GB2232777A - Spring-balance - Google Patents

Abstract

A spring-balance 1 of a two-revolution type has a plastics clip-on indicator element 2 of U-shape clipped to rods 5 screwed into spring restraints 7. Each limb 2a, 2b of element 2 co-operates with an associated dial viewing window 3a, 3b so that one is always unobscured by the pointer 4. Thus the particular revolution of the pointer 4 on the dial 3 is indicated immediately through either viewing window 3a, 3b. A zero setting knob is provided on the hanger H of the casing. A second spring-balance 101 has a rack and pinion assembly with an air damper 104 (preferably comprising a graphite piston 104a and brass cylinder 104b) mounted to casing it by a plain pin 105 which passes through rectangular block 104c at the closed end of cylinder 104b. Dial support plate 12 is used to captivate damper 104 on assembly of the balance 101. Damper 104 is directly coupled to rack 16 via linkage L in between rack 16 and piston 104a. Damper 104 acts to reduce oscillations of pointer 4 about the weight reading on the dial during the weighing process. <IMAGE>

Description

WEIGHING APPARATUS This invention relates to weighing apparatus more particularly of a spring balance type.

In such weighing apparatus involving purely a mechanical action, as opposed to incorporating electronics to give a digital readout of the weight of an object, there have been relatively few dramatic improvements made in recent years; this is because the technology employed is tried and tested and could now be described as being based upon yesterday's technology.

Nevertheless, High-tech products involving electronics can be considerably more expensive to produce and may be disadvantageous in other ways and, therefore, there is still a demand for a purely mechanical weighing apparatus of the spring balance type. Even so it is believed that existing mechanical spring balances tend to he disadvantageous from some points of view, in their overall design, ease of component assembly, accuracy, ease of use, and durability, especially when contrasted against their electronic counterparts.

One particular type of spring balance used, for example, in angling, is a multi-revolution machine and the weight reading on the dial of the balance can only be determined from realising the number of past revolutions made by the pointer. It is believed that determining the weight reading on the dial tends to be made more difficult than need be the case and in some instances certain weight readings may be substantially indeterminate.

Additional problems are involved with balances which are required to meet more exacting trading standards compared to the type disclosed in our co-pending British Patent Application No.. 8825432.1, the content of which is hereby incorporated by reference. Some of these problems are related to the production of a spring balance of greater accuracy than that shown in Patent Application No. 8825432.1 and to spring design and dial location and adjustment. In particular, further problems tend to occur-with trade balances which require an even higher degree of accuracy as well as damping.

It is an object of the present invention to provide weighing apparatus which is improved in one or more respects.

According to one aspect of the present invention there is provided weighing apparatus comprising a pointer and a dial, the pointer being capable of making more than one revolution on the dial, said dial being provided with indicating means to indicate immediately on the dial the par.ticular revolution of the pointer, said indicating mean simultaneously showing the past revolution or revolutions made by the pointer, and/or the indicating means being such that a reading therefrom is always unobscured by the pointer itself, said apparatus, preferably having a zero adjusting mechanism comprising adjusting support links pivotable by an adjusting screw having a head seated in a top hanger portion of the apparatus, said head having guide notches for guiding the ends of support links during pivotal movement of the support links, in order to adjust the zero location of the pointer.

Conveniently, the indicating means comprises a clipon indicator element co-operable with a viewing window or windows in the dial. The indicator element may be clipped onto rods attached to tension springs of the apparatus and/or to a lower support portion of the apparatus. Preferably, the indicator element is vertically reciprocable in use, in unison with the lower support portion. Advantageously, the guide notches in the adjusting screw head provide an improved, more reliable, smooth pivoting action of the support links during zero adjustment as well as holding the support links steady during a weighing operation.

In one embodiment of the present invention, the indicating means includes two parallel, elongate viewing windows, each providing an identical reading in cooperation with the indication element. Thus, in use, where one of the viewing windows might be obscured to some extent by the pointer a reading can still be ascertained readily from the other, unobscured window.

It is possible that identical information need not be provided at each viewing window. One window could be provided with revolution counter whilst the other could be provided with a graduated scale.

