the installation of the central arc shielding plate such that the central arc shielding plate can be aligned in a radial direction.

Disclosed are a power transmission device for a vacuum interrupter, and a vacuum breaker having the same. The device includes: a driving link coupled to an adjuster; a driven link coupled to a movable electrode of a vacuum interrupter; connection links configured to connect the driving link and the driven link with each other, and coupled to the driving link and the driven link such that an interval between the driving link and the driven link is varied; cams coupled to the connection links in a perpendicular direction; and cam guides having guide recesses for slidably coupling the cams, and configured to guide the interval between the driving link and the driven link to be changed.

A method of manufacturing a power contactor from an existing contactor having a magnetic amplifier that comprises a blowout coil and a ferromagnetic core, and an arc chute for extinguishing an arc generated by opening the existing contactor under a current load is disclosed. The method includes removing a bolt assembly from the existing contactor and at least one side plate from the existing contactor. The method also includes removing the ferromagnetic core from the existing contactor.

The invention relates to a medium voltage switchgear assembly which comprises at least one disconnector and whose drive unit is disposed inside or outside a gas chamber according to the generic part of claim 1. In order to further develop a switchgear assembly of the generic type so as to render the same more compact and more functional, the disconnector is embodied as a three-position vacuum chamber switch.

The invention relates to a tap changer for the interruption-free switchover between winding taps of a tap-changing transformer. Furthermore, the present invention relates to a novel vacuum interrupter which is particularly suitable for such a tap changer. The tap changer according to the invention is based on the general concept of combining in each case one main contact (V1) and one mechanical switching means (U1), connected in series therewith, of a first load branch and an additional resistive contact (V3) of a second load branch in only a single vacuum interrupter (1) with a common housing (5). The vacuum interrupter (1) according to the invention is furthermore based on the general inventive concept of replacing the functionalities of two required vacuum interrupters in accordance with the prior art and an additional mechanical switching means with a single vacuum interrupter (1) according to the invention by virtue of combining the design of a vacuum interrupter (1) with a plurality of moveable contact systems (I, II, III), which are arranged in separate vacuum interrupter chambers (2, 3, 4) which are sealed with respect to one another.

An electric switch for application to high- and very high-voltage circuit breakers and switches comprising a flexible toroidal helical spring (8) placed in a groove of a control rod (1) carrying a movable resistance-insertion contact (2), and springs (4) placed about the movable resistance-insertion contact to cause the springs to be compressed until a certain value is reached, at which value the movable resistance-insertion contact causes the flexible toroidal helical spring (8) to deform under pressure enabling the movable resistance-insertion contact (2) to be withdrawn. Among other uses, the switch is suitable for use in a resistance-inserting device that does not need additional mechanical moving parts. For application to high- and very high-voltage circuit breakers and switches.

A sealed solenoid, magnetically operated electric power switch is suitable for use as capacitor, line and load switch operating at transmission and distribution voltages that includes no dynamically moving seals through the sealed container housing the contactor portion of the switch. The sealed solenoid switch includes a magnetically operated drive system with an actuator that magnetically couples across the container wall to avoid the use of a moving or sliding seal as part of the drive system. The sealed solenoid switch may also include a ballast resistor and resistor contact located inside the sealed container to avoid another seal as part of the ballast system. A magnetic latch holds the switch in a closed position, and a spring holds the switch in the closed position, to avoid the need for an energizing current to maintain the switch in either position.

In a vacuum circuit breaker corresponding to three-phase, which is configured by linearly arranging three pressure tanks respectively corresponding to one-phase, in which insulation gas is encapsulated, and a vacuum valve is installed, each pressure tank has a nearly longitudinal shape or a nearly square shape, viewed from a plane surface, and the vacuum valve is arranged in each of the pressure tanks in a state where a drive direction of the movable conductor is aligned with an upper lower direction, and the movable conductor is positioned lower than the vacuum valve, and keeps a sufficient insulation distance with respect to the movable-side connection conductor, and is neared to a position in one of diagonal directions or longitudinal directions of the pressure tank having a nearly square shape or nearly ellipsoidal shape, and moreover, the operation mechanism is arranged and configured at a position, which is lower than the vacuum valve.

