Load clamping mechanism with limited play in arms
United States Patent Farmer LOAD CLAMPING MECHANISM WITH LIMITED PLAY IN ARMS [75] Inventor: Stanley F. Farmer, Gresham. Oreg.  
 [73] Assignee: Cascade Corporation, Portland,  
 Oreg.  
 [22] Filed: June 7, 1973 [2]] Appl. No.: 367,764  
 [52] US. Cl. 92/51; 92/61; 92/84; 92/113; 92/131; 294/88 [51] Int. Cl. F0lb 31/00; F16j 1/10 [58] Field of Search 92/131,5L61, 113;  
 [56] I References Cited UNITED STATES PATENTS 2,527,727 10/1950 Hobbs 92/131 2.966.888 111961 Jania ct al 92/131 3.034.483 5/1962 Rasmussen 92/131 3.741.517 6/1973 Pogonowski 294/88 Primary E.\&#39;aminerPaul E. Maslousky Altorney, Agent, or FirmKolisch, Hartwell, Dickinson &amp; Stuart [57] ABSTRACT Load clamping mechanism including opposed clamping arm structures adapted to be brought together to clamp onto a load. Means for actuating a clamping arm structure comprising a fluid-powered ram which is extended and contracted to actuate the arm. The ram has a rod assembly including a sleeve part and a rod part received within the sleeve part. A coiled compression spring within the sleeve part and interposed between spring seats which are axially displaceable on the rod part urges said spring seats apart toward a position of maximum relative axial spacing defined on the rod part. The rod part is relatively displaceable axially of the sleeve part with compression of said spring for a limited distance. The construction described accommodates limited swinging of the arm structure actuated by the ram yieldably resisted by the coiled compression spring.  
 2 Claims, 2 Drawing Figures LOAD CLAMPING MECHANISM WITH LIMITED PLAY IN ARMS This invention concerns clamping mechanism of the type comprising opposed clamping arm structures mounted on a frame. which are brought together to clamp onto the sides of a load. The clamping mechanism may form an attachment for a lift truck. as the means employed for lifting up the load which is to be transported by the truck.  
  ln handling loads and utilizing clamping mechanism of the type described. prior to clamping onto the load the arm structures or arms must be positioned so as approximately to straddle the load. whereby when the arms are brought together the load will be properly clamped. This positioning of the arms requires a certain skill in the operator of the mechanism. since it is a matter ofjudgment as to how wide a spacing should be produced in the arms whereby they will properly straddle the load. and skill is required in advancing the arms whereby they may be moved forwardly to become&#39;positioned on either side of the load without one striking the load or perhaps other structure which is positioned closely adjacent the load. If the clamping mechanism is a roll clamp. for instance, and the loads being handled are paper rolls stacked on end on a floor. misjudgment in a lift truck operator with respect to arm spacing and how they are advanced may result in damage either to the roll it is desired to pick up or to adjacent rolls from which it is desired to pick out&#34; a roll.  
  In US. Pat. No. 3.690.714. there is disclosed a roll clamp wherein a limited amount of swinging movement is provided in the forward end of an arm structure. where such arm structure supports the usual pad that is provided for contacting the side of a roll. With such swinging movement. an operator is not required exactly to space the arms and to position the arms and pads with respect to a roll prior to picking it up. As a result. roll damage during handling tends to be reduced. and roll handling may beperformed more speedily. In general terms. this invention concerns an improved form of such clamping mechanism. applicable to roll clamps. as well as other types of clamping mechanisms. wherein a limited amount of swinging movement or play is provided in an arm structure to accomplish the ends generally above indicated.  
  A general object of the invention, therefore, is to provide improved load clamping mechanism having opposed arm structures for clamping onto a load. wherein one or preferably both arm structures in the mechanism have forward ends permitted limited swinging to facilitate arm positioning in picking up a load.  
  More specifically. an object of the invention is to provide clamping mechanism including opposed arm structures for pickup of a load. wherein such swinging movement is obtained by providing a limited amount of contractibility and extensibility in the fluid-powered ram which is included for actuating the arm. which movement is independent of any change in the length of the ram produced by reason of fluid-powered actuation of the ram. This limited movement is resisted by a coiled compression spring which serves to maintain relatively extensible parts in the ram in a position intermediate fully relatively extended and fully relatively contracted positions.  
  A more specific object of the invention is to provide clamping mechanism of the type indicated. which includes a pivoted clamping arm which is swung to move it toward and away an opposed arm to effect clamping onto and release of a load. and a fluidpowered ram actuated to produce powered movement of the arm. the ram including a rod assembly with relatively extensible and contractible parts and a coiled compression spring held internally in the rod assembly maintaining such parts in a position intermediate fully relatively extended and fully relatively contracted positions.  
  These and other objects and advantages of the inven tion will become more fully apparent as the following description is read in conjunction with the accompanying drawings. wherein:  
  FIG. 1 is a plan view showing a roll clamp constructed according to the invention with such mounted on forward portions of a lift truck; and  
  FIG. 2 is a view. on a larger scale. illustrating a fluidpowered ram used in actuating a clamping arm structure in the roll clamp shown in FIG. 1.  
