Patent Application
20080251773
This invention relates to jacks or lifts for raising heavy machines or equipment, and is more particularly concerned with a hand-operated cam jack which is convenient in size and weight, and which employs simple lever action to lift a machine up off the supporting floor surface, and which can hold the same stably at an elevated position.
At present, there is no simple means available for raising heavy equipment off the floor when it is necessary to service the equipment. For most types of equipment, a heavy service equipment item, such as railroad jack, or sometimes a forklift, is brought in and the forks are slid under the machine. This is almost always an inconvenient and time consuming procedure, and an expensive use of resources.
One example of an application for a simple jack in a materials handling vehicle, such as a pallet transporter, which typically has groups of wheels held in place on horizontal support legs at the base of the unit. In a typical warehouse operation, these wheels can wear unevenly, and need to be replaced rather frequently. When that is needed, a device must be inserted under the support leg(s) to lift the same, and to relieve the weight from the wheels. Then the wheels can be changed out. The difficulty in this maintenance function has been that it requires a heavy, cumbersome tool such as a railroad jack, and there is no effective light-weight, convenient lifting mechanism for raising the machine a short distance off the floor and then also serving as a stable support to hold the unit securely in that position until the wheels have been changed out. Of course, any device would need to ensure that the operation is conducted in a safe manner, and can be carried out without difficulty, both in raising the machine and in lowering it again after the wheel replacement has been completed.
Accordingly, it is an object of this invention to provide simple, convenient, light-weight, and effective lifting tool capable of safely and securely lifting heavy equipment, and which avoids the drawbacks of the prior art.
It is another object to provide a cam jack that is of simple, sturdy construction.
It is a further object to provide a cam jack that capable of being operated by hand, and which is quick and convenient to insert in place under the equipment, and which can raise the equipment using a simple lever operation.
It is another object to provide a cam jack that holds the equipment in a stable, secure elevated position until it is lowered by lever action.
A still further object is to avoid creating a tripping hazard on the factory or warehouse floor.
Yet another object is to provide a cam jack that is fabricated in a way that ensures that it can be used in lifting very heavy equipment without danger of breakage or failure.
In accordance with an aspect of the present invention, a cam jack is adapted for lifting a heavy machine off a supporting floor surface. The cam jack has a body member in the form of an L-shaped cam member, which is unitarily formed of a single piece of steel. This body member is shaped so as to define a lever arm portion, a cam finger, and an elbow formed between the lever arm portion and the cam finger. An axle is attached at the elbow and extends to its right and left sides. There are left and right rollers supported on the axle on the respective sides of said elbow. These rollers have a selected, predetermined diameter, to the top surface of the rollers are at a desired upper level above the floor surface. The cam finger projects from the elbow and axle at a near right angle in respect to said lever arm portion. The cam finger has an upper surface, considered from when said lever arm is oriented vertically, which is disposed at or below the upper level of said rollers. This cam finger also has a lobe tip which, when the lever arm is tipped down to horizontal, projects above the upper surface of the rollers a distance sufficient to lift the intended machine or equipment off the floor. The cam jack also has an over-the-center action, so that when the cam jack is in this horizontal position (with the machine or equipment supported off the floor) the lobe tip is displaced outward a short distance over the axle, that is, the lobe tip is displaced towards the lever arm member in respect to a vertical plane through the axle. This ensures that the cam jack remains locked in the lifting position until the cam jack is affirmatively lifted back towards the vertical position.
Preferably, the lever arm member has a socket or other fitting at its proximal end, permitting the cam jack to accept a removable lever handle. The lever handle is used for lifting and releasing the load, but can be removed when the cam jack is in place under the load so as to avoid having the lever handle constitute a tripping hazard.
The cam jack unitary body portion can be formed by cutting it with a water jet or similar tool, and this allows the body portion to be created so that the lever arm portion has generally planar left and right sides, a planar front surface, and a rear surface that has a major planar portion. Favorably, the major planar portion of the rear surface is oriented at an angle of substantially ten degrees in respect to said front surface. In a preferred implementation, the axle is formed of a single steel round rod that is supported at the elbow, and the rod projects to the left and right sides of the cam member.
In another possible implementation, the cam jack is also provided with a set of auxiliary rollers positioned at left and right sides of lever arm portion proximally of the main rollers. This arrangement allows the cam jack to be used as a dolly for moving heavy equipment.
The removable handle lever can be a bar, rod or tube. This may be of fixed length or may be constituted as an adjustable length handle.
The above and many other objects, features, and advantages of this invention will become apparent to persons skilled in the art from the ensuing description of a preferred embodiment, which is to be read in conjunction with the accompanying Drawing.
With reference to the Drawing,
The body portion 12 is a generally L-shaped member, with a lever arm 14, and an elbow 16 formed at the distal end of the lever arm 14. There are rollers 18 mounted on an axle rod 20 that is supported in the elbow 16. A cam finger 22 projects from the elbow 16 at a nearly right angle with respect to the lever arm 14. As will be discussed later, the tip of the cam finger is angled slightly back, so that there is an over-the-center action to lock the cam jack in place in the raised position.
As can be seen in
With reference to
In this embodiment, the preferred rollers 18 are 1-⅝ inch diameter and also 1-⅝ inch axially, with the axle 20 being formed of ⅝ inch round steel rod. The body lever arm portion 14 is about seven inches from the elbow 16 to the proximal end, and the latter can be a square 1-¼ inches by 1-¼ inches. The cam finger 22 projects about ½ inch beyond the rollers 18. Of course, for different applications, the cam jack can be formed with other dimensions suited to that application. The rollers 18 can be held in place on the axle 20 using spring clamps that fit into an annular groove formed on the axle.
While the invention has been described in detail with respect to one preferred embodiment, it should be recognized that there are many alternative embodiments that would become apparent to persons of skill in the art. Many modifications and variations are possible which would not depart from the scope and spirit of this invention, as defined in the appended claims.