The high voltage relay consists of a main body (1). One set of electrical contacts (2a, 2b) upper and lower respectively. High voltage connections to connect the voltage being switched (3a, 3b) are electrically connected to the upper and lower contacts respectively. Several size options for the electrical contacts will allow for a wide range of currents. A cylinder (4) driven by a fluid (e.g. Air, Nitrogen, Hydraulic fluid) moves the electrical contacts together during the ON state of the device. During the OFF state of the device the cylinder moves the electrical contacts apart to isolate the switch voltage. The greater the High Voltage being switched the greater the distance the electrical contacts must be moved apart in the OFF state. The cylinder is supplied the fluid power from a small solenoid (5) on the device. This solenoid has control voltage connections to actuate the device.

An arc chamber for a circuit breaker has first and second mounting bodies. The mounting bodies are disposed at the ends of an electrically insulating insulation section of the arc chamber. The insulation section is formed of at least two shell-shaped partial sections. The partial sections are curved concavely relative to a longitudinal axis of the arc chamber. A gap is formed between the edges of the bodies of the partial sections.

A circuit protection device is provided for use with a circuit that includes at least one pair of conductors. The protection device is configured to generate an arc. The protection device includes at least a pair of electrode assemblies electrically coupled to the at least one pair of conductors and a conductor base to support the pair of electrode assemblies. The protection device includes a cover coupled to the conductor base and defining at least one isolation chamber, wherein the electrode assemblies are disposed within the isolation chamber. The protection device includes a containment shield moveably coupled to the cover. The containment shield defines a containment chamber configured to contain charged particles produced by the arc. The containment shield is operative to move relative to the cover in response to a change in pressure produced by the arc within the containment chamber. An isolation assembly is coupled to at least one of the cover and the containment shield and configured to prevent the cover from contacting the containment shield.

Provided is a sector gear including: a drive gear having a drive part that forms a part of a circle and has a plurality of teeth and a non-drive part that forms a remaining part of the circle and provides a non-contact angle of at least approximately 90 degrees; first and second movers forming a disconnector and a grounded breaking switch, respectively; and first and second driven gears engaged with the drive gear and respectively engaged with the first and second movers and configured to make the first mover or the second mover operate in conjunction with the drive part of the drive gear according to a direction of rotation of the drive gear, wherein an intermediate angle between the first and second movers is between approximately 90-135 degrees. The present invention can reduce the size of the gas-insulated switchgear having the sector gear.

Equipment protection systems, arc containment devices, and methods of assembling arc containment devices are disclosed. In one example, an electrical isolation structure includes a conductor base, a cover coupled to the conductor base and defining an isolation chamber, a containment shield disposed on the conductor base within the isolation chamber, and a biasing assembly positioned between the cover and the containment shield. The containment shield defines a containment chamber configured to enclose the plurality of electrode assemblies. The containment shield is configured to at least partially contain the arc products within the containment chamber. The biasing assembly is configured to permit the containment shield to move away from the conductor base to thereby define a gap between the conductor base and the containment shield to enable at least some of the arc gases to vent from the containment chamber.

Disclosed is a curable composition comprising an epoxy resin and a filler composition, a cured product obtained by curing said curable composition as well as the use of the cured products as electrically insulating construction material for electrical or electronic components.

An electrode assembly for a circuit breaker is provided. The electrode assembly includes a conductive assembly and a heat transfer assembly. The conductive assembly includes a stem portion and a contact portion. The heat transfer assembly includes a number of elongated bodies, a first heat transfer surface, and a second heat transfer surface. The first heat transfer surface is disposed on the conductive assembly. Each heat transfer assembly body includes a second heat transfer surface. Each heat transfer assembly body is coupled to the conductive assembly with the first heat transfer surface coupled to a number of second heat transfer surfaces.

A flexible shunt for a vacuum circuit breaker can have a reduced straight length and improved flexibility even with an increased thickness within a predetermined accommodation space of a main circuit part. The flexible shunt comprises a pair of conductive plates, each including a clamp connecting portion configured as a flat conductive member, the clamp connecting portion being connected the clamp, a terminal side connecting portion configured as a flat conductive member, the terminal side connecting portion being connected to the terminal side, and a flexible curved portion configured to connect the clamp connecting portion to the terminal side connecting portion, the flexible curved portion being formed to be projected outwardly.