Further advantageous features of the indicating means will be evident from the description and drawings which follow later.

Preferably, the weighing apparatus has a dial support plate underlying the dial and having access apertures to enable adjustment of springs, or of said tension springs, of the apparatus, said dial plate having means to hold a pointer spindle (on which the pointer is mountable) steady relative to a casing of the apparatus during said adjustment. Conveniently, the dial support plate is designed to assist in maintaining rigidity of the apparatus.

The support links may be mounted in a symmetric arrangement with a direct acting adjusting wheel, preferably mounted in a window and on an axis radial of the dial, said adjusting wheel (preferably being spring loaded and frustoconical) operatively threadably engaging (preferably via a nut incorporated in a recess in the wheel) said adjusting screw.

Further advantageous features of the weighing apparatus in accordance with the first aspect of the invention will be evident from the later description and drawings.

According to a second aspect of the present invention there is provided weighing apparatus comprising a rack and pinion assembly, the pinion being mounted in a pinion housing and a pointer mounted on a spindle projecting from the pinion, said pointer being rotatable on the spindle to register a weight reading on a dial of said apparatus, said apparatus having a damper to damp any oscillations of the pointer about a weight reading on the dial, and said damper being coupled to said rack of the rack and pinion assembly.

Usually, the damper will be an air damper in the form of a piston and cylinder, the piston preferably being coupled directly to the rack by a linkage.

Advantageously, the damper may be swingably mounted in between a casing and a dial support plate in order to ensure constant alignment with said rack. The casing may include an integrally moulded boss with a damper mounting recess and the dial support plate may be provided with a similar boss and mounting recess, said recesses receiving a pin on which the cylinder of the damper is swingably mounted.

Further advantages of the weighing appratus in accordance with the penultimate paragraph will be evident from the following description and drawings.

Two embodiments of spring balance weighing apparatus in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIGURE 1 shows the first embodiment in the form of a cutaway front view of a two-revolution spring balance in accordance with the present invention; FIGURE 2 shows a sectional side view taken on line II-II of FIGURE 1; FIGURE 3 shows a sectional view taken on line III-III of FIGURE 1; FIGURE 4 shows a sectional view taken on line IV-IV of FIGURE 1; FIGURES 5 and 6 show enlarged fragmentary views of indicating means of the apparatus shown in FIGURES 1 to 4; FIGURE 7 shows a perspective view of an indicator element of the first embodiment; ; FIGURES 8 and 9 show front and rear views of a dial support plate of the two revolution machine, which machine is also utilised in the second embodiment of a spring balance which is a one-revolution balance to trade use specification; FIGURE 10 shows a view similar to FIGURE 1 but of the second embodiment; FIGURE 11 shows a sectional view taken on line X1-X1 of FIGURE 10; FIGURE 12 shows an enlarged sectional detail view of a damping arrangement of said second embodiment; FIGURE 13 shows a further sectional detail view taken on line XIII-XIII of FIGURE 12; and FIGURE 14 shows yet a further detail common to both embodiments.

Referring to FIGURES 1 to 9, a spring-balance weighing apparatus 1 of a two-revolution type, which may in some instances be designed as an anglers balance or more generally for commerical use, has a maximum capacity of 50 kg (but may be designed to have a capacity of 100 lb) and an accuracy to at least 1 part in 500.

The apparatus 1 is much larger than that shown in our co-pending application No. 8825432.1 which has an accuracy to 1 part in 250.

Advantageously, apparatus 1 has indicating means comprising in part a plastics clip - on indicator element 2 of U-shape (see FIGURE 7) shown partly as hidden detail in FIGURE 1. Each limb 2a, 2b of the indicator element 2 co-operates with an associated dial viewing window 3a, 3b (see FIGURES 5 and 6). The indicator element 2 and viewing windows 3a, 3b in dial 3 together constitute indicating means which indicates immediately the particular revolution of the pointer on the dial (i.e. in this instance whether the pointer is on its first or second revolution of the dial).

