US2701031A

US2701031A - Lift truck

Info

Publication number: US2701031A
Application number: US298159A
Authority: US
Inventors: George U Brumbaugh
Original assignee: PETERBILT MOTORS Co
Current assignee: PETERBILT MOTORS Co
Priority date: 1952-07-10
Filing date: 1952-07-10
Publication date: 1955-02-01
Anticipated expiration: 1972-02-01

Description

Feb. 1, 1955 G. u. BRUMBAUGH LIFT TRUCK 2 Sheet's-Sheet l Filed July l0, 1952 INVENTQR.

GEORGE UB/QUMBAWH IIIIIIM ATTORNEY Feb. 1, 1955 G. u. BRUMBAUGH LIFT TRUCK 2 Sheets-Sheet 2 Filed July 1o, 14952 INVENTOR.

ATTORNEY United States Patent O LIFT TRUCK George U. Brumbaugh, Palo Alto, Calif., assigner to Peterbilt Motors Company, Oakland, Calif., a corporation of California Application July 10, 1952, Serial No. 298,159

6 Claims. (Cl. IS7- 9) This invention relates to improvements in attachments for lift trucks.

In particular the invention relates to a lifting mast arrangement which makes it possible for the carriage to lift a weight a substantial height off the oor with no increase in the height of the mast, while still retaining operability of the mast to lift to its full lifting height.

One problem solved by this invention involves the heretofore existing restricted use of lift trucks in the loading of freight cars and in like restricted areas where the roof and door openings are not much higher than the mast when the latter is in its down position.

Another problem solved is in arranging the lift cylinders so as to get full lifting strength without having the pressure retained by the piston rod packing.

Another problem solved is in providing a practical fool-proof device with just one control lever and by which the mast must be retracted before the carriage can be lowered.

Objects of the present invention are to provide for lifting the carriage (and supported freight) without lifting the mast; to provide a simplified free lift device with a minimum of parts and ease of manufacture and servicing; to provide means for lifting an object off the floor (01' from high on a stack and then for lowering it and the mast) so that entry can be made into a space where there is a low ceiling; and to provide other advantages which will become apparent from the following description.

Variations in structural details from the preferred embodiment described herein pursuant to Revised Statutes No. 4888 are contemplated as being included in the patent.

In the drawings:

Fig. l is an isometric diagrammatic broken away view of parts of the device (with the lift truck omitted) showing the carriage bracket at the top of its free lift stroke, and with the three sections of the mast in partially raised position;

Fig. 2 is a view in vertical section taken on the line 2-2 of Fig. l;

Fig. 3 is a similar view taken on the line 3-3 of Fig. 1;

Fig. 4 is a plan view partly in section taken on about the line 4 4 of Fig. 2, except that-the carriage is in its lowered position;

' Fig. 5 is a View in side elevation of the portion of the carriage which slides in the mast;

Fig. 6 is a diagrammatic View of the device with the carriage in its lowermost position;

Fig. 7 is a like view with the carriage at the top of its free lift position and with the mast in its lowest position when working within confined areas;

Fig. 8 is a diagrammatic view showing the carriage and the mast raised full height; and

Fig. 9 is an enlarged detail of the piston rod packing and leakage return means.

While the device is illustrated with only the base portion of the carriage shown, the stub shaft is adapted to support a clamp for handling rolls of paper. A fork or other weight supporting means may be substituted on the carriage. Also the device is shown adapted to be detachably secured to the front end of the truck body because it may be used on any make of vehicle. The hydraulic valves, hose, and pressure source to actuate the pistons in the lift cylinders are omitted because such are well known in this art. Briey summarized, the pressure system beyond the valve is connected to the inlet at the base of each lift cylinder where it works on a solid piston ICC with the usual packing. The operation will be described later. The invention has also to do with the new and simplified combination of parts whereby the carriage is mounted in the channel of a plurality of nested mast sections and the lift cylinders are mounted in a novel manner within the confines of the mast structure.

In the drawings, the carriage base plates 10 are shown secured to a face plate 11 on which are secured the stub shaft 12 and the brackets 13 to support a set of paper clamping jaws so that a heavy roll of paper can be held while being lifted about. The construction of these lifting clamps is now well known and no further description is necessary except to say that the driver may move the lift truck so the jaws are on opposite sides of a roll of paper and by moving suitable valve levers the jaws Will clamp the roll of paper tightly enough to support it free of the floor or other support.

