Sack Truck News

A hydraulic toe jack comprising: an oil pressure supply and discharge part; and a toe jack part connected to the oil pressure supply and discharge part through a flow passage, said toe jack part being provided with a hydraulic cylinder, a pantograph type link connected to the hydraulic cylinder through a driving link, and a wheel provided on the pantograph type link, said pantograph type link comprising a pair of rotatable lower links, a pair of upper links pivotally mounted on extreme ends of the lower links through shafts, and a pressure receiving plate provided on upper ends of said upper links, said driving link being rotatably connected between the hydraulic cylinder and the lower links, wherein the lower links and the upper links are provided in a paired relation as front links and rear links before and behind said hydraulic cylinder respectively, and the wheel is rotatably mounted on said shaft of said front links.

2. The hydraulic toe jack according to claim 1, wherein a guide tube comprising an outer tube and an inner tube slidably inserted into the outer tube is connected to the toe jack part, the oil pressure supply and discharge part is provided with a holder member; said flow passage includes a pipe is inserted into the guide tube, and the guide tube is connected to the holder member separable and rotatably.

3. The hydraulic toe jack according to claim 2, wherein an operating rod extending in a direction opposite to the guide tube is connected to the holder member.

4. The hydraulic toe jack according to claim 2, wherein the toe jack part has a base plate movably placed on an installing surface, and the base plate is connected to the inner tube through a connecting construction.

5. The hydraulic toe jack according to claim 1, wherein the oil pressure supply and discharge part has a pump and a tank, said tank comprising a bellows type bladder for setting a volume chamber therein, and a protective casing formed of a visible material for receiving the bladder therein.

6. A hydraulic toe jack comprising: a pressure supply/discharge part; a flow passage connected to said supply/discharge part; a toe jack part in communication with said supply/discharge part through said flow passage, said toe jack part including a hydraulic cylinder with a hydraulic piston connected to a driving link, and a pantograph linkage connected to said hydraulic piston through said driving link, said pantograph linkage including first links with first and second ends, said first ends being pivotally connected to said hydraulic cylinder, said second ends including a shaft, said pantograph linkage having second links with first and second ends, said first ends of said second links being pivotally connected to said shafts of said second ends of said first links, said toe jack part includes a pressure receiving plate connected to said second ends of said second links; a wheel pivotally mounted on one of said shafts connecting said first and second links.

7. A hydraulic toe jack comprising: a toe jack part including a hydraulic cylinder with a hydraulic piston connected to a driving link, and a pantograph linkage connected to said hydraulic piston through said driving link; a wheel rotatably connected to said pantograph linkage; a flow passage connected to said toe jack part; a pressure supply/discharge part in communication with said toe jack part through said flow passage, said oil pressure supply and discharge part including a pump and a tank, said tank including a bellows type bladder for setting a volume chamber in said tank, said tank also including a protective casing formed of a visible material for receiving said bladder.

Various proposals have been heretofore made in connection with an hydraulic toe jack set of the manually-operated type. In principle, as shown in FIG. 4, the toe jack comprises an oil pressure supply and discharge part 1 and a toe jack part 2. The oil pressure supply and discharge part 1 converts unpressurized oil from a tank 13 into pressure oil by means of an oscillating operation of an operating lever 11 with respect to a pump 12, and supplies the oil to the toe jack part 2 through a pipe 3. On the other hand, oil from the toe jack part 2 is returned to the tank 13 by an opening a depressurizing valve 14. It is set so that the toe jack part 2 extends when pressure oil from the oil pressure supply and discharge part 1 is supplied, and the toe jack part 2 contracts when pressure oil is discharged.

Accordingly, in the conventional hydraulic toe jack, for example, the toe jack part 2 is located at a desired position for extension and contraction thereof to enable movement of heavy articles up and down. Further, where the toe jack part 2 is a pantograph type, it is possible to set an elevating stroke higher than when the toe jack part 2 is a cylinder type.

However, when the toe jack part 2 is a pantograph type, the elevating stroke is large, and therefore, it is necessary to stabilize the toe jack when the toe jack is placed on the installing surface such as the surface of the earth. For example, though not shown, a base plate or the like constituting the lower end of the toe jack part 2 is formed as large as possible.