As pointer 4 moves clockwise on the dial, at some stage during the first revolution (see FIGURE 5) the pointer crosses limb 2b of indicator element 2 and viewing window 3b and obscures or impedes view at least to some extent. In order that the user is able to ascertain a reading immediately without an obscured view, the indicating means (2,3a,3b) provides an unobscured reading of indicator limb 2a through viewing window 3a.

When the pointer has moved further around the scale and crosses limb 2a and viewing window 3a, thereby obscuring view, a correct reading can be taken from limb 2b through window 3b which is unobscured by the pointer (see FIGURE 6). Additionally, FIGURE 6 shows the pointer on its second revolution around the dial.

Thus, in FIGURE 6, the indicating means 2,3a,3b provides an immediately visible record showing that a first, past revolution has been made by the pointer whilst simultaneously indicating that the pointer is now on its second revolution.

As should be evident from FIGURES 1 to 9, and in particular FIGURES 1,5 and 6, an additional scale is provided adjacent to each viewing window 3a, 3b (which scale runs from 0 to 20); 0 to 10 of the scale represents a first revolution of the pointer, indicated by the words "lust Rev" and 10 to 20 of the scale represents a second revolution of the pointer indicator by the words "2nd Rev". "lust Rev" and "2nd Rev" may be provided adjacent each viewing window 3a, 3b although are only shown adjacent to viewing window 3b, for ease of illustration.

Preferably, again to aid in formulating a quick clear reading, the scale markings 0-10 and "lust Rev" indicating panels P1 may be of one colour (e.g. black) whilst the remaining scale markings and "2nd Rev" indicating panels may be of a contrasting colour (e.g. red). The indicator limbs are preferably of a clearly contrasting colour (e.g. yellow).

As will be evident from FIGURES 1,3,4 and 9 each limb 2a, 2b has an integral, inherently resilient clip Cl, C2 , projecting out of the main plane of the indicating element, and each clip C1, C2 is snap-engaged onto an associated one of two parallel rods 5. Each rod 5 has a threaded end 5a which is received in a threaded collar 6 permanently fixed to a lower end of an associated close-coiled tension spring 7. The upper ends of the springs 7 (see FIGURE 1) are attached to adjusting support links 8 of an adjusting support mechanism which is virtually identical to that shown in Patent Application No. 8825432.1 (see FIGURE 11 of that specification).

FIGURE 3 shows that bridging portion 2c of the indicator element 2 has clips C3, C4, each comprising a pair of parallel, resilient tapered tongues which snap into slots S (see FIGURE 1 and also FIGURE 10) in lower support piece 9, from which the rods 5 extend upwardly.

However, the indicator element 2 is omitted from the balance 101 shown in FIGURE 10 since balance 101 is a single revolution machine (trade version). The tongues T1, T2 each of clip C3, C4 deflect towards one another as they are inserted into the slots S and move outwardly substantially back to their original position once neck portions N of the tongues T1, T2 have been introduced into the slots (see FIGURE 4). Thus the indicator element 2 is firmly (but releasably) locked to the rods 5 and to the lower support piece 9. The lower support piece 9 is similar to that shown in Patent Application No. 8825432.1 but is now made of Verton in a similar manner to the top hanger H and is partly of I-crosssection for additional strength. The rods 5 are moulded in situ into the lower support piece 9 in such manner that they cannot rotate relative thereto or be pulled out therefrom.The rods have knurled ends (not shown) and undercut stops (not shown) which prevent them from being pulled out the lower support piece 9.

In use when a weight is suspended from the lower support piece 9, the indicator element 2 will move downwardly with rods 5 and lower support piece 9 relative to the windows 3a, 3b in the dial in a manner which should be self-explanatory. The design of the indicator element and its positioning is such that the dial 3 rests in close proximity to the indicator element 2 so that, advantageously, the indicator element moves in a closely controlled manner very close to its associated window 3a, 3b in the dial.

Since the balance 1 shown in FIGURES 1 to 9 (and more particularly the balance 101 shown in the remaining figures) needs to be very accurate the present invention provides that the tension springs 7 may be adjusted.

The pinion and pinion housing h and mounting thereof to the plastics casing 11 of the balance is exactly as shown and described in 8825432.1.