An exemplary medium or high voltage switch has a first set of contact elements and a second set of contact elements. Each contact element includes an insulating carrier carrying conducting elements. In the closed state of the switch, the conducting elements align to form one or more current paths between terminals of the switch along an axial direction. For opening the switch, the contact elements are mutually displaced by means of one or two drives along a direction perpendicular to the axial direction. The switching arrangement is arranged in a fluid-tight housing in a gas of elevated pressure or in a liquid. The switch has a high voltage withstand capability and fast switching times.

An electrode assembly for a vacuum interrupter is configured such that supporting members can support most of a contact electrode plate and a supporting electrode plate in an axial direction with coil conductors interposed therebetween. Accordingly, an impact generated between electrode assemblies upon a closing operation of the vacuum interrupter may be evenly distributed onto the supporting members, which may result in preventing each of the electrode plates and the coil conductors from being deformed. Also, the supporting members are inserted into the electrode plates and the coil conductors, thereby effectively preventing a current from flowing via the supporting members. In addition, the supporting member may be wide and large so as to simplify an assembly operation and reduce an assembly time.

A removable faceplate for a portable electronic device is provided. The faceplate permits a user to change the physical appearance of a surface of the device while retaining access to the mechanisms for controlling the function of the device. Preferably, the removable faceplate and electronic device are configured with a means for association and dissociation that can be activated without the use of a tool and the means is not visible when the faceplate is attached. Additionally, an improved packaging system is provided to enable a vendor or manufacturer to package faceplates with the devices that they will cover and to allow substitution of faceplates in the packaging without disturbing the packaging of the electronic device itself. Further, there is a method for distribution of the packaging system.

A food container stacking device comprising: a horizontal member, with a first longitudinal side, a second longitudinal side, a top surface, and a bottom surface, a first corner, second corner, third corner, and fourth corner; the food container stacking device configured to lay on the top surface of a first food container, and further configure to support a second food container on the top surface, thereby allowing for the stacking of the first and second food containers. A food container stacking system, comprising: a first food container; a first food container stacking device configured to lay on the top surface of the first food container, the first food container stacking device comprising: a horizontal member, with a first longitudinal sinusoidal shaped side, a second longitudinal sinusoidal shaped side, a top surface, and a bottom surface, a first corner, second corner, third corner, and fourth corner; a first pin removeably attachable to the first hole, and extending from the bottom surface; a second pin removeably attachable to the second hole, and extending from the bottom surface; a third pin removeably attachable to the third hole, and extending from the bottom surface; a fourth pin removeably attachable to the fourth hole, and extending from the bottom surface, where the first and second pins are configured to lay outside of the perimeter of the first food container, and where the third and fourth pins are configured to lay outside of the perimeter of the first food container, on an opposite side of the first food container.

A packaging device includes first and second thermoplastic films superposed with each other, wherein predetermined portions of the thermoplastic films are bonded creating a plurality of fluid containers, a plurality of check valves each connected to a corresponding fluid container, a fluid passage in a first direction connected to the check valves, and a second border between an inflated section including the plurality of fluid containers and an uninflated section, wherein the first and second thermoplastic films are folded and two side edges of the films are bonded and a first portion of a first border connecting the inflated section to a second section is folded and an overlapped portion of the first portion is bonded leaving a remaining portion of the first border unbonded wherein the uninflated section forms a loop, and wherein the uninflated section forming the loop is folded into the inflated section to form a lining.

The present invention provides an assembly for the preparation of a medical device having a porous coating comprising hydrogen peroxide. Particularly interesting medical devices are catheters (such as urinary catheters), endoscopes, laryngoscopes, tubes for feeding, tubes for drainage, guide wires, condoms, urisheaths, barrier coatings e.g. for gloves, stents and other implants, extra corporeal blood conduits, membranes e.g. for dialysis, blood filters, devices for circulatory assistance, dressings for wound care, and ostomy bags. The coating is in particular a hydrophilic coating formed from cross-linked polyvinylpyrrolidone. In one embodiment, the assembly holds a dry catheter element in one compartment of a package and an aqueous hydrogen peroxide solution in another compartment. The solution may also comprise stabilizers, e.g. chelators, and osmolality increasing agents. The catheter for insertion in the urethra is useful for the treatment, alleviation or prophylaxis of microbial infections such as urinary tract infections (UTI).

