US3330383A - Mast snubber - Google Patents

Description

July 11, 1967 R. J. PUSZTAY MAST SNUBBER Filed March 28, 1966 United States Patent O 3,330,383 MAST SNUBBER Russell J. Pusztay, Dalton, Ill., assigner to Allis-Chalmers Manufacturing Company, Milwaukee, Wis. Filed Mar. 28, 1966, Ser. No. 537,869 Claims. (Cl. 187-9) This invention relates to means for retarding the free fall of the inner section of an extra lift mast.

In a typical extra lift mast the crosshead of the lift cylinder has a lost motion connection with the inner section of the mast and thus does not pick up the inner section of the mast until the carriage has been raised a predetermined distance from the oor. This initial movement of the carriage does not increase the height of the mast assembly and is commonly referred to as free lift. At the upper end of the lift ram stroke the carriage will lift the inner section of the mast off the crosshead. When the mast is retracted from such a fully extended position the weight of the inner section may be insufficient to overcome binding or friction lbetween the inner and outer mast sections. When this occurs, the crosshead will move downwardly through a part or all of its lost motion connection with the inner section before the binding or friction is overcome. When the inner section is freed it will drop by gravity onto the lift ram crosshead. This dropping of the inner section of the mast not only imposes shock load on various components, but also the sound of impact is annoying and distracting to the operator and personnel in the vicinity of lift truck use.

Heretofore others have employed latches to positively effect proper cycling of the mast components; however, such mechanisms are costly and do not have satisfactory service life.

It is an object of this invention to reduce the speed and force of the drop of the inner mast section relative to the lift cylinder crosshead.

It is a further object to provide a snubbing mechanism to retard the descent of an inner mast section when dropping by gravity.

It is a further object of this invention to provide a snubber or retarder for an inner mast section which is adjustable and automatic in operation.

It is a further object of this invention to provide a mast snubber of the nature hereinbefore outlined which is economical to manufacture, easy to install and service and reliable in operation.

These and other objects and advantages of this invention will be apparent when the following description is read in conjunction with the drawings in which:

FIG. 1 is a rear view of a mast assembly for a lift truck in which the present invention is incorporated;

FIG. 2 is a top view of the mast assembly of FIG. l;

FIG. 3 is a section view taken along the line III-III of FIG. 1;

FIG. 4 is a section view of the mast snubbing mechanism of this invention;

FIG. 5 is a section view taken along the line V-V of FIG. 4; and

FIGS. 6, 7 and 8 are section views showing the mast and carriage in different positions of operation.

The mast assembly illustrated in the drawings includes an outer section 11 adapted for connection to the body of a lift truck through pivot brackets 12, 13, 14, 1S and an inner section 16 telescopically mounted for vertical reciprocable movement on the outer mast section 11. The mast assembly also includes a carriage 17, lift ram 18 and chains 19 interconnecting the ram and carriage. A piston 21 of ram 18 has a portion extending out of the top of the ram cylinder 22 which carries a crosshead 23 with sprockets 24 over which chains 19 are reeved. The

3,336,383 Patented July 11, 1967 ICC carriage moves up and down the channel members 26, 27 of the inner section 16 of the mast assembly on four spaced rollers 28 journaled on the back of the carriage. A pair of guide rods 31, welded to struts 32, 35 of the inner section 16, maintain the ram 18 in a vertical attitude by a sliding, loose tit connection with vertical openings 30 in crosshead 23, thus providing a lost motion connection between the crosshead 23 and inner mast section 16.

When the ram is expanded the piston 21 and its crosshead 23 move upwardly causing the carriage 17 to be raised. When the crosshead 23 abuts the underside of strut 32 welded to the upper ends of channels 26, 27, it will pick up the inner mast section .16 upon further expansion or extension of the lift ram 18 as shown in FIG. 6. During further extension of the ram, the rearwardly extending roller supports 33, 34 of the carriage will pick up the inner section 16 as shown in FIG. 7 and carry it to the upper extreme of its lost motion connection with the crosshead.

