GB2062168A - Spring testing machines - Google Patents

Abstract

A spring testing machine having a frame, a support 39 mounted on the frame and carrying a load cell, a first engagement member 49 on the load cell for engaging one end of a spring to be tested, a second engagement member 16 on the frame for engaging the other end of a spring to be tested, the first and second engagement members being relatively movable towards and away from each other, means for indicating the relative distance between the engagement members 59, and means associated with the load cell for displaying the load applied in use to a spring between the engagement members. <IMAGE>

Description

SPECIFICATION Spring testing machine This invention relates to a spring testing machine.

According to the invention there is provided a spring testing machine having a frame, a support mounted on the frame and carrying a load cell, a first engagement member on the load cell for engaging one end of a spring to be tested, a second engagement member on the frame for engaging the other end of a spring to be tested, the first and second engagement member being relatively movable towards and away from each.

other, means for indicating the relative distance between the engagement members, and means associated with the load cell for displaying the load applied in use to a spring between the engagement members.

Most load cells have a fixed part and a movable part, although the extent of movement between the parts is rarely more than 0.0005 inch. The movable part is connected in this invention to the first engagement member to form a movable assembly, while the fixed part is connected to the support to form a fixed assembly. As a result there is the same amount of movement between the first engagement member and the support, and if this movement is not entirely axial towards the load cell frictional forces can be introduced, distorting the readings. This problem can arise if in use the spring is not centred precisely on the engagement members, as lateral forces are then introduced. To combat this means can be provided for preventing lateral movement, for example a diaphragm, between the movable and fixed assemblies of the machine.

The diaphragm may extend between an end portion of the support and the movable assembly.

A second diaphragm is preferably provided to act together with the first diaphragm, being secured to the fixed assembly and to rods extending from the first engagement member. The diaphragms are most effectively disposed in parallel planes. The rods preferably pass freely through apertures in the first diaphragm.

The engaging members may be provided with the capability of dealing with either compression or tension springs, or both. For the former the members may have opposed flat faces, for example as platens, and for the latter they may have screw-threaded apertures for receiving corresponding end portions of the springs.

The support may be movable on the frame by a rack-and-pinion arrangement for presetting the starting-point for testing the spring.

In a convenient and effective form of the invention stop means are provided for selectively limiting the extent of relative movement between the engagement members, and the stop means may be in the form of axially adjustable laterally spaced screws on the frame disposed so as to engage with a plate movable with the second engagement member to limit its travel, the plate being pivotal to align selectively with any one of the screws.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a sping testing machine of this invention; Fig. 2 is a side sectional view of the lower part of a machine of the invention; Fig. 3 is a side sectional view of the upper part of a machine of the invention; and Fig. 4 is a section on A-A of Fig. 3.

In this embodiment of the invention the machine has a main frame 1 of rigid hollow section steel tubing, having a base 2 and an upright column 3 welded together. Mounted on the base 2 and welded to the column 3 is a load applicator assembly 4, while the column 3 supports a slideway 5 within which is held a load cell support assembly 6. The slideway 5 has a rack 7 with which a pinion wheel 8 (Fig. 3) engages.

The pinion wheel 8 is keyed to a shaft 9 rotatable through worm gearing 10 (Fig. 4) by a handle 11 on a shaft 12 thereby to cause the assembly 6 to move up or down the slideway 5 and thus away from or towards the load applicator assembly 4.

Referring now to Figs. 1 and 2, the load applicator assembly comprises a housing 13 through which extends a vertically slideable shaft 14 which carries at its top end an anvil 1 5. The anvil 1 5 has a flat, horizontal upper face 1 6 interrupted by a screw-threaded recess 7.

The slideable shaft 14 carries a trunnion 1 8 which passes through elongate apertures 19 in the arms of a fork 20 pivotally mounted on a shaft 21. The fork is rigidly connected to a handoperated lever 22, the action of the lever 22 thus causes the shaft 14 to slide up or down in the housing 13, taking the anvil 1 5 towards or away from the support assembly 6.