A housing shell for electrical measuring, controlling and communication devices, in particular the lower housing part of a cellphone, has very great flexural and torsional rigidity in spite of an extremely small wall thickness if it is formed as a part created by a forming operation from the planar blank of a thermoplastically impregnated long-fibered multi-layered mat. Fine-membered functional elements of likewise thermoplastic material are then molded onto the housing shell in an injection mold.

Protective mailer capable of being processed by postal processing equipment without causing damage to the article held by the mailer. The pocket holding the article inside the mailer is offset relative to one edge, when folded, by a distance sufficient to prevent damage when the mailer is oriented and processed. The mailer may include a resizing flap that, when unfolded and deployed, changes the dimensions of the mailer so that the mailer is processed by the postal processing equipment as a non-letter or flat mailpiece.

A holder is for supporting a portable electronic device, including at least one sheet. A base portion, a first supporting portion and a second supporting portion formed on the at least one sheet. The base portion, the first supporting portion and the second supporting portion are parallel with each other and folded relative to each other. A latching piece is formed on the base portion, the latching piece having a bendable portion. The first supporting portion is folded relative to the base portion, and the second supporting portion is folded relative to the first supporting portion until the second supporting portion is held by the latching piece, the base portion, the first supporting portion and the second supporting portion cooperatively form a three-dimensional structure that can support the portable electronic device at an angle relative to the at least one sheet without collapsing.

A catheter assembly including an elongate member having a proximal end and a distal end. The distal end has at least one drainage opening. A hydrophilic coating is provided on at least a portion of the elongate end of the catheter. A fluid containing member is provided and is either arranged on the elongate member or within a separate area of the container. The fluid containing member contains sufficient hydrating fluid to hydrate the coating of the catheter. A container contains the elongate member and the fluid containing member and incorporates at least one foil layer to prevent evaporation of the hydrating fluid. A method of using the catheter includes inserting a catheter into a user's body and draining fluid from the user's body.

Tamper-evident package comprises a container, a primary cap, and a secondary cap. The container comprises a sidewall defining a chamber and a rim defining a mouth to the chamber. The primary cap is removably-attachable to the rim of the container to selectively close the mouth of the container. The secondary cap is positioned over the primary cap to prevent removal of the primary cap when positioned thereover. The secondary cap includes a single-use lock, such as a cable tie, to secure the secondary cap in position over the primary cap. The package thus provides evidence that someone has tampered with or attempted to tamper with the container if the single-use lock is removed or damaged. Method of using the tamper-evident package is also disclosed.

A bed-side system for preventing infection that uses a flush and swab caddy attached to an IV pole or other bed-side equipment. By providing convenient and secure storage for pre-filled syringes, alcohol swabs, and other medical supplies, it can improve individual patient care. In an embodiment, the caddy attaches to the IV pole and comprises a locking compartment for pre-filled syringes and an open tray for alcohol swabs and other medical supplies. The syringes may be filled with saline, heparin, or another solution.

A method of treating a cancer of the central nervous system in a subject in need thereof is provided. The method comprising administering to the subject a therapeutically effective amount of an agent which reduces blood glutamate levels and enhances brain to blood glutamate efflux to thereby treat the cancer of the central nervous system in the subject.

A bottled drink includes a cap and a bottle where a granular supplement containing multiple constituents in a stable manner is stored in the cap and a solution suitable for dispersing the granules is filled in the bottle. Granules which contains mutually incompatible multiple chemical agents or nutritional constituents and whose surface is coated with polyglyceryl fatty acid ester are stored in the cap of the bottle and the bottle is filled with a solution whose viscosity at a shear deformation speed of 0.01 s−1 is 10 to 300 Pa·s.

