US2955676A

US2955676A - Upright pull-down

Info

Publication number: US2955676A
Application number: US756675A
Authority: US
Inventors: Charles S Schroeder
Original assignee: Yale and Towne Manufacturing Co
Current assignee: Yale and Towne Manufacturing Co
Priority date: 1958-08-22
Filing date: 1958-08-22
Publication date: 1960-10-11
Anticipated expiration: 1977-10-11

Description

c. s. SCHROEDER 2,955,676h.

UPRIGHT PULL-DOWN Oct. 11., 1960 Filed Aug. 22, 1958 4 Sheets-Sheet 1 INVENTOR. CAI/11? 68 J Sci/@0606? 4 Sheets-Sheet 2 Filed Au 22, 1958 INVENTOR Campus 6. SCI-b90500? Filed Aug. 22. 1958 C. S. SCHROEDER UPRIGHT PULL-DOWN Oct. 11, 1960 4 Sheets-Sheet 4 1 lfQ WW M MINI. m

IN VEN TOR. C/Mg4e5 S. Sc/wgocosg BY WM United States PatentlO UPRIGHT PULL-DOWN Charles S. Schroeder, Villanova, Pa., assignor to The Yale and Towne Manufacturing Company, Stamford, Bonn, a corporation of Connecticut Filed Aug. 22, 1958, Ser. No. 756,675

Claims. (Cl. 187-9) This invention relates to industrial trucks and, more particularly, to such trucks in which a hydraulic ram is employed to lift a load relatively to uprights carried by the truck.

Heretofore, it has been a frequent practice to construct trucks of the class described in which a carriage is elevated relatively to secondary uprights, and the secondary uprights are, in turn, elevated relatively to primary uprights, all through the operation of a single hydraulic ram. This hydraulic ram lifts the carriage through a set of chains, the ram moving freely of the secondary uprights for a short distance during which it lifts the carriage twice the distance of its own movement due to the run of the chains. This movement of the carriage relatively to the secondary uprights is known as the free lift. After the free lift, it is usual for the piston of the lifting ram to contact the secondary uprights and elevate them directly while the carriage continuesv to 'move at double the piston speed. After some lifting in secondary uprights to cock and jamb or stick in an upper position because there is no positive connection between the uprights and the piston. Then after some vibration due to further downward movement of the. piston ,and

carriage, the secondary uprights frequentlyfbecome 2,178,370, as the best available means of combatting this problem. Dunham taught the use of a long bolt extending between the secondary uprights and the ram piston by a lost motion connection so that the piston would pull the secondary uprights down after moving a distance corresponding to the free lift of the carriage. While 7 this construction was recognized as a partial remedy, it was never completely satisfactory due to the fact that the secondary uprights could still drop sharply a sufficient distance to cause serious damage.

Other efforts were directed towards cushioning the drop I of the secondary uprights, it being generally well recognized that a drop of material consequence is inherent in trucks of the class described.

Ihave conceived by my invention a novel construction that enables me to eliminate entirely any sharp dropping of the secondary uprights relatively to the primary uprights.

In essence, my invention resides in the utilizationv of yielding means continuously urging the secondary'up-.

rights downwardly relatively to the primaryuprights.

2,955,676 Patented Oct. 1 1', 1960 While it is felt that my invention is of greatest utility in the combination I have outlined, it is quite readily seen that the contribution I have made may be utilized to control the lowering movement of load members other than secondary uprights.

As a feature of my invention, I connect one end of the yielding means to a part that is urged downwardly by whatever load has been raised by the hydraulic ram. In the preferred structure this part is the ram piston itself. Therefore, I connect the yielding means to the ram piston at one end while the other end is connected to the secondary uprights. As a more particular feature of this aspect of my invention, I prefer to use as my yielding means a helical spring that I mount inside the ram, preferably within the piston of the ram which is hollow, one end of the spring being connected to the piston. To the other end of this spring, I connect a rod that extends outwardly of the piston and is fixed to the secondary uprights.