The carriage base plates 10 have rollers 14 journaled on pins 15. These rollers just tit inside the channels 16 of the inner channel section 17 of the liftable mast 18. The carriage and rollers move up or down in the channel track. The liftable mast 18 is made with the three

nested channel sections

17, 19 and 20.

The outer mast section 20 is made up of the

channel sections

20, 20 with a bottom cross member 21 and a cross member 22 near its upper end. The mast section 20 has the ears 23 with notches 24 to pivot the mast to an axle shaft supported on the front end of the truck body. The upper end of the mast 20 :is supported near its tlcp by a brace (not shown) which extends from the truc The inner section 17 of the mast is made up of the channel sections 17 with a bottom tie cross member 25 welded securely to the channel section 17 because it is on this base that the free lift cylinders 26 are fastened. A hole 27 is provided in this cross member 25 with suflicient clearance to run free of the main mast lift cylinder 28 which extends through it and is fastened to the base 21.

The mid section 19 of the mast is made up of the channel sections 19 which are tied at the top by the cross member 29 having the strengthening tubular member 30 and the extension 31 which extends in between the free lift chains and over the main cylinder 28. No cross member is needed at the base of the mid section 19 as its slides between the

channels

17 and 20. The

mast sections

17, 19 and 20 have a free sliding t with each other so they move up and down without substantial resistance.

Fig. 3 shows the chains 32 by which the carriage 10 is lifted and lowered in the inner mast section 17. Each chain is secured at 33 to the cross tie 25 and at 34 to the carriage plate 10. Between these points each chain is passed over its sheave 35 mounted on the end of the ram rod 36 of each free lift cylinder 26. In Fig. 3, the free lift is shown extended its full length which has brought the carriage to the top of the channel section 17. The piston 37 is shown in the cylinder 26. Fluid under pressure is introduced and removed through. the fitting 38.

Fig. 2 shows the chains 39 and mast lift cylinder 28 by which the mast sections are extended and lowered. The chains 39 are secured at 40 to the cross tie of the inner mast section 17 and at 41 to the cross tie 22 of the outer mast section 20. The cylinder piston rod 42 has a cross head 43 with sheaves 44 over `which the chains pass. The cross head 43 preferably is secured to the under side of the cross member 31 of the mid mast section 19. The piston 45 is shown at the bottom of Fig. 2. The net result of this compact and eicient structure is that the mid-mast section 19 is always kept in an evenly spaced position vertically in relation to the inner and

outer mast sections

17 and 20 because it is moved positively by the piston rod 42. The two to one lifting ratio of the sheaves 44 in relation to the inner mast section 17 means that the latter moves up twice as fast as the mid section 19.

Fluid pressure to effect movement of the piston 45 enters and exits through the fittings 46.

An important improvement in the present device over the prior art is in having the lifting pressure introduced against a solid piston and having no lifting pressure applied against the seals around the piston rods. What small amount of oil escapes past the

pistons

37 or 45 is bled off through the ttings 49. This arrangement is shown in Figs. 2, 3, and in Fig. 9 where the upper end of one of the free lift cylinders 36 is shown with its piston rod 36 extending beyond the end of the cylinder. The packing 47 need only seal the uid against atmospheric pressure because there is no pressure in the area 48 above the piston and the bleed connection 49 carries back to the iluid reservoir which is at atmospheric pressure. The same arrangement is used on the mast lift cylinder and its piston rod.

The combined area of the pistons in the free lift cylinders 26 is greater than the area of the piston in the mast lift cylinder 28. Since there is a common connection to the

ttings

33, 46 on all the cylinders and a single control valve to control the admission of tluid thereto, the result is that the free lift will be actuated for its full lifting stroke before the mast will lift and on opening of the control valve to release the lluid pressure, the mast will come down ahead of the carriage. This is an important operating characteristic because it removes all choice from the operator who, with certain earlier types of devices, could drop the carriage before the mast was down. Not only is the present device fool-proof from an actuation standpoint, but it also is constructed so the lifting pressure does not canse trouble with the packings.

Figs. 6, 7 and 8 are only diagrammatic to show typical positions of the lift parts. lowest position and the carriage is at its lowest position. In Fig. 7 only the carriage 10 has been raised to the top of its travel in the channel 17 by the full stroke of its rams 26. The mast remains at its lowest position so there can be free access through doors or into cars with low overhead clearances. In Fig. 8 the mast has been extended to its full height by the ram 28 as when depositing or picking up an object high on a stack.

The invention gives great ilexibility of operation to the device and makes possible its use in very confined spaces with low vertical clearance, and yet it enables hehoperator to deposit or to pick up objects several tiers The sheaves 35 illustrated in this description may be sprockets, rollers, or any other form of anti-friction support for a chain or cable by which the carriage is raised or lowered.