On the other hand, when the hydraulic toe jack of this kind is located at a deep position, in most case, the operating lever 11 included in the oil pressure supply and discharge part 1 is used as a pressing/positioning member by which the toe jack part 2 is slidably moved and fed into the desired position.

In this case, the larger the base plate or the like constituting the lower end of the toe jack part 2, which enhances the stability when installed, as described above, here poses an inconvenience in that the feeding operation is difficult.

This invention has been designed in view of the aforementioned circumstances. An object of the invention is to provide a hydraulic toe jack in which feeding/positioning a toe jack part into a desired position is optimized for a wide use of the toe jack in different applications.

For achieving the aforesaid object, a means of the present invention comprises an oil pressure supply and discharge part, and a toe jack part connected to the oil pressure supply and discharge part through a flow passage. The toe jack part is provided with a hydraulic cylinder, a pantograph type link connected to the hydraulic cylinder through a driving link, and a wheel provided at a suitable position of the pantograph type link.

In this case, preferably, the pantograph type link comprises a pair of rotatable lower links, a pair of upper links pivotally mounted on extreme ends of the lower links, respectively, through shafts, and pressure receiving plates provided on the upper ends of the upper links, respectively, the driving link is connected rotatably between the hydraulic cylinder and the lower links, and the wheel is mounted on one of the shafts.

In this case, preferably, the lower links and the upper links are provided in a paired relation before and behind the hydraulic cylinder, and the wheel is mounted on the front shaft for pivotally mounting the front lower link and the front upper link.

Further, in the above-described means, preferably, a guide tube comprising an outer tube, and an inner tube slidably inserted into the outer tube, is connected to the toe jack part. The oil pressure supply and discharge part is provided with a holder member, the pipe is inserted into the guide tube, and the guide tube is connected to the holder member reparably and rotatably.

In this case, preferably, an operating rod extending in a direction opposite to the guide tube is connected to the holder member.

Further, preferably, the toe jack part has a base plate movably placed on the installing surface, and the base plate is connected to the inner tube through a connecting construction.

Furthermore, preferably, the oil pressure supply and discharge part has a pump and a tank. The tank comprising a bellows type bladder for setting a volume chamber therein, and a protective casing formed of a visible material for receiving the bladder therein.

A machine toe jack for mounting on a machine body, the toe jack having an extensible leg projectable from a hollow toe jack housing and attached to the machine body along the length of the housing. A piston cooperating in a cylinder in the extensible leg extends the leg from the housing. A hydraulic fluid reservoir is formed in the extensible leg in an annular space surrounding the cylinder. A valve block is coextensive with the extensible leg at the foot of the leg and contains the valves and pumping piston for the toe jack. Valving in the valve block permits manual extension and retraction of the extensible leg.

1. An extensible toe jack comprising:

a piston hydraulically operable in a cylinder;

a hydraulic fluid reservoir surrounding the cylinder along a substantial portion of its length;

a housing connected to the piston;

a valve block coextensive with the reservoir and at the base of the cylinder, said valve block fitting telescopically within the housing and comprising at least one hydraulic conduit therein in fluid communication between the reservoir andcylinder and having at least one check valve in the conduit, said valve block further comprising means for accessing the check valve through the exterior of the valve block, said accessing means being essentially flush with the exterior surface of thevalve block so as to permit substantially all of the valve block to be recessed telescopically into the housing so as to permit the housing to slidably cover the valve block when the piston is fully retracted into the cylinder; and

hydraulic fluid pumping means for pumping fluid from the reservoir to the cylinder.

