GB2110178A - Resilient connectors - Google Patents

Abstract

A resilient connector, e.g. a vehicle towing connector, comprises a first part 1 connectible to one of two members to be interconnected, a second part 2 mounted for movement between limits relative to said first part and connectible to the other of said members, and first and second resilient means 9, 13, 19 acting between said first and second parts to cushion said relative movement in respective directions from a mean position of balance, wherein at least one of said resilient means comprises two separate elements 13, 19 which are both continuously loaded in operation, one of such elements 13 being arranged to act between said first and second parts throughout the relative movement thereof on one side of said position of balance but over not more than part of such relative movement (if at all) on the other side thereof, whilst the other element 19 is arranged so as to act throughout said relative movement on the other side of said position of balance but over not more than part of such relative movement (if at all) on the one side thereof. The illustrated resilient connector comprises a towing jaw 3. The resilient element 19 eliminates "snatching" upon changeover from overrun to towing. <IMAGE>

Description

SPECIFICATION Resilient connectors This invention relates to resilient connectors, particularly but not exclusively for use in interconnecting two road vehicles for towing purposes, e.g.

in breakdown recovery.

A known resilient connector for this purpose comprises a tubular housing for mounting on the towing vehicle, a shaft slidably mounted in said housing for movement between limits relative thereto and having towing connector means at one end, and first and second helical compression springs acting between the shaft and the housing for cushioning relative movement thereof in respective directions from a mean position of balance, i.e.

during towing and overrun respectively.

This type of connector has operated satisfactorily when used in the context for which it was designed, i.e. for towing vehicles of up to about 16 tons gross weight. However a problem has arisen with the advent of much larger road vehicles, of 32 tows gross weight or more, in that at least that one of the said springs which cushions said relative movement in the towing direction, and as such has to absorb substantially greater loads than the other, needs to be made so strong that it tends to become unloaded during overrun, which is undesirable for a number of reasons, in particular because it causes "snatching" during the change-over from overrun to towing.

Viewed from one aspect the present invention provides a resilient connector comprising a first part connectible to one of two members to be interconnected, a second part mounted for movement between limits relative to said first part and connectible to the other of said members, and first and second resilient means acting between said first and second parts to cushion said relative movement in respective directions from a mean position of balance, wherein at least one of said resilient means comprises two separate elements which are both continuously loaded in operation, one of such elements being arranged to act between said first and second parts throughout the relative movement thereof on one side of said position of balance but over not more than part of such relative movement (if at all) on the other side thereof, whilst the other element is arranged so to act throughout said relative movement on the other side of said position of balance but over not more than part of such relative movement (if at all) on one side thereof.

With such an arrangement both of said elements are continuously loaded but each is only necessarily called upon to act when the said first and second parts of the connector are on one or other side of their said mean position of balance, such action being taken over by the other element when the parts are on the other side of such position. When applied to a towing connector, for example, this enables a strong, continuously loaded, resilient element constituting a major element of the combination to be used to cushion movement in the towing direction, when the interconnected parts are on one side of their mean position, whilst snatching upon change-over from overrun to towing is prevented by the action of a weaker element constituting a minor element of the combination.

In a preferred form of the invention the continuous loading of the said major element is achieved by mounting it under continuous load in a separate "floating" housing or cartridge so as only to come into operation at the appropriate time.

As may readily be envisaged, both of the said resilient means of a connector according to the invention may be split into respective elements as aforesaid if the intended use of the connector requires it.

A further problem that has arisen from the necessity to increase the strength of connectors of the aforementioned type for use with heavier vehicles is that the spring which cushions towing movement has had to be made so large that the connector as a whole can become too large to satisfy other design requirements. We have found that this further problem can readily be overcome, particularly in the context of the features of the present invention already set out above, by employing stacked disc springs as the said resilient means. However, if the size of the connector is not a serious factor, any other convenient form of resilient means may be employed in the practice of the invention, for example helical springs or rubber buffers.

The said first and second parts of the connector, for connection to the two members to be interconnected, may take any desired form depending on the intended use of connector, so long as they are arranged for relative movement between limits. In one form of the invention intended particularly for use as a towing connector, such parts may conveniently comprise a housing and a shaft slidably mounted therein, as in the known connector already referred to.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawing which is a general view of a resilient connector according to the invention partly in elevation and partly in axial cross-section.

The illustrated apparatus is a towing connector for breakdown recovery, designed particularly to cope with towed vehicles of up to about 50 tons gross weight. Conventional calculations show that for such a purpose, and assuming a towing vehicle gross weight of up to about 30 tons, the resilient means for cushioning the towing load needs to be capable of absorbing a maximum load of about 6.5 tons, and the illustrated connector has been designed with this in mind.