What is claimed is:

l. In a mast for a lift truck the combination of a three section extensible mast of nested channel sections, a mast-lift cylinder and ram, free-lift cylinders, mast lift chains, and free lift chains; in which the outer section has a bearing means at the bottom adapted to engage the truck on which it is mounted, a bottom cross member on which the mast lift cylinder is secured, and a top cross member; the mid section has a cross member near its top and to which the ram of said mast lift cylinder is secured; the inner section has a cross member near its top, a bottom cross member on which the free lift cylinders are mounted and the free lift chains and the mast lift chains are secured; a carriage slidable in the channel of said inner mast section, and connected to one end of said free lift chains; a ram in each free lift cylinder, each having a sheave over which said free lift chains extend; a cross-head on said mast lift cylinder ram near its point of attachment to said mid mast section, with a sheave on each side of said cross-head over which said mast lift chains extend; and means for introducing iluid under pressure into said cylinders to cause the rams therein to move upwardly.

2. The device of claim l in which the ram in each cylinder is a solid piston.

3. The device of claim 2 in which the top of each cylinder is provided with an outlet through which any fluid that leaks past the piston may be vented from the cylinder.

4. The device of claim l in which said mast lift ram projects through an opening provided in the bottom cross member of said inner mast section and said cylinders are all contained within the contines of said nested channel mast sections.

5. A mast for a lift truck adapted to position all its lifting apparatus substantially along a single vertical In Fig. 6, the mast is at its plane closely adjacent the front axle of the truck, including in combination: an extensible mast having an outer section, a midsection nested in said outer section, and an inner section nested in said midsection; said outer section having a bottom cross member with a rearwardly-extending bearing means adapted to engage the truck axle on which the mast is mounted, a pair of parallel upwardly-extending channels secured to said bottom cross member, and a top cross member joining together the rear surfaces of said channels; said midsection having a pair of parallel, upwardly-extending channels nested for vertical movement in the channels of said outer section, and a single cross member extending across its said channels near its top; said inner section having a pair of parallel upwardly-extending channels nested in the channels of said midsection, a cross member adjacent its top, and a bottom cross member with an opening therethrough; a mast lit't cylinder secured on the bottom cross member of said outer section and extending up through the opening in the bottom cross member of said inner section when the inner section is in its lower position, with its ram secured to the cross member of said midsection, so as to be enclosed within said mast; a pair of free-lift cylinders mounted on the bottom cross member of said inner section, each said free-lift cylinder having a ram with a sheave thereon, said free-lift cylinders also lying within the confines of said mast; a carriage slidable in the channels of said inner mast section; free-lift chains extending over said sheaves, having one end secured to the bottom cross member of said inner mast section and its opposite end connected to said carriage; a cross head on said mast lift cylinder ram near its point of attachment to said mast midsection, with a sheave on each side of said cross-head; mast lift chains extending over said sheaves and each secured at one end to the bottom cross member of said inner mast section and at the other end to the top cross member of said outer mast section, whereby said midsection is always kept evenly spaced vertically in relation to the inner and outer mast sections so as to atord the maximum in stability; and means for introducing uid under pressure into said cylinders to cause the rams therein to move upwardly, all the lifting being donel along what is substantially the vertical plane of said mast.

6. A mast for a lift truck including in combination: a three-section extensible mast with the sections comprising nested channels, the outer section having a bottom cross member with a rearwardly-extending bearing means securable to the truck on which the mast is mounted and a top cross member, the midsection having a single cross member extending across its channels near its top, and the inner section having a cross member adjacent its top and a bottom cross member; rst extensible power means secured on the bottom cross member of said outer section with its ram secured to the cross member of said midsection, so as to be enclosed within said mast; a pair of free-lift extensible power means mounted on the bottom cross member of said inner section, each said free-lift means having a ram with rotatable means thereon, said free-lift means also lying within the contines of said mast; a carriage slidable in the channels of said inner mast section; free-lift non-expansible flexible linking means extending over said rotatable means, having one end secured to the bottom cross member of said inner mast section and its opposite end connected to said carriage; cross means on said first extensible power means near its point of attachment to said mast midsection, with rotatable means on each side of said cross means; mast-lift non-expansible flexible linking means extending over said rotatable means and each secured at one end to the bottom cross member of said inner mast section and at the other end to the top cross member of said outer mast section; and means for extending said extensible means to cause their rams to move upwardly.

Guerin May 7, 1946 Lehman Jan. 22, 1952