2. An extensible toe jack comprising:

a piston hydraulically operable in a elongated cylinder;

a hydraulic fluid reservoir formed by a space between the cylinder and a wall of an extensible leg of the toe jack;

a housing connected to the piston;

a valve block coextensive with the extensible leg and at the base of the cylinder, said valve block fitting telescopically within the housing and comprising first hydraulic fluid communication means having first and second check valves thereinfor unidirectionally conducting fluid from the reservoir to the cylinder, said first hydraulic fluid communication means further comprising first and second plugs, said plugs being essentially flush with the external surface of the valve block so as topermit the extensible leg and substantially all of the valve block to be recessed telescopically into the housing when the piston is fully retracted, said plugs also having means adapted to receive a tool for removal of the plugs to provide access to thefirst and second check valves, said valve block further comprising second hydraulic fluid communication means operable between the cylinder and the reservoir having a manually controlled valve interposed therein; and

hydraulic fluid pumping means in communication with the first fluid communication means and between the first and second check valves.

1. Field of the Invention

The present invention relates to toe jacks which are mountable on a machine body and are useful for loading, removal, and/or leveling of the machine body.

2. The Prior Art

Currently there is a plethora of machine jacks available on the market ranging from simple mechanical toe jacks to sophisticated hydraulic units and are either demountable or are permanently mounted on the machine body.

One prior art machine toe jack, in particular, is attachable to a machine body only along a relatively short distance of the mid-section of the toe jack. An enlarged hydraulic fluid reservoir precludes snug engagement of the machine toe jack to the machinebody, and brackets must be used to bridge the resultant gap at the mid-section of the toe jack. Accordingly, the toe jack is attached to the machine body in a relatively insecure manner, particularly since attachment at the hydraulic fluid reservoir itself isnot possible. The reservoir also occupies a segment of the toe jack body which would otherwise be occupied, to some extent, by the extensible leg of the toe jack resulting, therefore, in a shorter extensibility of the toe jack.

With the valving mechanism and hydraulic fluid pumping apparatus of the toe jack located on top of the reservoir, the working level of the pump is elevated and is continually changing during operation of the toe jack. The constantly changing elevationof the working level is inconvenient and subjects to toe jack attachment point to undue stresses when the machine body tends to wobble.

A further problem arises from the upper hydraulic fluid reservoir because leaks, when they occur, result in hydraulic fluid staining a substantial portion of the length of the toe jack and thus serving to collect dust and debris on the toe jack.

Generally, manual extension of prior machine skates is possible only to a limited extent. Lowering of the extensible leg of the toe jack to contact with the ground so as to support a machine is, therefore, possible only through operation of the pumpingmechanism. This is both tedious and inconvenient, particularly if the extensible leg must be extended a considerable distance before it contacts the ground surface.

The present invention is a machine toe jack for mounting upon movable bodies such as machine bodies for facile raising, lowering, and leveling of the movable bodies. The toe jack is securely attachable to a machine body. Snug securement is possible sincethe hydraulic fluid reservoir is an integral part of the extensible leg and is formed in the annular space surrounding the toe jack cylinder. An elongated piston cooperates in the cylinder and is attached to a housing which completely enclosed theextensible leg upon retraction. A valve block coextensive with the extensible leg and at the base thereof contains the hydraulic fluid valving and pumping mechanisms. Access to all of the hydraulic fluid valving and pumping apparatus is easilyavailable from the external periphery of the valve block.

Facile manual extension and retraction are possible since the valving mechanism is located below the hydraulic fluid reservoir and the toe jack cylinder easily permitting transfer of hydraulic fluid from one to the other without operation of thepumping mechanism. Additionally, leaks, if they occur, stain only a small portion of the base of the toe jack and not the entire length thereof.

Not only does the housing serve to protect the toe jack apparatus during transit but also presents a uniform profile since the cross-sectional area of the toe jack is uniform along its entire length.

It is, therefore, a primary object of this invention to provide improvements in machine toe jacks.

It is another object of this invention to provide a machine toe jack wherein a substantial portion of the operating mechanism of the toe jack is retractable within a protective housing.

It is a further object of this invention to provide a machine toe jack wherein the operating level of the hydraulic pumping mechanism remains constant at ground level.

Another object of this invention is to provide a toe jack with an extensible leg that is manually extensible and retractable.

Another object of this invention is to provide a hydraulic toe jack with a hydraulic valve block wherein all hydraulic fluid control devices are readily accessible from the external periphery of the valve block.

These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompanying drawing.