US2923491A - Spring balancer drum - Google Patents

Description

1960 H. R. FISCHER ETAL SPRING BALANCER DRUM Original Filed April 27, 1954 m\ 3 \w Q 3 mm w I N m 3 mm Q Mm mu m. A r-.. L h HWMHHW 1%.. mm 3v 0 \Q Q Q \N Q \em 0 RN R United States Patent O SPRING BALANCER DRUM Howard R. Fischer and Marcel P. DHaem, Utica, N.Y., assignors to Chicago Pneumatic Tool Company, New York, N.Y., a corporation of New Jersey Original application April 27, 1954, Serial No. 425,858,

now Patent No. 2,801,814, dated August 6, 1957. Dividetl and this application April 5, 1957, Serial No. 651,062

2 Claims. (Cl. 242-107) This application is a division of our parent application for a Spring Balancer filed April 27, 1954 and bearing Serial No. 425,858, now Patent No. 2,801,814.

This application relates to weight balancing devices of the spring counterbalancing type. More particularly, it relates to improvements in the drum structure thereof.

Weight balancing devices are commonly, used for the support of portable tools; such for example, as riveting tools. By means of this device the tool may be conveniently held and maneuvered about in a work operation. As a rule, a weight balancing device includes a rotatable drum, a load supporting cable wound about the drum, and spring means for counterbalancing the loaded cable as the latter is Wound and unwound from the drum. In the use of the device the load, which is usually a tool carried at the end of the cable, normally has an elevated position. When the operator manually pulls down on the tool, the cable unwinds from the drum as the tool load descends, causing the counterbalancing spring means to tighten. When the operator manually releases the tool, the spring means acts to rewind the cable about the drum and to restore the tool to its elevated position. The drum is tapered or conical. This enables the leverage arm of the load to lengthen as the load descends and the counter-pull of the spring means increases; and enables the leverage arm to shorten as the load rises and the counterpull of the spring means decreases. Accordingly, the drum requires a spiral groove for guiding the winding and unwinding movements of the cable. To accommodate this groove the conventional drum is of heavy cast structure, and the groove is formed when the drum is cast. The drum wall must,- therefore, be very thick to permit the groove to be formed therein.

A general object, therefore, of this invention is to provide new and useful improvements in the drum structure of a spring balancer device.

A further object of this invention is to provide in a spring balancer device a drum of lightweight structure.

A more particular object of this invention is to provide a lightweight balancer drum wherein the cable groove is formed by a separate strap of sturdy material spirally wound about the conical surface of the drum and secured thereto in suitable manner.

These and further objects and features of the invention will become more apparent from an understanding of the following description and the accompanying drawings wherein:

Fig. 1 is a longitudinal sectional view of a spring balancer embodying the invention;

Fig. 2 is a side view of Fig. 1, but with the housing cover removed and with certain parts broken away to show structural features of the balancer; and

Fig. 3 is an enlarged detail of a section of the angle iron removed from the drum.

Referring now to the drawings, numeral 16 indicates a spring balancer embodying the structural features of the invention. The balancer includes a cable drum housing 17, and a housing cover 18 which is aflixed to the housing by a plurality of bolts 19. The housing 17 has a pair of flanges 21 at its upper end supporting between them a guide rod 22 and an adjusting screw, 23 arranged parallel to each other. A swivel hook 24 is arranged for swivel movement in bearings 27 of an adjusting plate 26. Plate 26 is supported by the guide rod 22 and by the adjusting screw 23, and can be laterally positioned along these elements by reason of its threaded engagement with the adjusting screw. The swivel hook 24 (Fig. 2) is offset with respect to the vertical center line of the housing so that the balancer will assume the position illustratedwhen supporting a load. A swivel hook guard piece 28 is pivotally affixed to the hook to prevent accidental removal of the hook from its support.

A cable drum shaft 29 is rotatably supported within the balancer, one end 31 of the shaft being positioned in a bore 32 formed in the housing 17, while the other end 33 of the shaft is located in a bore 34 formed in the housing cover 18. Rotatably supported upon the shaft 29 by ball bearings 36 is a cable drum assembly comprising a cable drum 37 and a cover 38. The latter has a snug fit inthe open end of the drum, as shown in Fig. 1. A major portion 39 of the peripheral surface of the drum is tapered to provide a frusto-conical shape. Spirally wound upon the drum surface 39 and welded in position is a length or strap of angle iron 40. This winding provides a spiral groove 15 for a cable 41. One end of the cable is disposed in a hole of the drum and 'is thickened by a leaded slug 45, whereby the cable end is made secure in the latter hole. The cable is wound in the groove 15 formed about the drum, and the free or loading end of the cable passes through a slot, not shown, in the bottom of a guide shield 77 of the housing 17.