The connector comprises a first part in the form of a tubular housing assembly 1 adapted to be rigidly secured to a towing vehicle, and second part in the form of a shaft 2 slidable in the housing 1 and having a towing jaw 3 at its rear end. Relative sliding movement of the housing 1 and shaft 2 is limited in one direction (the towing direction) by the abutment of the rear face 4 of a flanged bushing 5 slidable on the shaft with the forward end 6 of the housing assembly, and in the other direction (the overrun direction) by the abutment of the forward face 7 of the towing jaw with a rear face 8 of the housing.The spacing between faces 4 and 6 in the stationary condition of the connector, i.e. with no towing or overrun load and the housing 1 and shaft 2 thus in their mean position of balance, is required to be 12 mm,to give that much cushioned relative movement when a towing load is applied. The corresponding spacing to cushion overrun, between faces 7 and 8, is required to be 7.5 mm.

First resilient means for cushioning overrun load comprises a stack of 14 disc springs 9 mounted on the shaft 2 between an external shoulder 10 on the shaft and an internal shoulder 11 on the body 12 of the housing 1.

Second resilient means for cushioning towing load comprises a major element in the form of a stack of 24 disc springs 13 mounted on the shaft 2 and enclosed in a floating cylindrical cartridge 14 forming part of the housing assembly 1 and slidably mounted on the housing body 12 at 15, the springs 13 being located between an internal shoulder 16 of the cartridge and a washer 17 and circlip 18 so as to be continuously loaded. The said second resilient means further comprises a minor element in the form of a stack of 10 disc springs 19 located between the shoulder 16 of the cartridge and the forward end face 20 of the housing body 12.

A nut 21 on the forward end of the shaft 2 engages the bushing 5 which in turn engages the washer 17.

Tightening the nut 21 pre-loads the spring stacks 9 and 19, and the stack 13 to some extent, and the design is such that ail three of the spring stacks will be pre-loaded to the desired extent when the rear end 22 of the cartridge 14 just abuts an external shoulder 23 on the housing body 12.

In operation, overrun load is cushioned in the normal way by the spring stack 9. Towing load is cushioned only by the spring stack 13 but upon changeover from overrun to towing snatching is prevented, despite the fact that the stack 13 no longer operates once the washer 17 has engaged the circlip 18, by the action of the spring stack 19 whose action replaces that of the stack 13 as soon as such engagement occurs.

Dimensions of, and operating loads on, the three disc stacks in the illustrated embodiment are set out in the foliowing table.

SPRING DATA STACK9 STACK 19 STACK 13 Disc Dimensions 80 x 43 x 4 x 6.2C 80 x 43 x 4 x 6.20 B0 x 43 x 5 x 6.70 No. ofDiscs (Stacking) 14 (14x1) 10 (10x1) 24 (12x2) Total Free Length of Stack 86.8 62.0 136.8 Acceptable Working Length-Max. 82.18 58.7 133.74 -Min. 62.16 44.4 120.48 Actual Working Length - Max. 82.0 57.5 133.4 -Min. 62.5 50.0 121.4 Length as Assembled. 70.0 50.0 133.4 Load on Stack- As assembied 1.787 ton 1.787 ton 1.656 ton* - With 7.5 Overrun Travel 2.380 ton 0.756 ton - With 12.0 Towing Travel 0.576 ton 6.763 ton * Before tightening nuts to close gap 22/23 - Load then 1.787 ton. CLAIMS (Filed on 24 Nov 1982) 1.A resilient connector comprising a first part connectibleto one of two members to be interconnected, a second part mounted for movement between limits relative to said first part and connectible to the other of said members, and first and second resilient means acting between said first and second parts to cushion said relative movement in respective directions from a mean position of balance, wherein at least one of said resilient means comprises two separate elements which are both continuously loaded in operation, one of such elements being arranged to act between said first and second parts throughout the relative movement thereof on one side of said position of balance but over not more than part of such relative movement (if at all) on the other side thereof, whilst the other element is arranged so to act throughout said relative movement on the other side of said position of balance but over not more than part of such relative movement (if at all) on the one side thereof.

2. A resilient connector as claimed in claim 1, wherein said one of said elements is substantially stronger than the other.

3. A resilient connector as claimed in claim 2, which is a towing connector for a vehicle said one of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   one direction (the towing direction) by the abutment of the rear face 4 of a flanged bushing 5 slidable on the shaft with the forward end 6 of the housing assembly, and in the other direction (the overrun direction) by the abutment of the forward face 7 of the towing jaw with a rear face 8 of the housing. The spacing between faces 4 and 6 in the stationary condition of the connector, i.e. with no towing or overrun load and the housing 1 and shaft 2 thus in their mean position of balance, is required to be 12 mm,to give that much cushioned relative movement when a towing load is applied. The corresponding spacing to cushion overrun, between faces 7 and 8, is required to be 7.5 mm.

