Cat® K Series Small Wheel Loaders—924K, 930K and 938K, when announced in 2012, reflected a fundamentally different design than that of their H Series predecessors, using a fuel-efficient Cat C6.6 engine, electronically controlled hydrostatic drive system, new operator station and optimized Z-bar loader linkage, which combines aggressive digging power with parallel lift. The K Series design has now been further refined with engineering enhancements for the drive system, implement controls, auxiliary hydraulic system and loader linkage. The new features, except the linkage modification, are backward compatible with all K Series machines and can be quickly installed by local Cat dealers.
Caterpillarengineers enhanced operator control of the hydrostatic drive system by adding software that allows selecting one of four performance modes designed to tailor the machine to operator preferences or specific working conditions. The modes are selected through the optional secondary display or with the Cat Electronic Technician.
When TC or Torque Converter Mode is selected, the loader will more closely mimic characteristics commonly found with a traditional powershift, torque converter transmission, such as freewheel coasting, softened shifts to neutral and reduced low idle wheel torque. In Hystat Mode the loader will have responses similar to a conventional hydrostatic driven machine with more aggressive dynamic braking and no movement when placed in forward or reverse until the throttle pedal is applied, unlike TC mode. For specialized applications, the loader can be placed in Ice Mode. This is a dedicated mode for use when the operating surface offers near zero grip, such as when the loader is pushing snow without studded tires or chains. This is particularly useful where ultimate modulation of the power train is a must to control wheel slip in extremely low traction conditions. The base setting is the Default mode, which provides the optimal blend of both torque converter and hystat modes.
As a further enhancement to the TC mode, Caterpillar engineers have adjusted the system to provide more exact torque-converter-like performance when the machine engages the pile. This modification delivers a smoother, more controlled balance of power, which operators accustomed to powershift machines will appreciate. This feature also can be applied to K Series machines in service.
The left control pedal in K Series models functions both as a decelerator to control ground speed and as a brake. The new design lowers the angle of the pedal to a more comfortable position, shortens the decelerator zone and allows the brake zone to activate sooner. The net result is added control with less pedal effort, helping the operator maintain smooth ground-speed modulation and safe, predictable braking. This feature can be incorporated into existing models by installing a larger roller at the base of the pedal and recalibrating the Hystat system.
Electro-hydraulic implement controls enable tuning the joystick relative to the response rate of the implement. In certain applications, a crisper response is desired for precise movement of the bucket or other tool. Software to allow adjusting lift and tilt functions independently became available after the K Series initial release, but adjustments had to be made using Cat Electronic Technician.
The latest software now allows the operator to adjust levels through the secondary display in the cab. This new feature allows immediate access to any of the response levels, and it can be added to any K Series machine having the secondary display. For machines without the secondary display, Cat dealers can set a specific response mode for both lift and tilt.
Caterpillar has replaced the conventional push-to-connect quick-disconnect couplers on the auxiliary-hydraulic circuit with connect-under-pressure couplers. The new quick disconnects feature thread-to-connect technology and use a patented internal valve that facilitates connection/disconnection under high residual pressure, considerably simplifying the process. The coupler design eliminates premature wear often associated with push-to-connect couplers.
The ends of the new couplers thread together and feature a yellow O-ring that disappears from view when the connection is secure. Protective caps for the two sides of the coupling thread together when not in use and can be stored adjacent to the connection in a rubber holder. Cat dealers can supply retrofit kits that allow modifying existing machines and existing work tools with the new quick-disconnect system.
New loader linkage
The Patented Optimized Z-Bar linkage has been redesigned to allow for even better visibility down the lift arms. The new design incorporates a torque tube that significantly improves forward visibility to the work tool and working surface. At higher boom angles, such as when truck loading, the operator’s view beneath the narrower torque tube provides unimpeded sight lines to the truck or bin.