A reversible folio for a tablet computer has a tablet shell with a cavity removably receiving the tablet computer. A keyboard is pivotally and removably coupled to the tablet shell. A channel is pivotally coupled to an edge of the keyboard. An interior of the channel removably receives the proximal edge of the tablet shell, and has a profile mating with a profile of the tablet shell. The channel and proximal edge have first and second symmetrical magnet arrays, respectively. The proximal edge of the tablet shell physically mates with the channel of the keyboard, and the second magnet array of the tablet shell magnetically mates with the first magnet array of the channel, in both a first orientation and an opposite second orientation.

A method for sanitary beverage can packaging incorporates a plastic sanitation sheet between the tops of the beverage cans and a plastic can retainer. The sanitation sheet covers the tops of the cans, protecting them from dust and overhead spills. Some embodiments use a watertight or airtight seal of the sanitation sheet around the can rim. Some embodiments include visible indicators of seal breakage or direct contamination, using moisture or oxygen detection. Some indicators create a hole in the sanitation sheet. Other indicators provide visible warning text or symbols. The sheet and indicators provide both actual contaminant protection and visible indication of contamination. Embodiments include the plastic sanitation sheet, integration with beverage cans, and a method for use in providing assured sanitary cans to consumers.

A container (10) for consumer goods comprises a first panel (16) having a pattern (22) applied to an area (20) of the external surface thereof; and a second panel (26) comprising a transparent optical element. The first panel (16) and the second panel (26) are moveable relative to each other between a first position, in which the transparent optical element in the second panel (26) does not overlie the pattern (22) on the first panel (16), and a second position, in which the transparent optical element in the second panel (26) at least partially overlies the pattern (22) on the first panel (16), whereby an altered image of the pattern is visible through the transparent optical element.

A multi-compartmented food storage device having a top hermetic storage compartment, a bottom hermetic storage compartment and a central hermetic storage compartment that is interposed there between. Each of the top and bottom compartments being hingedly secured to the central compartment along an upper and lower end.

A multifunctional case is configured for receiving or supporting a portable electronic device. The case includes a first layer and a second layer. The second layer is connected to the first layer by the edges. A receiving space is formed between the first and second layers for receiving the portable electronic device. The second layer is provided with a base portion, a main supporting portion, two side supporting portions and two remaining portions are formed on the second layer. The two side supporting portions and the remaining portions are symmetrically positioned at two sides of the main supporting portion. When the case is folded up as a support, the main supporting portion is angled with the base portion. The remaining portions are stacked on the base portion. The side supporting portions are perpendicular to the remaining portions and the main supporting portion.

A container storing an anesthetic is disclosed. The container is sealed by a closure and stores a liquid anesthetic solution. The anesthetic is from 0.1% to 10% by weight of the liquid anesthetic solution. The container is made of a material that is inert to the anesthetic and the closure is made of siliconized rubber or a metal. A concentration of the anesthetic in a liquid anesthetic solution stored in the container following a predetermined time period is at least 93% of a concentration of the anesthetic in a liquid anesthetic solution before the liquid anesthetic solution is stored in the container.

An ultra removable booklet with label for application to media is described. The booklet with label includes a release liner, an ultra removable adhesive layer, a paper stock layer, a booklet, an adhesive layer, and a clear plastic cover layer. The clear plastic cover layer has the adhesive layer applied to a bottom surface thereof and the bottom surface is positioned over the booklet. The booklet is positioned over the paper stock. The ultra removable adhesive layer is attached to the lower surface of the paper stock. The release liner is applied to the ultra removable adhesive layer. A process for forming an ultra removable booklet with label for application to media is also described.

A cover (10) is disclosed for holding objects such as papers and reports. The cover (10) is formed of a member (20) having a front cover (22), a spine (24) and a back cover (26). A first portion (32) and a second portion (38) are folded over to encapsulate a prong fastener (12). The second portion (38) is then fastened to the back cover (26) with adhesive tape (58). The first and second portions (32, 38) can be part of a fastener assembly (70) having a third portion (72) that is secured to the inner surface (62) of the back cover (26). In a modification, a flap (128) can be hinged to the side of the back cover (126).

