Platform-type Scale

Abstract

A platform-type scale comprising a base plate, a platform and a load sensing mechanism in the form of a lever system suspended on the base plate and carrying the platform by means of pivotal power transmitting means. When the load is placed on the platform, the lever system indicates the measured load.

Description

The present invention relates to a platform-type scale comprising a base plate having four knife edge means disposed in square relationship for a load sensing mechanism having a pair of first levers and a pair of second levers, said first levers being coupled to a common balance plate disposed approximately in central position at one side of the base plate and said first levers diverging towards the two knife edge means which are opposite to the balance plate and against which said first levers rest, while the second levers rest with their one ends on each of said two other knife edge means and have their other ends pivotally connected each to one of said first levers between the ends thereof, and each lever is formed at some distance inside its knife edge means on the base plate with an upwardly open recess in which rests a power transmitting means carrying the load receiving platform, and the scale also comprises an indicating mechanism actuated by the load sensing mechanism for visual indication of a measured load.

To avoid sliding friction at the movements of the lever system in such scales the knife edge means and suspension points of the levers must have adequate opportunity to shift to some extent mainly in the axial direction of the levers. In an earlier solution of this problem the levers rested on the base plate by the intermediary of upwardly directed and pivotally mounted knife edge plates disposed on the base plate, while the platform was provided with fixedly arranged downwardly directed knife edge means consisting of downwardly directed lugs punched from the sheet material of the platform and resting in V-shaped notches at the outer ends of the levers. There has also been suggested an embodiment in which the scale platform at its underside is provided with downwardly directed brackets arranged in pairs and carrying between them pivotal means formed with downwardly directed recesses and engaging the levers.

The primary disadvantage inherent in said prior art constructions is that they render the manufacture and the automatic assembly of the scale in continuous operation difficult, thus making both the manufacture and the assembly much more expensive.

The present invention has for its object to overcome this and other disadvantages, by providing a scale in which each power transmitting means at its upper end is formed with a tongue disposed in a boss formed in the load receiving platform and having a crater therein, while said power transmitting means at its lower end is formed with a downwardly open slot of a width slightly larger than the thickness of the lever and having its bottom resting in the upwardly open recess of the lever.

Each power transmitting means at its upper end is provided with lugs situated adjacent the surface of the load receiving platform outside the boss, said lugs being directed substantially parallel with the associated scale lever to limit the tilting movement of the power transmitting means by abutting said surface of the platform.

Each scale lever adjacent its upwardly open recess is formed with means serving to prevent keeling over of the power transmitting means.

When the platform of the scale is made of pressed sheet metal the bosses are in the form of upstanding punched portions in the sheet metal material of the platform.

The invention will now be more fully described hereinbelow with reference to the accompanying drawings in which:

FIG. 1 is a plan view of a scale according to the invention having a load receiving platform which is here broken away to show the interior construction of the scale;

FIG. 2 is a section on line A-A in FIG. 1;

FIG. 3 shows a power transmitting means viewed in the longitudinal direction of the lever;

FIG. 4 is an enlarged view of a corner of the scale shown in FIG. 1.

As illustrated in FIGS. 1 and 2 a scale has a base plate 1 with a rim 2 integrally formed therewith. The base plate may be made for instance by compression molding of sheet metal and may have any desired shape whatever, although it is substantially rectangular in the embodiment illustrated in FIG. 1.

The load sensing mechanism of the scale comprises a pair of first levers 3 and a pair of second levers 4 which are interconnected and rest on the upwardly folded rim of the base plate. The levers in turn carry a load receiving platform 6. A depression of the levers under the weight of a load placed on the platform will actuate a weight indicating mechanism. Said mechanism has a graduation 7 which can be viewed through an aperture (not shown) in the platform 6 where it moves past a fixed index (not shown) to indicate the load resting on the platform. The scale also includes a zeroizing device by means of which the graduation can be zeroized when the platform 6 carries no load. The weight indicating mechanism with associated means is not shown in detail since it is of prior art design and is no part of the invention.