As a further feature of my invention, the spring is connected so as to have an initial torsion when the carriage and secondary uprights are in their normal lowermost position.

As another feature of my invention, the initial tension on the spring is such that during the free lift, as the piston rises but the secondary uprights remain stationary, the spring will not be collapsed sufliciently'to reach a state of no tension. By reason of this arrangement, the

spring continuously exerts a downward pull on the sec ondary uprights, regardless of the relative positions of the various parts.

I have thus outlined rather broadly the more important features of my invention in order that the detailed description thereof that follows may be better understood, and in order that vmy contribution to the art may be better appreciated. There are, of course, additional features of my invention that will bedescribed hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception on which my disclosure is based may readily be utilized as a basis for the designing of other structures for'carrying out the several purposes of my invention. It is important therefore, that the claims be regarded as including such equivalent constructions as do not depart from the spirit and scope of my'in'vention, in order to prevent the appropriation of my invention by those skilled in the art.

A specific embodiment of the invention has been chosen for purposes of illustration and description, and

:is shown in the accompanying drawings.

In the drawings: g

Fig. 1 is a side view of a truck embodying my novel pull-down; i

Fig. 2 is a plan'view taken along line 2+2 of Fig. 1;

Fig. 3 is a partial view taken along line 3-3 of Fig. 2;

V Fig. 4 is a longitudinal section view illustrating details ofthe pulls-down with the ram piston partially extended to lift the load carriagej Fig. 5 is a view similar to Fig. 4 but illustrating the relation of the parts with the secondary uprights partially elevated; and p I Fig. 6 is a view taken along line 66"of Fig. 1 and partly broken away to illustrate the relation of the parts when the carriage and secondary uprights are in" their normal lowermost position.

Referring now to the drawings, and particularly to Fig.

1, there is shown an industrial truck T having a pair of primary uprights 10, a pair of secondary uprights 1'1, and a load carriage 12 provided with lifting forks 14.

The primary uprights 10 are integrally connected by an upper cross member 15, a lower cross member 16 and an intermediate cross member 17. A cross member 18' integrally connects the secondary uprights at their upper ends.

As shown in Fig. 2, the uprights and 11 are formed as channel members, with rollers 19 engaged inthe channels of the primary uprights 10 to guide the secondary uprights 11 for vertical movement relatively to the primary uprights, and rollers 20 similarly guiding the carriage 12 for vertical movement relatively to the secondary uprights.

In Figs. 1, 2 and 3, I show a pair of rollers 21 on the upper cross member for guiding lateral movement of the secondary uprights. A further pair of rollers 22 serve a similar purpose at the lower ends of the uprights 11 as shown in Figs. 2 and 6. Additionally, the carriage 12 has a pair of rollers 23 (Fig. 2) for guiding it laterally relatively to the secondary uprights 11, and a pair of lugs 24 for a purpose to be later described.

A hydraulic ram 25 is supported on the lower cross member 16 and serves to lift both the load carriage 12 and the secondary uprights 11. This ram 25 has a cylinder 26 mounted on the cross member 16 between the secondary uprights 11. A piston 27 is disposed within the cylinder 26 and a packing gland 29 (Figs. 4 and 5) is applied between the piston and cylinder to prevent leakage of hydraulic fluid.

On the upper end of the piston 27 is a cross head 30 having a pair of grooved wheels or sheaves 3 1 over which lifting chains 32 are reeved. These chains 32 are secured at one end to the ram cylinder 26 through a bracket 34 (Figs. 1 and 3), and at the other end to the load carriage 12 through brackets 35 (Fig. 6).

From the description thus far, it will be seen that as the ram piston 27 is first extended upwardly from its position shown in Figs. 1 and 6 to its position shown in Fig. 4, the carriage 12 is raised through chains 62. When the cross head 30 engages the cross member 18 of the secondary uprights, as shown in Fig. 4, further extension of the ram piston 27 moves the secondary uprights 11 upwardly relatively to the primary uprights as the carriage 12 continues to move upwardly at double the piston speed. When the carriage 12 reaches the limit of its upward movement relatively to the secondary uprights 11, the carriage lugs 24 engage the cross member 18 of the secondary uprights to lift these uprights whereby the carriage causes the cross member 18 to draw away from the cross head 30 on the piston 27.