An apparatus (10) for transporting items includes a base (12), a handle element (16) extending from the base (12), a pair of rollers or wheels (20) mounted to the base (12) and a platform (14) mounted to the base (12) and adapted for movement between a stored condition and an operative position. The platform (14) includes first and second leg elements (24) and a platform support (26) connected to the first and second leg elements (24) and extending therebetween. The platform (14) is dimensioned and adapted to carry an object when in the operative position. The platform support (26) may comprise a flexible material such as a fabric material.

A binding cover having a transparent overlay cover disposed over and around the spine of the binding is configured to provide a label pocket on the spine portion of the binding cover wherein a label may be inserted easily without tools or rigid label material. In several embodiments the label pocket provides a fixed label space. In another embodiment the label pocket opens along the spine when the binding cover is opened, and returns to a closed position when closed, thereby retaining a label inserted therein. In another embodiment a method for forming the label pocket is provided.

A communications device may include a near-field communication (NFC) circuit device, and a radio frequency (RF) signal blocking member adhesively coupled with the NFC device. The RF signal blocking member may be configured to block RF signal communication by the NFC device while coupled therewith. The RF signal blocking member may comprise an electrical conductor. In accordance with an example, the RF signal blocking member may comprise a frangible layer. In another example, a pressure sensitive adhesive layer may be included for adhesively securing the RF signal blocking member with the NFC device.

Sheets are bound to form a bound document by fastening together the sheets and a binding strip. A spacer is applied to a back sheet adjacent to the feet of the fasteners. A wraparound portion of the binding strip is folded around the spine edges of the sheets so that adhesive on the strip contacts the spacer or the back sheet farther from the spine than the feet of the fasteners. The adhesive is affixed to the back sheet. The binding strip includes a spacer adjacent to the heads of the fasteners, protruding above the face-attachment portion at least as far as the heads of the fasteners do.

A bound system including a plurality of pages and a cover and/or divider including a bound outer edge and a plurality of free outer edges. The cover and/or divider may be bound to the plurality of pages along the bound edge. The cover and/or divider may include one or more discreet tabs extending generally outwardly relative to one of the edges. Each tab may be integrally formed from a single piece of material with the rest of the cover and/or divider. Each tab further may have an opening formed therethrough and is configured to receive at least part of a binding device therethrough to thereby couple the cover and/or divider to the binding device.

The invention relates to a device for holding sheets in a binder which form a folded stack, comprising a holding element (3) connected to the spine (2) of the binder (1). According to the invention, the holding element (3) engages behind the innermost sheet of the stack (4) at its fold (9).

The invention provides a method and apparatus for applying shipping labels over both folded or non-folded packing slips, or the like, at a single print-and-apply station, either through use of a label configured for application to a substrate and also in a superposed registered manner to another label of identical construction previously attached to the substrate, or by using a shipping label having a non-aggressive adhesive applied to a removable center section of the shipping label for attachment of the packing list, or the like, to the shipping label prior to application of the shipping label to the substrate.

Method for binding a bundle of loose leaves or the like in a cover. The method includes the step of providing an end leaf that includes a fixing strip on a side edge, with the fixing strip partly fixed to the end leaf and provided with a strip of glue on a part of the fixing strip which is not fixed to the end leaf. On the side of the fixing strip turned away from the end leaf, said strip of glue being provided with a removable foil. Another step is binding a free edge of the bundle of loose leaves together with the end leaf. Further steps include removing the foil, and providing the bound edge of the bundle of leaves and the end leaf in the back of the cover and fixing thereof in the cover only by the strip of glue.

A book protection apparatus and method are provided, that include a pair of substantially right angled sheets configured in a parallel fashion, the sheets being joined by a joining mechanism having a tension setting mechanism configured between the pair of sheets, to enable forcibly coupling the binding device to a coupled corner of a book.

A response form security device is provided for use with a generally planar response form having an answer area bearing answer blanks upon which a respondent makes marks to indicate a plurality of responses. The security device includes a sleeve adapted and constructed to slidably receive and cover the response form. An access window is formed in the sleeve, and permits visual access by the respondent to a number of fewer than all of the answer areas of the response form. The length of the sleeve and the configuration of the answer window are chosen so as to prevent anyone other than the user from seeing a number of marks on the answer area sufficient to observe a repeatable pattern of marks.