  Referring now to the drawings and first of all mor particularly to FIG. 1, the load clamping mechanism illustrated comprises a roll clamp 10 including a pair of opposed clamping arm structures or arms. shown at 12 and 14, mounted on a frame 16. The roll clamp comprises an attachment for a lift truck. portions of which are shown at 20. The roll clamp includes a rotator 22 which. as is conventional in the art. is utilized to rotate or turn the frame 16 and the arms mounted thereon about an axis extending substantially horizontally and along the longitudinal axis of the truck. With the roll clamp positioned as illustrated in FIG. 1, i.e.. with the arm structures projecting forwardly from either side of the truck. the roll clamp may be utilized in the picking up of rolls that are resting on end on the floor. Turning of the frame to place the arms so that one is on top of the other positions the roll clamp to pick up rolls which are on their sides. The roll clamp is mounted on a vertically movable carriage 24 disposed in front of a conventional extensible mast assembly 26. With raising of the carriage the roll clamp is raised to lift the load gripped thereby.  
  Each of the arm structures l2. 14 is mounted adjacent its rear end on frame 16 through a pivot means 28. The pivot means permits an arm structure to be swung toward and away from an opposing arm structure. to permit the clamping onto and the release of a roll. The roll clamp thus falls into a class generally known as a bear hug&#34; type clamp. in that movement of the arm structures toward and away from each other is produced by swinging pivotally mounted arm structures. Adjusted pivotal movement of each arm structure is produced under power. through the actuation of one or more fluid-powered rams interposed between an arm structure and the frame 16, exemplified by the ram 30 shown for arm structure 12 and ram 32 shown for arm structure 10. Each of these rams has its cylinder end pivotally mounted on the frame. as at 34, and its rod end pivotally mounted on an arm structure. as at 36.  
  Each of the rams which is provided to actuate a clamping arm structure may be constructed as described in connection with ram 32 illustrated on a somewhat larger scale in FIG. 2.  
  Referring to FIG. 2, it will be seen that ram 32 includes a cylinder 40 closed at which is referred to herein as the cylinder end of the ram by an end wall 42 which mounts car 44 forming part of pivot means 34. Mounted for reciprocation within cylinder 40 is what is referred to herein as a rod assembly 50 including piston 52 and rod 54. The rod assembly projects outwardly from the right end of the cylinder 40 through a retainer 56. The rod assembly at the extreme right end thereof in FIG. 2 includes an car 58 at what is referred to as the rod end of the ram forming part of pivot means 36.  
  Considering in further detail the construction of rod assembly 50, with actuation of the ram, piston 52 moves between limit positions defined by end wall 42 and retainer 56 at the opposite end of the cylinder. Encircling the piston is a bearing 60. Providing a dynamic seal between the piston and the inner wall of cylinder 40 is seal assembly 62.  
  Rod assembly 50 of ram 32 comprises relatively axially displaceable rod parts in the form of a sleeve 64 and a rod element 66. Sleeve 64 has its left end secured, as by welding. to piston 52. The right end of the sleeve in FIG. 2 extends through retainer 56. A seal assembly 68 provides a fluid-tight seal between the retainer and the periphery of the sleeve.  
 With continued reference to FIG. 2, rod element 66 is formed with a pair of axially spaced annular channels shown at 70 and 72, respectively. Mounted in channel 70 is what is referred to herein as a spring seat 74. The spring seat is axially displaceable with respect to the rod element between shoulder 76 defining one limit position on one side of channel 70 and shoulder 78 on the other side of the channel defining a second limit position. Seated within channel 72 and also relatively axially displaceable with respect to the rod element is another spring seat 80. Such spring seat is afforded limited axial movement with respect to the rod element between a shoulder 82 defining one limit position and on one side of the channel 72, and a shoulder 84 on the other side of the channel defining a second limit position. Encircling the rod element and with ends seated on spring seat 74, 80 is a coiled compression spring 86. The spring exerts a constant bias on the spring seats tending to urge them apart to the limit positions defined by shoulders 76 and 82.  
  Mounted within sleeve 64 adjacent the left end of the sleeve in FIG. 2 is a spacer 90. The right end of the spacer in FIG. 2 constitutes an abutment means positioning spring seat 74 in a predetermined position with respect to sleeve 64 with spring seats 74, 80 spread apart and against shoulders 76, 82, as illustrated. Mounted within the right end of sleeve 64 is a retainer 92. The left end of this retainer constitutes an abutment means defining a predetermined position for the spring seat 80 with the spring seats in this spread-apart condition just described.  
  From this description of ram 32 it will be noted that the ram has a limited amount of extensibility and contractibility which is resisted by coiled spring 86 and which is independent of extensibility or contractibility obtained by actuation of the ram through controlled supply of pressurefluid to the ram. lt is this limited extensibility and contractibility which permits an arm structure powered by the ram to swing in or out to a limited degree, as in response to striking an obstruction, without any change in the relative position of the piston within the cylinder. Furthermore, the construction is such that rod element 66 is always biased by the spring to a position intermediate a fully extended and a fully contracted position relative to sleeve 64.  