The present invention may provide dial support plate 12 (see FIGURES 8 and 9) having a central recess 12a matching the diameter of the nose on the pinion housing bush (see also FIGURE 14 which shows a fragmentary detail of the dial 3 overlying the dial support plate 12). The dial support plate 12 is firmly and securely positioned on casing 11 by the central engagement of said bush nose in the central recess 12a by the elongate bosses B on the rear of the support plate 12 (which bosses co-operate with the internal ribs r on the inside of casing 11) and by appropriate peripheral locating means.

The spindle bush is held still by the dial plate.

Adjustment of the springs 7 is possible with the dial support plate 12 in place, since dial support plate 12 is provided with large spring accessing apertures A.

Additionally, the rigidity of the balance is assisted by the dial support plate 12.

Due to the size of the dial 3, two further holes 3c, 3d are provided on either side of the central hole 3e in the dial plate. Holes 3c, 3d, 3e align with, but are slightly larger than, similarly placed holes 12a, 12b, 12c in the dial support plate 12. A self-tapping screw (not shown) is passed through pairs of aligned holes 3c, 12b and 3d, 12c and into receiving means R1, R2 integrally moulded into the casing 11. It should be noted that the holes 3c, 3d, 3e in the dial 3 are somewhat larger than the adjacent holes 12a, 12b, 12c in the underlying dial plate; this feature coupled with the fact that the external periphery of the dial 3 does not extend quite as far as that of the dial support plate 12 allows for some additional fine adjustments during assembly. Thus after appropriate alignment the centre of dial 3 and the support plate 12 are firmly screwed down to the casing.This retains the dial 3 maintaining the accuracy of the balance.

Transparent cover C is snapped onto the casing 11 and also secured thereto by two screws (not shown) in holes h1, h2 in order to secure the cover from becoming accidentally dislodged from the casing, for example if the balance 1 receives a sudden impact or shock.

A further feature of the balance 1 shown in FIGURES 1 to 9 is the zinc diecast stop member M (see FIGURES 1 and 10 for comparison) and the location of same onto the casing 11. Member M is mounted onto casing 11 by means of two opposed screws and respective washers in mounting holes 13 (see FIGURE 1). Additionally, member M is located onto two relatively large annular protrusions 14, said protrusions being integral with the casing 11. The protrusions 14 extend through matching holes in the member M. Thus, in use, the overload is shared between the two annular protrusions 14 thus spreading the load from the stop member M to the casing 11. Stop member M has two upper, spaced prongs 15 (see FIGURE 10 also), against which the lower support piece 9 is urged by way of the tension springs 7.Thus stop member M takes the reaction force and dissipates it to the casing 11 over a wide area due to the protrusions 14. Additionally, the stop member M acts as a counter weight when the balance is in a hanging position (i.e. hung up by the hanger H).

A further improvement is that, for more reliable operation, the rack 16 of the rack and pinion assembly is mounted in a slot in the lower support piece 9 (see FIGURE 10 in particular) rather than just by a pin as shown in GB 8825432.1.

The material of the casing 11 is thicker than that shown in GB 8825432.1 and has a more complex rib network r, in order to increase rigidity of the balance (ribs r co-operating with the dial support plate 12 in a manner previously described).

The casing 11 is provided with a boss 17 having a damper mounting recess 17' (see FIGURE 1 underneath the adjusting support links 8). The damper mounting recess 17' is not used in this embodiment since a damper is not fitted but is used in the balance 101 shown in FIGURES 10 to 14, which balance 101 is a one-revolution balance up to trade standard.

Remaining features of the balance 1 as shown in FIGURES 1 TO 9 which are not further described should be evident from the drawings and from a reading of GB 8825432.1 (for example the hanger H and zero adjusting mechanism with support links 8).

Referring to FIGURES 10 to 14, the second balance 101 is constructed using similar parts to the first described balance 1. In the balance 101 the same casing 11 is employed with the same lower support piece 9, and similar rack and pinion assembly as in balance 1.

