Quick Answer

The LCN 4840 is a pneumatic multi-door auto equalizer operator. Before ordering any LCN 4840 parts, confirm these key points:

• Model first: The 4840, 4810, and 4820 share similar part naming but are different models. Confirm the 4840 label is on the closer body before ordering. Parts between these models are not interchangeable.
• 3077CNS vs 3077SCNS vs 3077EDA: Three arm configurations exist. The 3077CNS uses a block-and-shoe cushion stop. The 3077SCNS uses a spring-based cushion. The 3077EDA is the extra duty arm for high-traffic applications. Choose based on what is installed and what failed.
• Pneumatic hinge (4840-460): This hinge carries the air line through the pivot point. If the equalizer function is slow or absent and tubing pressure is confirmed, the pneumatic hinge is the component to replace.
• Door loop kit (4840-459): Carries the flexible pneumatic line between the fixed frame and the swinging door. Replace when tubing is cracked, kinked, or function is inconsistent.
• 25 LCN 4840 parts are stocked at Security Parts across arms, hinges, adapters, covers, spacers, and screw packs.

Call 845-935-0301 for pre-order compatibility support before placing your order.

What the LCN 4840 Is

The LCN 4840 is a pneumatic multi-door auto equalizer operator designed to simultaneously control the opening force across multiple doors from a single compressed air source. It equalizes the opening resistance on doors along an accessible route so that a person using a wheelchair or mobility aid can open the door without encountering uneven or excessive resistance.

The 4840 is the multi-door version of the LCN pneumatic auto equalizer family. The 4810 and 4820 serve single-door applications. The 4840 is specified where a single pneumatic control point must manage several doors on the same accessible corridor simultaneously.

The 4840 is not an electric automatic opener and not a door closer in the traditional sense. It is a pneumatically powered force-equalizer. Its parts catalog reflects this: the key components are arms, a pneumatic hinge, a door loop kit, a spring cush block, and the mechanical accessories that support and cover the system. For the broader LCN auto equalizer family context and related sentronic products, see the LCN Sentronic and Auto Equalizer parts guide. For general LCN automatic door operator coverage, see the commercial door operators guide.

LCN 4840 Arm Configurations

LCN 4840-3077CNS CUSH-N-STOP Arm. View product page and order.

Three arm configurations are stocked for the LCN 4840. The arm connects the closer body spindle to the door panel and controls the opening arc. Selecting the wrong arm type is the most common ordering error on 4840 service calls.

4840-3077CNS: CUSH-N-STOP Arm

The 4840-3077CNS is the standard CUSH-N-STOP arm. It uses a rigid cush shoe and spring cush block assembly to provide a controlled cushioned stop at the fully open position. The cushion absorbs the final impact of the door reaching its open limit, reducing noise and mechanical stress on the frame. Replace when the arm is bent, the spindle connection is stripped, or the cushion stop no longer functions at the full open position.

4840-3077SCNS: Spring CUSH-N-STOP Arm

The 4840-3077SCNS is the Spring CUSH-N-STOP arm. It uses an integrated spring mechanism within the arm assembly for cushioning at the open position, rather than the separate block-and-shoe configuration of the CNS arm. The SCNS arm is specified when the installation requires spring-loaded cushion action. Confirm which arm is installed before replacing: the CNS and SCNS are not interchangeable.

4840-3077EDA: Extra Duty Arm

The 4840-3077EDA is the Extra Duty Arm, reinforced for high-traffic and high-abuse applications. If a standard CNS or SCNS arm has failed prematurely on a high-cycle accessible route entry, the EDA is the correct upgrade. Installing a standard arm on an EDA application will produce the same premature failure.

Arm Hardware: Arm Screw and Blade Stop Spacer

• 4840-159 arm screw: Secures the arm to the closer spindle. Replace when the arm is loose at the spindle and tightening the existing screw does not hold. A loose arm screw is responsible for a significant share of 4840 performance calls that initially appear to be arm failures.
• 4840-61 blade stop spacer: Adjusts the door open limit. Replace when missing or when the door is making contact with an adjacent surface before the arm reaches its natural stop position.

LCN 4840 Pneumatic Hinge: 4840-460

LCN 4840-460 Pneumatic Hinge. View product page and order.

The 4840-460 pneumatic hinge is a specialized hinge that carries the compressed air supply line through the door pivot point. A standard hinge cannot perform this function because the tubing cannot cross a hinge knuckle without crimping or breaking during door cycles. The pneumatic hinge has an internal air passage machined through the hinge barrel that allows air to flow continuously from the fixed frame to the moving door panel regardless of door position.

Replace the pneumatic hinge when:

• The auto equalizer function is slow or absent and the air supply pressure at the source has been confirmed as adequate
• The door loop kit tubing is intact and unobstructed
• Air pressure at the door panel side of the hinge is lower than at the frame side
• The hinge shows visible corrosion at the barrel that could be restricting the internal air passage

LCN 4840 Panel Adapter: 4840-419

LCN 4840-419 Panel Adapter. View product page and order.

The 4840-419 panel adapter is required on aluminum storefront and narrow-stile glass doors where the door bottom rail does not provide sufficient mounting surface for the standard 4840 closer body. The panel adapter creates the necessary clearance and mounting geometry between the closer body and the narrow door rail.

If a 4840 was installed without the panel adapter on a narrow-rail door and the arm geometry is incorrect or the closer body is contacting the door rail, confirm whether the panel adapter was included in the original installation before replacing other components.

LCN 4840 Door Loop Kit: 4840-459

LCN 4840-459 Door Loop Kit. View product page and order.

The 4840-459 door loop kit carries the flexible pneumatic supply line from the fixed door frame to the swinging door panel. Because the door pivots on its hinges, a rigid tube cannot connect the two sides. The door loop provides a coiled or looped flexible tube that extends and contracts smoothly with every door cycle.