Upon lowering the piston 27, the carriage 12 begins to move downwardly allowing the secondary uprights also to descend. During the descent of the secondary uprights, the cross member 18 comes into contact with the cross head 30 and, remaining in such contact, is guided in its downward movement by the piston 27 until the secondary uprights reach their normal lowermost. position, after which the carriage continues to move downwardly a distance equal to its free lift.

At any time during the descent of the secondary uprights, they may tend to cock in a transverse or longitudinal direction and to jamb. This may be due to eccentric loading or unevenness of the ground surface.

I shall now describe in detail the novel construction of my pull-down by which I prevent jambing of. the secondary uprights relatively to the primary uprights.

Referring to Figs. 4 and 6, I show the lower end of the cylinder 26 formed with a depending pin 36 extending into a suitable hole in the cross member 16 of the primary uprights. The piston 27 in the cylinder has a head 37 provided with a suitable packing gland 39 to prevent leakage of hydraulic fluid between the piston head and the interior wall of the cylinder. Secured, to the inner surface of the piston head 37 is a U-shaped bracket 40 having a central hole 41. A bolt 42 extends through this hole 41 and is fixed to a circular spring block 44 which may be formed with helical grooves to receive several of the end turns of a helical spring 45 so as to facilitate securing the block and spring together. The other end of the spring 45 is similarly secured to a second spring block 46 that is in turn fixed through a short stud 47 to a rod 49. This rod 49 extends upwardly through a packing gland 50 at the upper end of the piston, through the cross head 30 to the cross member 18 at the top of the secondary uprights. The rod 49 is fixed to this cross member by a bolt 51.

As I have already mentioned, and as shown in Fig. 6, the spring 45 is connected so as to have an initial tension when the carriage and secondary uprights are in their lowermost position. With this in mind, I shall now describe the operation of my present contribution.

Referring now to Fig. 4, it will be seen that as the ram piston is extended it first raises the cross head 30 that in turn raises the sheaves 31 causing the chains 32 to elevate the carriage 12 at a rate of speed double that of the piston. During this phase of the operation, the secondary uprights 11 are stationary as is the rod 49. Since the lower end of the spring 45 moves with the piston, it will be seen that the spring, having had an initial tension, is brought to a position of less tension. I prefer that the spring be so arranged relatively to the rod 49 and the piston that it be under tension even when the piston is at its highest position relatively to the rod 49.

When the cross head 30 reaches a position adjacent the secondary upright cross member 18, it begins to lift that member, as already described. During this movement, the piston and secondary uprights move together so that the spring tension remains unchanged.

As the carriage 12 catches up to the cross member 18, it engages this member and draws it, along with the secondary uprights, upwardly at a faster rate than the piston until the secondary uprights are brought to a position of maximum elevation due to the lifting action of the carriage. The spring, therefore, is stretched from its position of minimum tension to one of greater tension.

As the carriage is lowered, the relationship of the parts is reversed. That is, the secondary uprights are first permitted to descend at the same rate of speed as the carriage, or at double the piston speed, until the cross member 18 contacts the piston cross head 30. During this movement, the rod 49 moves downwardly faster than the piston so that the spring returns to its condition of minimum tension pulling the secondary uprights downwardly. Following contact between cross member 18 and cross head 30, the secondary uprights are permitted to descend at the same speed as the piston until their lowermost position is reached. During this movement the spring tension pulling the secondary uprights downwardly remains unchanged.