In contrast with the usual type of cable drum for balancers, which is formed by casting and wherein sufficient metal must be provided in the body of the drum so that a cable groove can be formed therein, thecable drum assembly of the subject invention is of extremely lightweight and simple structure. The drum of the present invention is in the nature of a thin walled shell, and it may be pressed out of sturdy lightweight sheet metal.

Counterbalancing means is provided within the hollow interior of the drum for counterbalancing the cable load as the cable is unwound and wound about the drum. This counterbalancing means comprises one or more coil spring assemblies 44 carried on the shaft 29. These are cooperable with abutment means, generally indicated at 57 and carried by the interior wall of the drum, for counterbalancing the cable load as the cable is wound and unwound about the drum, all as more particularly detailed in the parent application earlier mentioned. Suitable cranking means, as indicated by a worm gear 43 on the shaft 29 and by a crank worm 42, is provided to rotate shaft 29 so as to initially wind a coil spring 47 in each assembly 44 to a proper degree. Thereafter, the coil spring is adapted to be further wound and relaxed to counterbalance the cable load, accordingly as the cable is unwound or rewound about the drum.

It is to be noted (Figs. 1 and 3) that the angle iron 40 forming the spiral groove 15 is L-shaped.' It has an arm 13 integral with a second arm 14 at right angles thereto.

Arm 13 lies flush upon the tapered smooth outer surface of the drum. The windings of the angle iron about the drum are adjacent to one another so that the forward edge of the arm 13 of each winding abuts the rear of the next adjacent winding, as in Fig. 1. The spiral groove 15 formed between the windings is relatively wider than the diameter of the cable 41 that is movable therein. This allows easy winding and unwinding movement of the cable. The height of the continuous upwardly projecting wall of the groove formed by arm 14 is greater Patented Feb. 2, 1960 v than the diameter of the cable. This prevents the cable from ridingover the top of wall 14 as the cableunwinds from the drum. The latter action might otherwise occur due to the natural tendency of the cableto press downwardand towards the taper of the drum as it-' is unwound.

What is claimed is: l V

1. In a tool counterbalancing' device of the character described, a frusto-conical drum rotatably mounted upon a horizontal shaft and having a counterbalancing coil spring connected with the shaft adapted to wind or unwind inverselyto the directional rotation of the drum, the drum being of' rigid light gauge sheet metal having a smooth tapered surface; a-right-angle iron strap spirally wound about the said surface so that the longitudinal edges of the windings abut one another and define a U-channel having a floor and a pair of opposed Walls upstanding at right angles thereto; and a cable received in the channel adapted to ride therein so as to wind about the drum or unwind therefrom accordingly as the drum is rotated in one direction or the other; the floor of the channel being substantially wider than the diameter of the cable, inclined and lying fiat upon the tapered surface of the drum whereby the channel has a lower longitudinal vertex and an upper longitudinal vertex;

2. A cable drum for a tool counterbalancing device of the character described, comprising a frusto-conical shell of rigid light gauge sheet metal having its narrow end closed with an integral wall portion and having its opposite wider end closed with a removable cover, having flanged axial openings respectively in the said wall portion and in the cover adapted to fit about bearings on a cable drum shaft, the interior of the shell being adapted to house counterbalancing spring means for the shell, and the shell having a smooth tapered surface; and a cable guide channel defined by the arms of a right-angle iron strap spirally wound about the tapered surface of the shell, wherein the windingsrare contiguous to one an: other, a first arm of the strap defining an inclined floor of the channel having its free longitudinal leading edge extending up the said tapered surface, the other arm of the strap extending upward at right angles frornrthe lower longitudinal edge of the first arm and being in abutment at its base with the leading edge of the said first arm of the winding next, below, and the floor of the channel being substantially wider than the diameter of a cable received in the channel whereby a broad underlying hearing surface is provided for the cable to ride over, and wherein the floorof the channel is welded to the surface of the shell whereby the shell is relatively thicker and stronger in the area over which the cable is adapted to ride.

References Cited in the file. of this patent UNITED STATESPATENIS' 2,072,582 Douglass Mar. 2, 1937 2,204,938- Le Bus June 18, 11940

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