Between the anvil 15 and the shaft 14 is a rotatable collar 24 from which extends a handle 25 for its movement. The collar 24 also has an extension 26 which carries a plug 27. The limit of rotation of the collar 24 is defined by the engagement of a fixed projection 28 within an arcuate slot 28a in the collar 24.

A support 29 is slidably mounted on the slideway 5, being fixed in preselected position by screws 30. The support 29 carries brackets 31 on which are mounted stop members 32, 33. The stop members are adjustable in position on the brackets 31 by being screw-threaded and engaging in corresponding-threaded holes in the brackets, and the brackets 31 are themselves adjustable in position on the support 29 by being locatable in selected holes 34 through bolts 35.

The stop members 32, 33 are laterally spaced in a manner whereby the collar 24 can be rotated selectively to align the plug 27 with either stop member 32, 33.

The anvil 1 5 carries a collar 36 above the collar 24, and this has an extension 37 having a projection 38 whose upper face is flat and horizontal.

Referring now to Figs. 1, 3 and 4, the support assembly has a housing 39 within which is a "DATASENSE" load cell 40 having an upper portion 41 and a lower portion 42. The upper portion 41 is fixed to the housing 39 through jointed shafts 43, 44 and a nut 45 on the shaft 44.

The lower portion 42 is connected through jointed shafts 46, 47 to a second anvil 48 whose lower face 49 is flat and horizontal and aligned directly above the upper face 1 6 and the anvil 1 5 (Fig. 1).

A screwed recess 1 7a is formed in the anvil 48.

The second anvil 48 has upward-facing screwed holes in which are fixed the lower ends of upright rods 50. The rods 50 are secured at their upper ends to a collar 51 which is in two parts 51a, Sib.

Between these parts 51 a, Sib is clamped the outer periphery of a first annular diaphragm 52 whose inner periphery is clamped to a shoulder on the shaft 44.

At its lower part the housing 39 has an annular plate 53 and the outer periphery of a second annular diaphragm 54 is clamped between them.

The inner periphery is clamped to a shoulder on the shaft 47.

The load cel lower portion 42 can move very slightly towards and away from the upper portion 41 in use, the movement being of the order of one half of one thousandth of an inch, so the lower portion 42, the shafts 46 and 47, the second anvil 48 and the rods 50 form a movable assembly to that extent; the upper portion 41 of the cell, the shafts 43 and 44 and the housing 39 for a fixed assembly. These two assemblies are connected to one another through the load cell 40 and through the diaphragms 52 and 54. The diaphragms are flexible axially to allow the limited vertical movement within the load cell 40 but are rigid laterally to prevent any lateral force components from arising between the assemblies.

The load cell is powered from the mains and a cable 55 leads to a digital read-out 56 displaying the applied load between the anvils 1 5 and 48.

On an outside face of the housing 39 is secured a bracket 57 holding the casing 58 of a probe 59. A handle 60 is connected to a screw 61 for securing or releasing the casing 58 in the bracket 57, so that the probe 59 can be moved up or down relative to the housing 39. The probe 59 is aligned directly above the projection 38 on the extension 37 of the load applicator assembly 4, and is spring-loaded downwards in the casing 58.

The probe 59 is connected to a cable 62 leading to a digital read-out 63 displaying the extent of retraction of the probe 59 into the casing 58 from its starting position. Alternatively the cable 62 can lead to a dial indicator for displaying the same information.

In use of the machine, a compression spring (not shown) to be tested is placed upright on the upper face 1 6 of the lower anvil 1 5, and the handle 11 is turned to move the support assembly 6 downwards of the slideway 15 through the rack-and-pinion arrangement 7, 8 until the lower face 49 of the upper anvil 48 just engages the upper end of the spring. The spring is then in a noload and uncompressed condition. The read-out 56 displays zero loading. The assembly 6 is secured at this position on the slideway by tightening screws 64 by means of handles 65. The probe casing 58 is then moved within the bracket 57 until the lower end of the probe 59 just engages the projection 38 on the load applicator assembly 4. The digital read-out 63 then indicates zero and this sets the starting position.

