Material or article handling – Vertically swinging load support – Shovel or fork type
Reexamination Certificate
1998-12-10
2001-07-31
Underwood, Donald W. (Department: 3652)
Material or article handling
Vertically swinging load support
Shovel or fork type
C414S694000, C091S437000
Reexamination Certificate
active
06267548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control circuit for assisting operator effected storage of a hydraulically operated articulated work arm into an “over center” storage position. By permitting simplified operation of the work arm into the storage position, the functionality of the apparatus is increased. The control circuit includes an electrically operated valve, which may be a solenoid valve, that is operably connected to the hydraulic operating system of the work arm. Further, the control circuit includes a controller for the solenoid so that operation of the work arm into various selected positions is simplified.
2. Description of Related Art
Mobile construction equipment such as tractors outfitted with a hydraulically operated articulated work arm carrying any one of a variety of attachments are used for a wide variety of applications. In particular, they are critical machines in the construction of buildings, transportation channels, and almost any other man-made structure. A practical matter involves the transport of such equipment, such as, for example, a backhoe between the physical locations where it will be used. If the equipment is driven to the desired location over roadways, difficulties associated with the weight distribution of the equipment often arise. In particular, the overhanging, leveraged weight of the backhoe linkage assembly increases the difficulty of controlling the equipment during transportation. The effective weight of the backhoe linkage assembly can affect equipment weight balance sufficiently such that the weight remaining on the front wheels is lessened and steering control and ride comfort may be compromised.
To date, the most common approach to dealing with the undesirable weight distribution of this type of construction equipment is to add weight to the front of the machine to counter the weight of the backhoe linkage assembly. However, this solution is undesirable for several reasons. The additional weight causes the equipment to become more difficult to maneuver, especially in soft ground, more difficult to steer, and more clumsy to operate. In addition, fuel consumption is increased and the equipment cost effectiveness is decreased.
A more desirable solution to the problem of weight distribution has been to move the backhoe linkage assembly into a stored position where its weight is closer to the center of the equipment. For example, Case Corporation of Racine, Wisconsin builds backhoe-type machines with a distinctive feature, known as an “over center” system, that permits the weight of the backhoe to be moved closer to the center of the equipment, whereby the weight moment arm is reduced. By shifting the weight of the backhoe toward the equipment's center of gravity, the need for a front-end counter weight is eliminated. The “over center” position of the backhoe linkage assembly is frequently known as the “carry,” the “latched,” or the “transport” position. The “over center” system, as noted above, increases the maneuverability of the equipment, particularly in soft ground, and increases the stability of the equipment during road transportation.
While the “over center” system provides significant benefits, use of the system requires operator skills that are acquired only through experience. Thus, while not always difficult for regular users of the equipment, the technique may often be awkward for new or occasional users of the machine. The technique involves a combination of operator actions that must be completed in timed sequence. The technique of moving the backhoe into the “over center” position requires the operator to activate the lift cylinder and raise the work arm toward its uppermost position. At the moment that the lift cylinder is at its minimum length, the operator must then rapidly change the direction of the hydraulic control spool to reverse the direction of the lift cylinder operation to thereby drive the backhoe into the “over center” transport position. If the control spool is not operated at the right moment, the backhoe assembly will stop moving and will not reach the transport position. The entire process must then be repeated. First time operators and operators without significant experience often have difficulty performing the technique.
The present invention for the first time provides an apparatus for reducing the heretofore important nature of operator performance in placing equipment work arms into the over-center storage/transport position. Thus, new and less experienced operators can prepare the backhoe for travel between work sites.
SUMMARY OF THE INVENTION
The purpose and advantages of the invention are set forth in and will be apparent from the description and drawings that follow. Additional advantages of the invention will be realized and attained by the elements of the device particularly pointed out in the appended claims.
The present invention is directed to a control circuit for use in combination with an apparatus having a hydraulically operated articulated work arm that is movable over a range of positions. More particularly, the present invention involves a control circuit for use in combination with an apparatus having a hydraulically operated work arm, such as a backhoe machine, for which there are desired arm positions, such as an “over center” transport position.
The present invention can be applied to any hydraulically operated articulated work arm in which it is necessary to reverse the flow of fluid through the hydraulic cylinder in order to achieve a desired position of the work arm. The control circuit that is used in combination with the apparatus comprises a valve, preferably a solenoid valve, a source of electricity for operating the solenoid valve, and a switching mechanism. The solenoid valve is operably connected with the work arm hydraulic operating system.
The switching mechanism is electrically connected in series between the electrical source and the solenoid valve in order to control operation of the solenoid valve. In operation, the solenoid valve is either in a closed or open position and therefore either prevents or permits the flow of hydraulic fluid into the head side of the cylinder. If the solenoid valve is configured to be in a “closed” position when there is no electrical flow, when the switching mechanism is activated to permit the flow of electricity to the solenoid valve, the solenoid valve will change to an “open” position so that hydraulic fluid can flow to the head side of the cylinder. In one embodiment of the present invention, the work arm hydraulic operating system comprises one or more supply lines leading to the work arm. The solenoid valve is then positioned between the supply lines to control the flow of hydraulic fluid.
The switching mechanism of the invention includes a first manually actuated operator switch and a second position actuated switch connected serially with the first switch. The position actuated switch is located remotely from the manually actuated operator switch. The position actuated switch is in an operative position associated with the work arm and responsive to the position of the work arm so that electricity will flow to the solenoid valve when the first manually actuated operator switch is closed and the work arm is located at a preselected position. In one embodiment of the invention, the second position actuated switch is located on the work arm. While the position actuated switch can be set to respond to any preselected position of the work arm, in a preferred embodiment of the invention, the position actuated switch is indexed to a vertical position of the work arm. In applications where the position actuated switch is indexed to the work arm's vertical position, the work arm can be pulled into the “over center” or transport position.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and provided for purposes of explanation only, and are not restrictive of the invention, as claimed.
REFEREN
Lech Richard J.
Mickelson Roger D.
Wawiorka Robert E.
Case Corporation
Mayer Brown & Platt
Underwood Donald W.
LandOfFree
Automatic over center system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automatic over center system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic over center system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2545714