  Further explaining. it will be noted that rod element 66 is displaceable to the left with respect to sleeve 64. This movement to the left is accompanied with movement of spring seat to the left with such spring seat abutted against shoulder 82. Spring seat 74 is pre vented from moving by reason of seating against the right end of spacer 90. As a consequence, this movement to the left is accompanied with deformation of spring 86, more specifically a further compressing of the spring. Movement to the left is limited by shoulder 78 coming up against the right side of spring seat 74. The rod element can extend from the sleeve 64 for a limited distance, such also being accompanied with compression of spring 86. Specifically, with movement of the rod element to the right, spring seat 74 moves to the right while abutted against shoulder 76. Spring seat 80 remains in place against retainer 92. When shoulder 84 strikes spring seat 80, further extension of the rod element from the sleeve is prevented.  
  It will be noted that with the construction, regardless of the yieldability selected for spring 86, the rod element always will be urged to a position intermediate defined limit positions. The force required to displace the rod element with respect to the sleeve, whether it be a contractive movement or one of extension, is the same.  
  Continuing with the description of ram 32, shown at and 102 are hoses for the supply and exhaust of pressure fluid to the ram. Hose 102 through passage 104 and tube 106 connects with the left end of the cylinder 40 in FIG. 2. Hose 100 through passage 108 connects with the right end of the cylinder 40. To extend the ram, fluid under pressure such as hydraulic fluid is admitted to the left end of the cylinder and is permitted to exhaust from the right end. With the ram extended and to contract the ram. fluid under pressure is admitted to the right end of the cylinder and permitted to exhaust from the left end, in a conventional manner. Suitable valve means (not shown) is provided to enable an operator to make controlled adjustments in the length of the ram.  
  Referring again to FIG. 1, it will be noted that arm structure 10 in dashed outline 10A is shown deflected inwardly from the position shown in solid outline for the arm structure. This inward movement of the arm structure is accompanied with extension of the overall length of ram 32. This movement is afforded the clamping arm structure without hydraulic actuation of ram 32 with rod element 66 moving outwardly from sleeve 64. The arm structure may swing to the right or to the position shown at 10B in dashed outline, with contraction of the ram and without hydraulic actuation thereof, with rod element 66 moving inwardly into sleeve 64.  
  It should be apparent that the clamping mechanism described permits an operator to handle loads with less skill and exactness required in positioning the arm structures prior to picking up a load. The arm structures may move in and out to a a limited degree, as the result of striking an adjacent obstruction or prematurely engaging the roll which is to be picked up. The limited amount of play permitted in each arm structure is accomplished in a relatively simple manner, i.e., in permitting limited extensibility and contractibility in the ram which powers movement of an arm structure.  
 What is claimed is:  
  1. In a roll clamp including a swingable clamping arm structure which is pivotally mounted on a frame for swinging movement relative thereto thus to clamp onto a load a fluid-operated ram interposed between the frame and arm structure operable, on actuation. to produce adjusted swinging movement of the arm structure.  
 said ram including a cylinder and a piston rod assembly with the piston rod assembly extensible from the cylinder.  
 said piston rod assembly including a rod part telescopically received within a sleeve part, a pair of axially spaced spring seats encircling the rod part and mounted thereon for axial movement therealong each spring seat being movable axially between a pair of limit positions defined on the rod part a coiled compression spring interposed between the spring seats urging said seats apart to a position of maximum relative axial spacing, and means on the sleeve part positioning said spring seats with respect to the sleeve part with the seats in said position of maximum relative axial spacing.  
  2. ln load clamping mechanism including a frame and a pair of opposed arm structures mounted on said frame actuatable to clamp onto a load.  
 a fluid-powered ram for actuating atleast one arm structure including a piston rod assembly and a cylinder that are extendable and contractible with respect to&#39;each other on operation of the ram,  
 said rod assembly comprising a sleeve element and an extensible rod element received within said sleeve element. said rod element having a pair of axially spaced spring seats mounted thereon which are axially displaceable with respect to the rod element,  
 a coiled compression spring encircling the rod element interposed between said spring seats to spread them apart said rod element further including limit means defining limit positions thereon for said spring seats. the sleeve element including abutment means positioning the spring seats in a predetermined position relative to the sleeve element with said spring seats spread apart against said limit means.  
  UNTTED STATES PATENT OFFICE (IETEHCATE @F CQRECTEQN PATENT NO. 1 3,878,769  
 D T 1 April 22, 1975 lNVENTORtS) Stanley E. Farmer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 The correct name of the inventor is -Stanley E. Farmer.  
 sale ta&#39;s fifth ay 09 August 1975 [SEAL] AIIGSI.  
 RUTH C. MASON C. MARSHALL DANN Alresring Officer (mnmr&#39;ssimu&#39;r 0f Parents and Trademarks