The rim 2 formed at the periphery of the base plate carries the levers 3, 4 at the corners of the substantially rectangular base plate. Said levers 3, 4 are set on edge with respect to the base plate and formed with V-shaped notches 9 whereby they can rest on the rim 2 of the base plate. The first levers 3 are coupled with and preferably fastened to a common balance plate 11 which is situated approximately midway between two of the corners of the base plate, and said first levers diverge towards the opposite corners of the base plate 2 whereby the two first levers constitute a single V-shaped lever. The second levers 4 have their one ends resting on each of the two other corners of the base plate 1 and are hingedly connected with their other ends to each of the first levers 3 between the ends thereof by means of per se known suspension brackets 12 which engage in grooves in the levers 3 and 4. The load receiving platform 6 rests in V-shaped slots 5 in the levers 3, 4 by the intermediary of intervening power transmitting means or load transmitting member 13 which will be described more in detail hereinbelow.

The power transmitting means 13 which for instance may be punched from sheet metal are formed with a downwardly open slot 14 so that each of them can straddle a lever in the V-shaped recess 5 thereof and tilt with respect to the lever. The upper edge of the power transmitting means 13 is formed with a tongue 15 by means of which the power transmitting means rests so as to permit tilting in a boss 16 formed in the load receiving platform 6, said boss having a crater therein. The bosses 16 are in the shape of upstanding punched portions in the metal sheet of the platform and the craters are conical with a cone angle slightly larger than the apex angle of the tongues 15, for which reason the surface of engagement between each power transmitting means 13 and the load receiving platform 6 will be substantially punctiform and will be situated at the apex of the crater and the tongue, respectively. The space between the upper edge of the power transmitting means and the lower surface of the load receiving platform, which space is due to the different angles, increases with the distance from the point of engagement so that the power transmitting means has the possibility of effecting a tilting movement. At the upper part of the power transmitting means 13 there are arranged two lugs 17 bent approximately in parallel with the lever and in opposite directions, said lugs being situated close to the lower surface of the load receiving platform 6 outside the bosses 16 and serving to restrict the tilting movement of the power transmitting means by abutting against the platform.

The rim 2 of the base plate 1 is outwardly bent at each of the four corners of the base plate to provide guide means 18 parallel with the plane of the bottom plate and being formed with a recess 19 for the fixation of the lateral position of the lever.

To facilitate mounting of the power transmitting means 13 on the levers 3, 4 said levers may be provided on either side of a vertical line drawn through the apex of the V-shaped recess 5 with outwardly projecting or outwardly folded parts 20 which prevent too large a deviation of the power transmitting means from the vertical plane.

For the same purpose it is also possible to give the V-shaped recess 5 so large a depth and to arrange its limbs at such an angle with respect to the vertical as to restrict the tilting movement of the upper part of the power transmitting means.

The design of the power transmitting means 13 in accordance with the invention results in considerably savings of cost, inasmuch as said means 13 in the automatic scale assembling operation can be hooked onto the levers 3, 4 from above and will remain in such a position that also the mounting of the load receiving platform 6 is facilitated and can be performed without manual intervention. At the mounting of the load receiving platform the tongues 15 of the power transmitting means 13 will automatically take their correct central position in the craters of the bosses 16.

Claims

What we claim and desire to secure by Letters Patent is:

1. In a weighing scale having a base, a platform upon which a load to be weighed is received, a load sensing mechanism, indicator means associated with said load sensing mechanism to indicate the load sensed thereby, and lever means that transmit load forces to the load sensing mechanism in accordance with the load received on said platform, the improvement which comprises a plurality of levers coupled to said load sensing mechanism to transmit load forces thereto, a plurality of bosses on said platform each having a cratered surface, and a plurality of load transmitting members each disposed for engagement with a corresponding lever and for engagement with a corresponding boss on said platform to transmit load forces therefrom to the lever, said load transmitting members having surfaces complementary to the cratered surfaces of said bosses and disposed for captive engagement therewith to stably engage same without connection thereto, said load transmitting members having surfaces complementary to the surfaces of said levers and disposed for captive engagement therewith to stably engage said levers without connection thereto.

2. The improvement according to claim 1 wherein said load transmitting member has a slot which receives the lever in close fitting straddling engagement therewith.

3. The improvement according to claim 1 wherein said load transmitting member has at least one lug disposed to limit the tilting of said member by abuttment with said platform.

4. The improvement according to claim 1 wherein said lever has a notch receiving the load transmitting member and positioned to stabilize same against tilting displacement.

5. The improvement according to claim 1 wherein said lever has at least one lug disposed to limit the tilting movement of said load transmitting member by abuttment therewith.