After the secondary uprights have reached their lowermost position, the cross member then abutting the cross member 15, the carriage continues downwardly a distance equal to its free lift as the piston continues to lower, its cross head 30 moving away from secondary upright cross member 18. As this movement occurs, it will be seen that the rod 49 remains stationary while the piston moves towards its lowermost position so that the spring is again stretched from a position of minimum tension to one of greater tension, to complete a full cycle of operation, the parts once again assuming the positions shown in Fig. 6.

From the foregoing description, it will be seen that I havecontributed a novel upright pull-down by which I have eliminated entirely any sharp dropping of the secondary uprights relatively to the primary. uprights. It will further be seen that my contribution is based upon means that continuously and positively urge the secondary uprights downwardly relatively to the primary uprights.

I believe that the construction and operation of my novel invention will now be understood, and that the advantages of my contribution will be fully appreciated by those persons skilled. in the art.

I now claim:

1. In a truck of the class having a main frame, a primary upright, a secondary upright movable vertically on said primary upright, a carriage movable vertically on said secondary upright, and a hydraulic ram for lifting said carriage through the intermediary of a chain at double the speed of movement of the ram piston, with said piston contacting and moving the secondary upright only after said carriage has been moved a predetermined degree on said secondary upright while said secondary upright is stationary, the improvement comprising a connection between said ram piston and secondary upright including a spring means that allows separation of said secondary upright from said ram piston while urging said ram'piston and secondary upright toward one another.

2. In a truck of the class described, a main frame, a

primary upright mounted on said main frame, a secondary upright movable vertically on said primary upright, a

carriage movable vertically on said secondary upright,

a hydraulic ram comprising a piston and cylinder, means mounting said cylinder for support on said primary upright with the piston separated from said secondary upright when the piston is in its fully retracted position and the secondary upright is'fully lowered, a multiplying chain through which the piston when moved vertically relatively to said cylinder lifts the carriage on said secondary upright at double the speed of movement of said piston, the said carriage moving on said secondary upright and said secondary upright remaining stationary until the piston is extended to abut a portion of the secondary upright, and a connection between said ram piston and said secondary upright including a spring means that allows separation of said secondary upright from said ram piston while urging said ram piston and secondary upright toward one another.

3. In a truck of the class described, a main frame, a primary upright mounted on said main frame, a secondary upright movable vertically on said primary upright, a carriage movable vertically on said secondary upright,

a hydraulic ram comprising apiston and cylinder, means mounting said cylinder for support on said primary upright with the piston separated from said secondary upright when the piston is in its fully retracted position and the secondary upright is fully lowered, a multiplying chain through which the piston when moved vertically relatively to said cylinder lifts the carriage on said secondary upright at double the speed of movement of said piston, the said carriage moving on said secondary upright and said secondary upright remaining stationary until the piston is extended to abut a portion of the secondary upright, the piston thereafter lifting the secondary upright until the carriage contacts the secondary upright to lift the secondary upright at double the speed of movement primary upright mounted on said main frame, a secondary upright movable vertically on said primary upright, a carriage movable vertically on said secondary upright, a hydraulic ram comprising a movable part and a stationary part, means mounting said stationary part for support on said primary upright, a multiplying chain through which the movable part when moved vertically relative to said stationary part lifts the carriage on said secondary upright at double the speed of movement of said movable part, said movable part contacting and moving said secondary upright until the carriage contacts the secondary upright and moves the secondary upright away from said movable part, and a resilient connection between said movable part and the secondary upright allowing separation of said secondary upright from said movable part while urging said movable part and the secondary upright towards one another.

5. In a truck of the class having a main frame, a primary upright, a secondary upright movable vertically on said primary upright, a carriage movable vertically on said secondary upright, and a hydraulic ram for lifting said carriage through the intermediary of a chain at double the speed of movement of the ram piston, with said piston contacting and moving the secondary upright only after said carriage has been moved a predetermined degree on said secondary upright while said secondary upright is stationary, the improvement comprising a resilient connection between said ram piston and secondary upright that allows separation of said secondary upright from said ram piston while urging said ram piston and secondary upright toward one another.

References Cited in the file of this patent UNITED STATES PATENTS