The door loop kit is a wear component. On high-cycle accessible route entries, the tubing flexes thousands of times per year. Replace when:

• The tubing is visibly cracked, kinked, or hardened
• The equalizer function is inconsistent despite confirmed adequate air supply pressure
• Air leaks are audible or detectable at the door loop fitting connections
• The loop no longer returns to its rest position freely after the door closes

CUSH Components: Spring Cush Block and Cush Shoe Support

The CUSH-N-STOP arm assembly depends on two components that work together to cushion the door at the open position. They are separate parts with different failure modes.

• 4840-3080 spring cush block: The spring-loaded block inside the cush shoe that provides the primary cushioning action when the arm reaches the open limit. Replace when the cushion stop is no longer present at the fully open position, even though the arm itself is undamaged. A failed spring cush block allows the door to open to its limit without any cushioned resistance.
• 4840-30 cush shoe support: The structural bracket that positions and supports the cush shoe in the correct engagement geometry. Replace when the support is bent or cracked, which typically occurs after repeated hard-door-open impacts on installations with high opening force or where the door is being pushed against its stop repeatedly.

When diagnosing a failed cushion stop, start with the spring cush block (4840-3080) before replacing the arm. A failed spring cush block produces the same symptom as a worn arm (no cushion at the open position), but it is a far less expensive and quicker repair. If replacing the spring cush block restores the cushion stop function, the arm itself does not need replacement. Only replace the arm if the spindle connection is stripped, the arm tube is bent, or the cush shoe support bracket is cracked beyond use.

On installations where the cush shoe support (4840-30) is bent, inspect the door frame stop at the corresponding open-position contact point. A bent support bracket almost always indicates that the door has been repeatedly pushed hard against a physical stop. If the door stop position can be adjusted, do so before installing the new bracket, or the replacement will experience the same impact damage.

Spacers, Stand-Off, and Mounting Hardware

• 4840-201 fifth screw spacer: A mounting spacer used in certain 4840 installation configurations to provide clearance between the closer body and the door or frame face. Replace when the spacer is damaged or missing from the original installation.
• 4840-182 stand-off: A stand-off bracket that positions the closer body at the correct distance from the door surface. Required in installations where the door panel geometry creates a gap between the closer mounting position and the door face.
• 4840-124 plug: Fills unused mounting holes in the 4840 closer body. Replace when plugs are missing, which exposes the closer housing interior to dust and moisture.

Cover Components

• 4840-72MC metal cover: The heavy-duty metal cover over the 4840 closer body. Specified in high-traffic and abuse-prone accessible route entries. Replace when the cover is damaged, dented, or no longer clips to the body correctly.
• 4840-334 cover endcap: The endcap at the terminal end of the cover that closes the housing. Replace when missing or cracked.
• 4840-163 cover insert: The insert that fills the space between the cover body and the closer mechanism. Keeps the interior free of debris.
• 4840-31 cover screw and 4840-31L long cover screw: Fasteners that secure the cover to the closer body. The long version (31L) is used in installations with additional spacer or stand-off components that require a longer fastener reach.

Decals

• 4840-155-2 activation decal: The user-facing label that indicates how the door is activated. Required on accessible route doors where visual instruction must be provided to users approaching the door.
• 4840-155-1 caution decal: The safety decal that warns users of the door operation. Replace when faded, missing, or illegible. Accessibility compliance on ADA routes typically requires that safety decals remain legible.

Screw Pack Selection

Two screw pack configurations are stocked for the LCN 4840. Selecting the wrong pack for the substrate is the most common fastener mismatch on 4840 installations.

• 4840-TBWMS: Thru-bolt with wood and machine screw pack. Used when the 4840 is mounted to a wood substrate door or when the installation requires both wood and machine screws in the same configuration. The most common screw pack for standard 4840 installations.
• 4840-WMS: Wood and machine screw pack without thru-bolts. Used in installations where thru-bolt mounting is not required or not possible. Confirm the original installation method before ordering the replacement screw pack.

Complete LCN 4840 Parts Reference

Source LCN 4840 Parts at Security Parts

Security Parts stocks all 25 LCN 4840 parts across arms, pneumatic components, mounting hardware, covers, screw packs, and decals. Same-day shipping on stocked components. Call 845-935-0301 for pre-order compatibility support.

The LCN 4840 is commonly found in healthcare corridor entries, university accessible route doors, and government facility main entries where multiple doors on the same accessible path must be controlled simultaneously. A single pneumatic source on the 4840 equalizes the opening force across all connected doors, ensuring consistent compliance with ADA force requirements along the entire route. When one door in a 4840 multi-door system fails, confirm whether the failure is isolated to that door (arm, pneumatic hinge, or door loop) or system-wide (air supply, control unit) before ordering parts. A system-wide failure will not be resolved by replacing a single door component.

For the broader LCN auto equalizer and pneumatic operator catalog, see the LCN Sentronic and Auto Equalizer parts guide and the door operators parts guide. For general LCN door closer parts, see the door closers parts guide and the LCN 4040XP parts guide.

For OEM versus aftermarket guidance on LCN parts, see the OEM vs aftermarket commercial door hardware guide. For accessibility and ADA-compliant door hardware in healthcare settings, see the healthcare door hardware guide. For maintenance and inspection requirements, see the commercial door hardware maintenance checklist.

About the Author

This guide was written by the Security Parts team, a commercial door hardware specialist serving locksmiths, facilities managers, general contractors, and accessibility compliance consultants since 2001. Security Parts stocks the complete LCN 4840 parts catalog across all arm configurations, pneumatic components, mounting hardware, covers, and screw packs, with same-day shipping on stocked components and pre-order compatibility support at 845-935-0301.