Standard sealing plugs 102 and stamping plate 103 are additionally provided as is required for trade. There needs to be a maximum variation of 4% in setting which has to be done by a tool rather than by hand. A tool (not shown) is also used to remove the cover C.

Unlike in the first described embodiment balance 101 is provided with an air damper 104 (comprising a graphite piston 104a and brass cylinder or pot 104b - a more cost effective alternative is the use of anodised aluminium extrusions for the piston and cylinder/pot) which damper is mounted to the casing 11 by means of a plain pin 105 which passes through the rectangular block 104c at the closed end of the cylinder 104 (see FIGURE 12). Pin 105 slots into the damper mounting recess 17' of boss 17 integrally formed with casing 11 in order to provide a pivotal connection for the damper 104. Advantageously, the dial support plate 12 is used to captivate the damper 104 on assembly of the balance and has an integral mounting recess 12d (see FIGURES 9 and 11) which receives the end of the pin 105 opposite to the end received in recess 17.Thus the block 104c is sandwiched in between the dial support plate 12 and casing 11.

Advantageously, the damper 104 is directly coupled to the rack 16 via a linkage L in between the rack 16 and piston 104a.

The damper 104 acts to reduce oscillations of the pointer about the weight reading on the dial during the weighing process so that the pointer comes to rest quickly at the correct mark on the dial scale.

Although it is known to employ damping in balances of this general type, it tends to be a problem to provide suitable, effective damping mainly because of the lack of available space in the interior of the balance for such damping.

It is believed to be unique to connect the damper directly to the rack rather than to an alternative part of the system. It is important that the movement of the rack 16 into and out of the cylinder 104b does not affect or restrict the movement of the rack itself in order to avoid inaccuracies occurring; thus the end of the rack connected to the linkage L must be effectively free floating. Advantageously, the damper assists in shock absorption between the rack and pinion, and mounting the damper between the casing 11 and dial support plate 12 helps distribute the load between them. In an alternative arrangement, the linkage L may be replaced by a synthetic (e.g. plastics, rubber) flexible joint affording self-alignment.

Dial D is similar to dial 3 of the first described embodiment except that no viewing windows are provided therein, since balance 101 is a one-revolution machine not provided with any revolution indicating means.

Balance 101 has an accuracy to 1 part in 1000 and a 50 kg trade capacity. The pointer is a steel pointer rather than a plastics pointer because of trade regulations which restrict the point width of the pointer.

The stop member M of the first balance 1 is replaced by stop member M' in balance 101. Stop member M' is similar to member M except that member M' has an additional lower plate M'a to hold an adjustable screw stop M'b to limit maximum load indication.

It is to be understood that the scope of the present invention is not to be unduly limited by the particular choice of terminology and that a specific term may be replaced by any equivalent or generic term where sensible. Further it is to be understood that individual features, method or features related to the weighing apparatus or combinations thereof might be individually patentably inventive.

Claims (29)

1. Weighing apparatus comprising a pointer and a dial, the pointer being capable of making more than one revolution on the dial, said dial being provided with indicating means to indicate immediately on the dial the particular revolution of the pointer, said indicating means simultaneously showing the past revolution or revolutions made by the pointer, and/or the indicating means being such that a reading therefrom is always unobscured by the pointer itself, said apparatus, preferably having a zero adjusting mechanism comprising adjusting support links pivotable by an adjusting screw having a head seated in a top hanger portion of the apparatus, said head having guide notches for guiding the ends of support links during pivotal movement of the support links, in order to adjust the zero location of the pointer.

2. Apparatus as claimed in Claim 1 in which the indicating means comprises a clip-on indicator element co-operable with a viewing window or windows in the dial.

3. Apparatus as claimed in Claim 2 in which the indicator element is clipped onto rods attached to tension springs of the apparatus and/or to a lower support portion of the apparatus.

4. Apparatus as claimed in Claim 3 in which the indicator element is vertically reciprocable in use, in unison with the lower support portion.

5. Apparatus as claimed in any one of claims 2 to 4 in which the indicating means includes two parallel, elongate viewing windows, each providing a reading in cooperation with the indicator element.