Occasionally the inner mast section 16 will bind with the outer mast section 11 causing it to hang up during lowering of the carriage and when the ram is retracted the inner section 16 will not follow the carriage roller `supports 33, 34 or crosshead 23 as it should for a proper cycling sequence. FIG. 8 shows the inner mast section 16 hung up, with the carriage 17 and crosshead 23 lowered from their uppermost positions. As the ram piston 21 is retracted further, the crosshead 23 will reach the lower extreme of its lost motion connection with the inner mast section 16 and the latter will be pulled down overcoming the frictional forces causing it to hang up. Heretofore, on miscycling, the inner section 16 would drop by gravity, when freed, through a portion of the lost motion distance with the strut 32 banging against the top of the crosshead 23 with a loud irritating noise and with considerable attending shock load.

In order to reduce the speed of the falling inner section 16, I provide a snubber mechanism 41 which is secured by cap screw 42 to the underside of the cro-sshead 23. The snubber mechanism 41 includes a body part or block 43 having a pair of conical bores 45 which are coaxial to the axes of rods 31, respectively.

As shown in FIGS. 4 and 5 the block 43 is adjustably spaced from the crosshead 23 by shim means in the form of washers 44. A frictional drag is imposed on each rod by three wedging elements or segments 46 which are i biased toward their position of greatest wedging eiect tby a wave spring 47. The biasing eifect of the wave spring 47 may be adjusted by adding or removing one or more Washers 44. When the inner mast section 16 and its guide rods 31 move upwardly relative to the crosshead 23, the wedging segments 46 tend to shift upwardly against the biasing action of spring 47 thereby decreasing the frictional drag on the rods 31. However, when the inner section 16 moves downwardly relative to the crosshead 23, the frictional engagement between the inner cylindrical surfaces of the segments 46 and the rods tend to shift the lsegments downwardly and the outer conical surfaces of the segments cam against the surface of conical bore 45 to apply increased radial thrust against the rod 31, thereby increasing resistance to downward movement of the inner section 16 relative to the crosshead 23. Thus the -snubber mechanism acts as a one-way friction device to reduce the speed and impact force of a free falling inner mast section.

The conical surfaces of the tapered bores 45 and the segments 46 are preferably coated with a dry lubricant, which may be baked on or air dried, to insure proper operation. The angle of the taper bore may be changed to suit the requirements of the weight of the inner mast section and the amount of braking force desired.

The embodiments of the invention for which an exclusive property or privilege is claimed are defined as follows: Y

1. In a lift truck mast assembly, the combination cornprising:

a vertically Vdisposed lift ram having a vertically `reciprocable head structure,

a vertically reciprocable mast section structure,

connecting means interconnecting said structures for a predetermined amount of vertical lost motion, and

a mechanical snubbing mechanism secured to one of said structures and frictionally engaging the other of said structures to retard downward movement of said mast section structure relative to said head structure, said mechanism affording markedly less resistance to upward movement of said mast section structure relative to said head structure than to said downward movement.

2. The `combination of claim 1 wherein said snubbing mechanism includes a spring loaded tapered Wedging element.

3. The combination of claim 2 wherein said one strucing through whichV said rod concentrically extends, aVV

plurality of tapered wedging elements in said tapered opening engaging said rod and spring means biasing saidV tapered wedging elements toward increased frictional engagement with said rod.

5. The combination of claim 4 wherein said snubbing mechanism includes means for adjusting the biasing effect of said spring means.

References Cited UNITED STATES PATENTS 3,231,047 l/l966 Quayle r 187-'9 FOREIGN PATENTS 1,071,064 lll/1954 France.

EVON C. BLUNK, Primary Examiner. H. C. HORNSBY, Assismm Examiner.

Claims (1)

1. IN A LIFT TRUCK MAST ASSEMBLY, THE COMBINATION COMPRISING: A VERTICALLY DISPOSED LIFT RAM HAVING A VERTICALLY RECIPROCABLE HEAD STRUCTURE, A VERTICALLY RECIPROCABLE MAST SECTION STRUCTURE, CONNECTING MEANS INTERCONNECTING SAID STRUCTURES FOR A PREDETERMINED AMOUNT OF VERTICAL LOST MOTION, AND A MECHANICAL SNUBBING MECHANISM SECURED TO ONE OF SAID STRUCTURES AND FRICTIONALLY ENGAGING THE OTHER OF SAID STRUCTURES TO RETARD DOWNWARD MOVEMENT OF SAID MAST SECTION STRUCTURE RELATIVE TO SAID HEAD

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