   First resilient means for cushioning overrun load comprises a stack of 14 disc springs 9 mounted on the shaft 2 between an external shoulder 10 on the shaft and an internal shoulder 11 on the body 12 of the housing 1.

   Second resilient means for cushioning towing load comprises a major element in the form of a stack of 24 disc springs 13 mounted on the shaft 2 and enclosed in a floating cylindrical cartridge 14 forming part of the housing assembly 1 and slidably mounted on the housing body 12 at 15, the springs 13 being located between an internal shoulder 16 of the cartridge and a washer 17 and circlip 18 so as to be continuously loaded. The said second resilient means further comprises a minor element in the form of a stack of 10 disc springs 19 located between the shoulder 16 of the cartridge and the forward end face 20 of the housing body 12.

   A nut 21 on the forward end of the shaft 2 engages the bushing 5 which in turn engages the washer 17.

   Tightening the nut 21 pre-loads the spring stacks 9 and 19, and the stack 13 to some extent, and the design is such that ail three of the spring stacks will be pre-loaded to the desired extent when the rear end 22 of the cartridge 14 just abuts an external shoulder 23 on the housing body 12.

   In operation, overrun load is cushioned in the normal way by the spring stack 9. Towing load is cushioned only by the spring stack 13 but upon changeover from overrun to towing snatching is prevented, despite the fact that the stack 13 no longer operates once the washer 17 has engaged the circlip 18, by the action of the spring stack 19 whose action replaces that of the stack 13 as soon as such engagement occurs.

   Dimensions of, and operating loads on, the three disc stacks in the illustrated embodiment are set out in the foliowing table.

   SPRING DATA STACK9 STACK 19 STACK 13 Disc Dimensions 80 x 43 x 4 x 6.2C 80 x 43 x 4 x 6.20 B0 x 43 x 5 x 6.70 No. ofDiscs (Stacking) 14 (14x1) 10 (10x1) 24 (12x2) Total Free Length of Stack 86.8 62.0 136.8 Acceptable Working Length-Max. 82.18 58.7 133.74 -Min. 62.16 44.4 120.48 Actual Working Length - Max. 82.0 57.5 133.4 -Min. 62.5 50.0 121.4 Length as Assembled. 70.0 50.0 133.4 Load on Stack- As assembied 1.787 ton 1.787 ton 1.656 ton* - With 7.5 Overrun Travel 2.380 ton 0.756 ton - With 12.0 Towing Travel 0.576 ton 6.763 ton * Before tightening nuts to close gap 22/23 - Load then 1.787 ton. CLAIMS (Filed on 24 Nov 1982) 1.A resilient connector comprising a first part connectibleto one of two members to be interconnected, a second part mounted for movement between limits relative to said first part and connectible to the other of said members, and first and second resilient means acting between said first and second parts to cushion said relative movement in respective directions from a mean position of balance, wherein at least one of said resilient means comprises two separate elements which are both continuously loaded in operation, one of such elements being arranged to act between said first and second parts throughout the relative movement thereof on one side of said position of balance but over not more than part of such relative movement (if at all) on the other side thereof, whilst the other element is arranged so to act throughout said relative movement on the other side of said position of balance but over not more than part of such relative movement (if at all) on the one side thereof.
2. 2. A resilient connector as claimed in claim 1, wherein said one of said elements is substantially stronger than the other.
3. 3. A resilient connector as claimed in claim 2, which is a towing connector for a vehicle said one of

   said elements being arranged to cushion relative movement of said parts caused by towing (as opposed to overrun).
4. 4. A resilient connector as claimed in claim 2 or 3, wherein said one of said elements is mounted under continuous load in a cartridge incorporated in its associated one of said parts.
5. 5. A resilient connector as claimed in any of the preceding claims, wherein the said first and second parts of the connector comprise a housing and a shaft slidably mounted therein.
6. 6. A resilient connector as claimed in claims 4 and 5, wherein the said cartridge is slidably mounted both on the said shaft and relatively to the said housing.
7. 7. A resilient connector as claimed in claim 6, wherein said other of said elements acts between said housing and said cartridge.
8. 8. A resilient connector as claimed in any of the preceding claims, wherein the said resilient means comprise stacks of disc springs.
9. 9. A resilient connector substantially as hereinbefore described with reference to the accompanying drawings.
10. 10. A vehicle provided with towing apparatus comprising a resilient connector as claimed in any of claims 1 to 9.