The position of the stop member 32 is then set by sliding the support 29 on the slideway 5 and/or securing the bracket 31 to the support 29 as desired by locating the bolts 35 in the appropriate holes 34 and/or screwing the stop member itself in the hole in the bracket 31 The position of the stop member 32 is set by dependence on the desired amount of deflection for a spring under test and is defined by the vertical distance between the lower face of the stop member and the head of the plug 27. The collar 24 is rotated until the plug 27 is directly below the stop member 32.

The lever 22 is then pivoted downwards, moving the slidable shaft 14 upwards and causing the lower anvil 1 5 to approach the upper anvil 48, compressing the spring and pushing the probe 59 into its casing 58. As the spring compresses it produces a reaction to the applied load and actuates the load cell 40. This involves a very slight upward movement of the lower portion 42 of the cell towards the upper portion 41. In some instances the spring may not be exactly centred on the anvils 1 5, 48 and this tends to cause the lateral component of force to be introduced, instead of a desired pure vertical force.This lateral component is prevented from affecting the true situation by the presence of the diaphragms 52, 54 which flex only in a vertical direction, so restricting the movement of the lower portion 42 of the cell 40 to pure vertical movement.

The lever 22 is pivoted until the plug 27 engages the stop member 32, preventing further compression of the spring. At this preset position the digital read-outs 56 and 63 are noted,-giving the load on the spring for the distance through which it is compressed. The lever 22 is then returned to its starting position and the spring replaced with another to be tested.

A large number of springs can be tested in this way very accurately, quickly and easily to the same extent of compression set by the position of the stop member 32. The other stop member 33 can also be preset for a different strength of spring so that the machine can be switched from one to the other simply by rotating the collar 24.

Tension springs can be tested in a similar manner by screwing their ends into the recesses 17 and 1 7a and arranging the load applicator assembly to move downwards instead of upwards to tension the spring.

Modifications and improvements may be made without departing from the scope of the invention.

Claims (13)

1. A spring testing machine having a frame, a support mounted on the frame and carrying a load cell, a first engagement member on the load cell for engaging one end of a spring to be tested, a second engagement member on the frame for engaging the other end of a spring to be tested, the first and second engagement members being relatively movable towards and away from each other, means for indicating the relative distance between the engagement members, and means associated with the load cell for displaying the load applied in use to a spring between the engagement members.

2. A machine according to Claim 1, wherein the load cell has a movable part and a fixed part, the movable part being connected to the first engagement member to form a movable assembly and the fixed part being connected to the support to form a fixed assembly, the movable and fixed assembly being interconnected through means allowing relative axial movement but preventing relative lateral movement between them.

3. A machine according to Claim 2, wherein the means includes a diaphragm.

4. A machine according to Claim 3, wherein the diaphragm extends between one end portion of the support and the movable assembly.

5. A machine according to Claim 3 or 4, wherein a second diaphragm extends between the movable and fixed assemblies, being secured to rods extending from the first engagement member, the diaphragms being disposed in parallel planes to prevent lateral movement between the assemblies.

6. A machine according to Claim 5, wherein the rods pass freely through apertures in the first diaphragm adjacent the first engagement member to form part of the movable assembly.

7. A machine according to any one of the preceding claims, wherein the first and second engagement members include opposed faces for engaging the opposite ends of a compression spring to be tested.

8. A machine according to any one of the preceding claims, wherein the first and second engagement members include threaded apertures for receiving opposite ends of a tension spring to be tested.

9. A machine according to any one of the preceding claims, wherein the support is movable on the frame by means of a rack-and-pinion arrangement.

10. A machine according to any one of the preceding claims, wherein the indicating means comprises a deflectabie member on the support engageable with and biassed towards a fixed abutment on the frame and connected to a display which indicates the amount of deflection of the deflectable member.

11. A machine according to any one of the preceding claims, wherein stop means are provided for selectively limiting the extent of relative movement between the engagement members.

12. A machine according to Claim 11, wherein the stop means are axially-adjustable laterallyspaced screws on the frame disposed so as to engage with a plate movable with the second engagement member, the plate being pivotal so as to align selectively with any one of the screws.

13. A spring testing machine substantially as hereinbefore described with reference to and as shown in the acompanying drawings.