6. Apparatus as claimed in Claim 5 in which identical information is provided at each viewing window.

7. Apparatus as claimed in Claim 6 in which each window is provided with a revolution counter and a graduated scale.

8. Apparatus as claimed in any one of Claims 2 to 7 in which the indicator element is of U-shape having two limbs, each limb being co-operative with an associated viewing window.

9. Apparatus as claimed in Claim 3 or any claim dependent therefrom in which the indicator element has clips comprising a pair of parallel resilient tapered tongues which snap into slots on the lower support portion.

10. Apparatus as claimed in any one of Claims 2 to 9 in which the dial rests in close proximity to the indicator element so that the indicator element moves in a closely controlled manner close to its associated window.

11. Apparatus as claimed in any one of the preceding claims comprising a dial support plate underlying the dial and having access apertures to enable adjustment of springs, or of said tension springs, of the apparatus, said dial support plate having means to hold a pinion housing bush (on which pinion a pointer is mountable) steady relative to a casing of the apparatus during said adjustment.

12. Apparatus as claimed in Claim 10 in which the dial support plate is designed to assist in maintaining rigidity of the apparatus.

13. Apparatus as claimed in Claim 11 or 12 in which the dial support plate has a central recess matching the diameter of a nose of the bush, said support plate, preferably, having elongate bosses on the rear thereof co-operable with internal ribs on the casing.

14. Apparatus as claimed in any one of Claims 11 to 13 in which the dial support plate is provided with two holes, each of said holes being on opposite sides of the central recess and alignable with similarly placed, but larger, holes in the dial, screws being passed through said holes in the dial support plate and through said holes in the dial aligned therewith into receiving means on the casing.

15. Apparatus as claimed in Claim 14 in which the external periphery of the dial does not extend quite as far as that of the dial support plate.

16. Apparatus as claimed in any one of Claims 11 to 15 in which a stop member is mounted onto the casing by two opposed screws and respective washers in mounting holes, said member being located on two annular protrusions integral with the casing, said protrusions extending through matching holes in the stop member.

17. Apparatus as claimed in Claim 16 in which the stop member has two upper, spaced prongs against which the lower support piece is urged by way of the tension springs.

18. Apparatus as claimed in any one of the preceding claims including a rack and pinion assembly in which the rack is mounted in a slot in a, or the, lower support portion of the apparatus.

19. Apparatus as claimed in any one of the preceding claims in which the support links are mounted in a symmetric arrangement with a direct acting adjusting wheel.

20. Apparatus as claimed in Claim 19 in which said wheel is mounted in a window and on an axis radial of the dial, said adjusting wheel (preferably being spring loaded and frustoconical) operatively threadably engaging (preferably via a nut incorporated in a recess in the wheel) said adjusting screw.

21. Weighing apparatus substantially as herein described and illustrated with reference to FIGURES 1 to 7 and 14 of the accompanying drawings.

22. Weighing apparatus comprising a rack and pinion assembly, the pinion being mounted in a pinion housing and a pointer mounted on a spindle projecting from the pinion, said pointer being rotatable on the spindle to register a weight reading on a dial of said apparatus, said apparatus having a damper to damp any oscillations of the pointer about a weight reading on the dial, and said damper being coupled to said rack of the rack and pinion assembly.

23. Apparatus as claimed in Claim 22 in which the damper is an air damper in the form of a piston and cylinder.

24. Apparatus as claimed in Claim 23 in which the piston is coupled directly to the rack by a linkage.

25. Apparatus as claimed in any one of Claims 22 to 26 in which the damper is swingably mounted in between a casing and a dial support plate in order to ensure constant alignment with said rack.

26. Apparatus as claimed in Claim 25 in which the casing includes an integrally moulded boss with a damper mounting recess.

27. Apparatus as claimed in Claim 26 in which the dial support plate is provided with a boss and mounting recess, said mounting recesses receiving a pin on which the cylinder of the damper is swingably mounted.

28. Apparatus as claimed in any one of Claims 22 to 27 having one or more features as herein described.

29. Weighing apparatus substantially as herein described and illustrated with reference to FIGURES 8 to 14 of the accompanying drawings.